clang/lib/Sema/SemaExprCXX.cpp

//===--- SemaExprCXX.cpp - Semantic Analysis for Expressions --------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// \file
/// \brief Implements semantic analysis for C++ expressions.
///
//===----------------------------------------------------------------------===//

#include "clang/Sema/SemaInternal.h"
#include "TreeTransform.h"
#include "TypeLocBuilder.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaLambda.h"
#include "clang/Sema/TemplateDeduction.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ErrorHandling.h"
using namespace clang;
using namespace sema;

/// \brief Handle the result of the special case name lookup for inheriting
/// constructor declarations. 'NS::X::X' and 'NS::X<...>::X' are treated as
/// constructor names in member using declarations, even if 'X' is not the
/// name of the corresponding type.
ParsedType Sema::getInheritingConstructorName(CXXScopeSpec &SS,
                                              SourceLocation NameLoc,
                                              IdentifierInfo &Name) {
  NestedNameSpecifier *NNS = SS.getScopeRep();

  // Convert the nested-name-specifier into a type.
  QualType Type;
  switch (NNS->getKind()) {
  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate:
    Type = QualType(NNS->getAsType(), 0);
    break;

  case NestedNameSpecifier::Identifier:
    // Strip off the last layer of the nested-name-specifier and build a
    // typename type for it.
    assert(NNS->getAsIdentifier() == &Name && "not a constructor name");
    Type = Context.getDependentNameType(ETK_None, NNS->getPrefix(),
                                        NNS->getAsIdentifier());
    break;

  case NestedNameSpecifier::Global:
  case NestedNameSpecifier::Super:
  case NestedNameSpecifier::Namespace:
  case NestedNameSpecifier::NamespaceAlias:
    llvm_unreachable("Nested name specifier is not a type for inheriting ctor");
  }

  // This reference to the type is located entirely at the location of the
  // final identifier in the qualified-id.
  return CreateParsedType(Type,
                          Context.getTrivialTypeSourceInfo(Type, NameLoc));
}

ParsedType Sema::getDestructorName(SourceLocation TildeLoc,
                                   IdentifierInfo &II,
                                   SourceLocation NameLoc,
                                   Scope *S, CXXScopeSpec &SS,
                                   ParsedType ObjectTypePtr,
                                   bool EnteringContext) {
  // Determine where to perform name lookup.

  // FIXME: This area of the standard is very messy, and the current
  // wording is rather unclear about which scopes we search for the
  // destructor name; see core issues 399 and 555. Issue 399 in
  // particular shows where the current description of destructor name
  // lookup is completely out of line with existing practice, e.g.,
  // this appears to be ill-formed:
  //
  //   namespace N {
  //     template <typename T> struct S {
  //       ~S();
  //     };
  //   }
  //
  //   void f(N::S<int>* s) {
  //     s->N::S<int>::~S();
  //   }
  //
  // See also PR6358 and PR6359.
  // For this reason, we're currently only doing the C++03 version of this
  // code; the C++0x version has to wait until we get a proper spec.
  QualType SearchType;
  DeclContext *LookupCtx = nullptr;
  bool isDependent = false;
  bool LookInScope = false;

  if (SS.isInvalid())
    return ParsedType();

  // If we have an object type, it's because we are in a
  // pseudo-destructor-expression or a member access expression, and
  // we know what type we're looking for.
  if (ObjectTypePtr)
    SearchType = GetTypeFromParser(ObjectTypePtr);

  if (SS.isSet()) {
    NestedNameSpecifier *NNS = SS.getScopeRep();

    bool AlreadySearched = false;
    bool LookAtPrefix = true;
    // C++11 [basic.lookup.qual]p6:
    //   If a pseudo-destructor-name (5.2.4) contains a nested-name-specifier,
    //   the type-names are looked up as types in the scope designated by the
    //   nested-name-specifier. Similarly, in a qualified-id of the form:
    //
    //     nested-name-specifier[opt] class-name :: ~ class-name
    //
    //   the second class-name is looked up in the same scope as the first.
    //
    // Here, we determine whether the code below is permitted to look at the
    // prefix of the nested-name-specifier.
    DeclContext *DC = computeDeclContext(SS, EnteringContext);
    if (DC && DC->isFileContext()) {
      AlreadySearched = true;
      LookupCtx = DC;
      isDependent = false;
    } else if (DC && isa<CXXRecordDecl>(DC)) {
      LookAtPrefix = false;
      LookInScope = true;
    }

    // The second case from the C++03 rules quoted further above.
    NestedNameSpecifier *Prefix = nullptr;
    if (AlreadySearched) {
      // Nothing left to do.
    } else if (LookAtPrefix && (Prefix = NNS->getPrefix())) {
      CXXScopeSpec PrefixSS;
      PrefixSS.Adopt(NestedNameSpecifierLoc(Prefix, SS.location_data()));
      LookupCtx = computeDeclContext(PrefixSS, EnteringContext);
      isDependent = isDependentScopeSpecifier(PrefixSS);
    } else if (ObjectTypePtr) {
      LookupCtx = computeDeclContext(SearchType);
      isDependent = SearchType->isDependentType();
    } else {
      LookupCtx = computeDeclContext(SS, EnteringContext);
      isDependent = LookupCtx && LookupCtx->isDependentContext();
    }
  } else if (ObjectTypePtr) {
    // C++ [basic.lookup.classref]p3:
    //   If the unqualified-id is ~type-name, the type-name is looked up
    //   in the context of the entire postfix-expression. If the type T
    //   of the object expression is of a class type C, the type-name is
    //   also looked up in the scope of class C. At least one of the
    //   lookups shall find a name that refers to (possibly
    //   cv-qualified) T.
    LookupCtx = computeDeclContext(SearchType);
    isDependent = SearchType->isDependentType();
    assert((isDependent || !SearchType->isIncompleteType()) &&
           "Caller should have completed object type");

    LookInScope = true;
  } else {
    // Perform lookup into the current scope (only).
    LookInScope = true;
  }

  TypeDecl *NonMatchingTypeDecl = nullptr;
  LookupResult Found(*this, &II, NameLoc, LookupOrdinaryName);
  for (unsigned Step = 0; Step != 2; ++Step) {
    // Look for the name first in the computed lookup context (if we
    // have one) and, if that fails to find a match, in the scope (if
    // we're allowed to look there).
    Found.clear();
    if (Step == 0 && LookupCtx)
      LookupQualifiedName(Found, LookupCtx);
    else if (Step == 1 && LookInScope && S)
      LookupName(Found, S);
    else
      continue;

    // FIXME: Should we be suppressing ambiguities here?
    if (Found.isAmbiguous())
      return ParsedType();

    if (TypeDecl *Type = Found.getAsSingle<TypeDecl>()) {
      QualType T = Context.getTypeDeclType(Type);
      MarkAnyDeclReferenced(Type->getLocation(), Type, /*OdrUse=*/false);

      if (SearchType.isNull() || SearchType->isDependentType() ||
          Context.hasSameUnqualifiedType(T, SearchType)) {
        // We found our type!

        return CreateParsedType(T,
                                Context.getTrivialTypeSourceInfo(T, NameLoc));
      }

      if (!SearchType.isNull())
        NonMatchingTypeDecl = Type;
    }

    // If the name that we found is a class template name, and it is
    // the same name as the template name in the last part of the
    // nested-name-specifier (if present) or the object type, then
    // this is the destructor for that class.
    // FIXME: This is a workaround until we get real drafting for core
    // issue 399, for which there isn't even an obvious direction.
    if (ClassTemplateDecl *Template = Found.getAsSingle<ClassTemplateDecl>()) {
      QualType MemberOfType;
      if (SS.isSet()) {
        if (DeclContext *Ctx = computeDeclContext(SS, EnteringContext)) {
          // Figure out the type of the context, if it has one.
          if (CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(Ctx))
            MemberOfType = Context.getTypeDeclType(Record);
        }
      }
      if (MemberOfType.isNull())
        MemberOfType = SearchType;

      if (MemberOfType.isNull())
        continue;

      // We're referring into a class template specialization. If the
      // class template we found is the same as the template being
      // specialized, we found what we are looking for.
      if (const RecordType *Record = MemberOfType->getAs<RecordType>()) {
        if (ClassTemplateSpecializationDecl *Spec
              = dyn_cast<ClassTemplateSpecializationDecl>(Record->getDecl())) {
          if (Spec->getSpecializedTemplate()->getCanonicalDecl() ==
                Template->getCanonicalDecl())
            return CreateParsedType(
                MemberOfType,
                Context.getTrivialTypeSourceInfo(MemberOfType, NameLoc));
        }

        continue;
      }

      // We're referring to an unresolved class template
      // specialization. Determine whether we class template we found
      // is the same as the template being specialized or, if we don't
      // know which template is being specialized, that it at least
      // has the same name.
      if (const TemplateSpecializationType *SpecType
            = MemberOfType->getAs<TemplateSpecializationType>()) {
        TemplateName SpecName = SpecType->getTemplateName();

        // The class template we found is the same template being
        // specialized.
        if (TemplateDecl *SpecTemplate = SpecName.getAsTemplateDecl()) {
          if (SpecTemplate->getCanonicalDecl() == Template->getCanonicalDecl())
            return CreateParsedType(
                MemberOfType,
                Context.getTrivialTypeSourceInfo(MemberOfType, NameLoc));

          continue;
        }

        // The class template we found has the same name as the
        // (dependent) template name being specialized.
        if (DependentTemplateName *DepTemplate
                                    = SpecName.getAsDependentTemplateName()) {
          if (DepTemplate->isIdentifier() &&
              DepTemplate->getIdentifier() == Template->getIdentifier())
            return CreateParsedType(
                MemberOfType,
                Context.getTrivialTypeSourceInfo(MemberOfType, NameLoc));

          continue;
        }
      }
    }
  }

  if (isDependent) {
    // We didn't find our type, but that's okay: it's dependent
    // anyway.
    
    // FIXME: What if we have no nested-name-specifier?
    QualType T = CheckTypenameType(ETK_None, SourceLocation(),
                                   SS.getWithLocInContext(Context),
                                   II, NameLoc);
    return ParsedType::make(T);
  }

  if (NonMatchingTypeDecl) {
    QualType T = Context.getTypeDeclType(NonMatchingTypeDecl);
    Diag(NameLoc, diag::err_destructor_expr_type_mismatch)
      << T << SearchType;
    Diag(NonMatchingTypeDecl->getLocation(), diag::note_destructor_type_here)
      << T;
  } else if (ObjectTypePtr)
    Diag(NameLoc, diag::err_ident_in_dtor_not_a_type)
      << &II;
  else {
    SemaDiagnosticBuilder DtorDiag = Diag(NameLoc,
                                          diag::err_destructor_class_name);
    if (S) {
      const DeclContext *Ctx = S->getEntity();
      if (const CXXRecordDecl *Class = dyn_cast_or_null<CXXRecordDecl>(Ctx))
        DtorDiag << FixItHint::CreateReplacement(SourceRange(NameLoc),
                                                 Class->getNameAsString());
    }
  }

  return ParsedType();
}

ParsedType Sema::getDestructorType(const DeclSpec& DS, ParsedType ObjectType) {
    if (DS.getTypeSpecType() == DeclSpec::TST_error || !ObjectType)
      return ParsedType();
    assert(DS.getTypeSpecType() == DeclSpec::TST_decltype 
           && "only get destructor types from declspecs");
    QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc());
    QualType SearchType = GetTypeFromParser(ObjectType);
    if (SearchType->isDependentType() || Context.hasSameUnqualifiedType(SearchType, T)) {
      return ParsedType::make(T);
    }
      
    Diag(DS.getTypeSpecTypeLoc(), diag::err_destructor_expr_type_mismatch)
      << T << SearchType;
    return ParsedType();
}

bool Sema::checkLiteralOperatorId(const CXXScopeSpec &SS,
                                  const UnqualifiedId &Name) {
  assert(Name.getKind() == UnqualifiedId::IK_LiteralOperatorId);

  if (!SS.isValid())
    return false;

  switch (SS.getScopeRep()->getKind()) {
  case NestedNameSpecifier::Identifier:
  case NestedNameSpecifier::TypeSpec:
  case NestedNameSpecifier::TypeSpecWithTemplate:
    // Per C++11 [over.literal]p2, literal operators can only be declared at
    // namespace scope. Therefore, this unqualified-id cannot name anything.
    // Reject it early, because we have no AST representation for this in the
    // case where the scope is dependent.
    Diag(Name.getLocStart(), diag::err_literal_operator_id_outside_namespace)
      << SS.getScopeRep();
    return true;

  case NestedNameSpecifier::Global:
  case NestedNameSpecifier::Super:
  case NestedNameSpecifier::Namespace:
  case NestedNameSpecifier::NamespaceAlias:
    return false;
  }

  llvm_unreachable("unknown nested name specifier kind");
}

/// \brief Build a C++ typeid expression with a type operand.
ExprResult Sema::BuildCXXTypeId(QualType TypeInfoType,
                                SourceLocation TypeidLoc,
                                TypeSourceInfo *Operand,
                                SourceLocation RParenLoc) {
  // C++ [expr.typeid]p4:
  //   The top-level cv-qualifiers of the lvalue expression or the type-id
  //   that is the operand of typeid are always ignored.
  //   If the type of the type-id is a class type or a reference to a class
  //   type, the class shall be completely-defined.
  Qualifiers Quals;
  QualType T
    = Context.getUnqualifiedArrayType(Operand->getType().getNonReferenceType(),
                                      Quals);
  if (T->getAs<RecordType>() &&
      RequireCompleteType(TypeidLoc, T, diag::err_incomplete_typeid))
    return ExprError();

  if (T->isVariablyModifiedType())
    return ExprError(Diag(TypeidLoc, diag::err_variably_modified_typeid) << T);

  return new (Context) CXXTypeidExpr(TypeInfoType.withConst(), Operand,
                                     SourceRange(TypeidLoc, RParenLoc));
}

/// \brief Build a C++ typeid expression with an expression operand.
ExprResult Sema::BuildCXXTypeId(QualType TypeInfoType,
                                SourceLocation TypeidLoc,
                                Expr *E,
                                SourceLocation RParenLoc) {
  bool WasEvaluated = false;
  if (E && !E->isTypeDependent()) {
    if (E->getType()->isPlaceholderType()) {
      ExprResult result = CheckPlaceholderExpr(E);
      if (result.isInvalid()) return ExprError();
      E = result.get();
    }

    QualType T = E->getType();
    if (const RecordType *RecordT = T->getAs<RecordType>()) {
      CXXRecordDecl *RecordD = cast<CXXRecordDecl>(RecordT->getDecl());
      // C++ [expr.typeid]p3:
      //   [...] If the type of the expression is a class type, the class
      //   shall be completely-defined.
      if (RequireCompleteType(TypeidLoc, T, diag::err_incomplete_typeid))
        return ExprError();

      // C++ [expr.typeid]p3:
      //   When typeid is applied to an expression other than an glvalue of a
      //   polymorphic class type [...] [the] expression is an unevaluated
      //   operand. [...]
      if (RecordD->isPolymorphic() && E->isGLValue()) {
        // The subexpression is potentially evaluated; switch the context
        // and recheck the subexpression.
        ExprResult Result = TransformToPotentiallyEvaluated(E);
        if (Result.isInvalid()) return ExprError();
        E = Result.get();

        // We require a vtable to query the type at run time.
        MarkVTableUsed(TypeidLoc, RecordD);
        WasEvaluated = true;
      }
    }

    // C++ [expr.typeid]p4:
    //   [...] If the type of the type-id is a reference to a possibly
    //   cv-qualified type, the result of the typeid expression refers to a
    //   std::type_info object representing the cv-unqualified referenced
    //   type.
    Qualifiers Quals;
    QualType UnqualT = Context.getUnqualifiedArrayType(T, Quals);
    if (!Context.hasSameType(T, UnqualT)) {
      T = UnqualT;
      E = ImpCastExprToType(E, UnqualT, CK_NoOp, E->getValueKind()).get();
    }
  }

  if (E->getType()->isVariablyModifiedType())
    return ExprError(Diag(TypeidLoc, diag::err_variably_modified_typeid)
                     << E->getType());
  else if (ActiveTemplateInstantiations.empty() &&
           E->HasSideEffects(Context, WasEvaluated)) {
    // The expression operand for typeid is in an unevaluated expression
    // context, so side effects could result in unintended consequences.
    Diag(E->getExprLoc(), WasEvaluated
                              ? diag::warn_side_effects_typeid
                              : diag::warn_side_effects_unevaluated_context);
  }

  return new (Context) CXXTypeidExpr(TypeInfoType.withConst(), E,
                                     SourceRange(TypeidLoc, RParenLoc));
}

/// ActOnCXXTypeidOfType - Parse typeid( type-id ) or typeid (expression);
ExprResult
Sema::ActOnCXXTypeid(SourceLocation OpLoc, SourceLocation LParenLoc,
                     bool isType, void *TyOrExpr, SourceLocation RParenLoc) {
  // Find the std::type_info type.
  if (!getStdNamespace())
    return ExprError(Diag(OpLoc, diag::err_need_header_before_typeid));

  if (!CXXTypeInfoDecl) {
    IdentifierInfo *TypeInfoII = &PP.getIdentifierTable().get("type_info");
    LookupResult R(*this, TypeInfoII, SourceLocation(), LookupTagName);
    LookupQualifiedName(R, getStdNamespace());
    CXXTypeInfoDecl = R.getAsSingle<RecordDecl>();
    // Microsoft's typeinfo doesn't have type_info in std but in the global
    // namespace if _HAS_EXCEPTIONS is defined to 0. See PR13153.
    if (!CXXTypeInfoDecl && LangOpts.MSVCCompat) {
      LookupQualifiedName(R, Context.getTranslationUnitDecl());
      CXXTypeInfoDecl = R.getAsSingle<RecordDecl>();
    }
    if (!CXXTypeInfoDecl)
      return ExprError(Diag(OpLoc, diag::err_need_header_before_typeid));
  }

  if (!getLangOpts().RTTI) {
    return ExprError(Diag(OpLoc, diag::err_no_typeid_with_fno_rtti));
  }

  QualType TypeInfoType = Context.getTypeDeclType(CXXTypeInfoDecl);

  if (isType) {
    // The operand is a type; handle it as such.
    TypeSourceInfo *TInfo = nullptr;
    QualType T = GetTypeFromParser(ParsedType::getFromOpaquePtr(TyOrExpr),
                                   &TInfo);
    if (T.isNull())
      return ExprError();

    if (!TInfo)
      TInfo = Context.getTrivialTypeSourceInfo(T, OpLoc);

    return BuildCXXTypeId(TypeInfoType, OpLoc, TInfo, RParenLoc);
  }

  // The operand is an expression.
  return BuildCXXTypeId(TypeInfoType, OpLoc, (Expr*)TyOrExpr, RParenLoc);
}

/// \brief Build a Microsoft __uuidof expression with a type operand.
ExprResult Sema::BuildCXXUuidof(QualType TypeInfoType,
                                SourceLocation TypeidLoc,
                                TypeSourceInfo *Operand,
                                SourceLocation RParenLoc) {
  if (!Operand->getType()->isDependentType()) {
    bool HasMultipleGUIDs = false;
    if (!CXXUuidofExpr::GetUuidAttrOfType(Operand->getType(),
                                          &HasMultipleGUIDs)) {
      if (HasMultipleGUIDs)
        return ExprError(Diag(TypeidLoc, diag::err_uuidof_with_multiple_guids));
      else
        return ExprError(Diag(TypeidLoc, diag::err_uuidof_without_guid));
    }
  }

  return new (Context) CXXUuidofExpr(TypeInfoType.withConst(), Operand,
                                     SourceRange(TypeidLoc, RParenLoc));
}

/// \brief Build a Microsoft __uuidof expression with an expression operand.
ExprResult Sema::BuildCXXUuidof(QualType TypeInfoType,
                                SourceLocation TypeidLoc,
                                Expr *E,
                                SourceLocation RParenLoc) {
  if (!E->getType()->isDependentType()) {
    bool HasMultipleGUIDs = false;
    if (!CXXUuidofExpr::GetUuidAttrOfType(E->getType(), &HasMultipleGUIDs) &&
        !E->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull)) {
      if (HasMultipleGUIDs)
        return ExprError(Diag(TypeidLoc, diag::err_uuidof_with_multiple_guids));
      else
        return ExprError(Diag(TypeidLoc, diag::err_uuidof_without_guid));
    }
  }

  return new (Context) CXXUuidofExpr(TypeInfoType.withConst(), E,
                                     SourceRange(TypeidLoc, RParenLoc));
}

/// ActOnCXXUuidof - Parse __uuidof( type-id ) or __uuidof (expression);
ExprResult
Sema::ActOnCXXUuidof(SourceLocation OpLoc, SourceLocation LParenLoc,
                     bool isType, void *TyOrExpr, SourceLocation RParenLoc) {
  // If MSVCGuidDecl has not been cached, do the lookup.
  if (!MSVCGuidDecl) {
    IdentifierInfo *GuidII = &PP.getIdentifierTable().get("_GUID");
    LookupResult R(*this, GuidII, SourceLocation(), LookupTagName);
    LookupQualifiedName(R, Context.getTranslationUnitDecl());
    MSVCGuidDecl = R.getAsSingle<RecordDecl>();
    if (!MSVCGuidDecl)
      return ExprError(Diag(OpLoc, diag::err_need_header_before_ms_uuidof));
  }

  QualType GuidType = Context.getTypeDeclType(MSVCGuidDecl);

  if (isType) {
    // The operand is a type; handle it as such.
    TypeSourceInfo *TInfo = nullptr;
    QualType T = GetTypeFromParser(ParsedType::getFromOpaquePtr(TyOrExpr),
                                   &TInfo);
    if (T.isNull())
      return ExprError();

    if (!TInfo)
      TInfo = Context.getTrivialTypeSourceInfo(T, OpLoc);

    return BuildCXXUuidof(GuidType, OpLoc, TInfo, RParenLoc);
  }

  // The operand is an expression.
  return BuildCXXUuidof(GuidType, OpLoc, (Expr*)TyOrExpr, RParenLoc);
}

/// ActOnCXXBoolLiteral - Parse {true,false} literals.
ExprResult
Sema::ActOnCXXBoolLiteral(SourceLocation OpLoc, tok::TokenKind Kind) {
  assert((Kind == tok::kw_true || Kind == tok::kw_false) &&
         "Unknown C++ Boolean value!");
  return new (Context)
      CXXBoolLiteralExpr(Kind == tok::kw_true, Context.BoolTy, OpLoc);
}

/// ActOnCXXNullPtrLiteral - Parse 'nullptr'.
ExprResult
Sema::ActOnCXXNullPtrLiteral(SourceLocation Loc) {
  return new (Context) CXXNullPtrLiteralExpr(Context.NullPtrTy, Loc);
}

/// ActOnCXXThrow - Parse throw expressions.
ExprResult
Sema::ActOnCXXThrow(Scope *S, SourceLocation OpLoc, Expr *Ex) {
  bool IsThrownVarInScope = false;
  if (Ex) {
    // C++0x [class.copymove]p31:
    //   When certain criteria are met, an implementation is allowed to omit the
    //   copy/move construction of a class object [...]
    //
    //     - in a throw-expression, when the operand is the name of a
    //       non-volatile automatic object (other than a function or catch-
    //       clause parameter) whose scope does not extend beyond the end of the
    //       innermost enclosing try-block (if there is one), the copy/move
    //       operation from the operand to the exception object (15.1) can be
    //       omitted by constructing the automatic object directly into the
    //       exception object
    if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Ex->IgnoreParens()))
      if (VarDecl *Var = dyn_cast<VarDecl>(DRE->getDecl())) {
        if (Var->hasLocalStorage() && !Var->getType().isVolatileQualified()) {
          for( ; S; S = S->getParent()) {
            if (S->isDeclScope(Var)) {
              IsThrownVarInScope = true;
              break;
            }
            
            if (S->getFlags() &
                (Scope::FnScope | Scope::ClassScope | Scope::BlockScope |
                 Scope::FunctionPrototypeScope | Scope::ObjCMethodScope |
                 Scope::TryScope))
              break;
          }
        }
      }
  }
  
  return BuildCXXThrow(OpLoc, Ex, IsThrownVarInScope);
}

ExprResult Sema::BuildCXXThrow(SourceLocation OpLoc, Expr *Ex, 
                               bool IsThrownVarInScope) {
  // Don't report an error if 'throw' is used in system headers.
  if (!getLangOpts().CXXExceptions &&
      !getSourceManager().isInSystemHeader(OpLoc))
    Diag(OpLoc, diag::err_exceptions_disabled) << "throw";

  if (getCurScope() && getCurScope()->isOpenMPSimdDirectiveScope())
    Diag(OpLoc, diag::err_omp_simd_region_cannot_use_stmt) << "throw";

  if (Ex && !Ex->isTypeDependent()) {
    QualType ExceptionObjectTy = Context.getExceptionObjectType(Ex->getType());
    if (CheckCXXThrowOperand(OpLoc, ExceptionObjectTy, Ex))
      return ExprError();

    // Initialize the exception result.  This implicitly weeds out
    // abstract types or types with inaccessible copy constructors.

    // C++0x [class.copymove]p31:
    //   When certain criteria are met, an implementation is allowed to omit the
    //   copy/move construction of a class object [...]
    //
    //     - in a throw-expression, when the operand is the name of a
    //       non-volatile automatic object (other than a function or
    //       catch-clause
    //       parameter) whose scope does not extend beyond the end of the
    //       innermost enclosing try-block (if there is one), the copy/move
    //       operation from the operand to the exception object (15.1) can be
    //       omitted by constructing the automatic object directly into the
    //       exception object
    const VarDecl *NRVOVariable = nullptr;
    if (IsThrownVarInScope)
      NRVOVariable = getCopyElisionCandidate(QualType(), Ex, false);

    InitializedEntity Entity = InitializedEntity::InitializeException(
        OpLoc, ExceptionObjectTy,
        /*NRVO=*/NRVOVariable != nullptr);
    ExprResult Res = PerformMoveOrCopyInitialization(
        Entity, NRVOVariable, QualType(), Ex, IsThrownVarInScope);
    if (Res.isInvalid())
      return ExprError();
    Ex = Res.get();
  }

  return new (Context)
      CXXThrowExpr(Ex, Context.VoidTy, OpLoc, IsThrownVarInScope);
}

static void
collectPublicBases(CXXRecordDecl *RD,
                   llvm::DenseMap<CXXRecordDecl *, unsigned> &SubobjectsSeen,
                   llvm::SmallPtrSetImpl<CXXRecordDecl *> &VBases,
                   llvm::SetVector<CXXRecordDecl *> &PublicSubobjectsSeen,
                   bool ParentIsPublic) {
  for (const CXXBaseSpecifier &BS : RD->bases()) {
    CXXRecordDecl *BaseDecl = BS.getType()->getAsCXXRecordDecl();
    bool NewSubobject;
    // Virtual bases constitute the same subobject.  Non-virtual bases are
    // always distinct subobjects.
    if (BS.isVirtual())
      NewSubobject = VBases.insert(BaseDecl).second;
    else
      NewSubobject = true;

    if (NewSubobject)
      ++SubobjectsSeen[BaseDecl];

    // Only add subobjects which have public access throughout the entire chain.
    bool PublicPath = ParentIsPublic && BS.getAccessSpecifier() == AS_public;
    if (PublicPath)
      PublicSubobjectsSeen.insert(BaseDecl);

    // Recurse on to each base subobject.
    collectPublicBases(BaseDecl, SubobjectsSeen, VBases, PublicSubobjectsSeen,
                       PublicPath);
  }
}

static void getUnambiguousPublicSubobjects(
    CXXRecordDecl *RD, llvm::SmallVectorImpl<CXXRecordDecl *> &Objects) {
  llvm::DenseMap<CXXRecordDecl *, unsigned> SubobjectsSeen;
  llvm::SmallSet<CXXRecordDecl *, 2> VBases;
  llvm::SetVector<CXXRecordDecl *> PublicSubobjectsSeen;
  SubobjectsSeen[RD] = 1;
  PublicSubobjectsSeen.insert(RD);
  collectPublicBases(RD, SubobjectsSeen, VBases, PublicSubobjectsSeen,
                     /*ParentIsPublic=*/true);

  for (CXXRecordDecl *PublicSubobject : PublicSubobjectsSeen) {
    // Skip ambiguous objects.
    if (SubobjectsSeen[PublicSubobject] > 1)
      continue;

    Objects.push_back(PublicSubobject);
  }
}

/// CheckCXXThrowOperand - Validate the operand of a throw.
bool Sema::CheckCXXThrowOperand(SourceLocation ThrowLoc,
                                QualType ExceptionObjectTy, Expr *E) {
  //   If the type of the exception would be an incomplete type or a pointer
  //   to an incomplete type other than (cv) void the program is ill-formed.
  QualType Ty = ExceptionObjectTy;
  bool isPointer = false;
  if (const PointerType* Ptr = Ty->getAs<PointerType>()) {
    Ty = Ptr->getPointeeType();
    isPointer = true;
  }
  if (!isPointer || !Ty->isVoidType()) {
    if (RequireCompleteType(ThrowLoc, Ty,
                            isPointer ? diag::err_throw_incomplete_ptr
                                      : diag::err_throw_incomplete,
                            E->getSourceRange()))
      return true;

    if (RequireNonAbstractType(ThrowLoc, ExceptionObjectTy,
                               diag::err_throw_abstract_type, E))
      return true;
  }

  // If the exception has class type, we need additional handling.
  CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
  if (!RD)
    return false;

  // If we are throwing a polymorphic class type or pointer thereof,
  // exception handling will make use of the vtable.
  MarkVTableUsed(ThrowLoc, RD);

  // If a pointer is thrown, the referenced object will not be destroyed.
  if (isPointer)
    return false;

  // If the class has a destructor, we must be able to call it.
  if (!RD->hasIrrelevantDestructor()) {
    if (CXXDestructorDecl *Destructor = LookupDestructor(RD)) {
      MarkFunctionReferenced(E->getExprLoc(), Destructor);
      CheckDestructorAccess(E->getExprLoc(), Destructor,
                            PDiag(diag::err_access_dtor_exception) << Ty);
      if (DiagnoseUseOfDecl(Destructor, E->getExprLoc()))
        return true;
    }
  }

  // The MSVC ABI creates a list of all types which can catch the exception
  // object.  This list also references the appropriate copy constructor to call
  // if the object is caught by value and has a non-trivial copy constructor.
  if (Context.getTargetInfo().getCXXABI().isMicrosoft()) {
    // We are only interested in the public, unambiguous bases contained within
    // the exception object.  Bases which are ambiguous or otherwise
    // inaccessible are not catchable types.
    llvm::SmallVector<CXXRecordDecl *, 2> UnambiguousPublicSubobjects;
    getUnambiguousPublicSubobjects(RD, UnambiguousPublicSubobjects);

    for (CXXRecordDecl *Subobject : UnambiguousPublicSubobjects) {
      // Attempt to lookup the copy constructor.  Various pieces of machinery
      // will spring into action, like template instantiation, which means this
      // cannot be a simple walk of the class's decls.  Instead, we must perform
      // lookup and overload resolution.
      CXXConstructorDecl *CD = LookupCopyingConstructor(Subobject, 0);
      if (!CD)
        continue;

      // Mark the constructor referenced as it is used by this throw expression.
      MarkFunctionReferenced(E->getExprLoc(), CD);

      // Skip this copy constructor if it is trivial, we don't need to record it
      // in the catchable type data.
      if (CD->isTrivial())
        continue;

      // The copy constructor is non-trivial, create a mapping from this class
      // type to this constructor.
      // N.B.  The selection of copy constructor is not sensitive to this
      // particular throw-site.  Lookup will be performed at the catch-site to
      // ensure that the copy constructor is, in fact, accessible (via
      // friendship or any other means).
      Context.addCopyConstructorForExceptionObject(Subobject, CD);

      // We don't keep the instantiated default argument expressions around so
      // we must rebuild them here.
      for (unsigned I = 1, E = CD->getNumParams(); I != E; ++I) {
        // Skip any default arguments that we've already instantiated.
        if (Context.getDefaultArgExprForConstructor(CD, I))
          continue;

        Expr *DefaultArg =
            BuildCXXDefaultArgExpr(ThrowLoc, CD, CD->getParamDecl(I)).get();
        Context.addDefaultArgExprForConstructor(CD, I, DefaultArg);
      }
    }
  }

  return false;
}

QualType Sema::getCurrentThisType() {
  DeclContext *DC = getFunctionLevelDeclContext();
  QualType ThisTy = CXXThisTypeOverride;
  if (CXXMethodDecl *method = dyn_cast<CXXMethodDecl>(DC)) {
    if (method && method->isInstance())
      ThisTy = method->getThisType(Context);
  }
  if (ThisTy.isNull()) {
    if (isGenericLambdaCallOperatorSpecialization(CurContext) &&
        CurContext->getParent()->getParent()->isRecord()) {
      // This is a generic lambda call operator that is being instantiated
      // within a default initializer - so use the enclosing class as 'this'.
      // There is no enclosing member function to retrieve the 'this' pointer
      // from.
      QualType ClassTy = Context.getTypeDeclType(
          cast<CXXRecordDecl>(CurContext->getParent()->getParent()));
      // There are no cv-qualifiers for 'this' within default initializers, 
      // per [expr.prim.general]p4.
      return Context.getPointerType(ClassTy);
    }
  }
  return ThisTy;
}

Sema::CXXThisScopeRAII::CXXThisScopeRAII(Sema &S, 
                                         Decl *ContextDecl,
                                         unsigned CXXThisTypeQuals,
                                         bool Enabled) 
  : S(S), OldCXXThisTypeOverride(S.CXXThisTypeOverride), Enabled(false)
{
  if (!Enabled || !ContextDecl)
    return;

  CXXRecordDecl *Record = nullptr;
  if (ClassTemplateDecl *Template = dyn_cast<ClassTemplateDecl>(ContextDecl))
    Record = Template->getTemplatedDecl();
  else
    Record = cast<CXXRecordDecl>(ContextDecl);
    
  S.CXXThisTypeOverride
    = S.Context.getPointerType(
        S.Context.getRecordType(Record).withCVRQualifiers(CXXThisTypeQuals));
  
  this->Enabled = true;
}


Sema::CXXThisScopeRAII::~CXXThisScopeRAII() {
  if (Enabled) {
    S.CXXThisTypeOverride = OldCXXThisTypeOverride;
  }
}

static Expr *captureThis(ASTContext &Context, RecordDecl *RD,
                         QualType ThisTy, SourceLocation Loc) {
  FieldDecl *Field
    = FieldDecl::Create(Context, RD, Loc, Loc, nullptr, ThisTy,
                        Context.getTrivialTypeSourceInfo(ThisTy, Loc),
                        nullptr, false, ICIS_NoInit);
  Field->setImplicit(true);
  Field->setAccess(AS_private);
  RD->addDecl(Field);
  return new (Context) CXXThisExpr(Loc, ThisTy, /*isImplicit*/true);
}

bool Sema::CheckCXXThisCapture(SourceLocation Loc, bool Explicit, 
    bool BuildAndDiagnose, const unsigned *const FunctionScopeIndexToStopAt) {
  // We don't need to capture this in an unevaluated context.
  if (isUnevaluatedContext() && !Explicit)
    return true;

  const unsigned MaxFunctionScopesIndex = FunctionScopeIndexToStopAt ?
    *FunctionScopeIndexToStopAt : FunctionScopes.size() - 1;  
 // Otherwise, check that we can capture 'this'.
  unsigned NumClosures = 0;
  for (unsigned idx = MaxFunctionScopesIndex; idx != 0; idx--) {
    if (CapturingScopeInfo *CSI =
            dyn_cast<CapturingScopeInfo>(FunctionScopes[idx])) {
      if (CSI->CXXThisCaptureIndex != 0) {
        // 'this' is already being captured; there isn't anything more to do.
        break;
      }
      LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(CSI);
      if (LSI && isGenericLambdaCallOperatorSpecialization(LSI->CallOperator)) {
        // This context can't implicitly capture 'this'; fail out.
        if (BuildAndDiagnose)
          Diag(Loc, diag::err_this_capture) << Explicit;
        return true;
      }
      if (CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_LambdaByref ||
          CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_LambdaByval ||
          CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_Block ||
          CSI->ImpCaptureStyle == CapturingScopeInfo::ImpCap_CapturedRegion ||
          Explicit) {
        // This closure can capture 'this'; continue looking upwards.
        NumClosures++;
        Explicit = false;
        continue;
      }
      // This context can't implicitly capture 'this'; fail out.
      if (BuildAndDiagnose)
        Diag(Loc, diag::err_this_capture) << Explicit;
      return true;
    }
    break;
  }
  if (!BuildAndDiagnose) return false;
  // Mark that we're implicitly capturing 'this' in all the scopes we skipped.
  // FIXME: We need to delay this marking in PotentiallyPotentiallyEvaluated
  // contexts.
  for (unsigned idx = MaxFunctionScopesIndex; NumClosures; 
      --idx, --NumClosures) {
    CapturingScopeInfo *CSI = cast<CapturingScopeInfo>(FunctionScopes[idx]);
    Expr *ThisExpr = nullptr;
    QualType ThisTy = getCurrentThisType();
    if (LambdaScopeInfo *LSI = dyn_cast<LambdaScopeInfo>(CSI))
      // For lambda expressions, build a field and an initializing expression.
      ThisExpr = captureThis(Context, LSI->Lambda, ThisTy, Loc);
    else if (CapturedRegionScopeInfo *RSI
        = dyn_cast<CapturedRegionScopeInfo>(FunctionScopes[idx]))
      ThisExpr = captureThis(Context, RSI->TheRecordDecl, ThisTy, Loc);

    bool isNested = NumClosures > 1;
    CSI->addThisCapture(isNested, Loc, ThisTy, ThisExpr);
  }
  return false;
}

ExprResult Sema::ActOnCXXThis(SourceLocation Loc) {
  /// C++ 9.3.2: In the body of a non-static member function, the keyword this
  /// is a non-lvalue expression whose value is the address of the object for
  /// which the function is called.

