text: //===- Lexer.cpp - C Language Family Lexer --------------------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  //  This file implements the Lexer and Token interfaces.
  //
  //===----------------------------------------------------------------------===//
  
  #include "clang/Lex/Lexer.h"
  #include "UnicodeCharSets.h"
  #include "clang/Basic/CharInfo.h"
  #include "clang/Basic/IdentifierTable.h"
  #include "clang/Basic/LangOptions.h"
  #include "clang/Basic/SourceLocation.h"
  #include "clang/Basic/SourceManager.h"
  #include "clang/Basic/TokenKinds.h"
  #include "clang/Lex/LexDiagnostic.h"
  #include "clang/Lex/LiteralSupport.h"
  #include "clang/Lex/MultipleIncludeOpt.h"
  #include "clang/Lex/Preprocessor.h"
  #include "clang/Lex/PreprocessorOptions.h"
  #include "clang/Lex/Token.h"
  #include "clang/Basic/Diagnostic.h"
  #include "clang/Basic/LLVM.h"
  #include "clang/Basic/TokenKinds.h"
  #include "llvm/ADT/None.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/ADT/StringSwitch.h"
  #include "llvm/ADT/StringRef.h"
  #include "llvm/Support/Compiler.h"
  #include "llvm/Support/ConvertUTF.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/MemoryBuffer.h"
  #include "llvm/Support/NativeFormatting.h"
  #include "llvm/Support/UnicodeCharRanges.h"
  #include <algorithm>
  #include <cassert>
  #include <cstddef>
  #include <cstdint>
  #include <cstring>
  #include <string>
  #include <tuple>
  #include <utility>
  
  using namespace clang;
  
  //===----------------------------------------------------------------------===//
  // Token Class Implementation
  //===----------------------------------------------------------------------===//
  
  /// isObjCAtKeyword - Return true if we have an ObjC keyword identifier.
  bool Token::isObjCAtKeyword(tok::ObjCKeywordKind objcKey) const {
    if (isAnnotation())
      return false;
    if (IdentifierInfo *II = getIdentifierInfo())
      return II->getObjCKeywordID() == objcKey;
    return false;
  }
  
  /// getObjCKeywordID - Return the ObjC keyword kind.
  tok::ObjCKeywordKind Token::getObjCKeywordID() const {
    if (isAnnotation())
      return tok::objc_not_keyword;
    IdentifierInfo *specId = getIdentifierInfo();
    return specId ? specId->getObjCKeywordID() : tok::objc_not_keyword;
  }
  
  //===----------------------------------------------------------------------===//
  // Lexer Class Implementation
  //===----------------------------------------------------------------------===//
  
  void Lexer::anchor() {}
  
  void Lexer::InitLexer(const char *BufStart, const char *BufPtr,
                        const char *BufEnd) {
    BufferStart = BufStart;
    BufferPtr = BufPtr;
    BufferEnd = BufEnd;
  
    assert(BufEnd[0] == 0 &&
           "We assume that the input buffer has a null character at the end"
           " to simplify lexing!");
  
    // Check whether we have a BOM in the beginning of the buffer. If yes - act
    // accordingly. Right now we support only UTF-8 with and without BOM, so, just
    // skip the UTF-8 BOM if it's present.
    if (BufferStart == BufferPtr) {
      // Determine the size of the BOM.
      StringRef Buf(BufferStart, BufferEnd - BufferStart);
      size_t BOMLength = llvm::StringSwitch<size_t>(Buf)
        .StartsWith("\xEF\xBB\xBF", 3) // UTF-8 BOM
        .Default(0);
  
      // Skip the BOM.
      BufferPtr += BOMLength;
    }
  
    Is_PragmaLexer = false;
    CurrentConflictMarkerState = CMK_None;
  
    // Start of the file is a start of line.
    IsAtStartOfLine = true;
    IsAtPhysicalStartOfLine = true;
  
    HasLeadingSpace = false;
    HasLeadingEmptyMacro = false;
  
    // We are not after parsing a #.
    ParsingPreprocessorDirective = false;
  
    // We are not after parsing #include.
    ParsingFilename = false;
  
    // We are not in raw mode.  Raw mode disables diagnostics and interpretation
    // of tokens (e.g. identifiers, thus disabling macro expansion).  It is used
    // to quickly lex the tokens of the buffer, e.g. when handling a "#if 0" block
    // or otherwise skipping over tokens.
    LexingRawMode = false;
  
    // Default to not keeping comments.
    ExtendedTokenMode = 0;
  }
  
  /// Lexer constructor - Create a new lexer object for the specified buffer
  /// with the specified preprocessor managing the lexing process.  This lexer
  /// assumes that the associated file buffer and Preprocessor objects will
  /// outlive it, so it doesn't take ownership of either of them.
  Lexer::Lexer(FileID FID, const llvm::MemoryBuffer *InputFile, Preprocessor &PP)
      : PreprocessorLexer(&PP, FID),
        FileLoc(PP.getSourceManager().getLocForStartOfFile(FID)),
        LangOpts(PP.getLangOpts()) {
    InitLexer(InputFile->getBufferStart(), InputFile->getBufferStart(),
              InputFile->getBufferEnd());
  
    resetExtendedTokenMode();
  }
  
  /// Lexer constructor - Create a new raw lexer object.  This object is only
  /// suitable for calls to 'LexFromRawLexer'.  This lexer assumes that the text
  /// range will outlive it, so it doesn't take ownership of it.
  Lexer::Lexer(SourceLocation fileloc, const LangOptions &langOpts,
               const char *BufStart, const char *BufPtr, const char *BufEnd)
      : FileLoc(fileloc), LangOpts(langOpts) {
    InitLexer(BufStart, BufPtr, BufEnd);
  
    // We *are* in raw mode.
    LexingRawMode = true;
  }
  
  /// Lexer constructor - Create a new raw lexer object.  This object is only
  /// suitable for calls to 'LexFromRawLexer'.  This lexer assumes that the text
  /// range will outlive it, so it doesn't take ownership of it.
  Lexer::Lexer(FileID FID, const llvm::MemoryBuffer *FromFile,
               const SourceManager &SM, const LangOptions &langOpts)
      : Lexer(SM.getLocForStartOfFile(FID), langOpts, FromFile->getBufferStart(),
              FromFile->getBufferStart(), FromFile->getBufferEnd()) {}
  
  void Lexer::resetExtendedTokenMode() {
    assert(PP && "Cannot reset token mode without a preprocessor");
    if (LangOpts.TraditionalCPP)
      SetKeepWhitespaceMode(true);
    else
      SetCommentRetentionState(PP->getCommentRetentionState());
  }
  
  /// Create_PragmaLexer: Lexer constructor - Create a new lexer object for
  /// _Pragma expansion.  This has a variety of magic semantics that this method
  /// sets up.  It returns a new'd Lexer that must be delete'd when done.
  ///
  /// On entrance to this routine, TokStartLoc is a macro location which has a
  /// spelling loc that indicates the bytes to be lexed for the token and an
  /// expansion location that indicates where all lexed tokens should be
  /// "expanded from".
  ///
  /// TODO: It would really be nice to make _Pragma just be a wrapper around a
  /// normal lexer that remaps tokens as they fly by.  This would require making
  /// Preprocessor::Lex virtual.  Given that, we could just dump in a magic lexer
  /// interface that could handle this stuff.  This would pull GetMappedTokenLoc
  /// out of the critical path of the lexer!
  ///
  Lexer *Lexer::Create_PragmaLexer(SourceLocation SpellingLoc,
                                   SourceLocation ExpansionLocStart,
                                   SourceLocation ExpansionLocEnd,
                                   unsigned TokLen, Preprocessor &PP) {
    SourceManager &SM = PP.getSourceManager();
  
    // Create the lexer as if we were going to lex the file normally.
    FileID SpellingFID = SM.getFileID(SpellingLoc);
    const llvm::MemoryBuffer *InputFile = SM.getBuffer(SpellingFID);
    Lexer *L = new Lexer(SpellingFID, InputFile, PP);
  
    // Now that the lexer is created, change the start/end locations so that we
    // just lex the subsection of the file that we want.  This is lexing from a
    // scratch buffer.
    const char *StrData = SM.getCharacterData(SpellingLoc);
  
    L->BufferPtr = StrData;
    L->BufferEnd = StrData+TokLen;
    assert(L->BufferEnd[0] == 0 && "Buffer is not nul terminated!");
  
    // Set the SourceLocation with the remapping information.  This ensures that
    // GetMappedTokenLoc will remap the tokens as they are lexed.
    L->FileLoc = SM.createExpansionLoc(SM.getLocForStartOfFile(SpellingFID),
                                       ExpansionLocStart,
                                       ExpansionLocEnd, TokLen);
  
    // Ensure that the lexer thinks it is inside a directive, so that end \n will
    // return an EOD token.
    L->ParsingPreprocessorDirective = true;
  
    // This lexer really is for _Pragma.
    L->Is_PragmaLexer = true;
    return L;
  }
  
  template <typename T> static void StringifyImpl(T &Str, char Quote) {
    typename T::size_type i = 0, e = Str.size();
    while (i < e) {
      if (Str[i] == '\\' || Str[i] == Quote) {
        Str.insert(Str.begin() + i, '\\');
        i += 2;
        ++e;
      } else if (Str[i] == '\n' || Str[i] == '\r') {
        // Replace '\r\n' and '\n\r' to '\\' followed by 'n'.
        if ((i < e - 1) && (Str[i + 1] == '\n' || Str[i + 1] == '\r') &&
            Str[i] != Str[i + 1]) {
          Str[i] = '\\';
          Str[i + 1] = 'n';
        } else {
          // Replace '\n' and '\r' to '\\' followed by 'n'.
          Str[i] = '\\';
          Str.insert(Str.begin() + i + 1, 'n');
          ++e;
        }
        i += 2;
      } else
        ++i;
    }
  }
  
  std::string Lexer::Stringify(StringRef Str, bool Charify) {
    std::string Result = Str;
    char Quote = Charify ? '\'' : '"';
    StringifyImpl(Result, Quote);
    return Result;
  }
  
  void Lexer::Stringify(SmallVectorImpl<char> &Str) { StringifyImpl(Str, '"'); }
  
  //===----------------------------------------------------------------------===//
  // Token Spelling
  //===----------------------------------------------------------------------===//
  
  /// Slow case of getSpelling. Extract the characters comprising the
  /// spelling of this token from the provided input buffer.
  static size_t getSpellingSlow(const Token &Tok, const char *BufPtr,
                                const LangOptions &LangOpts, char *Spelling) {
    assert(Tok.needsCleaning() && "getSpellingSlow called on simple token");
  
    size_t Length = 0;
    const char *BufEnd = BufPtr + Tok.getLength();
  
    if (tok::isStringLiteral(Tok.getKind())) {
      // Munch the encoding-prefix and opening double-quote.
      while (BufPtr < BufEnd) {
        unsigned Size;
        Spelling[Length++] = Lexer::getCharAndSizeNoWarn(BufPtr, Size, LangOpts);
        BufPtr += Size;
  
        if (Spelling[Length - 1] == '"')
          break;
      }
  
      // Raw string literals need special handling; trigraph expansion and line
      // splicing do not occur within their d-char-sequence nor within their
      // r-char-sequence.
      if (Length >= 2 &&
          Spelling[Length - 2] == 'R' && Spelling[Length - 1] == '"') {
        // Search backwards from the end of the token to find the matching closing
        // quote.
        const char *RawEnd = BufEnd;
        do --RawEnd; while (*RawEnd != '"');
        size_t RawLength = RawEnd - BufPtr + 1;
  
        // Everything between the quotes is included verbatim in the spelling.
        memcpy(Spelling + Length, BufPtr, RawLength);
        Length += RawLength;
        BufPtr += RawLength;
  
        // The rest of the token is lexed normally.
      }
    }
  
    while (BufPtr < BufEnd) {
      unsigned Size;
      Spelling[Length++] = Lexer::getCharAndSizeNoWarn(BufPtr, Size, LangOpts);
      BufPtr += Size;
    }
  
    assert(Length < Tok.getLength() &&
           "NeedsCleaning flag set on token that didn't need cleaning!");
    return Length;
  }
  
  /// getSpelling() - Return the 'spelling' of this token.  The spelling of a
  /// token are the characters used to represent the token in the source file
  /// after trigraph expansion and escaped-newline folding.  In particular, this
  /// wants to get the true, uncanonicalized, spelling of things like digraphs
  /// UCNs, etc.
  StringRef Lexer::getSpelling(SourceLocation loc,
                               SmallVectorImpl<char> &buffer,
                               const SourceManager &SM,
                               const LangOptions &options,
                               bool *invalid) {
    // Break down the source location.
    std::pair<FileID, unsigned> locInfo = SM.getDecomposedLoc(loc);
  
    // Try to the load the file buffer.
    bool invalidTemp = false;
    StringRef file = SM.getBufferData(locInfo.first, &invalidTemp);
    if (invalidTemp) {
      if (invalid) *invalid = true;
      return {};
    }
  
    const char *tokenBegin = file.data() + locInfo.second;
  
    // Lex from the start of the given location.
    Lexer lexer(SM.getLocForStartOfFile(locInfo.first), options,
                file.begin(), tokenBegin, file.end());
    Token token;
    lexer.LexFromRawLexer(token);
  
    unsigned length = token.getLength();
  
    // Common case:  no need for cleaning.
    if (!token.needsCleaning())
      return StringRef(tokenBegin, length);
  
    // Hard case, we need to relex the characters into the string.
    buffer.resize(length);
    buffer.resize(getSpellingSlow(token, tokenBegin, options, buffer.data()));
    return StringRef(buffer.data(), buffer.size());
  }
  
  /// getSpelling() - Return the 'spelling' of this token.  The spelling of a
  /// token are the characters used to represent the token in the source file
  /// after trigraph expansion and escaped-newline folding.  In particular, this
  /// wants to get the true, uncanonicalized, spelling of things like digraphs
  /// UCNs, etc.
  std::string Lexer::getSpelling(const Token &Tok, const SourceManager &SourceMgr,
                                 const LangOptions &LangOpts, bool *Invalid) {
    assert((int)Tok.getLength() >= 0 && "Token character range is bogus!");
  
    bool CharDataInvalid = false;
    const char *TokStart = SourceMgr.getCharacterData(Tok.getLocation(),
                                                      &CharDataInvalid);
    if (Invalid)
      *Invalid = CharDataInvalid;
    if (CharDataInvalid)
      return {};
  
    // If this token contains nothing interesting, return it directly.
    if (!Tok.needsCleaning())
      return std::string(TokStart, TokStart + Tok.getLength());
  
    std::string Result;
    Result.resize(Tok.getLength());
    Result.resize(getSpellingSlow(Tok, TokStart, LangOpts, &*Result.begin()));
    return Result;
  }
  
