Merge pull request microsoft#1278 from Microsoft/preserveConstEnums2

Emit modules that contain only const enums, if the preserveConstEnum flag is provided.

Author: CyrusNajmabadi

src/compiler/emitter.ts

@@ -715,7 +715,7 @@ module ts {
                 };
             }
         }
-
+
         function emitEnumDeclaration(node: EnumDeclaration) {
             if (resolver.isDeclarationVisible(node)) {
                 emitJsDocComments(node);
@@ -3176,7 +3176,10 @@ module ts {
             }
 
             function emitModuleDeclaration(node: ModuleDeclaration) {
-                if (getModuleInstanceState(node) !== ModuleInstanceState.Instantiated) {
+                var shouldEmit = getModuleInstanceState(node) === ModuleInstanceState.Instantiated ||
+                    (getModuleInstanceState(node) === ModuleInstanceState.ConstEnumOnly && compilerOptions.preserveConstEnums);
+
+                if (!shouldEmit) {
                     return emitPinnedOrTripleSlashComments(node);
                 }
                 emitLeadingComments(node);
@@ -3558,7 +3561,7 @@ module ts {
                 return leadingComments;
             }
 
-
+
             function getLeadingCommentsToEmit(node: Node) {
                 // Emit the leading comments only if the parent's pos doesn't match because parent should take care of emitting these comments
                 if (node.parent.kind === SyntaxKind.SourceFile || node.pos !== node.parent.pos) {