tools/clang/lib/Sema/SemaExpr.cpp

reference, declaration → definition
definition → references, declarations, derived classes, virtual overrides
reference to multiple definitions → definitions
unreferenced

//===--- SemaExpr.cpp - Semantic Analysis for Expressions -----------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
//  This file implements semantic analysis for expressions.
//
//===----------------------------------------------------------------------===//

#include "TreeTransform.h"
#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTLambda.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/EvaluatedExprVisitor.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/ExprObjC.h"
#include "clang/AST/ExprOpenMP.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/TypeLoc.h"
#include "clang/Basic/FixedPoint.h"
#include "clang/Basic/PartialDiagnostic.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/LiteralSupport.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/AnalysisBasedWarnings.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Designator.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/Overload.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaFixItUtils.h"
#include "clang/Sema/SemaInternal.h"
#include "clang/Sema/Template.h"
#include "llvm/Support/ConvertUTF.h"
using namespace clang;
using namespace sema;

/// Determine whether the use of this declaration is valid, without
/// emitting diagnostics.
bool Sema::CanUseDecl(NamedDecl *D, bool TreatUnavailableAsInvalid) {
  // See if this is an auto-typed variable whose initializer we are parsing.
  if (ParsingInitForAutoVars.count(D))
    return false;

  // See if this is a deleted function.
  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->isDeleted())
      return false;

    // If the function has a deduced return type, and we can't deduce it,
    // then we can't use it either.
    if (getLangOpts().CPlusPlus14 && FD->getReturnType()->isUndeducedType() &&
        DeduceReturnType(FD, SourceLocation(), /*Diagnose*/ false))
      return false;

    // See if this is an aligned allocation/deallocation function that is
    // unavailable.
    if (TreatUnavailableAsInvalid &&
        isUnavailableAlignedAllocationFunction(*FD))
      return false;
  }

  // See if this function is unavailable.
  if (TreatUnavailableAsInvalid && D->getAvailability() == AR_Unavailable &&
      cast<Decl>(CurContext)->getAvailability() != AR_Unavailable)
    return false;

  return true;
}

static void DiagnoseUnusedOfDecl(Sema &S, NamedDecl *D, SourceLocation Loc) {
  // Warn if this is used but marked unused.
  if (const auto *A = D->getAttr<UnusedAttr>()) {
    // [[maybe_unused]] should not diagnose uses, but __attribute__((unused))
    // should diagnose them.
    if (A->getSemanticSpelling() != UnusedAttr::CXX11_maybe_unused &&
        A->getSemanticSpelling() != UnusedAttr::C2x_maybe_unused) {
      const Decl *DC = cast_or_null<Decl>(S.getCurObjCLexicalContext());
      if (DC && !DC->hasAttr<UnusedAttr>())
        S.Diag(Loc, diag::warn_used_but_marked_unused) << D->getDeclName();
    }
  }
}

/// Emit a note explaining that this function is deleted.
void Sema::NoteDeletedFunction(FunctionDecl *Decl) {
  assert(Decl->isDeleted());

  CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Decl);

  if (Method && Method->isDeleted() && Method->isDefaulted()) {
    // If the method was explicitly defaulted, point at that declaration.
    if (!Method->isImplicit())
      Diag(Decl->getLocation(), diag::note_implicitly_deleted);

    // Try to diagnose why this special member function was implicitly
    // deleted. This might fail, if that reason no longer applies.
    CXXSpecialMember CSM = getSpecialMember(Method);
    if (CSM != CXXInvalid)
      ShouldDeleteSpecialMember(Method, CSM, nullptr, /*Diagnose=*/true);

    return;
  }

  auto *Ctor = dyn_cast<CXXConstructorDecl>(Decl);
  if (Ctor && Ctor->isInheritingConstructor())
    return NoteDeletedInheritingConstructor(Ctor);

  Diag(Decl->getLocation(), diag::note_availability_specified_here)
    << Decl << 1;
}

/// Determine whether a FunctionDecl was ever declared with an
/// explicit storage class.
static bool hasAnyExplicitStorageClass(const FunctionDecl *D) {
  for (auto I : D->redecls()) {
    if (I->getStorageClass() != SC_None)
      return true;
  }
  return false;
}

/// Check whether we're in an extern inline function and referring to a
/// variable or function with internal linkage (C11 6.7.4p3).
///
/// This is only a warning because we used to silently accept this code, but
/// in many cases it will not behave correctly. This is not enabled in C++ mode
/// because the restriction language is a bit weaker (C++11 [basic.def.odr]p6)
/// and so while there may still be user mistakes, most of the time we can't
/// prove that there are errors.
static void diagnoseUseOfInternalDeclInInlineFunction(Sema &S,
                                                      const NamedDecl *D,
                                                      SourceLocation Loc) {
  // This is disabled under C++; there are too many ways for this to fire in
  // contexts where the warning is a false positive, or where it is technically
  // correct but benign.
  if (S.getLangOpts().CPlusPlus)
    return;

  // Check if this is an inlined function or method.
  FunctionDecl *Current = S.getCurFunctionDecl();
  if (!Current)
    return;
  if (!Current->isInlined())
    return;
  if (!Current->isExternallyVisible())
    return;

  // Check if the decl has internal linkage.
  if (D->getFormalLinkage() != InternalLinkage)
    return;

  // Downgrade from ExtWarn to Extension if
  //  (1) the supposedly external inline function is in the main file,
  //      and probably won't be included anywhere else.
  //  (2) the thing we're referencing is a pure function.
  //  (3) the thing we're referencing is another inline function.
  // This last can give us false negatives, but it's better than warning on
  // wrappers for simple C library functions.
  const FunctionDecl *UsedFn = dyn_cast<FunctionDecl>(D);
  bool DowngradeWarning = S.getSourceManager().isInMainFile(Loc);
  if (!DowngradeWarning && UsedFn)
    DowngradeWarning = UsedFn->isInlined() || UsedFn->hasAttr<ConstAttr>();

  S.Diag(Loc, DowngradeWarning ? diag::ext_internal_in_extern_inline_quiet
                               : diag::ext_internal_in_extern_inline)
    << /*IsVar=*/!UsedFn << D;

  S.MaybeSuggestAddingStaticToDecl(Current);

  S.Diag(D->getCanonicalDecl()->getLocation(), diag::note_entity_declared_at)
      << D;
}

void Sema::MaybeSuggestAddingStaticToDecl(const FunctionDecl *Cur) {
  const FunctionDecl *First = Cur->getFirstDecl();

  // Suggest "static" on the function, if possible.
  if (!hasAnyExplicitStorageClass(First)) {
    SourceLocation DeclBegin = First->getSourceRange().getBegin();
    Diag(DeclBegin, diag::note_convert_inline_to_static)
      << Cur << FixItHint::CreateInsertion(DeclBegin, "static ");
  }
}

/// Determine whether the use of this declaration is valid, and
/// emit any corresponding diagnostics.
///
/// This routine diagnoses various problems with referencing
/// declarations that can occur when using a declaration. For example,
/// it might warn if a deprecated or unavailable declaration is being
/// used, or produce an error (and return true) if a C++0x deleted
/// function is being used.
///
/// \returns true if there was an error (this declaration cannot be
/// referenced), false otherwise.
///
bool Sema::DiagnoseUseOfDecl(NamedDecl *D, ArrayRef<SourceLocation> Locs,
                             const ObjCInterfaceDecl *UnknownObjCClass,
                             bool ObjCPropertyAccess,
                             bool AvoidPartialAvailabilityChecks,
                             ObjCInterfaceDecl *ClassReceiver) {
  SourceLocation Loc = Locs.front();
  if (getLangOpts().CPlusPlus && isa<FunctionDecl>(D)) {
    // If there were any diagnostics suppressed by template argument deduction,
    // emit them now.
    auto Pos = SuppressedDiagnostics.find(D->getCanonicalDecl());
    if (Pos != SuppressedDiagnostics.end()) {
      for (const PartialDiagnosticAt &Suppressed : Pos->second)
        Diag(Suppressed.first, Suppressed.second);

      // Clear out the list of suppressed diagnostics, so that we don't emit
      // them again for this specialization. However, we don't obsolete this
      // entry from the table, because we want to avoid ever emitting these
      // diagnostics again.
      Pos->second.clear();
    }

    // C++ [basic.start.main]p3:
    //   The function 'main' shall not be used within a program.
    if (cast<FunctionDecl>(D)->isMain())
      Diag(Loc, diag::ext_main_used);

    diagnoseUnavailableAlignedAllocation(*cast<FunctionDecl>(D), Loc);
  }

  // See if this is an auto-typed variable whose initializer we are parsing.
  if (ParsingInitForAutoVars.count(D)) {
    if (isa<BindingDecl>(D)) {
      Diag(Loc, diag::err_binding_cannot_appear_in_own_initializer)
        << D->getDeclName();
    } else {
      Diag(Loc, diag::err_auto_variable_cannot_appear_in_own_initializer)
        << D->getDeclName() << cast<VarDecl>(D)->getType();
    }
    return true;
  }

  // See if this is a deleted function.
  if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->isDeleted()) {
      auto *Ctor = dyn_cast<CXXConstructorDecl>(FD);
      if (Ctor && Ctor->isInheritingConstructor())
        Diag(Loc, diag::err_deleted_inherited_ctor_use)
            << Ctor->getParent()
            << Ctor->getInheritedConstructor().getConstructor()->getParent();
      else
        Diag(Loc, diag::err_deleted_function_use);
      NoteDeletedFunction(FD);
      return true;
    }

