Use proper xcconfigs to fix CI

Allow enumerating fields of value types
Useheaders from Swift repo for runtime introspection
2019-11-29 22:06:34 +03:00 · 2019-11-29 21:08:51 +03:00 · 2019-11-29 19:05:13 +03:00 · 2019-11-29 15:58:42 +03:00 · 2019-11-29 15:41:58 +03:00 · 2019-11-26 17:56:01 +03:00
202 changed files with 35820 additions and 4702 deletions
@@ -0,0 +1,400 @@
+version: 2
+jobs:
+  "Execute tests on macOS 10.15.0 (Xcode 11.2.1, Swift 5.1.2)":
+    macos:
+      xcode: "11.2.1"
+    environment:
+      SWIFT_VERSION: "5.1.2"
+    steps:
+      - checkout
+      - run:
+          name: Building and running tests in debug mode with coverage
+          command: |
+            make test-debug \
+              SWIFT_TEST_FLAGS="--enable-code-coverage --build-path .build-test-debug"
+            xcrun llvm-cov show \
+              -instr-profile=.build-test-debug/debug/codecov/default.profdata \
+              .build-test-debug/debug/OpenCombinePackageTests.xctest/Contents/MacOS/OpenCombinePackageTests \
+              > coverage.txt
+      - run:
+          name: Building and running tests in debug mode with TSan
+          command: |
+            make test-debug-sanitize-thread \
+              SWIFT_TEST_FLAGS="--build-path .build-test-debug-sanitize-thread"
+      - run:
+          name: Building and running tests in release mode
+          command: |
+            make test-release \
+              SWIFT_TEST_FLAGS="--build-path .build-test-release"
+      - run:
+          name: Generating Xcode project
+          command: make generate-xcodeproj
+      - run:
+          name: Building for testing on macOS 10.15.0 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild build-for-testing \
+                   -scheme OpenCombine-Package \
+                   -sdk macosx10.15 \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_build-for-testing.log \
+              | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing on macOS 10.15.0 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -sdk macosx10.15 \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash) -D DerivedData
+
+  "Execute compatibility tests on iOS 13.2.2 (Xcode 11.2.1, Swift 5.1.2)":
+    macos:
+      xcode: "11.2.1"
+    environment:
+      SWIFT_VERSION: "5.1.2"
+    steps:
+      - checkout
+      - run:
+          name: Generating Xcode project
+          command: make generate-compatibility-xcodeproj
+      - run:
+          name: Building for testing on iOS 13.2.2 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild build-for-testing \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone 11,OS=13.2.2" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_build-for-testing.log \
+              | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing against Combine on iOS 13.2.2 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone 11,OS=13.2.2" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+
+  "Execute tests on iOS 9.3 (Xcode 10.2.1, Swift 5.0.1)":
+    macos:
+      xcode: "10.2.1"
+    environment:
+      BUNDLE_PATH: .bundle # path to install gems and use for caching
+      SWIFT_VERSION: "5.0.1"
+    steps:
+      - checkout
+      - run:
+          name: Installing gem dependencies
+          command: bundle install && bundle clean
+      - restore_cache:
+           keys:
+             - v1-simulator-cache-{{ arch }}
+      - run:
+          # CircleCI doesn't have an iOS 9 simulator, so we need to install it manually.
+          name: Installing iOS 9 simulator
+          command: |
+            bundle exec xcversion simulators --install="iOS 9.3"
+            bundle exec xcversion simulators
+            xcrun simctl list
+      - save_cache:
+           key: v1-simulator-cache-{{ arch }}
+           paths:
+             - ~/Library/Caches/XcodeInstall
+      - run:
+          name: Generating Xcode project
+          command: |
+            make generate-xcodeproj
+            xcodebuild -scheme OpenCombine-Package -showdestinations
+      - run:
+           name: Building for testing on iOS 9.3 with xcodebuild
+           command: |
+             set -o pipefail \
+               && xcodebuild build-for-testing \
+                    -scheme OpenCombine-Package \
+                    -destination "platform=iOS Simulator,name=iPhone 4s,OS=9.3" \
+                    -derivedDataPath DerivedData \
+               | tee xcodebuild_build-for-testing.log \
+               | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing on iOS 9.3 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone 4s,OS=9.3" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash) -D DerivedData
+
+  "Execute tests on iOS 11.4 (Xcode 11.1.0, Swift 5.1.0)":
+    macos:
+      xcode: "11.1.0"
+    environment:
+      SWIFT_VERSION: "5.1.0"
+    steps:
+      - checkout
+      - run:
+          name: Generating Xcode project
+          command: |
+            make generate-xcodeproj
+            xcodebuild -scheme OpenCombine-Package -showdestinations
+      - run:
+           name: Building for testing on iOS 11.4 with xcodebuild
+           command: |
+             set -o pipefail \
+               && xcodebuild build-for-testing \
+                    -scheme OpenCombine-Package \
+                    -destination "platform=iOS Simulator,name=iPhone X,OS=11.4" \
+                    -derivedDataPath DerivedData \
+               | tee xcodebuild_build-for-testing.log \
+               | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing on iOS 11.4 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone X,OS=11.4" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash) -D DerivedData
+
+  "Execute tests on iOS 12.2 (Xcode 11.2.1, Swift 5.1.2)":
+    macos:
+      xcode: "11.2.1"
+    environment:
+      SWIFT_VERSION: "5.1.2"
+    steps:
+      - checkout
+      - run:
+          name: Generating Xcode project
+          command: |
+            make generate-xcodeproj
+            xcodebuild -scheme OpenCombine-Package -showdestinations
+      - run:
+           name: Building for testing on iOS 12.2 with xcodebuild
+           command: |
+             set -o pipefail \
+               && xcodebuild build-for-testing \
+                    -scheme OpenCombine-Package \
+                    -destination "platform=iOS Simulator,name=iPhone X,OS=12.2" \
+                    -derivedDataPath DerivedData \
+               | tee xcodebuild_build-for-testing.log \
+               | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing on iOS 12.2 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone X,OS=12.2" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash) -D DerivedData
+
+  "Execute tests on iOS 13.2.2 (Xcode 11.2.1, Swift 5.1.2)":
+    macos:
+      xcode: "11.2.1"
+    environment:
+      SWIFT_VERSION: "5.1.2"
+    steps:
+      - checkout
+      - run:
+          name: Generating Xcode project
+          command: |
+            make generate-xcodeproj
+            xcodebuild -scheme OpenCombine-Package -showdestinations
+      - run:
+           name: Building for testing on iOS 13.2.2 with xcodebuild
+           command: |
+             set -o pipefail \
+               && xcodebuild build-for-testing \
+                    -scheme OpenCombine-Package \
+                    -destination "platform=iOS Simulator,name=iPhone 11,OS=13.2.2" \
+                    -derivedDataPath DerivedData \
+               | tee xcodebuild_build-for-testing.log \
+               | xcpretty
+      - store_artifacts:
+          path: xcodebuild_build-for-testing.log
+      - run:
+          name: Testing on iOS 13.2.2 with xcodebuild
+          command: |
+            set -o pipefail \
+              && xcodebuild test-without-building \
+                   -scheme OpenCombine-Package \
+                   -destination "platform=iOS Simulator,name=iPhone 11,OS=13.2.2" \
+                   -derivedDataPath DerivedData \
+              | tee xcodebuild_test-without-building.log \
+              | xcpretty --report junit -o build/reports/results.xml
+      - store_artifacts:
+          path: xcodebuild_test-without-building.log
+      - store_test_results:
+          path: build/reports
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash) -D DerivedData
+
+  "Execute tests on Ubuntu 18.04 (Swift 5.1.1)":
+    docker:
+      - image: swift:5.1.1-bionic
+    environment:
+      SWIFT_VERSION: "5.1.1"
+    steps:
+      - checkout
+      - run:
+          name: Installing dependencies
+          command: |
+            apt update -y
+            apt upgrade -y
+            apt install -y curl
+      - run:
+          name: Building and running tests in debug mode with coverage
+          command: | # We need to run the test command twice because of https://bugs.swift.org/browse/SR-10783
+            make test-debug \
+              SWIFT_TEST_FLAGS="--enable-test-discovery \
+                                --enable-index-store \
+                                --enable-code-coverage \
+                                --build-path .build-test-debug" \
+              > /dev/null 2>&1 \
+              || true
+            make test-debug \
+              SWIFT_TEST_FLAGS="--enable-test-discovery \
+                                --enable-index-store \
+                                --enable-code-coverage \
+                                --build-path .build-test-debug"
+            llvm-cov show \
+              -instr-profile=.build-test-debug/debug/codecov/default.profdata \
+              .build-test-debug/debug/OpenCombinePackageTests.xctest \
+              > coverage.txt
+      - run:
+          name: Building and running tests in debug mode with TSan
+          command: | # We need to run the test command twice because of https://bugs.swift.org/browse/SR-10783
+            make test-debug-sanitize-thread \
+              SWIFT_TEST_FLAGS="--enable-test-discovery \
+                                --enable-index-store \
+                                --build-path .build-test-debug-sanitize-thread" \
+              > /dev/null 2>&1 \
+              || true
+            make test-debug-sanitize-thread \
+              SWIFT_TEST_FLAGS="--enable-test-discovery \
+                                --enable-index-store \
+                                --build-path .build-test-debug-sanitize-thread" \
+      - run:
+          name: Building and running tests in release mode
+          command: |
+            make test-release \
+              SWIFT_TEST_FLAGS="--enable-test-discovery \
+                                --enable-index-store \
+                                --build-path .build-test-release"
+      - run:
+          name: Uploading code coverage
+          command: |
+            bash <(curl -s https://codecov.io/bash)
+
+  "Run SwiftLint and Danger":
+    macos:
+      xcode: "11.2.0"
+    environment:
+      HOMEBREW_NO_AUTO_UPDATE: "1"
+    steps:
+      - checkout
+      - run:
+          name: Install SwiftLint
+          command: |
+            brew install swiftlint
+      - run:
+          name: Install danger-swift
+          command: |
+            brew install danger/tap/danger-swift
+      - run:
+          name: Run danger-swift
+          command: danger-swift ci
+
+  "Run Pod spec lint":
+    macos:
+      xcode: "11.2.0"
+    environment:
+      HOMEBREW_NO_AUTO_UPDATE: "1"
+    steps:
+      - checkout
+      - run:
+          name: Pod lib lint
+          command: |
+            pod lib lint --allow-warnings --verbose
+
+workflows:
+  version: 2
+  "OpenCombine: execute tests on macOS":
+    jobs:
+      - "Execute tests on macOS 10.15.0 (Xcode 11.2.1, Swift 5.1.2)"
+  "OpenCombine: execute compatibility tests":
+    jobs:
+      - "Execute compatibility tests on iOS 13.2.2 (Xcode 11.2.1, Swift 5.1.2)"
+  "OpenCombine: execute tests on iOS":
+    jobs:
+      - "Execute tests on iOS 9.3 (Xcode 10.2.1, Swift 5.0.1)"
+      - "Execute tests on iOS 11.4 (Xcode 11.1.0, Swift 5.1.0)"
+      - "Execute tests on iOS 12.2 (Xcode 11.2.1, Swift 5.1.2)"
+      - "Execute tests on iOS 13.2.2 (Xcode 11.2.1, Swift 5.1.2)"
+  "OpenCombine: execute tests on Linux":
+    jobs:
+      - "Execute tests on Ubuntu 18.04 (Swift 5.1.1)"
+  "OpenCombine: run SwiftLint and Danger":
+    jobs:
+      - "Run SwiftLint and Danger"
+  "OpenCombine: validate podspec files":
+    jobs:
+      - "Run Pod spec lint"
@@ -0,0 +1,3 @@
+*.swift.gyb linguist-language=Swift
+
+**/GENERATED-* linguist-generated=true
@@ -2,6 +2,7 @@
 /.build
 /Packages
 /*.xcodeproj
+/.swiftpm

 # Created by https://www.gitignore.io/api/Xcode
 # Edit at https://www.gitignore.io/?templates=Xcode
@@ -42,3 +43,116 @@ DerivedData/
 # End of https://www.gitignore.io/api/Xcode

 .idea
+
+# Created by https://www.gitignore.io/api/Python
+# Edit at https://www.gitignore.io/?templates=Python
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+pip-wheel-metadata/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+.hypothesis/
+.pytest_cache/
+
+# Translations
+*.mo
+*.pot
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+target/
+
+# pyenv
+.python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# celery beat schedule file
+celerybeat-schedule
+
+# SageMath parsed files
+*.sage.py
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# Mr Developer
+.mr.developer.cfg
+.project
+.pydevproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# End of https://www.gitignore.io/api/Python
+
+.bundle/
+node_modules/
@@ -16,6 +16,8 @@ disabled_rules:
  - identifier_name
  - nesting
  - notification_center_detachment
+  - no_fallthrough_only
+  - no_space_in_method_call
  - redundant_string_enum_value
  - todo
  - trailing_comma
@@ -59,7 +61,6 @@ opt_in_rules:
  - unneeded_parentheses_in_closure_argument
  - untyped_error_in_catch
  - unused_import
-  - unused_private_declaration
  - vertical_parameter_alignment_on_call
  - vertical_whitespace_closing_braces
  - yoda_condition
@@ -75,3 +76,35 @@ generic_type_name:
 attributes:
  always_on_line_above:
    - "@usableFromInline"
+
+custom_rules:
+  no_foundation_dependency:
+    included: Sources/OpenCombine/
+    name: "No Foundation Dependency"
+    regex: "^import.*Foundation.*$"
+    message: "We don't want to depend on Foundation"
+    severity: error
+
+  no_dispatch_dependency:
+    included: Sources/OpenCombine/
+    name: "No Dispatch Dependency"
+    regex: "^import.*Dispatch.*$"
+    message: "We don't want to depend on Dispatch"
+    severity: error
+
+  inheritance_colon:
+    name: "Inheritance Colon"
+    regex: '\s[A-Z_]\w*(<[\w\s:\.,]+>)?(?: +:\s*|:(?:\s{0}|\s{2,}))([\[|\(]*\S)'
+    message: "Colons should be next to the identifier of the inheriting type"
+    severity: warning
+    match_kinds:
+      - identifier
+      - typeidentifier
+
+  dictionary_type_colon:
+    name: "Dictionary Type Colon"
+    regex: '\[\w+(?:(?:\s{0}|\s{2,}):| :(?:\s{0}|\s{2,})\w)'
+    message: "Colon should be surrounded by a single whitespace in a dictionary literal"
+    severity: warning
+    match_kinds:
+      - typeidentifier
@@ -1,7 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<Workspace
-   version = "1.0">
-   <FileRef
-      location = "self:">
-   </FileRef>
-</Workspace>
@@ -1,8 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
-<plist version="1.0">
-<dict>
-	<key>IDEDidComputeMac32BitWarning</key>
-	<true/>
-</dict>
-</plist>
@@ -1,102 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<Scheme
-   LastUpgradeVersion = "1100"
-   version = "1.3">
-   <BuildAction
-      parallelizeBuildables = "YES"
-      buildImplicitDependencies = "YES">
-      <BuildActionEntries>
-         <BuildActionEntry
-            buildForTesting = "YES"
-            buildForRunning = "YES"
-            buildForProfiling = "YES"
-            buildForArchiving = "YES"
-            buildForAnalyzing = "YES">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "OpenCombine"
-               BuildableName = "OpenCombine"
-               BlueprintName = "OpenCombine"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </BuildActionEntry>
-         <BuildActionEntry
-            buildForTesting = "YES"
-            buildForRunning = "YES"
-            buildForProfiling = "YES"
-            buildForArchiving = "YES"
-            buildForAnalyzing = "YES">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "OpenCombineTests"
-               BuildableName = "OpenCombineTests"
-               BlueprintName = "OpenCombineTests"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </BuildActionEntry>
-      </BuildActionEntries>
-   </BuildAction>
-   <TestAction
-      buildConfiguration = "Debug"
-      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
-      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      enableThreadSanitizer = "YES"
-      codeCoverageEnabled = "YES">
-      <CodeCoverageTargets>
-         <BuildableReference
-            BuildableIdentifier = "primary"
-            BlueprintIdentifier = "OpenCombine"
-            BuildableName = "OpenCombine"
-            BlueprintName = "OpenCombine"
-            ReferencedContainer = "container:">
-         </BuildableReference>
-      </CodeCoverageTargets>
-      <Testables>
-         <TestableReference
-            skipped = "NO">
-            <BuildableReference
-               BuildableIdentifier = "primary"
-               BlueprintIdentifier = "OpenCombineTests"
-               BuildableName = "OpenCombineTests"
-               BlueprintName = "OpenCombineTests"
-               ReferencedContainer = "container:">
-            </BuildableReference>
-         </TestableReference>
-      </Testables>
-   </TestAction>
-   <LaunchAction
-      buildConfiguration = "Debug"
-      selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
-      selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
-      launchStyle = "0"
-      useCustomWorkingDirectory = "NO"
-      ignoresPersistentStateOnLaunch = "NO"
-      debugDocumentVersioning = "YES"
-      debugServiceExtension = "internal"
-      allowLocationSimulation = "YES">
-   </LaunchAction>
-   <ProfileAction
-      buildConfiguration = "Release"
-      shouldUseLaunchSchemeArgsEnv = "YES"
-      savedToolIdentifier = ""
-      useCustomWorkingDirectory = "NO"
-      debugDocumentVersioning = "YES">
-      <MacroExpansion>
-         <BuildableReference
-            BuildableIdentifier = "primary"
-            BlueprintIdentifier = "OpenCombine"
-            BuildableName = "OpenCombine"
-            BlueprintName = "OpenCombine"
-            ReferencedContainer = "container:">
-         </BuildableReference>
-      </MacroExpansion>
-   </ProfileAction>
-   <AnalyzeAction
-      buildConfiguration = "Debug">
-   </AnalyzeAction>
-   <ArchiveAction
-      buildConfiguration = "Release"
-      revealArchiveInOrganizer = "YES">
-   </ArchiveAction>
-</Scheme>
@@ -1,58 +0,0 @@
-language: generic
-
-addons:
-  homebrew:
-    packages:
-      - swiftlint
-    update: true
-
-matrix:
-  include:
-    - name: "Ubuntu 16.04 | Swift 5.1 | Tests"
-      os: linux
-      dist: xenial
-      sudo: required
-      env: SWIFT_VERSION="swift-5.1-DEVELOPMENT-SNAPSHOT-2019-06-16-a" OPENCOMBINE_TEST="YES"
-    - name: "macOS 10.14 | Swift 5.0 | Tests"
-      os: osx
-      osx_image: xcode10.2
-      env: SWIFT_VERSION="5.0" CODE_COVERAGE="YES" OPENCOMBINE_TEST="YES"
-    # - name: "iOS 13.0 | Swift 5.1 | Compatibility Tests"
-    #   os: osx
-    #   osx_image: xcode11
-    #   env: SWIFT_VERSION="5.1" OPENCOMBINE_COMPATIBILITY_TEST="YES"
-    - name: "macOS 10.14 | Swift 5.0 | SwiftLint"
-      os: osx
-      osx_image: xcode10.2
-      env: SWIFT_VERSION="5.0" SWIFT_LINT="YES"
-before_install:
-  - if [[ $TRAVIS_OS_NAME == "linux" ]]; then
-      cat /proc/cpuinfo;
-    fi
-install:
-  - if [[ $TRAVIS_OS_NAME == "linux" ]]; then
-      eval "$(curl -sL https://swiftenv.fuller.li/install.sh)";
-    fi
-  - if [[ $CODE_COVERAGE == "YES" ]]; then
-      gem install xcpretty;
-    fi
-script:
-  - if [[ $OPENCOMBINE_TEST == "YES" ]]; then
-      swift test -c debug --enable-code-coverage --sanitize thread;
-    fi
-  - if [[ $OPENCOMBINE_TEST == "YES" ]]; then
-      swift test -c release;
-    fi
-  - if [[ $OPENCOMBINE_COMPATIBILITY_TEST == "YES" ]]; then
-      swift package generate-xcodeproj --xcconfig-overrides iOS-Combine-Compatibility.xcconfig;
-      set -o pipefail && xcodebuild -scheme OpenCombine-Package -sdk iphonesimulator13.0 -destination "platform=iOS Simulator,name=iPhone Xs,OS=13.0" build test | xcpretty;
-    fi
-  - if [[ $SWIFT_LINT == "YES" ]]; then
-      swiftlint lint --strict --reporter "emoji";
-    fi
-after_success:
-  - if [[ $CODE_COVERAGE == "YES" ]]; then
-      swift package generate-xcodeproj --enable-code-coverage;
-      xcodebuild -scheme OpenCombine-Package build test | xcpretty;
-      bash <(curl -s https://codecov.io/bash);
-    fi
@@ -1 +1,2 @@
 OTHER_SWIFT_FLAGS = $(inherited) -DOPENCOMBINE_COMPATIBILITY_TEST
+#include "OpenCombineSPM.xcconfig"
@@ -0,0 +1,3 @@
+SWIFT_VERSION = 5.0
+OTHER_LDFLAGS = $(inherited) -L"$(TOOLCHAIN_DIR)/usr/lib/swift-$(SWIFT_VERSION)/$(PLATFORM_NAME)" -lobjc -lswiftCore
+HEADER_SEARCH_PATHS = $(SRCROOT)/Sources/COpenCombineHelpers
@@ -0,0 +1,28 @@
+Pod::Spec.new do |spec|
+  spec.name          = "COpenCombineHelpers"
+  spec.version       = "0.5.0"
+  spec.summary       = "C++ Helpers for OpenCombine"
+
+  spec.description   = <<-DESC
+  C++ helpers necessary for the implementation of OpenCombine
+  DESC
+
+  spec.homepage      = "https://github.com/broadwaylamb/OpenCombine/"
+  spec.license       = "MIT"
+
+  spec.authors       = { "Sergej Jaskiewicz" => "jaskiewiczs@icloud.com" }
+  spec.source        = { :git => "https://github.com/broadwaylamb/OpenCombine.git", :tag => "#{spec.version}" }
+
+  spec.osx.deployment_target     = "10.10"
+  spec.ios.deployment_target     = "8.0"
+  spec.watchos.deployment_target = "2.0"
+  spec.tvos.deployment_target    = "9.0"
+
+  spec.header_mappings_dir       = "Sources/COpenCombineHelpers/include"
+  spec.source_files              = "Sources/COpenCombineHelpers/**/*.{cpp,h}"
+  spec.libraries                 = "c++"
+  
+  spec.pod_target_xcconfig = {
+    "DEFINES_MODULE" => "YES"
+  }
+end
@@ -0,0 +1,76 @@
+import Danger
+import Foundation
+
+extension StringProtocol {
+    func dropSuffix<S: StringProtocol>(_ suffix: S) -> SubSequence {
+        if hasSuffix(suffix) {
+            return self[..<index(endIndex, offsetBy: -suffix.count)]
+        } else {
+            return self[...]
+        }
+    }
+
+    func directoryAndFileName() -> (SubSequence, SubSequence) {
+        let lastPathSeparator = lastIndex(of: "/")
+        if let lastPathSeparator = lastPathSeparator {
+            return (self[..<lastPathSeparator], self[index(after: lastPathSeparator)...])
+        } else {
+            return (".", self[...])
+        }
+    }
+}
+
+let danger = Danger()
+
+let allCreatedAndModified = danger.git.createdFiles + danger.git.modifiedFiles
+
+do {
+    // Fail if the committer modified a GYB template but forgot to run `make gyb`.
+
+    let modifiedTemplates = allCreatedAndModified.filter { $0.hasSuffix(".gyb") }
+
+    for modifiedTemplate in modifiedTemplates {
+        let (directory, filename) = modifiedTemplate.directoryAndFileName()
+        let generated = "\(directory)/GENERATED-\(filename.dropSuffix(".gyb"))"
+
+        if !allCreatedAndModified.contains(generated) {
+            fail("""
+            A template \(modifiedTemplate) was modified, but the file \(generated) \
+            was not regenerated.
+
+            Run `make gyb` from the root of the project and commit the changes.
+            """)
+        }
+    }
+}
+
+do {
+    // Fail if the committer modified a generated file.
+    // A template should be modified instead.
+
+    for modifiedGeneratedFile in danger.git.modifiedFiles
+        where modifiedGeneratedFile.contains("GENERATED-")
+    {
+        let template = modifiedGeneratedFile
+            .replacingOccurrences(of: "GENERATED-", with: "") + ".gyb"
+
+        if !danger.git.modifiedFiles.contains(template) {
+            fail("""
+            A generated file \(modifiedGeneratedFile) was modified, but \
+            the template it was generated from was not modified.
+
+            Please modify the template \(template) instead, \
+            run `make gyb` from the root of the project and commit the changes.
+            """)
+        }
+    }
+}
+
+SwiftLint.lint(inline: true,
+               configFile: ".swiftlint.yml",
+               strict: true,
+               lintAllFiles: true)
+
+if danger.warnings.isEmpty, danger.fails.isEmpty {
+    markdown("LGTM")
+}
@@ -0,0 +1,3 @@
+source 'https://rubygems.org'
+
+gem 'xcode-install'
@@ -0,0 +1,162 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    CFPropertyList (3.0.1)
+    addressable (2.7.0)
+      public_suffix (>= 2.0.2, < 5.0)
+    atomos (0.1.3)
+    babosa (1.0.3)
+    claide (1.0.3)
+    colored (1.2)
+    colored2 (3.1.2)
+    commander-fastlane (4.4.6)
+      highline (~> 1.7.2)
+    declarative (0.0.10)
+    declarative-option (0.1.0)
+    digest-crc (0.4.1)
+    domain_name (0.5.20190701)
+      unf (>= 0.0.5, < 1.0.0)
+    dotenv (2.7.5)
+    emoji_regex (1.0.1)
+    excon (0.68.0)
+    faraday (0.17.0)
+      multipart-post (>= 1.2, < 3)
+    faraday-cookie_jar (0.0.6)
+      faraday (>= 0.7.4)
+      http-cookie (~> 1.0.0)
+    faraday_middleware (0.13.1)
+      faraday (>= 0.7.4, < 1.0)
+    fastimage (2.1.7)
+    fastlane (2.134.0)
+      CFPropertyList (>= 2.3, < 4.0.0)
+      addressable (>= 2.3, < 3.0.0)
+      babosa (>= 1.0.2, < 2.0.0)
+      bundler (>= 1.12.0, < 3.0.0)
+      colored
+      commander-fastlane (>= 4.4.6, < 5.0.0)
+      dotenv (>= 2.1.1, < 3.0.0)
+      emoji_regex (>= 0.1, < 2.0)
+      excon (>= 0.45.0, < 1.0.0)
+      faraday (~> 0.17)
+      faraday-cookie_jar (~> 0.0.6)
+      faraday_middleware (~> 0.13.1)
+      fastimage (>= 2.1.0, < 3.0.0)
+      gh_inspector (>= 1.1.2, < 2.0.0)
+      google-api-client (>= 0.21.2, < 0.24.0)
+      google-cloud-storage (>= 1.15.0, < 2.0.0)
+      highline (>= 1.7.2, < 2.0.0)
+      json (< 3.0.0)
+      jwt (~> 2.1.0)
+      mini_magick (>= 4.9.4, < 5.0.0)
+      multi_xml (~> 0.5)
+      multipart-post (~> 2.0.0)
+      plist (>= 3.1.0, < 4.0.0)
+      public_suffix (~> 2.0.0)
+      rubyzip (>= 1.3.0, < 2.0.0)
+      security (= 0.1.3)
+      simctl (~> 1.6.3)
+      slack-notifier (>= 2.0.0, < 3.0.0)
+      terminal-notifier (>= 2.0.0, < 3.0.0)
+      terminal-table (>= 1.4.5, < 2.0.0)
+      tty-screen (>= 0.6.3, < 1.0.0)
+      tty-spinner (>= 0.8.0, < 1.0.0)
+      word_wrap (~> 1.0.0)
+      xcodeproj (>= 1.8.1, < 2.0.0)
+      xcpretty (~> 0.3.0)
+      xcpretty-travis-formatter (>= 0.0.3)
+    gh_inspector (1.1.3)
+    google-api-client (0.23.9)
+      addressable (~> 2.5, >= 2.5.1)
+      googleauth (>= 0.5, < 0.7.0)
+      httpclient (>= 2.8.1, < 3.0)
+      mime-types (~> 3.0)
+      representable (~> 3.0)
+      retriable (>= 2.0, < 4.0)
+      signet (~> 0.9)
+    google-cloud-core (1.3.2)
+      google-cloud-env (~> 1.0)
+    google-cloud-env (1.2.1)
+      faraday (~> 0.11)
+    google-cloud-storage (1.16.0)
+      digest-crc (~> 0.4)
+      google-api-client (~> 0.23)
+      google-cloud-core (~> 1.2)
+      googleauth (>= 0.6.2, < 0.10.0)
+    googleauth (0.6.7)
+      faraday (~> 0.12)
+      jwt (>= 1.4, < 3.0)
+      memoist (~> 0.16)
+      multi_json (~> 1.11)
+      os (>= 0.9, < 2.0)
+      signet (~> 0.7)
+    highline (1.7.10)
+    http-cookie (1.0.3)
+      domain_name (~> 0.5)
+    httpclient (2.8.3)
+    json (2.2.0)
+    jwt (2.1.0)
+    memoist (0.16.1)
+    mime-types (3.3)
+      mime-types-data (~> 3.2015)
+    mime-types-data (3.2019.1009)
+    mini_magick (4.9.5)
+    multi_json (1.14.1)
+    multi_xml (0.6.0)
+    multipart-post (2.0.0)
+    nanaimo (0.2.6)
+    naturally (2.2.0)
+    os (1.0.1)
+    plist (3.5.0)
+    public_suffix (2.0.5)
+    representable (3.0.4)
+      declarative (< 0.1.0)
+      declarative-option (< 0.2.0)
+      uber (< 0.2.0)
+    retriable (3.1.2)
+    rouge (2.0.7)
+    rubyzip (1.3.0)
+    security (0.1.3)
+    signet (0.11.0)
+      addressable (~> 2.3)
+      faraday (~> 0.9)
+      jwt (>= 1.5, < 3.0)
+      multi_json (~> 1.10)
+    simctl (1.6.6)
+      CFPropertyList
+      naturally
+    slack-notifier (2.3.2)
+    terminal-notifier (2.0.0)
+    terminal-table (1.8.0)
+      unicode-display_width (~> 1.1, >= 1.1.1)
+    tty-cursor (0.7.0)
+    tty-screen (0.7.0)
+    tty-spinner (0.9.1)
+      tty-cursor (~> 0.7)
+    uber (0.1.0)
+    unf (0.1.4)
+      unf_ext
+    unf_ext (0.0.7.6)
+    unicode-display_width (1.6.0)
+    word_wrap (1.0.0)
+    xcode-install (2.6.2)
+      claide (>= 0.9.1, < 1.1.0)
+      fastlane (>= 2.1.0, < 3.0.0)
+    xcodeproj (1.13.0)
+      CFPropertyList (>= 2.3.3, < 4.0)
+      atomos (~> 0.1.3)
+      claide (>= 1.0.2, < 2.0)
+      colored2 (~> 3.1)
+      nanaimo (~> 0.2.6)
+    xcpretty (0.3.0)
+      rouge (~> 2.0.7)
+    xcpretty-travis-formatter (1.0.0)
+      xcpretty (~> 0.2, >= 0.0.7)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  xcode-install
+
+BUNDLED WITH
+   2.0.1
@@ -0,0 +1,52 @@
+SWIFT_EXE=swift
+SWIFT_TEST_FLAGS=
+SWIFT_BUILD_FLAGS=-Xcc -Wunguarded-availability
+
+debug:
+	$(SWIFT_EXE) build -c debug $(SWIFT_BUILD_FLAGS)
+
+release:
+	$(SWIFT_EXE) build -c release $(SWIFT_BUILD_FLAGS)
+
+test-debug: export ASAN_OPTIONS=detect_leaks=0
+
+test-debug:
+	$(SWIFT_EXE) test -c debug --sanitize address $(SWIFT_BUILD_FLAGS) $(SWIFT_TEST_FLAGS)
+
+test-debug-sanitize-thread:
+	$(SWIFT_EXE) test -c debug --sanitize thread $(SWIFT_BUILD_FLAGS) $(SWIFT_TEST_FLAGS)
+
+test-release:
+	$(SWIFT_EXE) test -c release $(SWIFT_BUILD_FLAGS) $(SWIFT_TEST_FLAGS)
+
+swift-version:
+	$(SWIFT_EXE) -version
+
+test-compatibility:
+	$(SWIFT_EXE) test -Xswiftc -DOPENCOMBINE_COMPATIBILITY_TEST
+
+generate-compatibility-xcodeproj:
+	$(SWIFT_EXE) package generate-xcodeproj \
+		--xcconfig-overrides .xcconfigs/Combine-Compatibility.xcconfig; \
+	open OpenCombine.xcodeproj
+
+generate-xcodeproj:
+	$(SWIFT_EXE) package $(SWIFT_BUILD_FLAGS) generate-xcodeproj \
+		--enable-code-coverage  \
+		--xcconfig-overrides .xcconfigs/OpenCombineSPM.xcconfig
+
+gyb:
+	$(shell ./utils/recursively_gyb.sh)
+
+clean:
+	rm -rf .build
+
+.PHONY: debug release \
+	    test-debug \
+	    test-release \
+	    swift-version \
+	    test-compatibility-debug \
+	    generate-compatibility-xcodeproj \
+	    generate-xcodeproj \
+	    gyb \
+	    clean
@@ -0,0 +1,25 @@
+Pod::Spec.new do |spec|
+  spec.name          = "OpenCombine"
+  spec.version       = "0.5.0"
+  spec.summary       = "Open source implementation of Apple's Combine framework for processing values over time."
+
+  spec.description   = <<-DESC
+  An open source implementation of Apple's Combine framework for processing values over time.
+  DESC
+
+  spec.homepage      = "https://github.com/broadwaylamb/OpenCombine/"
+  spec.license       = "MIT"
+
+  spec.authors       = { "Sergej Jaskiewicz" => "jaskiewiczs@icloud.com" }
+  spec.source        = { :git => "https://github.com/broadwaylamb/OpenCombine.git", :tag => "#{spec.version}" }
+
+  spec.swift_version = "5.0"
+
+  spec.osx.deployment_target     = "10.10"
+  spec.ios.deployment_target     = "8.0"
+  spec.watchos.deployment_target = "2.0"
+  spec.tvos.deployment_target    = "9.0"
+
+  spec.source_files = "Sources/OpenCombine/**/*.swift"
+  spec.dependency     "COpenCombineHelpers"
+end
@@ -0,0 +1,25 @@
+Pod::Spec.new do |spec|
+  spec.name          = "OpenCombineDispatch"
+  spec.version       = "0.5.0"
+  spec.summary       = "OpenCombine Dispatching"
+
+  spec.description   = <<-DESC
+  Extends `DispatchQueue` with new methods and nested types.
+  DESC
+
+  spec.homepage      = "https://github.com/broadwaylamb/OpenCombine/"
+  spec.license       = "MIT"
+
+  spec.authors       = { "Sergej Jaskiewicz" => "jaskiewiczs@icloud.com" }
+  spec.source        = { :git => "https://github.com/broadwaylamb/OpenCombine.git", :tag => "#{spec.version}" }
+
+  spec.swift_version = "5.0"
+
+  spec.osx.deployment_target     = "10.10"
+  spec.ios.deployment_target     = "8.0"
+  spec.watchos.deployment_target = "2.0"
+  spec.tvos.deployment_target    = "9.0"
+
+  spec.source_files = "Sources/OpenCombineDispatch/**/*.swift"
+  spec.dependency     "OpenCombine"
+end
@@ -1,25 +0,0 @@
-{
-  "object": {
-    "pins": [
-      {
-        "package": "GottaGoFast",
-        "repositoryURL": "https://github.com/broadwaylamb/GottaGoFast.git",
-        "state": {
-          "branch": null,
-          "revision": "85e1f5104fb1ede87d6f31acc0445555007c474c",
-          "version": "0.1.0"
-        }
-      },
-      {
-        "package": "Yams",
-        "repositoryURL": "https://github.com/jpsim/Yams.git",
-        "state": {
-          "branch": null,
-          "revision": "c947a306d2e80ecb2c0859047b35c73b8e1ca27f",
-          "version": "2.0.0"
-        }
-      }
-    ]
-  },
-  "version": 1
-}
@@ -6,13 +6,16 @@ let package = Package(
    name: "OpenCombine",
    products: [
        .library(name: "OpenCombine", targets: ["OpenCombine"]),
-    ],
-    dependencies: [
-        .package(url: "https://github.com/broadwaylamb/GottaGoFast.git", from: "0.1.0")
+        .library(name: "OpenCombineDispatch", targets: ["OpenCombineDispatch"]),
    ],
    targets: [
-        .target(name: "OpenCombine"),
+        .target(name: "COpenCombineHelpers", cxxSettings: [.headerSearchPath(".")]),
+        .target(name: "OpenCombine", dependencies: ["COpenCombineHelpers"]),
+        .target(name: "OpenCombineDispatch", dependencies: ["OpenCombine"]),
        .testTarget(name: "OpenCombineTests",
-                    dependencies: ["OpenCombine", "GottaGoFast"])
-    ]
+                    dependencies: ["OpenCombine",
+                                   "OpenCombineDispatch"],
+                    swiftSettings: [.unsafeFlags(["-enable-testing"])])
+    ],
+    cxxLanguageStandard: .cxx14
 )
@@ -1,8 +1,9 @@
 # OpenCombine
-[![Build Status](https://travis-ci.org/broadwaylamb/OpenCombine.svg?branch=master)](https://travis-ci.org/broadwaylamb/OpenCombine)
+[![CircleCI](https://circleci.com/gh/broadwaylamb/OpenCombine/tree/master.svg?style=svg)](https://circleci.com/gh/broadwaylamb/OpenCombine/tree/master)
 [![codecov](https://codecov.io/gh/broadwaylamb/OpenCombine/branch/master/graph/badge.svg)](https://codecov.io/gh/broadwaylamb/OpenCombine)
 ![Language](https://img.shields.io/badge/Swift-5.0-orange.svg)
 ![Platform](https://img.shields.io/badge/platform-Linux%20%7C%20macOS%20%7C%20iOS%20%7C%20watchOS%20%7C%20tvOS-lightgrey.svg)
+[<img src="https://img.shields.io/badge/slack-OpenCombine-yellow.svg?logo=slack">](https://join.slack.com/t/opencombine/shared_invite/enQtNzE2MjE5NzkxODI0LTYxMjkzNDUxZWViZWI1Njc2YjBhODgxNjRjOTdkZTcxOGU2ZjJjZjYxMGI3NWZkN2RkNGFmZTUzNmU3MGE2ZWM)

 Open-source implementation of Apple's [Combine](https://developer.apple.com/documentation/combine) framework for processing values over time.

@@ -10,6 +11,42 @@ The main goal of this project is to provide a compatible, reliable and efficient

 The project is in early development.

+### Installation
+`OpenCombine` contains two public targets: `OpenCombine` and `OpenCombineDispatch` (the third one, `COpenCombineHelpers`, is considered private. Don't import it in your projects).
+
+OpenCombine itself does not have any dependencies. Not even Foundation or Dispatch. If you want to use OpenCombine with Dispatch (for example for using `DispatchQueue` as `Scheduler` for operators like `debounce`, `receive(on:)` etc.), you will need to import both `OpenCombine` and `OpenCombineDispatch`.
+
+##### Swift Package Manager
+###### Swift Package
+To add `OpenCombine` to your [SPM](https://swift.org/package-manager/) package, add the `OpenCombine` package to the list of package and target dependencies in your `Package.swift` file.
+
+```swift
+dependencies: [
+    .package(url: "https://github.com/broadwaylamb/OpenCombine.git", from: "0.5.0")
+],
+targets: [
+    .target(name: "MyAwesomePackage", dependencies: ["OpenCombine", "OpenCombineDispatch"])
+]
+```
+
+###### Xcode
+`OpenCombine` can also be added as a SPM dependency directly in your Xcode project *(requires Xcode 11 upwards)*.
+
+To do so, open Xcode, use **File** → **Swift Packages** → **Add Package Dependency…**, enter the [repository URL](https://github.com/broadwaylamb/OpenCombine.git), choose the latest available version, and activate the checkboxes:
+
+<p align="center">
+<img alt="Select the OpenCombine and OpenCombineDispatch targets" 
+	src="https://user-images.githubusercontent.com/16309982/67618468-bd379f80-f7f8-11e9-917f-e76e878a1aee.png" width="70%">
+</p>
+
+##### CocoaPods
+To add `OpenCombine` to a project using [CocoaPods](https://cocoapods.org/), add `OpenCombine` and `OpenCombineDispatch` to the list of target dependencies in your `Podfile`. 
+
+```ruby
+pod 'OpenCombine', '~> 0.5.0'
+pod 'OpenCombineDispatch', '~> 0.5.0'
+```
+
 ### Contributing

 In order to work on this project you will need Xcode 10.2 and Swift 5.0 or later.
@@ -21,9 +58,30 @@ You can refer to [this gist](https://gist.github.com/broadwaylamb/c2c8550d76b3ff
 You can run compatibility tests against Apple's Combine. In order to do that you will need either macOS 10.14 with iOS 13 simulator installed (since the only way we can get Apple's Combine on macOS 10.14 is using the simulator), or macOS 10.15 (Apple's Combine is bundled with the OS). Execute the following command from the root of the package:

 ```
-$ swift test -Xswiftc -DOPENCOMBINE_COMPATIBILITY_TEST
+$ make test-compatibility
 ```

 Or enable the `-DOPENCOMBINE_COMPATIBILITY_TEST` compiler flag in Xcode's build settings. Note that on iOS only the latter will work.

