SemaDeclAttr.cpp

//===--- SemaDeclAttr.cpp - Declaration Attribute Handling ----------------===//
//
// 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 decl-related attribute processing.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTConsumer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/ASTMutationListener.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/Mangle.h"
#include "clang/AST/RecursiveASTVisitor.h"
#include "clang/AST/Type.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Basic/DarwinSDKInfo.h"
#include "clang/Basic/HLSLRuntime.h"
#include "clang/Basic/LangOptions.h"
#include "clang/Basic/SourceLocation.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetBuiltins.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Lex/Preprocessor.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/DelayedDiagnostic.h"
#include "clang/Sema/Initialization.h"
#include "clang/Sema/Lookup.h"
#include "clang/Sema/ParsedAttr.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/ScopeInfo.h"
#include "clang/Sema/SemaInternal.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/Assumptions.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/Support/Error.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <optional>

using namespace clang;
using namespace sema;

namespace AttributeLangSupport {
  enum LANG {
    C,
    Cpp,
    ObjC
  };
} // end namespace AttributeLangSupport

//===----------------------------------------------------------------------===//
//  Helper functions
//===----------------------------------------------------------------------===//

/// isFunctionOrMethod - Return true if the given decl has function
/// type (function or function-typed variable) or an Objective-C
/// method.
static bool isFunctionOrMethod(const Decl *D) {
  return (D->getFunctionType() != nullptr) || isa<ObjCMethodDecl>(D);
}

/// Return true if the given decl has function type (function or
/// function-typed variable) or an Objective-C method or a block.
static bool isFunctionOrMethodOrBlock(const Decl *D) {
  return isFunctionOrMethod(D) || isa<BlockDecl>(D);
}

/// Return true if the given decl has a declarator that should have
/// been processed by Sema::GetTypeForDeclarator.
static bool hasDeclarator(const Decl *D) {
  // In some sense, TypedefDecl really *ought* to be a DeclaratorDecl.
  return isa<DeclaratorDecl>(D) || isa<BlockDecl>(D) || isa<TypedefNameDecl>(D) ||
         isa<ObjCPropertyDecl>(D);
}

/// hasFunctionProto - Return true if the given decl has a argument
/// information. This decl should have already passed
/// isFunctionOrMethod or isFunctionOrMethodOrBlock.
static bool hasFunctionProto(const Decl *D) {
  if (const FunctionType *FnTy = D->getFunctionType())
    return isa<FunctionProtoType>(FnTy);
  return isa<ObjCMethodDecl>(D) || isa<BlockDecl>(D);
}

/// getFunctionOrMethodNumParams - Return number of function or method
/// parameters. It is an error to call this on a K&R function (use
/// hasFunctionProto first).
static unsigned getFunctionOrMethodNumParams(const Decl *D) {
  if (const FunctionType *FnTy = D->getFunctionType())
    return cast<FunctionProtoType>(FnTy)->getNumParams();
  if (const auto *BD = dyn_cast<BlockDecl>(D))
    return BD->getNumParams();
  return cast<ObjCMethodDecl>(D)->param_size();
}

static const ParmVarDecl *getFunctionOrMethodParam(const Decl *D,
                                                   unsigned Idx) {
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    return FD->getParamDecl(Idx);
  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
    return MD->getParamDecl(Idx);
  if (const auto *BD = dyn_cast<BlockDecl>(D))
    return BD->getParamDecl(Idx);
  return nullptr;
}

static QualType getFunctionOrMethodParamType(const Decl *D, unsigned Idx) {
  if (const FunctionType *FnTy = D->getFunctionType())
    return cast<FunctionProtoType>(FnTy)->getParamType(Idx);
  if (const auto *BD = dyn_cast<BlockDecl>(D))
    return BD->getParamDecl(Idx)->getType();

  return cast<ObjCMethodDecl>(D)->parameters()[Idx]->getType();
}

static SourceRange getFunctionOrMethodParamRange(const Decl *D, unsigned Idx) {
  if (auto *PVD = getFunctionOrMethodParam(D, Idx))
    return PVD->getSourceRange();
  return SourceRange();
}

static QualType getFunctionOrMethodResultType(const Decl *D) {
  if (const FunctionType *FnTy = D->getFunctionType())
    return FnTy->getReturnType();
  return cast<ObjCMethodDecl>(D)->getReturnType();
}

static SourceRange getFunctionOrMethodResultSourceRange(const Decl *D) {
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    return FD->getReturnTypeSourceRange();
  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
    return MD->getReturnTypeSourceRange();
  return SourceRange();
}

static bool isFunctionOrMethodVariadic(const Decl *D) {
  if (const FunctionType *FnTy = D->getFunctionType())
    return cast<FunctionProtoType>(FnTy)->isVariadic();
  if (const auto *BD = dyn_cast<BlockDecl>(D))
    return BD->isVariadic();
  return cast<ObjCMethodDecl>(D)->isVariadic();
}

static bool isInstanceMethod(const Decl *D) {
  if (const auto *MethodDecl = dyn_cast<CXXMethodDecl>(D))
    return MethodDecl->isInstance();
  return false;
}

static inline bool isNSStringType(QualType T, ASTContext &Ctx,
                                  bool AllowNSAttributedString = false) {
  const auto *PT = T->getAs<ObjCObjectPointerType>();
  if (!PT)
    return false;

  ObjCInterfaceDecl *Cls = PT->getObjectType()->getInterface();
  if (!Cls)
    return false;

  IdentifierInfo* ClsName = Cls->getIdentifier();

  if (AllowNSAttributedString &&
      ClsName == &Ctx.Idents.get("NSAttributedString"))
    return true;
  // FIXME: Should we walk the chain of classes?
  return ClsName == &Ctx.Idents.get("NSString") ||
         ClsName == &Ctx.Idents.get("NSMutableString");
}

static inline bool isCFStringType(QualType T, ASTContext &Ctx) {
  const auto *PT = T->getAs<PointerType>();
  if (!PT)
    return false;

  const auto *RT = PT->getPointeeType()->getAs<RecordType>();
  if (!RT)
    return false;

  const RecordDecl *RD = RT->getDecl();
  if (RD->getTagKind() != TTK_Struct)
    return false;

  return RD->getIdentifier() == &Ctx.Idents.get("__CFString");
}

static unsigned getNumAttributeArgs(const ParsedAttr &AL) {
  // FIXME: Include the type in the argument list.
  return AL.getNumArgs() + AL.hasParsedType();
}

/// A helper function to provide Attribute Location for the Attr types
/// AND the ParsedAttr.
template <typename AttrInfo>
static std::enable_if_t<std::is_base_of_v<Attr, AttrInfo>, SourceLocation>
getAttrLoc(const AttrInfo &AL) {
  return AL.getLocation();
}
static SourceLocation getAttrLoc(const ParsedAttr &AL) { return AL.getLoc(); }

/// If Expr is a valid integer constant, get the value of the integer
/// expression and return success or failure. May output an error.
///
/// Negative argument is implicitly converted to unsigned, unless
/// \p StrictlyUnsigned is true.
template <typename AttrInfo>
static bool checkUInt32Argument(Sema &S, const AttrInfo &AI, const Expr *Expr,
                                uint32_t &Val, unsigned Idx = UINT_MAX,
                                bool StrictlyUnsigned = false) {
  std::optional<llvm::APSInt> I = llvm::APSInt(32);
  if (Expr->isTypeDependent() ||
      !(I = Expr->getIntegerConstantExpr(S.Context))) {
    if (Idx != UINT_MAX)
      S.Diag(getAttrLoc(AI), diag::err_attribute_argument_n_type)
          << &AI << Idx << AANT_ArgumentIntegerConstant
          << Expr->getSourceRange();
    else
      S.Diag(getAttrLoc(AI), diag::err_attribute_argument_type)
          << &AI << AANT_ArgumentIntegerConstant << Expr->getSourceRange();
    return false;
  }

  if (!I->isIntN(32)) {
    S.Diag(Expr->getExprLoc(), diag::err_ice_too_large)
        << toString(*I, 10, false) << 32 << /* Unsigned */ 1;
    return false;
  }

  if (StrictlyUnsigned && I->isSigned() && I->isNegative()) {
    S.Diag(getAttrLoc(AI), diag::err_attribute_requires_positive_integer)
        << &AI << /*non-negative*/ 1;
    return false;
  }

  Val = (uint32_t)I->getZExtValue();
  return true;
}

/// Wrapper around checkUInt32Argument, with an extra check to be sure
/// that the result will fit into a regular (signed) int. All args have the same
/// purpose as they do in checkUInt32Argument.
template <typename AttrInfo>
static bool checkPositiveIntArgument(Sema &S, const AttrInfo &AI, const Expr *Expr,
                                     int &Val, unsigned Idx = UINT_MAX) {
  uint32_t UVal;
  if (!checkUInt32Argument(S, AI, Expr, UVal, Idx))
    return false;

  if (UVal > (uint32_t)std::numeric_limits<int>::max()) {
    llvm::APSInt I(32); // for toString
    I = UVal;
    S.Diag(Expr->getExprLoc(), diag::err_ice_too_large)
        << toString(I, 10, false) << 32 << /* Unsigned */ 0;
    return false;
  }

  Val = UVal;
  return true;
}

/// Diagnose mutually exclusive attributes when present on a given
/// declaration. Returns true if diagnosed.
template <typename AttrTy>
static bool checkAttrMutualExclusion(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (const auto *A = D->getAttr<AttrTy>()) {
    S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
        << AL << A
        << (AL.isRegularKeywordAttribute() || A->isRegularKeywordAttribute());
    S.Diag(A->getLocation(), diag::note_conflicting_attribute);
    return true;
  }
  return false;
}

template <typename AttrTy>
static bool checkAttrMutualExclusion(Sema &S, Decl *D, const Attr &AL) {
  if (const auto *A = D->getAttr<AttrTy>()) {
    S.Diag(AL.getLocation(), diag::err_attributes_are_not_compatible)
        << &AL << A
        << (AL.isRegularKeywordAttribute() || A->isRegularKeywordAttribute());
    S.Diag(A->getLocation(), diag::note_conflicting_attribute);
    return true;
  }
  return false;
}

/// Check if IdxExpr is a valid parameter index for a function or
/// instance method D.  May output an error.
///
/// \returns true if IdxExpr is a valid index.
template <typename AttrInfo>
static bool checkFunctionOrMethodParameterIndex(
    Sema &S, const Decl *D, const AttrInfo &AI, unsigned AttrArgNum,
    const Expr *IdxExpr, ParamIdx &Idx, bool CanIndexImplicitThis = false) {
  assert(isFunctionOrMethodOrBlock(D));

  // In C++ the implicit 'this' function parameter also counts.
  // Parameters are counted from one.
  bool HP = hasFunctionProto(D);
  bool HasImplicitThisParam = isInstanceMethod(D);
  bool IV = HP && isFunctionOrMethodVariadic(D);
  unsigned NumParams =
      (HP ? getFunctionOrMethodNumParams(D) : 0) + HasImplicitThisParam;

  std::optional<llvm::APSInt> IdxInt;
  if (IdxExpr->isTypeDependent() ||
      !(IdxInt = IdxExpr->getIntegerConstantExpr(S.Context))) {
    S.Diag(getAttrLoc(AI), diag::err_attribute_argument_n_type)
        << &AI << AttrArgNum << AANT_ArgumentIntegerConstant
        << IdxExpr->getSourceRange();
    return false;
  }

  unsigned IdxSource = IdxInt->getLimitedValue(UINT_MAX);
  if (IdxSource < 1 || (!IV && IdxSource > NumParams)) {
    S.Diag(getAttrLoc(AI), diag::err_attribute_argument_out_of_bounds)
        << &AI << AttrArgNum << IdxExpr->getSourceRange();
    return false;
  }
  if (HasImplicitThisParam && !CanIndexImplicitThis) {
    if (IdxSource == 1) {
      S.Diag(getAttrLoc(AI), diag::err_attribute_invalid_implicit_this_argument)
          << &AI << IdxExpr->getSourceRange();
      return false;
    }
  }

  Idx = ParamIdx(IdxSource, D);
  return true;
}

/// Check if the argument \p E is a ASCII string literal. If not emit an error
/// and return false, otherwise set \p Str to the value of the string literal
/// and return true.
bool Sema::checkStringLiteralArgumentAttr(const AttributeCommonInfo &CI,
                                          const Expr *E, StringRef &Str,
                                          SourceLocation *ArgLocation) {
  const auto *Literal = dyn_cast<StringLiteral>(E->IgnoreParenCasts());
  if (ArgLocation)
    *ArgLocation = E->getBeginLoc();

  if (!Literal || !Literal->isOrdinary()) {
    Diag(E->getBeginLoc(), diag::err_attribute_argument_type)
        << CI << AANT_ArgumentString;
    return false;
  }

  Str = Literal->getString();
  return true;
}

/// Check if the argument \p ArgNum of \p Attr is a ASCII string literal.
/// If not emit an error and return false. If the argument is an identifier it
/// will emit an error with a fixit hint and treat it as if it was a string
/// literal.
bool Sema::checkStringLiteralArgumentAttr(const ParsedAttr &AL, unsigned ArgNum,
                                          StringRef &Str,
                                          SourceLocation *ArgLocation) {
  // Look for identifiers. If we have one emit a hint to fix it to a literal.
  if (AL.isArgIdent(ArgNum)) {
    IdentifierLoc *Loc = AL.getArgAsIdent(ArgNum);
    Diag(Loc->Loc, diag::err_attribute_argument_type)
        << AL << AANT_ArgumentString
        << FixItHint::CreateInsertion(Loc->Loc, "\"")
        << FixItHint::CreateInsertion(getLocForEndOfToken(Loc->Loc), "\"");
    Str = Loc->Ident->getName();
    if (ArgLocation)
      *ArgLocation = Loc->Loc;
    return true;
  }

  // Now check for an actual string literal.
  Expr *ArgExpr = AL.getArgAsExpr(ArgNum);
  return checkStringLiteralArgumentAttr(AL, ArgExpr, Str, ArgLocation);
}

/// Applies the given attribute to the Decl without performing any
/// additional semantic checking.
template <typename AttrType>
static void handleSimpleAttribute(Sema &S, Decl *D,
                                  const AttributeCommonInfo &CI) {
  D->addAttr(::new (S.Context) AttrType(S.Context, CI));
}

template <typename... DiagnosticArgs>
static const Sema::SemaDiagnosticBuilder&
appendDiagnostics(const Sema::SemaDiagnosticBuilder &Bldr) {
  return Bldr;
}

template <typename T, typename... DiagnosticArgs>
static const Sema::SemaDiagnosticBuilder&
appendDiagnostics(const Sema::SemaDiagnosticBuilder &Bldr, T &&ExtraArg,
                  DiagnosticArgs &&... ExtraArgs) {
  return appendDiagnostics(Bldr << std::forward<T>(ExtraArg),
                           std::forward<DiagnosticArgs>(ExtraArgs)...);
}

/// Add an attribute @c AttrType to declaration @c D, provided that
/// @c PassesCheck is true.
/// Otherwise, emit diagnostic @c DiagID, passing in all parameters
/// specified in @c ExtraArgs.
template <typename AttrType, typename... DiagnosticArgs>
static void handleSimpleAttributeOrDiagnose(Sema &S, Decl *D,
                                            const AttributeCommonInfo &CI,
                                            bool PassesCheck, unsigned DiagID,
                                            DiagnosticArgs &&... ExtraArgs) {
  if (!PassesCheck) {
    Sema::SemaDiagnosticBuilder DB = S.Diag(D->getBeginLoc(), DiagID);
    appendDiagnostics(DB, std::forward<DiagnosticArgs>(ExtraArgs)...);
    return;
  }
  handleSimpleAttribute<AttrType>(S, D, CI);
}

/// Check if the passed-in expression is of type int or bool.
static bool isIntOrBool(Expr *Exp) {
  QualType QT = Exp->getType();
  return QT->isBooleanType() || QT->isIntegerType();
}