  /// getSpelling - This method is used to get the spelling of a token into a
  /// preallocated buffer, instead of as an std::string.  The caller is required
  /// to allocate enough space for the token, which is guaranteed to be at least
  /// Tok.getLength() bytes long.  The actual length of the token is returned.
  ///
  /// Note that this method may do two possible things: it may either fill in
  /// the buffer specified with characters, or it may *change the input pointer*
  /// to point to a constant buffer with the data already in it (avoiding a
  /// copy).  The caller is not allowed to modify the returned buffer pointer
  /// if an internal buffer is returned.
  unsigned Lexer::getSpelling(const Token &Tok, const char *&Buffer,
                              const SourceManager &SourceMgr,
                              const LangOptions &LangOpts, bool *Invalid) {
    assert((int)Tok.getLength() >= 0 && "Token character range is bogus!");
  
    const char *TokStart = nullptr;
    // NOTE: this has to be checked *before* testing for an IdentifierInfo.
    if (Tok.is(tok::raw_identifier))
      TokStart = Tok.getRawIdentifier().data();
    else if (!Tok.hasUCN()) {
      if (const IdentifierInfo *II = Tok.getIdentifierInfo()) {
        // Just return the string from the identifier table, which is very quick.
        Buffer = II->getNameStart();
        return II->getLength();
      }
    }
  
    // NOTE: this can be checked even after testing for an IdentifierInfo.
    if (Tok.isLiteral())
      TokStart = Tok.getLiteralData();
  
    if (!TokStart) {
      // Compute the start of the token in the input lexer buffer.
      bool CharDataInvalid = false;
      TokStart = SourceMgr.getCharacterData(Tok.getLocation(), &CharDataInvalid);
      if (Invalid)
        *Invalid = CharDataInvalid;
      if (CharDataInvalid) {
        Buffer = "";
        return 0;
      }
    }
  
    // If this token contains nothing interesting, return it directly.
    if (!Tok.needsCleaning()) {
      Buffer = TokStart;
      return Tok.getLength();
    }
  
    // Otherwise, hard case, relex the characters into the string.
    return getSpellingSlow(Tok, TokStart, LangOpts, const_cast<char*>(Buffer));
  }
  
  /// MeasureTokenLength - Relex the token at the specified location and return
  /// its length in bytes in the input file.  If the token needs cleaning (e.g.
  /// includes a trigraph or an escaped newline) then this count includes bytes
  /// that are part of that.
  unsigned Lexer::MeasureTokenLength(SourceLocation Loc,
                                     const SourceManager &SM,
                                     const LangOptions &LangOpts) {
    Token TheTok;
    if (getRawToken(Loc, TheTok, SM, LangOpts))
      return 0;
    return TheTok.getLength();
  }
  
  /// Relex the token at the specified location.
  /// \returns true if there was a failure, false on success.
  bool Lexer::getRawToken(SourceLocation Loc, Token &Result,
                          const SourceManager &SM,
                          const LangOptions &LangOpts,
                          bool IgnoreWhiteSpace) {
    // TODO: this could be special cased for common tokens like identifiers, ')',
    // etc to make this faster, if it mattered.  Just look at StrData[0] to handle
    // all obviously single-char tokens.  This could use
    // Lexer::isObviouslySimpleCharacter for example to handle identifiers or
    // something.
  
    // If this comes from a macro expansion, we really do want the macro name, not
    // the token this macro expanded to.
    Loc = SM.getExpansionLoc(Loc);
    std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
    bool Invalid = false;
    StringRef Buffer = SM.getBufferData(LocInfo.first, &Invalid);
    if (Invalid)
      return true;
  
    const char *StrData = Buffer.data()+LocInfo.second;
  
    if (!IgnoreWhiteSpace && isWhitespace(StrData[0]))
      return true;
  
    // Create a lexer starting at the beginning of this token.
    Lexer TheLexer(SM.getLocForStartOfFile(LocInfo.first), LangOpts,
                   Buffer.begin(), StrData, Buffer.end());
    TheLexer.SetCommentRetentionState(true);
    TheLexer.LexFromRawLexer(Result);
    return false;
  }
  
  /// Returns the pointer that points to the beginning of line that contains
  /// the given offset, or null if the offset if invalid.
  static const char *findBeginningOfLine(StringRef Buffer, unsigned Offset) {
    const char *BufStart = Buffer.data();
    if (Offset >= Buffer.size())
      return nullptr;
  
    const char *LexStart = BufStart + Offset;
    for (; LexStart != BufStart; --LexStart) {
      if (isVerticalWhitespace(LexStart[0]) &&
          !Lexer::isNewLineEscaped(BufStart, LexStart)) {
        // LexStart should point at first character of logical line.
        ++LexStart;
        break;
      }
    }
    return LexStart;
  }
  
  static SourceLocation getBeginningOfFileToken(SourceLocation Loc,
                                                const SourceManager &SM,
                                                const LangOptions &LangOpts) {
    assert(Loc.isFileID());
    std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
    if (LocInfo.first.isInvalid())
      return Loc;
  
    bool Invalid = false;
    StringRef Buffer = SM.getBufferData(LocInfo.first, &Invalid);
    if (Invalid)
      return Loc;
  
    // Back up from the current location until we hit the beginning of a line
    // (or the buffer). We'll relex from that point.
    const char *StrData = Buffer.data() + LocInfo.second;
    const char *LexStart = findBeginningOfLine(Buffer, LocInfo.second);
    if (!LexStart || LexStart == StrData)
      return Loc;
  
    // Create a lexer starting at the beginning of this token.
    SourceLocation LexerStartLoc = Loc.getLocWithOffset(-LocInfo.second);
    Lexer TheLexer(LexerStartLoc, LangOpts, Buffer.data(), LexStart,
                   Buffer.end());
    TheLexer.SetCommentRetentionState(true);
  
    // Lex tokens until we find the token that contains the source location.
    Token TheTok;
    do {
      TheLexer.LexFromRawLexer(TheTok);
  
      if (TheLexer.getBufferLocation() > StrData) {
        // Lexing this token has taken the lexer past the source location we're
        // looking for. If the current token encompasses our source location,
        // return the beginning of that token.
        if (TheLexer.getBufferLocation() - TheTok.getLength() <= StrData)
          return TheTok.getLocation();
  
        // We ended up skipping over the source location entirely, which means
        // that it points into whitespace. We're done here.
        break;
      }
    } while (TheTok.getKind() != tok::eof);
  
    // We've passed our source location; just return the original source location.
    return Loc;
  }
  
  SourceLocation Lexer::GetBeginningOfToken(SourceLocation Loc,
                                            const SourceManager &SM,
                                            const LangOptions &LangOpts) {
    if (Loc.isFileID())
      return getBeginningOfFileToken(Loc, SM, LangOpts);
  
    if (!SM.isMacroArgExpansion(Loc))
      return Loc;
  
    SourceLocation FileLoc = SM.getSpellingLoc(Loc);
    SourceLocation BeginFileLoc = getBeginningOfFileToken(FileLoc, SM, LangOpts);
    std::pair<FileID, unsigned> FileLocInfo = SM.getDecomposedLoc(FileLoc);
    std::pair<FileID, unsigned> BeginFileLocInfo =
        SM.getDecomposedLoc(BeginFileLoc);
    assert(FileLocInfo.first == BeginFileLocInfo.first &&
           FileLocInfo.second >= BeginFileLocInfo.second);
    return Loc.getLocWithOffset(BeginFileLocInfo.second - FileLocInfo.second);
  }
  
  namespace {
  
  enum PreambleDirectiveKind {
    PDK_Skipped,
    PDK_Unknown
  };
  
  } // namespace
  
  PreambleBounds Lexer::ComputePreamble(StringRef Buffer,
                                        const LangOptions &LangOpts,
                                        unsigned MaxLines) {
    // Create a lexer starting at the beginning of the file. Note that we use a
    // "fake" file source location at offset 1 so that the lexer will track our
    // position within the file.
    const unsigned StartOffset = 1;
    SourceLocation FileLoc = SourceLocation::getFromRawEncoding(StartOffset);
    Lexer TheLexer(FileLoc, LangOpts, Buffer.begin(), Buffer.begin(),
                   Buffer.end());
    TheLexer.SetCommentRetentionState(true);
  
    bool InPreprocessorDirective = false;
    Token TheTok;
    SourceLocation ActiveCommentLoc;
  
    unsigned MaxLineOffset = 0;
    if (MaxLines) {
      const char *CurPtr = Buffer.begin();
      unsigned CurLine = 0;
      while (CurPtr != Buffer.end()) {
        char ch = *CurPtr++;
        if (ch == '\n') {
          ++CurLine;
          if (CurLine == MaxLines)
            break;
        }
      }
      if (CurPtr != Buffer.end())
        MaxLineOffset = CurPtr - Buffer.begin();
    }
  
    do {
      TheLexer.LexFromRawLexer(TheTok);
  
      if (InPreprocessorDirective) {
        // If we've hit the end of the file, we're done.
        if (TheTok.getKind() == tok::eof) {
          break;
        }
  
        // If we haven't hit the end of the preprocessor directive, skip this
        // token.
        if (!TheTok.isAtStartOfLine())
          continue;
  
        // We've passed the end of the preprocessor directive, and will look
        // at this token again below.
        InPreprocessorDirective = false;
      }
  
      // Keep track of the # of lines in the preamble.
      if (TheTok.isAtStartOfLine()) {
        unsigned TokOffset = TheTok.getLocation().getRawEncoding() - StartOffset;
  
        // If we were asked to limit the number of lines in the preamble,
        // and we're about to exceed that limit, we're done.
        if (MaxLineOffset && TokOffset >= MaxLineOffset)
          break;
      }
  
      // Comments are okay; skip over them.
      if (TheTok.getKind() == tok::comment) {
        if (ActiveCommentLoc.isInvalid())
          ActiveCommentLoc = TheTok.getLocation();
        continue;
      }
  
      if (TheTok.isAtStartOfLine() && TheTok.getKind() == tok::hash) {
        // This is the start of a preprocessor directive.
        Token HashTok = TheTok;
        InPreprocessorDirective = true;
        ActiveCommentLoc = SourceLocation();
  
        // Figure out which directive this is. Since we're lexing raw tokens,
        // we don't have an identifier table available. Instead, just look at
        // the raw identifier to recognize and categorize preprocessor directives.
        TheLexer.LexFromRawLexer(TheTok);
        if (TheTok.getKind() == tok::raw_identifier && !TheTok.needsCleaning()) {
          StringRef Keyword = TheTok.getRawIdentifier();
          PreambleDirectiveKind PDK
            = llvm::StringSwitch<PreambleDirectiveKind>(Keyword)
                .Case("include", PDK_Skipped)
                .Case("__include_macros", PDK_Skipped)
                .Case("define", PDK_Skipped)
                .Case("undef", PDK_Skipped)
                .Case("line", PDK_Skipped)
                .Case("error", PDK_Skipped)
                .Case("pragma", PDK_Skipped)
                .Case("import", PDK_Skipped)
                .Case("include_next", PDK_Skipped)
                .Case("warning", PDK_Skipped)
                .Case("ident", PDK_Skipped)
                .Case("sccs", PDK_Skipped)
                .Case("assert", PDK_Skipped)
                .Case("unassert", PDK_Skipped)
                .Case("if", PDK_Skipped)
                .Case("ifdef", PDK_Skipped)
                .Case("ifndef", PDK_Skipped)
                .Case("elif", PDK_Skipped)
                .Case("else", PDK_Skipped)
                .Case("endif", PDK_Skipped)
                .Default(PDK_Unknown);
  
          switch (PDK) {
          case PDK_Skipped:
            continue;
  
          case PDK_Unknown:
            // We don't know what this directive is; stop at the '#'.
            break;
          }
        }
  
        // We only end up here if we didn't recognize the preprocessor
        // directive or it was one that can't occur in the preamble at this
        // point. Roll back the current token to the location of the '#'.
        InPreprocessorDirective = false;
        TheTok = HashTok;
      }
  
      // We hit a token that we don't recognize as being in the
      // "preprocessing only" part of the file, so we're no longer in
      // the preamble.
      break;
    } while (true);
  
    SourceLocation End;
    if (ActiveCommentLoc.isValid())
      End = ActiveCommentLoc; // don't truncate a decl comment.
    else
      End = TheTok.getLocation();
  
    return PreambleBounds(End.getRawEncoding() - FileLoc.getRawEncoding(),
                          TheTok.isAtStartOfLine());
  }
  
  unsigned Lexer::getTokenPrefixLength(SourceLocation TokStart, unsigned CharNo,
                                       const SourceManager &SM,
                                       const LangOptions &LangOpts) {
    // Figure out how many physical characters away the specified expansion
    // character is.  This needs to take into consideration newlines and
    // trigraphs.
    bool Invalid = false;
    const char *TokPtr = SM.getCharacterData(TokStart, &Invalid);
  
    // If they request the first char of the token, we're trivially done.
    if (Invalid || (CharNo == 0 && Lexer::isObviouslySimpleCharacter(*TokPtr)))
      return 0;
  
    unsigned PhysOffset = 0;
  
    // The usual case is that tokens don't contain anything interesting.  Skip
    // over the uninteresting characters.  If a token only consists of simple
    // chars, this method is extremely fast.
    while (Lexer::isObviouslySimpleCharacter(*TokPtr)) {
      if (CharNo == 0)
        return PhysOffset;
      ++TokPtr;
      --CharNo;
      ++PhysOffset;
    }
  
    // If we have a character that may be a trigraph or escaped newline, use a
    // lexer to parse it correctly.
    for (; CharNo; --CharNo) {
      unsigned Size;
      Lexer::getCharAndSizeNoWarn(TokPtr, Size, LangOpts);
      TokPtr += Size;
      PhysOffset += Size;
    }
  
