//===--- ParseDeclCXX.cpp - C++ Declaration Parsing -------------*- C++ -*-===//
//
// 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 the C++ Declaration portions of the Parser interfaces.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/PrettyDeclStackTrace.h"
#include "clang/Basic/AttributeCommonInfo.h"
#include "clang/Basic/Attributes.h"
#include "clang/Basic/CharInfo.h"
#include "clang/Basic/OperatorKinds.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/TokenKinds.h"
#include "clang/Lex/LiteralSupport.h"
#include "clang/Parse/ParseDiagnostic.h"
#include "clang/Parse/Parser.h"
#include "clang/Parse/RAIIObjectsForParser.h"
#include "clang/Sema/DeclSpec.h"
#include "clang/Sema/EnterExpressionEvaluationContext.h"
#include "clang/Sema/ParsedTemplate.h"
#include "clang/Sema/Scope.h"
#include "clang/Sema/SemaCodeCompletion.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Support/TimeProfiler.h"
#include <optional>

using namespace clang;

/// ParseNamespace - We know that the current token is a namespace keyword. This
/// may either be a top level namespace or a block-level namespace alias. If
/// there was an inline keyword, it has already been parsed.
///
///       namespace-definition: [C++: namespace.def]
///         named-namespace-definition
///         unnamed-namespace-definition
///         nested-namespace-definition
///
///       named-namespace-definition:
///         'inline'[opt] 'namespace' attributes[opt] identifier '{'
///         namespace-body '}'
///
///       unnamed-namespace-definition:
///         'inline'[opt] 'namespace' attributes[opt] '{' namespace-body '}'
///
///       nested-namespace-definition:
///         'namespace' enclosing-namespace-specifier '::' 'inline'[opt]
///         identifier '{' namespace-body '}'
///
///       enclosing-namespace-specifier:
///         identifier
///         enclosing-namespace-specifier '::' 'inline'[opt] identifier
///
///       namespace-alias-definition:  [C++ 7.3.2: namespace.alias]
///         'namespace' identifier '=' qualified-namespace-specifier ';'
///
Parser::DeclGroupPtrTy Parser::ParseNamespace(DeclaratorContext Context,
                                              SourceLocation &DeclEnd,
                                              SourceLocation InlineLoc) {
  assert(Tok.is(tok::kw_namespace) && "Not a namespace!");
  SourceLocation NamespaceLoc = ConsumeToken(); // eat the 'namespace'.
  ObjCDeclContextSwitch ObjCDC(*this);

  if (Tok.is(tok::code_completion)) {
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteNamespaceDecl(getCurScope());
    return nullptr;
  }

  SourceLocation IdentLoc;
  IdentifierInfo *Ident = nullptr;
  InnerNamespaceInfoList ExtraNSs;
  SourceLocation FirstNestedInlineLoc;

  ParsedAttributes attrs(AttrFactory);

  auto ReadAttributes = [&] {
    bool MoreToParse;
    do {
      MoreToParse = false;
      if (Tok.is(tok::kw___attribute)) {
        ParseGNUAttributes(attrs);
        MoreToParse = true;
      }
      if (getLangOpts().CPlusPlus11 && isCXX11AttributeSpecifier()) {
        Diag(Tok.getLocation(), getLangOpts().CPlusPlus17
                                    ? diag::warn_cxx14_compat_ns_enum_attribute
                                    : diag::ext_ns_enum_attribute)
            << 0 /*namespace*/;
        ParseCXX11Attributes(attrs);
        MoreToParse = true;
      }
    } while (MoreToParse);
  };

  ReadAttributes();

  if (Tok.is(tok::identifier)) {
    Ident = Tok.getIdentifierInfo();
    IdentLoc = ConsumeToken(); // eat the identifier.
    while (Tok.is(tok::coloncolon) &&
           (NextToken().is(tok::identifier) ||
            (NextToken().is(tok::kw_inline) &&
             GetLookAheadToken(2).is(tok::identifier)))) {

      InnerNamespaceInfo Info;
      Info.NamespaceLoc = ConsumeToken();

      if (Tok.is(tok::kw_inline)) {
        Info.InlineLoc = ConsumeToken();
        if (FirstNestedInlineLoc.isInvalid())
          FirstNestedInlineLoc = Info.InlineLoc;
      }

      Info.Ident = Tok.getIdentifierInfo();
      Info.IdentLoc = ConsumeToken();

      ExtraNSs.push_back(Info);
    }
  }

  ReadAttributes();

  SourceLocation attrLoc = attrs.Range.getBegin();

  // A nested namespace definition cannot have attributes.
  if (!ExtraNSs.empty() && attrLoc.isValid())
    Diag(attrLoc, diag::err_unexpected_nested_namespace_attribute);

  if (Tok.is(tok::equal)) {
    if (!Ident) {
      Diag(Tok, diag::err_expected) << tok::identifier;
      // Skip to end of the definition and eat the ';'.
      SkipUntil(tok::semi);
      return nullptr;
    }
    if (!ExtraNSs.empty()) {
      Diag(ExtraNSs.front().NamespaceLoc,
           diag::err_unexpected_qualified_namespace_alias)
          << SourceRange(ExtraNSs.front().NamespaceLoc,
                         ExtraNSs.back().IdentLoc);
      SkipUntil(tok::semi);
      return nullptr;
    }
    if (attrLoc.isValid())
      Diag(attrLoc, diag::err_unexpected_namespace_attributes_alias);
    if (InlineLoc.isValid())
      Diag(InlineLoc, diag::err_inline_namespace_alias)
          << FixItHint::CreateRemoval(InlineLoc);
    Decl *NSAlias = ParseNamespaceAlias(NamespaceLoc, IdentLoc, Ident, DeclEnd);
    return Actions.ConvertDeclToDeclGroup(NSAlias);
  }

  BalancedDelimiterTracker T(*this, tok::l_brace);
  if (T.consumeOpen()) {
    if (Ident)
      Diag(Tok, diag::err_expected) << tok::l_brace;
    else
      Diag(Tok, diag::err_expected_either) << tok::identifier << tok::l_brace;
    return nullptr;
  }

  if (getCurScope()->isClassScope() || getCurScope()->isTemplateParamScope() ||
      getCurScope()->isInObjcMethodScope() || getCurScope()->getBlockParent() ||
      getCurScope()->getFnParent()) {
    Diag(T.getOpenLocation(), diag::err_namespace_nonnamespace_scope);
    SkipUntil(tok::r_brace);
    return nullptr;
  }

  if (ExtraNSs.empty()) {
    // Normal namespace definition, not a nested-namespace-definition.
  } else if (InlineLoc.isValid()) {
    Diag(InlineLoc, diag::err_inline_nested_namespace_definition);
  } else if (getLangOpts().CPlusPlus20) {
    Diag(ExtraNSs[0].NamespaceLoc,
         diag::warn_cxx14_compat_nested_namespace_definition);
    if (FirstNestedInlineLoc.isValid())
      Diag(FirstNestedInlineLoc,
           diag::warn_cxx17_compat_inline_nested_namespace_definition);
  } else if (getLangOpts().CPlusPlus17) {
    Diag(ExtraNSs[0].NamespaceLoc,
         diag::warn_cxx14_compat_nested_namespace_definition);
    if (FirstNestedInlineLoc.isValid())
      Diag(FirstNestedInlineLoc, diag::ext_inline_nested_namespace_definition);
  } else {
    TentativeParsingAction TPA(*this);
    SkipUntil(tok::r_brace, StopBeforeMatch);
    Token rBraceToken = Tok;
    TPA.Revert();

    if (!rBraceToken.is(tok::r_brace)) {
      Diag(ExtraNSs[0].NamespaceLoc, diag::ext_nested_namespace_definition)
          << SourceRange(ExtraNSs.front().NamespaceLoc,
                         ExtraNSs.back().IdentLoc);
    } else {
      std::string NamespaceFix;
      for (const auto &ExtraNS : ExtraNSs) {
        NamespaceFix += " { ";
        if (ExtraNS.InlineLoc.isValid())
          NamespaceFix += "inline ";
        NamespaceFix += "namespace ";
        NamespaceFix += ExtraNS.Ident->getName();
      }

      std::string RBraces;
      for (unsigned i = 0, e = ExtraNSs.size(); i != e; ++i)
        RBraces += "} ";

      Diag(ExtraNSs[0].NamespaceLoc, diag::ext_nested_namespace_definition)
          << FixItHint::CreateReplacement(
                 SourceRange(ExtraNSs.front().NamespaceLoc,
                             ExtraNSs.back().IdentLoc),
                 NamespaceFix)
          << FixItHint::CreateInsertion(rBraceToken.getLocation(), RBraces);
    }

    // Warn about nested inline namespaces.
    if (FirstNestedInlineLoc.isValid())
      Diag(FirstNestedInlineLoc, diag::ext_inline_nested_namespace_definition);
  }

  // If we're still good, complain about inline namespaces in non-C++0x now.
  if (InlineLoc.isValid())
    Diag(InlineLoc, getLangOpts().CPlusPlus11
                        ? diag::warn_cxx98_compat_inline_namespace
                        : diag::ext_inline_namespace);

  // Enter a scope for the namespace.
  ParseScope NamespaceScope(this, Scope::DeclScope);

  UsingDirectiveDecl *ImplicitUsingDirectiveDecl = nullptr;
  Decl *NamespcDecl = Actions.ActOnStartNamespaceDef(
      getCurScope(), InlineLoc, NamespaceLoc, IdentLoc, Ident,
      T.getOpenLocation(), attrs, ImplicitUsingDirectiveDecl, false);

  PrettyDeclStackTraceEntry CrashInfo(Actions.Context, NamespcDecl,
                                      NamespaceLoc, "parsing namespace");

  // Parse the contents of the namespace.  This includes parsing recovery on
  // any improperly nested namespaces.
  ParseInnerNamespace(ExtraNSs, 0, InlineLoc, attrs, T);

  // Leave the namespace scope.
  NamespaceScope.Exit();

  DeclEnd = T.getCloseLocation();
  Actions.ActOnFinishNamespaceDef(NamespcDecl, DeclEnd);

  return Actions.ConvertDeclToDeclGroup(NamespcDecl,
                                        ImplicitUsingDirectiveDecl);
}

/// ParseInnerNamespace - Parse the contents of a namespace.
void Parser::ParseInnerNamespace(const InnerNamespaceInfoList &InnerNSs,
                                 unsigned int index, SourceLocation &InlineLoc,
                                 ParsedAttributes &attrs,
                                 BalancedDelimiterTracker &Tracker) {
  if (index == InnerNSs.size()) {
    while (!tryParseMisplacedModuleImport() && Tok.isNot(tok::r_brace) &&
           Tok.isNot(tok::eof)) {
      ParsedAttributes DeclAttrs(AttrFactory);
      MaybeParseCXX11Attributes(DeclAttrs);
      ParsedAttributes EmptyDeclSpecAttrs(AttrFactory);
      ParseExternalDeclaration(DeclAttrs, EmptyDeclSpecAttrs);
    }

    // The caller is what called check -- we are simply calling
    // the close for it.
    Tracker.consumeClose();

    return;
  }

  // Handle a nested namespace definition.
  // FIXME: Preserve the source information through to the AST rather than
  // desugaring it here.
  ParseScope NamespaceScope(this, Scope::DeclScope);
  UsingDirectiveDecl *ImplicitUsingDirectiveDecl = nullptr;
  Decl *NamespcDecl = Actions.ActOnStartNamespaceDef(
      getCurScope(), InnerNSs[index].InlineLoc, InnerNSs[index].NamespaceLoc,
      InnerNSs[index].IdentLoc, InnerNSs[index].Ident,
      Tracker.getOpenLocation(), attrs, ImplicitUsingDirectiveDecl, true);
  assert(!ImplicitUsingDirectiveDecl &&
         "nested namespace definition cannot define anonymous namespace");

  ParseInnerNamespace(InnerNSs, ++index, InlineLoc, attrs, Tracker);

  NamespaceScope.Exit();
  Actions.ActOnFinishNamespaceDef(NamespcDecl, Tracker.getCloseLocation());
}

/// ParseNamespaceAlias - Parse the part after the '=' in a namespace
/// alias definition.
///
Decl *Parser::ParseNamespaceAlias(SourceLocation NamespaceLoc,
                                  SourceLocation AliasLoc,
                                  IdentifierInfo *Alias,
                                  SourceLocation &DeclEnd) {
  assert(Tok.is(tok::equal) && "Not equal token");

  ConsumeToken(); // eat the '='.

  if (Tok.is(tok::code_completion)) {
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteNamespaceAliasDecl(getCurScope());
    return nullptr;
  }

  CXXScopeSpec SS;
  // Parse (optional) nested-name-specifier.
  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                 /*ObjectHasErrors=*/false,
                                 /*EnteringContext=*/false,
                                 /*MayBePseudoDestructor=*/nullptr,
                                 /*IsTypename=*/false,
                                 /*LastII=*/nullptr,
                                 /*OnlyNamespace=*/true);

  if (Tok.isNot(tok::identifier)) {
    Diag(Tok, diag::err_expected_namespace_name);
    // Skip to end of the definition and eat the ';'.
    SkipUntil(tok::semi);
    return nullptr;
  }

  if (SS.isInvalid()) {
    // Diagnostics have been emitted in ParseOptionalCXXScopeSpecifier.
    // Skip to end of the definition and eat the ';'.
    SkipUntil(tok::semi);
    return nullptr;
  }

  // Parse identifier.
  IdentifierInfo *Ident = Tok.getIdentifierInfo();
  SourceLocation IdentLoc = ConsumeToken();

  // Eat the ';'.
  DeclEnd = Tok.getLocation();
  if (ExpectAndConsume(tok::semi, diag::err_expected_semi_after_namespace_name))
    SkipUntil(tok::semi);

  return Actions.ActOnNamespaceAliasDef(getCurScope(), NamespaceLoc, AliasLoc,
                                        Alias, SS, IdentLoc, Ident);
}

/// ParseLinkage - We know that the current token is a string_literal
/// and just before that, that extern was seen.
///
///       linkage-specification: [C++ 7.5p2: dcl.link]
///         'extern' string-literal '{' declaration-seq[opt] '}'
///         'extern' string-literal declaration
///
Decl *Parser::ParseLinkage(ParsingDeclSpec &DS, DeclaratorContext Context) {
  assert(isTokenStringLiteral() && "Not a string literal!");
  ExprResult Lang = ParseUnevaluatedStringLiteralExpression();

  ParseScope LinkageScope(this, Scope::DeclScope);
  Decl *LinkageSpec =
      Lang.isInvalid()
          ? nullptr
          : Actions.ActOnStartLinkageSpecification(
                getCurScope(), DS.getSourceRange().getBegin(), Lang.get(),
                Tok.is(tok::l_brace) ? Tok.getLocation() : SourceLocation());

  ParsedAttributes DeclAttrs(AttrFactory);
  ParsedAttributes DeclSpecAttrs(AttrFactory);

  while (MaybeParseCXX11Attributes(DeclAttrs) ||
         MaybeParseGNUAttributes(DeclSpecAttrs))
    ;

  if (Tok.isNot(tok::l_brace)) {
    // Reset the source range in DS, as the leading "extern"
    // does not really belong to the inner declaration ...
    DS.SetRangeStart(SourceLocation());
    DS.SetRangeEnd(SourceLocation());
    // ... but anyway remember that such an "extern" was seen.
    DS.setExternInLinkageSpec(true);
    ParseExternalDeclaration(DeclAttrs, DeclSpecAttrs, &DS);
    return LinkageSpec ? Actions.ActOnFinishLinkageSpecification(
                             getCurScope(), LinkageSpec, SourceLocation())
                       : nullptr;
  }

  DS.abort();

  ProhibitAttributes(DeclAttrs);

  BalancedDelimiterTracker T(*this, tok::l_brace);
  T.consumeOpen();

  unsigned NestedModules = 0;
  while (true) {
    switch (Tok.getKind()) {
    case tok::annot_module_begin:
      ++NestedModules;
      ParseTopLevelDecl();
      continue;

    case tok::annot_module_end:
      if (!NestedModules)
        break;
      --NestedModules;
      ParseTopLevelDecl();
      continue;

    case tok::annot_module_include:
      ParseTopLevelDecl();
      continue;

    case tok::eof:
      break;

    case tok::r_brace:
      if (!NestedModules)
        break;
      [[fallthrough]];
    default:
      ParsedAttributes DeclAttrs(AttrFactory);
      MaybeParseCXX11Attributes(DeclAttrs);
      ParseExternalDeclaration(DeclAttrs, DeclSpecAttrs);
      continue;
    }

    break;
  }

  T.consumeClose();
  return LinkageSpec ? Actions.ActOnFinishLinkageSpecification(
                           getCurScope(), LinkageSpec, T.getCloseLocation())
                     : nullptr;
}

/// Parse a standard C++ Modules export-declaration.
///
///       export-declaration:
///         'export' declaration
///         'export' '{' declaration-seq[opt] '}'
///
Decl *Parser::ParseExportDeclaration() {
  assert(Tok.is(tok::kw_export));
  SourceLocation ExportLoc = ConsumeToken();

  ParseScope ExportScope(this, Scope::DeclScope);
  Decl *ExportDecl = Actions.ActOnStartExportDecl(
      getCurScope(), ExportLoc,
      Tok.is(tok::l_brace) ? Tok.getLocation() : SourceLocation());

  if (Tok.isNot(tok::l_brace)) {
    // FIXME: Factor out a ParseExternalDeclarationWithAttrs.
    ParsedAttributes DeclAttrs(AttrFactory);
    MaybeParseCXX11Attributes(DeclAttrs);
    ParsedAttributes EmptyDeclSpecAttrs(AttrFactory);
    ParseExternalDeclaration(DeclAttrs, EmptyDeclSpecAttrs);
    return Actions.ActOnFinishExportDecl(getCurScope(), ExportDecl,
                                         SourceLocation());
  }

  BalancedDelimiterTracker T(*this, tok::l_brace);
  T.consumeOpen();

  while (!tryParseMisplacedModuleImport() && Tok.isNot(tok::r_brace) &&
         Tok.isNot(tok::eof)) {
    ParsedAttributes DeclAttrs(AttrFactory);
    MaybeParseCXX11Attributes(DeclAttrs);
    ParsedAttributes EmptyDeclSpecAttrs(AttrFactory);
    ParseExternalDeclaration(DeclAttrs, EmptyDeclSpecAttrs);
  }

  T.consumeClose();
  return Actions.ActOnFinishExportDecl(getCurScope(), ExportDecl,
                                       T.getCloseLocation());
}

/// ParseUsingDirectiveOrDeclaration - Parse C++ using using-declaration or
/// using-directive. Assumes that current token is 'using'.
Parser::DeclGroupPtrTy Parser::ParseUsingDirectiveOrDeclaration(
    DeclaratorContext Context, const ParsedTemplateInfo &TemplateInfo,
    SourceLocation &DeclEnd, ParsedAttributes &Attrs) {
  assert(Tok.is(tok::kw_using) && "Not using token");
  ObjCDeclContextSwitch ObjCDC(*this);

  // Eat 'using'.
  SourceLocation UsingLoc = ConsumeToken();

  if (Tok.is(tok::code_completion)) {
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteUsing(getCurScope());
    return nullptr;
  }

  // Consume unexpected 'template' keywords.
  while (Tok.is(tok::kw_template)) {
    SourceLocation TemplateLoc = ConsumeToken();
    Diag(TemplateLoc, diag::err_unexpected_template_after_using)
        << FixItHint::CreateRemoval(TemplateLoc);
  }

  // 'using namespace' means this is a using-directive.
  if (Tok.is(tok::kw_namespace)) {
    // Template parameters are always an error here.
    if (TemplateInfo.Kind) {
      SourceRange R = TemplateInfo.getSourceRange();
      Diag(UsingLoc, diag::err_templated_using_directive_declaration)
          << 0 /* directive */ << R << FixItHint::CreateRemoval(R);
    }

    Decl *UsingDir = ParseUsingDirective(Context, UsingLoc, DeclEnd, Attrs);
    return Actions.ConvertDeclToDeclGroup(UsingDir);
  }

  // Otherwise, it must be a using-declaration or an alias-declaration.
  return ParseUsingDeclaration(Context, TemplateInfo, UsingLoc, DeclEnd, Attrs,
                               AS_none);
}

/// ParseUsingDirective - Parse C++ using-directive, assumes
/// that current token is 'namespace' and 'using' was already parsed.
///
///       using-directive: [C++ 7.3.p4: namespace.udir]
///        'using' 'namespace' ::[opt] nested-name-specifier[opt]
///                 namespace-name ;
/// [GNU] using-directive:
///        'using' 'namespace' ::[opt] nested-name-specifier[opt]
///                 namespace-name attributes[opt] ;
///
Decl *Parser::ParseUsingDirective(DeclaratorContext Context,
                                  SourceLocation UsingLoc,
                                  SourceLocation &DeclEnd,
                                  ParsedAttributes &attrs) {
  assert(Tok.is(tok::kw_namespace) && "Not 'namespace' token");

  // Eat 'namespace'.
  SourceLocation NamespcLoc = ConsumeToken();

  if (Tok.is(tok::code_completion)) {
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteUsingDirective(getCurScope());
    return nullptr;
  }

  CXXScopeSpec SS;
  // Parse (optional) nested-name-specifier.
  ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                 /*ObjectHasErrors=*/false,
                                 /*EnteringContext=*/false,
                                 /*MayBePseudoDestructor=*/nullptr,
                                 /*IsTypename=*/false,
                                 /*LastII=*/nullptr,
                                 /*OnlyNamespace=*/true);

  IdentifierInfo *NamespcName = nullptr;
  SourceLocation IdentLoc = SourceLocation();

  // Parse namespace-name.
  if (Tok.isNot(tok::identifier)) {
    Diag(Tok, diag::err_expected_namespace_name);
    // If there was invalid namespace name, skip to end of decl, and eat ';'.
    SkipUntil(tok::semi);
    // FIXME: Are there cases, when we would like to call ActOnUsingDirective?
    return nullptr;
  }

  if (SS.isInvalid()) {
    // Diagnostics have been emitted in ParseOptionalCXXScopeSpecifier.
    // Skip to end of the definition and eat the ';'.
    SkipUntil(tok::semi);
    return nullptr;
  }

  // Parse identifier.
  NamespcName = Tok.getIdentifierInfo();
  IdentLoc = ConsumeToken();

  // Parse (optional) attributes (most likely GNU strong-using extension).
  bool GNUAttr = false;
  if (Tok.is(tok::kw___attribute)) {
    GNUAttr = true;
    ParseGNUAttributes(attrs);
  }

  // Eat ';'.
  DeclEnd = Tok.getLocation();
  if (ExpectAndConsume(tok::semi,
                       GNUAttr ? diag::err_expected_semi_after_attribute_list
                               : diag::err_expected_semi_after_namespace_name))
    SkipUntil(tok::semi);

  return Actions.ActOnUsingDirective(getCurScope(), UsingLoc, NamespcLoc, SS,
                                     IdentLoc, NamespcName, attrs);
}

/// Parse a using-declarator (or the identifier in a C++11 alias-declaration).
///
///     using-declarator:
///       'typename'[opt] nested-name-specifier unqualified-id
///
bool Parser::ParseUsingDeclarator(DeclaratorContext Context,
                                  UsingDeclarator &D) {
  D.clear();

  // Ignore optional 'typename'.
  // FIXME: This is wrong; we should parse this as a typename-specifier.
  TryConsumeToken(tok::kw_typename, D.TypenameLoc);

  if (Tok.is(tok::kw___super)) {
    Diag(Tok.getLocation(), diag::err_super_in_using_declaration);
    return true;
  }

  // Parse nested-name-specifier.
  const IdentifierInfo *LastII = nullptr;
  if (ParseOptionalCXXScopeSpecifier(D.SS, /*ObjectType=*/nullptr,
                                     /*ObjectHasErrors=*/false,
                                     /*EnteringContext=*/false,
                                     /*MayBePseudoDtor=*/nullptr,
                                     /*IsTypename=*/false,
                                     /*LastII=*/&LastII,
                                     /*OnlyNamespace=*/false,
                                     /*InUsingDeclaration=*/true))

    return true;
  if (D.SS.isInvalid())
    return true;

  // Parse the unqualified-id. We allow parsing of both constructor and
  // destructor names and allow the action module to diagnose any semantic
  // errors.
  //
  // C++11 [class.qual]p2:
  //   [...] in a using-declaration that is a member-declaration, if the name
  //   specified after the nested-name-specifier is the same as the identifier
  //   or the simple-template-id's template-name in the last component of the
  //   nested-name-specifier, the name is [...] considered to name the
  //   constructor.
  if (getLangOpts().CPlusPlus11 && Context == DeclaratorContext::Member &&
      Tok.is(tok::identifier) &&
      (NextToken().is(tok::semi) || NextToken().is(tok::comma) ||
       NextToken().is(tok::ellipsis) || NextToken().is(tok::l_square) ||
       NextToken().isRegularKeywordAttribute() ||
       NextToken().is(tok::kw___attribute)) &&
      D.SS.isNotEmpty() && LastII == Tok.getIdentifierInfo() &&
      !D.SS.getScopeRep()->getAsNamespace() &&
      !D.SS.getScopeRep()->getAsNamespaceAlias()) {
    SourceLocation IdLoc = ConsumeToken();
    ParsedType Type =
        Actions.getInheritingConstructorName(D.SS, IdLoc, *LastII);
    D.Name.setConstructorName(Type, IdLoc, IdLoc);
  } else {
    if (ParseUnqualifiedId(
            D.SS, /*ObjectType=*/nullptr,
            /*ObjectHadErrors=*/false, /*EnteringContext=*/false,
            /*AllowDestructorName=*/true,
            /*AllowConstructorName=*/
            !(Tok.is(tok::identifier) && NextToken().is(tok::equal)),
            /*AllowDeductionGuide=*/false, nullptr, D.Name))
      return true;
  }

  if (TryConsumeToken(tok::ellipsis, D.EllipsisLoc))
    Diag(Tok.getLocation(), getLangOpts().CPlusPlus17
                                ? diag::warn_cxx17_compat_using_declaration_pack
                                : diag::ext_using_declaration_pack);

  return false;
}

/// ParseUsingDeclaration - Parse C++ using-declaration or alias-declaration.
/// Assumes that 'using' was already seen.
///
///     using-declaration: [C++ 7.3.p3: namespace.udecl]
///       'using' using-declarator-list[opt] ;
///
///     using-declarator-list: [C++1z]
///       using-declarator '...'[opt]
///       using-declarator-list ',' using-declarator '...'[opt]
///
///     using-declarator-list: [C++98-14]
///       using-declarator
///
///     alias-declaration: C++11 [dcl.dcl]p1
///       'using' identifier attribute-specifier-seq[opt] = type-id ;
///
///     using-enum-declaration: [C++20, dcl.enum]
///       'using' elaborated-enum-specifier ;
///       The terminal name of the elaborated-enum-specifier undergoes
///       type-only lookup
///
///     elaborated-enum-specifier:
///       'enum' nested-name-specifier[opt] identifier
Parser::DeclGroupPtrTy Parser::ParseUsingDeclaration(
    DeclaratorContext Context, const ParsedTemplateInfo &TemplateInfo,
    SourceLocation UsingLoc, SourceLocation &DeclEnd,
    ParsedAttributes &PrefixAttrs, AccessSpecifier AS) {
  SourceLocation UELoc;
  bool InInitStatement = Context == DeclaratorContext::SelectionInit ||
                         Context == DeclaratorContext::ForInit;

  if (TryConsumeToken(tok::kw_enum, UELoc) && !InInitStatement) {
    // C++20 using-enum
    Diag(UELoc, getLangOpts().CPlusPlus20
                    ? diag::warn_cxx17_compat_using_enum_declaration
                    : diag::ext_using_enum_declaration);