    // If the function has a deduced return type, and we can't deduce it,
    // then we can't use it either.
    if (getLangOpts().CPlusPlus14 && FD->getReturnType()->isUndeducedType() &&
        DeduceReturnType(FD, Loc))
      return true;

    if (getLangOpts().CUDA && !CheckCUDACall(Loc, FD))
      return true;
  }

  if (auto *MD = dyn_cast<CXXMethodDecl>(D)) {
    // Lambdas are only default-constructible or assignable in C++2a onwards.
    if (MD->getParent()->isLambda() &&
        ((isa<CXXConstructorDecl>(MD) &&
          cast<CXXConstructorDecl>(MD)->isDefaultConstructor()) ||
         MD->isCopyAssignmentOperator() || MD->isMoveAssignmentOperator())) {
      Diag(Loc, diag::warn_cxx17_compat_lambda_def_ctor_assign)
        << !isa<CXXConstructorDecl>(MD);
    }
  }

  auto getReferencedObjCProp = [](const NamedDecl *D) ->
                                      const ObjCPropertyDecl * {
    if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
      return MD->findPropertyDecl();
    return nullptr;
  };
  if (const ObjCPropertyDecl *ObjCPDecl = getReferencedObjCProp(D)) {
    if (diagnoseArgIndependentDiagnoseIfAttrs(ObjCPDecl, Loc))
      return true;
  } else if (diagnoseArgIndependentDiagnoseIfAttrs(D, Loc)) {
      return true;
  }

  // [OpenMP 4.0], 2.15 declare reduction Directive, Restrictions
  // Only the variables omp_in and omp_out are allowed in the combiner.
  // Only the variables omp_priv and omp_orig are allowed in the
  // initializer-clause.
  auto *DRD = dyn_cast<OMPDeclareReductionDecl>(CurContext);
  if (LangOpts.OpenMP && DRD && !CurContext->containsDecl(D) &&
      isa<VarDecl>(D)) {
    Diag(Loc, diag::err_omp_wrong_var_in_declare_reduction)
        << getCurFunction()->HasOMPDeclareReductionCombiner;
    Diag(D->getLocation(), diag::note_entity_declared_at) << D;
    return true;
  }

  // [OpenMP 5.0], 2.19.7.3. declare mapper Directive, Restrictions
  //  List-items in map clauses on this construct may only refer to the declared
  //  variable var and entities that could be referenced by a procedure defined
  //  at the same location
  auto *DMD = dyn_cast<OMPDeclareMapperDecl>(CurContext);
  if (LangOpts.OpenMP && DMD && !CurContext->containsDecl(D) &&
      isa<VarDecl>(D)) {
    Diag(Loc, diag::err_omp_declare_mapper_wrong_var)
        << DMD->getVarName().getAsString();
    Diag(D->getLocation(), diag::note_entity_declared_at) << D;
    return true;
  }

  DiagnoseAvailabilityOfDecl(D, Locs, UnknownObjCClass, ObjCPropertyAccess,
                             AvoidPartialAvailabilityChecks, ClassReceiver);

  DiagnoseUnusedOfDecl(*this, D, Loc);

  diagnoseUseOfInternalDeclInInlineFunction(*this, D, Loc);

  return false;
}

/// DiagnoseSentinelCalls - This routine checks whether a call or
/// message-send is to a declaration with the sentinel attribute, and
/// if so, it checks that the requirements of the sentinel are
/// satisfied.
void Sema::DiagnoseSentinelCalls(NamedDecl *D, SourceLocation Loc,
                                 ArrayRef<Expr *> Args) {
  const SentinelAttr *attr = D->getAttr<SentinelAttr>();
  if (!attr)
    return;

  // The number of formal parameters of the declaration.
  unsigned numFormalParams;

  // The kind of declaration.  This is also an index into a %select in
  // the diagnostic.
  enum CalleeType { CT_Function, CT_Method, CT_Block } calleeType;

  if (ObjCMethodDecl *MD = dyn_cast<ObjCMethodDecl>(D)) {
    numFormalParams = MD->param_size();
    calleeType = CT_Method;
  } else if (FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    numFormalParams = FD->param_size();
    calleeType = CT_Function;
  } else if (isa<VarDecl>(D)) {
    QualType type = cast<ValueDecl>(D)->getType();
    const FunctionType *fn = nullptr;
    if (const PointerType *ptr = type->getAs<PointerType>()) {
      fn = ptr->getPointeeType()->getAs<FunctionType>();
      if (!fn) return;
      calleeType = CT_Function;
    } else if (const BlockPointerType *ptr = type->getAs<BlockPointerType>()) {
      fn = ptr->getPointeeType()->castAs<FunctionType>();
      calleeType = CT_Block;
    } else {
      return;
    }

    if (const FunctionProtoType *proto = dyn_cast<FunctionProtoType>(fn)) {
      numFormalParams = proto->getNumParams();
    } else {
      numFormalParams = 0;
    }
  } else {
    return;
  }

  // "nullPos" is the number of formal parameters at the end which
  // effectively count as part of the variadic arguments.  This is
  // useful if you would prefer to not have *any* formal parameters,
  // but the language forces you to have at least one.
  unsigned nullPos = attr->getNullPos();
  assert((nullPos == 0 || nullPos == 1) && "invalid null position on sentinel");
  numFormalParams = (nullPos > numFormalParams ? 0 : numFormalParams - nullPos);

  // The number of arguments which should follow the sentinel.
  unsigned numArgsAfterSentinel = attr->getSentinel();

  // If there aren't enough arguments for all the formal parameters,
  // the sentinel, and the args after the sentinel, complain.
  if (Args.size() < numFormalParams + numArgsAfterSentinel + 1) {
    Diag(Loc, diag::warn_not_enough_argument) << D->getDeclName();
    Diag(D->getLocation(), diag::note_sentinel_here) << int(calleeType);
    return;
  }

  // Otherwise, find the sentinel expression.
  Expr *sentinelExpr = Args[Args.size() - numArgsAfterSentinel - 1];
  if (!sentinelExpr) return;
  if (sentinelExpr->isValueDependent()) return;
  if (Context.isSentinelNullExpr(sentinelExpr)) return;

  // Pick a reasonable string to insert.  Optimistically use 'nil', 'nullptr',
  // or 'NULL' if those are actually defined in the context.  Only use
  // 'nil' for ObjC methods, where it's much more likely that the
  // variadic arguments form a list of object pointers.
  SourceLocation MissingNilLoc = getLocForEndOfToken(sentinelExpr->getEndLoc());
  std::string NullValue;
  if (calleeType == CT_Method && PP.isMacroDefined("nil"))
    NullValue = "nil";
  else if (getLangOpts().CPlusPlus11)
    NullValue = "nullptr";
  else if (PP.isMacroDefined("NULL"))
    NullValue = "NULL";
  else
    NullValue = "(void*) 0";

  if (MissingNilLoc.isInvalid())
    Diag(Loc, diag::warn_missing_sentinel) << int(calleeType);
  else
    Diag(MissingNilLoc, diag::warn_missing_sentinel)
      << int(calleeType)
      << FixItHint::CreateInsertion(MissingNilLoc, ", " + NullValue);
  Diag(D->getLocation(), diag::note_sentinel_here) << int(calleeType);
}

SourceRange Sema::getExprRange(Expr *E) const {
  return E ? E->getSourceRange() : SourceRange();
}

//===----------------------------------------------------------------------===//
//  Standard Promotions and Conversions
//===----------------------------------------------------------------------===//

/// DefaultFunctionArrayConversion (C99 6.3.2.1p3, C99 6.3.2.1p4).
ExprResult Sema::DefaultFunctionArrayConversion(Expr *E, bool Diagnose) {
  // Handle any placeholder expressions which made it here.
  if (E->getType()->isPlaceholderType()) {
    ExprResult result = CheckPlaceholderExpr(E);
    if (result.isInvalid()) return ExprError();
    E = result.get();
  }

  QualType Ty = E->getType();
  assert(!Ty.isNull() && "DefaultFunctionArrayConversion - missing type");

  if (Ty->isFunctionType()) {
    if (auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenCasts()))
      if (auto *FD = dyn_cast<FunctionDecl>(DRE->getDecl()))
        if (!checkAddressOfFunctionIsAvailable(FD, Diagnose, E->getExprLoc()))
          return ExprError();