  QualType ThisTy = getCurrentThisType();
  if (ThisTy.isNull()) return Diag(Loc, diag::err_invalid_this_use);

  CheckCXXThisCapture(Loc);
  return new (Context) CXXThisExpr(Loc, ThisTy, /*isImplicit=*/false);
}

bool Sema::isThisOutsideMemberFunctionBody(QualType BaseType) {
  // If we're outside the body of a member function, then we'll have a specified
  // type for 'this'.
  if (CXXThisTypeOverride.isNull())
    return false;
  
  // Determine whether we're looking into a class that's currently being
  // defined.
  CXXRecordDecl *Class = BaseType->getAsCXXRecordDecl();
  return Class && Class->isBeingDefined();
}

ExprResult
Sema::ActOnCXXTypeConstructExpr(ParsedType TypeRep,
                                SourceLocation LParenLoc,
                                MultiExprArg exprs,
                                SourceLocation RParenLoc) {
  if (!TypeRep)
    return ExprError();

  TypeSourceInfo *TInfo;
  QualType Ty = GetTypeFromParser(TypeRep, &TInfo);
  if (!TInfo)
    TInfo = Context.getTrivialTypeSourceInfo(Ty, SourceLocation());

  return BuildCXXTypeConstructExpr(TInfo, LParenLoc, exprs, RParenLoc);
}

/// ActOnCXXTypeConstructExpr - Parse construction of a specified type.
/// Can be interpreted either as function-style casting ("int(x)")
/// or class type construction ("ClassType(x,y,z)")
/// or creation of a value-initialized type ("int()").
ExprResult
Sema::BuildCXXTypeConstructExpr(TypeSourceInfo *TInfo,
                                SourceLocation LParenLoc,
                                MultiExprArg Exprs,
                                SourceLocation RParenLoc) {
  QualType Ty = TInfo->getType();
  SourceLocation TyBeginLoc = TInfo->getTypeLoc().getBeginLoc();

  if (Ty->isDependentType() || CallExpr::hasAnyTypeDependentArguments(Exprs)) {
    return CXXUnresolvedConstructExpr::Create(Context, TInfo, LParenLoc, Exprs,
                                              RParenLoc);
  }

  bool ListInitialization = LParenLoc.isInvalid();
  assert((!ListInitialization || (Exprs.size() == 1 && isa<InitListExpr>(Exprs[0])))
         && "List initialization must have initializer list as expression.");
  SourceRange FullRange = SourceRange(TyBeginLoc,
      ListInitialization ? Exprs[0]->getSourceRange().getEnd() : RParenLoc);

  // C++ [expr.type.conv]p1:
  // If the expression list is a single expression, the type conversion
  // expression is equivalent (in definedness, and if defined in meaning) to the
  // corresponding cast expression.
  if (Exprs.size() == 1 && !ListInitialization) {
    Expr *Arg = Exprs[0];
    return BuildCXXFunctionalCastExpr(TInfo, LParenLoc, Arg, RParenLoc);
  }

  QualType ElemTy = Ty;
  if (Ty->isArrayType()) {
    if (!ListInitialization)
      return ExprError(Diag(TyBeginLoc,
                            diag::err_value_init_for_array_type) << FullRange);
    ElemTy = Context.getBaseElementType(Ty);
  }

  if (!Ty->isVoidType() &&
      RequireCompleteType(TyBeginLoc, ElemTy,
                          diag::err_invalid_incomplete_type_use, FullRange))
    return ExprError();

  if (RequireNonAbstractType(TyBeginLoc, Ty,
                             diag::err_allocation_of_abstract_type))
    return ExprError();

  InitializedEntity Entity = InitializedEntity::InitializeTemporary(TInfo);
  InitializationKind Kind =
      Exprs.size() ? ListInitialization
      ? InitializationKind::CreateDirectList(TyBeginLoc)
      : InitializationKind::CreateDirect(TyBeginLoc, LParenLoc, RParenLoc)
      : InitializationKind::CreateValue(TyBeginLoc, LParenLoc, RParenLoc);
  InitializationSequence InitSeq(*this, Entity, Kind, Exprs);
  ExprResult Result = InitSeq.Perform(*this, Entity, Kind, Exprs);

  if (Result.isInvalid() || !ListInitialization)
    return Result;

  Expr *Inner = Result.get();
  if (CXXBindTemporaryExpr *BTE = dyn_cast_or_null<CXXBindTemporaryExpr>(Inner))
    Inner = BTE->getSubExpr();
  if (!isa<CXXTemporaryObjectExpr>(Inner)) {
    // If we created a CXXTemporaryObjectExpr, that node also represents the
    // functional cast. Otherwise, create an explicit cast to represent
    // the syntactic form of a functional-style cast that was used here.
    //
    // FIXME: Creating a CXXFunctionalCastExpr around a CXXConstructExpr
    // would give a more consistent AST representation than using a
    // CXXTemporaryObjectExpr. It's also weird that the functional cast
    // is sometimes handled by initialization and sometimes not.
    QualType ResultType = Result.get()->getType();
    Result = CXXFunctionalCastExpr::Create(
        Context, ResultType, Expr::getValueKindForType(TInfo->getType()), TInfo,
        CK_NoOp, Result.get(), /*Path=*/nullptr, LParenLoc, RParenLoc);
  }

  return Result;
}

/// doesUsualArrayDeleteWantSize - Answers whether the usual
/// operator delete[] for the given type has a size_t parameter.
static bool doesUsualArrayDeleteWantSize(Sema &S, SourceLocation loc,
                                         QualType allocType) {
  const RecordType *record =
    allocType->getBaseElementTypeUnsafe()->getAs<RecordType>();
  if (!record) return false;

  // Try to find an operator delete[] in class scope.

  DeclarationName deleteName =
    S.Context.DeclarationNames.getCXXOperatorName(OO_Array_Delete);
  LookupResult ops(S, deleteName, loc, Sema::LookupOrdinaryName);
  S.LookupQualifiedName(ops, record->getDecl());

  // We're just doing this for information.
  ops.suppressDiagnostics();

  // Very likely: there's no operator delete[].
  if (ops.empty()) return false;

  // If it's ambiguous, it should be illegal to call operator delete[]
  // on this thing, so it doesn't matter if we allocate extra space or not.
  if (ops.isAmbiguous()) return false;

  LookupResult::Filter filter = ops.makeFilter();
  while (filter.hasNext()) {
    NamedDecl *del = filter.next()->getUnderlyingDecl();

    // C++0x [basic.stc.dynamic.deallocation]p2:
    //   A template instance is never a usual deallocation function,
    //   regardless of its signature.
    if (isa<FunctionTemplateDecl>(del)) {
      filter.erase();
      continue;
    }

    // C++0x [basic.stc.dynamic.deallocation]p2:
    //   If class T does not declare [an operator delete[] with one
    //   parameter] but does declare a member deallocation function
    //   named operator delete[] with exactly two parameters, the
    //   second of which has type std::size_t, then this function
    //   is a usual deallocation function.
    if (!cast<CXXMethodDecl>(del)->isUsualDeallocationFunction()) {
      filter.erase();
      continue;
    }
  }
  filter.done();

  if (!ops.isSingleResult()) return false;

  const FunctionDecl *del = cast<FunctionDecl>(ops.getFoundDecl());
  return (del->getNumParams() == 2);
}

/// \brief Parsed a C++ 'new' expression (C++ 5.3.4).
///
/// E.g.:
/// @code new (memory) int[size][4] @endcode
/// or
/// @code ::new Foo(23, "hello") @endcode
///
/// \param StartLoc The first location of the expression.
/// \param UseGlobal True if 'new' was prefixed with '::'.
/// \param PlacementLParen Opening paren of the placement arguments.
/// \param PlacementArgs Placement new arguments.
/// \param PlacementRParen Closing paren of the placement arguments.
/// \param TypeIdParens If the type is in parens, the source range.
/// \param D The type to be allocated, as well as array dimensions.
/// \param Initializer The initializing expression or initializer-list, or null
///   if there is none.
ExprResult
Sema::ActOnCXXNew(SourceLocation StartLoc, bool UseGlobal,
                  SourceLocation PlacementLParen, MultiExprArg PlacementArgs,
                  SourceLocation PlacementRParen, SourceRange TypeIdParens,
                  Declarator &D, Expr *Initializer) {
  bool TypeContainsAuto = D.getDeclSpec().containsPlaceholderType();

  Expr *ArraySize = nullptr;
  // If the specified type is an array, unwrap it and save the expression.
  if (D.getNumTypeObjects() > 0 &&
      D.getTypeObject(0).Kind == DeclaratorChunk::Array) {
     DeclaratorChunk &Chunk = D.getTypeObject(0);
    if (TypeContainsAuto)
      return ExprError(Diag(Chunk.Loc, diag::err_new_array_of_auto)
        << D.getSourceRange());
    if (Chunk.Arr.hasStatic)
      return ExprError(Diag(Chunk.Loc, diag::err_static_illegal_in_new)
        << D.getSourceRange());
    if (!Chunk.Arr.NumElts)
      return ExprError(Diag(Chunk.Loc, diag::err_array_new_needs_size)
        << D.getSourceRange());

    ArraySize = static_cast<Expr*>(Chunk.Arr.NumElts);
    D.DropFirstTypeObject();
  }

  // Every dimension shall be of constant size.
  if (ArraySize) {
    for (unsigned I = 0, N = D.getNumTypeObjects(); I < N; ++I) {
      if (D.getTypeObject(I).Kind != DeclaratorChunk::Array)
        break;

      DeclaratorChunk::ArrayTypeInfo &Array = D.getTypeObject(I).Arr;
      if (Expr *NumElts = (Expr *)Array.NumElts) {
        if (!NumElts->isTypeDependent() && !NumElts->isValueDependent()) {
          if (getLangOpts().CPlusPlus14) {
	    // C++1y [expr.new]p6: Every constant-expression in a noptr-new-declarator
	    //   shall be a converted constant expression (5.19) of type std::size_t
	    //   and shall evaluate to a strictly positive value.
            unsigned IntWidth = Context.getTargetInfo().getIntWidth();
            assert(IntWidth && "Builtin type of size 0?");
            llvm::APSInt Value(IntWidth);
            Array.NumElts
             = CheckConvertedConstantExpression(NumElts, Context.getSizeType(), Value,
                                                CCEK_NewExpr)
                 .get();
          } else {
            Array.NumElts
              = VerifyIntegerConstantExpression(NumElts, nullptr,
                                                diag::err_new_array_nonconst)
                  .get();
          }
          if (!Array.NumElts)
            return ExprError();
        }
      }
    }
  }

  TypeSourceInfo *TInfo = GetTypeForDeclarator(D, /*Scope=*/nullptr);
  QualType AllocType = TInfo->getType();
  if (D.isInvalidType())
    return ExprError();

  SourceRange DirectInitRange;
  if (ParenListExpr *List = dyn_cast_or_null<ParenListExpr>(Initializer))
    DirectInitRange = List->getSourceRange();

  return BuildCXXNew(SourceRange(StartLoc, D.getLocEnd()), UseGlobal,
                     PlacementLParen,
                     PlacementArgs,
                     PlacementRParen,
                     TypeIdParens,
                     AllocType,
                     TInfo,
                     ArraySize,
                     DirectInitRange,
                     Initializer,
                     TypeContainsAuto);
}

static bool isLegalArrayNewInitializer(CXXNewExpr::InitializationStyle Style,
                                       Expr *Init) {
  if (!Init)
    return true;
  if (ParenListExpr *PLE = dyn_cast<ParenListExpr>(Init))
    return PLE->getNumExprs() == 0;
  if (isa<ImplicitValueInitExpr>(Init))
    return true;
  else if (CXXConstructExpr *CCE = dyn_cast<CXXConstructExpr>(Init))
    return !CCE->isListInitialization() &&
           CCE->getConstructor()->isDefaultConstructor();
  else if (Style == CXXNewExpr::ListInit) {
    assert(isa<InitListExpr>(Init) &&
           "Shouldn't create list CXXConstructExprs for arrays.");
    return true;
  }
  return false;
}

ExprResult
Sema::BuildCXXNew(SourceRange Range, bool UseGlobal,
                  SourceLocation PlacementLParen,
                  MultiExprArg PlacementArgs,
                  SourceLocation PlacementRParen,
                  SourceRange TypeIdParens,
                  QualType AllocType,
                  TypeSourceInfo *AllocTypeInfo,
                  Expr *ArraySize,
                  SourceRange DirectInitRange,
                  Expr *Initializer,
                  bool TypeMayContainAuto) {
  SourceRange TypeRange = AllocTypeInfo->getTypeLoc().getSourceRange();
  SourceLocation StartLoc = Range.getBegin();

  CXXNewExpr::InitializationStyle initStyle;
  if (DirectInitRange.isValid()) {
    assert(Initializer && "Have parens but no initializer.");
    initStyle = CXXNewExpr::CallInit;
  } else if (Initializer && isa<InitListExpr>(Initializer))
    initStyle = CXXNewExpr::ListInit;
  else {
    assert((!Initializer || isa<ImplicitValueInitExpr>(Initializer) ||
            isa<CXXConstructExpr>(Initializer)) &&
           "Initializer expression that cannot have been implicitly created.");
    initStyle = CXXNewExpr::NoInit;
  }

  Expr **Inits = &Initializer;
  unsigned NumInits = Initializer ? 1 : 0;
  if (ParenListExpr *List = dyn_cast_or_null<ParenListExpr>(Initializer)) {
    assert(initStyle == CXXNewExpr::CallInit && "paren init for non-call init");
    Inits = List->getExprs();
    NumInits = List->getNumExprs();
  }

  // C++11 [dcl.spec.auto]p6. Deduce the type which 'auto' stands in for.
  if (TypeMayContainAuto && AllocType->isUndeducedType()) {
    if (initStyle == CXXNewExpr::NoInit || NumInits == 0)
      return ExprError(Diag(StartLoc, diag::err_auto_new_requires_ctor_arg)
                       << AllocType << TypeRange);
    if (initStyle == CXXNewExpr::ListInit ||
        (NumInits == 1 && isa<InitListExpr>(Inits[0])))
      return ExprError(Diag(Inits[0]->getLocStart(),
                            diag::err_auto_new_list_init)
                       << AllocType << TypeRange);
    if (NumInits > 1) {
      Expr *FirstBad = Inits[1];
      return ExprError(Diag(FirstBad->getLocStart(),
                            diag::err_auto_new_ctor_multiple_expressions)
                       << AllocType << TypeRange);
    }
    Expr *Deduce = Inits[0];
    QualType DeducedType;
    if (DeduceAutoType(AllocTypeInfo, Deduce, DeducedType) == DAR_Failed)
      return ExprError(Diag(StartLoc, diag::err_auto_new_deduction_failure)
                       << AllocType << Deduce->getType()
                       << TypeRange << Deduce->getSourceRange());
    if (DeducedType.isNull())
      return ExprError();
    AllocType = DeducedType;
  }

  // Per C++0x [expr.new]p5, the type being constructed may be a
  // typedef of an array type.
  if (!ArraySize) {
    if (const ConstantArrayType *Array
                              = Context.getAsConstantArrayType(AllocType)) {
      ArraySize = IntegerLiteral::Create(Context, Array->getSize(),
                                         Context.getSizeType(),
                                         TypeRange.getEnd());
      AllocType = Array->getElementType();
    }
  }

  if (CheckAllocatedType(AllocType, TypeRange.getBegin(), TypeRange))
    return ExprError();

  if (initStyle == CXXNewExpr::ListInit &&
      isStdInitializerList(AllocType, nullptr)) {
    Diag(AllocTypeInfo->getTypeLoc().getBeginLoc(),
         diag::warn_dangling_std_initializer_list)
        << /*at end of FE*/0 << Inits[0]->getSourceRange();
  }

  // In ARC, infer 'retaining' for the allocated 
  if (getLangOpts().ObjCAutoRefCount &&
      AllocType.getObjCLifetime() == Qualifiers::OCL_None &&
      AllocType->isObjCLifetimeType()) {
    AllocType = Context.getLifetimeQualifiedType(AllocType,
                                    AllocType->getObjCARCImplicitLifetime());
  }

  QualType ResultType = Context.getPointerType(AllocType);
    
  if (ArraySize && ArraySize->getType()->isNonOverloadPlaceholderType()) {
    ExprResult result = CheckPlaceholderExpr(ArraySize);
    if (result.isInvalid()) return ExprError();
    ArraySize = result.get();
  }
  // C++98 5.3.4p6: "The expression in a direct-new-declarator shall have
  //   integral or enumeration type with a non-negative value."
  // C++11 [expr.new]p6: The expression [...] shall be of integral or unscoped
  //   enumeration type, or a class type for which a single non-explicit
  //   conversion function to integral or unscoped enumeration type exists.
  // C++1y [expr.new]p6: The expression [...] is implicitly converted to
  //   std::size_t.
  if (ArraySize && !ArraySize->isTypeDependent()) {
    ExprResult ConvertedSize;
    if (getLangOpts().CPlusPlus14) {
      assert(Context.getTargetInfo().getIntWidth() && "Builtin type of size 0?");

      ConvertedSize = PerformImplicitConversion(ArraySize, Context.getSizeType(),
						AA_Converting);

      if (!ConvertedSize.isInvalid() && 
          ArraySize->getType()->getAs<RecordType>())
        // Diagnose the compatibility of this conversion.
        Diag(StartLoc, diag::warn_cxx98_compat_array_size_conversion)
          << ArraySize->getType() << 0 << "'size_t'";
    } else {
      class SizeConvertDiagnoser : public ICEConvertDiagnoser {
      protected:
        Expr *ArraySize;
  
      public:
        SizeConvertDiagnoser(Expr *ArraySize)
            : ICEConvertDiagnoser(/*AllowScopedEnumerations*/false, false, false),
              ArraySize(ArraySize) {}

        SemaDiagnosticBuilder diagnoseNotInt(Sema &S, SourceLocation Loc,
                                             QualType T) override {
          return S.Diag(Loc, diag::err_array_size_not_integral)
                   << S.getLangOpts().CPlusPlus11 << T;
        }

        SemaDiagnosticBuilder diagnoseIncomplete(
            Sema &S, SourceLocation Loc, QualType T) override {
          return S.Diag(Loc, diag::err_array_size_incomplete_type)
                   << T << ArraySize->getSourceRange();
        }

        SemaDiagnosticBuilder diagnoseExplicitConv(
            Sema &S, SourceLocation Loc, QualType T, QualType ConvTy) override {
          return S.Diag(Loc, diag::err_array_size_explicit_conversion) << T << ConvTy;
        }

        SemaDiagnosticBuilder noteExplicitConv(
            Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
          return S.Diag(Conv->getLocation(), diag::note_array_size_conversion)
                   << ConvTy->isEnumeralType() << ConvTy;
        }

        SemaDiagnosticBuilder diagnoseAmbiguous(
            Sema &S, SourceLocation Loc, QualType T) override {
          return S.Diag(Loc, diag::err_array_size_ambiguous_conversion) << T;
        }

        SemaDiagnosticBuilder noteAmbiguous(
            Sema &S, CXXConversionDecl *Conv, QualType ConvTy) override {
          return S.Diag(Conv->getLocation(), diag::note_array_size_conversion)
                   << ConvTy->isEnumeralType() << ConvTy;
        }

        SemaDiagnosticBuilder diagnoseConversion(Sema &S, SourceLocation Loc,
                                                 QualType T,
                                                 QualType ConvTy) override {
          return S.Diag(Loc,
                        S.getLangOpts().CPlusPlus11
                          ? diag::warn_cxx98_compat_array_size_conversion
                          : diag::ext_array_size_conversion)
                   << T << ConvTy->isEnumeralType() << ConvTy;
        }
      } SizeDiagnoser(ArraySize);

      ConvertedSize = PerformContextualImplicitConversion(StartLoc, ArraySize,
                                                          SizeDiagnoser);
    }
    if (ConvertedSize.isInvalid())
      return ExprError();

    ArraySize = ConvertedSize.get();
    QualType SizeType = ArraySize->getType();

    if (!SizeType->isIntegralOrUnscopedEnumerationType())
      return ExprError();

    // C++98 [expr.new]p7:
    //   The expression in a direct-new-declarator shall have integral type
    //   with a non-negative value.
    //
    // Let's see if this is a constant < 0. If so, we reject it out of
    // hand. Otherwise, if it's not a constant, we must have an unparenthesized
    // array type.
    //
    // Note: such a construct has well-defined semantics in C++11: it throws
    // std::bad_array_new_length.
    if (!ArraySize->isValueDependent()) {
      llvm::APSInt Value;
      // We've already performed any required implicit conversion to integer or
      // unscoped enumeration type.
      if (ArraySize->isIntegerConstantExpr(Value, Context)) {
        if (Value < llvm::APSInt(
                        llvm::APInt::getNullValue(Value.getBitWidth()),
                                 Value.isUnsigned())) {
          if (getLangOpts().CPlusPlus11)
            Diag(ArraySize->getLocStart(),
                 diag::warn_typecheck_negative_array_new_size)
              << ArraySize->getSourceRange();
          else
            return ExprError(Diag(ArraySize->getLocStart(),
                                  diag::err_typecheck_negative_array_size)
                             << ArraySize->getSourceRange());
        } else if (!AllocType->isDependentType()) {
          unsigned ActiveSizeBits =
            ConstantArrayType::getNumAddressingBits(Context, AllocType, Value);
          if (ActiveSizeBits > ConstantArrayType::getMaxSizeBits(Context)) {
            if (getLangOpts().CPlusPlus11)
              Diag(ArraySize->getLocStart(),
                   diag::warn_array_new_too_large)
                << Value.toString(10)
                << ArraySize->getSourceRange();
            else
              return ExprError(Diag(ArraySize->getLocStart(),
                                    diag::err_array_too_large)
                               << Value.toString(10)
                               << ArraySize->getSourceRange());
          }
        }
      } else if (TypeIdParens.isValid()) {
        // Can't have dynamic array size when the type-id is in parentheses.
        Diag(ArraySize->getLocStart(), diag::ext_new_paren_array_nonconst)
          << ArraySize->getSourceRange()
          << FixItHint::CreateRemoval(TypeIdParens.getBegin())
          << FixItHint::CreateRemoval(TypeIdParens.getEnd());

        TypeIdParens = SourceRange();
      }
    }

    // Note that we do *not* convert the argument in any way.  It can
    // be signed, larger than size_t, whatever.
  }

  FunctionDecl *OperatorNew = nullptr;
  FunctionDecl *OperatorDelete = nullptr;

  if (!AllocType->isDependentType() &&
      !Expr::hasAnyTypeDependentArguments(PlacementArgs) &&
      FindAllocationFunctions(StartLoc,
                              SourceRange(PlacementLParen, PlacementRParen),
                              UseGlobal, AllocType, ArraySize, PlacementArgs,
                              OperatorNew, OperatorDelete))
    return ExprError();

  // If this is an array allocation, compute whether the usual array
  // deallocation function for the type has a size_t parameter.
  bool UsualArrayDeleteWantsSize = false;
  if (ArraySize && !AllocType->isDependentType())
    UsualArrayDeleteWantsSize
      = doesUsualArrayDeleteWantSize(*this, StartLoc, AllocType);

  SmallVector<Expr *, 8> AllPlaceArgs;
  if (OperatorNew) {
    const FunctionProtoType *Proto =
        OperatorNew->getType()->getAs<FunctionProtoType>();
    VariadicCallType CallType = Proto->isVariadic() ? VariadicFunction
                                                    : VariadicDoesNotApply;

    // We've already converted the placement args, just fill in any default
    // arguments. Skip the first parameter because we don't have a corresponding
    // argument.
    if (GatherArgumentsForCall(PlacementLParen, OperatorNew, Proto, 1,
                               PlacementArgs, AllPlaceArgs, CallType))
      return ExprError();

    if (!AllPlaceArgs.empty())
      PlacementArgs = AllPlaceArgs;

    // FIXME: This is wrong: PlacementArgs misses out the first (size) argument.
    DiagnoseSentinelCalls(OperatorNew, PlacementLParen, PlacementArgs);

    // FIXME: Missing call to CheckFunctionCall or equivalent
  }

  // Warn if the type is over-aligned and is being allocated by global operator
  // new.
  if (PlacementArgs.empty() && OperatorNew &&
      (OperatorNew->isImplicit() ||
       getSourceManager().isInSystemHeader(OperatorNew->getLocStart()))) {
    if (unsigned Align = Context.getPreferredTypeAlign(AllocType.getTypePtr())){
      unsigned SuitableAlign = Context.getTargetInfo().getSuitableAlign();
      if (Align > SuitableAlign)
        Diag(StartLoc, diag::warn_overaligned_type)
            << AllocType
            << unsigned(Align / Context.getCharWidth())
            << unsigned(SuitableAlign / Context.getCharWidth());
    }
  }

  QualType InitType = AllocType;
  // Array 'new' can't have any initializers except empty parentheses.
  // Initializer lists are also allowed, in C++11. Rely on the parser for the
  // dialect distinction.
  if (ResultType->isArrayType() || ArraySize) {
    if (!isLegalArrayNewInitializer(initStyle, Initializer)) {
      SourceRange InitRange(Inits[0]->getLocStart(),
                            Inits[NumInits - 1]->getLocEnd());
      Diag(StartLoc, diag::err_new_array_init_args) << InitRange;
      return ExprError();
    }
    if (InitListExpr *ILE = dyn_cast_or_null<InitListExpr>(Initializer)) {
      // We do the initialization typechecking against the array type
      // corresponding to the number of initializers + 1 (to also check
      // default-initialization).
      unsigned NumElements = ILE->getNumInits() + 1;
      InitType = Context.getConstantArrayType(AllocType,
          llvm::APInt(Context.getTypeSize(Context.getSizeType()), NumElements),
                                              ArrayType::Normal, 0);
    }
  }

  // If we can perform the initialization, and we've not already done so,
  // do it now.
  if (!AllocType->isDependentType() &&
      !Expr::hasAnyTypeDependentArguments(
          llvm::makeArrayRef(Inits, NumInits))) {
    // C++11 [expr.new]p15:
    //   A new-expression that creates an object of type T initializes that
    //   object as follows:
    InitializationKind Kind
    //     - If the new-initializer is omitted, the object is default-
    //       initialized (8.5); if no initialization is performed,
    //       the object has indeterminate value
      = initStyle == CXXNewExpr::NoInit
          ? InitializationKind::CreateDefault(TypeRange.getBegin())
    //     - Otherwise, the new-initializer is interpreted according to the
    //       initialization rules of 8.5 for direct-initialization.
          : initStyle == CXXNewExpr::ListInit
              ? InitializationKind::CreateDirectList(TypeRange.getBegin())
              : InitializationKind::CreateDirect(TypeRange.getBegin(),
                                                 DirectInitRange.getBegin(),
                                                 DirectInitRange.getEnd());

    InitializedEntity Entity
      = InitializedEntity::InitializeNew(StartLoc, InitType);
    InitializationSequence InitSeq(*this, Entity, Kind, MultiExprArg(Inits, NumInits));
    ExprResult FullInit = InitSeq.Perform(*this, Entity, Kind,
                                          MultiExprArg(Inits, NumInits));
    if (FullInit.isInvalid())
      return ExprError();

    // FullInit is our initializer; strip off CXXBindTemporaryExprs, because
    // we don't want the initialized object to be destructed.
    if (CXXBindTemporaryExpr *Binder =
            dyn_cast_or_null<CXXBindTemporaryExpr>(FullInit.get()))
      FullInit = Binder->getSubExpr();

    Initializer = FullInit.get();
  }

  // Mark the new and delete operators as referenced.
  if (OperatorNew) {
    if (DiagnoseUseOfDecl(OperatorNew, StartLoc))
      return ExprError();
    MarkFunctionReferenced(StartLoc, OperatorNew);
  }
  if (OperatorDelete) {
    if (DiagnoseUseOfDecl(OperatorDelete, StartLoc))
      return ExprError();
    MarkFunctionReferenced(StartLoc, OperatorDelete);
  }

  // C++0x [expr.new]p17:
  //   If the new expression creates an array of objects of class type,
  //   access and ambiguity control are done for the destructor.
  QualType BaseAllocType = Context.getBaseElementType(AllocType);
  if (ArraySize && !BaseAllocType->isDependentType()) {
    if (const RecordType *BaseRecordType = BaseAllocType->getAs<RecordType>()) {
      if (CXXDestructorDecl *dtor = LookupDestructor(
              cast<CXXRecordDecl>(BaseRecordType->getDecl()))) {
        MarkFunctionReferenced(StartLoc, dtor);
        CheckDestructorAccess(StartLoc, dtor, 
                              PDiag(diag::err_access_dtor)
                                << BaseAllocType);
        if (DiagnoseUseOfDecl(dtor, StartLoc))
          return ExprError();
      }
    }
  }

  return new (Context)
      CXXNewExpr(Context, UseGlobal, OperatorNew, OperatorDelete,
                 UsualArrayDeleteWantsSize, PlacementArgs, TypeIdParens,
                 ArraySize, initStyle, Initializer, ResultType, AllocTypeInfo,
                 Range, DirectInitRange);
}

/// \brief Checks that a type is suitable as the allocated type
/// in a new-expression.
bool Sema::CheckAllocatedType(QualType AllocType, SourceLocation Loc,
                              SourceRange R) {
  // C++ 5.3.4p1: "[The] type shall be a complete object type, but not an
  //   abstract class type or array thereof.
  if (AllocType->isFunctionType())
    return Diag(Loc, diag::err_bad_new_type)
      << AllocType << 0 << R;
  else if (AllocType->isReferenceType())
    return Diag(Loc, diag::err_bad_new_type)
      << AllocType << 1 << R;
  else if (!AllocType->isDependentType() &&
           RequireCompleteType(Loc, AllocType, diag::err_new_incomplete_type,R))
    return true;
  else if (RequireNonAbstractType(Loc, AllocType,
                                  diag::err_allocation_of_abstract_type))
    return true;
  else if (AllocType->isVariablyModifiedType())
    return Diag(Loc, diag::err_variably_modified_new_type)
             << AllocType;
  else if (unsigned AddressSpace = AllocType.getAddressSpace())
    return Diag(Loc, diag::err_address_space_qualified_new)
      << AllocType.getUnqualifiedType() << AddressSpace;
  else if (getLangOpts().ObjCAutoRefCount) {
    if (const ArrayType *AT = Context.getAsArrayType(AllocType)) {
      QualType BaseAllocType = Context.getBaseElementType(AT);
      if (BaseAllocType.getObjCLifetime() == Qualifiers::OCL_None &&
          BaseAllocType->isObjCLifetimeType())
        return Diag(Loc, diag::err_arc_new_array_without_ownership)
          << BaseAllocType;
    }
  }
           
  return false;
}

/// \brief Determine whether the given function is a non-placement
/// deallocation function.
static bool isNonPlacementDeallocationFunction(Sema &S, FunctionDecl *FD) {
  if (FD->isInvalidDecl())
    return false;

  if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(FD))
    return Method->isUsualDeallocationFunction();

  if (FD->getOverloadedOperator() != OO_Delete &&
      FD->getOverloadedOperator() != OO_Array_Delete)
    return false;

  if (FD->getNumParams() == 1)
    return true;

  return S.getLangOpts().SizedDeallocation && FD->getNumParams() == 2 &&
         S.Context.hasSameUnqualifiedType(FD->getParamDecl(1)->getType(),
                                          S.Context.getSizeType());
}

/// FindAllocationFunctions - Finds the overloads of operator new and delete
/// that are appropriate for the allocation.
bool Sema::FindAllocationFunctions(SourceLocation StartLoc, SourceRange Range,
                                   bool UseGlobal, QualType AllocType,
                                   bool IsArray, MultiExprArg PlaceArgs,
                                   FunctionDecl *&OperatorNew,
                                   FunctionDecl *&OperatorDelete) {
  // --- Choosing an allocation function ---
  // C++ 5.3.4p8 - 14 & 18
  // 1) If UseGlobal is true, only look in the global scope. Else, also look
  //   in the scope of the allocated class.
  // 2) If an array size is given, look for operator new[], else look for
  //   operator new.
  // 3) The first argument is always size_t. Append the arguments from the
  //   placement form.