 > NOTE: Before starting to work on some feature, please consult the [GitHub project](https://github.com/broadwaylamb/OpenCombine/projects/2) to make sure that nobody's already making progress on the same feature! If not, then please create a draft PR to indicate that you're beginning your work.
+
+#### GYB
+
+Some publishers in OpenCombine (like `Publishers.MapKeyPath`, `Publishers.Merge`) exist in several
+different flavors in order to support several arities. For example, there are also `Publishers.MapKeyPath2`
+and `Publishers.MapKeyPath3`, which are very similar but different enough that Swift's type system
+can't help us here (because there's no support for variadic generics). Maintaining multiple instances of
+those generic types is tedious and error-prone (they can get out of sync), so we use the GYB tool for
+generating those instances from a template.
+
+GYB is a Python script that evaluates Python code written inside a template file, so it's very flexible —
+templates can be arbitrarily complex. There is a good article about GYB on
+[NSHipster](https://nshipster.com/swift-gyb/).
+
+GYB is part of the [Swift Open Source Project](https://github.com/apple/swift/blob/master/utils/gyb.py)
+and can be distributed under the same license as Swift itself.
+
+GYB template files have the `.gyb` extension. Run `make gyb` to generate Swift code from those
+templates. The generated files are prefixed with `GENERATED-`  and are checked into source control. Those
+files should never be edited directly. Instead, the `.gyb` template should be edited, and after that the files
+should be regenerated using `make gyb`.
@@ -0,0 +1,34 @@
+//
+//  BackDeployment.cpp
+//  
+//
+//  Created by Sergej Jaskiewicz on 31.10.2019.
+//
+
+// The content of this file is based on
+// https://github.com/apple/swift/blob/master/stdlib/public/runtime/BackDeployment.cpp
+// and must be updated accordingly.
+
+#if defined(__APPLE__) && defined(__MACH__)
+#include "swift/Runtime/Config.h"
+
+/// Returns true if the current OS version, at runtime, is a back-deployment
+/// version.
+static bool isBackDeploying() {
+    if (__builtin_available(macOS 10.14.4, watchOS 5.2.0, iOS 12.2.0, tvOS 12.2.0, *)) {
+        return false;
+    } else {
+        // We're in a pre-ABI-stable world
+        return true;
+    }
+}
+
+static unsigned long long computeIsSwiftMask() {
+    return isBackDeploying() ? 1ULL : 2ULL;
+}
+
+namespace opencombine {
+unsigned long long classIsSwiftMask = computeIsSwiftMask();
+}
+
+#endif
@@ -0,0 +1,42 @@
+//===--- Demangler.cpp - String to Node-Tree Demangling -------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements new Swift de-mangler.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Some functions have been removed.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#include "swift/Demangling/Demangle.h"
+
+using namespace opencombine;
+using namespace swift;
+
+string_view
+swift::Demangle::makeSymbolicMangledNameStringRef(const char *base) {
+  if (!base)
+    return {};
+
+  auto end = base;
+  while (*end != '\0') {
+    // Skip over symbolic references.
+    if (*end >= '\x01' && *end <= '\x17')
+      end += sizeof(uint32_t);
+    else if (*end >= '\x18' && *end <= '\x1F')
+      end += sizeof(void*);
+    ++end;
+  }
+  return { base, size_t(end - base) };
+}
@@ -0,0 +1,119 @@
+//
+//  EnumerateFields.cpp
+//  
+//
+//  Created by Sergej Jaskiewicz on 25.10.2019.
+//
+
+#include "COpenCombineHelpers.h"
+#include "swift/ABI/Metadata.h"
+#include "swift/Runtime/Metadata.h"
+#include "swift/Reflection/Records.h"
+#include "stl_polyfill/string_view.h"
+
+using namespace opencombine;
+using namespace swift;
+using namespace reflection;
+
+// This function is defined in the Swift runtime.
+OPENCOMBINE_SWIFT_CALLING_CONVENTION
+extern "C"
+const Metadata *
+swift_getTypeByMangledNameInContext(const char* typeNameStart,
+                                    size_t typeNameLength,
+                                    const ContextDescriptor* context,
+                                    const Metadata* const* genericArgs);
+
+namespace {
+const Metadata* getTypeMetadata(const FieldRecord& record,
+                                const Metadata* fieldOwner) {
+    string_view mangledTypeName = record.getMangledTypeName(0);
+    return swift_getTypeByMangledNameInContext(mangledTypeName.data(),
+                                               mangledTypeName.size(),
+                                               fieldOwner->getTypeContextDescriptor(),
+                                               fieldOwner->getGenericArgs());
+}
+
+string_view nextTupleLabel(const char*& labels) {
+    const char* start = labels;
+    while (true) {
+        char current = *labels++;
+        if (current == ' ' || current == '\0') {
+            break;
+        }
+    }
+    return { start, size_t(labels - start - 1) };
+}
+
+} // end anonymous namespace
+
+bool opencombine_enumerate_fields(const void* opaqueMetadataPtr,
+                                        bool allowResilientSuperclasses,
+                                        void* enumeratorContext,
+                                        OpenCombineFieldEnumerator enumerator) {
+
+    auto enumerateFields = [&](const auto* metadata,
+                               const TypeContextDescriptor* description) -> bool {
+        const auto* fieldOffsets = metadata->getFieldOffsets();
+        const FieldDescriptor& fieldDescriptor = *description->Fields;
+
+        for (const FieldRecord& fieldRecord : fieldDescriptor) {
+            if (!enumerator(enumeratorContext,
+                            fieldRecord.getFieldName(0).data(),
+                            *fieldOffsets++,
+                            getTypeMetadata(fieldRecord, metadata))) {
+                return false;
+            }
+        }
+
+        return true;
+    };
+
+    const Metadata* metadata = static_cast<const Metadata*>(opaqueMetadataPtr);
+
+    if (metadata->isClassObject()) {
+        auto anyClassMetadata = static_cast<const AnyClassMetadata*>(metadata);
+        if (!anyClassMetadata->isTypeMetadata()) {
+            return true;
+        }
+        auto classMetadata = static_cast<const ClassMetadata*>(anyClassMetadata);
+
+        const ClassDescriptor* description = classMetadata->getDescription();
+
+        if (!allowResilientSuperclasses && description->hasResilientSuperclass()) {
+            return false;
+        }
+
+        if (auto superclassMetadata = classMetadata->Superclass) {
+            if (!opencombine_enumerate_fields(superclassMetadata,
+                                              allowResilientSuperclasses,
+                                              enumeratorContext,
+                                              enumerator)) {
+                return false;
+            }
+        }
+
+        return enumerateFields(classMetadata, description);
+    }
+
+    if (const auto* structMetadata = llvm::dyn_cast<StructMetadata>(metadata)) {
+        return enumerateFields(structMetadata, structMetadata->getDescription());
+    }
+
+    if (const auto* tupleMetadata = llvm::dyn_cast<TupleTypeMetadata>(metadata)) {
+        const char* labels = tupleMetadata->Labels;
+        for (TupleTypeMetadata::StoredSize i = 0; i < tupleMetadata->NumElements; ++i) {
+            const TupleTypeMetadata::Element& element = tupleMetadata->getElement(i);
+            string_view nextLabel = nextTupleLabel(labels);
+            std::string label(nextLabel.data(), nextLabel.size());
+            if (!enumerator(enumeratorContext,
+                            label.c_str(),
+                            element.Offset,
+                            element.Type)) {
+                return false;
+            }
+        }
+    }
+
+    return false;
+}
@@ -0,0 +1,238 @@
+//
+//  Locking.cpp
+//  
+//
+//  Created by Sergej Jaskiewicz on 23/09/2019.
+//
+
+#include "COpenCombineHelpers.h"
+
+#include <atomic>
+#include <cstdlib>
+#include <system_error>
+#include <pthread.h>
+
+#ifdef __APPLE__
+#include <os/lock.h>
+#endif // __APPLE__
+
+// Throwing exceptions through language boundaries is undefined behavior,
+// so we must catch all of them in our extern "C" functions.
+#define OPENCOMBINE_HANDLE_EXCEPTION_BEGIN try {
+
+// std::terminate will print the type and the error message of the in-flight exception.
+#define OPENCOMBINE_HANDLE_EXCEPTION_END } catch (...) { std::terminate(); }
+
+// See 'double expansion trick'
+#define OPENCOMBINE_STRINGIFY(value) #value
+#define OPENCOMBINE_STRINGIFY_(value) OPENCOMBINE_STRINGIFY(value)
+#define OPENCOMBINE_STRING_LINE_NUMBER OPENCOMBINE_STRINGIFY_(__LINE__)
+
+// Throw an exception if the argument is non-zero with filename and line where the error
+// occured.
+#define OPENCOMBINE_HANDLE_PTHREAD_CALL(errc) \
+    if ((errc) != 0) { \
+        const char* what = __FILE__ ":" OPENCOMBINE_STRING_LINE_NUMBER ": " #errc; \
+        throw std::system_error((errc), std::system_category(), what); \
+    }
+
+namespace {
+
+std::atomic<uint64_t> next_combine_identifier;
+
+class PlatformIndependentMutex {
+public:
+    virtual void lock() = 0;
+    virtual void unlock() = 0;
+    virtual void assertOwner() {}
+
+    virtual ~PlatformIndependentMutex() noexcept(false) {}
+};
+
+class PThreadMutex : PlatformIndependentMutex {
+private:
+    pthread_mutex_t mutex_;
+public:
+    PThreadMutex() {
+        Attributes attrs;
+        attrs.setErrorCheck();
+        initialize(attrs);
+    }
+
+    PThreadMutex(const PThreadMutex&) = delete;
+    PThreadMutex& operator=(const PThreadMutex&) = delete;
+
+    PThreadMutex(PThreadMutex&&) = delete;
+    PThreadMutex& operator=(PThreadMutex&&) = delete;
+
+    void lock() override final {
+        OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutex_lock(&mutex_));
+    }
+
+    void unlock() override final {
+        OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutex_unlock(&mutex_));
+    }
+
+    ~PThreadMutex() {
+        // Yep, this destructor may throw. This is deliberate, since pthread_mutex_destroy
+        // may fail.
+        //
+        // The altrenative is to just silently ignore the error, which is even worse.
+        OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutex_destroy(&mutex_));
+    }
+protected:
+    class Attributes {
+        pthread_mutexattr_t attrs_;
+    public:
+        Attributes() {
+            OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutexattr_init(&attrs_));
+        }
+
+        Attributes(const Attributes&) = delete;
+        Attributes& operator=(const Attributes&) = delete;
+
+        Attributes(Attributes&&) = delete;
+        Attributes& operator=(Attributes&&) = delete;
+
+        const pthread_mutexattr_t* raw() const noexcept {
+            return &attrs_;
+        }
+
+        void setRecursive() {
+            setType(PTHREAD_MUTEX_RECURSIVE);
+        }
+
+        void setErrorCheck() {
+            setType(PTHREAD_MUTEX_ERRORCHECK);
+        }
+
+        ~Attributes() noexcept(false) {
+            // Yep, this destructor may throw. This is deliberate,
+            // since pthread_mutexattr_destroy may fail.
+            //
+            // The altrenative is to just silently ignore the error, which is even worse.
+            OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutexattr_destroy(&attrs_));
+        }
+    private:
+        void setType(int type) {
+            OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutexattr_settype(&attrs_, type));
+        }
+    };
+
+    void initialize(const Attributes& attributes) {
+        OPENCOMBINE_HANDLE_PTHREAD_CALL(pthread_mutex_init(&mutex_, attributes.raw()));
+    }
+};
+
+class PThreadRecursiveMutex final : PThreadMutex {
+public:
+    PThreadRecursiveMutex() {
+        Attributes attrs;
+        attrs.setRecursive();
+        initialize(attrs);
+    }
+
+    PThreadRecursiveMutex(const PThreadRecursiveMutex&) = delete;
+    PThreadRecursiveMutex& operator=(const PThreadRecursiveMutex&) = delete;
+
+    PThreadRecursiveMutex(PThreadRecursiveMutex&&) = delete;
+    PThreadRecursiveMutex& operator=(PThreadRecursiveMutex&&) = delete;
+};
+
+#ifdef __APPLE__
+
+class OS_UNFAIR_LOCK_AVAILABILITY OSUnfairLock final : PlatformIndependentMutex {
+    os_unfair_lock mutex_ = OS_UNFAIR_LOCK_INIT;
+public:
+    OSUnfairLock() = default;
+
+    OSUnfairLock(const OSUnfairLock&) = delete;
+    OSUnfairLock& operator=(const OSUnfairLock&) = delete;
+
+    OSUnfairLock(OSUnfairLock&&) = delete;
+    OSUnfairLock& operator=(OSUnfairLock&&) = delete;
+
+    void lock() override {
+        os_unfair_lock_lock(&mutex_);
+    }
+
+    void unlock() override {
+        os_unfair_lock_unlock(&mutex_);
+    }
+
+    void assertOwner() override {
+        os_unfair_lock_assert_owner(&mutex_);
+    }
+};
+#endif // __APPLE__
+
+} // end anonymous namespace
+
+extern "C" {
+
+uint64_t opencombine_next_combine_identifier(void) {
+    return next_combine_identifier.fetch_add(1);
+}
+
+OpenCombineUnfairLock opencombine_unfair_lock_alloc(void) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+
+#ifdef __APPLE__
+    if (__builtin_available(macOS 10.12, iOS 10.0, tvOS 10.0, watchOS 3.0, *)) {
+        return {new OSUnfairLock};
+    } else {
+        return {new PThreadMutex};
+    }
+#else
+    return {new PThreadMutex};
+#endif
+
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+OpenCombineUnfairRecursiveLock opencombine_unfair_recursive_lock_alloc(void) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    // TODO: Use os_unfair_recursive_lock on Darwin as soon as it becomes public API.
+    return {new PThreadRecursiveMutex};
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_lock_lock(OpenCombineUnfairLock lock) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    static_cast<PlatformIndependentMutex*>(lock.opaque)->lock();
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_lock_unlock(OpenCombineUnfairLock mutex) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    static_cast<PlatformIndependentMutex*>(mutex.opaque)->unlock();
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_lock_assert_owner(OpenCombineUnfairLock mutex) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    static_cast<PlatformIndependentMutex*>(mutex.opaque)->assertOwner();
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_recursive_lock_lock(OpenCombineUnfairRecursiveLock lock) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    static_cast<PlatformIndependentMutex*>(lock.opaque)->lock();
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_recursive_lock_unlock(OpenCombineUnfairRecursiveLock mutex) {
+    OPENCOMBINE_HANDLE_EXCEPTION_BEGIN
+    static_cast<PlatformIndependentMutex*>(mutex.opaque)->unlock();
+    OPENCOMBINE_HANDLE_EXCEPTION_END
+}
+
+void opencombine_unfair_lock_dealloc(OpenCombineUnfairLock lock) {
+    return delete static_cast<PlatformIndependentMutex*>(lock.opaque);
+}
+
+void opencombine_unfair_recursive_lock_dealloc(OpenCombineUnfairRecursiveLock lock) {
+    return delete static_cast<PlatformIndependentMutex*>(lock.opaque);
+}
+
+} // extern "C"
@@ -0,0 +1,123 @@
+//===--- Metadata.cpp - Swift Language ABI Metadata Support ---------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Implementations of the metadata ABI functions.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Some functions have been removed.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#include "swift/Runtime/Metadata.h"
+
+using namespace opencombine;
+using namespace swift;
+
+#if OPENCOMBINE_SWIFT_OBJC_INTEROP
+static ClassMetadataBounds computeMetadataBoundsForObjCClass(Class cls) {
+  cls = swift_getInitializedObjCClass(cls);
+  auto metadata = reinterpret_cast<const ClassMetadata *>(cls);
+  return metadata->getClassBoundsAsSwiftSuperclass();
+}
+#endif
+
+static ClassMetadataBounds
+computeMetadataBoundsForSuperclass(const void *ref,
+                                   TypeReferenceKind refKind) {
+  switch (refKind) {
+  case TypeReferenceKind::IndirectTypeDescriptor: {
+    auto description = *reinterpret_cast<const ClassDescriptor * const *>(ref);
+    if (!description) {
+//      swift::fatalError(0, "instantiating class metadata for class with "
+//                           "missing weak-linked ancestor");
+        abort();
+    }
+    return description->getMetadataBounds();
+  }
+
+  case TypeReferenceKind::DirectTypeDescriptor: {
+    auto description = reinterpret_cast<const ClassDescriptor *>(ref);
+    return description->getMetadataBounds();
+  }
+
+  case TypeReferenceKind::DirectObjCClassName: {
+#if OPENCOMBINE_SWIFT_OBJC_INTEROP
+    auto cls = objc_lookUpClass(reinterpret_cast<const char *>(ref));
+    return computeMetadataBoundsForObjCClass(cls);
+#else
+    break;
+#endif
+  }
+
+  case TypeReferenceKind::IndirectObjCClass: {
+#if OPENCOMBINE_SWIFT_OBJC_INTEROP
+    auto cls = *reinterpret_cast<const Class *>(ref);
+    return computeMetadataBoundsForObjCClass(cls);
+#else
+    break;
+#endif
+  }
+  }
+  opencombine_swift_runtime_unreachable("unsupported superclass reference kind");
+}
+
+static ClassMetadataBounds computeMetadataBoundsFromSuperclass(
+                                      const ClassDescriptor *description,
+                                      StoredClassMetadataBounds &storedBounds) {
+  ClassMetadataBounds bounds;
+
+  // Compute the bounds for the superclass, extending it to the minimum
+  // bounds of a Swift class.
+  if (const void *superRef = description->getResilientSuperclass()) {
+    bounds = computeMetadataBoundsForSuperclass(superRef,
+                           description->getResilientSuperclassReferenceKind());
+  } else {
+    bounds = ClassMetadataBounds::forSwiftRootClass();
+  }
+
+  // Add the subclass's immediate members.
+  bounds.adjustForSubclass(description->areImmediateMembersNegative(),
+                           description->NumImmediateMembers);
+
+  // Cache before returning.
+  storedBounds.initialize(bounds);
+  return bounds;
+}
+
+ClassMetadataBounds
+swift::getResilientMetadataBounds(const ClassDescriptor *description) {
+  assert(description->hasResilientSuperclass());
+  auto &storedBounds = *description->ResilientMetadataBounds.get();
+
+  ClassMetadataBounds bounds;
+  if (storedBounds.tryGet(bounds)) {
+    return bounds;
+  }
+
+  return computeMetadataBoundsFromSuperclass(description, storedBounds);
+}
+
+int32_t
+swift::getResilientImmediateMembersOffset(const ClassDescriptor *description) {
+  assert(description->hasResilientSuperclass());
+  auto &storedBounds = *description->ResilientMetadataBounds.get();
+
+  ptrdiff_t result;
+  if (storedBounds.tryGetImmediateMembersOffset(result)) {
+    return result / sizeof(void*);
+  }
+
+  auto bounds = computeMetadataBoundsFromSuperclass(description, storedBounds);
+  return bounds.ImmediateMembersOffset / sizeof(void*);
+}
@@ -0,0 +1,94 @@
+//
+//  COpenCombineHelpers.h
+//  
+//
+//  Created by Sergej Jaskiewicz on 23/09/2019.
+//
+
+#ifndef COPENCOMBINEHELPERS_H
+#define COPENCOMBINEHELPERS_H
+
+#include <stdint.h>
+#include <stddef.h>
+#include <stdbool.h>
+
+#if __has_attribute(swift_name)
+# define OPENCOMBINE_SWIFT_NAME(_name) __attribute__((swift_name(#_name)))
+#else
+# define OPENCOMBINE_SWIFT_NAME(_name)
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#pragma mark - CombineIdentifier
+
+uint64_t opencombine_next_combine_identifier(void)
+    OPENCOMBINE_SWIFT_NAME(nextCombineIdentifier());
+
+#pragma mark - OpenCombineUnfairLock
+
+/// A wrapper around an opaque pointer for type safety in Swift.
+typedef struct OpenCombineUnfairLock {
+    void* _Nonnull opaque;
+} OPENCOMBINE_SWIFT_NAME(UnfairLock) OpenCombineUnfairLock;
+
+/// Allocates a lock object. The allocated object must be destroyed by calling
+/// the destroy() method.
+OpenCombineUnfairLock opencombine_unfair_lock_alloc(void)
+    OPENCOMBINE_SWIFT_NAME(UnfairLock.allocate());
+
+void opencombine_unfair_lock_lock(OpenCombineUnfairLock)
+    OPENCOMBINE_SWIFT_NAME(UnfairLock.lock(self:));
+
+void opencombine_unfair_lock_unlock(OpenCombineUnfairLock)
+    OPENCOMBINE_SWIFT_NAME(UnfairLock.unlock(self:));
+
+void opencombine_unfair_lock_assert_owner(OpenCombineUnfairLock mutex)
+    OPENCOMBINE_SWIFT_NAME(UnfairLock.assertOwner(self:));
+
+void opencombine_unfair_lock_dealloc(OpenCombineUnfairLock lock)
+    OPENCOMBINE_SWIFT_NAME(UnfairLock.deallocate(self:));
+
+#pragma mark - OpenCombineUnfairRecursiveLock
+
+/// A wrapper around an opaque pointer for type safety in Swift.
+typedef struct OpenCombineUnfairRecursiveLock {
+    void* _Nonnull opaque;
+} OPENCOMBINE_SWIFT_NAME(UnfairRecursiveLock) OpenCombineUnfairRecursiveLock;
+
+OpenCombineUnfairRecursiveLock opencombine_unfair_recursive_lock_alloc(void)
+    OPENCOMBINE_SWIFT_NAME(UnfairRecursiveLock.allocate());
+
+void opencombine_unfair_recursive_lock_lock(OpenCombineUnfairRecursiveLock)
+    OPENCOMBINE_SWIFT_NAME(UnfairRecursiveLock.lock(self:));
+
+void opencombine_unfair_recursive_lock_unlock(OpenCombineUnfairRecursiveLock)
+    OPENCOMBINE_SWIFT_NAME(UnfairRecursiveLock.unlock(self:));
+
+void opencombine_unfair_recursive_lock_dealloc(OpenCombineUnfairRecursiveLock lock)
+    OPENCOMBINE_SWIFT_NAME(UnfairRecursiveLock.deallocate(self:));
+
+#pragma mark - Type metadata
+
+typedef bool(*_Nonnull OpenCombineFieldEnumerator)(
+    void* _Nullable enumeratorContext,
+    const char* _Nonnull fieldName,
+    size_t fieldOffset,
+    const void* _Nonnull fieldTypeMetadataPtr
+);
+
+bool
+opencombine_enumerate_fields(
+    const void* _Nonnull type_metadata,
+    bool allowResilientSuperclasses,
+    void* _Nullable enumerator_context,
+    OpenCombineFieldEnumerator enumerator
+) OPENCOMBINE_SWIFT_NAME(enumerateFields(typeMetadata:allowResilientSuperclasses:enumeratorContext:enumerator:));
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif /* COPENCOMBINEHELPERS_H */
@@ -0,0 +1,32 @@
+//===-- None.h - Simple null value for implicit construction ------*- C++ -*-=//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file provides None, an enumerator for use in implicit constructors
+//  of various (usually templated) types to make such construction more
+//  terse.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_ADT_NONE_H
+#define OPENCOMBINE_LLVM_ADT_NONE_H
+
+namespace opencombine {
+namespace llvm {
+/// A simple null object to allow implicit construction of Optional<T>
+/// and similar types without having to spell out the specialization's name.
+// (constant value 1 in an attempt to workaround MSVC build issue... )
+enum class NoneType { None = 1 };
+const NoneType None = NoneType::None;
+}
+}
+
+#endif
@@ -0,0 +1,435 @@
+//===- Optional.h - Simple variant for passing optional values --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file provides Optional, a template class modeled in the spirit of
+//  OCaml's 'opt' variant.  The idea is to strongly type whether or not
+//  a value can be optional.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_ADT_OPTIONAL_H
+#define OPENCOMBINE_LLVM_ADT_OPTIONAL_H
+
+#include "llvm/ADT/None.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/type_traits.h"
+#include <cassert>
+#include <memory>
+#include <new>
+#include <utility>
+
+namespace opencombine {
+namespace llvm {
+
+class raw_ostream;
+
+namespace optional_detail {
+
+struct in_place_t {};
+
+/// Storage for any type.
+template <typename T, bool = is_trivially_copyable<T>::value>
+class OptionalStorage {
+  union {
+    char empty;
+    T value;
+  };
+  bool hasVal;
+
+public:
+  ~OptionalStorage() { reset(); }
+
+  OptionalStorage() noexcept : empty(), hasVal(false) {}
+
+  OptionalStorage(OptionalStorage const &other) : OptionalStorage() {
+    if (other.hasValue()) {
+      emplace(other.value);
+    }
+  }
+  OptionalStorage(OptionalStorage &&other) : OptionalStorage() {
+    if (other.hasValue()) {
+      emplace(std::move(other.value));
+    }
+  }
+
+  template <class... Args>
+  explicit OptionalStorage(in_place_t, Args &&... args)
+      : value(std::forward<Args>(args)...), hasVal(true) {}
+
+  void reset() noexcept {
+    if (hasVal) {
+      value.~T();
+      hasVal = false;
+    }
+  }
+
+  bool hasValue() const noexcept { return hasVal; }
+
+  T &getValue() LLVM_LVALUE_FUNCTION noexcept {
+    assert(hasVal);
+    return value;
+  }
+  T const &getValue() const LLVM_LVALUE_FUNCTION noexcept {
+    assert(hasVal);
+    return value;
+  }
+#if LLVM_HAS_RVALUE_REFERENCE_THIS
+  T &&getValue() && noexcept {
+    assert(hasVal);
+    return std::move(value);
+  }
+#endif
+
+  template <class... Args> void emplace(Args &&... args) {
+    reset();
+    ::new ((void *)std::addressof(value)) T(std::forward<Args>(args)...);
+    hasVal = true;
+  }
+
+  OptionalStorage &operator=(T const &y) {
+    if (hasValue()) {
+      value = y;
+    } else {
+      ::new ((void *)std::addressof(value)) T(y);
+      hasVal = true;
+    }
+    return *this;
+  }
+  OptionalStorage &operator=(T &&y) {
+    if (hasValue()) {
+      value = std::move(y);
+    } else {
+      ::new ((void *)std::addressof(value)) T(std::move(y));
+      hasVal = true;
+    }
+    return *this;
+  }
+
+  OptionalStorage &operator=(OptionalStorage const &other) {
+    if (other.hasValue()) {
+      if (hasValue()) {
+        value = other.value;
+      } else {
+        ::new ((void *)std::addressof(value)) T(other.value);
+        hasVal = true;
+      }
+    } else {
+      reset();
+    }
+    return *this;
+  }
+
+  OptionalStorage &operator=(OptionalStorage &&other) {
+    if (other.hasValue()) {
+      if (hasValue()) {
+        value = std::move(other.value);
+      } else {
+        ::new ((void *)std::addressof(value)) T(std::move(other.value));
+        hasVal = true;
+      }
+    } else {
+      reset();
+    }
+    return *this;
+  }
+};
+
+template <typename T> class OptionalStorage<T, true> {
+  union {
+    char empty;
+    T value;
+  };
+  bool hasVal = false;
+
+public:
+  ~OptionalStorage() = default;
+
+  OptionalStorage() noexcept : empty{} {}
+
+  OptionalStorage(OptionalStorage const &other) = default;
+  OptionalStorage(OptionalStorage &&other) = default;
+
+  OptionalStorage &operator=(OptionalStorage const &other) = default;
+  OptionalStorage &operator=(OptionalStorage &&other) = default;
+
+  template <class... Args>
+  explicit OptionalStorage(in_place_t, Args &&... args)
+      : value(std::forward<Args>(args)...), hasVal(true) {}
+
+  void reset() noexcept {
+    if (hasVal) {
+      value.~T();
+      hasVal = false;
+    }
+  }
+
+  bool hasValue() const noexcept { return hasVal; }
+
+  T &getValue() LLVM_LVALUE_FUNCTION noexcept {
+    assert(hasVal);
+    return value;
+  }
+  T const &getValue() const LLVM_LVALUE_FUNCTION noexcept {
+    assert(hasVal);
+    return value;
+  }
+#if LLVM_HAS_RVALUE_REFERENCE_THIS
+  T &&getValue() && noexcept {
+    assert(hasVal);
+    return std::move(value);
+  }
+#endif
+
+  template <class... Args> void emplace(Args &&... args) {
+    reset();
+    ::new ((void *)std::addressof(value)) T(std::forward<Args>(args)...);
+    hasVal = true;
+  }
+
+  OptionalStorage &operator=(T const &y) {
+    if (hasValue()) {
+      value = y;
+    } else {
+      ::new ((void *)std::addressof(value)) T(y);
+      hasVal = true;
+    }
+    return *this;
+  }
+  OptionalStorage &operator=(T &&y) {
+    if (hasValue()) {
+      value = std::move(y);
+    } else {
+      ::new ((void *)std::addressof(value)) T(std::move(y));
+      hasVal = true;
+    }
+    return *this;
+  }
+};
+
+} // namespace optional_detail
+
+template <typename T> class Optional {
+  optional_detail::OptionalStorage<T> Storage;
+
+public:
+  using value_type = T;
+
+  constexpr Optional() {}
+  constexpr Optional(NoneType) {}
+
+  Optional(const T &y) : Storage(optional_detail::in_place_t{}, y) {}
+  Optional(const Optional &O) = default;
+
+  Optional(T &&y) : Storage(optional_detail::in_place_t{}, std::move(y)) {}
+  Optional(Optional &&O) = default;
+
+  Optional &operator=(T &&y) {
+    Storage = std::move(y);
+    return *this;
+  }
+  Optional &operator=(Optional &&O) = default;
+
+  /// Create a new object by constructing it in place with the given arguments.
+  template <typename... ArgTypes> void emplace(ArgTypes &&... Args) {
+    Storage.emplace(std::forward<ArgTypes>(Args)...);
+  }
+
+  static inline Optional create(const T *y) {
+    return y ? Optional(*y) : Optional();
+  }
+
+  Optional &operator=(const T &y) {
+    Storage = y;
+    return *this;
+  }
+  Optional &operator=(const Optional &O) = default;
+
+  void reset() { Storage.reset(); }
+
+  const T *getPointer() const { return &Storage.getValue(); }
+  T *getPointer() { return &Storage.getValue(); }
+  const T &getValue() const LLVM_LVALUE_FUNCTION { return Storage.getValue(); }
+  T &getValue() LLVM_LVALUE_FUNCTION { return Storage.getValue(); }
+
+  explicit operator bool() const { return hasValue(); }
+  bool hasValue() const { return Storage.hasValue(); }
+  const T *operator->() const { return getPointer(); }
+  T *operator->() { return getPointer(); }
+  const T &operator*() const LLVM_LVALUE_FUNCTION { return getValue(); }
+  T &operator*() LLVM_LVALUE_FUNCTION { return getValue(); }
+
+  template <typename U>
+  constexpr T getValueOr(U &&value) const LLVM_LVALUE_FUNCTION {
+    return hasValue() ? getValue() : std::forward<U>(value);
+  }
+
+#if LLVM_HAS_RVALUE_REFERENCE_THIS
+  T &&getValue() && { return std::move(Storage.getValue()); }
+  T &&operator*() && { return std::move(Storage.getValue()); }
+
+  template <typename U>
+  T getValueOr(U &&value) && {
+    return hasValue() ? std::move(getValue()) : std::forward<U>(value);
+  }
+#endif
+};
+
+template <typename T, typename U>
+bool operator==(const Optional<T> &X, const Optional<U> &Y) {
+  if (X && Y)
+    return *X == *Y;
+  return X.hasValue() == Y.hasValue();
+}
+
+template <typename T, typename U>
+bool operator!=(const Optional<T> &X, const Optional<U> &Y) {
+  return !(X == Y);
+}
+
+template <typename T, typename U>
+bool operator<(const Optional<T> &X, const Optional<U> &Y) {
+  if (X && Y)
+    return *X < *Y;
+  return X.hasValue() < Y.hasValue();
+}
+
+template <typename T, typename U>
+bool operator<=(const Optional<T> &X, const Optional<U> &Y) {
+  return !(Y < X);
+}
+
+template <typename T, typename U>
+bool operator>(const Optional<T> &X, const Optional<U> &Y) {
+  return Y < X;
+}
+
+template <typename T, typename U>
+bool operator>=(const Optional<T> &X, const Optional<U> &Y) {
+  return !(X < Y);
+}
+
+template<typename T>
+bool operator==(const Optional<T> &X, NoneType) {
+  return !X;
+}
+
+template<typename T>
+bool operator==(NoneType, const Optional<T> &X) {
+  return X == None;
+}
+
+template<typename T>
+bool operator!=(const Optional<T> &X, NoneType) {
+  return !(X == None);
+}
+
+template<typename T>
+bool operator!=(NoneType, const Optional<T> &X) {
+  return X != None;
+}
+
+template <typename T> bool operator<(const Optional<T> &X, NoneType) {
+  return false;
+}
+
+template <typename T> bool operator<(NoneType, const Optional<T> &X) {
+  return X.hasValue();
+}
+
+template <typename T> bool operator<=(const Optional<T> &X, NoneType) {
+  return !(None < X);
+}
+
+template <typename T> bool operator<=(NoneType, const Optional<T> &X) {
+  return !(X < None);
+}
+
+template <typename T> bool operator>(const Optional<T> &X, NoneType) {
+  return None < X;
+}
+
+template <typename T> bool operator>(NoneType, const Optional<T> &X) {
+  return X < None;
+}
+
+template <typename T> bool operator>=(const Optional<T> &X, NoneType) {
+  return None <= X;
+}
+
+template <typename T> bool operator>=(NoneType, const Optional<T> &X) {
+  return X <= None;
+}
+
+template <typename T> bool operator==(const Optional<T> &X, const T &Y) {
+  return X && *X == Y;
+}
+
+template <typename T> bool operator==(const T &X, const Optional<T> &Y) {
+  return Y && X == *Y;
+}
+
+template <typename T> bool operator!=(const Optional<T> &X, const T &Y) {
+  return !(X == Y);
+}
+
+template <typename T> bool operator!=(const T &X, const Optional<T> &Y) {
+  return !(X == Y);
+}
+
+template <typename T> bool operator<(const Optional<T> &X, const T &Y) {
+  return !X || *X < Y;
+}
+
+template <typename T> bool operator<(const T &X, const Optional<T> &Y) {
+  return Y && X < *Y;
+}
+
+template <typename T> bool operator<=(const Optional<T> &X, const T &Y) {
+  return !(Y < X);
+}
+
+template <typename T> bool operator<=(const T &X, const Optional<T> &Y) {
+  return !(Y < X);
+}
+
+template <typename T> bool operator>(const Optional<T> &X, const T &Y) {
+  return Y < X;
+}
+
+template <typename T> bool operator>(const T &X, const Optional<T> &Y) {
+  return Y < X;
+}
+
+template <typename T> bool operator>=(const Optional<T> &X, const T &Y) {
+  return !(X < Y);
+}
+
+template <typename T> bool operator>=(const T &X, const Optional<T> &Y) {
+  return !(X < Y);
+}
+
+raw_ostream &operator<<(raw_ostream &OS, NoneType);
+
+template <typename T, typename = decltype(std::declval<raw_ostream &>()
+                                          << std::declval<const T &>())>
+raw_ostream &operator<<(raw_ostream &OS, const Optional<T> &O) {
+  if (O)
+    OS << *O;
+  else
+    OS << None;
+  return OS;
+}
+
+} // end namespace llvm
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_LLVM_ADT_OPTIONAL_H
@@ -0,0 +1,61 @@
+//===--- AlignOf.h - Portable calculation of type alignment -----*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the AlignedCharArrayUnion class.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_ALIGNOF_H
+#define OPENCOMBINE_LLVM_SUPPORT_ALIGNOF_H
+
+#include "llvm/Support/Compiler.h"
+#include <cstddef>
+
+namespace opencombine {
+namespace llvm {
+
+namespace detail {
+
+template <typename T, typename... Ts> class AlignerImpl {
+  T t;
+  AlignerImpl<Ts...> rest;
+  AlignerImpl() = delete;
+};
+
+template <typename T> class AlignerImpl<T> {
+  T t;
+  AlignerImpl() = delete;
+};
+
+template <typename T, typename... Ts> union SizerImpl {
+  char arr[sizeof(T)];
+  SizerImpl<Ts...> rest;
+};
+
+template <typename T> union SizerImpl<T> { char arr[sizeof(T)]; };
+} // end namespace detail
+
+/// A suitably aligned and sized character array member which can hold elements
+/// of any type.
+///
+/// These types may be arrays, structs, or any other types. This exposes a
+/// `buffer` member which can be used as suitable storage for a placement new of
+/// any of these types.
+template <typename T, typename... Ts> struct AlignedCharArrayUnion {
+  alignas(detail::AlignerImpl<T, Ts...>) char buffer[sizeof(
+      llvm::detail::SizerImpl<T, Ts...>)];
+};
+
+} // end namespace llvm
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_LLVM_SUPPORT_ALIGNOF_H
@@ -0,0 +1,409 @@
+//===-- llvm/Support/Alignment.h - Useful alignment functions ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains types to represent alignments.
+// They are instrumented to guarantee some invariants are preserved and prevent
+// invalid manipulations.
+//
+// - Align represents an alignment in bytes, it is always set and always a valid
+// power of two, its minimum value is 1 which means no alignment requirements.
+//
+// - MaybeAlign is an optional type, it may be undefined or set. When it's set
+// you can get the underlying Align type by using the getValue() method.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_ALIGNMENT_H_
+#define OPENCOMBINE_LLVM_SUPPORT_ALIGNMENT_H_
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MathExtras.h"
+#include <cassert>
+#include <limits>
+
+namespace opencombine {
+namespace llvm {
+
+#define ALIGN_CHECK_ISPOSITIVE(decl)                                           \
+  assert(decl > 0 && (#decl " should be defined"))
+#define ALIGN_CHECK_ISSET(decl)                                                \
+  assert(decl.hasValue() && (#decl " should be defined"))
+
+/// This struct is a compact representation of a valid (non-zero power of two)
+/// alignment.
+/// It is suitable for use as static global constants.
+struct Align {
+private:
+  uint8_t ShiftValue = 0; /// The log2 of the required alignment.
+                          /// ShiftValue is less than 64 by construction.
+
+  friend struct MaybeAlign;
+  friend unsigned Log2(Align);
+  friend bool operator==(Align Lhs, Align Rhs);
+  friend bool operator!=(Align Lhs, Align Rhs);
+  friend bool operator<=(Align Lhs, Align Rhs);
+  friend bool operator>=(Align Lhs, Align Rhs);
+  friend bool operator<(Align Lhs, Align Rhs);
+  friend bool operator>(Align Lhs, Align Rhs);
+  friend unsigned encode(struct MaybeAlign A);
+  friend struct MaybeAlign decodeMaybeAlign(unsigned Value);
+
+  /// A trivial type to allow construction of constexpr Align.
+  /// This is currently needed to workaround a bug in GCC 5.3 which prevents
+  /// definition of constexpr assign operators.
+  /// https://stackoverflow.com/questions/46756288/explicitly-defaulted-function-cannot-be-declared-as-constexpr-because-the-implic
+  /// FIXME: Remove this, make all assign operators constexpr and introduce user
+  /// defined literals when we don't have to support GCC 5.3 anymore.
+  /// https://llvm.org/docs/GettingStarted.html#getting-a-modern-host-c-toolchain
+  struct LogValue {
+    uint8_t Log;
+  };
+
+public:
+  /// Default is byte-aligned.
+  constexpr Align() = default;
+  /// Do not perform checks in case of copy/move construct/assign, because the
+  /// checks have been performed when building `Other`.
+  constexpr Align(const Align &Other) = default;
+  constexpr Align(Align &&Other) = default;
+  Align &operator=(const Align &Other) = default;
+  Align &operator=(Align &&Other) = default;
+
+  explicit Align(uint64_t Value) {
+    assert(Value > 0 && "Value must not be 0");
+    assert(llvm::isPowerOf2_64(Value) && "Alignment is not a power of 2");
+    ShiftValue = Log2_64(Value);
+    assert(ShiftValue < 64 && "Broken invariant");
+  }
+
+  /// This is a hole in the type system and should not be abused.
+  /// Needed to interact with C for instance.
+  uint64_t value() const { return uint64_t(1) << ShiftValue; }
+
+  /// Returns a default constructed Align which corresponds to no alignment.
+  /// This is useful to test for unalignment as it conveys clear semantic.
+  /// `if (A != Align::None())`
+  /// would be better than
+  /// `if (A > Align(1))`
+  constexpr static const Align None() { return Align(); }
+
+  /// Allow constructions of constexpr Align.
+  template <size_t kValue> constexpr static LogValue Constant() {
+    return LogValue{static_cast<uint8_t>(CTLog2<kValue>())};
+  }
+
+  /// Allow constructions of constexpr Align from types.
+  /// Compile time equivalent to Align(alignof(T)).
+  template <typename T> constexpr static LogValue Of() {
+    return Constant<std::alignment_of<T>::value>();
+  }
+
+  /// Constexpr constructor from LogValue type.
+  constexpr Align(LogValue CA) : ShiftValue(CA.Log) {}
+};
+
+/// Treats the value 0 as a 1, so Align is always at least 1.
+inline Align assumeAligned(uint64_t Value) {
+  return Value ? Align(Value) : Align();
+}
+
+/// This struct is a compact representation of a valid (power of two) or
+/// undefined (0) alignment.
+struct MaybeAlign : public llvm::Optional<Align> {
+private:
+  using UP = llvm::Optional<Align>;
+
+public:
+  /// Default is undefined.
+  MaybeAlign() = default;
+  /// Do not perform checks in case of copy/move construct/assign, because the
+  /// checks have been performed when building `Other`.
+  MaybeAlign(const MaybeAlign &Other) = default;
+  MaybeAlign &operator=(const MaybeAlign &Other) = default;
+  MaybeAlign(MaybeAlign &&Other) = default;
+  MaybeAlign &operator=(MaybeAlign &&Other) = default;
+
+  /// Use llvm::Optional<Align> constructor.
+  using UP::UP;
+
+  explicit MaybeAlign(uint64_t Value) {
+    assert((Value == 0 || llvm::isPowerOf2_64(Value)) &&
+           "Alignment is neither 0 nor a power of 2");
+    if (Value)
+      emplace(Value);
+  }
+
+  /// For convenience, returns a valid alignment or 1 if undefined.
+  Align valueOrOne() const { return hasValue() ? getValue() : Align(); }
+};
+
+/// Checks that SizeInBytes is a multiple of the alignment.
+inline bool isAligned(Align Lhs, uint64_t SizeInBytes) {
+  return SizeInBytes % Lhs.value() == 0;
+}
+
+/// Checks that SizeInBytes is a multiple of the alignment.
+/// Returns false if the alignment is undefined.
+inline bool isAligned(MaybeAlign Lhs, uint64_t SizeInBytes) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return SizeInBytes % (*Lhs).value() == 0;
+}
+
+/// Checks that Addr is a multiple of the alignment.
+inline bool isAddrAligned(Align Lhs, const void *Addr) {
+  return isAligned(Lhs, reinterpret_cast<uintptr_t>(Addr));
+}
+
+/// Returns a multiple of A needed to store `Size` bytes.
+inline uint64_t alignTo(uint64_t Size, Align A) {
+  const uint64_t value = A.value();
+  // The following line is equivalent to `(Size + value - 1) / value * value`.
+
+  // The division followed by a multiplication can be thought of as a right
+  // shift followed by a left shift which zeros out the extra bits produced in
+  // the bump; `~(value - 1)` is a mask where all those bits being zeroed out
+  // are just zero.
+
+  // Most compilers can generate this code but the pattern may be missed when
+  // multiple functions gets inlined.
+  return (Size + value - 1) & ~(value - 1);
+}
+
+/// Returns a multiple of A needed to store `Size` bytes.
+/// Returns `Size` if current alignment is undefined.
+inline uint64_t alignTo(uint64_t Size, MaybeAlign A) {
+  return A ? alignTo(Size, A.getValue()) : Size;
+}
+
+/// Aligns `Addr` to `Alignment` bytes, rounding up.
+inline uintptr_t alignAddr(const void *Addr, Align Alignment) {
+  uintptr_t ArithAddr = reinterpret_cast<uintptr_t>(Addr);
+  assert(static_cast<uintptr_t>(ArithAddr + Alignment.value() - 1) >=
+             ArithAddr && "Overflow");
+  return alignTo(ArithAddr, Alignment);
+}
+
+/// Returns the offset to the next integer (mod 2**64) that is greater than
+/// or equal to \p Value and is a multiple of \p Align.
+inline uint64_t offsetToAlignment(uint64_t Value, Align Alignment) {
+  return alignTo(Value, Alignment) - Value;
+}
+
+/// Returns the necessary adjustment for aligning `Addr` to `Alignment`
+/// bytes, rounding up.
+inline uint64_t offsetToAlignedAddr(const void *Addr, Align Alignment) {
+  return offsetToAlignment(reinterpret_cast<uintptr_t>(Addr), Alignment);
+}
+
+/// Returns the log2 of the alignment.
+inline unsigned Log2(Align A) { return A.ShiftValue; }
+
+/// Returns the log2 of the alignment.
+/// \pre A must be defined.
+inline unsigned Log2(MaybeAlign A) {
+  ALIGN_CHECK_ISSET(A);
+  return Log2(A.getValue());
+}
+
+/// Returns the alignment that satisfies both alignments.
+/// Same semantic as MinAlign.
+inline Align commonAlignment(Align A, Align B) { return std::min(A, B); }
+
+/// Returns the alignment that satisfies both alignments.
+/// Same semantic as MinAlign.
+inline Align commonAlignment(Align A, uint64_t Offset) {
+  return Align(MinAlign(A.value(), Offset));
+}
+
+/// Returns the alignment that satisfies both alignments.
+/// Same semantic as MinAlign.
+inline MaybeAlign commonAlignment(MaybeAlign A, MaybeAlign B) {
+  return A && B ? commonAlignment(*A, *B) : A ? A : B;
+}
+
+/// Returns the alignment that satisfies both alignments.
+/// Same semantic as MinAlign.
+inline MaybeAlign commonAlignment(MaybeAlign A, uint64_t Offset) {
+  return MaybeAlign(MinAlign((*A).value(), Offset));
+}
+
+/// Returns a representation of the alignment that encodes undefined as 0.
+inline unsigned encode(MaybeAlign A) { return A ? A->ShiftValue + 1 : 0; }
+
+/// Dual operation of the encode function above.
+inline MaybeAlign decodeMaybeAlign(unsigned Value) {
+  if (Value == 0)
+    return MaybeAlign();
+  Align Out;
+  Out.ShiftValue = Value - 1;
+  return Out;
+}
+
+/// Returns a representation of the alignment, the encoded value is positive by
+/// definition.
+inline unsigned encode(Align A) { return encode(MaybeAlign(A)); }
+
+/// Comparisons between Align and scalars. Rhs must be positive.
+inline bool operator==(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() == Rhs;
+}
+inline bool operator!=(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() != Rhs;
+}
+inline bool operator<=(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() <= Rhs;
+}
+inline bool operator>=(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() >= Rhs;
+}
+inline bool operator<(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() < Rhs;
+}
+inline bool operator>(Align Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return Lhs.value() > Rhs;
+}
+
+/// Comparisons between MaybeAlign and scalars.
+inline bool operator==(MaybeAlign Lhs, uint64_t Rhs) {
+  return Lhs ? (*Lhs).value() == Rhs : Rhs == 0;
+}
+inline bool operator!=(MaybeAlign Lhs, uint64_t Rhs) {
+  return Lhs ? (*Lhs).value() != Rhs : Rhs != 0;
+}
+inline bool operator<=(MaybeAlign Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return (*Lhs).value() <= Rhs;
+}
+inline bool operator>=(MaybeAlign Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return (*Lhs).value() >= Rhs;
+}
+inline bool operator<(MaybeAlign Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return (*Lhs).value() < Rhs;
+}
+inline bool operator>(MaybeAlign Lhs, uint64_t Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  ALIGN_CHECK_ISPOSITIVE(Rhs);
+  return (*Lhs).value() > Rhs;
+}
+
+/// Comparisons operators between Align.
+inline bool operator==(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue == Rhs.ShiftValue;
+}
+inline bool operator!=(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue != Rhs.ShiftValue;
+}
+inline bool operator<=(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue <= Rhs.ShiftValue;
+}
+inline bool operator>=(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue >= Rhs.ShiftValue;
+}
+inline bool operator<(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue < Rhs.ShiftValue;
+}
+inline bool operator>(Align Lhs, Align Rhs) {
+  return Lhs.ShiftValue > Rhs.ShiftValue;
+}
+
+/// Comparisons operators between Align and MaybeAlign.
+inline bool operator==(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() == (*Rhs).value();
+}
+inline bool operator!=(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() != (*Rhs).value();
+}
+inline bool operator<=(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() <= (*Rhs).value();
+}
+inline bool operator>=(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() >= (*Rhs).value();
+}
+inline bool operator<(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() < (*Rhs).value();
+}
+inline bool operator>(Align Lhs, MaybeAlign Rhs) {
+  ALIGN_CHECK_ISSET(Rhs);
+  return Lhs.value() > (*Rhs).value();
+}
+
+/// Comparisons operators between MaybeAlign and Align.
+inline bool operator==(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() == Rhs.value();
+}
+inline bool operator!=(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() != Rhs.value();
+}
+inline bool operator<=(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() <= Rhs.value();
+}
+inline bool operator>=(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() >= Rhs.value();
+}
+inline bool operator<(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() < Rhs.value();
+}
+inline bool operator>(MaybeAlign Lhs, Align Rhs) {
+  ALIGN_CHECK_ISSET(Lhs);
+  return Lhs && (*Lhs).value() > Rhs.value();
+}
+
+inline Align operator/(Align Lhs, uint64_t Divisor) {
+  assert(llvm::isPowerOf2_64(Divisor) &&
+         "Divisor must be positive and a power of 2");
+  assert(Lhs != 1 && "Can't halve byte alignment");
+  return Align(Lhs.value() / Divisor);
+}
+
+inline MaybeAlign operator/(MaybeAlign Lhs, uint64_t Divisor) {
+  assert(llvm::isPowerOf2_64(Divisor) &&
+         "Divisor must be positive and a power of 2");
+  return Lhs ? Lhs.getValue() / Divisor : MaybeAlign();
+}
+
+inline Align max(MaybeAlign Lhs, Align Rhs) {
+  return Lhs && *Lhs > Rhs ? *Lhs : Rhs;
+}
+
+inline Align max(Align Lhs, MaybeAlign Rhs) {
+  return Rhs && *Rhs > Lhs ? *Rhs : Lhs;
+}
+
+#undef ALIGN_CHECK_ISPOSITIVE
+#undef ALIGN_CHECK_ISSET
+
+} // namespace llvm
+} // namespace opencombine
+
+#endif // OPENCOMBINE_LLVM_SUPPORT_ALIGNMENT_H_
@@ -0,0 +1,414 @@
+//===- llvm/Support/Casting.h - Allow flexible, checked, casts --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the isa<X>(), cast<X>(), dyn_cast<X>(), cast_or_null<X>(),
+// and dyn_cast_or_null<X>() templates.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_CASTING_H
+#define OPENCOMBINE_LLVM_SUPPORT_CASTING_H
+
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/type_traits.h"
+#include <cassert>
+#include <memory>
+#include <type_traits>
+
+namespace opencombine {
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+//                          isa<x> Support Templates
+//===----------------------------------------------------------------------===//
+
+// Define a template that can be specialized by smart pointers to reflect the
+// fact that they are automatically dereferenced, and are not involved with the
+// template selection process...  the default implementation is a noop.
+//
+template<typename From> struct simplify_type {
+  using SimpleType = From; // The real type this represents...
+
+  // An accessor to get the real value...
+  static SimpleType &getSimplifiedValue(From &Val) { return Val; }
+};
+
+template<typename From> struct simplify_type<const From> {
+  using NonConstSimpleType = typename simplify_type<From>::SimpleType;
+  using SimpleType =
+      typename add_const_past_pointer<NonConstSimpleType>::type;
+  using RetType =
+      typename add_lvalue_reference_if_not_pointer<SimpleType>::type;
+
+  static RetType getSimplifiedValue(const From& Val) {
+    return simplify_type<From>::getSimplifiedValue(const_cast<From&>(Val));
+  }
+};
+
+// The core of the implementation of isa<X> is here; To and From should be
+// the names of classes.  This template can be specialized to customize the
+// implementation of isa<> without rewriting it from scratch.
+template <typename To, typename From, typename Enabler = void>
+struct isa_impl {
+  static inline bool doit(const From &Val) {
+    return To::classof(&Val);
+  }
+};
+
+/// Always allow upcasts, and perform no dynamic check for them.
+template <typename To, typename From>
+struct isa_impl<
+    To, From, typename std::enable_if<std::is_base_of<To, From>::value>::type> {
+  static inline bool doit(const From &) { return true; }
+};
+
+template <typename To, typename From> struct isa_impl_cl {
+  static inline bool doit(const From &Val) {
+    return isa_impl<To, From>::doit(Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From> {
+  static inline bool doit(const From &Val) {
+    return isa_impl<To, From>::doit(Val);
+  }
+};
+
+template <typename To, typename From>
+struct isa_impl_cl<To, const std::unique_ptr<From>> {
+  static inline bool doit(const std::unique_ptr<From> &Val) {
+    assert(Val && "isa<> used on a null pointer");
+    return isa_impl_cl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, From*> {
+  static inline bool doit(const From *Val) {
+    assert(Val && "isa<> used on a null pointer");
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, From*const> {
+  static inline bool doit(const From *Val) {
+    assert(Val && "isa<> used on a null pointer");
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From*> {
+  static inline bool doit(const From *Val) {
+    assert(Val && "isa<> used on a null pointer");
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template <typename To, typename From> struct isa_impl_cl<To, const From*const> {
+  static inline bool doit(const From *Val) {
+    assert(Val && "isa<> used on a null pointer");
+    return isa_impl<To, From>::doit(*Val);
+  }
+};
+
+template<typename To, typename From, typename SimpleFrom>
+struct isa_impl_wrap {
+  // When From != SimplifiedType, we can simplify the type some more by using
+  // the simplify_type template.
+  static bool doit(const From &Val) {
+    return isa_impl_wrap<To, SimpleFrom,
+      typename simplify_type<SimpleFrom>::SimpleType>::doit(
+                          simplify_type<const From>::getSimplifiedValue(Val));
+  }
+};
+
+template<typename To, typename FromTy>
+struct isa_impl_wrap<To, FromTy, FromTy> {
+  // When From == SimpleType, we are as simple as we are going to get.
+  static bool doit(const FromTy &Val) {
+    return isa_impl_cl<To,FromTy>::doit(Val);
+  }
+};
+
+// isa<X> - Return true if the parameter to the template is an instance of the
+// template type argument.  Used like this:
+//
+//  if (isa<Type>(myVal)) { ... }
+//
+template <class X, class Y> LLVM_NODISCARD inline bool isa(const Y &Val) {
+  return isa_impl_wrap<X, const Y,
+                       typename simplify_type<const Y>::SimpleType>::doit(Val);
+}
+
+// isa_and_nonnull<X> - Functionally identical to isa, except that a null value
+// is accepted.
+//
+template <class X, class Y>
+LLVM_NODISCARD inline bool isa_and_nonnull(const Y &Val) {
+  if (!Val)
+    return false;
+  return isa<X>(Val);
+}
+
+//===----------------------------------------------------------------------===//
+//                          cast<x> Support Templates
+//===----------------------------------------------------------------------===//
+
+template<class To, class From> struct cast_retty;
+
+// Calculate what type the 'cast' function should return, based on a requested
+// type of To and a source type of From.
+template<class To, class From> struct cast_retty_impl {
+  using ret_type = To &;       // Normal case, return Ty&
+};
+template<class To, class From> struct cast_retty_impl<To, const From> {
+  using ret_type = const To &; // Normal case, return Ty&
+};
+
+template<class To, class From> struct cast_retty_impl<To, From*> {
+  using ret_type = To *;       // Pointer arg case, return Ty*
+};
+
+template<class To, class From> struct cast_retty_impl<To, const From*> {
+  using ret_type = const To *; // Constant pointer arg case, return const Ty*
+};
+
+template<class To, class From> struct cast_retty_impl<To, const From*const> {
+  using ret_type = const To *; // Constant pointer arg case, return const Ty*
+};
+
+template <class To, class From>
+struct cast_retty_impl<To, std::unique_ptr<From>> {
+private:
+  using PointerType = typename cast_retty_impl<To, From *>::ret_type;
+  using ResultType = typename std::remove_pointer<PointerType>::type;
+
+public:
+  using ret_type = std::unique_ptr<ResultType>;
+};
+
+template<class To, class From, class SimpleFrom>
+struct cast_retty_wrap {
+  // When the simplified type and the from type are not the same, use the type
+  // simplifier to reduce the type, then reuse cast_retty_impl to get the
+  // resultant type.
+  using ret_type = typename cast_retty<To, SimpleFrom>::ret_type;
+};
+
+template<class To, class FromTy>
+struct cast_retty_wrap<To, FromTy, FromTy> {
+  // When the simplified type is equal to the from type, use it directly.
+  using ret_type = typename cast_retty_impl<To,FromTy>::ret_type;
+};
+
+template<class To, class From>
+struct cast_retty {
+  using ret_type = typename cast_retty_wrap<
+      To, From, typename simplify_type<From>::SimpleType>::ret_type;
+};
+
+// Ensure the non-simple values are converted using the simplify_type template
+// that may be specialized by smart pointers...
+//
+template<class To, class From, class SimpleFrom> struct cast_convert_val {
+  // This is not a simple type, use the template to simplify it...
+  static typename cast_retty<To, From>::ret_type doit(From &Val) {
+    return cast_convert_val<To, SimpleFrom,
+      typename simplify_type<SimpleFrom>::SimpleType>::doit(
+                          simplify_type<From>::getSimplifiedValue(Val));
+  }
+};
+
+template<class To, class FromTy> struct cast_convert_val<To,FromTy,FromTy> {
+  // This _is_ a simple type, just cast it.
+  static typename cast_retty<To, FromTy>::ret_type doit(const FromTy &Val) {
+    typename cast_retty<To, FromTy>::ret_type Res2
+     = (typename cast_retty<To, FromTy>::ret_type)const_cast<FromTy&>(Val);
+    return Res2;
+  }
+};
+
+template <class X> struct is_simple_type {
+  static const bool value =
+      std::is_same<X, typename simplify_type<X>::SimpleType>::value;
+};
+
+// cast<X> - Return the argument parameter cast to the specified type.  This
+// casting operator asserts that the type is correct, so it does not return null
+// on failure.  It does not allow a null argument (use cast_or_null for that).
+// It is typically used like this:
+//
+//  cast<Instruction>(myVal)->getParent()
+//
+template <class X, class Y>
+inline typename std::enable_if<!is_simple_type<Y>::value,
+                               typename cast_retty<X, const Y>::ret_type>::type
+cast(const Y &Val) {
+  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
+  return cast_convert_val<
+      X, const Y, typename simplify_type<const Y>::SimpleType>::doit(Val);
+}
+
+template <class X, class Y>
+inline typename cast_retty<X, Y>::ret_type cast(Y &Val) {
+  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
+  return cast_convert_val<X, Y,
+                          typename simplify_type<Y>::SimpleType>::doit(Val);
+}
+
+template <class X, class Y>
+inline typename cast_retty<X, Y *>::ret_type cast(Y *Val) {
+  assert(isa<X>(Val) && "cast<Ty>() argument of incompatible type!");
+  return cast_convert_val<X, Y*,
+                          typename simplify_type<Y*>::SimpleType>::doit(Val);
+}
+
+template <class X, class Y>
+inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type
+cast(std::unique_ptr<Y> &&Val) {
+  assert(isa<X>(Val.get()) && "cast<Ty>() argument of incompatible type!");
+  using ret_type = typename cast_retty<X, std::unique_ptr<Y>>::ret_type;
+  return ret_type(
+      cast_convert_val<X, Y *, typename simplify_type<Y *>::SimpleType>::doit(
+          Val.release()));
+}
+
+// cast_or_null<X> - Functionally identical to cast, except that a null value is
+// accepted.
+//
+template <class X, class Y>
+LLVM_NODISCARD inline
+    typename std::enable_if<!is_simple_type<Y>::value,
+                            typename cast_retty<X, const Y>::ret_type>::type
+    cast_or_null(const Y &Val) {
+  if (!Val)
+    return nullptr;
+  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
+  return cast<X>(Val);
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline
+    typename std::enable_if<!is_simple_type<Y>::value,
+                            typename cast_retty<X, Y>::ret_type>::type
+    cast_or_null(Y &Val) {
+  if (!Val)
+    return nullptr;
+  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
+  return cast<X>(Val);
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
+cast_or_null(Y *Val) {
+  if (!Val) return nullptr;
+  assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
+  return cast<X>(Val);
+}
+
+template <class X, class Y>
+inline typename cast_retty<X, std::unique_ptr<Y>>::ret_type
+cast_or_null(std::unique_ptr<Y> &&Val) {
+  if (!Val)
+    return nullptr;
+  return cast<X>(std::move(Val));
+}
+
+// dyn_cast<X> - Return the argument parameter cast to the specified type.  This
+// casting operator returns null if the argument is of the wrong type, so it can
+// be used to test for a type as well as cast if successful.  This should be
+// used in the context of an if statement like this:
+//
+//  if (const Instruction *I = dyn_cast<Instruction>(myVal)) { ... }
+//
+
+template <class X, class Y>
+LLVM_NODISCARD inline
+    typename std::enable_if<!is_simple_type<Y>::value,
+                            typename cast_retty<X, const Y>::ret_type>::type
+    dyn_cast(const Y &Val) {
+  return isa<X>(Val) ? cast<X>(Val) : nullptr;
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline typename cast_retty<X, Y>::ret_type dyn_cast(Y &Val) {
+  return isa<X>(Val) ? cast<X>(Val) : nullptr;
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type dyn_cast(Y *Val) {
+  return isa<X>(Val) ? cast<X>(Val) : nullptr;
+}
+
+// dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
+// value is accepted.
+//
+template <class X, class Y>
+LLVM_NODISCARD inline
+    typename std::enable_if<!is_simple_type<Y>::value,
+                            typename cast_retty<X, const Y>::ret_type>::type
+    dyn_cast_or_null(const Y &Val) {
+  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline
+    typename std::enable_if<!is_simple_type<Y>::value,
+                            typename cast_retty<X, Y>::ret_type>::type
+    dyn_cast_or_null(Y &Val) {
+  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline typename cast_retty<X, Y *>::ret_type
+dyn_cast_or_null(Y *Val) {
+  return (Val && isa<X>(Val)) ? cast<X>(Val) : nullptr;
+}
+
+// unique_dyn_cast<X> - Given a unique_ptr<Y>, try to return a unique_ptr<X>,
+// taking ownership of the input pointer iff isa<X>(Val) is true.  If the
+// cast is successful, From refers to nullptr on exit and the casted value
+// is returned.  If the cast is unsuccessful, the function returns nullptr
+// and From is unchanged.
+template <class X, class Y>
+LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &Val)
+    -> decltype(cast<X>(Val)) {
+  if (!isa<X>(Val))
+    return nullptr;
+  return cast<X>(std::move(Val));
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline auto unique_dyn_cast(std::unique_ptr<Y> &&Val)
+    -> decltype(cast<X>(Val)) {
+  return unique_dyn_cast<X, Y>(Val);
+}
+
+// dyn_cast_or_null<X> - Functionally identical to unique_dyn_cast, except that
+// a null value is accepted.
+template <class X, class Y>
+LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &Val)
+    -> decltype(cast<X>(Val)) {
+  if (!Val)
+    return nullptr;
+  return unique_dyn_cast<X, Y>(Val);
+}
+
+template <class X, class Y>
+LLVM_NODISCARD inline auto unique_dyn_cast_or_null(std::unique_ptr<Y> &&Val)
+    -> decltype(cast<X>(Val)) {
+  return unique_dyn_cast_or_null<X, Y>(Val);
+}
+
+} // end namespace llvm
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_LLVM_SUPPORT_CASTING_H
@@ -0,0 +1,590 @@
+//===-- llvm/Support/Compiler.h - Compiler abstraction support --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines several macros, based on the current compiler.  This allows
+// use of compiler-specific features in a way that remains portable. This header
+// can be included from either C or C++.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+// - Some macros have been removed.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_COMPILER_H
+#define OPENCOMBINE_LLVM_SUPPORT_COMPILER_H
+
+#ifdef __cplusplus
+#include <new>
+#endif
+#include <stddef.h>
+
+#if defined(_MSC_VER)
+#include <sal.h>
+#endif
+
+#ifndef __has_feature
+# define __has_feature(x) 0
+#endif
+
+#ifndef __has_extension
+# define __has_extension(x) 0
+#endif
+
+#ifndef __has_attribute
+# define __has_attribute(x) 0
+#endif
+
+#ifndef __has_builtin
+# define __has_builtin(x) 0
+#endif
+
+// Only use __has_cpp_attribute in C++ mode. GCC defines __has_cpp_attribute in
+// C mode, but the :: in __has_cpp_attribute(scoped::attribute) is invalid.
+#ifndef LLVM_HAS_CPP_ATTRIBUTE
+#if defined(__cplusplus) && defined(__has_cpp_attribute)
+# define LLVM_HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
+#else
+# define LLVM_HAS_CPP_ATTRIBUTE(x) 0
+#endif
+#endif
+
+/// \macro LLVM_GNUC_PREREQ
+/// Extend the default __GNUC_PREREQ even if glibc's features.h isn't
+/// available.
+#ifndef LLVM_GNUC_PREREQ
+# if defined(__GNUC__) && defined(__GNUC_MINOR__) && defined(__GNUC_PATCHLEVEL__)
+#  define LLVM_GNUC_PREREQ(maj, min, patch) \
+    ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) + __GNUC_PATCHLEVEL__ >= \
+     ((maj) << 20) + ((min) << 10) + (patch))
+# elif defined(__GNUC__) && defined(__GNUC_MINOR__)
+#  define LLVM_GNUC_PREREQ(maj, min, patch) \
+    ((__GNUC__ << 20) + (__GNUC_MINOR__ << 10) >= ((maj) << 20) + ((min) << 10))
+# else
+#  define LLVM_GNUC_PREREQ(maj, min, patch) 0
+# endif
+#endif
+
+/// \macro LLVM_MSC_PREREQ
+/// Is the compiler MSVC of at least the specified version?
+/// The common \param version values to check for are:
+/// * 1910: VS2017, version 15.1 & 15.2
+/// * 1911: VS2017, version 15.3 & 15.4
+/// * 1912: VS2017, version 15.5
+/// * 1913: VS2017, version 15.6
+/// * 1914: VS2017, version 15.7
+/// * 1915: VS2017, version 15.8
+/// * 1916: VS2017, version 15.9
+/// * 1920: VS2019, version 16.0
+/// * 1921: VS2019, version 16.1
+#ifdef _MSC_VER
+#define LLVM_MSC_PREREQ(version) (_MSC_VER >= (version))
+
+// We require at least MSVC 2017.
+#if !LLVM_MSC_PREREQ(1910)
+#error LLVM requires at least MSVC 2017.
+#endif
+
+#else
+#define LLVM_MSC_PREREQ(version) 0
+#endif
+
+/// Does the compiler support ref-qualifiers for *this?
+///
+/// Sadly, this is separate from just rvalue reference support because GCC
+/// and MSVC implemented this later than everything else.
+#if __has_feature(cxx_rvalue_references) || LLVM_GNUC_PREREQ(4, 8, 1)
+#define LLVM_HAS_RVALUE_REFERENCE_THIS 1
+#else
+#define LLVM_HAS_RVALUE_REFERENCE_THIS 0
+#endif
+
+/// Expands to '&' if ref-qualifiers for *this are supported.
+///
+/// This can be used to provide lvalue/rvalue overrides of member functions.
+/// The rvalue override should be guarded by LLVM_HAS_RVALUE_REFERENCE_THIS
+#if LLVM_HAS_RVALUE_REFERENCE_THIS
+#define LLVM_LVALUE_FUNCTION &
+#else
+#define LLVM_LVALUE_FUNCTION
+#endif
+
+/// LLVM_LIBRARY_VISIBILITY - If a class marked with this attribute is linked
+/// into a shared library, then the class should be private to the library and
+/// not accessible from outside it.  Can also be used to mark variables and
+/// functions, making them private to any shared library they are linked into.
+/// On PE/COFF targets, library visibility is the default, so this isn't needed.
+#if (__has_attribute(visibility) || LLVM_GNUC_PREREQ(4, 0, 0)) &&              \
+    !defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32)
+#define LLVM_LIBRARY_VISIBILITY __attribute__ ((visibility("hidden")))
+#else
+#define LLVM_LIBRARY_VISIBILITY
+#endif
+
+#if defined(__GNUC__)
+#define LLVM_PREFETCH(addr, rw, locality) __builtin_prefetch(addr, rw, locality)
+#else
+#define LLVM_PREFETCH(addr, rw, locality)
+#endif
+
+#if __has_attribute(used) || LLVM_GNUC_PREREQ(3, 1, 0)
+#define LLVM_ATTRIBUTE_USED __attribute__((__used__))
+#else
+#define LLVM_ATTRIBUTE_USED
+#endif
+
+/// LLVM_NODISCARD - Warn if a type or return value is discarded.
+
+// Use the 'nodiscard' attribute in C++17 or newer mode.
+#if __cplusplus > 201402L && LLVM_HAS_CPP_ATTRIBUTE(nodiscard)
+#define LLVM_NODISCARD [[nodiscard]]
+#elif LLVM_HAS_CPP_ATTRIBUTE(clang::warn_unused_result)
+#define LLVM_NODISCARD [[clang::warn_unused_result]]
+// Clang in C++14 mode claims that it has the 'nodiscard' attribute, but also
+// warns in the pedantic mode that 'nodiscard' is a C++17 extension (PR33518).
+// Use the 'nodiscard' attribute in C++14 mode only with GCC.
+// TODO: remove this workaround when PR33518 is resolved.
+#elif defined(__GNUC__) && LLVM_HAS_CPP_ATTRIBUTE(nodiscard)
+#define LLVM_NODISCARD [[nodiscard]]
+#else
+#define LLVM_NODISCARD
+#endif
+
+// Indicate that a non-static, non-const C++ member function reinitializes
+// the entire object to a known state, independent of the previous state of
+// the object.
+//
+// The clang-tidy check bugprone-use-after-move recognizes this attribute as a
+// marker that a moved-from object has left the indeterminate state and can be
+// reused.
+#if LLVM_HAS_CPP_ATTRIBUTE(clang::reinitializes)
+#define LLVM_ATTRIBUTE_REINITIALIZES [[clang::reinitializes]]
+#else
+#define LLVM_ATTRIBUTE_REINITIALIZES
+#endif
+
+// Some compilers warn about unused functions. When a function is sometimes
+// used or not depending on build settings (e.g. a function only called from
+// within "assert"), this attribute can be used to suppress such warnings.
+//
+// However, it shouldn't be used for unused *variables*, as those have a much
+// more portable solution:
+//   (void)unused_var_name;
+// Prefer cast-to-void wherever it is sufficient.
+#if __has_attribute(unused) || LLVM_GNUC_PREREQ(3, 1, 0)
+#define LLVM_ATTRIBUTE_UNUSED __attribute__((__unused__))
+#else
+#define LLVM_ATTRIBUTE_UNUSED
+#endif
+
+// FIXME: Provide this for PE/COFF targets.
+#if (__has_attribute(weak) || LLVM_GNUC_PREREQ(4, 0, 0)) &&                    \
+    (!defined(__MINGW32__) && !defined(__CYGWIN__) && !defined(_WIN32))
+#define LLVM_ATTRIBUTE_WEAK __attribute__((__weak__))
+#else
+#define LLVM_ATTRIBUTE_WEAK
+#endif
+
+// Prior to clang 3.2, clang did not accept any spelling of
+// __has_attribute(const), so assume it is supported.
+#if defined(__clang__) || defined(__GNUC__)
+// aka 'CONST' but following LLVM Conventions.
+#define LLVM_READNONE __attribute__((__const__))
+#else
+#define LLVM_READNONE
+#endif
+
+#if __has_attribute(pure) || defined(__GNUC__)
+// aka 'PURE' but following LLVM Conventions.
+#define LLVM_READONLY __attribute__((__pure__))
+#else
+#define LLVM_READONLY
+#endif
+
+#if __has_builtin(__builtin_expect) || LLVM_GNUC_PREREQ(4, 0, 0)
+#define LLVM_LIKELY(EXPR) __builtin_expect((bool)(EXPR), true)
+#define LLVM_UNLIKELY(EXPR) __builtin_expect((bool)(EXPR), false)
+#else
+#define LLVM_LIKELY(EXPR) (EXPR)
+#define LLVM_UNLIKELY(EXPR) (EXPR)
+#endif
+
+/// LLVM_ATTRIBUTE_NOINLINE - On compilers where we have a directive to do so,
+/// mark a method "not for inlining".
+#if __has_attribute(noinline) || LLVM_GNUC_PREREQ(3, 4, 0)
+#define LLVM_ATTRIBUTE_NOINLINE __attribute__((noinline))
+#elif defined(_MSC_VER)
+#define LLVM_ATTRIBUTE_NOINLINE __declspec(noinline)
+#else
+#define LLVM_ATTRIBUTE_NOINLINE
+#endif
+
+/// LLVM_ATTRIBUTE_ALWAYS_INLINE - On compilers where we have a directive to do
+/// so, mark a method "always inline" because it is performance sensitive. GCC
+/// 3.4 supported this but is buggy in various cases and produces unimplemented
+/// errors, just use it in GCC 4.0 and later.
+#if __has_attribute(always_inline) || LLVM_GNUC_PREREQ(4, 0, 0)
+#define LLVM_ATTRIBUTE_ALWAYS_INLINE __attribute__((always_inline))
+#elif defined(_MSC_VER)
+#define LLVM_ATTRIBUTE_ALWAYS_INLINE __forceinline
+#else
+#define LLVM_ATTRIBUTE_ALWAYS_INLINE
+#endif
+
+#ifdef __GNUC__
+#define LLVM_ATTRIBUTE_NORETURN __attribute__((noreturn))
+#elif defined(_MSC_VER)
+#define LLVM_ATTRIBUTE_NORETURN __declspec(noreturn)
+#else
+#define LLVM_ATTRIBUTE_NORETURN
+#endif
+
+#if __has_attribute(returns_nonnull) || LLVM_GNUC_PREREQ(4, 9, 0)
+#define LLVM_ATTRIBUTE_RETURNS_NONNULL __attribute__((returns_nonnull))
+#elif defined(_MSC_VER)
+#define LLVM_ATTRIBUTE_RETURNS_NONNULL _Ret_notnull_
+#else
+#define LLVM_ATTRIBUTE_RETURNS_NONNULL
+#endif
+
+/// \macro LLVM_ATTRIBUTE_RETURNS_NOALIAS Used to mark a function as returning a
+/// pointer that does not alias any other valid pointer.
+#ifdef __GNUC__
+#define LLVM_ATTRIBUTE_RETURNS_NOALIAS __attribute__((__malloc__))
+#elif defined(_MSC_VER)
+#define LLVM_ATTRIBUTE_RETURNS_NOALIAS __declspec(restrict)
+#else
+#define LLVM_ATTRIBUTE_RETURNS_NOALIAS
+#endif
+
+/// LLVM_FALLTHROUGH - Mark fallthrough cases in switch statements.
+#if __cplusplus > 201402L && LLVM_HAS_CPP_ATTRIBUTE(fallthrough)
+#define LLVM_FALLTHROUGH [[fallthrough]]
+#elif LLVM_HAS_CPP_ATTRIBUTE(gnu::fallthrough)
+#define LLVM_FALLTHROUGH [[gnu::fallthrough]]
+#elif __has_attribute(fallthrough)
+#define LLVM_FALLTHROUGH __attribute__((fallthrough))
+#elif LLVM_HAS_CPP_ATTRIBUTE(clang::fallthrough)
+#define LLVM_FALLTHROUGH [[clang::fallthrough]]
+#else
+#define LLVM_FALLTHROUGH
+#endif
+
+/// LLVM_REQUIRE_CONSTANT_INITIALIZATION - Apply this to globals to ensure that
+/// they are constant initialized.
