Initial implementation of -modules-earch-all option, for searching for symbols in non-imported modules.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@206977 91177308-0d34-0410-b5e6-96231b3b80d8

34 files changed, 287 insertions, 68 deletions

diff --git a/docs/Modules.rst b/docs/Modules.rst
index 59daebcc93..ce1e717bc2 100644
--- a/docs/Modules.rst
+++ b/docs/Modules.rst
@@ -198,6 +198,9 @@ Command-line parameters
 ``-fmodule-map-file=<file>``
   Load the given module map file if a header from its directory or one of its subdirectories is loaded.
 
+``-fmodules-search-all``
+  If a symbol is not found, search modules referenced in the current module maps but not imported for symbols, so the error message can reference the module by name.  Note that if the global module index has not been built before, this might take some time as it needs to build all the modules.  Note that this option doesn't apply in module builds, to avoid the recursion.
+
 Module Semantics
 ================
 
diff --git a/include/clang/Basic/LangOptions.def b/include/clang/Basic/LangOptions.def
index 3295ca4a27..699bf1fa4d 100644
--- a/include/clang/Basic/LangOptions.def
+++ b/include/clang/Basic/LangOptions.def
@@ -96,6 +96,7 @@ LANGOPT(MathErrno         , 1, 1, "errno support for math functions")
 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")
diff --git a/include/clang/Driver/Options.td b/include/clang/Driver/Options.td
index b734280a89..d6b22795e0 100644
--- a/include/clang/Driver/Options.td
+++ b/include/clang/Driver/Options.td
@@ -583,6 +583,9 @@ def fmodules_prune_interval : Joined<["-"], "fmodules-prune-interval=">, Group<i
 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_decluse : Flag <["-"], "fmodules-decluse">, Group<f_Group>,
 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>;
diff --git a/include/clang/Frontend/ASTUnit.h b/include/clang/Frontend/ASTUnit.h
index ceabaa75e9..666e5dd7c7 100644
--- a/include/clang/Frontend/ASTUnit.h
+++ b/include/clang/Frontend/ASTUnit.h
@@ -874,6 +874,8 @@ public:
   void makeModuleVisible(Module *Mod, Module::NameVisibilityKind Visibility,
                          SourceLocation ImportLoc, bool Complain) override {}
 
+  GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc)
+    { return 0; }
 };
 
 } // namespace clang
diff --git a/include/clang/Frontend/CompilerInstance.h b/include/clang/Frontend/CompilerInstance.h
index ee97d9bec3..1a89a8a156 100644
--- a/include/clang/Frontend/CompilerInstance.h
+++ b/include/clang/Frontend/CompilerInstance.h
@@ -124,6 +124,9 @@ class CompilerInstance : public ModuleLoader {
   /// 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 @@ class CompilerInstance : public ModuleLoader {
   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 @@ public:
 
   /// }
 
+  // Create module manager.
+  void createModuleManager();
+
   ModuleLoadResult loadModule(SourceLocation ImportLoc, ModuleIdPath Path,
                               Module::NameVisibilityKind Visibility,
                               bool IsInclusionDirective) override;
@@ -694,6 +700,7 @@ public:
     return ModuleLoader::HadFatalFailure;
   }
 
+  GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc);
 };
 
 } // end namespace clang
diff --git a/include/clang/Lex/HeaderSearch.h b/include/clang/Lex/HeaderSearch.h
index 507ede583f..a62a710d78 100644
--- a/include/clang/Lex/HeaderSearch.h
+++ b/include/clang/Lex/HeaderSearch.h
@@ -511,7 +511,6 @@ public:
   /// \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,
diff --git a/include/clang/Lex/ModuleLoader.h b/include/clang/Lex/ModuleLoader.h
index 254ab36fe9..0a690812a9 100644
--- a/include/clang/Lex/ModuleLoader.h
+++ b/include/clang/Lex/ModuleLoader.h
@@ -21,6 +21,7 @@
 
 namespace clang {
 
+class GlobalModuleIndex;
 class IdentifierInfo;
 class Module;
 