// Check to see if the type is a smart pointer of some kind.  We assume
// it's a smart pointer if it defines both operator-> and operator*.
static bool threadSafetyCheckIsSmartPointer(Sema &S, const RecordType* RT) {
  auto IsOverloadedOperatorPresent = [&S](const RecordDecl *Record,
                                          OverloadedOperatorKind Op) {
    DeclContextLookupResult Result =
        Record->lookup(S.Context.DeclarationNames.getCXXOperatorName(Op));
    return !Result.empty();
  };

  const RecordDecl *Record = RT->getDecl();
  bool foundStarOperator = IsOverloadedOperatorPresent(Record, OO_Star);
  bool foundArrowOperator = IsOverloadedOperatorPresent(Record, OO_Arrow);
  if (foundStarOperator && foundArrowOperator)
    return true;

  const CXXRecordDecl *CXXRecord = dyn_cast<CXXRecordDecl>(Record);
  if (!CXXRecord)
    return false;

  for (const auto &BaseSpecifier : CXXRecord->bases()) {
    if (!foundStarOperator)
      foundStarOperator = IsOverloadedOperatorPresent(
          BaseSpecifier.getType()->getAsRecordDecl(), OO_Star);
    if (!foundArrowOperator)
      foundArrowOperator = IsOverloadedOperatorPresent(
          BaseSpecifier.getType()->getAsRecordDecl(), OO_Arrow);
  }

  if (foundStarOperator && foundArrowOperator)
    return true;

  return false;
}

/// Check if passed in Decl is a pointer type.
/// Note that this function may produce an error message.
/// \return true if the Decl is a pointer type; false otherwise
static bool threadSafetyCheckIsPointer(Sema &S, const Decl *D,
                                       const ParsedAttr &AL) {
  const auto *VD = cast<ValueDecl>(D);
  QualType QT = VD->getType();
  if (QT->isAnyPointerType())
    return true;

  if (const auto *RT = QT->getAs<RecordType>()) {
    // If it's an incomplete type, it could be a smart pointer; skip it.
    // (We don't want to force template instantiation if we can avoid it,
    // since that would alter the order in which templates are instantiated.)
    if (RT->isIncompleteType())
      return true;

    if (threadSafetyCheckIsSmartPointer(S, RT))
      return true;
  }

  S.Diag(AL.getLoc(), diag::warn_thread_attribute_decl_not_pointer) << AL << QT;
  return false;
}

/// Checks that the passed in QualType either is of RecordType or points
/// to RecordType. Returns the relevant RecordType, null if it does not exit.
static const RecordType *getRecordType(QualType QT) {
  if (const auto *RT = QT->getAs<RecordType>())
    return RT;

  // Now check if we point to record type.
  if (const auto *PT = QT->getAs<PointerType>())
    return PT->getPointeeType()->getAs<RecordType>();

  return nullptr;
}

template <typename AttrType>
static bool checkRecordDeclForAttr(const RecordDecl *RD) {
  // Check if the record itself has the attribute.
  if (RD->hasAttr<AttrType>())
    return true;

  // Else check if any base classes have the attribute.
  if (const auto *CRD = dyn_cast<CXXRecordDecl>(RD)) {
    if (!CRD->forallBases([](const CXXRecordDecl *Base) {
          return !Base->hasAttr<AttrType>();
        }))
      return true;
  }
  return false;
}

static bool checkRecordTypeForCapability(Sema &S, QualType Ty) {
  const RecordType *RT = getRecordType(Ty);

  if (!RT)
    return false;

  // Don't check for the capability if the class hasn't been defined yet.
  if (RT->isIncompleteType())
    return true;

  // Allow smart pointers to be used as capability objects.
  // FIXME -- Check the type that the smart pointer points to.
  if (threadSafetyCheckIsSmartPointer(S, RT))
    return true;

  return checkRecordDeclForAttr<CapabilityAttr>(RT->getDecl());
}

static bool checkTypedefTypeForCapability(QualType Ty) {
  const auto *TD = Ty->getAs<TypedefType>();
  if (!TD)
    return false;

  TypedefNameDecl *TN = TD->getDecl();
  if (!TN)
    return false;

  return TN->hasAttr<CapabilityAttr>();
}

static bool typeHasCapability(Sema &S, QualType Ty) {
  if (checkTypedefTypeForCapability(Ty))
    return true;

  if (checkRecordTypeForCapability(S, Ty))
    return true;

  return false;
}

static bool isCapabilityExpr(Sema &S, const Expr *Ex) {
  // Capability expressions are simple expressions involving the boolean logic
  // operators &&, || or !, a simple DeclRefExpr, CastExpr or a ParenExpr. Once
  // a DeclRefExpr is found, its type should be checked to determine whether it
  // is a capability or not.

  if (const auto *E = dyn_cast<CastExpr>(Ex))
    return isCapabilityExpr(S, E->getSubExpr());
  else if (const auto *E = dyn_cast<ParenExpr>(Ex))
    return isCapabilityExpr(S, E->getSubExpr());
  else if (const auto *E = dyn_cast<UnaryOperator>(Ex)) {
    if (E->getOpcode() == UO_LNot || E->getOpcode() == UO_AddrOf ||
        E->getOpcode() == UO_Deref)
      return isCapabilityExpr(S, E->getSubExpr());
    return false;
  } else if (const auto *E = dyn_cast<BinaryOperator>(Ex)) {
    if (E->getOpcode() == BO_LAnd || E->getOpcode() == BO_LOr)
      return isCapabilityExpr(S, E->getLHS()) &&
             isCapabilityExpr(S, E->getRHS());
    return false;
  }

  return typeHasCapability(S, Ex->getType());
}

/// Checks that all attribute arguments, starting from Sidx, resolve to
/// a capability object.
/// \param Sidx The attribute argument index to start checking with.
/// \param ParamIdxOk Whether an argument can be indexing into a function
/// parameter list.
static void checkAttrArgsAreCapabilityObjs(Sema &S, Decl *D,
                                           const ParsedAttr &AL,
                                           SmallVectorImpl<Expr *> &Args,
                                           unsigned Sidx = 0,
                                           bool ParamIdxOk = false) {
  if (Sidx == AL.getNumArgs()) {
    // If we don't have any capability arguments, the attribute implicitly
    // refers to 'this'. So we need to make sure that 'this' exists, i.e. we're
    // a non-static method, and that the class is a (scoped) capability.
    const auto *MD = dyn_cast<const CXXMethodDecl>(D);
    if (MD && !MD->isStatic()) {
      const CXXRecordDecl *RD = MD->getParent();
      // FIXME -- need to check this again on template instantiation
      if (!checkRecordDeclForAttr<CapabilityAttr>(RD) &&
          !checkRecordDeclForAttr<ScopedLockableAttr>(RD))
        S.Diag(AL.getLoc(),
               diag::warn_thread_attribute_not_on_capability_member)
            << AL << MD->getParent();
    } else {
      S.Diag(AL.getLoc(), diag::warn_thread_attribute_not_on_non_static_member)
          << AL;
    }
  }

  for (unsigned Idx = Sidx; Idx < AL.getNumArgs(); ++Idx) {
    Expr *ArgExp = AL.getArgAsExpr(Idx);

    if (ArgExp->isTypeDependent()) {
      // FIXME -- need to check this again on template instantiation
      Args.push_back(ArgExp);
      continue;
    }

    if (const auto *StrLit = dyn_cast<StringLiteral>(ArgExp)) {
      if (StrLit->getLength() == 0 ||
          (StrLit->isOrdinary() && StrLit->getString() == StringRef("*"))) {
        // Pass empty strings to the analyzer without warnings.
        // Treat "*" as the universal lock.
        Args.push_back(ArgExp);
        continue;
      }

      // We allow constant strings to be used as a placeholder for expressions
      // that are not valid C++ syntax, but warn that they are ignored.
      S.Diag(AL.getLoc(), diag::warn_thread_attribute_ignored) << AL;
      Args.push_back(ArgExp);
      continue;
    }

    QualType ArgTy = ArgExp->getType();

    // A pointer to member expression of the form  &MyClass::mu is treated
    // specially -- we need to look at the type of the member.
    if (const auto *UOp = dyn_cast<UnaryOperator>(ArgExp))
      if (UOp->getOpcode() == UO_AddrOf)
        if (const auto *DRE = dyn_cast<DeclRefExpr>(UOp->getSubExpr()))
          if (DRE->getDecl()->isCXXInstanceMember())
            ArgTy = DRE->getDecl()->getType();

    // First see if we can just cast to record type, or pointer to record type.
    const RecordType *RT = getRecordType(ArgTy);

    // Now check if we index into a record type function param.
    if(!RT && ParamIdxOk) {
      const auto *FD = dyn_cast<FunctionDecl>(D);
      const auto *IL = dyn_cast<IntegerLiteral>(ArgExp);
      if(FD && IL) {
        unsigned int NumParams = FD->getNumParams();
        llvm::APInt ArgValue = IL->getValue();
        uint64_t ParamIdxFromOne = ArgValue.getZExtValue();
        uint64_t ParamIdxFromZero = ParamIdxFromOne - 1;
        if (!ArgValue.isStrictlyPositive() || ParamIdxFromOne > NumParams) {
          S.Diag(AL.getLoc(),
                 diag::err_attribute_argument_out_of_bounds_extra_info)
              << AL << Idx + 1 << NumParams;
          continue;
        }
        ArgTy = FD->getParamDecl(ParamIdxFromZero)->getType();
      }
    }

    // If the type does not have a capability, see if the components of the
    // expression have capabilities. This allows for writing C code where the
    // capability may be on the type, and the expression is a capability
    // boolean logic expression. Eg) requires_capability(A || B && !C)
    if (!typeHasCapability(S, ArgTy) && !isCapabilityExpr(S, ArgExp))
      S.Diag(AL.getLoc(), diag::warn_thread_attribute_argument_not_lockable)
          << AL << ArgTy;

    Args.push_back(ArgExp);
  }
}

//===----------------------------------------------------------------------===//
// Attribute Implementations
//===----------------------------------------------------------------------===//

static void handlePtGuardedVarAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!threadSafetyCheckIsPointer(S, D, AL))
    return;

  D->addAttr(::new (S.Context) PtGuardedVarAttr(S.Context, AL));
}

static bool checkGuardedByAttrCommon(Sema &S, Decl *D, const ParsedAttr &AL,
                                     Expr *&Arg) {
  SmallVector<Expr *, 1> Args;
  // check that all arguments are lockable objects
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args);
  unsigned Size = Args.size();
  if (Size != 1)
    return false;

  Arg = Args[0];

  return true;
}

static void handleGuardedByAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  Expr *Arg = nullptr;
  if (!checkGuardedByAttrCommon(S, D, AL, Arg))
    return;

  D->addAttr(::new (S.Context) GuardedByAttr(S.Context, AL, Arg));
}

static void handlePtGuardedByAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  Expr *Arg = nullptr;
  if (!checkGuardedByAttrCommon(S, D, AL, Arg))
    return;

  if (!threadSafetyCheckIsPointer(S, D, AL))
    return;

  D->addAttr(::new (S.Context) PtGuardedByAttr(S.Context, AL, Arg));
}

static bool checkAcquireOrderAttrCommon(Sema &S, Decl *D, const ParsedAttr &AL,
                                        SmallVectorImpl<Expr *> &Args) {
  if (!AL.checkAtLeastNumArgs(S, 1))
    return false;

  // Check that this attribute only applies to lockable types.
  QualType QT = cast<ValueDecl>(D)->getType();
  if (!QT->isDependentType() && !typeHasCapability(S, QT)) {
    S.Diag(AL.getLoc(), diag::warn_thread_attribute_decl_not_lockable) << AL;
    return false;
  }

  // Check that all arguments are lockable objects.
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args);
  if (Args.empty())
    return false;

  return true;
}

static void handleAcquiredAfterAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  SmallVector<Expr *, 1> Args;
  if (!checkAcquireOrderAttrCommon(S, D, AL, Args))
    return;

  Expr **StartArg = &Args[0];
  D->addAttr(::new (S.Context)
                 AcquiredAfterAttr(S.Context, AL, StartArg, Args.size()));
}

static void handleAcquiredBeforeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  SmallVector<Expr *, 1> Args;
  if (!checkAcquireOrderAttrCommon(S, D, AL, Args))
    return;

  Expr **StartArg = &Args[0];
  D->addAttr(::new (S.Context)
                 AcquiredBeforeAttr(S.Context, AL, StartArg, Args.size()));
}

static bool checkLockFunAttrCommon(Sema &S, Decl *D, const ParsedAttr &AL,
                                   SmallVectorImpl<Expr *> &Args) {
  // zero or more arguments ok
  // check that all arguments are lockable objects
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args, 0, /*ParamIdxOk=*/true);

  return true;
}

static void handleAssertSharedLockAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  SmallVector<Expr *, 1> Args;
  if (!checkLockFunAttrCommon(S, D, AL, Args))
    return;

  unsigned Size = Args.size();
  Expr **StartArg = Size == 0 ? nullptr : &Args[0];
  D->addAttr(::new (S.Context)
                 AssertSharedLockAttr(S.Context, AL, StartArg, Size));
}

static void handleAssertExclusiveLockAttr(Sema &S, Decl *D,
                                          const ParsedAttr &AL) {
  SmallVector<Expr *, 1> Args;
  if (!checkLockFunAttrCommon(S, D, AL, Args))
    return;

  unsigned Size = Args.size();
  Expr **StartArg = Size == 0 ? nullptr : &Args[0];
  D->addAttr(::new (S.Context)
                 AssertExclusiveLockAttr(S.Context, AL, StartArg, Size));
}

/// Checks to be sure that the given parameter number is in bounds, and
/// is an integral type. Will emit appropriate diagnostics if this returns
/// false.
///
/// AttrArgNo is used to actually retrieve the argument, so it's base-0.
template <typename AttrInfo>
static bool checkParamIsIntegerType(Sema &S, const Decl *D, const AttrInfo &AI,
                                    unsigned AttrArgNo) {
  assert(AI.isArgExpr(AttrArgNo) && "Expected expression argument");
  Expr *AttrArg = AI.getArgAsExpr(AttrArgNo);
  ParamIdx Idx;
  if (!checkFunctionOrMethodParameterIndex(S, D, AI, AttrArgNo + 1, AttrArg,
                                           Idx))
    return false;

  QualType ParamTy = getFunctionOrMethodParamType(D, Idx.getASTIndex());
  if (!ParamTy->isIntegerType() && !ParamTy->isCharType()) {
    SourceLocation SrcLoc = AttrArg->getBeginLoc();
    S.Diag(SrcLoc, diag::err_attribute_integers_only)
        << AI << getFunctionOrMethodParamRange(D, Idx.getASTIndex());
    return false;
  }
  return true;
}

static void handleAllocSizeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!AL.checkAtLeastNumArgs(S, 1) || !AL.checkAtMostNumArgs(S, 2))
    return;

  assert(isFunctionOrMethod(D) && hasFunctionProto(D));

  QualType RetTy = getFunctionOrMethodResultType(D);
  if (!RetTy->isPointerType()) {
    S.Diag(AL.getLoc(), diag::warn_attribute_return_pointers_only) << AL;
    return;
  }

  const Expr *SizeExpr = AL.getArgAsExpr(0);
  int SizeArgNoVal;
  // Parameter indices are 1-indexed, hence Index=1
  if (!checkPositiveIntArgument(S, AL, SizeExpr, SizeArgNoVal, /*Idx=*/1))
    return;
  if (!checkParamIsIntegerType(S, D, AL, /*AttrArgNo=*/0))
    return;
  ParamIdx SizeArgNo(SizeArgNoVal, D);

  ParamIdx NumberArgNo;
  if (AL.getNumArgs() == 2) {
    const Expr *NumberExpr = AL.getArgAsExpr(1);
    int Val;
    // Parameter indices are 1-based, hence Index=2
    if (!checkPositiveIntArgument(S, AL, NumberExpr, Val, /*Idx=*/2))
      return;
    if (!checkParamIsIntegerType(S, D, AL, /*AttrArgNo=*/1))
      return;
    NumberArgNo = ParamIdx(Val, D);
  }

  D->addAttr(::new (S.Context)
                 AllocSizeAttr(S.Context, AL, SizeArgNo, NumberArgNo));
}

static bool checkTryLockFunAttrCommon(Sema &S, Decl *D, const ParsedAttr &AL,
                                      SmallVectorImpl<Expr *> &Args) {
  if (!AL.checkAtLeastNumArgs(S, 1))
    return false;

  if (!isIntOrBool(AL.getArgAsExpr(0))) {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
        << AL << 1 << AANT_ArgumentIntOrBool;
    return false;
  }

  // check that all arguments are lockable objects
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args, 1);

  return true;
}

static void handleSharedTrylockFunctionAttr(Sema &S, Decl *D,
                                            const ParsedAttr &AL) {
  SmallVector<Expr*, 2> Args;
  if (!checkTryLockFunAttrCommon(S, D, AL, Args))
    return;

