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(ModulesStrictDeclUse, 1, 0, "require declaration of module uses and all headers to be in modules")
 LANGOPT(Optimize          , 1, 0, "__OPTIMIZE__ predefined macro")
 LANGOPT(OptimizeSize      , 1, 0, "__OPTIMIZE_SIZE__ predefined macro")
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -583,6 +583,9 @@
 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">;
@@ -613,6 +616,8 @@
 def fmodules_strict_decluse : Flag <["-"], "fmodules-strict-decluse">, Group<f_Group>,
   Flags<[DriverOption,CC1Option]>,
   HelpText<"Like -fmodules-decluse but requires all headers to be in modules">;
+def fno_modules_search_all : Flag <["-"], "fno-modules-search-all">, Group<f_Group>,
+  Flags<[DriverOption, CC1Option]>;
 def fretain_comments_from_system_headers : Flag<["-"], "fretain-comments-from-system-headers">, Group<f_Group>, Flags<[CC1Option]>;
 
 def fmudflapth : Flag<["-"], "fmudflapth">, Group<f_Group>;
Index: include/clang/Frontend/ASTUnit.h
===================================================================
--- include/clang/Frontend/ASTUnit.h
+++ include/clang/Frontend/ASTUnit.h
@@ -869,6 +869,7 @@
   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();
+  explicit CompilerInstance(bool BuildingModule = 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
@@ -511,7 +511,6 @@
   /// \returns The module with the given name.
   Module *lookupModule(StringRef ModuleName, bool AllowSearch = true);
 
-
   /// \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) {}
+  explicit ModuleLoader(bool BuildingModule = false) :
+    BuildingModule(BuildingModule),
+    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
@@ -2600,10 +2600,16 @@
                           VisibleDeclConsumer &Consumer,
                           bool IncludeGlobalScope = true);
 
+  enum CTModeKind {
+    CTNonError,       // CorrectTypo used in a non error recovery situation.
+    CTErrorRecovery   // CorrectTypo used in normal error recovery.
+  };
+
   TypoCorrection CorrectTypo(const DeclarationNameInfo &Typo,
                              Sema::LookupNameKind LookupKind,
                              Scope *S, CXXScopeSpec *SS,
                              CorrectionCandidateCallback &CCC,
+                             CTModeKind Mode,
                              DeclContext *MemberContext = 0,
                              bool EnteringContext = false,
                              const ObjCObjectPointerType *OPT = 0,
Index: include/clang/Serialization/ASTReader.h
===================================================================
--- include/clang/Serialization/ASTReader.h
+++ include/clang/Serialization/ASTReader.h
@@ -1365,6 +1365,12 @@
   /// \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: 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 BuildingModule)
+  : ModuleLoader(BuildingModule),
+    Invocation(new CompilerInvocation()), ModuleManager(0),
+    BuildGlobalModuleIndex(false), HaveFullGlobalModuleIndex(false),
+    ModuleBuildFailed(false) {
 }
 
 CompilerInstance::~CompilerInstance() {
@@ -830,7 +833,7 @@
   
   // 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(
@@ -1097,6 +1100,43 @@
   }
 }
 
+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,
@@ -1143,41 +1183,9 @@
     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);
 
@@ -1403,3 +1411,59 @@
   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
@@ -1357,6 +1357,9 @@
   Opts.ModulesStrictDeclUse = Args.hasArg(OPT_fmodules_strict_decluse);
   Opts.ModulesDeclUse =
       Args.hasArg(OPT_fmodules_decluse) || Opts.ModulesStrictDeclUse;
+  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/Sema/SemaCXXScopeSpec.cpp
===================================================================
--- lib/Sema/SemaCXXScopeSpec.cpp
+++ lib/Sema/SemaCXXScopeSpec.cpp
@@ -547,7 +547,8 @@
     Found.clear();
     if (TypoCorrection Corrected =
             CorrectTypo(Found.getLookupNameInfo(), Found.getLookupKind(), S,
-                        &SS, Validator, LookupCtx, EnteringContext)) {
+                        &SS, Validator, CTErrorRecovery, LookupCtx,
+                        EnteringContext)) {
       if (LookupCtx) {
         bool DroppedSpecifier =
             Corrected.WillReplaceSpecifier() &&
Index: lib/Sema/SemaDecl.cpp
===================================================================
--- lib/Sema/SemaDecl.cpp
+++ lib/Sema/SemaDecl.cpp
@@ -218,7 +218,8 @@
     if (CorrectedII) {
       TypeNameValidatorCCC Validator(true, isClassName);
       TypoCorrection Correction = CorrectTypo(Result.getLookupNameInfo(),
-                                              Kind, S, SS, Validator);
+                                              Kind, S, SS, Validator,
+                                              CTErrorRecovery);
       IdentifierInfo *NewII = Correction.getCorrectionAsIdentifierInfo();
       TemplateTy Template;
       bool MemberOfUnknownSpecialization;
@@ -408,7 +409,7 @@
   TypeNameValidatorCCC Validator(false, false, AllowClassTemplates);
   if (TypoCorrection Corrected = CorrectTypo(DeclarationNameInfo(II, IILoc),
                                              LookupOrdinaryName, S, SS,
-                                             Validator)) {
+                                             Validator, CTErrorRecovery)) {
     if (Corrected.isKeyword()) {
       // We corrected to a keyword.
       diagnoseTypo(Corrected, PDiag(diag::err_unknown_typename_suggest) << II);
@@ -650,7 +651,7 @@
       SecondTry = true;
       if (TypoCorrection Corrected = CorrectTypo(Result.getLookupNameInfo(),
                                                  Result.getLookupKind(), S, 
-                                                 &SS, *CCC)) {
+                                                 &SS, *CCC, CTErrorRecovery)) {
         unsigned UnqualifiedDiag = diag::err_undeclared_var_use_suggest;
         unsigned QualifiedDiag = diag::err_no_member_suggest;
 
