[ClangImporter] Support loading clang modules that are aliased

Author: xymus

lib/ClangImporter/ClangImporter.cpp

@@ -1926,20 +1926,26 @@ bool ClangImporter::canImportModule(ImportPath::Module modulePath,
 ModuleDecl *ClangImporter::Implementation::loadModuleClang(
     SourceLoc importLoc, ImportPath::Module path) {
   auto &clangHeaderSearch = getClangPreprocessor().getHeaderSearchInfo();
+  auto realModuleName = SwiftContext.getRealModuleName(path.front().Item).str();
 
   // Look up the top-level module first, to see if it exists at all.
   clang::Module *clangModule = clangHeaderSearch.lookupModule(
-      path.front().Item.str(), /*ImportLoc=*/clang::SourceLocation(),
+      realModuleName, /*ImportLoc=*/clang::SourceLocation(),
       /*AllowSearch=*/true, /*AllowExtraModuleMapSearch=*/true);
   if (!clangModule)
     return nullptr;
 
   // Convert the Swift import path over to a Clang import path.
   SmallVector<std::pair<clang::IdentifierInfo *, clang::SourceLocation>, 4>
       clangPath;
+  bool isTopModuleComponent = true;
   for (auto component : path) {
+    StringRef item = isTopModuleComponent? realModuleName:
+                                           component.Item.str();
+    isTopModuleComponent = false;
+
     clangPath.emplace_back(
-        getClangPreprocessor().getIdentifierInfo(component.Item.str()),
+        getClangPreprocessor().getIdentifierInfo(item),
         exportSourceLoc(component.Loc));
   }