  D->addAttr(::new (S.Context) SharedTrylockFunctionAttr(
      S.Context, AL, AL.getArgAsExpr(0), Args.data(), Args.size()));
}

static void handleExclusiveTrylockFunctionAttr(Sema &S, Decl *D,
                                               const ParsedAttr &AL) {
  SmallVector<Expr*, 2> Args;
  if (!checkTryLockFunAttrCommon(S, D, AL, Args))
    return;

  D->addAttr(::new (S.Context) ExclusiveTrylockFunctionAttr(
      S.Context, AL, AL.getArgAsExpr(0), Args.data(), Args.size()));
}

static void handleLockReturnedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // check that the argument is lockable object
  SmallVector<Expr*, 1> Args;
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args);
  unsigned Size = Args.size();
  if (Size == 0)
    return;

  D->addAttr(::new (S.Context) LockReturnedAttr(S.Context, AL, Args[0]));
}

static void handleLocksExcludedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!AL.checkAtLeastNumArgs(S, 1))
    return;

  // check that all arguments are lockable objects
  SmallVector<Expr*, 1> Args;
  checkAttrArgsAreCapabilityObjs(S, D, AL, Args);
  unsigned Size = Args.size();
  if (Size == 0)
    return;
  Expr **StartArg = &Args[0];

  D->addAttr(::new (S.Context)
                 LocksExcludedAttr(S.Context, AL, StartArg, Size));
}

static bool checkFunctionConditionAttr(Sema &S, Decl *D, const ParsedAttr &AL,
                                       Expr *&Cond, StringRef &Msg) {
  Cond = AL.getArgAsExpr(0);
  if (!Cond->isTypeDependent()) {
    ExprResult Converted = S.PerformContextuallyConvertToBool(Cond);
    if (Converted.isInvalid())
      return false;
    Cond = Converted.get();
  }

  if (!S.checkStringLiteralArgumentAttr(AL, 1, Msg))
    return false;

  if (Msg.empty())
    Msg = "<no message provided>";

  SmallVector<PartialDiagnosticAt, 8> Diags;
  if (isa<FunctionDecl>(D) && !Cond->isValueDependent() &&
      !Expr::isPotentialConstantExprUnevaluated(Cond, cast<FunctionDecl>(D),
                                                Diags)) {
    S.Diag(AL.getLoc(), diag::err_attr_cond_never_constant_expr) << AL;
    for (const PartialDiagnosticAt &PDiag : Diags)
      S.Diag(PDiag.first, PDiag.second);
    return false;
  }
  return true;
}

static void handleEnableIfAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  S.Diag(AL.getLoc(), diag::ext_clang_enable_if);

  Expr *Cond;
  StringRef Msg;
  if (checkFunctionConditionAttr(S, D, AL, Cond, Msg))
    D->addAttr(::new (S.Context) EnableIfAttr(S.Context, AL, Cond, Msg));
}

static void handleErrorAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  StringRef NewUserDiagnostic;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, NewUserDiagnostic))
    return;
  if (ErrorAttr *EA = S.mergeErrorAttr(D, AL, NewUserDiagnostic))
    D->addAttr(EA);
}

namespace {
/// Determines if a given Expr references any of the given function's
/// ParmVarDecls, or the function's implicit `this` parameter (if applicable).
class ArgumentDependenceChecker
    : public RecursiveASTVisitor<ArgumentDependenceChecker> {
#ifndef NDEBUG
  const CXXRecordDecl *ClassType;
#endif
  llvm::SmallPtrSet<const ParmVarDecl *, 16> Parms;
  bool Result;

public:
  ArgumentDependenceChecker(const FunctionDecl *FD) {
#ifndef NDEBUG
    if (const auto *MD = dyn_cast<CXXMethodDecl>(FD))
      ClassType = MD->getParent();
    else
      ClassType = nullptr;
#endif
    Parms.insert(FD->param_begin(), FD->param_end());
  }

  bool referencesArgs(Expr *E) {
    Result = false;
    TraverseStmt(E);
    return Result;
  }

  bool VisitCXXThisExpr(CXXThisExpr *E) {
    assert(E->getType()->getPointeeCXXRecordDecl() == ClassType &&
           "`this` doesn't refer to the enclosing class?");
    Result = true;
    return false;
  }

  bool VisitDeclRefExpr(DeclRefExpr *DRE) {
    if (const auto *PVD = dyn_cast<ParmVarDecl>(DRE->getDecl()))
      if (Parms.count(PVD)) {
        Result = true;
        return false;
      }
    return true;
  }
};
}

static void handleDiagnoseAsBuiltinAttr(Sema &S, Decl *D,
                                        const ParsedAttr &AL) {
  const auto *DeclFD = cast<FunctionDecl>(D);

  if (const auto *MethodDecl = dyn_cast<CXXMethodDecl>(DeclFD))
    if (!MethodDecl->isStatic()) {
      S.Diag(AL.getLoc(), diag::err_attribute_no_member_function) << AL;
      return;
    }

  auto DiagnoseType = [&](unsigned Index, AttributeArgumentNType T) {
    SourceLocation Loc = [&]() {
      auto Union = AL.getArg(Index - 1);
      if (Union.is<Expr *>())
        return Union.get<Expr *>()->getBeginLoc();
      return Union.get<IdentifierLoc *>()->Loc;
    }();

    S.Diag(Loc, diag::err_attribute_argument_n_type) << AL << Index << T;
  };

  FunctionDecl *AttrFD = [&]() -> FunctionDecl * {
    if (!AL.isArgExpr(0))
      return nullptr;
    auto *F = dyn_cast_or_null<DeclRefExpr>(AL.getArgAsExpr(0));
    if (!F)
      return nullptr;
    return dyn_cast_or_null<FunctionDecl>(F->getFoundDecl());
  }();

  if (!AttrFD || !AttrFD->getBuiltinID(true)) {
    DiagnoseType(1, AANT_ArgumentBuiltinFunction);
    return;
  }

  if (AttrFD->getNumParams() != AL.getNumArgs() - 1) {
    S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments_for)
        << AL << AttrFD << AttrFD->getNumParams();
    return;
  }

  SmallVector<unsigned, 8> Indices;

  for (unsigned I = 1; I < AL.getNumArgs(); ++I) {
    if (!AL.isArgExpr(I)) {
      DiagnoseType(I + 1, AANT_ArgumentIntegerConstant);
      return;
    }

    const Expr *IndexExpr = AL.getArgAsExpr(I);
    uint32_t Index;

    if (!checkUInt32Argument(S, AL, IndexExpr, Index, I + 1, false))
      return;

    if (Index > DeclFD->getNumParams()) {
      S.Diag(AL.getLoc(), diag::err_attribute_bounds_for_function)
          << AL << Index << DeclFD << DeclFD->getNumParams();
      return;
    }

    QualType T1 = AttrFD->getParamDecl(I - 1)->getType();
    QualType T2 = DeclFD->getParamDecl(Index - 1)->getType();

    if (T1.getCanonicalType().getUnqualifiedType() !=
        T2.getCanonicalType().getUnqualifiedType()) {
      S.Diag(IndexExpr->getBeginLoc(), diag::err_attribute_parameter_types)
          << AL << Index << DeclFD << T2 << I << AttrFD << T1;
      return;
    }

    Indices.push_back(Index - 1);
  }

  D->addAttr(::new (S.Context) DiagnoseAsBuiltinAttr(
      S.Context, AL, AttrFD, Indices.data(), Indices.size()));
}

static void handleDiagnoseIfAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  S.Diag(AL.getLoc(), diag::ext_clang_diagnose_if);

  Expr *Cond;
  StringRef Msg;
  if (!checkFunctionConditionAttr(S, D, AL, Cond, Msg))
    return;

  StringRef DiagTypeStr;
  if (!S.checkStringLiteralArgumentAttr(AL, 2, DiagTypeStr))
    return;

  DiagnoseIfAttr::DiagnosticType DiagType;
  if (!DiagnoseIfAttr::ConvertStrToDiagnosticType(DiagTypeStr, DiagType)) {
    S.Diag(AL.getArgAsExpr(2)->getBeginLoc(),
           diag::err_diagnose_if_invalid_diagnostic_type);
    return;
  }

  bool ArgDependent = false;
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    ArgDependent = ArgumentDependenceChecker(FD).referencesArgs(Cond);
  D->addAttr(::new (S.Context) DiagnoseIfAttr(
      S.Context, AL, Cond, Msg, DiagType, ArgDependent, cast<NamedDecl>(D)));
}

static void handleNoBuiltinAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  static constexpr const StringRef kWildcard = "*";

  llvm::SmallVector<StringRef, 16> Names;
  bool HasWildcard = false;

  const auto AddBuiltinName = [&Names, &HasWildcard](StringRef Name) {
    if (Name == kWildcard)
      HasWildcard = true;
    Names.push_back(Name);
  };

  // Add previously defined attributes.
  if (const auto *NBA = D->getAttr<NoBuiltinAttr>())
    for (StringRef BuiltinName : NBA->builtinNames())
      AddBuiltinName(BuiltinName);

  // Add current attributes.
  if (AL.getNumArgs() == 0)
    AddBuiltinName(kWildcard);
  else
    for (unsigned I = 0, E = AL.getNumArgs(); I != E; ++I) {
      StringRef BuiltinName;
      SourceLocation LiteralLoc;
      if (!S.checkStringLiteralArgumentAttr(AL, I, BuiltinName, &LiteralLoc))
        return;

      if (Builtin::Context::isBuiltinFunc(BuiltinName))
        AddBuiltinName(BuiltinName);
      else
        S.Diag(LiteralLoc, diag::warn_attribute_no_builtin_invalid_builtin_name)
            << BuiltinName << AL;
    }

  // Repeating the same attribute is fine.
  llvm::sort(Names);
  Names.erase(std::unique(Names.begin(), Names.end()), Names.end());

  // Empty no_builtin must be on its own.
  if (HasWildcard && Names.size() > 1)
    S.Diag(D->getLocation(),
           diag::err_attribute_no_builtin_wildcard_or_builtin_name)
        << AL;

  if (D->hasAttr<NoBuiltinAttr>())
    D->dropAttr<NoBuiltinAttr>();
  D->addAttr(::new (S.Context)
                 NoBuiltinAttr(S.Context, AL, Names.data(), Names.size()));
}

static void handlePassObjectSizeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (D->hasAttr<PassObjectSizeAttr>()) {
    S.Diag(D->getBeginLoc(), diag::err_attribute_only_once_per_parameter) << AL;
    return;
  }

  Expr *E = AL.getArgAsExpr(0);
  uint32_t Type;
  if (!checkUInt32Argument(S, AL, E, Type, /*Idx=*/1))
    return;

  // pass_object_size's argument is passed in as the second argument of
  // __builtin_object_size. So, it has the same constraints as that second
  // argument; namely, it must be in the range [0, 3].
  if (Type > 3) {
    S.Diag(E->getBeginLoc(), diag::err_attribute_argument_out_of_range)
        << AL << 0 << 3 << E->getSourceRange();
    return;
  }

  // pass_object_size is only supported on constant pointer parameters; as a
  // kindness to users, we allow the parameter to be non-const for declarations.
  // At this point, we have no clue if `D` belongs to a function declaration or
  // definition, so we defer the constness check until later.
  if (!cast<ParmVarDecl>(D)->getType()->isPointerType()) {
    S.Diag(D->getBeginLoc(), diag::err_attribute_pointers_only) << AL << 1;
    return;
  }

  D->addAttr(::new (S.Context) PassObjectSizeAttr(S.Context, AL, (int)Type));
}

static void handleConsumableAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  ConsumableAttr::ConsumedState DefaultState;

  if (AL.isArgIdent(0)) {
    IdentifierLoc *IL = AL.getArgAsIdent(0);
    if (!ConsumableAttr::ConvertStrToConsumedState(IL->Ident->getName(),
                                                   DefaultState)) {
      S.Diag(IL->Loc, diag::warn_attribute_type_not_supported) << AL
                                                               << IL->Ident;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
        << AL << AANT_ArgumentIdentifier;
    return;
  }

  D->addAttr(::new (S.Context) ConsumableAttr(S.Context, AL, DefaultState));
}

static bool checkForConsumableClass(Sema &S, const CXXMethodDecl *MD,
                                    const ParsedAttr &AL) {
  QualType ThisType = MD->getThisType()->getPointeeType();

  if (const CXXRecordDecl *RD = ThisType->getAsCXXRecordDecl()) {
    if (!RD->hasAttr<ConsumableAttr>()) {
      S.Diag(AL.getLoc(), diag::warn_attr_on_unconsumable_class) << RD;

      return false;
    }
  }

  return true;
}

static void handleCallableWhenAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!AL.checkAtLeastNumArgs(S, 1))
    return;

  if (!checkForConsumableClass(S, cast<CXXMethodDecl>(D), AL))
    return;

  SmallVector<CallableWhenAttr::ConsumedState, 3> States;
  for (unsigned ArgIndex = 0; ArgIndex < AL.getNumArgs(); ++ArgIndex) {
    CallableWhenAttr::ConsumedState CallableState;

    StringRef StateString;
    SourceLocation Loc;
    if (AL.isArgIdent(ArgIndex)) {
      IdentifierLoc *Ident = AL.getArgAsIdent(ArgIndex);
      StateString = Ident->Ident->getName();
      Loc = Ident->Loc;
    } else {
      if (!S.checkStringLiteralArgumentAttr(AL, ArgIndex, StateString, &Loc))
        return;
    }

    if (!CallableWhenAttr::ConvertStrToConsumedState(StateString,
                                                     CallableState)) {
      S.Diag(Loc, diag::warn_attribute_type_not_supported) << AL << StateString;
      return;
    }

    States.push_back(CallableState);
  }

  D->addAttr(::new (S.Context)
                 CallableWhenAttr(S.Context, AL, States.data(), States.size()));
}

static void handleParamTypestateAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  ParamTypestateAttr::ConsumedState ParamState;

  if (AL.isArgIdent(0)) {
    IdentifierLoc *Ident = AL.getArgAsIdent(0);
    StringRef StateString = Ident->Ident->getName();

    if (!ParamTypestateAttr::ConvertStrToConsumedState(StateString,
                                                       ParamState)) {
      S.Diag(Ident->Loc, diag::warn_attribute_type_not_supported)
          << AL << StateString;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
        << AL << AANT_ArgumentIdentifier;
    return;
  }

  // FIXME: This check is currently being done in the analysis.  It can be
  //        enabled here only after the parser propagates attributes at
  //        template specialization definition, not declaration.
  //QualType ReturnType = cast<ParmVarDecl>(D)->getType();
  //const CXXRecordDecl *RD = ReturnType->getAsCXXRecordDecl();
  //
  //if (!RD || !RD->hasAttr<ConsumableAttr>()) {
  //    S.Diag(AL.getLoc(), diag::warn_return_state_for_unconsumable_type) <<
  //      ReturnType.getAsString();
  //    return;
  //}

  D->addAttr(::new (S.Context) ParamTypestateAttr(S.Context, AL, ParamState));
}

static void handleReturnTypestateAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  ReturnTypestateAttr::ConsumedState ReturnState;

  if (AL.isArgIdent(0)) {
    IdentifierLoc *IL = AL.getArgAsIdent(0);
    if (!ReturnTypestateAttr::ConvertStrToConsumedState(IL->Ident->getName(),
                                                        ReturnState)) {
      S.Diag(IL->Loc, diag::warn_attribute_type_not_supported) << AL
                                                               << IL->Ident;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
        << AL << AANT_ArgumentIdentifier;
    return;
  }

  // FIXME: This check is currently being done in the analysis.  It can be
  //        enabled here only after the parser propagates attributes at
  //        template specialization definition, not declaration.
  //QualType ReturnType;
  //
  //if (const ParmVarDecl *Param = dyn_cast<ParmVarDecl>(D)) {
  //  ReturnType = Param->getType();
  //
  //} else if (const CXXConstructorDecl *Constructor =
  //             dyn_cast<CXXConstructorDecl>(D)) {
  //  ReturnType = Constructor->getThisType()->getPointeeType();
  //
  //} else {
  //
  //  ReturnType = cast<FunctionDecl>(D)->getCallResultType();
  //}
  //
  //const CXXRecordDecl *RD = ReturnType->getAsCXXRecordDecl();
  //
  //if (!RD || !RD->hasAttr<ConsumableAttr>()) {
  //    S.Diag(Attr.getLoc(), diag::warn_return_state_for_unconsumable_type) <<
  //      ReturnType.getAsString();
  //    return;
  //}

