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

Author: nowy

src/compiler/checker.ts

@@ -1642,6 +1642,11 @@ namespace ts {
                 return;
             }
 
+            if (moduleReference.substr(0, 7) === "@types/") {
+                const diag = Diagnostics.Cannot_import_type_declaration_files_Consider_importing_0_instead_of_1;
+                error(errorNode, diag, moduleName.substr(7), moduleName);
+            }
+
             const ambientModule = tryFindAmbientModule(moduleName, /*withAugmentations*/ true);
             if (ambientModule) {
                 return ambientModule;

src/compiler/diagnosticMessages.json

@@ -2135,6 +2135,10 @@
         "category": "Error",
         "code": 2710
     },
+    "Cannot import type declaration files. Consider importing '{0}' instead of '{1}'.": {
+        "category": "Error",
+        "code": 2711
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/importDeclTypes.errors.txt

@@ -0,0 +1,14 @@
+tests/cases/compiler/a.ts(1,21): error TS2711: 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 TS2711: Cannot import type declaration files. Consider importing 'foo-bar' instead of '@types/foo-bar'.
+    

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;

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";