Emit declaration if its identifier is used in export assignment of external module

src/compiler/checker.ts

@@ -5706,6 +5706,22 @@ module ts {
             return false;
         }
 
+        function isReferencedInExportAssignment(node: Declaration): boolean {
+            var exportAssignedSymbol = getExportAssignmentSymbol(getSymbolOfNode(node.parent));
+            if (exportAssignedSymbol) {
+                var symbol = getSymbolOfNode(node);
+                if (exportAssignedSymbol === symbol) {
+                    // This symbol was export assigned symbol
+                    return true;
+                }
+
+                // TODO(shkamat): if export assignment is alias, the alias target would make the node as referenced in export assignment 
+                
+            }
+
+            return false;
+        }
+
         function getNodeCheckFlags(node: Node): NodeCheckFlags {
             return getNodeLinks(node).flags;
         }
@@ -5725,7 +5741,8 @@ module ts {
                 getNodeCheckFlags: getNodeCheckFlags,
                 getEnumMemberValue: getEnumMemberValue,
                 isTopLevelValueImportedViaEntityName: isTopLevelValueImportedViaEntityName,
-                shouldEmitDeclarations: shouldEmitDeclarations
+                shouldEmitDeclarations: shouldEmitDeclarations,
+                isReferencedInExportAssignment: isReferencedInExportAssignment
             };
             checkProgram();
             return emitFiles(resolver);

src/compiler/emitter.ts

@@ -1922,16 +1922,13 @@ module ts {
                 return true;
             }
 
-            if (node.parent.kind === SyntaxKind.SourceFile) {
-                // Global context nodes - emit this declaration
-                if (!(node.parent.flags & NodeFlags.ExternalModule)) {
-                    return true;
-                }
+            // If this node is in external module, check if this is export assigned 
+            if (node.parent.flags & NodeFlags.ExternalModule) {
+                return resolver.isReferencedInExportAssignment(node);
             }
 
-            // TODO(shkamat): check if this node is part of export assignment in the external module
-
-            return false;
+            // emit the declaration if this is global source file
+            return node.parent.kind === SyntaxKind.SourceFile;
         }
 
         function emitDeclarationFlags(node: Declaration) {

src/compiler/types.ts

@@ -601,6 +601,7 @@ module ts {
         getNodeCheckFlags(node: Node): NodeCheckFlags;
         getEnumMemberValue(node: EnumMember): number;
         shouldEmitDeclarations(): boolean;
+        isReferencedInExportAssignment(node: Declaration): boolean;
     }
 
     export enum SymbolFlags {