[Sema][NFCI] Don't allocate storage for the various CorrectionCandidateCallback unless we are going to do some typo correction

The various CorrectionCandidateCallbacks are currently heap-allocated
unconditionally. This was needed because of delayed typo correction.
However these allocations represent currently 15.4% of all allocations
(number of allocations) when parsing all of Boost (!), mostly because
of ParseCastExpression, ParseStatementOrDeclarationAfterAttrtibutes
and isCXXDeclarationSpecifier. Note that all of these callback objects
are small. Let's not do this.

Instead initially allocate the callback on the stack, and only do a
heap allocation if we are going to do some typo correction. Do this by:

1. Adding a clone function to each callback, which will do a polymorphic
   clone of the callback. This clone function is required to be implemented
   by every callback (of which there is a fair amount). Make sure this is
   the case by making it pure virtual.

2. Use this clone function when we are going to try to correct a typo.

This additionally cut the time of -fsyntax-only on all of Boost by 0.5%
(not that much, but still something). No functional changes intended.

Differential Revision: https://reviews.llvm.org/D58827

Reviewed By: rnk



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@356925 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Parse/Parser.h

@@ -789,9 +789,8 @@ private:
     /// Annotation was successful.
     ANK_Success
   };
-  AnnotatedNameKind
-  TryAnnotateName(bool IsAddressOfOperand,
-                  std::unique_ptr<CorrectionCandidateCallback> CCC = nullptr);
+  AnnotatedNameKind TryAnnotateName(bool IsAddressOfOperand,
+                                    CorrectionCandidateCallback *CCC = nullptr);
 
   /// Push a tok::annot_cxxscope token onto the token stream.
   void AnnotateScopeToken(CXXScopeSpec &SS, bool IsNewAnnotation);

include/clang/Sema/Sema.h

@@ -1914,11 +1914,11 @@ public:
   ///        expression.
   ///
   /// \param CCC The correction callback, if typo correction is desired.
-  NameClassification
-  ClassifyName(Scope *S, CXXScopeSpec &SS, IdentifierInfo *&Name,
-               SourceLocation NameLoc, const Token &NextToken,
-               bool IsAddressOfOperand,
-               std::unique_ptr<CorrectionCandidateCallback> CCC = nullptr);
+  NameClassification ClassifyName(Scope *S, CXXScopeSpec &SS,
+                                  IdentifierInfo *&Name, SourceLocation NameLoc,
+                                  const Token &NextToken,
+                                  bool IsAddressOfOperand,
+                                  CorrectionCandidateCallback *CCC = nullptr);
 
   /// Describes the detailed kind of a template name. Used in diagnostics.
   enum class TemplateNameKindForDiagnostics {
@@ -3266,7 +3266,7 @@ private:
   makeTypoCorrectionConsumer(const DeclarationNameInfo &Typo,
                              Sema::LookupNameKind LookupKind, Scope *S,
                              CXXScopeSpec *SS,
-                             std::unique_ptr<CorrectionCandidateCallback> CCC,
+                             CorrectionCandidateCallback &CCC,
                              DeclContext *MemberContext, bool EnteringContext,
                              const ObjCObjectPointerType *OPT,
                              bool ErrorRecovery);
@@ -3350,7 +3350,7 @@ public:
   TypoCorrection CorrectTypo(const DeclarationNameInfo &Typo,
                              Sema::LookupNameKind LookupKind,
                              Scope *S, CXXScopeSpec *SS,
-                             std::unique_ptr<CorrectionCandidateCallback> CCC,
+                             CorrectionCandidateCallback &CCC,
                              CorrectTypoKind Mode,
                              DeclContext *MemberContext = nullptr,
                              bool EnteringContext = false,
@@ -3360,7 +3360,7 @@ public:
   TypoExpr *CorrectTypoDelayed(const DeclarationNameInfo &Typo,
                                Sema::LookupNameKind LookupKind, Scope *S,
                                CXXScopeSpec *SS,
-                               std::unique_ptr<CorrectionCandidateCallback> CCC,
+                               CorrectionCandidateCallback &CCC,
                                TypoDiagnosticGenerator TDG,
                                TypoRecoveryCallback TRC, CorrectTypoKind Mode,
                                DeclContext *MemberContext = nullptr,
@@ -4230,7 +4230,7 @@ public:
   ExprResult ActOnIdExpression(
       Scope *S, CXXScopeSpec &SS, SourceLocation TemplateKWLoc,
       UnqualifiedId &Id, bool HasTrailingLParen, bool IsAddressOfOperand,
-      std::unique_ptr<CorrectionCandidateCallback> CCC = nullptr,
+      CorrectionCandidateCallback *CCC = nullptr,
       bool IsInlineAsmIdentifier = false, Token *KeywordReplacement = nullptr);
 
   void DecomposeUnqualifiedId(const UnqualifiedId &Id,
@@ -4240,7 +4240,7 @@ public:
 
   bool
   DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
-                      std::unique_ptr<CorrectionCandidateCallback> CCC,
+                      CorrectionCandidateCallback &CCC,
                       TemplateArgumentListInfo *ExplicitTemplateArgs = nullptr,
                       ArrayRef<Expr *> Args = None, TypoExpr **Out = nullptr);
 

include/clang/Sema/TypoCorrection.h

@@ -312,6 +312,13 @@ public:
                : InvalidDistance;
   }
 
+  /// Clone this CorrectionCandidateCallback. CorrectionCandidateCallbacks are
+  /// initially stack-allocated. However in case where delayed typo-correction
+  /// is done we need to move the callback to storage with a longer lifetime.
+  /// Every class deriving from CorrectionCandidateCallback must implement
+  /// this method.
+  virtual std::unique_ptr<CorrectionCandidateCallback> clone() = 0;
+
   void setTypoName(IdentifierInfo *II) { Typo = II; }
   void setTypoNNS(NestedNameSpecifier *NNS) { TypoNNS = NNS; }
 
@@ -342,14 +349,28 @@ protected:
   NestedNameSpecifier *TypoNNS;
 };
 
+class DefaultFilterCCC final : public CorrectionCandidateCallback {
+public:
+  explicit DefaultFilterCCC(IdentifierInfo *Typo = nullptr,
+                            NestedNameSpecifier *TypoNNS = nullptr)
+      : CorrectionCandidateCallback(Typo, TypoNNS) {}
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<DefaultFilterCCC>(*this);
+  }
+};
+
 /// Simple template class for restricting typo correction candidates
 /// to ones having a single Decl* of the given type.
 template <class C>
-class DeclFilterCCC : public CorrectionCandidateCallback {
+class DeclFilterCCC final : public CorrectionCandidateCallback {
 public:
   bool ValidateCandidate(const TypoCorrection &candidate) override {
     return candidate.getCorrectionDeclAs<C>();
   }
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<DeclFilterCCC>(*this);
+  }
 };
 
 // Callback class to limit the allowed keywords and to only accept typo
@@ -362,6 +383,9 @@ public:
                         MemberExpr *ME = nullptr);
 
   bool ValidateCandidate(const TypoCorrection &candidate) override;
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<FunctionCallFilterCCC>(*this);
+  }
 
 private:
   unsigned NumArgs;
@@ -371,7 +395,7 @@ private:
 };
 
 // Callback class that effectively disabled typo correction
-class NoTypoCorrectionCCC : public CorrectionCandidateCallback {
+class NoTypoCorrectionCCC final : public CorrectionCandidateCallback {
 public:
   NoTypoCorrectionCCC() {
     WantTypeSpecifiers = false;
@@ -384,6 +408,9 @@ public:
   bool ValidateCandidate(const TypoCorrection &candidate) override {
     return false;
   }
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<NoTypoCorrectionCCC>(*this);
+  }
 };
 