  SmallVector<Expr*, 8> AllocArgs(1 + PlaceArgs.size());
  // We don't care about the actual value of this argument.
  // FIXME: Should the Sema create the expression and embed it in the syntax
  // tree? Or should the consumer just recalculate the value?
  IntegerLiteral Size(Context, llvm::APInt::getNullValue(
                      Context.getTargetInfo().getPointerWidth(0)),
                      Context.getSizeType(),
                      SourceLocation());
  AllocArgs[0] = &Size;
  std::copy(PlaceArgs.begin(), PlaceArgs.end(), AllocArgs.begin() + 1);

  // C++ [expr.new]p8:
  //   If the allocated type is a non-array type, the allocation
  //   function's name is operator new and the deallocation function's
  //   name is operator delete. If the allocated type is an array
  //   type, the allocation function's name is operator new[] and the
  //   deallocation function's name is operator delete[].
  DeclarationName NewName = Context.DeclarationNames.getCXXOperatorName(
                                        IsArray ? OO_Array_New : OO_New);
  DeclarationName DeleteName = Context.DeclarationNames.getCXXOperatorName(
                                        IsArray ? OO_Array_Delete : OO_Delete);

  QualType AllocElemType = Context.getBaseElementType(AllocType);

  if (AllocElemType->isRecordType() && !UseGlobal) {
    CXXRecordDecl *Record
      = cast<CXXRecordDecl>(AllocElemType->getAs<RecordType>()->getDecl());
    if (FindAllocationOverload(StartLoc, Range, NewName, AllocArgs, Record,
                               /*AllowMissing=*/true, OperatorNew))
      return true;
  }

  if (!OperatorNew) {
    // Didn't find a member overload. Look for a global one.
    DeclareGlobalNewDelete();
    DeclContext *TUDecl = Context.getTranslationUnitDecl();
    bool FallbackEnabled = IsArray && Context.getLangOpts().MSVCCompat;
    if (FindAllocationOverload(StartLoc, Range, NewName, AllocArgs, TUDecl,
                               /*AllowMissing=*/FallbackEnabled, OperatorNew,
                               /*Diagnose=*/!FallbackEnabled)) {
      if (!FallbackEnabled)
        return true;

      // MSVC will fall back on trying to find a matching global operator new
      // if operator new[] cannot be found.  Also, MSVC will leak by not
      // generating a call to operator delete or operator delete[], but we
      // will not replicate that bug.
      NewName = Context.DeclarationNames.getCXXOperatorName(OO_New);
      DeleteName = Context.DeclarationNames.getCXXOperatorName(OO_Delete);
      if (FindAllocationOverload(StartLoc, Range, NewName, AllocArgs, TUDecl,
                               /*AllowMissing=*/false, OperatorNew))
      return true;
    }
  }

  // We don't need an operator delete if we're running under
  // -fno-exceptions.
  if (!getLangOpts().Exceptions) {
    OperatorDelete = nullptr;
    return false;
  }

  // C++ [expr.new]p19:
  //
  //   If the new-expression begins with a unary :: operator, the
  //   deallocation function's name is looked up in the global
  //   scope. Otherwise, if the allocated type is a class type T or an
  //   array thereof, the deallocation function's name is looked up in
  //   the scope of T. If this lookup fails to find the name, or if
  //   the allocated type is not a class type or array thereof, the
  //   deallocation function's name is looked up in the global scope.
  LookupResult FoundDelete(*this, DeleteName, StartLoc, LookupOrdinaryName);
  if (AllocElemType->isRecordType() && !UseGlobal) {
    CXXRecordDecl *RD
      = cast<CXXRecordDecl>(AllocElemType->getAs<RecordType>()->getDecl());
    LookupQualifiedName(FoundDelete, RD);
  }
  if (FoundDelete.isAmbiguous())
    return true; // FIXME: clean up expressions?

  if (FoundDelete.empty()) {
    DeclareGlobalNewDelete();
    LookupQualifiedName(FoundDelete, Context.getTranslationUnitDecl());
  }

  FoundDelete.suppressDiagnostics();

  SmallVector<std::pair<DeclAccessPair,FunctionDecl*>, 2> Matches;

  // Whether we're looking for a placement operator delete is dictated
  // by whether we selected a placement operator new, not by whether
  // we had explicit placement arguments.  This matters for things like
  //   struct A { void *operator new(size_t, int = 0); ... };
  //   A *a = new A()
  bool isPlacementNew = (!PlaceArgs.empty() || OperatorNew->param_size() != 1);

  if (isPlacementNew) {
    // C++ [expr.new]p20:
    //   A declaration of a placement deallocation function matches the
    //   declaration of a placement allocation function if it has the
    //   same number of parameters and, after parameter transformations
    //   (8.3.5), all parameter types except the first are
    //   identical. [...]
    //
    // To perform this comparison, we compute the function type that
    // the deallocation function should have, and use that type both
    // for template argument deduction and for comparison purposes.
    //
    // FIXME: this comparison should ignore CC and the like.
    QualType ExpectedFunctionType;
    {
      const FunctionProtoType *Proto
        = OperatorNew->getType()->getAs<FunctionProtoType>();

      SmallVector<QualType, 4> ArgTypes;
      ArgTypes.push_back(Context.VoidPtrTy);
      for (unsigned I = 1, N = Proto->getNumParams(); I < N; ++I)
        ArgTypes.push_back(Proto->getParamType(I));

      FunctionProtoType::ExtProtoInfo EPI;
      EPI.Variadic = Proto->isVariadic();

      ExpectedFunctionType
        = Context.getFunctionType(Context.VoidTy, ArgTypes, EPI);
    }

    for (LookupResult::iterator D = FoundDelete.begin(),
                             DEnd = FoundDelete.end();
         D != DEnd; ++D) {
      FunctionDecl *Fn = nullptr;
      if (FunctionTemplateDecl *FnTmpl
            = dyn_cast<FunctionTemplateDecl>((*D)->getUnderlyingDecl())) {
        // Perform template argument deduction to try to match the
        // expected function type.
        TemplateDeductionInfo Info(StartLoc);
        if (DeduceTemplateArguments(FnTmpl, nullptr, ExpectedFunctionType, Fn,
                                    Info))
          continue;
      } else
        Fn = cast<FunctionDecl>((*D)->getUnderlyingDecl());

      if (Context.hasSameType(Fn->getType(), ExpectedFunctionType))
        Matches.push_back(std::make_pair(D.getPair(), Fn));
    }
  } else {
    // C++ [expr.new]p20:
    //   [...] Any non-placement deallocation function matches a
    //   non-placement allocation function. [...]
    for (LookupResult::iterator D = FoundDelete.begin(),
                             DEnd = FoundDelete.end();
         D != DEnd; ++D) {
      if (FunctionDecl *Fn = dyn_cast<FunctionDecl>((*D)->getUnderlyingDecl()))
        if (isNonPlacementDeallocationFunction(*this, Fn))
          Matches.push_back(std::make_pair(D.getPair(), Fn));
    }

    // C++1y [expr.new]p22:
    //   For a non-placement allocation function, the normal deallocation
    //   function lookup is used
    // C++1y [expr.delete]p?:
    //   If [...] deallocation function lookup finds both a usual deallocation
    //   function with only a pointer parameter and a usual deallocation
    //   function with both a pointer parameter and a size parameter, then the
    //   selected deallocation function shall be the one with two parameters.
    //   Otherwise, the selected deallocation function shall be the function
    //   with one parameter.
    if (getLangOpts().SizedDeallocation && Matches.size() == 2) {
      if (Matches[0].second->getNumParams() == 1)
        Matches.erase(Matches.begin());
      else
        Matches.erase(Matches.begin() + 1);
      assert(Matches[0].second->getNumParams() == 2 &&
             "found an unexpected usual deallocation function");
    }
  }

  // C++ [expr.new]p20:
  //   [...] If the lookup finds a single matching deallocation
  //   function, that function will be called; otherwise, no
  //   deallocation function will be called.
  if (Matches.size() == 1) {
    OperatorDelete = Matches[0].second;

    // C++0x [expr.new]p20:
    //   If the lookup finds the two-parameter form of a usual
    //   deallocation function (3.7.4.2) and that function, considered
    //   as a placement deallocation function, would have been
    //   selected as a match for the allocation function, the program
    //   is ill-formed.
    if (!PlaceArgs.empty() && getLangOpts().CPlusPlus11 &&
        isNonPlacementDeallocationFunction(*this, OperatorDelete)) {
      Diag(StartLoc, diag::err_placement_new_non_placement_delete)
        << SourceRange(PlaceArgs.front()->getLocStart(),
                       PlaceArgs.back()->getLocEnd());
      if (!OperatorDelete->isImplicit())
        Diag(OperatorDelete->getLocation(), diag::note_previous_decl)
          << DeleteName;
    } else {
      CheckAllocationAccess(StartLoc, Range, FoundDelete.getNamingClass(),
                            Matches[0].first);
    }
  }

  return false;
}

/// \brief Find an fitting overload for the allocation function
/// in the specified scope.
///
/// \param StartLoc The location of the 'new' token.
/// \param Range The range of the placement arguments.
/// \param Name The name of the function ('operator new' or 'operator new[]').
/// \param Args The placement arguments specified.
/// \param Ctx The scope in which we should search; either a class scope or the
///        translation unit.
/// \param AllowMissing If \c true, report an error if we can't find any
///        allocation functions. Otherwise, succeed but don't fill in \p
///        Operator.
/// \param Operator Filled in with the found allocation function. Unchanged if
///        no allocation function was found.
/// \param Diagnose If \c true, issue errors if the allocation function is not
///        usable.
bool Sema::FindAllocationOverload(SourceLocation StartLoc, SourceRange Range,
                                  DeclarationName Name, MultiExprArg Args,
                                  DeclContext *Ctx,
                                  bool AllowMissing, FunctionDecl *&Operator,
                                  bool Diagnose) {
  LookupResult R(*this, Name, StartLoc, LookupOrdinaryName);
  LookupQualifiedName(R, Ctx);
  if (R.empty()) {
    if (AllowMissing || !Diagnose)
      return false;
    return Diag(StartLoc, diag::err_ovl_no_viable_function_in_call)
      << Name << Range;
  }

  if (R.isAmbiguous())
    return true;

  R.suppressDiagnostics();

  OverloadCandidateSet Candidates(StartLoc, OverloadCandidateSet::CSK_Normal);
  for (LookupResult::iterator Alloc = R.begin(), AllocEnd = R.end();
       Alloc != AllocEnd; ++Alloc) {
    // Even member operator new/delete are implicitly treated as
    // static, so don't use AddMemberCandidate.
    NamedDecl *D = (*Alloc)->getUnderlyingDecl();

    if (FunctionTemplateDecl *FnTemplate = dyn_cast<FunctionTemplateDecl>(D)) {
      AddTemplateOverloadCandidate(FnTemplate, Alloc.getPair(),
                                   /*ExplicitTemplateArgs=*/nullptr,
                                   Args, Candidates,
                                   /*SuppressUserConversions=*/false);
      continue;
    }

    FunctionDecl *Fn = cast<FunctionDecl>(D);
    AddOverloadCandidate(Fn, Alloc.getPair(), Args, Candidates,
                         /*SuppressUserConversions=*/false);
  }

  // Do the resolution.
  OverloadCandidateSet::iterator Best;
  switch (Candidates.BestViableFunction(*this, StartLoc, Best)) {
  case OR_Success: {
    // Got one!
    FunctionDecl *FnDecl = Best->Function;
    if (CheckAllocationAccess(StartLoc, Range, R.getNamingClass(),
                              Best->FoundDecl, Diagnose) == AR_inaccessible)
      return true;

    Operator = FnDecl;
    return false;
  }

  case OR_No_Viable_Function:
    if (Diagnose) {
      Diag(StartLoc, diag::err_ovl_no_viable_function_in_call)
        << Name << Range;
      Candidates.NoteCandidates(*this, OCD_AllCandidates, Args);
    }
    return true;

  case OR_Ambiguous:
    if (Diagnose) {
      Diag(StartLoc, diag::err_ovl_ambiguous_call)
        << Name << Range;
      Candidates.NoteCandidates(*this, OCD_ViableCandidates, Args);
    }
    return true;

  case OR_Deleted: {
    if (Diagnose) {
      Diag(StartLoc, diag::err_ovl_deleted_call)
        << Best->Function->isDeleted()
        << Name 
        << getDeletedOrUnavailableSuffix(Best->Function)
        << Range;
      Candidates.NoteCandidates(*this, OCD_AllCandidates, Args);
    }
    return true;
  }
  }
  llvm_unreachable("Unreachable, bad result from BestViableFunction");
}


/// DeclareGlobalNewDelete - Declare the global forms of operator new and
/// delete. These are:
/// @code
///   // C++03:
///   void* operator new(std::size_t) throw(std::bad_alloc);
///   void* operator new[](std::size_t) throw(std::bad_alloc);
///   void operator delete(void *) throw();
///   void operator delete[](void *) throw();
///   // C++11:
///   void* operator new(std::size_t);
///   void* operator new[](std::size_t);
///   void operator delete(void *) noexcept;
///   void operator delete[](void *) noexcept;
///   // C++1y:
///   void* operator new(std::size_t);
///   void* operator new[](std::size_t);
///   void operator delete(void *) noexcept;
///   void operator delete[](void *) noexcept;
///   void operator delete(void *, std::size_t) noexcept;
///   void operator delete[](void *, std::size_t) noexcept;
/// @endcode
/// Note that the placement and nothrow forms of new are *not* implicitly
/// declared. Their use requires including \<new\>.
void Sema::DeclareGlobalNewDelete() {
  if (GlobalNewDeleteDeclared)
    return;

  // C++ [basic.std.dynamic]p2:
  //   [...] The following allocation and deallocation functions (18.4) are
  //   implicitly declared in global scope in each translation unit of a
  //   program
  //
  //     C++03:
  //     void* operator new(std::size_t) throw(std::bad_alloc);
  //     void* operator new[](std::size_t) throw(std::bad_alloc);
  //     void  operator delete(void*) throw();
  //     void  operator delete[](void*) throw();
  //     C++11:
  //     void* operator new(std::size_t);
  //     void* operator new[](std::size_t);
  //     void  operator delete(void*) noexcept;
  //     void  operator delete[](void*) noexcept;
  //     C++1y:
  //     void* operator new(std::size_t);
  //     void* operator new[](std::size_t);
  //     void  operator delete(void*) noexcept;
  //     void  operator delete[](void*) noexcept;
  //     void  operator delete(void*, std::size_t) noexcept;
  //     void  operator delete[](void*, std::size_t) noexcept;
  //
  //   These implicit declarations introduce only the function names operator
  //   new, operator new[], operator delete, operator delete[].
  //
  // Here, we need to refer to std::bad_alloc, so we will implicitly declare
  // "std" or "bad_alloc" as necessary to form the exception specification.
  // However, we do not make these implicit declarations visible to name
  // lookup.
  if (!StdBadAlloc && !getLangOpts().CPlusPlus11) {
    // The "std::bad_alloc" class has not yet been declared, so build it
    // implicitly.
    StdBadAlloc = CXXRecordDecl::Create(Context, TTK_Class,
                                        getOrCreateStdNamespace(),
                                        SourceLocation(), SourceLocation(),
                                      &PP.getIdentifierTable().get("bad_alloc"),
                                        nullptr);
    getStdBadAlloc()->setImplicit(true);
  }

  GlobalNewDeleteDeclared = true;

  QualType VoidPtr = Context.getPointerType(Context.VoidTy);
  QualType SizeT = Context.getSizeType();
  bool AssumeSaneOperatorNew = getLangOpts().AssumeSaneOperatorNew;

  DeclareGlobalAllocationFunction(
      Context.DeclarationNames.getCXXOperatorName(OO_New),
      VoidPtr, SizeT, QualType(), AssumeSaneOperatorNew);
  DeclareGlobalAllocationFunction(
      Context.DeclarationNames.getCXXOperatorName(OO_Array_New),
      VoidPtr, SizeT, QualType(), AssumeSaneOperatorNew);
  DeclareGlobalAllocationFunction(
      Context.DeclarationNames.getCXXOperatorName(OO_Delete),
      Context.VoidTy, VoidPtr);
  DeclareGlobalAllocationFunction(
      Context.DeclarationNames.getCXXOperatorName(OO_Array_Delete),
      Context.VoidTy, VoidPtr);
  if (getLangOpts().SizedDeallocation) {
    DeclareGlobalAllocationFunction(
        Context.DeclarationNames.getCXXOperatorName(OO_Delete),
        Context.VoidTy, VoidPtr, Context.getSizeType());
    DeclareGlobalAllocationFunction(
        Context.DeclarationNames.getCXXOperatorName(OO_Array_Delete),
        Context.VoidTy, VoidPtr, Context.getSizeType());
  }
}

/// DeclareGlobalAllocationFunction - Declares a single implicit global
/// allocation function if it doesn't already exist.
void Sema::DeclareGlobalAllocationFunction(DeclarationName Name,
                                           QualType Return,
                                           QualType Param1, QualType Param2,
                                           bool AddRestrictAttr) {
  DeclContext *GlobalCtx = Context.getTranslationUnitDecl();
  unsigned NumParams = Param2.isNull() ? 1 : 2;

  // Check if this function is already declared.
  DeclContext::lookup_result R = GlobalCtx->lookup(Name);
  for (DeclContext::lookup_iterator Alloc = R.begin(), AllocEnd = R.end();
       Alloc != AllocEnd; ++Alloc) {
    // Only look at non-template functions, as it is the predefined,
    // non-templated allocation function we are trying to declare here.
    if (FunctionDecl *Func = dyn_cast<FunctionDecl>(*Alloc)) {
      if (Func->getNumParams() == NumParams) {
        QualType InitialParam1Type =
            Context.getCanonicalType(Func->getParamDecl(0)
                                         ->getType().getUnqualifiedType());
        QualType InitialParam2Type =
            NumParams == 2
                ? Context.getCanonicalType(Func->getParamDecl(1)
                                               ->getType().getUnqualifiedType())
                : QualType();
        // FIXME: Do we need to check for default arguments here?
        if (InitialParam1Type == Param1 &&
            (NumParams == 1 || InitialParam2Type == Param2)) {
          if (AddRestrictAttr && !Func->hasAttr<RestrictAttr>())
            Func->addAttr(RestrictAttr::CreateImplicit(
                Context, RestrictAttr::GNU_malloc));
          // Make the function visible to name lookup, even if we found it in
          // an unimported module. It either is an implicitly-declared global
          // allocation function, or is suppressing that function.
          Func->setHidden(false);
          return;
        }
      }
    }
  }

  FunctionProtoType::ExtProtoInfo EPI;

  QualType BadAllocType;
  bool HasBadAllocExceptionSpec
    = (Name.getCXXOverloadedOperator() == OO_New ||
       Name.getCXXOverloadedOperator() == OO_Array_New);
  if (HasBadAllocExceptionSpec) {
    if (!getLangOpts().CPlusPlus11) {
      BadAllocType = Context.getTypeDeclType(getStdBadAlloc());
      assert(StdBadAlloc && "Must have std::bad_alloc declared");
      EPI.ExceptionSpec.Type = EST_Dynamic;
      EPI.ExceptionSpec.Exceptions = llvm::makeArrayRef(BadAllocType);
    }
  } else {
    EPI.ExceptionSpec =
        getLangOpts().CPlusPlus11 ? EST_BasicNoexcept : EST_DynamicNone;
  }

  QualType Params[] = { Param1, Param2 };

  QualType FnType = Context.getFunctionType(
      Return, llvm::makeArrayRef(Params, NumParams), EPI);
  FunctionDecl *Alloc =
    FunctionDecl::Create(Context, GlobalCtx, SourceLocation(),
                         SourceLocation(), Name,
                         FnType, /*TInfo=*/nullptr, SC_None, false, true);
  Alloc->setImplicit();
  
  // Implicit sized deallocation functions always have default visibility.
  Alloc->addAttr(VisibilityAttr::CreateImplicit(Context,
                                                VisibilityAttr::Default));

  if (AddRestrictAttr)
    Alloc->addAttr(
        RestrictAttr::CreateImplicit(Context, RestrictAttr::GNU_malloc));

  ParmVarDecl *ParamDecls[2];
  for (unsigned I = 0; I != NumParams; ++I) {
    ParamDecls[I] = ParmVarDecl::Create(Context, Alloc, SourceLocation(),
                                        SourceLocation(), nullptr,
                                        Params[I], /*TInfo=*/nullptr,
                                        SC_None, nullptr);
    ParamDecls[I]->setImplicit();
  }
  Alloc->setParams(llvm::makeArrayRef(ParamDecls, NumParams));

  Context.getTranslationUnitDecl()->addDecl(Alloc);
  IdResolver.tryAddTopLevelDecl(Alloc, Name);
}

FunctionDecl *Sema::FindUsualDeallocationFunction(SourceLocation StartLoc,
                                                  bool CanProvideSize,
                                                  DeclarationName Name) {
  DeclareGlobalNewDelete();

  LookupResult FoundDelete(*this, Name, StartLoc, LookupOrdinaryName);
  LookupQualifiedName(FoundDelete, Context.getTranslationUnitDecl());

  // C++ [expr.new]p20:
  //   [...] Any non-placement deallocation function matches a
  //   non-placement allocation function. [...]
  llvm::SmallVector<FunctionDecl*, 2> Matches;
  for (LookupResult::iterator D = FoundDelete.begin(),
                           DEnd = FoundDelete.end();
       D != DEnd; ++D) {
    if (FunctionDecl *Fn = dyn_cast<FunctionDecl>(*D))
      if (isNonPlacementDeallocationFunction(*this, Fn))
        Matches.push_back(Fn);
  }

  // C++1y [expr.delete]p?:
  //   If the type is complete and deallocation function lookup finds both a
  //   usual deallocation function with only a pointer parameter and a usual
  //   deallocation function with both a pointer parameter and a size
  //   parameter, then the selected deallocation function shall be the one
  //   with two parameters.  Otherwise, the selected deallocation function
  //   shall be the function with one parameter.
  if (getLangOpts().SizedDeallocation && Matches.size() == 2) {
    unsigned NumArgs = CanProvideSize ? 2 : 1;
    if (Matches[0]->getNumParams() != NumArgs)
      Matches.erase(Matches.begin());
    else
      Matches.erase(Matches.begin() + 1);
    assert(Matches[0]->getNumParams() == NumArgs &&
           "found an unexpected usual deallocation function");
  }

  assert(Matches.size() == 1 &&
         "unexpectedly have multiple usual deallocation functions");
  return Matches.front();
}

bool Sema::FindDeallocationFunction(SourceLocation StartLoc, CXXRecordDecl *RD,
                                    DeclarationName Name,
                                    FunctionDecl* &Operator, bool Diagnose) {
  LookupResult Found(*this, Name, StartLoc, LookupOrdinaryName);
  // Try to find operator delete/operator delete[] in class scope.
  LookupQualifiedName(Found, RD);

  if (Found.isAmbiguous())
    return true;

  Found.suppressDiagnostics();

  SmallVector<DeclAccessPair,4> Matches;
  for (LookupResult::iterator F = Found.begin(), FEnd = Found.end();
       F != FEnd; ++F) {
    NamedDecl *ND = (*F)->getUnderlyingDecl();

    // Ignore template operator delete members from the check for a usual
    // deallocation function.
    if (isa<FunctionTemplateDecl>(ND))
      continue;

    if (cast<CXXMethodDecl>(ND)->isUsualDeallocationFunction())
      Matches.push_back(F.getPair());
  }

  // There's exactly one suitable operator;  pick it.
  if (Matches.size() == 1) {
    Operator = cast<CXXMethodDecl>(Matches[0]->getUnderlyingDecl());

    if (Operator->isDeleted()) {
      if (Diagnose) {
        Diag(StartLoc, diag::err_deleted_function_use);
        NoteDeletedFunction(Operator);
      }
      return true;
    }

    if (CheckAllocationAccess(StartLoc, SourceRange(), Found.getNamingClass(),
                              Matches[0], Diagnose) == AR_inaccessible)
      return true;

    return false;

  // We found multiple suitable operators;  complain about the ambiguity.
  } else if (!Matches.empty()) {
    if (Diagnose) {
      Diag(StartLoc, diag::err_ambiguous_suitable_delete_member_function_found)
        << Name << RD;

      for (SmallVectorImpl<DeclAccessPair>::iterator
             F = Matches.begin(), FEnd = Matches.end(); F != FEnd; ++F)
        Diag((*F)->getUnderlyingDecl()->getLocation(),
             diag::note_member_declared_here) << Name;
    }
    return true;
  }

  // We did find operator delete/operator delete[] declarations, but
  // none of them were suitable.
  if (!Found.empty()) {
    if (Diagnose) {
      Diag(StartLoc, diag::err_no_suitable_delete_member_function_found)
        << Name << RD;

      for (LookupResult::iterator F = Found.begin(), FEnd = Found.end();
           F != FEnd; ++F)
        Diag((*F)->getUnderlyingDecl()->getLocation(),
             diag::note_member_declared_here) << Name;
    }
    return true;
  }

  Operator = nullptr;
  return false;
}

namespace {
/// \brief Checks whether delete-expression, and new-expression used for
///  initializing deletee have the same array form.
class MismatchingNewDeleteDetector {
public:
  enum MismatchResult {
    /// Indicates that there is no mismatch or a mismatch cannot be proven.
    NoMismatch,
    /// Indicates that variable is initialized with mismatching form of \a new.
    VarInitMismatches,
    /// Indicates that member is initialized with mismatching form of \a new.
    MemberInitMismatches,
    /// Indicates that 1 or more constructors' definitions could not been
    /// analyzed, and they will be checked again at the end of translation unit.
    AnalyzeLater
  };

  /// \param EndOfTU True, if this is the final analysis at the end of
  /// translation unit. False, if this is the initial analysis at the point
  /// delete-expression was encountered.
  explicit MismatchingNewDeleteDetector(bool EndOfTU)
      : IsArrayForm(false), Field(nullptr), EndOfTU(EndOfTU),
        HasUndefinedConstructors(false) {}

  /// \brief Checks whether pointee of a delete-expression is initialized with
  /// matching form of new-expression.
  ///
  /// If return value is \c VarInitMismatches or \c MemberInitMismatches at the
  /// point where delete-expression is encountered, then a warning will be
  /// issued immediately. If return value is \c AnalyzeLater at the point where
  /// delete-expression is seen, then member will be analyzed at the end of
  /// translation unit. \c AnalyzeLater is returned iff at least one constructor
  /// couldn't be analyzed. If at least one constructor initializes the member
  /// with matching type of new, the return value is \c NoMismatch.
  MismatchResult analyzeDeleteExpr(const CXXDeleteExpr *DE);
  /// \brief Analyzes a class member.
  /// \param Field Class member to analyze.
  /// \param DeleteWasArrayForm Array form-ness of the delete-expression used
  /// for deleting the \p Field.
  MismatchResult analyzeField(FieldDecl *Field, bool DeleteWasArrayForm);
  /// List of mismatching new-expressions used for initialization of the pointee
  llvm::SmallVector<const CXXNewExpr *, 4> NewExprs;
  /// Indicates whether delete-expression was in array form.
  bool IsArrayForm;
  FieldDecl *Field;

private:
  const bool EndOfTU;
  /// \brief Indicates that there is at least one constructor without body.
  bool HasUndefinedConstructors;
  /// \brief Returns \c CXXNewExpr from given initialization expression.
  /// \param E Expression used for initializing pointee in delete-expression.
  /// \param E can be a single-element \c InitListExpr consisting of
  /// \param E new-expression.
  const CXXNewExpr *getNewExprFromInitListOrExpr(const Expr *E);
  /// \brief Returns whether member is initialized with mismatching form of
  /// \c new either by the member initializer or in-class initialization.
  ///
  /// If bodies of all constructors are not visible at the end of translation
  /// unit or at least one constructor initializes member with the matching
  /// form of \c new, mismatch cannot be proven, and this function will return
  /// \c NoMismatch.
  MismatchResult analyzeMemberExpr(const MemberExpr *ME);
  /// \brief Returns whether variable is initialized with mismatching form of
  /// \c new.
  ///
  /// If variable is initialized with matching form of \c new or variable is not
  /// initialized with a \c new expression, this function will return true.
  /// If variable is initialized with mismatching form of \c new, returns false.
  /// \param D Variable to analyze.
  bool hasMatchingVarInit(const DeclRefExpr *D);
  /// \brief Checks whether the constructor initializes pointee with mismatching
  /// form of \c new.
  ///
  /// Returns true, if member is initialized with matching form of \c new in
  /// member initializer list. Returns false, if member is initialized with the
  /// matching form of \c new in this constructor's initializer or given
  /// constructor isn't defined at the point where delete-expression is seen, or
  /// member isn't initialized by the constructor.
  bool hasMatchingNewInCtor(const CXXConstructorDecl *CD);
  /// \brief Checks whether member is initialized with matching form of
  /// \c new in member initializer list.
  bool hasMatchingNewInCtorInit(const CXXCtorInitializer *CI);
  /// Checks whether member is initialized with mismatching form of \c new by
  /// in-class initializer.
  MismatchResult analyzeInClassInitializer();
};
}

MismatchingNewDeleteDetector::MismatchResult
MismatchingNewDeleteDetector::analyzeDeleteExpr(const CXXDeleteExpr *DE) {
  NewExprs.clear();
  assert(DE && "Expected delete-expression");
  IsArrayForm = DE->isArrayForm();
  const Expr *E = DE->getArgument()->IgnoreParenImpCasts();
  if (const MemberExpr *ME = dyn_cast<const MemberExpr>(E)) {
    return analyzeMemberExpr(ME);
  } else if (const DeclRefExpr *D = dyn_cast<const DeclRefExpr>(E)) {
    if (!hasMatchingVarInit(D))
      return VarInitMismatches;
  }
  return NoMismatch;
}

const CXXNewExpr *
MismatchingNewDeleteDetector::getNewExprFromInitListOrExpr(const Expr *E) {
  assert(E != nullptr && "Expected a valid initializer expression");
  E = E->IgnoreParenImpCasts();
  if (const InitListExpr *ILE = dyn_cast<const InitListExpr>(E)) {
    if (ILE->getNumInits() == 1)
      E = dyn_cast<const CXXNewExpr>(ILE->getInit(0)->IgnoreParenImpCasts());
  }

  return dyn_cast_or_null<const CXXNewExpr>(E);
}

bool MismatchingNewDeleteDetector::hasMatchingNewInCtorInit(
    const CXXCtorInitializer *CI) {
  const CXXNewExpr *NE = nullptr;
  if (Field == CI->getMember() &&
      (NE = getNewExprFromInitListOrExpr(CI->getInit()))) {
    if (NE->isArray() == IsArrayForm)
      return true;
    else
      NewExprs.push_back(NE);
  }
  return false;
}

bool MismatchingNewDeleteDetector::hasMatchingNewInCtor(
    const CXXConstructorDecl *CD) {
  if (CD->isImplicit())
    return false;
  const FunctionDecl *Definition = CD;
  if (!CD->isThisDeclarationADefinition() && !CD->isDefined(Definition)) {
    HasUndefinedConstructors = true;
    return EndOfTU;
  }
  for (const auto *CI : cast<const CXXConstructorDecl>(Definition)->inits()) {
    if (hasMatchingNewInCtorInit(CI))
      return true;
  }
  return false;
}

MismatchingNewDeleteDetector::MismatchResult
MismatchingNewDeleteDetector::analyzeInClassInitializer() {
  assert(Field != nullptr && "This should be called only for members");
  if (const CXXNewExpr *NE =
          getNewExprFromInitListOrExpr(Field->getInClassInitializer())) {
    if (NE->isArray() != IsArrayForm) {
      NewExprs.push_back(NE);
      return MemberInitMismatches;
    }
  }
  return NoMismatch;
}

MismatchingNewDeleteDetector::MismatchResult
MismatchingNewDeleteDetector::analyzeField(FieldDecl *Field,
                                           bool DeleteWasArrayForm) {
  assert(Field != nullptr && "Analysis requires a valid class member.");
  this->Field = Field;
  IsArrayForm = DeleteWasArrayForm;
  const CXXRecordDecl *RD = cast<const CXXRecordDecl>(Field->getParent());
  for (const auto *CD : RD->ctors()) {
    if (hasMatchingNewInCtor(CD))
      return NoMismatch;
  }
  if (HasUndefinedConstructors)
    return EndOfTU ? NoMismatch : AnalyzeLater;
  if (!NewExprs.empty())
    return MemberInitMismatches;
  return Field->hasInClassInitializer() ? analyzeInClassInitializer()
                                        : NoMismatch;
}

MismatchingNewDeleteDetector::MismatchResult
MismatchingNewDeleteDetector::analyzeMemberExpr(const MemberExpr *ME) {
  assert(ME != nullptr && "Expected a member expression");
  if (FieldDecl *F = dyn_cast<FieldDecl>(ME->getMemberDecl()))
    return analyzeField(F, IsArrayForm);
  return NoMismatch;
}

bool MismatchingNewDeleteDetector::hasMatchingVarInit(const DeclRefExpr *D) {
  const CXXNewExpr *NE = nullptr;
  if (const VarDecl *VD = dyn_cast<const VarDecl>(D->getDecl())) {
    if (VD->hasInit() && (NE = getNewExprFromInitListOrExpr(VD->getInit())) &&
        NE->isArray() != IsArrayForm) {
      NewExprs.push_back(NE);
    }
  }
  return NewExprs.empty();
}

static void
DiagnoseMismatchedNewDelete(Sema &SemaRef, SourceLocation DeleteLoc,
                            const MismatchingNewDeleteDetector &Detector) {
  SourceLocation EndOfDelete = SemaRef.getLocForEndOfToken(DeleteLoc);
  FixItHint H;
  if (!Detector.IsArrayForm)
    H = FixItHint::CreateInsertion(EndOfDelete, "[]");
  else {
    SourceLocation RSquare = Lexer::findLocationAfterToken(
        DeleteLoc, tok::l_square, SemaRef.getSourceManager(),
        SemaRef.getLangOpts(), true);
    if (RSquare.isValid())
      H = FixItHint::CreateRemoval(SourceRange(EndOfDelete, RSquare));
  }
  SemaRef.Diag(DeleteLoc, diag::warn_mismatched_delete_new)
      << Detector.IsArrayForm << H;

  for (const auto *NE : Detector.NewExprs)
    SemaRef.Diag(NE->getExprLoc(), diag::note_allocated_here)
        << Detector.IsArrayForm;
}

void Sema::AnalyzeDeleteExprMismatch(const CXXDeleteExpr *DE) {
  if (Diags.isIgnored(diag::warn_mismatched_delete_new, SourceLocation()))
    return;
  MismatchingNewDeleteDetector Detector(/*EndOfTU=*/false);
  switch (Detector.analyzeDeleteExpr(DE)) {
  case MismatchingNewDeleteDetector::VarInitMismatches:
  case MismatchingNewDeleteDetector::MemberInitMismatches: {
    DiagnoseMismatchedNewDelete(*this, DE->getLocStart(), Detector);
    break;
  }
  case MismatchingNewDeleteDetector::AnalyzeLater: {
    DeleteExprs[Detector.Field].push_back(
        std::make_pair(DE->getLocStart(), DE->isArrayForm()));
    break;
  }
  case MismatchingNewDeleteDetector::NoMismatch:
    break;
  }
}

void Sema::AnalyzeDeleteExprMismatch(FieldDecl *Field, SourceLocation DeleteLoc,
                                     bool DeleteWasArrayForm) {
  MismatchingNewDeleteDetector Detector(/*EndOfTU=*/true);
  switch (Detector.analyzeField(Field, DeleteWasArrayForm)) {
  case MismatchingNewDeleteDetector::VarInitMismatches:
    llvm_unreachable("This analysis should have been done for class members.");
  case MismatchingNewDeleteDetector::AnalyzeLater:
    llvm_unreachable("Analysis cannot be postponed any point beyond end of "
                     "translation unit.");
  case MismatchingNewDeleteDetector::MemberInitMismatches:
    DiagnoseMismatchedNewDelete(*this, DeleteLoc, Detector);
    break;
  case MismatchingNewDeleteDetector::NoMismatch:
    break;
  }
}

/// ActOnCXXDelete - Parsed a C++ 'delete' expression (C++ 5.3.5), as in:
/// @code ::delete ptr; @endcode
/// or
/// @code delete [] ptr; @endcode
ExprResult
Sema::ActOnCXXDelete(SourceLocation StartLoc, bool UseGlobal,
                     bool ArrayForm, Expr *ExE) {
  // C++ [expr.delete]p1:
  //   The operand shall have a pointer type, or a class type having a single
  //   non-explicit conversion function to a pointer type. The result has type
  //   void.
  //
  // DR599 amends "pointer type" to "pointer to object type" in both cases.