  D->addAttr(::new (S.Context) ReturnTypestateAttr(S.Context, AL, ReturnState));
}

static void handleSetTypestateAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!checkForConsumableClass(S, cast<CXXMethodDecl>(D), AL))
    return;

  SetTypestateAttr::ConsumedState NewState;
  if (AL.isArgIdent(0)) {
    IdentifierLoc *Ident = AL.getArgAsIdent(0);
    StringRef Param = Ident->Ident->getName();
    if (!SetTypestateAttr::ConvertStrToConsumedState(Param, NewState)) {
      S.Diag(Ident->Loc, diag::warn_attribute_type_not_supported) << AL
                                                                  << Param;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
        << AL << AANT_ArgumentIdentifier;
    return;
  }

  D->addAttr(::new (S.Context) SetTypestateAttr(S.Context, AL, NewState));
}

static void handleTestTypestateAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!checkForConsumableClass(S, cast<CXXMethodDecl>(D), AL))
    return;

  TestTypestateAttr::ConsumedState TestState;
  if (AL.isArgIdent(0)) {
    IdentifierLoc *Ident = AL.getArgAsIdent(0);
    StringRef Param = Ident->Ident->getName();
    if (!TestTypestateAttr::ConvertStrToConsumedState(Param, TestState)) {
      S.Diag(Ident->Loc, diag::warn_attribute_type_not_supported) << AL
                                                                  << Param;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
        << AL << AANT_ArgumentIdentifier;
    return;
  }

  D->addAttr(::new (S.Context) TestTypestateAttr(S.Context, AL, TestState));
}

static void handleExtVectorTypeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Remember this typedef decl, we will need it later for diagnostics.
  S.ExtVectorDecls.push_back(cast<TypedefNameDecl>(D));
}

static void handlePackedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (auto *TD = dyn_cast<TagDecl>(D))
    TD->addAttr(::new (S.Context) PackedAttr(S.Context, AL));
  else if (auto *FD = dyn_cast<FieldDecl>(D)) {
    bool BitfieldByteAligned = (!FD->getType()->isDependentType() &&
                                !FD->getType()->isIncompleteType() &&
                                FD->isBitField() &&
                                S.Context.getTypeAlign(FD->getType()) <= 8);

    if (S.getASTContext().getTargetInfo().getTriple().isPS()) {
      if (BitfieldByteAligned)
        // The PS4/PS5 targets need to maintain ABI backwards compatibility.
        S.Diag(AL.getLoc(), diag::warn_attribute_ignored_for_field_of_type)
            << AL << FD->getType();
      else
        FD->addAttr(::new (S.Context) PackedAttr(S.Context, AL));
    } else {
      // Report warning about changed offset in the newer compiler versions.
      if (BitfieldByteAligned)
        S.Diag(AL.getLoc(), diag::warn_attribute_packed_for_bitfield);

      FD->addAttr(::new (S.Context) PackedAttr(S.Context, AL));
    }

  } else
    S.Diag(AL.getLoc(), diag::warn_attribute_ignored) << AL;
}

static void handlePreferredName(Sema &S, Decl *D, const ParsedAttr &AL) {
  auto *RD = cast<CXXRecordDecl>(D);
  ClassTemplateDecl *CTD = RD->getDescribedClassTemplate();
  assert(CTD && "attribute does not appertain to this declaration");

  ParsedType PT = AL.getTypeArg();
  TypeSourceInfo *TSI = nullptr;
  QualType T = S.GetTypeFromParser(PT, &TSI);
  if (!TSI)
    TSI = S.Context.getTrivialTypeSourceInfo(T, AL.getLoc());

  if (!T.hasQualifiers() && T->isTypedefNameType()) {
    // Find the template name, if this type names a template specialization.
    const TemplateDecl *Template = nullptr;
    if (const auto *CTSD = dyn_cast_or_null<ClassTemplateSpecializationDecl>(
            T->getAsCXXRecordDecl())) {
      Template = CTSD->getSpecializedTemplate();
    } else if (const auto *TST = T->getAs<TemplateSpecializationType>()) {
      while (TST && TST->isTypeAlias())
        TST = TST->getAliasedType()->getAs<TemplateSpecializationType>();
      if (TST)
        Template = TST->getTemplateName().getAsTemplateDecl();
    }

    if (Template && declaresSameEntity(Template, CTD)) {
      D->addAttr(::new (S.Context) PreferredNameAttr(S.Context, AL, TSI));
      return;
    }
  }

  S.Diag(AL.getLoc(), diag::err_attribute_preferred_name_arg_invalid)
      << T << CTD;
  if (const auto *TT = T->getAs<TypedefType>())
    S.Diag(TT->getDecl()->getLocation(), diag::note_entity_declared_at)
        << TT->getDecl();
}

static bool checkIBOutletCommon(Sema &S, Decl *D, const ParsedAttr &AL) {
  // The IBOutlet/IBOutletCollection attributes only apply to instance
  // variables or properties of Objective-C classes.  The outlet must also
  // have an object reference type.
  if (const auto *VD = dyn_cast<ObjCIvarDecl>(D)) {
    if (!VD->getType()->getAs<ObjCObjectPointerType>()) {
      S.Diag(AL.getLoc(), diag::warn_iboutlet_object_type)
          << AL << VD->getType() << 0;
      return false;
    }
  }
  else if (const auto *PD = dyn_cast<ObjCPropertyDecl>(D)) {
    if (!PD->getType()->getAs<ObjCObjectPointerType>()) {
      S.Diag(AL.getLoc(), diag::warn_iboutlet_object_type)
          << AL << PD->getType() << 1;
      return false;
    }
  }
  else {
    S.Diag(AL.getLoc(), diag::warn_attribute_iboutlet) << AL;
    return false;
  }

  return true;
}

static void handleIBOutlet(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!checkIBOutletCommon(S, D, AL))
    return;

  D->addAttr(::new (S.Context) IBOutletAttr(S.Context, AL));
}

static void handleIBOutletCollection(Sema &S, Decl *D, const ParsedAttr &AL) {

  // The iboutletcollection attribute can have zero or one arguments.
  if (AL.getNumArgs() > 1) {
    S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments) << AL << 1;
    return;
  }

  if (!checkIBOutletCommon(S, D, AL))
    return;

  ParsedType PT;

  if (AL.hasParsedType())
    PT = AL.getTypeArg();
  else {
    PT = S.getTypeName(S.Context.Idents.get("NSObject"), AL.getLoc(),
                       S.getScopeForContext(D->getDeclContext()->getParent()));
    if (!PT) {
      S.Diag(AL.getLoc(), diag::err_iboutletcollection_type) << "NSObject";
      return;
    }
  }

  TypeSourceInfo *QTLoc = nullptr;
  QualType QT = S.GetTypeFromParser(PT, &QTLoc);
  if (!QTLoc)
    QTLoc = S.Context.getTrivialTypeSourceInfo(QT, AL.getLoc());

  // Diagnose use of non-object type in iboutletcollection attribute.
  // FIXME. Gnu attribute extension ignores use of builtin types in
  // attributes. So, __attribute__((iboutletcollection(char))) will be
  // treated as __attribute__((iboutletcollection())).
  if (!QT->isObjCIdType() && !QT->isObjCObjectType()) {
    S.Diag(AL.getLoc(),
           QT->isBuiltinType() ? diag::err_iboutletcollection_builtintype
                               : diag::err_iboutletcollection_type) << QT;
    return;
  }

  D->addAttr(::new (S.Context) IBOutletCollectionAttr(S.Context, AL, QTLoc));
}

bool Sema::isValidPointerAttrType(QualType T, bool RefOkay) {
  if (RefOkay) {
    if (T->isReferenceType())
      return true;
  } else {
    T = T.getNonReferenceType();
  }

  // The nonnull attribute, and other similar attributes, can be applied to a
  // transparent union that contains a pointer type.
  if (const RecordType *UT = T->getAsUnionType()) {
    if (UT && UT->getDecl()->hasAttr<TransparentUnionAttr>()) {
      RecordDecl *UD = UT->getDecl();
      for (const auto *I : UD->fields()) {
        QualType QT = I->getType();
        if (QT->isAnyPointerType() || QT->isBlockPointerType())
          return true;
      }
    }
  }

  return T->isAnyPointerType() || T->isBlockPointerType();
}

static bool attrNonNullArgCheck(Sema &S, QualType T, const ParsedAttr &AL,
                                SourceRange AttrParmRange,
                                SourceRange TypeRange,
                                bool isReturnValue = false) {
  if (!S.isValidPointerAttrType(T)) {
    if (isReturnValue)
      S.Diag(AL.getLoc(), diag::warn_attribute_return_pointers_only)
          << AL << AttrParmRange << TypeRange;
    else
      S.Diag(AL.getLoc(), diag::warn_attribute_pointers_only)
          << AL << AttrParmRange << TypeRange << 0;
    return false;
  }
  return true;
}

static void handleNonNullAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  SmallVector<ParamIdx, 8> NonNullArgs;
  for (unsigned I = 0; I < AL.getNumArgs(); ++I) {
    Expr *Ex = AL.getArgAsExpr(I);
    ParamIdx Idx;
    if (!checkFunctionOrMethodParameterIndex(S, D, AL, I + 1, Ex, Idx))
      return;

    // Is the function argument a pointer type?
    if (Idx.getASTIndex() < getFunctionOrMethodNumParams(D) &&
        !attrNonNullArgCheck(
            S, getFunctionOrMethodParamType(D, Idx.getASTIndex()), AL,
            Ex->getSourceRange(),
            getFunctionOrMethodParamRange(D, Idx.getASTIndex())))
      continue;

    NonNullArgs.push_back(Idx);
  }

  // If no arguments were specified to __attribute__((nonnull)) then all pointer
  // arguments have a nonnull attribute; warn if there aren't any. Skip this
  // check if the attribute came from a macro expansion or a template
  // instantiation.
  if (NonNullArgs.empty() && AL.getLoc().isFileID() &&
      !S.inTemplateInstantiation()) {
    bool AnyPointers = isFunctionOrMethodVariadic(D);
    for (unsigned I = 0, E = getFunctionOrMethodNumParams(D);
         I != E && !AnyPointers; ++I) {
      QualType T = getFunctionOrMethodParamType(D, I);
      if (T->isDependentType() || S.isValidPointerAttrType(T))
        AnyPointers = true;
    }

    if (!AnyPointers)
      S.Diag(AL.getLoc(), diag::warn_attribute_nonnull_no_pointers);
  }

  ParamIdx *Start = NonNullArgs.data();
  unsigned Size = NonNullArgs.size();
  llvm::array_pod_sort(Start, Start + Size);
  D->addAttr(::new (S.Context) NonNullAttr(S.Context, AL, Start, Size));
}

static void handleNonNullAttrParameter(Sema &S, ParmVarDecl *D,
                                       const ParsedAttr &AL) {
  if (AL.getNumArgs() > 0) {
    if (D->getFunctionType()) {
      handleNonNullAttr(S, D, AL);
    } else {
      S.Diag(AL.getLoc(), diag::warn_attribute_nonnull_parm_no_args)
        << D->getSourceRange();
    }
    return;
  }

  // Is the argument a pointer type?
  if (!attrNonNullArgCheck(S, D->getType(), AL, SourceRange(),
                           D->getSourceRange()))
    return;

  D->addAttr(::new (S.Context) NonNullAttr(S.Context, AL, nullptr, 0));
}

static void handleReturnsNonNullAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  QualType ResultType = getFunctionOrMethodResultType(D);
  SourceRange SR = getFunctionOrMethodResultSourceRange(D);
  if (!attrNonNullArgCheck(S, ResultType, AL, SourceRange(), SR,
                           /* isReturnValue */ true))
    return;

  D->addAttr(::new (S.Context) ReturnsNonNullAttr(S.Context, AL));
}

static void handleNoEscapeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (D->isInvalidDecl())
    return;

  // noescape only applies to pointer types.
  QualType T = cast<ParmVarDecl>(D)->getType();
  if (!S.isValidPointerAttrType(T, /* RefOkay */ true)) {
    S.Diag(AL.getLoc(), diag::warn_attribute_pointers_only)
        << AL << AL.getRange() << 0;
    return;
  }

  D->addAttr(::new (S.Context) NoEscapeAttr(S.Context, AL));
}

static void handleAssumeAlignedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  Expr *E = AL.getArgAsExpr(0),
       *OE = AL.getNumArgs() > 1 ? AL.getArgAsExpr(1) : nullptr;
  S.AddAssumeAlignedAttr(D, AL, E, OE);
}

static void handleAllocAlignAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  S.AddAllocAlignAttr(D, AL, AL.getArgAsExpr(0));
}

void Sema::AddAssumeAlignedAttr(Decl *D, const AttributeCommonInfo &CI, Expr *E,
                                Expr *OE) {
  QualType ResultType = getFunctionOrMethodResultType(D);
  SourceRange SR = getFunctionOrMethodResultSourceRange(D);

  AssumeAlignedAttr TmpAttr(Context, CI, E, OE);
  SourceLocation AttrLoc = TmpAttr.getLocation();

  if (!isValidPointerAttrType(ResultType, /* RefOkay */ true)) {
    Diag(AttrLoc, diag::warn_attribute_return_pointers_refs_only)
        << &TmpAttr << TmpAttr.getRange() << SR;
    return;
  }

  if (!E->isValueDependent()) {
    std::optional<llvm::APSInt> I = llvm::APSInt(64);
    if (!(I = E->getIntegerConstantExpr(Context))) {
      if (OE)
        Diag(AttrLoc, diag::err_attribute_argument_n_type)
          << &TmpAttr << 1 << AANT_ArgumentIntegerConstant
          << E->getSourceRange();
      else
        Diag(AttrLoc, diag::err_attribute_argument_type)
          << &TmpAttr << AANT_ArgumentIntegerConstant
          << E->getSourceRange();
      return;
    }

    if (!I->isPowerOf2()) {
      Diag(AttrLoc, diag::err_alignment_not_power_of_two)
        << E->getSourceRange();
      return;
    }

    if (*I > Sema::MaximumAlignment)
      Diag(CI.getLoc(), diag::warn_assume_aligned_too_great)
          << CI.getRange() << Sema::MaximumAlignment;
  }

  if (OE && !OE->isValueDependent() && !OE->isIntegerConstantExpr(Context)) {
    Diag(AttrLoc, diag::err_attribute_argument_n_type)
        << &TmpAttr << 2 << AANT_ArgumentIntegerConstant
        << OE->getSourceRange();
    return;
  }

  D->addAttr(::new (Context) AssumeAlignedAttr(Context, CI, E, OE));
}

void Sema::AddAllocAlignAttr(Decl *D, const AttributeCommonInfo &CI,
                             Expr *ParamExpr) {
  QualType ResultType = getFunctionOrMethodResultType(D);

  AllocAlignAttr TmpAttr(Context, CI, ParamIdx());
  SourceLocation AttrLoc = CI.getLoc();

  if (!ResultType->isDependentType() &&
      !isValidPointerAttrType(ResultType, /* RefOkay */ true)) {
    Diag(AttrLoc, diag::warn_attribute_return_pointers_refs_only)
        << &TmpAttr << CI.getRange() << getFunctionOrMethodResultSourceRange(D);
    return;
  }

  ParamIdx Idx;
  const auto *FuncDecl = cast<FunctionDecl>(D);
  if (!checkFunctionOrMethodParameterIndex(*this, FuncDecl, TmpAttr,
                                           /*AttrArgNum=*/1, ParamExpr, Idx))
    return;

  QualType Ty = getFunctionOrMethodParamType(D, Idx.getASTIndex());
  if (!Ty->isDependentType() && !Ty->isIntegralType(Context) &&
      !Ty->isAlignValT()) {
    Diag(ParamExpr->getBeginLoc(), diag::err_attribute_integers_only)
        << &TmpAttr
        << FuncDecl->getParamDecl(Idx.getASTIndex())->getSourceRange();
    return;
  }

