Index: include/clang/Basic/DiagnosticGroups.td
===================================================================
--- include/clang/Basic/DiagnosticGroups.td
+++ include/clang/Basic/DiagnosticGroups.td
@@ -213,6 +213,7 @@
 def MismatchedTags : DiagGroup<"mismatched-tags">;
 def MissingFieldInitializers : DiagGroup<"missing-field-initializers">;
 def ModuleConflict : DiagGroup<"module-conflict">;
+def NeedImport : DiagGroup<"need-import">;
 def NewlineEOF : DiagGroup<"newline-eof">;
 def NullArithmetic : DiagGroup<"null-arithmetic">;
 def NullCharacter : DiagGroup<"null-character">;
Index: include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- include/clang/Basic/DiagnosticSemaKinds.td
+++ include/clang/Basic/DiagnosticSemaKinds.td
@@ -6958,10 +6958,9 @@
 def err_module_private_local_class : Error<
   "local %select{struct|interface|union|class|enum}0 cannot be declared "
   "__module_private__">;
-def err_module_private_declaration : Error<
-  "declaration of %0 must be imported from module '%1' before it is required">;
-def err_module_private_definition : Error<
-  "definition of %0 must be imported from module '%1' before it is required">;
+def warn_need_module_import : Warning<
+  "use of identifier '%0' requires import/inclusion of the module '%1'">,
+  InGroup<NeedImport>;
 def err_module_import_in_extern_c : Error<
   "import of C++ module '%0' appears within extern \"C\" language linkage "
   "specification">;
Index: include/clang/Basic/LangOptions.def
===================================================================
--- include/clang/Basic/LangOptions.def
+++ include/clang/Basic/LangOptions.def
@@ -96,6 +96,7 @@
 BENIGN_LANGOPT(HeinousExtensions , 1, 0, "Extensions that we really don't like and may be ripped out at any time")
 LANGOPT(Modules           , 1, 0, "modules extension to C")
 LANGOPT(ModulesDeclUse    , 1, 0, "require declaration of module uses")
+LANGOPT(ModulesSearchAll  , 1, 1, "search even non-imported modules to find unresolved references")
 LANGOPT(Optimize          , 1, 0, "__OPTIMIZE__ predefined macro")
 LANGOPT(OptimizeSize      , 1, 0, "__OPTIMIZE_SIZE__ predefined macro")
 LANGOPT(Static            , 1, 0, "__STATIC__ predefined macro (as opposed to __DYNAMIC__)")
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -579,6 +579,9 @@
 def fmodules_prune_after : Joined<["-"], "fmodules-prune-after=">, Group<i_Group>,
   Flags<[CC1Option]>, MetaVarName<"<seconds>">,
   HelpText<"Specify the interval (in seconds) after which a module file will be considered unused">;
+def fmodules_search_all : Flag <["-"], "fmodules-search-all">, Group<f_Group>,
+  Flags<[DriverOption, CC1Option]>,
+  HelpText<"Search even non-imported modules to resolve references">;
 def fbuild_session_timestamp : Joined<["-"], "fbuild-session-timestamp=">,
   Group<i_Group>, Flags<[CC1Option]>, MetaVarName<"<time since Epoch in seconds>">,
   HelpText<"Time when the current build session started">;
@@ -665,6 +668,9 @@
   Flags<[DriverOption]>;
 def fno_modules_decluse : Flag <["-"], "fno-modules-decluse">, Group<f_Group>,
   Flags<[DriverOption]>;
+def fno_modules_search_all : Flag <["-"], "fno-modules-search-all">, Group<f_Group>,
+  Flags<[DriverOption, CC1Option]>,
+  HelpText<"Inhibit search of non-imported modules to resolve references">;
 def fno_ms_extensions : Flag<["-"], "fno-ms-extensions">, Group<f_Group>;
 def fno_ms_compatibility : Flag<["-"], "fno-ms-compatibility">, Group<f_Group>;
 def fno_delayed_template_parsing : Flag<["-"], "fno-delayed-template-parsing">, Group<f_Group>;
Index: include/clang/Frontend/ASTUnit.h
===================================================================
--- include/clang/Frontend/ASTUnit.h
+++ include/clang/Frontend/ASTUnit.h
@@ -869,6 +869,8 @@
   void makeModuleVisible(Module *Mod, Module::NameVisibilityKind Visibility,
                          SourceLocation ImportLoc, bool Complain) override {}
 
+
+  GlobalModuleIndex *loadGlobalModuleIndex() { return 0; }
 };
 
 } // namespace clang
Index: include/clang/Frontend/CompilerInstance.h
===================================================================
--- include/clang/Frontend/CompilerInstance.h
+++ include/clang/Frontend/CompilerInstance.h
@@ -124,6 +124,9 @@
   /// have finished with this translation unit.
   bool BuildGlobalModuleIndex;
 
+  /// \brief We have a full global module index, with all modules.
+  bool HaveFullGlobalModuleIndex;
+
   /// \brief One or more modules failed to build.
   bool ModuleBuildFailed;
 
@@ -148,7 +151,7 @@
   CompilerInstance(const CompilerInstance &) LLVM_DELETED_FUNCTION;
   void operator=(const CompilerInstance &) LLVM_DELETED_FUNCTION;
 public:
-  CompilerInstance();
+  CompilerInstance(bool BuildingModuleFlag = false);
   ~CompilerInstance();
 
   /// @name High-Level Operations
@@ -683,6 +686,9 @@
 
   /// }
 
+  // Create module manager.
+  void createModuleManager();
+
   ModuleLoadResult loadModule(SourceLocation ImportLoc, ModuleIdPath Path,
                               Module::NameVisibilityKind Visibility,
                               bool IsInclusionDirective) override;
@@ -694,6 +700,8 @@
     return ModuleLoader::HadFatalFailure;
   }
 
+  virtual GlobalModuleIndex *loadGlobalModuleIndex();
+
 };
 
 } // end namespace clang
Index: include/clang/Lex/HeaderSearch.h
===================================================================
--- include/clang/Lex/HeaderSearch.h
+++ include/clang/Lex/HeaderSearch.h
@@ -508,7 +508,14 @@
   /// \returns The module with the given name.
   Module *lookupModule(StringRef ModuleName, bool AllowSearch = true);
 
+  /// \brief Lookup a top level module given its file name.
+  ///
+  /// \param ModuleFileName The name of the module file.
+  ///
+  /// \returns The module with the given name.
+  Module *lookupModuleFromFile(StringRef ModuleFileName);
 