+#if LLVM_HAS_CPP_ATTRIBUTE(clang::require_constant_initialization)
+#define LLVM_REQUIRE_CONSTANT_INITIALIZATION                                   \
+  [[clang::require_constant_initialization]]
+#else
+#define LLVM_REQUIRE_CONSTANT_INITIALIZATION
+#endif
+
+/// LLVM_EXTENSION - Support compilers where we have a keyword to suppress
+/// pedantic diagnostics.
+#ifdef __GNUC__
+#define LLVM_EXTENSION __extension__
+#else
+#define LLVM_EXTENSION
+#endif
+
+// LLVM_ATTRIBUTE_DEPRECATED(decl, "message")
+#if __has_feature(attribute_deprecated_with_message)
+# define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
+  decl __attribute__((deprecated(message)))
+#elif defined(__GNUC__)
+# define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
+  decl __attribute__((deprecated))
+#elif defined(_MSC_VER)
+# define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
+  __declspec(deprecated(message)) decl
+#else
+# define LLVM_ATTRIBUTE_DEPRECATED(decl, message) \
+  decl
+#endif
+
+/// LLVM_BUILTIN_UNREACHABLE - On compilers which support it, expands
+/// to an expression which states that it is undefined behavior for the
+/// compiler to reach this point.  Otherwise is not defined.
+#if __has_builtin(__builtin_unreachable) || LLVM_GNUC_PREREQ(4, 5, 0)
+# define LLVM_BUILTIN_UNREACHABLE __builtin_unreachable()
+#elif defined(_MSC_VER)
+# define LLVM_BUILTIN_UNREACHABLE __assume(false)
+#endif
+
+/// LLVM_BUILTIN_TRAP - On compilers which support it, expands to an expression
+/// which causes the program to exit abnormally.
+#if __has_builtin(__builtin_trap) || LLVM_GNUC_PREREQ(4, 3, 0)
+# define LLVM_BUILTIN_TRAP __builtin_trap()
+#elif defined(_MSC_VER)
+// The __debugbreak intrinsic is supported by MSVC, does not require forward
+// declarations involving platform-specific typedefs (unlike RaiseException),
+// results in a call to vectored exception handlers, and encodes to a short
+// instruction that still causes the trapping behavior we want.
+# define LLVM_BUILTIN_TRAP __debugbreak()
+#else
+# define LLVM_BUILTIN_TRAP *(volatile int*)0x11 = 0
+#endif
+
+/// LLVM_BUILTIN_DEBUGTRAP - On compilers which support it, expands to
+/// an expression which causes the program to break while running
+/// under a debugger.
+#if __has_builtin(__builtin_debugtrap)
+# define LLVM_BUILTIN_DEBUGTRAP __builtin_debugtrap()
+#elif defined(_MSC_VER)
+// The __debugbreak intrinsic is supported by MSVC and breaks while
+// running under the debugger, and also supports invoking a debugger
+// when the OS is configured appropriately.
+# define LLVM_BUILTIN_DEBUGTRAP __debugbreak()
+#else
+// Just continue execution when built with compilers that have no
+// support. This is a debugging aid and not intended to force the
+// program to abort if encountered.
+# define LLVM_BUILTIN_DEBUGTRAP
+#endif
+
+/// \macro LLVM_ASSUME_ALIGNED
+/// Returns a pointer with an assumed alignment.
+#if __has_builtin(__builtin_assume_aligned) || LLVM_GNUC_PREREQ(4, 7, 0)
+# define LLVM_ASSUME_ALIGNED(p, a) __builtin_assume_aligned(p, a)
+#elif defined(LLVM_BUILTIN_UNREACHABLE)
+// As of today, clang does not support __builtin_assume_aligned.
+# define LLVM_ASSUME_ALIGNED(p, a) \
+           (((uintptr_t(p) % (a)) == 0) ? (p) : (LLVM_BUILTIN_UNREACHABLE, (p)))
+#else
+# define LLVM_ASSUME_ALIGNED(p, a) (p)
+#endif
+
+/// \macro LLVM_PACKED
+/// Used to specify a packed structure.
+/// LLVM_PACKED(
+///    struct A {
+///      int i;
+///      int j;
+///      int k;
+///      long long l;
+///   });
+///
+/// LLVM_PACKED_START
+/// struct B {
+///   int i;
+///   int j;
+///   int k;
+///   long long l;
+/// };
+/// LLVM_PACKED_END
+#ifdef _MSC_VER
+# define LLVM_PACKED(d) __pragma(pack(push, 1)) d __pragma(pack(pop))
+# define LLVM_PACKED_START __pragma(pack(push, 1))
+# define LLVM_PACKED_END   __pragma(pack(pop))
+#else
+# define LLVM_PACKED(d) d __attribute__((packed))
+# define LLVM_PACKED_START _Pragma("pack(push, 1)")
+# define LLVM_PACKED_END   _Pragma("pack(pop)")
+#endif
+
+/// \macro LLVM_PTR_SIZE
+/// A constant integer equivalent to the value of sizeof(void*).
+/// Generally used in combination with alignas or when doing computation in the
+/// preprocessor.
+#ifdef __SIZEOF_POINTER__
+# define LLVM_PTR_SIZE __SIZEOF_POINTER__
+#elif defined(_WIN64)
+# define LLVM_PTR_SIZE 8
+#elif defined(_WIN32)
+# define LLVM_PTR_SIZE 4
+#elif defined(_MSC_VER)
+# error "could not determine LLVM_PTR_SIZE as a constant int for MSVC"
+#else
+# define LLVM_PTR_SIZE sizeof(void *)
+#endif
+
+/// \macro LLVM_MEMORY_SANITIZER_BUILD
+/// Whether LLVM itself is built with MemorySanitizer instrumentation.
+#if __has_feature(memory_sanitizer)
+# define LLVM_MEMORY_SANITIZER_BUILD 1
+# include <sanitizer/msan_interface.h>
+#else
+# define LLVM_MEMORY_SANITIZER_BUILD 0
+# define __msan_allocated_memory(p, size)
+# define __msan_unpoison(p, size)
+#endif
+
+/// \macro LLVM_ADDRESS_SANITIZER_BUILD
+/// Whether LLVM itself is built with AddressSanitizer instrumentation.
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+# define LLVM_ADDRESS_SANITIZER_BUILD 1
+# include <sanitizer/asan_interface.h>
+#else
+# define LLVM_ADDRESS_SANITIZER_BUILD 0
+# define __asan_poison_memory_region(p, size)
+# define __asan_unpoison_memory_region(p, size)
+#endif
+
+/// \macro LLVM_THREAD_SANITIZER_BUILD
+/// Whether LLVM itself is built with ThreadSanitizer instrumentation.
+#if __has_feature(thread_sanitizer) || defined(__SANITIZE_THREAD__)
+# define LLVM_THREAD_SANITIZER_BUILD 1
+#else
+# define LLVM_THREAD_SANITIZER_BUILD 0
+#endif
+
+#if LLVM_THREAD_SANITIZER_BUILD
+// Thread Sanitizer is a tool that finds races in code.
+// See http://code.google.com/p/data-race-test/wiki/DynamicAnnotations .
+// tsan detects these exact functions by name.
+#ifdef __cplusplus
+extern "C" {
+#endif
+void AnnotateHappensAfter(const char *file, int line, const volatile void *cv);
+void AnnotateHappensBefore(const char *file, int line, const volatile void *cv);
+void AnnotateIgnoreWritesBegin(const char *file, int line);
+void AnnotateIgnoreWritesEnd(const char *file, int line);
+#ifdef __cplusplus
+}
+#endif
+
+// This marker is used to define a happens-before arc. The race detector will
+// infer an arc from the begin to the end when they share the same pointer
+// argument.
+# define TsanHappensBefore(cv) AnnotateHappensBefore(__FILE__, __LINE__, cv)
+
+// This marker defines the destination of a happens-before arc.
+# define TsanHappensAfter(cv) AnnotateHappensAfter(__FILE__, __LINE__, cv)
+
+// Ignore any races on writes between here and the next TsanIgnoreWritesEnd.
+# define TsanIgnoreWritesBegin() AnnotateIgnoreWritesBegin(__FILE__, __LINE__)
+
+// Resume checking for racy writes.
+# define TsanIgnoreWritesEnd() AnnotateIgnoreWritesEnd(__FILE__, __LINE__)
+#else
+# define TsanHappensBefore(cv)
+# define TsanHappensAfter(cv)
+# define TsanIgnoreWritesBegin()
+# define TsanIgnoreWritesEnd()
+#endif
+
+/// \macro LLVM_NO_SANITIZE
+/// Disable a particular sanitizer for a function.
+#if __has_attribute(no_sanitize)
+#define LLVM_NO_SANITIZE(KIND) __attribute__((no_sanitize(KIND)))
+#else
+#define LLVM_NO_SANITIZE(KIND)
+#endif
+
+/// Mark debug helper function definitions like dump() that should not be
+/// stripped from debug builds.
+/// Note that you should also surround dump() functions with
+/// `#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)` so they do always
+/// get stripped in release builds.
+// FIXME: Move this to a private config.h as it's not usable in public headers.
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+#define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE LLVM_ATTRIBUTE_USED
+#else
+#define LLVM_DUMP_METHOD LLVM_ATTRIBUTE_NOINLINE
+#endif
+
+/// \macro LLVM_PRETTY_FUNCTION
+/// Gets a user-friendly looking function signature for the current scope
+/// using the best available method on each platform.  The exact format of the
+/// resulting string is implementation specific and non-portable, so this should
+/// only be used, for example, for logging or diagnostics.
+#if defined(_MSC_VER)
+#define LLVM_PRETTY_FUNCTION __FUNCSIG__
+#elif defined(__GNUC__) || defined(__clang__)
+#define LLVM_PRETTY_FUNCTION __PRETTY_FUNCTION__
+#else
+#define LLVM_PRETTY_FUNCTION __func__
+#endif
+
+/// \macro LLVM_THREAD_LOCAL
+/// A thread-local storage specifier which can be used with globals,
+/// extern globals, and static globals.
+///
+/// This is essentially an extremely restricted analog to C++11's thread_local
+/// support, and uses that when available. However, it falls back on
+/// platform-specific or vendor-provided extensions when necessary. These
+/// extensions don't support many of the C++11 thread_local's features. You
+/// should only use this for PODs that you can statically initialize to
+/// some constant value. In almost all circumstances this is most appropriate
+/// for use with a pointer, integer, or small aggregation of pointers and
+/// integers.
+#if LLVM_ENABLE_THREADS
+#if __has_feature(cxx_thread_local)
+#define LLVM_THREAD_LOCAL thread_local
+#elif defined(_MSC_VER)
+// MSVC supports this with a __declspec.
+#define LLVM_THREAD_LOCAL __declspec(thread)
+#else
+// Clang, GCC, and other compatible compilers used __thread prior to C++11 and
+// we only need the restricted functionality that provides.
+#define LLVM_THREAD_LOCAL __thread
+#endif
+#else // !LLVM_ENABLE_THREADS
+// If threading is disabled entirely, this compiles to nothing and you get
+// a normal global variable.
+#define LLVM_THREAD_LOCAL
+#endif
+
+/// \macro LLVM_ENABLE_EXCEPTIONS
+/// Whether LLVM is built with exception support.
+#if __has_feature(cxx_exceptions)
+#define LLVM_ENABLE_EXCEPTIONS 1
+#elif defined(__GNUC__) && defined(__EXCEPTIONS)
+#define LLVM_ENABLE_EXCEPTIONS 1
+#elif defined(_MSC_VER) && defined(_CPPUNWIND)
+#define LLVM_ENABLE_EXCEPTIONS 1
+#endif
+
+#ifdef __cplusplus
+namespace opencombine {
+namespace llvm {
+
+/// Allocate a buffer of memory with the given size and alignment.
+///
+/// When the compiler supports aligned operator new, this will use it to to
+/// handle even over-aligned allocations.
+///
+/// However, this doesn't make any attempt to leverage the fancier techniques
+/// like posix_memalign due to portability. It is mostly intended to allow
+/// compatibility with platforms that, after aligned allocation was added, use
+/// reduced default alignment.
+inline void *allocate_buffer(size_t Size, size_t Alignment) {
+  return ::operator new(Size
+#ifdef __cpp_aligned_new
+                        ,
+                        std::align_val_t(Alignment)
+#endif
+  );
+}
+
+/// Deallocate a buffer of memory with the given size and alignment.
+///
+/// If supported, this will used the sized delete operator. Also if supported,
+/// this will pass the alignment to the delete operator.
+///
+/// The pointer must have been allocated with the corresponding new operator,
+/// most likely using the above helper.
+inline void deallocate_buffer(void *Ptr, size_t Size, size_t Alignment) {
+  ::operator delete(Ptr
+#ifdef __cpp_sized_deallocation
+                    ,
+                    Size
+#endif
+#ifdef __cpp_aligned_new
+                    ,
+                    std::align_val_t(Alignment)
+#endif
+  );
+}
+
+} // End namespace llvm
+} // End namespace opencombine
+
+#endif // __cplusplus
+#endif
@@ -0,0 +1,94 @@
+/*===-- include/llvm-c/DataTypes.h - Define fixed size types ------*- C -*-===*\
+|*                                                                            *|
+|* Part of the LLVM Project, under the Apache License v2.0 with LLVM          *|
+|* Exceptions.                                                                *|
+|* See https://llvm.org/LICENSE.txt for license information.                  *|
+|* SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception                    *|
+|*                                                                            *|
+|*===----------------------------------------------------------------------===*|
+|*                                                                            *|
+|* This file contains definitions to figure out the size of _HOST_ data types.*|
+|* This file is important because different host OS's define different macros,*|
+|* which makes portability tough.  This file exports the following            *|
+|* definitions:                                                               *|
+|*                                                                            *|
+|*   [u]int(32|64)_t : typedefs for signed and unsigned 32/64 bit system types*|
+|*   [U]INT(8|16|32|64)_(MIN|MAX) : Constants for the min and max values.     *|
+|*                                                                            *|
+|* No library is required when using these functions.                         *|
+|*                                                                            *|
+|*===----------------------------------------------------------------------===*/
+
+/* Please leave this file C-compatible. */
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_C_DATATYPES_H
+#define OPENCOMBINE_LLVM_C_DATATYPES_H
+
+#ifdef __cplusplus
+#include <cmath>
+#else
+#include <math.h>
+#endif
+
+#include <inttypes.h>
+#include <stdint.h>
+
+#ifndef _MSC_VER
+
+#if !defined(UINT32_MAX)
+# error "The standard header <cstdint> is not C++11 compliant. Must #define "\
+        "__STDC_LIMIT_MACROS before #including llvm-c/DataTypes.h"
+#endif
+
+#if !defined(UINT32_C)
+# error "The standard header <cstdint> is not C++11 compliant. Must #define "\
+        "__STDC_CONSTANT_MACROS before #including llvm-c/DataTypes.h"
+#endif
+
+/* Note that <inttypes.h> includes <stdint.h>, if this is a C99 system. */
+#include <sys/types.h>
+
+#ifdef _AIX
+// GCC is strict about defining large constants: they must have LL modifier.
+#undef INT64_MAX
+#undef INT64_MIN
+#endif
+
+#else /* _MSC_VER */
+#ifdef __cplusplus
+#include <cstddef>
+#include <cstdlib>
+#else
+#include <stddef.h>
+#include <stdlib.h>
+#endif
+#include <sys/types.h>
+
+#if defined(_WIN64)
+typedef signed __int64 ssize_t;
+#else
+typedef signed int ssize_t;
+#endif /* _WIN64 */
+
+#endif /* _MSC_VER */
+
+/* Set defaults for constants which we cannot find. */
+#if !defined(INT64_MAX)
+# define INT64_MAX 9223372036854775807LL
+#endif
+#if !defined(INT64_MIN)
+# define INT64_MIN ((-INT64_MAX)-1)
+#endif
+#if !defined(UINT64_MAX)
+# define UINT64_MAX 0xffffffffffffffffULL
+#endif
+
+#ifndef HUGE_VALF
+#define HUGE_VALF (float)HUGE_VAL
+#endif
+
+#endif /* OPENCOMBINE_LLVM_C_DATATYPES_H */
@@ -0,0 +1,957 @@
+//===-- llvm/Support/MathExtras.h - Useful math functions -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file contains some functions that are useful for math stuff.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_MATHEXTRAS_H
+#define OPENCOMBINE_LLVM_SUPPORT_MATHEXTRAS_H
+
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/SwapByteOrder.h"
+#include <algorithm>
+#include <cassert>
+#include <climits>
+#include <cstring>
+#include <limits>
+#include <type_traits>
+
+#ifdef __ANDROID_NDK__
+#include <android/api-level.h>
+#endif
+
+#ifdef _MSC_VER
+// Declare these intrinsics manually rather including intrin.h. It's very
+// expensive, and MathExtras.h is popular.
+// #include <intrin.h>
+extern "C" {
+unsigned char _BitScanForward(unsigned long *_Index, unsigned long _Mask);
+unsigned char _BitScanForward64(unsigned long *_Index, unsigned __int64 _Mask);
+unsigned char _BitScanReverse(unsigned long *_Index, unsigned long _Mask);
+unsigned char _BitScanReverse64(unsigned long *_Index, unsigned __int64 _Mask);
+}
+#endif
+
+namespace opencombine {
+namespace llvm {
+
+/// The behavior an operation has on an input of 0.
+enum ZeroBehavior {
+  /// The returned value is undefined.
+  ZB_Undefined,
+  /// The returned value is numeric_limits<T>::max()
+  ZB_Max,
+  /// The returned value is numeric_limits<T>::digits
+  ZB_Width
+};
+
+/// Mathematical constants.
+namespace numbers {
+// TODO: Track C++20 std::numbers.
+// TODO: Favor using the hexadecimal FP constants (requires C++17).
+constexpr double e          = 2.7182818284590452354, // (0x1.5bf0a8b145749P+1) https://oeis.org/A001113
+                 egamma     = .57721566490153286061, // (0x1.2788cfc6fb619P-1) https://oeis.org/A001620
+                 ln2        = .69314718055994530942, // (0x1.62e42fefa39efP-1) https://oeis.org/A002162
+                 ln10       = 2.3025850929940456840, // (0x1.24bb1bbb55516P+1) https://oeis.org/A002392
+                 log2e      = 1.4426950408889634074, // (0x1.71547652b82feP+0)
+                 log10e     = .43429448190325182765, // (0x1.bcb7b1526e50eP-2)
+                 pi         = 3.1415926535897932385, // (0x1.921fb54442d18P+1) https://oeis.org/A000796
+                 inv_pi     = .31830988618379067154, // (0x1.45f306bc9c883P-2) https://oeis.org/A049541
+                 sqrtpi     = 1.7724538509055160273, // (0x1.c5bf891b4ef6bP+0) https://oeis.org/A002161
+                 inv_sqrtpi = .56418958354775628695, // (0x1.20dd750429b6dP-1) https://oeis.org/A087197
+                 sqrt2      = 1.4142135623730950488, // (0x1.6a09e667f3bcdP+0) https://oeis.org/A00219
+                 inv_sqrt2  = .70710678118654752440, // (0x1.6a09e667f3bcdP-1)
+                 sqrt3      = 1.7320508075688772935, // (0x1.bb67ae8584caaP+0) https://oeis.org/A002194
+                 inv_sqrt3  = .57735026918962576451, // (0x1.279a74590331cP-1)
+                 phi        = 1.6180339887498948482; // (0x1.9e3779b97f4a8P+0) https://oeis.org/A001622
+constexpr float ef          = 2.71828183F, // (0x1.5bf0a8P+1) https://oeis.org/A001113
+                egammaf     = .577215665F, // (0x1.2788d0P-1) https://oeis.org/A001620
+                ln2f        = .693147181F, // (0x1.62e430P-1) https://oeis.org/A002162
+                ln10f       = 2.30258509F, // (0x1.26bb1cP+1) https://oeis.org/A002392
+                log2ef      = 1.44269504F, // (0x1.715476P+0)
+                log10ef     = .434294482F, // (0x1.bcb7b2P-2)
+                pif         = 3.14159265F, // (0x1.921fb6P+1) https://oeis.org/A000796
+                inv_pif     = .318309886F, // (0x1.45f306P-2) https://oeis.org/A049541
+                sqrtpif     = 1.77245385F, // (0x1.c5bf8aP+0) https://oeis.org/A002161
+                inv_sqrtpif = .564189584F, // (0x1.20dd76P-1) https://oeis.org/A087197
+                sqrt2f      = 1.41421356F, // (0x1.6a09e6P+0) https://oeis.org/A002193
+                inv_sqrt2f  = .707106781F, // (0x1.6a09e6P-1)
+                sqrt3f      = 1.73205081F, // (0x1.bb67aeP+0) https://oeis.org/A002194
+                inv_sqrt3f  = .577350269F, // (0x1.279a74P-1)
+                phif        = 1.61803399F; // (0x1.9e377aP+0) https://oeis.org/A001622
+} // namespace numbers
+
+namespace detail {
+template <typename T, std::size_t SizeOfT> struct TrailingZerosCounter {
+  static unsigned count(T Val, ZeroBehavior) {
+    if (!Val)
+      return std::numeric_limits<T>::digits;
+    if (Val & 0x1)
+      return 0;
+
+    // Bisection method.
+    unsigned ZeroBits = 0;
+    T Shift = std::numeric_limits<T>::digits >> 1;
+    T Mask = std::numeric_limits<T>::max() >> Shift;
+    while (Shift) {
+      if ((Val & Mask) == 0) {
+        Val >>= Shift;
+        ZeroBits |= Shift;
+      }
+      Shift >>= 1;
+      Mask >>= Shift;
+    }
+    return ZeroBits;
+  }
+};
+
+#if defined(__GNUC__) || defined(_MSC_VER)
+template <typename T> struct TrailingZerosCounter<T, 4> {
+  static unsigned count(T Val, ZeroBehavior ZB) {
+    if (ZB != ZB_Undefined && Val == 0)
+      return 32;
+
+#if __has_builtin(__builtin_ctz) || defined(__GNUC__)
+    return __builtin_ctz(Val);
+#elif defined(_MSC_VER)
+    unsigned long Index;
+    _BitScanForward(&Index, Val);
+    return Index;
+#endif
+  }
+};
+
+#if !defined(_MSC_VER) || defined(_M_X64)
+template <typename T> struct TrailingZerosCounter<T, 8> {
+  static unsigned count(T Val, ZeroBehavior ZB) {
+    if (ZB != ZB_Undefined && Val == 0)
+      return 64;
+
+#if __has_builtin(__builtin_ctzll) || defined(__GNUC__)
+    return __builtin_ctzll(Val);
+#elif defined(_MSC_VER)
+    unsigned long Index;
+    _BitScanForward64(&Index, Val);
+    return Index;
+#endif
+  }
+};
+#endif
+#endif
+} // namespace detail
+
+/// Count number of 0's from the least significant bit to the most
+///   stopping at the first 1.
+///
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
+///   valid arguments.
+template <typename T>
+unsigned countTrailingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
+  static_assert(std::numeric_limits<T>::is_integer &&
+                    !std::numeric_limits<T>::is_signed,
+                "Only unsigned integral types are allowed.");
+  return llvm::detail::TrailingZerosCounter<T, sizeof(T)>::count(Val, ZB);
+}
+
+namespace detail {
+template <typename T, std::size_t SizeOfT> struct LeadingZerosCounter {
+  static unsigned count(T Val, ZeroBehavior) {
+    if (!Val)
+      return std::numeric_limits<T>::digits;
+
+    // Bisection method.
+    unsigned ZeroBits = 0;
+    for (T Shift = std::numeric_limits<T>::digits >> 1; Shift; Shift >>= 1) {
+      T Tmp = Val >> Shift;
+      if (Tmp)
+        Val = Tmp;
+      else
+        ZeroBits |= Shift;
+    }
+    return ZeroBits;
+  }
+};
+
+#if defined(__GNUC__) || defined(_MSC_VER)
+template <typename T> struct LeadingZerosCounter<T, 4> {
+  static unsigned count(T Val, ZeroBehavior ZB) {
+    if (ZB != ZB_Undefined && Val == 0)
+      return 32;
+
+#if __has_builtin(__builtin_clz) || defined(__GNUC__)
+    return __builtin_clz(Val);
+#elif defined(_MSC_VER)
+    unsigned long Index;
+    _BitScanReverse(&Index, Val);
+    return Index ^ 31;
+#endif
+  }
+};
+
+#if !defined(_MSC_VER) || defined(_M_X64)
+template <typename T> struct LeadingZerosCounter<T, 8> {
+  static unsigned count(T Val, ZeroBehavior ZB) {
+    if (ZB != ZB_Undefined && Val == 0)
+      return 64;
+
+#if __has_builtin(__builtin_clzll) || defined(__GNUC__)
+    return __builtin_clzll(Val);
+#elif defined(_MSC_VER)
+    unsigned long Index;
+    _BitScanReverse64(&Index, Val);
+    return Index ^ 63;
+#endif
+  }
+};
+#endif
+#endif
+} // namespace detail
+
+/// Count number of 0's from the most significant bit to the least
+///   stopping at the first 1.
+///
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of 0. Only ZB_Width and ZB_Undefined are
+///   valid arguments.
+template <typename T>
+unsigned countLeadingZeros(T Val, ZeroBehavior ZB = ZB_Width) {
+  static_assert(std::numeric_limits<T>::is_integer &&
+                    !std::numeric_limits<T>::is_signed,
+                "Only unsigned integral types are allowed.");
+  return llvm::detail::LeadingZerosCounter<T, sizeof(T)>::count(Val, ZB);
+}
+
+/// Get the index of the first set bit starting from the least
+///   significant bit.
+///
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
+///   valid arguments.
+template <typename T> T findFirstSet(T Val, ZeroBehavior ZB = ZB_Max) {
+  if (ZB == ZB_Max && Val == 0)
+    return std::numeric_limits<T>::max();
+
+  return countTrailingZeros(Val, ZB_Undefined);
+}
+
+/// Create a bitmask with the N right-most bits set to 1, and all other
+/// bits set to 0.  Only unsigned types are allowed.
+template <typename T> T maskTrailingOnes(unsigned N) {
+  static_assert(std::is_unsigned<T>::value, "Invalid type!");
+  const unsigned Bits = CHAR_BIT * sizeof(T);
+  assert(N <= Bits && "Invalid bit index");
+  return N == 0 ? 0 : (T(-1) >> (Bits - N));
+}
+
+/// Create a bitmask with the N left-most bits set to 1, and all other
+/// bits set to 0.  Only unsigned types are allowed.
+template <typename T> T maskLeadingOnes(unsigned N) {
+  return ~maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N);
+}
+
+/// Create a bitmask with the N right-most bits set to 0, and all other
+/// bits set to 1.  Only unsigned types are allowed.
+template <typename T> T maskTrailingZeros(unsigned N) {
+  return maskLeadingOnes<T>(CHAR_BIT * sizeof(T) - N);
+}
+
+/// Create a bitmask with the N left-most bits set to 0, and all other
+/// bits set to 1.  Only unsigned types are allowed.
+template <typename T> T maskLeadingZeros(unsigned N) {
+  return maskTrailingOnes<T>(CHAR_BIT * sizeof(T) - N);
+}
+
+/// Get the index of the last set bit starting from the least
+///   significant bit.
+///
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of 0. Only ZB_Max and ZB_Undefined are
+///   valid arguments.
+template <typename T> T findLastSet(T Val, ZeroBehavior ZB = ZB_Max) {
+  if (ZB == ZB_Max && Val == 0)
+    return std::numeric_limits<T>::max();
+
+  // Use ^ instead of - because both gcc and llvm can remove the associated ^
+  // in the __builtin_clz intrinsic on x86.
+  return countLeadingZeros(Val, ZB_Undefined) ^
+         (std::numeric_limits<T>::digits - 1);
+}
+
+/// Macro compressed bit reversal table for 256 bits.
+///
+/// http://graphics.stanford.edu/~seander/bithacks.html#BitReverseTable
+static const unsigned char BitReverseTable256[256] = {
+#define R2(n) n, n + 2 * 64, n + 1 * 64, n + 3 * 64
+#define R4(n) R2(n), R2(n + 2 * 16), R2(n + 1 * 16), R2(n + 3 * 16)
+#define R6(n) R4(n), R4(n + 2 * 4), R4(n + 1 * 4), R4(n + 3 * 4)
+  R6(0), R6(2), R6(1), R6(3)
+#undef R2
+#undef R4
+#undef R6
+};
+
+/// Reverse the bits in \p Val.
+template <typename T>
+T reverseBits(T Val) {
+  unsigned char in[sizeof(Val)];
+  unsigned char out[sizeof(Val)];
+  std::memcpy(in, &Val, sizeof(Val));
+  for (unsigned i = 0; i < sizeof(Val); ++i)
+    out[(sizeof(Val) - i) - 1] = BitReverseTable256[in[i]];
+  std::memcpy(&Val, out, sizeof(Val));
+  return Val;
+}
+
+// NOTE: The following support functions use the _32/_64 extensions instead of
+// type overloading so that signed and unsigned integers can be used without
+// ambiguity.
+
+/// Return the high 32 bits of a 64 bit value.
+constexpr inline uint32_t Hi_32(uint64_t Value) {
+  return static_cast<uint32_t>(Value >> 32);
+}
+
+/// Return the low 32 bits of a 64 bit value.
+constexpr inline uint32_t Lo_32(uint64_t Value) {
+  return static_cast<uint32_t>(Value);
+}
+
+/// Make a 64-bit integer from a high / low pair of 32-bit integers.
+constexpr inline uint64_t Make_64(uint32_t High, uint32_t Low) {
+  return ((uint64_t)High << 32) | (uint64_t)Low;
+}
+
+/// Checks if an integer fits into the given bit width.
+template <unsigned N> constexpr inline bool isInt(int64_t x) {
+  return N >= 64 || (-(INT64_C(1)<<(N-1)) <= x && x < (INT64_C(1)<<(N-1)));
+}
+// Template specializations to get better code for common cases.
+template <> constexpr inline bool isInt<8>(int64_t x) {
+  return static_cast<int8_t>(x) == x;
+}
+template <> constexpr inline bool isInt<16>(int64_t x) {
+  return static_cast<int16_t>(x) == x;
+}
+template <> constexpr inline bool isInt<32>(int64_t x) {
+  return static_cast<int32_t>(x) == x;
+}
+
+/// Checks if a signed integer is an N bit number shifted left by S.
+template <unsigned N, unsigned S>
+constexpr inline bool isShiftedInt(int64_t x) {
+  static_assert(
+      N > 0, "isShiftedInt<0> doesn't make sense (refers to a 0-bit number.");
+  static_assert(N + S <= 64, "isShiftedInt<N, S> with N + S > 64 is too wide.");
+  return isInt<N + S>(x) && (x % (UINT64_C(1) << S) == 0);
+}
+
+/// Checks if an unsigned integer fits into the given bit width.
+///
+/// This is written as two functions rather than as simply
+///
+///   return N >= 64 || X < (UINT64_C(1) << N);
+///
+/// to keep MSVC from (incorrectly) warning on isUInt<64> that we're shifting
+/// left too many places.
+template <unsigned N>
+constexpr inline typename std::enable_if<(N < 64), bool>::type
+isUInt(uint64_t X) {
+  static_assert(N > 0, "isUInt<0> doesn't make sense");
+  return X < (UINT64_C(1) << (N));
+}
+template <unsigned N>
+constexpr inline typename std::enable_if<N >= 64, bool>::type
+isUInt(uint64_t X) {
+  return true;
+}
+
+// Template specializations to get better code for common cases.
+template <> constexpr inline bool isUInt<8>(uint64_t x) {
+  return static_cast<uint8_t>(x) == x;
+}
+template <> constexpr inline bool isUInt<16>(uint64_t x) {
+  return static_cast<uint16_t>(x) == x;
+}
+template <> constexpr inline bool isUInt<32>(uint64_t x) {
+  return static_cast<uint32_t>(x) == x;
+}
+
+/// Checks if a unsigned integer is an N bit number shifted left by S.
+template <unsigned N, unsigned S>
+constexpr inline bool isShiftedUInt(uint64_t x) {
+  static_assert(
+      N > 0, "isShiftedUInt<0> doesn't make sense (refers to a 0-bit number)");
+  static_assert(N + S <= 64,
+                "isShiftedUInt<N, S> with N + S > 64 is too wide.");
+  // Per the two static_asserts above, S must be strictly less than 64.  So
+  // 1 << S is not undefined behavior.
+  return isUInt<N + S>(x) && (x % (UINT64_C(1) << S) == 0);
+}
+
+/// Gets the maximum value for a N-bit unsigned integer.
+inline uint64_t maxUIntN(uint64_t N) {
+  assert(N > 0 && N <= 64 && "integer width out of range");
+
+  // uint64_t(1) << 64 is undefined behavior, so we can't do
+  //   (uint64_t(1) << N) - 1
+  // without checking first that N != 64.  But this works and doesn't have a
+  // branch.
+  return UINT64_MAX >> (64 - N);
+}
+
+/// Gets the minimum value for a N-bit signed integer.
+inline int64_t minIntN(int64_t N) {
+  assert(N > 0 && N <= 64 && "integer width out of range");
+
+  return -(UINT64_C(1)<<(N-1));
+}
+
+/// Gets the maximum value for a N-bit signed integer.
+inline int64_t maxIntN(int64_t N) {
+  assert(N > 0 && N <= 64 && "integer width out of range");
+
+  // This relies on two's complement wraparound when N == 64, so we convert to
+  // int64_t only at the very end to avoid UB.
+  return (UINT64_C(1) << (N - 1)) - 1;
+}
+
+/// Checks if an unsigned integer fits into the given (dynamic) bit width.
+inline bool isUIntN(unsigned N, uint64_t x) {
+  return N >= 64 || x <= maxUIntN(N);
+}
+
+/// Checks if an signed integer fits into the given (dynamic) bit width.
+inline bool isIntN(unsigned N, int64_t x) {
+  return N >= 64 || (minIntN(N) <= x && x <= maxIntN(N));
+}
+
+/// Return true if the argument is a non-empty sequence of ones starting at the
+/// least significant bit with the remainder zero (32 bit version).
+/// Ex. isMask_32(0x0000FFFFU) == true.
+constexpr inline bool isMask_32(uint32_t Value) {
+  return Value && ((Value + 1) & Value) == 0;
+}
+
+/// Return true if the argument is a non-empty sequence of ones starting at the
+/// least significant bit with the remainder zero (64 bit version).
+constexpr inline bool isMask_64(uint64_t Value) {
+  return Value && ((Value + 1) & Value) == 0;
+}
+
+/// Return true if the argument contains a non-empty sequence of ones with the
+/// remainder zero (32 bit version.) Ex. isShiftedMask_32(0x0000FF00U) == true.
+constexpr inline bool isShiftedMask_32(uint32_t Value) {
+  return Value && isMask_32((Value - 1) | Value);
+}
+
+/// Return true if the argument contains a non-empty sequence of ones with the
+/// remainder zero (64 bit version.)
+constexpr inline bool isShiftedMask_64(uint64_t Value) {
+  return Value && isMask_64((Value - 1) | Value);
+}
+
+/// Return true if the argument is a power of two > 0.
+/// Ex. isPowerOf2_32(0x00100000U) == true (32 bit edition.)
+constexpr inline bool isPowerOf2_32(uint32_t Value) {
+  return Value && !(Value & (Value - 1));
+}
+
+/// Return true if the argument is a power of two > 0 (64 bit edition.)
+constexpr inline bool isPowerOf2_64(uint64_t Value) {
+  return Value && !(Value & (Value - 1));
+}
+
+/// Return a byte-swapped representation of the 16-bit argument.
+inline uint16_t ByteSwap_16(uint16_t Value) {
+  return sys::SwapByteOrder_16(Value);
+}
+
+/// Return a byte-swapped representation of the 32-bit argument.
+inline uint32_t ByteSwap_32(uint32_t Value) {
+  return sys::SwapByteOrder_32(Value);
+}
+
+/// Return a byte-swapped representation of the 64-bit argument.
+inline uint64_t ByteSwap_64(uint64_t Value) {
+  return sys::SwapByteOrder_64(Value);
+}
+
+/// Count the number of ones from the most significant bit to the first
+/// zero bit.
+///
+/// Ex. countLeadingOnes(0xFF0FFF00) == 8.
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of all ones. Only ZB_Width and
+/// ZB_Undefined are valid arguments.
+template <typename T>
+unsigned countLeadingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
+  static_assert(std::numeric_limits<T>::is_integer &&
+                    !std::numeric_limits<T>::is_signed,
+                "Only unsigned integral types are allowed.");
+  return countLeadingZeros<T>(~Value, ZB);
+}
+
+/// Count the number of ones from the least significant bit to the first
+/// zero bit.
+///
+/// Ex. countTrailingOnes(0x00FF00FF) == 8.
+/// Only unsigned integral types are allowed.
+///
+/// \param ZB the behavior on an input of all ones. Only ZB_Width and
+/// ZB_Undefined are valid arguments.
+template <typename T>
+unsigned countTrailingOnes(T Value, ZeroBehavior ZB = ZB_Width) {
+  static_assert(std::numeric_limits<T>::is_integer &&
+                    !std::numeric_limits<T>::is_signed,
+                "Only unsigned integral types are allowed.");
+  return countTrailingZeros<T>(~Value, ZB);
+}
+
+namespace detail {
+template <typename T, std::size_t SizeOfT> struct PopulationCounter {
+  static unsigned count(T Value) {
+    // Generic version, forward to 32 bits.
+    static_assert(SizeOfT <= 4, "Not implemented!");
+#if defined(__GNUC__)
+    return __builtin_popcount(Value);
+#else
+    uint32_t v = Value;
+    v = v - ((v >> 1) & 0x55555555);
+    v = (v & 0x33333333) + ((v >> 2) & 0x33333333);
+    return ((v + (v >> 4) & 0xF0F0F0F) * 0x1010101) >> 24;
+#endif
+  }
+};
+
+template <typename T> struct PopulationCounter<T, 8> {
+  static unsigned count(T Value) {
+#if defined(__GNUC__)
+    return __builtin_popcountll(Value);
+#else
+    uint64_t v = Value;
+    v = v - ((v >> 1) & 0x5555555555555555ULL);
+    v = (v & 0x3333333333333333ULL) + ((v >> 2) & 0x3333333333333333ULL);
+    v = (v + (v >> 4)) & 0x0F0F0F0F0F0F0F0FULL;
+    return unsigned((uint64_t)(v * 0x0101010101010101ULL) >> 56);
+#endif
+  }
+};
+} // namespace detail
+
+/// Count the number of set bits in a value.
+/// Ex. countPopulation(0xF000F000) = 8
+/// Returns 0 if the word is zero.
+template <typename T>
+inline unsigned countPopulation(T Value) {
+  static_assert(std::numeric_limits<T>::is_integer &&
+                    !std::numeric_limits<T>::is_signed,
+                "Only unsigned integral types are allowed.");
+  return detail::PopulationCounter<T, sizeof(T)>::count(Value);
+}
+
+/// Compile time Log2.
+/// Valid only for positive powers of two.
+template <size_t kValue> constexpr inline size_t CTLog2() {
+  static_assert(kValue > 0 && llvm::isPowerOf2_64(kValue),
+                "Value is not a valid power of 2");
+  return 1 + CTLog2<kValue / 2>();
+}
+
+template <> constexpr inline size_t CTLog2<1>() { return 0; }
+
+/// Return the log base 2 of the specified value.
+inline double Log2(double Value) {
+#if defined(__ANDROID_API__) && __ANDROID_API__ < 18
+  return __builtin_log(Value) / __builtin_log(2.0);
+#else
+  return log2(Value);
+#endif
+}
+
+/// Return the floor log base 2 of the specified value, -1 if the value is zero.
+/// (32 bit edition.)
+/// Ex. Log2_32(32) == 5, Log2_32(1) == 0, Log2_32(0) == -1, Log2_32(6) == 2
+inline unsigned Log2_32(uint32_t Value) {
+  return 31 - countLeadingZeros(Value);
+}
+
+/// Return the floor log base 2 of the specified value, -1 if the value is zero.
+/// (64 bit edition.)
+inline unsigned Log2_64(uint64_t Value) {
+  return 63 - countLeadingZeros(Value);
+}
+
+/// Return the ceil log base 2 of the specified value, 32 if the value is zero.
+/// (32 bit edition).
+/// Ex. Log2_32_Ceil(32) == 5, Log2_32_Ceil(1) == 0, Log2_32_Ceil(6) == 3
+inline unsigned Log2_32_Ceil(uint32_t Value) {
+  return 32 - countLeadingZeros(Value - 1);
+}
+
+/// Return the ceil log base 2 of the specified value, 64 if the value is zero.
+/// (64 bit edition.)
+inline unsigned Log2_64_Ceil(uint64_t Value) {
+  return 64 - countLeadingZeros(Value - 1);
+}
+
+/// Return the greatest common divisor of the values using Euclid's algorithm.
+template <typename T>
+inline T greatestCommonDivisor(T A, T B) {
+  while (B) {
+    T Tmp = B;
+    B = A % B;
+    A = Tmp;
+  }
+  return A;
+}
+
+inline uint64_t GreatestCommonDivisor64(uint64_t A, uint64_t B) {
+  return greatestCommonDivisor<uint64_t>(A, B);
+}
+
+/// This function takes a 64-bit integer and returns the bit equivalent double.
+inline double BitsToDouble(uint64_t Bits) {
+  double D;
+  static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
+  memcpy(&D, &Bits, sizeof(Bits));
+  return D;
+}
+
+/// This function takes a 32-bit integer and returns the bit equivalent float.
+inline float BitsToFloat(uint32_t Bits) {
+  float F;
+  static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
+  memcpy(&F, &Bits, sizeof(Bits));
+  return F;
+}
+
+/// This function takes a double and returns the bit equivalent 64-bit integer.
+/// Note that copying doubles around changes the bits of NaNs on some hosts,
+/// notably x86, so this routine cannot be used if these bits are needed.
+inline uint64_t DoubleToBits(double Double) {
+  uint64_t Bits;
+  static_assert(sizeof(uint64_t) == sizeof(double), "Unexpected type sizes");
+  memcpy(&Bits, &Double, sizeof(Double));
+  return Bits;
+}
+
+/// This function takes a float and returns the bit equivalent 32-bit integer.
+/// Note that copying floats around changes the bits of NaNs on some hosts,
+/// notably x86, so this routine cannot be used if these bits are needed.
+inline uint32_t FloatToBits(float Float) {
+  uint32_t Bits;
+  static_assert(sizeof(uint32_t) == sizeof(float), "Unexpected type sizes");
+  memcpy(&Bits, &Float, sizeof(Float));
+  return Bits;
+}
+
+/// A and B are either alignments or offsets. Return the minimum alignment that
+/// may be assumed after adding the two together.
+constexpr inline uint64_t MinAlign(uint64_t A, uint64_t B) {
+  // The largest power of 2 that divides both A and B.
+  //
+  // Replace "-Value" by "1+~Value" in the following commented code to avoid
+  // MSVC warning C4146
+  //    return (A | B) & -(A | B);
+  return (A | B) & (1 + ~(A | B));
+}
+
+/// Returns the next power of two (in 64-bits) that is strictly greater than A.
+/// Returns zero on overflow.
+inline uint64_t NextPowerOf2(uint64_t A) {
+  A |= (A >> 1);
+  A |= (A >> 2);
+  A |= (A >> 4);
+  A |= (A >> 8);
+  A |= (A >> 16);
+  A |= (A >> 32);
+  return A + 1;
+}
+
+/// Returns the power of two which is less than or equal to the given value.
+/// Essentially, it is a floor operation across the domain of powers of two.
+inline uint64_t PowerOf2Floor(uint64_t A) {
+  if (!A) return 0;
+  return 1ull << (63 - countLeadingZeros(A, ZB_Undefined));
+}
+
+/// Returns the power of two which is greater than or equal to the given value.
+/// Essentially, it is a ceil operation across the domain of powers of two.
+inline uint64_t PowerOf2Ceil(uint64_t A) {
+  if (!A)
+    return 0;
+  return NextPowerOf2(A - 1);
+}
+
+/// Returns the next integer (mod 2**64) that is greater than or equal to
+/// \p Value and is a multiple of \p Align. \p Align must be non-zero.
+///
+/// If non-zero \p Skew is specified, the return value will be a minimal
+/// integer that is greater than or equal to \p Value and equal to
+/// \p Align * N + \p Skew for some integer N. If \p Skew is larger than
+/// \p Align, its value is adjusted to '\p Skew mod \p Align'.
+///
+/// Examples:
+/// \code
+///   alignTo(5, 8) = 8
+///   alignTo(17, 8) = 24
+///   alignTo(~0LL, 8) = 0
+///   alignTo(321, 255) = 510
+///
+///   alignTo(5, 8, 7) = 7
+///   alignTo(17, 8, 1) = 17
+///   alignTo(~0LL, 8, 3) = 3
+///   alignTo(321, 255, 42) = 552
+/// \endcode
+inline uint64_t alignTo(uint64_t Value, uint64_t Align, uint64_t Skew = 0) {
+  assert(Align != 0u && "Align can't be 0.");
+  Skew %= Align;
+  return (Value + Align - 1 - Skew) / Align * Align + Skew;
+}
+
+/// Returns the next integer (mod 2**64) that is greater than or equal to
+/// \p Value and is a multiple of \c Align. \c Align must be non-zero.
+template <uint64_t Align> constexpr inline uint64_t alignTo(uint64_t Value) {
+  static_assert(Align != 0u, "Align must be non-zero");
+  return (Value + Align - 1) / Align * Align;
+}
+
+/// Returns the integer ceil(Numerator / Denominator).
+inline uint64_t divideCeil(uint64_t Numerator, uint64_t Denominator) {
+  return alignTo(Numerator, Denominator) / Denominator;
+}
+
+/// Returns the largest uint64_t less than or equal to \p Value and is
+/// \p Skew mod \p Align. \p Align must be non-zero
+inline uint64_t alignDown(uint64_t Value, uint64_t Align, uint64_t Skew = 0) {
+  assert(Align != 0u && "Align can't be 0.");
+  Skew %= Align;
+  return (Value - Skew) / Align * Align + Skew;
+}
+
+/// Sign-extend the number in the bottom B bits of X to a 32-bit integer.
+/// Requires 0 < B <= 32.
+template <unsigned B> constexpr inline int32_t SignExtend32(uint32_t X) {
+  static_assert(B > 0, "Bit width can't be 0.");
+  static_assert(B <= 32, "Bit width out of range.");
+  return int32_t(X << (32 - B)) >> (32 - B);
+}
+
+/// Sign-extend the number in the bottom B bits of X to a 32-bit integer.
+/// Requires 0 < B < 32.
+inline int32_t SignExtend32(uint32_t X, unsigned B) {
+  assert(B > 0 && "Bit width can't be 0.");
+  assert(B <= 32 && "Bit width out of range.");
+  return int32_t(X << (32 - B)) >> (32 - B);
+}
+
+/// Sign-extend the number in the bottom B bits of X to a 64-bit integer.
+/// Requires 0 < B < 64.
+template <unsigned B> constexpr inline int64_t SignExtend64(uint64_t x) {
+  static_assert(B > 0, "Bit width can't be 0.");
+  static_assert(B <= 64, "Bit width out of range.");
+  return int64_t(x << (64 - B)) >> (64 - B);
+}
+
+/// Sign-extend the number in the bottom B bits of X to a 64-bit integer.
+/// Requires 0 < B < 64.
+inline int64_t SignExtend64(uint64_t X, unsigned B) {
+  assert(B > 0 && "Bit width can't be 0.");
+  assert(B <= 64 && "Bit width out of range.");
+  return int64_t(X << (64 - B)) >> (64 - B);
+}
+
+/// Subtract two unsigned integers, X and Y, of type T and return the absolute
+/// value of the result.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+AbsoluteDifference(T X, T Y) {
+  return std::max(X, Y) - std::min(X, Y);
+}
+
+/// Add two unsigned integers, X and Y, of type T.  Clamp the result to the
+/// maximum representable value of T on overflow.  ResultOverflowed indicates if
+/// the result is larger than the maximum representable value of type T.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+SaturatingAdd(T X, T Y, bool *ResultOverflowed = nullptr) {
+  bool Dummy;
+  bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
+  // Hacker's Delight, p. 29
+  T Z = X + Y;
+  Overflowed = (Z < X || Z < Y);
+  if (Overflowed)
+    return std::numeric_limits<T>::max();
+  else
+    return Z;
+}
+
+/// Multiply two unsigned integers, X and Y, of type T.  Clamp the result to the
+/// maximum representable value of T on overflow.  ResultOverflowed indicates if
+/// the result is larger than the maximum representable value of type T.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+SaturatingMultiply(T X, T Y, bool *ResultOverflowed = nullptr) {
+  bool Dummy;
+  bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
+
+  // Hacker's Delight, p. 30 has a different algorithm, but we don't use that
+  // because it fails for uint16_t (where multiplication can have undefined
+  // behavior due to promotion to int), and requires a division in addition
+  // to the multiplication.
+
+  Overflowed = false;
+
+  // Log2(Z) would be either Log2Z or Log2Z + 1.
+  // Special case: if X or Y is 0, Log2_64 gives -1, and Log2Z
+  // will necessarily be less than Log2Max as desired.
+  int Log2Z = Log2_64(X) + Log2_64(Y);
+  const T Max = std::numeric_limits<T>::max();
+  int Log2Max = Log2_64(Max);
+  if (Log2Z < Log2Max) {
+    return X * Y;
+  }
+  if (Log2Z > Log2Max) {
+    Overflowed = true;
+    return Max;
+  }
+
+  // We're going to use the top bit, and maybe overflow one
+  // bit past it. Multiply all but the bottom bit then add
+  // that on at the end.
+  T Z = (X >> 1) * Y;
+  if (Z & ~(Max >> 1)) {
+    Overflowed = true;
+    return Max;
+  }
+  Z <<= 1;
+  if (X & 1)
+    return SaturatingAdd(Z, Y, ResultOverflowed);
+
+  return Z;
+}
+
+/// Multiply two unsigned integers, X and Y, and add the unsigned integer, A to
+/// the product. Clamp the result to the maximum representable value of T on
+/// overflow. ResultOverflowed indicates if the result is larger than the
+/// maximum representable value of type T.
+template <typename T>
+typename std::enable_if<std::is_unsigned<T>::value, T>::type
+SaturatingMultiplyAdd(T X, T Y, T A, bool *ResultOverflowed = nullptr) {
+  bool Dummy;
+  bool &Overflowed = ResultOverflowed ? *ResultOverflowed : Dummy;
+
+  T Product = SaturatingMultiply(X, Y, &Overflowed);
+  if (Overflowed)
+    return Product;
+
+  return SaturatingAdd(A, Product, &Overflowed);
+}
+
+/// Use this rather than HUGE_VALF; the latter causes warnings on MSVC.
+extern const float huge_valf;
+
+
+/// Add two signed integers, computing the two's complement truncated result,
+/// returning true if overflow occured.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, T>::type
+AddOverflow(T X, T Y, T &Result) {
+#if __has_builtin(__builtin_add_overflow)
+  return __builtin_add_overflow(X, Y, &Result);
+#else
+  // Perform the unsigned addition.
+  using U = typename std::make_unsigned<T>::type;
+  const U UX = static_cast<U>(X);
+  const U UY = static_cast<U>(Y);
+  const U UResult = UX + UY;
+
+  // Convert to signed.
+  Result = static_cast<T>(UResult);
+
+  // Adding two positive numbers should result in a positive number.
+  if (X > 0 && Y > 0)
+    return Result <= 0;
+  // Adding two negatives should result in a negative number.
+  if (X < 0 && Y < 0)
+    return Result >= 0;
+  return false;
+#endif
+}
+
+/// Subtract two signed integers, computing the two's complement truncated
+/// result, returning true if an overflow ocurred.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, T>::type
+SubOverflow(T X, T Y, T &Result) {
+#if __has_builtin(__builtin_sub_overflow)
+  return __builtin_sub_overflow(X, Y, &Result);
+#else
+  // Perform the unsigned addition.
+  using U = typename std::make_unsigned<T>::type;
+  const U UX = static_cast<U>(X);
+  const U UY = static_cast<U>(Y);
+  const U UResult = UX - UY;
+
+  // Convert to signed.
+  Result = static_cast<T>(UResult);
+
+  // Subtracting a positive number from a negative results in a negative number.
+  if (X <= 0 && Y > 0)
+    return Result >= 0;
+  // Subtracting a negative number from a positive results in a positive number.
+  if (X >= 0 && Y < 0)
+    return Result <= 0;
+  return false;
+#endif
+}
+
+
+/// Multiply two signed integers, computing the two's complement truncated
+/// result, returning true if an overflow ocurred.
+template <typename T>
+typename std::enable_if<std::is_signed<T>::value, T>::type
+MulOverflow(T X, T Y, T &Result) {
+  // Perform the unsigned multiplication on absolute values.
+  using U = typename std::make_unsigned<T>::type;
+  const U UX = X < 0 ? (0 - static_cast<U>(X)) : static_cast<U>(X);
+  const U UY = Y < 0 ? (0 - static_cast<U>(Y)) : static_cast<U>(Y);
+  const U UResult = UX * UY;
+
+  // Convert to signed.
+  const bool IsNegative = (X < 0) ^ (Y < 0);
+  Result = IsNegative ? (0 - UResult) : UResult;
+
+  // If any of the args was 0, result is 0 and no overflow occurs.
+  if (UX == 0 || UY == 0)
+    return false;
+
+  // UX and UY are in [1, 2^n], where n is the number of digits.
+  // Check how the max allowed absolute value (2^n for negative, 2^(n-1) for
+  // positive) divided by an argument compares to the other.
+  if (IsNegative)
+    return UX > (static_cast<U>(std::numeric_limits<T>::max()) + U(1)) / UY;
+  else
+    return UX > (static_cast<U>(std::numeric_limits<T>::max())) / UY;
+}
+
+} // End llvm namespace
+} // End opencombine namespace
+
+#endif
@@ -0,0 +1,166 @@
+//===- SwapByteOrder.h - Generic and optimized byte swaps -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file declares generic and optimized functions to swap the byte order of
+// an integral type.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_SWAPBYTEORDER_H
+#define OPENCOMBINE_LLVM_SUPPORT_SWAPBYTEORDER_H
+
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/DataTypes.h"
+#include <cstddef>
+#include <type_traits>
+#if defined(_MSC_VER) && !defined(_DEBUG)
+#include <stdlib.h>
+#endif
+
+#if defined(__linux__) || defined(__GNU__) || defined(__HAIKU__)
+#include <endian.h>
+#elif defined(_AIX)
+#include <sys/machine.h>
+#elif defined(__sun)
+/* Solaris provides _BIG_ENDIAN/_LITTLE_ENDIAN selector in sys/types.h */
+#include <sys/types.h>
+#define BIG_ENDIAN 4321
+#define LITTLE_ENDIAN 1234
+#if defined(_BIG_ENDIAN)
+#define BYTE_ORDER BIG_ENDIAN
+#else
+#define BYTE_ORDER LITTLE_ENDIAN
+#endif
+#else
+#if !defined(BYTE_ORDER) && !defined(_WIN32)
+#include <machine/endian.h>
+#endif
+#endif
+
+namespace opencombine {
+namespace llvm {
+namespace sys {
+
+#if defined(BYTE_ORDER) && defined(BIG_ENDIAN) && BYTE_ORDER == BIG_ENDIAN
+constexpr bool IsBigEndianHost = true;
+#else
+constexpr bool IsBigEndianHost = false;
+#endif
+
+static const bool IsLittleEndianHost = !IsBigEndianHost;
+
+/// SwapByteOrder_16 - This function returns a byte-swapped representation of
+/// the 16-bit argument.
+inline uint16_t SwapByteOrder_16(uint16_t value) {
+#if defined(_MSC_VER) && !defined(_DEBUG)
+  // The DLL version of the runtime lacks these functions (bug!?), but in a
+  // release build they're replaced with BSWAP instructions anyway.
+  return _byteswap_ushort(value);
+#else
+  uint16_t Hi = value << 8;
+  uint16_t Lo = value >> 8;
+  return Hi | Lo;
+#endif
+}
+
+/// This function returns a byte-swapped representation of the 32-bit argument.
+inline uint32_t SwapByteOrder_32(uint32_t value) {
+#if defined(__llvm__) || (defined(__GNUC__) && !defined(__ICC))
+  return __builtin_bswap32(value);
+#elif defined(_MSC_VER) && !defined(_DEBUG)
+  return _byteswap_ulong(value);
+#else
+  uint32_t Byte0 = value & 0x000000FF;
+  uint32_t Byte1 = value & 0x0000FF00;
+  uint32_t Byte2 = value & 0x00FF0000;
+  uint32_t Byte3 = value & 0xFF000000;
+  return (Byte0 << 24) | (Byte1 << 8) | (Byte2 >> 8) | (Byte3 >> 24);
+#endif
+}
+
+/// This function returns a byte-swapped representation of the 64-bit argument.
+inline uint64_t SwapByteOrder_64(uint64_t value) {
+#if defined(__llvm__) || (defined(__GNUC__) && !defined(__ICC))
+  return __builtin_bswap64(value);
+#elif defined(_MSC_VER) && !defined(_DEBUG)
+  return _byteswap_uint64(value);
+#else
+  uint64_t Hi = SwapByteOrder_32(uint32_t(value));
+  uint32_t Lo = SwapByteOrder_32(uint32_t(value >> 32));
+  return (Hi << 32) | Lo;
+#endif
+}
+
+inline unsigned char  getSwappedBytes(unsigned char C) { return C; }
+inline   signed char  getSwappedBytes(signed char C) { return C; }
+inline          char  getSwappedBytes(char C) { return C; }
+
+inline unsigned short getSwappedBytes(unsigned short C) { return SwapByteOrder_16(C); }
+inline   signed short getSwappedBytes(  signed short C) { return SwapByteOrder_16(C); }
+
+inline unsigned int   getSwappedBytes(unsigned int   C) { return SwapByteOrder_32(C); }
+inline   signed int   getSwappedBytes(  signed int   C) { return SwapByteOrder_32(C); }
+
+#if __LONG_MAX__ == __INT_MAX__
+inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_32(C); }
+inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_32(C); }
+#elif __LONG_MAX__ == __LONG_LONG_MAX__
+inline unsigned long  getSwappedBytes(unsigned long  C) { return SwapByteOrder_64(C); }
+inline   signed long  getSwappedBytes(  signed long  C) { return SwapByteOrder_64(C); }
+#else
+#error "Unknown long size!"
+#endif
+
+inline unsigned long long getSwappedBytes(unsigned long long C) {
+  return SwapByteOrder_64(C);
+}
+inline signed long long getSwappedBytes(signed long long C) {
+  return SwapByteOrder_64(C);
+}
+
+inline float getSwappedBytes(float C) {
+  union {
+    uint32_t i;
+    float f;
+  } in, out;
+  in.f = C;
+  out.i = SwapByteOrder_32(in.i);
+  return out.f;
+}
+
+inline double getSwappedBytes(double C) {
+  union {
+    uint64_t i;
+    double d;
+  } in, out;
+  in.d = C;
+  out.i = SwapByteOrder_64(in.i);
+  return out.d;
+}
+
+template <typename T>
+inline typename std::enable_if<std::is_enum<T>::value, T>::type
+getSwappedBytes(T C) {
+  return static_cast<T>(
+      getSwappedBytes(static_cast<typename std::underlying_type<T>::type>(C)));
+}
+
+template<typename T>
+inline void swapByteOrder(T &Value) {
+  Value = getSwappedBytes(Value);
+}
+
+} // end namespace sys
+} // end namespace llvm
+} // end namespace opencombine
+
+#endif
@@ -0,0 +1,198 @@
+//===- llvm/Support/type_traits.h - Simplfied type traits -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides useful additions to the standard type_traits library.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The llvm namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_LLVM_SUPPORT_TYPE_TRAITS_H
+#define OPENCOMBINE_LLVM_SUPPORT_TYPE_TRAITS_H
+
+#include "llvm/Support/Compiler.h"
+#include <type_traits>
+#include <utility>
+
+namespace opencombine {
+namespace llvm {
+
+
+/// Metafunction that determines whether the given type is either an
+/// integral type or an enumeration type, including enum classes.
+///
+/// Note that this accepts potentially more integral types than is_integral
+/// because it is based on being implicitly convertible to an integral type.
+/// Also note that enum classes aren't implicitly convertible to integral types,
+/// the value may therefore need to be explicitly converted before being used.
+template <typename T> class is_integral_or_enum {
+  using UnderlyingT = typename std::remove_reference<T>::type;
+
+public:
+  static const bool value =
+      !std::is_class<UnderlyingT>::value && // Filter conversion operators.
+      !std::is_pointer<UnderlyingT>::value &&
+      !std::is_floating_point<UnderlyingT>::value &&
+      (std::is_enum<UnderlyingT>::value ||
+       std::is_convertible<UnderlyingT, unsigned long long>::value);
+};
+
+/// If T is a pointer, just return it. If it is not, return T&.
+template<typename T, typename Enable = void>
+struct add_lvalue_reference_if_not_pointer { using type = T &; };
+
+template <typename T>
+struct add_lvalue_reference_if_not_pointer<
+    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
+  using type = T;
+};
+
+/// If T is a pointer to X, return a pointer to const X. If it is not,
+/// return const T.
+template<typename T, typename Enable = void>
+struct add_const_past_pointer { using type = const T; };
+
+template <typename T>
+struct add_const_past_pointer<
+    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
+  using type = const typename std::remove_pointer<T>::type *;
+};
+
+template <typename T, typename Enable = void>
+struct const_pointer_or_const_ref {
+  using type = const T &;
+};
+template <typename T>
+struct const_pointer_or_const_ref<
+    T, typename std::enable_if<std::is_pointer<T>::value>::type> {
+  using type = typename add_const_past_pointer<T>::type;
+};
+
+namespace detail {
+/// Internal utility to detect trivial copy construction.
+template<typename T> union copy_construction_triviality_helper {
+    T t;
+    copy_construction_triviality_helper() = default;
+    copy_construction_triviality_helper(const copy_construction_triviality_helper&) = default;
+    ~copy_construction_triviality_helper() = default;
+};
+/// Internal utility to detect trivial move construction.
+template<typename T> union move_construction_triviality_helper {
+    T t;
+    move_construction_triviality_helper() = default;
+    move_construction_triviality_helper(move_construction_triviality_helper&&) = default;
+    ~move_construction_triviality_helper() = default;
+};
+
+template<class T>
+union trivial_helper {
+    T t;
+};
+
+} // end namespace detail
+
+/// An implementation of `std::is_trivially_copy_constructible` since we have
+/// users with STLs that don't yet include it.
+template <typename T>
+struct is_trivially_copy_constructible
+    : std::is_copy_constructible<
+          ::opencombine::llvm::detail::copy_construction_triviality_helper<T>> {};
+template <typename T>
+struct is_trivially_copy_constructible<T &> : std::true_type {};
+template <typename T>
+struct is_trivially_copy_constructible<T &&> : std::false_type {};
+
+/// An implementation of `std::is_trivially_move_constructible` since we have
+/// users with STLs that don't yet include it.
+template <typename T>
+struct is_trivially_move_constructible
+    : std::is_move_constructible<
+          ::opencombine::llvm::detail::move_construction_triviality_helper<T>> {};
+template <typename T>
+struct is_trivially_move_constructible<T &> : std::true_type {};
+template <typename T>
+struct is_trivially_move_constructible<T &&> : std::true_type {};
+
+
+template <typename T>
+struct is_copy_assignable {
+  template<class F>
+    static auto get(F*) -> decltype(std::declval<F &>() = std::declval<const F &>(), std::true_type{});
+    static std::false_type get(...);
+    static constexpr bool value = decltype(get((T*)nullptr))::value;
+};
+
+template <typename T>
+struct is_move_assignable {
+  template<class F>
+    static auto get(F*) -> decltype(std::declval<F &>() = std::declval<F &&>(), std::true_type{});
+    static std::false_type get(...);
+    static constexpr bool value = decltype(get((T*)nullptr))::value;
+};
+
+
+// An implementation of `std::is_trivially_copyable` since STL version
+// is not equally supported by all compilers, especially GCC 4.9.
+// Uniform implementation of this trait is important for ABI compatibility
+// as it has an impact on SmallVector's ABI (among others).
+template <typename T>
+class is_trivially_copyable {
+
+  // copy constructors
+  static constexpr bool has_trivial_copy_constructor =
+      std::is_copy_constructible<detail::trivial_helper<T>>::value;
+  static constexpr bool has_deleted_copy_constructor =
+      !std::is_copy_constructible<T>::value;
+
+  // move constructors
+  static constexpr bool has_trivial_move_constructor =
+      std::is_move_constructible<detail::trivial_helper<T>>::value;
+  static constexpr bool has_deleted_move_constructor =
+      !std::is_move_constructible<T>::value;
+
+  // copy assign
+  static constexpr bool has_trivial_copy_assign =
+      is_copy_assignable<detail::trivial_helper<T>>::value;
+  static constexpr bool has_deleted_copy_assign =
+      !is_copy_assignable<T>::value;
+
+  // move assign
+  static constexpr bool has_trivial_move_assign =
+      is_move_assignable<detail::trivial_helper<T>>::value;
+  static constexpr bool has_deleted_move_assign =
+      !is_move_assignable<T>::value;
+
+  // destructor
+  static constexpr bool has_trivial_destructor =
+      std::is_destructible<detail::trivial_helper<T>>::value;
+
+  public:
+
+  static constexpr bool value =
+      has_trivial_destructor &&
+      (has_deleted_move_assign || has_trivial_move_assign) &&
+      (has_deleted_move_constructor || has_trivial_move_constructor) &&
+      (has_deleted_copy_assign || has_trivial_copy_assign) &&
+      (has_deleted_copy_constructor || has_trivial_copy_constructor);
+
+#ifdef HAVE_STD_IS_TRIVIALLY_COPYABLE
+  static_assert(value == std::is_trivially_copyable<T>::value,
+                "inconsistent behavior between llvm:: and std:: implementation of is_trivially_copyable");
+#endif
+};
+template <typename T>
+class is_trivially_copyable<T*> : public std::true_type {
+};
+
+
+} // end namespace llvm
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_LLVM_SUPPORT_TYPE_TRAITS_H
@@ -0,0 +1,78 @@
+//
+//  span.h
+//  
+//
+//  Created by Sergej Jaskiewicz on 30.10.2019.
+//
+
+#ifndef OPENCOMBINE_SPAN_H
+#define OPENCOMBINE_SPAN_H
+
+#include <cstddef>
+#include <type_traits>
+#include <iterator>
+
+namespace opencombine {
+
+// This is a very simplified implementation of std::span from C++20.
+// Not all compilers support it yet.
+template <typename T>
+class span {
+public:
+    using element_type = T;
+    using value_type = std::remove_cv<T>;
+    using index_type = size_t;
+    using differenc_type = ptrdiff_t;
+    using pointer = T*;
+    using const_pointer = const T*;
+    using reference = T&;
+    using const_reference = const T&;
+    using iterator = T*;
+    using const_iterator = const T*;
+    using reverse_iterator = std::reverse_iterator<iterator>;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+
+    constexpr span() noexcept: data_(nullptr), size_(0) {}
+    constexpr span(pointer ptr, index_type count): data_(ptr), size_(count) {}
+    constexpr span(pointer first, pointer last): span(first, last - first) {}
+    constexpr span(const span& other) noexcept = default;
+
+    constexpr span& operator=(const span& other) noexcept = default;
+
+    constexpr const_reference operator[](index_type index) const noexcept {
+        assert(index < size_);
+        return data_[index];
+    }
+
+    constexpr reference operator[](index_type index) noexcept {
+        assert(index < size_);
+        return data_[index];
+    }
+
+    const_pointer data() const noexcept { return data_; }
+
+    pointer data() noexcept { return data_; }
+
+    index_type size() const noexcept { return size_; }
+
+    const_iterator begin() const noexcept { return data_; }
+    iterator begin() noexcept { return data_; }
+
+    const_iterator end() const noexcept { return data_ + size_; }
+    iterator end() noexcept { return data_ + size_; }
+
+    bool operator==(const span& other) const {
+        return size_ == other.size_ && std::equal(begin(), end(), other.begin());
+    }
+
+    bool operator!=(const span& other) const {
+        return !operator==(other);
+    }
+private:
+    pointer data_;
+    index_type size_;
+};
+
+} // end namespace opencombine
+
+#endif /* OPENCOMBINE_SPAN_H */
@@ -0,0 +1,56 @@
+//
+//  string_view.h
+//  
+//
+//  Created by Sergej Jaskiewicz on 31.10.2019.
+//
+
+#ifndef OPENCOMBINE_STRING_VIEW_H
+#define OPENCOMBINE_STRING_VIEW_H
+
+#include <iterator>
+#include <cstddef>
+#include <cstring>
+
+namespace opencombine {
+
+// This is a very simplified implementation of std::string_view from C++17.
+// Not all compilers support it yet.
+struct string_view {
+    using traits_type = void;
+    using value_type = char;
+    using pointer = char*;
+    using const_pointer = const char*;
+    using reference = char&;
+    using const_reference = const char&;
+    using const_iterator = const char*;
+    using iterator = const_iterator;
+    using const_reverse_iterator = std::reverse_iterator<const_iterator>;
+    using reverse_iterator = const_reverse_iterator;
+    using size_type = size_t;
+    using difference_type = ptrdiff_t;
+
+    string_view() noexcept : string_view(nullptr, 0) {}
+    string_view(const string_view& other) noexcept = default;
+    string_view(const char* data, size_type size) : data_(data), size_(size) {}
+    string_view(const char* data) : string_view(data, strlen(data)) {}
+
+    string_view& operator=(const string_view& view) noexcept = default;
+
+    const_pointer data() const noexcept { return data_; }
+
+    constexpr size_type size() const noexcept { return size_; }
+
+    const_iterator begin() const noexcept { return data_; }
+    iterator begin() noexcept { return data_; }
+
+    const_iterator end() const noexcept { return data_ + size_; }
+    iterator end() noexcept { return data_ + size_; }
+private:
+    const_pointer data_;
+    size_type size_;
+};
+
+} // end namespace opencombine
+
+#endif /* OPENCOMBINE_STRING_VIEW_H */
@@ -0,0 +1,93 @@
+//===--- MetadataKind.def ---------------------------------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This is a file that enables metaprogramming with metadata kinds.
+//
+//===----------------------------------------------------------------------===//
+
+/// METADATAKIND(Name, Value)
+///   Represents a swift native runtime metadata kind. Name is the Name of the
+///   metadata kind and Value is the integral value used to identify the value.
+#ifndef METADATAKIND
+#define METADATAKIND(Name, Value)
+#endif
+
+/// ABSTRACTMETADATAKIND(Name, Start, End)
+///   Represents an abstraction categorization of a range of metadata kind
+///   values. Name is the identifier of the range and Start, End are the
+///   beginning and end of the range.
+#ifndef ABSTRACTMETADATAKIND
+#define ABSTRACTMETADATAKIND(Name, Start, End)
+#endif
+
+/// NOMINALTYPEMETADATAKIND(Name, Value)
+///   Represents the native metadata kind for a swift nominal type. Name is the
+///   name of the kind and Value is the integral value used to identify the
+///   value. Delegates to METADATAKIND if not defined.
+#ifndef NOMINALTYPEMETADATAKIND
+#define NOMINALTYPEMETADATAKIND(Name, Value) METADATAKIND(Name, Value)
+#endif
+
+/// A class type.
+NOMINALTYPEMETADATAKIND(Class, 0)
+
+/// A struct type.
+NOMINALTYPEMETADATAKIND(Struct, 0 | MetadataKindIsNonHeap)
+
+/// An enum type.
+/// If we add reference enums, that needs to go here.
+NOMINALTYPEMETADATAKIND(Enum, 1 | MetadataKindIsNonHeap)
+
+/// An optional type.
+NOMINALTYPEMETADATAKIND(Optional, 2 | MetadataKindIsNonHeap)
+
+/// A foreign class, such as a Core Foundation class.
+METADATAKIND(ForeignClass, 3 | MetadataKindIsNonHeap)
+
+/// A type whose value is not exposed in the metadata system.
+METADATAKIND(Opaque, 0 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// A tuple.
+METADATAKIND(Tuple, 1 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// A monomorphic function.
+METADATAKIND(Function, 2 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// An existential type.
+METADATAKIND(Existential, 3 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// A metatype.
+METADATAKIND(Metatype, 4 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// An ObjC class wrapper.
+METADATAKIND(ObjCClassWrapper, 5 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// An existential metatype.
+METADATAKIND(ExistentialMetatype, 6 | MetadataKindIsRuntimePrivate | MetadataKindIsNonHeap)
+
+/// A heap-allocated local variable using statically-generated metadata.
+METADATAKIND(HeapLocalVariable, 0 | MetadataKindIsNonType)
+
+/// A heap-allocated local variable using runtime-instantiated metadata.
+METADATAKIND(HeapGenericLocalVariable,
+             0 | MetadataKindIsNonType | MetadataKindIsRuntimePrivate)
+
+/// A native error object.
+METADATAKIND(ErrorObject,
+             1 | MetadataKindIsNonType | MetadataKindIsRuntimePrivate)
+
+// getEnumeratedMetadataKind assumes that all the enumerated values here
+// will be <= LastEnumeratedMetadataKind.
+
+#undef ABSTRACTMETADATAKIND
+#undef NOMINALTYPEMETADATAKIND
+#undef METADATAKIND
@@ -0,0 +1,395 @@
+//===--- TrailingObjects.h - Variable-length, Swift-ABI classes -*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This header is a fork of the LLVM TrailingObjects template. It has the
+/// additional constraint over llvm::TrailingObjects of having to maintain ABI
+/// stability across versions. The following documentation is copied from
+/// the original TrailingObjects implementation:
+///
+/// This header defines support for implementing classes that have
+/// some trailing object (or arrays of objects) appended to them. The
+/// main purpose is to make it obvious where this idiom is being used,
+/// and to make the usage more idiomatic and more difficult to get
+/// wrong.
+///
+/// The TrailingObject template abstracts away the reinterpret_cast,
+/// pointer arithmetic, and size calculations used for the allocation
+/// and access of appended arrays of objects, and takes care that they
+/// are all allocated at their required alignment. Additionally, it
+/// ensures that the base type is final -- deriving from a class that
+/// expects data appended immediately after it is typically not safe.
+///
+/// Users are expected to derive from this template, and provide
+/// numTrailingObjects implementations for each trailing type except
+/// the last, e.g. like this sample:
+///
+/// \code
+/// class VarLengthObj : private TrailingObjects<VarLengthObj, int, double> {
+///   friend TrailingObjects;
+///
+///   unsigned NumInts, NumDoubles;
+///   size_t numTrailingObjects(OverloadToken<int>) const { return NumInts; }
+///  };
+/// \endcode
+///
+/// You can access the appended arrays via 'getTrailingObjects', and
+/// determine the size needed for allocation via
+/// 'additionalSizeToAlloc' and 'totalSizeToAlloc'.
+///
+/// All the methods implemented by this class are are intended for use
+/// by the implementation of the class, not as part of its interface
+/// (thus, private inheritance is suggested).
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef OPENCOMBINE_TRAILINGOBJECTS_H
+#define OPENCOMBINE_TRAILINGOBJECTS_H
+
+#include "llvm/Support/AlignOf.h"
+#include "llvm/Support/Alignment.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/type_traits.h"
+#include <new>
+#include <type_traits>
+
+namespace opencombine {
+namespace swift {
+namespace ABI {
+
+namespace trailing_objects_internal {
+/// Helper template to calculate the max alignment requirement for a set of
+/// objects.
+template <typename First, typename... Rest> class AlignmentCalcHelper {
+private:
+  enum {
+    FirstAlignment = alignof(First),
+    RestAlignment = AlignmentCalcHelper<Rest...>::Alignment,
+  };
+
+public:
+  enum {
+    Alignment = FirstAlignment > RestAlignment ? FirstAlignment : RestAlignment
+  };
+};
+
+template <typename First> class AlignmentCalcHelper<First> {
+public:
+  enum { Alignment = alignof(First) };
+};
+
+/// The base class for TrailingObjects* classes.
+class TrailingObjectsBase {
+protected:
+  /// OverloadToken's purpose is to allow specifying function overloads
+  /// for different types, without actually taking the types as
+  /// parameters. (Necessary because member function templates cannot
+  /// be specialized, so overloads must be used instead of
+  /// specialization.)
+  template <typename T> struct OverloadToken {};
+};
+
+template <int Align>
+class TrailingObjectsAligner : public TrailingObjectsBase {};
+template <>
+class alignas(1) TrailingObjectsAligner<1> : public TrailingObjectsBase {};
+template <>
+class alignas(2) TrailingObjectsAligner<2> : public TrailingObjectsBase {};
+template <>
+class alignas(4) TrailingObjectsAligner<4> : public TrailingObjectsBase {};
+template <>
+class alignas(8) TrailingObjectsAligner<8> : public TrailingObjectsBase {};
+template <>
+class alignas(16) TrailingObjectsAligner<16> : public TrailingObjectsBase {};
+template <>
+class alignas(32) TrailingObjectsAligner<32> : public TrailingObjectsBase {};
+
+// Just a little helper for transforming a type pack into the same
+// number of a different type. e.g.:
+//   ExtractSecondType<Foo..., int>::type
+template <typename Ty1, typename Ty2> struct ExtractSecondType {
+  typedef Ty2 type;
+};
+
+// TrailingObjectsImpl is somewhat complicated, because it is a
+// recursively inheriting template, in order to handle the template
+// varargs. Each level of inheritance picks off a single trailing type
+// then recurses on the rest. The "Align", "BaseTy", and
+// "TopTrailingObj" arguments are passed through unchanged through the
+// recursion. "PrevTy" is, at each level, the type handled by the
+// level right above it.
+
+template <int Align, typename BaseTy, typename TopTrailingObj, typename PrevTy,
+          typename... MoreTys>
+class TrailingObjectsImpl {