    // Final detail: if we end up on an escaped newline, we want to return the
    // location of the actual byte of the token.  For example foo\<newline>bar
    // advanced by 3 should return the location of b, not of \\.  One compounding
    // detail of this is that the escape may be made by a trigraph.
    if (!Lexer::isObviouslySimpleCharacter(*TokPtr))
      PhysOffset += Lexer::SkipEscapedNewLines(TokPtr)-TokPtr;
  
    return PhysOffset;
  }
  
  /// Computes the source location just past the end of the
  /// token at this source location.
  ///
  /// This routine can be used to produce a source location that
  /// points just past the end of the token referenced by \p Loc, and
  /// is generally used when a diagnostic needs to point just after a
  /// token where it expected something different that it received. If
  /// the returned source location would not be meaningful (e.g., if
  /// it points into a macro), this routine returns an invalid
  /// source location.
  ///
  /// \param Offset an offset from the end of the token, where the source
  /// location should refer to. The default offset (0) produces a source
  /// location pointing just past the end of the token; an offset of 1 produces
  /// a source location pointing to the last character in the token, etc.
  SourceLocation Lexer::getLocForEndOfToken(SourceLocation Loc, unsigned Offset,
                                            const SourceManager &SM,
                                            const LangOptions &LangOpts) {
    if (Loc.isInvalid())
      return {};
  
    if (Loc.isMacroID()) {
      if (Offset > 0 || !isAtEndOfMacroExpansion(Loc, SM, LangOpts, &Loc))
        return {}; // Points inside the macro expansion.
    }
  
    unsigned Len = Lexer::MeasureTokenLength(Loc, SM, LangOpts);
    if (Len > Offset)
      Len = Len - Offset;
    else
      return Loc;
  
    return Loc.getLocWithOffset(Len);
  }
  
  /// Returns true if the given MacroID location points at the first
  /// token of the macro expansion.
  bool Lexer::isAtStartOfMacroExpansion(SourceLocation loc,
                                        const SourceManager &SM,
                                        const LangOptions &LangOpts,
                                        SourceLocation *MacroBegin) {
    assert(loc.isValid() && loc.isMacroID() && "Expected a valid macro loc");
  
    SourceLocation expansionLoc;
    if (!SM.isAtStartOfImmediateMacroExpansion(loc, &expansionLoc))
      return false;
  
    if (expansionLoc.isFileID()) {
      // No other macro expansions, this is the first.
      if (MacroBegin)
        *MacroBegin = expansionLoc;
      return true;
    }
  
    return isAtStartOfMacroExpansion(expansionLoc, SM, LangOpts, MacroBegin);
  }
  
  /// Returns true if the given MacroID location points at the last
  /// token of the macro expansion.
  bool Lexer::isAtEndOfMacroExpansion(SourceLocation loc,
                                      const SourceManager &SM,
                                      const LangOptions &LangOpts,
                                      SourceLocation *MacroEnd) {
    assert(loc.isValid() && loc.isMacroID() && "Expected a valid macro loc");
  
    SourceLocation spellLoc = SM.getSpellingLoc(loc);
    unsigned tokLen = MeasureTokenLength(spellLoc, SM, LangOpts);
    if (tokLen == 0)
      return false;
  
    SourceLocation afterLoc = loc.getLocWithOffset(tokLen);
    SourceLocation expansionLoc;
    if (!SM.isAtEndOfImmediateMacroExpansion(afterLoc, &expansionLoc))
      return false;
  
    if (expansionLoc.isFileID()) {
      // No other macro expansions.
      if (MacroEnd)
        *MacroEnd = expansionLoc;
      return true;
    }
  
    return isAtEndOfMacroExpansion(expansionLoc, SM, LangOpts, MacroEnd);
  }
  
  static CharSourceRange makeRangeFromFileLocs(CharSourceRange Range,
                                               const SourceManager &SM,
                                               const LangOptions &LangOpts) {
    SourceLocation Begin = Range.getBegin();
    SourceLocation End = Range.getEnd();
    assert(Begin.isFileID() && End.isFileID());
    if (Range.isTokenRange()) {
      End = Lexer::getLocForEndOfToken(End, 0, SM,LangOpts);
      if (End.isInvalid())
        return {};
    }
  
    // Break down the source locations.
    FileID FID;
    unsigned BeginOffs;
    std::tie(FID, BeginOffs) = SM.getDecomposedLoc(Begin);
    if (FID.isInvalid())
      return {};
  
    unsigned EndOffs;
    if (!SM.isInFileID(End, FID, &EndOffs) ||
        BeginOffs > EndOffs)
      return {};
  
    return CharSourceRange::getCharRange(Begin, End);
  }
  
  CharSourceRange Lexer::makeFileCharRange(CharSourceRange Range,
                                           const SourceManager &SM,
                                           const LangOptions &LangOpts) {
    SourceLocation Begin = Range.getBegin();
    SourceLocation End = Range.getEnd();
    if (Begin.isInvalid() || End.isInvalid())
      return {};
  
    if (Begin.isFileID() && End.isFileID())
      return makeRangeFromFileLocs(Range, SM, LangOpts);
  
    if (Begin.isMacroID() && End.isFileID()) {
      if (!isAtStartOfMacroExpansion(Begin, SM, LangOpts, &Begin))
        return {};
      Range.setBegin(Begin);
      return makeRangeFromFileLocs(Range, SM, LangOpts);
    }
  
    if (Begin.isFileID() && End.isMacroID()) {
      if ((Range.isTokenRange() && !isAtEndOfMacroExpansion(End, SM, LangOpts,
                                                            &End)) ||
          (Range.isCharRange() && !isAtStartOfMacroExpansion(End, SM, LangOpts,
                                                             &End)))
        return {};
      Range.setEnd(End);
      return makeRangeFromFileLocs(Range, SM, LangOpts);
    }
  
    assert(Begin.isMacroID() && End.isMacroID());
    SourceLocation MacroBegin, MacroEnd;
    if (isAtStartOfMacroExpansion(Begin, SM, LangOpts, &MacroBegin) &&
        ((Range.isTokenRange() && isAtEndOfMacroExpansion(End, SM, LangOpts,
                                                          &MacroEnd)) ||
         (Range.isCharRange() && isAtStartOfMacroExpansion(End, SM, LangOpts,
                                                           &MacroEnd)))) {
      Range.setBegin(MacroBegin);
      Range.setEnd(MacroEnd);
      return makeRangeFromFileLocs(Range, SM, LangOpts);
    }
  
    bool Invalid = false;
    const SrcMgr::SLocEntry &BeginEntry = SM.getSLocEntry(SM.getFileID(Begin),
                                                          &Invalid);
    if (Invalid)
      return {};
  
    if (BeginEntry.getExpansion().isMacroArgExpansion()) {
      const SrcMgr::SLocEntry &EndEntry = SM.getSLocEntry(SM.getFileID(End),
                                                          &Invalid);
      if (Invalid)
        return {};
  
      if (EndEntry.getExpansion().isMacroArgExpansion() &&
          BeginEntry.getExpansion().getExpansionLocStart() ==
              EndEntry.getExpansion().getExpansionLocStart()) {
        Range.setBegin(SM.getImmediateSpellingLoc(Begin));
        Range.setEnd(SM.getImmediateSpellingLoc(End));
        return makeFileCharRange(Range, SM, LangOpts);
      }
    }
  
    return {};
  }
  
  StringRef Lexer::getSourceText(CharSourceRange Range,
                                 const SourceManager &SM,
                                 const LangOptions &LangOpts,
                                 bool *Invalid) {
    Range = makeFileCharRange(Range, SM, LangOpts);
    if (Range.isInvalid()) {
      if (Invalid) *Invalid = true;
      return {};
    }
  
    // Break down the source location.
    std::pair<FileID, unsigned> beginInfo = SM.getDecomposedLoc(Range.getBegin());
    if (beginInfo.first.isInvalid()) {
      if (Invalid) *Invalid = true;
      return {};
    }
  
    unsigned EndOffs;
    if (!SM.isInFileID(Range.getEnd(), beginInfo.first, &EndOffs) ||
        beginInfo.second > EndOffs) {
      if (Invalid) *Invalid = true;
      return {};
    }
  
    // Try to the load the file buffer.
    bool invalidTemp = false;
    StringRef file = SM.getBufferData(beginInfo.first, &invalidTemp);
    if (invalidTemp) {
      if (Invalid) *Invalid = true;
      return {};
    }
  
    if (Invalid) *Invalid = false;
    return file.substr(beginInfo.second, EndOffs - beginInfo.second);
  }
  
  StringRef Lexer::getImmediateMacroName(SourceLocation Loc,
                                         const SourceManager &SM,
                                         const LangOptions &LangOpts) {
    assert(Loc.isMacroID() && "Only reasonable to call this on macros");
  
    // Find the location of the immediate macro expansion.
    while (true) {
      FileID FID = SM.getFileID(Loc);
      const SrcMgr::SLocEntry *E = &SM.getSLocEntry(FID);
      const SrcMgr::ExpansionInfo &Expansion = E->getExpansion();
      Loc = Expansion.getExpansionLocStart();
      if (!Expansion.isMacroArgExpansion())
        break;
  
      // For macro arguments we need to check that the argument did not come
      // from an inner macro, e.g: "MAC1( MAC2(foo) )"
  
      // Loc points to the argument id of the macro definition, move to the
      // macro expansion.
      Loc = SM.getImmediateExpansionRange(Loc).getBegin();
      SourceLocation SpellLoc = Expansion.getSpellingLoc();
      if (SpellLoc.isFileID())
        break; // No inner macro.
  
      // If spelling location resides in the same FileID as macro expansion
      // location, it means there is no inner macro.
      FileID MacroFID = SM.getFileID(Loc);
      if (SM.isInFileID(SpellLoc, MacroFID))
        break;
  
      // Argument came from inner macro.
      Loc = SpellLoc;
    }
  
    // Find the spelling location of the start of the non-argument expansion
    // range. This is where the macro name was spelled in order to begin
    // expanding this macro.
    Loc = SM.getSpellingLoc(Loc);
  
    // Dig out the buffer where the macro name was spelled and the extents of the
    // name so that we can render it into the expansion note.
    std::pair<FileID, unsigned> ExpansionInfo = SM.getDecomposedLoc(Loc);
    unsigned MacroTokenLength = Lexer::MeasureTokenLength(Loc, SM, LangOpts);
    StringRef ExpansionBuffer = SM.getBufferData(ExpansionInfo.first);
    return ExpansionBuffer.substr(ExpansionInfo.second, MacroTokenLength);
  }
  
  StringRef Lexer::getImmediateMacroNameForDiagnostics(
      SourceLocation Loc, const SourceManager &SM, const LangOptions &LangOpts) {
    assert(Loc.isMacroID() && "Only reasonable to call this on macros");
    // Walk past macro argument expansions.
    while (SM.isMacroArgExpansion(Loc))
      Loc = SM.getImmediateExpansionRange(Loc).getBegin();
  
    // If the macro's spelling has no FileID, then it's actually a token paste
    // or stringization (or similar) and not a macro at all.
    if (!SM.getFileEntryForID(SM.getFileID(SM.getSpellingLoc(Loc))))
      return {};
  
    // Find the spelling location of the start of the non-argument expansion
    // range. This is where the macro name was spelled in order to begin
    // expanding this macro.
    Loc = SM.getSpellingLoc(SM.getImmediateExpansionRange(Loc).getBegin());
  
    // Dig out the buffer where the macro name was spelled and the extents of the
    // name so that we can render it into the expansion note.
    std::pair<FileID, unsigned> ExpansionInfo = SM.getDecomposedLoc(Loc);
    unsigned MacroTokenLength = Lexer::MeasureTokenLength(Loc, SM, LangOpts);
    StringRef ExpansionBuffer = SM.getBufferData(ExpansionInfo.first);
    return ExpansionBuffer.substr(ExpansionInfo.second, MacroTokenLength);
  }
  
  bool Lexer::isIdentifierBodyChar(char c, const LangOptions &LangOpts) {
    return isIdentifierBody(c, LangOpts.DollarIdents);
  }
  
  bool Lexer::isNewLineEscaped(const char *BufferStart, const char *Str) {
    assert(isVerticalWhitespace(Str[0]));
    if (Str - 1 < BufferStart)
      return false;
  
    if ((Str[0] == '\n' && Str[-1] == '\r') ||
        (Str[0] == '\r' && Str[-1] == '\n')) {
      if (Str - 2 < BufferStart)
        return false;
      --Str;
    }
    --Str;
  
    // Rewind to first non-space character:
    while (Str > BufferStart && isHorizontalWhitespace(*Str))
      --Str;
  
    return *Str == '\\';
  }
  
  StringRef Lexer::getIndentationForLine(SourceLocation Loc,
                                         const SourceManager &SM) {
    if (Loc.isInvalid() || Loc.isMacroID())
      return {};
    std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
    if (LocInfo.first.isInvalid())
      return {};
    bool Invalid = false;
    StringRef Buffer = SM.getBufferData(LocInfo.first, &Invalid);
    if (Invalid)
      return {};
    const char *Line = findBeginningOfLine(Buffer, LocInfo.second);
    if (!Line)
      return {};
    StringRef Rest = Buffer.substr(Line - Buffer.data());
    size_t NumWhitespaceChars = Rest.find_first_not_of(" \t");
    return NumWhitespaceChars == StringRef::npos
               ? ""
               : Rest.take_front(NumWhitespaceChars);
  }
  
  //===----------------------------------------------------------------------===//
  // Diagnostics forwarding code.
  //===----------------------------------------------------------------------===//
  
  /// GetMappedTokenLoc - If lexing out of a 'mapped buffer', where we pretend the
  /// lexer buffer was all expanded at a single point, perform the mapping.
  /// This is currently only used for _Pragma implementation, so it is the slow
  /// path of the hot getSourceLocation method.  Do not allow it to be inlined.
  static LLVM_ATTRIBUTE_NOINLINE SourceLocation GetMappedTokenLoc(
      Preprocessor &PP, SourceLocation FileLoc, unsigned CharNo, unsigned TokLen);
  static SourceLocation GetMappedTokenLoc(Preprocessor &PP,
                                          SourceLocation FileLoc,
                                          unsigned CharNo, unsigned TokLen) {
    assert(FileLoc.isMacroID() && "Must be a macro expansion");
  
    // Otherwise, we're lexing "mapped tokens".  This is used for things like
    // _Pragma handling.  Combine the expansion location of FileLoc with the
    // spelling location.
    SourceManager &SM = PP.getSourceManager();
  
    // Create a new SLoc which is expanded from Expansion(FileLoc) but whose
    // characters come from spelling(FileLoc)+Offset.
    SourceLocation SpellingLoc = SM.getSpellingLoc(FileLoc);
    SpellingLoc = SpellingLoc.getLocWithOffset(CharNo);
  
    // Figure out the expansion loc range, which is the range covered by the
    // original _Pragma(...) sequence.
    CharSourceRange II = SM.getImmediateExpansionRange(FileLoc);
  
    return SM.createExpansionLoc(SpellingLoc, II.getBegin(), II.getEnd(), TokLen);
  }
  
  /// getSourceLocation - Return a source location identifier for the specified
  /// offset in the current file.
  SourceLocation Lexer::getSourceLocation(const char *Loc,
                                          unsigned TokLen) const {
    assert(Loc >= BufferStart && Loc <= BufferEnd &&
           "Location out of range for this buffer!");
  
    // In the normal case, we're just lexing from a simple file buffer, return
    // the file id from FileLoc with the offset specified.
    unsigned CharNo = Loc-BufferStart;
    if (FileLoc.isFileID())
      return FileLoc.getLocWithOffset(CharNo);
  