+
   /// \brief Try to find a module map file in the given directory, returning
   /// \c nullptr if none is found.
   const FileEntry *lookupModuleMapFile(const DirectoryEntry *Dir,
Index: include/clang/Lex/ModuleLoader.h
===================================================================
--- include/clang/Lex/ModuleLoader.h
+++ include/clang/Lex/ModuleLoader.h
@@ -21,6 +21,7 @@
 
 namespace clang {
 
+class GlobalModuleIndex;
 class IdentifierInfo;
 class Module;
 
@@ -53,11 +54,24 @@
 /// for resolving a module name (e.g., "std") to an actual module file, and
 /// then loading that module.
 class ModuleLoader {
+  // Building a module if true.
+  bool BuildingModule;
 public:
-  ModuleLoader() : HadFatalFailure(false) {}
+  ModuleLoader(bool BuildingModuleFlag = false) :
+    BuildingModule(BuildingModuleFlag),
+    HadFatalFailure(false) {}
 
   virtual ~ModuleLoader();
-  
+ 
+  /// \brief Returns true if this instance is building a module.
+  bool buildingModule() const {
+    return BuildingModule;
+  }
+  /// \brief Flag indicating whether this instance is building a module.
+  void setBuildingModule(bool BuildingModuleFlag) {
+    BuildingModule = BuildingModuleFlag;
+  }
+ 
   /// \brief Attempt to load the given module.
   ///
   /// This routine attempts to load the module described by the given 
@@ -88,6 +102,17 @@
                                  SourceLocation ImportLoc,
                                  bool Complain) = 0;
 
+  /// \brief Load, create, or return global module.
+  /// This function returns an existing global module index, if one
+  /// had already been loaded or created, or loads one if it
+  /// exists, or creates one if it doesn't exist.
+  /// Also, importantly, if the index doesn't cover all the modules
+  /// in the module map, it will be update to do so here, because
+  /// of its use in searching for needed module imports and
+  /// associated fixit messages.
+  /// \returns Returns null if load failed.
+  virtual GlobalModuleIndex *loadGlobalModuleIndex() = 0;
+
   bool HadFatalFailure;
 };
   
Index: include/clang/Sema/Sema.h
===================================================================
--- include/clang/Sema/Sema.h
+++ include/clang/Sema/Sema.h
@@ -2569,7 +2569,8 @@
                              DeclContext *MemberContext = 0,
                              bool EnteringContext = false,
                              const ObjCObjectPointerType *OPT = 0,
-                             bool RecordFailure = true);
+                             bool RecordFailure = true,
+                             bool ErrorRecovery = true);
 
   void diagnoseTypo(const TypoCorrection &Correction,
                     const PartialDiagnostic &TypoDiag,
Index: include/clang/Serialization/ASTReader.h
===================================================================
--- include/clang/Serialization/ASTReader.h
+++ include/clang/Serialization/ASTReader.h
@@ -1358,6 +1358,12 @@
   /// \brief Determine whether this AST reader has a global index.
   bool hasGlobalIndex() const { return (bool)GlobalIndex; }
 
+  /// \brief Return global module index.
+  GlobalModuleIndex *getGlobalIndex() { return GlobalIndex.get(); }
+
+  /// \brief Reset reader for a reload try.
+  void resetForReload() { TriedLoadingGlobalIndex = false; }
+
   /// \brief Attempts to load the global index.
   ///
   /// \returns true if loading the global index has failed for any reason.
Index: include/clang/Serialization/GlobalModuleIndex.h
===================================================================
--- include/clang/Serialization/GlobalModuleIndex.h
+++ include/clang/Serialization/GlobalModuleIndex.h
@@ -186,6 +186,9 @@
   /// \brief Print statistics to standard error.
   void printStats();
 
+  /// \brief Print debugging view to standard error.
+  void dump();
+
   /// \brief Write a global index into the given
   ///
   /// \param FileMgr The file manager to use to load module files.
Index: lib/Frontend/CompilerInstance.cpp
===================================================================
--- lib/Frontend/CompilerInstance.cpp
+++ lib/Frontend/CompilerInstance.cpp
@@ -31,6 +31,7 @@
 #include "clang/Sema/CodeCompleteConsumer.h"
 #include "clang/Sema/Sema.h"
 #include "clang/Serialization/ASTReader.h"
+#include "clang/Serialization/GlobalModuleIndex.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/Config/config.h"
 #include "llvm/Support/CrashRecoveryContext.h"
@@ -49,9 +50,11 @@
 
 using namespace clang;
 
-CompilerInstance::CompilerInstance()
-  : Invocation(new CompilerInvocation()), ModuleManager(0),
-    BuildGlobalModuleIndex(false), ModuleBuildFailed(false) {
+CompilerInstance::CompilerInstance(bool BuildingModuleFlag)
+  : ModuleLoader(BuildingModuleFlag),
+    Invocation(new CompilerInvocation()), ModuleManager(0),
+    BuildGlobalModuleIndex(false), HaveFullGlobalModuleIndex(false),
+    ModuleBuildFailed(false) {
 }
 
 CompilerInstance::~CompilerInstance() {
@@ -851,7 +854,7 @@
   
   // Construct a compiler instance that will be used to actually create the
   // module.
-  CompilerInstance Instance;
+  CompilerInstance Instance(true);
   Instance.setInvocation(&*Invocation);
 
   Instance.createDiagnostics(new ForwardingDiagnosticConsumer(
@@ -1085,6 +1088,43 @@
   }
 }
 