    E = ImpCastExprToType(E, Context.getPointerType(Ty),
                          CK_FunctionToPointerDecay).get();
  } else if (Ty->isArrayType()) {
    // In C90 mode, arrays only promote to pointers if the array expression is
    // an lvalue.  The relevant legalese is C90 6.2.2.1p3: "an lvalue that has
    // type 'array of type' is converted to an expression that has type 'pointer
    // to type'...".  In C99 this was changed to: C99 6.3.2.1p3: "an expression
    // that has type 'array of type' ...".  The relevant change is "an lvalue"
    // (C90) to "an expression" (C99).
    //
    // C++ 4.2p1:
    // An lvalue or rvalue of type "array of N T" or "array of unknown bound of
    // T" can be converted to an rvalue of type "pointer to T".
    //
    if (getLangOpts().C99 || getLangOpts().CPlusPlus || E->isLValue())
      E = ImpCastExprToType(E, Context.getArrayDecayedType(Ty),
                            CK_ArrayToPointerDecay).get();
  }
  return E;
}

static void CheckForNullPointerDereference(Sema &S, Expr *E) {
  // Check to see if we are dereferencing a null pointer.  If so,
  // and if not volatile-qualified, this is undefined behavior that the
  // optimizer will delete, so warn about it.  People sometimes try to use this
  // to get a deterministic trap and are surprised by clang's behavior.  This
  // only handles the pattern "*null", which is a very syntactic check.
  if (UnaryOperator *UO = dyn_cast<UnaryOperator>(E->IgnoreParenCasts()))
    if (UO->getOpcode() == UO_Deref &&
        UO->getSubExpr()->IgnoreParenCasts()->
          isNullPointerConstant(S.Context, Expr::NPC_ValueDependentIsNotNull) &&
        !UO->getType().isVolatileQualified()) {
    S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
                          S.PDiag(diag::warn_indirection_through_null)
                            << UO->getSubExpr()->getSourceRange());
    S.DiagRuntimeBehavior(UO->getOperatorLoc(), UO,
                        S.PDiag(diag::note_indirection_through_null));
  }
}

static void DiagnoseDirectIsaAccess(Sema &S, const ObjCIvarRefExpr *OIRE,
                                    SourceLocation AssignLoc,
                                    const Expr* RHS) {
  const ObjCIvarDecl *IV = OIRE->getDecl();
  if (!IV)
    return;

  DeclarationName MemberName = IV->getDeclName();
  IdentifierInfo *Member = MemberName.getAsIdentifierInfo();
  if (!Member || !Member->isStr("isa"))
    return;

  const Expr *Base = OIRE->getBase();
  QualType BaseType = Base->getType();
  if (OIRE->isArrow())
    BaseType = BaseType->getPointeeType();
  if (const ObjCObjectType *OTy = BaseType->getAs<ObjCObjectType>())
    if (ObjCInterfaceDecl *IDecl = OTy->getInterface()) {
      ObjCInterfaceDecl *ClassDeclared = nullptr;
      ObjCIvarDecl *IV = IDecl->lookupInstanceVariable(Member, ClassDeclared);
      if (!ClassDeclared->getSuperClass()
          && (*ClassDeclared->ivar_begin()) == IV) {
        if (RHS) {
          NamedDecl *ObjectSetClass =
            S.LookupSingleName(S.TUScope,
                               &S.Context.Idents.get("object_setClass"),
                               SourceLocation(), S.LookupOrdinaryName);
          if (ObjectSetClass) {
            SourceLocation RHSLocEnd = S.getLocForEndOfToken(RHS->getEndLoc());
            S.Diag(OIRE->getExprLoc(), diag::warn_objc_isa_assign)
                << FixItHint::CreateInsertion(OIRE->getBeginLoc(),
                                              "object_setClass(")
                << FixItHint::CreateReplacement(
                       SourceRange(OIRE->getOpLoc(), AssignLoc), ",")
                << FixItHint::CreateInsertion(RHSLocEnd, ")");
          }
          else
            S.Diag(OIRE->getLocation(), diag::warn_objc_isa_assign);
        } else {
          NamedDecl *ObjectGetClass =
            S.LookupSingleName(S.TUScope,
                               &S.Context.Idents.get("object_getClass"),
                               SourceLocation(), S.LookupOrdinaryName);
          if (ObjectGetClass)
            S.Diag(OIRE->getExprLoc(), diag::warn_objc_isa_use)
                << FixItHint::CreateInsertion(OIRE->getBeginLoc(),
                                              "object_getClass(")
                << FixItHint::CreateReplacement(
                       SourceRange(OIRE->getOpLoc(), OIRE->getEndLoc()), ")");
          else
            S.Diag(OIRE->getLocation(), diag::warn_objc_isa_use);
        }
        S.Diag(IV->getLocation(), diag::note_ivar_decl);
      }
    }
}

ExprResult Sema::DefaultLvalueConversion(Expr *E) {
  // Handle any placeholder expressions which made it here.
  if (E->getType()->isPlaceholderType()) {
    ExprResult result = CheckPlaceholderExpr(E);
    if (result.isInvalid()) return ExprError();
    E = result.get();
  }

  // C++ [conv.lval]p1:
  //   A glvalue of a non-function, non-array type T can be
  //   converted to a prvalue.
  if (!E->isGLValue()) return E;

  QualType T = E->getType();
  assert(!T.isNull() && "r-value conversion on typeless expression?");

  // We don't want to throw lvalue-to-rvalue casts on top of
  // expressions of certain types in C++.
  if (getLangOpts().CPlusPlus &&
      (E->getType() == Context.OverloadTy ||
       T->isDependentType() ||
       T->isRecordType()))
    return E;

  // The C standard is actually really unclear on this point, and
  // DR106 tells us what the result should be but not why.  It's
  // generally best to say that void types just doesn't undergo
  // lvalue-to-rvalue at all.  Note that expressions of unqualified
  // 'void' type are never l-values, but qualified void can be.
  if (T->isVoidType())
    return E;

  // OpenCL usually rejects direct accesses to values of 'half' type.
  if (getLangOpts().OpenCL && !getOpenCLOptions().isEnabled("cl_khr_fp16") &&
      T->isHalfType()) {
    Diag(E->getExprLoc(), diag::err_opencl_half_load_store)
      << 0 << T;
    return ExprError();
  }

  CheckForNullPointerDereference(*this, E);
  if (const ObjCIsaExpr *OISA = dyn_cast<ObjCIsaExpr>(E->IgnoreParenCasts())) {
    NamedDecl *ObjectGetClass = LookupSingleName(TUScope,
                                     &Context.Idents.get("object_getClass"),
                                     SourceLocation(), LookupOrdinaryName);
    if (ObjectGetClass)
      Diag(E->getExprLoc(), diag::warn_objc_isa_use)
          << FixItHint::CreateInsertion(OISA->getBeginLoc(), "object_getClass(")
          << FixItHint::CreateReplacement(
                 SourceRange(OISA->getOpLoc(), OISA->getIsaMemberLoc()), ")");
    else
      Diag(E->getExprLoc(), diag::warn_objc_isa_use);
  }
  else if (const ObjCIvarRefExpr *OIRE =
            dyn_cast<ObjCIvarRefExpr>(E->IgnoreParenCasts()))
    DiagnoseDirectIsaAccess(*this, OIRE, SourceLocation(), /* Expr*/nullptr);

  // C++ [conv.lval]p1:
  //   [...] If T is a non-class type, the type of the prvalue is the
  //   cv-unqualified version of T. Otherwise, the type of the
  //   rvalue is T.
  //
  // C99 6.3.2.1p2:
  //   If the lvalue has qualified type, the value has the unqualified
  //   version of the type of the lvalue; otherwise, the value has the
  //   type of the lvalue.
  if (T.hasQualifiers())
    T = T.getUnqualifiedType();

  // Under the MS ABI, lock down the inheritance model now.
  if (T->isMemberPointerType() &&
      Context.getTargetInfo().getCXXABI().isMicrosoft())
    (void)isCompleteType(E->getExprLoc(), T);

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

  // Loading a __weak object implicitly retains the value, so we need a cleanup to
  // balance that.
  if (E->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
    Cleanup.setExprNeedsCleanups(true);

  // C++ [conv.lval]p3:
  //   If T is cv std::nullptr_t, the result is a null pointer constant.
  CastKind CK = T->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue;
  Res = ImplicitCastExpr::Create(Context, T, CK, E, nullptr, VK_RValue);

  // C11 6.3.2.1p2:
  //   ... if the lvalue has atomic type, the value has the non-atomic version
  //   of the type of the lvalue ...
  if (const AtomicType *Atomic = T->getAs<AtomicType>()) {
    T = Atomic->getValueType().getUnqualifiedType();
    Res = ImplicitCastExpr::Create(Context, T, CK_AtomicToNonAtomic, Res.get(),
                                   nullptr, VK_RValue);
  }

  return Res;
}

ExprResult Sema::DefaultFunctionArrayLvalueConversion(Expr *E, bool Diagnose) {
  ExprResult Res = DefaultFunctionArrayConversion(E, Diagnose);
  if (Res.isInvalid())
    return ExprError();
  Res = DefaultLvalueConversion(Res.get());
  if (Res.isInvalid())
    return ExprError();
  return Res;
}

/// CallExprUnaryConversions - a special case of an unary conversion
/// performed on a function designator of a call expression.
ExprResult Sema::CallExprUnaryConversions(Expr *E) {
  QualType Ty = E->getType();
  ExprResult Res = E;
  // Only do implicit cast for a function type, but not for a pointer
  // to function type.
  if (Ty->isFunctionType()) {
    Res = ImpCastExprToType(E, Context.getPointerType(Ty),
                            CK_FunctionToPointerDecay).get();
    if (Res.isInvalid())
      return ExprError();
  }
  Res = DefaultLvalueConversion(Res.get());
  if (Res.isInvalid())
    return ExprError();
  return Res.get();
}

