From 056a656937944f9f7366f630d278b2ececa39cd4 Mon Sep 17 00:00:00 2001
From: Nathan Shively-Sanders <293473+sandersn@users.noreply.github.com>
Date: Thu, 24 Oct 2019 08:37:10 -0700
Subject: [PATCH] Restore delayed merge check to getTypeFromJSDocValueReference

This is needed when a function merges with a prototype assignment. The
resulting *merged* symbol is a constructor function marked with
SymbolFlags.Class. However, the merge doesn't happen until
getTypeOfFuncClassEnumModule is called, which, in the
getTypeReferenceType code path, doesn't happen until
getTypeFromJSDocValueReference. That means the check for
SymbolFlags.Class is missed.

Previously, getTypeFromJSDocValueReference had a weird check
`symbol !== getTypeOfSymbol(symbol).symbol`, which, if true, ran
getTypeReferenceType again on `getTypeOfSymbol(symbol).symbol`. For
JS "aliases", this had the effect of dereferencing the alias, and for
function-prototype merges, this had the effect of ... just trying again
after the merge had happened.

This is a confusing way to run things. getTypeReferenceType should
instead detect a function-prototype merge, cause it to happen, and
*then* run the rest of its code instead of relying on try-again logic at
the very end. However, for the RC, I want to fix this code by restoring
the old check, with an additional check to make sure that #33106 doesn't
break again:

```ts
const valueType = getTypeOfSymbol(symbol)
symbol !== valueType.symbol && getMergedSymbol(symbol) === valueType.symbol
```