  D->addAttr(::new (Context) AllocAlignAttr(Context, CI, Idx));
}

/// Check if \p AssumptionStr is a known assumption and warn if not.
static void checkAssumptionAttr(Sema &S, SourceLocation Loc,
                                StringRef AssumptionStr) {
  if (llvm::KnownAssumptionStrings.count(AssumptionStr))
    return;

  unsigned BestEditDistance = 3;
  StringRef Suggestion;
  for (const auto &KnownAssumptionIt : llvm::KnownAssumptionStrings) {
    unsigned EditDistance =
        AssumptionStr.edit_distance(KnownAssumptionIt.getKey());
    if (EditDistance < BestEditDistance) {
      Suggestion = KnownAssumptionIt.getKey();
      BestEditDistance = EditDistance;
    }
  }

  if (!Suggestion.empty())
    S.Diag(Loc, diag::warn_assume_attribute_string_unknown_suggested)
        << AssumptionStr << Suggestion;
  else
    S.Diag(Loc, diag::warn_assume_attribute_string_unknown) << AssumptionStr;
}

static void handleAssumumptionAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Handle the case where the attribute has a text message.
  StringRef Str;
  SourceLocation AttrStrLoc;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &AttrStrLoc))
    return;

  checkAssumptionAttr(S, AttrStrLoc, Str);

  D->addAttr(::new (S.Context) AssumptionAttr(S.Context, AL, Str));
}

/// Normalize the attribute, __foo__ becomes foo.
/// Returns true if normalization was applied.
static bool normalizeName(StringRef &AttrName) {
  if (AttrName.size() > 4 && AttrName.startswith("__") &&
      AttrName.endswith("__")) {
    AttrName = AttrName.drop_front(2).drop_back(2);
    return true;
  }
  return false;
}

static void handleOwnershipAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // This attribute must be applied to a function declaration. The first
  // argument to the attribute must be an identifier, the name of the resource,
  // for example: malloc. The following arguments must be argument indexes, the
  // arguments must be of integer type for Returns, otherwise of pointer type.
  // The difference between Holds and Takes is that a pointer may still be used
  // after being held. free() should be __attribute((ownership_takes)), whereas
  // a list append function may well be __attribute((ownership_holds)).

  if (!AL.isArgIdent(0)) {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
        << AL << 1 << AANT_ArgumentIdentifier;
    return;
  }

  // Figure out our Kind.
  OwnershipAttr::OwnershipKind K =
      OwnershipAttr(S.Context, AL, nullptr, nullptr, 0).getOwnKind();

  // Check arguments.
  switch (K) {
  case OwnershipAttr::Takes:
  case OwnershipAttr::Holds:
    if (AL.getNumArgs() < 2) {
      S.Diag(AL.getLoc(), diag::err_attribute_too_few_arguments) << AL << 2;
      return;
    }
    break;
  case OwnershipAttr::Returns:
    if (AL.getNumArgs() > 2) {
      S.Diag(AL.getLoc(), diag::err_attribute_too_many_arguments) << AL << 1;
      return;
    }
    break;
  }

  IdentifierInfo *Module = AL.getArgAsIdent(0)->Ident;

  StringRef ModuleName = Module->getName();
  if (normalizeName(ModuleName)) {
    Module = &S.PP.getIdentifierTable().get(ModuleName);
  }

  SmallVector<ParamIdx, 8> OwnershipArgs;
  for (unsigned i = 1; i < AL.getNumArgs(); ++i) {
    Expr *Ex = AL.getArgAsExpr(i);
    ParamIdx Idx;
    if (!checkFunctionOrMethodParameterIndex(S, D, AL, i, Ex, Idx))
      return;

    // Is the function argument a pointer type?
    QualType T = getFunctionOrMethodParamType(D, Idx.getASTIndex());
    int Err = -1;  // No error
    switch (K) {
      case OwnershipAttr::Takes:
      case OwnershipAttr::Holds:
        if (!T->isAnyPointerType() && !T->isBlockPointerType())
          Err = 0;
        break;
      case OwnershipAttr::Returns:
        if (!T->isIntegerType())
          Err = 1;
        break;
    }
    if (-1 != Err) {
      S.Diag(AL.getLoc(), diag::err_ownership_type) << AL << Err
                                                    << Ex->getSourceRange();
      return;
    }

    // Check we don't have a conflict with another ownership attribute.
    for (const auto *I : D->specific_attrs<OwnershipAttr>()) {
      // Cannot have two ownership attributes of different kinds for the same
      // index.
      if (I->getOwnKind() != K && llvm::is_contained(I->args(), Idx)) {
          S.Diag(AL.getLoc(), diag::err_attributes_are_not_compatible)
              << AL << I
              << (AL.isRegularKeywordAttribute() ||
                  I->isRegularKeywordAttribute());
          return;
      } else if (K == OwnershipAttr::Returns &&
                 I->getOwnKind() == OwnershipAttr::Returns) {
        // A returns attribute conflicts with any other returns attribute using
        // a different index.
        if (!llvm::is_contained(I->args(), Idx)) {
          S.Diag(I->getLocation(), diag::err_ownership_returns_index_mismatch)
              << I->args_begin()->getSourceIndex();
          if (I->args_size())
            S.Diag(AL.getLoc(), diag::note_ownership_returns_index_mismatch)
                << Idx.getSourceIndex() << Ex->getSourceRange();
          return;
        }
      }
    }
    OwnershipArgs.push_back(Idx);
  }

  ParamIdx *Start = OwnershipArgs.data();
  unsigned Size = OwnershipArgs.size();
  llvm::array_pod_sort(Start, Start + Size);
  D->addAttr(::new (S.Context)
                 OwnershipAttr(S.Context, AL, Module, Start, Size));
}

static void handleWeakRefAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Check the attribute arguments.
  if (AL.getNumArgs() > 1) {
    S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments) << AL << 1;
    return;
  }

  // gcc rejects
  // class c {
  //   static int a __attribute__((weakref ("v2")));
  //   static int b() __attribute__((weakref ("f3")));
  // };
  // and ignores the attributes of
  // void f(void) {
  //   static int a __attribute__((weakref ("v2")));
  // }
  // we reject them
  const DeclContext *Ctx = D->getDeclContext()->getRedeclContext();
  if (!Ctx->isFileContext()) {
    S.Diag(AL.getLoc(), diag::err_attribute_weakref_not_global_context)
        << cast<NamedDecl>(D);
    return;
  }

  // The GCC manual says
  //
  // At present, a declaration to which `weakref' is attached can only
  // be `static'.
  //
  // It also says
  //
  // Without a TARGET,
  // given as an argument to `weakref' or to `alias', `weakref' is
  // equivalent to `weak'.
  //
  // gcc 4.4.1 will accept
  // int a7 __attribute__((weakref));
  // as
  // int a7 __attribute__((weak));
  // This looks like a bug in gcc. We reject that for now. We should revisit
  // it if this behaviour is actually used.

  // GCC rejects
  // static ((alias ("y"), weakref)).
  // Should we? How to check that weakref is before or after alias?

  // FIXME: it would be good for us to keep the WeakRefAttr as-written instead
  // of transforming it into an AliasAttr.  The WeakRefAttr never uses the
  // StringRef parameter it was given anyway.
  StringRef Str;
  if (AL.getNumArgs() && S.checkStringLiteralArgumentAttr(AL, 0, Str))
    // GCC will accept anything as the argument of weakref. Should we
    // check for an existing decl?
    D->addAttr(::new (S.Context) AliasAttr(S.Context, AL, Str));

  D->addAttr(::new (S.Context) WeakRefAttr(S.Context, AL));
}

static void handleIFuncAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  StringRef Str;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str))
    return;

  // Aliases should be on declarations, not definitions.
  const auto *FD = cast<FunctionDecl>(D);
  if (FD->isThisDeclarationADefinition()) {
    S.Diag(AL.getLoc(), diag::err_alias_is_definition) << FD << 1;
    return;
  }

  D->addAttr(::new (S.Context) IFuncAttr(S.Context, AL, Str));
}

static void handleAliasAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  StringRef Str;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str))
    return;

  if (S.Context.getTargetInfo().getTriple().isOSDarwin()) {
    S.Diag(AL.getLoc(), diag::err_alias_not_supported_on_darwin);
    return;
  }
  if (S.Context.getTargetInfo().getTriple().isNVPTX()) {
    S.Diag(AL.getLoc(), diag::err_alias_not_supported_on_nvptx);
  }

  // Aliases should be on declarations, not definitions.
  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->isThisDeclarationADefinition()) {
      S.Diag(AL.getLoc(), diag::err_alias_is_definition) << FD << 0;
      return;
    }
  } else {
    const auto *VD = cast<VarDecl>(D);
    if (VD->isThisDeclarationADefinition() && VD->isExternallyVisible()) {
      S.Diag(AL.getLoc(), diag::err_alias_is_definition) << VD << 0;
      return;
    }
  }

  // Mark target used to prevent unneeded-internal-declaration warnings.
  if (!S.LangOpts.CPlusPlus) {
    // FIXME: demangle Str for C++, as the attribute refers to the mangled
    // linkage name, not the pre-mangled identifier.
    const DeclarationNameInfo target(&S.Context.Idents.get(Str), AL.getLoc());
    LookupResult LR(S, target, Sema::LookupOrdinaryName);
    if (S.LookupQualifiedName(LR, S.getCurLexicalContext()))
      for (NamedDecl *ND : LR)
        ND->markUsed(S.Context);
  }

  D->addAttr(::new (S.Context) AliasAttr(S.Context, AL, Str));
}

static void handleTLSModelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  StringRef Model;
  SourceLocation LiteralLoc;
  // Check that it is a string.
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Model, &LiteralLoc))
    return;

  // Check that the value.
  if (Model != "global-dynamic" && Model != "local-dynamic"
      && Model != "initial-exec" && Model != "local-exec") {
    S.Diag(LiteralLoc, diag::err_attr_tlsmodel_arg);
    return;
  }

  if (S.Context.getTargetInfo().getTriple().isOSAIX() &&
      Model != "global-dynamic") {
    S.Diag(LiteralLoc, diag::err_aix_attr_unsupported_tls_model) << Model;
    return;
  }

  D->addAttr(::new (S.Context) TLSModelAttr(S.Context, AL, Model));
}

static void handleRestrictAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  QualType ResultType = getFunctionOrMethodResultType(D);
  if (ResultType->isAnyPointerType() || ResultType->isBlockPointerType()) {
    D->addAttr(::new (S.Context) RestrictAttr(S.Context, AL));
    return;
  }

  S.Diag(AL.getLoc(), diag::warn_attribute_return_pointers_only)
      << AL << getFunctionOrMethodResultSourceRange(D);
}

static void handleCPUSpecificAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Ensure we don't combine these with themselves, since that causes some
  // confusing behavior.
  if (AL.getParsedKind() == ParsedAttr::AT_CPUDispatch) {
    if (checkAttrMutualExclusion<CPUSpecificAttr>(S, D, AL))
      return;

    if (const auto *Other = D->getAttr<CPUDispatchAttr>()) {
      S.Diag(AL.getLoc(), diag::err_disallowed_duplicate_attribute) << AL;
      S.Diag(Other->getLocation(), diag::note_conflicting_attribute);
      return;
    }
  } else if (AL.getParsedKind() == ParsedAttr::AT_CPUSpecific) {
    if (checkAttrMutualExclusion<CPUDispatchAttr>(S, D, AL))
      return;

    if (const auto *Other = D->getAttr<CPUSpecificAttr>()) {
      S.Diag(AL.getLoc(), diag::err_disallowed_duplicate_attribute) << AL;
      S.Diag(Other->getLocation(), diag::note_conflicting_attribute);
      return;
    }
  }

  FunctionDecl *FD = cast<FunctionDecl>(D);

  if (const auto *MD = dyn_cast<CXXMethodDecl>(D)) {
    if (MD->getParent()->isLambda()) {
      S.Diag(AL.getLoc(), diag::err_attribute_dll_lambda) << AL;
      return;
    }
  }

  if (!AL.checkAtLeastNumArgs(S, 1))
    return;

  SmallVector<IdentifierInfo *, 8> CPUs;
  for (unsigned ArgNo = 0; ArgNo < getNumAttributeArgs(AL); ++ArgNo) {
    if (!AL.isArgIdent(ArgNo)) {
      S.Diag(AL.getLoc(), diag::err_attribute_argument_type)
          << AL << AANT_ArgumentIdentifier;
      return;
    }

    IdentifierLoc *CPUArg = AL.getArgAsIdent(ArgNo);
    StringRef CPUName = CPUArg->Ident->getName().trim();

    if (!S.Context.getTargetInfo().validateCPUSpecificCPUDispatch(CPUName)) {
      S.Diag(CPUArg->Loc, diag::err_invalid_cpu_specific_dispatch_value)
          << CPUName << (AL.getKind() == ParsedAttr::AT_CPUDispatch);
      return;
    }

    const TargetInfo &Target = S.Context.getTargetInfo();
    if (llvm::any_of(CPUs, [CPUName, &Target](const IdentifierInfo *Cur) {
          return Target.CPUSpecificManglingCharacter(CPUName) ==
                 Target.CPUSpecificManglingCharacter(Cur->getName());
        })) {
      S.Diag(AL.getLoc(), diag::warn_multiversion_duplicate_entries);
      return;
    }
    CPUs.push_back(CPUArg->Ident);
  }

  FD->setIsMultiVersion(true);
  if (AL.getKind() == ParsedAttr::AT_CPUSpecific)
    D->addAttr(::new (S.Context)
                   CPUSpecificAttr(S.Context, AL, CPUs.data(), CPUs.size()));
  else
    D->addAttr(::new (S.Context)
                   CPUDispatchAttr(S.Context, AL, CPUs.data(), CPUs.size()));
}

static void handleCommonAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (S.LangOpts.CPlusPlus) {
    S.Diag(AL.getLoc(), diag::err_attribute_not_supported_in_lang)
        << AL << AttributeLangSupport::Cpp;
    return;
  }

  D->addAttr(::new (S.Context) CommonAttr(S.Context, AL));
}

static void handleCmseNSEntryAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (S.LangOpts.CPlusPlus && !D->getDeclContext()->isExternCContext()) {
    S.Diag(AL.getLoc(), diag::err_attribute_not_clinkage) << AL;
    return;
  }

  const auto *FD = cast<FunctionDecl>(D);
  if (!FD->isExternallyVisible()) {
    S.Diag(AL.getLoc(), diag::warn_attribute_cmse_entry_static);
    return;
  }

  D->addAttr(::new (S.Context) CmseNSEntryAttr(S.Context, AL));
}

static void handleNakedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (AL.isDeclspecAttribute()) {
    const auto &Triple = S.getASTContext().getTargetInfo().getTriple();
    const auto &Arch = Triple.getArch();
    if (Arch != llvm::Triple::x86 &&
        (Arch != llvm::Triple::arm && Arch != llvm::Triple::thumb)) {
      S.Diag(AL.getLoc(), diag::err_attribute_not_supported_on_arch)
          << AL << Triple.getArchName();
      return;
    }

    // This form is not allowed to be written on a member function (static or
    // nonstatic) when in Microsoft compatibility mode.
    if (S.getLangOpts().MSVCCompat && isa<CXXMethodDecl>(D)) {
      S.Diag(AL.getLoc(), diag::err_attribute_wrong_decl_type_str)
          << AL << AL.isRegularKeywordAttribute() << "non-member functions";
      return;
    }
  }

  D->addAttr(::new (S.Context) NakedAttr(S.Context, AL));
}

static void handleNoReturnAttr(Sema &S, Decl *D, const ParsedAttr &Attrs) {
  if (hasDeclarator(D)) return;

  if (!isa<ObjCMethodDecl>(D)) {
    S.Diag(Attrs.getLoc(), diag::warn_attribute_wrong_decl_type)
        << Attrs << Attrs.isRegularKeywordAttribute()
        << ExpectedFunctionOrMethod;
    return;
  }

  D->addAttr(::new (S.Context) NoReturnAttr(S.Context, Attrs));
}

static void handleStandardNoReturnAttr(Sema &S, Decl *D, const ParsedAttr &A) {
  // The [[_Noreturn]] spelling is deprecated in C2x, so if that was used,
  // issue an appropriate diagnostic. However, don't issue a diagnostic if the
  // attribute name comes from a macro expansion. We don't want to punish users
  // who write [[noreturn]] after including <stdnoreturn.h> (where 'noreturn'
  // is defined as a macro which expands to '_Noreturn').
  if (!S.getLangOpts().CPlusPlus &&
      A.getSemanticSpelling() == CXX11NoReturnAttr::C2x_Noreturn &&
      !(A.getLoc().isMacroID() &&
        S.getSourceManager().isInSystemMacro(A.getLoc())))
    S.Diag(A.getLoc(), diag::warn_deprecated_noreturn_spelling) << A.getRange();

  D->addAttr(::new (S.Context) CXX11NoReturnAttr(S.Context, A));
}

static void handleNoCfCheckAttr(Sema &S, Decl *D, const ParsedAttr &Attrs) {
  if (!S.getLangOpts().CFProtectionBranch)
    S.Diag(Attrs.getLoc(), diag::warn_nocf_check_attribute_ignored);
  else
    handleSimpleAttribute<AnyX86NoCfCheckAttr>(S, D, Attrs);
}

bool Sema::CheckAttrNoArgs(const ParsedAttr &Attrs) {
  if (!Attrs.checkExactlyNumArgs(*this, 0)) {
    Attrs.setInvalid();
    return true;
  }

  return false;
}

bool Sema::CheckAttrTarget(const ParsedAttr &AL) {
  // Check whether the attribute is valid on the current target.
  if (!AL.existsInTarget(Context.getTargetInfo())) {
    Diag(AL.getLoc(), AL.isRegularKeywordAttribute()
                          ? diag::err_keyword_not_supported_on_target
                          : diag::warn_unknown_attribute_ignored)
        << AL << AL.getRange();
    AL.setInvalid();
    return true;
  }

  return false;
}

static void handleAnalyzerNoReturnAttr(Sema &S, Decl *D, const ParsedAttr &AL) {

  // The checking path for 'noreturn' and 'analyzer_noreturn' are different
  // because 'analyzer_noreturn' does not impact the type.
  if (!isFunctionOrMethodOrBlock(D)) {
    ValueDecl *VD = dyn_cast<ValueDecl>(D);
    if (!VD || (!VD->getType()->isBlockPointerType() &&
                !VD->getType()->isFunctionPointerType())) {
      S.Diag(AL.getLoc(), AL.isStandardAttributeSyntax()
                              ? diag::err_attribute_wrong_decl_type
                              : diag::warn_attribute_wrong_decl_type)
          << AL << AL.isRegularKeywordAttribute()
          << ExpectedFunctionMethodOrBlock;
      return;
    }
  }

  D->addAttr(::new (S.Context) AnalyzerNoReturnAttr(S.Context, AL));
}

// PS3 PPU-specific.
static void handleVecReturnAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  /*
    Returning a Vector Class in Registers

    According to the PPU ABI specifications, a class with a single member of
    vector type is returned in memory when used as the return value of a
    function.
    This results in inefficient code when implementing vector classes. To return
    the value in a single vector register, add the vecreturn attribute to the
    class definition. This attribute is also applicable to struct types.