  ExprResult Ex = ExE;
  FunctionDecl *OperatorDelete = nullptr;
  bool ArrayFormAsWritten = ArrayForm;
  bool UsualArrayDeleteWantsSize = false;

  if (!Ex.get()->isTypeDependent()) {
    // Perform lvalue-to-rvalue cast, if needed.
    Ex = DefaultLvalueConversion(Ex.get());
    if (Ex.isInvalid())
      return ExprError();

    QualType Type = Ex.get()->getType();

    class DeleteConverter : public ContextualImplicitConverter {
    public:
      DeleteConverter() : ContextualImplicitConverter(false, true) {}

      bool match(QualType ConvType) override {
        // FIXME: If we have an operator T* and an operator void*, we must pick
        // the operator T*.
        if (const PointerType *ConvPtrType = ConvType->getAs<PointerType>())
          if (ConvPtrType->getPointeeType()->isIncompleteOrObjectType())
            return true;
        return false;
      }

      SemaDiagnosticBuilder diagnoseNoMatch(Sema &S, SourceLocation Loc,
                                            QualType T) override {
        return S.Diag(Loc, diag::err_delete_operand) << T;
      }

      SemaDiagnosticBuilder diagnoseIncomplete(Sema &S, SourceLocation Loc,
                                               QualType T) override {
        return S.Diag(Loc, diag::err_delete_incomplete_class_type) << T;
      }

      SemaDiagnosticBuilder diagnoseExplicitConv(Sema &S, SourceLocation Loc,
                                                 QualType T,
                                                 QualType ConvTy) override {
        return S.Diag(Loc, diag::err_delete_explicit_conversion) << T << ConvTy;
      }

      SemaDiagnosticBuilder noteExplicitConv(Sema &S, CXXConversionDecl *Conv,
                                             QualType ConvTy) override {
        return S.Diag(Conv->getLocation(), diag::note_delete_conversion)
          << ConvTy;
      }

      SemaDiagnosticBuilder diagnoseAmbiguous(Sema &S, SourceLocation Loc,
                                              QualType T) override {
        return S.Diag(Loc, diag::err_ambiguous_delete_operand) << T;
      }

      SemaDiagnosticBuilder noteAmbiguous(Sema &S, CXXConversionDecl *Conv,
                                          QualType ConvTy) override {
        return S.Diag(Conv->getLocation(), diag::note_delete_conversion)
          << ConvTy;
      }

      SemaDiagnosticBuilder diagnoseConversion(Sema &S, SourceLocation Loc,
                                               QualType T,
                                               QualType ConvTy) override {
        llvm_unreachable("conversion functions are permitted");
      }
    } Converter;

    Ex = PerformContextualImplicitConversion(StartLoc, Ex.get(), Converter);
    if (Ex.isInvalid())
      return ExprError();
    Type = Ex.get()->getType();
    if (!Converter.match(Type))
      // FIXME: PerformContextualImplicitConversion should return ExprError
      //        itself in this case.
      return ExprError();

    QualType Pointee = Type->getAs<PointerType>()->getPointeeType();
    QualType PointeeElem = Context.getBaseElementType(Pointee);

    if (unsigned AddressSpace = Pointee.getAddressSpace())
      return Diag(Ex.get()->getLocStart(), 
                  diag::err_address_space_qualified_delete)
               << Pointee.getUnqualifiedType() << AddressSpace;

    CXXRecordDecl *PointeeRD = nullptr;
    if (Pointee->isVoidType() && !isSFINAEContext()) {
      // The C++ standard bans deleting a pointer to a non-object type, which
      // effectively bans deletion of "void*". However, most compilers support
      // this, so we treat it as a warning unless we're in a SFINAE context.
      Diag(StartLoc, diag::ext_delete_void_ptr_operand)
        << Type << Ex.get()->getSourceRange();
    } else if (Pointee->isFunctionType() || Pointee->isVoidType()) {
      return ExprError(Diag(StartLoc, diag::err_delete_operand)
        << Type << Ex.get()->getSourceRange());
    } else if (!Pointee->isDependentType()) {
      if (!RequireCompleteType(StartLoc, Pointee,
                               diag::warn_delete_incomplete, Ex.get())) {
        if (const RecordType *RT = PointeeElem->getAs<RecordType>())
          PointeeRD = cast<CXXRecordDecl>(RT->getDecl());
      }
    }

    if (Pointee->isArrayType() && !ArrayForm) {
      Diag(StartLoc, diag::warn_delete_array_type)
          << Type << Ex.get()->getSourceRange()
          << FixItHint::CreateInsertion(PP.getLocForEndOfToken(StartLoc), "[]");
      ArrayForm = true;
    }

    DeclarationName DeleteName = Context.DeclarationNames.getCXXOperatorName(
                                      ArrayForm ? OO_Array_Delete : OO_Delete);

    if (PointeeRD) {
      if (!UseGlobal &&
          FindDeallocationFunction(StartLoc, PointeeRD, DeleteName,
                                   OperatorDelete))
        return ExprError();

      // If we're allocating an array of records, check whether the
      // usual operator delete[] has a size_t parameter.
      if (ArrayForm) {
        // If the user specifically asked to use the global allocator,
        // we'll need to do the lookup into the class.
        if (UseGlobal)
          UsualArrayDeleteWantsSize =
            doesUsualArrayDeleteWantSize(*this, StartLoc, PointeeElem);

        // Otherwise, the usual operator delete[] should be the
        // function we just found.
        else if (OperatorDelete && isa<CXXMethodDecl>(OperatorDelete))
          UsualArrayDeleteWantsSize = (OperatorDelete->getNumParams() == 2);
      }

      if (!PointeeRD->hasIrrelevantDestructor())
        if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
          MarkFunctionReferenced(StartLoc,
                                    const_cast<CXXDestructorDecl*>(Dtor));
          if (DiagnoseUseOfDecl(Dtor, StartLoc))
            return ExprError();
        }

      // C++ [expr.delete]p3:
      //   In the first alternative (delete object), if the static type of the
      //   object to be deleted is different from its dynamic type, the static
      //   type shall be a base class of the dynamic type of the object to be
      //   deleted and the static type shall have a virtual destructor or the
      //   behavior is undefined.
      //
      // Note: a final class cannot be derived from, no issue there
      if (PointeeRD->isPolymorphic() && !PointeeRD->hasAttr<FinalAttr>()) {
        CXXDestructorDecl *dtor = PointeeRD->getDestructor();
        if (dtor && !dtor->isVirtual()) {
          if (PointeeRD->isAbstract()) {
            // If the class is abstract, we warn by default, because we're
            // sure the code has undefined behavior.
            Diag(StartLoc, diag::warn_delete_abstract_non_virtual_dtor)
                << PointeeElem;
          } else if (!ArrayForm) {
            // Otherwise, if this is not an array delete, it's a bit suspect,
            // but not necessarily wrong.
            Diag(StartLoc, diag::warn_delete_non_virtual_dtor) << PointeeElem;
          }
        }
      }

    }

    if (!OperatorDelete)
      // Look for a global declaration.
      OperatorDelete = FindUsualDeallocationFunction(
          StartLoc, !RequireCompleteType(StartLoc, Pointee, 0) &&
                    (!ArrayForm || UsualArrayDeleteWantsSize ||
                     Pointee.isDestructedType()),
          DeleteName);

    MarkFunctionReferenced(StartLoc, OperatorDelete);

    // Check access and ambiguity of operator delete and destructor.
    if (PointeeRD) {
      if (CXXDestructorDecl *Dtor = LookupDestructor(PointeeRD)) {
          CheckDestructorAccess(Ex.get()->getExprLoc(), Dtor, 
                      PDiag(diag::err_access_dtor) << PointeeElem);
      }
    }
  }

  CXXDeleteExpr *Result = new (Context) CXXDeleteExpr(
      Context.VoidTy, UseGlobal, ArrayForm, ArrayFormAsWritten,
      UsualArrayDeleteWantsSize, OperatorDelete, Ex.get(), StartLoc);
  AnalyzeDeleteExprMismatch(Result);
  return Result;
}

/// \brief Check the use of the given variable as a C++ condition in an if,
/// while, do-while, or switch statement.
ExprResult Sema::CheckConditionVariable(VarDecl *ConditionVar,
                                        SourceLocation StmtLoc,
                                        bool ConvertToBoolean) {
  if (ConditionVar->isInvalidDecl())
    return ExprError();

  QualType T = ConditionVar->getType();

  // C++ [stmt.select]p2:
  //   The declarator shall not specify a function or an array.
  if (T->isFunctionType())
    return ExprError(Diag(ConditionVar->getLocation(),
                          diag::err_invalid_use_of_function_type)
                       << ConditionVar->getSourceRange());
  else if (T->isArrayType())
    return ExprError(Diag(ConditionVar->getLocation(),
                          diag::err_invalid_use_of_array_type)
                     << ConditionVar->getSourceRange());

  ExprResult Condition = DeclRefExpr::Create(
      Context, NestedNameSpecifierLoc(), SourceLocation(), ConditionVar,
      /*enclosing*/ false, ConditionVar->getLocation(),
      ConditionVar->getType().getNonReferenceType(), VK_LValue);

  MarkDeclRefReferenced(cast<DeclRefExpr>(Condition.get()));

  if (ConvertToBoolean) {
    Condition = CheckBooleanCondition(Condition.get(), StmtLoc);
    if (Condition.isInvalid())
      return ExprError();
  }

  return Condition;
}

/// CheckCXXBooleanCondition - Returns true if a conversion to bool is invalid.
ExprResult Sema::CheckCXXBooleanCondition(Expr *CondExpr) {
  // C++ 6.4p4:
  // The value of a condition that is an initialized declaration in a statement
  // other than a switch statement is the value of the declared variable
  // implicitly converted to type bool. If that conversion is ill-formed, the
  // program is ill-formed.
  // The value of a condition that is an expression is the value of the
  // expression, implicitly converted to bool.
  //
  return PerformContextuallyConvertToBool(CondExpr);
}

/// Helper function to determine whether this is the (deprecated) C++
/// conversion from a string literal to a pointer to non-const char or
/// non-const wchar_t (for narrow and wide string literals,
/// respectively).
bool
Sema::IsStringLiteralToNonConstPointerConversion(Expr *From, QualType ToType) {
  // Look inside the implicit cast, if it exists.
  if (ImplicitCastExpr *Cast = dyn_cast<ImplicitCastExpr>(From))
    From = Cast->getSubExpr();

  // A string literal (2.13.4) that is not a wide string literal can
  // be converted to an rvalue of type "pointer to char"; a wide
  // string literal can be converted to an rvalue of type "pointer
  // to wchar_t" (C++ 4.2p2).
  if (StringLiteral *StrLit = dyn_cast<StringLiteral>(From->IgnoreParens()))
    if (const PointerType *ToPtrType = ToType->getAs<PointerType>())
      if (const BuiltinType *ToPointeeType
          = ToPtrType->getPointeeType()->getAs<BuiltinType>()) {
        // This conversion is considered only when there is an
        // explicit appropriate pointer target type (C++ 4.2p2).
        if (!ToPtrType->getPointeeType().hasQualifiers()) {
          switch (StrLit->getKind()) {
            case StringLiteral::UTF8:
            case StringLiteral::UTF16:
            case StringLiteral::UTF32:
              // We don't allow UTF literals to be implicitly converted
              break;
            case StringLiteral::Ascii:
              return (ToPointeeType->getKind() == BuiltinType::Char_U ||
                      ToPointeeType->getKind() == BuiltinType::Char_S);
            case StringLiteral::Wide:
              return ToPointeeType->isWideCharType();
          }
        }
      }

  return false;
}

static ExprResult BuildCXXCastArgument(Sema &S,
                                       SourceLocation CastLoc,
                                       QualType Ty,
                                       CastKind Kind,
                                       CXXMethodDecl *Method,
                                       DeclAccessPair FoundDecl,
                                       bool HadMultipleCandidates,
                                       Expr *From) {
  switch (Kind) {
  default: llvm_unreachable("Unhandled cast kind!");
  case CK_ConstructorConversion: {
    CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(Method);
    SmallVector<Expr*, 8> ConstructorArgs;

    if (S.RequireNonAbstractType(CastLoc, Ty,
                                 diag::err_allocation_of_abstract_type))
      return ExprError();

    if (S.CompleteConstructorCall(Constructor, From, CastLoc, ConstructorArgs))
      return ExprError();

    S.CheckConstructorAccess(CastLoc, Constructor,
                             InitializedEntity::InitializeTemporary(Ty),
                             Constructor->getAccess());
    if (S.DiagnoseUseOfDecl(Method, CastLoc))
      return ExprError();

    ExprResult Result = S.BuildCXXConstructExpr(
        CastLoc, Ty, cast<CXXConstructorDecl>(Method),
        ConstructorArgs, HadMultipleCandidates,
        /*ListInit*/ false, /*StdInitListInit*/ false, /*ZeroInit*/ false,
        CXXConstructExpr::CK_Complete, SourceRange());
    if (Result.isInvalid())
      return ExprError();

    return S.MaybeBindToTemporary(Result.getAs<Expr>());
  }

  case CK_UserDefinedConversion: {
    assert(!From->getType()->isPointerType() && "Arg can't have pointer type!");

    S.CheckMemberOperatorAccess(CastLoc, From, /*arg*/ nullptr, FoundDecl);
    if (S.DiagnoseUseOfDecl(Method, CastLoc))
      return ExprError();

    // Create an implicit call expr that calls it.
    CXXConversionDecl *Conv = cast<CXXConversionDecl>(Method);
    ExprResult Result = S.BuildCXXMemberCallExpr(From, FoundDecl, Conv,
                                                 HadMultipleCandidates);
    if (Result.isInvalid())
      return ExprError();
    // Record usage of conversion in an implicit cast.
    Result = ImplicitCastExpr::Create(S.Context, Result.get()->getType(),
                                      CK_UserDefinedConversion, Result.get(),
                                      nullptr, Result.get()->getValueKind());

    return S.MaybeBindToTemporary(Result.get());
  }
  }
}

/// PerformImplicitConversion - Perform an implicit conversion of the
/// expression From to the type ToType using the pre-computed implicit
/// conversion sequence ICS. Returns the converted
/// expression. Action is the kind of conversion we're performing,
/// used in the error message.
ExprResult
Sema::PerformImplicitConversion(Expr *From, QualType ToType,
                                const ImplicitConversionSequence &ICS,
                                AssignmentAction Action, 
                                CheckedConversionKind CCK) {
  switch (ICS.getKind()) {
  case ImplicitConversionSequence::StandardConversion: {
    ExprResult Res = PerformImplicitConversion(From, ToType, ICS.Standard,
                                               Action, CCK);
    if (Res.isInvalid())
      return ExprError();
    From = Res.get();
    break;
  }

  case ImplicitConversionSequence::UserDefinedConversion: {

      FunctionDecl *FD = ICS.UserDefined.ConversionFunction;
      CastKind CastKind;
      QualType BeforeToType;
      assert(FD && "no conversion function for user-defined conversion seq");
      if (const CXXConversionDecl *Conv = dyn_cast<CXXConversionDecl>(FD)) {
        CastKind = CK_UserDefinedConversion;

        // If the user-defined conversion is specified by a conversion function,
        // the initial standard conversion sequence converts the source type to
        // the implicit object parameter of the conversion function.
        BeforeToType = Context.getTagDeclType(Conv->getParent());
      } else {
        const CXXConstructorDecl *Ctor = cast<CXXConstructorDecl>(FD);
        CastKind = CK_ConstructorConversion;
        // Do no conversion if dealing with ... for the first conversion.
        if (!ICS.UserDefined.EllipsisConversion) {
          // If the user-defined conversion is specified by a constructor, the
          // initial standard conversion sequence converts the source type to
          // the type required by the argument of the constructor
          BeforeToType = Ctor->getParamDecl(0)->getType().getNonReferenceType();
        }
      }
      // Watch out for ellipsis conversion.
      if (!ICS.UserDefined.EllipsisConversion) {
        ExprResult Res =
          PerformImplicitConversion(From, BeforeToType,
                                    ICS.UserDefined.Before, AA_Converting,
                                    CCK);
        if (Res.isInvalid())
          return ExprError();
        From = Res.get();
      }

      ExprResult CastArg
        = BuildCXXCastArgument(*this,
                               From->getLocStart(),
                               ToType.getNonReferenceType(),
                               CastKind, cast<CXXMethodDecl>(FD),
                               ICS.UserDefined.FoundConversionFunction,
                               ICS.UserDefined.HadMultipleCandidates,
                               From);

      if (CastArg.isInvalid())
        return ExprError();

      From = CastArg.get();

      return PerformImplicitConversion(From, ToType, ICS.UserDefined.After,
                                       AA_Converting, CCK);
  }

  case ImplicitConversionSequence::AmbiguousConversion:
    ICS.DiagnoseAmbiguousConversion(*this, From->getExprLoc(),
                          PDiag(diag::err_typecheck_ambiguous_condition)
                            << From->getSourceRange());
     return ExprError();

  case ImplicitConversionSequence::EllipsisConversion:
    llvm_unreachable("Cannot perform an ellipsis conversion");

  case ImplicitConversionSequence::BadConversion:
    return ExprError();
  }

  // Everything went well.
  return From;
}

/// PerformImplicitConversion - Perform an implicit conversion of the
/// expression From to the type ToType by following the standard
/// conversion sequence SCS. Returns the converted
/// expression. Flavor is the context in which we're performing this
/// conversion, for use in error messages.
ExprResult
Sema::PerformImplicitConversion(Expr *From, QualType ToType,
                                const StandardConversionSequence& SCS,
                                AssignmentAction Action, 
                                CheckedConversionKind CCK) {
  bool CStyle = (CCK == CCK_CStyleCast || CCK == CCK_FunctionalCast);
  
  // Overall FIXME: we are recomputing too many types here and doing far too
  // much extra work. What this means is that we need to keep track of more
  // information that is computed when we try the implicit conversion initially,
  // so that we don't need to recompute anything here.
  QualType FromType = From->getType();
  
  if (SCS.CopyConstructor) {
    // FIXME: When can ToType be a reference type?
    assert(!ToType->isReferenceType());
    if (SCS.Second == ICK_Derived_To_Base) {
      SmallVector<Expr*, 8> ConstructorArgs;
      if (CompleteConstructorCall(cast<CXXConstructorDecl>(SCS.CopyConstructor),
                                  From, /*FIXME:ConstructLoc*/SourceLocation(),
                                  ConstructorArgs))
        return ExprError();
      return BuildCXXConstructExpr(
          /*FIXME:ConstructLoc*/ SourceLocation(), ToType, SCS.CopyConstructor,
          ConstructorArgs, /*HadMultipleCandidates*/ false,
          /*ListInit*/ false, /*StdInitListInit*/ false, /*ZeroInit*/ false,
          CXXConstructExpr::CK_Complete, SourceRange());
    }
    return BuildCXXConstructExpr(
        /*FIXME:ConstructLoc*/ SourceLocation(), ToType, SCS.CopyConstructor,
        From, /*HadMultipleCandidates*/ false,
        /*ListInit*/ false, /*StdInitListInit*/ false, /*ZeroInit*/ false,
        CXXConstructExpr::CK_Complete, SourceRange());
  }

  // Resolve overloaded function references.
  if (Context.hasSameType(FromType, Context.OverloadTy)) {
    DeclAccessPair Found;
    FunctionDecl *Fn = ResolveAddressOfOverloadedFunction(From, ToType,
                                                          true, Found);
    if (!Fn)
      return ExprError();

    if (DiagnoseUseOfDecl(Fn, From->getLocStart()))
      return ExprError();

    From = FixOverloadedFunctionReference(From, Found, Fn);
    FromType = From->getType();
  }

  // If we're converting to an atomic type, first convert to the corresponding
  // non-atomic type.
  QualType ToAtomicType;
  if (const AtomicType *ToAtomic = ToType->getAs<AtomicType>()) {
    ToAtomicType = ToType;
    ToType = ToAtomic->getValueType();
  }

  // Perform the first implicit conversion.
  switch (SCS.First) {
  case ICK_Identity:
    if (const AtomicType *FromAtomic = FromType->getAs<AtomicType>()) {
      FromType = FromAtomic->getValueType().getUnqualifiedType();
      From = ImplicitCastExpr::Create(Context, FromType, CK_AtomicToNonAtomic,
                                      From, /*BasePath=*/nullptr, VK_RValue);
    }
    break;

  case ICK_Lvalue_To_Rvalue: {
    assert(From->getObjectKind() != OK_ObjCProperty);
    ExprResult FromRes = DefaultLvalueConversion(From);
    assert(!FromRes.isInvalid() && "Can't perform deduced conversion?!");
    From = FromRes.get();
    FromType = From->getType();
    break;
  }

  case ICK_Array_To_Pointer:
    FromType = Context.getArrayDecayedType(FromType);
    From = ImpCastExprToType(From, FromType, CK_ArrayToPointerDecay, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Function_To_Pointer:
    FromType = Context.getPointerType(FromType);
    From = ImpCastExprToType(From, FromType, CK_FunctionToPointerDecay, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  default:
    llvm_unreachable("Improper first standard conversion");
  }

  // Perform the second implicit conversion
  switch (SCS.Second) {
  case ICK_Identity:
    // C++ [except.spec]p5:
    //   [For] assignment to and initialization of pointers to functions,
    //   pointers to member functions, and references to functions: the
    //   target entity shall allow at least the exceptions allowed by the
    //   source value in the assignment or initialization.
    switch (Action) {
    case AA_Assigning:
    case AA_Initializing:
      // Note, function argument passing and returning are initialization.
    case AA_Passing:
    case AA_Returning:
    case AA_Sending:
    case AA_Passing_CFAudited:
      if (CheckExceptionSpecCompatibility(From, ToType))
        return ExprError();
      break;

    case AA_Casting:
    case AA_Converting:
      // Casts and implicit conversions are not initialization, so are not
      // checked for exception specification mismatches.
      break;
    }
    // Nothing else to do.
    break;

  case ICK_NoReturn_Adjustment:
    // If both sides are functions (or pointers/references to them), there could
    // be incompatible exception declarations.
    if (CheckExceptionSpecCompatibility(From, ToType))
      return ExprError();

    From = ImpCastExprToType(From, ToType, CK_NoOp, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Integral_Promotion:
  case ICK_Integral_Conversion:
    if (ToType->isBooleanType()) {
      assert(FromType->castAs<EnumType>()->getDecl()->isFixed() &&
             SCS.Second == ICK_Integral_Promotion &&
             "only enums with fixed underlying type can promote to bool");
      From = ImpCastExprToType(From, ToType, CK_IntegralToBoolean,
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    } else {
      From = ImpCastExprToType(From, ToType, CK_IntegralCast,
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    }
    break;

  case ICK_Floating_Promotion:
  case ICK_Floating_Conversion:
    From = ImpCastExprToType(From, ToType, CK_FloatingCast, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Complex_Promotion:
  case ICK_Complex_Conversion: {
    QualType FromEl = From->getType()->getAs<ComplexType>()->getElementType();
    QualType ToEl = ToType->getAs<ComplexType>()->getElementType();
    CastKind CK;
    if (FromEl->isRealFloatingType()) {
      if (ToEl->isRealFloatingType())
        CK = CK_FloatingComplexCast;
      else
        CK = CK_FloatingComplexToIntegralComplex;
    } else if (ToEl->isRealFloatingType()) {
      CK = CK_IntegralComplexToFloatingComplex;
    } else {
      CK = CK_IntegralComplexCast;
    }
    From = ImpCastExprToType(From, ToType, CK, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;
  }

  case ICK_Floating_Integral:
    if (ToType->isRealFloatingType())
      From = ImpCastExprToType(From, ToType, CK_IntegralToFloating, 
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    else
      From = ImpCastExprToType(From, ToType, CK_FloatingToIntegral, 
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Compatible_Conversion:
      From = ImpCastExprToType(From, ToType, CK_NoOp, 
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Writeback_Conversion:
  case ICK_Pointer_Conversion: {
    if (SCS.IncompatibleObjC && Action != AA_Casting) {
      // Diagnose incompatible Objective-C conversions
      if (Action == AA_Initializing || Action == AA_Assigning)
        Diag(From->getLocStart(),
             diag::ext_typecheck_convert_incompatible_pointer)
          << ToType << From->getType() << Action
          << From->getSourceRange() << 0;
      else
        Diag(From->getLocStart(),
             diag::ext_typecheck_convert_incompatible_pointer)
          << From->getType() << ToType << Action
          << From->getSourceRange() << 0;

      if (From->getType()->isObjCObjectPointerType() &&
          ToType->isObjCObjectPointerType())
        EmitRelatedResultTypeNote(From);
    } 
    else if (getLangOpts().ObjCAutoRefCount &&
             !CheckObjCARCUnavailableWeakConversion(ToType, 
                                                    From->getType())) {
      if (Action == AA_Initializing)
        Diag(From->getLocStart(), 
             diag::err_arc_weak_unavailable_assign);
      else
        Diag(From->getLocStart(),
             diag::err_arc_convesion_of_weak_unavailable) 
          << (Action == AA_Casting) << From->getType() << ToType 
          << From->getSourceRange();
    }
             
    CastKind Kind = CK_Invalid;
    CXXCastPath BasePath;
    if (CheckPointerConversion(From, ToType, Kind, BasePath, CStyle))
      return ExprError();

    // Make sure we extend blocks if necessary.
    // FIXME: doing this here is really ugly.
    if (Kind == CK_BlockPointerToObjCPointerCast) {
      ExprResult E = From;
      (void) PrepareCastToObjCObjectPointer(E);
      From = E.get();
    }
    if (getLangOpts().ObjCAutoRefCount)
      CheckObjCARCConversion(SourceRange(), ToType, From, CCK);
    From = ImpCastExprToType(From, ToType, Kind, VK_RValue, &BasePath, CCK)
             .get();
    break;
  }

  case ICK_Pointer_Member: {
    CastKind Kind = CK_Invalid;
    CXXCastPath BasePath;
    if (CheckMemberPointerConversion(From, ToType, Kind, BasePath, CStyle))
      return ExprError();
    if (CheckExceptionSpecCompatibility(From, ToType))
      return ExprError();

    // We may not have been able to figure out what this member pointer resolved
    // to up until this exact point.  Attempt to lock-in it's inheritance model.
    QualType FromType = From->getType();
    if (FromType->isMemberPointerType())
      if (Context.getTargetInfo().getCXXABI().isMicrosoft())
        RequireCompleteType(From->getExprLoc(), FromType, 0);

    From = ImpCastExprToType(From, ToType, Kind, VK_RValue, &BasePath, CCK)
             .get();
    break;
  }

  case ICK_Boolean_Conversion:
    // Perform half-to-boolean conversion via float.
    if (From->getType()->isHalfType()) {
      From = ImpCastExprToType(From, Context.FloatTy, CK_FloatingCast).get();
      FromType = Context.FloatTy;
    }

    From = ImpCastExprToType(From, Context.BoolTy,
                             ScalarTypeToBooleanCastKind(FromType), 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Derived_To_Base: {
    CXXCastPath BasePath;
    if (CheckDerivedToBaseConversion(From->getType(),
                                     ToType.getNonReferenceType(),
                                     From->getLocStart(),
                                     From->getSourceRange(),
                                     &BasePath,
                                     CStyle))
      return ExprError();

    From = ImpCastExprToType(From, ToType.getNonReferenceType(),
                      CK_DerivedToBase, From->getValueKind(),
                      &BasePath, CCK).get();
    break;
  }

  case ICK_Vector_Conversion:
    From = ImpCastExprToType(From, ToType, CK_BitCast, 
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;

  case ICK_Vector_Splat:
    // Vector splat from any arithmetic type to a vector.
    // Cast to the element type.
    {
      QualType elType = ToType->getAs<ExtVectorType>()->getElementType();
      if (elType != From->getType()) {
        ExprResult E = From;
        From = ImpCastExprToType(From, elType,
                                 PrepareScalarCast(E, elType)).get();
      }
      From = ImpCastExprToType(From, ToType, CK_VectorSplat,
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();
    }
    break;

  case ICK_Complex_Real:
    // Case 1.  x -> _Complex y
    if (const ComplexType *ToComplex = ToType->getAs<ComplexType>()) {
      QualType ElType = ToComplex->getElementType();
      bool isFloatingComplex = ElType->isRealFloatingType();

      // x -> y
      if (Context.hasSameUnqualifiedType(ElType, From->getType())) {
        // do nothing
      } else if (From->getType()->isRealFloatingType()) {
        From = ImpCastExprToType(From, ElType,
                isFloatingComplex ? CK_FloatingCast : CK_FloatingToIntegral).get();
      } else {
        assert(From->getType()->isIntegerType());
        From = ImpCastExprToType(From, ElType,
                isFloatingComplex ? CK_IntegralToFloating : CK_IntegralCast).get();
      }
      // y -> _Complex y
      From = ImpCastExprToType(From, ToType,
                   isFloatingComplex ? CK_FloatingRealToComplex
                                     : CK_IntegralRealToComplex).get();

    // Case 2.  _Complex x -> y
    } else {
      const ComplexType *FromComplex = From->getType()->getAs<ComplexType>();
      assert(FromComplex);

      QualType ElType = FromComplex->getElementType();
      bool isFloatingComplex = ElType->isRealFloatingType();

      // _Complex x -> x
      From = ImpCastExprToType(From, ElType,
                   isFloatingComplex ? CK_FloatingComplexToReal
                                     : CK_IntegralComplexToReal, 
                               VK_RValue, /*BasePath=*/nullptr, CCK).get();