@@ -53,11 +54,24 @@ public:
 /// 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 +102,19 @@ public:
                                  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.
+  /// \param TriggerLoc The location for what triggered the load.
+  /// \returns Returns null if load failed.
+  virtual GlobalModuleIndex *loadGlobalModuleIndex(
+                                            SourceLocation TriggerLoc) = 0;
+
   bool HadFatalFailure;
 };
   
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index fc6c42265a..4d4fd360a3 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -2601,10 +2601,16 @@ public:
                           VisibleDeclConsumer &Consumer,
                           bool IncludeGlobalScope = true);
 
+  enum CorrectTypoKind {
+    CTK_NonError,     // CorrectTypo used in a non error recovery situation.
+    CTK_ErrorRecovery // CorrectTypo used in normal error recovery.
+  };
+
   TypoCorrection CorrectTypo(const DeclarationNameInfo &Typo,
                              Sema::LookupNameKind LookupKind,
                              Scope *S, CXXScopeSpec *SS,
                              CorrectionCandidateCallback &CCC,
+                             CorrectTypoKind Mode,
                              DeclContext *MemberContext = 0,
                              bool EnteringContext = false,
                              const ObjCObjectPointerType *OPT = 0,
diff --git a/include/clang/Serialization/ASTReader.h b/include/clang/Serialization/ASTReader.h
index 881d24b22e..ccf3822d69 100644
--- a/include/clang/Serialization/ASTReader.h
+++ b/include/clang/Serialization/ASTReader.h
@@ -1384,8 +1384,15 @@ public:
   /// \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.
   ///
+  /// \param TriggerLoc The location for what triggered the load.
   /// \returns true if loading the global index has failed for any reason.
   bool loadGlobalIndex();
 
diff --git a/lib/Frontend/CompilerInstance.cpp b/lib/Frontend/CompilerInstance.cpp
index 267d318fa9..f06633ca51 100644
--- a/lib/Frontend/CompilerInstance.cpp
+++ b/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 @@ static void compileModuleImpl(CompilerInstance &ImportingInstance,
   
   // Construct a compiler instance that will be used to actually create the
   // module.
-  CompilerInstance Instance;
+  CompilerInstance Instance(/*BuildingModule=*/true);
   Instance.setInvocation(&*Invocation);
 
   Instance.createDiagnostics(new ForwardingDiagnosticConsumer(
@@ -1097,6 +1100,43 @@ static void pruneModuleCache(const HeaderSearchOptions &HSOpts) {
   }
 }
 
+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,
@@ -1143,40 +1183,8 @@ CompilerInstance::loadModule(SourceLocation ImportLoc,
     std::string ModuleFileName = PP->getHeaderSearchInfo().getModuleFileName(Module);
 
     // If we don't already have an ASTReader, create one now.
-    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());
-    }
+    if (!ModuleManager)
+      createModuleManager();
 
     if (TheDependencyFileGenerator)
       TheDependencyFileGenerator->AttachToASTReader(*ModuleManager);
@@ -1403,3 +1411,58 @@ void CompilerInstance::makeModuleVisible(Module *Mod,
   ModuleManager->makeModuleVisible(Mod, Visibility, ImportLoc, Complain);
 }
 