@@ -1422,7 +1423,7 @@
     DeclFilterCCC<ObjCInterfaceDecl> Validator;
     if (TypoCorrection C = CorrectTypo(DeclarationNameInfo(Id, IdLoc),
                                        LookupOrdinaryName, TUScope, NULL,
-                                       Validator)) {
+                                       Validator, CTErrorRecovery)) {
       diagnoseTypo(C, PDiag(diag::err_undef_interface_suggest) << Id);
       IDecl = C.getCorrectionDeclAs<ObjCInterfaceDecl>();
       Id = IDecl->getIdentifier();
@@ -6172,7 +6173,7 @@
   // If the qualified name lookup yielded nothing, try typo correction
   } else if ((Correction = SemaRef.CorrectTypo(
                  Prev.getLookupNameInfo(), Prev.getLookupKind(), S,
-                 &ExtraArgs.D.getCXXScopeSpec(), Validator,
+                 &ExtraArgs.D.getCXXScopeSpec(), Validator, Sema::CTErrorRecovery,
                  IsLocalFriend ? 0 : NewDC))) {
     // Set up everything for the call to ActOnFunctionDeclarator
     ExtraArgs.D.SetIdentifier(Correction.getCorrectionAsIdentifierInfo(),
@@ -10119,7 +10120,8 @@
     TypoCorrection Corrected;
     DeclFilterCCC<FunctionDecl> Validator;
     if (S && (Corrected = CorrectTypo(DeclarationNameInfo(&II, Loc),
-                                      LookupOrdinaryName, S, 0, Validator)))
+                                      LookupOrdinaryName, S, 0, Validator,
+                                      CTNonError)))
       diagnoseTypo(Corrected, PDiag(diag::note_function_suggestion),
                    /*ErrorRecovery*/false);
   }
Index: lib/Sema/SemaDeclCXX.cpp
===================================================================
--- lib/Sema/SemaDeclCXX.cpp
+++ lib/Sema/SemaDeclCXX.cpp
@@ -2603,7 +2603,7 @@
       MemInitializerValidatorCCC Validator(ClassDecl);
       if (R.empty() && BaseType.isNull() &&
           (Corr = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, &SS,
-                              Validator, ClassDecl))) {
+                              Validator, CTErrorRecovery, ClassDecl))) {
         if (FieldDecl *Member = Corr.getCorrectionDeclAs<FieldDecl>()) {
           // We have found a non-static data member with a similar
           // name to what was typed; complain and initialize that
@@ -6898,7 +6898,8 @@
   R.clear();
   if (TypoCorrection Corrected = S.CorrectTypo(R.getLookupNameInfo(),
                                                R.getLookupKind(), Sc, &SS,
-                                               Validator)) {
+                                               Validator,
+                                               Sema::CTErrorRecovery)) {
     if (DeclContext *DC = S.computeDeclContext(SS, false)) {
       std::string CorrectedStr(Corrected.getAsString(S.getLangOpts()));
       bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
@@ -7469,7 +7470,8 @@
     UsingValidatorCCC CCC(HasTypenameKeyword, IsInstantiation,
                           CurContext->isRecord());
     if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
-                                               R.getLookupKind(), S, &SS, CCC)){
+                                               R.getLookupKind(), S, &SS, CCC,
+                                               CTErrorRecovery)){
       // We reject any correction for which ND would be NULL.
       NamedDecl *ND = Corrected.getCorrectionDecl();
       R.setLookupName(Corrected.getCorrection());
Index: lib/Sema/SemaDeclObjC.cpp
===================================================================
--- lib/Sema/SemaDeclObjC.cpp
+++ lib/Sema/SemaDeclObjC.cpp
@@ -524,7 +524,7 @@
       ObjCInterfaceValidatorCCC Validator(IDecl);
       if (TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(SuperName, SuperLoc), LookupOrdinaryName, TUScope,
-          NULL, Validator)) {
+          NULL, Validator, CTErrorRecovery)) {
         diagnoseTypo(Corrected, PDiag(diag::err_undef_superclass_suggest)
                                     << SuperName << ClassName);
         PrevDecl = Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>();
@@ -794,7 +794,7 @@
       DeclFilterCCC<ObjCProtocolDecl> Validator;
       TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(ProtocolId[i].first, ProtocolId[i].second),
-          LookupObjCProtocolName, TUScope, NULL, Validator);
+          LookupObjCProtocolName, TUScope, NULL, Validator, CTErrorRecovery);
       if ((PDecl = Corrected.getCorrectionDeclAs<ObjCProtocolDecl>()))
         diagnoseTypo(Corrected, PDiag(diag::err_undeclared_protocol_suggest)
                                     << ProtocolId[i].first);
@@ -1034,7 +1034,8 @@
     ObjCInterfaceValidatorCCC Validator;
     TypoCorrection Corrected =
             CorrectTypo(DeclarationNameInfo(ClassName, ClassLoc),
-                        LookupOrdinaryName, TUScope, NULL, Validator);
+                        LookupOrdinaryName, TUScope, NULL, Validator,
+                        CTNonError);
     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/SemaExpr.cpp
===================================================================
--- lib/Sema/SemaExpr.cpp
+++ lib/Sema/SemaExpr.cpp
@@ -1843,7 +1843,7 @@
   // We didn't find anything, so try to correct for a typo.
   TypoCorrection Corrected;
   if (S && (Corrected = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(),
-                                    S, &SS, CCC))) {
+                                    S, &SS, CCC, CTErrorRecovery))) {
     std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
     bool DroppedSpecifier =
         Corrected.WillReplaceSpecifier() && Name.getAsString() == CorrectedStr;
@@ -4003,7 +4003,8 @@
 