    // Otherwise, this is the _Pragma lexer case, which pretends that all of the
    // tokens are lexed from where the _Pragma was defined.
    assert(PP && "This doesn't work on raw lexers");
    return GetMappedTokenLoc(*PP, FileLoc, CharNo, TokLen);
  }
  
  /// Diag - Forwarding function for diagnostics.  This translate a source
  /// position in the current buffer into a SourceLocation object for rendering.
  DiagnosticBuilder Lexer::Diag(const char *Loc, unsigned DiagID) const {
    return PP->Diag(getSourceLocation(Loc), DiagID);
  }
  
  //===----------------------------------------------------------------------===//
  // Trigraph and Escaped Newline Handling Code.
  //===----------------------------------------------------------------------===//
  
  /// GetTrigraphCharForLetter - Given a character that occurs after a ?? pair,
  /// return the decoded trigraph letter it corresponds to, or '\0' if nothing.
  static char GetTrigraphCharForLetter(char Letter) {
    switch (Letter) {
    default:   return 0;
    case '=':  return '#';
    case ')':  return ']';
    case '(':  return '[';
    case '!':  return '|';
    case '\'': return '^';
    case '>':  return '}';
    case '/':  return '\\';
    case '<':  return '{';
    case '-':  return '~';
    }
  }
  
  /// DecodeTrigraphChar - If the specified character is a legal trigraph when
  /// prefixed with ??, emit a trigraph warning.  If trigraphs are enabled,
  /// return the result character.  Finally, emit a warning about trigraph use
  /// whether trigraphs are enabled or not.
  static char DecodeTrigraphChar(const char *CP, Lexer *L) {
    char Res = GetTrigraphCharForLetter(*CP);
    if (!Res || !L) return Res;
  
    if (!L->getLangOpts().Trigraphs) {
      if (!L->isLexingRawMode())
        L->Diag(CP-2, diag::trigraph_ignored);
      return 0;
    }
  
    if (!L->isLexingRawMode())
      L->Diag(CP-2, diag::trigraph_converted) << StringRef(&Res, 1);
    return Res;
  }
  
  /// getEscapedNewLineSize - Return the size of the specified escaped newline,
  /// or 0 if it is not an escaped newline. P[-1] is known to be a "\" or a
  /// trigraph equivalent on entry to this function.
  unsigned Lexer::getEscapedNewLineSize(const char *Ptr) {
    unsigned Size = 0;
    while (isWhitespace(Ptr[Size])) {
      ++Size;
  
      if (Ptr[Size-1] != '\n' && Ptr[Size-1] != '\r')
        continue;
  
      // If this is a \r\n or \n\r, skip the other half.
      if ((Ptr[Size] == '\r' || Ptr[Size] == '\n') &&
          Ptr[Size-1] != Ptr[Size])
        ++Size;
  
      return Size;
    }
  
    // Not an escaped newline, must be a \t or something else.
    return 0;
  }
  
  /// SkipEscapedNewLines - If P points to an escaped newline (or a series of
  /// them), skip over them and return the first non-escaped-newline found,
  /// otherwise return P.
  const char *Lexer::SkipEscapedNewLines(const char *P) {
    while (true) {
      const char *AfterEscape;
      if (*P == '\\') {
        AfterEscape = P+1;
      } else if (*P == '?') {
        // If not a trigraph for escape, bail out.
        if (P[1] != '?' || P[2] != '/')
          return P;
        // FIXME: Take LangOpts into account; the language might not
        // support trigraphs.
        AfterEscape = P+3;
      } else {
        return P;
      }
  
      unsigned NewLineSize = Lexer::getEscapedNewLineSize(AfterEscape);
      if (NewLineSize == 0) return P;
      P = AfterEscape+NewLineSize;
    }
  }
  
  Optional<Token> Lexer::findNextToken(SourceLocation Loc,
                                       const SourceManager &SM,
                                       const LangOptions &LangOpts) {
    if (Loc.isMacroID()) {
      if (!Lexer::isAtEndOfMacroExpansion(Loc, SM, LangOpts, &Loc))
        return None;
    }
    Loc = Lexer::getLocForEndOfToken(Loc, 0, SM, LangOpts);
  
    // Break down the source location.
    std::pair<FileID, unsigned> LocInfo = SM.getDecomposedLoc(Loc);
  
    // Try to load the file buffer.
    bool InvalidTemp = false;
    StringRef File = SM.getBufferData(LocInfo.first, &InvalidTemp);
    if (InvalidTemp)
      return None;
  
    const char *TokenBegin = File.data() + LocInfo.second;
  
    // Lex from the start of the given location.
    Lexer lexer(SM.getLocForStartOfFile(LocInfo.first), LangOpts, File.begin(),
                                        TokenBegin, File.end());
    // Find the token.
    Token Tok;
    lexer.LexFromRawLexer(Tok);
    return Tok;
  }
  
  /// Checks that the given token is the first token that occurs after the
  /// given location (this excludes comments and whitespace). Returns the location
  /// immediately after the specified token. If the token is not found or the
  /// location is inside a macro, the returned source location will be invalid.
  SourceLocation Lexer::findLocationAfterToken(
      SourceLocation Loc, tok::TokenKind TKind, const SourceManager &SM,
      const LangOptions &LangOpts, bool SkipTrailingWhitespaceAndNewLine) {
    Optional<Token> Tok = findNextToken(Loc, SM, LangOpts);
    if (!Tok || Tok->isNot(TKind))
      return {};
    SourceLocation TokenLoc = Tok->getLocation();
  
    // Calculate how much whitespace needs to be skipped if any.
    unsigned NumWhitespaceChars = 0;
    if (SkipTrailingWhitespaceAndNewLine) {
      const char *TokenEnd = SM.getCharacterData(TokenLoc) + Tok->getLength();
      unsigned char C = *TokenEnd;
      while (isHorizontalWhitespace(C)) {
        C = *(++TokenEnd);
        NumWhitespaceChars++;
      }
  
      // Skip \r, \n, \r\n, or \n\r
      if (C == '\n' || C == '\r') {
        char PrevC = C;
        C = *(++TokenEnd);
        NumWhitespaceChars++;
        if ((C == '\n' || C == '\r') && C != PrevC)
          NumWhitespaceChars++;
      }
    }
  
    return TokenLoc.getLocWithOffset(Tok->getLength() + NumWhitespaceChars);
  }
  
  /// getCharAndSizeSlow - Peek a single 'character' from the specified buffer,
  /// get its size, and return it.  This is tricky in several cases:
  ///   1. If currently at the start of a trigraph, we warn about the trigraph,
  ///      then either return the trigraph (skipping 3 chars) or the '?',
  ///      depending on whether trigraphs are enabled or not.
  ///   2. If this is an escaped newline (potentially with whitespace between
  ///      the backslash and newline), implicitly skip the newline and return
  ///      the char after it.
  ///
  /// This handles the slow/uncommon case of the getCharAndSize method.  Here we
  /// know that we can accumulate into Size, and that we have already incremented
  /// Ptr by Size bytes.
  ///
  /// NOTE: When this method is updated, getCharAndSizeSlowNoWarn (below) should
  /// be updated to match.
  char Lexer::getCharAndSizeSlow(const char *Ptr, unsigned &Size,
                                 Token *Tok) {
    // If we have a slash, look for an escaped newline.
    if (Ptr[0] == '\\') {
      ++Size;
      ++Ptr;
  Slash:
      // Common case, backslash-char where the char is not whitespace.
      if (!isWhitespace(Ptr[0])) return '\\';
  
      // See if we have optional whitespace characters between the slash and
      // newline.
      if (unsigned EscapedNewLineSize = getEscapedNewLineSize(Ptr)) {
        // Remember that this token needs to be cleaned.
        if (Tok) Tok->setFlag(Token::NeedsCleaning);
  
        // Warn if there was whitespace between the backslash and newline.
        if (Ptr[0] != '\n' && Ptr[0] != '\r' && Tok && !isLexingRawMode())
          Diag(Ptr, diag::backslash_newline_space);
  
        // Found backslash<whitespace><newline>.  Parse the char after it.
        Size += EscapedNewLineSize;
        Ptr  += EscapedNewLineSize;
  
        // Use slow version to accumulate a correct size field.
        return getCharAndSizeSlow(Ptr, Size, Tok);
      }
  
      // Otherwise, this is not an escaped newline, just return the slash.
      return '\\';
    }
  
    // If this is a trigraph, process it.
    if (Ptr[0] == '?' && Ptr[1] == '?') {
      // If this is actually a legal trigraph (not something like "??x"), emit
      // a trigraph warning.  If so, and if trigraphs are enabled, return it.
      if (char C = DecodeTrigraphChar(Ptr+2, Tok ? this : nullptr)) {
        // Remember that this token needs to be cleaned.
        if (Tok) Tok->setFlag(Token::NeedsCleaning);
  
        Ptr += 3;
        Size += 3;
        if (C == '\\') goto Slash;
        return C;
      }
    }
  
    // If this is neither, return a single character.
    ++Size;
    return *Ptr;
  }
  
  /// getCharAndSizeSlowNoWarn - Handle the slow/uncommon case of the
  /// getCharAndSizeNoWarn method.  Here we know that we can accumulate into Size,
  /// and that we have already incremented Ptr by Size bytes.
  ///
  /// NOTE: When this method is updated, getCharAndSizeSlow (above) should
  /// be updated to match.
  char Lexer::getCharAndSizeSlowNoWarn(const char *Ptr, unsigned &Size,
                                       const LangOptions &LangOpts) {
    // If we have a slash, look for an escaped newline.
    if (Ptr[0] == '\\') {
      ++Size;
      ++Ptr;
  Slash:
      // Common case, backslash-char where the char is not whitespace.
      if (!isWhitespace(Ptr[0])) return '\\';
  
      // See if we have optional whitespace characters followed by a newline.
      if (unsigned EscapedNewLineSize = getEscapedNewLineSize(Ptr)) {
        // Found backslash<whitespace><newline>.  Parse the char after it.
        Size += EscapedNewLineSize;
        Ptr  += EscapedNewLineSize;
  
        // Use slow version to accumulate a correct size field.
        return getCharAndSizeSlowNoWarn(Ptr, Size, LangOpts);
      }
  
      // Otherwise, this is not an escaped newline, just return the slash.
      return '\\';
    }
  
    // If this is a trigraph, process it.
    if (LangOpts.Trigraphs && Ptr[0] == '?' && Ptr[1] == '?') {
      // If this is actually a legal trigraph (not something like "??x"), return
      // it.
      if (char C = GetTrigraphCharForLetter(Ptr[2])) {
        Ptr += 3;
        Size += 3;
        if (C == '\\') goto Slash;
        return C;
      }
    }
  
    // If this is neither, return a single character.
    ++Size;
    return *Ptr;
  }
  
  //===----------------------------------------------------------------------===//
  // Helper methods for lexing.
  //===----------------------------------------------------------------------===//
  
  /// Routine that indiscriminately sets the offset into the source file.
  void Lexer::SetByteOffset(unsigned Offset, bool StartOfLine) {
    BufferPtr = BufferStart + Offset;
    if (BufferPtr > BufferEnd)
      BufferPtr = BufferEnd;
    // FIXME: What exactly does the StartOfLine bit mean?  There are two
    // possible meanings for the "start" of the line: the first token on the
    // unexpanded line, or the first token on the expanded line.
    IsAtStartOfLine = StartOfLine;
    IsAtPhysicalStartOfLine = StartOfLine;
  }
  
  static bool isAllowedIDChar(uint32_t C, const LangOptions &LangOpts) {
    if (LangOpts.AsmPreprocessor) {
      return false;
    } else if (LangOpts.CPlusPlus11 || LangOpts.C11) {
      static const llvm::sys::UnicodeCharSet C11AllowedIDChars(
          C11AllowedIDCharRanges);
      return C11AllowedIDChars.contains(C);
    } else if (LangOpts.CPlusPlus) {
      static const llvm::sys::UnicodeCharSet CXX03AllowedIDChars(
          CXX03AllowedIDCharRanges);
      return CXX03AllowedIDChars.contains(C);
    } else {
      static const llvm::sys::UnicodeCharSet C99AllowedIDChars(
          C99AllowedIDCharRanges);
      return C99AllowedIDChars.contains(C);
    }
  }
  
  static bool isAllowedInitiallyIDChar(uint32_t C, const LangOptions &LangOpts) {
    assert(isAllowedIDChar(C, LangOpts));
    if (LangOpts.AsmPreprocessor) {
      return false;
    } else if (LangOpts.CPlusPlus11 || LangOpts.C11) {
      static const llvm::sys::UnicodeCharSet C11DisallowedInitialIDChars(
          C11DisallowedInitialIDCharRanges);
      return !C11DisallowedInitialIDChars.contains(C);
    } else if (LangOpts.CPlusPlus) {
      return true;
    } else {
      static const llvm::sys::UnicodeCharSet C99DisallowedInitialIDChars(
          C99DisallowedInitialIDCharRanges);
      return !C99DisallowedInitialIDChars.contains(C);
    }
  }
  
  static inline CharSourceRange makeCharRange(Lexer &L, const char *Begin,
                                              const char *End) {
    return CharSourceRange::getCharRange(L.getSourceLocation(Begin),
                                         L.getSourceLocation(End));
  }
  
  static void maybeDiagnoseIDCharCompat(DiagnosticsEngine &Diags, uint32_t C,
                                        CharSourceRange Range, bool IsFirst) {
    // Check C99 compatibility.
    if (!Diags.isIgnored(diag::warn_c99_compat_unicode_id, Range.getBegin())) {
      enum {
        CannotAppearInIdentifier = 0,
        CannotStartIdentifier
      };
  
      static const llvm::sys::UnicodeCharSet C99AllowedIDChars(
          C99AllowedIDCharRanges);
      static const llvm::sys::UnicodeCharSet C99DisallowedInitialIDChars(
          C99DisallowedInitialIDCharRanges);
      if (!C99AllowedIDChars.contains(C)) {
        Diags.Report(Range.getBegin(), diag::warn_c99_compat_unicode_id)
          << Range
          << CannotAppearInIdentifier;
      } else if (IsFirst && C99DisallowedInitialIDChars.contains(C)) {
        Diags.Report(Range.getBegin(), diag::warn_c99_compat_unicode_id)
          << Range
          << CannotStartIdentifier;
      }
    }
  
    // Check C++98 compatibility.
    if (!Diags.isIgnored(diag::warn_cxx98_compat_unicode_id, Range.getBegin())) {
      static const llvm::sys::UnicodeCharSet CXX03AllowedIDChars(
          CXX03AllowedIDCharRanges);
      if (!CXX03AllowedIDChars.contains(C)) {
        Diags.Report(Range.getBegin(), diag::warn_cxx98_compat_unicode_id)
          << Range;
      }
    }
  }
  