    DiagnoseCXX11AttributeExtension(PrefixAttrs);

    if (TemplateInfo.Kind) {
      SourceRange R = TemplateInfo.getSourceRange();
      Diag(UsingLoc, diag::err_templated_using_directive_declaration)
          << 1 /* declaration */ << R << FixItHint::CreateRemoval(R);
      SkipUntil(tok::semi);
      return nullptr;
    }
    CXXScopeSpec SS;
    if (ParseOptionalCXXScopeSpecifier(SS, /*ParsedType=*/nullptr,
                                       /*ObectHasErrors=*/false,
                                       /*EnteringConttext=*/false,
                                       /*MayBePseudoDestructor=*/nullptr,
                                       /*IsTypename=*/true,
                                       /*IdentifierInfo=*/nullptr,
                                       /*OnlyNamespace=*/false,
                                       /*InUsingDeclaration=*/true)) {
      SkipUntil(tok::semi);
      return nullptr;
    }

    if (Tok.is(tok::code_completion)) {
      cutOffParsing();
      Actions.CodeCompletion().CodeCompleteUsing(getCurScope());
      return nullptr;
    }

    Decl *UED = nullptr;

    // FIXME: identifier and annot_template_id handling is very similar to
    // ParseBaseTypeSpecifier. It should be factored out into a function.
    if (Tok.is(tok::identifier)) {
      IdentifierInfo *IdentInfo = Tok.getIdentifierInfo();
      SourceLocation IdentLoc = ConsumeToken();

      ParsedType Type = Actions.getTypeName(
          *IdentInfo, IdentLoc, getCurScope(), &SS, /*isClassName=*/true,
          /*HasTrailingDot=*/false,
          /*ObjectType=*/nullptr, /*IsCtorOrDtorName=*/false,
          /*WantNontrivialTypeSourceInfo=*/true);

      UED = Actions.ActOnUsingEnumDeclaration(
          getCurScope(), AS, UsingLoc, UELoc, IdentLoc, *IdentInfo, Type, &SS);
    } else if (Tok.is(tok::annot_template_id)) {
      TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);

      if (TemplateId->mightBeType()) {
        AnnotateTemplateIdTokenAsType(SS, ImplicitTypenameContext::No,
                                      /*IsClassName=*/true);

        assert(Tok.is(tok::annot_typename) && "template-id -> type failed");
        TypeResult Type = getTypeAnnotation(Tok);
        SourceRange Loc = Tok.getAnnotationRange();
        ConsumeAnnotationToken();

        UED = Actions.ActOnUsingEnumDeclaration(getCurScope(), AS, UsingLoc,
                                                UELoc, Loc, *TemplateId->Name,
                                                Type.get(), &SS);
      } else {
        Diag(Tok.getLocation(), diag::err_using_enum_not_enum)
            << TemplateId->Name->getName()
            << SourceRange(TemplateId->TemplateNameLoc, TemplateId->RAngleLoc);
      }
    } else {
      Diag(Tok.getLocation(), diag::err_using_enum_expect_identifier)
          << Tok.is(tok::kw_enum);
      SkipUntil(tok::semi);
      return nullptr;
    }

    if (!UED) {
      SkipUntil(tok::semi);
      return nullptr;
    }

    DeclEnd = Tok.getLocation();
    if (ExpectAndConsume(tok::semi, diag::err_expected_after,
                         "using-enum declaration"))
      SkipUntil(tok::semi);

    return Actions.ConvertDeclToDeclGroup(UED);
  }

  // Check for misplaced attributes before the identifier in an
  // alias-declaration.
  ParsedAttributes MisplacedAttrs(AttrFactory);
  MaybeParseCXX11Attributes(MisplacedAttrs);

  if (InInitStatement && Tok.isNot(tok::identifier))
    return nullptr;

  UsingDeclarator D;
  bool InvalidDeclarator = ParseUsingDeclarator(Context, D);

  ParsedAttributes Attrs(AttrFactory);
  MaybeParseAttributes(PAKM_GNU | PAKM_CXX11, Attrs);

  // If we had any misplaced attributes from earlier, this is where they
  // should have been written.
  if (MisplacedAttrs.Range.isValid()) {
    auto *FirstAttr =
        MisplacedAttrs.empty() ? nullptr : &MisplacedAttrs.front();
    auto &Range = MisplacedAttrs.Range;
    (FirstAttr && FirstAttr->isRegularKeywordAttribute()
         ? Diag(Range.getBegin(), diag::err_keyword_not_allowed) << FirstAttr
         : Diag(Range.getBegin(), diag::err_attributes_not_allowed))
        << FixItHint::CreateInsertionFromRange(
               Tok.getLocation(), CharSourceRange::getTokenRange(Range))
        << FixItHint::CreateRemoval(Range);
    Attrs.takeAllFrom(MisplacedAttrs);
  }

  // Maybe this is an alias-declaration.
  if (Tok.is(tok::equal) || InInitStatement) {
    if (InvalidDeclarator) {
      SkipUntil(tok::semi);
      return nullptr;
    }

    ProhibitAttributes(PrefixAttrs);

    Decl *DeclFromDeclSpec = nullptr;
    Scope *CurScope = getCurScope();
    if (CurScope)
      CurScope->setFlags(Scope::ScopeFlags::TypeAliasScope |
                         CurScope->getFlags());

    Decl *AD = ParseAliasDeclarationAfterDeclarator(
        TemplateInfo, UsingLoc, D, DeclEnd, AS, Attrs, &DeclFromDeclSpec);
    return Actions.ConvertDeclToDeclGroup(AD, DeclFromDeclSpec);
  }

  DiagnoseCXX11AttributeExtension(PrefixAttrs);

  // Diagnose an attempt to declare a templated using-declaration.
  // In C++11, alias-declarations can be templates:
  //   template <...> using id = type;
  if (TemplateInfo.Kind) {
    SourceRange R = TemplateInfo.getSourceRange();
    Diag(UsingLoc, diag::err_templated_using_directive_declaration)
        << 1 /* declaration */ << R << FixItHint::CreateRemoval(R);

    // Unfortunately, we have to bail out instead of recovering by
    // ignoring the parameters, just in case the nested name specifier
    // depends on the parameters.
    return nullptr;
  }

  SmallVector<Decl *, 8> DeclsInGroup;
  while (true) {
    // Parse (optional) attributes.
    MaybeParseAttributes(PAKM_GNU | PAKM_CXX11, Attrs);
    DiagnoseCXX11AttributeExtension(Attrs);
    Attrs.addAll(PrefixAttrs.begin(), PrefixAttrs.end());

    if (InvalidDeclarator)
      SkipUntil(tok::comma, tok::semi, StopBeforeMatch);
    else {
      // "typename" keyword is allowed for identifiers only,
      // because it may be a type definition.
      if (D.TypenameLoc.isValid() &&
          D.Name.getKind() != UnqualifiedIdKind::IK_Identifier) {
        Diag(D.Name.getSourceRange().getBegin(),
             diag::err_typename_identifiers_only)
            << FixItHint::CreateRemoval(SourceRange(D.TypenameLoc));
        // Proceed parsing, but discard the typename keyword.
        D.TypenameLoc = SourceLocation();
      }

      Decl *UD = Actions.ActOnUsingDeclaration(getCurScope(), AS, UsingLoc,
                                               D.TypenameLoc, D.SS, D.Name,
                                               D.EllipsisLoc, Attrs);
      if (UD)
        DeclsInGroup.push_back(UD);
    }

    if (!TryConsumeToken(tok::comma))
      break;

    // Parse another using-declarator.
    Attrs.clear();
    InvalidDeclarator = ParseUsingDeclarator(Context, D);
  }

  if (DeclsInGroup.size() > 1)
    Diag(Tok.getLocation(),
         getLangOpts().CPlusPlus17
             ? diag::warn_cxx17_compat_multi_using_declaration
             : diag::ext_multi_using_declaration);

  // Eat ';'.
  DeclEnd = Tok.getLocation();
  if (ExpectAndConsume(tok::semi, diag::err_expected_after,
                       !Attrs.empty()    ? "attributes list"
                       : UELoc.isValid() ? "using-enum declaration"
                                         : "using declaration"))
    SkipUntil(tok::semi);

  return Actions.BuildDeclaratorGroup(DeclsInGroup);
}

Decl *Parser::ParseAliasDeclarationAfterDeclarator(
    const ParsedTemplateInfo &TemplateInfo, SourceLocation UsingLoc,
    UsingDeclarator &D, SourceLocation &DeclEnd, AccessSpecifier AS,
    ParsedAttributes &Attrs, Decl **OwnedType) {
  if (ExpectAndConsume(tok::equal)) {
    SkipUntil(tok::semi);
    return nullptr;
  }

  Diag(Tok.getLocation(), getLangOpts().CPlusPlus11
                              ? diag::warn_cxx98_compat_alias_declaration
                              : diag::ext_alias_declaration);

  // Type alias templates cannot be specialized.
  int SpecKind = -1;
  if (TemplateInfo.Kind == ParsedTemplateInfo::Template &&
      D.Name.getKind() == UnqualifiedIdKind::IK_TemplateId)
    SpecKind = 0;
  if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitSpecialization)
    SpecKind = 1;
  if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation)
    SpecKind = 2;
  if (SpecKind != -1) {
    SourceRange Range;
    if (SpecKind == 0)
      Range = SourceRange(D.Name.TemplateId->LAngleLoc,
                          D.Name.TemplateId->RAngleLoc);
    else
      Range = TemplateInfo.getSourceRange();
    Diag(Range.getBegin(), diag::err_alias_declaration_specialization)
        << SpecKind << Range;
    SkipUntil(tok::semi);
    return nullptr;
  }

  // Name must be an identifier.
  if (D.Name.getKind() != UnqualifiedIdKind::IK_Identifier) {
    Diag(D.Name.StartLocation, diag::err_alias_declaration_not_identifier);
    // No removal fixit: can't recover from this.
    SkipUntil(tok::semi);
    return nullptr;
  } else if (D.TypenameLoc.isValid())
    Diag(D.TypenameLoc, diag::err_alias_declaration_not_identifier)
        << FixItHint::CreateRemoval(
               SourceRange(D.TypenameLoc, D.SS.isNotEmpty() ? D.SS.getEndLoc()
                                                            : D.TypenameLoc));
  else if (D.SS.isNotEmpty())
    Diag(D.SS.getBeginLoc(), diag::err_alias_declaration_not_identifier)
        << FixItHint::CreateRemoval(D.SS.getRange());
  if (D.EllipsisLoc.isValid())
    Diag(D.EllipsisLoc, diag::err_alias_declaration_pack_expansion)
        << FixItHint::CreateRemoval(SourceRange(D.EllipsisLoc));

  Decl *DeclFromDeclSpec = nullptr;
  TypeResult TypeAlias =
      ParseTypeName(nullptr,
                    TemplateInfo.Kind ? DeclaratorContext::AliasTemplate
                                      : DeclaratorContext::AliasDecl,
                    AS, &DeclFromDeclSpec, &Attrs);
  if (OwnedType)
    *OwnedType = DeclFromDeclSpec;

  // Eat ';'.
  DeclEnd = Tok.getLocation();
  if (ExpectAndConsume(tok::semi, diag::err_expected_after,
                       !Attrs.empty() ? "attributes list"
                                      : "alias declaration"))
    SkipUntil(tok::semi);

  TemplateParameterLists *TemplateParams = TemplateInfo.TemplateParams;
  MultiTemplateParamsArg TemplateParamsArg(
      TemplateParams ? TemplateParams->data() : nullptr,
      TemplateParams ? TemplateParams->size() : 0);
  return Actions.ActOnAliasDeclaration(getCurScope(), AS, TemplateParamsArg,
                                       UsingLoc, D.Name, Attrs, TypeAlias,
                                       DeclFromDeclSpec);
}

static FixItHint getStaticAssertNoMessageFixIt(const Expr *AssertExpr,
                                               SourceLocation EndExprLoc) {
  if (const auto *BO = dyn_cast_or_null<BinaryOperator>(AssertExpr)) {
    if (BO->getOpcode() == BO_LAnd &&
        isa<StringLiteral>(BO->getRHS()->IgnoreImpCasts()))
      return FixItHint::CreateReplacement(BO->getOperatorLoc(), ",");
  }
  return FixItHint::CreateInsertion(EndExprLoc, ", \"\"");
}

/// ParseStaticAssertDeclaration - Parse C++0x or C11 static_assert-declaration.
///
/// [C++0x] static_assert-declaration:
///           static_assert ( constant-expression  ,  string-literal  ) ;
///
/// [C11]   static_assert-declaration:
///           _Static_assert ( constant-expression  ,  string-literal  ) ;
///
Decl *Parser::ParseStaticAssertDeclaration(SourceLocation &DeclEnd) {
  assert(Tok.isOneOf(tok::kw_static_assert, tok::kw__Static_assert) &&
         "Not a static_assert declaration");

  // Save the token name used for static assertion.
  const char *TokName = Tok.getName();

  if (Tok.is(tok::kw__Static_assert))
    diagnoseUseOfC11Keyword(Tok);
  else if (Tok.is(tok::kw_static_assert)) {
    if (!getLangOpts().CPlusPlus) {
      if (getLangOpts().C23)
        Diag(Tok, diag::warn_c23_compat_keyword) << Tok.getName();
      else
        Diag(Tok, diag::ext_ms_static_assert) << FixItHint::CreateReplacement(
            Tok.getLocation(), "_Static_assert");
    } else
      Diag(Tok, diag::warn_cxx98_compat_static_assert);
  }

  SourceLocation StaticAssertLoc = ConsumeToken();

  BalancedDelimiterTracker T(*this, tok::l_paren);
  if (T.consumeOpen()) {
    Diag(Tok, diag::err_expected) << tok::l_paren;
    SkipMalformedDecl();
    return nullptr;
  }

  EnterExpressionEvaluationContext ConstantEvaluated(
      Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
  ExprResult AssertExpr(ParseConstantExpressionInExprEvalContext());
  if (AssertExpr.isInvalid()) {
    SkipMalformedDecl();
    return nullptr;
  }

  ExprResult AssertMessage;
  if (Tok.is(tok::r_paren)) {
    unsigned DiagVal;
    if (getLangOpts().CPlusPlus17)
      DiagVal = diag::warn_cxx14_compat_static_assert_no_message;
    else if (getLangOpts().CPlusPlus)
      DiagVal = diag::ext_cxx_static_assert_no_message;
    else if (getLangOpts().C23)
      DiagVal = diag::warn_c17_compat_static_assert_no_message;
    else
      DiagVal = diag::ext_c_static_assert_no_message;
    Diag(Tok, DiagVal) << getStaticAssertNoMessageFixIt(AssertExpr.get(),
                                                        Tok.getLocation());
  } else {
    if (ExpectAndConsume(tok::comma)) {
      SkipUntil(tok::semi);
      return nullptr;
    }

    bool ParseAsExpression = false;
    if (getLangOpts().CPlusPlus26) {
      for (unsigned I = 0;; ++I) {
        const Token &T = GetLookAheadToken(I);
        if (T.is(tok::r_paren))
          break;
        if (!tokenIsLikeStringLiteral(T, getLangOpts()) || T.hasUDSuffix()) {
          ParseAsExpression = true;
          break;
        }
      }
    }

    if (ParseAsExpression)
      AssertMessage = ParseConstantExpressionInExprEvalContext();
    else if (tokenIsLikeStringLiteral(Tok, getLangOpts()))
      AssertMessage = ParseUnevaluatedStringLiteralExpression();
    else {
      Diag(Tok, diag::err_expected_string_literal)
          << /*Source='static_assert'*/ 1;
      SkipMalformedDecl();
      return nullptr;
    }

    if (AssertMessage.isInvalid()) {
      SkipMalformedDecl();
      return nullptr;
    }
  }

  T.consumeClose();

  DeclEnd = Tok.getLocation();
  ExpectAndConsumeSemi(diag::err_expected_semi_after_static_assert, TokName);

  return Actions.ActOnStaticAssertDeclaration(StaticAssertLoc, AssertExpr.get(),
                                              AssertMessage.get(),
                                              T.getCloseLocation());
}

/// ParseDecltypeSpecifier - Parse a C++11 decltype specifier.
///
/// 'decltype' ( expression )
/// 'decltype' ( 'auto' )      [C++1y]
///
SourceLocation Parser::ParseDecltypeSpecifier(DeclSpec &DS) {
  assert(Tok.isOneOf(tok::kw_decltype, tok::annot_decltype) &&
         "Not a decltype specifier");

  ExprResult Result;
  SourceLocation StartLoc = Tok.getLocation();
  SourceLocation EndLoc;

  if (Tok.is(tok::annot_decltype)) {
    Result = getExprAnnotation(Tok);
    EndLoc = Tok.getAnnotationEndLoc();
    // Unfortunately, we don't know the LParen source location as the annotated
    // token doesn't have it.
    DS.setTypeArgumentRange(SourceRange(SourceLocation(), EndLoc));
    ConsumeAnnotationToken();
    if (Result.isInvalid()) {
      DS.SetTypeSpecError();
      return EndLoc;
    }
  } else {
    if (Tok.getIdentifierInfo()->isStr("decltype"))
      Diag(Tok, diag::warn_cxx98_compat_decltype);

    ConsumeToken();

    BalancedDelimiterTracker T(*this, tok::l_paren);
    if (T.expectAndConsume(diag::err_expected_lparen_after, "decltype",
                           tok::r_paren)) {
      DS.SetTypeSpecError();
      return T.getOpenLocation() == Tok.getLocation() ? StartLoc
                                                      : T.getOpenLocation();
    }

    // Check for C++1y 'decltype(auto)'.
    if (Tok.is(tok::kw_auto) && NextToken().is(tok::r_paren)) {
      // the typename-specifier in a function-style cast expression may
      // be 'auto' since C++23.
      Diag(Tok.getLocation(),
           getLangOpts().CPlusPlus14
               ? diag::warn_cxx11_compat_decltype_auto_type_specifier
               : diag::ext_decltype_auto_type_specifier);
      ConsumeToken();
    } else {
      // Parse the expression

      // C++11 [dcl.type.simple]p4:
      //   The operand of the decltype specifier is an unevaluated operand.
      EnterExpressionEvaluationContext Unevaluated(
          Actions, Sema::ExpressionEvaluationContext::Unevaluated, nullptr,
          Sema::ExpressionEvaluationContextRecord::EK_Decltype);
      Result = Actions.CorrectDelayedTyposInExpr(
          ParseExpression(), /*InitDecl=*/nullptr,
          /*RecoverUncorrectedTypos=*/false,
          [](Expr *E) { return E->hasPlaceholderType() ? ExprError() : E; });
      if (Result.isInvalid()) {
        DS.SetTypeSpecError();
        if (SkipUntil(tok::r_paren, StopAtSemi | StopBeforeMatch)) {
          EndLoc = ConsumeParen();
        } else {
          if (PP.isBacktrackEnabled() && Tok.is(tok::semi)) {
            // Backtrack to get the location of the last token before the semi.
            PP.RevertCachedTokens(2);
            ConsumeToken(); // the semi.
            EndLoc = ConsumeAnyToken();
            assert(Tok.is(tok::semi));
          } else {
            EndLoc = Tok.getLocation();
          }
        }
        return EndLoc;
      }

      Result = Actions.ActOnDecltypeExpression(Result.get());
    }

    // Match the ')'
    T.consumeClose();
    DS.setTypeArgumentRange(T.getRange());
    if (T.getCloseLocation().isInvalid()) {
      DS.SetTypeSpecError();
      // FIXME: this should return the location of the last token
      //        that was consumed (by "consumeClose()")
      return T.getCloseLocation();
    }

    if (Result.isInvalid()) {
      DS.SetTypeSpecError();
      return T.getCloseLocation();
    }

    EndLoc = T.getCloseLocation();
  }
  assert(!Result.isInvalid());

  const char *PrevSpec = nullptr;
  unsigned DiagID;
  const PrintingPolicy &Policy = Actions.getASTContext().getPrintingPolicy();
  // Check for duplicate type specifiers (e.g. "int decltype(a)").
  if (Result.get() ? DS.SetTypeSpecType(DeclSpec::TST_decltype, StartLoc,
                                        PrevSpec, DiagID, Result.get(), Policy)
                   : DS.SetTypeSpecType(DeclSpec::TST_decltype_auto, StartLoc,
                                        PrevSpec, DiagID, Policy)) {
    Diag(StartLoc, DiagID) << PrevSpec;
    DS.SetTypeSpecError();
  }
  return EndLoc;
}

void Parser::AnnotateExistingDecltypeSpecifier(const DeclSpec &DS,
                                               SourceLocation StartLoc,
                                               SourceLocation EndLoc) {
  // make sure we have a token we can turn into an annotation token
  if (PP.isBacktrackEnabled()) {
    PP.RevertCachedTokens(1);
    if (DS.getTypeSpecType() == TST_error) {
      // We encountered an error in parsing 'decltype(...)' so lets annotate all
      // the tokens in the backtracking cache - that we likely had to skip over
      // to get to a token that allows us to resume parsing, such as a
      // semi-colon.
      EndLoc = PP.getLastCachedTokenLocation();
    }
  } else
    PP.EnterToken(Tok, /*IsReinject*/ true);

  Tok.setKind(tok::annot_decltype);
  setExprAnnotation(Tok,
                    DS.getTypeSpecType() == TST_decltype ? DS.getRepAsExpr()
                    : DS.getTypeSpecType() == TST_decltype_auto ? ExprResult()
                                                                : ExprError());
  Tok.setAnnotationEndLoc(EndLoc);
  Tok.setLocation(StartLoc);
  PP.AnnotateCachedTokens(Tok);
}

SourceLocation Parser::ParsePackIndexingType(DeclSpec &DS) {
  assert(Tok.isOneOf(tok::annot_pack_indexing_type, tok::identifier) &&
         "Expected an identifier");

  TypeResult Type;
  SourceLocation StartLoc;
  SourceLocation EllipsisLoc;
  const char *PrevSpec;
  unsigned DiagID;
  const PrintingPolicy &Policy = Actions.getASTContext().getPrintingPolicy();

  if (Tok.is(tok::annot_pack_indexing_type)) {
    StartLoc = Tok.getLocation();
    SourceLocation EndLoc;
    Type = getTypeAnnotation(Tok);
    EndLoc = Tok.getAnnotationEndLoc();
    // Unfortunately, we don't know the LParen source location as the annotated
    // token doesn't have it.
    DS.setTypeArgumentRange(SourceRange(SourceLocation(), EndLoc));
    ConsumeAnnotationToken();
    if (Type.isInvalid()) {
      DS.SetTypeSpecError();
      return EndLoc;
    }
    DS.SetTypeSpecType(DeclSpec::TST_typename_pack_indexing, StartLoc, PrevSpec,
                       DiagID, Type, Policy);
    return EndLoc;
  }
  if (!NextToken().is(tok::ellipsis) ||
      !GetLookAheadToken(2).is(tok::l_square)) {
    DS.SetTypeSpecError();
    return Tok.getEndLoc();
  }

  ParsedType Ty = Actions.getTypeName(*Tok.getIdentifierInfo(),
                                      Tok.getLocation(), getCurScope());
  if (!Ty) {
    DS.SetTypeSpecError();
    return Tok.getEndLoc();
  }
  Type = Ty;

  StartLoc = ConsumeToken();
  EllipsisLoc = ConsumeToken();
  BalancedDelimiterTracker T(*this, tok::l_square);
  T.consumeOpen();
  ExprResult IndexExpr = ParseConstantExpression();
  T.consumeClose();

  DS.SetRangeStart(StartLoc);
  DS.SetRangeEnd(T.getCloseLocation());

  if (!IndexExpr.isUsable()) {
    ASTContext &C = Actions.getASTContext();
    IndexExpr = IntegerLiteral::Create(C, C.MakeIntValue(0, C.getSizeType()),
                                       C.getSizeType(), SourceLocation());
  }

  DS.SetTypeSpecType(DeclSpec::TST_typename, StartLoc, PrevSpec, DiagID, Type,
                     Policy);
  DS.SetPackIndexingExpr(EllipsisLoc, IndexExpr.get());
  return T.getCloseLocation();
}

void Parser::AnnotateExistingIndexedTypeNamePack(ParsedType T,
                                                 SourceLocation StartLoc,
                                                 SourceLocation EndLoc) {
  // make sure we have a token we can turn into an annotation token
  if (PP.isBacktrackEnabled()) {
    PP.RevertCachedTokens(1);
    if (!T) {
      // We encountered an error in parsing 'decltype(...)' so lets annotate all
      // the tokens in the backtracking cache - that we likely had to skip over
      // to get to a token that allows us to resume parsing, such as a
      // semi-colon.
      EndLoc = PP.getLastCachedTokenLocation();
    }
  } else
    PP.EnterToken(Tok, /*IsReinject*/ true);

  Tok.setKind(tok::annot_pack_indexing_type);
  setTypeAnnotation(Tok, T);
  Tok.setAnnotationEndLoc(EndLoc);
  Tok.setLocation(StartLoc);
  PP.AnnotateCachedTokens(Tok);
}

DeclSpec::TST Parser::TypeTransformTokToDeclSpec() {
  switch (Tok.getKind()) {
#define TRANSFORM_TYPE_TRAIT_DEF(_, Trait)                                     \
  case tok::kw___##Trait:                                                      \
    return DeclSpec::TST_##Trait;
#include "clang/Basic/TransformTypeTraits.def"
  default:
    llvm_unreachable("passed in an unhandled type transformation built-in");
  }
}

bool Parser::MaybeParseTypeTransformTypeSpecifier(DeclSpec &DS) {
  if (!NextToken().is(tok::l_paren)) {
    Tok.setKind(tok::identifier);
    return false;
  }
  DeclSpec::TST TypeTransformTST = TypeTransformTokToDeclSpec();
  SourceLocation StartLoc = ConsumeToken();