+  // The main template definition is never used -- the two
+  // specializations cover all possibilities.
+};
+
+template <int Align, typename BaseTy, typename TopTrailingObj, typename PrevTy,
+          typename NextTy, typename... MoreTys>
+class TrailingObjectsImpl<Align, BaseTy, TopTrailingObj, PrevTy, NextTy,
+                          MoreTys...>
+    : public TrailingObjectsImpl<Align, BaseTy, TopTrailingObj, NextTy,
+                                 MoreTys...> {
+
+  typedef TrailingObjectsImpl<Align, BaseTy, TopTrailingObj, NextTy, MoreTys...>
+      ParentType;
+
+  struct RequiresRealignment {
+    static const bool value = alignof(PrevTy) < alignof(NextTy);
+  };
+
+  static constexpr bool requiresRealignment() {
+    return RequiresRealignment::value;
+  }
+
+protected:
+  // Ensure the inherited getTrailingObjectsImpl is not hidden.
+  using ParentType::getTrailingObjectsImpl;
+
+  // These two functions are helper functions for
+  // TrailingObjects::getTrailingObjects. They recurse to the left --
+  // the result for each type in the list of trailing types depends on
+  // the result of calling the function on the type to the
+  // left. However, the function for the type to the left is
+  // implemented by a *subclass* of this class, so we invoke it via
+  // the TopTrailingObj, which is, via the
+  // curiously-recurring-template-pattern, the most-derived type in
+  // this recursion, and thus, contains all the overloads.
+  static const NextTy *
+  getTrailingObjectsImpl(const BaseTy *Obj,
+                         TrailingObjectsBase::OverloadToken<NextTy>) {
+    auto *Ptr = TopTrailingObj::getTrailingObjectsImpl(
+                    Obj, TrailingObjectsBase::OverloadToken<PrevTy>()) +
+                TopTrailingObj::callNumTrailingObjects(
+                    Obj, TrailingObjectsBase::OverloadToken<PrevTy>());
+
+    if (requiresRealignment())
+      return reinterpret_cast<const NextTy *>(
+          llvm::alignAddr(Ptr, llvm::Align(alignof(NextTy))));
+    else
+      return reinterpret_cast<const NextTy *>(Ptr);
+  }
+
+  static NextTy *
+  getTrailingObjectsImpl(BaseTy *Obj,
+                         TrailingObjectsBase::OverloadToken<NextTy>) {
+    auto *Ptr = TopTrailingObj::getTrailingObjectsImpl(
+                    Obj, TrailingObjectsBase::OverloadToken<PrevTy>()) +
+                TopTrailingObj::callNumTrailingObjects(
+                    Obj, TrailingObjectsBase::OverloadToken<PrevTy>());
+
+    if (requiresRealignment())
+      return reinterpret_cast<NextTy *>(llvm::alignAddr(Ptr, alignof(NextTy)));
+    else
+      return reinterpret_cast<NextTy *>(Ptr);
+  }
+
+  // Helper function for TrailingObjects::additionalSizeToAlloc: this
+  // function recurses to superclasses, each of which requires one
+  // fewer size_t argument, and adds its own size.
+  static constexpr size_t additionalSizeToAllocImpl(
+      size_t SizeSoFar, size_t Count1,
+      typename ExtractSecondType<MoreTys, size_t>::type... MoreCounts) {
+    return ParentType::additionalSizeToAllocImpl(
+        (requiresRealignment() ? llvm::alignTo<alignof(NextTy)>(SizeSoFar)
+                               : SizeSoFar) +
+            sizeof(NextTy) * Count1,
+        MoreCounts...);
+  }
+};
+
+// The base case of the TrailingObjectsImpl inheritance recursion,
+// when there's no more trailing types.
+template <int Align, typename BaseTy, typename TopTrailingObj, typename PrevTy>
+class TrailingObjectsImpl<Align, BaseTy, TopTrailingObj, PrevTy>
+    : public TrailingObjectsAligner<Align> {
+protected:
+  // This is a dummy method, only here so the "using" doesn't fail --
+  // it will never be called, because this function recurses backwards
+  // up the inheritance chain to subclasses.
+  static void getTrailingObjectsImpl();
+
+  static constexpr size_t additionalSizeToAllocImpl(size_t SizeSoFar) {
+    return SizeSoFar;
+  }
+
+  template <bool CheckAlignment> static void verifyTrailingObjectsAlignment() {}
+};
+
+} // end namespace trailing_objects_internal
+
+// Finally, the main type defined in this file, the one intended for users...
+
+/// See the file comment for details on the usage of the
+/// TrailingObjects type.
+template <typename BaseTy, typename... TrailingTys>
+class TrailingObjects : private trailing_objects_internal::TrailingObjectsImpl<
+                            trailing_objects_internal::AlignmentCalcHelper<
+                                TrailingTys...>::Alignment,
+                            BaseTy, TrailingObjects<BaseTy, TrailingTys...>,
+                            BaseTy, TrailingTys...> {
+
+  template <int A, typename B, typename T, typename P, typename... M>
+  friend class trailing_objects_internal::TrailingObjectsImpl;
+
+  template <typename... Tys> class Foo {};
+
+  typedef trailing_objects_internal::TrailingObjectsImpl<
+      trailing_objects_internal::AlignmentCalcHelper<TrailingTys...>::Alignment,
+      BaseTy, TrailingObjects<BaseTy, TrailingTys...>, BaseTy, TrailingTys...>
+      ParentType;
+  using TrailingObjectsBase = trailing_objects_internal::TrailingObjectsBase;
+
+  using ParentType::getTrailingObjectsImpl;
+
+  // These two methods are the base of the recursion for this method.
+  static const BaseTy *
+  getTrailingObjectsImpl(const BaseTy *Obj,
+                         TrailingObjectsBase::OverloadToken<BaseTy>) {
+    return Obj;
+  }
+
+  static BaseTy *
+  getTrailingObjectsImpl(BaseTy *Obj,
+                         TrailingObjectsBase::OverloadToken<BaseTy>) {
+    return Obj;
+  }
+
+  // callNumTrailingObjects simply calls numTrailingObjects on the
+  // provided Obj -- except when the type being queried is BaseTy
+  // itself. There is always only one of the base object, so that case
+  // is handled here. (An additional benefit of indirecting through
+  // this function is that consumers only say "friend
+  // TrailingObjects", and thus, only this class itself can call the
+  // numTrailingObjects function.)
+  static size_t
+  callNumTrailingObjects(const BaseTy *Obj,
+                         TrailingObjectsBase::OverloadToken<BaseTy>) {
+    return 1;
+  }
+
+  template <typename T>
+  static size_t callNumTrailingObjects(const BaseTy *Obj,
+                                       TrailingObjectsBase::OverloadToken<T>) {
+    return Obj->numTrailingObjects(TrailingObjectsBase::OverloadToken<T>());
+  }
+
+public:
+  // Make this (privately inherited) member public.
+#ifndef _MSC_VER
+  using ParentType::OverloadToken;
+#else
+  // MSVC bug prevents the above from working, at least up through CL
+  // 19.10.24629.
+  template <typename T>
+  using OverloadToken = typename ParentType::template OverloadToken<T>;
+#endif
+
+  /// Returns a pointer to the trailing object array of the given type
+  /// (which must be one of those specified in the class template). The
+  /// array may have zero or more elements in it.
+  template <typename T> const T *getTrailingObjects() const {
+    // Forwards to an impl function with overloads, since member
+    // function templates can't be specialized.
+    return this->getTrailingObjectsImpl(
+        static_cast<const BaseTy *>(this),
+        TrailingObjectsBase::OverloadToken<T>());
+  }
+
+  /// Returns a pointer to the trailing object array of the given type
+  /// (which must be one of those specified in the class template). The
+  /// array may have zero or more elements in it.
+  template <typename T> T *getTrailingObjects() {
+    // Forwards to an impl function with overloads, since member
+    // function templates can't be specialized.
+    return this->getTrailingObjectsImpl(
+        static_cast<BaseTy *>(this), TrailingObjectsBase::OverloadToken<T>());
+  }
+
+  /// Returns the size of the trailing data, if an object were
+  /// allocated with the given counts (The counts are in the same order
+  /// as the template arguments). This does not include the size of the
+  /// base object.  The template arguments must be the same as those
+  /// used in the class; they are supplied here redundantly only so
+  /// that it's clear what the counts are counting in callers.
+  template <typename... Tys>
+  static constexpr typename std::enable_if<
+      std::is_same<Foo<TrailingTys...>, Foo<Tys...>>::value, size_t>::type
+  additionalSizeToAlloc(typename trailing_objects_internal::ExtractSecondType<
+                        TrailingTys, size_t>::type... Counts) {
+    return ParentType::additionalSizeToAllocImpl(0, Counts...);
+  }
+
+  /// Returns the total size of an object if it were allocated with the
+  /// given trailing object counts. This is the same as
+  /// additionalSizeToAlloc, except it *does* include the size of the base
+  /// object.
+  template <typename... Tys>
+  static constexpr typename std::enable_if<
+      std::is_same<Foo<TrailingTys...>, Foo<Tys...>>::value, size_t>::type
+  totalSizeToAlloc(typename trailing_objects_internal::ExtractSecondType<
+                   TrailingTys, size_t>::type... Counts) {
+    return sizeof(BaseTy) + ParentType::additionalSizeToAllocImpl(0, Counts...);
+  }
+
+  /// A type where its ::with_counts template member has a ::type member
+  /// suitable for use as uninitialized storage for an object with the given
+  /// trailing object counts. The template arguments are similar to those
+  /// of additionalSizeToAlloc.
+  ///
+  /// Use with FixedSizeStorageOwner, e.g.:
+  ///
+  /// \code{.cpp}
+  ///
+  /// MyObj::FixedSizeStorage<void *>::with_counts<1u>::type myStackObjStorage;
+  /// MyObj::FixedSizeStorageOwner
+  ///     myStackObjOwner(new ((void *)&myStackObjStorage) MyObj);
+  /// MyObj *const myStackObjPtr = myStackObjOwner.get();
+  ///
+  /// \endcode
+  template <typename... Tys> struct FixedSizeStorage {
+    template <size_t... Counts> struct with_counts {
+      enum { Size = totalSizeToAlloc<Tys...>(Counts...) };
+      using type = std::aligned_storage<Size, alignof(BaseTy)>;
+    };
+  };
+
+  /// A type that acts as the owner for an object placed into fixed storage.
+  class FixedSizeStorageOwner {
+  public:
+    FixedSizeStorageOwner(BaseTy *p) : p(p) {}
+    ~FixedSizeStorageOwner() {
+      assert(p && "FixedSizeStorageOwner owns null?");
+      p->~BaseTy();
+    }
+
+    BaseTy *get() { return p; }
+    const BaseTy *get() const { return p; }
+
+  private:
+    FixedSizeStorageOwner(const FixedSizeStorageOwner &) = delete;
+    FixedSizeStorageOwner(FixedSizeStorageOwner &&) = delete;
+    FixedSizeStorageOwner &operator=(const FixedSizeStorageOwner &) = delete;
+    FixedSizeStorageOwner &operator=(FixedSizeStorageOwner &&) = delete;
+
+    BaseTy *const p;
+  };
+};
+
+} // end namespace ABI
+} // end namespace swift
+} // end namespace opencombine
+
+#endif
@@ -0,0 +1,314 @@
+//===--- ValueWitness.def - Value witness x-macros --------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// X-macro definition file for value witness tables.
+//
+//===----------------------------------------------------------------------===//
+
+// This file is "parameterized" in the sense that exactly one of the
+// following macros *must* be defined:
+
+/// WANT_ALL_VALUE_WITNESSES
+///   Define this to expand all value witnesses, not just the ones from
+///   a specific category.
+#if defined(WANT_ALL_VALUE_WITNESSES)
+#undef WANT_ALL_VALUE_WITNESSES
+#define WANT_REQUIRED_VALUE_WITNESSES         1
+#define WANT_ENUM_VALUE_WITNESSES             1
+
+/// WANT_ONLY_REQUIRED_VALUE_WITNESSES
+///   Define this to expand only the required value witnesses.
+#elif defined(WANT_ONLY_REQUIRED_VALUE_WITNESSES)
+#undef WANT_ONLY_REQUIRED_VALUE_WITNESSES
+#define WANT_REQUIRED_VALUE_WITNESSES         1
+#define WANT_ENUM_VALUE_WITNESSES             0
+
+/// WANT_ONLY_ENUM_VALUE_WITNESSES
+///   Define this to expand only the enum value witnesses.
+#elif  defined(WANT_ONLY_ENUM_VALUE_WITNESSES)
+#undef  WANT_ONLY_ENUM_VALUE_WITNESSES
+#define WANT_REQUIRED_VALUE_WITNESSES         0
+#define WANT_ENUM_VALUE_WITNESSES             1
+
+/// WANT_REQUIRED_VALUE_WITNESSES
+/// WANT_ENUM_VALUE_WITNESSES
+///   Define all of these to control exactly what to expand.
+#else
+#if !defined(WANT_REQUIRED_VALUE_WITNESSES) || !defined(WANT_ENUM_VALUE_WITNESSES)
+#error failed to define a WANT macro; possible typo?
+#endif
+#endif
+
+/// VALUE_WITNESS(lowerId, upperId)
+///   A fallback called for value witnesses if either of DATA_VALUE_WITNESS or
+///   FUNCTION_VALUE_WITNESS is not defined.
+
+/// FUNCTION_VALUE_WITNESS(lowerId, upperId, returnType, paramTypeList)
+///   A function value witness.  Types will be defined in terms of the
+///   following macros:
+///     MUTABLE_VALUE_TYPE - a pointer to a mutable opaque value
+///     IMMUTABLE_VALUE_TYPE - a pointer to an immutable opaque value
+///     MUTABLE_BUFFER_TYPE - a pointer to a fixed-size value buffer
+///     IMMUTABLE_BUFFER_TYPE - a pointer to an immutable fixed-size buffer
+///     TYPE_TYPE - a pointer to type metadata
+///     SIZE_TYPE - StoredSize
+///     INT_TYPE - int
+///     UINT_TYPE - unsigned int
+///     VOID_TYPE - void
+///   Defaults to VALUE_WITNESS.
+///   FIXME: The 'copy' witnesses should be using immutable types but aren't.
+#ifndef FUNCTION_VALUE_WITNESS
+#define FUNCTION_VALUE_WITNESS(lowerId, upperId, returnType, paramTypes) \
+  VALUE_WITNESS(lowerId, upperId)
+#endif
+
+/// DATA_VALUE_WITNESS(lowerId, upperId, type)
+///   A non-function value witness.  Types are specified as for
+///   FUNCTION_VALUE_WITNESS
+///   Defaults to VALUE_WITNESS.
+#ifndef DATA_VALUE_WITNESS
+#define DATA_VALUE_WITNESS(lowerId, upperId, type) \
+  VALUE_WITNESS(lowerId, upperId)
+#endif
+
+/// Begin a range of value witnesses.  This will be expanded immediately
+/// after the first value in the range, whose ID will be upperId.
+/// Range expansions do not interact well with the use of WANT_ONLY_*.
+#ifndef BEGIN_VALUE_WITNESS_RANGE
+#define BEGIN_VALUE_WITNESS_RANGE(rangeId, upperId)
+#endif
+
+/// End a range of value witnesses.  This will be expanded immediately
+/// after the last value in the range, whose ID will be upperId.
+/// Range expansions do not interact well with the use of WANT_ONLY_*.
+#ifndef END_VALUE_WITNESS_RANGE
+#define END_VALUE_WITNESS_RANGE(rangeId, upperId)
+#endif
+
+#if WANT_REQUIRED_VALUE_WITNESSES
+
+///   T *(*initializeBufferWithCopyOfBuffer)(B *dest, B *src, M *self);
+/// Given an invalid buffer, initialize it as a copy of the
+/// object in the source buffer.
+FUNCTION_VALUE_WITNESS(initializeBufferWithCopyOfBuffer,
+                       InitializeBufferWithCopyOfBuffer,
+                       MUTABLE_VALUE_TYPE,
+                       (MUTABLE_BUFFER_TYPE, MUTABLE_BUFFER_TYPE, TYPE_TYPE))
+
+BEGIN_VALUE_WITNESS_RANGE(ValueWitness,
+                          InitializeBufferWithCopyOfBuffer)
+BEGIN_VALUE_WITNESS_RANGE(RequiredValueWitness,
+                          InitializeBufferWithCopyOfBuffer)
+BEGIN_VALUE_WITNESS_RANGE(RequiredValueWitnessFunction,
+                          InitializeBufferWithCopyOfBuffer)
+
+///   void (*destroy)(T *object, witness_t *self);
+///
+/// Given a valid object of this type, destroy it, leaving it as an
+/// invalid object.  This is useful when generically destroying
+/// an object which has been allocated in-line, such as an array,
+/// struct, or tuple element.
+FUNCTION_VALUE_WITNESS(destroy,
+                       Destroy,
+                       VOID_TYPE,
+                       (MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+///   T *(*initializeWithCopy)(T *dest, T *src, M *self);
+///
+/// Given an invalid object of this type, initialize it as a copy of
+/// the source object.  Returns the dest object.
+FUNCTION_VALUE_WITNESS(initializeWithCopy,
+                       InitializeWithCopy,
+                       MUTABLE_VALUE_TYPE,
+                       (MUTABLE_VALUE_TYPE, MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+///   T *(*assignWithCopy)(T *dest, T *src, M *self);
+///
+/// Given a valid object of this type, change it to be a copy of the
+/// source object.  Returns the dest object.
+FUNCTION_VALUE_WITNESS(assignWithCopy,
+                       AssignWithCopy,
+                       MUTABLE_VALUE_TYPE,
+                       (MUTABLE_VALUE_TYPE, MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+///   T *(*initializeWithTake)(T *dest, T *src, M *self);
+///
+/// Given an invalid object of this type, initialize it by taking
+/// the value of the source object.  The source object becomes
+/// invalid.  Returns the dest object.
+FUNCTION_VALUE_WITNESS(initializeWithTake,
+                       InitializeWithTake,
+                       MUTABLE_VALUE_TYPE,
+                       (MUTABLE_VALUE_TYPE, MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+///   T *(*assignWithTake)(T *dest, T *src, M *self);
+///
+/// Given a valid object of this type, change it to be a copy of the
+/// source object.  The source object becomes invalid.  Returns the
+/// dest object.
+FUNCTION_VALUE_WITNESS(assignWithTake,
+                       AssignWithTake,
+                       MUTABLE_VALUE_TYPE,
+                       (MUTABLE_VALUE_TYPE, MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+/// unsigned (*getEnumTagSinglePayload)(const T* enum, UINT_TYPE emptyCases,
+///                                     M *self);
+/// Given an instance of valid single payload enum with a payload of this
+/// witness table's type (e.g Optional<ThisType>) , get the tag of the enum.
+FUNCTION_VALUE_WITNESS(getEnumTagSinglePayload,
+                       GetEnumTagSinglePayload,
+                       UINT_TYPE,
+                       (IMMUTABLE_VALUE_TYPE, UINT_TYPE, TYPE_TYPE))
+
+/// void (*storeEnumTagSinglePayload)(T* enum, UINT_TYPE whichCase,
+///                                   UINT_TYPE emptyCases, M *self);
+/// Given uninitialized memory for an instance of a single payload enum with a
+/// payload of this witness table's type (e.g Optional<ThisType>), store the
+/// tag.
+FUNCTION_VALUE_WITNESS(storeEnumTagSinglePayload,
+                       StoreEnumTagSinglePayload,
+                       VOID_TYPE,
+                       (MUTABLE_VALUE_TYPE, UINT_TYPE, UINT_TYPE, TYPE_TYPE))
+
+END_VALUE_WITNESS_RANGE(RequiredValueWitnessFunction,
+                        StoreEnumTagSinglePayload)
+
+///   SIZE_TYPE size;
+///
+/// The required storage size of a single object of this type.
+DATA_VALUE_WITNESS(size,
+                   Size,
+                   SIZE_TYPE)
+
+BEGIN_VALUE_WITNESS_RANGE(TypeLayoutWitness,
+                          Size)
+
+BEGIN_VALUE_WITNESS_RANGE(RequiredTypeLayoutWitness,
+                          Size)
+
+///   SIZE_TYPE stride;
+///
+/// The required size per element of an array of this type. It is at least
+/// one, even for zero-sized types, like the empty tuple.
+DATA_VALUE_WITNESS(stride,
+                   Stride,
+                   SIZE_TYPE)
+
+
+///   UINT_TYPE flags;
+///
+/// The ValueWitnessAlignmentMask bits represent the required
+/// alignment of the first byte of an object of this type, expressed
+/// as a mask of the low bits that must not be set in the pointer.
+/// This representation can be easily converted to the 'alignof'
+/// result by merely adding 1, but it is more directly useful for
+/// performing dynamic structure layouts, and it grants an
+/// additional bit of precision in a compact field without needing
+/// to switch to an exponent representation.
+///
+/// The ValueWitnessIsNonPOD bit is set if the type is not POD.
+///
+/// The ValueWitnessIsNonInline bit is set if the type cannot be
+/// represented in a fixed-size buffer or if it is not bitwise takable.
+///
+/// The ExtraInhabitantsMask bits represent the number of "extra inhabitants"
+/// of the bit representation of the value that do not form valid values of
+/// the type.
+///
+/// The Enum_HasSpareBits bit is set if the type's binary representation
+/// has unused bits.
+///
+/// The HasEnumWitnesses bit is set if the type is an enum type.
+DATA_VALUE_WITNESS(flags,
+                   Flags,
+                   UINT_TYPE)
+
+///   UINT_TYPE extraInhabitantCount;
+///
+/// The number of extra inhabitants in the type.
+DATA_VALUE_WITNESS(extraInhabitantCount,
+                   ExtraInhabitantCount,
+                   UINT_TYPE)
+
+END_VALUE_WITNESS_RANGE(RequiredTypeLayoutWitness,
+                        ExtraInhabitantCount)
+
+END_VALUE_WITNESS_RANGE(RequiredValueWitness,
+                        ExtraInhabitantCount)
+
+END_VALUE_WITNESS_RANGE(TypeLayoutWitness,
+                        ExtraInhabitantCount)
+
+#endif /* WANT_REQUIRED_VALUE_WITNESSES */
+
+#if WANT_ENUM_VALUE_WITNESSES
+
+// The following value witnesses are conditionally present if the witnessed
+// type is an enum.
+
+///   unsigned (*getEnumTag)(T *obj, M *self);
+///
+/// Given a valid object of this enum type, extracts the tag value indicating
+/// which case of the enum is inhabited. Returned values are in the range
+/// [0..NumElements-1].
+FUNCTION_VALUE_WITNESS(getEnumTag,
+                       GetEnumTag,
+                       INT_TYPE,
+                       (IMMUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+BEGIN_VALUE_WITNESS_RANGE(EnumValueWitness,
+                          GetEnumTag)
+
+///   void (*destructiveProjectEnumData)(T *obj, M *self);
+/// Given a valid object of this enum type, destructively extracts the
+/// associated payload.
+FUNCTION_VALUE_WITNESS(destructiveProjectEnumData,
+                       DestructiveProjectEnumData,
+                       VOID_TYPE,
+                       (MUTABLE_VALUE_TYPE, TYPE_TYPE))
+
+///   void (*destructiveInjectEnumTag)(T *obj, unsigned tag, M *self);
+/// Given an enum case tag and a valid object of case's payload type,
+/// destructively inserts the tag into the payload. The given tag value
+/// must be in the range [-ElementsWithPayload..ElementsWithNoPayload-1].
+FUNCTION_VALUE_WITNESS(destructiveInjectEnumTag,
+                       DestructiveInjectEnumTag,
+                       VOID_TYPE,
+                       (MUTABLE_VALUE_TYPE, UINT_TYPE, TYPE_TYPE))
+
+END_VALUE_WITNESS_RANGE(EnumValueWitness,
+                        DestructiveInjectEnumTag)
+
+END_VALUE_WITNESS_RANGE(ValueWitness,
+                        DestructiveInjectEnumTag)
+
+#endif /* WANT_ENUM_VALUE_WITNESSES */
+
+#undef MUTABLE_VALUE_TYPE
+#undef IMMUTABLE_VALUE_TYPE
+#undef MUTABLE_BUFFER_TYPE
+#undef IMMUTABLE_BUFFER_TYPE
+#undef TYPE_TYPE
+#undef SIZE_TYPE
+#undef INT_TYPE
+#undef VOID_TYPE
+
+#undef END_VALUE_WITNESS_RANGE
+#undef BEGIN_VALUE_WITNESS_RANGE
+#undef DATA_VALUE_WITNESS
+#undef FUNCTION_VALUE_WITNESS
+#undef VALUE_WITNESS
+#undef ENUM_VALUE_WITNESS
+#undef NON_REQUIRED_VALUE_WITNESS
+#undef REQUIRED_VALUE_WITNESS
+#undef WANT_ENUM_VALUE_WITNESSES
+#undef WANT_REQUIRED_VALUE_WITNESSES
@@ -0,0 +1,129 @@
+//===--- FlagSet.h - Helper class for opaque flag types ---------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the FlagSet template, a class which makes it easier to
+// define opaque flag types.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_SWIFT_BASIC_FLAGSET_H
+#define OPENCOMBINE_SWIFT_BASIC_FLAGSET_H
+
+#include <type_traits>
+#include <assert.h>
+
+namespace opencombine {
+namespace swift {
+
+/// A template designed to simplify the task of defining a wrapper type
+/// for a flags bitfield.
+///
+/// Unfortunately, this doesn't currently support functional-style
+/// building patterns, which means this can't practically be used for
+/// types that need to be used in constant expressions.
+template <typename IntType>
+class FlagSet {
+  static_assert(std::is_integral<IntType>::value,
+                "storage type for FlagSet must be an integral type");
+  IntType Bits;
+
+protected:
+  template <unsigned BitWidth>
+  static constexpr IntType lowMaskFor() {
+    return IntType((1 << BitWidth) - 1);
+  }
+
+  template <unsigned FirstBit, unsigned BitWidth = 1>
+  static constexpr IntType maskFor() {
+    return lowMaskFor<BitWidth>() << FirstBit;
+  }
+
+  constexpr FlagSet(IntType bits = 0) : Bits(bits) {}
+
+  /// Read a single-bit flag.
+  template <unsigned Bit>
+  bool getFlag() const {
+    return Bits & maskFor<Bit>();
+  }
+
+  /// Set a single-bit flag.
+  template <unsigned Bit>
+  void setFlag(bool value) {
+    if (value) {
+      Bits |= maskFor<Bit>();
+    } else {
+      Bits &= ~maskFor<Bit>();
+    }
+  }
+
+  /// Read a multi-bit field.
+  template <unsigned FirstBit, unsigned BitWidth, typename FieldType = IntType>
+  FieldType getField() const {
+    return FieldType((Bits >> FirstBit) & lowMaskFor<BitWidth>());
+  }
+
+  /// Assign to a multi-bit field.
+  template <unsigned FirstBit, unsigned BitWidth, typename FieldType = IntType>
+  void setField(typename std::enable_if<true, FieldType>::type value) {
+    // Note that we suppress template argument deduction for FieldType.
+    assert(IntType(value) <= lowMaskFor<BitWidth>() && "value out of range");
+    Bits = (Bits & ~maskFor<FirstBit, BitWidth>())
+         | (IntType(value) << FirstBit);
+  }
+
+  // A convenient macro for defining a getter and setter for a flag.
+  // Intended to be used in the body of a subclass of FlagSet.
+#define FLAGSET_DEFINE_FLAG_ACCESSORS(BIT, GETTER, SETTER) \
+  bool GETTER() const {                                    \
+    return this->template getFlag<BIT>();                  \
+  }                                                        \
+  void SETTER(bool value) {                                \
+    this->template setFlag<BIT>(value);                    \
+  }
+
+  // A convenient macro for defining a getter and setter for a field.
+  // Intended to be used in the body of a subclass of FlagSet.
+#define FLAGSET_DEFINE_FIELD_ACCESSORS(BIT, WIDTH, TYPE, GETTER, SETTER) \
+  TYPE GETTER() const {                                                  \
+    return this->template getField<BIT, WIDTH, TYPE>();                  \
+  }                                                                      \
+  void SETTER(TYPE value) {                                              \
+    this->template setField<BIT, WIDTH, TYPE>(value);                    \
+  }
+
+  // A convenient macro to expose equality operators.
+  // These can't be provided directly by FlagSet because that would allow
+  // different flag sets to be compared if they happen to have the same
+  // underlying type.
+#define FLAGSET_DEFINE_EQUALITY(TYPENAME)                                \
+  friend bool operator==(TYPENAME lhs, TYPENAME rhs) {                   \
+    return lhs.getOpaqueValue() == rhs.getOpaqueValue();                 \
+  }                                                                      \
+  friend bool operator!=(TYPENAME lhs, TYPENAME rhs) {                   \
+    return lhs.getOpaqueValue() != rhs.getOpaqueValue();                 \
+  }
+
+public:
+  /// Get the bits as an opaque integer value.
+  IntType getOpaqueValue() const {
+    return Bits;
+  }
+};
+
+} // end namespace swift
+} // end namespace opencombine
+
+#endif
@@ -0,0 +1,568 @@
+//===--- RelativePointer.h - Relative Pointer Support -----------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///
+/// Some data structures emitted by the Swift compiler use relative indirect
+/// addresses in order to minimize startup cost for a process. By referring to
+/// the offset of the global offset table entry for a symbol, instead of
+/// directly referring to the symbol, compiler-emitted data structures avoid
+/// requiring unnecessary relocation at dynamic linking time. This header
+/// contains types to help dereference these relative addresses.
+///
+/// Theory of references to objects
+/// -------------------------------
+///
+/// A reference can be absolute or relative:
+///
+///   - An absolute reference is a pointer to the object.
+///
+///   - A relative reference is a (signed) offset from the address of the
+///     reference to the address of its direct referent.
+///
+/// A relative reference can be direct, indirect, or symbolic.
+///
+/// In a direct reference, the direct referent is simply the target object.
+/// Generally, a statically-emitted relative reference can only be direct
+/// if it can be resolved to a constant offset by the linker, because loaders
+/// do not support forming relative references.  This means that either the
+/// reference and object must lie within the same linkage unit or the
+/// difference must be computed at runtime by code.
+///
+/// In a symbolic reference, the direct referent is a string holding the symbol
+/// name of the object.  A relative reference can only be symbolic if the
+/// object actually has a symbol at runtime, which may require exporting
+/// many internal symbols that would otherwise be strippable.
+///
+/// In an indirect reference, the direct referent is a variable holding an
+/// absolute reference to the object.  An indirect relative reference may
+/// refer to an arbitrary symbol, be it anonymous within the linkage unit
+/// or completely external to it, but it requires the introduction of an
+/// intermediate absolute reference that requires load-time initialization.
+/// However, this initialization can be shared among all indirect references
+/// within the linkage unit, and the linker will generally place all such
+/// references adjacent to one another to improve load-time locality.
+///
+/// A reference can be made a dynamic union of more than one of these options.
+/// This allows the compiler/linker to use a direct reference when possible
+/// and a less-efficient option where required.  However, it also requires
+/// the cases to be dynamically distinguished.  This can be done by setting
+/// a low bit of the offset, as long as the difference between the direct
+/// referent's address and the reference is a multiple of 2.  This works well
+/// for "indirectable" references because most objects are known to be
+/// well-aligned, and the cases that aren't (chiefly functions and strings)
+/// rarely need the flexibility of this kind of reference.  It does not
+/// work quite as well for "possibly symbolic" references because C strings
+/// are not naturally aligned, and making them aligned generally requires
+/// moving them out of the linker's ordinary string section; however, it's
+/// still workable.
+///
+/// Finally, a relative reference can be near or far.  A near reference
+/// is potentially smaller, but it requires the direct referent to lie
+/// within a certain distance of the reference, even if dynamically
+/// initialized.
+///
+/// In Swift, we always prefer to use a near direct relative reference
+/// when it is possible to do so: that is, when the relationship is always
+/// between two global objects emitted in the same linkage unit, and there
+/// is no compatibility constraint requiring the use of an absolute reference.
+///
+/// When more flexibility is required, there are several options:
+///
+///   1. Use an absolute reference.  Size penalty on 64-bit.  Requires
+///      load-time work.
+///
+///   2. Use a far direct relative reference.  Size penalty on 64-bit.
+///      Requires load-time work when object is outside linkage unit.
+///      Generally not directly supported by loaders.
+///
+///   3. Use an always-indirect relative reference.  Size penalty of one
+///      pointer (shared).  Requires load-time work even when object is
+///      within linkage unit.
+///
+///   4. Use a near indirectable relative reference.  Size penalty of one
+///      pointer (shared) when reference exceeds range.  Runtime / code-size
+///      penalty on access.  Requires load-time work (shared) only when
+///      object is outside linkage unit.
+///
+///   5. Use a far indirectable relative reference.  Size penalty on 64-bit.
+///      Size penalty of one pointer (shared) when reference exceeds range
+///      and is initialized statically.  Runtime / code-size penalty on access.
+///      Requires load-time work (shared) only when object is outside linkage
+///      unit.
+///
+///   6. Use a near or far symbolic relative reference.  No load-time work.
+///      Severe runtime penalty on access.  Requires custom logic to statically
+///      optimize.  Requires emission of symbol for target even if private
+///      to linkage unit.
+///
+///   7. Use a near or far direct-or-symbolic relative reference.  No
+///      load-time work.  Severe runtime penalty on access if object is
+///      outside of linkage unit.  Requires custom logic to statically optimize.
+///
+/// In general, it's our preference in Swift to use option #4 when there
+/// is no possibility of initializing the reference dynamically and option #5
+/// when there is.  This is because it is infeasible to actually share the
+/// memory for the intermediate absolute reference when it must be allocated
+/// dynamically.
+///
+/// Symbolic references are an interesting idea that we have not yet made
+/// use of.  They may be acceptable in reflective metadata cases where it
+/// is desirable to heavily bias towards never using the metadata.  However,
+/// they're only profitable if there wasn't any other indirect reference
+/// to the target, and it is likely that their optimal use requires a more
+/// intelligent toolchain from top to bottom.
+///
+/// Note that the cost of load-time work also includes a binary-size penalty
+/// to store the loader metadata necessary to perform that work.  Therefore
+/// it is better to avoid it even when there are dynamic optimizations in
+/// place to skip the work itself.
+///
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_SWIFT_BASIC_RELATIVEPOINTER_H
+#define OPENCOMBINE_SWIFT_BASIC_RELATIVEPOINTER_H
+
+#include <cstdint>
+
+namespace opencombine {
+namespace swift {
+
+namespace detail {
+
+/// Apply a relative offset to a base pointer. The offset is applied to the base
+/// pointer using sign-extended, wrapping arithmetic.
+template<typename BasePtrTy, typename Offset>
+static inline uintptr_t applyRelativeOffset(BasePtrTy *basePtr, Offset offset) {
+  static_assert(std::is_integral<Offset>::value &&
+                std::is_signed<Offset>::value,
+                "offset type should be signed integer");
+
+  auto base = reinterpret_cast<uintptr_t>(basePtr);
+  // We want to do wrapping arithmetic, but with a sign-extended
+  // offset. To do this in C, we need to do signed promotion to get
+  // the sign extension, but we need to perform arithmetic on unsigned values,
+  // since signed overflow is undefined behavior.
+  auto extendOffset = (uintptr_t)(intptr_t)offset;
+  return base + extendOffset;
+}
+
+/// Measure the relative offset between two pointers. This measures
+/// (referent - base) using wrapping arithmetic. The result is truncated if
+/// Offset is smaller than a pointer, with an assertion that the
+/// pre-truncation result is a sign extension of the truncated result.
+template<typename Offset, typename A, typename B>
+static inline Offset measureRelativeOffset(A *referent, B *base) {
+  static_assert(std::is_integral<Offset>::value &&
+                std::is_signed<Offset>::value,
+                "offset type should be signed integer");
+
+  auto distance = (uintptr_t)referent - (uintptr_t)base;
+  // Truncate as unsigned, then wrap around to signed.
+  auto truncatedDistance =
+    (Offset)(typename std::make_unsigned<Offset>::type)distance;
+  // Assert that the truncation didn't discard any non-sign-extended bits.
+  assert((intptr_t)truncatedDistance == (intptr_t)distance
+         && "pointers are too far apart to fit in offset type");
+  return truncatedDistance;
+}
+
+} // namespace detail
+
+/// A relative reference to an object stored in memory. The reference may be
+/// direct or indirect, and uses the low bit of the (assumed at least
+/// 2-byte-aligned) pointer to differentiate.
+template<typename ValueTy, bool Nullable = false, typename Offset = int32_t>
+class RelativeIndirectPointer {
+private:
+  static_assert(std::is_integral<Offset>::value &&
+                std::is_signed<Offset>::value,
+                "offset type should be signed integer");
+
+  /// The relative offset of the pointer's memory from the `this` pointer.
+  /// This is an indirect reference.
+  Offset RelativeOffset;
+
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeIndirectPointer() = delete;
+  RelativeIndirectPointer(RelativeIndirectPointer &&) = delete;
+  RelativeIndirectPointer(const RelativeIndirectPointer &) = delete;
+  RelativeIndirectPointer &operator=(RelativeIndirectPointer &&)
+    = delete;
+  RelativeIndirectPointer &operator=(const RelativeIndirectPointer &)
+    = delete;
+
+public:
+  const ValueTy *get() const & {
+    // Check for null.
+    if (Nullable && RelativeOffset == 0)
+      return nullptr;
+
+    uintptr_t address = detail::applyRelativeOffset(this, RelativeOffset);
+    return *reinterpret_cast<const ValueTy * const *>(address);
+  }
+
+  /// A zero relative offset encodes a null reference.
+  bool isNull() const & {
+    return RelativeOffset == 0;
+  }
+
+  operator const ValueTy* () const & {
+    return get();
+  }
+
+  const ValueTy *operator->() const & {
+    return get();
+  }
+};
+
+/// A relative reference to an object stored in memory. The reference may be
+/// direct or indirect, and uses the low bit of the (assumed at least
+/// 2-byte-aligned) pointer to differentiate.
+template<typename ValueTy, bool Nullable = false, typename Offset = int32_t>
+class RelativeIndirectablePointer {
+private:
+  static_assert(std::is_integral<Offset>::value &&
+                std::is_signed<Offset>::value,
+                "offset type should be signed integer");
+
+  /// The relative offset of the pointer's memory from the `this` pointer.
+  /// If the low bit is clear, this is a direct reference; otherwise, it is
+  /// an indirect reference.
+  Offset RelativeOffsetPlusIndirect;
+
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeIndirectablePointer() = delete;
+  RelativeIndirectablePointer(RelativeIndirectablePointer &&) = delete;
+  RelativeIndirectablePointer(const RelativeIndirectablePointer &) = delete;
+  RelativeIndirectablePointer &operator=(RelativeIndirectablePointer &&)
+    = delete;
+  RelativeIndirectablePointer &operator=(const RelativeIndirectablePointer &)
+    = delete;
+
+public:
+  /// Allow construction and reassignment from an absolute pointer.
+  /// These always produce a direct relative offset.
+  RelativeIndirectablePointer(ValueTy *absolute)
+  : RelativeOffsetPlusIndirect(
+      Nullable && absolute == nullptr
+        ? 0
+        : detail::measureRelativeOffset<Offset>(absolute, this)) {
+    if (!Nullable)
+      assert(absolute != nullptr &&
+             "constructing non-nullable relative pointer from null");
+  }
+
+  RelativeIndirectablePointer &operator=(ValueTy *absolute) & {
+    if (!Nullable)
+      assert(absolute != nullptr &&
+             "constructing non-nullable relative pointer from null");
+
+    RelativeOffsetPlusIndirect = Nullable && absolute == nullptr
+      ? 0
+      : detail::measureRelativeOffset<Offset>(absolute, this);
+    return *this;
+  }
+
+  const ValueTy *get() const & {
+    static_assert(alignof(ValueTy) >= 2 && alignof(Offset) >= 2,
+                  "alignment of value and offset must be at least 2 to "
+                  "make room for indirectable flag");
+
+    // Check for null.
+    if (Nullable && RelativeOffsetPlusIndirect == 0)
+      return nullptr;
+
+    Offset offsetPlusIndirect = RelativeOffsetPlusIndirect;
+    uintptr_t address = detail::applyRelativeOffset(this,
+                                                    offsetPlusIndirect & ~1);
+
+    // If the low bit is set, then this is an indirect address. Otherwise,
+    // it's direct.
+    if (offsetPlusIndirect & 1) {
+      return *reinterpret_cast<const ValueTy * const *>(address);
+    } else {
+      return reinterpret_cast<const ValueTy *>(address);
+    }
+  }
+
+  /// A zero relative offset encodes a null reference.
+  bool isNull() const & {
+    return RelativeOffsetPlusIndirect == 0;
+  }
+
+  operator const ValueTy* () const & {
+    return get();
+  }
+
+  const ValueTy *operator->() const & {
+    return get();
+  }
+};
+
+/// A relative reference to an aligned object stored in memory. The reference
+/// may be direct or indirect, and uses the low bit of the (assumed at least
+/// 2-byte-aligned) pointer to differentiate. The remaining low bits store
+/// an additional tiny integer value.
+template<typename ValueTy, typename IntTy, bool Nullable = false,
+         typename Offset = int32_t>
+class RelativeIndirectablePointerIntPair {
+private:
+  static_assert(std::is_integral<Offset>::value &&
+                std::is_signed<Offset>::value,
+                "offset type should be signed integer");
+
+  /// The relative offset of the pointer's memory from the `this` pointer.
+  /// If the low bit is clear, this is a direct reference; otherwise, it is
+  /// an indirect reference.
+  Offset RelativeOffsetPlusIndirectAndInt;
+
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeIndirectablePointerIntPair() = delete;
+  RelativeIndirectablePointerIntPair(
+                           RelativeIndirectablePointerIntPair &&) = delete;
+  RelativeIndirectablePointerIntPair(
+                      const RelativeIndirectablePointerIntPair &) = delete;
+  RelativeIndirectablePointerIntPair& operator=(
+                           RelativeIndirectablePointerIntPair &&) = delete;
+  RelativeIndirectablePointerIntPair &operator=(
+                      const RelativeIndirectablePointerIntPair &) = delete;
+
+  // Retrieve the mask for the stored integer value.
+  static Offset getIntMask() {
+    return (alignof(Offset) - 1) & ~(Offset)0x01;
+  }
+
+public:
+  const ValueTy *getPointer() const & {
+    static_assert(alignof(ValueTy) >= 2 && alignof(Offset) >= 2,
+                  "alignment of value and offset must be at least 2 to "
+                  "make room for indirectable flag");
+
+    Offset offset = (RelativeOffsetPlusIndirectAndInt & ~getIntMask());
+
+    // Check for null.
+    if (Nullable && offset == 0)
+      return nullptr;
+
+    Offset offsetPlusIndirect = offset;
+    uintptr_t address = detail::applyRelativeOffset(this,
+                                                    offsetPlusIndirect & ~1);
+
+    // If the low bit is set, then this is an indirect address. Otherwise,
+    // it's direct.
+    if (offsetPlusIndirect & 1) {
+      return *reinterpret_cast<const ValueTy * const *>(address);
+    } else {
+      return reinterpret_cast<const ValueTy *>(address);
+    }
+  }
+
+  /// A zero relative offset encodes a null reference.
+  bool isNull() const & {
+    Offset offset = (RelativeOffsetPlusIndirectAndInt & ~getIntMask());
+    return offset == 0;
+  }
+
+  IntTy getInt() const & {
+    return IntTy((RelativeOffsetPlusIndirectAndInt & getIntMask()) >> 1);
+  }
+};
+
+/// A relative reference to a function, intended to reference private metadata
+/// functions for the current executable or dynamic library image from
+/// position-independent constant data.
+template<typename T, bool Nullable, typename Offset>
+class RelativeDirectPointerImpl {
+private:
+  /// The relative offset of the function's entry point from *this.
+  Offset RelativeOffset;
+
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeDirectPointerImpl() = delete;
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeDirectPointerImpl(RelativeDirectPointerImpl &&) = delete;
+  RelativeDirectPointerImpl(const RelativeDirectPointerImpl &) = delete;
+  RelativeDirectPointerImpl &operator=(RelativeDirectPointerImpl &&)
+    = delete;
+  RelativeDirectPointerImpl &operator=(const RelativeDirectPointerImpl &)
+    = delete;
+
+
+public:
+  using ValueTy = T;
+  using PointerTy = T*;
+
+  // Allow construction and reassignment from an absolute pointer.
+  RelativeDirectPointerImpl(PointerTy absolute)
+    : RelativeOffset(Nullable && absolute == nullptr
+                       ? 0
+                       : detail::measureRelativeOffset<Offset>(absolute, this))
+  {
+    if (!Nullable)
+      assert(absolute != nullptr &&
+             "constructing non-nullable relative pointer from null");
+  }
+  explicit constexpr RelativeDirectPointerImpl(std::nullptr_t)
+  : RelativeOffset (0) {
+    static_assert(Nullable, "can't construct non-nullable pointer from null");
+  }
+
+  RelativeDirectPointerImpl &operator=(PointerTy absolute) & {
+    if (!Nullable)
+      assert(absolute != nullptr &&
+             "constructing non-nullable relative pointer from null");
+    RelativeOffset = Nullable && absolute == nullptr
+      ? 0
+      : detail::measureRelativeOffset<Offset>(absolute, this);
+    return *this;
+  }
+
+  PointerTy get() const & {
+    // Check for null.
+    if (Nullable && RelativeOffset == 0)
+      return nullptr;
+
+    // The value is addressed relative to `this`.
+    uintptr_t absolute = detail::applyRelativeOffset(this, RelativeOffset);
+    return reinterpret_cast<PointerTy>(absolute);
+  }
+
+  /// A zero relative offset encodes a null reference.
+  bool isNull() const & {
+    return RelativeOffset == 0;
+  }
+};
+
+/// A direct relative reference to an object.
+template<typename T, bool Nullable = true, typename Offset = int32_t>
+class RelativeDirectPointer :
+  private RelativeDirectPointerImpl<T, Nullable, Offset>
+{
+  using super = RelativeDirectPointerImpl<T, Nullable, Offset>;
+public:
+  using super::get;
+  using super::super;
+
+  RelativeDirectPointer &operator=(T *absolute) & {
+    super::operator=(absolute);
+    return *this;
+  }
+
+  operator typename super::PointerTy() const & {
+    return this->get();
+  }
+
+  const typename super::ValueTy *operator->() const & {
+    return this->get();
+  }
+
+  using super::isNull;
+};
+
+/// A specialization of RelativeDirectPointer for function pointers,
+/// allowing for calls.
+template<typename RetTy, typename...ArgTy, bool Nullable, typename Offset>
+class RelativeDirectPointer<RetTy (ArgTy...), Nullable, Offset> :
+  private RelativeDirectPointerImpl<RetTy (ArgTy...), Nullable, Offset>
+{
+  using super = RelativeDirectPointerImpl<RetTy (ArgTy...), Nullable, Offset>;
+public:
+  using super::get;
+  using super::super;
+
+  RelativeDirectPointer &operator=(RetTy (*absolute)(ArgTy...)) & {
+    super::operator=(absolute);
+    return *this;
+  }
+
+  operator typename super::PointerTy() const & {
+    return this->get();
+  }
+
+  RetTy operator()(ArgTy...arg) const {
+    return this->get()(std::forward<ArgTy>(arg)...);
+  }
+
+  using super::isNull;
+};
+
+/// A direct relative reference to an aligned object, with an additional
+/// tiny integer value crammed into its low bits.
+template<typename PointeeTy, typename IntTy, bool Nullable = false,
+         typename Offset = int32_t>
+class RelativeDirectPointerIntPair {
+  Offset RelativeOffsetPlusInt;
+
+  /// RelativePointers should appear in statically-generated metadata. They
+  /// shouldn't be constructed or copied.
+  RelativeDirectPointerIntPair() = delete;
+  RelativeDirectPointerIntPair(RelativeDirectPointerIntPair &&) = delete;
+  RelativeDirectPointerIntPair(const RelativeDirectPointerIntPair &) = delete;
+  RelativeDirectPointerIntPair &operator=(RelativeDirectPointerIntPair &&)
+    = delete;
+  RelativeDirectPointerIntPair &operator=(const RelativeDirectPointerIntPair&)
+    = delete;
+
+  static Offset getMask() {
+    return alignof(Offset) - 1;
+  }
+
+public:
+  using ValueTy = PointeeTy;
+  using PointerTy = PointeeTy*;
+
+  PointerTy getPointer() const & {
+    Offset offset = (RelativeOffsetPlusInt & ~getMask());
+
+    // Check for null.
+    if (Nullable && offset == 0)
+      return nullptr;
+
+    // The value is addressed relative to `this`.
+    uintptr_t absolute = detail::applyRelativeOffset(this, offset);
+    return reinterpret_cast<PointerTy>(absolute);
+  }
+
+  IntTy getInt() const & {
+    return IntTy(RelativeOffsetPlusInt & getMask());
+  }
+
+  Offset getOpaqueValue() const & {
+    return RelativeOffsetPlusInt;
+  }
+};
+
+// Type aliases for "far" relative pointers, which need to be able to reach
+// across the full address space instead of only across a single small-code-
+// model image.
+
+template<typename T, bool Nullable = false>
+using FarRelativeIndirectablePointer =
+  RelativeIndirectablePointer<T, Nullable, intptr_t>;
+
+template<typename T, bool Nullable = false>
+using FarRelativeDirectPointer = RelativeDirectPointer<T, Nullable, intptr_t>;
+
+} // end namespace swift
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_SWIFT_BASIC_RELATIVEPOINTER_H
@@ -0,0 +1,44 @@
+//===--- Demangle.h - Interface to Swift symbol demangling ------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// This file is the public API of the demangler library.
+// Tools which use the demangler library (like lldb) must include this - and
+// only this - header file.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Some declarations have been removed.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_SWIFT_DEMANGLING_DEMANGLE_H
+#define OPENCOMBINE_SWIFT_DEMANGLING_DEMANGLE_H
+
+#include <memory>
+#include <string>
+#include <cassert>
+#include <cstdint>
+#include "stl_polyfill/string_view.h"
+
+namespace opencombine {
+namespace swift {
+namespace Demangle {
+/// Form a StringRef around the mangled name starting at base, if the name may
+/// contain symbolic references.
+string_view makeSymbolicMangledNameStringRef(const char *base);
+
+} // end namespace Demangle
+} // end namespace swift
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_SWIFT_DEMANGLING_DEMANGLE_H
@@ -0,0 +1,664 @@
+//===--- Records.h - Swift Type Reflection Records --------------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Implements the structures of type reflection records.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Some declarations have been removed.
+// - The swift namespace is wrapped in the opencombine namespace.
+
+#ifndef OPENCOMBINE_SWIFT_REFLECTION_RECORDS_H
+#define OPENCOMBINE_SWIFT_REFLECTION_RECORDS_H
+
+#include "swift/Basic/RelativePointer.h"
+#include "swift/Demangling/Demangle.h"
+#include "stl_polyfill/string_view.h"
+#include "stl_polyfill/span.h"
+
+namespace opencombine {
+namespace swift {
+
+const uint16_t SWIFT_REFLECTION_METADATA_VERSION = 3; // superclass field
+
+namespace reflection {
+
+// Field records describe the type of a single stored property or case member
+// of a class, struct or enum.
+class FieldRecordFlags {
+  using int_type = uint32_t;
+  enum : int_type {
+    // Is this an indirect enum case?
+    IsIndirectCase = 0x1,
+    
+    // Is this a mutable `var` property?
+    IsVar = 0x2,
+  };
+  int_type Data = 0;
+
+public:
+  bool isIndirectCase() const {
+    return (Data & IsIndirectCase) == IsIndirectCase;
+  }
+
+  bool isVar() const {
+    return (Data & IsVar) == IsVar;
+  }
+
+  void setIsIndirectCase(bool IndirectCase=true) {
+    if (IndirectCase)
+      Data |= IsIndirectCase;
+    else
+      Data &= ~IsIndirectCase;
+  }
+
+  void setIsVar(bool Var=true) {
+    if (Var)
+      Data |= IsVar;
+    else
+      Data &= ~IsVar;
+  }
+
+  int_type getRawValue() const {
+    return Data;
+  }
+};
+
+class FieldRecord {
+  const FieldRecordFlags Flags;
+  const RelativeDirectPointer<const char> MangledTypeName;
+  const RelativeDirectPointer<const char> FieldName;
+
+public:
+  FieldRecord() = delete;
+
+  bool hasMangledTypeName() const {
+    return MangledTypeName;
+  }
+
+  string_view getMangledTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char *)((uintptr_t)MangledTypeName.get() + Offset));
+  }
+
+  string_view getFieldName(uintptr_t Offset)  const {
+    if (FieldName)
+      return (const char *)((uintptr_t)FieldName.get() + Offset);
+    return "";
+  }
+
+  bool isIndirectCase() const {
+    return Flags.isIndirectCase();
+  }
+};
+
+struct FieldRecordIterator {
+  const FieldRecord *Cur;
+  const FieldRecord * const End;
+
+  FieldRecordIterator(const FieldRecord *Cur, const FieldRecord * const End)
+    : Cur(Cur), End(End) {}
+
+  const FieldRecord &operator*() const {
+    return *Cur;
+  }
+
+  const FieldRecord *operator->() const {
+    return Cur;
+  }
+
+  FieldRecordIterator &operator++() {
+    ++Cur;
+    return *this;
+  }
+
+  bool operator==(const FieldRecordIterator &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(const FieldRecordIterator &other) const {
+    return !(*this == other);
+  }
+};
+
+enum class FieldDescriptorKind : uint16_t {
+  // Swift nominal types.
+  Struct,
+  Class,
+  Enum,
+
+  // Fixed-size multi-payload enums have a special descriptor format that
+  // encodes spare bits.
+  //
+  // FIXME: Actually implement this. For now, a descriptor with this kind
+  // just means we also have a builtin descriptor from which we get the
+  // size and alignment.
+  MultiPayloadEnum,
+
+  // A Swift opaque protocol. There are no fields, just a record for the
+  // type itself.
+  Protocol,
+
+  // A Swift class-bound protocol.
+  ClassProtocol,
+
+  // An Objective-C protocol, which may be imported or defined in Swift.
+  ObjCProtocol,
+
+  // An Objective-C class, which may be imported or defined in Swift.
+  // In the former case, field type metadata is not emitted, and
+  // must be obtained from the Objective-C runtime.
+  ObjCClass
+};
+
+// Field descriptors contain a collection of field records for a single
+// class, struct or enum declaration.
+class FieldDescriptor {
+  const FieldRecord *getFieldRecordBuffer() const {
+    return reinterpret_cast<const FieldRecord *>(this + 1);
+  }
+
+  const RelativeDirectPointer<const char> MangledTypeName;
+  const RelativeDirectPointer<const char> Superclass;
+
+public:
+  FieldDescriptor() = delete;
+
+  const FieldDescriptorKind Kind;
+  const uint16_t FieldRecordSize;
+  const uint32_t NumFields;
+
+  using const_iterator = FieldRecordIterator;
+
+  bool isEnum() const {
+    return (Kind == FieldDescriptorKind::Enum ||
+            Kind == FieldDescriptorKind::MultiPayloadEnum);
+  }
+
+  bool isClass() const {
+    return (Kind == FieldDescriptorKind::Class ||
+            Kind == FieldDescriptorKind::ObjCClass);
+  }
+
+  bool isProtocol() const {
+    return (Kind == FieldDescriptorKind::Protocol ||
+            Kind == FieldDescriptorKind::ClassProtocol ||
+            Kind == FieldDescriptorKind::ObjCProtocol);
+  }
+
+  bool isStruct() const {
+    return Kind == FieldDescriptorKind::Struct;
+  }
+
+  const_iterator begin() const {
+    auto Begin = getFieldRecordBuffer();
+    auto End = Begin + NumFields;
+    return const_iterator { Begin, End };
+  }
+
+  const_iterator end() const {
+    auto Begin = getFieldRecordBuffer();
+    auto End = Begin + NumFields;
+    return const_iterator { End, End };
+  }
+
+  span<const FieldRecord> getFields() const {
+    return {getFieldRecordBuffer(), NumFields};
+  }
+
+  bool hasMangledTypeName() const {
+    return MangledTypeName;
+  }
+
+  string_view getMangledTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char *)((uintptr_t)MangledTypeName.get() + Offset));
+  }
+
+  bool hasSuperclass() const {
+    return Superclass;
+  }
+
+  string_view getSuperclass(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)Superclass.get() + Offset));
+  }
+};
+
+class FieldDescriptorIterator
+  : public std::iterator<std::forward_iterator_tag, FieldDescriptor> {
+public:
+  const void *Cur;
+  const void * const End;
+  FieldDescriptorIterator(const void *Cur, const void * const End)
+    : Cur(Cur), End(End) {}
+
+  const FieldDescriptor &operator*() const {
+    return *reinterpret_cast<const FieldDescriptor *>(Cur);
+  }
+
+  const FieldDescriptor *operator->() const {
+    return reinterpret_cast<const FieldDescriptor *>(Cur);
+  }
+
+  FieldDescriptorIterator &operator++() {
+    const auto &FR = this->operator*();
+    const void *Next = reinterpret_cast<const char *>(Cur)
+      + sizeof(FieldDescriptor) + FR.NumFields * FR.FieldRecordSize;
+    Cur = Next;
+    return *this;
+  }
+
+  bool operator==(FieldDescriptorIterator const &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(FieldDescriptorIterator const &other) const {
+    return !(*this == other);
+  }
+};
+
+// Associated type records describe the mapping from an associated
+// type to the type witness of a conformance.
+class AssociatedTypeRecord {
+  const RelativeDirectPointer<const char> Name;
+  const RelativeDirectPointer<const char> SubstitutedTypeName;
+
+public:
+  string_view getName(uintptr_t Offset) const {
+    return (const char*)((uintptr_t)Name.get() + Offset);
+  }
+
+  string_view getMangledSubstitutedTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)SubstitutedTypeName.get() + Offset));
+  }
+};
+
+struct AssociatedTypeRecordIterator {
+  const AssociatedTypeRecord *Cur;
+  const AssociatedTypeRecord * const End;
+
+  AssociatedTypeRecordIterator()
+    : Cur(nullptr), End(nullptr) {}
+
+  AssociatedTypeRecordIterator(const AssociatedTypeRecord *Cur,
+                               const AssociatedTypeRecord * const End)
+    : Cur(Cur), End(End) {}
+
+  const AssociatedTypeRecord &operator*() const {
+    return *Cur;
+  }
+
+  const AssociatedTypeRecord *operator->() const {
+    return Cur;
+  }
+
+  AssociatedTypeRecordIterator &operator++() {
+    ++Cur;
+    return *this;
+  }
+
+  AssociatedTypeRecordIterator
+  operator=(const AssociatedTypeRecordIterator &Other) {
+    return { Other.Cur, Other.End };
+  }
+
+  bool operator==(const AssociatedTypeRecordIterator &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(const AssociatedTypeRecordIterator &other) const {
+    return !(*this == other);
+  }
+
+  operator bool() const {
+    return Cur && End;
+  }
+};
+
+// An associated type descriptor contains a collection of associated
+// type records for a conformance.
+struct AssociatedTypeDescriptor {
+private:
+  const RelativeDirectPointer<const char> ConformingTypeName;
+  const RelativeDirectPointer<const char> ProtocolTypeName;
+public:
+
+  uint32_t NumAssociatedTypes;
+  uint32_t AssociatedTypeRecordSize;
+
+  const AssociatedTypeRecord *getAssociatedTypeRecordBuffer() const {
+    return reinterpret_cast<const AssociatedTypeRecord *>(this + 1);
+  }
+
+  using const_iterator = AssociatedTypeRecordIterator;
+
+  const_iterator begin() const {
+    auto Begin = getAssociatedTypeRecordBuffer();
+    auto End = Begin + NumAssociatedTypes;
+    return const_iterator { Begin, End };
+  }
+
+  const_iterator end() const {
+    auto Begin = getAssociatedTypeRecordBuffer();
+    auto End = Begin + NumAssociatedTypes;
+    return const_iterator { End, End };
+  }
+
+  string_view getMangledProtocolTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)ProtocolTypeName.get() + Offset));
+  }
+
+  string_view getMangledConformingTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)ConformingTypeName.get() + Offset));
+  }
+};
+
+class AssociatedTypeIterator
+  : public std::iterator<std::forward_iterator_tag, AssociatedTypeDescriptor> {
+public:
+  const void *Cur;
+  const void * const End;
+  AssociatedTypeIterator(const void *Cur, const void * const End)
+    : Cur(Cur), End(End) {}
+
+  const AssociatedTypeDescriptor &operator*() const {
+    return *reinterpret_cast<const AssociatedTypeDescriptor *>(Cur);
+  }
+
+  const AssociatedTypeDescriptor *operator->() const {
+    return reinterpret_cast<const AssociatedTypeDescriptor *>(Cur);
+  }
+
+  AssociatedTypeIterator &operator++() {
+    const auto &ATR = this->operator*();
+    size_t Size = sizeof(AssociatedTypeDescriptor) +
+      ATR.NumAssociatedTypes * ATR.AssociatedTypeRecordSize;
+    const void *Next = reinterpret_cast<const char *>(Cur) + Size;
+    Cur = Next;
+    return *this;
+  }
+
+  bool operator==(AssociatedTypeIterator const &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(AssociatedTypeIterator const &other) const {
+    return !(*this == other);
+  }
+};
+
+// Builtin type records describe basic layout information about
+// any builtin types referenced from the other sections.
+class BuiltinTypeDescriptor {
+  const RelativeDirectPointer<const char> TypeName;
+
+public:
+  uint32_t Size;
+
+  // - Least significant 16 bits are the alignment.
+  // - Bit 16 is 'bitwise takable'.
+  // - Remaining bits are reserved.
+  uint32_t AlignmentAndFlags;
+
+  uint32_t Stride;
+  uint32_t NumExtraInhabitants;
+
+  bool isBitwiseTakable() const {
+    return (AlignmentAndFlags >> 16) & 1;
+  }
+
+  uint32_t getAlignment() const {
+    return AlignmentAndFlags & 0xffff;
+  }
+
+  bool hasMangledTypeName() const {
+    return TypeName;
+  }
+
+  string_view getMangledTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)TypeName.get() + Offset));
+  }
+};
+
+class BuiltinTypeDescriptorIterator
+  : public std::iterator<std::forward_iterator_tag, BuiltinTypeDescriptor> {
+public:
+  const void *Cur;
+  const void * const End;
+  BuiltinTypeDescriptorIterator(const void *Cur, const void * const End)
+    : Cur(Cur), End(End) {}
+
+  const BuiltinTypeDescriptor &operator*() const {
+    return *reinterpret_cast<const BuiltinTypeDescriptor *>(Cur);
+  }
+
+  const BuiltinTypeDescriptor *operator->() const {
+    return reinterpret_cast<const BuiltinTypeDescriptor *>(Cur);;
+  }
+
+  BuiltinTypeDescriptorIterator &operator++() {
+    const void *Next = reinterpret_cast<const char *>(Cur)
+      + sizeof(BuiltinTypeDescriptor);
+    Cur = Next;
+    return *this;
+  }
+
+  bool operator==(BuiltinTypeDescriptorIterator const &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(BuiltinTypeDescriptorIterator const &other) const {
+    return !(*this == other);
+  }
+};
+
+class CaptureTypeRecord {
+  const RelativeDirectPointer<const char> MangledTypeName;
+
+public:
+  CaptureTypeRecord() = delete;
+
+  bool hasMangledTypeName() const {
+    return MangledTypeName;
+  }
+
+  string_view getMangledTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)MangledTypeName.get() + Offset));
+  }
+};
+
+struct CaptureTypeRecordIterator {
+  const CaptureTypeRecord *Cur;
+  const CaptureTypeRecord * const End;
+
+  CaptureTypeRecordIterator(const CaptureTypeRecord *Cur,
+                            const CaptureTypeRecord * const End)
+    : Cur(Cur), End(End) {}
+
+  const CaptureTypeRecord &operator*() const {
+    return *Cur;
+  }
+
+  const CaptureTypeRecord *operator->() const {
+    return Cur;
+  }
+
+  CaptureTypeRecordIterator &operator++() {
+    ++Cur;
+    return *this;
+  }
+
+  bool operator==(const CaptureTypeRecordIterator &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(const CaptureTypeRecordIterator &other) const {
+    return !(*this == other);
+  }
+};
+
+class MetadataSourceRecord {
+  const RelativeDirectPointer<const char> MangledTypeName;
+  const RelativeDirectPointer<const char> MangledMetadataSource;
+
+public:
+  MetadataSourceRecord() = delete;
+
+  bool hasMangledTypeName() const {
+    return MangledTypeName;
+  }
+
+  string_view getMangledTypeName(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)MangledTypeName.get() + Offset));
+  }
+
+  bool hasMangledMetadataSource() const {
+    return MangledMetadataSource;
+  }
+
+  string_view getMangledMetadataSource(uintptr_t Offset) const {
+    return Demangle::makeSymbolicMangledNameStringRef(
+      (const char*)((uintptr_t)MangledMetadataSource.get() + Offset));
+  }
+};
+
+struct MetadataSourceRecordIterator {
+  const MetadataSourceRecord *Cur;
+  const MetadataSourceRecord * const End;
+
+  MetadataSourceRecordIterator(const MetadataSourceRecord *Cur,
+                            const MetadataSourceRecord * const End)
+    : Cur(Cur), End(End) {}
+
+  const MetadataSourceRecord &operator*() const {
+    return *Cur;
+  }
+
+  const MetadataSourceRecord *operator->() const {
+    return Cur;
+  }
+
+  MetadataSourceRecordIterator &operator++() {
+    ++Cur;
+    return *this;
+  }
+
+  bool operator==(const MetadataSourceRecordIterator &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(const MetadataSourceRecordIterator &other) const {
+    return !(*this == other);
+  }
+};
+
+// Capture descriptors describe the layout of a closure context
+// object. Unlike nominal types, the generic substitutions for a
+// closure context come from the object, and not the metadata.
+class CaptureDescriptor {
+  const CaptureTypeRecord *getCaptureTypeRecordBuffer() const {
+    return reinterpret_cast<const CaptureTypeRecord *>(this + 1);
+  }
+
+  const MetadataSourceRecord *getMetadataSourceRecordBuffer() const {
+    return reinterpret_cast<const MetadataSourceRecord *>(capture_end().End);
+  }
+
+public:
+  /// The number of captures in the closure and the number of typerefs that
+  /// immediately follow this struct.
+  uint32_t NumCaptureTypes;
+
+  /// The number of sources of metadata available in the MetadataSourceMap
+  /// directly following the list of capture's typerefs.
+  uint32_t NumMetadataSources;
+
+  /// The number of items in the NecessaryBindings structure at the head of
+  /// the closure.
+  uint32_t NumBindings;
+
+  using const_iterator = FieldRecordIterator;
+
+  CaptureTypeRecordIterator capture_begin() const {
+    auto Begin = getCaptureTypeRecordBuffer();
+    auto End = Begin + NumCaptureTypes;
+    return { Begin, End };
+  }
+
+  CaptureTypeRecordIterator capture_end() const {
+    auto Begin = getCaptureTypeRecordBuffer();
+    auto End = Begin + NumCaptureTypes;
+    return { End, End };
+  }
+
+  MetadataSourceRecordIterator source_begin() const {
+    auto Begin = getMetadataSourceRecordBuffer();
+    auto End = Begin + NumMetadataSources;
+    return { Begin, End };
+  }
+
+  MetadataSourceRecordIterator source_end() const {
+    auto Begin = getMetadataSourceRecordBuffer();
+    auto End = Begin + NumMetadataSources;
+    return { End, End };
+  }
+};
+
+class CaptureDescriptorIterator
+  : public std::iterator<std::forward_iterator_tag, CaptureDescriptor> {
+public:
+  const void *Cur;
+  const void * const End;
+  CaptureDescriptorIterator(const void *Cur, const void * const End)
+    : Cur(Cur), End(End) {}
+
+  const CaptureDescriptor &operator*() const {
+    return *reinterpret_cast<const CaptureDescriptor *>(Cur);
+  }
+
+  const CaptureDescriptor *operator->() const {
+    return reinterpret_cast<const CaptureDescriptor *>(Cur);
+  }
+
+  CaptureDescriptorIterator &operator++() {
+    const auto &CR = this->operator*();
+    const void *Next = reinterpret_cast<const char *>(Cur)
+      + sizeof(CaptureDescriptor)
+      + CR.NumCaptureTypes * sizeof(CaptureTypeRecord)
+      + CR.NumMetadataSources * sizeof(MetadataSourceRecord);
+    Cur = Next;
+    return *this;
+  }
+
+  bool operator==(CaptureDescriptorIterator const &other) const {
+    return Cur == other.Cur && End == other.End;
+  }
+
+  bool operator!=(CaptureDescriptorIterator const &other) const {
+    return !(*this == other);
+  }
+};
+
+} // end namespace reflection
+} // end namespace swift
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_SWIFT_REFLECTION_RECORDS_H
@@ -0,0 +1,73 @@
+//===--- Config.h - Swift Language Platform Configuration -------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Definitions of common interest in Swift.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// Some macros have been renamed or removed.
+
+#ifndef OPENCOMBINE_SWIFT_RUNTIME_CONFIG_H
+#define OPENCOMBINE_SWIFT_RUNTIME_CONFIG_H
+
+#ifdef __GNUC__
+#define OPENCOMBINE_SWIFT_RUNTIME_ATTRIBUTE_NORETURN __attribute__((noreturn))
+#elif defined(_MSC_VER)
+#define OPENCOMBINE_SWIFT_RUNTIME_ATTRIBUTE_NORETURN __declspec(noreturn)
+#else
+#define OPENCOMBINE_SWIFT_RUNTIME_ATTRIBUTE_NORETURN
+#endif
+
+/// Does the current Swift platform support "unbridged" interoperation
+/// with Objective-C?  If so, the implementations of various types must
+/// implicitly handle Objective-C pointers.
+///
+/// Apple platforms support this by default.
+#ifndef OPENCOMBINE_SWIFT_OBJC_INTEROP
+#ifdef __APPLE__
+#define OPENCOMBINE_SWIFT_OBJC_INTEROP 1
+#else
+#define OPENCOMBINE_SWIFT_OBJC_INTEROP 0
+#endif
+#endif
+
+/// Which bits in the class metadata are used to distinguish Swift classes
+/// from ObjC classes?
+#ifndef OPENCOMBINE_SWIFT_CLASS_IS_SWIFT_MASK
+
+# if !defined(__APPLE__)
+// Non-Apple platforms always use 1.
+#  define OPENCOMBINE_SWIFT_CLASS_IS_SWIFT_MASK 1ULL
+# else
+// Apple platforms with Swift in the OS (a.k.a. post-ABI-stability) use 2.
+namespace opencombine { extern unsigned long long classIsSwiftMask; }
+# define OPENCOMBINE_SWIFT_CLASS_IS_SWIFT_MASK classIsSwiftMask
+# endif
+#endif
+
+// Define mappings for calling conventions.
+
+#if __has_attribute(swiftcall)
+# define OPENCOMBINE_SWIFT_CALLING_CONVENTION __attribute__((swiftcall))
+# define OPENCOMBINE_SWIFT_CONTEXT __attribute__((swift_context))
+# define OPENCOMBINE_SWIFT_ERROR_RESULT __attribute__((swift_error_result))
+# define OPENCOMBINE_SWIFT_INDIRECT_RESULT __attribute__((swift_indirect_result))
+#else
+# define OPENCOMBINE_SWIFT_CALLING_CONVENTION
+# define OPENCOMBINE_SWIFT_CONTEXT
+# define OPENCOMBINE_SWIFT_ERROR_RESULT
+# define OPENCOMBINE_SWIFT_INDIRECT_RESULT
+#endif
+
+#endif // OPENCOMBINE_SWIFT_RUNTIME_CONFIG_H
@@ -0,0 +1,46 @@
+//===--- Metadata.h - Swift Language ABI Metadata Support -------*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+// Swift runtime support for generating and uniquing metadata.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef OPENCOMBINE_SWIFT_RUNTIME_METADATA_H
+#define OPENCOMBINE_SWIFT_RUNTIME_METADATA_H
+
+#include "swift/ABI/Metadata.h"
+#include "swift/Reflection/Records.h"
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Some declarations have been removed.
+// - The swift namespace is wrapped in the opencombine namespace.
+// - Replaced ArrayRef and StringRef with span and string_view
+
+namespace opencombine {
+namespace swift {
+
+/// Compute the bounds of class metadata with a resilient superclass.
+ClassMetadataBounds getResilientMetadataBounds(
+                                           const ClassDescriptor *descriptor);
+int32_t getResilientImmediateMembersOffset(const ClassDescriptor *descriptor);
+
+#if OPENCOMBINE_SWIFT_OBJC_INTEROP
+
+extern "C" Class swift_getInitializedObjCClass(Class c);
+
+#endif
+
+} // end namespace swift
+} // end namespace opencombine
+
+#endif // OPENCOMBINE_SWIFT_RUNTIME_METADATA_H
@@ -0,0 +1,37 @@
+//===--- Unreachable.h - Implements swift_runtime_unreachable ---*- C++ -*-===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2017 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file defines swift_runtime_unreachable, an LLVM-independent
+//  implementation of llvm_unreachable.
+//
+//===----------------------------------------------------------------------===//
+
+// MODIFICATION NOTE:
+// This file has been modified for the OpenCombine open source project.
+// - Symbols have been prefix with the 'opencombine' prefix.
+
+#ifndef OPENCOMBINE_SWIFT_RUNTIME_UNREACHABLE_H
+#define OPENCOMBINE_SWIFT_RUNTIME_UNREACHABLE_H
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include "swift/Runtime/Config.h"
+
+OPENCOMBINE_SWIFT_RUNTIME_ATTRIBUTE_NORETURN
+inline static void opencombine_swift_runtime_unreachable(const char *msg) {
+  assert(false && msg);
+  (void)msg;
+  abort();
+}
+
+#endif // OPENCOMBINE_SWIFT_RUNTIME_UNREACHABLE_H
@@ -10,6 +10,7 @@
 /// Subscriber implementations can use this type to provide a “cancellation token” that
 /// makes it possible for a caller to cancel a publisher, but not to use the
 /// `Subscription` object to request items.
+/// An AnyCancellable instance automatically calls `cancel()` when deinitialized.
 public final class AnyCancellable: Cancellable, Hashable {