+void CompilerInstance::createModuleManager() {
+  if (!ModuleManager) {
+    if (!hasASTContext())
+      createASTContext();
+
+    // If we're not recursively building a module, check whether we
+    // need to prune the module cache.
+    if (getSourceManager().getModuleBuildStack().empty() &&
+        getHeaderSearchOpts().ModuleCachePruneInterval > 0 &&
+        getHeaderSearchOpts().ModuleCachePruneAfter > 0) {
+      pruneModuleCache(getHeaderSearchOpts());
+    }
+
+    HeaderSearchOptions &HSOpts = getHeaderSearchOpts();
+    std::string Sysroot = HSOpts.Sysroot;
+    const PreprocessorOptions &PPOpts = getPreprocessorOpts();
+    ModuleManager = new ASTReader(getPreprocessor(), *Context,
+                                  Sysroot.empty() ? "" : Sysroot.c_str(),
+                                  PPOpts.DisablePCHValidation,
+                                  /*AllowASTWithCompilerErrors=*/false,
+                                  /*AllowConfigurationMismatch=*/false,
+                                  HSOpts.ModulesValidateSystemHeaders,
+                                  getFrontendOpts().UseGlobalModuleIndex);
+    if (hasASTConsumer()) {
+      ModuleManager->setDeserializationListener(
+        getASTConsumer().GetASTDeserializationListener());
+      getASTContext().setASTMutationListener(
+        getASTConsumer().GetASTMutationListener());
+    }
+    getASTContext().setExternalSource(ModuleManager);
+    if (hasSema())
+      ModuleManager->InitializeSema(getSema());
+    if (hasASTConsumer())
+      ModuleManager->StartTranslationUnit(&getASTConsumer());
+  }
+}
+
 ModuleLoadResult
 CompilerInstance::loadModule(SourceLocation ImportLoc,
                              ModuleIdPath Path,
@@ -1131,41 +1171,9 @@
     std::string ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(Module);
 
     // If we don't already have an ASTReader, create one now.
-    if (!ModuleManager) {
-      if (!hasASTContext())
-        createASTContext();
+    if (!ModuleManager)
+      createModuleManager();
 
-      // If we're not recursively building a module, check whether we
-      // need to prune the module cache.
-      if (getSourceManager().getModuleBuildStack().empty() &&
-          getHeaderSearchOpts().ModuleCachePruneInterval > 0 &&
-          getHeaderSearchOpts().ModuleCachePruneAfter > 0) {
-        pruneModuleCache(getHeaderSearchOpts());
-      }
-
-      HeaderSearchOptions &HSOpts = getHeaderSearchOpts();
-      std::string Sysroot = HSOpts.Sysroot;
-      const PreprocessorOptions &PPOpts = getPreprocessorOpts();
-      ModuleManager = new ASTReader(getPreprocessor(), *Context,
-                                    Sysroot.empty() ? "" : Sysroot.c_str(),
-                                    PPOpts.DisablePCHValidation,
-                                    /*AllowASTWithCompilerErrors=*/false,
-                                    /*AllowConfigurationMismatch=*/false,
-                                    HSOpts.ModulesValidateSystemHeaders,
-                                    getFrontendOpts().UseGlobalModuleIndex);
-      if (hasASTConsumer()) {
-        ModuleManager->setDeserializationListener(
-          getASTConsumer().GetASTDeserializationListener());
-        getASTContext().setASTMutationListener(
-          getASTConsumer().GetASTMutationListener());
-      }
-      getASTContext().setExternalSource(ModuleManager);
-      if (hasSema())
-        ModuleManager->InitializeSema(getSema());
-      if (hasASTConsumer())
-        ModuleManager->StartTranslationUnit(&getASTConsumer());
-    }
-
     if (TheDependencyFileGenerator)
       TheDependencyFileGenerator->AttachToASTReader(*ModuleManager);
 
@@ -1391,3 +1399,59 @@
   ModuleManager->makeModuleVisible(Mod, Visibility, ImportLoc, Complain);
 }
 
+GlobalModuleIndex *CompilerInstance::loadGlobalModuleIndex() {
+  if (!ModuleManager)
+    createModuleManager();
+  // Can't do anything if we don't have the module manager.
+  if (!ModuleManager)
+    return 0;
+  // Get an existing global index.  This loads it if not already
+  // loaded.
+  ModuleManager->loadGlobalIndex();
+  GlobalModuleIndex *GlobalIndex = ModuleManager->getGlobalIndex();
+  // If the global index doesn't exist, create it.
+  if (!GlobalIndex && shouldBuildGlobalModuleIndex() && hasFileManager() &&
+      hasPreprocessor()) {
+    llvm::sys::fs::create_directories(
+      getPreprocessor().getHeaderSearchInfo().getModuleCachePath());
+    GlobalModuleIndex::writeIndex(
+      getFileManager(),
+      getPreprocessor().getHeaderSearchInfo().getModuleCachePath());
+    ModuleManager->resetForReload();
+    ModuleManager->loadGlobalIndex();
+    GlobalIndex = ModuleManager->getGlobalIndex();
+  }
+  // For finding modules needing to be imported for fixit messages,
+  // we need to make the global index cover all modules, so we do that here.
+  if (!HaveFullGlobalModuleIndex && GlobalIndex && !buildingModule()) {
+    ModuleMap &MMap = getPreprocessor().getHeaderSearchInfo().getModuleMap();
+    bool recreateIndex = false;
+    for (ModuleMap::module_iterator I = MMap.module_begin(),
+        E = MMap.module_end(); I != E; ++I) {
+      Module *TheModule = I->second;
+      const FileEntry *Entry = TheModule->getASTFile();
+      if (!Entry) {
+        SourceLocation dummyLoc;
+        SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Path;
+        for (Module *Mod = TheModule; Mod; Mod = Mod->Parent)
+          Path.push_back(std::make_pair(
+				    getPreprocessor().getIdentifierInfo(Mod->Name), Mod->DefinitionLoc));
+          std::reverse(Path.begin(), Path.end());
+		    // Load a module as hidden.  This also adds it to the global index.
+        ModuleLoadResult Result = loadModule(TheModule->DefinitionLoc, Path,
+          Module::Hidden, false);
+        recreateIndex = true;
+      }
+    }
+    if (recreateIndex) {
+      GlobalModuleIndex::writeIndex(
+        getFileManager(),
+        getPreprocessor().getHeaderSearchInfo().getModuleCachePath());
+      ModuleManager->resetForReload();
+      ModuleManager->loadGlobalIndex();
+      GlobalIndex = ModuleManager->getGlobalIndex();
+    }
+    HaveFullGlobalModuleIndex = true;
+  }
+  return GlobalIndex;
+}
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -1344,6 +1344,9 @@
   Opts.BlocksRuntimeOptional = Args.hasArg(OPT_fblocks_runtime_optional);
   Opts.Modules = Args.hasArg(OPT_fmodules);
   Opts.ModulesDeclUse = Args.hasArg(OPT_fmodules_decluse);
+  Opts.ModulesSearchAll = Opts.Modules &&
+   (!Args.hasArg(OPT_fno_modules_search_all) ||
+     Args.hasArg(OPT_fmodules_search_all));
   Opts.CharIsSigned = Opts.OpenCL || !Args.hasArg(OPT_fno_signed_char);
   Opts.WChar = Opts.CPlusPlus && !Args.hasArg(OPT_fno_wchar);
   Opts.ShortWChar = Args.hasFlag(OPT_fshort_wchar, OPT_fno_short_wchar, false);
Index: lib/Lex/HeaderSearch.cpp
===================================================================
--- lib/Lex/HeaderSearch.cpp
+++ lib/Lex/HeaderSearch.cpp
@@ -205,6 +205,10 @@
   return Module;
 }
 