  BalancedDelimiterTracker T(*this, tok::l_paren);
  if (T.expectAndConsume(diag::err_expected_lparen_after, Tok.getName(),
                         tok::r_paren))
    return true;

  TypeResult Result = ParseTypeName();
  if (Result.isInvalid()) {
    SkipUntil(tok::r_paren, StopAtSemi);
    return true;
  }

  T.consumeClose();
  if (T.getCloseLocation().isInvalid())
    return true;

  const char *PrevSpec = nullptr;
  unsigned DiagID;
  if (DS.SetTypeSpecType(TypeTransformTST, StartLoc, PrevSpec, DiagID,
                         Result.get(),
                         Actions.getASTContext().getPrintingPolicy()))
    Diag(StartLoc, DiagID) << PrevSpec;
  DS.setTypeArgumentRange(T.getRange());
  return true;
}

/// ParseBaseTypeSpecifier - Parse a C++ base-type-specifier which is either a
/// class name or decltype-specifier. Note that we only check that the result
/// names a type; semantic analysis will need to verify that the type names a
/// class. The result is either a type or null, depending on whether a type
/// name was found.
///
///       base-type-specifier: [C++11 class.derived]
///         class-or-decltype
///       class-or-decltype: [C++11 class.derived]
///         nested-name-specifier[opt] class-name
///         decltype-specifier
///       class-name: [C++ class.name]
///         identifier
///         simple-template-id
///
/// In C++98, instead of base-type-specifier, we have:
///
///         ::[opt] nested-name-specifier[opt] class-name
TypeResult Parser::ParseBaseTypeSpecifier(SourceLocation &BaseLoc,
                                          SourceLocation &EndLocation) {
  // Ignore attempts to use typename
  if (Tok.is(tok::kw_typename)) {
    Diag(Tok, diag::err_expected_class_name_not_template)
        << FixItHint::CreateRemoval(Tok.getLocation());
    ConsumeToken();
  }

  // Parse optional nested-name-specifier
  CXXScopeSpec SS;
  if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                     /*ObjectHasErrors=*/false,
                                     /*EnteringContext=*/false))
    return true;

  BaseLoc = Tok.getLocation();

  // Parse decltype-specifier
  // tok == kw_decltype is just error recovery, it can only happen when SS
  // isn't empty
  if (Tok.isOneOf(tok::kw_decltype, tok::annot_decltype)) {
    if (SS.isNotEmpty())
      Diag(SS.getBeginLoc(), diag::err_unexpected_scope_on_base_decltype)
          << FixItHint::CreateRemoval(SS.getRange());
    // Fake up a Declarator to use with ActOnTypeName.
    DeclSpec DS(AttrFactory);

    EndLocation = ParseDecltypeSpecifier(DS);

    Declarator DeclaratorInfo(DS, ParsedAttributesView::none(),
                              DeclaratorContext::TypeName);
    return Actions.ActOnTypeName(DeclaratorInfo);
  }

  if (Tok.is(tok::annot_pack_indexing_type)) {
    DeclSpec DS(AttrFactory);
    ParsePackIndexingType(DS);
    Declarator DeclaratorInfo(DS, ParsedAttributesView::none(),
                              DeclaratorContext::TypeName);
    return Actions.ActOnTypeName(DeclaratorInfo);
  }

  // Check whether we have a template-id that names a type.
  // FIXME: identifier and annot_template_id handling in ParseUsingDeclaration
  // work very similarly. It should be refactored into a separate function.
  if (Tok.is(tok::annot_template_id)) {
    TemplateIdAnnotation *TemplateId = takeTemplateIdAnnotation(Tok);
    if (TemplateId->mightBeType()) {
      AnnotateTemplateIdTokenAsType(SS, ImplicitTypenameContext::No,
                                    /*IsClassName=*/true);

      assert(Tok.is(tok::annot_typename) && "template-id -> type failed");
      TypeResult Type = getTypeAnnotation(Tok);
      EndLocation = Tok.getAnnotationEndLoc();
      ConsumeAnnotationToken();
      return Type;
    }

    // Fall through to produce an error below.
  }

  if (Tok.isNot(tok::identifier)) {
    Diag(Tok, diag::err_expected_class_name);
    return true;
  }

  IdentifierInfo *Id = Tok.getIdentifierInfo();
  SourceLocation IdLoc = ConsumeToken();

  if (Tok.is(tok::less)) {
    // It looks the user intended to write a template-id here, but the
    // template-name was wrong. Try to fix that.
    // FIXME: Invoke ParseOptionalCXXScopeSpecifier in a "'template' is neither
    // required nor permitted" mode, and do this there.
    TemplateNameKind TNK = TNK_Non_template;
    TemplateTy Template;
    if (!Actions.DiagnoseUnknownTemplateName(*Id, IdLoc, getCurScope(), &SS,
                                             Template, TNK)) {
      Diag(IdLoc, diag::err_unknown_template_name) << Id;
    }

    // Form the template name
    UnqualifiedId TemplateName;
    TemplateName.setIdentifier(Id, IdLoc);

    // Parse the full template-id, then turn it into a type.
    if (AnnotateTemplateIdToken(Template, TNK, SS, SourceLocation(),
                                TemplateName))
      return true;
    if (Tok.is(tok::annot_template_id) &&
        takeTemplateIdAnnotation(Tok)->mightBeType())
      AnnotateTemplateIdTokenAsType(SS, ImplicitTypenameContext::No,
                                    /*IsClassName=*/true);

    // If we didn't end up with a typename token, there's nothing more we
    // can do.
    if (Tok.isNot(tok::annot_typename))
      return true;

    // Retrieve the type from the annotation token, consume that token, and
    // return.
    EndLocation = Tok.getAnnotationEndLoc();
    TypeResult Type = getTypeAnnotation(Tok);
    ConsumeAnnotationToken();
    return Type;
  }

  // We have an identifier; check whether it is actually a type.
  IdentifierInfo *CorrectedII = nullptr;
  ParsedType Type = Actions.getTypeName(
      *Id, IdLoc, getCurScope(), &SS, /*isClassName=*/true, false, nullptr,
      /*IsCtorOrDtorName=*/false,
      /*WantNontrivialTypeSourceInfo=*/true,
      /*IsClassTemplateDeductionContext=*/false, ImplicitTypenameContext::No,
      &CorrectedII);
  if (!Type) {
    Diag(IdLoc, diag::err_expected_class_name);
    return true;
  }

  // Consume the identifier.
  EndLocation = IdLoc;

  // Fake up a Declarator to use with ActOnTypeName.
  DeclSpec DS(AttrFactory);
  DS.SetRangeStart(IdLoc);
  DS.SetRangeEnd(EndLocation);
  DS.getTypeSpecScope() = SS;

  const char *PrevSpec = nullptr;
  unsigned DiagID;
  DS.SetTypeSpecType(TST_typename, IdLoc, PrevSpec, DiagID, Type,
                     Actions.getASTContext().getPrintingPolicy());

  Declarator DeclaratorInfo(DS, ParsedAttributesView::none(),
                            DeclaratorContext::TypeName);
  return Actions.ActOnTypeName(DeclaratorInfo);
}

void Parser::ParseMicrosoftInheritanceClassAttributes(ParsedAttributes &attrs) {
  while (Tok.isOneOf(tok::kw___single_inheritance,
                     tok::kw___multiple_inheritance,
                     tok::kw___virtual_inheritance)) {
    IdentifierInfo *AttrName = Tok.getIdentifierInfo();
    auto Kind = Tok.getKind();
    SourceLocation AttrNameLoc = ConsumeToken();
    attrs.addNew(AttrName, AttrNameLoc, nullptr, AttrNameLoc, nullptr, 0, Kind);
  }
}

void Parser::ParseNullabilityClassAttributes(ParsedAttributes &attrs) {
  while (Tok.is(tok::kw__Nullable)) {
    IdentifierInfo *AttrName = Tok.getIdentifierInfo();
    auto Kind = Tok.getKind();
    SourceLocation AttrNameLoc = ConsumeToken();
    attrs.addNew(AttrName, AttrNameLoc, nullptr, AttrNameLoc, nullptr, 0, Kind);
  }
}

/// Determine whether the following tokens are valid after a type-specifier
/// which could be a standalone declaration. This will conservatively return
/// true if there's any doubt, and is appropriate for insert-';' fixits.
bool Parser::isValidAfterTypeSpecifier(bool CouldBeBitfield) {
  // This switch enumerates the valid "follow" set for type-specifiers.
  switch (Tok.getKind()) {
  default:
    if (Tok.isRegularKeywordAttribute())
      return true;
    break;
  case tok::semi:              // struct foo {...} ;
  case tok::star:              // struct foo {...} *         P;
  case tok::amp:               // struct foo {...} &         R = ...
  case tok::ampamp:            // struct foo {...} &&        R = ...
  case tok::identifier:        // struct foo {...} V         ;
  case tok::r_paren:           //(struct foo {...} )         {4}
  case tok::coloncolon:        // struct foo {...} ::        a::b;
  case tok::annot_cxxscope:    // struct foo {...} a::       b;
  case tok::annot_typename:    // struct foo {...} a         ::b;
  case tok::annot_template_id: // struct foo {...} a<int>    ::b;
  case tok::kw_decltype:       // struct foo {...} decltype  (a)::b;
  case tok::l_paren:           // struct foo {...} (         x);
  case tok::comma:             // __builtin_offsetof(struct foo{...} ,
  case tok::kw_operator:       // struct foo       operator  ++() {...}
  case tok::kw___declspec:     // struct foo {...} __declspec(...)
  case tok::l_square:          // void f(struct f  [         3])
  case tok::ellipsis:          // void f(struct f  ...       [Ns])
  // FIXME: we should emit semantic diagnostic when declaration
  // attribute is in type attribute position.
  case tok::kw___attribute:    // struct foo __attribute__((used)) x;
  case tok::annot_pragma_pack: // struct foo {...} _Pragma(pack(pop));
  // struct foo {...} _Pragma(section(...));
  case tok::annot_pragma_ms_pragma:
  // struct foo {...} _Pragma(vtordisp(pop));
  case tok::annot_pragma_ms_vtordisp:
  // struct foo {...} _Pragma(pointers_to_members(...));
  case tok::annot_pragma_ms_pointers_to_members:
    return true;
  case tok::colon:
    return CouldBeBitfield || // enum E { ... }   :         2;
           ColonIsSacred;     // _Generic(..., enum E :     2);
  // Microsoft compatibility
  case tok::kw___cdecl:      // struct foo {...} __cdecl      x;
  case tok::kw___fastcall:   // struct foo {...} __fastcall   x;
  case tok::kw___stdcall:    // struct foo {...} __stdcall    x;
  case tok::kw___thiscall:   // struct foo {...} __thiscall   x;
  case tok::kw___vectorcall: // struct foo {...} __vectorcall x;
    // We will diagnose these calling-convention specifiers on non-function
    // declarations later, so claim they are valid after a type specifier.
    return getLangOpts().MicrosoftExt;
  // Type qualifiers
  case tok::kw_const:       // struct foo {...} const     x;
  case tok::kw_volatile:    // struct foo {...} volatile  x;
  case tok::kw_restrict:    // struct foo {...} restrict  x;
  case tok::kw__Atomic:     // struct foo {...} _Atomic   x;
  case tok::kw___unaligned: // struct foo {...} __unaligned *x;
  // Function specifiers
  // Note, no 'explicit'. An explicit function must be either a conversion
  // operator or a constructor. Either way, it can't have a return type.
  case tok::kw_inline:  // struct foo       inline    f();
  case tok::kw_virtual: // struct foo       virtual   f();
  case tok::kw_friend:  // struct foo       friend    f();
  // Storage-class specifiers
  case tok::kw_static:       // struct foo {...} static    x;
  case tok::kw_extern:       // struct foo {...} extern    x;
  case tok::kw_typedef:      // struct foo {...} typedef   x;
  case tok::kw_register:     // struct foo {...} register  x;
  case tok::kw_auto:         // struct foo {...} auto      x;
  case tok::kw_mutable:      // struct foo {...} mutable   x;
  case tok::kw_thread_local: // struct foo {...} thread_local x;
  case tok::kw_constexpr:    // struct foo {...} constexpr x;
  case tok::kw_consteval:    // struct foo {...} consteval x;
  case tok::kw_constinit:    // struct foo {...} constinit x;
    // As shown above, type qualifiers and storage class specifiers absolutely
    // can occur after class specifiers according to the grammar.  However,
    // almost no one actually writes code like this.  If we see one of these,
    // it is much more likely that someone missed a semi colon and the
    // type/storage class specifier we're seeing is part of the *next*
    // intended declaration, as in:
    //
    //   struct foo { ... }
    //   typedef int X;
    //
    // We'd really like to emit a missing semicolon error instead of emitting
    // an error on the 'int' saying that you can't have two type specifiers in
    // the same declaration of X.  Because of this, we look ahead past this
    // token to see if it's a type specifier.  If so, we know the code is
    // otherwise invalid, so we can produce the expected semi error.
    if (!isKnownToBeTypeSpecifier(NextToken()))
      return true;
    break;
  case tok::r_brace: // struct bar { struct foo {...} }
    // Missing ';' at end of struct is accepted as an extension in C mode.
    if (!getLangOpts().CPlusPlus)
      return true;
    break;
  case tok::greater:
    // template<class T = class X>
    return getLangOpts().CPlusPlus;
  }
  return false;
}

/// ParseClassSpecifier - Parse a C++ class-specifier [C++ class] or
/// elaborated-type-specifier [C++ dcl.type.elab]; we can't tell which
/// until we reach the start of a definition or see a token that
/// cannot start a definition.
///
///       class-specifier: [C++ class]
///         class-head '{' member-specification[opt] '}'
///         class-head '{' member-specification[opt] '}' attributes[opt]
///       class-head:
///         class-key identifier[opt] base-clause[opt]
///         class-key nested-name-specifier identifier base-clause[opt]
///         class-key nested-name-specifier[opt] simple-template-id
///                          base-clause[opt]
/// [GNU]   class-key attributes[opt] identifier[opt] base-clause[opt]
/// [GNU]   class-key attributes[opt] nested-name-specifier
///                          identifier base-clause[opt]
/// [GNU]   class-key attributes[opt] nested-name-specifier[opt]
///                          simple-template-id base-clause[opt]
///       class-key:
///         'class'
///         'struct'
///         'union'
///
///       elaborated-type-specifier: [C++ dcl.type.elab]
///         class-key ::[opt] nested-name-specifier[opt] identifier
///         class-key ::[opt] nested-name-specifier[opt] 'template'[opt]
///                          simple-template-id
///
///  Note that the C++ class-specifier and elaborated-type-specifier,
///  together, subsume the C99 struct-or-union-specifier:
///
///       struct-or-union-specifier: [C99 6.7.2.1]
///         struct-or-union identifier[opt] '{' struct-contents '}'
///         struct-or-union identifier
/// [GNU]   struct-or-union attributes[opt] identifier[opt] '{' struct-contents
///                                                         '}' attributes[opt]
/// [GNU]   struct-or-union attributes[opt] identifier
///       struct-or-union:
///         'struct'
///         'union'
void Parser::ParseClassSpecifier(tok::TokenKind TagTokKind,
                                 SourceLocation StartLoc, DeclSpec &DS,
                                 ParsedTemplateInfo &TemplateInfo,
                                 AccessSpecifier AS, bool EnteringContext,
                                 DeclSpecContext DSC,
                                 ParsedAttributes &Attributes) {
  DeclSpec::TST TagType;
  if (TagTokKind == tok::kw_struct)
    TagType = DeclSpec::TST_struct;
  else if (TagTokKind == tok::kw___interface)
    TagType = DeclSpec::TST_interface;
  else if (TagTokKind == tok::kw_class)
    TagType = DeclSpec::TST_class;
  else {
    assert(TagTokKind == tok::kw_union && "Not a class specifier");
    TagType = DeclSpec::TST_union;
  }

  if (Tok.is(tok::code_completion)) {
    // Code completion for a struct, class, or union name.
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteTag(getCurScope(), TagType);
    return;
  }

  // C++20 [temp.class.spec] 13.7.5/10
  //   The usual access checking rules do not apply to non-dependent names
  //   used to specify template arguments of the simple-template-id of the
  //   partial specialization.
  // C++20 [temp.spec] 13.9/6:
  //   The usual access checking rules do not apply to names in a declaration
  //   of an explicit instantiation or explicit specialization...
  const bool shouldDelayDiagsInTag =
      (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate);
  SuppressAccessChecks diagsFromTag(*this, shouldDelayDiagsInTag);

  ParsedAttributes attrs(AttrFactory);
  // If attributes exist after tag, parse them.
  for (;;) {
    MaybeParseAttributes(PAKM_CXX11 | PAKM_Declspec | PAKM_GNU, attrs);
    // Parse inheritance specifiers.
    if (Tok.isOneOf(tok::kw___single_inheritance,
                    tok::kw___multiple_inheritance,
                    tok::kw___virtual_inheritance)) {
      ParseMicrosoftInheritanceClassAttributes(attrs);
      continue;
    }
    if (Tok.is(tok::kw__Nullable)) {
      ParseNullabilityClassAttributes(attrs);
      continue;
    }
    break;
  }

  // Source location used by FIXIT to insert misplaced
  // C++11 attributes
  SourceLocation AttrFixitLoc = Tok.getLocation();

  if (TagType == DeclSpec::TST_struct && Tok.isNot(tok::identifier) &&
      !Tok.isAnnotation() && Tok.getIdentifierInfo() &&
      Tok.isOneOf(
#define TRANSFORM_TYPE_TRAIT_DEF(_, Trait) tok::kw___##Trait,
#include "clang/Basic/TransformTypeTraits.def"
          tok::kw___is_abstract,
          tok::kw___is_aggregate,
          tok::kw___is_arithmetic,
          tok::kw___is_array,
          tok::kw___is_assignable,
          tok::kw___is_base_of,
          tok::kw___is_bounded_array,
          tok::kw___is_class,
          tok::kw___is_complete_type,
          tok::kw___is_compound,
          tok::kw___is_const,
          tok::kw___is_constructible,
          tok::kw___is_convertible,
          tok::kw___is_convertible_to,
          tok::kw___is_destructible,
          tok::kw___is_empty,
          tok::kw___is_enum,
          tok::kw___is_floating_point,
          tok::kw___is_final,
          tok::kw___is_function,
          tok::kw___is_fundamental,
          tok::kw___is_integral,
          tok::kw___is_interface_class,
          tok::kw___is_literal,
          tok::kw___is_lvalue_expr,
          tok::kw___is_lvalue_reference,
          tok::kw___is_member_function_pointer,
          tok::kw___is_member_object_pointer,
          tok::kw___is_member_pointer,
          tok::kw___is_nothrow_assignable,
          tok::kw___is_nothrow_constructible,
          tok::kw___is_nothrow_convertible,
          tok::kw___is_nothrow_destructible,
          tok::kw___is_nullptr,
          tok::kw___is_object,
          tok::kw___is_pod,
          tok::kw___is_pointer,
          tok::kw___is_polymorphic,
          tok::kw___is_reference,
          tok::kw___is_referenceable,
          tok::kw___is_rvalue_expr,
          tok::kw___is_rvalue_reference,
          tok::kw___is_same,
          tok::kw___is_scalar,
          tok::kw___is_scoped_enum,
          tok::kw___is_sealed,
          tok::kw___is_signed,
          tok::kw___is_standard_layout,
          tok::kw___is_trivial,
          tok::kw___is_trivially_equality_comparable,
          tok::kw___is_trivially_assignable,
          tok::kw___is_trivially_constructible,
          tok::kw___is_trivially_copyable,
          tok::kw___is_unbounded_array,
          tok::kw___is_union,
          tok::kw___is_unsigned,
          tok::kw___is_void,
          tok::kw___is_volatile
      ))
    // GNU libstdc++ 4.2 and libc++ use certain intrinsic names as the
    // name of struct templates, but some are keywords in GCC >= 4.3
    // and Clang. Therefore, when we see the token sequence "struct
    // X", make X into a normal identifier rather than a keyword, to
    // allow libstdc++ 4.2 and libc++ to work properly.
    TryKeywordIdentFallback(true);

  struct PreserveAtomicIdentifierInfoRAII {
    PreserveAtomicIdentifierInfoRAII(Token &Tok, bool Enabled)
        : AtomicII(nullptr) {
      if (!Enabled)
        return;
      assert(Tok.is(tok::kw__Atomic));
      AtomicII = Tok.getIdentifierInfo();
      AtomicII->revertTokenIDToIdentifier();
      Tok.setKind(tok::identifier);
    }
    ~PreserveAtomicIdentifierInfoRAII() {
      if (!AtomicII)
        return;
      AtomicII->revertIdentifierToTokenID(tok::kw__Atomic);
    }
    IdentifierInfo *AtomicII;
  };

  // HACK: MSVC doesn't consider _Atomic to be a keyword and its STL
  // implementation for VS2013 uses _Atomic as an identifier for one of the
  // classes in <atomic>.  When we are parsing 'struct _Atomic', don't consider
  // '_Atomic' to be a keyword.  We are careful to undo this so that clang can
  // use '_Atomic' in its own header files.
  bool ShouldChangeAtomicToIdentifier = getLangOpts().MSVCCompat &&
                                        Tok.is(tok::kw__Atomic) &&
                                        TagType == DeclSpec::TST_struct;
  PreserveAtomicIdentifierInfoRAII AtomicTokenGuard(
      Tok, ShouldChangeAtomicToIdentifier);

  // Parse the (optional) nested-name-specifier.
  CXXScopeSpec &SS = DS.getTypeSpecScope();
  if (getLangOpts().CPlusPlus) {
    // "FOO : BAR" is not a potential typo for "FOO::BAR".  In this context it
    // is a base-specifier-list.
    ColonProtectionRAIIObject X(*this);

    CXXScopeSpec Spec;
    if (TemplateInfo.TemplateParams)
      Spec.setTemplateParamLists(*TemplateInfo.TemplateParams);

    bool HasValidSpec = true;
    if (ParseOptionalCXXScopeSpecifier(Spec, /*ObjectType=*/nullptr,
                                       /*ObjectHasErrors=*/false,
                                       EnteringContext)) {
      DS.SetTypeSpecError();
      HasValidSpec = false;
    }
    if (Spec.isSet())
      if (Tok.isNot(tok::identifier) && Tok.isNot(tok::annot_template_id)) {
        Diag(Tok, diag::err_expected) << tok::identifier;
        HasValidSpec = false;
      }
    if (HasValidSpec)
      SS = Spec;
  }

  TemplateParameterLists *TemplateParams = TemplateInfo.TemplateParams;

  auto RecoverFromUndeclaredTemplateName = [&](IdentifierInfo *Name,
                                               SourceLocation NameLoc,
                                               SourceRange TemplateArgRange,
                                               bool KnownUndeclared) {
    Diag(NameLoc, diag::err_explicit_spec_non_template)
        << (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation)
        << TagTokKind << Name << TemplateArgRange << KnownUndeclared;

    // Strip off the last template parameter list if it was empty, since
    // we've removed its template argument list.
    if (TemplateParams && TemplateInfo.LastParameterListWasEmpty) {
      if (TemplateParams->size() > 1) {
        TemplateParams->pop_back();
      } else {
        TemplateParams = nullptr;
        TemplateInfo.Kind = ParsedTemplateInfo::NonTemplate;
      }
    } else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation) {
      // Pretend this is just a forward declaration.
      TemplateParams = nullptr;
      TemplateInfo.Kind = ParsedTemplateInfo::NonTemplate;
      TemplateInfo.TemplateLoc = SourceLocation();
      TemplateInfo.ExternLoc = SourceLocation();
    }
  };

  // Parse the (optional) class name or simple-template-id.
  IdentifierInfo *Name = nullptr;
  SourceLocation NameLoc;
  TemplateIdAnnotation *TemplateId = nullptr;
  if (Tok.is(tok::identifier)) {
    Name = Tok.getIdentifierInfo();
    NameLoc = ConsumeToken();
    DS.SetRangeEnd(NameLoc);

    if (Tok.is(tok::less) && getLangOpts().CPlusPlus) {
      // The name was supposed to refer to a template, but didn't.
      // Eat the template argument list and try to continue parsing this as
      // a class (or template thereof).
      TemplateArgList TemplateArgs;
      SourceLocation LAngleLoc, RAngleLoc;
      if (ParseTemplateIdAfterTemplateName(true, LAngleLoc, TemplateArgs,
                                           RAngleLoc)) {
        // We couldn't parse the template argument list at all, so don't
        // try to give any location information for the list.
        LAngleLoc = RAngleLoc = SourceLocation();
      }
      RecoverFromUndeclaredTemplateName(
          Name, NameLoc, SourceRange(LAngleLoc, RAngleLoc), false);
    }
  } else if (Tok.is(tok::annot_template_id)) {
    TemplateId = takeTemplateIdAnnotation(Tok);
    NameLoc = ConsumeAnnotationToken();

    if (TemplateId->Kind == TNK_Undeclared_template) {
      // Try to resolve the template name to a type template. May update Kind.
      Actions.ActOnUndeclaredTypeTemplateName(
          getCurScope(), TemplateId->Template, TemplateId->Kind, NameLoc, Name);
      if (TemplateId->Kind == TNK_Undeclared_template) {
        RecoverFromUndeclaredTemplateName(
            Name, NameLoc,
            SourceRange(TemplateId->LAngleLoc, TemplateId->RAngleLoc), true);
        TemplateId = nullptr;
      }
    }

    if (TemplateId && !TemplateId->mightBeType()) {
      // The template-name in the simple-template-id refers to
      // something other than a type template. Give an appropriate
      // error message and skip to the ';'.
      SourceRange Range(NameLoc);
      if (SS.isNotEmpty())
        Range.setBegin(SS.getBeginLoc());

      // FIXME: Name may be null here.
      Diag(TemplateId->LAngleLoc, diag::err_template_spec_syntax_non_template)
          << TemplateId->Name << static_cast<int>(TemplateId->Kind) << Range;

      DS.SetTypeSpecError();
      SkipUntil(tok::semi, StopBeforeMatch);
      return;
    }
  }

  // There are four options here.
  //  - If we are in a trailing return type, this is always just a reference,
  //    and we must not try to parse a definition. For instance,
  //      [] () -> struct S { };
  //    does not define a type.
  //  - If we have 'struct foo {...', 'struct foo :...',
  //    'struct foo final :' or 'struct foo final {', then this is a definition.
  //  - If we have 'struct foo;', then this is either a forward declaration
  //    or a friend declaration, which have to be treated differently.
  //  - Otherwise we have something like 'struct foo xyz', a reference.
  //
  //  We also detect these erroneous cases to provide better diagnostic for
  //  C++11 attributes parsing.
  //  - attributes follow class name:
  //    struct foo [[]] {};
  //  - attributes appear before or after 'final':
  //    struct foo [[]] final [[]] {};
  //
  // However, in type-specifier-seq's, things look like declarations but are
  // just references, e.g.
  //   new struct s;
  // or
  //   &T::operator struct s;
  // For these, DSC is DeclSpecContext::DSC_type_specifier or
  // DeclSpecContext::DSC_alias_declaration.

