When loading a Swift framework module, see if it's also a Clang module.

In a framework containing both Clang headers and a Swift module, the Swift
module gets picked up first, but then automatically imports (and re-exports)
the Clang module as well.

One interesting case here is that it's possible for the Clang side to add
categories to a class declared in Swift. In order to support this, the
Clang importer can now find extensions for Swift classes marked @objc.
(I couldn't think of a way to test this separately; the previous commit
was supposed to do that, but worked without this change.)

<rdar://problem/16295937>

Swift SVN r15084

lib/Serialization/ModuleFile.cpp

@@ -803,6 +803,9 @@ bool ModuleFile::associateWithFileContext(FileUnit *file) {
     return false;
   }
 
+  if (Bits.IsFramework)
+    (void)getModule(FileContext->getParentModule()->Name);
+
   return getStatus() == ModuleStatus::Valid;
 }
 
@@ -870,6 +873,8 @@ void ModuleFile::getImportedModules(
     SmallVectorImpl<Module::ImportedModule> &results,
     Module::ImportFilter filter) {
   PrettyModuleFileDeserialization stackEntry(*this);
+  bool includeShadowedModule =
+    (filter != Module::ImportFilter::Private && Bits.IsFramework);
 
   for (auto &dep : Dependencies) {
     if (filter != Module::ImportFilter::All &&
@@ -877,7 +882,18 @@ void ModuleFile::getImportedModules(
       continue;
     assert(dep.isLoaded());
     results.push_back(dep.Import);
+
+    // FIXME: Do we want a way to limit re-exports?
+    if (includeShadowedModule && dep.Import.first.empty() &&
+        dep.Import.second == ShadowedModule)
+      includeShadowedModule = false;
   }
+
+  // Make sure to go through getModule() instead of accessing ShadowedModule
+  // directly, to force loading it.
+  if (includeShadowedModule)
+    if (ShadowedModule)
+      results.push_back({ {}, ShadowedModule });
 }
 
 void ModuleFile::getImportDecls(SmallVectorImpl<Decl *> &Results) {