+Module *HeaderSearch::lookupModuleFromFile(StringRef ModuleFileName) {
+  return lookupModule(llvm::sys::path::stem(ModuleFileName), false);
+}
+
 //===----------------------------------------------------------------------===//
 // File lookup within a DirectoryLookup scope
 //===----------------------------------------------------------------------===//
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -10068,7 +10068,8 @@
     TypoCorrection Corrected;
     DeclFilterCCC<FunctionDecl> Validator;
     if (S && (Corrected = CorrectTypo(DeclarationNameInfo(&II, Loc),
-                                      LookupOrdinaryName, S, 0, Validator)))
+                                      LookupOrdinaryName, S, 0, Validator,
+                                      0, false, 0, true, false)))
       diagnoseTypo(Corrected, PDiag(diag::note_function_suggestion),
                    /*ErrorRecovery*/false);
   }
Index: lib/Sema/SemaDeclObjC.cpp
===================================================================
--- lib/Sema/SemaDeclObjC.cpp
+++ lib/Sema/SemaDeclObjC.cpp
@@ -1034,7 +1034,8 @@
     ObjCInterfaceValidatorCCC Validator;
     TypoCorrection Corrected =
             CorrectTypo(DeclarationNameInfo(ClassName, ClassLoc),
-                        LookupOrdinaryName, TUScope, NULL, Validator);
+                        LookupOrdinaryName, TUScope, NULL, Validator,
+                        0, false, 0, true, false);
     if (Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>()) {
       // Suggest the (potentially) correct interface name. Don't provide a
       // code-modification hint or use the typo name for recovery, because
Index: lib/Sema/SemaLookup.cpp
===================================================================
--- lib/Sema/SemaLookup.cpp
+++ lib/Sema/SemaLookup.cpp
@@ -23,6 +23,9 @@
 #include "clang/AST/ExprCXX.h"
 #include "clang/Basic/Builtins.h"
 #include "clang/Basic/LangOptions.h"
+#include "clang/Lex/HeaderSearch.h"
+#include "clang/Lex/ModuleLoader.h"
+#include "clang/Lex/Preprocessor.h"
 #include "clang/Sema/DeclSpec.h"
 #include "clang/Sema/ExternalSemaSource.h"
 #include "clang/Sema/Overload.h"
@@ -32,6 +35,8 @@
 #include "clang/Sema/SemaInternal.h"
 #include "clang/Sema/TemplateDeduction.h"
 #include "clang/Sema/TypoCorrection.h"
+#include "clang/Serialization/GlobalModuleIndex.h"
+#include "clang/Serialization/Module.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallPtrSet.h"
@@ -3999,7 +4004,8 @@
                                  DeclContext *MemberContext,
                                  bool EnteringContext,
                                  const ObjCObjectPointerType *OPT,
-                                 bool RecordFailure) {
+                                 bool RecordFailure,
+                                 bool ErrorRecovery) {
   // Always let the ExternalSource have the first chance at correction, even
   // if we would otherwise have given up.
   if (ExternalSource) {
@@ -4050,10 +4056,63 @@
   if (getLangOpts().AltiVec && Typo->isStr("vector"))
     return TypoCorrection();
 
+  TypoCorrectionConsumer Consumer(*this, Typo);
+
+  // Get the module loader (usually compiler instance).
+  ModuleLoader &Loader = PP.getModuleLoader();
+
+  // Look for the symbol in non-imported modules, but only if an error
+  // actually occurred.
+  if (ErrorRecovery && !Loader.buildingModule()
+      && getLangOpts().Modules && getLangOpts().ModulesSearchAll) {
+    // Load global module index, or retrieve a previously loaded one.
+    GlobalModuleIndex *GlobalIndex = Loader.loadGlobalModuleIndex();
+
+    // Only if we have a global index.
+    if (GlobalIndex) {
+      GlobalModuleIndex::HitSet FoundModules;
+
+      // Find the modules that reference the identifier.
+      // Note that this only finds top-level modules.
+      // We'll let diagnoseTypo find the actual declaration module.
+      if (GlobalIndex->lookupIdentifier(Typo->getName(), FoundModules)) {
+        TypoCorrection TC(TypoName.getName(), (NestedNameSpecifier *)0, 0);
+        TC.setCorrectionRange(SS, TypoName);
+        // Walk the found modules that reference the identifier.
+        for (GlobalModuleIndex::HitSet::iterator I = FoundModules.begin(),
+            E = FoundModules.end(); I != E; ++I) {
+          ModuleFile *TheModuleFile = *I;
+          // Find the module from the file name.
+          Module *TheModule = PP.getHeaderSearchInfo().lookupModuleFromFile(
+            TheModuleFile->FileName);
+          assert(TheModule && "Should be able to find the module.");
+          // Make the module visible so we can do a name lookup.
+          Loader.makeModuleVisible(TheModule, Module::AllVisible,
+            TypoName.getLoc(), false);
+          // Do a name lookup.
+          LookupResult ModRes(*this, TypoName, LookupKind);
+          LookupPotentialTypoResult(*this, ModRes, Typo, S, SS, MemberContext,
+            EnteringContext, OPT, false);
+          // If we have an exact match, save the decl in the coorection
+          // to let diagnoseTypo do a fixit message.
+          if (ModRes.getResultKind() == LookupResult::Found)
+            TC.setCorrectionDecl(ModRes.getAsSingle<NamedDecl>());
+          // Hide the module again. diagnoseTypo will unhide the decl module.
+          Loader.makeModuleVisible(TheModule, Module::Hidden,
+            TypoName.getLoc(), false);
+        }
+        // If the name lookup found something, we set a flag to tell
+        // diagnoseTypo we have a case of possibly missing module import.
+        if (TC.isResolved()) {
+          TC.setRequiresImport(true);
+          return TC;
+        }
+      }
+    }
+  }
+
   NamespaceSpecifierSet Namespaces(Context, CurContext, SS);
 