  // If there are attributes after class name, parse them.
  MaybeParseCXX11Attributes(Attributes);

  const PrintingPolicy &Policy = Actions.getASTContext().getPrintingPolicy();
  TagUseKind TUK;
  if (isDefiningTypeSpecifierContext(DSC, getLangOpts().CPlusPlus) ==
          AllowDefiningTypeSpec::No ||
      (getLangOpts().OpenMP && OpenMPDirectiveParsing))
    TUK = TagUseKind::Reference;
  else if (Tok.is(tok::l_brace) ||
           (DSC != DeclSpecContext::DSC_association &&
            getLangOpts().CPlusPlus && Tok.is(tok::colon)) ||
           (isClassCompatibleKeyword() &&
            (NextToken().is(tok::l_brace) || NextToken().is(tok::colon)))) {
    if (DS.isFriendSpecified()) {
      // C++ [class.friend]p2:
      //   A class shall not be defined in a friend declaration.
      Diag(Tok.getLocation(), diag::err_friend_decl_defines_type)
          << SourceRange(DS.getFriendSpecLoc());

      // Skip everything up to the semicolon, so that this looks like a proper
      // friend class (or template thereof) declaration.
      SkipUntil(tok::semi, StopBeforeMatch);
      TUK = TagUseKind::Friend;
    } else {
      // Okay, this is a class definition.
      TUK = TagUseKind::Definition;
    }
  } else if (isClassCompatibleKeyword() &&
             (NextToken().is(tok::l_square) ||
              NextToken().is(tok::kw_alignas) ||
              NextToken().isRegularKeywordAttribute() ||
              isCXX11VirtSpecifier(NextToken()) != VirtSpecifiers::VS_None)) {
    // We can't tell if this is a definition or reference
    // until we skipped the 'final' and C++11 attribute specifiers.
    TentativeParsingAction PA(*this);

    // Skip the 'final', abstract'... keywords.
    while (isClassCompatibleKeyword()) {
      ConsumeToken();
    }

    // Skip C++11 attribute specifiers.
    while (true) {
      if (Tok.is(tok::l_square) && NextToken().is(tok::l_square)) {
        ConsumeBracket();
        if (!SkipUntil(tok::r_square, StopAtSemi))
          break;
      } else if (Tok.is(tok::kw_alignas) && NextToken().is(tok::l_paren)) {
        ConsumeToken();
        ConsumeParen();
        if (!SkipUntil(tok::r_paren, StopAtSemi))
          break;
      } else if (Tok.isRegularKeywordAttribute()) {
        bool TakesArgs = doesKeywordAttributeTakeArgs(Tok.getKind());
        ConsumeToken();
        if (TakesArgs) {
          BalancedDelimiterTracker T(*this, tok::l_paren);
          if (!T.consumeOpen())
            T.skipToEnd();
        }
      } else {
        break;
      }
    }

    if (Tok.isOneOf(tok::l_brace, tok::colon))
      TUK = TagUseKind::Definition;
    else
      TUK = TagUseKind::Reference;

    PA.Revert();
  } else if (!isTypeSpecifier(DSC) &&
             (Tok.is(tok::semi) ||
              (Tok.isAtStartOfLine() && !isValidAfterTypeSpecifier(false)))) {
    TUK = DS.isFriendSpecified() ? TagUseKind::Friend : TagUseKind::Declaration;
    if (Tok.isNot(tok::semi)) {
      const PrintingPolicy &PPol = Actions.getASTContext().getPrintingPolicy();
      // A semicolon was missing after this declaration. Diagnose and recover.
      ExpectAndConsume(tok::semi, diag::err_expected_after,
                       DeclSpec::getSpecifierName(TagType, PPol));
      PP.EnterToken(Tok, /*IsReinject*/ true);
      Tok.setKind(tok::semi);
    }
  } else
    TUK = TagUseKind::Reference;

  // Forbid misplaced attributes. In cases of a reference, we pass attributes
  // to caller to handle.
  if (TUK != TagUseKind::Reference) {
    // If this is not a reference, then the only possible
    // valid place for C++11 attributes to appear here
    // is between class-key and class-name. If there are
    // any attributes after class-name, we try a fixit to move
    // them to the right place.
    SourceRange AttrRange = Attributes.Range;
    if (AttrRange.isValid()) {
      auto *FirstAttr = Attributes.empty() ? nullptr : &Attributes.front();
      auto Loc = AttrRange.getBegin();
      (FirstAttr && FirstAttr->isRegularKeywordAttribute()
           ? Diag(Loc, diag::err_keyword_not_allowed) << FirstAttr
           : Diag(Loc, diag::err_attributes_not_allowed))
          << AttrRange
          << FixItHint::CreateInsertionFromRange(
                 AttrFixitLoc, CharSourceRange(AttrRange, true))
          << FixItHint::CreateRemoval(AttrRange);

      // Recover by adding misplaced attributes to the attribute list
      // of the class so they can be applied on the class later.
      attrs.takeAllFrom(Attributes);
    }
  }

  if (!Name && !TemplateId &&
      (DS.getTypeSpecType() == DeclSpec::TST_error ||
       TUK != TagUseKind::Definition)) {
    if (DS.getTypeSpecType() != DeclSpec::TST_error) {
      // We have a declaration or reference to an anonymous class.
      Diag(StartLoc, diag::err_anon_type_definition)
          << DeclSpec::getSpecifierName(TagType, Policy);
    }

    // If we are parsing a definition and stop at a base-clause, continue on
    // until the semicolon.  Continuing from the comma will just trick us into
    // thinking we are seeing a variable declaration.
    if (TUK == TagUseKind::Definition && Tok.is(tok::colon))
      SkipUntil(tok::semi, StopBeforeMatch);
    else
      SkipUntil(tok::comma, StopAtSemi);
    return;
  }

  // Create the tag portion of the class or class template.
  DeclResult TagOrTempResult = true; // invalid
  TypeResult TypeResult = true;      // invalid

  bool Owned = false;
  SkipBodyInfo SkipBody;
  if (TemplateId) {
    // Explicit specialization, class template partial specialization,
    // or explicit instantiation.
    ASTTemplateArgsPtr TemplateArgsPtr(TemplateId->getTemplateArgs(),
                                       TemplateId->NumArgs);
    if (TemplateId->isInvalid()) {
      // Can't build the declaration.
    } else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation &&
               TUK == TagUseKind::Declaration) {
      // This is an explicit instantiation of a class template.
      ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
                              diag::err_keyword_not_allowed,
                              /*DiagnoseEmptyAttrs=*/true);

      TagOrTempResult = Actions.ActOnExplicitInstantiation(
          getCurScope(), TemplateInfo.ExternLoc, TemplateInfo.TemplateLoc,
          TagType, StartLoc, SS, TemplateId->Template,
          TemplateId->TemplateNameLoc, TemplateId->LAngleLoc, TemplateArgsPtr,
          TemplateId->RAngleLoc, attrs);

      // Friend template-ids are treated as references unless
      // they have template headers, in which case they're ill-formed
      // (FIXME: "template <class T> friend class A<T>::B<int>;").
      // We diagnose this error in ActOnClassTemplateSpecialization.
    } else if (TUK == TagUseKind::Reference ||
               (TUK == TagUseKind::Friend &&
                TemplateInfo.Kind == ParsedTemplateInfo::NonTemplate)) {
      ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
                              diag::err_keyword_not_allowed,
                              /*DiagnoseEmptyAttrs=*/true);
      TypeResult = Actions.ActOnTagTemplateIdType(
          TUK, TagType, StartLoc, SS, TemplateId->TemplateKWLoc,
          TemplateId->Template, TemplateId->TemplateNameLoc,
          TemplateId->LAngleLoc, TemplateArgsPtr, TemplateId->RAngleLoc);
    } else {
      // This is an explicit specialization or a class template
      // partial specialization.
      TemplateParameterLists FakedParamLists;
      if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation) {
        // This looks like an explicit instantiation, because we have
        // something like
        //
        //   template class Foo<X>
        //
        // but it actually has a definition. Most likely, this was
        // meant to be an explicit specialization, but the user forgot
        // the '<>' after 'template'.
        // It this is friend declaration however, since it cannot have a
        // template header, it is most likely that the user meant to
        // remove the 'template' keyword.
        assert((TUK == TagUseKind::Definition || TUK == TagUseKind::Friend) &&
               "Expected a definition here");

        if (TUK == TagUseKind::Friend) {
          Diag(DS.getFriendSpecLoc(), diag::err_friend_explicit_instantiation);
          TemplateParams = nullptr;
        } else {
          SourceLocation LAngleLoc =
              PP.getLocForEndOfToken(TemplateInfo.TemplateLoc);
          Diag(TemplateId->TemplateNameLoc,
               diag::err_explicit_instantiation_with_definition)
              << SourceRange(TemplateInfo.TemplateLoc)
              << FixItHint::CreateInsertion(LAngleLoc, "<>");

          // Create a fake template parameter list that contains only
          // "template<>", so that we treat this construct as a class
          // template specialization.
          FakedParamLists.push_back(Actions.ActOnTemplateParameterList(
              0, SourceLocation(), TemplateInfo.TemplateLoc, LAngleLoc,
              std::nullopt, LAngleLoc, nullptr));
          TemplateParams = &FakedParamLists;
        }
      }

      // Build the class template specialization.
      TagOrTempResult = Actions.ActOnClassTemplateSpecialization(
          getCurScope(), TagType, TUK, StartLoc, DS.getModulePrivateSpecLoc(),
          SS, *TemplateId, attrs,
          MultiTemplateParamsArg(TemplateParams ? &(*TemplateParams)[0]
                                                : nullptr,
                                 TemplateParams ? TemplateParams->size() : 0),
          &SkipBody);
    }
  } else if (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation &&
             TUK == TagUseKind::Declaration) {
    // Explicit instantiation of a member of a class template
    // specialization, e.g.,
    //
    //   template struct Outer<int>::Inner;
    //
    ProhibitAttributes(attrs);

    TagOrTempResult = Actions.ActOnExplicitInstantiation(
        getCurScope(), TemplateInfo.ExternLoc, TemplateInfo.TemplateLoc,
        TagType, StartLoc, SS, Name, NameLoc, attrs);
  } else if (TUK == TagUseKind::Friend &&
             TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate) {
    ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
                            diag::err_keyword_not_allowed,
                            /*DiagnoseEmptyAttrs=*/true);

    TagOrTempResult = Actions.ActOnTemplatedFriendTag(
        getCurScope(), DS.getFriendSpecLoc(), TagType, StartLoc, SS, Name,
        NameLoc, attrs,
        MultiTemplateParamsArg(TemplateParams ? &(*TemplateParams)[0] : nullptr,
                               TemplateParams ? TemplateParams->size() : 0));
  } else {
    if (TUK != TagUseKind::Declaration && TUK != TagUseKind::Definition)
      ProhibitCXX11Attributes(attrs, diag::err_attributes_not_allowed,
                              diag::err_keyword_not_allowed,
                              /* DiagnoseEmptyAttrs=*/true);

    if (TUK == TagUseKind::Definition &&
        TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation) {
      // If the declarator-id is not a template-id, issue a diagnostic and
      // recover by ignoring the 'template' keyword.
      Diag(Tok, diag::err_template_defn_explicit_instantiation)
          << 1 << FixItHint::CreateRemoval(TemplateInfo.TemplateLoc);
      TemplateParams = nullptr;
    }

    bool IsDependent = false;

    // Don't pass down template parameter lists if this is just a tag
    // reference.  For example, we don't need the template parameters here:
    //   template <class T> class A *makeA(T t);
    MultiTemplateParamsArg TParams;
    if (TUK != TagUseKind::Reference && TemplateParams)
      TParams =
          MultiTemplateParamsArg(&(*TemplateParams)[0], TemplateParams->size());

    stripTypeAttributesOffDeclSpec(attrs, DS, TUK);

    // Declaration or definition of a class type
    TagOrTempResult = Actions.ActOnTag(
        getCurScope(), TagType, TUK, StartLoc, SS, Name, NameLoc, attrs, AS,
        DS.getModulePrivateSpecLoc(), TParams, Owned, IsDependent,
        SourceLocation(), false, clang::TypeResult(),
        DSC == DeclSpecContext::DSC_type_specifier,
        DSC == DeclSpecContext::DSC_template_param ||
            DSC == DeclSpecContext::DSC_template_type_arg,
        OffsetOfState, &SkipBody);

    // If ActOnTag said the type was dependent, try again with the
    // less common call.
    if (IsDependent) {
      assert(TUK == TagUseKind::Reference || TUK == TagUseKind::Friend);
      TypeResult = Actions.ActOnDependentTag(getCurScope(), TagType, TUK, SS,
                                             Name, StartLoc, NameLoc);
    }
  }

  // If this is an elaborated type specifier in function template,
  // and we delayed diagnostics before,
  // just merge them into the current pool.
  if (shouldDelayDiagsInTag) {
    diagsFromTag.done();
    if (TUK == TagUseKind::Reference &&
        TemplateInfo.Kind == ParsedTemplateInfo::Template)
      diagsFromTag.redelay();
  }

  // If there is a body, parse it and inform the actions module.
  if (TUK == TagUseKind::Definition) {
    assert(Tok.is(tok::l_brace) ||
           (getLangOpts().CPlusPlus && Tok.is(tok::colon)) ||
           isClassCompatibleKeyword());
    if (SkipBody.ShouldSkip)
      SkipCXXMemberSpecification(StartLoc, AttrFixitLoc, TagType,
                                 TagOrTempResult.get());
    else if (getLangOpts().CPlusPlus)
      ParseCXXMemberSpecification(StartLoc, AttrFixitLoc, attrs, TagType,
                                  TagOrTempResult.get());
    else {
      Decl *D =
          SkipBody.CheckSameAsPrevious ? SkipBody.New : TagOrTempResult.get();
      // Parse the definition body.
      ParseStructUnionBody(StartLoc, TagType, cast<RecordDecl>(D));
      if (SkipBody.CheckSameAsPrevious &&
          !Actions.ActOnDuplicateDefinition(TagOrTempResult.get(), SkipBody)) {
        DS.SetTypeSpecError();
        return;
      }
    }
  }

  if (!TagOrTempResult.isInvalid())
    // Delayed processing of attributes.
    Actions.ProcessDeclAttributeDelayed(TagOrTempResult.get(), attrs);

  const char *PrevSpec = nullptr;
  unsigned DiagID;
  bool Result;
  if (!TypeResult.isInvalid()) {
    Result = DS.SetTypeSpecType(DeclSpec::TST_typename, StartLoc,
                                NameLoc.isValid() ? NameLoc : StartLoc,
                                PrevSpec, DiagID, TypeResult.get(), Policy);
  } else if (!TagOrTempResult.isInvalid()) {
    Result = DS.SetTypeSpecType(
        TagType, StartLoc, NameLoc.isValid() ? NameLoc : StartLoc, PrevSpec,
        DiagID, TagOrTempResult.get(), Owned, Policy);
  } else {
    DS.SetTypeSpecError();
    return;
  }

  if (Result)
    Diag(StartLoc, DiagID) << PrevSpec;

  // At this point, we've successfully parsed a class-specifier in 'definition'
  // form (e.g. "struct foo { int x; }".  While we could just return here, we're
  // going to look at what comes after it to improve error recovery.  If an
  // impossible token occurs next, we assume that the programmer forgot a ; at
  // the end of the declaration and recover that way.
  //
  // Also enforce C++ [temp]p3:
  //   In a template-declaration which defines a class, no declarator
  //   is permitted.
  //
  // After a type-specifier, we don't expect a semicolon. This only happens in
  // C, since definitions are not permitted in this context in C++.
  if (TUK == TagUseKind::Definition &&
      (getLangOpts().CPlusPlus || !isTypeSpecifier(DSC)) &&
      (TemplateInfo.Kind || !isValidAfterTypeSpecifier(false))) {
    if (Tok.isNot(tok::semi)) {
      const PrintingPolicy &PPol = Actions.getASTContext().getPrintingPolicy();
      ExpectAndConsume(tok::semi, diag::err_expected_after,
                       DeclSpec::getSpecifierName(TagType, PPol));
      // Push this token back into the preprocessor and change our current token
      // to ';' so that the rest of the code recovers as though there were an
      // ';' after the definition.
      PP.EnterToken(Tok, /*IsReinject=*/true);
      Tok.setKind(tok::semi);
    }
  }
}

/// ParseBaseClause - Parse the base-clause of a C++ class [C++ class.derived].
///
///       base-clause : [C++ class.derived]
///         ':' base-specifier-list
///       base-specifier-list:
///         base-specifier '...'[opt]
///         base-specifier-list ',' base-specifier '...'[opt]
void Parser::ParseBaseClause(Decl *ClassDecl) {
  assert(Tok.is(tok::colon) && "Not a base clause");
  ConsumeToken();

  // Build up an array of parsed base specifiers.
  SmallVector<CXXBaseSpecifier *, 8> BaseInfo;

  while (true) {
    // Parse a base-specifier.
    BaseResult Result = ParseBaseSpecifier(ClassDecl);
    if (Result.isInvalid()) {
      // Skip the rest of this base specifier, up until the comma or
      // opening brace.
      SkipUntil(tok::comma, tok::l_brace, StopAtSemi | StopBeforeMatch);
    } else {
      // Add this to our array of base specifiers.
      BaseInfo.push_back(Result.get());
    }

    // If the next token is a comma, consume it and keep reading
    // base-specifiers.
    if (!TryConsumeToken(tok::comma))
      break;
  }

  // Attach the base specifiers
  Actions.ActOnBaseSpecifiers(ClassDecl, BaseInfo);
}

/// ParseBaseSpecifier - Parse a C++ base-specifier. A base-specifier is
/// one entry in the base class list of a class specifier, for example:
///    class foo : public bar, virtual private baz {
/// 'public bar' and 'virtual private baz' are each base-specifiers.
///
///       base-specifier: [C++ class.derived]
///         attribute-specifier-seq[opt] base-type-specifier
///         attribute-specifier-seq[opt] 'virtual' access-specifier[opt]
///                 base-type-specifier
///         attribute-specifier-seq[opt] access-specifier 'virtual'[opt]
///                 base-type-specifier
BaseResult Parser::ParseBaseSpecifier(Decl *ClassDecl) {
  bool IsVirtual = false;
  SourceLocation StartLoc = Tok.getLocation();

  ParsedAttributes Attributes(AttrFactory);
  MaybeParseCXX11Attributes(Attributes);

  // Parse the 'virtual' keyword.
  if (TryConsumeToken(tok::kw_virtual))
    IsVirtual = true;

  CheckMisplacedCXX11Attribute(Attributes, StartLoc);

  // Parse an (optional) access specifier.
  AccessSpecifier Access = getAccessSpecifierIfPresent();
  if (Access != AS_none) {
    ConsumeToken();
    if (getLangOpts().HLSL)
      Diag(Tok.getLocation(), diag::ext_hlsl_access_specifiers);
  }

  CheckMisplacedCXX11Attribute(Attributes, StartLoc);

  // Parse the 'virtual' keyword (again!), in case it came after the
  // access specifier.
  if (Tok.is(tok::kw_virtual)) {
    SourceLocation VirtualLoc = ConsumeToken();
    if (IsVirtual) {
      // Complain about duplicate 'virtual'
      Diag(VirtualLoc, diag::err_dup_virtual)
          << FixItHint::CreateRemoval(VirtualLoc);
    }

    IsVirtual = true;
  }

  CheckMisplacedCXX11Attribute(Attributes, StartLoc);

  // Parse the class-name.

  // HACK: MSVC doesn't consider _Atomic to be a keyword and its STL
  // implementation for VS2013 uses _Atomic as an identifier for one of the
  // classes in <atomic>.  Treat '_Atomic' to be an identifier when we are
  // parsing the class-name for a base specifier.
  if (getLangOpts().MSVCCompat && Tok.is(tok::kw__Atomic) &&
      NextToken().is(tok::less))
    Tok.setKind(tok::identifier);

  SourceLocation EndLocation;
  SourceLocation BaseLoc;
  TypeResult BaseType = ParseBaseTypeSpecifier(BaseLoc, EndLocation);
  if (BaseType.isInvalid())
    return true;

  // Parse the optional ellipsis (for a pack expansion). The ellipsis is
  // actually part of the base-specifier-list grammar productions, but we
  // parse it here for convenience.
  SourceLocation EllipsisLoc;
  TryConsumeToken(tok::ellipsis, EllipsisLoc);

  // Find the complete source range for the base-specifier.
  SourceRange Range(StartLoc, EndLocation);

  // Notify semantic analysis that we have parsed a complete
  // base-specifier.
  return Actions.ActOnBaseSpecifier(ClassDecl, Range, Attributes, IsVirtual,
                                    Access, BaseType.get(), BaseLoc,
                                    EllipsisLoc);
}

/// getAccessSpecifierIfPresent - Determine whether the next token is
/// a C++ access-specifier.
///
///       access-specifier: [C++ class.derived]
///         'private'
///         'protected'
///         'public'
AccessSpecifier Parser::getAccessSpecifierIfPresent() const {
  switch (Tok.getKind()) {
  default:
    return AS_none;
  case tok::kw_private:
    return AS_private;
  case tok::kw_protected:
    return AS_protected;
  case tok::kw_public:
    return AS_public;
  }
}

/// If the given declarator has any parts for which parsing has to be
/// delayed, e.g., default arguments or an exception-specification, create a
/// late-parsed method declaration record to handle the parsing at the end of
/// the class definition.
void Parser::HandleMemberFunctionDeclDelays(Declarator &DeclaratorInfo,
                                            Decl *ThisDecl) {
  DeclaratorChunk::FunctionTypeInfo &FTI = DeclaratorInfo.getFunctionTypeInfo();
  // If there was a late-parsed exception-specification, we'll need a
  // late parse
  bool NeedLateParse = FTI.getExceptionSpecType() == EST_Unparsed;

  if (!NeedLateParse) {
    // Look ahead to see if there are any default args
    for (unsigned ParamIdx = 0; ParamIdx < FTI.NumParams; ++ParamIdx) {
      const auto *Param = cast<ParmVarDecl>(FTI.Params[ParamIdx].Param);
      if (Param->hasUnparsedDefaultArg()) {
        NeedLateParse = true;
        break;
      }
    }
  }

  if (NeedLateParse) {
    // Push this method onto the stack of late-parsed method
    // declarations.
    auto LateMethod = new LateParsedMethodDeclaration(this, ThisDecl);
    getCurrentClass().LateParsedDeclarations.push_back(LateMethod);

    // Push tokens for each parameter. Those that do not have defaults will be
    // NULL. We need to track all the parameters so that we can push them into
    // scope for later parameters and perhaps for the exception specification.
    LateMethod->DefaultArgs.reserve(FTI.NumParams);
    for (unsigned ParamIdx = 0; ParamIdx < FTI.NumParams; ++ParamIdx)
      LateMethod->DefaultArgs.push_back(LateParsedDefaultArgument(
          FTI.Params[ParamIdx].Param,
          std::move(FTI.Params[ParamIdx].DefaultArgTokens)));

    // Stash the exception-specification tokens in the late-pased method.
    if (FTI.getExceptionSpecType() == EST_Unparsed) {
      LateMethod->ExceptionSpecTokens = FTI.ExceptionSpecTokens;
      FTI.ExceptionSpecTokens = nullptr;
    }
  }
}

/// isCXX11VirtSpecifier - Determine whether the given token is a C++11
/// virt-specifier.
///
///       virt-specifier:
///         override
///         final
///         __final
VirtSpecifiers::Specifier Parser::isCXX11VirtSpecifier(const Token &Tok) const {
  if (!getLangOpts().CPlusPlus || Tok.isNot(tok::identifier))
    return VirtSpecifiers::VS_None;

  const IdentifierInfo *II = Tok.getIdentifierInfo();

  // Initialize the contextual keywords.
  if (!Ident_final) {
    Ident_final = &PP.getIdentifierTable().get("final");
    if (getLangOpts().GNUKeywords)
      Ident_GNU_final = &PP.getIdentifierTable().get("__final");
    if (getLangOpts().MicrosoftExt) {
      Ident_sealed = &PP.getIdentifierTable().get("sealed");
      Ident_abstract = &PP.getIdentifierTable().get("abstract");
    }
    Ident_override = &PP.getIdentifierTable().get("override");
  }

  if (II == Ident_override)
    return VirtSpecifiers::VS_Override;

  if (II == Ident_sealed)
    return VirtSpecifiers::VS_Sealed;

  if (II == Ident_abstract)
    return VirtSpecifiers::VS_Abstract;

  if (II == Ident_final)
    return VirtSpecifiers::VS_Final;

  if (II == Ident_GNU_final)
    return VirtSpecifiers::VS_GNU_Final;

  return VirtSpecifiers::VS_None;
}

/// ParseOptionalCXX11VirtSpecifierSeq - Parse a virt-specifier-seq.
///
///       virt-specifier-seq:
///         virt-specifier
///         virt-specifier-seq virt-specifier
void Parser::ParseOptionalCXX11VirtSpecifierSeq(VirtSpecifiers &VS,
                                                bool IsInterface,
                                                SourceLocation FriendLoc) {
  while (true) {
    VirtSpecifiers::Specifier Specifier = isCXX11VirtSpecifier();
    if (Specifier == VirtSpecifiers::VS_None)
      return;

    if (FriendLoc.isValid()) {
      Diag(Tok.getLocation(), diag::err_friend_decl_spec)
          << VirtSpecifiers::getSpecifierName(Specifier)
          << FixItHint::CreateRemoval(Tok.getLocation())
          << SourceRange(FriendLoc, FriendLoc);
      ConsumeToken();
      continue;
    }