+GlobalModuleIndex *CompilerInstance::loadGlobalModuleIndex(
+    SourceLocation TriggerLoc) {
+  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) {
+        SmallVector<std::pair<IdentifierInfo *, SourceLocation>, 2> Path;
+        Path.push_back(std::make_pair(
+				  getPreprocessor().getIdentifierInfo(TheModule->Name), TriggerLoc));
+        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;
+}
diff --git a/lib/Frontend/CompilerInvocation.cpp b/lib/Frontend/CompilerInvocation.cpp
index e51d2cf852..d10edd81ea 100644
--- a/lib/Frontend/CompilerInvocation.cpp
+++ b/lib/Frontend/CompilerInvocation.cpp
@@ -1357,6 +1357,9 @@ static void ParseLangArgs(LangOptions &Opts, ArgList &Args, InputKind IK,
   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);
diff --git a/lib/Sema/SemaCXXScopeSpec.cpp b/lib/Sema/SemaCXXScopeSpec.cpp
index 7d038f72e9..707d1b2e81 100644
--- a/lib/Sema/SemaCXXScopeSpec.cpp
+++ b/lib/Sema/SemaCXXScopeSpec.cpp
@@ -547,7 +547,8 @@ bool Sema::BuildCXXNestedNameSpecifier(Scope *S,
     Found.clear();
     if (TypoCorrection Corrected =
             CorrectTypo(Found.getLookupNameInfo(), Found.getLookupKind(), S,
-                        &SS, Validator, LookupCtx, EnteringContext)) {
+                        &SS, Validator, CTK_ErrorRecovery, LookupCtx,
+                        EnteringContext)) {
       if (LookupCtx) {
         bool DroppedSpecifier =
             Corrected.WillReplaceSpecifier() &&
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 50462b7927..7603e2c254 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -218,7 +218,8 @@ ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
     if (CorrectedII) {
       TypeNameValidatorCCC Validator(true, isClassName);
       TypoCorrection Correction = CorrectTypo(Result.getLookupNameInfo(),
-                                              Kind, S, SS, Validator);
+                                              Kind, S, SS, Validator,
+                                              CTK_ErrorRecovery);
       IdentifierInfo *NewII = Correction.getCorrectionAsIdentifierInfo();
       TemplateTy Template;
       bool MemberOfUnknownSpecialization;
@@ -408,7 +409,7 @@ bool Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
   TypeNameValidatorCCC Validator(false, false, AllowClassTemplates);
   if (TypoCorrection Corrected = CorrectTypo(DeclarationNameInfo(II, IILoc),
                                              LookupOrdinaryName, S, SS,
-                                             Validator)) {
+                                             Validator, CTK_ErrorRecovery)) {
     if (Corrected.isKeyword()) {
       // We corrected to a keyword.
       diagnoseTypo(Corrected, PDiag(diag::err_unknown_typename_suggest) << II);
@@ -650,7 +651,8 @@ Corrected:
       SecondTry = true;
       if (TypoCorrection Corrected = CorrectTypo(Result.getLookupNameInfo(),
                                                  Result.getLookupKind(), S, 
-                                                 &SS, *CCC)) {
+                                                 &SS, *CCC,
+                                                 CTK_ErrorRecovery)) {
         unsigned UnqualifiedDiag = diag::err_undeclared_var_use_suggest;
         unsigned QualifiedDiag = diag::err_no_member_suggest;
 