-  TypoCorrectionConsumer Consumer(*this, Typo);
-
   // If a callback object considers an empty typo correction candidate to be
   // viable, assume it does not do any actual validation of the candidates.
   TypoCorrection EmptyCorrection;
@@ -4127,6 +4186,8 @@
   unsigned TypoLen = Typo->getName().size();
   bool AllowOnlyNNSChanges = TypoLen < 3;
 
+  // FIXME: Can we do this partial match check on modules known but not
+  // imported via the global module index?
   if (IsUnqualifiedLookup || SearchNamespaces) {
     // For unqualified lookup, look through all of the names that we have
     // seen in this translation unit.
@@ -4629,9 +4690,14 @@
     Module *Owner = Def->getOwningModule();
     assert(Owner && "definition of hidden declaration is not in a module");
 
-    Diag(Correction.getCorrectionRange().getBegin(),
-         diag::err_module_private_declaration)
-      << Def << Owner->getFullModuleName();
+    std::string fixit = "#import ";
+    fixit += Owner->Name;
+    SourceLocation TypoLoc = Correction.getCorrectionRange().getBegin();
+    // FIXME: Figure out how to find the right insertion point,
+    // For now we just use the type location.
+    Diag(TypoLoc, diag::warn_need_module_import)
+      << CorrectedStr << Owner->getFullModuleName() <<
+      FixItHint::CreateInsertion(TypoLoc, fixit);
     Diag(Def->getLocation(), diag::note_previous_declaration);
 
     // Recover by implicitly importing this module.
Index: lib/Sema/SemaType.cpp
===================================================================
--- lib/Sema/SemaType.cpp
+++ lib/Sema/SemaType.cpp
@@ -5097,7 +5097,7 @@
       // FIXME: Add a Fix-It that imports the corresponding module or includes
       // the header.
       Module *Owner = Def->getOwningModule();
-      Diag(Loc, diag::err_module_private_definition)
+      Diag(Loc, diag::warn_need_module_import)
         << T << Owner->getFullModuleName();
       Diag(Def->getLocation(), diag::note_previous_definition);
 
Index: lib/Serialization/GlobalModuleIndex.cpp
===================================================================
--- lib/Serialization/GlobalModuleIndex.cpp
+++ lib/Serialization/GlobalModuleIndex.cpp
@@ -342,6 +342,21 @@
   std::fprintf(stderr, "\n");
 }
 
+void GlobalModuleIndex::dump() {
+  std::fprintf(stderr, "*** Global Module Index Dump:\n");
+  std::fprintf(stderr, "Module files:\n");
+  for (llvm::SmallVector<ModuleInfo, 16>::iterator I = Modules.begin(),
+      E = Modules.end(); I != E; ++I) {
+    ModuleInfo *MI = (ModuleInfo*)I;
+    std::fprintf(stderr, "** %s\n", MI->FileName.c_str());
+    if (MI->File)
+      MI->File->dump();
+    else
+      std::fprintf(stderr, "\n");
+  }
+  std::fprintf(stderr, "\n");
+}
+
 //----------------------------------------------------------------------------//
 // Global module index writer.
 //----------------------------------------------------------------------------//
Index: test/Modules/Inputs/undefined-type-fixit/module.map
===================================================================
--- test/Modules/Inputs/undefined-type-fixit/module.map
+++ test/Modules/Inputs/undefined-type-fixit/module.map
@@ -0,0 +1,9 @@
+module public1 {
+  header "public1.h"
+}
+module public2 {
+  header "public2.h"
+  module public2sub {
+    header "public2sub.h"
+  }
+}
Index: test/Modules/Inputs/undefined-type-fixit/public1.h
===================================================================
--- test/Modules/Inputs/undefined-type-fixit/public1.h
+++ test/Modules/Inputs/undefined-type-fixit/public1.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC1_H
+#define PUBLIC1_H
+
+struct use_this1 { int field; };
+
+#endif
Index: test/Modules/Inputs/undefined-type-fixit/public2.h
===================================================================
--- test/Modules/Inputs/undefined-type-fixit/public2.h
+++ test/Modules/Inputs/undefined-type-fixit/public2.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC2_H
+#define PUBLIC2_H
+
+struct use_this2 { int field; };
+
+#endif
Index: test/Modules/Inputs/undefined-type-fixit/public2sub.h
===================================================================
--- test/Modules/Inputs/undefined-type-fixit/public2sub.h
+++ test/Modules/Inputs/undefined-type-fixit/public2sub.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC2SUB_H
+#define PUBLIC2SUB_H
+
+struct use_this2sub { int field; };
+
+#endif
Index: test/Modules/auto-module-import.m
===================================================================
--- test/Modules/auto-module-import.m
+++ test/Modules/auto-module-import.m
@@ -1,6 +1,6 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -Wauto-import -fmodules-cache-path=%t -fmodules -F %S/Inputs %s -verify -DERRORS
-// RUN: %clang_cc1 -Wauto-import -fmodules-cache-path=%t -fmodules -F %S/Inputs %s -verify
+// RUN: %clang_cc1 -Wauto-import -fmodules-cache-path=%t -fmodules -fno-modules-search-all -F %S/Inputs %s -verify -DERRORS
+// RUN: %clang_cc1 -Wauto-import -fmodules-cache-path=%t -fmodules -fno-modules-search-all -F %S/Inputs %s -verify
 // 
 // Test both with and without the declarations that refer to unimported
 // entities. For error recovery, those cases implicitly trigger an import.
@@ -16,7 +16,7 @@
 #endif
 
 #ifdef ERRORS
-Module *mod; // expected-error{{declaration of 'Module' must be imported from module 'Module' before it is required}}
+Module *mod; // expected-warning{{use of identifier 'Module' requires import/inclusion of the module 'Module'}}
 // expected-note@Inputs/Module.framework/Headers/Module.h:15 {{previous}}
 #else
 #import <AlsoDependsOnModule/AlsoDependsOnModule.h> // expected-warning{{treating #import as an import of module 'AlsoDependsOnModule'}}
@@ -27,7 +27,7 @@
 
 void testSubframeworkOther() {
 #ifdef ERRORS
-  double *sfo1 = sub_framework_other; // expected-error{{declaration of 'sub_framework_other' must be imported from module 'DependsOnModule.SubFramework.Other'}}
+  double *sfo1 = sub_framework_other; // expected-warning{{use of identifier 'sub_framework_other' requires import/inclusion of the module 'DependsOnModule.SubFramework.Other'}}
   // expected-note@Inputs/DependsOnModule.framework/Frameworks/SubFramework.framework/Headers/Other.h:15 {{previous}}
 #endif
 }
@@ -71,7 +71,7 @@
 #include <NoUmbrella/A_Private.h> // expected-warning{{treating #include as an import of module 'NoUmbrella.Private.A_Private'}}
 int getNoUmbrellaAPrivate() { return no_umbrella_A_private; }
 
