Error when importing shadowed internal module.

src/compiler/checker.ts

@@ -5720,6 +5720,13 @@ module ts {
             checkSourceElement(node.body);
         }
 
+        function getFirstIdentifier(node: EntityName): Identifier {
+            while (node.kind === SyntaxKind.QualifiedName) {
+                node = (<QualifiedName>node).left;
+            }
+            return <Identifier>node;
+        }
+
         function checkImportDeclaration(node: ImportDeclaration) {
             checkCollisionWithCapturedThisVariable(node, node.name);
             var symbol = getSymbolOfNode(node);
@@ -5730,8 +5737,15 @@ module ts {
                 // Import declaration for an internal module
                 if (target !== unknownSymbol) {
                     if (target.flags & SymbolFlags.Value) {
-                        // Target is a value symbol, check that it can be evaluated as an expression
-                        checkExpression(node.entityName);
+                        // Target is a value symbol, check that it is not hidden by a local declaration with the same name and
+                        // ensure it can be evaluated as an expression
+                        var moduleName = getFirstIdentifier(node.entityName);
+                        if (resolveEntityName(node, moduleName, SymbolFlags.Value | SymbolFlags.Namespace).flags & SymbolFlags.Namespace) {
+                            checkExpression(node.entityName);
+                        }
+                        else {
+                            error(moduleName, Diagnostics.Module_0_is_hidden_by_a_local_declaration_with_the_same_name, identifierToString(moduleName));
+                        }
                     }
                     if (target.flags & SymbolFlags.Type) {
                         checkTypeNameIsReserved(node.name, Diagnostics.Import_name_cannot_be_0);
@@ -5741,7 +5755,6 @@ module ts {
             else {
                 // Import declaration for an external module
                 if (node.parent.kind === SyntaxKind.SourceFile) {
-                    // Parent is a source file, check that external modules are enabled
                     target = resolveImport(symbol);
                 }
                 else if (node.parent.kind === SyntaxKind.ModuleBlock && (<ModuleDeclaration>node.parent.parent).name.kind === SyntaxKind.StringLiteral) {

src/compiler/diagnosticInformationMap.generated.ts

@@ -293,6 +293,7 @@ module ts {
         A_module_declaration_cannot_be_located_prior_to_a_class_or_function_with_which_it_is_merged: { code: -9999999, category: DiagnosticCategory.Error, key: "A module declaration cannot be located prior to a class or function with which it is merged" },
         Cannot_compile_external_modules_unless_the_module_flag_is_provided: { code: -9999999, category: DiagnosticCategory.Error, key: "Cannot compile external modules unless the '--module' flag is provided." },
         Import_declaration_conflicts_with_local_declaration_of_0: { code: -9999999, category: DiagnosticCategory.Error, key: "Import declaration conflicts with local declaration of '{0}'" },
+        Module_0_is_hidden_by_a_local_declaration_with_the_same_name: { code: -9999999, category: DiagnosticCategory.Error, key: "Module '{0}' is hidden by a local declaration with the same name" },
         Filename_0_differs_from_already_included_filename_1_only_in_casing: { code: -9999999, category: DiagnosticCategory.Error, key: "Filename '{0}' differs from already included filename '{1}' only in casing" },
         Argument_for_module_option_must_be_commonjs_or_amd: { code: -9999999, category: DiagnosticCategory.Error, key: "Argument for '--module' option must be 'commonjs' or 'amd'." },
         Argument_for_target_option_must_be_es3_or_es5: { code: -9999999, category: DiagnosticCategory.Error, key: "Argument for '--target' option must be 'es3' or 'es5'." },

src/compiler/diagnosticMessages.json

@@ -1193,6 +1193,10 @@
         "category": "Error",
         "code": -9999999
     },
+	"Module '{0}' is hidden by a local declaration with the same name": {
+        "category": "Error",
+        "code": -9999999
+	},
     "Filename '{0}' differs from already included filename '{1}' only in casing": {
         "category": "Error",
         "code": -9999999

tests/baselines/reference/internalImportInstantiatedModuleMergedWithClassNotReferencingInstance.errors.txt

@@ -0,0 +1,16 @@
+==== tests/cases/compiler/internalImportInstantiatedModuleMergedWithClassNotReferencingInstance.ts (1 errors) ====
+    class A {
+        aProp: string;
+    }
+    module A {
+        export interface X { s: string }
+        export var a = 10;
+    }
+
+    module B {
+        var A = 1;
+        import Y = A;
+                   ~
+!!! Module 'A' is hidden by a local declaration with the same name
+    }
+

tests/baselines/reference/internalImportInstantiatedModuleNotReferencingInstance.errors.txt

@@ -0,0 +1,13 @@
+==== tests/cases/compiler/internalImportInstantiatedModuleNotReferencingInstance.ts (1 errors) ====
+    module A {
+        export interface X { s: string }
+        export var a = 10;
+    }
+
+    module B {
+        var A = 1;
+        import Y = A;
+                   ~
+!!! Module 'A' is hidden by a local declaration with the same name
+    }
+

tests/baselines/reference/internalImportUnInstantiatedModuleMergedWithClassNotReferencingInstance.errors.txt

@@ -0,0 +1,15 @@
+==== tests/cases/compiler/internalImportUnInstantiatedModuleMergedWithClassNotReferencingInstance.ts (1 errors) ====
+    class A {
+        aProp: string;
+    }
+    module A {
+        export interface X { s: string }
+    }
+
+    module B {
+        var A = 1;
+        import Y = A;
+                   ~
+!!! Module 'A' is hidden by a local declaration with the same name
+    }
+

tests/baselines/reference/reboundIdentifierOnImportAlias.errors.txt

@@ -0,0 +1,10 @@
+==== tests/cases/compiler/reboundIdentifierOnImportAlias.ts (1 errors) ====
+    module Foo {
+        export var x = "hello";
+    }
+    module Bar {
+        var Foo = 1;
+        import F = Foo;
+                   ~~~
+!!! Module 'Foo' is hidden by a local declaration with the same name
+    }

tests/baselines/reference/shadowedInternalModule.errors.txt

@@ -1,4 +1,4 @@
-==== tests/cases/conformance/internalModules/importDeclarations/shadowedInternalModule.ts (1 errors) ====
+==== tests/cases/conformance/internalModules/importDeclarations/shadowedInternalModule.ts (2 errors) ====
     // all errors imported modules conflict with local variables
 
     module A {
@@ -12,6 +12,8 @@
     module B {
         var A = { x: 0, y: 0 };
         import Point = A;
+                       ~
+!!! Module 'A' is hidden by a local declaration with the same name
     }
 
     module X {