Add error for using generalized expressions with export assignments in ambient contexts (#18444)

src/compiler/checker.ts

@@ -22345,6 +22345,10 @@ namespace ts {
 
             checkExternalModuleExports(container);
 
+            if (isInAmbientContext(node) && !isEntityNameExpression(node.expression)) {
+                grammarErrorOnNode(node.expression, Diagnostics.The_expression_of_an_export_assignment_must_be_an_identifier_or_qualified_name_in_an_ambient_context);
+            }
+
             if (node.isExportEquals && !isInAmbientContext(node)) {
                 if (modulekind >= ModuleKind.ES2015) {
                     // export assignment is not supported in es6 modules

src/compiler/diagnosticMessages.json

@@ -2212,6 +2212,10 @@
         "category": "Error",
         "code": 2713
     },
+    "The expression of an export assignment must be an identifier or qualified name in an ambient context.": {
+        "category": "Error",
+        "code": 2714
+    },
 
     "Import declaration '{0}' is using private name '{1}'.": {
         "category": "Error",

tests/baselines/reference/ambientExportDefaultErrors.errors.txt

@@ -0,0 +1,41 @@
+tests/cases/compiler/foo.d.ts(1,16): error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+tests/cases/compiler/foo2.d.ts(1,10): error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+tests/cases/compiler/indirection.d.ts(3,20): error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+tests/cases/compiler/indirection2.d.ts(3,14): error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+
+
+==== tests/cases/compiler/consumer.ts (0 errors) ====
+    /// <reference path="./indirection.d.ts" />
+    /// <reference path="./indirection2.d.ts" />
+    import "indirect";
+    import "foo";
+    import "indirect2";
+    import "foo2";
+==== tests/cases/compiler/foo.d.ts (1 errors) ====
+    export default 2 + 2;
+                   ~~~~~
+!!! error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+    export as namespace Foo;
+    
+==== tests/cases/compiler/foo2.d.ts (1 errors) ====
+    export = 2 + 2;
+             ~~~~~
+!!! error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+    export as namespace Foo2;
+    
+==== tests/cases/compiler/indirection.d.ts (1 errors) ====
+    /// <reference path="./foo.d.ts" />
+    declare module "indirect" {
+        export default typeof Foo.default;
+                       ~~~~~~~~~~~~~~~~~~
+!!! error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+    }
+    
+==== tests/cases/compiler/indirection2.d.ts (1 errors) ====
+    /// <reference path="./foo2.d.ts" />
+    declare module "indirect2" {
+        export = typeof Foo2;
+                 ~~~~~~~~~~~
+!!! error TS2714: The expression of an export assignment must be an identifier or qualified name in an ambient context.
+    }
+    

tests/baselines/reference/ambientExportDefaultErrors.js

@@ -0,0 +1,39 @@
+//// [tests/cases/compiler/ambientExportDefaultErrors.ts] ////
+
+//// [foo.d.ts]
+export default 2 + 2;
+export as namespace Foo;
+
+//// [foo2.d.ts]
+export = 2 + 2;
+export as namespace Foo2;
+
+//// [indirection.d.ts]
+/// <reference path="./foo.d.ts" />
+declare module "indirect" {
+    export default typeof Foo.default;
+}
+
+//// [indirection2.d.ts]
+/// <reference path="./foo2.d.ts" />
+declare module "indirect2" {
+    export = typeof Foo2;
+}
+
+//// [consumer.ts]
+/// <reference path="./indirection.d.ts" />
+/// <reference path="./indirection2.d.ts" />
+import "indirect";
+import "foo";
+import "indirect2";
+import "foo2";
+
+//// [consumer.js]
+"use strict";
+exports.__esModule = true;
+/// <reference path="./indirection.d.ts" />
+/// <reference path="./indirection2.d.ts" />
+require("indirect");
+require("foo");
+require("indirect2");
+require("foo2");

tests/baselines/reference/es5-commonjs7.symbols

@@ -1,5 +1,7 @@
 === tests/cases/compiler/test.d.ts ===
-export default "test";
+export default undefined;
+>undefined : Symbol(default)
+
 export var __esModule;
 >__esModule : Symbol(__esModule, Decl(test.d.ts, 1, 10))
 

tests/baselines/reference/es5-commonjs7.types

@@ -1,5 +1,7 @@
 === tests/cases/compiler/test.d.ts ===
-export default "test";
+export default undefined;
+>undefined : undefined
+
 export var __esModule;
 >__esModule : any
 

tests/baselines/reference/typeAliasExport.js

@@ -1,6 +1,6 @@
 //// [typeAliasExport.ts]
 declare module "a" {
-  export default 0
+  export default undefined
   export var a;
   export type a = typeof a;
 }

tests/baselines/reference/typeAliasExport.symbols

@@ -1,6 +1,8 @@
 === tests/cases/compiler/typeAliasExport.ts ===
 declare module "a" {
-  export default 0
+  export default undefined
+>undefined : Symbol(default)
+
   export var a;
 >a : Symbol(a, Decl(typeAliasExport.ts, 2, 12), Decl(typeAliasExport.ts, 2, 15))
 

tests/baselines/reference/typeAliasExport.types

@@ -1,6 +1,8 @@
 === tests/cases/compiler/typeAliasExport.ts ===
 declare module "a" {
-  export default 0
+  export default undefined
+>undefined : undefined
+
   export var a;
 >a : any
 

tests/cases/compiler/ambientExportDefaultErrors.ts

@@ -0,0 +1,27 @@
+// @filename: foo.d.ts
+export default 2 + 2;
+export as namespace Foo;
+
+// @filename: foo2.d.ts
+export = 2 + 2;
+export as namespace Foo2;
+
+// @filename: indirection.d.ts
+/// <reference path="./foo.d.ts" />
+declare module "indirect" {
+    export default typeof Foo.default;
+}
+
+// @filename: indirection2.d.ts
+/// <reference path="./foo2.d.ts" />
+declare module "indirect2" {
+    export = typeof Foo2;
+}
+
+// @filename: consumer.ts
+/// <reference path="./indirection.d.ts" />
+/// <reference path="./indirection2.d.ts" />
+import "indirect";
+import "foo";
+import "indirect2";
+import "foo2";

tests/cases/compiler/es5-commonjs7.ts

@@ -4,5 +4,5 @@
 // @module: commonjs
 
 // @filename: test.d.ts
-export default "test";
+export default undefined;
 export var __esModule;

tests/cases/compiler/typeAliasExport.ts

@@ -1,5 +1,5 @@
 declare module "a" {
-  export default 0
+  export default undefined
   export var a;
   export type a = typeof a;
 }