-int getNoUmbrellaBPrivateFail() { return no_umbrella_B_private; } // expected-error{{declaration of 'no_umbrella_B_private' must be imported from module 'NoUmbrella.Private.B_Private'}}
+int getNoUmbrellaBPrivateFail() { return no_umbrella_B_private; } // expected-warning{{use of identifier 'no_umbrella_B_private' requires import/inclusion of the module 'NoUmbrella.Private.B_Private'}}
 // expected-note@Inputs/NoUmbrella.framework/PrivateHeaders/B_Private.h:1 {{previous}}
 
 // Test inclusion of headers that are under an umbrella directory but
Index: test/Modules/cxx-inline-namespace.cpp
===================================================================
--- test/Modules/cxx-inline-namespace.cpp
+++ test/Modules/cxx-inline-namespace.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodules-cache-path=%t -I %S/Inputs %s -verify -std=c++11
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fno-modules-search-all -fmodules-cache-path=%t -I %S/Inputs %s -verify -std=c++11
 
 @import cxx_inline_namespace;
 @import cxx_inline_namespace_b;
Index: test/Modules/cxx-linkage-cache.cpp
===================================================================
--- test/Modules/cxx-linkage-cache.cpp
+++ test/Modules/cxx-linkage-cache.cpp
@@ -1,5 +1,5 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -x objective-c++ -fmodules -fmodules-cache-path=%t -I %S/Inputs %s -verify -std=c++11
+// RUN: %clang_cc1 -x objective-c++ -fmodules -fno-modules-search-all -fmodules-cache-path=%t -I %S/Inputs %s -verify -std=c++11
 
 @import cxx_linkage_cache;
 
Index: test/Modules/cxx-templates.cpp
===================================================================
--- test/Modules/cxx-templates.cpp
+++ test/Modules/cxx-templates.cpp
@@ -71,7 +71,7 @@
   // Trigger the instantiation of a template in 'a' that uses a type defined in
   // 'b_impl'. That type is not visible here, nor in 'a'. This fails; there is
   // no reason why DefinedInBImpl should be visible here.
-  // expected-error@Inputs/cxx-templates-a.h:19 {{definition of 'DefinedInBImpl' must be imported}}
+  // expected-warning@Inputs/cxx-templates-a.h:19 {{use of identifier ''DefinedInBImpl'' requires import/inclusion of the module}}
   // expected-note@Inputs/cxx-templates-b-impl.h:1 {{definition is here}}
   PerformDelayedLookup(defined_in_b_impl); // expected-note {{in instantiation of}}
 
Index: test/Modules/decldef.m
===================================================================
--- test/Modules/decldef.m
+++ test/Modules/decldef.m
@@ -1,6 +1,6 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify -DUSE_EARLY
-// RUN: %clang_cc1 -fmodules -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify -DUSE_EARLY
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify
 
 // expected-note@Inputs/def.h:5 {{previous}}
 
@@ -9,7 +9,7 @@
 
 @import decldef;
 #ifdef USE_EARLY
-A *a1; // expected-error{{declaration of 'A' must be imported from module 'decldef.Def' before it is required}}
+A *a1; // expected-warning{{use of identifier 'A' requires import/inclusion of the module 'decldef.Def'}}
 #endif
 B *b1; // expected-error{{must use 'struct' tag to refer to type 'B'}}
 @import decldef.Decl;
@@ -20,7 +20,7 @@
 void testA(A *a) {
   a->ivar = 17;
 #ifndef USE_EARLY
-  // expected-error@-2{{definition of 'A' must be imported from module 'decldef.Def' before it is required}}
+  // expected-warning@-2{{use of identifier ''A'' requires import/inclusion of the module 'decldef.Def'}}
 #endif
 }
 
Index: test/Modules/decldef.mm
===================================================================
--- test/Modules/decldef.mm
+++ test/Modules/decldef.mm
@@ -1,6 +1,6 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify -DUSE_EARLY
-// RUN: %clang_cc1 -fmodules -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify -DUSE_EARLY
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -fobjc-arc -I %S/Inputs -fmodules-cache-path=%t %s -verify
 
 // expected-note@Inputs/def.h:5 {{previous}}
 
@@ -17,7 +17,7 @@
 
 @import decldef;
 #ifdef USE_EARLY
-A *a1; // expected-error{{declaration of 'A' must be imported from module 'decldef.Def'}}
+A *a1; // expected-warning{{use of identifier 'A' requires import/inclusion of the module 'decldef.Def'}}
 B *b1;
 #endif
 @import decldef.Decl;
@@ -28,7 +28,7 @@
 void testA(A *a) {
   a->ivar = 17;
 #ifndef USE_EARLY
-  // expected-error@-2{{definition of 'A' must be imported from module 'decldef.Def' before it is required}}
+  // expected-warning@-2{{use of identifier ''A'' requires import/inclusion of the module 'decldef.Def'}}
 #endif
 }
 
Index: test/Modules/extern_c.cpp
===================================================================
--- test/Modules/extern_c.cpp
+++ test/Modules/extern_c.cpp
@@ -1,16 +1,16 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DEXTERN_C
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DEXTERN_CXX
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DEXTERN_C -DEXTERN_CXX
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DEXTERN_C -DNAMESPACE
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DCXX_HEADER
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DCXX_HEADER -DEXTERN_CXX
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C -DEXTERN_CXX
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C -DNAMESPACE
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs -x c %s
-// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -I %S/Inputs/elsewhere -I %S/Inputs %s -DEXTERN_C -DINDIRECT
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DEXTERN_C
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DEXTERN_CXX
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DEXTERN_C -DEXTERN_CXX
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DEXTERN_C -DNAMESPACE
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DCXX_HEADER
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DCXX_HEADER -DEXTERN_CXX
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C -DEXTERN_CXX
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -DCXX_HEADER -DEXTERN_C -DNAMESPACE
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs -x c %s
+// RUN: %clang_cc1 -fmodules -verify -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs/elsewhere -I %S/Inputs %s -DEXTERN_C -DINDIRECT
 