    // C++ [class.mem]p8:
    //   A virt-specifier-seq shall contain at most one of each virt-specifier.
    const char *PrevSpec = nullptr;
    if (VS.SetSpecifier(Specifier, Tok.getLocation(), PrevSpec))
      Diag(Tok.getLocation(), diag::err_duplicate_virt_specifier)
          << PrevSpec << FixItHint::CreateRemoval(Tok.getLocation());

    if (IsInterface && (Specifier == VirtSpecifiers::VS_Final ||
                        Specifier == VirtSpecifiers::VS_Sealed)) {
      Diag(Tok.getLocation(), diag::err_override_control_interface)
          << VirtSpecifiers::getSpecifierName(Specifier);
    } else if (Specifier == VirtSpecifiers::VS_Sealed) {
      Diag(Tok.getLocation(), diag::ext_ms_sealed_keyword);
    } else if (Specifier == VirtSpecifiers::VS_Abstract) {
      Diag(Tok.getLocation(), diag::ext_ms_abstract_keyword);
    } else if (Specifier == VirtSpecifiers::VS_GNU_Final) {
      Diag(Tok.getLocation(), diag::ext_warn_gnu_final);
    } else {
      Diag(Tok.getLocation(),
           getLangOpts().CPlusPlus11
               ? diag::warn_cxx98_compat_override_control_keyword
               : diag::ext_override_control_keyword)
          << VirtSpecifiers::getSpecifierName(Specifier);
    }
    ConsumeToken();
  }
}

/// isCXX11FinalKeyword - Determine whether the next token is a C++11
/// 'final' or Microsoft 'sealed' contextual keyword.
bool Parser::isCXX11FinalKeyword() const {
  VirtSpecifiers::Specifier Specifier = isCXX11VirtSpecifier();
  return Specifier == VirtSpecifiers::VS_Final ||
         Specifier == VirtSpecifiers::VS_GNU_Final ||
         Specifier == VirtSpecifiers::VS_Sealed;
}

/// isClassCompatibleKeyword - Determine whether the next token is a C++11
/// 'final' or Microsoft 'sealed' or 'abstract' contextual keywords.
bool Parser::isClassCompatibleKeyword() const {
  VirtSpecifiers::Specifier Specifier = isCXX11VirtSpecifier();
  return Specifier == VirtSpecifiers::VS_Final ||
         Specifier == VirtSpecifiers::VS_GNU_Final ||
         Specifier == VirtSpecifiers::VS_Sealed ||
         Specifier == VirtSpecifiers::VS_Abstract;
}

/// Parse a C++ member-declarator up to, but not including, the optional
/// brace-or-equal-initializer or pure-specifier.
bool Parser::ParseCXXMemberDeclaratorBeforeInitializer(
    Declarator &DeclaratorInfo, VirtSpecifiers &VS, ExprResult &BitfieldSize,
    LateParsedAttrList &LateParsedAttrs) {
  // member-declarator:
  //   declarator virt-specifier-seq[opt] pure-specifier[opt]
  //   declarator requires-clause
  //   declarator brace-or-equal-initializer[opt]
  //   identifier attribute-specifier-seq[opt] ':' constant-expression
  //       brace-or-equal-initializer[opt]
  //   ':' constant-expression
  //
  // NOTE: the latter two productions are a proposed bugfix rather than the
  // current grammar rules as of C++20.
  if (Tok.isNot(tok::colon))
    ParseDeclarator(DeclaratorInfo);
  else
    DeclaratorInfo.SetIdentifier(nullptr, Tok.getLocation());

  if (getLangOpts().HLSL)
    MaybeParseHLSLAnnotations(DeclaratorInfo, nullptr,
                              /*CouldBeBitField*/ true);

  if (!DeclaratorInfo.isFunctionDeclarator() && TryConsumeToken(tok::colon)) {
    assert(DeclaratorInfo.isPastIdentifier() &&
           "don't know where identifier would go yet?");
    BitfieldSize = ParseConstantExpression();
    if (BitfieldSize.isInvalid())
      SkipUntil(tok::comma, StopAtSemi | StopBeforeMatch);
  } else if (Tok.is(tok::kw_requires)) {
    ParseTrailingRequiresClause(DeclaratorInfo);
  } else {
    ParseOptionalCXX11VirtSpecifierSeq(
        VS, getCurrentClass().IsInterface,
        DeclaratorInfo.getDeclSpec().getFriendSpecLoc());
    if (!VS.isUnset())
      MaybeParseAndDiagnoseDeclSpecAfterCXX11VirtSpecifierSeq(DeclaratorInfo,
                                                              VS);
  }

  // If a simple-asm-expr is present, parse it.
  if (Tok.is(tok::kw_asm)) {
    SourceLocation Loc;
    ExprResult AsmLabel(ParseSimpleAsm(/*ForAsmLabel*/ true, &Loc));
    if (AsmLabel.isInvalid())
      SkipUntil(tok::comma, StopAtSemi | StopBeforeMatch);

    DeclaratorInfo.setAsmLabel(AsmLabel.get());
    DeclaratorInfo.SetRangeEnd(Loc);
  }

  // If attributes exist after the declarator, but before an '{', parse them.
  // However, this does not apply for [[]] attributes (which could show up
  // before or after the __attribute__ attributes).
  DiagnoseAndSkipCXX11Attributes();
  MaybeParseGNUAttributes(DeclaratorInfo, &LateParsedAttrs);
  DiagnoseAndSkipCXX11Attributes();

  // For compatibility with code written to older Clang, also accept a
  // virt-specifier *after* the GNU attributes.
  if (BitfieldSize.isUnset() && VS.isUnset()) {
    ParseOptionalCXX11VirtSpecifierSeq(
        VS, getCurrentClass().IsInterface,
        DeclaratorInfo.getDeclSpec().getFriendSpecLoc());
    if (!VS.isUnset()) {
      // If we saw any GNU-style attributes that are known to GCC followed by a
      // virt-specifier, issue a GCC-compat warning.
      for (const ParsedAttr &AL : DeclaratorInfo.getAttributes())
        if (AL.isKnownToGCC() && !AL.isCXX11Attribute())
          Diag(AL.getLoc(), diag::warn_gcc_attribute_location);

      MaybeParseAndDiagnoseDeclSpecAfterCXX11VirtSpecifierSeq(DeclaratorInfo,
                                                              VS);
    }
  }

  // If this has neither a name nor a bit width, something has gone seriously
  // wrong. Skip until the semi-colon or }.
  if (!DeclaratorInfo.hasName() && BitfieldSize.isUnset()) {
    // If so, skip until the semi-colon or a }.
    SkipUntil(tok::r_brace, StopAtSemi | StopBeforeMatch);
    return true;
  }
  return false;
}

/// Look for declaration specifiers possibly occurring after C++11
/// virt-specifier-seq and diagnose them.
void Parser::MaybeParseAndDiagnoseDeclSpecAfterCXX11VirtSpecifierSeq(
    Declarator &D, VirtSpecifiers &VS) {
  DeclSpec DS(AttrFactory);

  // GNU-style and C++11 attributes are not allowed here, but they will be
  // handled by the caller.  Diagnose everything else.
  ParseTypeQualifierListOpt(
      DS, AR_NoAttributesParsed, false,
      /*IdentifierRequired=*/false, llvm::function_ref<void()>([&]() {
        Actions.CodeCompletion().CodeCompleteFunctionQualifiers(DS, D, &VS);
      }));
  D.ExtendWithDeclSpec(DS);

  if (D.isFunctionDeclarator()) {
    auto &Function = D.getFunctionTypeInfo();
    if (DS.getTypeQualifiers() != DeclSpec::TQ_unspecified) {
      auto DeclSpecCheck = [&](DeclSpec::TQ TypeQual, StringRef FixItName,
                               SourceLocation SpecLoc) {
        FixItHint Insertion;
        auto &MQ = Function.getOrCreateMethodQualifiers();
        if (!(MQ.getTypeQualifiers() & TypeQual)) {
          std::string Name(FixItName.data());
          Name += " ";
          Insertion = FixItHint::CreateInsertion(VS.getFirstLocation(), Name);
          MQ.SetTypeQual(TypeQual, SpecLoc);
        }
        Diag(SpecLoc, diag::err_declspec_after_virtspec)
            << FixItName
            << VirtSpecifiers::getSpecifierName(VS.getLastSpecifier())
            << FixItHint::CreateRemoval(SpecLoc) << Insertion;
      };
      DS.forEachQualifier(DeclSpecCheck);
    }

    // Parse ref-qualifiers.
    bool RefQualifierIsLValueRef = true;
    SourceLocation RefQualifierLoc;
    if (ParseRefQualifier(RefQualifierIsLValueRef, RefQualifierLoc)) {
      const char *Name = (RefQualifierIsLValueRef ? "& " : "&& ");
      FixItHint Insertion =
          FixItHint::CreateInsertion(VS.getFirstLocation(), Name);
      Function.RefQualifierIsLValueRef = RefQualifierIsLValueRef;
      Function.RefQualifierLoc = RefQualifierLoc;

      Diag(RefQualifierLoc, diag::err_declspec_after_virtspec)
          << (RefQualifierIsLValueRef ? "&" : "&&")
          << VirtSpecifiers::getSpecifierName(VS.getLastSpecifier())
          << FixItHint::CreateRemoval(RefQualifierLoc) << Insertion;
      D.SetRangeEnd(RefQualifierLoc);
    }
  }
}

/// ParseCXXClassMemberDeclaration - Parse a C++ class member declaration.
///
///       member-declaration:
///         decl-specifier-seq[opt] member-declarator-list[opt] ';'
///         function-definition ';'[opt]
///         ::[opt] nested-name-specifier template[opt] unqualified-id ';'[TODO]
///         using-declaration                                            [TODO]
/// [C++0x] static_assert-declaration
///         template-declaration
/// [GNU]   '__extension__' member-declaration
///
///       member-declarator-list:
///         member-declarator
///         member-declarator-list ',' member-declarator
///
///       member-declarator:
///         declarator virt-specifier-seq[opt] pure-specifier[opt]
/// [C++2a] declarator requires-clause
///         declarator constant-initializer[opt]
/// [C++11] declarator brace-or-equal-initializer[opt]
///         identifier[opt] ':' constant-expression
///
///       virt-specifier-seq:
///         virt-specifier
///         virt-specifier-seq virt-specifier
///
///       virt-specifier:
///         override
///         final
/// [MS]    sealed
///
///       pure-specifier:
///         '= 0'
///
///       constant-initializer:
///         '=' constant-expression
///
Parser::DeclGroupPtrTy Parser::ParseCXXClassMemberDeclaration(
    AccessSpecifier AS, ParsedAttributes &AccessAttrs,
    ParsedTemplateInfo &TemplateInfo, ParsingDeclRAIIObject *TemplateDiags) {
  assert(getLangOpts().CPlusPlus &&
         "ParseCXXClassMemberDeclaration should only be called in C++ mode");
  if (Tok.is(tok::at)) {
    if (getLangOpts().ObjC && NextToken().isObjCAtKeyword(tok::objc_defs))
      Diag(Tok, diag::err_at_defs_cxx);
    else
      Diag(Tok, diag::err_at_in_class);

    ConsumeToken();
    SkipUntil(tok::r_brace, StopAtSemi);
    return nullptr;
  }

  // Turn on colon protection early, while parsing declspec, although there is
  // nothing to protect there. It prevents from false errors if error recovery
  // incorrectly determines where the declspec ends, as in the example:
  //   struct A { enum class B { C }; };
  //   const int C = 4;
  //   struct D { A::B : C; };
  ColonProtectionRAIIObject X(*this);

  // Access declarations.
  bool MalformedTypeSpec = false;
  if (!TemplateInfo.Kind &&
      Tok.isOneOf(tok::identifier, tok::coloncolon, tok::kw___super)) {
    if (TryAnnotateCXXScopeToken())
      MalformedTypeSpec = true;

    bool isAccessDecl;
    if (Tok.isNot(tok::annot_cxxscope))
      isAccessDecl = false;
    else if (NextToken().is(tok::identifier))
      isAccessDecl = GetLookAheadToken(2).is(tok::semi);
    else
      isAccessDecl = NextToken().is(tok::kw_operator);

    if (isAccessDecl) {
      // Collect the scope specifier token we annotated earlier.
      CXXScopeSpec SS;
      ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                     /*ObjectHasErrors=*/false,
                                     /*EnteringContext=*/false);

      if (SS.isInvalid()) {
        SkipUntil(tok::semi);
        return nullptr;
      }

      // Try to parse an unqualified-id.
      SourceLocation TemplateKWLoc;
      UnqualifiedId Name;
      if (ParseUnqualifiedId(SS, /*ObjectType=*/nullptr,
                             /*ObjectHadErrors=*/false, false, true, true,
                             false, &TemplateKWLoc, Name)) {
        SkipUntil(tok::semi);
        return nullptr;
      }

      // TODO: recover from mistakenly-qualified operator declarations.
      if (ExpectAndConsume(tok::semi, diag::err_expected_after,
                           "access declaration")) {
        SkipUntil(tok::semi);
        return nullptr;
      }

      // FIXME: We should do something with the 'template' keyword here.
      return DeclGroupPtrTy::make(DeclGroupRef(Actions.ActOnUsingDeclaration(
          getCurScope(), AS, /*UsingLoc*/ SourceLocation(),
          /*TypenameLoc*/ SourceLocation(), SS, Name,
          /*EllipsisLoc*/ SourceLocation(),
          /*AttrList*/ ParsedAttributesView())));
    }
  }

  // static_assert-declaration. A templated static_assert declaration is
  // diagnosed in Parser::ParseDeclarationAfterTemplate.
  if (!TemplateInfo.Kind &&
      Tok.isOneOf(tok::kw_static_assert, tok::kw__Static_assert)) {
    SourceLocation DeclEnd;
    return DeclGroupPtrTy::make(
        DeclGroupRef(ParseStaticAssertDeclaration(DeclEnd)));
  }

  if (Tok.is(tok::kw_template)) {
    assert(!TemplateInfo.TemplateParams &&
           "Nested template improperly parsed?");
    ObjCDeclContextSwitch ObjCDC(*this);
    SourceLocation DeclEnd;
    return ParseTemplateDeclarationOrSpecialization(DeclaratorContext::Member,
                                                    DeclEnd, AccessAttrs, AS);
  }

  // Handle:  member-declaration ::= '__extension__' member-declaration
  if (Tok.is(tok::kw___extension__)) {
    // __extension__ silences extension warnings in the subexpression.
    ExtensionRAIIObject O(Diags); // Use RAII to do this.
    ConsumeToken();
    return ParseCXXClassMemberDeclaration(AS, AccessAttrs, TemplateInfo,
                                          TemplateDiags);
  }

  ParsedAttributes DeclAttrs(AttrFactory);
  // Optional C++11 attribute-specifier
  MaybeParseCXX11Attributes(DeclAttrs);

  // The next token may be an OpenMP pragma annotation token. That would
  // normally be handled from ParseCXXClassMemberDeclarationWithPragmas, but in
  // this case, it came from an *attribute* rather than a pragma. Handle it now.
  if (Tok.is(tok::annot_attr_openmp))
    return ParseOpenMPDeclarativeDirectiveWithExtDecl(AS, DeclAttrs);

  if (Tok.is(tok::kw_using)) {
    // Eat 'using'.
    SourceLocation UsingLoc = ConsumeToken();

    // Consume unexpected 'template' keywords.
    while (Tok.is(tok::kw_template)) {
      SourceLocation TemplateLoc = ConsumeToken();
      Diag(TemplateLoc, diag::err_unexpected_template_after_using)
          << FixItHint::CreateRemoval(TemplateLoc);
    }

    if (Tok.is(tok::kw_namespace)) {
      Diag(UsingLoc, diag::err_using_namespace_in_class);
      SkipUntil(tok::semi, StopBeforeMatch);
      return nullptr;
    }
    SourceLocation DeclEnd;
    // Otherwise, it must be a using-declaration or an alias-declaration.
    return ParseUsingDeclaration(DeclaratorContext::Member, TemplateInfo,
                                 UsingLoc, DeclEnd, DeclAttrs, AS);
  }

  ParsedAttributes DeclSpecAttrs(AttrFactory);
  MaybeParseMicrosoftAttributes(DeclSpecAttrs);

  // Hold late-parsed attributes so we can attach a Decl to them later.
  LateParsedAttrList CommonLateParsedAttrs;

  // decl-specifier-seq:
  // Parse the common declaration-specifiers piece.
  ParsingDeclSpec DS(*this, TemplateDiags);
  DS.takeAttributesFrom(DeclSpecAttrs);

  if (MalformedTypeSpec)
    DS.SetTypeSpecError();

  // Turn off usual access checking for templates explicit specialization
  // and instantiation.
  // C++20 [temp.spec] 13.9/6.
  // This disables the access checking rules for member function template
  // explicit instantiation and explicit specialization.
  bool IsTemplateSpecOrInst =
      (TemplateInfo.Kind == ParsedTemplateInfo::ExplicitInstantiation ||
       TemplateInfo.Kind == ParsedTemplateInfo::ExplicitSpecialization);
  SuppressAccessChecks diagsFromTag(*this, IsTemplateSpecOrInst);

  ParseDeclarationSpecifiers(DS, TemplateInfo, AS, DeclSpecContext::DSC_class,
                             &CommonLateParsedAttrs);

  if (IsTemplateSpecOrInst)
    diagsFromTag.done();

  // Turn off colon protection that was set for declspec.
  X.restore();

  // If we had a free-standing type definition with a missing semicolon, we
  // may get this far before the problem becomes obvious.
  if (DS.hasTagDefinition() &&
      TemplateInfo.Kind == ParsedTemplateInfo::NonTemplate &&
      DiagnoseMissingSemiAfterTagDefinition(DS, AS, DeclSpecContext::DSC_class,
                                            &CommonLateParsedAttrs))
    return nullptr;

  MultiTemplateParamsArg TemplateParams(
      TemplateInfo.TemplateParams ? TemplateInfo.TemplateParams->data()
                                  : nullptr,
      TemplateInfo.TemplateParams ? TemplateInfo.TemplateParams->size() : 0);

  if (TryConsumeToken(tok::semi)) {
    if (DS.isFriendSpecified())
      ProhibitAttributes(DeclAttrs);

    RecordDecl *AnonRecord = nullptr;
    Decl *TheDecl = Actions.ParsedFreeStandingDeclSpec(
        getCurScope(), AS, DS, DeclAttrs, TemplateParams, false, AnonRecord);
    Actions.ActOnDefinedDeclarationSpecifier(TheDecl);
    DS.complete(TheDecl);
    if (AnonRecord) {
      Decl *decls[] = {AnonRecord, TheDecl};
      return Actions.BuildDeclaratorGroup(decls);
    }
    return Actions.ConvertDeclToDeclGroup(TheDecl);
  }

  if (DS.hasTagDefinition())
    Actions.ActOnDefinedDeclarationSpecifier(DS.getRepAsDecl());

  ParsingDeclarator DeclaratorInfo(*this, DS, DeclAttrs,
                                   DeclaratorContext::Member);
  if (TemplateInfo.TemplateParams)
    DeclaratorInfo.setTemplateParameterLists(TemplateParams);
  VirtSpecifiers VS;

  // Hold late-parsed attributes so we can attach a Decl to them later.
  LateParsedAttrList LateParsedAttrs;

  SourceLocation EqualLoc;
  SourceLocation PureSpecLoc;

  auto TryConsumePureSpecifier = [&](bool AllowDefinition) {
    if (Tok.isNot(tok::equal))
      return false;

    auto &Zero = NextToken();
    SmallString<8> Buffer;
    if (Zero.isNot(tok::numeric_constant) ||
        PP.getSpelling(Zero, Buffer) != "0")
      return false;

    auto &After = GetLookAheadToken(2);
    if (!After.isOneOf(tok::semi, tok::comma) &&
        !(AllowDefinition &&
          After.isOneOf(tok::l_brace, tok::colon, tok::kw_try)))
      return false;

    EqualLoc = ConsumeToken();
    PureSpecLoc = ConsumeToken();
    return true;
  };

  SmallVector<Decl *, 8> DeclsInGroup;
  ExprResult BitfieldSize;
  ExprResult TrailingRequiresClause;
  bool ExpectSemi = true;

  // C++20 [temp.spec] 13.9/6.
  // This disables the access checking rules for member function template
  // explicit instantiation and explicit specialization.
  SuppressAccessChecks SAC(*this, IsTemplateSpecOrInst);

  // Parse the first declarator.
  if (ParseCXXMemberDeclaratorBeforeInitializer(
          DeclaratorInfo, VS, BitfieldSize, LateParsedAttrs)) {
    TryConsumeToken(tok::semi);
    return nullptr;
  }

  if (IsTemplateSpecOrInst)
    SAC.done();

  // Check for a member function definition.
  if (BitfieldSize.isUnset()) {
    // MSVC permits pure specifier on inline functions defined at class scope.
    // Hence check for =0 before checking for function definition.
    if (getLangOpts().MicrosoftExt && DeclaratorInfo.isDeclarationOfFunction())
      TryConsumePureSpecifier(/*AllowDefinition*/ true);

    FunctionDefinitionKind DefinitionKind = FunctionDefinitionKind::Declaration;
    // function-definition:
    //
    // In C++11, a non-function declarator followed by an open brace is a
    // braced-init-list for an in-class member initialization, not an
    // erroneous function definition.
    if (Tok.is(tok::l_brace) && !getLangOpts().CPlusPlus11) {
      DefinitionKind = FunctionDefinitionKind::Definition;
    } else if (DeclaratorInfo.isFunctionDeclarator()) {
      if (Tok.isOneOf(tok::l_brace, tok::colon, tok::kw_try)) {
        DefinitionKind = FunctionDefinitionKind::Definition;
      } else if (Tok.is(tok::equal)) {
        const Token &KW = NextToken();
        if (KW.is(tok::kw_default))
          DefinitionKind = FunctionDefinitionKind::Defaulted;
        else if (KW.is(tok::kw_delete))
          DefinitionKind = FunctionDefinitionKind::Deleted;
        else if (KW.is(tok::code_completion)) {
          cutOffParsing();
          Actions.CodeCompletion().CodeCompleteAfterFunctionEquals(
              DeclaratorInfo);
          return nullptr;
        }
      }
    }
    DeclaratorInfo.setFunctionDefinitionKind(DefinitionKind);

    // C++11 [dcl.attr.grammar] p4: If an attribute-specifier-seq appertains
    // to a friend declaration, that declaration shall be a definition.
    if (DeclaratorInfo.isFunctionDeclarator() &&
        DefinitionKind == FunctionDefinitionKind::Declaration &&
        DS.isFriendSpecified()) {
      // Diagnose attributes that appear before decl specifier:
      // [[]] friend int foo();
      ProhibitAttributes(DeclAttrs);
    }

    if (DefinitionKind != FunctionDefinitionKind::Declaration) {
      if (!DeclaratorInfo.isFunctionDeclarator()) {
        Diag(DeclaratorInfo.getIdentifierLoc(), diag::err_func_def_no_params);
        ConsumeBrace();
        SkipUntil(tok::r_brace);

        // Consume the optional ';'
        TryConsumeToken(tok::semi);

        return nullptr;
      }

      if (DS.getStorageClassSpec() == DeclSpec::SCS_typedef) {
        Diag(DeclaratorInfo.getIdentifierLoc(),
             diag::err_function_declared_typedef);

        // Recover by treating the 'typedef' as spurious.
        DS.ClearStorageClassSpecs();
      }

      Decl *FunDecl = ParseCXXInlineMethodDef(AS, AccessAttrs, DeclaratorInfo,
                                              TemplateInfo, VS, PureSpecLoc);

      if (FunDecl) {
        for (unsigned i = 0, ni = CommonLateParsedAttrs.size(); i < ni; ++i) {
          CommonLateParsedAttrs[i]->addDecl(FunDecl);
        }
        for (unsigned i = 0, ni = LateParsedAttrs.size(); i < ni; ++i) {
          LateParsedAttrs[i]->addDecl(FunDecl);
        }
      }
      LateParsedAttrs.clear();

      // Consume the ';' - it's optional unless we have a delete or default
      if (Tok.is(tok::semi))
        ConsumeExtraSemi(AfterMemberFunctionDefinition);

      return DeclGroupPtrTy::make(DeclGroupRef(FunDecl));
    }
  }

  // member-declarator-list:
  //   member-declarator
  //   member-declarator-list ',' member-declarator

  while (true) {
    InClassInitStyle HasInClassInit = ICIS_NoInit;
    bool HasStaticInitializer = false;
    if (Tok.isOneOf(tok::equal, tok::l_brace) && PureSpecLoc.isInvalid()) {
      // DRXXXX: Anonymous bit-fields cannot have a brace-or-equal-initializer.
      if (BitfieldSize.isUsable() && !DeclaratorInfo.hasName()) {
        // Diagnose the error and pretend there is no in-class initializer.
        Diag(Tok, diag::err_anon_bitfield_member_init);
        SkipUntil(tok::comma, StopAtSemi | StopBeforeMatch);
      } else if (DeclaratorInfo.isDeclarationOfFunction()) {
        // It's a pure-specifier.
        if (!TryConsumePureSpecifier(/*AllowFunctionDefinition*/ false))
          // Parse it as an expression so that Sema can diagnose it.
          HasStaticInitializer = true;
      } else if (DeclaratorInfo.getDeclSpec().getStorageClassSpec() !=
                     DeclSpec::SCS_static &&
                 DeclaratorInfo.getDeclSpec().getStorageClassSpec() !=
                     DeclSpec::SCS_typedef &&
                 !DS.isFriendSpecified() &&
                 TemplateInfo.Kind == ParsedTemplateInfo::NonTemplate) {
        // It's a default member initializer.
        if (BitfieldSize.get())
          Diag(Tok, getLangOpts().CPlusPlus20
                        ? diag::warn_cxx17_compat_bitfield_member_init
                        : diag::ext_bitfield_member_init);
        HasInClassInit = Tok.is(tok::equal) ? ICIS_CopyInit : ICIS_ListInit;
      } else {
        HasStaticInitializer = true;
      }
    }

    // NOTE: If Sema is the Action module and declarator is an instance field,
    // this call will *not* return the created decl; It will return null.
    // See Sema::ActOnCXXMemberDeclarator for details.