  /// After encountering UTF-8 character C and interpreting it as an identifier
  /// character, check whether it's a homoglyph for a common non-identifier
  /// source character that is unlikely to be an intentional identifier
  /// character and warn if so.
  static void maybeDiagnoseUTF8Homoglyph(DiagnosticsEngine &Diags, uint32_t C,
                                         CharSourceRange Range) {
    // FIXME: Handle Unicode quotation marks (smart quotes, fullwidth quotes).
    struct HomoglyphPair {
      uint32_t Character;
      char LooksLike;
      bool operator<(HomoglyphPair R) const { return Character < R.Character; }
    };
    static constexpr HomoglyphPair SortedHomoglyphs[] = {
      {U'\u00ad', 0},   // SOFT HYPHEN
      {U'\u01c3', '!'}, // LATIN LETTER RETROFLEX CLICK
      {U'\u037e', ';'}, // GREEK QUESTION MARK
      {U'\u200b', 0},   // ZERO WIDTH SPACE
      {U'\u200c', 0},   // ZERO WIDTH NON-JOINER
      {U'\u200d', 0},   // ZERO WIDTH JOINER
      {U'\u2060', 0},   // WORD JOINER
      {U'\u2061', 0},   // FUNCTION APPLICATION
      {U'\u2062', 0},   // INVISIBLE TIMES
      {U'\u2063', 0},   // INVISIBLE SEPARATOR
      {U'\u2064', 0},   // INVISIBLE PLUS
      {U'\u2212', '-'}, // MINUS SIGN
      {U'\u2215', '/'}, // DIVISION SLASH
      {U'\u2216', '\\'}, // SET MINUS
      {U'\u2217', '*'}, // ASTERISK OPERATOR
      {U'\u2223', '|'}, // DIVIDES
      {U'\u2227', '^'}, // LOGICAL AND
      {U'\u2236', ':'}, // RATIO
      {U'\u223c', '~'}, // TILDE OPERATOR
      {U'\ua789', ':'}, // MODIFIER LETTER COLON
      {U'\ufeff', 0},   // ZERO WIDTH NO-BREAK SPACE
      {U'\uff01', '!'}, // FULLWIDTH EXCLAMATION MARK
      {U'\uff03', '#'}, // FULLWIDTH NUMBER SIGN
      {U'\uff04', '$'}, // FULLWIDTH DOLLAR SIGN
      {U'\uff05', '%'}, // FULLWIDTH PERCENT SIGN
      {U'\uff06', '&'}, // FULLWIDTH AMPERSAND
      {U'\uff08', '('}, // FULLWIDTH LEFT PARENTHESIS
      {U'\uff09', ')'}, // FULLWIDTH RIGHT PARENTHESIS
      {U'\uff0a', '*'}, // FULLWIDTH ASTERISK
      {U'\uff0b', '+'}, // FULLWIDTH ASTERISK
      {U'\uff0c', ','}, // FULLWIDTH COMMA
      {U'\uff0d', '-'}, // FULLWIDTH HYPHEN-MINUS
      {U'\uff0e', '.'}, // FULLWIDTH FULL STOP
      {U'\uff0f', '/'}, // FULLWIDTH SOLIDUS
      {U'\uff1a', ':'}, // FULLWIDTH COLON
      {U'\uff1b', ';'}, // FULLWIDTH SEMICOLON
      {U'\uff1c', '<'}, // FULLWIDTH LESS-THAN SIGN
      {U'\uff1d', '='}, // FULLWIDTH EQUALS SIGN
      {U'\uff1e', '>'}, // FULLWIDTH GREATER-THAN SIGN
      {U'\uff1f', '?'}, // FULLWIDTH QUESTION MARK
      {U'\uff20', '@'}, // FULLWIDTH COMMERCIAL AT
      {U'\uff3b', '['}, // FULLWIDTH LEFT SQUARE BRACKET
      {U'\uff3c', '\\'}, // FULLWIDTH REVERSE SOLIDUS
      {U'\uff3d', ']'}, // FULLWIDTH RIGHT SQUARE BRACKET
      {U'\uff3e', '^'}, // FULLWIDTH CIRCUMFLEX ACCENT
      {U'\uff5b', '{'}, // FULLWIDTH LEFT CURLY BRACKET
      {U'\uff5c', '|'}, // FULLWIDTH VERTICAL LINE
      {U'\uff5d', '}'}, // FULLWIDTH RIGHT CURLY BRACKET
      {U'\uff5e', '~'}, // FULLWIDTH TILDE
      {0, 0}
    };
    auto Homoglyph =
        std::lower_bound(std::begin(SortedHomoglyphs),
                         std::end(SortedHomoglyphs) - 1, HomoglyphPair{C, '\0'});
    if (Homoglyph->Character == C) {
      llvm::SmallString<5> CharBuf;
      {
        llvm::raw_svector_ostream CharOS(CharBuf);
        llvm::write_hex(CharOS, C, llvm::HexPrintStyle::Upper, 4);
      }
      if (Homoglyph->LooksLike) {
        const char LooksLikeStr[] = {Homoglyph->LooksLike, 0};
        Diags.Report(Range.getBegin(), diag::warn_utf8_symbol_homoglyph)
            << Range << CharBuf << LooksLikeStr;
      } else {
        Diags.Report(Range.getBegin(), diag::warn_utf8_symbol_zero_width)
            << Range << CharBuf;
      }
    }
  }
  
  bool Lexer::tryConsumeIdentifierUCN(const char *&CurPtr, unsigned Size,
                                      Token &Result) {
    const char *UCNPtr = CurPtr + Size;
    uint32_t CodePoint = tryReadUCN(UCNPtr, CurPtr, /*Token=*/nullptr);
    if (CodePoint == 0 || !isAllowedIDChar(CodePoint, LangOpts))
      return false;
  
    if (!isLexingRawMode())
      maybeDiagnoseIDCharCompat(PP->getDiagnostics(), CodePoint,
                                makeCharRange(*this, CurPtr, UCNPtr),
                                /*IsFirst=*/false);
  
    Result.setFlag(Token::HasUCN);
    if ((UCNPtr - CurPtr ==  6 && CurPtr[1] == 'u') ||
        (UCNPtr - CurPtr == 10 && CurPtr[1] == 'U'))
      CurPtr = UCNPtr;
    else
      while (CurPtr != UCNPtr)
        (void)getAndAdvanceChar(CurPtr, Result);
    return true;
  }
  
  bool Lexer::tryConsumeIdentifierUTF8Char(const char *&CurPtr) {
    const char *UnicodePtr = CurPtr;
    llvm::UTF32 CodePoint;
    llvm::ConversionResult Result =
        llvm::convertUTF8Sequence((const llvm::UTF8 **)&UnicodePtr,
                                  (const llvm::UTF8 *)BufferEnd,
                                  &CodePoint,
                                  llvm::strictConversion);
    if (Result != llvm::conversionOK ||
        !isAllowedIDChar(static_cast<uint32_t>(CodePoint), LangOpts))
      return false;
  
    if (!isLexingRawMode()) {
      maybeDiagnoseIDCharCompat(PP->getDiagnostics(), CodePoint,
                                makeCharRange(*this, CurPtr, UnicodePtr),
                                /*IsFirst=*/false);
      maybeDiagnoseUTF8Homoglyph(PP->getDiagnostics(), CodePoint,
                                 makeCharRange(*this, CurPtr, UnicodePtr));
    }
  
    CurPtr = UnicodePtr;
    return true;
  }
  
  bool Lexer::LexIdentifier(Token &Result, const char *CurPtr) {
    // Match [_A-Za-z0-9]*, we have already matched [_A-Za-z$]
    unsigned Size;
    unsigned char C = *CurPtr++;
    while (isIdentifierBody(C))
      C = *CurPtr++;
  
    --CurPtr;   // Back up over the skipped character.
  
    // Fast path, no $,\,? in identifier found.  '\' might be an escaped newline
    // or UCN, and ? might be a trigraph for '\', an escaped newline or UCN.
    //
    // TODO: Could merge these checks into an InfoTable flag to make the
    // comparison cheaper
    if (isASCII(C) && C != '\\' && C != '?' &&
        (C != '$' || !LangOpts.DollarIdents)) {
  FinishIdentifier:
      const char *IdStart = BufferPtr;
      FormTokenWithChars(Result, CurPtr, tok::raw_identifier);
      Result.setRawIdentifierData(IdStart);
  
      // If we are in raw mode, return this identifier raw.  There is no need to
      // look up identifier information or attempt to macro expand it.
      if (LexingRawMode)
        return true;
  
      // Fill in Result.IdentifierInfo and update the token kind,
      // looking up the identifier in the identifier table.
      IdentifierInfo *II = PP->LookUpIdentifierInfo(Result);
      // Note that we have to call PP->LookUpIdentifierInfo() even for code
      // completion, it writes IdentifierInfo into Result, and callers rely on it.
  
      // If the completion point is at the end of an identifier, we want to treat
      // the identifier as incomplete even if it resolves to a macro or a keyword.
      // This allows e.g. 'class^' to complete to 'classifier'.
      if (isCodeCompletionPoint(CurPtr)) {
        // Return the code-completion token.
        Result.setKind(tok::code_completion);
        // Skip the code-completion char and all immediate identifier characters.
        // This ensures we get consistent behavior when completing at any point in
        // an identifier (i.e. at the start, in the middle, at the end). Note that
        // only simple cases (i.e. [a-zA-Z0-9_]) are supported to keep the code
        // simpler.
        assert(*CurPtr == 0 && "Completion character must be 0");
        ++CurPtr;
        // Note that code completion token is not added as a separate character
        // when the completion point is at the end of the buffer. Therefore, we need
        // to check if the buffer has ended.
        if (CurPtr < BufferEnd) {
          while (isIdentifierBody(*CurPtr))
            ++CurPtr;
        }
        BufferPtr = CurPtr;
        return true;
      }
  
      // Finally, now that we know we have an identifier, pass this off to the
      // preprocessor, which may macro expand it or something.
      if (II->isHandleIdentifierCase())
        return PP->HandleIdentifier(Result);
  
      return true;
    }
  
    // Otherwise, $,\,? in identifier found.  Enter slower path.
  
    C = getCharAndSize(CurPtr, Size);
    while (true) {
      if (C == '$') {
        // If we hit a $ and they are not supported in identifiers, we are done.
        if (!LangOpts.DollarIdents) goto FinishIdentifier;
  
        // Otherwise, emit a diagnostic and continue.
        if (!isLexingRawMode())
          Diag(CurPtr, diag::ext_dollar_in_identifier);
        CurPtr = ConsumeChar(CurPtr, Size, Result);
        C = getCharAndSize(CurPtr, Size);
        continue;
      } else if (C == '\\' && tryConsumeIdentifierUCN(CurPtr, Size, Result)) {
        C = getCharAndSize(CurPtr, Size);
        continue;
      } else if (!isASCII(C) && tryConsumeIdentifierUTF8Char(CurPtr)) {
        C = getCharAndSize(CurPtr, Size);
        continue;
      } else if (!isIdentifierBody(C)) {
        goto FinishIdentifier;
      }
  
      // Otherwise, this character is good, consume it.
      CurPtr = ConsumeChar(CurPtr, Size, Result);
  
      C = getCharAndSize(CurPtr, Size);
      while (isIdentifierBody(C)) {
        CurPtr = ConsumeChar(CurPtr, Size, Result);
        C = getCharAndSize(CurPtr, Size);
      }
    }
  }
  
  /// isHexaLiteral - Return true if Start points to a hex constant.
  /// in microsoft mode (where this is supposed to be several different tokens).
  bool Lexer::isHexaLiteral(const char *Start, const LangOptions &LangOpts) {
    unsigned Size;
    char C1 = Lexer::getCharAndSizeNoWarn(Start, Size, LangOpts);
    if (C1 != '0')
      return false;
    char C2 = Lexer::getCharAndSizeNoWarn(Start + Size, Size, LangOpts);
    return (C2 == 'x' || C2 == 'X');
  }
  
  /// LexNumericConstant - Lex the remainder of a integer or floating point
  /// constant. From[-1] is the first character lexed.  Return the end of the
  /// constant.
  bool Lexer::LexNumericConstant(Token &Result, const char *CurPtr) {
    unsigned Size;
    char C = getCharAndSize(CurPtr, Size);
    char PrevCh = 0;
    while (isPreprocessingNumberBody(C)) {
      CurPtr = ConsumeChar(CurPtr, Size, Result);
      PrevCh = C;
      C = getCharAndSize(CurPtr, Size);
    }
  
    // If we fell out, check for a sign, due to 1e+12.  If we have one, continue.
    if ((C == '-' || C == '+') && (PrevCh == 'E' || PrevCh == 'e')) {
      // If we are in Microsoft mode, don't continue if the constant is hex.
      // For example, MSVC will accept the following as 3 tokens: 0x1234567e+1
      if (!LangOpts.MicrosoftExt || !isHexaLiteral(BufferPtr, LangOpts))
        return LexNumericConstant(Result, ConsumeChar(CurPtr, Size, Result));
    }
  
    // If we have a hex FP constant, continue.
    if ((C == '-' || C == '+') && (PrevCh == 'P' || PrevCh == 'p')) {
      // Outside C99 and C++17, we accept hexadecimal floating point numbers as a
      // not-quite-conforming extension. Only do so if this looks like it's
      // actually meant to be a hexfloat, and not if it has a ud-suffix.
      bool IsHexFloat = true;
      if (!LangOpts.C99) {
        if (!isHexaLiteral(BufferPtr, LangOpts))
          IsHexFloat = false;
        else if (!getLangOpts().CPlusPlus17 &&
                 std::find(BufferPtr, CurPtr, '_') != CurPtr)
          IsHexFloat = false;
      }
      if (IsHexFloat)
        return LexNumericConstant(Result, ConsumeChar(CurPtr, Size, Result));
    }
  
    // If we have a digit separator, continue.
    if (C == '\'' && getLangOpts().CPlusPlus14) {
      unsigned NextSize;
      char Next = getCharAndSizeNoWarn(CurPtr + Size, NextSize, getLangOpts());
      if (isIdentifierBody(Next)) {
        if (!isLexingRawMode())
          Diag(CurPtr, diag::warn_cxx11_compat_digit_separator);
        CurPtr = ConsumeChar(CurPtr, Size, Result);
        CurPtr = ConsumeChar(CurPtr, NextSize, Result);
        return LexNumericConstant(Result, CurPtr);
      }
    }
  