I'll work on the real fix afterwards and put it into 3.8.
---
 src/compiler/checker.ts                       |  4 +-
 .../jsdocTypeReferenceToMergedClass.symbols   | 33 ++++++++++++++++
 .../jsdocTypeReferenceToMergedClass.types     | 39 +++++++++++++++++++
 .../jsdoc/jsdocTypeReferenceToMergedClass.ts  | 16 ++++++++
 4 files changed, 91 insertions(+), 1 deletion(-)
 create mode 100644 tests/baselines/reference/jsdocTypeReferenceToMergedClass.symbols
 create mode 100644 tests/baselines/reference/jsdocTypeReferenceToMergedClass.types
 create mode 100644 tests/cases/conformance/jsdoc/jsdocTypeReferenceToMergedClass.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index f30e765ab42..ed3057895fa 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -10766,7 +10766,9 @@ namespace ts {
                     && isCallExpression(decl.initializer)
                     && isRequireCall(decl.initializer, /*requireStringLiteralLikeArgument*/ true)
                     && valueType.symbol;
-                if (isRequireAlias || node.kind === SyntaxKind.ImportType) {
+                const isImportType = node.kind === SyntaxKind.ImportType;
+                const isDelayedMergeClass = symbol !== valueType.symbol && getMergedSymbol(symbol) === valueType.symbol;
+                if (isRequireAlias || isImportType || isDelayedMergeClass) {
                     typeType = getTypeReferenceType(node, valueType.symbol);
                 }
             }
diff --git a/tests/baselines/reference/jsdocTypeReferenceToMergedClass.symbols b/tests/baselines/reference/jsdocTypeReferenceToMergedClass.symbols
new file mode 100644
index 00000000000..25aebdb79d4
--- /dev/null
+++ b/tests/baselines/reference/jsdocTypeReferenceToMergedClass.symbols
@@ -0,0 +1,33 @@
+=== tests/cases/conformance/jsdoc/test.js ===
+/** @param {Workspace.Project} p */
+function demo(p) {
+>demo : Symbol(demo, Decl(test.js, 0, 0))
+>p : Symbol(p, Decl(test.js, 1, 14))
+
+    p.isServiceProject()
+>p.isServiceProject : Symbol(isServiceProject, Decl(mod1.js, 3, 31))
+>p : Symbol(p, Decl(test.js, 1, 14))
+>isServiceProject : Symbol(isServiceProject, Decl(mod1.js, 3, 31))
+}
+=== tests/cases/conformance/jsdoc/mod1.js ===
+// Note: mod1.js needs to appear second to trigger the bug
+var Workspace = {}
+>Workspace : Symbol(Workspace, Decl(mod1.js, 1, 3), Decl(mod1.js, 1, 18), Decl(mod1.js, 2, 37))
+
+Workspace.Project = function wp() { }
+>Workspace.Project : Symbol(Workspace.Project, Decl(mod1.js, 1, 18), Decl(mod1.js, 3, 10))
+>Workspace : Symbol(Workspace, Decl(mod1.js, 1, 3), Decl(mod1.js, 1, 18), Decl(mod1.js, 2, 37))
+>Project : Symbol(Workspace.Project, Decl(mod1.js, 1, 18), Decl(mod1.js, 3, 10))
+>wp : Symbol(wp, Decl(mod1.js, 2, 19))
+
+Workspace.Project.prototype = {
+>Workspace.Project.prototype : Symbol(Workspace.Project.prototype, Decl(mod1.js, 2, 37))
+>Workspace.Project : Symbol(Workspace.Project, Decl(mod1.js, 1, 18), Decl(mod1.js, 3, 10))
+>Workspace : Symbol(Workspace, Decl(mod1.js, 1, 3), Decl(mod1.js, 1, 18), Decl(mod1.js, 2, 37))
+>Project : Symbol(Workspace.Project, Decl(mod1.js, 1, 18), Decl(mod1.js, 3, 10))
+>prototype : Symbol(Workspace.Project.prototype, Decl(mod1.js, 2, 37))
+
+  isServiceProject() {}
+>isServiceProject : Symbol(isServiceProject, Decl(mod1.js, 3, 31))
+}
+
diff --git a/tests/baselines/reference/jsdocTypeReferenceToMergedClass.types b/tests/baselines/reference/jsdocTypeReferenceToMergedClass.types
new file mode 100644
index 00000000000..1e4e7ef654d
--- /dev/null
+++ b/tests/baselines/reference/jsdocTypeReferenceToMergedClass.types
@@ -0,0 +1,39 @@
+=== tests/cases/conformance/jsdoc/test.js ===
+/** @param {Workspace.Project} p */
+function demo(p) {
+>demo : (p: wp) => void
+>p : wp
+
+    p.isServiceProject()
+>p.isServiceProject() : void
+>p.isServiceProject : () => void
+>p : wp
+>isServiceProject : () => void
+}
+=== tests/cases/conformance/jsdoc/mod1.js ===
+// Note: mod1.js needs to appear second to trigger the bug
+var Workspace = {}
+>Workspace : typeof Workspace
+>{} : {}
+
+Workspace.Project = function wp() { }
+>Workspace.Project = function wp() { } : typeof wp
+>Workspace.Project : typeof wp
+>Workspace : typeof Workspace
+>Project : typeof wp
+>function wp() { } : typeof wp
+>wp : typeof wp
+
+Workspace.Project.prototype = {
+>Workspace.Project.prototype = {  isServiceProject() {}} : { isServiceProject(): void; }
+>Workspace.Project.prototype : { isServiceProject(): void; }
+>Workspace.Project : typeof wp
+>Workspace : typeof Workspace
+>Project : typeof wp
+>prototype : { isServiceProject(): void; }
+>{  isServiceProject() {}} : { isServiceProject(): void; }
+
+  isServiceProject() {}
+>isServiceProject : () => void
+}
+
diff --git a/tests/cases/conformance/jsdoc/jsdocTypeReferenceToMergedClass.ts b/tests/cases/conformance/jsdoc/jsdocTypeReferenceToMergedClass.ts
new file mode 100644
index 00000000000..d840b051d9b
--- /dev/null
+++ b/tests/cases/conformance/jsdoc/jsdocTypeReferenceToMergedClass.ts
@@ -0,0 +1,16 @@
+// @noEmit: true
+// @allowJs: true
+// @checkJs: true
+
+// @Filename: test.js
+/** @param {Workspace.Project} p */
+function demo(p) {
+    p.isServiceProject()
+}
+// @Filename: mod1.js
+// Note: mod1.js needs to appear second to trigger the bug
+var Workspace = {}
+Workspace.Project = function wp() { }
+Workspace.Project.prototype = {
+  isServiceProject() {}
+}