From 4cd20b1335b551abfcc4c2d74c3d40e1c1730c3b Mon Sep 17 00:00:00 2001
From: Noel Varanda <ncwvaranda@gmail.com>
Date: Fri, 19 May 2017 17:38:04 +0100
Subject: [PATCH] Fix #15540: Throw error when importing @types (#15866)

* Fix #15540: Throw error when importing @types

Fix issue: #15540

- Modify checker; external imports to account for imported modules
containing '@types/'.
- Add diagnostic message.
- Add test case

* FIX-15540: Review changes

- Replace `substr` with `startsWith`
- move diagnostics message to more relevant place
- Add `removePrefix` helper function
---
 src/compiler/checker.ts                           |  6 ++++++
 src/compiler/core.ts                              |  5 +++++
 src/compiler/diagnosticMessages.json              |  4 ++++
 .../reference/importDeclTypes.errors.txt          | 14 ++++++++++++++
 tests/baselines/reference/importDeclTypes.js      | 15 +++++++++++++++
 tests/cases/compiler/importDeclTypes.ts           |  9 +++++++++
 6 files changed, 53 insertions(+)
 create mode 100644 tests/baselines/reference/importDeclTypes.errors.txt
 create mode 100644 tests/baselines/reference/importDeclTypes.js
 create mode 100644 tests/cases/compiler/importDeclTypes.ts

diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 799cde7cdb3..9ce987c3f58 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1642,6 +1642,12 @@ namespace ts {
                 return;
             }
 
+            if (startsWith(moduleReference, "@types/")) {
+                const diag = Diagnostics.Cannot_import_type_declaration_files_Consider_importing_0_instead_of_1;
+                const withoutAtTypePrefix = removePrefix(moduleReference, "@types/");
+                error(errorNode, diag, withoutAtTypePrefix, moduleReference);
+            }
+
             const ambientModule = tryFindAmbientModule(moduleName, /*withAugmentations*/ true);
             if (ambientModule) {
                 return ambientModule;
diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 60553fdab01..4cb55f0fe30 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -1764,6 +1764,11 @@ namespace ts {
         return str.lastIndexOf(prefix, 0) === 0;
     }
 
+    /* @internal */
+    export function removePrefix(str: string, prefix: string): string {
+        return startsWith(str, prefix) ? str.substr(prefix.length) : str;
+    }
+
     /* @internal */
     export function endsWith(str: string, suffix: string): boolean {
         const expectedPos = str.length - suffix.length;
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index ffedb45c2e0..d4fc40399ed 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3061,6 +3061,10 @@
         "category": "Message",
         "code": 6136
     },
+    "Cannot import type declaration files. Consider importing '{0}' instead of '{1}'.": {
+        "category": "Error",
+        "code": 6137
+    },
     "Property '{0}' is declared but never used.": {
         "category": "Error",
         "code": 6138
diff --git a/tests/baselines/reference/importDeclTypes.errors.txt b/tests/baselines/reference/importDeclTypes.errors.txt
new file mode 100644
index 00000000000..dfb8fcb6f48
--- /dev/null
+++ b/tests/baselines/reference/importDeclTypes.errors.txt
@@ -0,0 +1,14 @@
+tests/cases/compiler/a.ts(1,21): error TS6137: Cannot import type declaration files. Consider importing 'foo-bar' instead of '@types/foo-bar'.
+
+
+==== /node_modules/@types/foo-bar/index.d.ts (0 errors) ====
+    export interface Foo {
+        bar: string;
+    }
+    
+    // This should error
+==== tests/cases/compiler/a.ts (1 errors) ====
+    import { Foo } from "@types/foo-bar";
+                        ~~~~~~~~~~~~~~~~
+!!! error TS6137: Cannot import type declaration files. Consider importing 'foo-bar' instead of '@types/foo-bar'.
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/importDeclTypes.js b/tests/baselines/reference/importDeclTypes.js
new file mode 100644
index 00000000000..640dd4a19b4
--- /dev/null
+++ b/tests/baselines/reference/importDeclTypes.js
@@ -0,0 +1,15 @@
+//// [tests/cases/compiler/importDeclTypes.ts] ////
+
+//// [index.d.ts]
+export interface Foo {
+    bar: string;
+}
+
+// This should error
+//// [a.ts]
+import { Foo } from "@types/foo-bar";
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
diff --git a/tests/cases/compiler/importDeclTypes.ts b/tests/cases/compiler/importDeclTypes.ts
new file mode 100644
index 00000000000..01fcd0e7b6f
--- /dev/null
+++ b/tests/cases/compiler/importDeclTypes.ts
@@ -0,0 +1,9 @@
+
+// @filename: /node_modules/@types/foo-bar/index.d.ts
+export interface Foo {
+    bar: string;
+}
+
+// This should error
+// @filename: a.ts
+import { Foo } from "@types/foo-bar";