    // If we have a UCN or UTF-8 character (perhaps in a ud-suffix), continue.
    if (C == '\\' && tryConsumeIdentifierUCN(CurPtr, Size, Result))
      return LexNumericConstant(Result, CurPtr);
    if (!isASCII(C) && tryConsumeIdentifierUTF8Char(CurPtr))
      return LexNumericConstant(Result, CurPtr);
  
    // Update the location of token as well as BufferPtr.
    const char *TokStart = BufferPtr;
    FormTokenWithChars(Result, CurPtr, tok::numeric_constant);
    Result.setLiteralData(TokStart);
    return true;
  }
  
  /// LexUDSuffix - Lex the ud-suffix production for user-defined literal suffixes
  /// in C++11, or warn on a ud-suffix in C++98.
  const char *Lexer::LexUDSuffix(Token &Result, const char *CurPtr,
                                 bool IsStringLiteral) {
    assert(getLangOpts().CPlusPlus);
  
    // Maximally munch an identifier.
    unsigned Size;
    char C = getCharAndSize(CurPtr, Size);
    bool Consumed = false;
  
    if (!isIdentifierHead(C)) {
      if (C == '\\' && tryConsumeIdentifierUCN(CurPtr, Size, Result))
        Consumed = true;
      else if (!isASCII(C) && tryConsumeIdentifierUTF8Char(CurPtr))
        Consumed = true;
      else
        return CurPtr;
    }
  
    if (!getLangOpts().CPlusPlus11) {
      if (!isLexingRawMode())
        Diag(CurPtr,
             C == '_' ? diag::warn_cxx11_compat_user_defined_literal
                      : diag::warn_cxx11_compat_reserved_user_defined_literal)
          << FixItHint::CreateInsertion(getSourceLocation(CurPtr), " ");
      return CurPtr;
    }
  
    // C++11 [lex.ext]p10, [usrlit.suffix]p1: A program containing a ud-suffix
    // that does not start with an underscore is ill-formed. As a conforming
    // extension, we treat all such suffixes as if they had whitespace before
    // them. We assume a suffix beginning with a UCN or UTF-8 character is more
    // likely to be a ud-suffix than a macro, however, and accept that.
    if (!Consumed) {
      bool IsUDSuffix = false;
      if (C == '_')
        IsUDSuffix = true;
      else if (IsStringLiteral && getLangOpts().CPlusPlus14) {
        // In C++1y, we need to look ahead a few characters to see if this is a
        // valid suffix for a string literal or a numeric literal (this could be
        // the 'operator""if' defining a numeric literal operator).
        const unsigned MaxStandardSuffixLength = 3;
        char Buffer[MaxStandardSuffixLength] = { C };
        unsigned Consumed = Size;
        unsigned Chars = 1;
        while (true) {
          unsigned NextSize;
          char Next = getCharAndSizeNoWarn(CurPtr + Consumed, NextSize,
                                           getLangOpts());
          if (!isIdentifierBody(Next)) {
            // End of suffix. Check whether this is on the whitelist.
            const StringRef CompleteSuffix(Buffer, Chars);
            IsUDSuffix = StringLiteralParser::isValidUDSuffix(getLangOpts(),
                                                              CompleteSuffix);
            break;
          }
  
          if (Chars == MaxStandardSuffixLength)
            // Too long: can't be a standard suffix.
            break;
  
          Buffer[Chars++] = Next;
          Consumed += NextSize;
        }
      }
  
      if (!IsUDSuffix) {
        if (!isLexingRawMode())
          Diag(CurPtr, getLangOpts().MSVCCompat
                           ? diag::ext_ms_reserved_user_defined_literal
                           : diag::ext_reserved_user_defined_literal)
            << FixItHint::CreateInsertion(getSourceLocation(CurPtr), " ");
        return CurPtr;
      }
  
      CurPtr = ConsumeChar(CurPtr, Size, Result);
    }
  
    Result.setFlag(Token::HasUDSuffix);
    while (true) {
      C = getCharAndSize(CurPtr, Size);
      if (isIdentifierBody(C)) { CurPtr = ConsumeChar(CurPtr, Size, Result); }
      else if (C == '\\' && tryConsumeIdentifierUCN(CurPtr, Size, Result)) {}
      else if (!isASCII(C) && tryConsumeIdentifierUTF8Char(CurPtr)) {}
      else break;
    }
  
    return CurPtr;
  }
  
  /// LexStringLiteral - Lex the remainder of a string literal, after having lexed
  /// either " or L" or u8" or u" or U".
  bool Lexer::LexStringLiteral(Token &Result, const char *CurPtr,
                               tok::TokenKind Kind) {
    const char *AfterQuote = CurPtr;
    // Does this string contain the \0 character?
    const char *NulCharacter = nullptr;
  
    if (!isLexingRawMode() &&
        (Kind == tok::utf8_string_literal ||
         Kind == tok::utf16_string_literal ||
         Kind == tok::utf32_string_literal))
      Diag(BufferPtr, getLangOpts().CPlusPlus
             ? diag::warn_cxx98_compat_unicode_literal
             : diag::warn_c99_compat_unicode_literal);
  
    char C = getAndAdvanceChar(CurPtr, Result);
    while (C != '"') {
      // Skip escaped characters.  Escaped newlines will already be processed by
      // getAndAdvanceChar.
      if (C == '\\')
        C = getAndAdvanceChar(CurPtr, Result);
  
      if (C == '\n' || C == '\r' ||             // Newline.
          (C == 0 && CurPtr-1 == BufferEnd)) {  // End of file.
        if (!isLexingRawMode() && !LangOpts.AsmPreprocessor)
          Diag(BufferPtr, diag::ext_unterminated_char_or_string) << 1;
        FormTokenWithChars(Result, CurPtr-1, tok::unknown);
        return true;
      }
  
      if (C == 0) {
        if (isCodeCompletionPoint(CurPtr-1)) {
          if (ParsingFilename)
            codeCompleteIncludedFile(AfterQuote, CurPtr - 1, /*IsAngled=*/false);
          else
            PP->CodeCompleteNaturalLanguage();
          FormTokenWithChars(Result, CurPtr - 1, tok::unknown);
          cutOffLexing();
          return true;
        }
  
        NulCharacter = CurPtr-1;
      }
      C = getAndAdvanceChar(CurPtr, Result);
    }
  
    // If we are in C++11, lex the optional ud-suffix.
    if (getLangOpts().CPlusPlus)
      CurPtr = LexUDSuffix(Result, CurPtr, true);
  
    // If a nul character existed in the string, warn about it.
    if (NulCharacter && !isLexingRawMode())
      Diag(NulCharacter, diag::null_in_char_or_string) << 1;
  
    // Update the location of the token as well as the BufferPtr instance var.
    const char *TokStart = BufferPtr;
    FormTokenWithChars(Result, CurPtr, Kind);
    Result.setLiteralData(TokStart);
    return true;
  }
  
  /// LexRawStringLiteral - Lex the remainder of a raw string literal, after
  /// having lexed R", LR", u8R", uR", or UR".
  bool Lexer::LexRawStringLiteral(Token &Result, const char *CurPtr,
                                  tok::TokenKind Kind) {
    // This function doesn't use getAndAdvanceChar because C++0x [lex.pptoken]p3:
    //  Between the initial and final double quote characters of the raw string,
    //  any transformations performed in phases 1 and 2 (trigraphs,
    //  universal-character-names, and line splicing) are reverted.
  
    if (!isLexingRawMode())
      Diag(BufferPtr, diag::warn_cxx98_compat_raw_string_literal);
  
    unsigned PrefixLen = 0;
  
    while (PrefixLen != 16 && isRawStringDelimBody(CurPtr[PrefixLen]))
      ++PrefixLen;
  
    // If the last character was not a '(', then we didn't lex a valid delimiter.
    if (CurPtr[PrefixLen] != '(') {
      if (!isLexingRawMode()) {
        const char *PrefixEnd = &CurPtr[PrefixLen];
        if (PrefixLen == 16) {
          Diag(PrefixEnd, diag::err_raw_delim_too_long);
        } else {
          Diag(PrefixEnd, diag::err_invalid_char_raw_delim)
            << StringRef(PrefixEnd, 1);
        }
      }
  
      // Search for the next '"' in hopes of salvaging the lexer. Unfortunately,
      // it's possible the '"' was intended to be part of the raw string, but
      // there's not much we can do about that.
      while (true) {
        char C = *CurPtr++;
  
        if (C == '"')
          break;
        if (C == 0 && CurPtr-1 == BufferEnd) {
          --CurPtr;
          break;
        }
      }
  
      FormTokenWithChars(Result, CurPtr, tok::unknown);
      return true;
    }
  
    // Save prefix and move CurPtr past it
    const char *Prefix = CurPtr;
    CurPtr += PrefixLen + 1; // skip over prefix and '('
  
    while (true) {
      char C = *CurPtr++;
  
      if (C == ')') {
        // Check for prefix match and closing quote.
        if (strncmp(CurPtr, Prefix, PrefixLen) == 0 && CurPtr[PrefixLen] == '"') {
          CurPtr += PrefixLen + 1; // skip over prefix and '"'
          break;
        }
      } else if (C == 0 && CurPtr-1 == BufferEnd) { // End of file.
        if (!isLexingRawMode())
          Diag(BufferPtr, diag::err_unterminated_raw_string)
            << StringRef(Prefix, PrefixLen);
        FormTokenWithChars(Result, CurPtr-1, tok::unknown);
        return true;
      }
    }
  
    // If we are in C++11, lex the optional ud-suffix.
    if (getLangOpts().CPlusPlus)
      CurPtr = LexUDSuffix(Result, CurPtr, true);
  
    // Update the location of token as well as BufferPtr.
    const char *TokStart = BufferPtr;
    FormTokenWithChars(Result, CurPtr, Kind);
    Result.setLiteralData(TokStart);
    return true;
  }
  
  /// LexAngledStringLiteral - Lex the remainder of an angled string literal,
  /// after having lexed the '<' character.  This is used for #include filenames.
  bool Lexer::LexAngledStringLiteral(Token &Result, const char *CurPtr) {
    // Does this string contain the \0 character?
    const char *NulCharacter = nullptr;
    const char *AfterLessPos = CurPtr;
    char C = getAndAdvanceChar(CurPtr, Result);
    while (C != '>') {
      // Skip escaped characters.  Escaped newlines will already be processed by
      // getAndAdvanceChar.
      if (C == '\\')
        C = getAndAdvanceChar(CurPtr, Result);
  
      if (C == '\n' || C == '\r' ||                // Newline.
          (C == 0 && (CurPtr - 1 == BufferEnd))) { // End of file.
        // If the filename is unterminated, then it must just be a lone <
        // character.  Return this as such.
        FormTokenWithChars(Result, AfterLessPos, tok::less);
        return true;
      }
  
      if (C == 0) {
        if (isCodeCompletionPoint(CurPtr - 1)) {
          codeCompleteIncludedFile(AfterLessPos, CurPtr - 1, /*IsAngled=*/true);
          cutOffLexing();
          FormTokenWithChars(Result, CurPtr - 1, tok::unknown);
          return true;
        }
        NulCharacter = CurPtr-1;
      }
      C = getAndAdvanceChar(CurPtr, Result);
    }
  
    // If a nul character existed in the string, warn about it.
    if (NulCharacter && !isLexingRawMode())
      Diag(NulCharacter, diag::null_in_char_or_string) << 1;
  
    // Update the location of token as well as BufferPtr.
    const char *TokStart = BufferPtr;
    FormTokenWithChars(Result, CurPtr, tok::angle_string_literal);
    Result.setLiteralData(TokStart);
    return true;
  }
  
  void Lexer::codeCompleteIncludedFile(const char *PathStart,
                                       const char *CompletionPoint,
                                       bool IsAngled) {
    // Completion only applies to the filename, after the last slash.
    StringRef PartialPath(PathStart, CompletionPoint - PathStart);
    auto Slash = PartialPath.find_last_of(LangOpts.MSVCCompat ? "/\\" : "/");
    StringRef Dir =
        (Slash == StringRef::npos) ? "" : PartialPath.take_front(Slash);
    const char *StartOfFilename =
        (Slash == StringRef::npos) ? PathStart : PathStart + Slash + 1;
    // Code completion filter range is the filename only, up to completion point.
    PP->setCodeCompletionIdentifierInfo(&PP->getIdentifierTable().get(
        StringRef(StartOfFilename, CompletionPoint - StartOfFilename)));
    // We should replace the characters up to the closing quote, if any.
    while (CompletionPoint < BufferEnd) {
      char Next = *(CompletionPoint + 1);
      if (Next == 0 || Next == '\r' || Next == '\n')
        break;
      ++CompletionPoint;
      if (Next == (IsAngled ? '>' : '"'))
        break;
    }
    PP->setCodeCompletionTokenRange(
        FileLoc.getLocWithOffset(StartOfFilename - BufferStart),
        FileLoc.getLocWithOffset(CompletionPoint - BufferStart));
    PP->CodeCompleteIncludedFile(Dir, IsAngled);
  }
  
  /// LexCharConstant - Lex the remainder of a character constant, after having
  /// lexed either ' or L' or u8' or u' or U'.
  bool Lexer::LexCharConstant(Token &Result, const char *CurPtr,
                              tok::TokenKind Kind) {
    // Does this character contain the \0 character?
    const char *NulCharacter = nullptr;
  
    if (!isLexingRawMode()) {
      if (Kind == tok::utf16_char_constant || Kind == tok::utf32_char_constant)
        Diag(BufferPtr, getLangOpts().CPlusPlus
                            ? diag::warn_cxx98_compat_unicode_literal
                            : diag::warn_c99_compat_unicode_literal);
      else if (Kind == tok::utf8_char_constant)
        Diag(BufferPtr, diag::warn_cxx14_compat_u8_character_literal);
    }
  
    char C = getAndAdvanceChar(CurPtr, Result);
    if (C == '\'') {
      if (!isLexingRawMode() && !LangOpts.AsmPreprocessor)
        Diag(BufferPtr, diag::ext_empty_character);
      FormTokenWithChars(Result, CurPtr, tok::unknown);
      return true;
    }
  
    while (C != '\'') {
      // Skip escaped characters.
      if (C == '\\')
        C = getAndAdvanceChar(CurPtr, Result);
  
      if (C == '\n' || C == '\r' ||             // Newline.
          (C == 0 && CurPtr-1 == BufferEnd)) {  // End of file.
        if (!isLexingRawMode() && !LangOpts.AsmPreprocessor)
          Diag(BufferPtr, diag::ext_unterminated_char_or_string) << 0;
        FormTokenWithChars(Result, CurPtr-1, tok::unknown);
        return true;
      }
  
      if (C == 0) {
        if (isCodeCompletionPoint(CurPtr-1)) {
          PP->CodeCompleteNaturalLanguage();
          FormTokenWithChars(Result, CurPtr-1, tok::unknown);
          cutOffLexing();
          return true;
        }
  