@@ -1422,7 +1424,7 @@ ObjCInterfaceDecl *Sema::getObjCInterfaceDecl(IdentifierInfo *&Id,
     DeclFilterCCC<ObjCInterfaceDecl> Validator;
     if (TypoCorrection C = CorrectTypo(DeclarationNameInfo(Id, IdLoc),
                                        LookupOrdinaryName, TUScope, NULL,
-                                       Validator)) {
+                                       Validator, CTK_ErrorRecovery)) {
       diagnoseTypo(C, PDiag(diag::err_undef_interface_suggest) << Id);
       IDecl = C.getCorrectionDeclAs<ObjCInterfaceDecl>();
       Id = IDecl->getIdentifier();
@@ -6160,7 +6162,7 @@ static NamedDecl *DiagnoseInvalidRedeclaration(
   } else if ((Correction = SemaRef.CorrectTypo(
                  Prev.getLookupNameInfo(), Prev.getLookupKind(), S,
                  &ExtraArgs.D.getCXXScopeSpec(), Validator,
-                 IsLocalFriend ? 0 : NewDC))) {
+                 Sema::CTK_ErrorRecovery, IsLocalFriend ? 0 : NewDC))) {
     // Set up everything for the call to ActOnFunctionDeclarator
     ExtraArgs.D.SetIdentifier(Correction.getCorrectionAsIdentifierInfo(),
                               ExtraArgs.D.getIdentifierLoc());
@@ -10100,7 +10102,8 @@ NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
     TypoCorrection Corrected;
     DeclFilterCCC<FunctionDecl> Validator;
     if (S && (Corrected = CorrectTypo(DeclarationNameInfo(&II, Loc),
-                                      LookupOrdinaryName, S, 0, Validator)))
+                                      LookupOrdinaryName, S, 0, Validator,
+                                      CTK_NonError)))
       diagnoseTypo(Corrected, PDiag(diag::note_function_suggestion),
                    /*ErrorRecovery*/false);
   }
diff --git a/lib/Sema/SemaDeclCXX.cpp b/lib/Sema/SemaDeclCXX.cpp
index 197518f99e..e3bedf78e6 100644
--- a/lib/Sema/SemaDeclCXX.cpp
+++ b/lib/Sema/SemaDeclCXX.cpp
@@ -2605,7 +2605,7 @@ Sema::BuildMemInitializer(Decl *ConstructorD,
       MemInitializerValidatorCCC Validator(ClassDecl);
       if (R.empty() && BaseType.isNull() &&
           (Corr = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, &SS,
-                              Validator, ClassDecl))) {
+                              Validator, CTK_ErrorRecovery, 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
@@ -6900,7 +6900,8 @@ static bool TryNamespaceTypoCorrection(Sema &S, LookupResult &R, Scope *Sc,
   R.clear();
   if (TypoCorrection Corrected = S.CorrectTypo(R.getLookupNameInfo(),
                                                R.getLookupKind(), Sc, &SS,
-                                               Validator)) {
+                                               Validator,
+                                               Sema::CTK_ErrorRecovery)) {
     if (DeclContext *DC = S.computeDeclContext(SS, false)) {
       std::string CorrectedStr(Corrected.getAsString(S.getLangOpts()));
       bool DroppedSpecifier = Corrected.WillReplaceSpecifier() &&
@@ -7471,7 +7472,8 @@ NamedDecl *Sema::BuildUsingDeclaration(Scope *S, AccessSpecifier AS,
     UsingValidatorCCC CCC(HasTypenameKeyword, IsInstantiation,
                           CurContext->isRecord());
     if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
-                                               R.getLookupKind(), S, &SS, CCC)){
+                                               R.getLookupKind(), S, &SS, CCC,
+                                               CTK_ErrorRecovery)){
       // We reject any correction for which ND would be NULL.
       NamedDecl *ND = Corrected.getCorrectionDecl();
       R.setLookupName(Corrected.getCorrection());
diff --git a/lib/Sema/SemaDeclObjC.cpp b/lib/Sema/SemaDeclObjC.cpp
index d59dd8b995..7fbca6aadb 100644
--- a/lib/Sema/SemaDeclObjC.cpp
+++ b/lib/Sema/SemaDeclObjC.cpp
@@ -524,7 +524,7 @@ ActOnStartClassInterface(SourceLocation AtInterfaceLoc,
       ObjCInterfaceValidatorCCC Validator(IDecl);
       if (TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(SuperName, SuperLoc), LookupOrdinaryName, TUScope,
-          NULL, Validator)) {
+          NULL, Validator, CTK_ErrorRecovery)) {
         diagnoseTypo(Corrected, PDiag(diag::err_undef_superclass_suggest)
                                     << SuperName << ClassName);
         PrevDecl = Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>();
@@ -794,7 +794,7 @@ Sema::FindProtocolDeclaration(bool WarnOnDeclarations,
       DeclFilterCCC<ObjCProtocolDecl> Validator;
       TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(ProtocolId[i].first, ProtocolId[i].second),
-          LookupObjCProtocolName, TUScope, NULL, Validator);
+          LookupObjCProtocolName, TUScope, NULL, Validator, CTK_ErrorRecovery);
       if ((PDecl = Corrected.getCorrectionDeclAs<ObjCProtocolDecl>()))
         diagnoseTypo(Corrected, PDiag(diag::err_undeclared_protocol_suggest)
                                     << ProtocolId[i].first);
@@ -1034,7 +1034,8 @@ Decl *Sema::ActOnStartClassImplementation(
     ObjCInterfaceValidatorCCC Validator;
     TypoCorrection Corrected =
             CorrectTypo(DeclarationNameInfo(ClassName, ClassLoc),
-                        LookupOrdinaryName, TUScope, NULL, Validator);
+                        LookupOrdinaryName, TUScope, NULL, Validator,
+                        CTK_NonError);
     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
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index a38c7c1ef8..1c6cfb8484 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -1843,7 +1843,7 @@ bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
   // 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, CTK_ErrorRecovery))) {
     std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
     bool DroppedSpecifier =
         Corrected.WillReplaceSpecifier() && Name.getAsString() == CorrectedStr;
@@ -4004,7 +4004,8 @@ static TypoCorrection TryTypoCorrectionForCall(Sema &S, Expr *Fn,
 