   if (TypoCorrection Corrected = S.CorrectTypo(
           DeclarationNameInfo(FuncName, NameLoc), Sema::LookupOrdinaryName,
-          S.getScopeForContext(S.CurContext), NULL, CCC)) {
+          S.getScopeForContext(S.CurContext), NULL, CCC,
+          Sema::CTErrorRecovery)) {
     if (NamedDecl *ND = Corrected.getCorrectionDecl()) {
       if (Corrected.isOverloaded()) {
         OverloadCandidateSet OCS(NameLoc);
Index: lib/Sema/SemaExprMember.cpp
===================================================================
--- lib/Sema/SemaExprMember.cpp
+++ lib/Sema/SemaExprMember.cpp
@@ -627,7 +627,8 @@
   RecordMemberExprValidatorCCC Validator(RTy);
   TypoCorrection Corrected = SemaRef.CorrectTypo(R.getLookupNameInfo(),
                                                  R.getLookupKind(), NULL,
-                                                 &SS, Validator, DC);
+                                                 &SS, Validator,
+                                                 Sema::CTErrorRecovery, DC);
   R.clear();
   if (Corrected.isResolved() && !Corrected.isKeyword()) {
     R.setLookupName(Corrected.getCorrection());
@@ -1270,7 +1271,8 @@
       Validator.IsObjCIvarLookup = IsArrow;
       if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
                                                  LookupMemberName, NULL, NULL,
-                                                 Validator, IDecl)) {
+                                                 Validator, CTErrorRecovery,
+                                                 IDecl)) {
         IV = Corrected.getCorrectionDeclAs<ObjCIvarDecl>();
         diagnoseTypo(Corrected,
                      PDiag(diag::err_typecheck_member_reference_ivar_suggest)
Index: lib/Sema/SemaExprObjC.cpp
===================================================================
--- lib/Sema/SemaExprObjC.cpp
+++ lib/Sema/SemaExprObjC.cpp
@@ -1669,7 +1669,7 @@
   DeclFilterCCC<ObjCPropertyDecl> Validator;
   if (TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(MemberName, MemberLoc), LookupOrdinaryName, NULL,
-          NULL, Validator, IFace, false, OPT)) {
+          NULL, Validator, CTErrorRecovery, IFace, false, OPT)) {
     diagnoseTypo(Corrected, PDiag(diag::err_property_not_found_suggest)
                               << MemberName << QualType(OPT, 0));
     DeclarationName TypoResult = Corrected.getCorrection();
@@ -1907,7 +1907,8 @@
   ObjCInterfaceOrSuperCCC Validator(getCurMethodDecl());
   if (TypoCorrection Corrected =
           CorrectTypo(Result.getLookupNameInfo(), Result.getLookupKind(), S,
-                      NULL, Validator, NULL, false, NULL, false)) {
+                      NULL, Validator, CTErrorRecovery, NULL, false, NULL,
+                      false)) {
     if (Corrected.isKeyword()) {
       // If we've found the keyword "super" (the only keyword that would be
       // returned by CorrectTypo), this is a send to super.
Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -1816,7 +1816,7 @@
         if (TypoCorrection Corrected = SemaRef.CorrectTypo(
                 DeclarationNameInfo(FieldName, D->getFieldLoc()),
                 Sema::LookupMemberName, /*Scope=*/ 0, /*SS=*/ 0, Validator,
-                RT->getDecl())) {
+                Sema::CTErrorRecovery, RT->getDecl())) {
           SemaRef.diagnoseTypo(
               Corrected,
               SemaRef.PDiag(diag::err_field_designator_unknown_suggest)
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"