        NulCharacter = CurPtr-1;
      }
      C = getAndAdvanceChar(CurPtr, Result);
    }
  
    // If we are in C++11, lex the optional ud-suffix.
    if (getLangOpts().CPlusPlus)
      CurPtr = LexUDSuffix(Result, CurPtr, false);
  
    // If a nul character existed in the character, warn about it.
    if (NulCharacter && !isLexingRawMode())
      Diag(NulCharacter, diag::null_in_char_or_string) << 0;
  
    // Update the location of token as well as BufferPtr.
    const char *TokStart = BufferPtr;
    FormTokenWithChars(Result, CurPtr, Kind);
    Result.setLiteralData(TokStart);
    return true;
  }
  
  /// SkipWhitespace - Efficiently skip over a series of whitespace characters.
  /// Update BufferPtr to point to the next non-whitespace character and return.
  ///
  /// This method forms a token and returns true if KeepWhitespaceMode is enabled.
  bool Lexer::SkipWhitespace(Token &Result, const char *CurPtr,
                             bool &TokAtPhysicalStartOfLine) {
    // Whitespace - Skip it, then return the token after the whitespace.
    bool SawNewline = isVerticalWhitespace(CurPtr[-1]);
  
    unsigned char Char = *CurPtr;
  
    // Skip consecutive spaces efficiently.
    while (true) {
      // Skip horizontal whitespace very aggressively.
      while (isHorizontalWhitespace(Char))
        Char = *++CurPtr;
  
      // Otherwise if we have something other than whitespace, we're done.
      if (!isVerticalWhitespace(Char))
        break;
  
      if (ParsingPreprocessorDirective) {
        // End of preprocessor directive line, let LexTokenInternal handle this.
        BufferPtr = CurPtr;
        return false;
      }
  
      // OK, but handle newline.
      SawNewline = true;
      Char = *++CurPtr;
    }
  
    // If the client wants us to return whitespace, return it now.
    if (isKeepWhitespaceMode()) {
      FormTokenWithChars(Result, CurPtr, tok::unknown);
      if (SawNewline) {
        IsAtStartOfLine = true;
        IsAtPhysicalStartOfLine = true;
      }
      // FIXME: The next token will not have LeadingSpace set.
      return true;
    }
  
    // If this isn't immediately after a newline, there is leading space.
    char PrevChar = CurPtr[-1];
    bool HasLeadingSpace = !isVerticalWhitespace(PrevChar);
  
    Result.setFlagValue(Token::LeadingSpace, HasLeadingSpace);
    if (SawNewline) {
      Result.setFlag(Token::StartOfLine);
      TokAtPhysicalStartOfLine = true;
    }
  
    BufferPtr = CurPtr;
    return false;
  }
  
  /// We have just read the // characters from input.  Skip until we find the
  /// newline character that terminates the comment.  Then update BufferPtr and
  /// return.
  ///
  /// If we're in KeepCommentMode or any CommentHandler has inserted
  /// some tokens, this will store the first token and return true.
  bool Lexer::SkipLineComment(Token &Result, const char *CurPtr,
                              bool &TokAtPhysicalStartOfLine) {
    // If Line comments aren't explicitly enabled for this language, emit an
    // extension warning.
    if (!LangOpts.LineComment && !isLexingRawMode()) {
      Diag(BufferPtr, diag::ext_line_comment);
  
      // Mark them enabled so we only emit one warning for this translation
      // unit.
      LangOpts.LineComment = true;
    }
  
    // Scan over the body of the comment.  The common case, when scanning, is that
    // the comment contains normal ascii characters with nothing interesting in
    // them.  As such, optimize for this case with the inner loop.
    //
    // This loop terminates with CurPtr pointing at the newline (or end of buffer)
    // character that ends the line comment.
    char C;
    while (true) {
      C = *CurPtr;
      // Skip over characters in the fast loop.
      while (C != 0 &&                // Potentially EOF.
             C != '\n' && C != '\r')  // Newline or DOS-style newline.
        C = *++CurPtr;
  
      const char *NextLine = CurPtr;
      if (C != 0) {
        // We found a newline, see if it's escaped.
        const char *EscapePtr = CurPtr-1;
        bool HasSpace = false;
        while (isHorizontalWhitespace(*EscapePtr)) { // Skip whitespace.
          --EscapePtr;
          HasSpace = true;
        }
  
        if (*EscapePtr == '\\')
          // Escaped newline.
          CurPtr = EscapePtr;
        else if (EscapePtr[0] == '/' && EscapePtr[-1] == '?' &&
                 EscapePtr[-2] == '?' && LangOpts.Trigraphs)
          // Trigraph-escaped newline.
          CurPtr = EscapePtr-2;
        else
          break; // This is a newline, we're done.
  
        // If there was space between the backslash and newline, warn about it.
        if (HasSpace && !isLexingRawMode())
          Diag(EscapePtr, diag::backslash_newline_space);
      }
  
      // Otherwise, this is a hard case.  Fall back on getAndAdvanceChar to
      // properly decode the character.  Read it in raw mode to avoid emitting
      // diagnostics about things like trigraphs.  If we see an escaped newline,
      // we'll handle it below.
      const char *OldPtr = CurPtr;
      bool OldRawMode = isLexingRawMode();
      LexingRawMode = true;
      C = getAndAdvanceChar(CurPtr, Result);
      LexingRawMode = OldRawMode;
  
      // If we only read only one character, then no special handling is needed.
      // We're done and can skip forward to the newline.
      if (C != 0 && CurPtr == OldPtr+1) {
        CurPtr = NextLine;
        break;
      }
  
      // If we read multiple characters, and one of those characters was a \r or
      // \n, then we had an escaped newline within the comment.  Emit diagnostic
      // unless the next line is also a // comment.
      if (CurPtr != OldPtr + 1 && C != '/' &&
          (CurPtr == BufferEnd + 1 || CurPtr[0] != '/')) {
        for (; OldPtr != CurPtr; ++OldPtr)
          if (OldPtr[0] == '\n' || OldPtr[0] == '\r') {
            // Okay, we found a // comment that ends in a newline, if the next
            // line is also a // comment, but has spaces, don't emit a diagnostic.
            if (isWhitespace(C)) {
              const char *ForwardPtr = CurPtr;
              while (isWhitespace(*ForwardPtr))  // Skip whitespace.
                ++ForwardPtr;
              if (ForwardPtr[0] == '/' && ForwardPtr[1] == '/')
                break;
            }
  
            if (!isLexingRawMode())
              Diag(OldPtr-1, diag::ext_multi_line_line_comment);
            break;
          }
      }
  
      if (C == '\r' || C == '\n' || CurPtr == BufferEnd + 1) {
        --CurPtr;
        break;
      }
  
      if (C == '\0' && isCodeCompletionPoint(CurPtr-1)) {
        PP->CodeCompleteNaturalLanguage();
        cutOffLexing();
        return false;
      }
    }
  
    // Found but did not consume the newline.  Notify comment handlers about the
    // comment unless we're in a #if 0 block.
    if (PP && !isLexingRawMode() &&
        PP->HandleComment(Result, SourceRange(getSourceLocation(BufferPtr),
                                              getSourceLocation(CurPtr)))) {
      BufferPtr = CurPtr;
      return true; // A token has to be returned.
    }
  
    // If we are returning comments as tokens, return this comment as a token.
    if (inKeepCommentMode())
      return SaveLineComment(Result, CurPtr);
  
    // If we are inside a preprocessor directive and we see the end of line,
    // return immediately, so that the lexer can return this as an EOD token.
    if (ParsingPreprocessorDirective || CurPtr == BufferEnd) {
      BufferPtr = CurPtr;
      return false;
    }
  
    // Otherwise, eat the \n character.  We don't care if this is a \n\r or
    // \r\n sequence.  This is an efficiency hack (because we know the \n can't
    // contribute to another token), it isn't needed for correctness.  Note that
    // this is ok even in KeepWhitespaceMode, because we would have returned the
    /// comment above in that mode.
    ++CurPtr;
  
    // The next returned token is at the start of the line.
    Result.setFlag(Token::StartOfLine);
    TokAtPhysicalStartOfLine = true;
    // No leading whitespace seen so far.
    Result.clearFlag(Token::LeadingSpace);
    BufferPtr = CurPtr;
    return false;
  }
  
  /// If in save-comment mode, package up this Line comment in an appropriate
  /// way and return it.
  bool Lexer::SaveLineComment(Token &Result, const char *CurPtr) {
    // If we're not in a preprocessor directive, just return the // comment
    // directly.
    FormTokenWithChars(Result, CurPtr, tok::comment);
  
    if (!ParsingPreprocessorDirective || LexingRawMode)
      return true;
  
    // If this Line-style comment is in a macro definition, transmogrify it into
    // a C-style block comment.
    bool Invalid = false;
    std::string Spelling = PP->getSpelling(Result, &Invalid);
    if (Invalid)
      return true;
  
    assert(Spelling[0] == '/' && Spelling[1] == '/' && "Not line comment?");
    Spelling[1] = '*';   // Change prefix to "/*".
    Spelling += "*/";    // add suffix.
  
    Result.setKind(tok::comment);
    PP->CreateString(Spelling, Result,
                     Result.getLocation(), Result.getLocation());
    return true;
  }
  
  /// isBlockCommentEndOfEscapedNewLine - Return true if the specified newline
  /// character (either \\n or \\r) is part of an escaped newline sequence.  Issue
  /// a diagnostic if so.  We know that the newline is inside of a block comment.
  static bool isEndOfBlockCommentWithEscapedNewLine(const char *CurPtr,
                                                    Lexer *L) {
    assert(CurPtr[0] == '\n' || CurPtr[0] == '\r');
  
    // Back up off the newline.
    --CurPtr;
  
    // If this is a two-character newline sequence, skip the other character.
    if (CurPtr[0] == '\n' || CurPtr[0] == '\r') {
      // \n\n or \r\r -> not escaped newline.
      if (CurPtr[0] == CurPtr[1])
        return false;
      // \n\r or \r\n -> skip the newline.
      --CurPtr;
    }
  
    // If we have horizontal whitespace, skip over it.  We allow whitespace
    // between the slash and newline.
    bool HasSpace = false;
    while (isHorizontalWhitespace(*CurPtr) || *CurPtr == 0) {
      --CurPtr;
      HasSpace = true;
    }
  
    // If we have a slash, we know this is an escaped newline.
    if (*CurPtr == '\\') {
      if (CurPtr[-1] != '*') return false;
    } else {
      // It isn't a slash, is it the ?? / trigraph?
      if (CurPtr[0] != '/' || CurPtr[-1] != '?' || CurPtr[-2] != '?' ||
          CurPtr[-3] != '*')
        return false;
  
      // This is the trigraph ending the comment.  Emit a stern warning!
      CurPtr -= 2;
  
      // If no trigraphs are enabled, warn that we ignored this trigraph and
      // ignore this * character.
      if (!L->getLangOpts().Trigraphs) {
        if (!L->isLexingRawMode())
          L->Diag(CurPtr, diag::trigraph_ignored_block_comment);
        return false;
      }
      if (!L->isLexingRawMode())
        L->Diag(CurPtr, diag::trigraph_ends_block_comment);
    }
  
    // Warn about having an escaped newline between the */ characters.
    if (!L->isLexingRawMode())
      L->Diag(CurPtr, diag::escaped_newline_block_comment_end);
  
    // If there was space between the backslash and newline, warn about it.
    if (HasSpace && !L->isLexingRawMode())
      L->Diag(CurPtr, diag::backslash_newline_space);
  
    return true;
  }
  
  #ifdef __SSE2__
  #include <emmintrin.h>
  #elif __ALTIVEC__
  #include <altivec.h>
  #undef bool
  #endif
  
  /// We have just read from input the / and * characters that started a comment.
  /// Read until we find the * and / characters that terminate the comment.
  /// Note that we don't bother decoding trigraphs or escaped newlines in block
  /// comments, because they cannot cause the comment to end.  The only thing
  /// that can happen is the comment could end with an escaped newline between
  /// the terminating * and /.
  ///
  /// If we're in KeepCommentMode or any CommentHandler has inserted
  /// some tokens, this will store the first token and return true.
  bool Lexer::SkipBlockComment(Token &Result, const char *CurPtr,
                               bool &TokAtPhysicalStartOfLine) {
    // Scan one character past where we should, looking for a '/' character.  Once
    // we find it, check to see if it was preceded by a *.  This common
    // optimization helps people who like to put a lot of * characters in their
    // comments.
  
    // The first character we get with newlines and trigraphs skipped to handle
    // the degenerate /*/ case below correctly if the * has an escaped newline
    // after it.
    unsigned CharSize;
    unsigned char C = getCharAndSize(CurPtr, CharSize);
    CurPtr += CharSize;
    if (C == 0 && CurPtr == BufferEnd+1) {
      if (!isLexingRawMode())
        Diag(BufferPtr, diag::err_unterminated_block_comment);
      --CurPtr;
  
      // KeepWhitespaceMode should return this broken comment as a token.  Since
      // it isn't a well formed comment, just return it as an 'unknown' token.
      if (isKeepWhitespaceMode()) {
        FormTokenWithChars(Result, CurPtr, tok::unknown);
        return true;
      }
  
      BufferPtr = CurPtr;
      return false;
    }
  
    // Check to see if the first character after the '/*' is another /.  If so,
    // then this slash does not end the block comment, it is part of it.
    if (C == '/')
      C = *CurPtr++;
  
    while (true) {
      // Skip over all non-interesting characters until we find end of buffer or a
      // (probably ending) '/' character.
      if (CurPtr + 24 < BufferEnd &&
          // If there is a code-completion point avoid the fast scan because it
          // doesn't check for '\0'.
          !(PP && PP->getCodeCompletionFileLoc() == FileLoc)) {
        // While not aligned to a 16-byte boundary.
        while (C != '/' && ((intptr_t)CurPtr & 0x0F) != 0)
          C = *CurPtr++;
  
        if (C == '/') goto FoundSlash;
  
  #ifdef __SSE2__
        __m128i Slashes = _mm_set1_epi8('/');
        while (CurPtr+16 <= BufferEnd) {
          int cmp = _mm_movemask_epi8(_mm_cmpeq_epi8(*(const __m128i*)CurPtr,
                                      Slashes));
          if (cmp != 0) {
            // Adjust the pointer to point directly after the first slash. It's
            // not necessary to set C here, it will be overwritten at the end of
            // the outer loop.
            CurPtr += llvm::countTrailingZeros<unsigned>(cmp) + 1;
            goto FoundSlash;
          }
          CurPtr += 16;
        }
  #elif __ALTIVEC__
        __vector unsigned char Slashes = {
          '/', '/', '/', '/',  '/', '/', '/', '/',
          '/', '/', '/', '/',  '/', '/', '/', '/'
        };
        while (CurPtr+16 <= BufferEnd &&
               !vec_any_eq(*(const vector unsigned char*)CurPtr, Slashes))
          CurPtr += 16;
  #else
        // Scan for '/' quickly.  Many block comments are very large.
        while (CurPtr[0] != '/' &&
               CurPtr[1] != '/' &&
               CurPtr[2] != '/' &&
               CurPtr[3] != '/' &&
               CurPtr+4 < BufferEnd) {
          CurPtr += 4;
        }
  #endif
  