 } // namespace clang

lib/Parse/ParseDecl.cpp

@@ -2854,7 +2854,7 @@ Parser::DiagnoseMissingSemiAfterTagDefinition(DeclSpec &DS, AccessSpecifier AS,
       IdentifierInfo *Name = AfterScope.getIdentifierInfo();
       Sema::NameClassification Classification = Actions.ClassifyName(
           getCurScope(), SS, Name, AfterScope.getLocation(), Next,
-          /*IsAddressOfOperand*/false);
+          /*IsAddressOfOperand=*/false, /*CCC=*/nullptr);
       switch (Classification.getKind()) {
       case Sema::NC_Error:
         SkipMalformedDecl();

lib/Parse/ParseExpr.cpp

@@ -543,7 +543,7 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
 }
 
 namespace {
-class CastExpressionIdValidator : public CorrectionCandidateCallback {
+class CastExpressionIdValidator final : public CorrectionCandidateCallback {
  public:
   CastExpressionIdValidator(Token Next, bool AllowTypes, bool AllowNonTypes)
       : NextToken(Next), AllowNonTypes(AllowNonTypes) {
@@ -572,6 +572,10 @@ class CastExpressionIdValidator : public CorrectionCandidateCallback {
     return false;
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<CastExpressionIdValidator>(*this);
+  }
+
  private:
   Token NextToken;
   bool AllowNonTypes;
@@ -1041,19 +1045,21 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
     CXXScopeSpec ScopeSpec;
     SourceLocation TemplateKWLoc;
     Token Replacement;
-    auto Validator = llvm::make_unique<CastExpressionIdValidator>(
-        Tok, isTypeCast != NotTypeCast, isTypeCast != IsTypeCast);
-    Validator->IsAddressOfOperand = isAddressOfOperand;
+    CastExpressionIdValidator Validator(
+        /*Next=*/Tok,
+        /*AllowTypes=*/isTypeCast != NotTypeCast,
+        /*AllowNonTypes=*/isTypeCast != IsTypeCast);
+    Validator.IsAddressOfOperand = isAddressOfOperand;
     if (Tok.isOneOf(tok::periodstar, tok::arrowstar)) {
-      Validator->WantExpressionKeywords = false;
-      Validator->WantRemainingKeywords = false;
+      Validator.WantExpressionKeywords = false;
+      Validator.WantRemainingKeywords = false;
     } else {
-      Validator->WantRemainingKeywords = Tok.isNot(tok::r_paren);
+      Validator.WantRemainingKeywords = Tok.isNot(tok::r_paren);
     }
     Name.setIdentifier(&II, ILoc);
     Res = Actions.ActOnIdExpression(
         getCurScope(), ScopeSpec, TemplateKWLoc, Name, Tok.is(tok::l_paren),
-        isAddressOfOperand, std::move(Validator),
+        isAddressOfOperand, &Validator,
         /*IsInlineAsmIdentifier=*/false,
         Tok.is(tok::r_paren) ? nullptr : &Replacement);
     if (!Res.isInvalid() && Res.isUnset()) {

lib/Parse/ParseExprCXX.cpp

@@ -563,7 +563,7 @@ ExprResult Parser::tryParseCXXIdExpression(CXXScopeSpec &SS, bool isAddressOfOpe
 
   ExprResult E = Actions.ActOnIdExpression(
       getCurScope(), SS, TemplateKWLoc, Name, Tok.is(tok::l_paren),
-      isAddressOfOperand, nullptr, /*IsInlineAsmIdentifier=*/false,
+      isAddressOfOperand, /*CCC=*/nullptr, /*IsInlineAsmIdentifier=*/false,
       &Replacement);
   if (!E.isInvalid() && !E.isUnset() && Tok.is(tok::less))
     checkPotentialAngleBracket(E);

lib/Parse/ParseStmt.cpp

@@ -116,7 +116,7 @@ Parser::ParseStatementOrDeclaration(StmtVector &Stmts,
 }
 
 namespace {
-class StatementFilterCCC : public CorrectionCandidateCallback {
+class StatementFilterCCC final : public CorrectionCandidateCallback {
 public:
   StatementFilterCCC(Token nextTok) : NextToken(nextTok) {
     WantTypeSpecifiers = nextTok.isOneOf(tok::l_paren, tok::less, tok::l_square,
@@ -139,6 +139,10 @@ public:
     return CorrectionCandidateCallback::ValidateCandidate(candidate);
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<StatementFilterCCC>(*this);
+  }
+
 private:
   Token NextToken;
 };
@@ -181,9 +185,8 @@ Retry:
     if (Next.isNot(tok::coloncolon)) {
       // Try to limit which sets of keywords should be included in typo
       // correction based on what the next token is.
-      if (TryAnnotateName(/*IsAddressOfOperand*/ false,
-                          llvm::make_unique<StatementFilterCCC>(Next)) ==
-          ANK_Error) {
+      StatementFilterCCC CCC(Next);
+      if (TryAnnotateName(/*IsAddressOfOperand*/ false, &CCC) == ANK_Error) {
         // Handle errors here by skipping up to the next semicolon or '}', and
         // eat the semicolon if that's what stopped us.
         SkipUntil(tok::r_brace, StopAtSemi | StopBeforeMatch);

lib/Parse/ParseTentative.cpp

@@ -1147,7 +1147,7 @@ bool Parser::isTentativelyDeclared(IdentifierInfo *II) {
 }
 
 namespace {
-class TentativeParseCCC : public CorrectionCandidateCallback {
+class TentativeParseCCC final : public CorrectionCandidateCallback {
 public:
   TentativeParseCCC(const Token &Next) {
     WantRemainingKeywords = false;
@@ -1165,6 +1165,10 @@ public:
 
     return CorrectionCandidateCallback::ValidateCandidate(Candidate);
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<TentativeParseCCC>(*this);
+  }
 };
 }
 /// isCXXDeclarationSpecifier - Returns TPResult::True if it is a declaration
@@ -1293,8 +1297,8 @@ Parser::isCXXDeclarationSpecifier(Parser::TPResult BracedCastResult,
       // a parse error one way or another. In that case, tell the caller that
       // this is ambiguous. Typo-correct to type and expression keywords and
       // to types and identifiers, in order to try to recover from errors.
-      switch (TryAnnotateName(false /* no nested name specifier */,
-                              llvm::make_unique<TentativeParseCCC>(Next))) {
+      TentativeParseCCC CCC(Next);
+      switch (TryAnnotateName(false /* no nested name specifier */, &CCC)) {
       case ANK_Error:
         return TPResult::Error;
       case ANK_TentativeDecl:

lib/Parse/Parser.cpp

@@ -1487,7 +1487,7 @@ void Parser::AnnotateScopeToken(CXXScopeSpec &SS, bool IsNewAnnotation) {
 ///        no typo correction will be performed.
 Parser::AnnotatedNameKind
 Parser::TryAnnotateName(bool IsAddressOfOperand,
-                        std::unique_ptr<CorrectionCandidateCallback> CCC) {
+                        CorrectionCandidateCallback *CCC) {
   assert(Tok.is(tok::identifier) || Tok.is(tok::annot_cxxscope));
 
   const bool EnteringContext = false;
@@ -1523,9 +1523,9 @@ Parser::TryAnnotateName(bool IsAddressOfOperand,
   // after a scope specifier, because in general we can't recover from typos
   // there (eg, after correcting 'A::template B<X>::C' [sic], we would need to
   // jump back into scope specifier parsing).
-  Sema::NameClassification Classification = Actions.ClassifyName(
-      getCurScope(), SS, Name, NameLoc, Next, IsAddressOfOperand,
-      SS.isEmpty() ? std::move(CCC) : nullptr);
+  Sema::NameClassification Classification =
+      Actions.ClassifyName(getCurScope(), SS, Name, NameLoc, Next,
+                           IsAddressOfOperand, SS.isEmpty() ? CCC : nullptr);
 
   switch (Classification.getKind()) {
   case Sema::NC_Error:

lib/Sema/SemaCXXScopeSpec.cpp

@@ -429,8 +429,9 @@ namespace {
 
 // Callback to only accept typo corrections that can be a valid C++ member
 // intializer: either a non-static field member or a base class.
-class NestedNameSpecifierValidatorCCC : public CorrectionCandidateCallback {
- public:
+class NestedNameSpecifierValidatorCCC final
+    : public CorrectionCandidateCallback {
+public:
   explicit NestedNameSpecifierValidatorCCC(Sema &SRef)
       : SRef(SRef) {}
 