    Example:

    struct Vector
    {
      __vector float xyzw;
    } __attribute__((vecreturn));

    Vector Add(Vector lhs, Vector rhs)
    {
      Vector result;
      result.xyzw = vec_add(lhs.xyzw, rhs.xyzw);
      return result; // This will be returned in a register
    }
  */
  if (VecReturnAttr *A = D->getAttr<VecReturnAttr>()) {
    S.Diag(AL.getLoc(), diag::err_repeat_attribute) << A;
    return;
  }

  const auto *R = cast<RecordDecl>(D);
  int count = 0;

  if (!isa<CXXRecordDecl>(R)) {
    S.Diag(AL.getLoc(), diag::err_attribute_vecreturn_only_vector_member);
    return;
  }

  if (!cast<CXXRecordDecl>(R)->isPOD()) {
    S.Diag(AL.getLoc(), diag::err_attribute_vecreturn_only_pod_record);
    return;
  }

  for (const auto *I : R->fields()) {
    if ((count == 1) || !I->getType()->isVectorType()) {
      S.Diag(AL.getLoc(), diag::err_attribute_vecreturn_only_vector_member);
      return;
    }
    count++;
  }

  D->addAttr(::new (S.Context) VecReturnAttr(S.Context, AL));
}

static void handleDependencyAttr(Sema &S, Scope *Scope, Decl *D,
                                 const ParsedAttr &AL) {
  if (isa<ParmVarDecl>(D)) {
    // [[carries_dependency]] can only be applied to a parameter if it is a
    // parameter of a function declaration or lambda.
    if (!(Scope->getFlags() & clang::Scope::FunctionDeclarationScope)) {
      S.Diag(AL.getLoc(),
             diag::err_carries_dependency_param_not_function_decl);
      return;
    }
  }

  D->addAttr(::new (S.Context) CarriesDependencyAttr(S.Context, AL));
}

static void handleUnusedAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  bool IsCXX17Attr = AL.isCXX11Attribute() && !AL.getScopeName();

  // If this is spelled as the standard C++17 attribute, but not in C++17, warn
  // about using it as an extension.
  if (!S.getLangOpts().CPlusPlus17 && IsCXX17Attr)
    S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;

  D->addAttr(::new (S.Context) UnusedAttr(S.Context, AL));
}

static void handleConstructorAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  uint32_t priority = ConstructorAttr::DefaultPriority;
  if (S.getLangOpts().HLSL && AL.getNumArgs()) {
    S.Diag(AL.getLoc(), diag::err_hlsl_init_priority_unsupported);
    return;
  }
  if (AL.getNumArgs() &&
      !checkUInt32Argument(S, AL, AL.getArgAsExpr(0), priority))
    return;

  D->addAttr(::new (S.Context) ConstructorAttr(S.Context, AL, priority));
}

static void handleDestructorAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  uint32_t priority = DestructorAttr::DefaultPriority;
  if (AL.getNumArgs() &&
      !checkUInt32Argument(S, AL, AL.getArgAsExpr(0), priority))
    return;

  D->addAttr(::new (S.Context) DestructorAttr(S.Context, AL, priority));
}

template <typename AttrTy>
static void handleAttrWithMessage(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Handle the case where the attribute has a text message.
  StringRef Str;
  if (AL.getNumArgs() == 1 && !S.checkStringLiteralArgumentAttr(AL, 0, Str))
    return;

  D->addAttr(::new (S.Context) AttrTy(S.Context, AL, Str));
}

static void handleObjCSuppresProtocolAttr(Sema &S, Decl *D,
                                          const ParsedAttr &AL) {
  if (!cast<ObjCProtocolDecl>(D)->isThisDeclarationADefinition()) {
    S.Diag(AL.getLoc(), diag::err_objc_attr_protocol_requires_definition)
        << AL << AL.getRange();
    return;
  }

  D->addAttr(::new (S.Context) ObjCExplicitProtocolImplAttr(S.Context, AL));
}

static bool checkAvailabilityAttr(Sema &S, SourceRange Range,
                                  IdentifierInfo *Platform,
                                  VersionTuple Introduced,
                                  VersionTuple Deprecated,
                                  VersionTuple Obsoleted) {
  StringRef PlatformName
    = AvailabilityAttr::getPrettyPlatformName(Platform->getName());
  if (PlatformName.empty())
    PlatformName = Platform->getName();

  // Ensure that Introduced <= Deprecated <= Obsoleted (although not all
  // of these steps are needed).
  if (!Introduced.empty() && !Deprecated.empty() &&
      !(Introduced <= Deprecated)) {
    S.Diag(Range.getBegin(), diag::warn_availability_version_ordering)
      << 1 << PlatformName << Deprecated.getAsString()
      << 0 << Introduced.getAsString();
    return true;
  }

  if (!Introduced.empty() && !Obsoleted.empty() &&
      !(Introduced <= Obsoleted)) {
    S.Diag(Range.getBegin(), diag::warn_availability_version_ordering)
      << 2 << PlatformName << Obsoleted.getAsString()
      << 0 << Introduced.getAsString();
    return true;
  }

  if (!Deprecated.empty() && !Obsoleted.empty() &&
      !(Deprecated <= Obsoleted)) {
    S.Diag(Range.getBegin(), diag::warn_availability_version_ordering)
      << 2 << PlatformName << Obsoleted.getAsString()
      << 1 << Deprecated.getAsString();
    return true;
  }

  return false;
}

/// Check whether the two versions match.
///
/// If either version tuple is empty, then they are assumed to match. If
/// \p BeforeIsOkay is true, then \p X can be less than or equal to \p Y.
static bool versionsMatch(const VersionTuple &X, const VersionTuple &Y,
                          bool BeforeIsOkay) {
  if (X.empty() || Y.empty())
    return true;

  if (X == Y)
    return true;

  if (BeforeIsOkay && X < Y)
    return true;

  return false;
}

AvailabilityAttr *Sema::mergeAvailabilityAttr(
    NamedDecl *D, const AttributeCommonInfo &CI, IdentifierInfo *Platform,
    bool Implicit, VersionTuple Introduced, VersionTuple Deprecated,
    VersionTuple Obsoleted, bool IsUnavailable, StringRef Message,
    bool IsStrict, StringRef Replacement, AvailabilityMergeKind AMK,
    int Priority) {
  VersionTuple MergedIntroduced = Introduced;
  VersionTuple MergedDeprecated = Deprecated;
  VersionTuple MergedObsoleted = Obsoleted;
  bool FoundAny = false;
  bool OverrideOrImpl = false;
  switch (AMK) {
  case AMK_None:
  case AMK_Redeclaration:
    OverrideOrImpl = false;
    break;

  case AMK_Override:
  case AMK_ProtocolImplementation:
  case AMK_OptionalProtocolImplementation:
    OverrideOrImpl = true;
    break;
  }

  if (D->hasAttrs()) {
    AttrVec &Attrs = D->getAttrs();
    for (unsigned i = 0, e = Attrs.size(); i != e;) {
      const auto *OldAA = dyn_cast<AvailabilityAttr>(Attrs[i]);
      if (!OldAA) {
        ++i;
        continue;
      }

      IdentifierInfo *OldPlatform = OldAA->getPlatform();
      if (OldPlatform != Platform) {
        ++i;
        continue;
      }

      // If there is an existing availability attribute for this platform that
      // has a lower priority use the existing one and discard the new
      // attribute.
      if (OldAA->getPriority() < Priority)
        return nullptr;

      // If there is an existing attribute for this platform that has a higher
      // priority than the new attribute then erase the old one and continue
      // processing the attributes.
      if (OldAA->getPriority() > Priority) {
        Attrs.erase(Attrs.begin() + i);
        --e;
        continue;
      }

      FoundAny = true;
      VersionTuple OldIntroduced = OldAA->getIntroduced();
      VersionTuple OldDeprecated = OldAA->getDeprecated();
      VersionTuple OldObsoleted = OldAA->getObsoleted();
      bool OldIsUnavailable = OldAA->getUnavailable();

      if (!versionsMatch(OldIntroduced, Introduced, OverrideOrImpl) ||
          !versionsMatch(Deprecated, OldDeprecated, OverrideOrImpl) ||
          !versionsMatch(Obsoleted, OldObsoleted, OverrideOrImpl) ||
          !(OldIsUnavailable == IsUnavailable ||
            (OverrideOrImpl && !OldIsUnavailable && IsUnavailable))) {
        if (OverrideOrImpl) {
          int Which = -1;
          VersionTuple FirstVersion;
          VersionTuple SecondVersion;
          if (!versionsMatch(OldIntroduced, Introduced, OverrideOrImpl)) {
            Which = 0;
            FirstVersion = OldIntroduced;
            SecondVersion = Introduced;
          } else if (!versionsMatch(Deprecated, OldDeprecated, OverrideOrImpl)) {
            Which = 1;
            FirstVersion = Deprecated;
            SecondVersion = OldDeprecated;
          } else if (!versionsMatch(Obsoleted, OldObsoleted, OverrideOrImpl)) {
            Which = 2;
            FirstVersion = Obsoleted;
            SecondVersion = OldObsoleted;
          }

          if (Which == -1) {
            Diag(OldAA->getLocation(),
                 diag::warn_mismatched_availability_override_unavail)
              << AvailabilityAttr::getPrettyPlatformName(Platform->getName())
              << (AMK == AMK_Override);
          } else if (Which != 1 && AMK == AMK_OptionalProtocolImplementation) {
            // Allow different 'introduced' / 'obsoleted' availability versions
            // on a method that implements an optional protocol requirement. It
            // makes less sense to allow this for 'deprecated' as the user can't
            // see if the method is 'deprecated' as 'respondsToSelector' will
            // still return true when the method is deprecated.
            ++i;
            continue;
          } else {
            Diag(OldAA->getLocation(),
                 diag::warn_mismatched_availability_override)
              << Which
              << AvailabilityAttr::getPrettyPlatformName(Platform->getName())
              << FirstVersion.getAsString() << SecondVersion.getAsString()
              << (AMK == AMK_Override);
          }
          if (AMK == AMK_Override)
            Diag(CI.getLoc(), diag::note_overridden_method);
          else
            Diag(CI.getLoc(), diag::note_protocol_method);
        } else {
          Diag(OldAA->getLocation(), diag::warn_mismatched_availability);
          Diag(CI.getLoc(), diag::note_previous_attribute);
        }

        Attrs.erase(Attrs.begin() + i);
        --e;
        continue;
      }

      VersionTuple MergedIntroduced2 = MergedIntroduced;
      VersionTuple MergedDeprecated2 = MergedDeprecated;
      VersionTuple MergedObsoleted2 = MergedObsoleted;

      if (MergedIntroduced2.empty())
        MergedIntroduced2 = OldIntroduced;
      if (MergedDeprecated2.empty())
        MergedDeprecated2 = OldDeprecated;
      if (MergedObsoleted2.empty())
        MergedObsoleted2 = OldObsoleted;

      if (checkAvailabilityAttr(*this, OldAA->getRange(), Platform,
                                MergedIntroduced2, MergedDeprecated2,
                                MergedObsoleted2)) {
        Attrs.erase(Attrs.begin() + i);
        --e;
        continue;
      }

      MergedIntroduced = MergedIntroduced2;
      MergedDeprecated = MergedDeprecated2;
      MergedObsoleted = MergedObsoleted2;
      ++i;
    }
  }

  if (FoundAny &&
      MergedIntroduced == Introduced &&
      MergedDeprecated == Deprecated &&
      MergedObsoleted == Obsoleted)
    return nullptr;

  // Only create a new attribute if !OverrideOrImpl, but we want to do
  // the checking.
  if (!checkAvailabilityAttr(*this, CI.getRange(), Platform, MergedIntroduced,
                             MergedDeprecated, MergedObsoleted) &&
      !OverrideOrImpl) {
    auto *Avail = ::new (Context) AvailabilityAttr(
        Context, CI, Platform, Introduced, Deprecated, Obsoleted, IsUnavailable,
        Message, IsStrict, Replacement, Priority);
    Avail->setImplicit(Implicit);
    return Avail;
  }
  return nullptr;
}

static void handleAvailabilityAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (isa<UsingDecl, UnresolvedUsingTypenameDecl, UnresolvedUsingValueDecl>(
          D)) {
    S.Diag(AL.getRange().getBegin(), diag::warn_deprecated_ignored_on_using)
        << AL;
    return;
  }

  if (!AL.checkExactlyNumArgs(S, 1))
    return;
  IdentifierLoc *Platform = AL.getArgAsIdent(0);

  IdentifierInfo *II = Platform->Ident;
  if (AvailabilityAttr::getPrettyPlatformName(II->getName()).empty())
    S.Diag(Platform->Loc, diag::warn_availability_unknown_platform)
      << Platform->Ident;

  auto *ND = dyn_cast<NamedDecl>(D);
  if (!ND) // We warned about this already, so just return.
    return;

  AvailabilityChange Introduced = AL.getAvailabilityIntroduced();
  AvailabilityChange Deprecated = AL.getAvailabilityDeprecated();
  AvailabilityChange Obsoleted = AL.getAvailabilityObsoleted();
  bool IsUnavailable = AL.getUnavailableLoc().isValid();
  bool IsStrict = AL.getStrictLoc().isValid();
  StringRef Str;
  if (const auto *SE = dyn_cast_or_null<StringLiteral>(AL.getMessageExpr()))
    Str = SE->getString();
  StringRef Replacement;
  if (const auto *SE = dyn_cast_or_null<StringLiteral>(AL.getReplacementExpr()))
    Replacement = SE->getString();

  if (II->isStr("swift")) {
    if (Introduced.isValid() || Obsoleted.isValid() ||
        (!IsUnavailable && !Deprecated.isValid())) {
      S.Diag(AL.getLoc(),
             diag::warn_availability_swift_unavailable_deprecated_only);
      return;
    }
  }

  if (II->isStr("fuchsia")) {
    std::optional<unsigned> Min, Sub;
    if ((Min = Introduced.Version.getMinor()) ||
        (Sub = Introduced.Version.getSubminor())) {
      S.Diag(AL.getLoc(), diag::warn_availability_fuchsia_unavailable_minor);
      return;
    }
  }

  int PriorityModifier = AL.isPragmaClangAttribute()
                             ? Sema::AP_PragmaClangAttribute
                             : Sema::AP_Explicit;
  AvailabilityAttr *NewAttr = S.mergeAvailabilityAttr(
      ND, AL, II, false /*Implicit*/, Introduced.Version, Deprecated.Version,
      Obsoleted.Version, IsUnavailable, Str, IsStrict, Replacement,
      Sema::AMK_None, PriorityModifier);
  if (NewAttr)
    D->addAttr(NewAttr);

