Error on invalid uses of namespace export (microsoft#37715)

Author: andrewbranch

src/compiler/checker.ts

@@ -34018,7 +34018,7 @@ namespace ts {
                 return false;
             }
             if (inAmbientExternalModule && isExternalModuleNameRelative(moduleName.text)) {
-                // we have already reported errors on top level imports\exports in external module augmentations in checkModuleDeclaration
+                // we have already reported errors on top level imports/exports in external module augmentations in checkModuleDeclaration
                 // no need to do this again.
                 if (!isTopLevelInExternalModuleAugmentation(node)) {
                     // TypeScript 1.0 spec (April 2013): 12.1.6
@@ -34154,16 +34154,10 @@ namespace ts {
 
             checkGrammarExportDeclaration(node);
             if (!node.moduleSpecifier || checkExternalImportOrExportDeclaration(node)) {
-                if (node.exportClause) {
+                if (node.exportClause && !isNamespaceExport(node.exportClause)) {
                     // export { x, y }
                     // export { x, y } from "foo"
-                    if (isNamedExports(node.exportClause)) {
-                        forEach(node.exportClause.elements, checkExportSpecifier);
-                    }
-                    else if(!isNamespaceExport(node.exportClause)) {
-                        checkImportBinding(node.exportClause);
-                    }
-
+                    forEach(node.exportClause.elements, checkExportSpecifier);
                     const inAmbientExternalModule = node.parent.kind === SyntaxKind.ModuleBlock && isAmbientModule(node.parent.parent);
                     const inAmbientNamespaceDeclaration = !inAmbientExternalModule && node.parent.kind === SyntaxKind.ModuleBlock &&
                         !node.moduleSpecifier && node.flags & NodeFlags.Ambient;
@@ -34177,7 +34171,9 @@ namespace ts {
                     if (moduleSymbol && hasExportAssignmentSymbol(moduleSymbol)) {
                         error(node.moduleSpecifier, Diagnostics.Module_0_uses_export_and_cannot_be_used_with_export_Asterisk, symbolToString(moduleSymbol));
                     }
-
+                    else if (node.exportClause) {
+                        checkAliasSymbol(node.exportClause);
+                    }
                     if (moduleKind !== ModuleKind.System && moduleKind < ModuleKind.ES2015) {
                         checkExternalEmitHelpers(node, ExternalEmitHelpers.ExportStar);
                     }

tests/baselines/reference/exportAsNamespace_exportAssignment.errors.txt

@@ -0,0 +1,11 @@
+tests/cases/conformance/es2020/modules/b.ts(1,21): error TS2498: Module '"tests/cases/conformance/es2020/modules/a"' uses 'export =' and cannot be used with 'export *'.
+
+
+==== tests/cases/conformance/es2020/modules/a.ts (0 errors) ====
+    export = {}
+    
+==== tests/cases/conformance/es2020/modules/b.ts (1 errors) ====
+    export * as ns from './a';
+                        ~~~~~
+!!! error TS2498: Module '"tests/cases/conformance/es2020/modules/a"' uses 'export =' and cannot be used with 'export *'.
+    

tests/baselines/reference/exportAsNamespace_exportAssignment.js

@@ -0,0 +1,35 @@
+//// [tests/cases/conformance/es2020/modules/exportAsNamespace_exportAssignment.ts] ////
+
+//// [a.ts]
+export = {}
+
+//// [b.ts]
+export * as ns from './a';
+
+
+//// [a.js]
+"use strict";
+module.exports = {};
+//// [b.js]
+"use strict";
+var __createBinding = (this && this.__createBinding) || (Object.create ? (function(o, m, k, k2) {
+    if (k2 === undefined) k2 = k;
+    Object.defineProperty(o, k2, { enumerable: true, get: function() { return m[k]; } });
+}) : (function(o, m, k, k2) {
+    if (k2 === undefined) k2 = k;
+    o[k2] = m[k];
+}));
+var __setModuleDefault = (this && this.__setModuleDefault) || (Object.create ? (function(o, v) {
+    Object.defineProperty(o, "default", { enumerable: true, value: v });
+}) : function(o, v) {
+    o["default"] = v;
+});
+var __importStar = (this && this.__importStar) || function (mod) {
+    if (mod && mod.__esModule) return mod;
+    var result = {};
+    if (mod != null) for (var k in mod) if (Object.hasOwnProperty.call(mod, k)) __createBinding(result, mod, k);
+    __setModuleDefault(result, mod);
+    return result;
+};
+exports.__esModule = true;
+exports.ns = __importStar(require("./a"));

tests/baselines/reference/exportAsNamespace_missingEmitHelpers.errors.txt

@@ -0,0 +1,11 @@
+tests/cases/conformance/es2020/modules/b.ts(1,1): error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.
+
+
+==== tests/cases/conformance/es2020/modules/a.ts (0 errors) ====
+    export {}
+    
+==== tests/cases/conformance/es2020/modules/b.ts (1 errors) ====
+    export * as ns from './a'; // Error
+    ~~~~~~~~~~~~~~~~~~~~~~~~~~
+!!! error TS2354: This syntax requires an imported helper but module 'tslib' cannot be found.
+    

tests/baselines/reference/exportAsNamespace_missingEmitHelpers.js

@@ -0,0 +1,16 @@
+//// [tests/cases/conformance/es2020/modules/exportAsNamespace_missingEmitHelpers.ts] ////
+
+//// [a.ts]
+export {}
+
+//// [b.ts]
+export * as ns from './a'; // Error
+
+
+//// [a.js]
+"use strict";
+exports.__esModule = true;
+//// [b.js]
+"use strict";
+exports.__esModule = true;
+exports.ns = require("./a"); // Error

tests/baselines/reference/exportAsNamespace_nonExistent.errors.txt

@@ -0,0 +1,8 @@
+tests/cases/conformance/es2020/modules/exportAsNamespace_nonExistent.ts(1,21): error TS2307: Cannot find module './nonexistent' or its corresponding type declarations.
+
+
+==== tests/cases/conformance/es2020/modules/exportAsNamespace_nonExistent.ts (1 errors) ====
+    export * as ns from './nonexistent'; // Error
+                        ~~~~~~~~~~~~~~~
+!!! error TS2307: Cannot find module './nonexistent' or its corresponding type declarations.
+    

tests/baselines/reference/exportAsNamespace_nonExistent.js

@@ -0,0 +1,6 @@
+//// [exportAsNamespace_nonExistent.ts]
+export * as ns from './nonexistent'; // Error
+
+
+//// [exportAsNamespace_nonExistent.js]
+export * as ns from './nonexistent'; // Error

tests/cases/conformance/es2020/modules/exportAsNamespace_exportAssignment.ts

@@ -0,0 +1,9 @@
+// @module: commonjs
+// @esModuleInterop: true
+// @noTypesAndSymbols: true
+
+// @Filename: a.ts
+export = {}
+
+// @Filename: b.ts
+export * as ns from './a';

tests/cases/conformance/es2020/modules/exportAsNamespace_missingEmitHelpers.ts

@@ -0,0 +1,9 @@
+// @module: commonjs
+// @importHelpers: true
+// @noTypesAndSymbols: true
+
+// @Filename: a.ts
+export {}
+
+// @Filename: b.ts
+export * as ns from './a'; // Error

tests/cases/conformance/es2020/modules/exportAsNamespace_nonExistent.ts

@@ -0,0 +1,4 @@
+// @module: esnext
+// @noTypesAndSymbols: true
+
+export * as ns from './nonexistent'; // Error