   if (TypoCorrection Corrected = S.CorrectTypo(
           DeclarationNameInfo(FuncName, NameLoc), Sema::LookupOrdinaryName,
-          S.getScopeForContext(S.CurContext), NULL, CCC)) {
+          S.getScopeForContext(S.CurContext), NULL, CCC,
+          Sema::CTK_ErrorRecovery)) {
     if (NamedDecl *ND = Corrected.getCorrectionDecl()) {
       if (Corrected.isOverloaded()) {
         OverloadCandidateSet OCS(NameLoc, OverloadCandidateSet::CSK_Normal);
diff --git a/lib/Sema/SemaExprMember.cpp b/lib/Sema/SemaExprMember.cpp
index 675c69fa88..95e3668f33 100644
--- a/lib/Sema/SemaExprMember.cpp
+++ b/lib/Sema/SemaExprMember.cpp
@@ -627,7 +627,8 @@ LookupMemberExprInRecord(Sema &SemaRef, LookupResult &R,
   RecordMemberExprValidatorCCC Validator(RTy);
   TypoCorrection Corrected = SemaRef.CorrectTypo(R.getLookupNameInfo(),
                                                  R.getLookupKind(), NULL,
-                                                 &SS, Validator, DC);
+                                                 &SS, Validator,
+                                                 Sema::CTK_ErrorRecovery, DC);
   R.clear();
   if (Corrected.isResolved() && !Corrected.isKeyword()) {
     R.setLookupName(Corrected.getCorrection());
@@ -1270,7 +1271,8 @@ Sema::LookupMemberExpr(LookupResult &R, ExprResult &BaseExpr,
       Validator.IsObjCIvarLookup = IsArrow;
       if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
                                                  LookupMemberName, NULL, NULL,
-                                                 Validator, IDecl)) {
+                                                 Validator, CTK_ErrorRecovery,
+                                                 IDecl)) {
         IV = Corrected.getCorrectionDeclAs<ObjCIvarDecl>();
         diagnoseTypo(Corrected,
                      PDiag(diag::err_typecheck_member_reference_ivar_suggest)
diff --git a/lib/Sema/SemaExprObjC.cpp b/lib/Sema/SemaExprObjC.cpp
index d316c13f94..7b0db1cfc1 100644
--- a/lib/Sema/SemaExprObjC.cpp
+++ b/lib/Sema/SemaExprObjC.cpp
@@ -1669,7 +1669,7 @@ HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
   DeclFilterCCC<ObjCPropertyDecl> Validator;
   if (TypoCorrection Corrected = CorrectTypo(
           DeclarationNameInfo(MemberName, MemberLoc), LookupOrdinaryName, NULL,
-          NULL, Validator, IFace, false, OPT)) {
+          NULL, Validator, CTK_ErrorRecovery, IFace, false, OPT)) {
     diagnoseTypo(Corrected, PDiag(diag::err_property_not_found_suggest)
                               << MemberName << QualType(OPT, 0));
     DeclarationName TypoResult = Corrected.getCorrection();
@@ -1901,7 +1901,8 @@ Sema::ObjCMessageKind Sema::getObjCMessageKind(Scope *S,
   ObjCInterfaceOrSuperCCC Validator(getCurMethodDecl());
   if (TypoCorrection Corrected =
           CorrectTypo(Result.getLookupNameInfo(), Result.getLookupKind(), S,
-                      NULL, Validator, NULL, false, NULL, false)) {
+                      NULL, Validator, CTK_ErrorRecovery, 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.
diff --git a/lib/Sema/SemaInit.cpp b/lib/Sema/SemaInit.cpp
index 9c90ac0d9a..2cf5598581 100644
--- a/lib/Sema/SemaInit.cpp
+++ b/lib/Sema/SemaInit.cpp
@@ -1816,7 +1816,7 @@ InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
         if (TypoCorrection Corrected = SemaRef.CorrectTypo(
                 DeclarationNameInfo(FieldName, D->getFieldLoc()),
                 Sema::LookupMemberName, /*Scope=*/ 0, /*SS=*/ 0, Validator,
-                RT->getDecl())) {
+                Sema::CTK_ErrorRecovery, RT->getDecl())) {
           SemaRef.diagnoseTypo(
               Corrected,
               SemaRef.PDiag(diag::err_field_designator_unknown_suggest)
diff --git a/lib/Sema/SemaLookup.cpp b/lib/Sema/SemaLookup.cpp
index 779d2d48e7..c0d49a7dd9 100644
--- a/lib/Sema/SemaLookup.cpp
+++ b/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"
@@ -3924,6 +3929,7 @@ TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
                                  Sema::LookupNameKind LookupKind,
                                  Scope *S, CXXScopeSpec *SS,
                                  CorrectionCandidateCallback &CCC,
+                                 CorrectTypoKind Mode,
                                  DeclContext *MemberContext,
                                  bool EnteringContext,
                                  const ObjCObjectPointerType *OPT,
@@ -3978,10 +3984,36 @@ TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
   if (getLangOpts().AltiVec && Typo->isStr("vector"))
     return TypoCorrection();
 