@@ -438,6 +439,10 @@ class NestedNameSpecifierValidatorCCC : public CorrectionCandidateCallback {
     return SRef.isAcceptableNestedNameSpecifier(candidate.getCorrectionDecl());
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<NestedNameSpecifierValidatorCCC>(*this);
+  }
+
  private:
   Sema &SRef;
 };
@@ -614,9 +619,9 @@ bool Sema::BuildCXXNestedNameSpecifier(Scope *S, NestedNameSpecInfo &IdInfo,
     // different kind of error, so look for typos.
     DeclarationName Name = Found.getLookupName();
     Found.clear();
+    NestedNameSpecifierValidatorCCC CCC(*this);
     if (TypoCorrection Corrected = CorrectTypo(
-            Found.getLookupNameInfo(), Found.getLookupKind(), S, &SS,
-            llvm::make_unique<NestedNameSpecifierValidatorCCC>(*this),
+            Found.getLookupNameInfo(), Found.getLookupKind(), S, &SS, CCC,
             CTK_ErrorRecovery, LookupCtx, EnteringContext)) {
       if (LookupCtx) {
         bool DroppedSpecifier =

lib/Sema/SemaCodeComplete.cpp

@@ -6407,8 +6407,9 @@ void Sema::CodeCompleteObjCSuperMessage(Scope *S, SourceLocation SuperLoc,
       SourceLocation TemplateKWLoc;
       UnqualifiedId id;
       id.setIdentifier(Super, SuperLoc);
-      ExprResult SuperExpr =
-          ActOnIdExpression(S, SS, TemplateKWLoc, id, false, false);
+      ExprResult SuperExpr = ActOnIdExpression(S, SS, TemplateKWLoc, id,
+                                               /*HasTrailingLParen=*/false,
+                                               /*IsAddressOfOperand=*/false);
       return CodeCompleteObjCInstanceMessage(S, (Expr *)SuperExpr.get(),
                                              SelIdents, AtArgumentExpression);
     }

lib/Sema/SemaDecl.cpp

@@ -61,7 +61,7 @@ Sema::DeclGroupPtrTy Sema::ConvertDeclToDeclGroup(Decl *Ptr, Decl *OwnedType) {
 
 namespace {
 
-class TypeNameValidatorCCC : public CorrectionCandidateCallback {
+class TypeNameValidatorCCC final : public CorrectionCandidateCallback {
  public:
    TypeNameValidatorCCC(bool AllowInvalid, bool WantClass = false,
                         bool AllowTemplates = false,
@@ -105,6 +105,10 @@ class TypeNameValidatorCCC : public CorrectionCandidateCallback {
     return !WantClassName && candidate.isKeyword();
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<TypeNameValidatorCCC>(*this);
+  }
+
  private:
   bool AllowInvalidDecl;
   bool WantClassName;
@@ -367,11 +371,10 @@ ParsedType Sema::getTypeName(const IdentifierInfo &II, SourceLocation NameLoc,
   case LookupResult::NotFound:
   case LookupResult::NotFoundInCurrentInstantiation:
     if (CorrectedII) {
-      TypoCorrection Correction =
-          CorrectTypo(Result.getLookupNameInfo(), Kind, S, SS,
-                      llvm::make_unique<TypeNameValidatorCCC>(
-                          true, isClassName, AllowDeducedTemplate),
-                      CTK_ErrorRecovery);
+      TypeNameValidatorCCC CCC(/*AllowInvalid=*/true, isClassName,
+                               AllowDeducedTemplate);
+      TypoCorrection Correction = CorrectTypo(Result.getLookupNameInfo(), Kind,
+                                              S, SS, CCC, CTK_ErrorRecovery);
       IdentifierInfo *NewII = Correction.getCorrectionAsIdentifierInfo();
       TemplateTy Template;
       bool MemberOfUnknownSpecialization;
@@ -664,11 +667,12 @@ void Sema::DiagnoseUnknownTypeName(IdentifierInfo *&II,
 
   // There may have been a typo in the name of the type. Look up typo
   // results, in case we have something that we can suggest.
+  TypeNameValidatorCCC CCC(/*AllowInvalid=*/false, /*WantClass=*/false,
+                           /*AllowTemplates=*/IsTemplateName,
+                           /*AllowNonTemplates=*/!IsTemplateName);
   if (TypoCorrection Corrected =
           CorrectTypo(DeclarationNameInfo(II, IILoc), LookupOrdinaryName, S, SS,
-                      llvm::make_unique<TypeNameValidatorCCC>(
-                          false, false, IsTemplateName, !IsTemplateName),
-                      CTK_ErrorRecovery)) {
+                      CCC, CTK_ErrorRecovery)) {
     // FIXME: Support error recovery for the template-name case.
     bool CanRecover = !IsTemplateName;
     if (Corrected.isKeyword()) {
@@ -843,8 +847,7 @@ static ParsedType buildNestedType(Sema &S, CXXScopeSpec &SS,
 Sema::NameClassification
 Sema::ClassifyName(Scope *S, CXXScopeSpec &SS, IdentifierInfo *&Name,
                    SourceLocation NameLoc, const Token &NextToken,
-                   bool IsAddressOfOperand,
-                   std::unique_ptr<CorrectionCandidateCallback> CCC) {
+                   bool IsAddressOfOperand, CorrectionCandidateCallback *CCC) {
   DeclarationNameInfo NameInfo(Name, NameLoc);
   ObjCMethodDecl *CurMethod = getCurMethodDecl();
 
@@ -926,10 +929,9 @@ Corrected:
     // close to this name.
     if (!SecondTry && CCC) {
       SecondTry = true;
-      if (TypoCorrection Corrected = CorrectTypo(Result.getLookupNameInfo(),
-                                                 Result.getLookupKind(), S,
-                                                 &SS, std::move(CCC),
-                                                 CTK_ErrorRecovery)) {
+      if (TypoCorrection Corrected =
+              CorrectTypo(Result.getLookupNameInfo(), Result.getLookupKind(), S,
+                          &SS, *CCC, CTK_ErrorRecovery)) {
         unsigned UnqualifiedDiag = diag::err_undeclared_var_use_suggest;
         unsigned QualifiedDiag = diag::err_no_member_suggest;
 
@@ -1865,10 +1867,10 @@ ObjCInterfaceDecl *Sema::getObjCInterfaceDecl(IdentifierInfo *&Id,
   if (!IDecl && DoTypoCorrection) {
     // Perform typo correction at the given location, but only if we
     // find an Objective-C class name.
-    if (TypoCorrection C = CorrectTypo(
-            DeclarationNameInfo(Id, IdLoc), LookupOrdinaryName, TUScope, nullptr,
-            llvm::make_unique<DeclFilterCCC<ObjCInterfaceDecl>>(),
-            CTK_ErrorRecovery)) {
+    DeclFilterCCC<ObjCInterfaceDecl> CCC{};
+    if (TypoCorrection C =
+            CorrectTypo(DeclarationNameInfo(Id, IdLoc), LookupOrdinaryName,
+                        TUScope, nullptr, CCC, CTK_ErrorRecovery)) {
       diagnoseTypo(C, PDiag(diag::err_undef_interface_suggest) << Id);
       IDecl = C.getCorrectionDeclAs<ObjCInterfaceDecl>();
       Id = IDecl->getIdentifier();
@@ -7688,7 +7690,7 @@ namespace {
 
 // Callback to only accept typo corrections that have a non-zero edit distance.
 // Also only accept corrections that have the same parent decl.
-class DifferentNameValidatorCCC : public CorrectionCandidateCallback {
+class DifferentNameValidatorCCC final : public CorrectionCandidateCallback {
  public:
   DifferentNameValidatorCCC(ASTContext &Context, FunctionDecl *TypoFD,
                             CXXRecordDecl *Parent)
@@ -7720,6 +7722,10 @@ class DifferentNameValidatorCCC : public CorrectionCandidateCallback {
     return false;
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<DifferentNameValidatorCCC>(*this);
+  }
+
  private:
   ASTContext &Context;
   FunctionDecl *OriginalFD;
@@ -7767,6 +7773,8 @@ static NamedDecl *DiagnoseInvalidRedeclaration(
   assert(!Prev.isAmbiguous() &&
          "Cannot have an ambiguity in previous-declaration lookup");
   CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
+  DifferentNameValidatorCCC CCC(SemaRef.Context, NewFD,
+                                MD ? MD->getParent() : nullptr);
   if (!Prev.empty()) {
     for (LookupResult::iterator Func = Prev.begin(), FuncEnd = Prev.end();
          Func != FuncEnd; ++Func) {
@@ -7783,10 +7791,8 @@ static NamedDecl *DiagnoseInvalidRedeclaration(
   // If the qualified name lookup yielded nothing, try typo correction
   } else if ((Correction = SemaRef.CorrectTypo(
                   Prev.getLookupNameInfo(), Prev.getLookupKind(), S,
-                  &ExtraArgs.D.getCXXScopeSpec(),
-                  llvm::make_unique<DifferentNameValidatorCCC>(
-                      SemaRef.Context, NewFD, MD ? MD->getParent() : nullptr),
-                  Sema::CTK_ErrorRecovery, IsLocalFriend ? nullptr : NewDC))) {
+                  &ExtraArgs.D.getCXXScopeSpec(), CCC, Sema::CTK_ErrorRecovery,
+                  IsLocalFriend ? nullptr : NewDC))) {
     // Set up everything for the call to ActOnFunctionDeclarator
     ExtraArgs.D.SetIdentifier(Correction.getCorrectionAsIdentifierInfo(),
                               ExtraArgs.D.getIdentifierLoc());
@@ -13538,10 +13544,10 @@ NamedDecl *Sema::ImplicitlyDefineFunction(SourceLocation Loc,
   // function declaration is going to be treated as an error.
   if (Diags.getDiagnosticLevel(diag_id, Loc) >= DiagnosticsEngine::Error) {
     TypoCorrection Corrected;
-    if (S &&
-        (Corrected = CorrectTypo(
-             DeclarationNameInfo(&II, Loc), LookupOrdinaryName, S, nullptr,
-             llvm::make_unique<DeclFilterCCC<FunctionDecl>>(), CTK_NonError)))
+    DeclFilterCCC<FunctionDecl> CCC{};
+    if (S && (Corrected =
+                  CorrectTypo(DeclarationNameInfo(&II, Loc), LookupOrdinaryName,
+                              S, nullptr, CCC, CTK_NonError)))
       diagnoseTypo(Corrected, PDiag(diag::note_function_suggestion),
                    /*ErrorRecovery*/false);
   }