    NamedDecl *ThisDecl = nullptr;
    if (DS.isFriendSpecified()) {
      // C++11 [dcl.attr.grammar] p4: If an attribute-specifier-seq appertains
      // to a friend declaration, that declaration shall be a definition.
      //
      // Diagnose attributes that appear in a friend member function declarator:
      //   friend int foo [[]] ();
      for (const ParsedAttr &AL : DeclaratorInfo.getAttributes())
        if (AL.isCXX11Attribute() || AL.isRegularKeywordAttribute()) {
          auto Loc = AL.getRange().getBegin();
          (AL.isRegularKeywordAttribute()
               ? Diag(Loc, diag::err_keyword_not_allowed) << AL
               : Diag(Loc, diag::err_attributes_not_allowed))
              << AL.getRange();
        }

      ThisDecl = Actions.ActOnFriendFunctionDecl(getCurScope(), DeclaratorInfo,
                                                 TemplateParams);
    } else {
      ThisDecl = Actions.ActOnCXXMemberDeclarator(
          getCurScope(), AS, DeclaratorInfo, TemplateParams, BitfieldSize.get(),
          VS, HasInClassInit);

      if (VarTemplateDecl *VT =
              ThisDecl ? dyn_cast<VarTemplateDecl>(ThisDecl) : nullptr)
        // Re-direct this decl to refer to the templated decl so that we can
        // initialize it.
        ThisDecl = VT->getTemplatedDecl();

      if (ThisDecl)
        Actions.ProcessDeclAttributeList(getCurScope(), ThisDecl, AccessAttrs);
    }

    // Error recovery might have converted a non-static member into a static
    // member.
    if (HasInClassInit != ICIS_NoInit &&
        DeclaratorInfo.getDeclSpec().getStorageClassSpec() ==
            DeclSpec::SCS_static) {
      HasInClassInit = ICIS_NoInit;
      HasStaticInitializer = true;
    }

    if (PureSpecLoc.isValid() && VS.getAbstractLoc().isValid()) {
      Diag(PureSpecLoc, diag::err_duplicate_virt_specifier) << "abstract";
    }
    if (ThisDecl && PureSpecLoc.isValid())
      Actions.ActOnPureSpecifier(ThisDecl, PureSpecLoc);
    else if (ThisDecl && VS.getAbstractLoc().isValid())
      Actions.ActOnPureSpecifier(ThisDecl, VS.getAbstractLoc());

    // Handle the initializer.
    if (HasInClassInit != ICIS_NoInit) {
      // The initializer was deferred; parse it and cache the tokens.
      Diag(Tok, getLangOpts().CPlusPlus11
                    ? diag::warn_cxx98_compat_nonstatic_member_init
                    : diag::ext_nonstatic_member_init);

      if (DeclaratorInfo.isArrayOfUnknownBound()) {
        // C++11 [dcl.array]p3: An array bound may also be omitted when the
        // declarator is followed by an initializer.
        //
        // A brace-or-equal-initializer for a member-declarator is not an
        // initializer in the grammar, so this is ill-formed.
        Diag(Tok, diag::err_incomplete_array_member_init);
        SkipUntil(tok::comma, StopAtSemi | StopBeforeMatch);

        // Avoid later warnings about a class member of incomplete type.
        if (ThisDecl)
          ThisDecl->setInvalidDecl();
      } else
        ParseCXXNonStaticMemberInitializer(ThisDecl);
    } else if (HasStaticInitializer) {
      // Normal initializer.
      ExprResult Init = ParseCXXMemberInitializer(
          ThisDecl, DeclaratorInfo.isDeclarationOfFunction(), EqualLoc);

      if (Init.isInvalid()) {
        if (ThisDecl)
          Actions.ActOnUninitializedDecl(ThisDecl);
        SkipUntil(tok::comma, StopAtSemi | StopBeforeMatch);
      } else if (ThisDecl)
        Actions.AddInitializerToDecl(ThisDecl, Init.get(),
                                     EqualLoc.isInvalid());
    } else if (ThisDecl && DeclaratorInfo.isStaticMember())
      // No initializer.
      Actions.ActOnUninitializedDecl(ThisDecl);

    if (ThisDecl) {
      if (!ThisDecl->isInvalidDecl()) {
        // Set the Decl for any late parsed attributes
        for (unsigned i = 0, ni = CommonLateParsedAttrs.size(); i < ni; ++i)
          CommonLateParsedAttrs[i]->addDecl(ThisDecl);

        for (unsigned i = 0, ni = LateParsedAttrs.size(); i < ni; ++i)
          LateParsedAttrs[i]->addDecl(ThisDecl);
      }
      Actions.FinalizeDeclaration(ThisDecl);
      DeclsInGroup.push_back(ThisDecl);

      if (DeclaratorInfo.isFunctionDeclarator() &&
          DeclaratorInfo.getDeclSpec().getStorageClassSpec() !=
              DeclSpec::SCS_typedef)
        HandleMemberFunctionDeclDelays(DeclaratorInfo, ThisDecl);
    }
    LateParsedAttrs.clear();

    DeclaratorInfo.complete(ThisDecl);

    // If we don't have a comma, it is either the end of the list (a ';')
    // or an error, bail out.
    SourceLocation CommaLoc;
    if (!TryConsumeToken(tok::comma, CommaLoc))
      break;

    if (Tok.isAtStartOfLine() &&
        !MightBeDeclarator(DeclaratorContext::Member)) {
      // This comma was followed by a line-break and something which can't be
      // the start of a declarator. The comma was probably a typo for a
      // semicolon.
      Diag(CommaLoc, diag::err_expected_semi_declaration)
          << FixItHint::CreateReplacement(CommaLoc, ";");
      ExpectSemi = false;
      break;
    }

    // C++23 [temp.pre]p5:
    //   In a template-declaration, explicit specialization, or explicit
    //   instantiation the init-declarator-list in the declaration shall
    //   contain at most one declarator.
    if (TemplateInfo.Kind != ParsedTemplateInfo::NonTemplate &&
        DeclaratorInfo.isFirstDeclarator()) {
      Diag(CommaLoc, diag::err_multiple_template_declarators)
          << TemplateInfo.Kind;
    }

    // Parse the next declarator.
    DeclaratorInfo.clear();
    VS.clear();
    BitfieldSize = ExprResult(/*Invalid=*/false);
    EqualLoc = PureSpecLoc = SourceLocation();
    DeclaratorInfo.setCommaLoc(CommaLoc);

    // GNU attributes are allowed before the second and subsequent declarator.
    // However, this does not apply for [[]] attributes (which could show up
    // before or after the __attribute__ attributes).
    DiagnoseAndSkipCXX11Attributes();
    MaybeParseGNUAttributes(DeclaratorInfo);
    DiagnoseAndSkipCXX11Attributes();

    if (ParseCXXMemberDeclaratorBeforeInitializer(
            DeclaratorInfo, VS, BitfieldSize, LateParsedAttrs))
      break;
  }

  if (ExpectSemi &&
      ExpectAndConsume(tok::semi, diag::err_expected_semi_decl_list)) {
    // Skip to end of block or statement.
    SkipUntil(tok::r_brace, StopAtSemi | StopBeforeMatch);
    // If we stopped at a ';', eat it.
    TryConsumeToken(tok::semi);
    return nullptr;
  }

  return Actions.FinalizeDeclaratorGroup(getCurScope(), DS, DeclsInGroup);
}

/// ParseCXXMemberInitializer - Parse the brace-or-equal-initializer.
/// Also detect and reject any attempted defaulted/deleted function definition.
/// The location of the '=', if any, will be placed in EqualLoc.
///
/// This does not check for a pure-specifier; that's handled elsewhere.
///
///   brace-or-equal-initializer:
///     '=' initializer-expression
///     braced-init-list
///
///   initializer-clause:
///     assignment-expression
///     braced-init-list
///
///   defaulted/deleted function-definition:
///     '=' 'default'
///     '=' 'delete'
///
/// Prior to C++0x, the assignment-expression in an initializer-clause must
/// be a constant-expression.
ExprResult Parser::ParseCXXMemberInitializer(Decl *D, bool IsFunction,
                                             SourceLocation &EqualLoc) {
  assert(Tok.isOneOf(tok::equal, tok::l_brace) &&
         "Data member initializer not starting with '=' or '{'");

  bool IsFieldInitialization = isa_and_present<FieldDecl>(D);

  EnterExpressionEvaluationContext Context(
      Actions,
      IsFieldInitialization
          ? Sema::ExpressionEvaluationContext::PotentiallyEvaluatedIfUsed
          : Sema::ExpressionEvaluationContext::PotentiallyEvaluated,
      D);

  // CWG2760
  // Default member initializers used to initialize a base or member subobject
  // [...] are considered to be part of the function body
  Actions.ExprEvalContexts.back().InImmediateEscalatingFunctionContext =
      IsFieldInitialization;

  if (TryConsumeToken(tok::equal, EqualLoc)) {
    if (Tok.is(tok::kw_delete)) {
      // In principle, an initializer of '= delete p;' is legal, but it will
      // never type-check. It's better to diagnose it as an ill-formed
      // expression than as an ill-formed deleted non-function member. An
      // initializer of '= delete p, foo' will never be parsed, because a
      // top-level comma always ends the initializer expression.
      const Token &Next = NextToken();
      if (IsFunction || Next.isOneOf(tok::semi, tok::comma, tok::eof)) {
        if (IsFunction)
          Diag(ConsumeToken(), diag::err_default_delete_in_multiple_declaration)
              << 1 /* delete */;
        else
          Diag(ConsumeToken(), diag::err_deleted_non_function);
        SkipDeletedFunctionBody();
        return ExprError();
      }
    } else if (Tok.is(tok::kw_default)) {
      if (IsFunction)
        Diag(Tok, diag::err_default_delete_in_multiple_declaration)
            << 0 /* default */;
      else
        Diag(ConsumeToken(), diag::err_default_special_members)
            << getLangOpts().CPlusPlus20;
      return ExprError();
    }
  }
  if (const auto *PD = dyn_cast_or_null<MSPropertyDecl>(D)) {
    Diag(Tok, diag::err_ms_property_initializer) << PD;
    return ExprError();
  }
  return ParseInitializer();
}

void Parser::SkipCXXMemberSpecification(SourceLocation RecordLoc,
                                        SourceLocation AttrFixitLoc,
                                        unsigned TagType, Decl *TagDecl) {
  // Skip the optional 'final' keyword.
  if (getLangOpts().CPlusPlus && Tok.is(tok::identifier)) {
    assert(isCXX11FinalKeyword() && "not a class definition");
    ConsumeToken();

    // Diagnose any C++11 attributes after 'final' keyword.
    // We deliberately discard these attributes.
    ParsedAttributes Attrs(AttrFactory);
    CheckMisplacedCXX11Attribute(Attrs, AttrFixitLoc);

    // This can only happen if we had malformed misplaced attributes;
    // we only get called if there is a colon or left-brace after the
    // attributes.
    if (Tok.isNot(tok::colon) && Tok.isNot(tok::l_brace))
      return;
  }

  // Skip the base clauses. This requires actually parsing them, because
  // otherwise we can't be sure where they end (a left brace may appear
  // within a template argument).
  if (Tok.is(tok::colon)) {
    // Enter the scope of the class so that we can correctly parse its bases.
    ParseScope ClassScope(this, Scope::ClassScope | Scope::DeclScope);
    ParsingClassDefinition ParsingDef(*this, TagDecl, /*NonNestedClass*/ true,
                                      TagType == DeclSpec::TST_interface);
    auto OldContext =
        Actions.ActOnTagStartSkippedDefinition(getCurScope(), TagDecl);

    // Parse the bases but don't attach them to the class.
    ParseBaseClause(nullptr);

    Actions.ActOnTagFinishSkippedDefinition(OldContext);

    if (!Tok.is(tok::l_brace)) {
      Diag(PP.getLocForEndOfToken(PrevTokLocation),
           diag::err_expected_lbrace_after_base_specifiers);
      return;
    }
  }

  // Skip the body.
  assert(Tok.is(tok::l_brace));
  BalancedDelimiterTracker T(*this, tok::l_brace);
  T.consumeOpen();
  T.skipToEnd();

  // Parse and discard any trailing attributes.
  if (Tok.is(tok::kw___attribute)) {
    ParsedAttributes Attrs(AttrFactory);
    MaybeParseGNUAttributes(Attrs);
  }
}

Parser::DeclGroupPtrTy Parser::ParseCXXClassMemberDeclarationWithPragmas(
    AccessSpecifier &AS, ParsedAttributes &AccessAttrs, DeclSpec::TST TagType,
    Decl *TagDecl) {
  ParenBraceBracketBalancer BalancerRAIIObj(*this);

  switch (Tok.getKind()) {
  case tok::kw___if_exists:
  case tok::kw___if_not_exists:
    ParseMicrosoftIfExistsClassDeclaration(TagType, AccessAttrs, AS);
    return nullptr;

  case tok::semi:
    // Check for extraneous top-level semicolon.
    ConsumeExtraSemi(InsideStruct, TagType);
    return nullptr;

    // Handle pragmas that can appear as member declarations.
  case tok::annot_pragma_vis:
    HandlePragmaVisibility();
    return nullptr;
  case tok::annot_pragma_pack:
    HandlePragmaPack();
    return nullptr;
  case tok::annot_pragma_align:
    HandlePragmaAlign();
    return nullptr;
  case tok::annot_pragma_ms_pointers_to_members:
    HandlePragmaMSPointersToMembers();
    return nullptr;
  case tok::annot_pragma_ms_pragma:
    HandlePragmaMSPragma();
    return nullptr;
  case tok::annot_pragma_ms_vtordisp:
    HandlePragmaMSVtorDisp();
    return nullptr;
  case tok::annot_pragma_dump:
    HandlePragmaDump();
    return nullptr;

  case tok::kw_namespace:
    // If we see a namespace here, a close brace was missing somewhere.
    DiagnoseUnexpectedNamespace(cast<NamedDecl>(TagDecl));
    return nullptr;

  case tok::kw_private:
    // FIXME: We don't accept GNU attributes on access specifiers in OpenCL mode
    // yet.
    if (getLangOpts().OpenCL && !NextToken().is(tok::colon)) {
      ParsedTemplateInfo TemplateInfo;
      return ParseCXXClassMemberDeclaration(AS, AccessAttrs, TemplateInfo);
    }
    [[fallthrough]];
  case tok::kw_public:
  case tok::kw_protected: {
    if (getLangOpts().HLSL)
      Diag(Tok.getLocation(), diag::ext_hlsl_access_specifiers);
    AccessSpecifier NewAS = getAccessSpecifierIfPresent();
    assert(NewAS != AS_none);
    // Current token is a C++ access specifier.
    AS = NewAS;
    SourceLocation ASLoc = Tok.getLocation();
    unsigned TokLength = Tok.getLength();
    ConsumeToken();
    AccessAttrs.clear();
    MaybeParseGNUAttributes(AccessAttrs);

    SourceLocation EndLoc;
    if (TryConsumeToken(tok::colon, EndLoc)) {
    } else if (TryConsumeToken(tok::semi, EndLoc)) {
      Diag(EndLoc, diag::err_expected)
          << tok::colon << FixItHint::CreateReplacement(EndLoc, ":");
    } else {
      EndLoc = ASLoc.getLocWithOffset(TokLength);
      Diag(EndLoc, diag::err_expected)
          << tok::colon << FixItHint::CreateInsertion(EndLoc, ":");
    }

    // The Microsoft extension __interface does not permit non-public
    // access specifiers.
    if (TagType == DeclSpec::TST_interface && AS != AS_public) {
      Diag(ASLoc, diag::err_access_specifier_interface) << (AS == AS_protected);
    }

    if (Actions.ActOnAccessSpecifier(NewAS, ASLoc, EndLoc, AccessAttrs)) {
      // found another attribute than only annotations
      AccessAttrs.clear();
    }

    return nullptr;
  }

  case tok::annot_attr_openmp:
  case tok::annot_pragma_openmp:
    return ParseOpenMPDeclarativeDirectiveWithExtDecl(
        AS, AccessAttrs, /*Delayed=*/true, TagType, TagDecl);
  case tok::annot_pragma_openacc:
    return ParseOpenACCDirectiveDecl();

  default:
    if (tok::isPragmaAnnotation(Tok.getKind())) {
      Diag(Tok.getLocation(), diag::err_pragma_misplaced_in_decl)
          << DeclSpec::getSpecifierName(
                 TagType, Actions.getASTContext().getPrintingPolicy());
      ConsumeAnnotationToken();
      return nullptr;
    }
    ParsedTemplateInfo TemplateInfo;
    return ParseCXXClassMemberDeclaration(AS, AccessAttrs, TemplateInfo);
  }
}

/// ParseCXXMemberSpecification - Parse the class definition.
///
///       member-specification:
///         member-declaration member-specification[opt]
///         access-specifier ':' member-specification[opt]
///
void Parser::ParseCXXMemberSpecification(SourceLocation RecordLoc,
                                         SourceLocation AttrFixitLoc,
                                         ParsedAttributes &Attrs,
                                         unsigned TagType, Decl *TagDecl) {
  assert((TagType == DeclSpec::TST_struct ||
          TagType == DeclSpec::TST_interface ||
          TagType == DeclSpec::TST_union || TagType == DeclSpec::TST_class) &&
         "Invalid TagType!");

  llvm::TimeTraceScope TimeScope("ParseClass", [&]() {
    if (auto *TD = dyn_cast_or_null<NamedDecl>(TagDecl))
      return TD->getQualifiedNameAsString();
    return std::string("<anonymous>");
  });

  PrettyDeclStackTraceEntry CrashInfo(Actions.Context, TagDecl, RecordLoc,
                                      "parsing struct/union/class body");

  // Determine whether this is a non-nested class. Note that local
  // classes are *not* considered to be nested classes.
  bool NonNestedClass = true;
  if (!ClassStack.empty()) {
    for (const Scope *S = getCurScope(); S; S = S->getParent()) {
      if (S->isClassScope()) {
        // We're inside a class scope, so this is a nested class.
        NonNestedClass = false;

        // The Microsoft extension __interface does not permit nested classes.
        if (getCurrentClass().IsInterface) {
          Diag(RecordLoc, diag::err_invalid_member_in_interface)
              << /*ErrorType=*/6
              << (isa<NamedDecl>(TagDecl)
                      ? cast<NamedDecl>(TagDecl)->getQualifiedNameAsString()
                      : "(anonymous)");
        }
        break;
      }

      if (S->isFunctionScope())
        // If we're in a function or function template then this is a local
        // class rather than a nested class.
        break;
    }
  }

  // Enter a scope for the class.
  ParseScope ClassScope(this, Scope::ClassScope | Scope::DeclScope);

  // Note that we are parsing a new (potentially-nested) class definition.
  ParsingClassDefinition ParsingDef(*this, TagDecl, NonNestedClass,
                                    TagType == DeclSpec::TST_interface);

  if (TagDecl)
    Actions.ActOnTagStartDefinition(getCurScope(), TagDecl);

  SourceLocation FinalLoc;
  SourceLocation AbstractLoc;
  bool IsFinalSpelledSealed = false;
  bool IsAbstract = false;

  // Parse the optional 'final' keyword.
  if (getLangOpts().CPlusPlus && Tok.is(tok::identifier)) {
    while (true) {
      VirtSpecifiers::Specifier Specifier = isCXX11VirtSpecifier(Tok);
      if (Specifier == VirtSpecifiers::VS_None)
        break;
      if (isCXX11FinalKeyword()) {
        if (FinalLoc.isValid()) {
          auto Skipped = ConsumeToken();
          Diag(Skipped, diag::err_duplicate_class_virt_specifier)
              << VirtSpecifiers::getSpecifierName(Specifier);
        } else {
          FinalLoc = ConsumeToken();
          if (Specifier == VirtSpecifiers::VS_Sealed)
            IsFinalSpelledSealed = true;
        }
      } else {
        if (AbstractLoc.isValid()) {
          auto Skipped = ConsumeToken();
          Diag(Skipped, diag::err_duplicate_class_virt_specifier)
              << VirtSpecifiers::getSpecifierName(Specifier);
        } else {
          AbstractLoc = ConsumeToken();
          IsAbstract = true;
        }
      }
      if (TagType == DeclSpec::TST_interface)
        Diag(FinalLoc, diag::err_override_control_interface)
            << VirtSpecifiers::getSpecifierName(Specifier);
      else if (Specifier == VirtSpecifiers::VS_Final)
        Diag(FinalLoc, getLangOpts().CPlusPlus11
                           ? diag::warn_cxx98_compat_override_control_keyword
                           : diag::ext_override_control_keyword)
            << VirtSpecifiers::getSpecifierName(Specifier);
      else if (Specifier == VirtSpecifiers::VS_Sealed)
        Diag(FinalLoc, diag::ext_ms_sealed_keyword);
      else if (Specifier == VirtSpecifiers::VS_Abstract)
        Diag(AbstractLoc, diag::ext_ms_abstract_keyword);
      else if (Specifier == VirtSpecifiers::VS_GNU_Final)
        Diag(FinalLoc, diag::ext_warn_gnu_final);
    }
    assert((FinalLoc.isValid() || AbstractLoc.isValid()) &&
           "not a class definition");

    // Parse any C++11 attributes after 'final' keyword.
    // These attributes are not allowed to appear here,
    // and the only possible place for them to appertain
    // to the class would be between class-key and class-name.
    CheckMisplacedCXX11Attribute(Attrs, AttrFixitLoc);

    // ParseClassSpecifier() does only a superficial check for attributes before
    // deciding to call this method.  For example, for
    // `class C final alignas ([l) {` it will decide that this looks like a
    // misplaced attribute since it sees `alignas '(' ')'`.  But the actual
    // attribute parsing code will try to parse the '[' as a constexpr lambda
    // and consume enough tokens that the alignas parsing code will eat the
    // opening '{'.  So bail out if the next token isn't one we expect.
    if (!Tok.is(tok::colon) && !Tok.is(tok::l_brace)) {
      if (TagDecl)
        Actions.ActOnTagDefinitionError(getCurScope(), TagDecl);
      return;
    }
  }

  if (Tok.is(tok::colon)) {
    ParseScope InheritanceScope(this, getCurScope()->getFlags() |
                                          Scope::ClassInheritanceScope);

    ParseBaseClause(TagDecl);
    if (!Tok.is(tok::l_brace)) {
      bool SuggestFixIt = false;
      SourceLocation BraceLoc = PP.getLocForEndOfToken(PrevTokLocation);
      if (Tok.isAtStartOfLine()) {
        switch (Tok.getKind()) {
        case tok::kw_private:
        case tok::kw_protected:
        case tok::kw_public:
          SuggestFixIt = NextToken().getKind() == tok::colon;
          break;
        case tok::kw_static_assert:
        case tok::r_brace:
        case tok::kw_using:
        // base-clause can have simple-template-id; 'template' can't be there
        case tok::kw_template:
          SuggestFixIt = true;
          break;
        case tok::identifier:
          SuggestFixIt = isConstructorDeclarator(true);
          break;
        default:
          SuggestFixIt = isCXXSimpleDeclaration(/*AllowForRangeDecl=*/false);
          break;
        }
      }
      DiagnosticBuilder LBraceDiag =
          Diag(BraceLoc, diag::err_expected_lbrace_after_base_specifiers);
      if (SuggestFixIt) {
        LBraceDiag << FixItHint::CreateInsertion(BraceLoc, " {");
        // Try recovering from missing { after base-clause.
        PP.EnterToken(Tok, /*IsReinject*/ true);
        Tok.setKind(tok::l_brace);
      } else {
        if (TagDecl)
          Actions.ActOnTagDefinitionError(getCurScope(), TagDecl);
        return;
      }
    }
  }

  assert(Tok.is(tok::l_brace));
  BalancedDelimiterTracker T(*this, tok::l_brace);
  T.consumeOpen();

  if (TagDecl)
    Actions.ActOnStartCXXMemberDeclarations(getCurScope(), TagDecl, FinalLoc,
                                            IsFinalSpelledSealed, IsAbstract,
                                            T.getOpenLocation());

  // C++ 11p3: Members of a class defined with the keyword class are private
  // by default. Members of a class defined with the keywords struct or union
  // are public by default.
  // HLSL: In HLSL members of a class are public by default.
  AccessSpecifier CurAS;
  if (TagType == DeclSpec::TST_class && !getLangOpts().HLSL)
    CurAS = AS_private;
  else
    CurAS = AS_public;
  ParsedAttributes AccessAttrs(AttrFactory);

  if (TagDecl) {
    // While we still have something to read, read the member-declarations.
    while (!tryParseMisplacedModuleImport() && Tok.isNot(tok::r_brace) &&
           Tok.isNot(tok::eof)) {
      // Each iteration of this loop reads one member-declaration.
      ParseCXXClassMemberDeclarationWithPragmas(
          CurAS, AccessAttrs, static_cast<DeclSpec::TST>(TagType), TagDecl);
      MaybeDestroyTemplateIds();
    }
    T.consumeClose();
  } else {
    SkipUntil(tok::r_brace);
  }

  // If attributes exist after class contents, parse them.
  ParsedAttributes attrs(AttrFactory);
  MaybeParseGNUAttributes(attrs);

  if (TagDecl)
    Actions.ActOnFinishCXXMemberSpecification(getCurScope(), RecordLoc, TagDecl,
                                              T.getOpenLocation(),
                                              T.getCloseLocation(), attrs);

  // C++11 [class.mem]p2:
  //   Within the class member-specification, the class is regarded as complete
  //   within function bodies, default arguments, exception-specifications, and
  //   brace-or-equal-initializers for non-static data members (including such
  //   things in nested classes).
  if (TagDecl && NonNestedClass) {
    // We are not inside a nested class. This class and its nested classes
    // are complete and we can parse the delayed portions of method
    // declarations and the lexed inline method definitions, along with any
    // delayed attributes.