-  NamespaceSpecifierSet Namespaces(Context, CurContext, SS);
-
   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 == CTK_ErrorRecovery) && !Loader.buildingModule() &&
+      getLangOpts().Modules && getLangOpts().ModulesSearchAll) {
+    // Load global module index, or retrieve a previously loaded one.
+    GlobalModuleIndex *GlobalIndex = Loader.loadGlobalModuleIndex(
+      TypoName.getLocStart());
+
+    // 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);
+
   // 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;
diff --git a/lib/Sema/SemaOpenMP.cpp b/lib/Sema/SemaOpenMP.cpp
index 0c592a6144..b4d359edb4 100644
--- a/lib/Sema/SemaOpenMP.cpp
+++ b/lib/Sema/SemaOpenMP.cpp
@@ -429,7 +429,7 @@ ExprResult Sema::ActOnOpenMPIdExpression(Scope *CurScope,
   if (!Lookup.isSingleResult()) {
     VarDeclFilterCCC Validator(*this);
     if (TypoCorrection Corrected = CorrectTypo(Id, LookupOrdinaryName, CurScope,
-                                               0, Validator)) {
+                                               0, Validator, CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(Lookup.empty()? diag::err_undeclared_var_use_suggest
                                        : diag::err_omp_expected_var_arg_suggest)
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index a7764d8df9..64c3263805 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -325,7 +325,8 @@ void Sema::LookupTemplateName(LookupResult &Found,
     FilterCCC.WantCXXNamedCasts = true;
     if (TypoCorrection Corrected = CorrectTypo(Found.getLookupNameInfo(),
                                                Found.getLookupKind(), S, &SS,
-                                               FilterCCC, LookupCtx)) {
+                                               FilterCCC, CTK_ErrorRecovery,
+                                               LookupCtx)) {
       Found.setLookupName(Corrected.getCorrection());
       if (Corrected.getCorrectionDecl())
         Found.addDecl(Corrected.getCorrectionDecl());
diff --git a/lib/Sema/SemaTemplateVariadic.cpp b/lib/Sema/SemaTemplateVariadic.cpp
index de850e3901..8439f9f7d0 100644
--- a/lib/Sema/SemaTemplateVariadic.cpp
+++ b/lib/Sema/SemaTemplateVariadic.cpp
@@ -810,7 +810,7 @@ ExprResult Sema::ActOnSizeofParameterPackExpr(Scope *S,
   case LookupResult::NotFoundInCurrentInstantiation:
     if (TypoCorrection Corrected = CorrectTypo(R.getLookupNameInfo(),
                                                R.getLookupKind(), S, 0,
-                                               Validator)) {
+                                               Validator, CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(diag::err_sizeof_pack_no_pack_name_suggest) << &Name,
                    PDiag(diag::note_parameter_pack_here));
diff --git a/test/Modules/Inputs/undefined-type-fixit/module.map b/test/Modules/Inputs/undefined-type-fixit/module.map
new file mode 100644
index 0000000000..f5ce34b8fc
--- /dev/null
+++ b/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"
+  }
+}
diff --git a/test/Modules/Inputs/undefined-type-fixit/public1.h b/test/Modules/Inputs/undefined-type-fixit/public1.h
new file mode 100644
index 0000000000..bc98ca9e0e
--- /dev/null
+++ b/test/Modules/Inputs/undefined-type-fixit/public1.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC1_H
+#define PUBLIC1_H
+
+struct use_this1 { int field; };
+
+#endif
diff --git a/test/Modules/Inputs/undefined-type-fixit/public2.h b/test/Modules/Inputs/undefined-type-fixit/public2.h
new file mode 100644
index 0000000000..2aa3e9614c
--- /dev/null
+++ b/test/Modules/Inputs/undefined-type-fixit/public2.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC2_H
+#define PUBLIC2_H
+
+struct use_this2 { int field; };
+
+#endif
diff --git a/test/Modules/Inputs/undefined-type-fixit/public2sub.h b/test/Modules/Inputs/undefined-type-fixit/public2sub.h
new file mode 100644
index 0000000000..4c8c3cce03
--- /dev/null
+++ b/test/Modules/Inputs/undefined-type-fixit/public2sub.h
@@ -0,0 +1,6 @@
+#ifndef PUBLIC2SUB_H
+#define PUBLIC2SUB_H
+
+struct use_this2sub { int field; };
+
+#endif
diff --git a/test/Modules/undefined-type-fixit1.cpp b/test/Modules/undefined-type-fixit1.cpp
new file mode 100644
index 0000000000..78ce174f54
--- /dev/null
+++ b/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}}
diff --git a/unittests/Basic/SourceManagerTest.cpp b/unittests/Basic/SourceManagerTest.cpp
index d94cfe9c3f..b3796c34fe 100644
--- a/unittests/Basic/SourceManagerTest.cpp
+++ b/unittests/Basic/SourceManagerTest.cpp
@@ -63,6 +63,9 @@ class VoidModuleLoader : public ModuleLoader {
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc)
+    { return 0; }
 };
 