      // x -> y
      if (Context.hasSameUnqualifiedType(ElType, ToType)) {
        // do nothing
      } else if (ToType->isRealFloatingType()) {
        From = ImpCastExprToType(From, ToType,
                   isFloatingComplex ? CK_FloatingCast : CK_IntegralToFloating, 
                                 VK_RValue, /*BasePath=*/nullptr, CCK).get();
      } else {
        assert(ToType->isIntegerType());
        From = ImpCastExprToType(From, ToType,
                   isFloatingComplex ? CK_FloatingToIntegral : CK_IntegralCast, 
                                 VK_RValue, /*BasePath=*/nullptr, CCK).get();
      }
    }
    break;
  
  case ICK_Block_Pointer_Conversion: {
    From = ImpCastExprToType(From, ToType.getUnqualifiedType(), CK_BitCast,
                             VK_RValue, /*BasePath=*/nullptr, CCK).get();
    break;
  }
      
  case ICK_TransparentUnionConversion: {
    ExprResult FromRes = From;
    Sema::AssignConvertType ConvTy =
      CheckTransparentUnionArgumentConstraints(ToType, FromRes);
    if (FromRes.isInvalid())
      return ExprError();
    From = FromRes.get();
    assert ((ConvTy == Sema::Compatible) &&
            "Improper transparent union conversion");
    (void)ConvTy;
    break;
  }

  case ICK_Zero_Event_Conversion:
    From = ImpCastExprToType(From, ToType,
                             CK_ZeroToOCLEvent,
                             From->getValueKind()).get();
    break;

  case ICK_Lvalue_To_Rvalue:
  case ICK_Array_To_Pointer:
  case ICK_Function_To_Pointer:
  case ICK_Qualification:
  case ICK_Num_Conversion_Kinds:
    llvm_unreachable("Improper second standard conversion");
  }

  switch (SCS.Third) {
  case ICK_Identity:
    // Nothing to do.
    break;

  case ICK_Qualification: {
    // The qualification keeps the category of the inner expression, unless the
    // target type isn't a reference.
    ExprValueKind VK = ToType->isReferenceType() ?
                                  From->getValueKind() : VK_RValue;
    From = ImpCastExprToType(From, ToType.getNonLValueExprType(Context),
                             CK_NoOp, VK, /*BasePath=*/nullptr, CCK).get();

    if (SCS.DeprecatedStringLiteralToCharPtr &&
        !getLangOpts().WritableStrings) {
      Diag(From->getLocStart(), getLangOpts().CPlusPlus11
           ? diag::ext_deprecated_string_literal_conversion
           : diag::warn_deprecated_string_literal_conversion)
        << ToType.getNonReferenceType();
    }

    break;
  }

  default:
    llvm_unreachable("Improper third standard conversion");
  }

  // If this conversion sequence involved a scalar -> atomic conversion, perform
  // that conversion now.
  if (!ToAtomicType.isNull()) {
    assert(Context.hasSameType(
        ToAtomicType->castAs<AtomicType>()->getValueType(), From->getType()));
    From = ImpCastExprToType(From, ToAtomicType, CK_NonAtomicToAtomic,
                             VK_RValue, nullptr, CCK).get();
  }

  return From;
}

/// \brief Check the completeness of a type in a unary type trait.
///
/// If the particular type trait requires a complete type, tries to complete
/// it. If completing the type fails, a diagnostic is emitted and false
/// returned. If completing the type succeeds or no completion was required,
/// returns true.
static bool CheckUnaryTypeTraitTypeCompleteness(Sema &S, TypeTrait UTT,
                                                SourceLocation Loc,
                                                QualType ArgTy) {
  // C++0x [meta.unary.prop]p3:
  //   For all of the class templates X declared in this Clause, instantiating
  //   that template with a template argument that is a class template
  //   specialization may result in the implicit instantiation of the template
  //   argument if and only if the semantics of X require that the argument
  //   must be a complete type.
  // We apply this rule to all the type trait expressions used to implement
  // these class templates. We also try to follow any GCC documented behavior
  // in these expressions to ensure portability of standard libraries.
  switch (UTT) {
  default: llvm_unreachable("not a UTT");
    // is_complete_type somewhat obviously cannot require a complete type.
  case UTT_IsCompleteType:
    // Fall-through

    // These traits are modeled on the type predicates in C++0x
    // [meta.unary.cat] and [meta.unary.comp]. They are not specified as
    // requiring a complete type, as whether or not they return true cannot be
    // impacted by the completeness of the type.
  case UTT_IsVoid:
  case UTT_IsIntegral:
  case UTT_IsFloatingPoint:
  case UTT_IsArray:
  case UTT_IsPointer:
  case UTT_IsLvalueReference:
  case UTT_IsRvalueReference:
  case UTT_IsMemberFunctionPointer:
  case UTT_IsMemberObjectPointer:
  case UTT_IsEnum:
  case UTT_IsUnion:
  case UTT_IsClass:
  case UTT_IsFunction:
  case UTT_IsReference:
  case UTT_IsArithmetic:
  case UTT_IsFundamental:
  case UTT_IsObject:
  case UTT_IsScalar:
  case UTT_IsCompound:
  case UTT_IsMemberPointer:
    // Fall-through

    // These traits are modeled on type predicates in C++0x [meta.unary.prop]
    // which requires some of its traits to have the complete type. However,
    // the completeness of the type cannot impact these traits' semantics, and
    // so they don't require it. This matches the comments on these traits in
    // Table 49.
  case UTT_IsConst:
  case UTT_IsVolatile:
  case UTT_IsSigned:
  case UTT_IsUnsigned:
    return true;

    // C++0x [meta.unary.prop] Table 49 requires the following traits to be
    // applied to a complete type.
  case UTT_IsTrivial:
  case UTT_IsTriviallyCopyable:
  case UTT_IsStandardLayout:
  case UTT_IsPOD:
  case UTT_IsLiteral:
  case UTT_IsEmpty:
  case UTT_IsPolymorphic:
  case UTT_IsAbstract:
  case UTT_IsInterfaceClass:
  case UTT_IsDestructible:
  case UTT_IsNothrowDestructible:
    // Fall-through

  // These traits require a complete type.
  case UTT_IsFinal:
  case UTT_IsSealed:

    // These trait expressions are designed to help implement predicates in
    // [meta.unary.prop] despite not being named the same. They are specified
    // by both GCC and the Embarcadero C++ compiler, and require the complete
    // type due to the overarching C++0x type predicates being implemented
    // requiring the complete type.
  case UTT_HasNothrowAssign:
  case UTT_HasNothrowMoveAssign:
  case UTT_HasNothrowConstructor:
  case UTT_HasNothrowCopy:
  case UTT_HasTrivialAssign:
  case UTT_HasTrivialMoveAssign:
  case UTT_HasTrivialDefaultConstructor:
  case UTT_HasTrivialMoveConstructor:
  case UTT_HasTrivialCopy:
  case UTT_HasTrivialDestructor:
  case UTT_HasVirtualDestructor:
    // Arrays of unknown bound are expressly allowed.
    QualType ElTy = ArgTy;
    if (ArgTy->isIncompleteArrayType())
      ElTy = S.Context.getAsArrayType(ArgTy)->getElementType();

    // The void type is expressly allowed.
    if (ElTy->isVoidType())
      return true;

    return !S.RequireCompleteType(
      Loc, ElTy, diag::err_incomplete_type_used_in_type_trait_expr);
  }
}

static bool HasNoThrowOperator(const RecordType *RT, OverloadedOperatorKind Op,
                               Sema &Self, SourceLocation KeyLoc, ASTContext &C,
                               bool (CXXRecordDecl::*HasTrivial)() const, 
                               bool (CXXRecordDecl::*HasNonTrivial)() const, 
                               bool (CXXMethodDecl::*IsDesiredOp)() const)
{
  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
  if ((RD->*HasTrivial)() && !(RD->*HasNonTrivial)())
    return true;

  DeclarationName Name = C.DeclarationNames.getCXXOperatorName(Op);
  DeclarationNameInfo NameInfo(Name, KeyLoc);
  LookupResult Res(Self, NameInfo, Sema::LookupOrdinaryName);
  if (Self.LookupQualifiedName(Res, RD)) {
    bool FoundOperator = false;
    Res.suppressDiagnostics();
    for (LookupResult::iterator Op = Res.begin(), OpEnd = Res.end();
         Op != OpEnd; ++Op) {
      if (isa<FunctionTemplateDecl>(*Op))
        continue;

      CXXMethodDecl *Operator = cast<CXXMethodDecl>(*Op);
      if((Operator->*IsDesiredOp)()) {
        FoundOperator = true;
        const FunctionProtoType *CPT =
          Operator->getType()->getAs<FunctionProtoType>();
        CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
        if (!CPT || !CPT->isNothrow(C))
          return false;
      }
    }
    return FoundOperator;
  }
  return false;
}

static bool EvaluateUnaryTypeTrait(Sema &Self, TypeTrait UTT,
                                   SourceLocation KeyLoc, QualType T) {
  assert(!T->isDependentType() && "Cannot evaluate traits of dependent type");

  ASTContext &C = Self.Context;
  switch(UTT) {
  default: llvm_unreachable("not a UTT");
    // Type trait expressions corresponding to the primary type category
    // predicates in C++0x [meta.unary.cat].
  case UTT_IsVoid:
    return T->isVoidType();
  case UTT_IsIntegral:
    return T->isIntegralType(C);
  case UTT_IsFloatingPoint:
    return T->isFloatingType();
  case UTT_IsArray:
    return T->isArrayType();
  case UTT_IsPointer:
    return T->isPointerType();
  case UTT_IsLvalueReference:
    return T->isLValueReferenceType();
  case UTT_IsRvalueReference:
    return T->isRValueReferenceType();
  case UTT_IsMemberFunctionPointer:
    return T->isMemberFunctionPointerType();
  case UTT_IsMemberObjectPointer:
    return T->isMemberDataPointerType();
  case UTT_IsEnum:
    return T->isEnumeralType();
  case UTT_IsUnion:
    return T->isUnionType();
  case UTT_IsClass:
    return T->isClassType() || T->isStructureType() || T->isInterfaceType();
  case UTT_IsFunction:
    return T->isFunctionType();

    // Type trait expressions which correspond to the convenient composition
    // predicates in C++0x [meta.unary.comp].
  case UTT_IsReference:
    return T->isReferenceType();
  case UTT_IsArithmetic:
    return T->isArithmeticType() && !T->isEnumeralType();
  case UTT_IsFundamental:
    return T->isFundamentalType();
  case UTT_IsObject:
    return T->isObjectType();
  case UTT_IsScalar:
    // Note: semantic analysis depends on Objective-C lifetime types to be
    // considered scalar types. However, such types do not actually behave
    // like scalar types at run time (since they may require retain/release
    // operations), so we report them as non-scalar.
    if (T->isObjCLifetimeType()) {
      switch (T.getObjCLifetime()) {
      case Qualifiers::OCL_None:
      case Qualifiers::OCL_ExplicitNone:
        return true;

      case Qualifiers::OCL_Strong:
      case Qualifiers::OCL_Weak:
      case Qualifiers::OCL_Autoreleasing:
        return false;
      }
    }
      
    return T->isScalarType();
  case UTT_IsCompound:
    return T->isCompoundType();
  case UTT_IsMemberPointer:
    return T->isMemberPointerType();

    // Type trait expressions which correspond to the type property predicates
    // in C++0x [meta.unary.prop].
  case UTT_IsConst:
    return T.isConstQualified();
  case UTT_IsVolatile:
    return T.isVolatileQualified();
  case UTT_IsTrivial:
    return T.isTrivialType(Self.Context);
  case UTT_IsTriviallyCopyable:
    return T.isTriviallyCopyableType(Self.Context);
  case UTT_IsStandardLayout:
    return T->isStandardLayoutType();
  case UTT_IsPOD:
    return T.isPODType(Self.Context);
  case UTT_IsLiteral:
    return T->isLiteralType(Self.Context);
  case UTT_IsEmpty:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return !RD->isUnion() && RD->isEmpty();
    return false;
  case UTT_IsPolymorphic:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->isPolymorphic();
    return false;
  case UTT_IsAbstract:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->isAbstract();
    return false;
  case UTT_IsInterfaceClass:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->isInterface();
    return false;
  case UTT_IsFinal:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->hasAttr<FinalAttr>();
    return false;
  case UTT_IsSealed:
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      if (FinalAttr *FA = RD->getAttr<FinalAttr>())
        return FA->isSpelledAsSealed();
    return false;
  case UTT_IsSigned:
    return T->isSignedIntegerType();
  case UTT_IsUnsigned:
    return T->isUnsignedIntegerType();

    // Type trait expressions which query classes regarding their construction,
    // destruction, and copying. Rather than being based directly on the
    // related type predicates in the standard, they are specified by both
    // GCC[1] and the Embarcadero C++ compiler[2], and Clang implements those
    // specifications.
    //
    //   1: http://gcc.gnu/.org/onlinedocs/gcc/Type-Traits.html
    //   2: http://docwiki.embarcadero.com/RADStudio/XE/en/Type_Trait_Functions_(C%2B%2B0x)_Index
    //
    // Note that these builtins do not behave as documented in g++: if a class
    // has both a trivial and a non-trivial special member of a particular kind,
    // they return false! For now, we emulate this behavior.
    // FIXME: This appears to be a g++ bug: more complex cases reveal that it
    // does not correctly compute triviality in the presence of multiple special
    // members of the same kind. Revisit this once the g++ bug is fixed.
  case UTT_HasTrivialDefaultConstructor:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If __is_pod (type) is true then the trait is true, else if type is
    //   a cv class or union type (or array thereof) with a trivial default
    //   constructor ([class.ctor]) then the trait is true, else it is false.
    if (T.isPODType(Self.Context))
      return true;
    if (CXXRecordDecl *RD = C.getBaseElementType(T)->getAsCXXRecordDecl())
      return RD->hasTrivialDefaultConstructor() &&
             !RD->hasNonTrivialDefaultConstructor();
    return false;
  case UTT_HasTrivialMoveConstructor:
    //  This trait is implemented by MSVC 2012 and needed to parse the
    //  standard library headers. Specifically this is used as the logic
    //  behind std::is_trivially_move_constructible (20.9.4.3).
    if (T.isPODType(Self.Context))
      return true;
    if (CXXRecordDecl *RD = C.getBaseElementType(T)->getAsCXXRecordDecl())
      return RD->hasTrivialMoveConstructor() && !RD->hasNonTrivialMoveConstructor();
    return false;
  case UTT_HasTrivialCopy:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If __is_pod (type) is true or type is a reference type then
    //   the trait is true, else if type is a cv class or union type
    //   with a trivial copy constructor ([class.copy]) then the trait
    //   is true, else it is false.
    if (T.isPODType(Self.Context) || T->isReferenceType())
      return true;
    if (CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->hasTrivialCopyConstructor() &&
             !RD->hasNonTrivialCopyConstructor();
    return false;
  case UTT_HasTrivialMoveAssign:
    //  This trait is implemented by MSVC 2012 and needed to parse the
    //  standard library headers. Specifically it is used as the logic
    //  behind std::is_trivially_move_assignable (20.9.4.3)
    if (T.isPODType(Self.Context))
      return true;
    if (CXXRecordDecl *RD = C.getBaseElementType(T)->getAsCXXRecordDecl())
      return RD->hasTrivialMoveAssignment() && !RD->hasNonTrivialMoveAssignment();
    return false;
  case UTT_HasTrivialAssign:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If type is const qualified or is a reference type then the
    //   trait is false. Otherwise if __is_pod (type) is true then the
    //   trait is true, else if type is a cv class or union type with
    //   a trivial copy assignment ([class.copy]) then the trait is
    //   true, else it is false.
    // Note: the const and reference restrictions are interesting,
    // given that const and reference members don't prevent a class
    // from having a trivial copy assignment operator (but do cause
    // errors if the copy assignment operator is actually used, q.v.
    // [class.copy]p12).

    if (T.isConstQualified())
      return false;
    if (T.isPODType(Self.Context))
      return true;
    if (CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      return RD->hasTrivialCopyAssignment() &&
             !RD->hasNonTrivialCopyAssignment();
    return false;
  case UTT_IsDestructible:
  case UTT_IsNothrowDestructible:
    // FIXME: Implement UTT_IsDestructible and UTT_IsNothrowDestructible.
    // For now, let's fall through.
  case UTT_HasTrivialDestructor:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html
    //   If __is_pod (type) is true or type is a reference type
    //   then the trait is true, else if type is a cv class or union
    //   type (or array thereof) with a trivial destructor
    //   ([class.dtor]) then the trait is true, else it is
    //   false.
    if (T.isPODType(Self.Context) || T->isReferenceType())
      return true;
      
    // Objective-C++ ARC: autorelease types don't require destruction.
    if (T->isObjCLifetimeType() && 
        T.getObjCLifetime() == Qualifiers::OCL_Autoreleasing)
      return true;
      
    if (CXXRecordDecl *RD = C.getBaseElementType(T)->getAsCXXRecordDecl())
      return RD->hasTrivialDestructor();
    return false;
  // TODO: Propagate nothrowness for implicitly declared special members.
  case UTT_HasNothrowAssign:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If type is const qualified or is a reference type then the
    //   trait is false. Otherwise if __has_trivial_assign (type)
    //   is true then the trait is true, else if type is a cv class
    //   or union type with copy assignment operators that are known
    //   not to throw an exception then the trait is true, else it is
    //   false.
    if (C.getBaseElementType(T).isConstQualified())
      return false;
    if (T->isReferenceType())
      return false;
    if (T.isPODType(Self.Context) || T->isObjCLifetimeType())
      return true;

    if (const RecordType *RT = T->getAs<RecordType>())
      return HasNoThrowOperator(RT, OO_Equal, Self, KeyLoc, C,
                                &CXXRecordDecl::hasTrivialCopyAssignment,
                                &CXXRecordDecl::hasNonTrivialCopyAssignment,
                                &CXXMethodDecl::isCopyAssignmentOperator);
    return false;
  case UTT_HasNothrowMoveAssign:
    //  This trait is implemented by MSVC 2012 and needed to parse the
    //  standard library headers. Specifically this is used as the logic
    //  behind std::is_nothrow_move_assignable (20.9.4.3).
    if (T.isPODType(Self.Context))
      return true;

    if (const RecordType *RT = C.getBaseElementType(T)->getAs<RecordType>())
      return HasNoThrowOperator(RT, OO_Equal, Self, KeyLoc, C,
                                &CXXRecordDecl::hasTrivialMoveAssignment,
                                &CXXRecordDecl::hasNonTrivialMoveAssignment,
                                &CXXMethodDecl::isMoveAssignmentOperator);
    return false;
  case UTT_HasNothrowCopy:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If __has_trivial_copy (type) is true then the trait is true, else
    //   if type is a cv class or union type with copy constructors that are
    //   known not to throw an exception then the trait is true, else it is
    //   false.
    if (T.isPODType(C) || T->isReferenceType() || T->isObjCLifetimeType())
      return true;
    if (CXXRecordDecl *RD = T->getAsCXXRecordDecl()) {
      if (RD->hasTrivialCopyConstructor() &&
          !RD->hasNonTrivialCopyConstructor())
        return true;

      bool FoundConstructor = false;
      unsigned FoundTQs;
      DeclContext::lookup_result R = Self.LookupConstructors(RD);
      for (DeclContext::lookup_iterator Con = R.begin(),
           ConEnd = R.end(); Con != ConEnd; ++Con) {
        // A template constructor is never a copy constructor.
        // FIXME: However, it may actually be selected at the actual overload
        // resolution point.
        if (isa<FunctionTemplateDecl>(*Con))
          continue;
        CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(*Con);
        if (Constructor->isCopyConstructor(FoundTQs)) {
          FoundConstructor = true;
          const FunctionProtoType *CPT
              = Constructor->getType()->getAs<FunctionProtoType>();
          CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
          if (!CPT)
            return false;
          // TODO: check whether evaluating default arguments can throw.
          // For now, we'll be conservative and assume that they can throw.
          if (!CPT->isNothrow(Self.Context) || CPT->getNumParams() > 1)
            return false;
        }
      }

      return FoundConstructor;
    }
    return false;
  case UTT_HasNothrowConstructor:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html
    //   If __has_trivial_constructor (type) is true then the trait is
    //   true, else if type is a cv class or union type (or array
    //   thereof) with a default constructor that is known not to
    //   throw an exception then the trait is true, else it is false.
    if (T.isPODType(C) || T->isObjCLifetimeType())
      return true;
    if (CXXRecordDecl *RD = C.getBaseElementType(T)->getAsCXXRecordDecl()) {
      if (RD->hasTrivialDefaultConstructor() &&
          !RD->hasNonTrivialDefaultConstructor())
        return true;

      bool FoundConstructor = false;
      DeclContext::lookup_result R = Self.LookupConstructors(RD);
      for (DeclContext::lookup_iterator Con = R.begin(),
           ConEnd = R.end(); Con != ConEnd; ++Con) {
        // FIXME: In C++0x, a constructor template can be a default constructor.
        if (isa<FunctionTemplateDecl>(*Con))
          continue;
        CXXConstructorDecl *Constructor = cast<CXXConstructorDecl>(*Con);
        if (Constructor->isDefaultConstructor()) {
          FoundConstructor = true;
          const FunctionProtoType *CPT
              = Constructor->getType()->getAs<FunctionProtoType>();
          CPT = Self.ResolveExceptionSpec(KeyLoc, CPT);
          if (!CPT)
            return false;
          // FIXME: check whether evaluating default arguments can throw.
          // For now, we'll be conservative and assume that they can throw.
          if (!CPT->isNothrow(Self.Context) || CPT->getNumParams() > 0)
            return false;
        }
      }
      return FoundConstructor;
    }
    return false;
  case UTT_HasVirtualDestructor:
    // http://gcc.gnu.org/onlinedocs/gcc/Type-Traits.html:
    //   If type is a class type with a virtual destructor ([class.dtor])
    //   then the trait is true, else it is false.
    if (CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      if (CXXDestructorDecl *Destructor = Self.LookupDestructor(RD))
        return Destructor->isVirtual();
    return false;

    // These type trait expressions are modeled on the specifications for the
    // Embarcadero C++0x type trait functions:
    //   http://docwiki.embarcadero.com/RADStudio/XE/en/Type_Trait_Functions_(C%2B%2B0x)_Index
  case UTT_IsCompleteType:
    // http://docwiki.embarcadero.com/RADStudio/XE/en/Is_complete_type_(typename_T_):
    //   Returns True if and only if T is a complete type at the point of the
    //   function call.
    return !T->isIncompleteType();
  }
}

/// \brief Determine whether T has a non-trivial Objective-C lifetime in
/// ARC mode.
static bool hasNontrivialObjCLifetime(QualType T) {
  switch (T.getObjCLifetime()) {
  case Qualifiers::OCL_ExplicitNone:
    return false;

  case Qualifiers::OCL_Strong:
  case Qualifiers::OCL_Weak:
  case Qualifiers::OCL_Autoreleasing:
    return true;

  case Qualifiers::OCL_None:
    return T->isObjCLifetimeType();
  }

  llvm_unreachable("Unknown ObjC lifetime qualifier");
}

static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, QualType LhsT,
                                    QualType RhsT, SourceLocation KeyLoc);

static bool evaluateTypeTrait(Sema &S, TypeTrait Kind, SourceLocation KWLoc,
                              ArrayRef<TypeSourceInfo *> Args,
                              SourceLocation RParenLoc) {
  if (Kind <= UTT_Last)
    return EvaluateUnaryTypeTrait(S, Kind, KWLoc, Args[0]->getType());

  if (Kind <= BTT_Last)
    return EvaluateBinaryTypeTrait(S, Kind, Args[0]->getType(),
                                   Args[1]->getType(), RParenLoc);

  switch (Kind) {
  case clang::TT_IsConstructible:
  case clang::TT_IsNothrowConstructible:
  case clang::TT_IsTriviallyConstructible: {
    // C++11 [meta.unary.prop]:
    //   is_trivially_constructible is defined as:
    //
    //     is_constructible<T, Args...>::value is true and the variable
    //     definition for is_constructible, as defined below, is known to call
    //     no operation that is not trivial.
    //
    //   The predicate condition for a template specialization 
    //   is_constructible<T, Args...> shall be satisfied if and only if the 
    //   following variable definition would be well-formed for some invented 
    //   variable t:
    //
    //     T t(create<Args>()...);
    assert(!Args.empty());

    // Precondition: T and all types in the parameter pack Args shall be
    // complete types, (possibly cv-qualified) void, or arrays of
    // unknown bound.
    for (unsigned I = 0, N = Args.size(); I != N; ++I) {
      QualType ArgTy = Args[I]->getType();
      if (ArgTy->isVoidType() || ArgTy->isIncompleteArrayType())
        continue;

      if (S.RequireCompleteType(KWLoc, ArgTy, 
          diag::err_incomplete_type_used_in_type_trait_expr))
        return false;
    }

    // Make sure the first argument is a complete type.
    if (Args[0]->getType()->isIncompleteType())
      return false;

    // Make sure the first argument is not an abstract type.
    CXXRecordDecl *RD = Args[0]->getType()->getAsCXXRecordDecl();
    if (RD && RD->isAbstract())
      return false;

    SmallVector<OpaqueValueExpr, 2> OpaqueArgExprs;
    SmallVector<Expr *, 2> ArgExprs;
    ArgExprs.reserve(Args.size() - 1);
    for (unsigned I = 1, N = Args.size(); I != N; ++I) {
      QualType T = Args[I]->getType();
      if (T->isObjectType() || T->isFunctionType())
        T = S.Context.getRValueReferenceType(T);
      OpaqueArgExprs.push_back(
        OpaqueValueExpr(Args[I]->getTypeLoc().getLocStart(),
                        T.getNonLValueExprType(S.Context),
                        Expr::getValueKindForType(T)));
    }
    for (Expr &E : OpaqueArgExprs)
      ArgExprs.push_back(&E);

    // Perform the initialization in an unevaluated context within a SFINAE 
    // trap at translation unit scope.
    EnterExpressionEvaluationContext Unevaluated(S, Sema::Unevaluated);
    Sema::SFINAETrap SFINAE(S, /*AccessCheckingSFINAE=*/true);
    Sema::ContextRAII TUContext(S, S.Context.getTranslationUnitDecl());
    InitializedEntity To(InitializedEntity::InitializeTemporary(Args[0]));
    InitializationKind InitKind(InitializationKind::CreateDirect(KWLoc, KWLoc,
                                                                 RParenLoc));
    InitializationSequence Init(S, To, InitKind, ArgExprs);
    if (Init.Failed())
      return false;

    ExprResult Result = Init.Perform(S, To, InitKind, ArgExprs);
    if (Result.isInvalid() || SFINAE.hasErrorOccurred())
      return false;

    if (Kind == clang::TT_IsConstructible)
      return true;

    if (Kind == clang::TT_IsNothrowConstructible)
      return S.canThrow(Result.get()) == CT_Cannot;

    if (Kind == clang::TT_IsTriviallyConstructible) {
      // Under Objective-C ARC, if the destination has non-trivial Objective-C
      // lifetime, this is a non-trivial construction.
      if (S.getLangOpts().ObjCAutoRefCount &&
          hasNontrivialObjCLifetime(Args[0]->getType().getNonReferenceType()))
        return false;

      // The initialization succeeded; now make sure there are no non-trivial
      // calls.
      return !Result.get()->hasNonTrivialCall(S.Context);
    }

    llvm_unreachable("unhandled type trait");
    return false;
  }
    default: llvm_unreachable("not a TT");
  }
  
  return false;
}

ExprResult Sema::BuildTypeTrait(TypeTrait Kind, SourceLocation KWLoc, 
                                ArrayRef<TypeSourceInfo *> Args, 
                                SourceLocation RParenLoc) {
  QualType ResultType = Context.getLogicalOperationType();

  if (Kind <= UTT_Last && !CheckUnaryTypeTraitTypeCompleteness(
                               *this, Kind, KWLoc, Args[0]->getType()))
    return ExprError();

  bool Dependent = false;
  for (unsigned I = 0, N = Args.size(); I != N; ++I) {
    if (Args[I]->getType()->isDependentType()) {
      Dependent = true;
      break;
    }
  }

  bool Result = false;
  if (!Dependent)
    Result = evaluateTypeTrait(*this, Kind, KWLoc, Args, RParenLoc);

  return TypeTraitExpr::Create(Context, ResultType, KWLoc, Kind, Args,
                               RParenLoc, Result);
}

ExprResult Sema::ActOnTypeTrait(TypeTrait Kind, SourceLocation KWLoc,
                                ArrayRef<ParsedType> Args,
                                SourceLocation RParenLoc) {
  SmallVector<TypeSourceInfo *, 4> ConvertedArgs;
  ConvertedArgs.reserve(Args.size());
  
  for (unsigned I = 0, N = Args.size(); I != N; ++I) {
    TypeSourceInfo *TInfo;
    QualType T = GetTypeFromParser(Args[I], &TInfo);
    if (!TInfo)
      TInfo = Context.getTrivialTypeSourceInfo(T, KWLoc);
    
    ConvertedArgs.push_back(TInfo);    
  }

  return BuildTypeTrait(Kind, KWLoc, ConvertedArgs, RParenLoc);
}

static bool EvaluateBinaryTypeTrait(Sema &Self, TypeTrait BTT, QualType LhsT,
                                    QualType RhsT, SourceLocation KeyLoc) {
  assert(!LhsT->isDependentType() && !RhsT->isDependentType() &&
         "Cannot evaluate traits of dependent types");

  switch(BTT) {
  case BTT_IsBaseOf: {
    // C++0x [meta.rel]p2
    // Base is a base class of Derived without regard to cv-qualifiers or
    // Base and Derived are not unions and name the same class type without
    // regard to cv-qualifiers.

    const RecordType *lhsRecord = LhsT->getAs<RecordType>();
    if (!lhsRecord) return false;

    const RecordType *rhsRecord = RhsT->getAs<RecordType>();
    if (!rhsRecord) return false;

    assert(Self.Context.hasSameUnqualifiedType(LhsT, RhsT)
             == (lhsRecord == rhsRecord));

    if (lhsRecord == rhsRecord)
      return !lhsRecord->getDecl()->isUnion();

    // C++0x [meta.rel]p2:
    //   If Base and Derived are class types and are different types
    //   (ignoring possible cv-qualifiers) then Derived shall be a
    //   complete type.
    if (Self.RequireCompleteType(KeyLoc, RhsT, 
                          diag::err_incomplete_type_used_in_type_trait_expr))
      return false;

    return cast<CXXRecordDecl>(rhsRecord->getDecl())
      ->isDerivedFrom(cast<CXXRecordDecl>(lhsRecord->getDecl()));
  }
  case BTT_IsSame:
    return Self.Context.hasSameType(LhsT, RhsT);
  case BTT_TypeCompatible:
    return Self.Context.typesAreCompatible(LhsT.getUnqualifiedType(),
                                           RhsT.getUnqualifiedType());
  case BTT_IsConvertible:
  case BTT_IsConvertibleTo: {
    // C++0x [meta.rel]p4:
    //   Given the following function prototype:
    //
    //     template <class T> 
    //       typename add_rvalue_reference<T>::type create();
    //
    //   the predicate condition for a template specialization 
    //   is_convertible<From, To> shall be satisfied if and only if 
    //   the return expression in the following code would be 
    //   well-formed, including any implicit conversions to the return
    //   type of the function:
    //
    //     To test() { 
    //       return create<From>();
    //     }
    //
    //   Access checking is performed as if in a context unrelated to To and 
    //   From. Only the validity of the immediate context of the expression 
    //   of the return-statement (including conversions to the return type)
    //   is considered.
    //
    // We model the initialization as a copy-initialization of a temporary
    // of the appropriate type, which for this expression is identical to the
    // return statement (since NRVO doesn't apply).