/// UsualUnaryConversions - Performs various conversions that are common to most
/// operators (C99 6.3). The conversions of array and function types are
/// sometimes suppressed. For example, the array->pointer conversion doesn't
/// apply if the array is an argument to the sizeof or address (&) operators.
/// In these instances, this routine should *not* be called.
ExprResult Sema::UsualUnaryConversions(Expr *E) {
  // First, convert to an r-value.
  ExprResult Res = DefaultFunctionArrayLvalueConversion(E);
  if (Res.isInvalid())
    return ExprError();
  E = Res.get();

  QualType Ty = E->getType();
  assert(!Ty.isNull() && "UsualUnaryConversions - missing type");

  // Half FP have to be promoted to float unless it is natively supported
  if (Ty->isHalfType() && !getLangOpts().NativeHalfType)
    return ImpCastExprToType(Res.get(), Context.FloatTy, CK_FloatingCast);

  // Try to perform integral promotions if the object has a theoretically
  // promotable type.
  if (Ty->isIntegralOrUnscopedEnumerationType()) {
    // C99 6.3.1.1p2:
    //
    //   The following may be used in an expression wherever an int or
    //   unsigned int may be used:
    //     - an object or expression with an integer type whose integer
    //       conversion rank is less than or equal to the rank of int
    //       and unsigned int.
    //     - A bit-field of type _Bool, int, signed int, or unsigned int.
    //
    //   If an int can represent all values of the original type, the
    //   value is converted to an int; otherwise, it is converted to an
    //   unsigned int. These are called the integer promotions. All
    //   other types are unchanged by the integer promotions.

    QualType PTy = Context.isPromotableBitField(E);
    if (!PTy.isNull()) {
      E = ImpCastExprToType(E, PTy, CK_IntegralCast).get();
      return E;
    }
    if (Ty->isPromotableIntegerType()) {
      QualType PT = Context.getPromotedIntegerType(Ty);
      E = ImpCastExprToType(E, PT, CK_IntegralCast).get();
      return E;
    }
  }
  return E;
}

/// DefaultArgumentPromotion (C99 6.5.2.2p6). Used for function calls that
/// do not have a prototype. Arguments that have type float or __fp16
/// are promoted to double. All other argument types are converted by
/// UsualUnaryConversions().
ExprResult Sema::DefaultArgumentPromotion(Expr *E) {
  QualType Ty = E->getType();
  assert(!Ty.isNull() && "DefaultArgumentPromotion - missing type");

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

  // If this is a 'float'  or '__fp16' (CVR qualified or typedef)
  // promote to double.
  // Note that default argument promotion applies only to float (and
  // half/fp16); it does not apply to _Float16.
  const BuiltinType *BTy = Ty->getAs<BuiltinType>();
  if (BTy && (BTy->getKind() == BuiltinType::Half ||
              BTy->getKind() == BuiltinType::Float)) {
    if (getLangOpts().OpenCL &&
        !getOpenCLOptions().isEnabled("cl_khr_fp64")) {
        if (BTy->getKind() == BuiltinType::Half) {
            E = ImpCastExprToType(E, Context.FloatTy, CK_FloatingCast).get();
        }
    } else {
      E = ImpCastExprToType(E, Context.DoubleTy, CK_FloatingCast).get();
    }
  }

  // C++ performs lvalue-to-rvalue conversion as a default argument
  // promotion, even on class types, but note:
  //   C++11 [conv.lval]p2:
  //     When an lvalue-to-rvalue conversion occurs in an unevaluated
  //     operand or a subexpression thereof the value contained in the
  //     referenced object is not accessed. Otherwise, if the glvalue
  //     has a class type, the conversion copy-initializes a temporary
  //     of type T from the glvalue and the result of the conversion
  //     is a prvalue for the temporary.
  // FIXME: add some way to gate this entire thing for correctness in
  // potentially potentially evaluated contexts.
  if (getLangOpts().CPlusPlus && E->isGLValue() && !isUnevaluatedContext()) {
    ExprResult Temp = PerformCopyInitialization(
                       InitializedEntity::InitializeTemporary(E->getType()),
                                                E->getExprLoc(), E);
    if (Temp.isInvalid())
      return ExprError();
    E = Temp.get();
  }

  return E;
}

/// Determine the degree of POD-ness for an expression.
/// Incomplete types are considered POD, since this check can be performed
/// when we're in an unevaluated context.
Sema::VarArgKind Sema::isValidVarArgType(const QualType &Ty) {
  if (Ty->isIncompleteType()) {
    // C++11 [expr.call]p7:
    //   After these conversions, if the argument does not have arithmetic,
    //   enumeration, pointer, pointer to member, or class type, the program
    //   is ill-formed.
    //
    // Since we've already performed array-to-pointer and function-to-pointer
    // decay, the only such type in C++ is cv void. This also handles
    // initializer lists as variadic arguments.
    if (Ty->isVoidType())
      return VAK_Invalid;

    if (Ty->isObjCObjectType())
      return VAK_Invalid;
    return VAK_Valid;
  }

  if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
    return VAK_Invalid;

  if (Ty.isCXX98PODType(Context))
    return VAK_Valid;

  // C++11 [expr.call]p7:
  //   Passing a potentially-evaluated argument of class type (Clause 9)
  //   having a non-trivial copy constructor, a non-trivial move constructor,
  //   or a non-trivial destructor, with no corresponding parameter,
  //   is conditionally-supported with implementation-defined semantics.
  if (getLangOpts().CPlusPlus11 && !Ty->isDependentType())
    if (CXXRecordDecl *Record = Ty->getAsCXXRecordDecl())
      if (!Record->hasNonTrivialCopyConstructor() &&
          !Record->hasNonTrivialMoveConstructor() &&
          !Record->hasNonTrivialDestructor())
        return VAK_ValidInCXX11;

  if (getLangOpts().ObjCAutoRefCount && Ty->isObjCLifetimeType())
    return VAK_Valid;

  if (Ty->isObjCObjectType())
    return VAK_Invalid;

  if (getLangOpts().MSVCCompat)
    return VAK_MSVCUndefined;

  // FIXME: In C++11, these cases are conditionally-supported, meaning we're
  // permitted to reject them. We should consider doing so.
  return VAK_Undefined;
}

void Sema::checkVariadicArgument(const Expr *E, VariadicCallType CT) {
  // Don't allow one to pass an Objective-C interface to a vararg.
  const QualType &Ty = E->getType();
  VarArgKind VAK = isValidVarArgType(Ty);

  // Complain about passing non-POD types through varargs.
  switch (VAK) {
  case VAK_ValidInCXX11:
    DiagRuntimeBehavior(
        E->getBeginLoc(), nullptr,
        PDiag(diag::warn_cxx98_compat_pass_non_pod_arg_to_vararg) << Ty << CT);
    LLVM_FALLTHROUGH;
  case VAK_Valid:
    if (Ty->isRecordType()) {
      // This is unlikely to be what the user intended. If the class has a
      // 'c_str' member function, the user probably meant to call that.
      DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                          PDiag(diag::warn_pass_class_arg_to_vararg)
                              << Ty << CT << hasCStrMethod(E) << ".c_str()");
    }
    break;

  case VAK_Undefined:
  case VAK_MSVCUndefined:
    DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                        PDiag(diag::warn_cannot_pass_non_pod_arg_to_vararg)
                            << getLangOpts().CPlusPlus11 << Ty << CT);
    break;

  case VAK_Invalid:
    if (Ty.isDestructedType() == QualType::DK_nontrivial_c_struct)
      Diag(E->getBeginLoc(),
           diag::err_cannot_pass_non_trivial_c_struct_to_vararg)
          << Ty << CT;
    else if (Ty->isObjCObjectType())
      DiagRuntimeBehavior(E->getBeginLoc(), nullptr,
                          PDiag(diag::err_cannot_pass_objc_interface_to_vararg)
                              << Ty << CT);
    else
      Diag(E->getBeginLoc(), diag::err_cannot_pass_to_vararg)
          << isa<InitListExpr>(E) << Ty << CT;
    break;
  }
}

/// DefaultVariadicArgumentPromotion - Like DefaultArgumentPromotion, but
/// will create a trap if the resulting type is not a POD type.
ExprResult Sema::DefaultVariadicArgumentPromotion(Expr *E, VariadicCallType CT,
                                                  FunctionDecl *FDecl) {
  if (const BuiltinType *PlaceholderTy = E->getType()->getAsPlaceholderType()) {
    // Strip the unbridged-cast placeholder expression off, if applicable.
    if (PlaceholderTy->getKind() == BuiltinType::ARCUnbridgedCast &&
        (CT == VariadicMethod ||
         (FDecl && FDecl->hasAttr<CFAuditedTransferAttr>()))) {
      E = stripARCUnbridgedCast(E);

    // Otherwise, do normal placeholder checking.
    } else {
      ExprResult ExprRes = CheckPlaceholderExpr(E);
      if (ExprRes.isInvalid())
        return ExprError();
      E = ExprRes.get();
    }
  }

  ExprResult ExprRes = DefaultArgumentPromotion(E);
  if (ExprRes.isInvalid())
    return ExprError();
  E = ExprRes.get();

