Do not emit "export" for classes within modules, and do not write the name of an export default class

src/compiler/emitter.ts

@@ -4894,7 +4894,7 @@ module ts {
             }
 
             function emitClassDeclarationForES6AndHigher(node: ClassDeclaration) {
-                if (node.flags & NodeFlags.Export) {
+                if (isES6ModuleMemberDeclaration(node)) {
                     write("export ");
 
                     if (node.flags & NodeFlags.Default) {
@@ -4903,7 +4903,9 @@ module ts {
                 }
 
                 write("class ");
-                emitDeclarationName(node);
+                if (node.name || !(node.flags & NodeFlags.Default)) {
+                    emitDeclarationName(node);
+                }
                 var baseTypeNode = getClassBaseTypeNode(node);
                 if (baseTypeNode) {
                     write(" extends ");

tests/baselines/reference/es6ExportDefaultClassDeclaration2.js

@@ -6,7 +6,7 @@ export default class {
 
 
 //// [es6ExportDefaultClassDeclaration2.js]
-export default class _default {
+export default class  {
     method() {
     }
 }

tests/baselines/reference/es6ModuleClassDeclaration.js

@@ -149,7 +149,7 @@ new c();
 new c2();
 var m1;
 (function (m1) {
-    export class c3 {
+    class c3 {
         constructor() {
             this.x = 10;
             this.y = 30;
@@ -189,7 +189,7 @@ var m1;
 export { m1 };
 var m2;
 (function (m2) {
-    export class c3 {
+    class c3 {
         constructor() {
             this.x = 10;
             this.y = 30;

tests/baselines/reference/symbolDeclarationEmit12.js

@@ -15,7 +15,7 @@ module M {
 //// [symbolDeclarationEmit12.js]
 var M;
 (function (M) {
-    export class C {
+    class C {
         [Symbol.toPrimitive](x) {
         }
         [Symbol.isConcatSpreadable]() {