    private var _cancel: (() -> Void)?
@@ -5,6 +5,17 @@
 //  Created by Sergej Jaskiewicz on 10.06.2019.
 //

+extension Publisher {
+
+    /// Wraps this publisher with a type eraser.
+    ///
+    /// Use `eraseToAnyPublisher()` to expose an instance of `AnyPublisher` to
+    /// the downstream subscriber, rather than this publisher’s actual type.
+    public func eraseToAnyPublisher() -> AnyPublisher<Output, Failure> {
+        return .init(self)
+    }
+}
+
 /// A type-erasing publisher.
 ///
 /// Use `AnyPublisher` to wrap a publisher whose type has details you don’t want to expose
@@ -13,7 +24,6 @@ public struct AnyPublisher<Output, Failure: Error>
  : CustomStringConvertible,
    CustomPlaygroundDisplayConvertible
 {
-
    @usableFromInline
    internal let box: PublisherBoxBase<Output, Failure>

@@ -47,8 +57,8 @@ extension AnyPublisher: Publisher {
    ///     - subscriber: The subscriber to attach to this `Publisher`.
    ///                   once attached it can begin to receive values.
    @inlinable
-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Output == SubscriberType.Input, Failure == SubscriberType.Failure
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Output == Downstream.Input, Failure == Downstream.Failure
    {
        box.subscribe(subscriber)
    }
@@ -62,11 +72,11 @@ internal class PublisherBoxBase<Output, Failure: Error>: Publisher {
    @inlinable
    internal init() {}

-    @inlinable
-    internal func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Failure == SubscriberType.Failure, Output == SubscriberType.Input
+    @usableFromInline
+    internal func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Failure == Downstream.Failure, Output == Downstream.Input
    {
-        fatalError()
+        abstractMethod()
    }
 }

@@ -84,8 +94,8 @@ internal final class PublisherBox<PublisherType: Publisher>
    }

    @inlinable
-    override internal func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Failure == SubscriberType.Failure, Output == SubscriberType.Input
+    override internal func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Failure == Downstream.Failure, Output == Downstream.Input
    {
        base.subscribe(subscriber)
    }
@@ -137,17 +137,17 @@ internal class AnySubscriberBase<Input, Failure: Error>: Subscriber {

    @usableFromInline
    internal func receive(subscription: Subscription) {
-        fatalError()
+        abstractMethod()
    }

    @usableFromInline
    internal func receive(_ input: Input) -> Subscribers.Demand {
-        fatalError()
+        abstractMethod()
    }

    @usableFromInline
    internal func receive(completion: Subscribers.Completion<Failure>) {
-        fatalError()
+        abstractMethod()
    }
 }

@@ -222,52 +222,3 @@ internal final class ClosureBasedAnySubscriber<Input, Failure: Error>
        receiveCompletionThunk(completion)
    }
 }
-
-internal final class SubjectSubscriber<Downstream: Subject>
-    : Subscriber,
-      CustomStringConvertible,
-      CustomReflectable,
-      Subscription
-{
-    internal var downstreamSubject: Downstream?
-    internal var upstreamSubscription: Subscription?
-
-    internal init(_ parent: Downstream) {
-        self.downstreamSubject = parent
-    }
-
-    internal func receive(subscription: Subscription) {
-        guard upstreamSubscription == nil else { return }
-        upstreamSubscription = subscription
-        downstreamSubject?.send(subscription: self)
-    }
-
-    internal func receive(_ input: Downstream.Output) -> Subscribers.Demand {
-        downstreamSubject?.send(input)
-        return .none
-    }
-
-    internal func receive(completion: Subscribers.Completion<Downstream.Failure>) {
-        downstreamSubject?.send(completion: completion)
-    }
-
-    internal var description: String { return "Subject" }
-
-    internal var customMirror: Mirror {
-        let children: [(label: String?, value: Any)] = [
-            (label: "downstreamSubject", value: downstreamSubject as Any),
-            (label: "upstreamSubscription", value: upstreamSubscription as Any)
-        ]
-        return Mirror(self, children: children)
-    }
-
-    internal func request(_ demand: Subscribers.Demand) {
-        upstreamSubscription?.request(demand)
-    }
-
-    internal func cancel() {
-        upstreamSubscription?.cancel()
-        upstreamSubscription = nil
-        downstreamSubject = nil
-    }
-}
@@ -5,35 +5,21 @@
 //  Created by Sergej Jaskiewicz on 10.06.2019.
 //

+import func COpenCombineHelpers.nextCombineIdentifier
+
 public struct CombineIdentifier: Hashable, CustomStringConvertible {

-    @usableFromInline
-    internal static var _counter: UInt = 0
+    private let value: UInt64

-    @usableFromInline
-    internal static var _counterLock = Lock(recursive: false)
-
-    @usableFromInline
-    internal let _id: UInt
-
-    @inlinable
    public init() {
-
-        var id: UInt = 0
-
-        CombineIdentifier._counterLock.do {
-            id = CombineIdentifier._counter
-            CombineIdentifier._counter += 1
-        }
-
-        _id = id
+        value = nextCombineIdentifier()
    }

    public init(_ obj: AnyObject) {
-        _id = UInt(bitPattern: ObjectIdentifier(obj))
+        value = UInt64(UInt(bitPattern: ObjectIdentifier(obj)))
    }

    public var description: String {
-        return "0x\(String(_id, radix: 16))"
+        return "0x\(String(value, radix: 16))"
    }
 }
@@ -5,15 +5,19 @@
 //  Created by Sergej Jaskiewicz on 11.06.2019.
 //

+import COpenCombineHelpers
+
 /// A subject that wraps a single value and publishes a new element whenever the value
 /// changes.
 public final class CurrentValueSubject<Output, Failure: Error>: Subject {

-    private let _lock = Lock(recursive: true)
+    private let _lock = UnfairRecursiveLock.allocate()

    // TODO: Combine uses bag data structure
    private var _subscriptions: [Conduit] = []

+    private var _value: Output
+
    private var _completion: Subscribers.Completion<Failure>?

    internal var upstreamSubscriptions: [Subscription] = []
@@ -22,8 +26,11 @@ public final class CurrentValueSubject<Output, Failure: Error>: Subject {

    /// The value wrapped by this subject, published as a new element whenever it changes.
    public var value: Output {
-        didSet {
-            send(value)
+        get {
+            return _value
+        }
+        set {
+            send(newValue)
        }
    }