  // Diagnostics regarding non-POD argument types are
  // emitted along with format string checking in Sema::CheckFunctionCall().
  if (isValidVarArgType(E->getType()) == VAK_Undefined) {
    // Turn this into a trap.
    CXXScopeSpec SS;
    SourceLocation TemplateKWLoc;
    UnqualifiedId Name;
    Name.setIdentifier(PP.getIdentifierInfo("__builtin_trap"),
                       E->getBeginLoc());
    ExprResult TrapFn = ActOnIdExpression(TUScope, SS, TemplateKWLoc, Name,
                                          /*HasTrailingLParen=*/true,
                                          /*IsAddressOfOperand=*/false);
    if (TrapFn.isInvalid())
      return ExprError();

    ExprResult Call = BuildCallExpr(TUScope, TrapFn.get(), E->getBeginLoc(),
                                    None, E->getEndLoc());
    if (Call.isInvalid())
      return ExprError();

    ExprResult Comma =
        ActOnBinOp(TUScope, E->getBeginLoc(), tok::comma, Call.get(), E);
    if (Comma.isInvalid())
      return ExprError();
    return Comma.get();
  }

  if (!getLangOpts().CPlusPlus &&
      RequireCompleteType(E->getExprLoc(), E->getType(),
                          diag::err_call_incomplete_argument))
    return ExprError();

  return E;
}

/// Converts an integer to complex float type.  Helper function of
/// UsualArithmeticConversions()
///
/// \return false if the integer expression is an integer type and is
/// successfully converted to the complex type.
static bool handleIntegerToComplexFloatConversion(Sema &S, ExprResult &IntExpr,
                                                  ExprResult &ComplexExpr,
                                                  QualType IntTy,
                                                  QualType ComplexTy,
                                                  bool SkipCast) {
  if (IntTy->isComplexType() || IntTy->isRealFloatingType()) return true;
  if (SkipCast) return false;
  if (IntTy->isIntegerType()) {
    QualType fpTy = cast<ComplexType>(ComplexTy)->getElementType();
    IntExpr = S.ImpCastExprToType(IntExpr.get(), fpTy, CK_IntegralToFloating);
    IntExpr = S.ImpCastExprToType(IntExpr.get(), ComplexTy,
                                  CK_FloatingRealToComplex);
  } else {
    assert(IntTy->isComplexIntegerType());
    IntExpr = S.ImpCastExprToType(IntExpr.get(), ComplexTy,
                                  CK_IntegralComplexToFloatingComplex);
  }
  return false;
}

/// Handle arithmetic conversion with complex types.  Helper function of
/// UsualArithmeticConversions()
static QualType handleComplexFloatConversion(Sema &S, ExprResult &LHS,
                                             ExprResult &RHS, QualType LHSType,
                                             QualType RHSType,
                                             bool IsCompAssign) {
  // if we have an integer operand, the result is the complex type.
  if (!handleIntegerToComplexFloatConversion(S, RHS, LHS, RHSType, LHSType,
                                             /*skipCast*/false))
    return LHSType;
  if (!handleIntegerToComplexFloatConversion(S, LHS, RHS, LHSType, RHSType,
                                             /*skipCast*/IsCompAssign))
    return RHSType;

  // This handles complex/complex, complex/float, or float/complex.
  // When both operands are complex, the shorter operand is converted to the
  // type of the longer, and that is the type of the result. This corresponds
  // to what is done when combining two real floating-point operands.
  // The fun begins when size promotion occur across type domains.
  // From H&S 6.3.4: When one operand is complex and the other is a real
  // floating-point type, the less precise type is converted, within it's
  // real or complex domain, to the precision of the other type. For example,
  // when combining a "long double" with a "double _Complex", the
  // "double _Complex" is promoted to "long double _Complex".

  // Compute the rank of the two types, regardless of whether they are complex.
  int Order = S.Context.getFloatingTypeOrder(LHSType, RHSType);

  auto *LHSComplexType = dyn_cast<ComplexType>(LHSType);
  auto *RHSComplexType = dyn_cast<ComplexType>(RHSType);
  QualType LHSElementType =
      LHSComplexType ? LHSComplexType->getElementType() : LHSType;
  QualType RHSElementType =
      RHSComplexType ? RHSComplexType->getElementType() : RHSType;

  QualType ResultType = S.Context.getComplexType(LHSElementType);
  if (Order < 0) {
    // Promote the precision of the LHS if not an assignment.
    ResultType = S.Context.getComplexType(RHSElementType);
    if (!IsCompAssign) {
      if (LHSComplexType)
        LHS =
            S.ImpCastExprToType(LHS.get(), ResultType, CK_FloatingComplexCast);
      else
        LHS = S.ImpCastExprToType(LHS.get(), RHSElementType, CK_FloatingCast);
    }
  } else if (Order > 0) {
    // Promote the precision of the RHS.
    if (RHSComplexType)
      RHS = S.ImpCastExprToType(RHS.get(), ResultType, CK_FloatingComplexCast);
    else
      RHS = S.ImpCastExprToType(RHS.get(), LHSElementType, CK_FloatingCast);
  }
  return ResultType;
}

/// Handle arithmetic conversion from integer to float.  Helper function
/// of UsualArithmeticConversions()
static QualType handleIntToFloatConversion(Sema &S, ExprResult &FloatExpr,
                                           ExprResult &IntExpr,
                                           QualType FloatTy, QualType IntTy,
                                           bool ConvertFloat, bool ConvertInt) {
  if (IntTy->isIntegerType()) {
    if (ConvertInt)
      // Convert intExpr to the lhs floating point type.
      IntExpr = S.ImpCastExprToType(IntExpr.get(), FloatTy,
                                    CK_IntegralToFloating);
    return FloatTy;
  }

  // Convert both sides to the appropriate complex float.
  assert(IntTy->isComplexIntegerType());
  QualType result = S.Context.getComplexType(FloatTy);

  // _Complex int -> _Complex float
  if (ConvertInt)
    IntExpr = S.ImpCastExprToType(IntExpr.get(), result,
                                  CK_IntegralComplexToFloatingComplex);

  // float -> _Complex float
  if (ConvertFloat)
    FloatExpr = S.ImpCastExprToType(FloatExpr.get(), result,
                                    CK_FloatingRealToComplex);

  return result;
}

/// Handle arithmethic conversion with floating point types.  Helper
/// function of UsualArithmeticConversions()
static QualType handleFloatConversion(Sema &S, ExprResult &LHS,
                                      ExprResult &RHS, QualType LHSType,
                                      QualType RHSType, bool IsCompAssign) {
  bool LHSFloat = LHSType->isRealFloatingType();
  bool RHSFloat = RHSType->isRealFloatingType();

  // If we have two real floating types, convert the smaller operand
  // to the bigger result.
  if (LHSFloat && RHSFloat) {
    int order = S.Context.getFloatingTypeOrder(LHSType, RHSType);
    if (order > 0) {
      RHS = S.ImpCastExprToType(RHS.get(), LHSType, CK_FloatingCast);
      return LHSType;
    }

    assert(order < 0 && "illegal float comparison");
    if (!IsCompAssign)
      LHS = S.ImpCastExprToType(LHS.get(), RHSType, CK_FloatingCast);
    return RHSType;
  }

  if (LHSFloat) {
    // Half FP has to be promoted to float unless it is natively supported
    if (LHSType->isHalfType() && !S.getLangOpts().NativeHalfType)
      LHSType = S.Context.FloatTy;

    return handleIntToFloatConversion(S, LHS, RHS, LHSType, RHSType,
                                      /*ConvertFloat=*/!IsCompAssign,
                                      /*ConvertInt=*/ true);
  }
  assert(RHSFloat);
  return handleIntToFloatConversion(S, RHS, LHS, RHSType, LHSType,
                                    /*convertInt=*/ true,
                                    /*convertFloat=*/!IsCompAssign);
}

/// Diagnose attempts to convert between __float128 and long double if
/// there is no support for such conversion. Helper function of
/// UsualArithmeticConversions().
static bool unsupportedTypeConversion(const Sema &S, QualType LHSType,
                                      QualType RHSType) {
  /*  No issue converting if at least one of the types is not a floating point
      type or the two types have the same rank.
  */
  if (!LHSType->isFloatingType() || !RHSType->isFloatingType() ||
      S.Context.getFloatingTypeOrder(LHSType, RHSType) == 0)
    return false;

  assert(LHSType->isFloatingType() && RHSType->isFloatingType() &&
         "The remaining types must be floating point types.");

  auto *LHSComplex = LHSType->getAs<ComplexType>();
  auto *RHSComplex = RHSType->getAs<ComplexType>();

  QualType LHSElemType = LHSComplex ?
    LHSComplex->getElementType() : LHSType;
  QualType RHSElemType = RHSComplex ?
    RHSComplex->getElementType() : RHSType;

  // No issue if the two types have the same representation
  if (&S.Context.getFloatTypeSemantics(LHSElemType) ==
      &S.Context.getFloatTypeSemantics(RHSElemType))
    return false;

  bool Float128AndLongDouble = (LHSElemType == S.Context.Float128Ty &&
                                RHSElemType == S.Context.LongDoubleTy);
  Float128AndLongDouble |= (LHSElemType == S.Context.LongDoubleTy &&
                            RHSElemType == S.Context.Float128Ty);