lib/Sema/SemaDeclCXX.cpp

@@ -3781,7 +3781,7 @@ namespace {
 
 // Callback to only accept typo corrections that can be a valid C++ member
 // intializer: either a non-static field member or a base class.
-class MemInitializerValidatorCCC : public CorrectionCandidateCallback {
+class MemInitializerValidatorCCC final : public CorrectionCandidateCallback {
 public:
   explicit MemInitializerValidatorCCC(CXXRecordDecl *ClassDecl)
       : ClassDecl(ClassDecl) {}
@@ -3795,6 +3795,10 @@ public:
     return false;
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<MemInitializerValidatorCCC>(*this);
+  }
+
 private:
   CXXRecordDecl *ClassDecl;
 };
@@ -3924,11 +3928,10 @@ Sema::BuildMemInitializer(Decl *ConstructorD,
 
       // If no results were found, try to correct typos.
       TypoCorrection Corr;
+      MemInitializerValidatorCCC CCC(ClassDecl);
       if (R.empty() && BaseType.isNull() &&
-          (Corr = CorrectTypo(
-               R.getLookupNameInfo(), R.getLookupKind(), S, &SS,
-               llvm::make_unique<MemInitializerValidatorCCC>(ClassDecl),
-               CTK_ErrorRecovery, ClassDecl))) {
+          (Corr = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, &SS,
+                              CCC, 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
@@ -9353,13 +9356,17 @@ static bool IsUsingDirectiveInToplevelContext(DeclContext *CurContext) {
 namespace {
 
 // Callback to only accept typo corrections that are namespaces.
-class NamespaceValidatorCCC : public CorrectionCandidateCallback {
+class NamespaceValidatorCCC final : public CorrectionCandidateCallback {
 public:
   bool ValidateCandidate(const TypoCorrection &candidate) override {
     if (NamedDecl *ND = candidate.getCorrectionDecl())
       return isa<NamespaceDecl>(ND) || isa<NamespaceAliasDecl>(ND);
     return false;
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<NamespaceValidatorCCC>(*this);
+  }
 };
 
 }
@@ -9369,9 +9376,9 @@ static bool TryNamespaceTypoCorrection(Sema &S, LookupResult &R, Scope *Sc,
                                        SourceLocation IdentLoc,
                                        IdentifierInfo *Ident) {
   R.clear();
+  NamespaceValidatorCCC CCC{};
   if (TypoCorrection Corrected =
-          S.CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), Sc, &SS,
-                        llvm::make_unique<NamespaceValidatorCCC>(),
+          S.CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), Sc, &SS, CCC,
                         Sema::CTK_ErrorRecovery)) {
     if (DeclContext *DC = S.computeDeclContext(SS, false)) {
       std::string CorrectedStr(Corrected.getAsString(S.getLangOpts()));
@@ -9866,7 +9873,7 @@ static CXXBaseSpecifier *findDirectBaseWithType(CXXRecordDecl *Derived,
 }
 
 namespace {
-class UsingValidatorCCC : public CorrectionCandidateCallback {
+class UsingValidatorCCC final : public CorrectionCandidateCallback {
 public:
   UsingValidatorCCC(bool HasTypenameKeyword, bool IsInstantiation,
                     NestedNameSpecifier *NNS, CXXRecordDecl *RequireMemberOf)
@@ -9936,6 +9943,10 @@ public:
     return !HasTypenameKeyword;
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<UsingValidatorCCC>(*this);
+  }
+
 private:
   bool HasTypenameKeyword;
   bool IsInstantiation;
@@ -10092,12 +10103,11 @@ NamedDecl *Sema::BuildUsingDeclaration(
         isa<TranslationUnitDecl>(LookupContext) &&
         getSourceManager().isInSystemHeader(UsingLoc))
       return nullptr;
-    if (TypoCorrection Corrected = CorrectTypo(
-            R.getLookupNameInfo(), R.getLookupKind(), S, &SS,
-            llvm::make_unique<UsingValidatorCCC>(
-                HasTypenameKeyword, IsInstantiation, SS.getScopeRep(),
-                dyn_cast<CXXRecordDecl>(CurContext)),
-            CTK_ErrorRecovery)) {
+    UsingValidatorCCC CCC(HasTypenameKeyword, IsInstantiation, SS.getScopeRep(),
+                          dyn_cast<CXXRecordDecl>(CurContext));
+    if (TypoCorrection Corrected =
+            CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, &SS, CCC,
+                        CTK_ErrorRecovery)) {
       // We reject candidates where DroppedSpecifier == true, hence the
       // literal '0' below.
       diagnoseTypo(Corrected, PDiag(diag::err_no_member_suggest)

lib/Sema/SemaDeclObjC.cpp

@@ -499,7 +499,7 @@ namespace {
 // Callback to only accept typo corrections that are Objective-C classes.
 // If an ObjCInterfaceDecl* is given to the constructor, then the validation
 // function will reject corrections to that class.
-class ObjCInterfaceValidatorCCC : public CorrectionCandidateCallback {
+class ObjCInterfaceValidatorCCC final : public CorrectionCandidateCallback {
  public:
   ObjCInterfaceValidatorCCC() : CurrentIDecl(nullptr) {}
   explicit ObjCInterfaceValidatorCCC(ObjCInterfaceDecl *IDecl)
@@ -510,6 +510,10 @@ class ObjCInterfaceValidatorCCC : public CorrectionCandidateCallback {
     return ID && !declaresSameEntity(ID, CurrentIDecl);
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<ObjCInterfaceValidatorCCC>(*this);
+  }
+
  private:
   ObjCInterfaceDecl *CurrentIDecl;
 };
@@ -549,11 +553,10 @@ ActOnSuperClassOfClassInterface(Scope *S,
   if (!PrevDecl) {
     // Try to correct for a typo in the superclass name without correcting
     // to the class we're defining.
+    ObjCInterfaceValidatorCCC CCC(IDecl);
     if (TypoCorrection Corrected = CorrectTypo(
-            DeclarationNameInfo(SuperName, SuperLoc),
-            LookupOrdinaryName, TUScope,
-            nullptr, llvm::make_unique<ObjCInterfaceValidatorCCC>(IDecl),
-            CTK_ErrorRecovery)) {
+            DeclarationNameInfo(SuperName, SuperLoc), LookupOrdinaryName,
+            TUScope, nullptr, CCC, CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected, PDiag(diag::err_undef_superclass_suggest)
                    << SuperName << ClassName);
       PrevDecl = Corrected.getCorrectionDeclAs<ObjCInterfaceDecl>();
@@ -1292,11 +1295,10 @@ Sema::FindProtocolDeclaration(bool WarnOnDeclarations, bool ForObjCContainer,
   for (const IdentifierLocPair &Pair : ProtocolId) {
     ObjCProtocolDecl *PDecl = LookupProtocol(Pair.first, Pair.second);
     if (!PDecl) {
+      DeclFilterCCC<ObjCProtocolDecl> CCC{};
       TypoCorrection Corrected = CorrectTypo(
-          DeclarationNameInfo(Pair.first, Pair.second),
-          LookupObjCProtocolName, TUScope, nullptr,
-          llvm::make_unique<DeclFilterCCC<ObjCProtocolDecl>>(),
-          CTK_ErrorRecovery);
+          DeclarationNameInfo(Pair.first, Pair.second), LookupObjCProtocolName,
+          TUScope, nullptr, CCC, CTK_ErrorRecovery);
       if ((PDecl = Corrected.getCorrectionDeclAs<ObjCProtocolDecl>()))
         diagnoseTypo(Corrected, PDiag(diag::err_undeclared_protocol_suggest)
                                     << Pair.first);
@@ -1334,7 +1336,8 @@ Sema::FindProtocolDeclaration(bool WarnOnDeclarations, bool ForObjCContainer,
 namespace {
 // Callback to only accept typo corrections that are either
 // Objective-C protocols or valid Objective-C type arguments.
-class ObjCTypeArgOrProtocolValidatorCCC : public CorrectionCandidateCallback {
+class ObjCTypeArgOrProtocolValidatorCCC final
+    : public CorrectionCandidateCallback {
   ASTContext &Context;
   Sema::LookupNameKind LookupKind;
  public:
@@ -1381,6 +1384,10 @@ class ObjCTypeArgOrProtocolValidatorCCC : public CorrectionCandidateCallback {
 
     return false;
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<ObjCTypeArgOrProtocolValidatorCCC>(*this);
+  }
 };
 } // end anonymous namespace
 