  // Transcribe "ios" to "watchos" (and add a new attribute) if the versioning
  // matches before the start of the watchOS platform.
  if (S.Context.getTargetInfo().getTriple().isWatchOS()) {
    IdentifierInfo *NewII = nullptr;
    if (II->getName() == "ios")
      NewII = &S.Context.Idents.get("watchos");
    else if (II->getName() == "ios_app_extension")
      NewII = &S.Context.Idents.get("watchos_app_extension");

    if (NewII) {
      const auto *SDKInfo = S.getDarwinSDKInfoForAvailabilityChecking();
      const auto *IOSToWatchOSMapping =
          SDKInfo ? SDKInfo->getVersionMapping(
                        DarwinSDKInfo::OSEnvPair::iOStoWatchOSPair())
                  : nullptr;

      auto adjustWatchOSVersion =
          [IOSToWatchOSMapping](VersionTuple Version) -> VersionTuple {
        if (Version.empty())
          return Version;
        auto MinimumWatchOSVersion = VersionTuple(2, 0);

        if (IOSToWatchOSMapping) {
          if (auto MappedVersion = IOSToWatchOSMapping->map(
                  Version, MinimumWatchOSVersion, std::nullopt)) {
            return *MappedVersion;
          }
        }

        auto Major = Version.getMajor();
        auto NewMajor = Major >= 9 ? Major - 7 : 0;
        if (NewMajor >= 2) {
          if (Version.getMinor()) {
            if (Version.getSubminor())
              return VersionTuple(NewMajor, *Version.getMinor(),
                                  *Version.getSubminor());
            else
              return VersionTuple(NewMajor, *Version.getMinor());
          }
          return VersionTuple(NewMajor);
        }

        return MinimumWatchOSVersion;
      };

      auto NewIntroduced = adjustWatchOSVersion(Introduced.Version);
      auto NewDeprecated = adjustWatchOSVersion(Deprecated.Version);
      auto NewObsoleted = adjustWatchOSVersion(Obsoleted.Version);

      AvailabilityAttr *NewAttr = S.mergeAvailabilityAttr(
          ND, AL, NewII, true /*Implicit*/, NewIntroduced, NewDeprecated,
          NewObsoleted, IsUnavailable, Str, IsStrict, Replacement,
          Sema::AMK_None,
          PriorityModifier + Sema::AP_InferredFromOtherPlatform);
      if (NewAttr)
        D->addAttr(NewAttr);
    }
  } else if (S.Context.getTargetInfo().getTriple().isTvOS()) {
    // Transcribe "ios" to "tvos" (and add a new attribute) if the versioning
    // matches before the start of the tvOS platform.
    IdentifierInfo *NewII = nullptr;
    if (II->getName() == "ios")
      NewII = &S.Context.Idents.get("tvos");
    else if (II->getName() == "ios_app_extension")
      NewII = &S.Context.Idents.get("tvos_app_extension");

    if (NewII) {
      const auto *SDKInfo = S.getDarwinSDKInfoForAvailabilityChecking();
      const auto *IOSToTvOSMapping =
          SDKInfo ? SDKInfo->getVersionMapping(
                        DarwinSDKInfo::OSEnvPair::iOStoTvOSPair())
                  : nullptr;

      auto AdjustTvOSVersion =
          [IOSToTvOSMapping](VersionTuple Version) -> VersionTuple {
        if (Version.empty())
          return Version;

        if (IOSToTvOSMapping) {
          if (auto MappedVersion = IOSToTvOSMapping->map(
                  Version, VersionTuple(0, 0), std::nullopt)) {
            return *MappedVersion;
          }
        }
        return Version;
      };

      auto NewIntroduced = AdjustTvOSVersion(Introduced.Version);
      auto NewDeprecated = AdjustTvOSVersion(Deprecated.Version);
      auto NewObsoleted = AdjustTvOSVersion(Obsoleted.Version);

      AvailabilityAttr *NewAttr = S.mergeAvailabilityAttr(
          ND, AL, NewII, true /*Implicit*/, NewIntroduced, NewDeprecated,
          NewObsoleted, IsUnavailable, Str, IsStrict, Replacement,
          Sema::AMK_None,
          PriorityModifier + Sema::AP_InferredFromOtherPlatform);
      if (NewAttr)
        D->addAttr(NewAttr);
    }
  } else if (S.Context.getTargetInfo().getTriple().getOS() ==
                 llvm::Triple::IOS &&
             S.Context.getTargetInfo().getTriple().isMacCatalystEnvironment()) {
    auto GetSDKInfo = [&]() {
      return S.getDarwinSDKInfoForAvailabilityChecking(AL.getRange().getBegin(),
                                                       "macOS");
    };

    // Transcribe "ios" to "maccatalyst" (and add a new attribute).
    IdentifierInfo *NewII = nullptr;
    if (II->getName() == "ios")
      NewII = &S.Context.Idents.get("maccatalyst");
    else if (II->getName() == "ios_app_extension")
      NewII = &S.Context.Idents.get("maccatalyst_app_extension");
    if (NewII) {
      auto MinMacCatalystVersion = [](const VersionTuple &V) {
        if (V.empty())
          return V;
        if (V.getMajor() < 13 ||
            (V.getMajor() == 13 && V.getMinor() && *V.getMinor() < 1))
          return VersionTuple(13, 1); // The min Mac Catalyst version is 13.1.
        return V;
      };
      AvailabilityAttr *NewAttr = S.mergeAvailabilityAttr(
          ND, AL, NewII, true /*Implicit*/,
          MinMacCatalystVersion(Introduced.Version),
          MinMacCatalystVersion(Deprecated.Version),
          MinMacCatalystVersion(Obsoleted.Version), IsUnavailable, Str,
          IsStrict, Replacement, Sema::AMK_None,
          PriorityModifier + Sema::AP_InferredFromOtherPlatform);
      if (NewAttr)
        D->addAttr(NewAttr);
    } else if (II->getName() == "macos" && GetSDKInfo() &&
               (!Introduced.Version.empty() || !Deprecated.Version.empty() ||
                !Obsoleted.Version.empty())) {
      if (const auto *MacOStoMacCatalystMapping =
              GetSDKInfo()->getVersionMapping(
                  DarwinSDKInfo::OSEnvPair::macOStoMacCatalystPair())) {
        // Infer Mac Catalyst availability from the macOS availability attribute
        // if it has versioned availability. Don't infer 'unavailable'. This
        // inferred availability has lower priority than the other availability
        // attributes that are inferred from 'ios'.
        NewII = &S.Context.Idents.get("maccatalyst");
        auto RemapMacOSVersion =
            [&](const VersionTuple &V) -> std::optional<VersionTuple> {
          if (V.empty())
            return std::nullopt;
          // API_TO_BE_DEPRECATED is 100000.
          if (V.getMajor() == 100000)
            return VersionTuple(100000);
          // The minimum iosmac version is 13.1
          return MacOStoMacCatalystMapping->map(V, VersionTuple(13, 1),
                                                std::nullopt);
        };
        std::optional<VersionTuple> NewIntroduced =
                                        RemapMacOSVersion(Introduced.Version),
                                    NewDeprecated =
                                        RemapMacOSVersion(Deprecated.Version),
                                    NewObsoleted =
                                        RemapMacOSVersion(Obsoleted.Version);
        if (NewIntroduced || NewDeprecated || NewObsoleted) {
          auto VersionOrEmptyVersion =
              [](const std::optional<VersionTuple> &V) -> VersionTuple {
            return V ? *V : VersionTuple();
          };
          AvailabilityAttr *NewAttr = S.mergeAvailabilityAttr(
              ND, AL, NewII, true /*Implicit*/,
              VersionOrEmptyVersion(NewIntroduced),
              VersionOrEmptyVersion(NewDeprecated),
              VersionOrEmptyVersion(NewObsoleted), /*IsUnavailable=*/false, Str,
              IsStrict, Replacement, Sema::AMK_None,
              PriorityModifier + Sema::AP_InferredFromOtherPlatform +
                  Sema::AP_InferredFromOtherPlatform);
          if (NewAttr)
            D->addAttr(NewAttr);
        }
      }
    }
  }
}

static void handleExternalSourceSymbolAttr(Sema &S, Decl *D,
                                           const ParsedAttr &AL) {
  if (!AL.checkAtLeastNumArgs(S, 1) || !AL.checkAtMostNumArgs(S, 4))
    return;

  StringRef Language;
  if (const auto *SE = dyn_cast_or_null<StringLiteral>(AL.getArgAsExpr(0)))
    Language = SE->getString();
  StringRef DefinedIn;
  if (const auto *SE = dyn_cast_or_null<StringLiteral>(AL.getArgAsExpr(1)))
    DefinedIn = SE->getString();
  bool IsGeneratedDeclaration = AL.getArgAsIdent(2) != nullptr;
  StringRef USR;
  if (const auto *SE = dyn_cast_or_null<StringLiteral>(AL.getArgAsExpr(3)))
    USR = SE->getString();

  D->addAttr(::new (S.Context) ExternalSourceSymbolAttr(
      S.Context, AL, Language, DefinedIn, IsGeneratedDeclaration, USR));
}

template <class T>
static T *mergeVisibilityAttr(Sema &S, Decl *D, const AttributeCommonInfo &CI,
                              typename T::VisibilityType value) {
  T *existingAttr = D->getAttr<T>();
  if (existingAttr) {
    typename T::VisibilityType existingValue = existingAttr->getVisibility();
    if (existingValue == value)
      return nullptr;
    S.Diag(existingAttr->getLocation(), diag::err_mismatched_visibility);
    S.Diag(CI.getLoc(), diag::note_previous_attribute);
    D->dropAttr<T>();
  }
  return ::new (S.Context) T(S.Context, CI, value);
}

VisibilityAttr *Sema::mergeVisibilityAttr(Decl *D,
                                          const AttributeCommonInfo &CI,
                                          VisibilityAttr::VisibilityType Vis) {
  return ::mergeVisibilityAttr<VisibilityAttr>(*this, D, CI, Vis);
}

TypeVisibilityAttr *
Sema::mergeTypeVisibilityAttr(Decl *D, const AttributeCommonInfo &CI,
                              TypeVisibilityAttr::VisibilityType Vis) {
  return ::mergeVisibilityAttr<TypeVisibilityAttr>(*this, D, CI, Vis);
}

static void handleVisibilityAttr(Sema &S, Decl *D, const ParsedAttr &AL,
                                 bool isTypeVisibility) {
  // Visibility attributes don't mean anything on a typedef.
  if (isa<TypedefNameDecl>(D)) {
    S.Diag(AL.getRange().getBegin(), diag::warn_attribute_ignored) << AL;
    return;
  }

  // 'type_visibility' can only go on a type or namespace.
  if (isTypeVisibility && !(isa<TagDecl>(D) || isa<ObjCInterfaceDecl>(D) ||
                            isa<NamespaceDecl>(D))) {
    S.Diag(AL.getRange().getBegin(), diag::err_attribute_wrong_decl_type)
        << AL << AL.isRegularKeywordAttribute() << ExpectedTypeOrNamespace;
    return;
  }

  // Check that the argument is a string literal.
  StringRef TypeStr;
  SourceLocation LiteralLoc;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, TypeStr, &LiteralLoc))
    return;

  VisibilityAttr::VisibilityType type;
  if (!VisibilityAttr::ConvertStrToVisibilityType(TypeStr, type)) {
    S.Diag(LiteralLoc, diag::warn_attribute_type_not_supported) << AL
                                                                << TypeStr;
    return;
  }

  // Complain about attempts to use protected visibility on targets
  // (like Darwin) that don't support it.
  if (type == VisibilityAttr::Protected &&
      !S.Context.getTargetInfo().hasProtectedVisibility()) {
    S.Diag(AL.getLoc(), diag::warn_attribute_protected_visibility);
    type = VisibilityAttr::Default;
  }

  Attr *newAttr;
  if (isTypeVisibility) {
    newAttr = S.mergeTypeVisibilityAttr(
        D, AL, (TypeVisibilityAttr::VisibilityType)type);
  } else {
    newAttr = S.mergeVisibilityAttr(D, AL, type);
  }
  if (newAttr)
    D->addAttr(newAttr);
}

static void handleObjCDirectAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // objc_direct cannot be set on methods declared in the context of a protocol
  if (isa<ObjCProtocolDecl>(D->getDeclContext())) {
    S.Diag(AL.getLoc(), diag::err_objc_direct_on_protocol) << false;
    return;
  }

  if (S.getLangOpts().ObjCRuntime.allowsDirectDispatch()) {
    handleSimpleAttribute<ObjCDirectAttr>(S, D, AL);
  } else {
    S.Diag(AL.getLoc(), diag::warn_objc_direct_ignored) << AL;
  }
}

static void handleObjCDirectMembersAttr(Sema &S, Decl *D,
                                        const ParsedAttr &AL) {
  if (S.getLangOpts().ObjCRuntime.allowsDirectDispatch()) {
    handleSimpleAttribute<ObjCDirectMembersAttr>(S, D, AL);
  } else {
    S.Diag(AL.getLoc(), diag::warn_objc_direct_ignored) << AL;
  }
}

static void handleObjCMethodFamilyAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  const auto *M = cast<ObjCMethodDecl>(D);
  if (!AL.isArgIdent(0)) {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
        << AL << 1 << AANT_ArgumentIdentifier;
    return;
  }

  IdentifierLoc *IL = AL.getArgAsIdent(0);
  ObjCMethodFamilyAttr::FamilyKind F;
  if (!ObjCMethodFamilyAttr::ConvertStrToFamilyKind(IL->Ident->getName(), F)) {
    S.Diag(IL->Loc, diag::warn_attribute_type_not_supported) << AL << IL->Ident;
    return;
  }

  if (F == ObjCMethodFamilyAttr::OMF_init &&
      !M->getReturnType()->isObjCObjectPointerType()) {
    S.Diag(M->getLocation(), diag::err_init_method_bad_return_type)
        << M->getReturnType();
    // Ignore the attribute.
    return;
  }

  D->addAttr(new (S.Context) ObjCMethodFamilyAttr(S.Context, AL, F));
}

static void handleObjCNSObject(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (const auto *TD = dyn_cast<TypedefNameDecl>(D)) {
    QualType T = TD->getUnderlyingType();
    if (!T->isCARCBridgableType()) {
      S.Diag(TD->getLocation(), diag::err_nsobject_attribute);
      return;
    }
  }
  else if (const auto *PD = dyn_cast<ObjCPropertyDecl>(D)) {
    QualType T = PD->getType();
    if (!T->isCARCBridgableType()) {
      S.Diag(PD->getLocation(), diag::err_nsobject_attribute);
      return;
    }
  }
  else {
    // It is okay to include this attribute on properties, e.g.:
    //
    //  @property (retain, nonatomic) struct Bork *Q __attribute__((NSObject));
    //
    // In this case it follows tradition and suppresses an error in the above
    // case.
    S.Diag(D->getLocation(), diag::warn_nsobject_attribute);
  }
  D->addAttr(::new (S.Context) ObjCNSObjectAttr(S.Context, AL));
}

static void handleObjCIndependentClass(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (const auto *TD = dyn_cast<TypedefNameDecl>(D)) {
    QualType T = TD->getUnderlyingType();
    if (!T->isObjCObjectPointerType()) {
      S.Diag(TD->getLocation(), diag::warn_ptr_independentclass_attribute);
      return;
    }
  } else {
    S.Diag(D->getLocation(), diag::warn_independentclass_attribute);
    return;
  }
  D->addAttr(::new (S.Context) ObjCIndependentClassAttr(S.Context, AL));
}

static void handleBlocksAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!AL.isArgIdent(0)) {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
        << AL << 1 << AANT_ArgumentIdentifier;
    return;
  }

  IdentifierInfo *II = AL.getArgAsIdent(0)->Ident;
  BlocksAttr::BlockType type;
  if (!BlocksAttr::ConvertStrToBlockType(II->getName(), type)) {
    S.Diag(AL.getLoc(), diag::warn_attribute_type_not_supported) << AL << II;
    return;
  }