  // We've handled the situation where __float128 and long double have the same
  // representation. We allow all conversions for all possible long double types
  // except PPC's double double.
  return Float128AndLongDouble &&
    (&S.Context.getFloatTypeSemantics(S.Context.LongDoubleTy) ==
     &llvm::APFloat::PPCDoubleDouble());
}

typedef ExprResult PerformCastFn(Sema &S, Expr *operand, QualType toType);

namespace {
/// These helper callbacks are placed in an anonymous namespace to
/// permit their use as function template parameters.
ExprResult doIntegralCast(Sema &S, Expr *op, QualType toType) {
  return S.ImpCastExprToType(op, toType, CK_IntegralCast);
}

ExprResult doComplexIntegralCast(Sema &S, Expr *op, QualType toType) {
  return S.ImpCastExprToType(op, S.Context.getComplexType(toType),
                             CK_IntegralComplexCast);
}
}

/// Handle integer arithmetic conversions.  Helper function of
/// UsualArithmeticConversions()
template <PerformCastFn doLHSCast, PerformCastFn doRHSCast>
static QualType handleIntegerConversion(Sema &S, ExprResult &LHS,
                                        ExprResult &RHS, QualType LHSType,
                                        QualType RHSType, bool IsCompAssign) {
  // The rules for this case are in C99 6.3.1.8
  int order = S.Context.getIntegerTypeOrder(LHSType, RHSType);
  bool LHSSigned = LHSType->hasSignedIntegerRepresentation();
  bool RHSSigned = RHSType->hasSignedIntegerRepresentation();
  if (LHSSigned == RHSSigned) {
    // Same signedness; use the higher-ranked type
    if (order >= 0) {
      RHS = (*doRHSCast)(S, RHS.get(), LHSType);
      return LHSType;
    } else if (!IsCompAssign)
      LHS = (*doLHSCast)(S, LHS.get(), RHSType);
    return RHSType;
  } else if (order != (LHSSigned ? 1 : -1)) {
    // The unsigned type has greater than or equal rank to the
    // signed type, so use the unsigned type
    if (RHSSigned) {
      RHS = (*doRHSCast)(S, RHS.get(), LHSType);
      return LHSType;
    } else if (!IsCompAssign)
      LHS = (*doLHSCast)(S, LHS.get(), RHSType);
    return RHSType;
  } else if (S.Context.getIntWidth(LHSType) != S.Context.getIntWidth(RHSType)) {
    // The two types are different widths; if we are here, that
    // means the signed type is larger than the unsigned type, so
    // use the signed type.
    if (LHSSigned) {
      RHS = (*doRHSCast)(S, RHS.get(), LHSType);
      return LHSType;
    } else if (!IsCompAssign)
      LHS = (*doLHSCast)(S, LHS.get(), RHSType);
    return RHSType;
  } else {
    // The signed type is higher-ranked than the unsigned type,
    // but isn't actually any bigger (like unsigned int and long
    // on most 32-bit systems).  Use the unsigned type corresponding
    // to the signed type.
    QualType result =
      S.Context.getCorrespondingUnsignedType(LHSSigned ? LHSType : RHSType);
    RHS = (*doRHSCast)(S, RHS.get(), result);
    if (!IsCompAssign)
      LHS = (*doLHSCast)(S, LHS.get(), result);
    return result;
  }
}

/// Handle conversions with GCC complex int extension.  Helper function
/// of UsualArithmeticConversions()
static QualType handleComplexIntConversion(Sema &S, ExprResult &LHS,
                                           ExprResult &RHS, QualType LHSType,
                                           QualType RHSType,
                                           bool IsCompAssign) {
  const ComplexType *LHSComplexInt = LHSType->getAsComplexIntegerType();
  const ComplexType *RHSComplexInt = RHSType->getAsComplexIntegerType();

  if (LHSComplexInt && RHSComplexInt) {
    QualType LHSEltType = LHSComplexInt->getElementType();
    QualType RHSEltType = RHSComplexInt->getElementType();
    QualType ScalarType =
      handleIntegerConversion<doComplexIntegralCast, doComplexIntegralCast>
        (S, LHS, RHS, LHSEltType, RHSEltType, IsCompAssign);

    return S.Context.getComplexType(ScalarType);
  }

  if (LHSComplexInt) {
    QualType LHSEltType = LHSComplexInt->getElementType();
    QualType ScalarType =
      handleIntegerConversion<doComplexIntegralCast, doIntegralCast>
        (S, LHS, RHS, LHSEltType, RHSType, IsCompAssign);
    QualType ComplexType = S.Context.getComplexType(ScalarType);
    RHS = S.ImpCastExprToType(RHS.get(), ComplexType,
                              CK_IntegralRealToComplex);

    return ComplexType;
  }

  assert(RHSComplexInt);

  QualType RHSEltType = RHSComplexInt->getElementType();
  QualType ScalarType =
    handleIntegerConversion<doIntegralCast, doComplexIntegralCast>
      (S, LHS, RHS, LHSType, RHSEltType, IsCompAssign);
  QualType ComplexType = S.Context.getComplexType(ScalarType);

  if (!IsCompAssign)
    LHS = S.ImpCastExprToType(LHS.get(), ComplexType,
                              CK_IntegralRealToComplex);
  return ComplexType;
}

/// Return the rank of a given fixed point or integer type. The value itself
/// doesn't matter, but the values must be increasing with proper increasing
/// rank as described in N1169 4.1.1.
static unsigned GetFixedPointRank(QualType Ty) {
  const auto *BTy = Ty->getAs<BuiltinType>();
  assert(BTy && "Expected a builtin type.");

  switch (BTy->getKind()) {
  case BuiltinType::ShortFract:
  case BuiltinType::UShortFract:
  case BuiltinType::SatShortFract:
  case BuiltinType::SatUShortFract:
    return 1;
  case BuiltinType::Fract:
  case BuiltinType::UFract:
  case BuiltinType::SatFract:
  case BuiltinType::SatUFract:
    return 2;
  case BuiltinType::LongFract:
  case BuiltinType::ULongFract:
  case BuiltinType::SatLongFract:
  case BuiltinType::SatULongFract:
    return 3;
  case BuiltinType::ShortAccum:
  case BuiltinType::UShortAccum:
  case BuiltinType::SatShortAccum:
  case BuiltinType::SatUShortAccum:
    return 4;
  case BuiltinType::Accum:
  case BuiltinType::UAccum:
  case BuiltinType::SatAccum:
  case BuiltinType::SatUAccum:
    return 5;
  case BuiltinType::LongAccum:
  case BuiltinType::ULongAccum:
  case BuiltinType::SatLongAccum:
  case BuiltinType::SatULongAccum:
    return 6;
  default:
    if (BTy->isInteger())
      return 0;
    llvm_unreachable("Unexpected fixed point or integer type");
  }
}

/// handleFixedPointConversion - Fixed point operations between fixed
/// point types and integers or other fixed point types do not fall under
/// usual arithmetic conversion since these conversions could result in loss
/// of precsision (N1169 4.1.4). These operations should be calculated with
/// the full precision of their result type (N1169 4.1.6.2.1).
static QualType handleFixedPointConversion(Sema &S, QualType LHSTy,
                                           QualType RHSTy) {
  assert((LHSTy->isFixedPointType() || RHSTy->isFixedPointType()) &&
         "Expected at least one of the operands to be a fixed point type");
  assert((LHSTy->isFixedPointOrIntegerType() ||
          RHSTy->isFixedPointOrIntegerType()) &&
         "Special fixed point arithmetic operation conversions are only "
         "applied to ints or other fixed point types");

  // If one operand has signed fixed-point type and the other operand has
  // unsigned fixed-point type, then the unsigned fixed-point operand is
  // converted to its corresponding signed fixed-point type and the resulting
  // type is the type of the converted operand.
  if (RHSTy->isSignedFixedPointType() && LHSTy->isUnsignedFixedPointType())
    LHSTy = S.Context.getCorrespondingSignedFixedPointType(LHSTy);
  else if (RHSTy->isUnsignedFixedPointType() && LHSTy->isSignedFixedPointType())
    RHSTy = S.Context.getCorrespondingSignedFixedPointType(RHSTy);

  // The result type is the type with the highest rank, whereby a fixed-point
  // conversion rank is always greater than an integer conversion rank; if the
  // type of either of the operands is a saturating fixedpoint type, the result
  // type shall be the saturating fixed-point type corresponding to the type
  // with the highest rank; the resulting value is converted (taking into
  // account rounding and overflow) to the precision of the resulting type.
  // Same ranks between signed and unsigned types are resolved earlier, so both
  // types are either signed or both unsigned at this point.
  unsigned LHSTyRank = GetFixedPointRank(LHSTy);
  unsigned RHSTyRank = GetFixedPointRank(RHSTy);

  QualType ResultTy = LHSTyRank > RHSTyRank ? LHSTy : RHSTy;

  if (LHSTy->isSaturatedFixedPointType() || RHSTy->isSaturatedFixedPointType())
    ResultTy = S.Context.getCorrespondingSaturatedType(ResultTy);

  return ResultTy;
}

/// UsualArithmeticConversions - Performs various conversions that are common to
/// binary operators (C99 6.3.1.8). If both operands aren't arithmetic, this
/// routine returns the first non-arithmetic type found. The client is
/// responsible for emitting appropriate error diagnostics.
QualType Sema::UsualArithmeticConversions(ExprResult &LHS, ExprResult &RHS,
                                          bool IsCompAssign) {
  if (!IsCompAssign) {
    LHS = UsualUnaryConversions(LHS.get());
    if (LHS.isInvalid())
      return QualType();
  }

