Merge pull request #9897 from Microsoft/umd_export

Clarify code checking for UMD exports...

Author: Andy

src/compiler/checker.ts

@@ -18449,7 +18449,7 @@ namespace ts {
 
         // When resolved as an expression identifier, if the given node references an exported entity, return the declaration
         // node of the exported entity's container. Otherwise, return undefined.
-        function getReferencedExportContainer(node: Identifier, prefixLocals?: boolean): SourceFile | ModuleDeclaration | EnumDeclaration {
+        function getReferencedExportContainer(node: Identifier, prefixLocals?: boolean): SourceFile | ModuleDeclaration | EnumDeclaration | undefined {
             node = getParseTreeNode(node, isIdentifier);
             if (node) {
                 // When resolving the export container for the name of a module or enum
@@ -18471,10 +18471,11 @@ namespace ts {
                     const parentSymbol = getParentOfSymbol(symbol);
                     if (parentSymbol) {
                         if (parentSymbol.flags & SymbolFlags.ValueModule && parentSymbol.valueDeclaration.kind === SyntaxKind.SourceFile) {
+                            const symbolFile = <SourceFile>parentSymbol.valueDeclaration;
+                            const referenceFile = getSourceFileOfNode(node);
                             // If `node` accesses an export and that export isn't in the same file, then symbol is a namespace export, so return undefined.
-                            if (parentSymbol.valueDeclaration === getSourceFileOfNode(node)) {
-                                return <SourceFile>parentSymbol.valueDeclaration;
-                            }
+                            const symbolIsUmdExport = symbolFile !== referenceFile;
+                            return symbolIsUmdExport ? undefined : symbolFile;
                         }
                         for (let n = node.parent; n; n = n.parent) {
                             if (isModuleOrEnumDeclaration(n) && getSymbolOfNode(n) === parentSymbol) {
@@ -18484,8 +18485,6 @@ namespace ts {
                     }
                 }
             }
-
-            return undefined;
         }
 
         // When resolved as an expression identifier, if the given node references an import, return the declaration of