 #ifdef INDIRECT
 #include "c-header-indirect.h"
Index: test/Modules/lookup.cpp
===================================================================
--- test/Modules/lookup.cpp
+++ test/Modules/lookup.cpp
@@ -26,7 +26,7 @@
 // RUN: rm -rf %t
 // RUN: %clang_cc1 -fmodules -x objective-c++ -emit-module -fmodules-cache-path=%t -fmodule-name=lookup_left_cxx %S/Inputs/module.map -verify
 // RUN: %clang_cc1 -fmodules -x objective-c++ -emit-module -fmodules-cache-path=%t -fmodule-name=lookup_right_cxx %S/Inputs/module.map -verify
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -I %S/Inputs %s -verify
+// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -verify
 // RUN: %clang_cc1 -fmodules -ast-print -x objective-c++ -fmodules-cache-path=%t -I %S/Inputs %s | FileCheck -check-prefix=CHECK-PRINT %s
 // FIXME: When we have a syntax for modules in C++, use that.
 
Index: test/Modules/module-private.cpp
===================================================================
--- test/Modules/module-private.cpp
+++ test/Modules/module-private.cpp
@@ -1,7 +1,7 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -fmodule-name=module_private_left -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -fmodule-name=module_private_right -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -I %S/Inputs %s -verify
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -x objective-c++ -fmodules-cache-path=%t -fmodule-name=module_private_left -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -x objective-c++ -fmodules-cache-path=%t -fmodule-name=module_private_right -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -x objective-c++ -fmodules-cache-path=%t -I %S/Inputs %s -verify
 // FIXME: When we have a syntax for modules in C++, use that.
 
 @import module_private_left;
@@ -14,7 +14,7 @@
 int test_broken() {
   HiddenStruct hidden; // \
   // expected-error{{must use 'struct' tag to refer to type 'HiddenStruct' in this scope}} \
-  // expected-error{{definition of 'struct HiddenStruct' must be imported}}
+  // expected-warning{{use of identifier ''struct HiddenStruct'' requires import/inclusion of the module 'module_private_left'}}
   // expected-note@Inputs/module_private_left.h:3 {{previous definition is here}}
 
   Integer i; // expected-error{{unknown type name 'Integer'}}
Index: test/Modules/normal-module-map.cpp
===================================================================
--- test/Modules/normal-module-map.cpp
+++ test/Modules/normal-module-map.cpp
@@ -24,7 +24,7 @@
 
 int testNestedUmbrellaBFail() {
   return nested_umbrella_b;
-  // expected-error@-1{{declaration of 'nested_umbrella_b' must be imported from module 'nested_umbrella.b' before it is required}}
+  // expected-warning@-1{{use of identifier 'nested_umbrella_b' requires import/inclusion of the module 'nested_umbrella.b'}}
   // expected-note@Inputs/normal-module-map/nested_umbrella/b.h:1{{previous}}
 }
 
Index: test/Modules/objc-categories.m
===================================================================
--- test/Modules/objc-categories.m
+++ test/Modules/objc-categories.m
@@ -1,10 +1,10 @@
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -x objective-c -fmodule-name=category_top -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -x objective-c -fmodule-name=category_left -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -x objective-c -fmodule-name=category_right -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -x objective-c -fmodule-name=category_bottom -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -x objective-c -fmodule-name=category_other -emit-module %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs %s -verify
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -x objective-c -fmodule-name=category_top -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -x objective-c -fmodule-name=category_left -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -x objective-c -fmodule-name=category_right -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -x objective-c -fmodule-name=category_bottom -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -x objective-c -fmodule-name=category_other -emit-module %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -fno-modules-search-all -I %S/Inputs %s -verify
 
 @import category_bottom;
 
Index: test/Modules/redecl-namespaces.mm
===================================================================
--- test/Modules/redecl-namespaces.mm
+++ test/Modules/redecl-namespaces.mm
@@ -8,6 +8,6 @@
 }
 
 // RUN: rm -rf %t
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -emit-module -fmodule-name=redecl_namespaces_left %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -x objective-c++ -fmodules-cache-path=%t -emit-module -fmodule-name=redecl_namespaces_right %S/Inputs/module.map
-// RUN: %clang_cc1 -fmodules -fmodules-cache-path=%t -I %S/Inputs -w %s -verify
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -x objective-c++ -fmodules-cache-path=%t -emit-module -fmodule-name=redecl_namespaces_left %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -x objective-c++ -fmodules-cache-path=%t -emit-module -fmodule-name=redecl_namespaces_right %S/Inputs/module.map
+// RUN: %clang_cc1 -fmodules -fno-modules-search-all -fmodules-cache-path=%t -I %S/Inputs -w %s -verify
Index: test/Modules/subframeworks.m
===================================================================
--- test/Modules/subframeworks.m
+++ test/Modules/subframeworks.m
@@ -5,7 +5,7 @@
 @import DependsOnModule;
 
 void testSubFramework() {
-  float *sf1 = sub_framework; // expected-error{{declaration of 'sub_framework' must be imported from module 'DependsOnModule.SubFramework' before it is required}}
+  float *sf1 = sub_framework; // expected-warning{{use of identifier 'sub_framework' requires import/inclusion of the module 'DependsOnModule.SubFramework'}}
   // expected-note@Inputs/DependsOnModule.framework/Frameworks/SubFramework.framework/Headers/SubFramework.h:2 {{previous}}
 }
 
Index: test/Modules/submodules.cpp
===================================================================
--- test/Modules/submodules.cpp
+++ test/Modules/submodules.cpp
@@ -7,7 +7,7 @@
 vector<int> vi;
 
 // Note: remove_reference is not visible yet.
-remove_reference<int&>::type *int_ptr = 0; // expected-error{{declaration of 'remove_reference' must be imported from module 'std.type_traits' before it is required}}
+remove_reference<int&>::type *int_ptr = 0; // expected-warning{{use of identifier 'remove_reference' requires import/inclusion of the module 'std.type_traits'}}
 // expected-note@Inputs/submodules/type_traits.h:2{{previous}}
 // expected-note@Inputs/submodules/hash_map.h:1{{previous}}
 