@@ -1670,12 +1677,10 @@ void Sema::actOnObjCTypeArgsOrProtocolQualifiers(
     }
 
     // Perform typo correction on the name.
-    TypoCorrection corrected = CorrectTypo(
-        DeclarationNameInfo(identifiers[i], identifierLocs[i]), lookupKind, S,
-        nullptr,
-        llvm::make_unique<ObjCTypeArgOrProtocolValidatorCCC>(Context,
-                                                             lookupKind),
-        CTK_ErrorRecovery);
+    ObjCTypeArgOrProtocolValidatorCCC CCC(Context, lookupKind);
+    TypoCorrection corrected =
+        CorrectTypo(DeclarationNameInfo(identifiers[i], identifierLocs[i]),
+                    lookupKind, S, nullptr, CCC, CTK_ErrorRecovery);
     if (corrected) {
       // Did we find a protocol?
       if (auto proto = corrected.getCorrectionDeclAs<ObjCProtocolDecl>()) {
@@ -1967,9 +1972,10 @@ Decl *Sema::ActOnStartClassImplementation(
   } else {
     // We did not find anything with the name ClassName; try to correct for
     // typos in the class name.
-    TypoCorrection Corrected = CorrectTypo(
-        DeclarationNameInfo(ClassName, ClassLoc), LookupOrdinaryName, TUScope,
-        nullptr, llvm::make_unique<ObjCInterfaceValidatorCCC>(), CTK_NonError);
+    ObjCInterfaceValidatorCCC CCC{};
+    TypoCorrection Corrected =
+        CorrectTypo(DeclarationNameInfo(ClassName, ClassLoc),
+                    LookupOrdinaryName, TUScope, nullptr, CCC, 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

lib/Sema/SemaExpr.cpp

@@ -911,8 +911,9 @@ ExprResult Sema::DefaultVariadicArgumentPromotion(Expr *E, VariadicCallType CT,
     UnqualifiedId Name;
     Name.setIdentifier(PP.getIdentifierInfo("__builtin_trap"),
                        E->getBeginLoc());
-    ExprResult TrapFn = ActOnIdExpression(TUScope, SS, TemplateKWLoc,
-                                          Name, true, false);
+    ExprResult TrapFn = ActOnIdExpression(TUScope, SS, TemplateKWLoc, Name,
+                                          /*HasTrailingLParen=*/true,
+                                          /*IsAddressOfOperand=*/false);
     if (TrapFn.isInvalid())
       return ExprError();
 
@@ -1905,11 +1906,10 @@ static void emitEmptyLookupTypoDiagnostic(
 /// Diagnose an empty lookup.
 ///
 /// \return false if new lookup candidates were found
-bool
-Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
-                          std::unique_ptr<CorrectionCandidateCallback> CCC,
-                          TemplateArgumentListInfo *ExplicitTemplateArgs,
-                          ArrayRef<Expr *> Args, TypoExpr **Out) {
+bool Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
+                               CorrectionCandidateCallback &CCC,
+                               TemplateArgumentListInfo *ExplicitTemplateArgs,
+                               ArrayRef<Expr *> Args, TypoExpr **Out) {
   DeclarationName Name = R.getLookupName();
 
   unsigned diagnostic = diag::err_undeclared_var_use;
@@ -1998,7 +1998,7 @@ Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
     assert(!ExplicitTemplateArgs &&
            "Diagnosing an empty lookup with explicit template args!");
     *Out = CorrectTypoDelayed(
-        R.getLookupNameInfo(), R.getLookupKind(), S, &SS, std::move(CCC),
+        R.getLookupNameInfo(), R.getLookupKind(), S, &SS, CCC,
         [=](const TypoCorrection &TC) {
           emitEmptyLookupTypoDiagnostic(TC, *this, SS, Name, TypoLoc, Args,
                                         diagnostic, diagnostic_suggest);
@@ -2006,9 +2006,9 @@ Sema::DiagnoseEmptyLookup(Scope *S, CXXScopeSpec &SS, LookupResult &R,
         nullptr, CTK_ErrorRecovery);
     if (*Out)
       return true;
-  } else if (S && (Corrected =
-                       CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S,
-                                   &SS, std::move(CCC), CTK_ErrorRecovery))) {
+  } else if (S &&
+             (Corrected = CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(),
+                                      S, &SS, CCC, CTK_ErrorRecovery))) {
     std::string CorrectedStr(Corrected.getAsString(getLangOpts()));
     bool DroppedSpecifier =
         Corrected.WillReplaceSpecifier() && Name.getAsString() == CorrectedStr;
@@ -2157,7 +2157,7 @@ ExprResult
 Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
                         SourceLocation TemplateKWLoc, UnqualifiedId &Id,
                         bool HasTrailingLParen, bool IsAddressOfOperand,
-                        std::unique_ptr<CorrectionCandidateCallback> CCC,
+                        CorrectionCandidateCallback *CCC,
                         bool IsInlineAsmIdentifier, Token *KeywordReplacement) {
   assert(!(IsAddressOfOperand && HasTrailingLParen) &&
          "cannot be direct & operand and have a trailing lparen");
@@ -2279,9 +2279,9 @@ Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
     // If this name wasn't predeclared and if this is not a function
     // call, diagnose the problem.
     TypoExpr *TE = nullptr;
-    auto DefaultValidator = llvm::make_unique<CorrectionCandidateCallback>(
-        II, SS.isValid() ? SS.getScopeRep() : nullptr);
-    DefaultValidator->IsAddressOfOperand = IsAddressOfOperand;
+    DefaultFilterCCC DefaultValidator(II, SS.isValid() ? SS.getScopeRep()
+                                                       : nullptr);
+    DefaultValidator.IsAddressOfOperand = IsAddressOfOperand;
     assert((!CCC || CCC->IsAddressOfOperand == IsAddressOfOperand) &&
            "Typo correction callback misconfigured");
     if (CCC) {
@@ -2293,9 +2293,8 @@ Sema::ActOnIdExpression(Scope *S, CXXScopeSpec &SS,
     // FIXME: DiagnoseEmptyLookup produces bad diagnostics if we're looking for
     // a template name, but we happen to have always already looked up the name
     // before we get here if it must be a template name.
-    if (DiagnoseEmptyLookup(S, SS, R,
-                            CCC ? std::move(CCC) : std::move(DefaultValidator),
-                            nullptr, None, &TE)) {
+    if (DiagnoseEmptyLookup(S, SS, R, CCC ? *CCC : DefaultValidator, nullptr,
+                            None, &TE)) {
       if (TE && KeywordReplacement) {
         auto &State = getTypoExprState(TE);
         auto BestTC = State.Consumer->getNextCorrection();
@@ -2549,8 +2548,10 @@ Sema::LookupInObjCMethod(LookupResult &Lookup, Scope *S,
       SelfName.setKind(UnqualifiedIdKind::IK_ImplicitSelfParam);
       CXXScopeSpec SelfScopeSpec;
       SourceLocation TemplateKWLoc;
-      ExprResult SelfExpr = ActOnIdExpression(S, SelfScopeSpec, TemplateKWLoc,
-                                              SelfName, false, false);
+      ExprResult SelfExpr =
+          ActOnIdExpression(S, SelfScopeSpec, TemplateKWLoc, SelfName,
+                            /*HasTrailingLParen=*/false,
+                            /*IsAddressOfOperand=*/false);
       if (SelfExpr.isInvalid())
         return ExprError();
 