@@ -31,13 +38,14 @@ public final class CurrentValueSubject<Output, Failure: Error>: Subject {
    ///
    /// - Parameter value: The initial value to publish.
    public init(_ value: Output) {
-        self.value = value
+        self._value = value
    }

    deinit {
        for subscription in _subscriptions {
            subscription._downstream = nil
        }
+        _lock.deallocate()
    }

    public func send(subscription: Subscription) {
@@ -68,6 +76,7 @@ public final class CurrentValueSubject<Output, Failure: Error>: Subject {

    public func send(_ input: Output) {
        _lock.do {
+            _value = input
            for subscription in _subscriptions where !subscription.isCompleted {
                if subscription._demand > 0 {
                    subscription._offer(input)
@@ -0,0 +1,120 @@
+//
+//  Future.swift
+//  
+//
+//  Created by Max Desiatov on 24/11/2019.
+//
+
+import COpenCombineHelpers
+
+/// A publisher that eventually produces one value and then finishes or fails.
+public final class Future<Output, Failure>: Publisher where Failure: Error {
+
+    public typealias Promise = (Result<Output, Failure>) -> Void
+
+    private let _lock = UnfairRecursiveLock.allocate()
+    private var _subscriptions: [Conduit] = []
+
+    private var result: Result<Output, Failure>?
+
+    public init(
+        _ attemptToFulfill: @escaping (@escaping Promise) -> Void
+    ) {
+        attemptToFulfill { result in
+            self._lock.do {
+                guard self.result == nil else { return }
+                self.result = result
+                self._publish(result)
+            }
+        }
+    }
+
+    deinit {
+        _lock.deallocate()
+    }
+
+    /// This function is called to attach the specified `Subscriber` to this
+    /// `Publisher` by `subscribe(_:)`
+    ///
+    /// - SeeAlso: `subscribe(_:)`
+    /// - Parameters:
+    ///     - subscriber: The subscriber to attach to this `Publisher`.
+    ///                   once attached it can begin to receive values.
+    public func receive<Downstream: Subscriber>(
+        subscriber: Downstream
+    ) where Output == Downstream.Input, Failure == Downstream.Failure {
+        let subscription = Conduit(parent: self,
+                                   downstream: AnySubscriber(subscriber))
+
+        _subscriptions.append(subscription)
+       subscriber.receive(subscription: subscription)
+    }
+
+    private func _acknowledgeDownstreamDemand() {
+        _lock.do {
+            guard let result = result else { return }
+            _publish(result)
+        }
+    }
+
+    private func _publish(_ result: Result<Output, Failure>) {
+        for subscription in self._subscriptions where !subscription._isCompleted {
+            switch result {
+            case let .success(output) where subscription._demand > 0:
+                subscription._demand -= 1
+                subscription._demand += subscription._downstream?.receive(output) ?? .none
+                subscription._receive(completion: .finished)
+            case let .failure(error):
+                subscription._receive(completion: .failure(error))
+
+            // nothing to do if no demand
+            default: ()
+            }
+        }
+    }
+}
+
+extension Future {
+
+    fileprivate final class Conduit: Subscription {
+
+        fileprivate var _parent: Future<Output, Failure>?
+
+        fileprivate var _downstream: AnySubscriber<Output, Failure>?
+
+        fileprivate var _demand: Subscribers.Demand = .none
+
+        fileprivate var _isCompleted: Bool {
+            return _parent == nil
+        }
+
+        fileprivate init(parent: Future<Output, Failure>,
+                         downstream: AnySubscriber<Output, Failure>) {
+            _parent = parent
+            _downstream = downstream
+        }
+
+        fileprivate func _receive(completion: Subscribers.Completion<Failure>) {
+            if !_isCompleted {
+                _parent = nil
+                _downstream?.receive(completion: completion)
+            }
+        }
+
+        fileprivate func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            _parent?._lock.do {
+                _demand += demand
+            }
+            _parent?._acknowledgeDownstreamDemand()
+        }
+
+        fileprivate func cancel() {
+            _parent = nil
+        }
+    }
+}
+
+extension Future.Conduit: CustomStringConvertible {
+    fileprivate var description: String { return "Future" }
+}
@@ -0,0 +1,33 @@
+//
+//  EnumerateFields.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 31.10.2019.
+//
+
+import COpenCombineHelpers
+
+internal typealias FieldEnumerator =
+    (_ fieldName: UnsafePointer<CChar>, _ fieldOffset: Int, _ fieldType: Any.Type) -> Bool
+
+internal func enumerateFields(ofType type: Any.Type,
+                              allowResilientSuperclasses: Bool,
+                              enumerator: FieldEnumerator) {
+    // A neat trick to pass a Swift closure where a C function pointer is expected.
+    // (Unlike closures, function pointers cannot capture context)
+    withoutActuallyEscaping(enumerator) { enumerator in
+        var context = enumerator
+        enumerateFields(
+            typeMetadata: unsafeBitCast(type, to: UnsafeRawPointer.self),
+            allowResilientSuperclasses: allowResilientSuperclasses,
+            enumeratorContext: &context,
+            enumerator: { rawContext, fieldName, fieldOffset, rawMetadataPtr in
+                rawContext
+                    .unsafelyUnwrapped
+                    .assumingMemoryBound(to: FieldEnumerator.self)
+                    .pointee(fieldName,
+                             fieldOffset,
+                             unsafeBitCast(rawMetadataPtr, to: Any.Type.self))
+            })
+    }
+}
@@ -0,0 +1,178 @@
+//
+//  FilterProducer.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 23.10.2019.
+//
+
+import COpenCombineHelpers
+
+/// A helper class that acts like both subscriber and subscription.
+///
+/// Filter-like operators send an instance of their `Inner` class that is subclass
+/// of this class to the upstream publisher (as subscriber) and
+/// to the downstream subcriber (as subscription).
+///
+/// Filter-like operators include `Publishers.Filter`,
+/// `Publishers.RemoveDuplicates`, `Publishers.PrefixWhile` and more.
+///
+/// Subclasses must override the `receive(newValue:)` and `description`.
+internal class FilterProducer<Downstream: Subscriber,
+                              Input,
+                              Output,
+                              UpstreamFailure: Error,
+                              Filter>
+    : CustomStringConvertible,
+      CustomReflectable
+    where Downstream.Input == Output
+{
+    // NOTE: This class has been audited for thread safety
+
+    // MARK: - State
+
+    private enum State {
+        case awaitingSubscription
+        case connected(Subscription)
+        case completed
+    }
+
+    internal final let filter: Filter
+
+    internal final let downstream: Downstream
+
+    private let lock = UnfairLock.allocate()
+
+    private var state = State.awaitingSubscription
+
+    internal init(downstream: Downstream, filter: Filter) {
+        self.downstream = downstream
+        self.filter = filter
+    }
+
+    deinit {
+        lock.deallocate()
+    }
+
+    // MARK: - Abstract methods
+
+    internal func receive(
+        newValue: Input
+    ) -> PartialCompletion<Output?, Downstream.Failure> {
+        abstractMethod()
+    }
+
+    internal var description: String {
+        abstractMethod()
+    }
+
+    // MARK: - CustomReflectable
+
+    internal var customMirror: Mirror {
+        let children = CollectionOfOne<Mirror.Child>(("downstream", downstream))
+        return Mirror(self, children: children)
+    }
+}
+
+extension FilterProducer: Subscriber {
+
+    internal func receive(subscription: Subscription) {
+        lock.lock()
+        guard case .awaitingSubscription = state else {
+            lock.unlock()
+            subscription.cancel()
+            return
+        }
+        state = .connected(subscription)
+        lock.unlock()
+        downstream.receive(subscription: self)
+    }
+
+    internal func receive(_ input: Input) -> Subscribers.Demand {
+        lock.lock()
+        switch state {
+        case .awaitingSubscription:
+            lock.unlock()
+            fatalError("Invalid state: Received value before receiving subscription")
+        case .completed:
+            lock.unlock()
+        case let .connected(subscription):
+            lock.unlock()
+            switch receive(newValue: input) {
+            case let .continue(output?):
+                return downstream.receive(output)
+            case .continue(nil):
+                return .max(1)
+            case .finished:
+                lock.lock()
+                state = .completed
+                lock.unlock()
+                subscription.cancel()
+                downstream.receive(completion: .finished)
+            case let .failure(error):
+                lock.lock()
+                state = .completed
+                lock.unlock()
+                subscription.cancel()
+                downstream.receive(completion: .failure(error))
+            }
+        }
+
+        return .none
+    }
+
+    internal func receive(completion: Subscribers.Completion<UpstreamFailure>) {
+        lock.lock()
+        switch state {
+        case .awaitingSubscription:
+            lock.unlock()
+            fatalError("Invalid state: Received completion before receiving subscription")
+        case .completed:
+            lock.unlock()
+            return
+        case .connected:
+            state = .completed
+            lock.unlock()
+            switch completion {
+            case .finished:
+                downstream.receive(completion: .finished)
+            case let .failure(failure):
+                downstream.receive(completion: .failure(failure as! Downstream.Failure))
+            }
+        }
+    }
+}
+
+extension FilterProducer: Subscription {
+
+    internal func request(_ demand: Subscribers.Demand) {
+        demand.assertNonZero()
+        lock.lock()
+        switch state {
+        case .awaitingSubscription:
+            lock.unlock()
+            fatalError("Invalid state: Received request before sending subscription")
+        case .completed:
+            lock.unlock()
+            return
+        case let .connected(subscription):
+            lock.unlock()
+            subscription.request(demand)
+        }
+    }
+
+    internal func cancel() {
+        lock.lock()
+        guard case let .connected(subscription) = state else {
+            state = .completed
+            lock.unlock()
+            return
+        }
+        state = .completed
+        lock.unlock()
+        subscription.cancel()
+    }
+}
+
+extension FilterProducer: CustomPlaygroundDisplayConvertible {
+    internal var playgroundDescription: Any { return description }
+}
@@ -0,0 +1,18 @@
+//
+//  Locking.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 11.06.2019.
+//
+
+import COpenCombineHelpers
+
+extension UnfairRecursiveLock {
+
+    @inlinable
+    internal func `do`<Result>(_ body: () throws -> Result) rethrows -> Result {
+        lock()
+        defer { unlock() }
+        return try body()
+    }
+}
@@ -0,0 +1,26 @@
+//
+//  PartialCompletion.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 22.09.2019.
+//
+
+/// A value of this type is returned by the overridden `receive(newValue:)` method
+/// of the `ReduceProducer` and `FilterProducer` classes.
+internal enum PartialCompletion<Value, Failure: Error> {
+
+    /// Indicate that we should continue accepting the upstream's output.
+    case `continue`(Value)
+
+    /// Indicate that no values should be received from the upstream anymore.
+    case finished
+
+    /// Indicate that there was a failure and we should send it downstream.
+    case failure(Failure)
+}
+
+extension PartialCompletion where Value == Void {
+
+    /// Indicate that we should continue accepting the upstream's output.
+    internal static var `continue`: PartialCompletion { return .continue(()) }
+}
@@ -0,0 +1,252 @@
+//
+//  ReduceProducer.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 22.09.2019.
+//
+
+import COpenCombineHelpers
+
+/// A helper class that acts like both subscriber and subscription.
+///
+/// Reduce-like operators send an instance of their `Inner` class that is subclass
+/// of this class to the upstream publisher (as subscriber) and
+/// to the downstream subcriber (as subsription).
+///
+/// Reduce-like operators include `Publishers.Reduce`, `Publishers.TryReduce`,
+/// `Publishers.Count`, `Publishers.FirstWhere`, `Publishers.AllSatisfy` and more.
+///
+/// Subclasses must override the `receive(newValue:)` and `description`.
+internal class ReduceProducer<Downstream: Subscriber,
+                              Input,
+                              Output,
+                              UpstreamFailure: Error,
+                              Reducer>
+    : CustomStringConvertible,
+      CustomReflectable
+    where Downstream.Input == Output
+{
+    // NOTE: This class has been audited for thread safety
+
+    // MARK: - State
+
+    internal final var result: Output?
+
+    private let initial: Output?
+
+    internal final let reduce: Reducer
+
+    private var status = SubscriptionStatus.awaitingSubscription
+
+    private let downstream: Downstream
+
+    private let lock = UnfairLock.allocate()
+
+    private var downstreamRequested = false
+
+    private var cancelled = false
+
+    private var completed = false
+
+    private var upstreamCompleted = false
+
+    private var empty = true
+
+    internal init(downstream: Downstream, initial: Output?, reduce: Reducer) {
+        self.downstream = downstream
+        self.initial = initial
+        self.result = initial
+        self.reduce = reduce
+    }
+
+    deinit {
+        lock.deallocate()
+    }
+
+    // MARK: - Abstract methods
+
+    internal func receive(
+        newValue: Input
+    ) -> PartialCompletion<Void, Downstream.Failure> {
+        abstractMethod()
+    }
+
+    internal var description: String {
+        abstractMethod()
+    }
+
+    // MARK: - CustomReflectable
+
+    internal var customMirror: Mirror {
+        lock.lock()
+        defer { lock.unlock() }
+        let children: [Mirror.Child] = [
+            ("downstream", downstream),
+            ("result", result as Any),
+            ("initial", initial as Any),
+            ("status", status)
+        ]
+        return Mirror(self, children: children)
+    }
+
+    // MARK: - Private
+
+    /// - Precondition: `lock` is held.
+    private func receiveFinished() {
+        guard !cancelled, !completed, !upstreamCompleted else {
+            lock.unlock()
+            // This should never happen, because `receive(completion:)`
+            // (from which this function is called) early exists if
+            // `status` is `.terminal`.
+            assertionFailure("The subscription should have been terminated by now")
+            return
+        }
+        upstreamCompleted = true
+        self.completed = downstreamRequested || empty
+        let completed = self.completed
+        let result = self.result
+        lock.unlock()
+
+        if completed {
+            sendResultAndFinish(result)
+        }
+    }
+
+    /// - Precondition: `lock` is held.
+    private func receiveFailure(_ failure: UpstreamFailure) {
+        guard !cancelled, !completed, !upstreamCompleted else {
+            lock.unlock()
+            // This should never happen, because `receive(completion:)`
+            // (from which this function is called) early exists if
+            // `status` is `.terminal`.
+            assertionFailure("The subscription should have been terminated by now")
+            return
+        }
+        upstreamCompleted = true
+        completed = true
+        lock.unlock()
+        downstream.receive(completion: .failure(failure as! Downstream.Failure))
+    }
+
+    private func sendResultAndFinish(_ result: Output?) {
+        assert(completed && upstreamCompleted)
+        if let result = result {
+            _ = downstream.receive(result)
+        }
+        downstream.receive(completion: .finished)
+    }
+
+    // MARK: -
+}
+
+extension ReduceProducer: Subscriber {
+    internal func receive(subscription: Subscription) {
+        lock.lock()
+        guard case .awaitingSubscription = status else {
+            lock.unlock()
+            subscription.cancel()
+            return
+        }
+        status = .subscribed(subscription)
+        lock.unlock()
+        downstream.receive(subscription: self)
+        subscription.request(.unlimited)
+    }
+
+    internal func receive(_ input: Input) -> Subscribers.Demand {
+        lock.lock()
+        guard case let .subscribed(subscription) = status else {
+            lock.unlock()
+            return .none
+        }
+        empty = false
+        lock.unlock()
+
+        // Combine doesn't hold the lock when calling `receive(newValue:)`.
+        //
+        // This can lead to data races if the contract is violated
+        // (like when we receive input from multiple threads simultaneously).
+        switch self.receive(newValue: input) {
+        case .continue:
+            break
+        case .finished:
+            lock.lock()
+            upstreamCompleted = true
+            let downstreamRequested = self.downstreamRequested
+            if downstreamRequested {
+                completed = true
+            }
+            status = .terminal
+            let result = self.result
+            lock.unlock()
+
+            subscription.cancel()
+
+            guard downstreamRequested else { break }
+
+            sendResultAndFinish(result)
+        case let .failure(error):
+            lock.lock()
+            upstreamCompleted = true
+            completed = true
+            status = .terminal
+            lock.unlock()
+
+            subscription.cancel()
+            downstream.receive(completion: .failure(error))
+        }
+
+        return .none
+    }
+
+    internal func receive(completion: Subscribers.Completion<UpstreamFailure>) {
+        lock.lock()
+        guard case .subscribed = status else {
+            lock.unlock()
+            return
+        }
+        status = .terminal
+        switch completion {
+        case .finished:
+            receiveFinished()
+        case let .failure(error):
+            receiveFailure(error)
+        }
+    }
+}
+
+extension ReduceProducer: Subscription {
+    internal func request(_ demand: Subscribers.Demand) {
+        demand.assertNonZero()
+        lock.lock()
+        guard !downstreamRequested, !cancelled, !completed else {
+            lock.unlock()
+            return
+        }
+        downstreamRequested = true
+        guard upstreamCompleted else  {
+            lock.unlock()
+            return
+        }
+        completed = true
+        let result = self.result
+        lock.unlock()
+        sendResultAndFinish(result)
+    }
+
+    internal func cancel() {
+        lock.lock()
+        guard case let .subscribed(subscription) = status else {
+            lock.unlock()
+            return
+        }
+        cancelled = true
+        status = .terminal
+        lock.unlock()
+        subscription.cancel()
+    }
+}
+
+extension ReduceProducer: CustomPlaygroundDisplayConvertible {
+    internal var playgroundDescription: Any { return description }
+}
@@ -0,0 +1,105 @@
+//
+//  SubjectSubscriber.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 16/09/2019.
+//
+
+import COpenCombineHelpers
+
+// NOTE: This class has been audited for thread safety.
+internal final class SubjectSubscriber<Downstream: Subject>
+    : Subscriber,
+      CustomStringConvertible,
+      CustomReflectable,
+      CustomPlaygroundDisplayConvertible,
+      Subscription
+{
+    private let lock = UnfairLock.allocate()
+    private var downstreamSubject: Downstream?
+    private var upstreamSubscription: Subscription?
+
+    private var isCancelled: Bool { return downstreamSubject == nil }
+
+    internal init(_ parent: Downstream) {
+        self.downstreamSubject = parent
+    }
+
+    deinit {
+        lock.deallocate()
+    }
+
+    internal func receive(subscription: Subscription) {
+        lock.lock()
+        guard upstreamSubscription == nil, let subject = downstreamSubject else {
+            lock.unlock()
+            return
+        }
+        upstreamSubscription = subscription
+        lock.unlock()
+        subject.send(subscription: self)
+    }
+
+    internal func receive(_ input: Downstream.Output) -> Subscribers.Demand {
+        lock.lock()
+        guard let downstreamSubject = downstreamSubject else {
+            lock.unlock()
+            return .none
+        }
+        guard upstreamSubscription != nil else { APIViolationValueBeforeSubscription() }
+        lock.unlock()
+        downstreamSubject.send(input)
+        return .none
+    }
+
+    internal func receive(completion: Subscribers.Completion<Downstream.Failure>) {
+        lock.lock()
+        guard let subject = downstreamSubject else {
+            lock.unlock()
+            return
+        }
+        guard upstreamSubscription != nil else { APIViolationUnexpectedCompletion() }
+        lock.unlock()
+        subject.send(completion: completion)
+        downstreamSubject = nil
+    }
+
+    internal var description: String { return "Subject" }
+
+    internal var playgroundDescription: Any { return description }
+
+    internal var customMirror: Mirror {
+        let children: [Mirror.Child] = [
+            ("downstreamSubject", downstreamSubject as Any),
+            ("upstreamSubscription", upstreamSubscription as Any),
+            ("subject", downstreamSubject as Any)
+        ]
+        return Mirror(self, children: children)
+    }
+
+    internal func request(_ demand: Subscribers.Demand) {
+        lock.lock()
+        guard let subscription = upstreamSubscription else {
+            lock.unlock()
+            return
+        }
+        lock.unlock()
+        subscription.request(demand)
+    }
+
+    internal func cancel() {
+        lock.lock()
+        if isCancelled {
+            lock.unlock()
+            return
+        }
+        guard let subscription = upstreamSubscription else {
+            lock.unlock()
+            return
+        }
+        upstreamSubscription = nil
+        downstreamSubject = nil
+        lock.unlock()
+        subscription.cancel()
+    }
+}
@@ -0,0 +1,12 @@
+//
+//  SubscriptionStatus.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 21.09.2019.
+//
+
+internal enum SubscriptionStatus {
+    case awaitingSubscription
+    case subscribed(Subscription)
+    case terminal
+}
@@ -0,0 +1,33 @@
+//
+//  Violations.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 16/09/2019.
+//
+
+internal func APIViolationValueBeforeSubscription(file: StaticString = #file,
+                                                  line: UInt = #line) -> Never {
+    fatalError("""
+               API Violation: received an unexpected value before receiving a Subscription
+               """,
+               file: file,
+               line: line)
+}
+
+internal func APIViolationUnexpectedCompletion(file: StaticString = #file,
+                                               line: UInt = #line) -> Never {
+    fatalError("API Violation: received an unexpected completion", file: file, line: line)
+}
+
+internal func abstractMethod(file: StaticString = #file, line: UInt = #line) -> Never {
+    fatalError("Abstract method call", file: file, line: line)
+}
+
+extension Subscribers.Demand {
+    internal func assertNonZero(file: StaticString = #file,
+                                line: UInt = #line) {
+        if self == .none {
+            fatalError("API Violation: demand must not be zero", file: file, line: line)
+        }
+    }
+}
@@ -139,9 +139,7 @@ public struct ImmediateScheduler: Scheduler {
                         tolerance: SchedulerTimeType.Stride,
                         options: SchedulerOptions?,
                         _ action: @escaping () -> Void) {
-        fatalError(
-            "Attempt to schedule something in the future on the immediate scheduler"
-        )
+        action()
    }

    /// Performs the action at some time after the specified date, at the specified
@@ -151,8 +149,7 @@ public struct ImmediateScheduler: Scheduler {
                         tolerance: SchedulerTimeType.Stride,
                         options: SchedulerOptions?,
                         _ action: @escaping () -> Void) -> Cancellable {
-        fatalError(
-            "Attempt to schedule something in the future on the immediate scheduler"
-        )
+        action()
+        return Subscriptions.empty
    }
 }
@@ -1,53 +0,0 @@
-//
-//  Locking.swift
-//  
-//
-//  Created by Sergej Jaskiewicz on 11.06.2019.
-//
-
-#if canImport(Darwin)
-import Darwin
-#elseif canImport(Glibc)
-import Glibc
-#else
-#error("How to do locking on this platform?")
-#endif
-
-@usableFromInline
-internal final class Lock {
-
-    @usableFromInline
-    internal var _mutex = pthread_mutex_t()
-
-    @inlinable
-    internal init(recursive: Bool) {
-        var attrib = pthread_mutexattr_t()
-        pthread_mutexattr_init(&attrib)
-        if recursive {
-            pthread_mutexattr_settype(&attrib, Int32(PTHREAD_MUTEX_RECURSIVE))
-        }
-        pthread_mutex_init(&_mutex, &attrib)
-    }
-
-    @inlinable
-    deinit {
-        pthread_mutex_destroy(&_mutex)
-    }
-
-    @inlinable
-    internal func _lock() {
-        pthread_mutex_lock(&_mutex)
-    }
-
-    @inlinable
-    internal func _unlock() {
-        pthread_mutex_unlock(&_mutex)
-    }
-
-    @inlinable
-    internal func `do`<Result>(_ body: () throws -> Result) rethrows -> Result {
-        _lock()
-        defer { _unlock() }
-        return try body()
-    }
-}
@@ -0,0 +1,177 @@
+//
+//  ObservableObject.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 08/09/2019.
+//
+
+// We use type metadata in the implementation of ObservableObject,
+// but type metadata is stable only on Darwin. There are no such guarantees
+// on non-Apple platforms (yet).
+//
+// This means that on Linux the layout of type metadata can change in a new Swift release,
+// which will cause bugs that are hard to track (basically, undefined behavior).
+//
+// Whenever a new Swift version is available, we well test OpenCombine against it,
+// and if everything works, release an update as soon as possible where the maximum
+// supported Swift version is incremented.
+#if !canImport(Darwin) && swift(>=5.1.50)
+#warning("""
+ObservableObject is not guaranteed to work on non-Apple platforms with this version \
+of Swift because its implementation relies on ABI stability.
+
+In order to fix this warning, please update to the newest version of OpenCombine, \
+or create an issue at https://github.com/broadwaylamb/OpenCombine if there is no \
+newer version yet.
+""")
+#endif
+
+#if swift(>=5.1)
+private protocol _ObservableObjectProperty {
+    var objectWillChange: ObservableObjectPublisher? { get set }
+}
+
+extension _ObservableObjectProperty {
+
+    fileprivate static func installPublisher(
+        _ publisher: ObservableObjectPublisher,
+        on publishedStorage: UnsafeMutableRawPointer
+    ) {
+        // It is safe to call assumingMemoryBound here because we know for sure
+        // that the actual type of the pointee is Self.
+        publishedStorage
+            .assumingMemoryBound(to: Self.self)
+            .pointee
+            .objectWillChange = publisher
+    }
+
+    fileprivate static func getPublisher(
+        from publishedStorage: UnsafeMutableRawPointer
+    ) -> ObservableObjectPublisher? {
+        // It is safe to call assumingMemoryBound here because we know for sure
+        // that the actual type of the pointee is Self.
+        return publishedStorage
+            .assumingMemoryBound(to: Self.self)
+            .pointee
+            .objectWillChange
+    }
+}
+
+extension Published: _ObservableObjectProperty {}
+#endif
+
+/// A type of object with a publisher that emits before the object has changed.
+///
+/// By default an `ObservableObject` will synthesize an `objectWillChange`
+/// publisher that emits before any of its `@Published` properties changes:
+///
+///     class Contact : ObservableObject {
+///         @Published var name: String
+///         @Published var age: Int
+///
+///         init(name: String, age: Int) {
+///             self.name = name
+///             self.age = age
+///         }
+///
+///         func haveBirthday() -> Int {
+///             age += 1
+///         }
+///     }
+///
+///     let john = Contact(name: "John Appleseed", age: 24)
+///     john.objectWillChange.sink { _ in print("will change") }
+///     print(john.haveBirthday)
+///     // Prints "will change"
+///     // Prints "25"
+///
+public protocol ObservableObject: AnyObject {
+
+    /// The type of publisher that emits before the object has changed.
+    associatedtype ObjectWillChangePublisher: Publisher = ObservableObjectPublisher
+        where ObjectWillChangePublisher.Failure == Never
+
+    /// A publisher that emits before the object has changed.
+    var objectWillChange: ObjectWillChangePublisher { get }
+}
+
+extension ObservableObject where ObjectWillChangePublisher == ObservableObjectPublisher {
+
+    /// A publisher that emits before the object has changed.
+    public var objectWillChange: ObservableObjectPublisher {
+#if swift(>=5.1)
+        var installedPublisher: ObservableObjectPublisher?
+
+        enumerateFields(ofType: Self.self,
+                        allowResilientSuperclasses: false) { _, fieldOffset, fieldType in
+            let storage = Unmanaged
+                .passUnretained(self)
+                .toOpaque()
+                .advanced(by: fieldOffset)
+
+            guard let fieldType = fieldType as? _ObservableObjectProperty.Type else {
+                // Visit other fields until we meet a @Published field
+                return true
+            }
+
+            // Now we know that the field is @Published.
+
+            if let alreadyInstalledPublisher = fieldType.getPublisher(from: storage) {
+                installedPublisher = alreadyInstalledPublisher
+                // Don't visit other fields, as all @Published fields
+                // already have a publisher installed.
+                return false
+            }
+
+            // Okay, this field doesn't have a publisher installed.
+            // This means that other fields don't have it either
+            // (because we install it only once and fields can't be added at runtime).
+
+            var lazilyCreatedPublisher: ObjectWillChangePublisher {
+                if let publisher = installedPublisher {
+                    return publisher
+                }
+                let publisher = ObservableObjectPublisher()
+                installedPublisher = publisher
+                return publisher
+            }
+
+            fieldType.installPublisher(lazilyCreatedPublisher, on: storage)
+
+            // Continue visiting other fields.
+            return true
+        }
+
+        return installedPublisher ?? ObservableObjectPublisher()
+#else
+        // There are no @Published in Swift 5.0, so we act the same as in Swift 5.1
+        // with classes without @Published properties.
+        // We create a new instance every time.
+        return ObservableObjectPublisher()
+#endif // swift(>=5.1)
+    }
+}
+
+/// The default publisher of an `ObservableObject`.
+public final class ObservableObjectPublisher: Publisher {
+
+    public typealias Output = Void
+
+    public typealias Failure = Never
+
+    private let subject: PassthroughSubject<Void, Never>
+
+    public init() {
+        subject = .init()
+    }
+
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Downstream.Input == Void, Downstream.Failure == Never
+    {
+        subject.subscribe(subscriber)
+    }
+
+    public func send() {
+        subject.send()
+    }
+}
@@ -5,13 +5,15 @@
 //  Created by Sergej Jaskiewicz on 11.06.2019.
 //

+import COpenCombineHelpers
+
 /// A subject that passes along values and completion.
 ///
 /// Use a `PassthroughSubject` in unit tests when you want a publisher than can publish
 /// specific values on-demand during tests.
 public final class PassthroughSubject<Output, Failure: Error>: Subject  {

-    private let _lock = Lock(recursive: true)
+    private let _lock = UnfairRecursiveLock.allocate()

    private var _completion: Subscribers.Completion<Failure>?

@@ -28,6 +30,7 @@ public final class PassthroughSubject<Output, Failure: Error>: Subject  {
        for subscription in _subscriptions {
            subscription._downstream = nil
        }
+        _lock.deallocate()
    }

    public func send(subscription: Subscription) {
@@ -39,8 +42,8 @@ public final class PassthroughSubject<Output, Failure: Error>: Subject  {
        }
    }

-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Output == SubscriberType.Input, Failure == SubscriberType.Failure
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Output == Downstream.Input, Failure == Downstream.Failure
    {
        _lock.do {
            if let completion = _completion {
@@ -117,9 +120,9 @@ extension PassthroughSubject {
        }

        fileprivate func request(_ demand: Subscribers.Demand) {
-            precondition(demand > 0, "demand must not be zero")
+            demand.assertNonZero()
            _parent?._lock.do {
-                _demand = demand
+                _demand += demand
            }
            _parent?._acknowledgeDownstreamDemand()
        }
@@ -0,0 +1,103 @@
+//
+//  Published.swift
+//  OpenCombine
+//
+//  Created by Евгений Богомолов on 01/09/2019.
+//
+
+#if swift(>=5.1)
+/// Adds a `Publisher` to a property.
+///
+/// Properties annotated with `@Published` contain both the stored value
+/// and a publisher which sends any new values after the property value
+/// has been sent. New subscribers will receive the current value
+/// of the property first.
+/// Note that the `@Published` property is class-constrained.
+/// Use it with properties of classes, not with non-class types like structures.
+@available(swift, introduced: 5.1)
+@propertyWrapper
+public struct Published<Value> {
+
+    /// Initialize the storage of the `Published` property as well as the corresponding
+    /// `Publisher`.
+    public init(initialValue: Value) {
+        self.init(wrappedValue: initialValue)
+    }
+
+    /// Initialize the storage of the `Published` property as well as the corresponding
+    /// `Publisher`.
+    public init(wrappedValue: Value) {
+        value = wrappedValue
+    }
+
+    /// A publisher for properties marked with the `@Published` attribute.
+    public struct Publisher: OpenCombine.Publisher {
+
+        public typealias Output = Value
+
+        public typealias Failure = Never
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Input == Value, Downstream.Failure == Never
+        {
+            subject.subscribe(subscriber)
+        }
+
+        fileprivate let subject: OpenCombine.CurrentValueSubject<Value, Never>
+
+        fileprivate init(_ output: Output) {
+            subject = .init(output)
+        }
+    }
+
+    private var value: Value
+
+    private var publisher: Publisher?
+
+    internal var objectWillChange: ObservableObjectPublisher?
+
+    /// The property that can be accessed with the `$` syntax and allows access to
+    /// the `Publisher`
+    public var projectedValue: Publisher {
+        mutating get {
+            if let publisher = publisher {
+                return publisher
+            }
+            let publisher = Publisher(value)
+            self.publisher = publisher
+            return publisher
+        }
+    }
+
+    // swiftlint:disable let_var_whitespace
+    @available(*, unavailable, message: """
+               @Published is only available on properties of classes
+               """)
+    public var wrappedValue: Value {
+        get { fatalError() }
+        set { fatalError() } // swiftlint:disable:this unused_setter_value
+    }
+    // swiftlint:enable let_var_whitespace
+
+    public static subscript<EnclosingSelf: AnyObject>(
+        _enclosingInstance object: EnclosingSelf,
+        wrapped wrappedKeyPath: ReferenceWritableKeyPath<EnclosingSelf, Value>,
+        storage storageKeyPath: ReferenceWritableKeyPath<EnclosingSelf, Published<Value>>
+    ) -> Value {
+        get {
+            return object[keyPath: storageKeyPath].value
+        }
+        set {
+            object[keyPath: storageKeyPath].objectWillChange?.send()
+            object[keyPath: storageKeyPath].publisher?.subject.send(newValue)
+            object[keyPath: storageKeyPath].value = newValue
+        }
+        // TODO: Benchmark and explore a possibility to use _modify
+    }
+}
+#else
+
+@available(swift, introduced: 5.1)
+public typealias Published = Never
+
+#endif // swift(>=5.1)
@@ -38,9 +38,9 @@ public struct Deferred<DeferredPublisher: Publisher>: Publisher {
    /// - Parameters:
    ///     - subscriber: The subscriber to attach to this `Publisher`.
    ///                   once attached it can begin to receive values.
-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Failure == SubscriberType.Failure,
-              Output == SubscriberType.Input
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Failure == Downstream.Failure,
+              Output == Downstream.Input
    {
        let deferredPublisher = createPublisher()
        deferredPublisher.subscribe(subscriber)
@@ -42,8 +42,8 @@ public struct Empty<Output, Failure: Error>: Publisher, Equatable {
    /// to the subscriber. If `false`, it never completes.
    public let completeImmediately: Bool

-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Output == SubscriberType.Input, Failure == SubscriberType.Failure
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Output == Downstream.Input, Failure == Downstream.Failure
    {
        subscriber.receive(subscription: Subscriptions.empty)
        if completeImmediately {
@@ -30,8 +30,8 @@ public struct Fail<Output, Failure: Error>: Publisher {
    /// The failure to send when terminating the publisher.
    public let error: Failure

-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where Output == SubscriberType.Input, Failure == SubscriberType.Failure
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Output == Downstream.Input, Failure == Downstream.Failure
    {
        subscriber.receive(subscription: Subscriptions.empty)
        subscriber.receive(completion: .failure(error))
@@ -0,0 +1,254 @@
+// ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+// ┃                                                                                     ┃
+// ┃                   Auto-generated from GYB template. DO NOT EDIT!                    ┃
+// ┃                                                                                     ┃
+// ┃                                                                                     ┃
+// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+//
+//  Publishers.Encode.swift.gyb
+//
+//
+//  Created by Joseph Spadafora on 6/22/19.
+//
+
+extension Publisher {
+
+    /// Encodes the output from upstream using a specified `TopLevelEncoder`.
+    /// For example, use `JSONEncoder`.
+    public func encode<Coder: TopLevelEncoder>(
+        encoder: Coder
+    ) -> Publishers.Encode<Self, Coder> {
+        return .init(upstream: self, encoder: encoder)
+    }
+
+    /// Decodes the output from upstream using a specified `TopLevelDecoder`.
+    /// For example, use `JSONDecoder`.
+    public func decode<Item: Decodable, Coder: TopLevelDecoder>(
+        type: Item.Type,
+        decoder: Coder
+    ) -> Publishers.Decode<Self, Item, Coder> where Output == Coder.Input {
+        return .init(upstream: self, decoder: decoder)
+    }
+}
+
+extension Publishers {
+
+    public struct Encode<Upstream: Publisher, Coder: TopLevelEncoder>: Publisher
+        where Upstream.Output: Encodable
+    {
+        public typealias Failure = Error
+
+        public typealias Output = Coder.Output
+
+        public let upstream: Upstream
+
+        private let _encode: (Upstream.Output) throws -> Output
+
+        public init(upstream: Upstream, encoder: Coder) {
+            self.upstream = upstream
+            self._encode = encoder.encode
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, encode: _encode))
+        }
+    }
+
+    public struct Decode<Upstream: Publisher, Output: Decodable, Coder: TopLevelDecoder>
+        : Publisher
+        where Upstream.Output == Coder.Input
+    {
+        public typealias Failure = Error
+
+        public let upstream: Upstream
+
+        private let _decode: (Upstream.Output) throws -> Output
+
+        public init(upstream: Upstream, decoder: Coder) {
+            self.upstream = upstream
+            self._decode = { try decoder.decode(Output.self, from: $0) }
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, decode: _decode))
+        }
+    }
+}
+
+extension Publishers.Encode {
+    private final class Inner<Downstream: Subscriber>
+        : Subscriber,
+          Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Error
+    {
+        // NOTE: This class has been audited for thread safety.
+        // Combine doesn't use any locking here.
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let encode: (Upstream.Output) throws -> Output
+
+        private var finished = false
+
+        private var subscription: Subscription?
+
+        fileprivate init(
+            downstream: Downstream,
+            encode: @escaping (Upstream.Output) throws -> Output
+        ) {
+            self.downstream = downstream
+            self.encode = encode
+        }
+
+        func receive(subscription: Subscription) {
+            if finished || self.subscription != nil {
+                subscription.cancel()
+                return
+            }
+            self.subscription = subscription
+            downstream.receive(subscription: self)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            if finished { return .none }
+            do {
+                return try downstream.receive(encode(input))
+            } catch {
+                finished = true
+                subscription?.cancel()
+                subscription = nil
+                downstream.receive(completion: .failure(error))
+                return .none
+            }
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            if finished { return }
+            finished = true
+            subscription = nil
+            downstream.receive(completion: completion.eraseError())
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            subscription?.request(demand)
+        }
+
+        func cancel() {
+            guard let subscription = self.subscription, !finished else { return }
+            subscription.cancel()
+            self.subscription = nil
+            finished = true
+        }
+
+        var description: String { return "Encode" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("downstream", downstream),
+                ("finished", finished),
+                ("upstreamSubscription", subscription as Any)
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+
+extension Publishers.Decode {
+    private final class Inner<Downstream: Subscriber>
+        : Subscriber,
+          Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Error
+    {
+        // NOTE: This class has been audited for thread safety.
+        // Combine doesn't use any locking here.
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let decode: (Upstream.Output) throws -> Output
+
+        private var finished = false
+
+        private var subscription: Subscription?
+
+        fileprivate init(
+            downstream: Downstream,
+            decode: @escaping (Upstream.Output) throws -> Output
+        ) {
+            self.downstream = downstream
+            self.decode = decode
+        }
+
+        func receive(subscription: Subscription) {
+            if finished || self.subscription != nil {
+                subscription.cancel()
+                return
+            }
+            self.subscription = subscription
+            downstream.receive(subscription: self)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            if finished { return .none }
+            do {
+                return try downstream.receive(decode(input))
+            } catch {
+                finished = true
+                subscription?.cancel()
+                subscription = nil
+                downstream.receive(completion: .failure(error))
+                return .none
+            }
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            if finished { return }
+            finished = true
+            subscription = nil
+            downstream.receive(completion: completion.eraseError())
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            subscription?.request(demand)
+        }
+
+        func cancel() {
+            guard let subscription = self.subscription, !finished else { return }
+            subscription.cancel()
+            self.subscription = nil
+            finished = true
+        }
+
+        var description: String { return "Decode" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("downstream", downstream),
+                ("finished", finished),
+                ("upstreamSubscription", subscription as Any)
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
@@ -0,0 +1,316 @@
+// ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
+// ┃                                                                                     ┃
+// ┃                   Auto-generated from GYB template. DO NOT EDIT!                    ┃
+// ┃                                                                                     ┃
+// ┃                                                                                     ┃
+// ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
+//
+//  Publishers.MapKeyPath.swift.gyb
+//  
+//
+//  Created by Sergej Jaskiewicz on 03/10/2019.
+//
+
+extension Publisher {
+
+    /// Returns a publisher that publishes the values of a keyt path as a tuple.
+    ///
+    /// - Parameters:
+    ///    - keyPath: The key path of a property on `Output`
+    /// - Returns: A publisher that publishes the value of the key path.
+    public func map<Result>(
+        _ keyPath: KeyPath<Output, Result>
+    ) -> Publishers.MapKeyPath<Self, Result> {
+        return .init(
+            upstream: self,
+            keyPath: keyPath
+        )
+    }
+
+    /// Returns a publisher that publishes the values of two key paths as a tuple.
+    ///
+    /// - Parameters:
+    ///    - keyPath0: The key path of a property on `Output`
+    ///    - keyPath1: The key path of another property on `Output`
+    /// - Returns: A publisher that publishes the values of two key paths as a tuple.
+    public func map<Result0, Result1>(
+        _ keyPath0: KeyPath<Output, Result0>,
+        _ keyPath1: KeyPath<Output, Result1>
+    ) -> Publishers.MapKeyPath2<Self, Result0, Result1> {
+        return .init(
+            upstream: self,
+            keyPath0: keyPath0,
+            keyPath1: keyPath1
+        )
+    }
+
+    /// Returns a publisher that publishes the values of three key paths as a tuple.
+    ///
+    /// - Parameters:
+    ///    - keyPath0: The key path of a property on `Output`
+    ///    - keyPath1: The key path of another property on `Output`
+    ///    - keyPath2: The key path of a third property on `Output`
+    /// - Returns: A publisher that publishes the values of three key paths as a tuple.
+    public func map<Result0, Result1, Result2>(
+        _ keyPath0: KeyPath<Output, Result0>,
+        _ keyPath1: KeyPath<Output, Result1>,
+        _ keyPath2: KeyPath<Output, Result2>
+    ) -> Publishers.MapKeyPath3<Self, Result0, Result1, Result2> {
+        return .init(
+            upstream: self,
+            keyPath0: keyPath0,
+            keyPath1: keyPath1,
+            keyPath2: keyPath2
+        )
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that publishes the value of a key path.
+    public struct MapKeyPath<Upstream: Publisher, Output>: Publisher {
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The key path of a property to publish.
+        public let keyPath: KeyPath<Upstream.Output, Output>
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Failure == Downstream.Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, parent: self))
+        }
+    }
+
+    /// A publisher that publishes the values of two key paths as a tuple.
+    public struct MapKeyPath2<Upstream: Publisher, Output0, Output1>: Publisher {
+
+        public typealias Output = (Output0, Output1)
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The key path of a property to publish.
+        public let keyPath0: KeyPath<Upstream.Output, Output0>
+
+        /// The key path of a second property to publish.
+        public let keyPath1: KeyPath<Upstream.Output, Output1>
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Failure == Downstream.Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, parent: self))
+        }
+    }
+
+    /// A publisher that publishes the values of three key paths as a tuple.
+    public struct MapKeyPath3<Upstream: Publisher, Output0, Output1, Output2>: Publisher {
+
+        public typealias Output = (Output0, Output1, Output2)
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The key path of a property to publish.
+        public let keyPath0: KeyPath<Upstream.Output, Output0>
+
+        /// The key path of a second property to publish.
+        public let keyPath1: KeyPath<Upstream.Output, Output1>
+
+        /// The key path of a third property to publish.
+        public let keyPath2: KeyPath<Upstream.Output, Output2>
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Failure == Downstream.Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, parent: self))
+        }
+    }
+}
+
+extension Publishers.MapKeyPath {
+
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Upstream.Failure
+    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let keyPath: KeyPath<Input, Output>
+
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(
+            downstream: Downstream,
+            parent: Publishers.MapKeyPath<Upstream, Output>
+        ) {
+            self.downstream = downstream
+            self.keyPath = parent.keyPath
+        }
+
+        func receive(subscription: Subscription) {
+            downstream.receive(subscription: subscription)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            let output = (
+                input[keyPath: keyPath]
+            )
+            return downstream.receive(output)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            downstream.receive(completion: completion)
+        }
+
+        var description: String { return "ValueForKey" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("keyPath", keyPath),
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+
+extension Publishers.MapKeyPath2 {
+
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Upstream.Failure
+    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let keyPath0: KeyPath<Input, Output0>
+
+        private let keyPath1: KeyPath<Input, Output1>
+
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(
+            downstream: Downstream,
+            parent: Publishers.MapKeyPath2<Upstream, Output0, Output1>
+        ) {
+            self.downstream = downstream
+            self.keyPath0 = parent.keyPath0
+            self.keyPath1 = parent.keyPath1
+        }
+
+        func receive(subscription: Subscription) {
+            downstream.receive(subscription: subscription)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            let output = (
+                input[keyPath: keyPath0],
+                input[keyPath: keyPath1]
+            )
+            return downstream.receive(output)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            downstream.receive(completion: completion)
+        }
+
+        var description: String { return "ValueForKeys" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("keyPath0", keyPath0),
+                ("keyPath1", keyPath1),
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+
+extension Publishers.MapKeyPath3 {
+
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Upstream.Failure
+    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let keyPath0: KeyPath<Input, Output0>
+
+        private let keyPath1: KeyPath<Input, Output1>
+
+        private let keyPath2: KeyPath<Input, Output2>
+
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(
+            downstream: Downstream,
+            parent: Publishers.MapKeyPath3<Upstream, Output0, Output1, Output2>
+        ) {
+            self.downstream = downstream
+            self.keyPath0 = parent.keyPath0
+            self.keyPath1 = parent.keyPath1
+            self.keyPath2 = parent.keyPath2
+        }
+
+        func receive(subscription: Subscription) {
+            downstream.receive(subscription: subscription)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            let output = (
+                input[keyPath: keyPath0],
+                input[keyPath: keyPath1],
+                input[keyPath: keyPath2]
+            )
+            return downstream.receive(output)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            downstream.receive(completion: completion)
+        }
+
+        var description: String { return "ValueForKeys" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("keyPath0", keyPath0),
+                ("keyPath1", keyPath1),
+                ("keyPath2", keyPath2),
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
@@ -25,8 +25,8 @@ public struct Just<Output>: Publisher {
        self.output = output
    }

-    public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-        where SubscriberType.Input == Output, SubscriberType.Failure == Never
+    public func receive<Downstream: Subscriber>(subscriber: Downstream)
+        where Downstream.Input == Output, Downstream.Failure == Never
    {
        subscriber.receive(subscription: Inner(value: output, downstream: subscriber))
    }
@@ -251,33 +251,43 @@ extension Just {
    }
 }

-private final class Inner<SubscriberType: Subscriber>: Subscription,
-    CustomStringConvertible,
-    CustomReflectable
-{
-    private let _output: SubscriberType.Input
-    private var _downstream: SubscriberType?
+extension Just {
+    private final class Inner<Downstream: Subscriber>
+        : Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+    where Downstream.Input == Output
+    {
+        // NOTE: this class has been audited for thread safety.
+        // Combine doesn't use any locking here.

-    init(value: SubscriberType.Input, downstream: SubscriberType) {
-        _output = value
-        _downstream = downstream
-    }
+        private var downstream: Downstream?
+        private let value: Output

-    func request(_ demand: Subscribers.Demand) {
-        if let downstream = _downstream, demand > 0 {
-            _ = downstream.receive(_output)
-            downstream.receive(completion: .finished)
-            _downstream = nil
+        fileprivate init(value: Output, downstream: Downstream) {
+            self.downstream = downstream
+            self.value = value
        }
-    }

-    func cancel() {
-        _downstream = nil
-    }
+        func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            guard let downstream = self.downstream else { return }
+            self.downstream = nil
+            _ = downstream.receive(value)
+            downstream.receive(completion: .finished)
+        }

-    var description: String { return "Just" }
+        func cancel() {
+            downstream = nil
+        }

-    var customMirror: Mirror {
-        return Mirror(self, unlabeledChildren: CollectionOfOne(_output))
+        var description: String { return "Just" }
+
+        var customMirror: Mirror {
+            return Mirror(self, unlabeledChildren: CollectionOfOne(value))
+        }
+
+        var playgroundDescription: Any { return description }
    }
 }
@@ -1,25 +0,0 @@
-//
-//  OperatorSubscription.swift
-//  
-//
-//  Created by Sergej Jaskiewicz on 26.06.2019.
-//
-
-internal class OperatorSubscription<Downstream: Subscriber>: CustomReflectable {
-    internal var downstream: Downstream?
-    internal var upstreamSubscription: Subscription?
-
-    internal var customMirror: Mirror {
-        return Mirror(self, children: EmptyCollection())
-    }
-
-    internal init(downstream: Downstream) {
-        self.downstream = downstream
-    }
-
-    internal func cancel() {
-        upstreamSubscription?.cancel()
-        upstreamSubscription = nil
-        downstream = nil
-    }
-}
@@ -50,8 +50,8 @@ extension Optional {
                self.output = output
            }

-            public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-                where Output == SubscriberType.Input, Failure == SubscriberType.Failure
+            public func receive<Downstream: Subscriber>(subscriber: Downstream)
+                where Output == Downstream.Input, Failure == Downstream.Failure
            {
                if let output = output {
                    subscriber.receive(subscription: Inner(value: output,
@@ -74,34 +74,44 @@ extension Optional {
 #endif
 }

-private final class Inner<SubscriberType: Subscriber>: Subscription,
-                                                       CustomStringConvertible,
-                                                       CustomReflectable
-{
-    private let _output: SubscriberType.Input
-    private var _downstream: SubscriberType?
+extension Optional.OCombine {
+    private final class Inner<Downstream: Subscriber>
+        : Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Wrapped
+    {
+        // NOTE: this class has been audited for thread safety.
+        // Combine doesn't use any locking here.

-    init(value: SubscriberType.Input, downstream: SubscriberType) {
-        _output = value
-        _downstream = downstream
-    }
+        private var downstream: Downstream?
+        private let output: Wrapped

-    func request(_ demand: Subscribers.Demand) {
-        if let downstream = _downstream, demand > 0 {
-            _ = downstream.receive(_output)
-            downstream.receive(completion: .finished)
-            _downstream = nil
+        init(value: Wrapped, downstream: Downstream) {
+            self.output = value
+            self.downstream = downstream
        }
-    }

-    func cancel() {
-        _downstream = nil
-    }
+        func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            guard let downstream = self.downstream else { return }
+            self.downstream = nil
+            _ = downstream.receive(output)
+            downstream.receive(completion: .finished)
+        }

-    var description: String { return "Optional" }
+        func cancel() {
+            downstream = nil
+        }

-    var customMirror: Mirror {
-        return Mirror(self, unlabeledChildren: CollectionOfOne(_output))
+        var description: String { return "Optional" }
+
+        var customMirror: Mirror {
+            return Mirror(self, unlabeledChildren: CollectionOfOne(output))
+        }
+
+        var playgroundDescription: Any { return description }
    }
 }

@@ -138,7 +148,7 @@ extension Optional.OCombine.Publisher {
    }

    public func collect() -> Optional<[Output]>.OCombine.Publisher {
-        return .init(self.output.map { [$0] })
+        return .init(self.output.map { [$0] } ?? [])
    }

    public func compactMap<ElementOfResult>(
@@ -229,7 +239,9 @@ extension Optional.OCombine.Publisher {

        // I don't know why, but Combine has this precondition
        precondition(range.upperBound < .max - 1)
-        return .init(output.flatMap { range.contains(0) ? $0 : nil })
+        return .init(
+            output.flatMap { (range.lowerBound == 0 && range.upperBound != 0) ? $0 : nil }
+        )
    }