@@ -3998,6 +4003,7 @@
                                  Sema::LookupNameKind LookupKind,
                                  Scope *S, CXXScopeSpec *SS,
                                  CorrectionCandidateCallback &CCC,
+                                 CTModeKind Mode,
                                  DeclContext *MemberContext,
                                  bool EnteringContext,
                                  const ObjCObjectPointerType *OPT,
@@ -4052,10 +4058,35 @@
   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 ((Mode == CTErrorRecovery) && !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);
+        TC.setRequiresImport(true);
+      }
+    }
+  }
+
   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;
@@ -4129,6 +4160,8 @@
   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.
Index: lib/Sema/SemaOpenMP.cpp
===================================================================
--- lib/Sema/SemaOpenMP.cpp
+++ lib/Sema/SemaOpenMP.cpp
@@ -428,7 +428,7 @@
   if (!Lookup.isSingleResult()) {
     VarDeclFilterCCC Validator(*this);
     if (TypoCorrection Corrected = CorrectTypo(Id, LookupOrdinaryName, CurScope,
-                                               0, Validator)) {
+                                               0, Validator, CTErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(Lookup.empty()? diag::err_undeclared_var_use_suggest
                                        : diag::err_omp_expected_var_arg_suggest)
Index: lib/Sema/SemaTemplate.cpp
===================================================================
--- lib/Sema/SemaTemplate.cpp
+++ lib/Sema/SemaTemplate.cpp
@@ -325,7 +325,8 @@
     FilterCCC.WantCXXNamedCasts = true;
     if (TypoCorrection Corrected = CorrectTypo(Found.getLookupNameInfo(),
                                                Found.getLookupKind(), S, &SS,
-                                               FilterCCC, LookupCtx)) {
+                                               FilterCCC, CTErrorRecovery,
+                                               LookupCtx)) {
       Found.setLookupName(Corrected.getCorrection());
       if (Corrected.getCorrectionDecl())
         Found.addDecl(Corrected.getCorrectionDecl());
Index: lib/Sema/SemaTemplateVariadic.cpp
===================================================================
--- lib/Sema/SemaTemplateVariadic.cpp
+++ lib/Sema/SemaTemplateVariadic.cpp
@@ -810,7 +810,7 @@
   case LookupResult::NotFoundInCurrentInstantiation:
     if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
                                                R.getLookupKind(), S, 0,
-                                               Validator)) {
+                                               Validator, CTErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(diag::err_sizeof_pack_no_pack_name_suggest) << &Name,
                    PDiag(diag::note_parameter_pack_here));
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/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 -fmodules-search-all -I %S/Inputs/undefined-type-fixit %s -verify
+
+//#include "public1.h"
+#include "public2.h"
+#include "public2sub.h"
+
+use_this1 client_variable1; // expected-error{{declaration of 'use_this1' must be imported from module 'public1' before it is required}}
+use_this2 client_variable2;
+use_this2sub client_variable2sub;
+
+// expected-note@Inputs/undefined-type-fixit/public1.h:4 {{previous declaration is here}}
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) {