    // Functions aren't allowed to return function or array types.
    if (RhsT->isFunctionType() || RhsT->isArrayType())
      return false;

    // A return statement in a void function must have void type.
    if (RhsT->isVoidType())
      return LhsT->isVoidType();

    // A function definition requires a complete, non-abstract return type.
    if (Self.RequireCompleteType(KeyLoc, RhsT, 0) ||
        Self.RequireNonAbstractType(KeyLoc, RhsT, 0))
      return false;

    // Compute the result of add_rvalue_reference.
    if (LhsT->isObjectType() || LhsT->isFunctionType())
      LhsT = Self.Context.getRValueReferenceType(LhsT);

    // Build a fake source and destination for initialization.
    InitializedEntity To(InitializedEntity::InitializeTemporary(RhsT));
    OpaqueValueExpr From(KeyLoc, LhsT.getNonLValueExprType(Self.Context),
                         Expr::getValueKindForType(LhsT));
    Expr *FromPtr = &From;
    InitializationKind Kind(InitializationKind::CreateCopy(KeyLoc, 
                                                           SourceLocation()));
    
    // Perform the initialization in an unevaluated context within a SFINAE 
    // trap at translation unit scope.
    EnterExpressionEvaluationContext Unevaluated(Self, Sema::Unevaluated);
    Sema::SFINAETrap SFINAE(Self, /*AccessCheckingSFINAE=*/true);
    Sema::ContextRAII TUContext(Self, Self.Context.getTranslationUnitDecl());
    InitializationSequence Init(Self, To, Kind, FromPtr);
    if (Init.Failed())
      return false;

    ExprResult Result = Init.Perform(Self, To, Kind, FromPtr);
    return !Result.isInvalid() && !SFINAE.hasErrorOccurred();
  }

  case BTT_IsNothrowAssignable:
  case BTT_IsTriviallyAssignable: {
    // C++11 [meta.unary.prop]p3:
    //   is_trivially_assignable is defined as:
    //     is_assignable<T, U>::value is true and the assignment, as defined by
    //     is_assignable, is known to call no operation that is not trivial
    //
    //   is_assignable is defined as:
    //     The expression declval<T>() = declval<U>() is well-formed when 
    //     treated as an unevaluated operand (Clause 5).
    //
    //   For both, T and U shall be complete types, (possibly cv-qualified) 
    //   void, or arrays of unknown bound.
    if (!LhsT->isVoidType() && !LhsT->isIncompleteArrayType() &&
        Self.RequireCompleteType(KeyLoc, LhsT, 
          diag::err_incomplete_type_used_in_type_trait_expr))
      return false;
    if (!RhsT->isVoidType() && !RhsT->isIncompleteArrayType() &&
        Self.RequireCompleteType(KeyLoc, RhsT, 
          diag::err_incomplete_type_used_in_type_trait_expr))
      return false;

    // cv void is never assignable.
    if (LhsT->isVoidType() || RhsT->isVoidType())
      return false;

    // Build expressions that emulate the effect of declval<T>() and 
    // declval<U>().
    if (LhsT->isObjectType() || LhsT->isFunctionType())
      LhsT = Self.Context.getRValueReferenceType(LhsT);
    if (RhsT->isObjectType() || RhsT->isFunctionType())
      RhsT = Self.Context.getRValueReferenceType(RhsT);
    OpaqueValueExpr Lhs(KeyLoc, LhsT.getNonLValueExprType(Self.Context),
                        Expr::getValueKindForType(LhsT));
    OpaqueValueExpr Rhs(KeyLoc, RhsT.getNonLValueExprType(Self.Context),
                        Expr::getValueKindForType(RhsT));
    
    // Attempt the assignment in an unevaluated context within a SFINAE 
    // trap at translation unit scope.
    EnterExpressionEvaluationContext Unevaluated(Self, Sema::Unevaluated);
    Sema::SFINAETrap SFINAE(Self, /*AccessCheckingSFINAE=*/true);
    Sema::ContextRAII TUContext(Self, Self.Context.getTranslationUnitDecl());
    ExprResult Result = Self.BuildBinOp(/*S=*/nullptr, KeyLoc, BO_Assign, &Lhs,
                                        &Rhs);
    if (Result.isInvalid() || SFINAE.hasErrorOccurred())
      return false;

    if (BTT == BTT_IsNothrowAssignable)
      return Self.canThrow(Result.get()) == CT_Cannot;

    if (BTT == BTT_IsTriviallyAssignable) {
      // Under Objective-C ARC, if the destination has non-trivial Objective-C
      // lifetime, this is a non-trivial assignment.
      if (Self.getLangOpts().ObjCAutoRefCount &&
          hasNontrivialObjCLifetime(LhsT.getNonReferenceType()))
        return false;

      return !Result.get()->hasNonTrivialCall(Self.Context);
    }

    llvm_unreachable("unhandled type trait");
    return false;
  }
    default: llvm_unreachable("not a BTT");
  }
  llvm_unreachable("Unknown type trait or not implemented");
}

ExprResult Sema::ActOnArrayTypeTrait(ArrayTypeTrait ATT,
                                     SourceLocation KWLoc,
                                     ParsedType Ty,
                                     Expr* DimExpr,
                                     SourceLocation RParen) {
  TypeSourceInfo *TSInfo;
  QualType T = GetTypeFromParser(Ty, &TSInfo);
  if (!TSInfo)
    TSInfo = Context.getTrivialTypeSourceInfo(T);

  return BuildArrayTypeTrait(ATT, KWLoc, TSInfo, DimExpr, RParen);
}

static uint64_t EvaluateArrayTypeTrait(Sema &Self, ArrayTypeTrait ATT,
                                           QualType T, Expr *DimExpr,
                                           SourceLocation KeyLoc) {
  assert(!T->isDependentType() && "Cannot evaluate traits of dependent type");

  switch(ATT) {
  case ATT_ArrayRank:
    if (T->isArrayType()) {
      unsigned Dim = 0;
      while (const ArrayType *AT = Self.Context.getAsArrayType(T)) {
        ++Dim;
        T = AT->getElementType();
      }
      return Dim;
    }
    return 0;

  case ATT_ArrayExtent: {
    llvm::APSInt Value;
    uint64_t Dim;
    if (Self.VerifyIntegerConstantExpression(DimExpr, &Value,
          diag::err_dimension_expr_not_constant_integer,
          false).isInvalid())
      return 0;
    if (Value.isSigned() && Value.isNegative()) {
      Self.Diag(KeyLoc, diag::err_dimension_expr_not_constant_integer)
        << DimExpr->getSourceRange();
      return 0;
    }
    Dim = Value.getLimitedValue();

    if (T->isArrayType()) {
      unsigned D = 0;
      bool Matched = false;
      while (const ArrayType *AT = Self.Context.getAsArrayType(T)) {
        if (Dim == D) {
          Matched = true;
          break;
        }
        ++D;
        T = AT->getElementType();
      }

      if (Matched && T->isArrayType()) {
        if (const ConstantArrayType *CAT = Self.Context.getAsConstantArrayType(T))
          return CAT->getSize().getLimitedValue();
      }
    }
    return 0;
  }
  }
  llvm_unreachable("Unknown type trait or not implemented");
}

ExprResult Sema::BuildArrayTypeTrait(ArrayTypeTrait ATT,
                                     SourceLocation KWLoc,
                                     TypeSourceInfo *TSInfo,
                                     Expr* DimExpr,
                                     SourceLocation RParen) {
  QualType T = TSInfo->getType();

  // FIXME: This should likely be tracked as an APInt to remove any host
  // assumptions about the width of size_t on the target.
  uint64_t Value = 0;
  if (!T->isDependentType())
    Value = EvaluateArrayTypeTrait(*this, ATT, T, DimExpr, KWLoc);

  // While the specification for these traits from the Embarcadero C++
  // compiler's documentation says the return type is 'unsigned int', Clang
  // returns 'size_t'. On Windows, the primary platform for the Embarcadero
  // compiler, there is no difference. On several other platforms this is an
  // important distinction.
  return new (Context) ArrayTypeTraitExpr(KWLoc, ATT, TSInfo, Value, DimExpr,
                                          RParen, Context.getSizeType());
}

ExprResult Sema::ActOnExpressionTrait(ExpressionTrait ET,
                                      SourceLocation KWLoc,
                                      Expr *Queried,
                                      SourceLocation RParen) {
  // If error parsing the expression, ignore.
  if (!Queried)
    return ExprError();

  ExprResult Result = BuildExpressionTrait(ET, KWLoc, Queried, RParen);

  return Result;
}

static bool EvaluateExpressionTrait(ExpressionTrait ET, Expr *E) {
  switch (ET) {
  case ET_IsLValueExpr: return E->isLValue();
  case ET_IsRValueExpr: return E->isRValue();
  }
  llvm_unreachable("Expression trait not covered by switch");
}

ExprResult Sema::BuildExpressionTrait(ExpressionTrait ET,
                                      SourceLocation KWLoc,
                                      Expr *Queried,
                                      SourceLocation RParen) {
  if (Queried->isTypeDependent()) {
    // Delay type-checking for type-dependent expressions.
  } else if (Queried->getType()->isPlaceholderType()) {
    ExprResult PE = CheckPlaceholderExpr(Queried);
    if (PE.isInvalid()) return ExprError();
    return BuildExpressionTrait(ET, KWLoc, PE.get(), RParen);
  }

  bool Value = EvaluateExpressionTrait(ET, Queried);

  return new (Context)
      ExpressionTraitExpr(KWLoc, ET, Queried, Value, RParen, Context.BoolTy);
}

QualType Sema::CheckPointerToMemberOperands(ExprResult &LHS, ExprResult &RHS,
                                            ExprValueKind &VK,
                                            SourceLocation Loc,
                                            bool isIndirect) {
  assert(!LHS.get()->getType()->isPlaceholderType() &&
         !RHS.get()->getType()->isPlaceholderType() &&
         "placeholders should have been weeded out by now");

  // The LHS undergoes lvalue conversions if this is ->*.
  if (isIndirect) {
    LHS = DefaultLvalueConversion(LHS.get());
    if (LHS.isInvalid()) return QualType();
  }

  // The RHS always undergoes lvalue conversions.
  RHS = DefaultLvalueConversion(RHS.get());
  if (RHS.isInvalid()) return QualType();

  const char *OpSpelling = isIndirect ? "->*" : ".*";
  // C++ 5.5p2
  //   The binary operator .* [p3: ->*] binds its second operand, which shall
  //   be of type "pointer to member of T" (where T is a completely-defined
  //   class type) [...]
  QualType RHSType = RHS.get()->getType();
  const MemberPointerType *MemPtr = RHSType->getAs<MemberPointerType>();
  if (!MemPtr) {
    Diag(Loc, diag::err_bad_memptr_rhs)
      << OpSpelling << RHSType << RHS.get()->getSourceRange();
    return QualType();
  }

  QualType Class(MemPtr->getClass(), 0);

  // Note: C++ [expr.mptr.oper]p2-3 says that the class type into which the
  // member pointer points must be completely-defined. However, there is no
  // reason for this semantic distinction, and the rule is not enforced by
  // other compilers. Therefore, we do not check this property, as it is
  // likely to be considered a defect.

  // C++ 5.5p2
  //   [...] to its first operand, which shall be of class T or of a class of
  //   which T is an unambiguous and accessible base class. [p3: a pointer to
  //   such a class]
  QualType LHSType = LHS.get()->getType();
  if (isIndirect) {
    if (const PointerType *Ptr = LHSType->getAs<PointerType>())
      LHSType = Ptr->getPointeeType();
    else {
      Diag(Loc, diag::err_bad_memptr_lhs)
        << OpSpelling << 1 << LHSType
        << FixItHint::CreateReplacement(SourceRange(Loc), ".*");
      return QualType();
    }
  }

  if (!Context.hasSameUnqualifiedType(Class, LHSType)) {
    // If we want to check the hierarchy, we need a complete type.
    if (RequireCompleteType(Loc, LHSType, diag::err_bad_memptr_lhs,
                            OpSpelling, (int)isIndirect)) {
      return QualType();
    }

    if (!IsDerivedFrom(LHSType, Class)) {
      Diag(Loc, diag::err_bad_memptr_lhs) << OpSpelling
        << (int)isIndirect << LHS.get()->getType();
      return QualType();
    }

    CXXCastPath BasePath;
    if (CheckDerivedToBaseConversion(LHSType, Class, Loc,
                                     SourceRange(LHS.get()->getLocStart(),
                                                 RHS.get()->getLocEnd()),
                                     &BasePath))
      return QualType();

    // Cast LHS to type of use.
    QualType UseType = isIndirect ? Context.getPointerType(Class) : Class;
    ExprValueKind VK = isIndirect ? VK_RValue : LHS.get()->getValueKind();
    LHS = ImpCastExprToType(LHS.get(), UseType, CK_DerivedToBase, VK,
                            &BasePath);
  }

  if (isa<CXXScalarValueInitExpr>(RHS.get()->IgnoreParens())) {
    // Diagnose use of pointer-to-member type which when used as
    // the functional cast in a pointer-to-member expression.
    Diag(Loc, diag::err_pointer_to_member_type) << isIndirect;
     return QualType();
  }

  // C++ 5.5p2
  //   The result is an object or a function of the type specified by the
  //   second operand.
  // The cv qualifiers are the union of those in the pointer and the left side,
  // in accordance with 5.5p5 and 5.2.5.
  QualType Result = MemPtr->getPointeeType();
  Result = Context.getCVRQualifiedType(Result, LHSType.getCVRQualifiers());

  // C++0x [expr.mptr.oper]p6:
  //   In a .* expression whose object expression is an rvalue, the program is
  //   ill-formed if the second operand is a pointer to member function with
  //   ref-qualifier &. In a ->* expression or in a .* expression whose object
  //   expression is an lvalue, the program is ill-formed if the second operand
  //   is a pointer to member function with ref-qualifier &&.
  if (const FunctionProtoType *Proto = Result->getAs<FunctionProtoType>()) {
    switch (Proto->getRefQualifier()) {
    case RQ_None:
      // Do nothing
      break;

    case RQ_LValue:
      if (!isIndirect && !LHS.get()->Classify(Context).isLValue())
        Diag(Loc, diag::err_pointer_to_member_oper_value_classify)
          << RHSType << 1 << LHS.get()->getSourceRange();
      break;

    case RQ_RValue:
      if (isIndirect || !LHS.get()->Classify(Context).isRValue())
        Diag(Loc, diag::err_pointer_to_member_oper_value_classify)
          << RHSType << 0 << LHS.get()->getSourceRange();
      break;
    }
  }

  // C++ [expr.mptr.oper]p6:
  //   The result of a .* expression whose second operand is a pointer
  //   to a data member is of the same value category as its
  //   first operand. The result of a .* expression whose second
  //   operand is a pointer to a member function is a prvalue. The
  //   result of an ->* expression is an lvalue if its second operand
  //   is a pointer to data member and a prvalue otherwise.
  if (Result->isFunctionType()) {
    VK = VK_RValue;
    return Context.BoundMemberTy;
  } else if (isIndirect) {
    VK = VK_LValue;
  } else {
    VK = LHS.get()->getValueKind();
  }

  return Result;
}

/// \brief Try to convert a type to another according to C++0x 5.16p3.
///
/// This is part of the parameter validation for the ? operator. If either
/// value operand is a class type, the two operands are attempted to be
/// converted to each other. This function does the conversion in one direction.
/// It returns true if the program is ill-formed and has already been diagnosed
/// as such.
static bool TryClassUnification(Sema &Self, Expr *From, Expr *To,
                                SourceLocation QuestionLoc,
                                bool &HaveConversion,
                                QualType &ToType) {
  HaveConversion = false;
  ToType = To->getType();

  InitializationKind Kind = InitializationKind::CreateCopy(To->getLocStart(),
                                                           SourceLocation());
  // C++0x 5.16p3
  //   The process for determining whether an operand expression E1 of type T1
  //   can be converted to match an operand expression E2 of type T2 is defined
  //   as follows:
  //   -- If E2 is an lvalue:
  bool ToIsLvalue = To->isLValue();
  if (ToIsLvalue) {
    //   E1 can be converted to match E2 if E1 can be implicitly converted to
    //   type "lvalue reference to T2", subject to the constraint that in the
    //   conversion the reference must bind directly to E1.
    QualType T = Self.Context.getLValueReferenceType(ToType);
    InitializedEntity Entity = InitializedEntity::InitializeTemporary(T);

    InitializationSequence InitSeq(Self, Entity, Kind, From);
    if (InitSeq.isDirectReferenceBinding()) {
      ToType = T;
      HaveConversion = true;
      return false;
    }

    if (InitSeq.isAmbiguous())
      return InitSeq.Diagnose(Self, Entity, Kind, From);
  }

  //   -- If E2 is an rvalue, or if the conversion above cannot be done:
  //      -- if E1 and E2 have class type, and the underlying class types are
  //         the same or one is a base class of the other:
  QualType FTy = From->getType();
  QualType TTy = To->getType();
  const RecordType *FRec = FTy->getAs<RecordType>();
  const RecordType *TRec = TTy->getAs<RecordType>();
  bool FDerivedFromT = FRec && TRec && FRec != TRec &&
                       Self.IsDerivedFrom(FTy, TTy);
  if (FRec && TRec &&
      (FRec == TRec || FDerivedFromT || Self.IsDerivedFrom(TTy, FTy))) {
    //         E1 can be converted to match E2 if the class of T2 is the
    //         same type as, or a base class of, the class of T1, and
    //         [cv2 > cv1].
    if (FRec == TRec || FDerivedFromT) {
      if (TTy.isAtLeastAsQualifiedAs(FTy)) {
        InitializedEntity Entity = InitializedEntity::InitializeTemporary(TTy);
        InitializationSequence InitSeq(Self, Entity, Kind, From);
        if (InitSeq) {
          HaveConversion = true;
          return false;
        }

        if (InitSeq.isAmbiguous())
          return InitSeq.Diagnose(Self, Entity, Kind, From);
      }
    }

    return false;
  }

  //     -- Otherwise: E1 can be converted to match E2 if E1 can be
  //        implicitly converted to the type that expression E2 would have
  //        if E2 were converted to an rvalue (or the type it has, if E2 is
  //        an rvalue).
  //
  // This actually refers very narrowly to the lvalue-to-rvalue conversion, not
  // to the array-to-pointer or function-to-pointer conversions.
  if (!TTy->getAs<TagType>())
    TTy = TTy.getUnqualifiedType();

  InitializedEntity Entity = InitializedEntity::InitializeTemporary(TTy);
  InitializationSequence InitSeq(Self, Entity, Kind, From);
  HaveConversion = !InitSeq.Failed();
  ToType = TTy;
  if (InitSeq.isAmbiguous())
    return InitSeq.Diagnose(Self, Entity, Kind, From);

  return false;
}

/// \brief Try to find a common type for two according to C++0x 5.16p5.
///
/// This is part of the parameter validation for the ? operator. If either
/// value operand is a class type, overload resolution is used to find a
/// conversion to a common type.
static bool FindConditionalOverload(Sema &Self, ExprResult &LHS, ExprResult &RHS,
                                    SourceLocation QuestionLoc) {
  Expr *Args[2] = { LHS.get(), RHS.get() };
  OverloadCandidateSet CandidateSet(QuestionLoc,
                                    OverloadCandidateSet::CSK_Operator);
  Self.AddBuiltinOperatorCandidates(OO_Conditional, QuestionLoc, Args,
                                    CandidateSet);

  OverloadCandidateSet::iterator Best;
  switch (CandidateSet.BestViableFunction(Self, QuestionLoc, Best)) {
    case OR_Success: {
      // We found a match. Perform the conversions on the arguments and move on.
      ExprResult LHSRes =
        Self.PerformImplicitConversion(LHS.get(), Best->BuiltinTypes.ParamTypes[0],
                                       Best->Conversions[0], Sema::AA_Converting);
      if (LHSRes.isInvalid())
        break;
      LHS = LHSRes;

      ExprResult RHSRes =
        Self.PerformImplicitConversion(RHS.get(), Best->BuiltinTypes.ParamTypes[1],
                                       Best->Conversions[1], Sema::AA_Converting);
      if (RHSRes.isInvalid())
        break;
      RHS = RHSRes;
      if (Best->Function)
        Self.MarkFunctionReferenced(QuestionLoc, Best->Function);
      return false;
    }
    
    case OR_No_Viable_Function:

      // Emit a better diagnostic if one of the expressions is a null pointer
      // constant and the other is a pointer type. In this case, the user most
      // likely forgot to take the address of the other expression.
      if (Self.DiagnoseConditionalForNull(LHS.get(), RHS.get(), QuestionLoc))
        return true;

      Self.Diag(QuestionLoc, diag::err_typecheck_cond_incompatible_operands)
        << LHS.get()->getType() << RHS.get()->getType()
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return true;

    case OR_Ambiguous:
      Self.Diag(QuestionLoc, diag::err_conditional_ambiguous_ovl)
        << LHS.get()->getType() << RHS.get()->getType()
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      // FIXME: Print the possible common types by printing the return types of
      // the viable candidates.
      break;

    case OR_Deleted:
      llvm_unreachable("Conditional operator has only built-in overloads");
  }
  return true;
}

/// \brief Perform an "extended" implicit conversion as returned by
/// TryClassUnification.
static bool ConvertForConditional(Sema &Self, ExprResult &E, QualType T) {
  InitializedEntity Entity = InitializedEntity::InitializeTemporary(T);
  InitializationKind Kind = InitializationKind::CreateCopy(E.get()->getLocStart(),
                                                           SourceLocation());
  Expr *Arg = E.get();
  InitializationSequence InitSeq(Self, Entity, Kind, Arg);
  ExprResult Result = InitSeq.Perform(Self, Entity, Kind, Arg);
  if (Result.isInvalid())
    return true;

  E = Result;
  return false;
}

/// \brief Check the operands of ?: under C++ semantics.
///
/// See C++ [expr.cond]. Note that LHS is never null, even for the GNU x ?: y
/// extension. In this case, LHS == Cond. (But they're not aliases.)
QualType Sema::CXXCheckConditionalOperands(ExprResult &Cond, ExprResult &LHS,
                                           ExprResult &RHS, ExprValueKind &VK,
                                           ExprObjectKind &OK,
                                           SourceLocation QuestionLoc) {
  // FIXME: Handle C99's complex types, vector types, block pointers and Obj-C++
  // interface pointers.

  // C++11 [expr.cond]p1
  //   The first expression is contextually converted to bool.
  if (!Cond.get()->isTypeDependent()) {
    ExprResult CondRes = CheckCXXBooleanCondition(Cond.get());
    if (CondRes.isInvalid())
      return QualType();
    Cond = CondRes;
  }

  // Assume r-value.
  VK = VK_RValue;
  OK = OK_Ordinary;

  // Either of the arguments dependent?
  if (LHS.get()->isTypeDependent() || RHS.get()->isTypeDependent())
    return Context.DependentTy;

  // C++11 [expr.cond]p2
  //   If either the second or the third operand has type (cv) void, ...
  QualType LTy = LHS.get()->getType();
  QualType RTy = RHS.get()->getType();
  bool LVoid = LTy->isVoidType();
  bool RVoid = RTy->isVoidType();
  if (LVoid || RVoid) {
    //   ... one of the following shall hold:
    //   -- The second or the third operand (but not both) is a (possibly
    //      parenthesized) throw-expression; the result is of the type
    //      and value category of the other.
    bool LThrow = isa<CXXThrowExpr>(LHS.get()->IgnoreParenImpCasts());
    bool RThrow = isa<CXXThrowExpr>(RHS.get()->IgnoreParenImpCasts());
    if (LThrow != RThrow) {
      Expr *NonThrow = LThrow ? RHS.get() : LHS.get();
      VK = NonThrow->getValueKind();
      // DR (no number yet): the result is a bit-field if the
      // non-throw-expression operand is a bit-field.
      OK = NonThrow->getObjectKind();
      return NonThrow->getType();
    }

    //   -- Both the second and third operands have type void; the result is of
    //      type void and is a prvalue.
    if (LVoid && RVoid)
      return Context.VoidTy;

    // Neither holds, error.
    Diag(QuestionLoc, diag::err_conditional_void_nonvoid)
      << (LVoid ? RTy : LTy) << (LVoid ? 0 : 1)
      << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
    return QualType();
  }

  // Neither is void.

  // C++11 [expr.cond]p3
  //   Otherwise, if the second and third operand have different types, and
  //   either has (cv) class type [...] an attempt is made to convert each of
  //   those operands to the type of the other.
  if (!Context.hasSameType(LTy, RTy) &&
      (LTy->isRecordType() || RTy->isRecordType())) {
    // These return true if a single direction is already ambiguous.
    QualType L2RType, R2LType;
    bool HaveL2R, HaveR2L;
    if (TryClassUnification(*this, LHS.get(), RHS.get(), QuestionLoc, HaveL2R, L2RType))
      return QualType();
    if (TryClassUnification(*this, RHS.get(), LHS.get(), QuestionLoc, HaveR2L, R2LType))
      return QualType();

    //   If both can be converted, [...] the program is ill-formed.
    if (HaveL2R && HaveR2L) {
      Diag(QuestionLoc, diag::err_conditional_ambiguous)
        << LTy << RTy << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
      return QualType();
    }

    //   If exactly one conversion is possible, that conversion is applied to
    //   the chosen operand and the converted operands are used in place of the
    //   original operands for the remainder of this section.
    if (HaveL2R) {
      if (ConvertForConditional(*this, LHS, L2RType) || LHS.isInvalid())
        return QualType();
      LTy = LHS.get()->getType();
    } else if (HaveR2L) {
      if (ConvertForConditional(*this, RHS, R2LType) || RHS.isInvalid())
        return QualType();
      RTy = RHS.get()->getType();
    }
  }

  // C++11 [expr.cond]p3
  //   if both are glvalues of the same value category and the same type except
  //   for cv-qualification, an attempt is made to convert each of those
  //   operands to the type of the other.
  ExprValueKind LVK = LHS.get()->getValueKind();
  ExprValueKind RVK = RHS.get()->getValueKind();
  if (!Context.hasSameType(LTy, RTy) &&
      Context.hasSameUnqualifiedType(LTy, RTy) &&
      LVK == RVK && LVK != VK_RValue) {
    // Since the unqualified types are reference-related and we require the
    // result to be as if a reference bound directly, the only conversion
    // we can perform is to add cv-qualifiers.
    Qualifiers LCVR = Qualifiers::fromCVRMask(LTy.getCVRQualifiers());
    Qualifiers RCVR = Qualifiers::fromCVRMask(RTy.getCVRQualifiers());
    if (RCVR.isStrictSupersetOf(LCVR)) {
      LHS = ImpCastExprToType(LHS.get(), RTy, CK_NoOp, LVK);
      LTy = LHS.get()->getType();
    }
    else if (LCVR.isStrictSupersetOf(RCVR)) {
      RHS = ImpCastExprToType(RHS.get(), LTy, CK_NoOp, RVK);
      RTy = RHS.get()->getType();
    }
  }

  // C++11 [expr.cond]p4
  //   If the second and third operands are glvalues of the same value
  //   category and have the same type, the result is of that type and
  //   value category and it is a bit-field if the second or the third
  //   operand is a bit-field, or if both are bit-fields.
  // We only extend this to bitfields, not to the crazy other kinds of
  // l-values.
  bool Same = Context.hasSameType(LTy, RTy);
  if (Same && LVK == RVK && LVK != VK_RValue &&
      LHS.get()->isOrdinaryOrBitFieldObject() &&
      RHS.get()->isOrdinaryOrBitFieldObject()) {
    VK = LHS.get()->getValueKind();
    if (LHS.get()->getObjectKind() == OK_BitField ||
        RHS.get()->getObjectKind() == OK_BitField)
      OK = OK_BitField;
    return LTy;
  }

  // C++11 [expr.cond]p5
  //   Otherwise, the result is a prvalue. If the second and third operands
  //   do not have the same type, and either has (cv) class type, ...
  if (!Same && (LTy->isRecordType() || RTy->isRecordType())) {
    //   ... overload resolution is used to determine the conversions (if any)
    //   to be applied to the operands. If the overload resolution fails, the
    //   program is ill-formed.
    if (FindConditionalOverload(*this, LHS, RHS, QuestionLoc))
      return QualType();
  }

  // C++11 [expr.cond]p6
  //   Lvalue-to-rvalue, array-to-pointer, and function-to-pointer standard
  //   conversions are performed on the second and third operands.
  LHS = DefaultFunctionArrayLvalueConversion(LHS.get());
  RHS = DefaultFunctionArrayLvalueConversion(RHS.get());
  if (LHS.isInvalid() || RHS.isInvalid())
    return QualType();
  LTy = LHS.get()->getType();
  RTy = RHS.get()->getType();

  //   After those conversions, one of the following shall hold:
  //   -- The second and third operands have the same type; the result
  //      is of that type. If the operands have class type, the result
  //      is a prvalue temporary of the result type, which is
  //      copy-initialized from either the second operand or the third
  //      operand depending on the value of the first operand.
  if (Context.getCanonicalType(LTy) == Context.getCanonicalType(RTy)) {
    if (LTy->isRecordType()) {
      // The operands have class type. Make a temporary copy.
      if (RequireNonAbstractType(QuestionLoc, LTy,
                                 diag::err_allocation_of_abstract_type))
        return QualType();
      InitializedEntity Entity = InitializedEntity::InitializeTemporary(LTy);

      ExprResult LHSCopy = PerformCopyInitialization(Entity,
                                                     SourceLocation(),
                                                     LHS);
      if (LHSCopy.isInvalid())
        return QualType();

      ExprResult RHSCopy = PerformCopyInitialization(Entity,
                                                     SourceLocation(),
                                                     RHS);
      if (RHSCopy.isInvalid())
        return QualType();

      LHS = LHSCopy;
      RHS = RHSCopy;
    }

    return LTy;
  }

  // Extension: conditional operator involving vector types.
  if (LTy->isVectorType() || RTy->isVectorType())
    return CheckVectorOperands(LHS, RHS, QuestionLoc, /*isCompAssign*/false);

  //   -- The second and third operands have arithmetic or enumeration type;
  //      the usual arithmetic conversions are performed to bring them to a
  //      common type, and the result is of that type.
  if (LTy->isArithmeticType() && RTy->isArithmeticType()) {
    QualType ResTy = UsualArithmeticConversions(LHS, RHS);
    if (LHS.isInvalid() || RHS.isInvalid())
      return QualType();

    LHS = ImpCastExprToType(LHS.get(), ResTy, PrepareScalarCast(LHS, ResTy));
    RHS = ImpCastExprToType(RHS.get(), ResTy, PrepareScalarCast(RHS, ResTy));

    return ResTy;
  }

  //   -- The second and third operands have pointer type, or one has pointer
  //      type and the other is a null pointer constant, or both are null
  //      pointer constants, at least one of which is non-integral; pointer
  //      conversions and qualification conversions are performed to bring them
  //      to their composite pointer type. The result is of the composite
  //      pointer type.
  //   -- The second and third operands have pointer to member type, or one has
  //      pointer to member type and the other is a null pointer constant;
  //      pointer to member conversions and qualification conversions are
  //      performed to bring them to a common type, whose cv-qualification
  //      shall match the cv-qualification of either the second or the third
  //      operand. The result is of the common type.
  bool NonStandardCompositeType = false;
  QualType Composite = FindCompositePointerType(QuestionLoc, LHS, RHS,
                                 isSFINAEContext() ? nullptr
                                                   : &NonStandardCompositeType);
  if (!Composite.isNull()) {
    if (NonStandardCompositeType)
      Diag(QuestionLoc,
           diag::ext_typecheck_cond_incompatible_operands_nonstandard)
        << LTy << RTy << Composite
        << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();

    return Composite;
  }

  // Similarly, attempt to find composite type of two objective-c pointers.
  Composite = FindCompositeObjCPointerType(LHS, RHS, QuestionLoc);
  if (!Composite.isNull())
    return Composite;

  // Check if we are using a null with a non-pointer type.
  if (DiagnoseConditionalForNull(LHS.get(), RHS.get(), QuestionLoc))
    return QualType();

  Diag(QuestionLoc, diag::err_typecheck_cond_incompatible_operands)
    << LHS.get()->getType() << RHS.get()->getType()
    << LHS.get()->getSourceRange() << RHS.get()->getSourceRange();
  return QualType();
}

/// \brief Find a merged pointer type and convert the two expressions to it.
///
/// This finds the composite pointer type (or member pointer type) for @p E1
/// and @p E2 according to C++11 5.9p2. It converts both expressions to this
/// type and returns it.
/// It does not emit diagnostics.
///
/// \param Loc The location of the operator requiring these two expressions to
/// be converted to the composite pointer type.
///
/// If \p NonStandardCompositeType is non-NULL, then we are permitted to find
/// a non-standard (but still sane) composite type to which both expressions
/// can be converted. When such a type is chosen, \c *NonStandardCompositeType
/// will be set true.
QualType Sema::FindCompositePointerType(SourceLocation Loc,
                                        Expr *&E1, Expr *&E2,
                                        bool *NonStandardCompositeType) {
  if (NonStandardCompositeType)
    *NonStandardCompositeType = false;

  assert(getLangOpts().CPlusPlus && "This function assumes C++");
  QualType T1 = E1->getType(), T2 = E2->getType();

  // C++11 5.9p2
  //   Pointer conversions and qualification conversions are performed on
  //   pointer operands to bring them to their composite pointer type. If
  //   one operand is a null pointer constant, the composite pointer type is
  //   std::nullptr_t if the other operand is also a null pointer constant or,
  //   if the other operand is a pointer, the type of the other operand.
  if (!T1->isAnyPointerType() && !T1->isMemberPointerType() &&
      !T2->isAnyPointerType() && !T2->isMemberPointerType()) {
    if (T1->isNullPtrType() &&
        E2->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull)) {
      E2 = ImpCastExprToType(E2, T1, CK_NullToPointer).get();
      return T1;
    }
    if (T2->isNullPtrType() &&
        E1->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull)) {
      E1 = ImpCastExprToType(E1, T2, CK_NullToPointer).get();
      return T2;
    }
    return QualType();
  }

  if (E1->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull)) {
    if (T2->isMemberPointerType())
      E1 = ImpCastExprToType(E1, T2, CK_NullToMemberPointer).get();
    else
      E1 = ImpCastExprToType(E1, T2, CK_NullToPointer).get();
    return T2;
  }
  if (E2->isNullPointerConstant(Context, Expr::NPC_ValueDependentIsNull)) {
    if (T1->isMemberPointerType())
      E2 = ImpCastExprToType(E2, T1, CK_NullToMemberPointer).get();
    else
      E2 = ImpCastExprToType(E2, T1, CK_NullToPointer).get();
    return T1;
  }

  // Now both have to be pointers or member pointers.
  if ((!T1->isPointerType() && !T1->isMemberPointerType()) ||
      (!T2->isPointerType() && !T2->isMemberPointerType()))
    return QualType();

  //   Otherwise, of one of the operands has type "pointer to cv1 void," then
  //   the other has type "pointer to cv2 T" and the composite pointer type is
  //   "pointer to cv12 void," where cv12 is the union of cv1 and cv2.
  //   Otherwise, the composite pointer type is a pointer type similar to the
  //   type of one of the operands, with a cv-qualification signature that is
  //   the union of the cv-qualification signatures of the operand types.
  // In practice, the first part here is redundant; it's subsumed by the second.
  // What we do here is, we build the two possible composite types, and try the
  // conversions in both directions. If only one works, or if the two composite
  // types are the same, we have succeeded.
  // FIXME: extended qualifiers?
  typedef SmallVector<unsigned, 4> QualifierVector;
  QualifierVector QualifierUnion;
  typedef SmallVector<std::pair<const Type *, const Type *>, 4>
      ContainingClassVector;
  ContainingClassVector MemberOfClass;
  QualType Composite1 = Context.getCanonicalType(T1),
           Composite2 = Context.getCanonicalType(T2);
  unsigned NeedConstBefore = 0;
  do {
    const PointerType *Ptr1, *Ptr2;
    if ((Ptr1 = Composite1->getAs<PointerType>()) &&
        (Ptr2 = Composite2->getAs<PointerType>())) {
      Composite1 = Ptr1->getPointeeType();
      Composite2 = Ptr2->getPointeeType();

      // If we're allowed to create a non-standard composite type, keep track
      // of where we need to fill in additional 'const' qualifiers.
      if (NonStandardCompositeType &&
          Composite1.getCVRQualifiers() != Composite2.getCVRQualifiers())
        NeedConstBefore = QualifierUnion.size();

      QualifierUnion.push_back(
                 Composite1.getCVRQualifiers() | Composite2.getCVRQualifiers());
      MemberOfClass.push_back(std::make_pair(nullptr, nullptr));
      continue;
    }

    const MemberPointerType *MemPtr1, *MemPtr2;
    if ((MemPtr1 = Composite1->getAs<MemberPointerType>()) &&
        (MemPtr2 = Composite2->getAs<MemberPointerType>())) {
      Composite1 = MemPtr1->getPointeeType();
      Composite2 = MemPtr2->getPointeeType();

      // If we're allowed to create a non-standard composite type, keep track
      // of where we need to fill in additional 'const' qualifiers.
      if (NonStandardCompositeType &&
          Composite1.getCVRQualifiers() != Composite2.getCVRQualifiers())
        NeedConstBefore = QualifierUnion.size();

      QualifierUnion.push_back(
                 Composite1.getCVRQualifiers() | Composite2.getCVRQualifiers());
      MemberOfClass.push_back(std::make_pair(MemPtr1->getClass(),
                                             MemPtr2->getClass()));
      continue;
    }

    // FIXME: block pointer types?