    public func prefix(_ maxLength: Int) -> Optional<Output>.OCombine.Publisher {
@@ -0,0 +1,178 @@
+//
+//  Publishers.AllSatisfy.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 09.10.2019.
+//
+
+extension Publisher {
+
+    /// Publishes a single Boolean value that indicates whether all received elements pass
+    /// a given predicate.
+    ///
+    /// When this publisher receives an element, it runs the predicate against
+    /// the element. If the predicate returns `false`, the publisher produces a `false`
+    /// value and finishes. If the upstream publisher finishes normally, this publisher
+    /// produces a `true` value and finishes.
+    /// As a `reduce`-style operator, this publisher produces at most one value.
+    /// Backpressure note: Upon receiving any request greater than zero, this publisher
+    /// requests unlimited elements from the upstream publisher.
+    ///
+    /// - Parameter predicate: A closure that evaluates each received element.
+    ///   Return `true` to continue, or `false` to cancel the upstream and complete.
+    /// - Returns: A publisher that publishes a Boolean value that indicates whether
+    ///   all received elements pass a given predicate.
+    public func allSatisfy(
+        _ predicate: @escaping (Output) -> Bool
+    ) -> Publishers.AllSatisfy<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+
+    /// Publishes a single Boolean value that indicates whether all received elements pass
+    /// a given error-throwing predicate.
+    ///
+    /// When this publisher receives an element, it runs the predicate against
+    /// the element. If the predicate returns `false`, the publisher produces a `false`
+    /// value and finishes. If the upstream publisher finishes normally, this publisher
+    /// produces a `true` value and finishes. If the predicate throws an error,
+    /// the publisher fails, passing the error to its downstream.
+    /// As a `reduce`-style operator, this publisher produces at most one value.
+    /// Backpressure note: Upon receiving any request greater than zero, this publisher
+    /// requests unlimited elements from the upstream publisher.
+    ///
+    /// - Parameter predicate:  A closure that evaluates each received element.
+    ///   Return `true` to continue, or `false` to cancel the upstream and complete.
+    ///   The closure may throw, in which case the publisher cancels the upstream
+    ///   publisher and fails with the thrown error.
+    /// - Returns: A publisher that publishes a Boolean value that indicates whether
+    ///   all received elements pass a given predicate.
+    public func tryAllSatisfy(
+        _ predicate: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryAllSatisfy<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that publishes a single Boolean value that indicates whether
+    /// all received elements pass a given predicate.
+    public struct AllSatisfy<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Bool
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// A closure that evaluates each received element.
+        ///
+        ///  Return `true` to continue, or `false` to cancel the upstream and finish.
+        public let predicate: (Upstream.Output) -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Upstream.Output) -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure, Downstream.Input == Bool
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+
+    /// A publisher that publishes a single Boolean value that indicates whether
+    /// all received elements pass a given error-throwing predicate.
+    public struct TryAllSatisfy<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Bool
+
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// A closure that evaluates each received element.
+        ///
+        /// Return `true` to continue, or `false` to cancel the upstream and complete.
+        /// The closure may throw, in which case the publisher cancels the upstream
+        /// publisher and fails with the thrown error.
+        public let predicate: (Upstream.Output) throws -> Bool
+
+        public init(upstream: Upstream,
+                    predicate: @escaping (Upstream.Output) throws -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Failure == Error, Downstream.Input == Bool
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+}
+
+extension Publishers.AllSatisfy {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Bool,
+                         Upstream.Failure,
+                         (Upstream.Output) -> Bool>
+        where Downstream.Input == Output, Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) -> Bool) {
+            super.init(downstream: downstream, initial: true, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if !reduce(newValue) {
+                result = false
+                return .finished
+            }
+
+            return .continue
+        }
+
+        override var description: String { return "AllSatisfy" }
+    }
+}
+
+extension Publishers.TryAllSatisfy {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Bool,
+                         Upstream.Failure,
+                         (Upstream.Output) throws -> Bool>
+        where Downstream.Input == Output, Downstream.Failure == Error
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) throws -> Bool) {
+            super.init(downstream: downstream, initial: true, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            do {
+                if try !reduce(newValue) {
+                    result = false
+                    return .finished
+                }
+            } catch {
+                return .failure(error)
+            }
+
+            return .continue
+        }
+
+        override var description: String { return "TryAllSatisfy" }
+    }
+}
@@ -0,0 +1,189 @@
+//
+//  Publishers.Autoconnect.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 18/09/2019.
+//
+
+import COpenCombineHelpers
+
+extension ConnectablePublisher {
+
+    /// Automates the process of connecting or disconnecting from this connectable
+    /// publisher.
+    ///
+    /// Use `autoconnect()` to simplify working with `ConnectablePublisher` instances,
+    /// such as those created with `makeConnectable()`.
+    ///
+    ///     let autoconnectedPublisher = somePublisher
+    ///         .makeConnectable()
+    ///         .autoconnect()
+    ///         .subscribe(someSubscriber)
+    ///
+    /// - Returns: A publisher which automatically connects to its upstream connectable
+    ///   publisher.
+    public func autoconnect() -> Publishers.Autoconnect<Self> {
+        return .init(upstream: self)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that automatically connects and disconnects from this connectable
+    /// publisher.
+    public class Autoconnect<Upstream: ConnectablePublisher>: Publisher {
+
+        // NOTE: This class has been audited for thread safety
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        private enum State {
+            case disconnected
+            case connected(refcount: Int, connection: Cancellable)
+        }
+
+        /// The publisher from which this publisher receives elements.
+        public final let upstream: Upstream
+
+        private let lock = UnfairLock.allocate()
+
+        private var state = State.disconnected
+
+        public init(upstream: Upstream) {
+            self.upstream = upstream
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Input == Output, Downstream.Failure == Failure
+        {
+            let inner = Inner(parent: self, downstream: subscriber)
+            lock.lock()
+            switch state {
+            case let .connected(refcount, connection):
+                state = .connected(refcount: refcount + 1, connection: connection)
+                lock.unlock()
+                upstream.subscribe(inner)
+            case .disconnected:
+                lock.unlock()
+                upstream.subscribe(inner)
+                let connection = upstream.connect()
+                lock.lock()
+                state = .connected(refcount: 1, connection: connection)
+                lock.unlock()
+            }
+        }
+
+        fileprivate func willCancel() {
+            lock.lock()
+            switch state {
+            case let .connected(refcount, connection):
+                if refcount <= 1 {
+                    self.state = .disconnected
+                    lock.unlock()
+                    connection.cancel()
+                } else {
+                    state = .connected(refcount: refcount - 1, connection: connection)
+                    lock.unlock()
+                }
+            case .disconnected:
+                lock.unlock()
+            }
+        }
+    }
+}
+
+extension Publishers.Autoconnect {
+
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Failure
+    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        fileprivate let combineIdentifier = CombineIdentifier()
+
+        private let parent: Publishers.Autoconnect<Upstream>
+
+        private let downstream: Downstream
+
+        fileprivate init(parent: Publishers.Autoconnect<Upstream>,
+                         downstream: Downstream) {
+            self.parent = parent
+            self.downstream = downstream
+        }
+
+        fileprivate func receive(subscription: Subscription) {
+            let sideEffectSubscription = SideEffectSubscription(subscription,
+                                                                parent: parent)
+            downstream.receive(subscription: sideEffectSubscription)
+        }
+
+        fileprivate func receive(_ input: Upstream.Output) -> Subscribers.Demand {
+            return downstream.receive(input)
+        }
+
+        fileprivate func receive(completion: Subscribers.Completion<Failure>) {
+            downstream.receive(completion: completion)
+        }
+
+        fileprivate var description: String { return "Autoconnect" }
+
+        fileprivate var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("parent", parent),
+                ("downstream", downstream)
+            ]
+            return Mirror(self, children: children)
+        }
+
+        fileprivate var playgroundDescription: Any { return description }
+    }
+
+    private struct SideEffectSubscription
+        : Subscription,
+          CustomStringConvertible,
+          CustomPlaygroundDisplayConvertible
+    {
+        private let parent: Publishers.Autoconnect<Upstream>
+
+        private let upstreamSubscription: Subscription
+
+        fileprivate init(_ upstreamSubscription: Subscription,
+                         parent: Publishers.Autoconnect<Upstream>) {
+            self.parent = parent
+            self.upstreamSubscription = upstreamSubscription
+        }
+
+        fileprivate func request(_ demand: Subscribers.Demand) {
+            upstreamSubscription.request(demand)
+        }
+
+        fileprivate func cancel() {
+            parent.willCancel()
+            upstreamSubscription.cancel()
+        }
+
+        fileprivate var combineIdentifier: CombineIdentifier {
+            return upstreamSubscription.combineIdentifier
+        }
+
+        fileprivate var description: String {
+            return String(describing: upstreamSubscription)
+        }
+
+        var playgroundDescription: Any {
+            return description
+        }
+    }
+}
@@ -0,0 +1,85 @@
+//
+//  Publishers.Collect.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 09.10.2019.
+//
+
+extension Publisher {
+
+    /// Collects all received elements, and emits a single array of the collection when
+    /// the upstream publisher finishes.
+    ///
+    /// If the upstream publisher fails with an error, this publisher forwards the error
+    /// to the downstream receiver instead of sending its output.
+    /// This publisher requests an unlimited number of elements from the upstream
+    /// publisher. It only sends the collected array to its downstream after a request
+    /// whose demand is greater than 0 items.
+    /// Note: This publisher uses an unbounded amount of memory to store the received
+    /// values.
+    ///
+    /// - Returns: A publisher that collects all received items and returns them as
+    ///   an array upon completion.
+    public func collect() -> Publishers.Collect<Self> {
+        return .init(upstream: self)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that buffers items.
+    public struct Collect<Upstream: Publisher>: Publisher {
+
+        public typealias Output = [Upstream.Output]
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher that this publisher receives elements from.
+        public let upstream: Upstream
+
+        public init(upstream: Upstream) {
+            self.upstream = upstream
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure,
+                  Downstream.Input == [Upstream.Output]
+        {
+            upstream.subscribe(Inner(downstream: subscriber))
+        }
+    }
+}
+
+extension Publishers.Collect: Equatable where Upstream: Equatable {}
+
+extension Publishers.Collect {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         [Upstream.Output],
+                         Upstream.Failure,
+                         Void>
+        where Downstream.Input == [Upstream.Output],
+              Downstream.Failure == Upstream.Failure
+    {
+        fileprivate init(downstream: Downstream) {
+            super.init(downstream: downstream, initial: [], reduce: ())
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            result!.append(newValue)
+            return .continue
+        }
+
+        override var description: String {
+            return "Collect"
+        }
+
+        override var customMirror: Mirror {
+            let children: CollectionOfOne<Mirror.Child> = .init(("count", result!.count))
+            return Mirror(self, children: children)
+        }
+    }
+}
@@ -0,0 +1,168 @@
+//
+//  Publishers.CompactMap.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 11.07.2019.
+//
+
+extension Publisher {
+
+    /// Calls a closure with each received element and publishes any returned
+    /// optional that has a value.
+    ///
+    /// - Parameter transform: A closure that receives a value and returns
+    ///   an optional value.
+    /// - Returns: A publisher that republishes all non-`nil` results of calling
+    ///   the transform closure.
+    public func compactMap<ElementOfResult>(
+        _ transform: @escaping (Output) -> ElementOfResult?
+    ) -> Publishers.CompactMap<Self, ElementOfResult> {
+        return .init(upstream: self, transform: transform)
+    }
+
+    /// Calls an error-throwing closure with each received element and publishes
+    /// any returned optional that has a value.
+    ///
+    /// If the closure throws an error, the publisher cancels the upstream and sends
+    /// the thrown error to the downstream receiver as a `Failure`.
+    ///
+    /// - Parameter transform: an error-throwing closure that receives a value
+    ///   and returns an optional value.
+    /// - Returns: A publisher that republishes all non-`nil` results of calling
+    ///   the `transform` closure.
+    public func tryCompactMap<ElementOfResult>(
+        _ transform: @escaping (Output) throws -> ElementOfResult?
+    ) -> Publishers.TryCompactMap<Self, ElementOfResult> {
+        return .init(upstream: self, transform: transform)
+    }
+}
+
+extension Publishers.CompactMap {
+
+    public func compactMap<ElementOfResult>(
+        _ transform: @escaping (Output) -> ElementOfResult?
+    ) -> Publishers.CompactMap<Upstream, ElementOfResult> {
+        return .init(upstream: upstream,
+                     transform: { self.transform($0).flatMap(transform) })
+    }
+
+    public func map<ElementOfResult>(
+        _ transform: @escaping (Output) -> ElementOfResult
+    ) -> Publishers.CompactMap<Upstream, ElementOfResult> {
+        return .init(upstream: upstream,
+                     transform: { self.transform($0).map(transform) })
+    }
+}
+
+extension Publishers.TryCompactMap {
+
+    public func compactMap<ElementOfResult>(
+        _ transform: @escaping (Output) throws -> ElementOfResult?
+    ) -> Publishers.TryCompactMap<Upstream, ElementOfResult> {
+        return .init(upstream: upstream,
+                     transform: { try self.transform($0).flatMap(transform) })
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that republishes all non-`nil` results of calling a closure
+    /// with each received element.
+    public struct CompactMap<Upstream: Publisher, Output>: Publisher {
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// A closure that receives values from the upstream publisher
+        /// and returns optional values.
+        public let transform: (Upstream.Output) -> Output?
+
+        public init(upstream: Upstream,
+                    transform: @escaping (Upstream.Output) -> Output?) {
+            self.upstream = upstream
+            self.transform = transform
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Input == Output, Downstream.Failure == Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, filter: transform))
+        }
+    }
+
+    /// A publisher that republishes all non-`nil` results of calling an error-throwing
+    /// closure with each received element.
+    public struct TryCompactMap<Upstream: Publisher, Output>: Publisher {
+
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// An error-throwing closure that receives values from the upstream publisher
+        /// and returns optional values.
+        ///
+        /// If this closure throws an error, the publisher fails.
+        public let transform: (Upstream.Output) throws -> Output?
+
+        public init(upstream: Upstream,
+                    transform: @escaping (Upstream.Output) throws -> Output?) {
+            self.upstream = upstream
+            self.transform = transform
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Input == Output, Downstream.Failure == Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, filter: transform))
+        }
+    }
+}
+
+extension Publishers.CompactMap {
+    private final class Inner<Downstream: Subscriber>
+        : FilterProducer<Downstream,
+                         Upstream.Output,
+                         Output,
+                         Upstream.Failure,
+                         (Upstream.Output) -> Output?>
+        where Downstream.Failure == Upstream.Failure, Downstream.Input == Output
+    {
+        // NOTE: This class has been audited for thread safety
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Output?, Downstream.Failure> {
+            return .continue(filter(newValue))
+        }
+
+        override var description: String { return "CompactMap" }
+    }
+}
+
+extension Publishers.TryCompactMap {
+    private final class Inner<Downstream: Subscriber>
+        : FilterProducer<Downstream,
+                         Upstream.Output,
+                         Output,
+                         Upstream.Failure,
+                         (Upstream.Output) throws -> Output?>
+        where Downstream.Failure == Error, Downstream.Input == Output
+    {
+        // NOTE: This class has been audited for thread safety
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Output?, Error> {
+            do {
+                return try .continue(filter(newValue))
+            } catch {
+                return .failure(error)
+            }
+        }
+
+        override var description: String { return "TryCompactMap" }
+    }
+}
@@ -0,0 +1,246 @@
+//
+//  Publishers.Comparison.swift
+//  OpenCombine
+//
+//  Created by Ilija Puaca on 22/7/19.
+//
+
+extension Publisher where Output: Comparable {
+
+    /// Publishes the minimum value received from the upstream publisher, after it
+    /// finishes.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    ///
+    /// - Returns: A publisher that publishes the minimum value received from the upstream
+    ///   publisher, after the upstream publisher finishes.
+    public func min() -> Publishers.Comparison<Self> {
+        return max(by: >)
+    }
+
+    /// Publishes the maximum value received from the upstream publisher, after it
+    /// finishes.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    ///
+    /// - Returns: A publisher that publishes the maximum value received from the upstream
+    ///   publisher, after the upstream publisher finishes.
+    public func max() -> Publishers.Comparison<Self> {
+        return max(by: <)
+    }
+}
+
+extension Publisher {
+
+    /// Publishes the minimum value received from the upstream publisher, after it
+    /// finishes.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    ///
+    /// - Parameter areInIncreasingOrder: A closure that receives two elements and returns
+    ///   `true` if they are in increasing order.
+    /// - Returns: A publisher that publishes the minimum value received from the upstream
+    ///   publisher, after the upstream publisher finishes.
+    public func min(
+        by areInIncreasingOrder: @escaping (Output, Output) -> Bool
+    ) -> Publishers.Comparison<Self> {
+        return max(by: { areInIncreasingOrder($1, $0) })
+    }
+
+    /// Publishes the minimum value received from the upstream publisher, using the
+    /// provided error-throwing closure to order the items.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    ///
+    /// - Parameter areInIncreasingOrder: A throwing closure that receives two elements
+    ///   and returns `true` if they are in increasing order. If this closure throws, the
+    ///   publisher terminates with a `Failure`.
+    /// - Returns: A publisher that publishes the minimum value received from the upstream
+    ///   publisher, after the upstream publisher finishes.
+    public func tryMin(
+        by areInIncreasingOrder: @escaping (Output, Output) throws -> Bool
+    ) -> Publishers.TryComparison<Self> {
+        return tryMax(by: { try areInIncreasingOrder($1, $0) })
+    }
+
+    /// Publishes the maximum value received from the upstream publisher, using the
+    /// provided ordering closure.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    ///
+    /// - Parameter areInIncreasingOrder: A closure that receives two elements and returns
+    ///   `true` if they are in increasing order.
+    /// - Returns: A publisher that publishes the maximum value received from the upstream
+    ///   publisher, after the upstream publisher finishes.
+    public func max(
+        by areInIncreasingOrder: @escaping (Output, Output) -> Bool
+    ) -> Publishers.Comparison<Self> {
+        return .init(upstream: self, areInIncreasingOrder: areInIncreasingOrder)
+    }
+
+    /// Publishes the maximum value received from the upstream publisher, using the
+    /// provided error-throwing closure to order the items.
+    ///
+    /// After this publisher receives a request for more than 0 items, it requests
+    /// unlimited items from its upstream publisher.
+    /// - Parameter areInIncreasingOrder: A throwing closure that receives two elements
+    /// and returns `true` if they are in increasing order. If this closure throws, the
+    /// publisher terminates with a `Failure`.
+    /// - Returns: A publisher that publishes the maximum value received from the upstream
+    /// publisher, after the upstream publisher finishes.
+    public func tryMax(
+        by areInIncreasingOrder:  @escaping (Output, Output) throws -> Bool
+    ) -> Publishers.TryComparison<Self> {
+        return .init(upstream: self, areInIncreasingOrder: areInIncreasingOrder)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that republishes items from another publisher only if each new item is
+    /// in increasing order from the previously-published item.
+    public struct Comparison<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher that this publisher receives elements from.
+        public let upstream: Upstream
+
+        /// A closure that receives two elements and returns `true` if they are in
+        /// increasing order.
+        public let areInIncreasingOrder: (Upstream.Output, Upstream.Output) -> Bool
+
+        public init(
+            upstream: Upstream,
+            areInIncreasingOrder: @escaping (Upstream.Output, Upstream.Output) -> Bool
+        ) {
+            self.upstream = upstream
+            self.areInIncreasingOrder = areInIncreasingOrder
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure,
+                  Upstream.Output == Downstream.Input
+        {
+            let inner = Inner(downstream: subscriber,
+                              areInIncreasingOrder: areInIncreasingOrder)
+            upstream.subscribe(inner)
+        }
+    }
+
+    /// A publisher that republishes items from another publisher only if each new item is
+    /// in increasing order from the previously-published item, and fails if the ordering
+    /// logic throws an error.
+    public struct TryComparison<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Error
+
+        /// The publisher that this publisher receives elements from.
+        public let upstream: Upstream
+
+        /// A closure that receives two elements and returns `true` if they are in
+        /// increasing order.
+        public let areInIncreasingOrder: (Upstream.Output, Upstream.Output) throws -> Bool
+
+        public init(
+            upstream: Upstream,
+            areInIncreasingOrder:
+                @escaping (Upstream.Output, Upstream.Output) throws -> Bool
+        ) {
+            self.upstream = upstream
+            self.areInIncreasingOrder = areInIncreasingOrder
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Output == Downstream.Input, Downstream.Failure == Error
+        {
+            let inner = Inner(downstream: subscriber,
+                              areInIncreasingOrder: areInIncreasingOrder)
+            upstream.subscribe(inner)
+        }
+    }
+}
+
+extension Publishers.Comparison {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output, Upstream.Output) -> Bool>
+    where Downstream.Input == Upstream.Output, Downstream.Failure == Upstream.Failure
+    {
+        fileprivate init(
+            downstream: Downstream,
+            areInIncreasingOrder: @escaping (Upstream.Output, Upstream.Output) -> Bool
+        ) {
+            super.init(downstream: downstream, initial: nil, reduce: areInIncreasingOrder)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if let result = self.result {
+                if reduce(result, newValue) {
+                    self.result = newValue
+                }
+            } else {
+                self.result = newValue
+            }
+            return .continue
+        }
+
+        override var description: String {
+            return "Comparison"
+        }
+    }
+}
+
+extension Publishers.TryComparison {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output, Upstream.Output) throws -> Bool>
+    where Downstream.Input == Upstream.Output, Downstream.Failure == Error
+    {
+        fileprivate init(
+            downstream: Downstream,
+            areInIncreasingOrder:
+                @escaping (Upstream.Output, Upstream.Output) throws -> Bool
+        ) {
+            super.init(downstream: downstream, initial: nil, reduce: areInIncreasingOrder)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            do {
+                if let result = self.result {
+                    if try reduce(result, newValue) {
+                        self.result = newValue
+                    }
+                } else {
+                    self.result = newValue
+                }
+                return .continue
+            } catch {
+                return .failure(error)
+            }
+        }
+
+        override var description: String {
+            return "TryComparison"
+        }
+    }
+}
@@ -0,0 +1,235 @@
+//
+//  Publishers.Contains.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 09.10.2019.
+//
+
+extension Publisher where Output: Equatable {
+
+    /// Publishes a Boolean value upon receiving an element equal to the argument.
+    ///
+    /// The contains publisher consumes all received elements until the upstream publisher
+    /// produces a matching element. At that point, it emits `true` and finishes normally.
+    /// If the upstream finishes normally without producing a matching element,
+    /// this publisher emits `false`, then finishes.
+    ///
+    /// - Parameter output: An element to match against.
+    /// - Returns: A publisher that emits the Boolean value `true` when the upstream
+    ///   publisher emits a matching value.
+    public func contains(_ output: Output) -> Publishers.Contains<Self> {
+        return .init(upstream: self, output: output)
+    }
+}
+
+extension Publisher {
+
+    /// Publishes a Boolean value upon receiving an element that satisfies the predicate
+    /// closure.
+    ///
+    /// This operator consumes elements produced from the upstream publisher until
+    /// the upstream publisher produces a matching element.
+    ///
+    /// - Parameter predicate: A closure that takes an element as its parameter and
+    ///   returns a Boolean value indicating whether the element satisfies the closure’s
+    ///   comparison logic.
+    /// - Returns: A publisher that emits the Boolean value `true` when the upstream
+    ///   publisher emits a matching value.
+    public func contains(
+        where predicate: @escaping (Output) -> Bool
+    ) -> Publishers.ContainsWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+
+    /// Publishes a Boolean value upon receiving an element that satisfies
+    /// the throwing predicate closure.
+    ///
+    /// This operator consumes elements produced from the upstream publisher until
+    /// the upstream publisher produces a matching element. If the closure throws,
+    /// the stream fails with an error.
+    ///
+    /// - Parameter predicate: A closure that takes an element as its parameter and
+    ///   returns a Boolean value indicating whether the element satisfies the closure’s
+    ///   comparison logic.
+    /// - Returns: A publisher that emits the Boolean value `true` when the upstream
+    ///   publisher emits a matching value.
+    public func tryContains(
+        where predicate: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryContainsWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that emits a Boolean value when a specified element is received from
+    /// its upstream publisher.
+    public struct Contains<Upstream: Publisher>: Publisher
+        where Upstream.Output: Equatable
+    {
+        public typealias Output = Bool
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The element to scan for in the upstream publisher.
+        public let output: Upstream.Output
+
+        public init(upstream: Upstream, output: Upstream.Output) {
+            self.upstream = upstream
+            self.output = output
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure, Downstream.Input == Bool
+        {
+            upstream.subscribe(Inner(downstream: subscriber, output: output))
+        }
+    }
+
+    /// A publisher that emits a Boolean value upon receiving an element that satisfies
+    /// the predicate closure.
+    public struct ContainsWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Bool
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The closure that determines whether the publisher should consider an element
+        /// as a match.
+        public let predicate: (Upstream.Output) -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Upstream.Output) -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure, Downstream.Input == Bool
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+
+    /// A publisher that emits a Boolean value upon receiving an element that satisfies
+    /// the throwing predicate closure.
+    public struct TryContainsWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Bool
+
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The error-throwing closure that determines whether this publisher should
+        /// emit a `true` element.
+        public let predicate: (Upstream.Output) throws -> Bool
+
+        public init(upstream: Upstream,
+                    predicate: @escaping (Upstream.Output) throws -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Failure == Error, Downstream.Input == Bool
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+}
+
+extension Publishers.Contains {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream, Upstream.Output, Bool, Upstream.Failure, Void>
+        where Upstream.Failure == Downstream.Failure, Downstream.Input == Bool
+    {
+        private let output: Upstream.Output
+
+        fileprivate init(downstream: Downstream, output: Upstream.Output) {
+            self.output = output
+            super.init(downstream: downstream, initial: false, reduce: ())
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if newValue == output {
+                result = true
+                return .finished
+            }
+
+            return .continue
+        }
+
+        override var description: String { return "Contains" }
+    }
+}
+
+extension Publishers.Contains : Equatable where Upstream: Equatable {}
+
+extension Publishers.ContainsWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output, Bool,
+                         Upstream.Failure,
+                         (Upstream.Output) -> Bool>
+        where Upstream.Failure == Downstream.Failure, Downstream.Input == Bool
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) -> Bool) {
+            super.init(downstream: downstream, initial: false, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if reduce(newValue) {
+                result = true
+                return .finished
+            }
+
+            return .continue
+        }
+
+        override var description: String { return "ContainsWhere" }
+    }
+}
+
+extension Publishers.TryContainsWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output, Bool,
+                         Upstream.Failure,
+                         (Upstream.Output) throws -> Bool>
+        where Downstream.Failure == Error, Downstream.Input == Bool
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) throws -> Bool) {
+            super.init(downstream: downstream, initial: false, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            do {
+                if try reduce(newValue) {
+                    result = true
+                    return .finished
+                }
+            } catch {
+                return .failure(error)
+            }
+
+            return .continue
+        }
+
+        override var description: String { return "TryContainsWhere" }
+    }
+}
@@ -5,6 +5,17 @@
 //  Created by Joseph Spadafora on 6/25/19.
 //

+extension Publisher {
+
+    /// Publishes the number of elements received from the upstream publisher.
+    ///
+    /// - Returns: A publisher that consumes all elements until the upstream publisher
+    /// finishes, then emits a single value with the total number of elements received.
+    public func count() -> Publishers.Count<Self> {
+        return Publishers.Count(upstream: self)
+    }
+}
+
 extension Publishers {

    /// A publisher that publishes the number of elements received
@@ -33,62 +44,34 @@ extension Publishers {
        /// - Parameters:
        ///     - subscriber: The subscriber to attach to this `Publisher`.
        ///                   once attached it can begin to receive values.
-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Upstream.Failure == SubscriberType.Failure,
-                  SubscriberType.Input == Output
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure,
+                  Downstream.Input == Output
        {
-            let count = _Count<Upstream, SubscriberType>(downstream: subscriber)
-            upstream.subscribe(count)
+            upstream.subscribe(Inner(downstream: subscriber))
        }
    }
 }

-extension Publisher {
+extension Publishers.Count: Equatable where Upstream: Equatable {}

-    /// Publishes the number of elements received from the upstream publisher.
-    ///
-    /// - Returns: A publisher that consumes all elements until the upstream publisher
-    /// finishes, then emits a single value with the total number of elements received.
-    public func count() -> Publishers.Count<Self> {
-        return Publishers.Count(upstream: self)
-    }
-}
-
-private final class _Count<Upstream: Publisher, Downstream: Subscriber>
-    : OperatorSubscription<Downstream>,
-      Subscriber,
-      CustomStringConvertible,
-      Subscription
-    where Downstream.Input == Int,
-          Upstream.Failure == Downstream.Failure
-{
-
-    typealias Input = Upstream.Output
-    typealias Output = Int
-    typealias Failure = Downstream.Failure
-
-    private var _count = 0
-
-    var description: String { return "Count" }
-
-    func receive(subscription: Subscription) {
-        upstreamSubscription = subscription
-        downstream.receive(subscription: self)
-        upstreamSubscription?.request(.unlimited)
-    }
-
-    func receive(_ input: Input) -> Subscribers.Demand {
-        _count += 1
-        return .none
-    }
-
-    func receive(completion: Subscribers.Completion<Upstream.Failure>) {
-        if case .finished = completion {
-            _ = downstream.receive(_count)
+extension Publishers.Count {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream, Upstream.Output, Int, Failure, Void>
+        where Downstream.Input == Int,
+              Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream) {
+            super.init(downstream: downstream, initial: 0, reduce: ())
        }
-        downstream.receive(completion: completion)
-    }

-    func request(_ demand: Subscribers.Demand) {
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            result! += 1
+            return .continue
+        }
+
+        override var description: String { return "Count" }
    }
 }
@@ -1,109 +0,0 @@
-//
-//  Publishers.Decode.swift
-//
-//
-//  Created by Joseph Spadafora on 6/21/19.
-//
-
-extension Publishers {
-
-    public struct Decode<Upstream, Output, Coder>: Publisher
-        where Upstream: Publisher,
-              Output: Decodable,
-              Coder: TopLevelDecoder,
-              Upstream.Output == Coder.Input
-    {
-
-        /// The kind of errors this publisher might publish.
-        ///
-        /// Use `Never` if this `Publisher` does not publish errors.
-        public typealias Failure = Error
-
-        public let upstream: Upstream
-
-        private let _decoder: Coder
-
-        public init(upstream: Upstream, decoder: Coder) {
-            self.upstream = upstream
-            self._decoder = decoder
-        }
-
-        /// This function is called to attach the specified `Subscriber`
-        /// to this `Publisher` by `subscribe(_:)`
-        ///
-        /// - SeeAlso: `subscribe(_:)`
-        /// - Parameters:
-        ///     - subscriber: The subscriber to attach to this `Publisher`.
-        ///                   once attached it can begin to receive values.
-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Failure == SubscriberType.Failure, Output == SubscriberType.Input
-        {
-            let decodeSubscriber = _Decode<Upstream, SubscriberType, Coder>(
-                downstream: subscriber,
-                decoder: _decoder
-            )
-            upstream.subscribe(decodeSubscriber)
-        }
-    }
-}
-
-private final class _Decode<Upstream: Publisher,
-                            Downstream: Subscriber,
-                            Coder: TopLevelDecoder>
-    : OperatorSubscription<Downstream>,
-      Subscriber,
-      CustomStringConvertible,
-      Subscription
-    where Downstream.Input: Decodable,
-          Coder.Input == Upstream.Output,
-          Downstream.Failure == Error {
-
-    typealias Input = Upstream.Output
-    typealias Failure = Upstream.Failure
-    typealias Output = Downstream.Input
-
-    private let _decoder: Coder
-
-    var description: String { return "Decode" }
-
-    init(downstream: Downstream, decoder: Coder) {
-        self._decoder = decoder
-        super.init(downstream: downstream)
-    }
-
-    func receive(subscription: Subscription) {
-        upstreamSubscription = subscription
-        downstream.receive(subscription: self)
-    }
-
-    func receive(_ input: Input) -> Subscribers.Demand {
-        do {
-            let value = try _decoder.decode(Downstream.Input.self, from: input)
-            return downstream.receive(value)
-        } catch {
-            downstream.receive(completion: .failure(error))
-            cancel()
-            return .none
-        }
-    }
-
-    func receive(completion: Subscribers.Completion<Failure>) {
-        downstream.receive(completion: completion.eraseError())
-    }
-
-    func request(_ demand: Subscribers.Demand) {
-        upstreamSubscription?.request(demand)
-    }
-}
-
-extension Publisher {
-    public func decode<Item: Decodable,
-                       Coder: TopLevelDecoder>(
-        type: Item.Type,
-        decoder: Coder
-    ) -> Publishers.Decode<Self, Item, Coder>
-        where Self.Output == Coder.Input
-    {
-        return Publishers.Decode(upstream: self, decoder: decoder)
-    }
-}
@@ -0,0 +1,145 @@
+//
+//  Publishers.Drop.swift
+//
+//
+//  Created by Sven Weidauer on 03.10.2019.
+//
+
+import COpenCombineHelpers
+
+extension Publisher {
+    /// Omits the specified number of elements before republishing subsequent elements.
+    ///
+    /// - Parameter count: The number of elements to omit.
+    /// - Returns: A publisher that does not republish the first `count` elements.
+    public func dropFirst(_ count: Int = 1) -> Publishers.Drop<Self> {
+        return .init(upstream: self, count: count)
+    }
+}
+
+extension Publishers {
+    /// A publisher that omits a specified number of elements before republishing
+    /// later elements.
+    public struct Drop<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The number of elements to drop.
+        public let count: Int
+
+        public init(upstream: Upstream, count: Int) {
+            self.upstream = upstream
+            self.count = count
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure,
+                  Upstream.Output == Downstream.Input
+        {
+            let inner = Inner(downstream: subscriber, count: count)
+            upstream.subscribe(inner)
+            subscriber.receive(subscription: inner)
+        }
+    }
+}
+
+extension Publishers.Drop: Equatable where Upstream: Equatable {}
+
+extension Publishers.Drop {
+    private final class Inner<Downstream: Subscriber>
+        : Subscription,
+          Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Upstream.Output == Downstream.Input,
+              Upstream.Failure == Downstream.Failure
+    {
+        // NOTE: This class has been audited for thread safety.
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let lock = UnfairLock.allocate()
+
+        private var subscription: Subscription?
+
+        private var pendingDemand = Subscribers.Demand.none
+
+        private var count: Int
+
+        fileprivate init(downstream: Downstream, count: Int) {
+            self.downstream = downstream
+            self.count = count
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        func receive(subscription: Subscription) {
+            lock.lock()
+            guard self.subscription == nil else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            self.subscription = subscription
+            precondition(count >= 0, "count must not be negative")
+            let demandToRequestFromUpstream = pendingDemand + count
+            lock.unlock()
+            if demandToRequestFromUpstream > 0 {
+                subscription.request(demandToRequestFromUpstream)
+            }
+        }
+
+        func receive(_ input: Upstream.Output) -> Subscribers.Demand {
+            // Combine doesn't lock here!
+            if count > 0 {
+                count -= 1
+                return .none
+            }
+            return downstream.receive(input)
+        }
+
+        func receive(completion: Subscribers.Completion<Upstream.Failure>) {
+            // Combine doesn't lock here!
+            subscription = nil
+            downstream.receive(completion: completion)
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            lock.lock()
+            guard let subscription = self.subscription else {
+                self.pendingDemand += demand
+                lock.unlock()
+                return
+            }
+            lock.unlock()
+            subscription.request(demand)
+        }
+
+        func cancel() {
+            // Combine doesn't lock here!
+            subscription?.cancel()
+            subscription = nil
+        }
+
+        var description: String { return "Drop" }
+
+        var customMirror: Mirror {
+            return Mirror(self, children: EmptyCollection())
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
@@ -5,6 +5,42 @@
 //  Created by Sergej Jaskiewicz on 16.06.2019.
 //

+import COpenCombineHelpers
+
+extension Publisher {
+
+    /// Omits elements from the upstream publisher until a given closure returns false,
+    /// before republishing all remaining elements.
+    ///
+    /// - Parameter predicate: A closure that takes an element as a parameter and returns
+    ///   a Boolean value indicating whether to drop the element from the publisher’s
+    ///   output.
+    /// - Returns: A publisher that skips over elements until the provided closure returns
+    ///   `false`.
+    public func drop(
+        while predicate: @escaping (Output) -> Bool
+    ) -> Publishers.DropWhile<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+
+    /// Omits elements from the upstream publisher until an error-throwing closure returns
+    /// false, before republishing all remaining elements.
+    ///
+    /// If the predicate closure throws, the publisher fails with an error.
+    ///
+    /// - Parameter predicate: A closure that takes an element as a parameter and returns
+    ///   a Boolean value indicating whether to drop the element from the publisher’s
+    ///   output.
+    /// - Returns: A publisher that skips over elements until the provided closure returns
+    ///   `false`, and then republishes all remaining elements. If the predicate closure
+    ///   throws, the publisher fails with an error.
+    public func tryDrop(
+        while predicate: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryDropWhile<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+}
+
 extension Publishers {

    /// A publisher that omits elements from an upstream publisher until a given closure
@@ -26,11 +62,10 @@ extension Publishers {
            self.predicate = predicate
        }

-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Failure == SubscriberType.Failure, Output == SubscriberType.Input
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
        {
-            let inner = Inner(downstream: subscriber, predicate: catching(predicate))
-            upstream.subscribe(inner)
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
        }
    }

@@ -53,151 +88,252 @@ extension Publishers {
            self.predicate = predicate
        }

-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Output == SubscriberType.Input, SubscriberType.Failure == Error
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Downstream.Failure == Error
        {
-            let inner = Inner(downstream: subscriber, predicate: catching(predicate))
-            upstream.subscribe(inner)
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
        }
    }
 }

-private class _DropWhile<Upstream: Publisher, Downstream: Subscriber>
-    : OperatorSubscription<Downstream>,
-      Subscription
-    where Upstream.Output == Downstream.Input
-{
-    typealias Input = Upstream.Output
-    typealias Failure = Upstream.Failure
-    typealias Predicate = (Input) -> Result<Bool, Downstream.Failure>
-
-    /// The predicate is reset to `nil` as soon as it returns `false`.
-    var predicate: Predicate?
-    var isCompleted = false
-
-    init(downstream: Downstream, predicate: @escaping Predicate) {
-        self.predicate = predicate
-        super.init(downstream: downstream)
-    }
-
-    func receive(subscription: Subscription) {
-        upstreamSubscription = subscription
-        downstream.receive(subscription: self)
-    }
-
-    func receive(_ input: Input) -> Subscribers.Demand {
-
-        guard upstreamSubscription != nil else {
-            return .none
-        }
-
-        guard let predicate = self.predicate else {
-            return downstream.receive(input)
-        }
-
-        // NOTE: until the predicate returns false, we will ask the upstream publisher
-        // for elements one by one.
-        //
-        // However, IF the downstream requests anything, we accumulate this demand in the
-        // `demand` property so that later we can provide the downstream with the correct
-        // amount of values.
-        //
-        // As soon as the predicate returns false, we switch to the mode where
-        // we just forward all the requests from the downstream to the upstream.
-        switch predicate(input) {
-        case .success(true):
-            return .max(1)
-        case .success(false):
-            // Okay, we hit the first element not satisfying the predicate,
-            // from now on we just republish the values to the downstream.
-            self.predicate = nil
-            return downstream.receive(input)
-        case .failure(let error):
-            downstream.receive(completion: .failure(error))
-            isCompleted = true
-            cancel()
-            return .none
-        }
-    }
-
-    func request(_ demand: Subscribers.Demand) {
-        upstreamSubscription?.request(demand)
-    }
-
-    override func cancel() {
-        upstreamSubscription?.cancel()
-        upstreamSubscription = nil
-        // Don't zero out downstream, that's what Combine does (probably a bug)
-    }
-}
-
 extension Publishers.DropWhile {
-
    private final class Inner<Downstream: Subscriber>
-        : _DropWhile<Upstream, Downstream>,
+        : Subscriber,
+          Subscription,
          CustomStringConvertible,
-          Subscriber
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
        where Upstream.Output == Downstream.Input, Downstream.Failure == Upstream.Failure
    {
-        var description: String { return "DropWhile" }
+        // NOTE: This class has been audited for thread safety.

-        func receive(completion: Subscribers.Completion<Failure>) {
-            guard !isCompleted else {
-                assertionFailure("unreachable")
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private var status = SubscriptionStatus.awaitingSubscription
+
+        private let downstream: Downstream
+
+        private var predicate: ((Input) -> Bool)?
+
+        private var dropping = true
+
+        private let lock = UnfairLock.allocate()
+
+        fileprivate init(downstream: Downstream, predicate: @escaping (Input) -> Bool) {
+            self.downstream = downstream
+            self.predicate = predicate
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        func receive(subscription: Subscription) {
+            lock.lock()
+            guard case .awaitingSubscription = status else {
+                lock.unlock()
+                subscription.cancel()
                return
            }
+            status = .subscribed(subscription)
+            lock.unlock()
+            downstream.receive(subscription: self)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            lock.lock()
+            guard case .subscribed = status, let shouldDrop = predicate else {
+                lock.unlock()
+                return .none
+            }
+            let dropping = self.dropping
+            lock.unlock()
+
+            if dropping {
+                if shouldDrop(input) {
+                    return .max(1)
+                } else {
+                    lock.lock()
+                    self.dropping = false
+                    lock.unlock()
+                }
+            }
+
+            return downstream.receive(input)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            lock.lock()
+            guard case .subscribed = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            predicate = nil
+            lock.unlock()
            downstream.receive(completion: completion)
        }
+
+        func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            lock.unlock()
+            subscription.request(demand)
+        }
+
+        func cancel() {
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            predicate = nil
+            lock.unlock()
+            subscription.cancel()
+        }
+
+        var description: String { return "DropWhile" }
+
+        var customMirror: Mirror { return Mirror(self, children: EmptyCollection()) }
+
+        var playgroundDescription: Any { return description }
    }
 }

 extension Publishers.TryDropWhile {
-
    private final class Inner<Downstream: Subscriber>
-        : _DropWhile<Upstream, Downstream>,
+        : Subscriber,
+          Subscription,
          CustomStringConvertible,
-          Subscriber
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
        where Upstream.Output == Downstream.Input, Downstream.Failure == Error
    {
-        var description: String { return "TryDropWhile" }
+        // NOTE: This class has been audited for thread safety.
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private var status = SubscriptionStatus.awaitingSubscription
+
+        private let downstream: Downstream
+
+        private var predicate: ((Input) throws -> Bool)?
+
+        private var dropping = true
+
+        private var finished = false
+
+        private let lock = UnfairLock.allocate()
+
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Input) throws -> Bool) {
+            self.downstream = downstream
+            self.predicate = predicate
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        func receive(subscription: Subscription) {
+            lock.lock()
+            guard case .awaitingSubscription = status else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            status = .subscribed(subscription)
+            lock.unlock()
+            downstream.receive(subscription: self)
+        }
+
+        func receive(_ input: Upstream.Output) -> Subscribers.Demand {
+            lock.lock()
+            guard case let .subscribed(subscription) = status,
+                  let shouldDrop = predicate else {
+                lock.unlock()
+                return .none
+            }
+            let dropping = self.dropping
+            lock.unlock()
+
+            if dropping {
+                do {
+                    if try shouldDrop(input) {
+                        return .max(1)
+                    } else {
+                        lock.lock()
+                        self.dropping = false
+                        lock.unlock()
+                    }
+                } catch {
+                    lock.lock()
+                    status = .terminal
+                    predicate = nil
+                    finished = true
+                    lock.unlock()
+                    subscription.cancel()
+                    downstream.receive(completion: .failure(error))
+                    return .none
+                }
+            }
+
+            return downstream.receive(input)
+        }

        func receive(completion: Subscribers.Completion<Failure>) {
-            guard !isCompleted else { return }
-            downstream.receive(completion: completion.eraseError())
+            lock.lock()
+            guard case .subscribed = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            let wasFinished = finished
+            finished = true
+            lock.unlock()
+
+            if !wasFinished {
+                downstream.receive(completion: completion.eraseError())
+            }
        }
-    }
-}
-
-extension Publisher {
-
-    /// Omits elements from the upstream publisher until a given closure returns false,
-    /// before republishing all remaining elements.
-    ///
-    /// - Parameter predicate: A closure that takes an element as a parameter and returns
-    ///   a Boolean value indicating whether to drop the element from the publisher’s
-    ///   output.
-    /// - Returns: A publisher that skips over elements until the provided closure returns
-    ///   `false`.
-    public func drop(
-        while predicate: @escaping (Output) -> Bool
-    ) -> Publishers.DropWhile<Self> {
-        return Publishers.DropWhile(upstream: self, predicate: predicate)
-    }
-
-    /// Omits elements from the upstream publisher until an error-throwing closure returns
-    /// false, before republishing all remaining elements.
-    ///
-    /// If the predicate closure throws, the publisher fails with an error.
-    ///
-    /// - Parameter predicate: A closure that takes an element as a parameter and returns
-    ///   a Boolean value indicating whether to drop the element from the publisher’s
-    ///   output.
-    /// - Returns: A publisher that skips over elements until the provided closure returns
-    ///   `false`, and then republishes all remaining elements. If the predicate closure
-    ///   throws, the publisher fails with an error.
-    public func tryDrop(
-        while predicate: @escaping (Output) throws -> Bool
-    ) -> Publishers.TryDropWhile<Self> {
-        return Publishers.TryDropWhile(upstream: self, predicate: predicate)
+
+        func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            lock.unlock()
+            subscription.request(demand)
+        }
+
+        func cancel() {
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            predicate = nil
+            finished = true
+            lock.unlock()
+            subscription.cancel()
+        }
+
+        var description: String { return "TryDropWhile" }
+
+        var customMirror: Mirror { return Mirror(self, children: EmptyCollection()) }
+
+        var playgroundDescription: Any { return description }
    }
 }
@@ -1,109 +0,0 @@
-//
-//  Publishers.Encode.swift
-//
-//
-//  Created by Joseph Spadafora on 6/22/19.
-//
-
-extension Publishers {
-
-    public struct Encode<Upstream, Coder>: Publisher
-        where Upstream: Publisher,
-              Coder: TopLevelEncoder,
-              Upstream.Output: Encodable
-    {
-
-        /// The kind of errors this publisher might publish.
-        ///
-        /// Use `Never` if this `Publisher` does not publish errors.
-        public typealias Failure = Error
-
-        /// The kind of values published by this publisher.
-        public typealias Output = Coder.Output
-
-        public let upstream: Upstream
-
-        private let encoder: Coder
-
-        public init(upstream: Upstream, encoder: Coder) {
-            self.upstream = upstream
-            self.encoder = encoder
-        }
-
-        /// This function is called to attach the specified `Subscriber`
-        /// to this `Publisher` by `subscribe(_:)`
-        ///
-        /// - SeeAlso: `subscribe(_:)`
-        /// - Parameters:
-        ///     - subscriber: The subscriber to attach to this `Publisher`.
-        ///                   once attached it can begin to receive values.
-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Failure == SubscriberType.Failure, Output == SubscriberType.Input
-        {
-            let encodeSubscriber = _Encode<Upstream, SubscriberType, Coder>(
-                downstream: subscriber,
-                encoder: encoder
-            )
-            upstream.subscribe(encodeSubscriber)
-        }
-    }
-}
-
-private final class _Encode<Upstream: Publisher,
-                            Downstream: Subscriber,
-                            Coder: TopLevelEncoder>
-    : OperatorSubscription<Downstream>,
-      Subscriber,
-      CustomStringConvertible,
-      Subscription
-    where Coder.Output == Downstream.Input,
-          Upstream.Output: Encodable,
-          Downstream.Failure == Error {
-
-    typealias Input = Upstream.Output
-    typealias Failure = Upstream.Failure
-    typealias Output = Downstream.Input
-
-    private let _encoder: Coder
-
-    var description: String { return "Encode" }
-
-    init(downstream: Downstream, encoder: Coder) {
-        self._encoder = encoder
-        super.init(downstream: downstream)
-    }
-
-    func receive(subscription: Subscription) {
-        upstreamSubscription = subscription
-        downstream.receive(subscription: self)
-    }
-
-    func receive(_ input: Input) -> Subscribers.Demand {
-        do {
-            let value = try _encoder.encode(input)
-            return downstream.receive(value)
-        } catch {
-            downstream.receive(completion: .failure(error))
-            cancel()
-            return .none
-        }
-    }
-
-    func receive(completion: Subscribers.Completion<Failure>) {
-        downstream.receive(completion: completion.eraseError())
-    }
-
-    func request(_ demand: Subscribers.Demand) {
-        upstreamSubscription?.request(demand)
-    }
-}
-
-extension Publisher {
-    public func encode<Coder>(
-        encoder: Coder
-    ) -> Publishers.Encode<Self, Coder>
-        where Coder: TopLevelEncoder
-    {
-        return Publishers.Encode(upstream: self, encoder: encoder)
-    }
-}
@@ -0,0 +1,167 @@
+${template_header}
+//
+//  Publishers.Encode.swift.gyb
+//
+//
+//  Created by Joseph Spadafora on 6/22/19.
+//
+
+%{
+instantiations = ['Encode', 'Decode']
+}%
+extension Publisher {
+
+    /// Encodes the output from upstream using a specified `TopLevelEncoder`.
+    /// For example, use `JSONEncoder`.
+    public func encode<Coder: TopLevelEncoder>(
+        encoder: Coder
+    ) -> Publishers.Encode<Self, Coder> {
+        return .init(upstream: self, encoder: encoder)
+    }
+
+    /// Decodes the output from upstream using a specified `TopLevelDecoder`.
+    /// For example, use `JSONDecoder`.
+    public func decode<Item: Decodable, Coder: TopLevelDecoder>(
+        type: Item.Type,
+        decoder: Coder
+    ) -> Publishers.Decode<Self, Item, Coder> where Output == Coder.Input {
+        return .init(upstream: self, decoder: decoder)
+    }
+}
+
+extension Publishers {
+
+    public struct Encode<Upstream: Publisher, Coder: TopLevelEncoder>: Publisher
+        where Upstream.Output: Encodable
+    {
+        public typealias Failure = Error
+
+        public typealias Output = Coder.Output
+
+        public let upstream: Upstream
+
+        private let _encode: (Upstream.Output) throws -> Output
+
+        public init(upstream: Upstream, encoder: Coder) {
+            self.upstream = upstream
+            self._encode = encoder.encode
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, encode: _encode))
+        }
+    }
+
+    public struct Decode<Upstream: Publisher, Output: Decodable, Coder: TopLevelDecoder>
+        : Publisher
+        where Upstream.Output == Coder.Input
+    {
+        public typealias Failure = Error
+
+        public let upstream: Upstream
+
+        private let _decode: (Upstream.Output) throws -> Output
+
+        public init(upstream: Upstream, decoder: Coder) {
+            self.upstream = upstream
+            self._decode = { try decoder.decode(Output.self, from: $0) }
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, decode: _decode))
+        }
+    }
+}
+% for instantiation in instantiations:
+
+extension Publishers.${instantiation} {
+    private final class Inner<Downstream: Subscriber>
+        : Subscriber,
+          Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Error
+    {
+        // NOTE: This class has been audited for thread safety.
+        // Combine doesn't use any locking here.
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let ${instantiation.lower()}: (Upstream.Output) throws -> Output
+
+        private var finished = false
+
+        private var subscription: Subscription?
+
+        fileprivate init(
+            downstream: Downstream,
+            ${instantiation.lower()}: @escaping (Upstream.Output) throws -> Output
+        ) {
+            self.downstream = downstream
+            self.${instantiation.lower()} = ${instantiation.lower()}
+        }
+
+        func receive(subscription: Subscription) {
+            if finished || self.subscription != nil {
+                subscription.cancel()
+                return
+            }
+            self.subscription = subscription
+            downstream.receive(subscription: self)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            if finished { return .none }
+            do {
+                return try downstream.receive(${instantiation.lower()}(input))
+            } catch {
+                finished = true
+                subscription?.cancel()
+                subscription = nil
+                downstream.receive(completion: .failure(error))
+                return .none
+            }
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            if finished { return }
+            finished = true
+            subscription = nil
+            downstream.receive(completion: completion.eraseError())
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            subscription?.request(demand)
+        }
+
+        func cancel() {
+            guard let subscription = self.subscription, !finished else { return }
+            subscription.cancel()
+            self.subscription = nil
+            finished = true
+        }
+
+        var description: String { return "${instantiation}" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+                ("downstream", downstream),
+                ("finished", finished),
+                ("upstreamSubscription", subscription as Any)
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+% end
@@ -0,0 +1,188 @@
+//
+//  Publishers.Filter.swift
+//  
+//
+//  Created by Joseph Spadafora on 7/3/19.
+//
+
+extension Publisher {
+
+    /// Republishes all elements that match a provided closure.
+    ///
+    /// - Parameter isIncluded: A closure that takes one element and returns
+    ///   a Boolean value indicating whether to republish the element.
+    /// - Returns: A publisher that republishes all elements that satisfy the closure.
+    public func filter(
+        _ isIncluded: @escaping (Output) -> Bool
+    ) -> Publishers.Filter<Self> {
+        return Publishers.Filter(upstream: self, isIncluded: isIncluded)
+    }
+
+    /// Republishes all elements that match a provided error-throwing closure.
+    ///
+    /// If the `isIncluded` closure throws an error, the publisher fails with that error.
+    ///
+    /// - Parameter isIncluded:  A closure that takes one element and returns a
+    ///   Boolean value indicating whether to republish the element.
+    /// - Returns:  A publisher that republishes all elements that satisfy the closure.
+    public func tryFilter(
+        _ isIncluded: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryFilter<Self> {
+        return Publishers.TryFilter(upstream: self, isIncluded: isIncluded)
+    }
+}
+
+extension Publishers.Filter {
+
+    public func filter(
+        _ isIncluded: @escaping (Output) -> Bool
+    ) -> Publishers.Filter<Upstream> {
+        return .init(upstream: upstream) { self.isIncluded($0) && isIncluded($0) }
+    }
+
+    public func tryFilter(
+        _ isIncluded: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryFilter<Upstream> {
+        return .init(upstream: upstream) { try self.isIncluded($0) && isIncluded($0) }
+    }
+}
+
+extension Publishers.TryFilter {
+
+    public func filter(
+        _ isIncluded: @escaping (Output) -> Bool
+    ) -> Publishers.TryFilter<Upstream> {
+        return .init(upstream: upstream) { try self.isIncluded($0) && isIncluded($0) }
+    }
+
+    public func tryFilter(
+        _ isIncluded: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryFilter<Upstream> {
+        return .init(upstream: upstream) { try self.isIncluded($0) && isIncluded($0) }
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that republishes all elements that match a provided closure.
+    public struct Filter<Upstream: Publisher>: Publisher {
+
+        /// The kind of values published by this publisher.
+        public typealias Output = Upstream.Output
+
+        /// The kind of errors this publisher might publish.
+        ///
+        /// Use `Never` if this `Publisher` does not publish errors.
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// A closure that indicates whether to republish an element.
+        public let isIncluded: (Upstream.Output) -> Bool
+
+        public init(upstream: Upstream, isIncluded: @escaping (Output) -> Bool) {
+            self.upstream = upstream
+            self.isIncluded = isIncluded
+        }
+
+        /// This function is called to attach the specified `Subscriber`
+        /// to this `Publisher` by `subscribe(_:)`
+        ///
+        /// - SeeAlso: `subscribe(_:)`
+        /// - Parameters:
+        ///     - subscriber: The subscriber to attach to this `Publisher`.
+        ///                   once attached it can begin to receive values.
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Failure == Downstream.Failure,
+                  Upstream.Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, filter: isIncluded))
+        }
+    }
+
+    /// A publisher that republishes all elements that match
+    /// a provided error-throwing closure.
+    public struct TryFilter<Upstream>: Publisher where Upstream: Publisher {
+
+        /// The kind of values published by this publisher.
+        public typealias Output = Upstream.Output
+
+        /// The kind of errors this publisher might publish.
+        ///
+        /// Use `Never` if this `Publisher` does not publish errors.
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// A error-throwing closure that indicates whether to republish an element.
+        public let isIncluded: (Upstream.Output) throws -> Bool
+
+        public init(upstream: Upstream,
+                    isIncluded: @escaping (Upstream.Output) throws -> Bool) {
+            self.upstream = upstream
+            self.isIncluded = isIncluded
+        }
+
+        /// This function is called to attach the specified `Subscriber`
+        /// to this `Publisher` by `subscribe(_:)`
+        ///
+        /// - SeeAlso: `subscribe(_:)`
+        /// - Parameters:
+        ///     - subscriber: The subscriber to attach to this `Publisher`.
+        ///                   once attached it can begin to receive values.
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Upstream.Output == Downstream.Input,
+                  Downstream.Failure == Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, filter: isIncluded))
+        }
+    }
+}
+
+extension Publishers.Filter {
+    private final class Inner<Downstream: Subscriber>
+        : FilterProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output) -> Bool>
+        where Upstream.Output == Downstream.Input, Upstream.Failure == Downstream.Failure
+    {
+        // NOTE: This class has been audited for thread safety
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Upstream.Output?, Downstream.Failure> {
+            return filter(newValue) ? .continue(newValue) : .continue(nil)
+        }
+
+        override var description: String { return "Filter" }
+    }
+}
+
+extension Publishers.TryFilter {
+    private final class Inner<Downstream: Subscriber>
+        : FilterProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output) throws -> Bool>
+        where Downstream.Input == Upstream.Output, Downstream.Failure == Error
+    {
+        // NOTE: This class has been audited for thread safety
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Upstream.Output?, Error> {
+            do {
+                return try filter(newValue) ? .continue(newValue) : .continue(nil)
+            } catch {
+                return .failure(error)
+            }
+        }
+
+        override var description: String { return "TryFilter" }
+    }
+}
@@ -0,0 +1,210 @@
+//
+//  Publishers.First.swift
+//  
+//
+//  Created by Joseph Spadafora on 7/8/19.
+//
+
+extension Publisher {
+
+    /// Publishes the first element of a stream, then finishes.
+    ///
+    /// If this publisher doesn’t receive any elements, it finishes without publishing.
+    /// - Returns: A publisher that only publishes the first element of a stream.
+    public func first() -> Publishers.First<Self> {
+        return .init(upstream: self)
+    }
+
+    /// Publishes the first element of a stream to
+    /// satisfy a predicate closure, then finishes.
+    ///
+    /// The publisher ignores all elements after the first.
+    /// If this publisher doesn’t receive any elements,
+    /// it finishes without publishing.
+    /// - Parameter predicate: A closure that takes an element as a parameter and
+    ///   returns a Boolean value that indicates whether to publish the element.
+    /// - Returns: A publisher that only publishes the first element of a stream
+    ///   that satifies the predicate.
+    public func first(
+        where predicate: @escaping (Output) -> Bool
+    ) -> Publishers.FirstWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+
+    /// Publishes the first element of a stream to satisfy a
+    /// throwing predicate closure, then finishes.
+    ///
+    /// The publisher ignores all elements after the first. If this publisher
+    /// doesn’t receive any elements, it finishes without publishing. If the
+    /// predicate closure throws, the publisher fails with an error.
+    /// - Parameter predicate: A closure that takes an element as a parameter and
+    ///   returns a Boolean value that indicates whether to publish the element.
+    /// - Returns: A publisher that only publishes the first element of a stream
+    ///   that satifies the predicate.
+    public func tryFirst(
+        where predicate: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryFirstWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that publishes the first element of a stream, then finishes.
+    public struct First<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        public init(upstream: Upstream) {
+            self.upstream = upstream
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber))
+        }
+    }
+
+    /// A publisher that only publishes the first element of a
+    /// stream to satisfy a predicate closure.
+    public struct FirstWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The closure that determines whether to publish an element.
+        public let predicate: (Output) -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Output) -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+
+    /// A publisher that only publishes the first element of a stream
+    /// to satisfy a throwing predicate closure.
+    public struct TryFirstWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The error-throwing closure that determines whether to publish an element.
+        public let predicate: (Output) throws -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Output) throws -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+}
+
+extension Publishers.First: Equatable where Upstream: Equatable {}
+
+extension Publishers.First {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         Void>
+        where Upstream.Output == Downstream.Input,
+              Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream) {
+            super.init(downstream: downstream, initial: nil, reduce: ())
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            result = newValue
+            return .finished
+        }
+
+        override var description: String { return "First" }
+    }
+}
+
+extension Publishers.FirstWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream, Output, Output, Failure, (Output) -> Bool>
+        where Upstream.Output == Downstream.Input,
+              Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream, predicate: @escaping (Output) -> Bool) {
+            super.init(downstream: downstream, initial: nil, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if reduce(newValue) {
+                result = newValue
+                return .finished
+            } else {
+                return .continue
+            }
+        }
+
+        override var description: String { return "TryFirst" }
+    }
+}
+
+extension Publishers.TryFirstWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Output,
+                         Output,
+                         Upstream.Failure,
+                         (Output) throws -> Bool>
+        where Upstream.Output == Downstream.Input, Downstream.Failure == Error
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Output) throws -> Bool) {
+            super.init(downstream: downstream, initial: nil, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Output
+        ) -> PartialCompletion<Void, Error> {
+            do {
+                if try reduce(newValue) {
+                    result = newValue
+                    return .finished
+                } else {
+                    return .continue
+                }
+            } catch {
+                return .failure(error)
+            }
+        }
+
+        override var description: String { return "TryFirstWhere" }
+    }
+}
@@ -0,0 +1,428 @@
+//
+//  Publishers.FlatMap.swift
+//
+//  Created by Eric Patey on 16.08.2019.
+//
+
+import COpenCombineHelpers
+
+extension Publisher {
+    /// Transforms all elements from an upstream publisher into a new or existing
+    /// publisher.
+    ///
+    /// `flatMap` merges the output from all returned publishers into a single stream of
+    /// output.
+    ///
+    /// - Parameters:
+    ///   - maxPublishers: The maximum number of publishers produced by this method.
+    ///   - transform: A closure that takes an element as a parameter and returns a
+    ///     publisher that produces elements of that type.
+    /// - Returns: A publisher that transforms elements from an upstream publisher into
+    ///   a publisher of that element’s type.
+    public func flatMap<Result, Child: Publisher>(
+        maxPublishers: Subscribers.Demand = .unlimited,
+        _ transform: @escaping (Output) -> Child
+    ) -> Publishers.FlatMap<Child, Self>
+        where Result == Child.Output, Failure == Child.Failure {
+            return .init(upstream: self,
+                         maxPublishers: maxPublishers,
+                         transform: transform)
+    }
+}
+
+extension Publishers {
+    public struct FlatMap<Child: Publisher, Upstream: Publisher>: Publisher
+        where Child.Failure == Upstream.Failure
+    {
+        public typealias Output = Child.Output
+
+        public typealias Failure = Upstream.Failure
+
+        public let upstream: Upstream
+
+        public let maxPublishers: Subscribers.Demand
+
+        public let transform: (Upstream.Output) -> Child
+
+        public init(upstream: Upstream, maxPublishers: Subscribers.Demand,
+                    transform: @escaping (Upstream.Output) -> Child) {
+            self.upstream = upstream
+            self.maxPublishers = maxPublishers
+            self.transform = transform
+        }
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Child.Output == Downstream.Input, Upstream.Failure == Downstream.Failure
+        {
+            let inner = Inner(downstream: subscriber,
+                              maxPublishers: maxPublishers,
+                              map: transform)
+            subscriber.receive(subscription: inner)
+            upstream.subscribe(inner)
+        }
+    }
+}
+
+extension Publishers.FlatMap {
+    private final class Inner<Downstream: Subscriber>
+        : Subscriber,
+          Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Child.Output, Downstream.Failure == Upstream.Failure
+    {
+        typealias Input = Upstream.Output
+        typealias Failure = Upstream.Failure
+
+        private typealias SubscriptionIndex = Int
+
+        /// All requests to this subscription should be made with the `outerLock`
+        /// acquired.
+        private var outerSubscription: Subscription?
+
+        // Must be recursive lock. Probably a bug in Combine.
+        /// The lock for requesting from `outerSubscription`.
+        private let outerLock = UnfairLock.allocate()
+
+        /// The lock for modifying the state. All mutable state here should be
+        /// read and modified with this lock acquired.
+        /// The only exception is the `downstreamRecursive` field, which is guarded
+        /// by the `downstreamLock`.
+        private let lock = UnfairLock.allocate()
+
+        // Must be recursive lock. Probably a bug in Combine.
+        /// All the calls to the downstream subscriber should be made with this lock
+        /// acquired.
+        private let downstreamLock = UnfairLock.allocate()
+
+        private let downstream: Downstream
+
+        private var downstreamDemand = Subscribers.Demand.none
+
+        /// This variable is set to `true` whenever we call `downstream.receive(_:)`,
+        /// and then set back to `false`.
+        private var downstreamRecursive = false
+
+        private var innerRecursive = false
+        private var subscriptions = [SubscriptionIndex : Subscription]()
+        private var nextInnerIndex: SubscriptionIndex = 0
+        private var pendingSubscriptions = 0
+        private var buffer = [(SubscriptionIndex, Child.Output)]()
+        private let maxPublishers: Subscribers.Demand
+        private let map: (Input) -> Child
+        private var cancelledOrCompleted = false
+        private var outerFinished = false
+
+        init(downstream: Downstream,
+             maxPublishers: Subscribers.Demand,
+             map: @escaping (Upstream.Output) -> Child) {
+            self.downstream = downstream
+            self.maxPublishers = maxPublishers
+            self.map = map
+        }
+
+        deinit {
+            outerLock.deallocate()
+            lock.deallocate()
+            downstreamLock.deallocate()
+        }
+
+        // MARK: - Subscriber
+
+        fileprivate func receive(subscription: Subscription) {
+            lock.lock()
+            guard outerSubscription == nil, !cancelledOrCompleted else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            outerSubscription = subscription
+            lock.unlock()
+            subscription.request(maxPublishers)
+        }
+
+        fileprivate func receive(_ input: Upstream.Output) -> Subscribers.Demand {
+            lock.lock()
+            let cancelledOrCompleted = self.cancelledOrCompleted
+            lock.unlock()
+            if cancelledOrCompleted {
+                return .none
+            }
+            let child = map(input)
+            lock.lock()
+            let innerIndex = nextInnerIndex
+            nextInnerIndex += 1
+            pendingSubscriptions += 1
+            lock.unlock()
+            child.subscribe(Side(index: innerIndex, inner: self))
+            return .none
+        }
+
+        fileprivate func receive(completion: Subscribers.Completion<Child.Failure>) {
+            outerSubscription = nil
+            lock.lock()
+            outerFinished = true
+            switch completion {
+            case .finished:
+                releaseLockThenSendCompletionDownstreamIfNeeded(outerFinished: true)
+                return
+            case .failure:
+                let wasAlreadyCancelledOrCompleted = cancelledOrCompleted
+                cancelledOrCompleted = true
+                for (_, subscription) in subscriptions {
+                    subscription.cancel()
+                }
+                subscriptions = [:]
+                lock.unlock()
+                if wasAlreadyCancelledOrCompleted {
+                    return
+                }
+                downstreamLock.lock()
+                downstream.receive(completion: completion)
+                downstreamLock.unlock()
+            }
+        }
+
+        // MARK: - Subscription
+
+        fileprivate func request(_ demand: Subscribers.Demand) {
+            demand.assertNonZero()
+            if downstreamRecursive {
+                // downstreamRecursive being true means that downstreamLock
+                // is already acquired.
+                downstreamDemand += demand
+                return
+            }
+            lock.lock()
+            if cancelledOrCompleted {
+                lock.unlock()
+                return
+            }
+            if demand == .unlimited {
+                downstreamDemand = .unlimited
+                let buffer = self.buffer
+                self.buffer = []
+                let subscriptions = self.subscriptions
+                lock.unlock()
+                downstreamLock.lock()
+                downstreamRecursive = true
+                for (_, childOutput) in buffer {
+                    _ = downstream.receive(childOutput)
+                }
+                downstreamRecursive = false
+                downstreamLock.unlock()
+                for (_, subscription) in subscriptions {
+                    subscription.request(.unlimited)
+                }
+                lock.lock()
+            } else {
+                downstreamDemand += demand
+                while !buffer.isEmpty && downstreamDemand > 0 {
+                    // FIXME: This has quadratic complexity.
+                    // This is what Combine does.
+                    // Can we improve perfomance by using e. g. Deque instead of Array?
+                    // Or array's cache locality makes this solution more efficient?
+                    // Must benchmark before optimizing!
+                    //
+                    // https://www.cocoawithlove.com/blog/2016/09/22/deque.html
+                    let (index, value) = buffer.removeFirst()
+                    downstreamDemand -= 1
+                    let subscription = subscriptions[index]
+                    lock.unlock()
+                    downstreamLock.lock()
+                    downstreamRecursive = true
+                    let additionalDemand = downstream.receive(value)
+                    downstreamRecursive = false
+                    downstreamLock.unlock()
+                    if additionalDemand != .none {
+                        lock.lock()
+                        downstreamDemand += additionalDemand
+                        lock.unlock()
+                    }
+                    if let subscription = subscription {
+                        innerRecursive = true
+                        subscription.request(.max(1))
+                        innerRecursive = false
+                    }
+                    lock.lock()
+                }
+            }
+            releaseLockThenSendCompletionDownstreamIfNeeded(outerFinished: outerFinished)
+        }
+
+        fileprivate func cancel() {
+            lock.lock()
+            cancelledOrCompleted = true
+            let subscriptions = self.subscriptions
+            self.subscriptions = [:]
+            lock.unlock()
+            for (_, subscription) in subscriptions {
+                subscription.cancel()
+            }
+            // Combine doesn't acquire the lock here. Weird.
+            outerSubscription?.cancel()
+            outerSubscription = nil
+        }
+
+        // MARK: - Reflection
+
+        fileprivate var description: String { return "FlatMap" }
+
+        fileprivate var customMirror: Mirror {
+            return Mirror(self, children: EmptyCollection())
+        }
+
+        fileprivate var playgroundDescription: Any { return description }
+
+        // MARK: - Private
+
+        private func receiveInner(subscription: Subscription,
+                                  _ index: SubscriptionIndex) {
+            lock.lock()
+            pendingSubscriptions -= 1
+            subscriptions[index] = subscription
+
+            let demand = downstreamDemand == .unlimited
+                ? Subscribers.Demand.unlimited
+                : .max(1)
+
+            lock.unlock()
+            subscription.request(demand)
+        }
+
+        private func receiveInner(_ input: Child.Output,
+                                  _ index: SubscriptionIndex) -> Subscribers.Demand {
+            lock.lock()
+            if downstreamDemand == .unlimited {
+                lock.unlock()
+                downstreamLock.lock()
+                downstreamRecursive = true
+                _ = downstream.receive(input)
+                downstreamRecursive = false
+                downstreamLock.unlock()
+                return .none
+            }
+            if downstreamDemand == .none || innerRecursive {
+                buffer.append((index, input))
+                lock.unlock()
+                return .none
+            }
+            downstreamDemand -= 1
+            lock.unlock()
+            downstreamLock.lock()
+            downstreamRecursive = true
+            let newDemand = downstream.receive(input)
+            downstreamRecursive = false
+            downstreamLock.unlock()
+            if newDemand > 0 {
+                lock.lock()
+                downstreamDemand += newDemand
+                lock.unlock()
+            }
+            return .max(1)
+        }
+
+        private func receiveInner(completion: Subscribers.Completion<Child.Failure>,
+                                  _ index: SubscriptionIndex) {
+            switch completion {
+            case .finished:
+                lock.lock()
+                subscriptions.removeValue(forKey: index)
+                let downstreamCompleted = releaseLockThenSendCompletionDownstreamIfNeeded(
+                    outerFinished: outerFinished
+                )
+                if !downstreamCompleted {
+                    requestOneMorePublisher()
+                }
+            case .failure:
+                lock.lock()
+                if cancelledOrCompleted {
+                    lock.unlock()
+                    return
+                }
+                cancelledOrCompleted = true
+                let subscriptions = self.subscriptions
+                self.subscriptions = [:]
+                lock.unlock()
+                for (i, subscription) in subscriptions where i != index {
+                    subscription.cancel()
+                }
+                downstreamLock.lock()
+                downstream.receive(completion: completion)
+                downstreamLock.unlock()
+            }
+        }
+
+        private func requestOneMorePublisher() {
+            if maxPublishers != .unlimited {
+                outerLock.lock()
+                outerSubscription?.request(.max(1))
+                outerLock.unlock()
+            }
+        }
+
+        /// - Precondition: `lock` is acquired
+        /// - Postcondition: `lock` is released
+        ///
+        /// - Returns: `true` if a completion was sent downstream
+        @discardableResult
+        private func releaseLockThenSendCompletionDownstreamIfNeeded(
+            outerFinished: Bool
+        ) -> Bool {
+            #if DEBUG
+            lock.assertOwner() // Sanity check
+            #endif
+            if !cancelledOrCompleted && outerFinished && buffer.isEmpty &&
+                subscriptions.count + pendingSubscriptions == 0 {
+                cancelledOrCompleted = true
+                lock.unlock()
+                downstreamLock.lock()
+                downstream.receive(completion: .finished)
+                downstreamLock.unlock()
+                return true
+            }
+
+            lock.unlock()
+            return false
+        }
+
+        // MARK: - Side
+
+        private struct Side: Subscriber,
+                             CustomStringConvertible,
+                             CustomReflectable,
+                             CustomPlaygroundDisplayConvertible {
+            private let index: SubscriptionIndex
+            private let inner: Inner
+            fileprivate let combineIdentifier = CombineIdentifier()
+
+            fileprivate init(index: SubscriptionIndex, inner: Inner) {
+                self.index = index
+                self.inner = inner
+            }
+
+            fileprivate func receive(subscription: Subscription) {
+                inner.receiveInner(subscription: subscription, index)
+            }
+
+            fileprivate func receive(_ input: Child.Output) -> Subscribers.Demand {
+                return inner.receiveInner(input, index)
+            }
+
+            fileprivate func receive(completion: Subscribers.Completion<Child.Failure>) {
+                inner.receiveInner(completion: completion, index)
+            }
+
+            fileprivate var description: String { return "FlatMap" }
+
+            fileprivate var customMirror: Mirror {
+                let children = CollectionOfOne<Mirror.Child>(
+                    ("parentSubscription", inner.combineIdentifier)
+                )
+                return Mirror(self, children: children)
+            }
+
+            fileprivate var playgroundDescription: Any { return description }
+        }
+    }
+}
@@ -0,0 +1,134 @@
+//
+//  Publishers.IgnoreOutput.swift
+//
+//  Created by Eric Patey on 16.08.2019.
+//
+
+import COpenCombineHelpers
+
+extension Publisher {
+
+    /// Ingores all upstream elements, but passes along a completion
+    /// state (finished or failed).
+    ///
+    /// The output type of this publisher is `Never`.
+    /// - Returns: A publisher that ignores all upstream elements.
+    public func ignoreOutput() -> Publishers.IgnoreOutput<Self> {
+        return .init(upstream: self)
+    }
+}
+
+extension Publishers {
+    /// A publisher that ignores all upstream elements, but passes along a completion
+    /// state (finish or failed).
+    public struct IgnoreOutput<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Never
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        public init(upstream: Upstream) {
+            self.upstream = upstream
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Failure == Upstream.Failure, Downstream.Input == Never
+        {
+            upstream.subscribe(Inner<Downstream>(downstream: subscriber))
+        }
+    }
+}
+
+extension Publishers.IgnoreOutput {
+    private final class Inner<Downstream: Subscriber>
+        : Subscriber,
+          Subscription,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Never, Downstream.Failure == Upstream.Failure
+    {
+        // NOTE: This class has been audited for thread safety
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private var status = SubscriptionStatus.awaitingSubscription
+
+        private let lock = UnfairLock.allocate()
+
+        fileprivate init(downstream: Downstream) {
+            self.downstream = downstream
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        func receive(subscription: Subscription) {
+            lock.lock()
+            guard case .awaitingSubscription = status else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            status = .subscribed(subscription)
+            lock.unlock()
+            downstream.receive(subscription: self)
+            subscription.request(.unlimited)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            return .none
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            lock.lock()
+            guard case .subscribed = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            lock.unlock()
+            downstream.receive(completion: completion)
+        }
+
+        func request(_ demand: Subscribers.Demand) {
+            // ignore and requests from downstream since we'll never send
+            // any values
+        }
+
+        func cancel() {
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            lock.unlock()
+            subscription.cancel()
+        }
+
+        var description: String { return "IgnoreOutput" }
+
+        var customMirror: Mirror {
+            lock.lock()
+            defer { lock.unlock() }
+            let children: [Mirror.Child] = [
+                ("downstream", downstream),
+                ("status", status)
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+
+extension Publishers.IgnoreOutput: Equatable where Upstream: Equatable {}
@@ -0,0 +1,203 @@
+//
+//  Publishers.Last.swift
+//  
+//
+//  Created by Joseph Spadafora on 7/9/19.
+//
+
+extension Publisher {
+
+    /// Only publishes the last element of a stream, after the stream finishes.
+    /// - Returns: A publisher that only publishes the last element of a stream.
+    public func last() -> Publishers.Last<Self> {
+        return .init(upstream: self)
+    }
+
+    /// Only publishes the last element of a stream that satisfies a predicate closure,
+    /// after the stream finishes.
+    ///
+    /// - Parameter predicate: A closure that takes an element as its parameter and
+    ///   returns a Boolean value indicating whether to publish the element.
+    /// - Returns: A publisher that only publishes the last element satisfying
+    ///   the given predicate.
+    public func last(
+        where predicate: @escaping (Output) -> Bool
+    ) -> Publishers.LastWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+
+    /// Only publishes the last element of a stream that satisfies an error-throwing
+    /// predicate closure, after the stream finishes.
+    ///
+    /// If the predicate closure throws, the publisher fails with the thrown error.
+    /// - Parameter predicate: A closure that takes an element as its parameter and
+    ///   returns a Boolean value indicating whether to publish the element.
+    /// - Returns: A publisher that only publishes the last element satisfying
+    ///   the given predicate.
+    public func tryLast(
+        where predicate: @escaping (Output) throws -> Bool
+    ) -> Publishers.TryLastWhere<Self> {
+        return .init(upstream: self, predicate: predicate)
+    }
+}
+
+extension Publishers {
+
+    /// A publisher that only publishes the last element of a stream,
+    /// after the stream finishes.
+    public struct Last<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        public init(upstream: Upstream) {
+            self.upstream = upstream
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber))
+        }
+    }
+
+    /// A publisher that only publishes the last element of a stream that satisfies
+    /// a predicate closure, once the stream finishes.
+    public struct LastWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The closure that determines whether to publish an element.
+        public let predicate: (Upstream.Output) -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Output) -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+
+    /// A publisher that only publishes the last element of a stream that satisfies
+    /// an error-throwing predicate closure, once the stream finishes.
+    public struct TryLastWhere<Upstream: Publisher>: Publisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Error
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+        /// The error-throwing closure that determines whether to publish an element.
+        public let predicate: (Upstream.Output) throws -> Bool
+
+        public init(upstream: Upstream, predicate: @escaping (Output) throws -> Bool) {
+            self.upstream = upstream
+            self.predicate = predicate
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Failure == Error, Output == Downstream.Input
+        {
+            upstream.subscribe(Inner(downstream: subscriber, predicate: predicate))
+        }
+    }
+}
+
+extension Publishers.Last: Equatable where Upstream: Equatable {}
+
+extension Publishers.Last {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         Void>
+        where Upstream.Output == Downstream.Input, Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream) {
+            super.init(downstream: downstream, initial: nil, reduce: ())
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            result = newValue
+            return .continue
+        }
+
+        override var description: String { return "Last" }
+    }
+}
+
+extension Publishers.LastWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output) -> Bool>
+        where Upstream.Output == Downstream.Input, Upstream.Failure == Downstream.Failure
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) -> Bool) {
+            super.init(downstream: downstream, initial: nil, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            if reduce(newValue) {
+                result = newValue
+            }
+            return .continue
+        }
+
+        override var description: String { return "LastWhere" }
+    }
+}
+
+extension Publishers.TryLastWhere {
+    private final class Inner<Downstream: Subscriber>
+        : ReduceProducer<Downstream,
+                         Upstream.Output,
+                         Upstream.Output,
+                         Upstream.Failure,
+                         (Upstream.Output) throws -> Bool>
+        where Upstream.Output == Downstream.Input, Downstream.Failure == Error
+    {
+        fileprivate init(downstream: Downstream,
+                         predicate: @escaping (Upstream.Output) throws -> Bool) {
+            super.init(downstream: downstream, initial: nil, reduce: predicate)
+        }
+
+        override func receive(
+            newValue: Upstream.Output
+        ) -> PartialCompletion<Void, Downstream.Failure> {
+            do {
+                if try reduce(newValue) {
+                    result = newValue
+                }
+                return .continue
+            } catch {
+                return .failure(error)
+            }
+        }
+
+        override var description: String { return "TryLastWhere" }
+    }
+}
@@ -0,0 +1,42 @@
+//
+//  Publishers.MakeConnectable.swift
+//  
+//
+//  Created by Sergej Jaskiewicz on 18/09/2019.
+//
+
+extension Publisher where Failure == Never {
+
+    /// Creates a connectable wrapper around the publisher.
+    ///
+    /// - Returns: A `ConnectablePublisher` wrapping this publisher.
+    public func makeConnectable() -> Publishers.MakeConnectable<Self> {
+        return .init(upstream: self)
+    }
+}
+
+extension Publishers {
+
+    public struct MakeConnectable<Upstream: Publisher>: ConnectablePublisher {
+
+        public typealias Output = Upstream.Output
+
+        public typealias Failure = Upstream.Failure
+
+        private let inner: Multicast<Upstream, PassthroughSubject<Output, Failure>>
+
+        public init(upstream: Upstream) {
+            inner = upstream.multicast(subject: .init())
+        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Downstream.Failure == Failure, Downstream.Input == Output
+        {
+            inner.subscribe(subscriber)
+        }
+
+        public func connect() -> Cancellable {
+            return inner.connect()
+        }
+    }
+}
@@ -5,6 +5,8 @@
 //  Created by Anton Nazarov on 25.06.2019.
 //