    SourceLocation SavedPrevTokLocation = PrevTokLocation;
    ParseLexedPragmas(getCurrentClass());
    ParseLexedAttributes(getCurrentClass());
    ParseLexedMethodDeclarations(getCurrentClass());

    // We've finished with all pending member declarations.
    Actions.ActOnFinishCXXMemberDecls();

    ParseLexedMemberInitializers(getCurrentClass());
    ParseLexedMethodDefs(getCurrentClass());
    PrevTokLocation = SavedPrevTokLocation;

    // We've finished parsing everything, including default argument
    // initializers.
    Actions.ActOnFinishCXXNonNestedClass();
  }

  if (TagDecl)
    Actions.ActOnTagFinishDefinition(getCurScope(), TagDecl, T.getRange());

  // Leave the class scope.
  ParsingDef.Pop();
  ClassScope.Exit();
}

void Parser::DiagnoseUnexpectedNamespace(NamedDecl *D) {
  assert(Tok.is(tok::kw_namespace));

  // FIXME: Suggest where the close brace should have gone by looking
  // at indentation changes within the definition body.
  Diag(D->getLocation(), diag::err_missing_end_of_definition) << D;
  Diag(Tok.getLocation(), diag::note_missing_end_of_definition_before) << D;

  // Push '};' onto the token stream to recover.
  PP.EnterToken(Tok, /*IsReinject*/ true);

  Tok.startToken();
  Tok.setLocation(PP.getLocForEndOfToken(PrevTokLocation));
  Tok.setKind(tok::semi);
  PP.EnterToken(Tok, /*IsReinject*/ true);

  Tok.setKind(tok::r_brace);
}

/// ParseConstructorInitializer - Parse a C++ constructor initializer,
/// which explicitly initializes the members or base classes of a
/// class (C++ [class.base.init]). For example, the three initializers
/// after the ':' in the Derived constructor below:
///
/// @code
/// class Base { };
/// class Derived : Base {
///   int x;
///   float f;
/// public:
///   Derived(float f) : Base(), x(17), f(f) { }
/// };
/// @endcode
///
/// [C++]  ctor-initializer:
///          ':' mem-initializer-list
///
/// [C++]  mem-initializer-list:
///          mem-initializer ...[opt]
///          mem-initializer ...[opt] , mem-initializer-list
void Parser::ParseConstructorInitializer(Decl *ConstructorDecl) {
  assert(Tok.is(tok::colon) &&
         "Constructor initializer always starts with ':'");

  // Poison the SEH identifiers so they are flagged as illegal in constructor
  // initializers.
  PoisonSEHIdentifiersRAIIObject PoisonSEHIdentifiers(*this, true);
  SourceLocation ColonLoc = ConsumeToken();

  SmallVector<CXXCtorInitializer *, 4> MemInitializers;
  bool AnyErrors = false;

  do {
    if (Tok.is(tok::code_completion)) {
      cutOffParsing();
      Actions.CodeCompletion().CodeCompleteConstructorInitializer(
          ConstructorDecl, MemInitializers);
      return;
    }

    MemInitResult MemInit = ParseMemInitializer(ConstructorDecl);
    if (!MemInit.isInvalid())
      MemInitializers.push_back(MemInit.get());
    else
      AnyErrors = true;

    if (Tok.is(tok::comma))
      ConsumeToken();
    else if (Tok.is(tok::l_brace))
      break;
    // If the previous initializer was valid and the next token looks like a
    // base or member initializer, assume that we're just missing a comma.
    else if (!MemInit.isInvalid() &&
             Tok.isOneOf(tok::identifier, tok::coloncolon)) {
      SourceLocation Loc = PP.getLocForEndOfToken(PrevTokLocation);
      Diag(Loc, diag::err_ctor_init_missing_comma)
          << FixItHint::CreateInsertion(Loc, ", ");
    } else {
      // Skip over garbage, until we get to '{'.  Don't eat the '{'.
      if (!MemInit.isInvalid())
        Diag(Tok.getLocation(), diag::err_expected_either)
            << tok::l_brace << tok::comma;
      SkipUntil(tok::l_brace, StopAtSemi | StopBeforeMatch);
      break;
    }
  } while (true);

  Actions.ActOnMemInitializers(ConstructorDecl, ColonLoc, MemInitializers,
                               AnyErrors);
}

/// ParseMemInitializer - Parse a C++ member initializer, which is
/// part of a constructor initializer that explicitly initializes one
/// member or base class (C++ [class.base.init]). See
/// ParseConstructorInitializer for an example.
///
/// [C++] mem-initializer:
///         mem-initializer-id '(' expression-list[opt] ')'
/// [C++0x] mem-initializer-id braced-init-list
///
/// [C++] mem-initializer-id:
///         '::'[opt] nested-name-specifier[opt] class-name
///         identifier
MemInitResult Parser::ParseMemInitializer(Decl *ConstructorDecl) {
  // parse '::'[opt] nested-name-specifier[opt]
  CXXScopeSpec SS;
  if (ParseOptionalCXXScopeSpecifier(SS, /*ObjectType=*/nullptr,
                                     /*ObjectHasErrors=*/false,
                                     /*EnteringContext=*/false))
    return true;

  // : identifier
  IdentifierInfo *II = nullptr;
  SourceLocation IdLoc = Tok.getLocation();
  // : declype(...)
  DeclSpec DS(AttrFactory);
  // : template_name<...>
  TypeResult TemplateTypeTy;

  if (Tok.is(tok::identifier)) {
    // Get the identifier. This may be a member name or a class name,
    // but we'll let the semantic analysis determine which it is.
    II = Tok.getIdentifierInfo();
    ConsumeToken();
  } else if (Tok.is(tok::annot_decltype)) {
    // Get the decltype expression, if there is one.
    // Uses of decltype will already have been converted to annot_decltype by
    // ParseOptionalCXXScopeSpecifier at this point.
    // FIXME: Can we get here with a scope specifier?
    ParseDecltypeSpecifier(DS);
  } else if (Tok.is(tok::annot_pack_indexing_type)) {
    // Uses of T...[N] will already have been converted to
    // annot_pack_indexing_type by ParseOptionalCXXScopeSpecifier at this point.
    ParsePackIndexingType(DS);
  } else {
    TemplateIdAnnotation *TemplateId = Tok.is(tok::annot_template_id)
                                           ? takeTemplateIdAnnotation(Tok)
                                           : nullptr;
    if (TemplateId && TemplateId->mightBeType()) {
      AnnotateTemplateIdTokenAsType(SS, ImplicitTypenameContext::No,
                                    /*IsClassName=*/true);
      assert(Tok.is(tok::annot_typename) && "template-id -> type failed");
      TemplateTypeTy = getTypeAnnotation(Tok);
      ConsumeAnnotationToken();
    } else {
      Diag(Tok, diag::err_expected_member_or_base_name);
      return true;
    }
  }

  // Parse the '('.
  if (getLangOpts().CPlusPlus11 && Tok.is(tok::l_brace)) {
    Diag(Tok, diag::warn_cxx98_compat_generalized_initializer_lists);

    // FIXME: Add support for signature help inside initializer lists.
    ExprResult InitList = ParseBraceInitializer();
    if (InitList.isInvalid())
      return true;

    SourceLocation EllipsisLoc;
    TryConsumeToken(tok::ellipsis, EllipsisLoc);

    if (TemplateTypeTy.isInvalid())
      return true;
    return Actions.ActOnMemInitializer(ConstructorDecl, getCurScope(), SS, II,
                                       TemplateTypeTy.get(), DS, IdLoc,
                                       InitList.get(), EllipsisLoc);
  } else if (Tok.is(tok::l_paren)) {
    BalancedDelimiterTracker T(*this, tok::l_paren);
    T.consumeOpen();

    // Parse the optional expression-list.
    ExprVector ArgExprs;
    auto RunSignatureHelp = [&] {
      if (TemplateTypeTy.isInvalid())
        return QualType();
      QualType PreferredType =
          Actions.CodeCompletion().ProduceCtorInitMemberSignatureHelp(
              ConstructorDecl, SS, TemplateTypeTy.get(), ArgExprs, II,
              T.getOpenLocation(), /*Braced=*/false);
      CalledSignatureHelp = true;
      return PreferredType;
    };
    if (Tok.isNot(tok::r_paren) && ParseExpressionList(ArgExprs, [&] {
          PreferredType.enterFunctionArgument(Tok.getLocation(),
                                              RunSignatureHelp);
        })) {
      if (PP.isCodeCompletionReached() && !CalledSignatureHelp)
        RunSignatureHelp();
      SkipUntil(tok::r_paren, StopAtSemi);
      return true;
    }

    T.consumeClose();

    SourceLocation EllipsisLoc;
    TryConsumeToken(tok::ellipsis, EllipsisLoc);

    if (TemplateTypeTy.isInvalid())
      return true;
    return Actions.ActOnMemInitializer(
        ConstructorDecl, getCurScope(), SS, II, TemplateTypeTy.get(), DS, IdLoc,
        T.getOpenLocation(), ArgExprs, T.getCloseLocation(), EllipsisLoc);
  }

  if (TemplateTypeTy.isInvalid())
    return true;

  if (getLangOpts().CPlusPlus11)
    return Diag(Tok, diag::err_expected_either) << tok::l_paren << tok::l_brace;
  else
    return Diag(Tok, diag::err_expected) << tok::l_paren;
}

/// Parse a C++ exception-specification if present (C++0x [except.spec]).
///
///       exception-specification:
///         dynamic-exception-specification
///         noexcept-specification
///
///       noexcept-specification:
///         'noexcept'
///         'noexcept' '(' constant-expression ')'
ExceptionSpecificationType Parser::tryParseExceptionSpecification(
    bool Delayed, SourceRange &SpecificationRange,
    SmallVectorImpl<ParsedType> &DynamicExceptions,
    SmallVectorImpl<SourceRange> &DynamicExceptionRanges,
    ExprResult &NoexceptExpr, CachedTokens *&ExceptionSpecTokens) {
  ExceptionSpecificationType Result = EST_None;
  ExceptionSpecTokens = nullptr;

  // Handle delayed parsing of exception-specifications.
  if (Delayed) {
    if (Tok.isNot(tok::kw_throw) && Tok.isNot(tok::kw_noexcept))
      return EST_None;

    // Consume and cache the starting token.
    bool IsNoexcept = Tok.is(tok::kw_noexcept);
    Token StartTok = Tok;
    SpecificationRange = SourceRange(ConsumeToken());

    // Check for a '('.
    if (!Tok.is(tok::l_paren)) {
      // If this is a bare 'noexcept', we're done.
      if (IsNoexcept) {
        Diag(Tok, diag::warn_cxx98_compat_noexcept_decl);
        NoexceptExpr = nullptr;
        return EST_BasicNoexcept;
      }

      Diag(Tok, diag::err_expected_lparen_after) << "throw";
      return EST_DynamicNone;
    }

    // Cache the tokens for the exception-specification.
    ExceptionSpecTokens = new CachedTokens;
    ExceptionSpecTokens->push_back(StartTok);  // 'throw' or 'noexcept'
    ExceptionSpecTokens->push_back(Tok);       // '('
    SpecificationRange.setEnd(ConsumeParen()); // '('

    ConsumeAndStoreUntil(tok::r_paren, *ExceptionSpecTokens,
                         /*StopAtSemi=*/true,
                         /*ConsumeFinalToken=*/true);
    SpecificationRange.setEnd(ExceptionSpecTokens->back().getLocation());

    return EST_Unparsed;
  }

  // See if there's a dynamic specification.
  if (Tok.is(tok::kw_throw)) {
    Result = ParseDynamicExceptionSpecification(
        SpecificationRange, DynamicExceptions, DynamicExceptionRanges);
    assert(DynamicExceptions.size() == DynamicExceptionRanges.size() &&
           "Produced different number of exception types and ranges.");
  }

  // If there's no noexcept specification, we're done.
  if (Tok.isNot(tok::kw_noexcept))
    return Result;

  Diag(Tok, diag::warn_cxx98_compat_noexcept_decl);

  // If we already had a dynamic specification, parse the noexcept for,
  // recovery, but emit a diagnostic and don't store the results.
  SourceRange NoexceptRange;
  ExceptionSpecificationType NoexceptType = EST_None;

  SourceLocation KeywordLoc = ConsumeToken();
  if (Tok.is(tok::l_paren)) {
    // There is an argument.
    BalancedDelimiterTracker T(*this, tok::l_paren);
    T.consumeOpen();

    EnterExpressionEvaluationContext ConstantEvaluated(
        Actions, Sema::ExpressionEvaluationContext::ConstantEvaluated);
    NoexceptExpr = ParseConstantExpressionInExprEvalContext();

    T.consumeClose();
    if (!NoexceptExpr.isInvalid()) {
      NoexceptExpr =
          Actions.ActOnNoexceptSpec(NoexceptExpr.get(), NoexceptType);
      NoexceptRange = SourceRange(KeywordLoc, T.getCloseLocation());
    } else {
      NoexceptType = EST_BasicNoexcept;
    }
  } else {
    // There is no argument.
    NoexceptType = EST_BasicNoexcept;
    NoexceptRange = SourceRange(KeywordLoc, KeywordLoc);
  }

  if (Result == EST_None) {
    SpecificationRange = NoexceptRange;
    Result = NoexceptType;

    // If there's a dynamic specification after a noexcept specification,
    // parse that and ignore the results.
    if (Tok.is(tok::kw_throw)) {
      Diag(Tok.getLocation(), diag::err_dynamic_and_noexcept_specification);
      ParseDynamicExceptionSpecification(NoexceptRange, DynamicExceptions,
                                         DynamicExceptionRanges);
    }
  } else {
    Diag(Tok.getLocation(), diag::err_dynamic_and_noexcept_specification);
  }

  return Result;
}

static void diagnoseDynamicExceptionSpecification(Parser &P, SourceRange Range,
                                                  bool IsNoexcept) {
  if (P.getLangOpts().CPlusPlus11) {
    const char *Replacement = IsNoexcept ? "noexcept" : "noexcept(false)";
    P.Diag(Range.getBegin(), P.getLangOpts().CPlusPlus17 && !IsNoexcept
                                 ? diag::ext_dynamic_exception_spec
                                 : diag::warn_exception_spec_deprecated)
        << Range;
    P.Diag(Range.getBegin(), diag::note_exception_spec_deprecated)
        << Replacement << FixItHint::CreateReplacement(Range, Replacement);
  }
}

/// ParseDynamicExceptionSpecification - Parse a C++
/// dynamic-exception-specification (C++ [except.spec]).
///
///       dynamic-exception-specification:
///         'throw' '(' type-id-list [opt] ')'
/// [MS]    'throw' '(' '...' ')'
///
///       type-id-list:
///         type-id ... [opt]
///         type-id-list ',' type-id ... [opt]
///
ExceptionSpecificationType Parser::ParseDynamicExceptionSpecification(
    SourceRange &SpecificationRange, SmallVectorImpl<ParsedType> &Exceptions,
    SmallVectorImpl<SourceRange> &Ranges) {
  assert(Tok.is(tok::kw_throw) && "expected throw");

  SpecificationRange.setBegin(ConsumeToken());
  BalancedDelimiterTracker T(*this, tok::l_paren);
  if (T.consumeOpen()) {
    Diag(Tok, diag::err_expected_lparen_after) << "throw";
    SpecificationRange.setEnd(SpecificationRange.getBegin());
    return EST_DynamicNone;
  }

  // Parse throw(...), a Microsoft extension that means "this function
  // can throw anything".
  if (Tok.is(tok::ellipsis)) {
    SourceLocation EllipsisLoc = ConsumeToken();
    if (!getLangOpts().MicrosoftExt)
      Diag(EllipsisLoc, diag::ext_ellipsis_exception_spec);
    T.consumeClose();
    SpecificationRange.setEnd(T.getCloseLocation());
    diagnoseDynamicExceptionSpecification(*this, SpecificationRange, false);
    return EST_MSAny;
  }

  // Parse the sequence of type-ids.
  SourceRange Range;
  while (Tok.isNot(tok::r_paren)) {
    TypeResult Res(ParseTypeName(&Range));

    if (Tok.is(tok::ellipsis)) {
      // C++0x [temp.variadic]p5:
      //   - In a dynamic-exception-specification (15.4); the pattern is a
      //     type-id.
      SourceLocation Ellipsis = ConsumeToken();
      Range.setEnd(Ellipsis);
      if (!Res.isInvalid())
        Res = Actions.ActOnPackExpansion(Res.get(), Ellipsis);
    }

    if (!Res.isInvalid()) {
      Exceptions.push_back(Res.get());
      Ranges.push_back(Range);
    }

    if (!TryConsumeToken(tok::comma))
      break;
  }

  T.consumeClose();
  SpecificationRange.setEnd(T.getCloseLocation());
  diagnoseDynamicExceptionSpecification(*this, SpecificationRange,
                                        Exceptions.empty());
  return Exceptions.empty() ? EST_DynamicNone : EST_Dynamic;
}

/// ParseTrailingReturnType - Parse a trailing return type on a new-style
/// function declaration.
TypeResult Parser::ParseTrailingReturnType(SourceRange &Range,
                                           bool MayBeFollowedByDirectInit) {
  assert(Tok.is(tok::arrow) && "expected arrow");

  ConsumeToken();

  return ParseTypeName(&Range, MayBeFollowedByDirectInit
                                   ? DeclaratorContext::TrailingReturnVar
                                   : DeclaratorContext::TrailingReturn);
}

/// Parse a requires-clause as part of a function declaration.
void Parser::ParseTrailingRequiresClause(Declarator &D) {
  assert(Tok.is(tok::kw_requires) && "expected requires");

  SourceLocation RequiresKWLoc = ConsumeToken();

  // C++23 [basic.scope.namespace]p1:
  //   For each non-friend redeclaration or specialization whose target scope
  //   is or is contained by the scope, the portion after the declarator-id,
  //   class-head-name, or enum-head-name is also included in the scope.
  // C++23 [basic.scope.class]p1:
  //   For each non-friend redeclaration or specialization whose target scope
  //   is or is contained by the scope, the portion after the declarator-id,
  //   class-head-name, or enum-head-name is also included in the scope.
  //
  // FIXME: We should really be calling ParseTrailingRequiresClause in
  // ParseDirectDeclarator, when we are already in the declarator scope.
  // This would also correctly suppress access checks for specializations
  // and explicit instantiations, which we currently do not do.
  CXXScopeSpec &SS = D.getCXXScopeSpec();
  DeclaratorScopeObj DeclScopeObj(*this, SS);
  if (SS.isValid() && Actions.ShouldEnterDeclaratorScope(getCurScope(), SS))
    DeclScopeObj.EnterDeclaratorScope();

  ExprResult TrailingRequiresClause;
  ParseScope ParamScope(this, Scope::DeclScope |
                                  Scope::FunctionDeclarationScope |
                                  Scope::FunctionPrototypeScope);

  Actions.ActOnStartTrailingRequiresClause(getCurScope(), D);

  std::optional<Sema::CXXThisScopeRAII> ThisScope;
  InitCXXThisScopeForDeclaratorIfRelevant(D, D.getDeclSpec(), ThisScope);

  TrailingRequiresClause =
      ParseConstraintLogicalOrExpression(/*IsTrailingRequiresClause=*/true);

  TrailingRequiresClause =
      Actions.ActOnFinishTrailingRequiresClause(TrailingRequiresClause);

  if (!D.isDeclarationOfFunction()) {
    Diag(RequiresKWLoc,
         diag::err_requires_clause_on_declarator_not_declaring_a_function);
    return;
  }

  if (TrailingRequiresClause.isInvalid())
    SkipUntil({tok::l_brace, tok::arrow, tok::kw_try, tok::comma, tok::colon},
              StopAtSemi | StopBeforeMatch);
  else
    D.setTrailingRequiresClause(TrailingRequiresClause.get());

  // Did the user swap the trailing return type and requires clause?
  if (D.isFunctionDeclarator() && Tok.is(tok::arrow) &&
      D.getDeclSpec().getTypeSpecType() == TST_auto) {
    SourceLocation ArrowLoc = Tok.getLocation();
    SourceRange Range;
    TypeResult TrailingReturnType =
        ParseTrailingReturnType(Range, /*MayBeFollowedByDirectInit=*/false);

    if (!TrailingReturnType.isInvalid()) {
      Diag(ArrowLoc,
           diag::err_requires_clause_must_appear_after_trailing_return)
          << Range;
      auto &FunctionChunk = D.getFunctionTypeInfo();
      FunctionChunk.HasTrailingReturnType = TrailingReturnType.isUsable();
      FunctionChunk.TrailingReturnType = TrailingReturnType.get();
      FunctionChunk.TrailingReturnTypeLoc = Range.getBegin();
    } else
      SkipUntil({tok::equal, tok::l_brace, tok::arrow, tok::kw_try, tok::comma},
                StopAtSemi | StopBeforeMatch);
  }
}

/// We have just started parsing the definition of a new class,
/// so push that class onto our stack of classes that is currently
/// being parsed.
Sema::ParsingClassState Parser::PushParsingClass(Decl *ClassDecl,
                                                 bool NonNestedClass,
                                                 bool IsInterface) {
  assert((NonNestedClass || !ClassStack.empty()) &&
         "Nested class without outer class");
  ClassStack.push(new ParsingClass(ClassDecl, NonNestedClass, IsInterface));
  return Actions.PushParsingClass();
}

/// Deallocate the given parsed class and all of its nested
/// classes.
void Parser::DeallocateParsedClasses(Parser::ParsingClass *Class) {
  for (unsigned I = 0, N = Class->LateParsedDeclarations.size(); I != N; ++I)
    delete Class->LateParsedDeclarations[I];
  delete Class;
}

/// Pop the top class of the stack of classes that are
/// currently being parsed.
///
/// This routine should be called when we have finished parsing the
/// definition of a class, but have not yet popped the Scope
/// associated with the class's definition.
void Parser::PopParsingClass(Sema::ParsingClassState state) {
  assert(!ClassStack.empty() && "Mismatched push/pop for class parsing");

  Actions.PopParsingClass(state);

  ParsingClass *Victim = ClassStack.top();
  ClassStack.pop();
  if (Victim->TopLevelClass) {
    // Deallocate all of the nested classes of this class,
    // recursively: we don't need to keep any of this information.
    DeallocateParsedClasses(Victim);
    return;
  }
  assert(!ClassStack.empty() && "Missing top-level class?");

  if (Victim->LateParsedDeclarations.empty()) {
    // The victim is a nested class, but we will not need to perform
    // any processing after the definition of this class since it has
    // no members whose handling was delayed. Therefore, we can just
    // remove this nested class.
    DeallocateParsedClasses(Victim);
    return;
  }

  // This nested class has some members that will need to be processed
  // after the top-level class is completely defined. Therefore, add
  // it to the list of nested classes within its parent.
  assert(getCurScope()->isClassScope() &&
         "Nested class outside of class scope?");
  ClassStack.top()->LateParsedDeclarations.push_back(
      new LateParsedClass(this, Victim));
}

/// Try to parse an 'identifier' which appears within an attribute-token.
///
/// \return the parsed identifier on success, and 0 if the next token is not an
/// attribute-token.
///
/// C++11 [dcl.attr.grammar]p3:
///   If a keyword or an alternative token that satisfies the syntactic
///   requirements of an identifier is contained in an attribute-token,
///   it is considered an identifier.
IdentifierInfo *Parser::TryParseCXX11AttributeIdentifier(
    SourceLocation &Loc, SemaCodeCompletion::AttributeCompletion Completion,
    const IdentifierInfo *Scope) {
  switch (Tok.getKind()) {
  default:
    // Identifiers and keywords have identifier info attached.
    if (!Tok.isAnnotation()) {
      if (IdentifierInfo *II = Tok.getIdentifierInfo()) {
        Loc = ConsumeToken();
        return II;
      }
    }
    return nullptr;

  case tok::code_completion:
    cutOffParsing();
    Actions.CodeCompletion().CodeCompleteAttribute(
        getLangOpts().CPlusPlus ? ParsedAttr::AS_CXX11 : ParsedAttr::AS_C23,
        Completion, Scope);
    return nullptr;

  case tok::numeric_constant: {
    // If we got a numeric constant, check to see if it comes from a macro that
    // corresponds to the predefined __clang__ macro. If it does, warn the user
    // and recover by pretending they said _Clang instead.
    if (Tok.getLocation().isMacroID()) {
      SmallString<8> ExpansionBuf;
      SourceLocation ExpansionLoc =
          PP.getSourceManager().getExpansionLoc(Tok.getLocation());
      StringRef Spelling = PP.getSpelling(ExpansionLoc, ExpansionBuf);
      if (Spelling == "__clang__") {
        SourceRange TokRange(
            ExpansionLoc,
            PP.getSourceManager().getExpansionLoc(Tok.getEndLoc()));
        Diag(Tok, diag::warn_wrong_clang_attr_namespace)
            << FixItHint::CreateReplacement(TokRange, "_Clang");
        Loc = ConsumeToken();
        return &PP.getIdentifierTable().get("_Clang");
      }
    }
    return nullptr;
  }

  case tok::ampamp:       // 'and'
  case tok::pipe:         // 'bitor'
  case tok::pipepipe:     // 'or'
  case tok::caret:        // 'xor'
  case tok::tilde:        // 'compl'
  case tok::amp:          // 'bitand'
  case tok::ampequal:     // 'and_eq'
  case tok::pipeequal:    // 'or_eq'
  case tok::caretequal:   // 'xor_eq'
  case tok::exclaim:      // 'not'
  case tok::exclaimequal: // 'not_eq'
    // Alternative tokens do not have identifier info, but their spelling
    // starts with an alphabetical character.
    SmallString<8> SpellingBuf;
    SourceLocation SpellingLoc =
        PP.getSourceManager().getSpellingLoc(Tok.getLocation());
    StringRef Spelling = PP.getSpelling(SpellingLoc, SpellingBuf);
    if (isLetter(Spelling[0])) {
      Loc = ConsumeToken();
      return &PP.getIdentifierTable().get(Spelling);
    }
    return nullptr;
  }
}

void Parser::ParseOpenMPAttributeArgs(const IdentifierInfo *AttrName,
                                      CachedTokens &OpenMPTokens) {
  // Both 'sequence' and 'directive' attributes require arguments, so parse the
  // open paren for the argument list.
  BalancedDelimiterTracker T(*this, tok::l_paren);
  if (T.consumeOpen()) {
    Diag(Tok, diag::err_expected) << tok::l_paren;
    return;
  }

  if (AttrName->isStr("directive")) {
    // If the attribute is named `directive`, we can consume its argument list
    // and push the tokens from it into the cached token stream for a new OpenMP
    // pragma directive.
    Token OMPBeginTok;
    OMPBeginTok.startToken();
    OMPBeginTok.setKind(tok::annot_attr_openmp);
    OMPBeginTok.setLocation(Tok.getLocation());
    OpenMPTokens.push_back(OMPBeginTok);

    ConsumeAndStoreUntil(tok::r_paren, OpenMPTokens, /*StopAtSemi=*/false,
                         /*ConsumeFinalToken*/ false);
    Token OMPEndTok;
    OMPEndTok.startToken();
    OMPEndTok.setKind(tok::annot_pragma_openmp_end);
    OMPEndTok.setLocation(Tok.getLocation());
    OpenMPTokens.push_back(OMPEndTok);
  } else {
    assert(AttrName->isStr("sequence") &&
           "Expected either 'directive' or 'sequence'");
    // If the attribute is named 'sequence', its argument is a list of one or
    // more OpenMP attributes (either 'omp::directive' or 'omp::sequence',
    // where the 'omp::' is optional).
    do {
      // We expect to see one of the following:
      //  * An identifier (omp) for the attribute namespace followed by ::
      //  * An identifier (directive) or an identifier (sequence).
      SourceLocation IdentLoc;
      const IdentifierInfo *Ident = TryParseCXX11AttributeIdentifier(IdentLoc);

      // If there is an identifier and it is 'omp', a double colon is required
      // followed by the actual identifier we're after.
      if (Ident && Ident->isStr("omp") && !ExpectAndConsume(tok::coloncolon))
        Ident = TryParseCXX11AttributeIdentifier(IdentLoc);