 TEST_F(SourceManagerTest, isBeforeInTranslationUnit) {
diff --git a/unittests/Lex/CMakeLists.txt b/unittests/Lex/CMakeLists.txt
index 461e0d95fc..1fb57cfdfb 100644
--- a/unittests/Lex/CMakeLists.txt
+++ b/unittests/Lex/CMakeLists.txt
@@ -14,4 +14,5 @@ target_link_libraries(LexTests
   clangLex
   clangParse
   clangSema
+  clangSerialization
   )
diff --git a/unittests/Lex/LexerTest.cpp b/unittests/Lex/LexerTest.cpp
index 40ce928014..8aa95c966a 100644
--- a/unittests/Lex/LexerTest.cpp
+++ b/unittests/Lex/LexerTest.cpp
@@ -40,6 +40,9 @@ class VoidModuleLoader : public ModuleLoader {
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc)
+    { return 0; }
 };
 
 // The test fixture.
diff --git a/unittests/Lex/Makefile b/unittests/Lex/Makefile
index fa233ce25f..071d01c8b5 100644
--- a/unittests/Lex/Makefile
+++ b/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
diff --git a/unittests/Lex/PPCallbacksTest.cpp b/unittests/Lex/PPCallbacksTest.cpp
index e3a4a76a77..3c953c2091 100644
--- a/unittests/Lex/PPCallbacksTest.cpp
+++ b/unittests/Lex/PPCallbacksTest.cpp
@@ -45,6 +45,9 @@ class VoidModuleLoader : public ModuleLoader {
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc)
+    { return 0; }
 };
 
 // Stub to collect data from InclusionDirective callbacks.
diff --git a/unittests/Lex/PPConditionalDirectiveRecordTest.cpp b/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
index 58857fa5a1..4e22589069 100644
--- a/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
+++ b/unittests/Lex/PPConditionalDirectiveRecordTest.cpp
@@ -64,6 +64,9 @@ class VoidModuleLoader : public ModuleLoader {
                                  Module::NameVisibilityKind Visibility,
                                  SourceLocation ImportLoc,
                                  bool Complain) { }
+
+  virtual GlobalModuleIndex *loadGlobalModuleIndex(SourceLocation TriggerLoc)
+    { return 0; }
 };
 
 TEST_F(PPConditionalDirectiveRecordTest, PPRecAPI) {