Check for instantiation on export default in ES6

src/compiler/emitter.ts

@@ -3924,26 +3924,28 @@ module ts {
             }
 
             function emitExportAssignment(node: ExportAssignment) {
-                if (languageVersion >= ScriptTarget.ES6) {
-                    writeLine();
-                    emitStart(node);
-                    write("export default ");
-                    var expression = node.expression;
-                    emit(expression);
-                    if (expression.kind !== SyntaxKind.FunctionDeclaration &&
-                        expression.kind !== SyntaxKind.ClassDeclaration) {
-                        write(";");
+                if (!node.isExportEquals && resolver.isValueAliasDeclaration(node)) {
+                    if (languageVersion >= ScriptTarget.ES6) {
+                        writeLine();
+                        emitStart(node);
+                        write("export default ");
+                        var expression = node.expression;
+                        emit(expression);
+                        if (expression.kind !== SyntaxKind.FunctionDeclaration &&
+                            expression.kind !== SyntaxKind.ClassDeclaration) {
+                            write(";");
+                        }
+                        emitEnd(node);
+                    }
+                    else {
+                        writeLine();
+                        emitStart(node);
+                        emitContainingModuleName(node);
+                        write(".default = ");
+                        emit(node.expression);
+                        write(";");
+                        emitEnd(node);
                     }
-                    emitEnd(node);
-                }
-                else if (!node.isExportEquals && resolver.isValueAliasDeclaration(node)) {
-                    writeLine();
-                    emitStart(node);
-                    emitContainingModuleName(node);
-                    write(".default = ");
-                    emit(node.expression);
-                    write(";");
-                    emitEnd(node);
                 }
             }
 

tests/baselines/reference/es6ExportAssignment.js

@@ -5,4 +5,3 @@ export = a;
 
 //// [es6ExportAssignment.js]
 var a = 10;
-export default a;

tests/baselines/reference/es6ExportEquals.js

@@ -8,7 +8,6 @@ export = f;
 //// [es6ExportEquals.js]
 export function f() {
 }
-export default f;
 
 
 //// [es6ExportEquals.d.ts]

tests/baselines/reference/es6ImportEqualsDeclaration.js

@@ -10,5 +10,4 @@ import a = require("server");
 
 //// [server.js]
 var a = 10;
-export default a;
 //// [client.js]

tests/baselines/reference/es6ImportNamedImportInExportAssignment.js

@@ -12,7 +12,6 @@ export = a;
 export var a = 10;
 //// [es6ImportNamedImportInExportAssignment_1.js]
 import { a } from "es6ImportNamedImportInExportAssignment_0";
-export default a;
 
 
 //// [es6ImportNamedImportInExportAssignment_0.d.ts]

tests/baselines/reference/exportDefaultForNonInstantiatedModule.js

@@ -0,0 +1,10 @@
+//// [exportDefaultForNonInstantiatedModule.ts]
+
+module m {
+    export interface foo {
+    }
+}
+// Should not be emitted
+export default m;
+
+//// [exportDefaultForNonInstantiatedModule.js]

tests/baselines/reference/exportDefaultForNonInstantiatedModule.types

@@ -0,0 +1,13 @@
+=== tests/cases/compiler/exportDefaultForNonInstantiatedModule.ts ===
+
+module m {
+>m : unknown
+
+    export interface foo {
+>foo : foo
+    }
+}
+// Should not be emitted
+export default m;
+>m : unknown
+

tests/cases/compiler/exportDefaultForNonInstantiatedModule.ts

@@ -0,0 +1,8 @@
+// @target: ES6
+
+module m {
+    export interface foo {
+    }
+}
+// Should not be emitted
+export default m;