    // Cannot unwrap any more types.
    break;
  } while (true);

  if (NeedConstBefore && NonStandardCompositeType) {
    // Extension: Add 'const' to qualifiers that come before the first qualifier
    // mismatch, so that our (non-standard!) composite type meets the
    // requirements of C++ [conv.qual]p4 bullet 3.
    for (unsigned I = 0; I != NeedConstBefore; ++I) {
      if ((QualifierUnion[I] & Qualifiers::Const) == 0) {
        QualifierUnion[I] = QualifierUnion[I] | Qualifiers::Const;
        *NonStandardCompositeType = true;
      }
    }
  }

  // Rewrap the composites as pointers or member pointers with the union CVRs.
  ContainingClassVector::reverse_iterator MOC
    = MemberOfClass.rbegin();
  for (QualifierVector::reverse_iterator
         I = QualifierUnion.rbegin(),
         E = QualifierUnion.rend();
       I != E; (void)++I, ++MOC) {
    Qualifiers Quals = Qualifiers::fromCVRMask(*I);
    if (MOC->first && MOC->second) {
      // Rebuild member pointer type
      Composite1 = Context.getMemberPointerType(
                                    Context.getQualifiedType(Composite1, Quals),
                                    MOC->first);
      Composite2 = Context.getMemberPointerType(
                                    Context.getQualifiedType(Composite2, Quals),
                                    MOC->second);
    } else {
      // Rebuild pointer type
      Composite1
        = Context.getPointerType(Context.getQualifiedType(Composite1, Quals));
      Composite2
        = Context.getPointerType(Context.getQualifiedType(Composite2, Quals));
    }
  }

  // Try to convert to the first composite pointer type.
  InitializedEntity Entity1
    = InitializedEntity::InitializeTemporary(Composite1);
  InitializationKind Kind
    = InitializationKind::CreateCopy(Loc, SourceLocation());
  InitializationSequence E1ToC1(*this, Entity1, Kind, E1);
  InitializationSequence E2ToC1(*this, Entity1, Kind, E2);

  if (E1ToC1 && E2ToC1) {
    // Conversion to Composite1 is viable.
    if (!Context.hasSameType(Composite1, Composite2)) {
      // Composite2 is a different type from Composite1. Check whether
      // Composite2 is also viable.
      InitializedEntity Entity2
        = InitializedEntity::InitializeTemporary(Composite2);
      InitializationSequence E1ToC2(*this, Entity2, Kind, E1);
      InitializationSequence E2ToC2(*this, Entity2, Kind, E2);
      if (E1ToC2 && E2ToC2) {
        // Both Composite1 and Composite2 are viable and are different;
        // this is an ambiguity.
        return QualType();
      }
    }

    // Convert E1 to Composite1
    ExprResult E1Result
      = E1ToC1.Perform(*this, Entity1, Kind, E1);
    if (E1Result.isInvalid())
      return QualType();
    E1 = E1Result.getAs<Expr>();

    // Convert E2 to Composite1
    ExprResult E2Result
      = E2ToC1.Perform(*this, Entity1, Kind, E2);
    if (E2Result.isInvalid())
      return QualType();
    E2 = E2Result.getAs<Expr>();

    return Composite1;
  }

  // Check whether Composite2 is viable.
  InitializedEntity Entity2
    = InitializedEntity::InitializeTemporary(Composite2);
  InitializationSequence E1ToC2(*this, Entity2, Kind, E1);
  InitializationSequence E2ToC2(*this, Entity2, Kind, E2);
  if (!E1ToC2 || !E2ToC2)
    return QualType();

  // Convert E1 to Composite2
  ExprResult E1Result
    = E1ToC2.Perform(*this, Entity2, Kind, E1);
  if (E1Result.isInvalid())
    return QualType();
  E1 = E1Result.getAs<Expr>();

  // Convert E2 to Composite2
  ExprResult E2Result
    = E2ToC2.Perform(*this, Entity2, Kind, E2);
  if (E2Result.isInvalid())
    return QualType();
  E2 = E2Result.getAs<Expr>();

  return Composite2;
}

ExprResult Sema::MaybeBindToTemporary(Expr *E) {
  if (!E)
    return ExprError();

  assert(!isa<CXXBindTemporaryExpr>(E) && "Double-bound temporary?");

  // If the result is a glvalue, we shouldn't bind it.
  if (!E->isRValue())
    return E;

  // In ARC, calls that return a retainable type can return retained,
  // in which case we have to insert a consuming cast.
  if (getLangOpts().ObjCAutoRefCount &&
      E->getType()->isObjCRetainableType()) {

    bool ReturnsRetained;

    // For actual calls, we compute this by examining the type of the
    // called value.
    if (CallExpr *Call = dyn_cast<CallExpr>(E)) {
      Expr *Callee = Call->getCallee()->IgnoreParens();
      QualType T = Callee->getType();

      if (T == Context.BoundMemberTy) {
        // Handle pointer-to-members.
        if (BinaryOperator *BinOp = dyn_cast<BinaryOperator>(Callee))
          T = BinOp->getRHS()->getType();
        else if (MemberExpr *Mem = dyn_cast<MemberExpr>(Callee))
          T = Mem->getMemberDecl()->getType();
      }
      
      if (const PointerType *Ptr = T->getAs<PointerType>())
        T = Ptr->getPointeeType();
      else if (const BlockPointerType *Ptr = T->getAs<BlockPointerType>())
        T = Ptr->getPointeeType();
      else if (const MemberPointerType *MemPtr = T->getAs<MemberPointerType>())
        T = MemPtr->getPointeeType();
      
      const FunctionType *FTy = T->getAs<FunctionType>();
      assert(FTy && "call to value not of function type?");
      ReturnsRetained = FTy->getExtInfo().getProducesResult();

    // ActOnStmtExpr arranges things so that StmtExprs of retainable
    // type always produce a +1 object.
    } else if (isa<StmtExpr>(E)) {
      ReturnsRetained = true;

    // We hit this case with the lambda conversion-to-block optimization;
    // we don't want any extra casts here.
    } else if (isa<CastExpr>(E) &&
               isa<BlockExpr>(cast<CastExpr>(E)->getSubExpr())) {
      return E;

    // For message sends and property references, we try to find an
    // actual method.  FIXME: we should infer retention by selector in
    // cases where we don't have an actual method.
    } else {
      ObjCMethodDecl *D = nullptr;
      if (ObjCMessageExpr *Send = dyn_cast<ObjCMessageExpr>(E)) {
        D = Send->getMethodDecl();
      } else if (ObjCBoxedExpr *BoxedExpr = dyn_cast<ObjCBoxedExpr>(E)) {
        D = BoxedExpr->getBoxingMethod();
      } else if (ObjCArrayLiteral *ArrayLit = dyn_cast<ObjCArrayLiteral>(E)) {
        D = ArrayLit->getArrayWithObjectsMethod();
      } else if (ObjCDictionaryLiteral *DictLit
                                        = dyn_cast<ObjCDictionaryLiteral>(E)) {
        D = DictLit->getDictWithObjectsMethod();
      }

      ReturnsRetained = (D && D->hasAttr<NSReturnsRetainedAttr>());

      // Don't do reclaims on performSelector calls; despite their
      // return type, the invoked method doesn't necessarily actually
      // return an object.
      if (!ReturnsRetained &&
          D && D->getMethodFamily() == OMF_performSelector)
        return E;
    }

    // Don't reclaim an object of Class type.
    if (!ReturnsRetained && E->getType()->isObjCARCImplicitlyUnretainedType())
      return E;

    ExprNeedsCleanups = true;

    CastKind ck = (ReturnsRetained ? CK_ARCConsumeObject
                                   : CK_ARCReclaimReturnedObject);
    return ImplicitCastExpr::Create(Context, E->getType(), ck, E, nullptr,
                                    VK_RValue);
  }

  if (!getLangOpts().CPlusPlus)
    return E;

  // Search for the base element type (cf. ASTContext::getBaseElementType) with
  // a fast path for the common case that the type is directly a RecordType.
  const Type *T = Context.getCanonicalType(E->getType().getTypePtr());
  const RecordType *RT = nullptr;
  while (!RT) {
    switch (T->getTypeClass()) {
    case Type::Record:
      RT = cast<RecordType>(T);
      break;
    case Type::ConstantArray:
    case Type::IncompleteArray:
    case Type::VariableArray:
    case Type::DependentSizedArray:
      T = cast<ArrayType>(T)->getElementType().getTypePtr();
      break;
    default:
      return E;
    }
  }

  // That should be enough to guarantee that this type is complete, if we're
  // not processing a decltype expression.
  CXXRecordDecl *RD = cast<CXXRecordDecl>(RT->getDecl());
  if (RD->isInvalidDecl() || RD->isDependentContext())
    return E;

  bool IsDecltype = ExprEvalContexts.back().IsDecltype;
  CXXDestructorDecl *Destructor = IsDecltype ? nullptr : LookupDestructor(RD);

  if (Destructor) {
    MarkFunctionReferenced(E->getExprLoc(), Destructor);
    CheckDestructorAccess(E->getExprLoc(), Destructor,
                          PDiag(diag::err_access_dtor_temp)
                            << E->getType());
    if (DiagnoseUseOfDecl(Destructor, E->getExprLoc()))
      return ExprError();

    // If destructor is trivial, we can avoid the extra copy.
    if (Destructor->isTrivial())
      return E;

    // We need a cleanup, but we don't need to remember the temporary.
    ExprNeedsCleanups = true;
  }

  CXXTemporary *Temp = CXXTemporary::Create(Context, Destructor);
  CXXBindTemporaryExpr *Bind = CXXBindTemporaryExpr::Create(Context, Temp, E);

  if (IsDecltype)
    ExprEvalContexts.back().DelayedDecltypeBinds.push_back(Bind);

  return Bind;
}

ExprResult
Sema::MaybeCreateExprWithCleanups(ExprResult SubExpr) {
  if (SubExpr.isInvalid())
    return ExprError();

  return MaybeCreateExprWithCleanups(SubExpr.get());
}

Expr *Sema::MaybeCreateExprWithCleanups(Expr *SubExpr) {
  assert(SubExpr && "subexpression can't be null!");

  CleanupVarDeclMarking();

  unsigned FirstCleanup = ExprEvalContexts.back().NumCleanupObjects;
  assert(ExprCleanupObjects.size() >= FirstCleanup);
  assert(ExprNeedsCleanups || ExprCleanupObjects.size() == FirstCleanup);
  if (!ExprNeedsCleanups)
    return SubExpr;

  auto Cleanups = llvm::makeArrayRef(ExprCleanupObjects.begin() + FirstCleanup,
                                     ExprCleanupObjects.size() - FirstCleanup);

  Expr *E = ExprWithCleanups::Create(Context, SubExpr, Cleanups);
  DiscardCleanupsInEvaluationContext();

  return E;
}

Stmt *Sema::MaybeCreateStmtWithCleanups(Stmt *SubStmt) {
  assert(SubStmt && "sub-statement can't be null!");

  CleanupVarDeclMarking();

  if (!ExprNeedsCleanups)
    return SubStmt;

  // FIXME: In order to attach the temporaries, wrap the statement into
  // a StmtExpr; currently this is only used for asm statements.
  // This is hacky, either create a new CXXStmtWithTemporaries statement or
  // a new AsmStmtWithTemporaries.
  CompoundStmt *CompStmt = new (Context) CompoundStmt(Context, SubStmt,
                                                      SourceLocation(),
                                                      SourceLocation());
  Expr *E = new (Context) StmtExpr(CompStmt, Context.VoidTy, SourceLocation(),
                                   SourceLocation());
  return MaybeCreateExprWithCleanups(E);
}

/// Process the expression contained within a decltype. For such expressions,
/// certain semantic checks on temporaries are delayed until this point, and
/// are omitted for the 'topmost' call in the decltype expression. If the
/// topmost call bound a temporary, strip that temporary off the expression.
ExprResult Sema::ActOnDecltypeExpression(Expr *E) {
  assert(ExprEvalContexts.back().IsDecltype && "not in a decltype expression");

  // C++11 [expr.call]p11:
  //   If a function call is a prvalue of object type,
  // -- if the function call is either
  //   -- the operand of a decltype-specifier, or
  //   -- the right operand of a comma operator that is the operand of a
  //      decltype-specifier,
  //   a temporary object is not introduced for the prvalue.

  // Recursively rebuild ParenExprs and comma expressions to strip out the
  // outermost CXXBindTemporaryExpr, if any.
  if (ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
    ExprResult SubExpr = ActOnDecltypeExpression(PE->getSubExpr());
    if (SubExpr.isInvalid())
      return ExprError();
    if (SubExpr.get() == PE->getSubExpr())
      return E;
    return ActOnParenExpr(PE->getLParen(), PE->getRParen(), SubExpr.get());
  }
  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
    if (BO->getOpcode() == BO_Comma) {
      ExprResult RHS = ActOnDecltypeExpression(BO->getRHS());
      if (RHS.isInvalid())
        return ExprError();
      if (RHS.get() == BO->getRHS())
        return E;
      return new (Context) BinaryOperator(
          BO->getLHS(), RHS.get(), BO_Comma, BO->getType(), BO->getValueKind(),
          BO->getObjectKind(), BO->getOperatorLoc(), BO->isFPContractable());
    }
  }

  CXXBindTemporaryExpr *TopBind = dyn_cast<CXXBindTemporaryExpr>(E);
  CallExpr *TopCall = TopBind ? dyn_cast<CallExpr>(TopBind->getSubExpr())
                              : nullptr;
  if (TopCall)
    E = TopCall;
  else
    TopBind = nullptr;

  // Disable the special decltype handling now.
  ExprEvalContexts.back().IsDecltype = false;

  // In MS mode, don't perform any extra checking of call return types within a
  // decltype expression.
  if (getLangOpts().MSVCCompat)
    return E;

  // Perform the semantic checks we delayed until this point.
  for (unsigned I = 0, N = ExprEvalContexts.back().DelayedDecltypeCalls.size();
       I != N; ++I) {
    CallExpr *Call = ExprEvalContexts.back().DelayedDecltypeCalls[I];
    if (Call == TopCall)
      continue;

    if (CheckCallReturnType(Call->getCallReturnType(Context),
                            Call->getLocStart(),
                            Call, Call->getDirectCallee()))
      return ExprError();
  }

  // Now all relevant types are complete, check the destructors are accessible
  // and non-deleted, and annotate them on the temporaries.
  for (unsigned I = 0, N = ExprEvalContexts.back().DelayedDecltypeBinds.size();
       I != N; ++I) {
    CXXBindTemporaryExpr *Bind =
      ExprEvalContexts.back().DelayedDecltypeBinds[I];
    if (Bind == TopBind)
      continue;

    CXXTemporary *Temp = Bind->getTemporary();

    CXXRecordDecl *RD =
      Bind->getType()->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
    CXXDestructorDecl *Destructor = LookupDestructor(RD);
    Temp->setDestructor(Destructor);

    MarkFunctionReferenced(Bind->getExprLoc(), Destructor);
    CheckDestructorAccess(Bind->getExprLoc(), Destructor,
                          PDiag(diag::err_access_dtor_temp)
                            << Bind->getType());
    if (DiagnoseUseOfDecl(Destructor, Bind->getExprLoc()))
      return ExprError();

    // We need a cleanup, but we don't need to remember the temporary.
    ExprNeedsCleanups = true;
  }

  // Possibly strip off the top CXXBindTemporaryExpr.
  return E;
}

/// Note a set of 'operator->' functions that were used for a member access.
static void noteOperatorArrows(Sema &S,
                               ArrayRef<FunctionDecl *> OperatorArrows) {
  unsigned SkipStart = OperatorArrows.size(), SkipCount = 0;
  // FIXME: Make this configurable?
  unsigned Limit = 9;
  if (OperatorArrows.size() > Limit) {
    // Produce Limit-1 normal notes and one 'skipping' note.
    SkipStart = (Limit - 1) / 2 + (Limit - 1) % 2;
    SkipCount = OperatorArrows.size() - (Limit - 1);
  }

  for (unsigned I = 0; I < OperatorArrows.size(); /**/) {
    if (I == SkipStart) {
      S.Diag(OperatorArrows[I]->getLocation(),
             diag::note_operator_arrows_suppressed)
          << SkipCount;
      I += SkipCount;
    } else {
      S.Diag(OperatorArrows[I]->getLocation(), diag::note_operator_arrow_here)
          << OperatorArrows[I]->getCallResultType();
      ++I;
    }
  }
}

ExprResult Sema::ActOnStartCXXMemberReference(Scope *S, Expr *Base,
                                              SourceLocation OpLoc,
                                              tok::TokenKind OpKind,
                                              ParsedType &ObjectType,
                                              bool &MayBePseudoDestructor) {
  // Since this might be a postfix expression, get rid of ParenListExprs.
  ExprResult Result = MaybeConvertParenListExprToParenExpr(S, Base);
  if (Result.isInvalid()) return ExprError();
  Base = Result.get();

  Result = CheckPlaceholderExpr(Base);
  if (Result.isInvalid()) return ExprError();
  Base = Result.get();

  QualType BaseType = Base->getType();
  MayBePseudoDestructor = false;
  if (BaseType->isDependentType()) {
    // If we have a pointer to a dependent type and are using the -> operator,
    // the object type is the type that the pointer points to. We might still
    // have enough information about that type to do something useful.
    if (OpKind == tok::arrow)
      if (const PointerType *Ptr = BaseType->getAs<PointerType>())
        BaseType = Ptr->getPointeeType();

    ObjectType = ParsedType::make(BaseType);
    MayBePseudoDestructor = true;
    return Base;
  }

  // C++ [over.match.oper]p8:
  //   [...] When operator->returns, the operator-> is applied  to the value
  //   returned, with the original second operand.
  if (OpKind == tok::arrow) {
    QualType StartingType = BaseType;
    bool NoArrowOperatorFound = false;
    bool FirstIteration = true;
    FunctionDecl *CurFD = dyn_cast<FunctionDecl>(CurContext);
    // The set of types we've considered so far.
    llvm::SmallPtrSet<CanQualType,8> CTypes;
    SmallVector<FunctionDecl*, 8> OperatorArrows;
    CTypes.insert(Context.getCanonicalType(BaseType));

    while (BaseType->isRecordType()) {
      if (OperatorArrows.size() >= getLangOpts().ArrowDepth) {
        Diag(OpLoc, diag::err_operator_arrow_depth_exceeded)
          << StartingType << getLangOpts().ArrowDepth << Base->getSourceRange();
        noteOperatorArrows(*this, OperatorArrows);
        Diag(OpLoc, diag::note_operator_arrow_depth)
          << getLangOpts().ArrowDepth;
        return ExprError();
      }

      Result = BuildOverloadedArrowExpr(
          S, Base, OpLoc,
          // When in a template specialization and on the first loop iteration,
          // potentially give the default diagnostic (with the fixit in a
          // separate note) instead of having the error reported back to here
          // and giving a diagnostic with a fixit attached to the error itself.
          (FirstIteration && CurFD && CurFD->isFunctionTemplateSpecialization())
              ? nullptr
              : &NoArrowOperatorFound);
      if (Result.isInvalid()) {
        if (NoArrowOperatorFound) {
          if (FirstIteration) {
            Diag(OpLoc, diag::err_typecheck_member_reference_suggestion)
              << BaseType << 1 << Base->getSourceRange()
              << FixItHint::CreateReplacement(OpLoc, ".");
            OpKind = tok::period;
            break;
          }
          Diag(OpLoc, diag::err_typecheck_member_reference_arrow)
            << BaseType << Base->getSourceRange();
          CallExpr *CE = dyn_cast<CallExpr>(Base);
          if (Decl *CD = (CE ? CE->getCalleeDecl() : nullptr)) {
            Diag(CD->getLocStart(),
                 diag::note_member_reference_arrow_from_operator_arrow);
          }
        }
        return ExprError();
      }
      Base = Result.get();
      if (CXXOperatorCallExpr *OpCall = dyn_cast<CXXOperatorCallExpr>(Base))
        OperatorArrows.push_back(OpCall->getDirectCallee());
      BaseType = Base->getType();
      CanQualType CBaseType = Context.getCanonicalType(BaseType);
      if (!CTypes.insert(CBaseType).second) {
        Diag(OpLoc, diag::err_operator_arrow_circular) << StartingType;
        noteOperatorArrows(*this, OperatorArrows);
        return ExprError();
      }
      FirstIteration = false;
    }

    if (OpKind == tok::arrow &&
        (BaseType->isPointerType() || BaseType->isObjCObjectPointerType()))
      BaseType = BaseType->getPointeeType();
  }

  // Objective-C properties allow "." access on Objective-C pointer types,
  // so adjust the base type to the object type itself.
  if (BaseType->isObjCObjectPointerType())
    BaseType = BaseType->getPointeeType();
  
  // C++ [basic.lookup.classref]p2:
  //   [...] If the type of the object expression is of pointer to scalar
  //   type, the unqualified-id is looked up in the context of the complete
  //   postfix-expression.
  //
  // This also indicates that we could be parsing a pseudo-destructor-name.
  // Note that Objective-C class and object types can be pseudo-destructor
  // expressions or normal member (ivar or property) access expressions.
  if (BaseType->isObjCObjectOrInterfaceType()) {
    MayBePseudoDestructor = true;
  } else if (!BaseType->isRecordType()) {
    ObjectType = ParsedType();
    MayBePseudoDestructor = true;
    return Base;
  }

  // The object type must be complete (or dependent), or
  // C++11 [expr.prim.general]p3:
  //   Unlike the object expression in other contexts, *this is not required to
  //   be of complete type for purposes of class member access (5.2.5) outside 
  //   the member function body.
  if (!BaseType->isDependentType() &&
      !isThisOutsideMemberFunctionBody(BaseType) &&
      RequireCompleteType(OpLoc, BaseType, diag::err_incomplete_member_access))
    return ExprError();

  // C++ [basic.lookup.classref]p2:
  //   If the id-expression in a class member access (5.2.5) is an
  //   unqualified-id, and the type of the object expression is of a class
  //   type C (or of pointer to a class type C), the unqualified-id is looked
  //   up in the scope of class C. [...]
  ObjectType = ParsedType::make(BaseType);
  return Base;
}

static bool CheckArrow(Sema& S, QualType& ObjectType, Expr *&Base, 
                   tok::TokenKind& OpKind, SourceLocation OpLoc) {
  if (Base->hasPlaceholderType()) {
    ExprResult result = S.CheckPlaceholderExpr(Base);
    if (result.isInvalid()) return true;
    Base = result.get();
  }
  ObjectType = Base->getType();

  // C++ [expr.pseudo]p2:
  //   The left-hand side of the dot operator shall be of scalar type. The
  //   left-hand side of the arrow operator shall be of pointer to scalar type.
  //   This scalar type is the object type.
  // Note that this is rather different from the normal handling for the
  // arrow operator.
  if (OpKind == tok::arrow) {
    if (const PointerType *Ptr = ObjectType->getAs<PointerType>()) {
      ObjectType = Ptr->getPointeeType();
    } else if (!Base->isTypeDependent()) {
      // The user wrote "p->" when she probably meant "p."; fix it.
      S.Diag(OpLoc, diag::err_typecheck_member_reference_suggestion)
        << ObjectType << true
        << FixItHint::CreateReplacement(OpLoc, ".");
      if (S.isSFINAEContext())
        return true;

      OpKind = tok::period;
    }
  }

  return false;
}

ExprResult Sema::BuildPseudoDestructorExpr(Expr *Base,
                                           SourceLocation OpLoc,
                                           tok::TokenKind OpKind,
                                           const CXXScopeSpec &SS,
                                           TypeSourceInfo *ScopeTypeInfo,
                                           SourceLocation CCLoc,
                                           SourceLocation TildeLoc,
                                         PseudoDestructorTypeStorage Destructed) {
  TypeSourceInfo *DestructedTypeInfo = Destructed.getTypeSourceInfo();

  QualType ObjectType;
  if (CheckArrow(*this, ObjectType, Base, OpKind, OpLoc))
    return ExprError();

  if (!ObjectType->isDependentType() && !ObjectType->isScalarType() &&
      !ObjectType->isVectorType()) {
    if (getLangOpts().MSVCCompat && ObjectType->isVoidType())
      Diag(OpLoc, diag::ext_pseudo_dtor_on_void) << Base->getSourceRange();
    else {
      Diag(OpLoc, diag::err_pseudo_dtor_base_not_scalar)
        << ObjectType << Base->getSourceRange();
      return ExprError();
    }
  }

  // C++ [expr.pseudo]p2:
  //   [...] The cv-unqualified versions of the object type and of the type
  //   designated by the pseudo-destructor-name shall be the same type.
  if (DestructedTypeInfo) {
    QualType DestructedType = DestructedTypeInfo->getType();
    SourceLocation DestructedTypeStart
      = DestructedTypeInfo->getTypeLoc().getLocalSourceRange().getBegin();
    if (!DestructedType->isDependentType() && !ObjectType->isDependentType()) {
      if (!Context.hasSameUnqualifiedType(DestructedType, ObjectType)) {
        Diag(DestructedTypeStart, diag::err_pseudo_dtor_type_mismatch)
          << ObjectType << DestructedType << Base->getSourceRange()
          << DestructedTypeInfo->getTypeLoc().getLocalSourceRange();

        // Recover by setting the destructed type to the object type.
        DestructedType = ObjectType;
        DestructedTypeInfo = Context.getTrivialTypeSourceInfo(ObjectType,
                                                           DestructedTypeStart);
        Destructed = PseudoDestructorTypeStorage(DestructedTypeInfo);
      } else if (DestructedType.getObjCLifetime() != 
                                                ObjectType.getObjCLifetime()) {
        
        if (DestructedType.getObjCLifetime() == Qualifiers::OCL_None) {
          // Okay: just pretend that the user provided the correctly-qualified
          // type.
        } else {
          Diag(DestructedTypeStart, diag::err_arc_pseudo_dtor_inconstant_quals)
            << ObjectType << DestructedType << Base->getSourceRange()
            << DestructedTypeInfo->getTypeLoc().getLocalSourceRange();
        }
        
        // Recover by setting the destructed type to the object type.
        DestructedType = ObjectType;
        DestructedTypeInfo = Context.getTrivialTypeSourceInfo(ObjectType,
                                                           DestructedTypeStart);
        Destructed = PseudoDestructorTypeStorage(DestructedTypeInfo);
      }
    }
  }

  // C++ [expr.pseudo]p2:
  //   [...] Furthermore, the two type-names in a pseudo-destructor-name of the
  //   form
  //
  //     ::[opt] nested-name-specifier[opt] type-name :: ~ type-name
  //
  //   shall designate the same scalar type.
  if (ScopeTypeInfo) {
    QualType ScopeType = ScopeTypeInfo->getType();
    if (!ScopeType->isDependentType() && !ObjectType->isDependentType() &&
        !Context.hasSameUnqualifiedType(ScopeType, ObjectType)) {

      Diag(ScopeTypeInfo->getTypeLoc().getLocalSourceRange().getBegin(),
           diag::err_pseudo_dtor_type_mismatch)
        << ObjectType << ScopeType << Base->getSourceRange()
        << ScopeTypeInfo->getTypeLoc().getLocalSourceRange();

      ScopeType = QualType();
      ScopeTypeInfo = nullptr;
    }
  }

  Expr *Result
    = new (Context) CXXPseudoDestructorExpr(Context, Base,
                                            OpKind == tok::arrow, OpLoc,
                                            SS.getWithLocInContext(Context),
                                            ScopeTypeInfo,
                                            CCLoc,
                                            TildeLoc,
                                            Destructed);

  return Result;
}

ExprResult Sema::ActOnPseudoDestructorExpr(Scope *S, Expr *Base,
                                           SourceLocation OpLoc,
                                           tok::TokenKind OpKind,
                                           CXXScopeSpec &SS,
                                           UnqualifiedId &FirstTypeName,
                                           SourceLocation CCLoc,
                                           SourceLocation TildeLoc,
                                           UnqualifiedId &SecondTypeName) {
  assert((FirstTypeName.getKind() == UnqualifiedId::IK_TemplateId ||
          FirstTypeName.getKind() == UnqualifiedId::IK_Identifier) &&
         "Invalid first type name in pseudo-destructor");
  assert((SecondTypeName.getKind() == UnqualifiedId::IK_TemplateId ||
          SecondTypeName.getKind() == UnqualifiedId::IK_Identifier) &&
         "Invalid second type name in pseudo-destructor");

  QualType ObjectType;
  if (CheckArrow(*this, ObjectType, Base, OpKind, OpLoc))
    return ExprError();

  // Compute the object type that we should use for name lookup purposes. Only
  // record types and dependent types matter.
  ParsedType ObjectTypePtrForLookup;
  if (!SS.isSet()) {
    if (ObjectType->isRecordType())
      ObjectTypePtrForLookup = ParsedType::make(ObjectType);
    else if (ObjectType->isDependentType())
      ObjectTypePtrForLookup = ParsedType::make(Context.DependentTy);
  }

  // Convert the name of the type being destructed (following the ~) into a
  // type (with source-location information).
  QualType DestructedType;
  TypeSourceInfo *DestructedTypeInfo = nullptr;
  PseudoDestructorTypeStorage Destructed;
  if (SecondTypeName.getKind() == UnqualifiedId::IK_Identifier) {
    ParsedType T = getTypeName(*SecondTypeName.Identifier,
                               SecondTypeName.StartLocation,
                               S, &SS, true, false, ObjectTypePtrForLookup);
    if (!T &&
        ((SS.isSet() && !computeDeclContext(SS, false)) ||
         (!SS.isSet() && ObjectType->isDependentType()))) {
      // The name of the type being destroyed is a dependent name, and we
      // couldn't find anything useful in scope. Just store the identifier and
      // it's location, and we'll perform (qualified) name lookup again at
      // template instantiation time.
      Destructed = PseudoDestructorTypeStorage(SecondTypeName.Identifier,
                                               SecondTypeName.StartLocation);
    } else if (!T) {
      Diag(SecondTypeName.StartLocation,
           diag::err_pseudo_dtor_destructor_non_type)
        << SecondTypeName.Identifier << ObjectType;
      if (isSFINAEContext())
        return ExprError();

      // Recover by assuming we had the right type all along.
      DestructedType = ObjectType;
    } else
      DestructedType = GetTypeFromParser(T, &DestructedTypeInfo);
  } else {
    // Resolve the template-id to a type.
    TemplateIdAnnotation *TemplateId = SecondTypeName.TemplateId;
    ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
                                       TemplateId->NumArgs);
    TypeResult T = ActOnTemplateIdType(TemplateId->SS,
                                       TemplateId->TemplateKWLoc,
                                       TemplateId->Template,
                                       TemplateId->TemplateNameLoc,
                                       TemplateId->LAngleLoc,
                                       TemplateArgsPtr,
                                       TemplateId->RAngleLoc);
    if (T.isInvalid() || !T.get()) {
      // Recover by assuming we had the right type all along.
      DestructedType = ObjectType;
    } else
      DestructedType = GetTypeFromParser(T.get(), &DestructedTypeInfo);
  }

  // If we've performed some kind of recovery, (re-)build the type source
  // information.
  if (!DestructedType.isNull()) {
    if (!DestructedTypeInfo)
      DestructedTypeInfo = Context.getTrivialTypeSourceInfo(DestructedType,
                                                  SecondTypeName.StartLocation);
    Destructed = PseudoDestructorTypeStorage(DestructedTypeInfo);
  }

  // Convert the name of the scope type (the type prior to '::') into a type.
  TypeSourceInfo *ScopeTypeInfo = nullptr;
  QualType ScopeType;
  if (FirstTypeName.getKind() == UnqualifiedId::IK_TemplateId ||
      FirstTypeName.Identifier) {
    if (FirstTypeName.getKind() == UnqualifiedId::IK_Identifier) {
      ParsedType T = getTypeName(*FirstTypeName.Identifier,
                                 FirstTypeName.StartLocation,
                                 S, &SS, true, false, ObjectTypePtrForLookup);
      if (!T) {
        Diag(FirstTypeName.StartLocation,
             diag::err_pseudo_dtor_destructor_non_type)
          << FirstTypeName.Identifier << ObjectType;

        if (isSFINAEContext())
          return ExprError();