@@ -4893,7 +4894,7 @@ Sema::getVariadicCallType(FunctionDecl *FDecl, const FunctionProtoType *Proto,
 }
 
 namespace {
-class FunctionCallCCC : public FunctionCallFilterCCC {
+class FunctionCallCCC final : public FunctionCallFilterCCC {
 public:
   FunctionCallCCC(Sema &SemaRef, const IdentifierInfo *FuncName,
                   unsigned NumArgs, MemberExpr *ME)
@@ -4909,6 +4910,10 @@ public:
     return FunctionCallFilterCCC::ValidateCandidate(candidate);
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<FunctionCallCCC>(*this);
+  }
+
 private:
   const IdentifierInfo *const FunctionName;
 };
@@ -4921,11 +4926,10 @@ static TypoCorrection TryTypoCorrectionForCall(Sema &S, Expr *Fn,
   DeclarationName FuncName = FDecl->getDeclName();
   SourceLocation NameLoc = ME ? ME->getMemberLoc() : Fn->getBeginLoc();
 
+  FunctionCallCCC CCC(S, FuncName.getAsIdentifierInfo(), Args.size(), ME);
   if (TypoCorrection Corrected = S.CorrectTypo(
           DeclarationNameInfo(FuncName, NameLoc), Sema::LookupOrdinaryName,
-          S.getScopeForContext(S.CurContext), nullptr,
-          llvm::make_unique<FunctionCallCCC>(S, FuncName.getAsIdentifierInfo(),
-                                             Args.size(), ME),
+          S.getScopeForContext(S.CurContext), nullptr, CCC,
           Sema::CTK_ErrorRecovery)) {
     if (NamedDecl *ND = Corrected.getFoundDecl()) {
       if (Corrected.isOverloaded()) {

lib/Sema/SemaExprMember.cpp

@@ -590,7 +590,7 @@ namespace {
 // Callback to only accept typo corrections that are either a ValueDecl or a
 // FunctionTemplateDecl and are declared in the current record or, for a C++
 // classes, one of its base classes.
-class RecordMemberExprValidatorCCC : public CorrectionCandidateCallback {
+class RecordMemberExprValidatorCCC final : public CorrectionCandidateCallback {
 public:
   explicit RecordMemberExprValidatorCCC(const RecordType *RTy)
       : Record(RTy->getDecl()) {
@@ -628,6 +628,10 @@ public:
     return false;
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<RecordMemberExprValidatorCCC>(*this);
+  }
+
 private:
   const RecordDecl *const Record;
 };
@@ -696,9 +700,9 @@ static bool LookupMemberExprInRecord(Sema &SemaRef, LookupResult &R,
   };
   QueryState Q = {R.getSema(), R.getLookupNameInfo(), R.getLookupKind(),
                   R.redeclarationKind()};
+  RecordMemberExprValidatorCCC CCC(RTy);
   TE = SemaRef.CorrectTypoDelayed(
-      R.getLookupNameInfo(), R.getLookupKind(), nullptr, &SS,
-      llvm::make_unique<RecordMemberExprValidatorCCC>(RTy),
+      R.getLookupNameInfo(), R.getLookupKind(), nullptr, &SS, CCC,
       [=, &SemaRef](const TypoCorrection &TC) {
         if (TC) {
           assert(!TC.isKeyword() &&
@@ -1331,11 +1335,11 @@ static ExprResult LookupMemberExpr(Sema &S, LookupResult &R,
 
     if (!IV) {
       // Attempt to correct for typos in ivar names.
-      auto Validator = llvm::make_unique<DeclFilterCCC<ObjCIvarDecl>>();
-      Validator->IsObjCIvarLookup = IsArrow;
+      DeclFilterCCC<ObjCIvarDecl> Validator{};
+      Validator.IsObjCIvarLookup = IsArrow;
       if (TypoCorrection Corrected = S.CorrectTypo(
               R.getLookupNameInfo(), Sema::LookupMemberName, nullptr, nullptr,
-              std::move(Validator), Sema::CTK_ErrorRecovery, IDecl)) {
+              Validator, Sema::CTK_ErrorRecovery, IDecl)) {
         IV = Corrected.getCorrectionDeclAs<ObjCIvarDecl>();
         S.diagnoseTypo(
             Corrected,

lib/Sema/SemaExprObjC.cpp

@@ -1946,11 +1946,10 @@ HandleExprPropertyRefExpr(const ObjCObjectPointerType *OPT,
   }
 
   // Attempt to correct for typos in property names.
-  if (TypoCorrection Corrected =
-          CorrectTypo(DeclarationNameInfo(MemberName, MemberLoc),
-                      LookupOrdinaryName, nullptr, nullptr,
-                      llvm::make_unique<DeclFilterCCC<ObjCPropertyDecl>>(),
-                      CTK_ErrorRecovery, IFace, false, OPT)) {
+  DeclFilterCCC<ObjCPropertyDecl> CCC{};
+  if (TypoCorrection Corrected = CorrectTypo(
+          DeclarationNameInfo(MemberName, MemberLoc), LookupOrdinaryName,
+          nullptr, nullptr, CCC, CTK_ErrorRecovery, IFace, false, OPT)) {
     DeclarationName TypoResult = Corrected.getCorrection();
     if (TypoResult.isIdentifier() &&
         TypoResult.getAsIdentifierInfo() == Member) {
@@ -2107,7 +2106,7 @@ ActOnClassPropertyRefExpr(IdentifierInfo &receiverName,
 
 namespace {
 
-class ObjCInterfaceOrSuperCCC : public CorrectionCandidateCallback {
+class ObjCInterfaceOrSuperCCC final : public CorrectionCandidateCallback {
  public:
   ObjCInterfaceOrSuperCCC(ObjCMethodDecl *Method) {
     // Determine whether "super" is acceptable in the current context.
@@ -2119,6 +2118,10 @@ class ObjCInterfaceOrSuperCCC : public CorrectionCandidateCallback {
     return candidate.getCorrectionDeclAs<ObjCInterfaceDecl>() ||
         candidate.isKeyword("super");
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<ObjCInterfaceOrSuperCCC>(*this);
+  }
 };
 
 } // end anonymous namespace
@@ -2194,9 +2197,9 @@ Sema::ObjCMessageKind Sema::getObjCMessageKind(Scope *S,
   }
   }
 
+  ObjCInterfaceOrSuperCCC CCC(getCurMethodDecl());
   if (TypoCorrection Corrected = CorrectTypo(
-          Result.getLookupNameInfo(), Result.getLookupKind(), S, nullptr,
-          llvm::make_unique<ObjCInterfaceOrSuperCCC>(getCurMethodDecl()),
+          Result.getLookupNameInfo(), Result.getLookupKind(), S, nullptr, CCC,
           CTK_ErrorRecovery, nullptr, false, nullptr, false)) {
     if (Corrected.isKeyword()) {
       // If we've found the keyword "super" (the only keyword that would be

lib/Sema/SemaInit.cpp

@@ -2208,7 +2208,7 @@ namespace {
 
 // Callback to only accept typo corrections that are for field members of
 // the given struct or union.
-class FieldInitializerValidatorCCC : public CorrectionCandidateCallback {
+class FieldInitializerValidatorCCC final : public CorrectionCandidateCallback {
  public:
   explicit FieldInitializerValidatorCCC(RecordDecl *RD)
       : Record(RD) {}
@@ -2218,6 +2218,10 @@ class FieldInitializerValidatorCCC : public CorrectionCandidateCallback {
     return FD && FD->getDeclContext()->getRedeclContext()->Equals(Record);
   }
 
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<FieldInitializerValidatorCCC>(*this);
+  }
+
  private:
   RecordDecl *Record;
 };
@@ -2420,10 +2424,10 @@ InitListChecker::CheckDesignatedInitializer(const InitializedEntity &Entity,
 
