Improve test and comments

Test asserts that unused locals error works for untyped modules.
Comment no longer claims to check for untyped modules.

Author: sandersn

src/compiler/utilities.ts

@@ -438,7 +438,7 @@ namespace ts {
             ((<ModuleDeclaration>node).name.kind === SyntaxKind.StringLiteral || isGlobalScopeAugmentation(<ModuleDeclaration>node));
     }
 
-    /** Given a symbol for a module, checks that it is either an untyped import or a shorthand ambient module. */
+    /** Given a symbol for a module, checks that it is a shorthand ambient module. */
     export function isShorthandAmbientModuleSymbol(moduleSymbol: Symbol): boolean {
         return isShorthandAmbientModule(moduleSymbol.valueDeclaration);
     }

tests/baselines/reference/extendsUntypedModule.errors.txt

@@ -0,0 +1,18 @@
+/a.ts(2,8): error TS6133: 'Bar' is declared but never used.
+
+
+==== /a.ts (1 errors) ====
+    import Foo from "foo";
+    import Bar from "bar"; // error: unused
+           ~~~
+!!! error TS6133: 'Bar' is declared but never used.
+    export class A extends Foo { }
+    
+==== /node_modules/foo/index.js (0 errors) ====
+    // Test that extending an untyped module is an error, unlike extending unknownSymbol.
+    
+    This file is not read.
+    
+==== /node_modules/bar/index.js (0 errors) ====
+    Nor is this one.
+    

tests/baselines/reference/extendsUntypedModule.js

@@ -5,9 +5,13 @@
 
 This file is not read.
 
+//// [index.js]
+Nor is this one.
+
 //// [a.ts]
 import Foo from "foo";
-class A extends Foo { }
+import Bar from "bar"; // error: unused
+export class A extends Foo { }
 
 
 //// [a.js]
@@ -31,3 +35,4 @@ var A = (function (_super) {
     }
     return A;
 }(foo_1["default"]));
+exports.A = A;

tests/baselines/reference/extendsUntypedModule.symbols

@@ -1,9 +1,14 @@
 // Test that extending an untyped module is an error, unlike extending unknownSymbol.
 // @noImplicitReferences: true
+// @noUnusedLocals: true
 
 // @Filename: /node_modules/foo/index.js
 This file is not read.
 
+// @Filename: /node_modules/bar/index.js
+Nor is this one.
+
 // @Filename: /a.ts
 import Foo from "foo";
-class A extends Foo { }
+import Bar from "bar"; // error: unused
+export class A extends Foo { }