        // Just drop this type. It's unnecessary anyway.
        ScopeType = QualType();
      } else
        ScopeType = GetTypeFromParser(T, &ScopeTypeInfo);
    } else {
      // Resolve the template-id to a type.
      TemplateIdAnnotation *TemplateId = FirstTypeName.TemplateId;
      ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
                                         TemplateId->NumArgs);
      TypeResult T = ActOnTemplateIdType(TemplateId->SS,
                                         TemplateId->TemplateKWLoc,
                                         TemplateId->Template,
                                         TemplateId->TemplateNameLoc,
                                         TemplateId->LAngleLoc,
                                         TemplateArgsPtr,
                                         TemplateId->RAngleLoc);
      if (T.isInvalid() || !T.get()) {
        // Recover by dropping this type.
        ScopeType = QualType();
      } else
        ScopeType = GetTypeFromParser(T.get(), &ScopeTypeInfo);
    }
  }

  if (!ScopeType.isNull() && !ScopeTypeInfo)
    ScopeTypeInfo = Context.getTrivialTypeSourceInfo(ScopeType,
                                                  FirstTypeName.StartLocation);


  return BuildPseudoDestructorExpr(Base, OpLoc, OpKind, SS,
                                   ScopeTypeInfo, CCLoc, TildeLoc,
                                   Destructed);
}

ExprResult Sema::ActOnPseudoDestructorExpr(Scope *S, Expr *Base,
                                           SourceLocation OpLoc,
                                           tok::TokenKind OpKind,
                                           SourceLocation TildeLoc, 
                                           const DeclSpec& DS) {
  QualType ObjectType;
  if (CheckArrow(*this, ObjectType, Base, OpKind, OpLoc))
    return ExprError();

  QualType T = BuildDecltypeType(DS.getRepAsExpr(), DS.getTypeSpecTypeLoc(),
                                 false);

  TypeLocBuilder TLB;
  DecltypeTypeLoc DecltypeTL = TLB.push<DecltypeTypeLoc>(T);
  DecltypeTL.setNameLoc(DS.getTypeSpecTypeLoc());
  TypeSourceInfo *DestructedTypeInfo = TLB.getTypeSourceInfo(Context, T);
  PseudoDestructorTypeStorage Destructed(DestructedTypeInfo);

  return BuildPseudoDestructorExpr(Base, OpLoc, OpKind, CXXScopeSpec(),
                                   nullptr, SourceLocation(), TildeLoc,
                                   Destructed);
}

ExprResult Sema::BuildCXXMemberCallExpr(Expr *E, NamedDecl *FoundDecl,
                                        CXXConversionDecl *Method,
                                        bool HadMultipleCandidates) {
  if (Method->getParent()->isLambda() &&
      Method->getConversionType()->isBlockPointerType()) {
    // This is a lambda coversion to block pointer; check if the argument
    // is a LambdaExpr.
    Expr *SubE = E;
    CastExpr *CE = dyn_cast<CastExpr>(SubE);
    if (CE && CE->getCastKind() == CK_NoOp)
      SubE = CE->getSubExpr();
    SubE = SubE->IgnoreParens();
    if (CXXBindTemporaryExpr *BE = dyn_cast<CXXBindTemporaryExpr>(SubE))
      SubE = BE->getSubExpr();
    if (isa<LambdaExpr>(SubE)) {
      // For the conversion to block pointer on a lambda expression, we
      // construct a special BlockLiteral instead; this doesn't really make
      // a difference in ARC, but outside of ARC the resulting block literal
      // follows the normal lifetime rules for block literals instead of being
      // autoreleased.
      DiagnosticErrorTrap Trap(Diags);
      ExprResult Exp = BuildBlockForLambdaConversion(E->getExprLoc(),
                                                     E->getExprLoc(),
                                                     Method, E);
      if (Exp.isInvalid())
        Diag(E->getExprLoc(), diag::note_lambda_to_block_conv);
      return Exp;
    }
  }

  ExprResult Exp = PerformObjectArgumentInitialization(E, /*Qualifier=*/nullptr,
                                          FoundDecl, Method);
  if (Exp.isInvalid())
    return true;

  MemberExpr *ME = new (Context) MemberExpr(
      Exp.get(), /*IsArrow=*/false, SourceLocation(), Method, SourceLocation(),
      Context.BoundMemberTy, VK_RValue, OK_Ordinary);
  if (HadMultipleCandidates)
    ME->setHadMultipleCandidates(true);
  MarkMemberReferenced(ME);

  QualType ResultType = Method->getReturnType();
  ExprValueKind VK = Expr::getValueKindForType(ResultType);
  ResultType = ResultType.getNonLValueExprType(Context);

  CXXMemberCallExpr *CE =
    new (Context) CXXMemberCallExpr(Context, ME, None, ResultType, VK,
                                    Exp.get()->getLocEnd());
  return CE;
}

ExprResult Sema::BuildCXXNoexceptExpr(SourceLocation KeyLoc, Expr *Operand,
                                      SourceLocation RParen) {
  // If the operand is an unresolved lookup expression, the expression is ill-
  // formed per [over.over]p1, because overloaded function names cannot be used
  // without arguments except in explicit contexts.
  ExprResult R = CheckPlaceholderExpr(Operand);
  if (R.isInvalid())
    return R;

  // The operand may have been modified when checking the placeholder type.
  Operand = R.get();

  if (ActiveTemplateInstantiations.empty() &&
      Operand->HasSideEffects(Context, false)) {
    // The expression operand for noexcept is in an unevaluated expression
    // context, so side effects could result in unintended consequences.
    Diag(Operand->getExprLoc(), diag::warn_side_effects_unevaluated_context);
  }

  CanThrowResult CanThrow = canThrow(Operand);
  return new (Context)
      CXXNoexceptExpr(Context.BoolTy, Operand, CanThrow, KeyLoc, RParen);
}

ExprResult Sema::ActOnNoexceptExpr(SourceLocation KeyLoc, SourceLocation,
                                   Expr *Operand, SourceLocation RParen) {
  return BuildCXXNoexceptExpr(KeyLoc, Operand, RParen);
}

static bool IsSpecialDiscardedValue(Expr *E) {
  // In C++11, discarded-value expressions of a certain form are special,
  // according to [expr]p10:
  //   The lvalue-to-rvalue conversion (4.1) is applied only if the
  //   expression is an lvalue of volatile-qualified type and it has
  //   one of the following forms:
  E = E->IgnoreParens();

  //   - id-expression (5.1.1),
  if (isa<DeclRefExpr>(E))
    return true;

  //   - subscripting (5.2.1),
  if (isa<ArraySubscriptExpr>(E))
    return true;

  //   - class member access (5.2.5),
  if (isa<MemberExpr>(E))
    return true;

  //   - indirection (5.3.1),
  if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E))
    if (UO->getOpcode() == UO_Deref)
      return true;

  if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
    //   - pointer-to-member operation (5.5),
    if (BO->isPtrMemOp())
      return true;

    //   - comma expression (5.18) where the right operand is one of the above.
    if (BO->getOpcode() == BO_Comma)
      return IsSpecialDiscardedValue(BO->getRHS());
  }

  //   - conditional expression (5.16) where both the second and the third
  //     operands are one of the above, or
  if (ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E))
    return IsSpecialDiscardedValue(CO->getTrueExpr()) &&
           IsSpecialDiscardedValue(CO->getFalseExpr());
  // The related edge case of "*x ?: *x".
  if (BinaryConditionalOperator *BCO =
          dyn_cast<BinaryConditionalOperator>(E)) {
    if (OpaqueValueExpr *OVE = dyn_cast<OpaqueValueExpr>(BCO->getTrueExpr()))
      return IsSpecialDiscardedValue(OVE->getSourceExpr()) &&
             IsSpecialDiscardedValue(BCO->getFalseExpr());
  }

  // Objective-C++ extensions to the rule.
  if (isa<PseudoObjectExpr>(E) || isa<ObjCIvarRefExpr>(E))
    return true;

  return false;
}

/// Perform the conversions required for an expression used in a
/// context that ignores the result.
ExprResult Sema::IgnoredValueConversions(Expr *E) {
  if (E->hasPlaceholderType()) {
    ExprResult result = CheckPlaceholderExpr(E);
    if (result.isInvalid()) return E;
    E = result.get();
  }

  // C99 6.3.2.1:
  //   [Except in specific positions,] an lvalue that does not have
  //   array type is converted to the value stored in the
  //   designated object (and is no longer an lvalue).
  if (E->isRValue()) {
    // In C, function designators (i.e. expressions of function type)
    // are r-values, but we still want to do function-to-pointer decay
    // on them.  This is both technically correct and convenient for
    // some clients.
    if (!getLangOpts().CPlusPlus && E->getType()->isFunctionType())
      return DefaultFunctionArrayConversion(E);

    return E;
  }

  if (getLangOpts().CPlusPlus)  {
    // The C++11 standard defines the notion of a discarded-value expression;
    // normally, we don't need to do anything to handle it, but if it is a
    // volatile lvalue with a special form, we perform an lvalue-to-rvalue
    // conversion.
    if (getLangOpts().CPlusPlus11 && E->isGLValue() &&
        E->getType().isVolatileQualified() &&
        IsSpecialDiscardedValue(E)) {
      ExprResult Res = DefaultLvalueConversion(E);
      if (Res.isInvalid())
        return E;
      E = Res.get();
    } 
    return E;
  }

  // GCC seems to also exclude expressions of incomplete enum type.
  if (const EnumType *T = E->getType()->getAs<EnumType>()) {
    if (!T->getDecl()->isComplete()) {
      // FIXME: stupid workaround for a codegen bug!
      E = ImpCastExprToType(E, Context.VoidTy, CK_ToVoid).get();
      return E;
    }
  }

  ExprResult Res = DefaultFunctionArrayLvalueConversion(E);
  if (Res.isInvalid())
    return E;
  E = Res.get();

  if (!E->getType()->isVoidType())
    RequireCompleteType(E->getExprLoc(), E->getType(),
                        diag::err_incomplete_type);
  return E;
}

// If we can unambiguously determine whether Var can never be used
// in a constant expression, return true.
//  - if the variable and its initializer are non-dependent, then
//    we can unambiguously check if the variable is a constant expression.
//  - if the initializer is not value dependent - we can determine whether
//    it can be used to initialize a constant expression.  If Init can not
//    be used to initialize a constant expression we conclude that Var can 
//    never be a constant expression.
//  - FXIME: if the initializer is dependent, we can still do some analysis and
//    identify certain cases unambiguously as non-const by using a Visitor:
//      - such as those that involve odr-use of a ParmVarDecl, involve a new
//        delete, lambda-expr, dynamic-cast, reinterpret-cast etc...
static inline bool VariableCanNeverBeAConstantExpression(VarDecl *Var, 
    ASTContext &Context) {
  if (isa<ParmVarDecl>(Var)) return true;
  const VarDecl *DefVD = nullptr;

  // If there is no initializer - this can not be a constant expression.
  if (!Var->getAnyInitializer(DefVD)) return true;
  assert(DefVD);
  if (DefVD->isWeak()) return false;
  EvaluatedStmt *Eval = DefVD->ensureEvaluatedStmt();

  Expr *Init = cast<Expr>(Eval->Value);

  if (Var->getType()->isDependentType() || Init->isValueDependent()) {
    // FIXME: Teach the constant evaluator to deal with the non-dependent parts
    // of value-dependent expressions, and use it here to determine whether the
    // initializer is a potential constant expression.
    return false;
  }

  return !IsVariableAConstantExpression(Var, Context); 
}

/// \brief Check if the current lambda has any potential captures 
/// that must be captured by any of its enclosing lambdas that are ready to 
/// capture. If there is a lambda that can capture a nested 
/// potential-capture, go ahead and do so.  Also, check to see if any 
/// variables are uncaptureable or do not involve an odr-use so do not 
/// need to be captured.

static void CheckIfAnyEnclosingLambdasMustCaptureAnyPotentialCaptures(
    Expr *const FE, LambdaScopeInfo *const CurrentLSI, Sema &S) {

  assert(!S.isUnevaluatedContext());  
  assert(S.CurContext->isDependentContext()); 
  assert(CurrentLSI->CallOperator == S.CurContext && 
      "The current call operator must be synchronized with Sema's CurContext");

  const bool IsFullExprInstantiationDependent = FE->isInstantiationDependent();

  ArrayRef<const FunctionScopeInfo *> FunctionScopesArrayRef(
      S.FunctionScopes.data(), S.FunctionScopes.size());
  
  // All the potentially captureable variables in the current nested
  // lambda (within a generic outer lambda), must be captured by an
  // outer lambda that is enclosed within a non-dependent context.
  const unsigned NumPotentialCaptures =
      CurrentLSI->getNumPotentialVariableCaptures();
  for (unsigned I = 0; I != NumPotentialCaptures; ++I) {
    Expr *VarExpr = nullptr;
    VarDecl *Var = nullptr;
    CurrentLSI->getPotentialVariableCapture(I, Var, VarExpr);
    // If the variable is clearly identified as non-odr-used and the full
    // expression is not instantiation dependent, only then do we not 
    // need to check enclosing lambda's for speculative captures.
    // For e.g.:
    // Even though 'x' is not odr-used, it should be captured.
    // int test() {
    //   const int x = 10;
    //   auto L = [=](auto a) {
    //     (void) +x + a;
    //   };
    // }
    if (CurrentLSI->isVariableExprMarkedAsNonODRUsed(VarExpr) &&
        !IsFullExprInstantiationDependent)
      continue;

    // If we have a capture-capable lambda for the variable, go ahead and
    // capture the variable in that lambda (and all its enclosing lambdas).
    if (const Optional<unsigned> Index =
            getStackIndexOfNearestEnclosingCaptureCapableLambda(
                FunctionScopesArrayRef, Var, S)) {
      const unsigned FunctionScopeIndexOfCapturableLambda = Index.getValue();
      MarkVarDeclODRUsed(Var, VarExpr->getExprLoc(), S,
                         &FunctionScopeIndexOfCapturableLambda);
    } 
    const bool IsVarNeverAConstantExpression = 
        VariableCanNeverBeAConstantExpression(Var, S.Context);
    if (!IsFullExprInstantiationDependent || IsVarNeverAConstantExpression) {
      // This full expression is not instantiation dependent or the variable
      // can not be used in a constant expression - which means 
      // this variable must be odr-used here, so diagnose a 
      // capture violation early, if the variable is un-captureable.
      // This is purely for diagnosing errors early.  Otherwise, this
      // error would get diagnosed when the lambda becomes capture ready.
      QualType CaptureType, DeclRefType;
      SourceLocation ExprLoc = VarExpr->getExprLoc();
      if (S.tryCaptureVariable(Var, ExprLoc, S.TryCapture_Implicit,
                          /*EllipsisLoc*/ SourceLocation(), 
                          /*BuildAndDiagnose*/false, CaptureType, 
                          DeclRefType, nullptr)) {
        // We will never be able to capture this variable, and we need
        // to be able to in any and all instantiations, so diagnose it.
        S.tryCaptureVariable(Var, ExprLoc, S.TryCapture_Implicit,
                          /*EllipsisLoc*/ SourceLocation(), 
                          /*BuildAndDiagnose*/true, CaptureType, 
                          DeclRefType, nullptr);
      }
    }
  }

  // Check if 'this' needs to be captured.
  if (CurrentLSI->hasPotentialThisCapture()) {
    // If we have a capture-capable lambda for 'this', go ahead and capture
    // 'this' in that lambda (and all its enclosing lambdas).
    if (const Optional<unsigned> Index =
            getStackIndexOfNearestEnclosingCaptureCapableLambda(
                FunctionScopesArrayRef, /*0 is 'this'*/ nullptr, S)) {
      const unsigned FunctionScopeIndexOfCapturableLambda = Index.getValue();
      S.CheckCXXThisCapture(CurrentLSI->PotentialThisCaptureLocation,
                            /*Explicit*/ false, /*BuildAndDiagnose*/ true,
                            &FunctionScopeIndexOfCapturableLambda);
    }
  }

  // Reset all the potential captures at the end of each full-expression.
  CurrentLSI->clearPotentialCaptures();
}

static ExprResult attemptRecovery(Sema &SemaRef,
                                  const TypoCorrectionConsumer &Consumer,
                                  TypoCorrection TC) {
  LookupResult R(SemaRef, Consumer.getLookupResult().getLookupNameInfo(),
                 Consumer.getLookupResult().getLookupKind());
  const CXXScopeSpec *SS = Consumer.getSS();
  CXXScopeSpec NewSS;

  // Use an approprate CXXScopeSpec for building the expr.
  if (auto *NNS = TC.getCorrectionSpecifier())
    NewSS.MakeTrivial(SemaRef.Context, NNS, TC.getCorrectionRange());
  else if (SS && !TC.WillReplaceSpecifier())
    NewSS = *SS;

  if (auto *ND = TC.getCorrectionDecl()) {
    R.setLookupName(ND->getDeclName());
    R.addDecl(ND);
    if (ND->isCXXClassMember()) {
      // Figure out the correct naming class to add to the LookupResult.
      CXXRecordDecl *Record = nullptr;
      if (auto *NNS = TC.getCorrectionSpecifier())
        Record = NNS->getAsType()->getAsCXXRecordDecl();
      if (!Record)
        Record =
            dyn_cast<CXXRecordDecl>(ND->getDeclContext()->getRedeclContext());
      if (Record)
        R.setNamingClass(Record);

      // Detect and handle the case where the decl might be an implicit
      // member.
      bool MightBeImplicitMember;
      if (!Consumer.isAddressOfOperand())
        MightBeImplicitMember = true;
      else if (!NewSS.isEmpty())
        MightBeImplicitMember = false;
      else if (R.isOverloadedResult())
        MightBeImplicitMember = false;
      else if (R.isUnresolvableResult())
        MightBeImplicitMember = true;
      else
        MightBeImplicitMember = isa<FieldDecl>(ND) ||
                                isa<IndirectFieldDecl>(ND) ||
                                isa<MSPropertyDecl>(ND);

      if (MightBeImplicitMember)
        return SemaRef.BuildPossibleImplicitMemberExpr(
            NewSS, /*TemplateKWLoc*/ SourceLocation(), R,
            /*TemplateArgs*/ nullptr);
    } else if (auto *Ivar = dyn_cast<ObjCIvarDecl>(ND)) {
      return SemaRef.LookupInObjCMethod(R, Consumer.getScope(),
                                        Ivar->getIdentifier());
    }
  }

  return SemaRef.BuildDeclarationNameExpr(NewSS, R, /*NeedsADL*/ false,
                                          /*AcceptInvalidDecl*/ true);
}

namespace {
class FindTypoExprs : public RecursiveASTVisitor<FindTypoExprs> {
  llvm::SmallSetVector<TypoExpr *, 2> &TypoExprs;

public:
  explicit FindTypoExprs(llvm::SmallSetVector<TypoExpr *, 2> &TypoExprs)
      : TypoExprs(TypoExprs) {}
  bool VisitTypoExpr(TypoExpr *TE) {
    TypoExprs.insert(TE);
    return true;
  }
};

class TransformTypos : public TreeTransform<TransformTypos> {
  typedef TreeTransform<TransformTypos> BaseTransform;

  VarDecl *InitDecl; // A decl to avoid as a correction because it is in the
                     // process of being initialized.
  llvm::function_ref<ExprResult(Expr *)> ExprFilter;
  llvm::SmallSetVector<TypoExpr *, 2> TypoExprs, AmbiguousTypoExprs;
  llvm::SmallDenseMap<TypoExpr *, ExprResult, 2> TransformCache;
  llvm::SmallDenseMap<OverloadExpr *, Expr *, 4> OverloadResolution;

  /// \brief Emit diagnostics for all of the TypoExprs encountered.
  /// If the TypoExprs were successfully corrected, then the diagnostics should
  /// suggest the corrections. Otherwise the diagnostics will not suggest
  /// anything (having been passed an empty TypoCorrection).
  void EmitAllDiagnostics() {
    for (auto E : TypoExprs) {
      TypoExpr *TE = cast<TypoExpr>(E);
      auto &State = SemaRef.getTypoExprState(TE);
      if (State.DiagHandler) {
        TypoCorrection TC = State.Consumer->getCurrentCorrection();
        ExprResult Replacement = TransformCache[TE];

        // Extract the NamedDecl from the transformed TypoExpr and add it to the
        // TypoCorrection, replacing the existing decls. This ensures the right
        // NamedDecl is used in diagnostics e.g. in the case where overload
        // resolution was used to select one from several possible decls that
        // had been stored in the TypoCorrection.
        if (auto *ND = getDeclFromExpr(
                Replacement.isInvalid() ? nullptr : Replacement.get()))
          TC.setCorrectionDecl(ND);

        State.DiagHandler(TC);
      }
      SemaRef.clearDelayedTypo(TE);
    }
  }

  /// \brief If corrections for the first TypoExpr have been exhausted for a
  /// given combination of the other TypoExprs, retry those corrections against
  /// the next combination of substitutions for the other TypoExprs by advancing
  /// to the next potential correction of the second TypoExpr. For the second
  /// and subsequent TypoExprs, if its stream of corrections has been exhausted,
  /// the stream is reset and the next TypoExpr's stream is advanced by one (a
  /// TypoExpr's correction stream is advanced by removing the TypoExpr from the
  /// TransformCache). Returns true if there is still any untried combinations
  /// of corrections.
  bool CheckAndAdvanceTypoExprCorrectionStreams() {
    for (auto TE : TypoExprs) {
      auto &State = SemaRef.getTypoExprState(TE);
      TransformCache.erase(TE);
      if (!State.Consumer->finished())
        return true;
      State.Consumer->resetCorrectionStream();
    }
    return false;
  }

  NamedDecl *getDeclFromExpr(Expr *E) {
    if (auto *OE = dyn_cast_or_null<OverloadExpr>(E))
      E = OverloadResolution[OE];

    if (!E)
      return nullptr;
    if (auto *DRE = dyn_cast<DeclRefExpr>(E))
      return DRE->getDecl();
    if (auto *ME = dyn_cast<MemberExpr>(E))
      return ME->getMemberDecl();
    // FIXME: Add any other expr types that could be be seen by the delayed typo
    // correction TreeTransform for which the corresponding TypoCorrection could
    // contain multiple decls.
    return nullptr;
  }

  ExprResult TryTransform(Expr *E) {
    Sema::SFINAETrap Trap(SemaRef);
    ExprResult Res = TransformExpr(E);
    if (Trap.hasErrorOccurred() || Res.isInvalid())
      return ExprError();

    return ExprFilter(Res.get());
  }

public:
  TransformTypos(Sema &SemaRef, VarDecl *InitDecl, llvm::function_ref<ExprResult(Expr *)> Filter)
      : BaseTransform(SemaRef), InitDecl(InitDecl), ExprFilter(Filter) {}

  ExprResult RebuildCallExpr(Expr *Callee, SourceLocation LParenLoc,
                                   MultiExprArg Args,
                                   SourceLocation RParenLoc,
                                   Expr *ExecConfig = nullptr) {
    auto Result = BaseTransform::RebuildCallExpr(Callee, LParenLoc, Args,
                                                 RParenLoc, ExecConfig);
    if (auto *OE = dyn_cast<OverloadExpr>(Callee)) {
      if (Result.isUsable()) {
        Expr *ResultCall = Result.get();
        if (auto *BE = dyn_cast<CXXBindTemporaryExpr>(ResultCall))
          ResultCall = BE->getSubExpr();
        if (auto *CE = dyn_cast<CallExpr>(ResultCall))
          OverloadResolution[OE] = CE->getCallee();
      }
    }
    return Result;
  }

  ExprResult TransformLambdaExpr(LambdaExpr *E) { return Owned(E); }

  ExprResult Transform(Expr *E) {
    ExprResult Res;
    while (true) {
      Res = TryTransform(E);

      // Exit if either the transform was valid or if there were no TypoExprs
      // to transform that still have any untried correction candidates..
      if (!Res.isInvalid() ||
          !CheckAndAdvanceTypoExprCorrectionStreams())
        break;
    }

    // Ensure none of the TypoExprs have multiple typo correction candidates
    // with the same edit length that pass all the checks and filters.
    // TODO: Properly handle various permutations of possible corrections when
    // there is more than one potentially ambiguous typo correction.
    while (!AmbiguousTypoExprs.empty()) {
      auto TE  = AmbiguousTypoExprs.back();
      auto Cached = TransformCache[TE];
      auto &State = SemaRef.getTypoExprState(TE);
      State.Consumer->saveCurrentPosition();
      TransformCache.erase(TE);
      if (!TryTransform(E).isInvalid()) {
        State.Consumer->resetCorrectionStream();
        TransformCache.erase(TE);
        Res = ExprError();
        break;
      }
      AmbiguousTypoExprs.remove(TE);
      State.Consumer->restoreSavedPosition();
      TransformCache[TE] = Cached;
    }

    // Ensure that all of the TypoExprs within the current Expr have been found.
    if (!Res.isUsable())
      FindTypoExprs(TypoExprs).TraverseStmt(E);

    EmitAllDiagnostics();

    return Res;
  }

  ExprResult TransformTypoExpr(TypoExpr *E) {
    // If the TypoExpr hasn't been seen before, record it. Otherwise, return the
    // cached transformation result if there is one and the TypoExpr isn't the
    // first one that was encountered.
    auto &CacheEntry = TransformCache[E];
    if (!TypoExprs.insert(E) && !CacheEntry.isUnset()) {
      return CacheEntry;
    }

    auto &State = SemaRef.getTypoExprState(E);
    assert(State.Consumer && "Cannot transform a cleared TypoExpr");

    // For the first TypoExpr and an uncached TypoExpr, find the next likely
    // typo correction and return it.
    while (TypoCorrection TC = State.Consumer->getNextCorrection()) {
      if (InitDecl && TC.getCorrectionDecl() == InitDecl)
        continue;
      ExprResult NE = State.RecoveryHandler ?
          State.RecoveryHandler(SemaRef, E, TC) :
          attemptRecovery(SemaRef, *State.Consumer, TC);
      if (!NE.isInvalid()) {
        // Check whether there may be a second viable correction with the same
        // edit distance; if so, remember this TypoExpr may have an ambiguous
        // correction so it can be more thoroughly vetted later.
        TypoCorrection Next;
        if ((Next = State.Consumer->peekNextCorrection()) &&
            Next.getEditDistance(false) == TC.getEditDistance(false)) {
          AmbiguousTypoExprs.insert(E);
        } else {
          AmbiguousTypoExprs.remove(E);
        }
        assert(!NE.isUnset() &&
               "Typo was transformed into a valid-but-null ExprResult");
        return CacheEntry = NE;
      }
    }
    return CacheEntry = ExprError();
  }
};
}

ExprResult
Sema::CorrectDelayedTyposInExpr(Expr *E, VarDecl *InitDecl,
                                llvm::function_ref<ExprResult(Expr *)> Filter) {
  // If the current evaluation context indicates there are uncorrected typos
  // and the current expression isn't guaranteed to not have typos, try to
  // resolve any TypoExpr nodes that might be in the expression.
  if (E && !ExprEvalContexts.empty() && ExprEvalContexts.back().NumTypos &&
      (E->isTypeDependent() || E->isValueDependent() ||
       E->isInstantiationDependent())) {
    auto TyposInContext = ExprEvalContexts.back().NumTypos;
    assert(TyposInContext < ~0U && "Recursive call of CorrectDelayedTyposInExpr");
    ExprEvalContexts.back().NumTypos = ~0U;
    auto TyposResolved = DelayedTypos.size();
    auto Result = TransformTypos(*this, InitDecl, Filter).Transform(E);
    ExprEvalContexts.back().NumTypos = TyposInContext;
    TyposResolved -= DelayedTypos.size();
    if (Result.isInvalid() || Result.get() != E) {
      ExprEvalContexts.back().NumTypos -= TyposResolved;
      return Result;
    }
    assert(TyposResolved == 0 && "Corrected typo but got same Expr back?");
  }
  return E;
}

ExprResult Sema::ActOnFinishFullExpr(Expr *FE, SourceLocation CC,
                                     bool DiscardedValue,
                                     bool IsConstexpr, 
                                     bool IsLambdaInitCaptureInitializer) {
  ExprResult FullExpr = FE;

  if (!FullExpr.get())
    return ExprError();
 
  // If we are an init-expression in a lambdas init-capture, we should not 
  // diagnose an unexpanded pack now (will be diagnosed once lambda-expr 
  // containing full-expression is done).
  // template<class ... Ts> void test(Ts ... t) {
  //   test([&a(t)]() { <-- (t) is an init-expr that shouldn't be diagnosed now.
  //     return a;
  //   }() ...);
  // }
  // FIXME: This is a hack. It would be better if we pushed the lambda scope
  // when we parse the lambda introducer, and teach capturing (but not
  // unexpanded pack detection) to walk over LambdaScopeInfos which don't have a
  // corresponding class yet (that is, have LambdaScopeInfo either represent a
  // lambda where we've entered the introducer but not the body, or represent a
  // lambda where we've entered the body, depending on where the
  // parser/instantiation has got to).
  if (!IsLambdaInitCaptureInitializer && 
      DiagnoseUnexpandedParameterPack(FullExpr.get()))
    return ExprError();

  // Top-level expressions default to 'id' when we're in a debugger.
  if (DiscardedValue && getLangOpts().DebuggerCastResultToId &&
      FullExpr.get()->getType() == Context.UnknownAnyTy) {
    FullExpr = forceUnknownAnyToType(FullExpr.get(), Context.getObjCIdType());
    if (FullExpr.isInvalid())
      return ExprError();
  }

  if (DiscardedValue) {
    FullExpr = CheckPlaceholderExpr(FullExpr.get());
    if (FullExpr.isInvalid())
      return ExprError();

    FullExpr = IgnoredValueConversions(FullExpr.get());
    if (FullExpr.isInvalid())
      return ExprError();
  }

  FullExpr = CorrectDelayedTyposInExpr(FullExpr.get());
  if (FullExpr.isInvalid())
    return ExprError();

  CheckCompletedExpr(FullExpr.get(), CC, IsConstexpr);

  // At the end of this full expression (which could be a deeply nested 
  // lambda), if there is a potential capture within the nested lambda, 
  // have the outer capture-able lambda try and capture it.
  // Consider the following code:
  // void f(int, int);
  // void f(const int&, double);
  // void foo() {   
  //  const int x = 10, y = 20;
  //  auto L = [=](auto a) {
  //      auto M = [=](auto b) {
  //         f(x, b); <-- requires x to be captured by L and M
  //         f(y, a); <-- requires y to be captured by L, but not all Ms
  //      };
  //   };
  // }

  // FIXME: Also consider what happens for something like this that involves 
  // the gnu-extension statement-expressions or even lambda-init-captures:   
  //   void f() {
  //     const int n = 0;
  //     auto L =  [&](auto a) {
  //       +n + ({ 0; a; });
  //     };
  //   }
  // 
  // Here, we see +n, and then the full-expression 0; ends, so we don't 
  // capture n (and instead remove it from our list of potential captures), 
  // and then the full-expression +n + ({ 0; }); ends, but it's too late 
  // for us to see that we need to capture n after all.

  LambdaScopeInfo *const CurrentLSI = getCurLambda();
  // FIXME: PR 17877 showed that getCurLambda() can return a valid pointer 
  // even if CurContext is not a lambda call operator. Refer to that Bug Report
  // for an example of the code that might cause this asynchrony.  
  // By ensuring we are in the context of a lambda's call operator
  // we can fix the bug (we only need to check whether we need to capture
  // if we are within a lambda's body); but per the comments in that 
  // PR, a proper fix would entail :
  //   "Alternative suggestion:
  //   - Add to Sema an integer holding the smallest (outermost) scope 
  //     index that we are *lexically* within, and save/restore/set to 
  //     FunctionScopes.size() in InstantiatingTemplate's 
  //     constructor/destructor.
  //  - Teach the handful of places that iterate over FunctionScopes to 
  //    stop at the outermost enclosing lexical scope."
  const bool IsInLambdaDeclContext = isLambdaCallOperator(CurContext);
  if (IsInLambdaDeclContext && CurrentLSI &&
      CurrentLSI->hasPotentialCaptures() && !FullExpr.isInvalid())
    CheckIfAnyEnclosingLambdasMustCaptureAnyPotentialCaptures(FE, CurrentLSI,
                                                              *this);
  return MaybeCreateExprWithCleanups(FullExpr);
}

StmtResult Sema::ActOnFinishFullStmt(Stmt *FullStmt) {
  if (!FullStmt) return StmtError();

  return MaybeCreateStmtWithCleanups(FullStmt);
}

Sema::IfExistsResult 
Sema::CheckMicrosoftIfExistsSymbol(Scope *S,
                                   CXXScopeSpec &SS,
                                   const DeclarationNameInfo &TargetNameInfo) {
  DeclarationName TargetName = TargetNameInfo.getName();
  if (!TargetName)
    return IER_DoesNotExist;
  
  // If the name itself is dependent, then the result is dependent.
  if (TargetName.isDependentName())
    return IER_Dependent;
  
  // Do the redeclaration lookup in the current scope.
  LookupResult R(*this, TargetNameInfo, Sema::LookupAnyName,
                 Sema::NotForRedeclaration);
  LookupParsedName(R, S, &SS);
  R.suppressDiagnostics();
  
  switch (R.getResultKind()) {
  case LookupResult::Found:
  case LookupResult::FoundOverloaded:
  case LookupResult::FoundUnresolvedValue:
  case LookupResult::Ambiguous:
    return IER_Exists;
    
  case LookupResult::NotFound:
    return IER_DoesNotExist;
    
  case LookupResult::NotFoundInCurrentInstantiation:
    return IER_Dependent;
  }

  llvm_unreachable("Invalid LookupResult Kind!");
}

Sema::IfExistsResult 
Sema::CheckMicrosoftIfExistsSymbol(Scope *S, SourceLocation KeywordLoc,
                                   bool IsIfExists, CXXScopeSpec &SS,
                                   UnqualifiedId &Name) {
  DeclarationNameInfo TargetNameInfo = GetNameFromUnqualifiedId(Name);
  
  // Check for unexpanded parameter packs.
  SmallVector<UnexpandedParameterPack, 4> Unexpanded;
  collectUnexpandedParameterPacks(SS, Unexpanded);
  collectUnexpandedParameterPacks(TargetNameInfo, Unexpanded);
  if (!Unexpanded.empty()) {
    DiagnoseUnexpandedParameterPacks(KeywordLoc,
                                     IsIfExists? UPPC_IfExists 
                                               : UPPC_IfNotExists, 
                                     Unexpanded);
    return IER_Error;
  }
  
  return CheckMicrosoftIfExistsSymbol(S, SS, TargetNameInfo);
}