         // Name lookup didn't find anything.
         // Determine whether this was a typo for another field name.
+        FieldInitializerValidatorCCC CCC(RT->getDecl());
         if (TypoCorrection Corrected = SemaRef.CorrectTypo(
                 DeclarationNameInfo(FieldName, D->getFieldLoc()),
-                Sema::LookupMemberName, /*Scope=*/nullptr, /*SS=*/nullptr,
-                llvm::make_unique<FieldInitializerValidatorCCC>(RT->getDecl()),
+                Sema::LookupMemberName, /*Scope=*/nullptr, /*SS=*/nullptr, CCC,
                 Sema::CTK_ErrorRecovery, RT->getDecl())) {
           SemaRef.diagnoseTypo(
               Corrected,

lib/Sema/SemaLambda.cpp

@@ -1079,8 +1079,8 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
       if (R.empty()) {
         // FIXME: Disable corrections that would add qualification?
         CXXScopeSpec ScopeSpec;
-        if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R,
-                                llvm::make_unique<DeclFilterCCC<VarDecl>>()))
+        DeclFilterCCC<VarDecl> Validator{};
+        if (DiagnoseEmptyLookup(CurScope, ScopeSpec, R, Validator))
           continue;
       }
 

lib/Sema/SemaLookup.cpp

@@ -4572,8 +4572,7 @@ static void AddKeywordsToConsumer(Sema &SemaRef,
 
 std::unique_ptr<TypoCorrectionConsumer> Sema::makeTypoCorrectionConsumer(
     const DeclarationNameInfo &TypoName, Sema::LookupNameKind LookupKind,
-    Scope *S, CXXScopeSpec *SS,
-    std::unique_ptr<CorrectionCandidateCallback> CCC,
+    Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
     DeclContext *MemberContext, bool EnteringContext,
     const ObjCObjectPointerType *OPT, bool ErrorRecovery) {
 
@@ -4635,9 +4634,13 @@ std::unique_ptr<TypoCorrectionConsumer> Sema::makeTypoCorrectionConsumer(
                                            TypoName.getBeginLoc());
   }
 
-  CorrectionCandidateCallback &CCCRef = *CCC;
+  // Extend the lifetime of the callback. We delayed this until here
+  // to avoid allocations in the hot path (which is where no typo correction
+  // occurs). Note that CorrectionCandidateCallback is polymorphic and
+  // initially stack-allocated.
+  std::unique_ptr<CorrectionCandidateCallback> ClonedCCC = CCC.clone();
   auto Consumer = llvm::make_unique<TypoCorrectionConsumer>(
-      *this, TypoName, LookupKind, S, SS, std::move(CCC), MemberContext,
+      *this, TypoName, LookupKind, S, SS, std::move(ClonedCCC), MemberContext,
       EnteringContext);
 
   // Perform name lookup to find visible, similarly-named entities.
@@ -4689,7 +4692,9 @@ std::unique_ptr<TypoCorrectionConsumer> Sema::makeTypoCorrectionConsumer(
     }
   }
 
-  AddKeywordsToConsumer(*this, *Consumer, S, CCCRef, SS && SS->isNotEmpty());
+  AddKeywordsToConsumer(*this, *Consumer, S,
+                        *Consumer->getCorrectionValidator(),
+                        SS && SS->isNotEmpty());
 
   // Build the NestedNameSpecifiers for the KnownNamespaces, if we're going
   // to search those namespaces.
@@ -4743,19 +4748,18 @@ std::unique_ptr<TypoCorrectionConsumer> Sema::makeTypoCorrectionConsumer(
 TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
                                  Sema::LookupNameKind LookupKind,
                                  Scope *S, CXXScopeSpec *SS,
-                                 std::unique_ptr<CorrectionCandidateCallback> CCC,
+                                 CorrectionCandidateCallback &CCC,
                                  CorrectTypoKind Mode,
                                  DeclContext *MemberContext,
                                  bool EnteringContext,
                                  const ObjCObjectPointerType *OPT,
                                  bool RecordFailure) {
-  assert(CCC && "CorrectTypo requires a CorrectionCandidateCallback");
-
   // Always let the ExternalSource have the first chance at correction, even
   // if we would otherwise have given up.
   if (ExternalSource) {
-    if (TypoCorrection Correction = ExternalSource->CorrectTypo(
-        TypoName, LookupKind, S, SS, *CCC, MemberContext, EnteringContext, OPT))
+    if (TypoCorrection Correction =
+            ExternalSource->CorrectTypo(TypoName, LookupKind, S, SS, CCC,
+                                        MemberContext, EnteringContext, OPT))
       return Correction;
   }
 
@@ -4763,12 +4767,12 @@ TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
   // WantObjCSuper is only true for CTC_ObjCMessageReceiver and for
   // some instances of CTC_Unknown, while WantRemainingKeywords is true
   // for CTC_Unknown but not for CTC_ObjCMessageReceiver.
-  bool ObjCMessageReceiver = CCC->WantObjCSuper && !CCC->WantRemainingKeywords;
+  bool ObjCMessageReceiver = CCC.WantObjCSuper && !CCC.WantRemainingKeywords;
 
   IdentifierInfo *Typo = TypoName.getName().getAsIdentifierInfo();
-  auto Consumer = makeTypoCorrectionConsumer(
-      TypoName, LookupKind, S, SS, std::move(CCC), MemberContext,
-      EnteringContext, OPT, Mode == CTK_ErrorRecovery);
+  auto Consumer = makeTypoCorrectionConsumer(TypoName, LookupKind, S, SS, CCC,
+                                             MemberContext, EnteringContext,
+                                             OPT, Mode == CTK_ErrorRecovery);
 
   if (!Consumer)
     return TypoCorrection();
@@ -4878,16 +4882,13 @@ TypoCorrection Sema::CorrectTypo(const DeclarationNameInfo &TypoName,
 /// needed.
 TypoExpr *Sema::CorrectTypoDelayed(
     const DeclarationNameInfo &TypoName, Sema::LookupNameKind LookupKind,
-    Scope *S, CXXScopeSpec *SS,
-    std::unique_ptr<CorrectionCandidateCallback> CCC,
+    Scope *S, CXXScopeSpec *SS, CorrectionCandidateCallback &CCC,
     TypoDiagnosticGenerator TDG, TypoRecoveryCallback TRC, CorrectTypoKind Mode,
     DeclContext *MemberContext, bool EnteringContext,
     const ObjCObjectPointerType *OPT) {
-  assert(CCC && "CorrectTypoDelayed requires a CorrectionCandidateCallback");
-
-  auto Consumer = makeTypoCorrectionConsumer(
-      TypoName, LookupKind, S, SS, std::move(CCC), MemberContext,
-      EnteringContext, OPT, Mode == CTK_ErrorRecovery);
+  auto Consumer = makeTypoCorrectionConsumer(TypoName, LookupKind, S, SS, CCC,
+                                             MemberContext, EnteringContext,
+                                             OPT, Mode == CTK_ErrorRecovery);
 
   // Give the external sema source a chance to correct the typo.
   TypoCorrection ExternalTypo;

lib/Sema/SemaOpenMP.cpp

@@ -1955,6 +1955,11 @@ public:
     }
     return false;
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<VarDeclFilterCCC>(*this);
+  }
+
 };
 
 class VarOrFuncDeclFilterCCC final : public CorrectionCandidateCallback {
@@ -1972,6 +1977,10 @@ public:
     }
     return false;
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<VarOrFuncDeclFilterCCC>(*this);
+  }
 };
 
 } // namespace
@@ -1988,9 +1997,10 @@ ExprResult Sema::ActOnOpenMPIdExpression(Scope *CurScope,
 
   VarDecl *VD;
   if (!Lookup.isSingleResult()) {
-    if (TypoCorrection Corrected = CorrectTypo(
-            Id, LookupOrdinaryName, CurScope, nullptr,
-            llvm::make_unique<VarDeclFilterCCC>(*this), CTK_ErrorRecovery)) {
+    VarDeclFilterCCC CCC(*this);
+    if (TypoCorrection Corrected =
+            CorrectTypo(Id, LookupOrdinaryName, CurScope, nullptr, CCC,
+                        CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(Lookup.empty()
                              ? diag::err_undeclared_var_use_suggest
@@ -14379,9 +14389,9 @@ void Sema::ActOnOpenMPDeclareTargetName(Scope *CurScope,
   Lookup.suppressDiagnostics();
 
   if (!Lookup.isSingleResult()) {
+    VarOrFuncDeclFilterCCC CCC(*this);
     if (TypoCorrection Corrected =
-            CorrectTypo(Id, LookupOrdinaryName, CurScope, nullptr,
-                        llvm::make_unique<VarOrFuncDeclFilterCCC>(*this),
+            CorrectTypo(Id, LookupOrdinaryName, CurScope, nullptr, CCC,
                         CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected, PDiag(diag::err_undeclared_var_use_suggest)
                                   << Id.getName());

lib/Sema/SemaOverload.cpp

@@ -11892,15 +11892,6 @@ public:
 