  RHS = UsualUnaryConversions(RHS.get());
  if (RHS.isInvalid())
    return QualType();

  // For conversion purposes, we ignore any qualifiers.
  // For example, "const float" and "float" are equivalent.
  QualType LHSType =
    Context.getCanonicalType(LHS.get()->getType()).getUnqualifiedType();
  QualType RHSType =
    Context.getCanonicalType(RHS.get()->getType()).getUnqualifiedType();

  // For conversion purposes, we ignore any atomic qualifier on the LHS.
  if (const AtomicType *AtomicLHS = LHSType->getAs<AtomicType>())
    LHSType = AtomicLHS->getValueType();

  // If both types are identical, no conversion is needed.
  if (LHSType == RHSType)
    return LHSType;

  // If either side is a non-arithmetic type (e.g. a pointer), we are done.
  // The caller can deal with this (e.g. pointer + int).
  if (!LHSType->isArithmeticType() || !RHSType->isArithmeticType())
    return QualType();

  // Apply unary and bitfield promotions to the LHS's type.
  QualType LHSUnpromotedType = LHSType;
  if (LHSType->isPromotableIntegerType())
    LHSType = Context.getPromotedIntegerType(LHSType);
  QualType LHSBitfieldPromoteTy = Context.isPromotableBitField(LHS.get());
  if (!LHSBitfieldPromoteTy.isNull())
    LHSType = LHSBitfieldPromoteTy;
  if (LHSType != LHSUnpromotedType && !IsCompAssign)
    LHS = ImpCastExprToType(LHS.get(), LHSType, CK_IntegralCast);

  // If both types are identical, no conversion is needed.
  if (LHSType == RHSType)
    return LHSType;

  // At this point, we have two different arithmetic types.

  // Diagnose attempts to convert between __float128 and long double where
  // such conversions currently can't be handled.
  if (unsupportedTypeConversion(*this, LHSType, RHSType))
    return QualType();

  // Handle complex types first (C99 6.3.1.8p1).
  if (LHSType->isComplexType() || RHSType->isComplexType())
    return handleComplexFloatConversion(*this, LHS, RHS, LHSType, RHSType,
                                        IsCompAssign);

  // Now handle "real" floating types (i.e. float, double, long double).
  if (LHSType->isRealFloatingType() || RHSType->isRealFloatingType())
    return handleFloatConversion(*this, LHS, RHS, LHSType, RHSType,
                                 IsCompAssign);

  // Handle GCC complex int extension.
  if (LHSType->isComplexIntegerType() || RHSType->isComplexIntegerType())
    return handleComplexIntConversion(*this, LHS, RHS, LHSType, RHSType,
                                      IsCompAssign);

  if (LHSType->isFixedPointType() || RHSType->isFixedPointType())
    return handleFixedPointConversion(*this, LHSType, RHSType);

  // Finally, we have two differing integer types.
  return handleIntegerConversion<doIntegralCast, doIntegralCast>
           (*this, LHS, RHS, LHSType, RHSType, IsCompAssign);
}

//===----------------------------------------------------------------------===//
//  Semantic Analysis for various Expression Types
//===----------------------------------------------------------------------===//


ExprResult
Sema::ActOnGenericSelectionExpr(SourceLocation KeyLoc,
                                SourceLocation DefaultLoc,
                                SourceLocation RParenLoc,
                                Expr *ControllingExpr,
                                ArrayRef<ParsedType> ArgTypes,
                                ArrayRef<Expr *> ArgExprs) {
  unsigned NumAssocs = ArgTypes.size();
  assert(NumAssocs == ArgExprs.size());

  TypeSourceInfo **Types = new TypeSourceInfo*[NumAssocs];
  for (unsigned i = 0; i < NumAssocs; ++i) {
    if (ArgTypes[i])
      (void) GetTypeFromParser(ArgTypes[i], &Types[i]);
    else
      Types[i] = nullptr;
  }

  ExprResult ER = CreateGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
                                             ControllingExpr,
                                             llvm::makeArrayRef(Types, NumAssocs),
                                             ArgExprs);
  delete [] Types;
  return ER;
}

ExprResult
Sema::CreateGenericSelectionExpr(SourceLocation KeyLoc,
                                 SourceLocation DefaultLoc,
                                 SourceLocation RParenLoc,
                                 Expr *ControllingExpr,
                                 ArrayRef<TypeSourceInfo *> Types,
                                 ArrayRef<Expr *> Exprs) {
  unsigned NumAssocs = Types.size();
  assert(NumAssocs == Exprs.size());

  // Decay and strip qualifiers for the controlling expression type, and handle
  // placeholder type replacement. See committee discussion from WG14 DR423.
  {
    EnterExpressionEvaluationContext Unevaluated(
        *this, Sema::ExpressionEvaluationContext::Unevaluated);
    ExprResult R = DefaultFunctionArrayLvalueConversion(ControllingExpr);
    if (R.isInvalid())
      return ExprError();
    ControllingExpr = R.get();
  }

  // The controlling expression is an unevaluated operand, so side effects are
  // likely unintended.
  if (!inTemplateInstantiation() &&
      ControllingExpr->HasSideEffects(Context, false))
    Diag(ControllingExpr->getExprLoc(),
         diag::warn_side_effects_unevaluated_context);

  bool TypeErrorFound = false,
       IsResultDependent = ControllingExpr->isTypeDependent(),
       ContainsUnexpandedParameterPack
         = ControllingExpr->containsUnexpandedParameterPack();

  for (unsigned i = 0; i < NumAssocs; ++i) {
    if (Exprs[i]->containsUnexpandedParameterPack())
      ContainsUnexpandedParameterPack = true;

    if (Types[i]) {
      if (Types[i]->getType()->containsUnexpandedParameterPack())
        ContainsUnexpandedParameterPack = true;

      if (Types[i]->getType()->isDependentType()) {
        IsResultDependent = true;
      } else {
        // C11 6.5.1.1p2 "The type name in a generic association shall specify a
        // complete object type other than a variably modified type."
        unsigned D = 0;
        if (Types[i]->getType()->isIncompleteType())
          D = diag::err_assoc_type_incomplete;
        else if (!Types[i]->getType()->isObjectType())
          D = diag::err_assoc_type_nonobject;
        else if (Types[i]->getType()->isVariablyModifiedType())
          D = diag::err_assoc_type_variably_modified;

        if (D != 0) {
          Diag(Types[i]->getTypeLoc().getBeginLoc(), D)
            << Types[i]->getTypeLoc().getSourceRange()
            << Types[i]->getType();
          TypeErrorFound = true;
        }

        // C11 6.5.1.1p2 "No two generic associations in the same generic
        // selection shall specify compatible types."
        for (unsigned j = i+1; j < NumAssocs; ++j)
          if (Types[j] && !Types[j]->getType()->isDependentType() &&
              Context.typesAreCompatible(Types[i]->getType(),
                                         Types[j]->getType())) {
            Diag(Types[j]->getTypeLoc().getBeginLoc(),
                 diag::err_assoc_compatible_types)
              << Types[j]->getTypeLoc().getSourceRange()
              << Types[j]->getType()
              << Types[i]->getType();
            Diag(Types[i]->getTypeLoc().getBeginLoc(),
                 diag::note_compat_assoc)
              << Types[i]->getTypeLoc().getSourceRange()
              << Types[i]->getType();
            TypeErrorFound = true;
          }
      }
    }
  }
  if (TypeErrorFound)
    return ExprError();

  // If we determined that the generic selection is result-dependent, don't
  // try to compute the result expression.
  if (IsResultDependent)
    return GenericSelectionExpr::Create(Context, KeyLoc, ControllingExpr, Types,
                                        Exprs, DefaultLoc, RParenLoc,
                                        ContainsUnexpandedParameterPack);

  SmallVector<unsigned, 1> CompatIndices;
  unsigned DefaultIndex = -1U;
  for (unsigned i = 0; i < NumAssocs; ++i) {
    if (!Types[i])
      DefaultIndex = i;
    else if (Context.typesAreCompatible(ControllingExpr->getType(),
                                        Types[i]->getType()))
      CompatIndices.push_back(i);
  }

  // C11 6.5.1.1p2 "The controlling expression of a generic selection shall have
  // type compatible with at most one of the types named in its generic
  // association list."
  if (CompatIndices.size() > 1) {
    // We strip parens here because the controlling expression is typically
    // parenthesized in macro definitions.
    ControllingExpr = ControllingExpr->IgnoreParens();
    Diag(ControllingExpr->getBeginLoc(), diag::err_generic_sel_multi_match)
        << ControllingExpr->getSourceRange() << ControllingExpr->getType()
        << (unsigned)CompatIndices.size();
    for (unsigned I : CompatIndices) {
      Diag(Types[I]->getTypeLoc().getBeginLoc(),
           diag::note_compat_assoc)
        << Types[I]->getTypeLoc().getSourceRange()
        << Types[I]->getType();
    }
    return ExprError();
  }

  // C11 6.5.1.1p2 "If a generic selection has no default generic association,
  // its controlling expression shall have type compatible with exactly one of
  // the types named in its generic association list."
  if (DefaultIndex == -1U && CompatIndices.size() == 0) {
    // We strip parens here because the controlling expression is typically
    // parenthesized in macro definitions.
    ControllingExpr = ControllingExpr->IgnoreParens();
    Diag(ControllingExpr->getBeginLoc(), diag::err_generic_sel_no_match)
        << ControllingExpr->getSourceRange() << ControllingExpr->getType();
    return ExprError();
  }