      // If we failed to find an identifier (scoped or otherwise), or we found
      // an unexpected identifier, diagnose.
      if (!Ident || (!Ident->isStr("directive") && !Ident->isStr("sequence"))) {
        Diag(Tok.getLocation(), diag::err_expected_sequence_or_directive);
        SkipUntil(tok::r_paren, StopBeforeMatch);
        continue;
      }
      // We read an identifier. If the identifier is one of the ones we
      // expected, we can recurse to parse the args.
      ParseOpenMPAttributeArgs(Ident, OpenMPTokens);

      // There may be a comma to signal that we expect another directive in the
      // sequence.
    } while (TryConsumeToken(tok::comma));
  }
  // Parse the closing paren for the argument list.
  T.consumeClose();
}

static bool IsBuiltInOrStandardCXX11Attribute(IdentifierInfo *AttrName,
                                              IdentifierInfo *ScopeName) {
  switch (
      ParsedAttr::getParsedKind(AttrName, ScopeName, ParsedAttr::AS_CXX11)) {
  case ParsedAttr::AT_CarriesDependency:
  case ParsedAttr::AT_Deprecated:
  case ParsedAttr::AT_FallThrough:
  case ParsedAttr::AT_CXX11NoReturn:
  case ParsedAttr::AT_NoUniqueAddress:
  case ParsedAttr::AT_Likely:
  case ParsedAttr::AT_Unlikely:
    return true;
  case ParsedAttr::AT_WarnUnusedResult:
    return !ScopeName && AttrName->getName() == "nodiscard";
  case ParsedAttr::AT_Unused:
    return !ScopeName && AttrName->getName() == "maybe_unused";
  default:
    return false;
  }
}

/// Parse the argument to C++23's [[assume()]] attribute.
bool Parser::ParseCXXAssumeAttributeArg(ParsedAttributes &Attrs,
                                        IdentifierInfo *AttrName,
                                        SourceLocation AttrNameLoc,
                                        SourceLocation *EndLoc,
                                        ParsedAttr::Form Form) {
  assert(Tok.is(tok::l_paren) && "Not a C++11 attribute argument list");
  BalancedDelimiterTracker T(*this, tok::l_paren);
  T.consumeOpen();

  // [dcl.attr.assume]: The expression is potentially evaluated.
  EnterExpressionEvaluationContext Unevaluated(
      Actions, Sema::ExpressionEvaluationContext::PotentiallyEvaluated);

  TentativeParsingAction TPA(*this);
  ExprResult Res(
      Actions.CorrectDelayedTyposInExpr(ParseConditionalExpression()));
  if (Res.isInvalid()) {
    TPA.Commit();
    SkipUntil(tok::r_paren, tok::r_square, StopAtSemi | StopBeforeMatch);
    if (Tok.is(tok::r_paren))
      T.consumeClose();
    return true;
  }

  if (!Tok.isOneOf(tok::r_paren, tok::r_square)) {
    // Emit a better diagnostic if this is an otherwise valid expression that
    // is not allowed here.
    TPA.Revert();
    Res = ParseExpression();
    if (!Res.isInvalid()) {
      auto *E = Res.get();
      Diag(E->getExprLoc(), diag::err_assume_attr_expects_cond_expr)
          << AttrName << FixItHint::CreateInsertion(E->getBeginLoc(), "(")
          << FixItHint::CreateInsertion(PP.getLocForEndOfToken(E->getEndLoc()),
                                        ")")
          << E->getSourceRange();
    }

    T.consumeClose();
    return true;
  }

  TPA.Commit();
  ArgsUnion Assumption = Res.get();
  auto RParen = Tok.getLocation();
  T.consumeClose();
  Attrs.addNew(AttrName, SourceRange(AttrNameLoc, RParen), nullptr,
               SourceLocation(), &Assumption, 1, Form);

  if (EndLoc)
    *EndLoc = RParen;

  return false;
}

/// ParseCXX11AttributeArgs -- Parse a C++11 attribute-argument-clause.
///
/// [C++11] attribute-argument-clause:
///         '(' balanced-token-seq ')'
///
/// [C++11] balanced-token-seq:
///         balanced-token
///         balanced-token-seq balanced-token
///
/// [C++11] balanced-token:
///         '(' balanced-token-seq ')'
///         '[' balanced-token-seq ']'
///         '{' balanced-token-seq '}'
///         any token but '(', ')', '[', ']', '{', or '}'
bool Parser::ParseCXX11AttributeArgs(
    IdentifierInfo *AttrName, SourceLocation AttrNameLoc,
    ParsedAttributes &Attrs, SourceLocation *EndLoc, IdentifierInfo *ScopeName,
    SourceLocation ScopeLoc, CachedTokens &OpenMPTokens) {
  assert(Tok.is(tok::l_paren) && "Not a C++11 attribute argument list");
  SourceLocation LParenLoc = Tok.getLocation();
  const LangOptions &LO = getLangOpts();
  ParsedAttr::Form Form =
      LO.CPlusPlus ? ParsedAttr::Form::CXX11() : ParsedAttr::Form::C23();

  // Try parsing microsoft attributes
  if (getLangOpts().MicrosoftExt || getLangOpts().HLSL) {
    if (hasAttribute(AttributeCommonInfo::Syntax::AS_Microsoft, ScopeName,
                     AttrName, getTargetInfo(), getLangOpts()))
      Form = ParsedAttr::Form::Microsoft();
  }

  // If the attribute isn't known, we will not attempt to parse any
  // arguments.
  if (Form.getSyntax() != ParsedAttr::AS_Microsoft &&
      !hasAttribute(LO.CPlusPlus ? AttributeCommonInfo::Syntax::AS_CXX11
                                 : AttributeCommonInfo::Syntax::AS_C23,
                    ScopeName, AttrName, getTargetInfo(), getLangOpts())) {
    // Eat the left paren, then skip to the ending right paren.
    ConsumeParen();
    SkipUntil(tok::r_paren);
    return false;
  }

  if (ScopeName && (ScopeName->isStr("gnu") || ScopeName->isStr("__gnu__"))) {
    // GNU-scoped attributes have some special cases to handle GNU-specific
    // behaviors.
    ParseGNUAttributeArgs(AttrName, AttrNameLoc, Attrs, EndLoc, ScopeName,
                          ScopeLoc, Form, nullptr);
    return true;
  }

  // [[omp::directive]] and [[omp::sequence]] need special handling.
  if (ScopeName && ScopeName->isStr("omp") &&
      (AttrName->isStr("directive") || AttrName->isStr("sequence"))) {
    Diag(AttrNameLoc, getLangOpts().OpenMP >= 51
                          ? diag::warn_omp51_compat_attributes
                          : diag::ext_omp_attributes);

    ParseOpenMPAttributeArgs(AttrName, OpenMPTokens);

    // We claim that an attribute was parsed and added so that one is not
    // created for us by the caller.
    return true;
  }

  unsigned NumArgs;
  // Some Clang-scoped attributes have some special parsing behavior.
  if (ScopeName && (ScopeName->isStr("clang") || ScopeName->isStr("_Clang")))
    NumArgs = ParseClangAttributeArgs(AttrName, AttrNameLoc, Attrs, EndLoc,
                                      ScopeName, ScopeLoc, Form);
  // So does C++23's assume() attribute.
  else if (!ScopeName && AttrName->isStr("assume")) {
    if (ParseCXXAssumeAttributeArg(Attrs, AttrName, AttrNameLoc, EndLoc, Form))
      return true;
    NumArgs = 1;
  } else
    NumArgs = ParseAttributeArgsCommon(AttrName, AttrNameLoc, Attrs, EndLoc,
                                       ScopeName, ScopeLoc, Form);

  if (!Attrs.empty() &&
      IsBuiltInOrStandardCXX11Attribute(AttrName, ScopeName)) {
    ParsedAttr &Attr = Attrs.back();

    // Ignore attributes that don't exist for the target.
    if (!Attr.existsInTarget(getTargetInfo())) {
      Diag(LParenLoc, diag::warn_unknown_attribute_ignored) << AttrName;
      Attr.setInvalid(true);
      return true;
    }

    // If the attribute is a standard or built-in attribute and we are
    // parsing an argument list, we need to determine whether this attribute
    // was allowed to have an argument list (such as [[deprecated]]), and how
    // many arguments were parsed (so we can diagnose on [[deprecated()]]).
    if (Attr.getMaxArgs() && !NumArgs) {
      // The attribute was allowed to have arguments, but none were provided
      // even though the attribute parsed successfully. This is an error.
      Diag(LParenLoc, diag::err_attribute_requires_arguments) << AttrName;
      Attr.setInvalid(true);
    } else if (!Attr.getMaxArgs()) {
      // The attribute parsed successfully, but was not allowed to have any
      // arguments. It doesn't matter whether any were provided -- the
      // presence of the argument list (even if empty) is diagnosed.
      Diag(LParenLoc, diag::err_cxx11_attribute_forbids_arguments)
          << AttrName
          << FixItHint::CreateRemoval(SourceRange(LParenLoc, *EndLoc));
      Attr.setInvalid(true);
    }
  }
  return true;
}

/// Parse a C++11 or C23 attribute-specifier.
///
/// [C++11] attribute-specifier:
///         '[' '[' attribute-list ']' ']'
///         alignment-specifier
///
/// [C++11] attribute-list:
///         attribute[opt]
///         attribute-list ',' attribute[opt]
///         attribute '...'
///         attribute-list ',' attribute '...'
///
/// [C++11] attribute:
///         attribute-token attribute-argument-clause[opt]
///
/// [C++11] attribute-token:
///         identifier
///         attribute-scoped-token
///
/// [C++11] attribute-scoped-token:
///         attribute-namespace '::' identifier
///
/// [C++11] attribute-namespace:
///         identifier
void Parser::ParseCXX11AttributeSpecifierInternal(ParsedAttributes &Attrs,
                                                  CachedTokens &OpenMPTokens,
                                                  SourceLocation *EndLoc) {
  if (Tok.is(tok::kw_alignas)) {
    // alignas is a valid token in C23 but it is not an attribute, it's a type-
    // specifier-qualifier, which means it has different parsing behavior. We
    // handle this in ParseDeclarationSpecifiers() instead of here in C. We
    // should not get here for C any longer.
    assert(getLangOpts().CPlusPlus && "'alignas' is not an attribute in C");
    Diag(Tok.getLocation(), diag::warn_cxx98_compat_alignas);
    ParseAlignmentSpecifier(Attrs, EndLoc);
    return;
  }

  if (Tok.isRegularKeywordAttribute()) {
    SourceLocation Loc = Tok.getLocation();
    IdentifierInfo *AttrName = Tok.getIdentifierInfo();
    ParsedAttr::Form Form = ParsedAttr::Form(Tok.getKind());
    bool TakesArgs = doesKeywordAttributeTakeArgs(Tok.getKind());
    ConsumeToken();
    if (TakesArgs) {
      if (!Tok.is(tok::l_paren))
        Diag(Tok.getLocation(), diag::err_expected_lparen_after) << AttrName;
      else
        ParseAttributeArgsCommon(AttrName, Loc, Attrs, EndLoc,
                                 /*ScopeName*/ nullptr,
                                 /*ScopeLoc*/ Loc, Form);
    } else
      Attrs.addNew(AttrName, Loc, nullptr, Loc, nullptr, 0, Form);
    return;
  }

  assert(Tok.is(tok::l_square) && NextToken().is(tok::l_square) &&
         "Not a double square bracket attribute list");

  SourceLocation OpenLoc = Tok.getLocation();
  if (getLangOpts().CPlusPlus) {
    Diag(OpenLoc, getLangOpts().CPlusPlus11 ? diag::warn_cxx98_compat_attribute
                                            : diag::warn_ext_cxx11_attributes);
  } else {
    Diag(OpenLoc, getLangOpts().C23 ? diag::warn_pre_c23_compat_attributes
                                    : diag::warn_ext_c23_attributes);
  }

  ConsumeBracket();
  checkCompoundToken(OpenLoc, tok::l_square, CompoundToken::AttrBegin);
  ConsumeBracket();

  SourceLocation CommonScopeLoc;
  IdentifierInfo *CommonScopeName = nullptr;
  if (Tok.is(tok::kw_using)) {
    Diag(Tok.getLocation(), getLangOpts().CPlusPlus17
                                ? diag::warn_cxx14_compat_using_attribute_ns
                                : diag::ext_using_attribute_ns);
    ConsumeToken();

    CommonScopeName = TryParseCXX11AttributeIdentifier(
        CommonScopeLoc, SemaCodeCompletion::AttributeCompletion::Scope);
    if (!CommonScopeName) {
      Diag(Tok.getLocation(), diag::err_expected) << tok::identifier;
      SkipUntil(tok::r_square, tok::colon, StopBeforeMatch);
    }
    if (!TryConsumeToken(tok::colon) && CommonScopeName)
      Diag(Tok.getLocation(), diag::err_expected) << tok::colon;
  }

  bool AttrParsed = false;
  while (!Tok.isOneOf(tok::r_square, tok::semi, tok::eof)) {
    if (AttrParsed) {
      // If we parsed an attribute, a comma is required before parsing any
      // additional attributes.
      if (ExpectAndConsume(tok::comma)) {
        SkipUntil(tok::r_square, StopAtSemi | StopBeforeMatch);
        continue;
      }
      AttrParsed = false;
    }

    // Eat all remaining superfluous commas before parsing the next attribute.
    while (TryConsumeToken(tok::comma))
      ;

    SourceLocation ScopeLoc, AttrLoc;
    IdentifierInfo *ScopeName = nullptr, *AttrName = nullptr;

    AttrName = TryParseCXX11AttributeIdentifier(
        AttrLoc, SemaCodeCompletion::AttributeCompletion::Attribute,
        CommonScopeName);
    if (!AttrName)
      // Break out to the "expected ']'" diagnostic.
      break;

    // scoped attribute
    if (TryConsumeToken(tok::coloncolon)) {
      ScopeName = AttrName;
      ScopeLoc = AttrLoc;

      AttrName = TryParseCXX11AttributeIdentifier(
          AttrLoc, SemaCodeCompletion::AttributeCompletion::Attribute,
          ScopeName);
      if (!AttrName) {
        Diag(Tok.getLocation(), diag::err_expected) << tok::identifier;
        SkipUntil(tok::r_square, tok::comma, StopAtSemi | StopBeforeMatch);
        continue;
      }
    }

    if (CommonScopeName) {
      if (ScopeName) {
        Diag(ScopeLoc, diag::err_using_attribute_ns_conflict)
            << SourceRange(CommonScopeLoc);
      } else {
        ScopeName = CommonScopeName;
        ScopeLoc = CommonScopeLoc;
      }
    }

    // Parse attribute arguments
    if (Tok.is(tok::l_paren))
      AttrParsed = ParseCXX11AttributeArgs(AttrName, AttrLoc, Attrs, EndLoc,
                                           ScopeName, ScopeLoc, OpenMPTokens);

    if (!AttrParsed) {
      Attrs.addNew(
          AttrName,
          SourceRange(ScopeLoc.isValid() ? ScopeLoc : AttrLoc, AttrLoc),
          ScopeName, ScopeLoc, nullptr, 0,
          getLangOpts().CPlusPlus ? ParsedAttr::Form::CXX11()
                                  : ParsedAttr::Form::C23());
      AttrParsed = true;
    }

    if (TryConsumeToken(tok::ellipsis))
      Diag(Tok, diag::err_cxx11_attribute_forbids_ellipsis) << AttrName;
  }

  // If we hit an error and recovered by parsing up to a semicolon, eat the
  // semicolon and don't issue further diagnostics about missing brackets.
  if (Tok.is(tok::semi)) {
    ConsumeToken();
    return;
  }

  SourceLocation CloseLoc = Tok.getLocation();
  if (ExpectAndConsume(tok::r_square))
    SkipUntil(tok::r_square);
  else if (Tok.is(tok::r_square))
    checkCompoundToken(CloseLoc, tok::r_square, CompoundToken::AttrEnd);
  if (EndLoc)
    *EndLoc = Tok.getLocation();
  if (ExpectAndConsume(tok::r_square))
    SkipUntil(tok::r_square);
}

/// ParseCXX11Attributes - Parse a C++11 or C23 attribute-specifier-seq.
///
/// attribute-specifier-seq:
///       attribute-specifier-seq[opt] attribute-specifier
void Parser::ParseCXX11Attributes(ParsedAttributes &Attrs) {
  SourceLocation StartLoc = Tok.getLocation();
  SourceLocation EndLoc = StartLoc;

  do {
    ParseCXX11AttributeSpecifier(Attrs, &EndLoc);
  } while (isAllowedCXX11AttributeSpecifier());

  Attrs.Range = SourceRange(StartLoc, EndLoc);
}

void Parser::DiagnoseAndSkipCXX11Attributes() {
  auto Keyword =
      Tok.isRegularKeywordAttribute() ? Tok.getIdentifierInfo() : nullptr;
  // Start and end location of an attribute or an attribute list.
  SourceLocation StartLoc = Tok.getLocation();
  SourceLocation EndLoc = SkipCXX11Attributes();

  if (EndLoc.isValid()) {
    SourceRange Range(StartLoc, EndLoc);
    (Keyword ? Diag(StartLoc, diag::err_keyword_not_allowed) << Keyword
             : Diag(StartLoc, diag::err_attributes_not_allowed))
        << Range;
  }
}

SourceLocation Parser::SkipCXX11Attributes() {
  SourceLocation EndLoc;

  if (!isCXX11AttributeSpecifier())
    return EndLoc;

  do {
    if (Tok.is(tok::l_square)) {
      BalancedDelimiterTracker T(*this, tok::l_square);
      T.consumeOpen();
      T.skipToEnd();
      EndLoc = T.getCloseLocation();
    } else if (Tok.isRegularKeywordAttribute() &&
               !doesKeywordAttributeTakeArgs(Tok.getKind())) {
      EndLoc = Tok.getLocation();
      ConsumeToken();
    } else {
      assert((Tok.is(tok::kw_alignas) || Tok.isRegularKeywordAttribute()) &&
             "not an attribute specifier");
      ConsumeToken();
      BalancedDelimiterTracker T(*this, tok::l_paren);
      if (!T.consumeOpen())
        T.skipToEnd();
      EndLoc = T.getCloseLocation();
    }
  } while (isCXX11AttributeSpecifier());

  return EndLoc;
}

/// Parse uuid() attribute when it appears in a [] Microsoft attribute.
void Parser::ParseMicrosoftUuidAttributeArgs(ParsedAttributes &Attrs) {
  assert(Tok.is(tok::identifier) && "Not a Microsoft attribute list");
  IdentifierInfo *UuidIdent = Tok.getIdentifierInfo();
  assert(UuidIdent->getName() == "uuid" && "Not a Microsoft attribute list");

  SourceLocation UuidLoc = Tok.getLocation();
  ConsumeToken();

  // Ignore the left paren location for now.
  BalancedDelimiterTracker T(*this, tok::l_paren);
  if (T.consumeOpen()) {
    Diag(Tok, diag::err_expected) << tok::l_paren;
    return;
  }

  ArgsVector ArgExprs;
  if (isTokenStringLiteral()) {
    // Easy case: uuid("...") -- quoted string.
    ExprResult StringResult = ParseUnevaluatedStringLiteralExpression();
    if (StringResult.isInvalid())
      return;
    ArgExprs.push_back(StringResult.get());
  } else {
    // something like uuid({000000A0-0000-0000-C000-000000000049}) -- no
    // quotes in the parens. Just append the spelling of all tokens encountered
    // until the closing paren.

    SmallString<42> StrBuffer; // 2 "", 36 bytes UUID, 2 optional {}, 1 nul
    StrBuffer += "\"";

    // Since none of C++'s keywords match [a-f]+, accepting just tok::l_brace,
    // tok::r_brace, tok::minus, tok::identifier (think C000) and
    // tok::numeric_constant (0000) should be enough. But the spelling of the
    // uuid argument is checked later anyways, so there's no harm in accepting
    // almost anything here.
    // cl is very strict about whitespace in this form and errors out if any
    // is present, so check the space flags on the tokens.
    SourceLocation StartLoc = Tok.getLocation();
    while (Tok.isNot(tok::r_paren)) {
      if (Tok.hasLeadingSpace() || Tok.isAtStartOfLine()) {
        Diag(Tok, diag::err_attribute_uuid_malformed_guid);
        SkipUntil(tok::r_paren, StopAtSemi);
        return;
      }
      SmallString<16> SpellingBuffer;
      SpellingBuffer.resize(Tok.getLength() + 1);
      bool Invalid = false;
      StringRef TokSpelling = PP.getSpelling(Tok, SpellingBuffer, &Invalid);
      if (Invalid) {
        SkipUntil(tok::r_paren, StopAtSemi);
        return;
      }
      StrBuffer += TokSpelling;
      ConsumeAnyToken();
    }
    StrBuffer += "\"";

    if (Tok.hasLeadingSpace() || Tok.isAtStartOfLine()) {
      Diag(Tok, diag::err_attribute_uuid_malformed_guid);
      ConsumeParen();
      return;
    }

    // Pretend the user wrote the appropriate string literal here.
    // ActOnStringLiteral() copies the string data into the literal, so it's
    // ok that the Token points to StrBuffer.
    Token Toks[1];
    Toks[0].startToken();
    Toks[0].setKind(tok::string_literal);
    Toks[0].setLocation(StartLoc);
    Toks[0].setLiteralData(StrBuffer.data());
    Toks[0].setLength(StrBuffer.size());
    StringLiteral *UuidString =
        cast<StringLiteral>(Actions.ActOnUnevaluatedStringLiteral(Toks).get());
    ArgExprs.push_back(UuidString);
  }

  if (!T.consumeClose()) {
    Attrs.addNew(UuidIdent, SourceRange(UuidLoc, T.getCloseLocation()), nullptr,
                 SourceLocation(), ArgExprs.data(), ArgExprs.size(),
                 ParsedAttr::Form::Microsoft());
  }
}

/// ParseMicrosoftAttributes - Parse Microsoft attributes [Attr]
///
/// [MS] ms-attribute:
///             '[' token-seq ']'
///
/// [MS] ms-attribute-seq:
///             ms-attribute[opt]
///             ms-attribute ms-attribute-seq
void Parser::ParseMicrosoftAttributes(ParsedAttributes &Attrs) {
  assert(Tok.is(tok::l_square) && "Not a Microsoft attribute list");

  SourceLocation StartLoc = Tok.getLocation();
  SourceLocation EndLoc = StartLoc;
  do {
    // FIXME: If this is actually a C++11 attribute, parse it as one.
    BalancedDelimiterTracker T(*this, tok::l_square);
    T.consumeOpen();

    // Skip most ms attributes except for a specific list.
    while (true) {
      SkipUntil(tok::r_square, tok::identifier,
                StopAtSemi | StopBeforeMatch | StopAtCodeCompletion);
      if (Tok.is(tok::code_completion)) {
        cutOffParsing();
        Actions.CodeCompletion().CodeCompleteAttribute(
            AttributeCommonInfo::AS_Microsoft,
            SemaCodeCompletion::AttributeCompletion::Attribute,
            /*Scope=*/nullptr);
        break;
      }
      if (Tok.isNot(tok::identifier)) // ']', but also eof
        break;
      if (Tok.getIdentifierInfo()->getName() == "uuid")
        ParseMicrosoftUuidAttributeArgs(Attrs);
      else {
        IdentifierInfo *II = Tok.getIdentifierInfo();
        SourceLocation NameLoc = Tok.getLocation();
        ConsumeToken();
        ParsedAttr::Kind AttrKind =
            ParsedAttr::getParsedKind(II, nullptr, ParsedAttr::AS_Microsoft);
        // For HLSL we want to handle all attributes, but for MSVC compat, we
        // silently ignore unknown Microsoft attributes.
        if (getLangOpts().HLSL || AttrKind != ParsedAttr::UnknownAttribute) {
          bool AttrParsed = false;
          if (Tok.is(tok::l_paren)) {
            CachedTokens OpenMPTokens;
            AttrParsed =
                ParseCXX11AttributeArgs(II, NameLoc, Attrs, &EndLoc, nullptr,
                                        SourceLocation(), OpenMPTokens);
            ReplayOpenMPAttributeTokens(OpenMPTokens);
          }
          if (!AttrParsed) {
            Attrs.addNew(II, NameLoc, nullptr, SourceLocation(), nullptr, 0,
                         ParsedAttr::Form::Microsoft());
          }
        }
      }
    }

    T.consumeClose();
    EndLoc = T.getCloseLocation();
  } while (Tok.is(tok::l_square));

  Attrs.Range = SourceRange(StartLoc, EndLoc);
}

void Parser::ParseMicrosoftIfExistsClassDeclaration(
    DeclSpec::TST TagType, ParsedAttributes &AccessAttrs,
    AccessSpecifier &CurAS) {
  IfExistsCondition Result;
  if (ParseMicrosoftIfExistsCondition(Result))
    return;

  BalancedDelimiterTracker Braces(*this, tok::l_brace);
  if (Braces.consumeOpen()) {
    Diag(Tok, diag::err_expected) << tok::l_brace;
    return;
  }

  switch (Result.Behavior) {
  case IEB_Parse:
    // Parse the declarations below.
    break;

  case IEB_Dependent:
    Diag(Result.KeywordLoc, diag::warn_microsoft_dependent_exists)
        << Result.IsIfExists;
    // Fall through to skip.
    [[fallthrough]];

  case IEB_Skip:
    Braces.skipToEnd();
    return;
  }

  while (Tok.isNot(tok::r_brace) && !isEofOrEom()) {
    // __if_exists, __if_not_exists can nest.
    if (Tok.isOneOf(tok::kw___if_exists, tok::kw___if_not_exists)) {
      ParseMicrosoftIfExistsClassDeclaration(TagType, AccessAttrs, CurAS);
      continue;
    }

    // Check for extraneous top-level semicolon.
    if (Tok.is(tok::semi)) {
      ConsumeExtraSemi(InsideStruct, TagType);
      continue;
    }

    AccessSpecifier AS = getAccessSpecifierIfPresent();
    if (AS != AS_none) {
      // Current token is a C++ access specifier.
      CurAS = AS;
      SourceLocation ASLoc = Tok.getLocation();
      ConsumeToken();
      if (Tok.is(tok::colon))
        Actions.ActOnAccessSpecifier(AS, ASLoc, Tok.getLocation(),
                                     ParsedAttributesView{});
      else
        Diag(Tok, diag::err_expected) << tok::colon;
      ConsumeToken();
      continue;
    }

    ParsedTemplateInfo TemplateInfo;
    // Parse all the comma separated declarators.
    ParseCXXClassMemberDeclaration(CurAS, AccessAttrs, TemplateInfo);
  }

  Braces.consumeClose();
}