 }
 
-static std::unique_ptr<CorrectionCandidateCallback>
-MakeValidator(Sema &SemaRef, MemberExpr *ME, size_t NumArgs,
-              bool HasTemplateArgs, bool AllowTypoCorrection) {
-  if (!AllowTypoCorrection)
-    return llvm::make_unique<NoTypoCorrectionCCC>();
-  return llvm::make_unique<FunctionCallFilterCCC>(SemaRef, NumArgs,
-                                                  HasTemplateArgs, ME);
-}
-
 /// Attempts to recover from a call where no functions were found.
 ///
 /// Returns true if new candidates were found.
@@ -11935,16 +11926,22 @@ BuildRecoveryCallExpr(Sema &SemaRef, Scope *S, Expr *Fn,
   LookupResult R(SemaRef, ULE->getName(), ULE->getNameLoc(),
                  Sema::LookupOrdinaryName);
   bool DoDiagnoseEmptyLookup = EmptyLookup;
-  if (!DiagnoseTwoPhaseLookup(SemaRef, Fn->getExprLoc(), SS, R,
-                              OverloadCandidateSet::CSK_Normal,
-                              ExplicitTemplateArgs, Args,
-                              &DoDiagnoseEmptyLookup) &&
-    (!DoDiagnoseEmptyLookup || SemaRef.DiagnoseEmptyLookup(
-        S, SS, R,
-        MakeValidator(SemaRef, dyn_cast<MemberExpr>(Fn), Args.size(),
-                      ExplicitTemplateArgs != nullptr, AllowTypoCorrection),
-        ExplicitTemplateArgs, Args)))
-    return ExprError();
+  if (!DiagnoseTwoPhaseLookup(
+          SemaRef, Fn->getExprLoc(), SS, R, OverloadCandidateSet::CSK_Normal,
+          ExplicitTemplateArgs, Args, &DoDiagnoseEmptyLookup)) {
+    NoTypoCorrectionCCC NoTypoValidator{};
+    FunctionCallFilterCCC FunctionCallValidator(SemaRef, Args.size(),
+                                                ExplicitTemplateArgs != nullptr,
+                                                dyn_cast<MemberExpr>(Fn));
+    CorrectionCandidateCallback &Validator =
+        AllowTypoCorrection
+            ? static_cast<CorrectionCandidateCallback &>(FunctionCallValidator)
+            : static_cast<CorrectionCandidateCallback &>(NoTypoValidator);
+    if (!DoDiagnoseEmptyLookup ||
+        SemaRef.DiagnoseEmptyLookup(S, SS, R, Validator, ExplicitTemplateArgs,
+                                    Args))
+      return ExprError();
+  }
 
   assert(!R.empty() && "lookup results empty despite recovery");
 

lib/Sema/SemaTemplate.cpp

@@ -410,14 +410,14 @@ bool Sema::LookupTemplateName(LookupResult &Found,
     DeclarationName Name = Found.getLookupName();
     Found.clear();
     // Simple filter callback that, for keywords, only accepts the C++ *_cast
-    auto FilterCCC = llvm::make_unique<CorrectionCandidateCallback>();
-    FilterCCC->WantTypeSpecifiers = false;
-    FilterCCC->WantExpressionKeywords = false;
-    FilterCCC->WantRemainingKeywords = false;
-    FilterCCC->WantCXXNamedCasts = true;
-    if (TypoCorrection Corrected = CorrectTypo(
-            Found.getLookupNameInfo(), Found.getLookupKind(), S, &SS,
-            std::move(FilterCCC), CTK_ErrorRecovery, LookupCtx)) {
+    DefaultFilterCCC FilterCCC{};
+    FilterCCC.WantTypeSpecifiers = false;
+    FilterCCC.WantExpressionKeywords = false;
+    FilterCCC.WantRemainingKeywords = false;
+    FilterCCC.WantCXXNamedCasts = true;
+    if (TypoCorrection Corrected =
+            CorrectTypo(Found.getLookupNameInfo(), Found.getLookupKind(), S,
+                        &SS, FilterCCC, CTK_ErrorRecovery, LookupCtx)) {
       Found.setLookupName(Corrected.getCorrection());
       if (auto *ND = Corrected.getFoundDecl())
         Found.addDecl(ND);
@@ -579,13 +579,16 @@ void Sema::diagnoseExprIntendedAsTemplateName(Scope *S, ExprResult TemplateName,
         return S.getAsTemplateNameDecl(ND);
       return Candidate.isKeyword();
     }
+
+    std::unique_ptr<CorrectionCandidateCallback> clone() override {
+      return llvm::make_unique<TemplateCandidateFilter>(*this);
+    }
   };
 
   DeclarationName Name = NameInfo.getName();
-  if (TypoCorrection Corrected =
-          CorrectTypo(NameInfo, LookupKind, S, &SS,
-                      llvm::make_unique<TemplateCandidateFilter>(*this),
-                      CTK_ErrorRecovery, LookupCtx)) {
+  TemplateCandidateFilter CCC(*this);
+  if (TypoCorrection Corrected = CorrectTypo(NameInfo, LookupKind, S, &SS, CCC,
+                                             CTK_ErrorRecovery, LookupCtx)) {
     auto *ND = Corrected.getFoundDecl();
     if (ND)
       ND = getAsTemplateNameDecl(ND);

lib/Sema/SemaTemplateVariadic.cpp

@@ -924,12 +924,16 @@ bool Sema::containsUnexpandedParameterPacks(Declarator &D) {
 namespace {
 
 // Callback to only accept typo corrections that refer to parameter packs.
-class ParameterPackValidatorCCC : public CorrectionCandidateCallback {
+class ParameterPackValidatorCCC final : public CorrectionCandidateCallback {
  public:
   bool ValidateCandidate(const TypoCorrection &candidate) override {
     NamedDecl *ND = candidate.getCorrectionDecl();
     return ND && ND->isParameterPack();
   }
+
+  std::unique_ptr<CorrectionCandidateCallback> clone() override {
+    return llvm::make_unique<ParameterPackValidatorCCC>(*this);
+  }
 };
 
 }
@@ -965,18 +969,18 @@ ExprResult Sema::ActOnSizeofParameterPackExpr(Scope *S,
     break;
 
   case LookupResult::NotFound:
-  case LookupResult::NotFoundInCurrentInstantiation:
+  case LookupResult::NotFoundInCurrentInstantiation: {
+    ParameterPackValidatorCCC CCC{};
     if (TypoCorrection Corrected =
             CorrectTypo(R.getLookupNameInfo(), R.getLookupKind(), S, nullptr,
-                        llvm::make_unique<ParameterPackValidatorCCC>(),
-                        CTK_ErrorRecovery)) {
+                        CCC, CTK_ErrorRecovery)) {
       diagnoseTypo(Corrected,
                    PDiag(diag::err_sizeof_pack_no_pack_name_suggest) << &Name,
                    PDiag(diag::note_parameter_pack_here));
       ParameterPack = Corrected.getCorrectionDecl();
     }
     break;
-
+  }
   case LookupResult::FoundOverloaded:
   case LookupResult::FoundUnresolvedValue:
     break;

lib/Sema/SemaType.cpp

@@ -5913,7 +5913,8 @@ static void HandleAddressSpaceTypeAttribute(QualType &Type,
       id.setIdentifier(Attr.getArgAsIdent(0)->Ident, Attr.getLoc());
 
       ExprResult AddrSpace = S.ActOnIdExpression(
-          S.getCurScope(), SS, TemplateKWLoc, id, false, false);
+          S.getCurScope(), SS, TemplateKWLoc, id, /*HasTrailingLParen=*/false,
+          /*IsAddressOfOperand=*/false);
       if (AddrSpace.isInvalid())
         return;
 
@@ -7043,7 +7044,8 @@ static void HandleVectorSizeAttr(QualType &CurType, const ParsedAttr &Attr,
     Id.setIdentifier(Attr.getArgAsIdent(0)->Ident, Attr.getLoc());
 
     ExprResult Size = S.ActOnIdExpression(S.getCurScope(), SS, TemplateKWLoc,
-                                          Id, false, false);
+                                          Id, /*HasTrailingLParen=*/false,
+                                          /*IsAddressOfOperand=*/false);
 
     if (Size.isInvalid())
       return;
@@ -7080,7 +7082,8 @@ static void HandleExtVectorTypeAttr(QualType &CurType, const ParsedAttr &Attr,
     id.setIdentifier(Attr.getArgAsIdent(0)->Ident, Attr.getLoc());
 
     ExprResult Size = S.ActOnIdExpression(S.getCurScope(), SS, TemplateKWLoc,
-                                          id, false, false);
+                                          id, /*HasTrailingLParen=*/false,
+                                          /*IsAddressOfOperand=*/false);
     if (Size.isInvalid())
       return;