@@ -21,14 +21,14 @@
 @import std; // import everything in 'std'
 
 // hash_map still isn't available.
-hash_map<int, float> ints_to_floats; // expected-error{{declaration of 'hash_map' must be imported from module 'std.hash_map' before it is required}}
+hash_map<int, float> ints_to_floats; // expected-warning{{use of identifier 'hash_map' requires import/inclusion of the module 'std.hash_map}}
 
 @import std.hash_map;
 
 hash_map<int, float> ints_to_floats2;
 
 @import import_self.b;
-extern MyTypeA import_self_test_a; // expected-error {{must be imported from module 'import_self.a'}}
+extern MyTypeA import_self_test_a; // expected-warning {{use of identifier 'MyTypeA' requires import/inclusion of the module 'import_self.a'}}
 // expected-note@import-self-a.h:1 {{here}}
 extern MyTypeC import_self_test_c;
 extern MyTypeD import_self_test_d;
Index: test/Modules/template-specialization-visibility.cpp
===================================================================
--- test/Modules/template-specialization-visibility.cpp
+++ test/Modules/template-specialization-visibility.cpp
@@ -13,7 +13,7 @@
 int k1 = implicit_inst_class_template.n;
 
 #ifdef ERR1
-S<char> explicit_inst_class_template; // expected-error {{must be imported from module 'tsv.e'}}
+S<char> explicit_inst_class_template; // expected-warning {{requires import/inclusion of the module 'tsv.e'}}
 // expected-note@e.h:4 {{previous}}
 int k2 = explicit_inst_class_template.n;
 #endif
@@ -24,7 +24,7 @@
 int k3 = implicit_inst_member_class_template.n;
 
 #ifdef ERR2
-T<char>::S explicit_inst_member_class_template; // expected-error {{must be imported from module 'tsv.e'}}
+T<char>::S explicit_inst_member_class_template; // expected-warning {{requires import/inclusion of the module 'tsv.e'}}
 // expected-note@e.h:5 {{previous}}
 int k4 = explicit_inst_member_class_template.n;
 #endif
@@ -33,7 +33,7 @@
 int k5 = decltype(implicit_inst_member_enum_template)::e;
 
 #ifdef ERR3
-T<char>::E explicit_inst_member_enum_template; // expected-error {{must be imported from module 'tsv.e'}}
+T<char>::E explicit_inst_member_enum_template; // expected-warning {{requires import/inclusion of the module 'tsv.e'}}
 // expected-note@e.h:5 {{previous}}
 int k6 = decltype(explicit_inst_member_enum_template)::e;
 #endif
Index: test/Modules/undefined-type-fixit1.cpp
===================================================================
--- test/Modules/undefined-type-fixit1.cpp
+++ test/Modules/undefined-type-fixit1.cpp
@@ -0,0 +1,12 @@
+// RUN: rm -rf %t
+// RUN: %clang_cc1 -fmodules-cache-path=%t -fmodules -I %S/Inputs/undefined-type-fixit %s -verify
+
+//#include "public1.h"
+#include "public2.h"
+#include "public2sub.h"
+
+use_this1 client_variable1; // expected-warning {{use of identifier 'use_this1' requires import/inclusion of the module 'public1'}}
+use_this2 client_variable2;
+use_this2sub client_variable2sub;
+
+// expected-note@Inputs/undefined-type-fixit/public1.h:4 {{previous declaration is here}}
Index: test/Modules/wildcard-submodule-exports.cpp
===================================================================
--- test/Modules/wildcard-submodule-exports.cpp
+++ test/Modules/wildcard-submodule-exports.cpp
@@ -4,10 +4,12 @@
 
 @import C.One;
 
+// expected-note@Inputs/wildcard-submodule-exports/B_one.h:1 {{previous declaration is here}}
+
 void test_C_One() {
   int *A1_ptr = A1;
   long *C1_ptr = C1;
-  (void)B1; // expected-error{{use of undeclared identifier 'B1'}}
+  (void)B1; // expected-warning{{use of identifier 'B1' requires import/inclusion of the module 'B.One'}}
 }
 
 @import C.Two;
Index: unittests/Basic/SourceManagerTest.cpp
===================================================================
--- unittests/Basic/SourceManagerTest.cpp
+++ unittests/Basic/SourceManagerTest.cpp
@@ -63,6 +63,8 @@
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex() { return 0; }
 };
 
 TEST_F(SourceManagerTest, isBeforeInTranslationUnit) {
Index: unittests/Lex/CMakeLists.txt
===================================================================
--- unittests/Lex/CMakeLists.txt
+++ unittests/Lex/CMakeLists.txt
@@ -14,4 +14,5 @@
   clangLex
   clangParse
   clangSema
+  clangSerialization
   )
Index: unittests/Lex/LexerTest.cpp
===================================================================
--- unittests/Lex/LexerTest.cpp
+++ unittests/Lex/LexerTest.cpp
@@ -40,6 +40,8 @@
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex() { return 0; }
 };
 
 // The test fixture.
Index: unittests/Lex/Makefile
===================================================================
--- unittests/Lex/Makefile
+++ unittests/Lex/Makefile
@@ -9,8 +9,8 @@
 
 CLANG_LEVEL = ../..
 TESTNAME = Lex
-LINK_COMPONENTS := mcparser support mc
+LINK_COMPONENTS := mcparser support mc bitreader
 USEDLIBS = clangParse.a clangSema.a clangAnalysis.a clangEdit.a \
-	clangAST.a clangLex.a clangBasic.a 
+	clangSerialization.a clangAST.a clangLex.a clangBasic.a 
 
 include $(CLANG_LEVEL)/unittests/Makefile
Index: unittests/Lex/PPCallbacksTest.cpp
===================================================================
--- unittests/Lex/PPCallbacksTest.cpp
+++ unittests/Lex/PPCallbacksTest.cpp
@@ -45,6 +45,8 @@
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex() { return 0; }
 };
 
 // Stub to collect data from InclusionDirective callbacks.
Index: unittests/Lex/PPConditionalDirectiveRecordTest.cpp
===================================================================
--- unittests/Lex/PPConditionalDirectiveRecordTest.cpp
+++ unittests/Lex/PPConditionalDirectiveRecordTest.cpp
@@ -64,6 +64,8 @@
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex() { return 0; }
 };
 
 TEST_F(PPConditionalDirectiveRecordTest, PPRecAPI) {