  // C11 6.5.1.1p3 "If a generic selection has a generic association with a
  // type name that is compatible with the type of the controlling expression,
  // then the result expression of the generic selection is the expression
  // in that generic association. Otherwise, the result expression of the
  // generic selection is the expression in the default generic association."
  unsigned ResultIndex =
    CompatIndices.size() ? CompatIndices[0] : DefaultIndex;

  return GenericSelectionExpr::Create(
      Context, KeyLoc, ControllingExpr, Types, Exprs, DefaultLoc, RParenLoc,
      ContainsUnexpandedParameterPack, ResultIndex);
}

/// getUDSuffixLoc - Create a SourceLocation for a ud-suffix, given the
/// location of the token and the offset of the ud-suffix within it.
static SourceLocation getUDSuffixLoc(Sema &S, SourceLocation TokLoc,
                                     unsigned Offset) {
  return Lexer::AdvanceToTokenCharacter(TokLoc, Offset, S.getSourceManager(),
                                        S.getLangOpts());
}

/// BuildCookedLiteralOperatorCall - A user-defined literal was found. Look up
/// the corresponding cooked (non-raw) literal operator, and build a call to it.
static ExprResult BuildCookedLiteralOperatorCall(Sema &S, Scope *Scope,
                                                 IdentifierInfo *UDSuffix,
                                                 SourceLocation UDSuffixLoc,
                                                 ArrayRef<Expr*> Args,
                                                 SourceLocation LitEndLoc) {
  assert(Args.size() <= 2 && "too many arguments for literal operator");

  QualType ArgTy[2];
  for (unsigned ArgIdx = 0; ArgIdx != Args.size(); ++ArgIdx) {
    ArgTy[ArgIdx] = Args[ArgIdx]->getType();
    if (ArgTy[ArgIdx]->isArrayType())
      ArgTy[ArgIdx] = S.Context.getArrayDecayedType(ArgTy[ArgIdx]);
  }

  DeclarationName OpName =
    S.Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
  DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
  OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);

  LookupResult R(S, OpName, UDSuffixLoc, Sema::LookupOrdinaryName);
  if (S.LookupLiteralOperator(Scope, R, llvm::makeArrayRef(ArgTy, Args.size()),
                              /*AllowRaw*/ false, /*AllowTemplate*/ false,
                              /*AllowStringTemplate*/ false,
                              /*DiagnoseMissing*/ true) == Sema::LOLR_Error)
    return ExprError();

  return S.BuildLiteralOperatorCall(R, OpNameInfo, Args, LitEndLoc);
}

/// ActOnStringLiteral - The specified tokens were lexed as pasted string
/// fragments (e.g. "foo" "bar" L"baz").  The result string has to handle string
/// concatenation ([C99 5.1.1.2, translation phase #6]), so it may come from
/// multiple tokens.  However, the common case is that StringToks points to one
/// string.
///
ExprResult
Sema::ActOnStringLiteral(ArrayRef<Token> StringToks, Scope *UDLScope) {
  assert(!StringToks.empty() && "Must have at least one string!");

  StringLiteralParser Literal(StringToks, PP);
  if (Literal.hadError)
    return ExprError();

  SmallVector<SourceLocation, 4> StringTokLocs;
  for (const Token &Tok : StringToks)
    StringTokLocs.push_back(Tok.getLocation());

  QualType CharTy = Context.CharTy;
  StringLiteral::StringKind Kind = StringLiteral::Ascii;
  if (Literal.isWide()) {
    CharTy = Context.getWideCharType();
    Kind = StringLiteral::Wide;
  } else if (Literal.isUTF8()) {
    if (getLangOpts().Char8)
      CharTy = Context.Char8Ty;
    Kind = StringLiteral::UTF8;
  } else if (Literal.isUTF16()) {
    CharTy = Context.Char16Ty;
    Kind = StringLiteral::UTF16;
  } else if (Literal.isUTF32()) {
    CharTy = Context.Char32Ty;
    Kind = StringLiteral::UTF32;
  } else if (Literal.isPascal()) {
    CharTy = Context.UnsignedCharTy;
  }

  // Warn on initializing an array of char from a u8 string literal; this
  // becomes ill-formed in C++2a.
  if (getLangOpts().CPlusPlus && !getLangOpts().CPlusPlus2a &&
      !getLangOpts().Char8 && Kind == StringLiteral::UTF8) {
    Diag(StringTokLocs.front(), diag::warn_cxx2a_compat_utf8_string);

    // Create removals for all 'u8' prefixes in the string literal(s). This
    // ensures C++2a compatibility (but may change the program behavior when
    // built by non-Clang compilers for which the execution character set is
    // not always UTF-8).
    auto RemovalDiag = PDiag(diag::note_cxx2a_compat_utf8_string_remove_u8);
    SourceLocation RemovalDiagLoc;
    for (const Token &Tok : StringToks) {
      if (Tok.getKind() == tok::utf8_string_literal) {
        if (RemovalDiagLoc.isInvalid())
          RemovalDiagLoc = Tok.getLocation();
        RemovalDiag << FixItHint::CreateRemoval(CharSourceRange::getCharRange(
            Tok.getLocation(),
            Lexer::AdvanceToTokenCharacter(Tok.getLocation(), 2,
                                           getSourceManager(), getLangOpts())));
      }
    }
    Diag(RemovalDiagLoc, RemovalDiag);
  }

  QualType StrTy =
      Context.getStringLiteralArrayType(CharTy, Literal.GetNumStringChars());

  // Pass &StringTokLocs[0], StringTokLocs.size() to factory!
  StringLiteral *Lit = StringLiteral::Create(Context, Literal.GetString(),
                                             Kind, Literal.Pascal, StrTy,
                                             &StringTokLocs[0],
                                             StringTokLocs.size());
  if (Literal.getUDSuffix().empty())
    return Lit;

  // We're building a user-defined literal.
  IdentifierInfo *UDSuffix = &Context.Idents.get(Literal.getUDSuffix());
  SourceLocation UDSuffixLoc =
    getUDSuffixLoc(*this, StringTokLocs[Literal.getUDSuffixToken()],
                   Literal.getUDSuffixOffset());

  // Make sure we're allowed user-defined literals here.
  if (!UDLScope)
    return ExprError(Diag(UDSuffixLoc, diag::err_invalid_string_udl));

  // C++11 [lex.ext]p5: The literal L is treated as a call of the form
  //   operator "" X (str, len)
  QualType SizeType = Context.getSizeType();

  DeclarationName OpName =
    Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
  DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
  OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);

  QualType ArgTy[] = {
    Context.getArrayDecayedType(StrTy), SizeType
  };

  LookupResult R(*this, OpName, UDSuffixLoc, LookupOrdinaryName);
  switch (LookupLiteralOperator(UDLScope, R, ArgTy,
                                /*AllowRaw*/ false, /*AllowTemplate*/ false,
                                /*AllowStringTemplate*/ true,
                                /*DiagnoseMissing*/ true)) {

  case LOLR_Cooked: {
    llvm::APInt Len(Context.getIntWidth(SizeType), Literal.GetNumStringChars());
    IntegerLiteral *LenArg = IntegerLiteral::Create(Context, Len, SizeType,
                                                    StringTokLocs[0]);
    Expr *Args[] = { Lit, LenArg };

    return BuildLiteralOperatorCall(R, OpNameInfo, Args, StringTokLocs.back());
  }

  case LOLR_StringTemplate: {
    TemplateArgumentListInfo ExplicitArgs;

    unsigned CharBits = Context.getIntWidth(CharTy);
    bool CharIsUnsigned = CharTy->isUnsignedIntegerType();
    llvm::APSInt Value(CharBits, CharIsUnsigned);

    TemplateArgument TypeArg(CharTy);
    TemplateArgumentLocInfo TypeArgInfo(Context.getTrivialTypeSourceInfo(CharTy));
    ExplicitArgs.addArgument(TemplateArgumentLoc(TypeArg, TypeArgInfo));

    for (unsigned I = 0, N = Lit->getLength(); I != N; ++I) {
      Value = Lit->getCodeUnit(I);
      TemplateArgument Arg(Context, Value, CharTy);
      TemplateArgumentLocInfo ArgInfo;
      ExplicitArgs.addArgument(TemplateArgumentLoc(Arg, ArgInfo));
    }
    return BuildLiteralOperatorCall(R, OpNameInfo, None, StringTokLocs.back(),
                                    &ExplicitArgs);
  }
  case LOLR_Raw:
  case LOLR_Template:
  case LOLR_ErrorNoDiagnostic:
    llvm_unreachable("unexpected literal operator lookup result");
  case LOLR_Error:
    return ExprError();
  }
  llvm_unreachable("unexpected literal operator lookup result");
}

DeclRefExpr *
Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                       SourceLocation Loc,
                       const CXXScopeSpec *SS) {
  DeclarationNameInfo NameInfo(D->getDeclName(), Loc);
  return BuildDeclRefExpr(D, Ty, VK, NameInfo, SS);
}

DeclRefExpr *
Sema::BuildDeclRefExpr(ValueDecl *D, QualType Ty, ExprValueKind VK,
                       const