+import COpenCombineHelpers
+
 extension Publisher {

    /// Transforms all elements from the upstream publisher with a provided closure.
@@ -30,7 +32,7 @@ extension Publisher {
    /// - Returns: A publisher that uses the provided closure to map elements from
    ///   the upstream publisher to new elements that it then publishes.
    public func tryMap<Result>(
-        _ transform: @escaping (Self.Output) throws -> Result
+        _ transform: @escaping (Output) throws -> Result
    ) -> Publishers.TryMap<Self, Result> {
        return Publishers.TryMap(upstream: self, transform: transform)
    }
@@ -39,7 +41,7 @@ extension Publisher {
 extension Publishers {
    /// A publisher that transforms all elements from the upstream publisher with
    /// a provided closure.
-    public struct Map<Upstream: Publisher, Output> : Publisher {
+    public struct Map<Upstream: Publisher, Output>: Publisher {

        public typealias Failure = Upstream.Failure

@@ -54,6 +56,12 @@ extension Publishers {
            self.upstream = upstream
            self.transform = transform
        }
+
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Downstream.Failure == Upstream.Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, map: transform))
+        }
    }

    /// A publisher that transforms all elements from the upstream publisher
@@ -78,12 +86,6 @@ extension Publishers {
 }

 extension Publishers.Map {
-    public func receive<Downstream: Subscriber>(subscriber: Downstream)
-        where Output == Downstream.Input, Downstream.Failure == Upstream.Failure
-    {
-        let inner = Inner(downstream: subscriber, transform: catching(transform))
-        upstream.subscribe(inner)
-    }

    public func map<Result>(
        _ transform: @escaping (Output) -> Result
@@ -103,8 +105,7 @@ extension Publishers.TryMap {
    public func receive<Downstream: Subscriber>(subscriber: Downstream)
        where Output == Downstream.Input, Downstream.Failure == Error
    {
-        let inner = Inner(downstream: subscriber, transform: catching(transform))
-        upstream.subscribe(inner)
+        upstream.subscribe(Inner(downstream: subscriber, map: transform))
    }

    public func map<Result>(
@@ -120,89 +121,158 @@ extension Publishers.TryMap {
    }
 }

-private class _Map<Upstream: Publisher, Downstream: Subscriber>
-    : OperatorSubscription<Downstream>
-{
-    typealias Input = Upstream.Output
-    typealias Failure = Upstream.Failure
-    typealias Transform = (Input) -> Result<Downstream.Input, Downstream.Failure>
-
-    fileprivate var _transform: Transform?
-
-    var isCompleted: Bool {
-        return _transform == nil
-    }
-
-    init(downstream: Downstream, transform: @escaping Transform) {
-        _transform = transform
-        super.init(downstream: downstream)
-    }
-
-    func receive(_ input: Input) -> Subscribers.Demand {
-        switch _transform?(input) {
-        case .success(let output)?:
-            return downstream.receive(output)
-        case .failure(let error)?:
-            downstream.receive(completion: .failure(error))
-            _transform = nil
-            return .none
-        case nil:
-            return .none
-        }
-    }
-}
-
 extension Publishers.Map {

-    private final class Inner<Downstream: Subscriber>
-        : _Map<Upstream, Downstream>,
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
          CustomStringConvertible,
-          Subscriber
-        where Downstream.Failure == Upstream.Failure
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Upstream.Failure
    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let map: (Input) -> Output
+
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(downstream: Downstream, map: @escaping (Input) -> Output) {
+            self.downstream = downstream
+            self.map = map
+        }

        func receive(subscription: Subscription) {
            downstream.receive(subscription: subscription)
        }

+        func receive(_ input: Input) -> Subscribers.Demand {
+            return downstream.receive(map(input))
+        }
+
        func receive(completion: Subscribers.Completion<Failure>) {
            downstream.receive(completion: completion)
        }

        var description: String { return "Map" }
+
+        var customMirror: Mirror {
+            return Mirror(self, children: EmptyCollection())
+        }
+
+        var playgroundDescription: Any { return description }
    }
 }

 extension Publishers.TryMap {

    private final class Inner<Downstream: Subscriber>
-        : _Map<Upstream, Downstream>,
+        : Subscriber,
          Subscription,
          CustomStringConvertible,
-          Subscriber
-        where Downstream.Failure == Error
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Error
    {
+        // NOTE: This class has been audited for thread-safety
+
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+        private let map: (Input) throws -> Output
+
+        private var status = SubscriptionStatus.awaitingSubscription
+
+        private let lock = UnfairLock.allocate()
+
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(downstream: Downstream,
+                         map: @escaping (Input) throws -> Output) {
+            self.downstream = downstream
+            self.map = map
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
        func receive(subscription: Subscription) {
-            upstreamSubscription = subscription
+            lock.lock()
+            guard case .awaitingSubscription = status else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            status = .subscribed(subscription)
+            lock.unlock()
            downstream.receive(subscription: self)
        }

-        func receive(completion: Subscribers.Completion<Failure>) {
-            if !isCompleted {
-                _transform = nil
-                downstream.receive(completion: completion.eraseError())
+        func receive(_ input: Input) -> Subscribers.Demand {
+            do {
+                return try downstream.receive(map(input))
+            } catch {
+                lock.lock()
+                let subscription: Subscription?
+                switch status {
+                case let .subscribed(upstreamSubscription):
+                    subscription = upstreamSubscription
+                case .awaitingSubscription, .terminal:
+                    subscription = nil
+                }
+                status = .terminal
+                lock.unlock()
+                subscription?.cancel()
+                downstream.receive(completion: .failure(error))
+                return .none
            }
        }

-        func request(_ demand: Subscribers.Demand) {
-            upstreamSubscription?.request(demand)
+        func receive(completion: Subscribers.Completion<Failure>) {
+            lock.lock()
+            guard case .subscribed = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            lock.unlock()
+            downstream.receive(completion: completion.eraseError())
        }

-        override func cancel() {
-            _transform = nil
-            super.cancel()
+        func request(_ demand: Subscribers.Demand) {
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            lock.unlock()
+            subscription.request(demand)
+        }
+
+        func cancel() {
+            lock.lock()
+            guard case let .subscribed(subscription) = status else {
+                lock.unlock()
+                return
+            }
+            status = .terminal
+            lock.unlock()
+            subscription.cancel()
        }

        var description: String { return "TryMap" }
+
+        var customMirror: Mirror {
+            return Mirror(self, children: EmptyCollection())
+        }
+
+        var playgroundDescription: Any { return description }
    }
 }
@@ -32,15 +32,11 @@ extension Publishers {
        /// - Parameters:
        ///     - subscriber: The subscriber to attach to this `Publisher`.
        ///                   once attached it can begin to receive values.
-        public func receive<SubscriberType: Subscriber>(subscriber: SubscriberType)
-            where Failure == SubscriberType.Failure,
-                  Upstream.Output == SubscriberType.Input
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Failure == Downstream.Failure,
+                  Upstream.Output == Downstream.Input
        {
-            let mapErrorSubscriber = _MapError<Upstream, SubscriberType>(
-                downstream: subscriber,
-                transform: transform
-            )
-            upstream.subscribe(mapErrorSubscriber)
+            upstream.subscribe(Inner(downstream: subscriber, map: transform))
        }
    }
 }
@@ -57,48 +53,57 @@ extension Publisher {
    /// - Returns: A publisher that replaces any upstream failure with a
    /// new error produced by the `transform` closure.
    public func mapError<NewFailure: Error>(
-        _ transform: @escaping (Self.Failure) -> NewFailure
+        _ transform: @escaping (Failure) -> NewFailure
    ) -> Publishers.MapError<Self, NewFailure>
    {
        return Publishers.MapError(upstream: self, transform)
    }
 }

-private final class _MapError<Upstream: Publisher, Downstream: Subscriber>
-    : OperatorSubscription<Downstream>,
-      Subscriber,
-      CustomStringConvertible
-    where Upstream.Output == Downstream.Input
-{
-    typealias Input = Upstream.Output
-    typealias Failure = Upstream.Failure
-    typealias Output = Downstream.Input
+extension Publishers.MapError {

-    private let _transform: (Upstream.Failure) -> Downstream.Failure
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Upstream.Output == Downstream.Input
+    {
+        typealias Input = Upstream.Output
+        typealias Failure = Upstream.Failure

-    var description: String { return "MapError" }
+        private let downstream: Downstream
+        private let map: (Upstream.Failure) -> Downstream.Failure

-    init(downstream: Downstream,
-         transform: @escaping (Upstream.Failure) -> Downstream.Failure) {
-        self._transform = transform
-        super.init(downstream: downstream)
-    }
+        let combineIdentifier = CombineIdentifier()

-    func receive(subscription: Subscription) {
-        upstreamSubscription = subscription
-        downstream.receive(subscription: subscription)
-    }
+        var description: String { return "MapError" }

-    func receive(_ input: Input) -> Subscribers.Demand {
-        return downstream.receive(input)
-    }
+        var customMirror: Mirror { return Mirror(self, children: EmptyCollection()) }

-    func receive(completion: Subscribers.Completion<Failure>) {
-        switch completion {
-        case .finished:
-            downstream.receive(completion: .finished)
-        case .failure(let error):
-            downstream.receive(completion: .failure(_transform(error)))
+        var playgroundDescription: Any { return description }
+
+        init(downstream: Downstream,
+             map: @escaping (Upstream.Failure) -> Downstream.Failure) {
+            self.downstream = downstream
+            self.map = map
+        }
+
+        func receive(subscription: Subscription) {
+            downstream.receive(subscription: subscription)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+            return downstream.receive(input)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            switch completion {
+            case .finished:
+                downstream.receive(completion: .finished)
+            case .failure(let error):
+                downstream.receive(completion: .failure(map(error)))
+            }
        }
    }
 }
@@ -0,0 +1,175 @@
+${template_header}
+//
+//  Publishers.MapKeyPath.swift.gyb
+//  
+//
+//  Created by Sergej Jaskiewicz on 03/10/2019.
+//
+
+%{
+from gyb_opencombine_support import (
+    suffix_variadic,
+    list_with_suffix_variadic
+)
+
+instantiations = [(1, '', ''),
+                  (2, 'two', 'second '),
+                  (3, 'three', 'third ')]
+
+def key_path_var(index, arity):
+    return suffix_variadic('keyPath', index, arity)
+
+def make_publisher_name(arity):
+    return suffix_variadic('MapKeyPath', arity, arity)
+
+def make_output_types(arity):
+    return list_with_suffix_variadic('Output', arity)
+}%
+extension Publisher {
+% for arity, cardinal, _ in instantiations:
+%     result_types = list_with_suffix_variadic('Result', arity)
+%     cs_result_types = ', '.join(result_types)
+%
+%     method_args = \
+%         ['_ {}: KeyPath<Output, {}>'.format(key_path_var(i, arity), result_types[i]) \
+%          for i in range(arity)]
+%     method_args_joined = ',\n        '.join(method_args)
+%
+%     init_args = ['{}: {}'.format(key_path_var(i, arity), key_path_var(i, arity)) \
+%                  for i in range(arity)]
+%     init_args_joined = ',\n            '.join(init_args)
+%
+%     publisher_name = make_publisher_name(arity)
+%
+%     doc_cardinal = 'a keyt path' if arity == 1 else cardinal + ' key paths'
+
+    /// Returns a publisher that publishes the values of ${doc_cardinal} as a tuple.
+    ///
+    /// - Parameters:
+%     for i in range(arity):
+%         ordinal = 'another ' if i == 1 else 'a ' + instantiations[i][2]
+    ///    - ${key_path_var(i, arity)}: The key path of ${ordinal}property on `Output`
+%     end
+%
+%   doc_comment_suffix = 'value of the key path' \
+%       if arity == 1 else 'values of {} key paths as a tuple'.format(cardinal)
+    /// - Returns: A publisher that publishes the ${doc_comment_suffix}.
+    public func map<${cs_result_types}>(
+        ${method_args_joined}
+    ) -> Publishers.${publisher_name}<Self, ${cs_result_types}> {
+        return .init(
+            upstream: self,
+            ${init_args_joined}
+        )
+    }
+% end
+}
+
+extension Publishers {
+% for arity, cardinal, ordinal in instantiations:
+%
+%     doc_comment_suffix = 'value of a key path' \
+%         if arity == 1 else 'values of {} key paths as a tuple'.format(cardinal)
+%
+%     output_types = make_output_types(arity)
+%     cs_output_types = ', '.join(output_types)
+%
+%     publisher_name = make_publisher_name(arity)
+
+    /// A publisher that publishes the ${doc_comment_suffix}.
+    public struct ${publisher_name}<Upstream: Publisher, ${cs_output_types}>: Publisher {
+
+%     if arity != 1:
+        public typealias Output = (${cs_output_types})
+
+%     end
+        public typealias Failure = Upstream.Failure
+
+        /// The publisher from which this publisher receives elements.
+        public let upstream: Upstream
+
+%     for i in range(arity):
+%         ordinal = instantiations[i][2]
+        /// The key path of a ${ordinal}property to publish.
+        public let ${key_path_var(i, arity)}: KeyPath<Upstream.Output, ${output_types[i]}>
+
+%     end
+        public func receive<Downstream: Subscriber>(subscriber: Downstream)
+            where Output == Downstream.Input, Failure == Downstream.Failure
+        {
+            upstream.subscribe(Inner(downstream: subscriber, parent: self))
+        }
+    }
+% end
+}
+% for arity, _, _ in instantiations:
+%     output_types = make_output_types(arity)
+%     cs_output_types = ', '.join(output_types)
+%
+%     publisher_name = make_publisher_name(arity)
+
+extension Publishers.${publisher_name} {
+
+    private struct Inner<Downstream: Subscriber>
+        : Subscriber,
+          CustomStringConvertible,
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
+        where Downstream.Input == Output, Downstream.Failure == Upstream.Failure
+    {
+        typealias Input = Upstream.Output
+
+        typealias Failure = Upstream.Failure
+
+        private let downstream: Downstream
+
+%     for i in range(arity):
+        private let ${key_path_var(i, arity)}: KeyPath<Input, ${output_types[i]}>
+
+%     end
+        let combineIdentifier = CombineIdentifier()
+
+        fileprivate init(
+            downstream: Downstream,
+            parent: Publishers.${publisher_name}<Upstream, ${cs_output_types}>
+        ) {
+            self.downstream = downstream
+%     for i in range(arity):
+            self.${key_path_var(i, arity)} = parent.${key_path_var(i, arity)}
+%     end
+        }
+
+        func receive(subscription: Subscription) {
+            downstream.receive(subscription: subscription)
+        }
+
+        func receive(_ input: Input) -> Subscribers.Demand {
+%     output_components = \
+%         ['input[keyPath: {}]'.format(key_path_var(i, arity)) for i in range(arity)]
+%     output_components_joined = ',\n                '.join(output_components)
+            let output = (
+                ${output_components_joined}
+            )
+            return downstream.receive(output)
+        }
+
+        func receive(completion: Subscribers.Completion<Failure>) {
+            downstream.receive(completion: completion)
+        }
+
+%     inner_description = 'ValueForKey' + ('' if arity == 1 else 's')
+        var description: String { return "${inner_description}" }
+
+        var customMirror: Mirror {
+            let children: [Mirror.Child] = [
+%     for i in range(arity):
+                ("${key_path_var(i, arity)}", ${key_path_var(i, arity)}),
+%     end
+            ]
+            return Mirror(self, children: children)
+        }
+
+        var playgroundDescription: Any { return description }
+    }
+}
+% end
@@ -5,8 +5,19 @@
 //  Created by Sergej Jaskiewicz on 14.06.2019.
 //

+import COpenCombineHelpers
+
 extension Publisher {

+    /// Applies a closure to create a subject that delivers elements to subscribers.
+    ///
+    /// Use a multicast publisher when you have multiple downstream subscribers, but you
+    /// want upstream publishers to only process one `receive(_:)` call per event.
+    /// In contrast with `multicast(subject:)`, this method produces a publisher that
+    /// creates a separate Subject for each subscriber.
+    ///
+    /// - Parameter createSubject: A closure to create a new Subject each time
+    ///   a subscriber attaches to the multicast publisher.
    public func multicast<SubjectType: Subject>(
        _ createSubject: @escaping () -> SubjectType
    ) -> Publishers.Multicast<Self, SubjectType>
@@ -15,6 +26,14 @@ extension Publisher {
        return Publishers.Multicast(upstream: self, createSubject: createSubject)
    }

+    /// Provides a subject to deliver elements to multiple subscribers.
+    ///
+    /// Use a multicast publisher when you have multiple downstream subscribers, but you
+    /// want upstream publishers to only process one `receive(_:)` call per event.
+    /// In contrast with `multicast(_:)`, this method produces a publisher shares
+    /// the provided Subject among all the downstream subscribers.
+    ///
+    /// - Parameter subject: A subject to deliver elements to downstream subscribers.
    public func multicast<SubjectType: Subject>(
        subject: SubjectType
    ) -> Publishers.Multicast<Self, SubjectType>
@@ -26,43 +45,67 @@ extension Publisher {

 extension Publishers {

+    /// A publisher that uses a subject to deliver elements to multiple subscribers.
    public final class Multicast<Upstream: Publisher, SubjectType: Subject>
        : ConnectablePublisher
-            where Upstream.Failure == SubjectType.Failure,
-                  Upstream.Output == SubjectType.Output
+        where Upstream.Failure == SubjectType.Failure,
+              Upstream.Output == SubjectType.Output
    {
+        // NOTE: This class has been audited for thread safety

        public typealias Output = Upstream.Output

        public typealias Failure = Upstream.Failure

+        /// The publisher from which this publisher receives elements.
        public let upstream: Upstream

+        /// A closure to create a new Subject each time a subscriber attaches
+        /// to the multicast publisher.
        public let createSubject: () -> SubjectType

-        private lazy var _subject: SubjectType = self.createSubject()
+        private let lock = UnfairLock.allocate()

+        private var subject: SubjectType?
+
+        private var lazySubject: SubjectType {
+            lock.lock()
+            if let subject = subject {
+                lock.unlock()
+                return subject
+            }
+
+            let subject = createSubject()
+            self.subject = subject
+            lock.unlock()
+            return subject
+        }
+
+        /// Creates a multicast publisher that applies a closure to create a subject
+        /// that delivers elements to subscribers.
+        ///
+        /// - Parameter upstream: The publisher from which this publisher receives
+        ///   elements.
+        /// - Parameter createSubject: A closure to create a new Subject each time
+        ///   a subscriber attaches to the multicast publisher.
        public init(upstream: Upstream, createSubject: @escaping () -> SubjectType) {
            self.upstream = upstream
            self.createSubject = createSubject
        }

+        deinit {
+            lock.deallocate()
+        }
+
        public func receive<Downstream: Subscriber>(subscriber: Downstream)
            where SubjectType.Failure == Downstream.Failure,
                  SubjectType.Output == Downstream.Input
        {
-            _subject.subscribe(Inner(downstream: subscriber))
+            lazySubject.subscribe(Inner(parent: self, downstream: subscriber))
        }

        public func connect() -> Cancellable {
-
-            let subscriber = SubjectSubscriber(_subject)
-
-            upstream.subscribe(subscriber)
-
-            return AnyCancellable {
-                subscriber.downstreamSubject = nil
-            }
+            return upstream.subscribe(lazySubject)
        }
    }
 }
@@ -70,32 +113,106 @@ extension Publishers {
 extension Publishers.Multicast {

    private final class Inner<Downstream: Subscriber>
-        : OperatorSubscription<Downstream>,
-          Subscriber,
+        : Subscriber,
+          Subscription,
          CustomStringConvertible,
-          Subscription
+          CustomReflectable,
+          CustomPlaygroundDisplayConvertible
        where Upstream.Output == Downstream.Input, Upstream.Failure == Downstream.Failure
    {
+        // NOTE: This class has been audited for thread safety
+
        typealias Input = Upstream.Output
+
        typealias Failure = Upstream.Failure

-        var description: String { return "Multicast" }
+        private enum State {
+            case ready(upstream: Upstream, downstream: Downstream)
+            case subscribed(upstream: Upstream,
+                            downstream: Downstream,
+                            subjectSubscription: Subscription)
+            case terminal
+        }
+
+        private let lock = UnfairLock.allocate()
+
+        private var state: State
+
+        fileprivate init(parent: Publishers.Multicast<Upstream, SubjectType>,
+                         downstream: Downstream) {
+            state = .ready(upstream: parent.upstream, downstream: downstream)
+        }
+
+        deinit {
+            lock.deallocate()
+        }
+
+        fileprivate var description: String { return "Multicast" }
+
+        fileprivate var customMirror: Mirror {
+            return Mirror(self, children: EmptyCollection())
+        }
+
+        fileprivate var playgroundDescription: Any { return description }

        func receive(subscription: Subscription) {
-            upstreamSubscription = subscription
+            lock.lock()
+            guard case let .ready(upstream, downstream) = state else {
+                lock.unlock()
+                subscription.cancel()
+                return
+            }
+            state = .subscribed(upstream: upstream,
+                                downstream: downstream,
+                                subjectSubscription: subscription)
+            lock.unlock()
            downstream.receive(subscription: self)
        }

        func receive(_ input: Input) -> Subscribers.Demand {
-            return downstream.receive(input)
+            lock.lock()
+            guard case let .subscribed(_, downstream, subjectSubscription) = state else {
+                lock.unlock()
+                return .none
+            }
+            lock.unlock()
+            let newDemand = downstream.receive(input)
+            if newDemand > 0 {
+                subjectSubscription.request(newDemand)
+            }
+            return .none
        }

        func receive(completion: Subscribers.Completion<Failure>) {
+            lock.lock()
+            guard case let .subscribed(_, downstream, _) = state else {
+                lock.unlock()
+                return
+            }
+            state = .terminal
+            lock.unlock()
            downstream.receive(completion: completion)
        }

        func request(_ demand: Subscribers.Demand) {
-            upstreamSubscription?.request(demand)
+            lock.lock()
+            guard case let .subscribed(_, _, subjectSubscription) = state else {
+                lock.unlock()
+                return
+            }
+            lock.unlock()
+            subjectSubscription.request(demand)
+        }
+
+        func cancel() {
+            lock.lock()
+            guard case let .subscribed(_, _, subjectSubscription) = state else {
+                lock.unlock()
+                return
+            }
+            state = .terminal
+            lock.unlock()
+            subjectSubscription.cancel()
        }
    }
 }
--- a/Show More
+++ b/Show More
Author	SHA1	Message	Date
Sergej Jaskiewicz	b6aea2957a	Use proper xcconfigs to fix CI	2019-11-29 22:06:34 +03:00
Sergej Jaskiewicz	9219c8841c	Allow enumerating fields of value types	2019-11-29 21:08:51 +03:00
Sergej Jaskiewicz	5a41e2976c	Useheaders from Swift repo for runtime introspection	2019-11-29 19:05:13 +03:00
Sergej Jaskiewicz	e48d5d4492	Move headers into folders	2019-11-29 15:58:42 +03:00
Sergej Jaskiewicz	9b81672df8	Add dedicated tests for enumerateFields	2019-11-29 15:41:58 +03:00
Sergej Jaskiewicz	d5944290e6	Make ObservableObject.objectWillChange available in Swift 5.0	2019-11-26 17:56:01 +03:00
Sergej Jaskiewicz	a3e361a29a	Add TrailingObjects.h [skip ci]	2019-11-26 17:51:08 +03:00
Sergej Jaskiewicz	0dc2015ec6	Add SWIFT_VERSION setting to Combine-Compatibility.xcconfig	2019-11-26 17:51:08 +03:00
Sergej Jaskiewicz	1e6a7cd3b6	[WIP] Support generic `ObservableObject`s	2019-11-26 17:49:17 +03:00
Sergej Jaskiewicz	acb1b5996a	[ObservableObject] Add a test for NSObject subclass	2019-11-26 17:49:17 +03:00
Sergej Jaskiewicz	77e7ff75fb	Compute OPENCOMBINE_SWIFT_CLASS_IS_SWIFT_MASK at runtime based on the OS version.	2019-11-26 17:49:17 +03:00
Sergej Jaskiewicz	26d6dc9971	[COpenCombineHelpers] Support C++ 14 The CI complains about missing headers, so let's reimplement std::string_view ourselves.	2019-11-26 17:49:17 +03:00
Sergej Jaskiewicz	280ea0ac9a	Fix ObservableObject behavior for subclasses of resilient classes	2019-11-26 17:49:17 +03:00
Sergej Jaskiewicz	8798739caa	[WIP] [ObservableObject] Make some tests pass	2019-11-26 17:49:07 +03:00
Sergej Jaskiewicz	c6c79144c5	Implement ObservableObject protocol	2019-11-26 17:48:50 +03:00
Sergej Jaskiewicz	7c5a76cf2b	Fix @Published (#112 )	2019-11-26 17:46:01 +03:00
Max Desiatov	668c292245	Add more tests for the Future publisher (#111 )	2019-11-26 14:23:51 +03:00
Max Desiatov	981ab4fa09	Add Future publisher with tests (#107 )	2019-11-26 02:15:43 +03:00
Sergej Jaskiewicz	8cf71e0122	If Multicast receives subscription twice, cancel the second one (#110 )	2019-11-25 16:52:55 +03:00
Max Desiatov	130125cb66	Use demand.assertNonZero() in PassthroughSubject (#108 )	2019-11-24 21:44:14 +03:00
Daniel Peter	7b3ceae666	CocoaPods support (#103 )	2019-11-24 21:17:13 +03:00
Max Desiatov	56202b1663	Fix typo in FilterProducer.swift > subsription	2019-11-22 20:12:34 +03:00
Sergej Jaskiewicz	d0a02de7c5	Warn about unguarded availability in C++ code. Fix the warnings.	2019-11-21 20:18:28 +03:00
Sergej Jaskiewicz	c8058edc5f	Test that Sink calls the callbacks even without upstream subscription	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	8b685f78a3	Test that ReplaceError saves demand until subscription arrives	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	0816abe33c	Remove superfluous 'disable' swiftlint command	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	b6c7560f4c	Use pthread_mutex_t instead of std::mutex on non-Darwin platforms std::mutex doesn't guarantee error checks. With pthread, we can enable them manually. Error checks are essential, since the client code may bay be crafted in such a way that causes a non-recursive lock to be recursively acuired, which is undefined behavior with std::mutex.	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	7a9e8b22d2	Bump iOS version for compatibility tests in CircleCI config	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	26f9acd75a	Reimplement FlatMap to make all the tests pass	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	4c42b434ca	Add more tests for FlatMap	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	8afe945325	Test that CombineIdentifier uses UInt64 under the hood	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	eb879213ef	Automatically confirm apt install	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	e402fb3980	Remove redundant Self	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	4f96378c02	Remove OperatorSubscription class	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	243f3d200e	Implement PrefixWhile, TryPrefixWhile using FilterProducer	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	f1fb5552b5	Implement RemoveDuplicates, TryRemoveDuplicates using FilterProducer	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	bfd875ccba	Simplify CompactMap and TryCompactMap using FilterProducer	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	27da28f378	Simplify Filter and TryFilter using FilterProducer	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	cba3a69e74	Implement FilterProducer	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	d634a76c39	A more robust test for Subscribers.Assign	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	b5e31a43ef	Fix ReplaceError subscription behavior	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	1bb3583a36	More tests for contract violations in operators - test the behavior when a value arrives earlier than the subscription - test the behavior when a completion arrives earlier than the subscription - test the behavior when requesting before a subscription arrives - test the behavior when cancelling before a subscription arrives	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	449b8eef48	Test that Record doesn't finilize its Recording	2019-11-19 18:38:01 +03:00
Sergej Jaskiewicz	d4bdd83a00	Implement the Record publisher	2019-11-12 17:31:29 +03:00
Sergej Jaskiewicz	f1cc94adff	Implement Publishers.Output	2019-11-11 20:26:31 +03:00
Sergej Jaskiewicz	5e1e10a780	Add CircleCI badge	2019-11-10 15:00:50 +03:00
Sergej Jaskiewicz	5b7358111c	Remove redundant	2019-11-10 15:00:50 +03:00
Sergej Jaskiewicz	5f90c4c85f	Add Gemfile.lock	2019-11-10 15:00:50 +03:00
Sergej Jaskiewicz	0dec30fcad	Switch from Travis CI to CircleCI. CircleCI has significantly faster builds. They also update their build machines sooner than Travis CI.	2019-11-09 15:26:50 +03:00
Sergej Jaskiewicz	a5ec9723e2	Make the tests pass on 32-bit platforms	2019-11-09 15:26:50 +03:00
Sergej Jaskiewicz	25ac4dfa5f	Fix SwiftLint crash https://github.com/realm/SwiftLint/issues/2793	2019-11-09 15:26:50 +03:00
Sergej Jaskiewicz	f5645f605b	Remove old benchmarking infrastructure	2019-11-09 15:26:50 +03:00
Sergej Jaskiewicz	ffef3ac76c	Update CI configuration to run compatibility tests on Xcode 11.2	2019-10-31 14:01:44 +03:00
Sergej Jaskiewicz	36a9f1999c	They fix bugs in Combine, we update our awesome test suite! The bug fixes happened in macOS 10.15.1	2019-10-31 14:01:44 +03:00
Sergej Jaskiewicz	f069f9b9fa	Audit DropWhile/TryDropWhile for thread safety (#87 ) Add more tests, make them pass	2019-10-25 15:45:40 +03:00
Sergej Jaskiewicz	55bdbba0f9	Publishers.Print: cancel new subscription if Inner is already subscribed (#92 )	2019-10-24 15:11:55 +03:00
Sergej Jaskiewicz	1290545c49	Audit IgnoreOutput for thread safety, add more tests, make them pass (#88 )	2019-10-23 23:44:59 +03:00
Sergej Jaskiewicz	aed074af43	Add tests for Subscriptions.empty	2019-10-23 20:30:46 +03:00
Sergej Jaskiewicz	11ec7c89e6	Gybify Encode/Decode, add more tests, make them pass	2019-10-23 20:30:46 +03:00
Sergej Jaskiewicz	46007658a1	Add missing Equatable comformances - Collect - Contains - Count - Drop - Last	2019-10-17 14:40:56 +03:00
Sergej Jaskiewicz	c4c7f2172d	Add more tests for Scan, TryScan	2019-10-17 14:40:56 +03:00
Eric Patey	5b0a21a0b9	Implement Publishers.Scan	2019-10-17 14:40:56 +03:00
Sergej Jaskiewicz	f4e191b2ff	Add more tests for Publishers.Drop (#82 )	2019-10-17 09:41:53 +03:00
Sven	c275e51cdc	Implement Publishers.Drop (#70 )	2019-10-16 13:26:10 +03:00
Sergej Jaskiewicz	a84105133c	Increase timeout for DispatchQueueSchedulerTests.testScheduleActionOnceNow	2019-10-16 02:10:47 +03:00
Sergej Jaskiewicz	ef3ebd965a	Extract locking API into COpenCombineHelpers module	2019-10-16 02:10:47 +03:00
Sergej Jaskiewicz	a08b99c886	Fix a compiler crash on Linux This crash could only be reproduced in release configuration	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	3398499540	Remove Unreachable.swift	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	1bf193ddaa	Bump Swift version on Linux CI	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	3a88dfd76b	Implemented Comparison. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	bd0b69d7cb	Implement Collect. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	dba76c3c41	Implement Contains, ContainsWhere, TryContainsWhere. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	5863492753	Implement AllSatisfy, TryAllSatisfy. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Joe Spadafora	2f2e16ee1f	Implement Last, LastWhere, TryLastWhere. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	bca131c2a4	Simplify Publishers.Count. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	e999fafdce	Simplify First, FirstWhere, TryFirstWhere. Use ReduceProducer.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	b38830e0f1	Implement Reduce, TryReduce. Use ReduceProducer	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	525405f64d	Implement ReduceProducer ReduceProducer is a helper class that makes implementing reduce-like operators trivial.	2019-10-15 20:51:44 +03:00
Sergej Jaskiewicz	693d1145f8	Reenable compatibility tests (#79 )	2019-10-13 20:22:03 +03:00
Sergej Jaskiewicz	2f9ddc2229	Bump Swift version on Travis for Linux (#78 )	2019-10-10 10:52:18 +03:00
Sergej Jaskiewicz	bcd1b727f8	Fix SwiftLint	2019-10-09 23:29:50 +03:00
Sergej Jaskiewicz	5d1034fcc0	Fix Linux build failure due to PTHREAD_MUTEX_ERRORCHECK there being Int, not Int32	2019-10-09 23:03:35 +03:00
Sergej Jaskiewicz	2378f3d97e	Better error handling for pthread calls	2019-10-09 20:08:24 +03:00
Sergej Jaskiewicz	4a965830e7	Update docs to match Xcode 11.1 (#77 )	2019-10-09 17:51:52 +03:00
Sergej Jaskiewicz	9eabadb7c9	Mention GYB in README.md	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	dcfaec2c9d	Add tests for Publishers.MapKeyPath	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	219ee38119	Update RemainingCombineInterface.swift	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	3a5389d398	GYB cleanup	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	69ead1c8fb	Fix indentation	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	8e6404592e	Add .gitattributes	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	14b7ced2fe	Use gyb tool to implement MapKeyPath	2019-10-09 00:12:07 +03:00
Sergej Jaskiewicz	d7b9e87f6d	Execute tests in parallel	2019-10-08 14:26:09 +03:00
Sergej Jaskiewicz	4fd04b8a00	Test Publishers.Print for printing to stdout	2019-10-08 14:26:09 +03:00
Sergej Jaskiewicz	5f92ee05d2	Fix the semantics to be compatible with Xcode 11.1 (#74 )	2019-10-08 11:20:42 +03:00
Sven	bdd703abb3	Fix Sequence cancellation (#73 ) * Add test to cancel after first value received from Sequence publisher * Stop sending values from sequence if cancelled	2019-10-07 23:19:05 +03:00
Sergej Jaskiewicz	e41c48a5cd	Use UInt64 as CombineIdentifier (instead of UInt)	2019-10-03 15:37:44 +03:00
Sergej Jaskiewicz	df0b8b08db	Add tests for Publishers.Share	2019-10-03 15:22:18 +03:00
Sergej Jaskiewicz	7056143b99	Add tests for Publishers.Autoconnect	2019-10-03 15:22:18 +03:00
Sergej Jaskiewicz	0a965ba60a	Adopt new locking API	2019-10-03 15:22:18 +03:00
Sergej Jaskiewicz	7dfaa4edea	Implement Publishers.Share	2019-10-03 15:22:18 +03:00
Sergej Jaskiewicz	3e8f2774a4	Implement Publishers.Autoconnect	2019-10-03 15:22:18 +03:00
Sergej Jaskiewicz	68e9bbe164	Extract generation of a next CombineIdentifier to COpenCombineHelpers (#69 )	2019-10-02 23:28:09 +03:00
Sergej Jaskiewicz	0f71c33d72	Add header guards	2019-09-23 16:21:08 +03:00
Sergej Jaskiewicz	3f61648f82	Use CInt instead of Int32	2019-09-23 16:21:08 +03:00
Sergej Jaskiewicz	c621ceb267	Rename OpenCombineAtomics -> COpenCombineAtomics	2019-09-23 16:21:08 +03:00
Sergej Jaskiewicz	2aa297ec39	Fix access race detected by TSan	2019-09-23 16:21:08 +03:00
Sergej Jaskiewicz	9cb27bb91b	Better Locking internal API	2019-09-23 16:21:08 +03:00
Sergej Jaskiewicz	d74f68da86	Audit Subscribers.Assign for thread safety (nothing to do here)	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	f68dcd520f	Audit Subscribers.Sink for thread safety (nothing to do here)	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	432fd4f48f	Audit Publishers.ReplaceError for thread safety	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	9c6bbda0c4	Make Publishers.MapError.Inner a struct	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	3990ec2afb	Audit Publishers.Sequence for thread safety	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	39dd9e40bf	Add reflection test for Publishers.ReplaceNil	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	fd7c0459b9	Make Publishers.SetFailureType.Inner a struct	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	f7145e7fa5	Fix TryMap compatibility tests	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	ecd4766129	Audit Optional.Publisher for thread safety (nothing to do here)	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	e00a6f06fc	Audit Optional.Publisher for thread safety (nothing to do here)	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	23ee3a4b7b	Audit Just for thread safety (nothing to do there)	2019-09-22 23:10:54 +03:00
Sergej Jaskiewicz	9c913124eb	Audit TryMap for thread safety, fix its semantics (#64 )	2019-09-21 22:09:48 +03:00
Sergej Jaskiewicz	7ddd15b334	Audit Publishers.Multicast for thread safety (#63 )	2019-09-20 16:15:35 +03:00
Sergej Jaskiewicz	72753ef93c	Implement Publishers.MakeConnectable (#61 ) * Implement Publishers.MakeConnectable * Add MakeConnectable tests	2019-09-19 14:06:57 +03:00
Sergej Jaskiewicz	816426b48c	Fix iterator.next() being called twice in Publishers.Sequence	2019-09-19 05:10:34 +03:00
Sergej Jaskiewicz	47fb390081	Add eraseToAnyPublisher() method	2019-09-18 16:55:48 +03:00
Sergej Jaskiewicz	1d3327f6bf	Revert "Remove XCTUnwrap implementation" This reverts commit `16690e6f1f`.	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	eb7478d430	Add Unreachable optimizer hint	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	f69621f0e2	Remove XCTUnwrap implementation	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	7f3cccf1ae	Audit SubjectSubscriber for thread-safety	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	ec037dbb3d	Fix semantics of Publishers.Print	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	8a39f35d3f	Simplify Publishers.Multicast.connect() method	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	7fb92bffc6	Replace SubscriberType with Downstream in generic params	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	e441ea3048	Add missing Equatable conformances for First, ReplaceError	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	22f7b6d10d	Fix code style issues with FlatMap	2019-09-16 19:13:24 +03:00
Sergej Jaskiewicz	7431d21c9c	Increase timeouts for DispatchQueueSchedulerTests	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	1d901fca7f	Remove flaky test for DispatchQueue scheduler	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	9834eab0ea	Remove some nasty unsafe code from tests https://twitter.com/UINT_MIN/status/1168581618753163264	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	1ce9660ce9	Remove .swiftpm	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	313d6befa6	Fix a data race in DispatchQueueSchedulerTests Also gitignore .swiftpm and make SwiftLint happy	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	8c7f061892	Fully cover DispatchQueue extension with tests	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	2ac2470579	Initial implementation of DispatchQueue scheduler	2019-09-15 16:07:52 +03:00
Sergej Jaskiewicz	57c9ae8590	Initial implementation of DispatchQueue scheduler	2019-09-15 16:07:52 +03:00
Eric Patey	d57c878651	FlatMap (#45 ) Implement FlatMap	2019-09-13 10:57:17 -04:00
Eric Patey	7fa91778c2	Fix failing tests caused by Apple changes in GM Seed. (#56 ) Update tests and implementation to match Apple changes in gm seed.	2019-09-13 10:50:38 -04:00
Sergej Jaskiewicz	d15e604764	Remove mention of XCTestManifests from the Dangerfile	2019-09-13 14:45:28 +03:00
Evgeniy	07c7a98d72	@propertyWrapper Published (#52 )	2019-09-07 18:10:53 +03:00
Sergej Jaskiewicz	01ef05be1f	Pass --enable-index-store flag when testing in release mode	2019-09-07 16:32:34 +03:00
Sergej Jaskiewicz	beee9d0d51	Remove allTests properties in test classes	2019-09-07 16:32:34 +03:00
Sergej Jaskiewicz	aacd1a326c	Remove LinuxMain.swift	2019-09-07 16:32:34 +03:00
Sergej Jaskiewicz	5528adcc67	Enable test discovery on Linux	2019-09-07 16:32:34 +03:00
Sergej Jaskiewicz	1b810d0536	Update Swift version on Linux	2019-09-07 16:32:34 +03:00
Bogdan Vlad	8b25238154	ReplaceError implementation (#50 )	2019-09-01 22:05:44 +03:00
Sergej Jaskiewicz	9b9915bde7	Fix Optional.Publisher.collect() operator specialization Update for Xcode 11.0 beta 6	2019-08-26 03:51:12 +03:00
Eric Patey	27f01e5f21	Implement IgnoreOutput (#44 )	2019-08-20 17:32:33 +03:00
Sergej Jaskiewicz	739eb47409	Update for Xcode 11 beta 6 Yes, it's the only change.	2019-08-20 10:54:17 +03:00
Sergej Jaskiewicz	14d5a90e89	Add Slack badge	2019-08-05 19:57:58 +03:00
Sergej Jaskiewicz	0e869bc861	Implement CompactMap (#32 )	2019-08-02 18:59:53 +03:00
Joe Spadafora	2f38069166	First where (#29 )	2019-08-02 18:55:51 +03:00
Sergej Jaskiewicz	97d07d0a14	Better linting for inheritance clauses and dictionary literals	2019-08-02 14:18:17 +03:00
Joe Spadafora	d3888a3808	Implement Filter/TryFilter (#22 ) * Adds filter and try filter implementations * Implement Filter * Remove @testable declaration * Fix linting * Updates tests and creates testing helper * Fix allTests to include all tests * Renames TestHelper to OperatorTestHelper and adds documentation * Adds more test coverage * Updates to use subclasses for filter / tryfilter * Adds subscription test * Fix subscriber demand to be lazy * Fix CustomPublisherBase changes from master * Fix iOS availability on test helper * Updates availability for test functions * Simplify Filter implementation, add more tests * Ensure test suite consistency on Darwin and Linux * Add missing tests to XCTestManifests.swift	2019-08-02 00:20:35 +03:00
Franz Busch	d2b8709afb	Store newly send value in internal variable inside CurrentValueObject (#39 )	2019-08-01 23:34:27 +03:00
Sergej Jaskiewicz	a28177e9c5	Cache homebrew artifacts	2019-08-01 15:49:00 +03:00
Sergej Jaskiewicz	cef19fce4b	Use Danger CI	2019-08-01 15:49:00 +03:00
Sergej Jaskiewicz	7f6bba62de	Add .hound.yml	2019-08-01 11:52:46 +03:00