  D->addAttr(::new (S.Context) BlocksAttr(S.Context, AL, type));
}

static void handleSentinelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  unsigned sentinel = (unsigned)SentinelAttr::DefaultSentinel;
  if (AL.getNumArgs() > 0) {
    Expr *E = AL.getArgAsExpr(0);
    std::optional<llvm::APSInt> Idx = llvm::APSInt(32);
    if (E->isTypeDependent() || !(Idx = E->getIntegerConstantExpr(S.Context))) {
      S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
          << AL << 1 << AANT_ArgumentIntegerConstant << E->getSourceRange();
      return;
    }

    if (Idx->isSigned() && Idx->isNegative()) {
      S.Diag(AL.getLoc(), diag::err_attribute_sentinel_less_than_zero)
        << E->getSourceRange();
      return;
    }

    sentinel = Idx->getZExtValue();
  }

  unsigned nullPos = (unsigned)SentinelAttr::DefaultNullPos;
  if (AL.getNumArgs() > 1) {
    Expr *E = AL.getArgAsExpr(1);
    std::optional<llvm::APSInt> Idx = llvm::APSInt(32);
    if (E->isTypeDependent() || !(Idx = E->getIntegerConstantExpr(S.Context))) {
      S.Diag(AL.getLoc(), diag::err_attribute_argument_n_type)
          << AL << 2 << AANT_ArgumentIntegerConstant << E->getSourceRange();
      return;
    }
    nullPos = Idx->getZExtValue();

    if ((Idx->isSigned() && Idx->isNegative()) || nullPos > 1) {
      // FIXME: This error message could be improved, it would be nice
      // to say what the bounds actually are.
      S.Diag(AL.getLoc(), diag::err_attribute_sentinel_not_zero_or_one)
        << E->getSourceRange();
      return;
    }
  }

  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    const FunctionType *FT = FD->getType()->castAs<FunctionType>();
    if (isa<FunctionNoProtoType>(FT)) {
      S.Diag(AL.getLoc(), diag::warn_attribute_sentinel_named_arguments);
      return;
    }

    if (!cast<FunctionProtoType>(FT)->isVariadic()) {
      S.Diag(AL.getLoc(), diag::warn_attribute_sentinel_not_variadic) << 0;
      return;
    }
  } else if (const auto *MD = dyn_cast<ObjCMethodDecl>(D)) {
    if (!MD->isVariadic()) {
      S.Diag(AL.getLoc(), diag::warn_attribute_sentinel_not_variadic) << 0;
      return;
    }
  } else if (const auto *BD = dyn_cast<BlockDecl>(D)) {
    if (!BD->isVariadic()) {
      S.Diag(AL.getLoc(), diag::warn_attribute_sentinel_not_variadic) << 1;
      return;
    }
  } else if (const auto *V = dyn_cast<VarDecl>(D)) {
    QualType Ty = V->getType();
    if (Ty->isBlockPointerType() || Ty->isFunctionPointerType()) {
      const FunctionType *FT = Ty->isFunctionPointerType()
                                   ? D->getFunctionType()
                                   : Ty->castAs<BlockPointerType>()
                                         ->getPointeeType()
                                         ->castAs<FunctionType>();
      if (!cast<FunctionProtoType>(FT)->isVariadic()) {
        int m = Ty->isFunctionPointerType() ? 0 : 1;
        S.Diag(AL.getLoc(), diag::warn_attribute_sentinel_not_variadic) << m;
        return;
      }
    } else {
      S.Diag(AL.getLoc(), diag::warn_attribute_wrong_decl_type)
          << AL << AL.isRegularKeywordAttribute()
          << ExpectedFunctionMethodOrBlock;
      return;
    }
  } else {
    S.Diag(AL.getLoc(), diag::warn_attribute_wrong_decl_type)
        << AL << AL.isRegularKeywordAttribute()
        << ExpectedFunctionMethodOrBlock;
    return;
  }
  D->addAttr(::new (S.Context) SentinelAttr(S.Context, AL, sentinel, nullPos));
}

static void handleWarnUnusedResult(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (D->getFunctionType() &&
      D->getFunctionType()->getReturnType()->isVoidType() &&
      !isa<CXXConstructorDecl>(D)) {
    S.Diag(AL.getLoc(), diag::warn_attribute_void_function_method) << AL << 0;
    return;
  }
  if (const auto *MD = dyn_cast<ObjCMethodDecl>(D))
    if (MD->getReturnType()->isVoidType()) {
      S.Diag(AL.getLoc(), diag::warn_attribute_void_function_method) << AL << 1;
      return;
    }

  StringRef Str;
  if (AL.isStandardAttributeSyntax() && !AL.getScopeName()) {
    // The standard attribute cannot be applied to variable declarations such
    // as a function pointer.
    if (isa<VarDecl>(D))
      S.Diag(AL.getLoc(), diag::warn_attribute_wrong_decl_type_str)
          << AL << AL.isRegularKeywordAttribute()
          << "functions, classes, or enumerations";

    // If this is spelled as the standard C++17 attribute, but not in C++17,
    // warn about using it as an extension. If there are attribute arguments,
    // then claim it's a C++2a extension instead.
    // FIXME: If WG14 does not seem likely to adopt the same feature, add an
    // extension warning for C2x mode.
    const LangOptions &LO = S.getLangOpts();
    if (AL.getNumArgs() == 1) {
      if (LO.CPlusPlus && !LO.CPlusPlus20)
        S.Diag(AL.getLoc(), diag::ext_cxx20_attr) << AL;

      // Since this is spelled [[nodiscard]], get the optional string
      // literal. If in C++ mode, but not in C++2a mode, diagnose as an
      // extension.
      // FIXME: C2x should support this feature as well, even as an extension.
      if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, nullptr))
        return;
    } else if (LO.CPlusPlus && !LO.CPlusPlus17)
      S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;
  }

  if ((!AL.isGNUAttribute() &&
       !(AL.isStandardAttributeSyntax() && AL.isClangScope())) &&
      isa<TypedefNameDecl>(D)) {
    S.Diag(AL.getLoc(), diag::warn_unused_result_typedef_unsupported_spelling)
        << AL.isGNUScope();
    return;
  }

  D->addAttr(::new (S.Context) WarnUnusedResultAttr(S.Context, AL, Str));
}

static void handleWeakImportAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // weak_import only applies to variable & function declarations.
  bool isDef = false;
  if (!D->canBeWeakImported(isDef)) {
    if (isDef)
      S.Diag(AL.getLoc(), diag::warn_attribute_invalid_on_definition)
        << "weak_import";
    else if (isa<ObjCPropertyDecl>(D) || isa<ObjCMethodDecl>(D) ||
             (S.Context.getTargetInfo().getTriple().isOSDarwin() &&
              (isa<ObjCInterfaceDecl>(D) || isa<EnumDecl>(D)))) {
      // Nothing to warn about here.
    } else
      S.Diag(AL.getLoc(), diag::warn_attribute_wrong_decl_type)
          << AL << AL.isRegularKeywordAttribute() << ExpectedVariableOrFunction;

    return;
  }

  D->addAttr(::new (S.Context) WeakImportAttr(S.Context, AL));
}

// Handles reqd_work_group_size and work_group_size_hint.
template <typename WorkGroupAttr>
static void handleWorkGroupSize(Sema &S, Decl *D, const ParsedAttr &AL) {
  uint32_t WGSize[3];
  for (unsigned i = 0; i < 3; ++i) {
    const Expr *E = AL.getArgAsExpr(i);
    if (!checkUInt32Argument(S, AL, E, WGSize[i], i,
                             /*StrictlyUnsigned=*/true))
      return;
    if (WGSize[i] == 0) {
      S.Diag(AL.getLoc(), diag::err_attribute_argument_is_zero)
          << AL << E->getSourceRange();
      return;
    }
  }

  WorkGroupAttr *Existing = D->getAttr<WorkGroupAttr>();
  if (Existing && !(Existing->getXDim() == WGSize[0] &&
                    Existing->getYDim() == WGSize[1] &&
                    Existing->getZDim() == WGSize[2]))
    S.Diag(AL.getLoc(), diag::warn_duplicate_attribute) << AL;

  D->addAttr(::new (S.Context)
                 WorkGroupAttr(S.Context, AL, WGSize[0], WGSize[1], WGSize[2]));
}

// Handles intel_reqd_sub_group_size.
static void handleSubGroupSize(Sema &S, Decl *D, const ParsedAttr &AL) {
  uint32_t SGSize;
  const Expr *E = AL.getArgAsExpr(0);
  if (!checkUInt32Argument(S, AL, E, SGSize))
    return;
  if (SGSize == 0) {
    S.Diag(AL.getLoc(), diag::err_attribute_argument_is_zero)
        << AL << E->getSourceRange();
    return;
  }

  OpenCLIntelReqdSubGroupSizeAttr *Existing =
      D->getAttr<OpenCLIntelReqdSubGroupSizeAttr>();
  if (Existing && Existing->getSubGroupSize() != SGSize)
    S.Diag(AL.getLoc(), diag::warn_duplicate_attribute) << AL;

  D->addAttr(::new (S.Context)
                 OpenCLIntelReqdSubGroupSizeAttr(S.Context, AL, SGSize));
}

static void handleVecTypeHint(Sema &S, Decl *D, const ParsedAttr &AL) {
  if (!AL.hasParsedType()) {
    S.Diag(AL.getLoc(), diag::err_attribute_wrong_number_arguments) << AL << 1;
    return;
  }

  TypeSourceInfo *ParmTSI = nullptr;
  QualType ParmType = S.GetTypeFromParser(AL.getTypeArg(), &ParmTSI);
  assert(ParmTSI && "no type source info for attribute argument");

  if (!ParmType->isExtVectorType() && !ParmType->isFloatingType() &&
      (ParmType->isBooleanType() ||
       !ParmType->isIntegralType(S.getASTContext()))) {
    S.Diag(AL.getLoc(), diag::err_attribute_invalid_argument) << 2 << AL;
    return;
  }

  if (VecTypeHintAttr *A = D->getAttr<VecTypeHintAttr>()) {
    if (!S.Context.hasSameType(A->getTypeHint(), ParmType)) {
      S.Diag(AL.getLoc(), diag::warn_duplicate_attribute) << AL;
      return;
    }
  }

  D->addAttr(::new (S.Context) VecTypeHintAttr(S.Context, AL, ParmTSI));
}

SectionAttr *Sema::mergeSectionAttr(Decl *D, const AttributeCommonInfo &CI,
                                    StringRef Name) {
  // Explicit or partial specializations do not inherit
  // the section attribute from the primary template.
  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    if (CI.getAttributeSpellingListIndex() == SectionAttr::Declspec_allocate &&
        FD->isFunctionTemplateSpecialization())
      return nullptr;
  }
  if (SectionAttr *ExistingAttr = D->getAttr<SectionAttr>()) {
    if (ExistingAttr->getName() == Name)
      return nullptr;
    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_section)
         << 1 /*section*/;
    Diag(CI.getLoc(), diag::note_previous_attribute);
    return nullptr;
  }
  return ::new (Context) SectionAttr(Context, CI, Name);
}

/// Used to implement to perform semantic checking on
/// attribute((section("foo"))) specifiers.
///
/// In this case, "foo" is passed in to be checked.  If the section
/// specifier is invalid, return an Error that indicates the problem.
///
/// This is a simple quality of implementation feature to catch errors
/// and give good diagnostics in cases when the assembler or code generator
/// would otherwise reject the section specifier.
llvm::Error Sema::isValidSectionSpecifier(StringRef SecName) {
  if (!Context.getTargetInfo().getTriple().isOSDarwin())
    return llvm::Error::success();

  // Let MCSectionMachO validate this.
  StringRef Segment, Section;
  unsigned TAA, StubSize;
  bool HasTAA;
  return llvm::MCSectionMachO::ParseSectionSpecifier(SecName, Segment, Section,
                                                     TAA, HasTAA, StubSize);
}

bool Sema::checkSectionName(SourceLocation LiteralLoc, StringRef SecName) {
  if (llvm::Error E = isValidSectionSpecifier(SecName)) {
    Diag(LiteralLoc, diag::err_attribute_section_invalid_for_target)
        << toString(std::move(E)) << 1 /*'section'*/;
    return false;
  }
  return true;
}

static void handleSectionAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  // Make sure that there is a string literal as the sections's single
  // argument.
  StringRef Str;
  SourceLocation LiteralLoc;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &LiteralLoc))
    return;

  if (!S.checkSectionName(LiteralLoc, Str))
    return;

  SectionAttr *NewAttr = S.mergeSectionAttr(D, AL, Str);
  if (NewAttr) {
    D->addAttr(NewAttr);
    if (isa<FunctionDecl, FunctionTemplateDecl, ObjCMethodDecl,
            ObjCPropertyDecl>(D))
      S.UnifySection(NewAttr->getName(),
                     ASTContext::PSF_Execute | ASTContext::PSF_Read,
                     cast<NamedDecl>(D));
  }
}

// This is used for `__declspec(code_seg("segname"))` on a decl.
// `#pragma code_seg("segname")` uses checkSectionName() instead.
static bool checkCodeSegName(Sema &S, SourceLocation LiteralLoc,
                             StringRef CodeSegName) {
  if (llvm::Error E = S.isValidSectionSpecifier(CodeSegName)) {
    S.Diag(LiteralLoc, diag::err_attribute_section_invalid_for_target)
        << toString(std::move(E)) << 0 /*'code-seg'*/;
    return false;
  }

  return true;
}

CodeSegAttr *Sema::mergeCodeSegAttr(Decl *D, const AttributeCommonInfo &CI,
                                    StringRef Name) {
  // Explicit or partial specializations do not inherit
  // the code_seg attribute from the primary template.
  if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    if (FD->isFunctionTemplateSpecialization())
      return nullptr;
  }
  if (const auto *ExistingAttr = D->getAttr<CodeSegAttr>()) {
    if (ExistingAttr->getName() == Name)
      return nullptr;
    Diag(ExistingAttr->getLocation(), diag::warn_mismatched_section)
         << 0 /*codeseg*/;
    Diag(CI.getLoc(), diag::note_previous_attribute);
    return nullptr;
  }
  return ::new (Context) CodeSegAttr(Context, CI, Name);
}

static void handleCodeSegAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
  StringRef Str;
  SourceLocation LiteralLoc;
  if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, &LiteralLoc))
    return;
  if (!checkCodeSegName(S, LiteralLoc, Str))
    return;
  if (const auto *ExistingAttr = D->getAttr<CodeSegAttr>()) {
    if (!ExistingAttr->isImplicit()) {
      S.Diag(AL.getLoc(),
             ExistingAttr->getName() == Str
             ? diag::warn_duplicate_codeseg_attribute
             : diag::err_conflicting_codeseg_attribute);
      return;
    }
    D->dropAttr<CodeSegAttr>();
  }
  if (CodeSegAttr *CSA = S.mergeCodeSegAttr(D, AL, Str))
    D->addAttr(CSA);
}

// Check for things we'd like to warn about. Multiversioning issues are
// handled later in the process, once we know how many exist.
bool Sema::checkTargetAttr(SourceLocation LiteralLoc, StringRef AttrStr) {
  enum FirstParam { Unsupported, Duplicate, Unknown };
  enum SecondParam { None, CPU, Tune };
  enum ThirdParam { Target, TargetClones };
  if (AttrStr.contains("fpmath="))
    return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
           << Unsupported << None << "fpmath=" << Target;

  // Diagnose use of tune if target doesn't support it.
  if (!Context.getTargetInfo().supportsTargetAttributeTune() &&
      AttrStr.contains("tune="))
    return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
           << Unsupported << None << "tune=" << Target;

  ParsedTargetAttr ParsedAttrs =
      Context.getTargetInfo().parseTargetAttr(AttrStr);

  if (!ParsedAttrs.CPU.empty() &&
      !Context.getTargetInfo().isValidCPUName(ParsedAttrs.CPU))
    return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
           << Unknown << CPU << ParsedAttrs.CPU << Target;

  if (!ParsedAttrs.Tune.empty() &&
      !Context.getTargetInfo().isValidCPUName(ParsedAttrs.Tune))
    return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
           << Unknown << Tune << ParsedAttrs.Tune << Target;

  if (ParsedAttrs.Duplicate != "")
    return Diag(LiteralLoc, diag::warn_unsupported_target_attribute)
           << Duplicate << None << ParsedAttrs.Duplicate << Target;