        // It has to be one of the bytes scanned, increment to it and read one.
        C = *CurPtr++;
      }
  
      // Loop to scan the remainder.
      while (C != '/' && C != '\0')
        C = *CurPtr++;
  
      if (C == '/') {
    FoundSlash:
        if (CurPtr[-2] == '*')  // We found the final */.  We're done!
          break;
  
        if ((CurPtr[-2] == '\n' || CurPtr[-2] == '\r')) {
          if (isEndOfBlockCommentWithEscapedNewLine(CurPtr-2, this)) {
            // We found the final */, though it had an escaped newline between the
            // * and /.  We're done!
            break;
          }
        }
        if (CurPtr[0] == '*' && CurPtr[1] != '/') {
          // If this is a /* inside of the comment, emit a warning.  Don't do this
          // if this is a /*/, which will end the comment.  This misses cases with
          // embedded escaped newlines, but oh well.
          if (!isLexingRawMode())
            Diag(CurPtr-1, diag::warn_nested_block_comment);
        }
      } else if (C == 0 && CurPtr == BufferEnd+1) {
        if (!isLexingRawMode())
          Diag(BufferPtr, diag::err_unterminated_block_comment);
        // Note: the user probably forgot a */.  We could continue immediately
        // after the /*, but this would involve lexing a lot of what really is the
        // comment, which surely would confuse the parser.
        --CurPtr;
  
        // KeepWhitespaceMode should return this broken comment as a token.  Since
        // it isn't a well formed comment, just return it as an 'unknown' token.
        if (isKeepWhitespaceMode()) {
          FormTokenWithChars(Result, CurPtr, tok::unknown);
          return true;
        }
  
        BufferPtr = CurPtr;
        return false;
      } else if (C == '\0' && isCodeCompletionPoint(CurPtr-1)) {
        PP->CodeCompleteNaturalLanguage();
        cutOffLexing();
        return false;
      }
  
      C = *CurPtr++;
    }
  
    // Notify comment handlers about the comment unless we're in a #if 0 block.
    if (PP && !isLexingRawMode() &&
        PP->HandleComment(Result, SourceRange(getSourceLocation(BufferPtr),
                                              getSourceLocation(CurPtr)))) {
      BufferPtr = CurPtr;
      return true; // A token has to be returned.
    }
  
    // If we are returning comments as tokens, return this comment as a token.
    if (inKeepCommentMode()) {
      FormTokenWithChars(Result, CurPtr, tok::comment);
      return true;
    }
  
    // It is common for the tokens immediately after a /**/ comment to be
    // whitespace.  Instead of going through the big switch, handle it
    // efficiently now.  This is safe even in KeepWhitespaceMode because we would
    // have already returned above with the comment as a token.
    if (isHorizontalWhitespace(*CurPtr)) {
      SkipWhitespace(Result, CurPtr+1, TokAtPhysicalStartOfLine);
      return false;
    }
  
    // Otherwise, just return so that the next character will be lexed as a token.
    BufferPtr = CurPtr;
    Result.setFlag(Token::LeadingSpace);
    return false;
  }
  
  //===----------------------------------------------------------------------===//
  // Primary Lexing Entry Points
  //===----------------------------------------------------------------------===//
  
  /// ReadToEndOfLine - Read the rest of the current preprocessor line as an
  /// uninterpreted string.  This switches the lexer out of directive mode.
  void Lexer::ReadToEndOfLine(SmallVectorImpl<char> *Result) {
    assert(ParsingPreprocessorDirective && ParsingFilename == false &&
           "Must be in a preprocessing directive!");
    Token Tmp;
  
    // CurPtr - Cache BufferPtr in an automatic variable.
    const char *CurPtr = BufferPtr;
    while (true) {
      char Char = getAndAdvanceChar(CurPtr, Tmp);
      switch (Char) {
      default:
        if (Result)
          Result->push_back(Char);
        break;
      case 0:  // Null.
        // Found end of file?
        if (CurPtr-1 != BufferEnd) {
          if (isCodeCompletionPoint(CurPtr-1)) {
            PP->CodeCompleteNaturalLanguage();
            cutOffLexing();
            return;
          }
  
          // Nope, normal character, continue.
          if (Result)
            Result->push_back(Char);
          break;
        }
        // FALL THROUGH.
        LLVM_FALLTHROUGH;
      case '\r':
      case '\n':
        // Okay, we found the end of the line. First, back up past the \0, \r, \n.
        assert(CurPtr[-1] == Char && "Trigraphs for newline?");
        BufferPtr = CurPtr-1;
  
        // Next, lex the character, which should handle the EOD transition.
        Lex(Tmp);
        if (Tmp.is(tok::code_completion)) {
          if (PP)
            PP->CodeCompleteNaturalLanguage();
          Lex(Tmp);
        }
        assert(Tmp.is(tok::eod) && "Unexpected token!");
  
        // Finally, we're done;
        return;
      }
    }
  }
  
  /// LexEndOfFile - CurPtr points to the end of this file.  Handle this
  /// condition, reporting diagnostics and handling other edge cases as required.
  /// This returns true if Result contains a token, false if PP.Lex should be
  /// called again.
  bool Lexer::LexEndOfFile(Token &Result, const char *CurPtr) {
    // If we hit the end of the file while parsing a preprocessor directive,
    // end the preprocessor directive first.  The next token returned will
    // then be the end of file.
    if (ParsingPreprocessorDirective) {
      // Done parsing the "line".
      ParsingPreprocessorDirective = false;
      // Update the location of token as well as BufferPtr.
      FormTokenWithChars(Result, CurPtr, tok::eod);
  
      // Restore comment saving mode, in case it was disabled for directive.
      if (PP)
        resetExtendedTokenMode();
      return true;  // Have a token.
    }
  
    // If we are in raw mode, return this event as an EOF token.  Let the caller
    // that put us in raw mode handle the event.
    if (isLexingRawMode()) {
      Result.startToken();
      BufferPtr = BufferEnd;
      FormTokenWithChars(Result, BufferEnd, tok::eof);
      return true;
    }
  
    if (PP->isRecordingPreamble() && PP->isInPrimaryFile()) {
      PP->setRecordedPreambleConditionalStack(ConditionalStack);
      ConditionalStack.clear();
    }
  
    // Issue diagnostics for unterminated #if and missing newline.
  
    // If we are in a #if directive, emit an error.
    while (!ConditionalStack.empty()) {
      if (PP->getCodeCompletionFileLoc() != FileLoc)
        PP->Diag(ConditionalStack.back().IfLoc,
                 diag::err_pp_unterminated_conditional);
      ConditionalStack.pop_back();
    }
  
    // C99 5.1.1.2p2: If the file is non-empty and didn't end in a newline, issue
    // a pedwarn.
    if (CurPtr != BufferStart && (CurPtr[-1] != '\n' && CurPtr[-1] != '\r')) {
      DiagnosticsEngine &Diags = PP->getDiagnostics();
      SourceLocation EndLoc = getSourceLocation(BufferEnd);
      unsigned DiagID;
  
      if (LangOpts.CPlusPlus11) {
        // C++11 [lex.phases] 2.2 p2
        // Prefer the C++98 pedantic compatibility warning over the generic,
        // non-extension, user-requested "missing newline at EOF" warning.
        if (!Diags.isIgnored(diag::warn_cxx98_compat_no_newline_eof, EndLoc)) {
          DiagID = diag::warn_cxx98_compat_no_newline_eof;
        } else {
          DiagID = diag::warn_no_newline_eof;
        }
      } else {
        DiagID = diag::ext_no_newline_eof;
      }
  
      Diag(BufferEnd, DiagID)
        << FixItHint::CreateInsertion(EndLoc, "\n");
    }
  
    BufferPtr = CurPtr;
  
    // Finally, let the preprocessor handle this.
    return PP->HandleEndOfFile(Result, isPragmaLexer());
  }
  
  /// isNextPPTokenLParen - Return 1 if the next unexpanded token lexed from
  /// the specified lexer will return a tok::l_paren token, 0 if it is something
  /// else and 2 if there are no more tokens in the buffer controlled by the
  /// lexer.
  unsigned Lexer::isNextPPTokenLParen() {
    assert(!LexingRawMode && "How can we expand a macro from a skipping buffer?");
  
    // Switch to 'skipping' mode.  This will ensure that we can lex a token
    // without emitting diagnostics, disables macro expansion, and will cause EOF
    // to return an EOF token instead of popping the include stack.
    LexingRawMode = true;
  
    // Save state that can be changed while lexing so that we can restore it.
    const char *TmpBufferPtr = BufferPtr;
    bool inPPDirectiveMode = ParsingPreprocessorDirective;
    bool atStartOfLine = IsAtStartOfLine;
    bool atPhysicalStartOfLine = IsAtPhysicalStartOfLine;
    bool leadingSpace = HasLeadingSpace;
  
    Token Tok;
    Lex(Tok);
  
    // Restore state that may have changed.
    BufferPtr = TmpBufferPtr;
    ParsingPreprocessorDirective = inPPDirectiveMode;
    HasLeadingSpace = leadingSpace;
    IsAtStartOfLine = atStartOfLine;
    IsAtPhysicalStartOfLine = atPhysicalStartOfLine;
  
    // Restore the lexer back to non-skipping mode.
    LexingRawMode = false;
  
    if (Tok.is(tok::eof))
      return 2;
    return Tok.is(tok::l_paren);
  }
  
  /// Find the end of a version control conflict marker.
  static const char *FindConflictEnd(const char *CurPtr, const char *BufferEnd,
                                     ConflictMarkerKind CMK) {
    const char *Terminator = CMK == CMK_Perforce ? "<<<<\n" : ">>>>>>>";
    size_t TermLen = CMK == CMK_Perforce ? 5 : 7;
    auto RestOfBuffer = StringRef(CurPtr, BufferEnd - CurPtr).substr(TermLen);
    size_t Pos = RestOfBuffer.find(Terminator);
    while (Pos != StringRef::npos) {
      // Must occur at start of line.
      if (Pos == 0 ||
          (RestOfBuffer[Pos - 1] != '\r' && RestOfBuffer[Pos - 1] != '\n')) {
        RestOfBuffer = RestOfBuffer.substr(Pos+TermLen);
        Pos = RestOfBuffer.find(Terminator);
        continue;
      }
      return RestOfBuffer.data()+Pos;
    }
    return nullptr;
  }
  
  /// IsStartOfConflictMarker - If the specified pointer is the start of a version
  /// control conflict marker like '<<<<<<<', recognize it as such, emit an error
  /// and recover nicely.  This returns true if it is a conflict marker and false
  /// if not.
  bool Lexer::IsStartOfConflictMarker(const char *CurPtr) {
    // Only a conflict marker if it starts at the beginning of a line.
    if (CurPtr != BufferStart &&
        CurPtr[-1] != '\n' && CurPtr[-1] != '\r')
      return false;
  
    // Check to see if we have <<<<<<< or >>>>.
    if (!StringRef(CurPtr, BufferEnd - CurPtr).startswith("<<<<<<<") &&
        !StringRef(CurPtr, BufferEnd - CurPtr).startswith(">>>> "))
      return false;
  
    // If we have a situation where we don't care about conflict markers, ignore
    // it.
    if (CurrentConflictMarkerState || isLexingRawMode())
      return false;
  
    ConflictMarkerKind Kind = *CurPtr == '<' ? CMK_Normal : CMK_Perforce;
  
    // Check to see if there is an ending marker somewhere in the buffer at the
    // start of a line to terminate this conflict marker.
    if (FindConflictEnd(CurPtr, BufferEnd, Kind)) {
      // We found a match.  We are really in a conflict marker.
      // Diagnose this, and ignore to the end of line.
      Diag(CurPtr, diag::err_conflict_marker);
      CurrentConflictMarkerState = Kind;
  
      // Skip ahead to the end of line.  We know this exists because the
      // end-of-conflict marker starts with \r or \n.
      while (*CurPtr != '\r' && *CurPtr != '\n') {
        assert(CurPtr != BufferEnd && "Didn't find end of line");
        ++CurPtr;
      }
      BufferPtr = CurPtr;
      return true;
    }
  
    // No end of conflict marker found.
    return false;
  }
  
  /// HandleEndOfConflictMarker - If this is a '====' or '||||' or '>>>>', or if
  /// it is '<<<<' and the conflict marker started with a '>>>>' marker, then it
  /// is the end of a conflict marker.  Handle it by ignoring up until the end of
  /// the line.  This returns true if it is a conflict marker and false if not.
  bool Lexer::HandleEndOfConflictMarker(const char *CurPtr) {
    // Only a conflict marker if it starts at the beginning of a line.
    if (CurPtr != BufferStart &&
        CurPtr[-1] != '\n' && CurPtr[-1] != '\r')
      return false;
  
    // If we have a situation where we don't care about conflict markers, ignore
    // it.
    if (!CurrentConflictMarkerState || isLexingRawMode())
      return false;
  
    // Check to see if we have the marker (4 characters in a row).
    for (unsigned i = 1; i != 4; ++i)
      if (CurPtr[i] != CurPtr[0])
        return false;
  
    // If we do have it, search for the end of the conflict marker.  This could
    // fail if it got skipped with a '#if 0' or something.  Note that CurPtr might
    // be the end of conflict marker.
    if (const char *End = FindConflictEnd(CurPtr, BufferEnd,
                                          CurrentConflictMarkerState)) {
      CurPtr = End;
  
      // Skip ahead to the end of line.
      while (CurPtr != BufferEnd && *CurPtr != '\r' && *CurPtr != '\n')
        ++CurPtr;
  
      BufferPtr = CurPtr;
  
      // No longer in the conflict marker.
      CurrentConflictMarkerState = CMK_None;
      return true;
    }
  
    return false;
  }
  
  static const char *findPlaceholderEnd(const char *CurPtr,
                                        const char *BufferEnd) {
    if (CurPtr == BufferEnd)
      return nullptr;
    BufferEnd -= 1; // Scan until the second last character.
    for (; CurPtr != BufferEnd; ++CurPtr) {
      if (CurPtr[0] == '#' && CurPtr[1] == '>')
        return CurPtr + 2;
    }
    return nullptr;
  }
  
  bool Lexer::lexEditorPlaceholder(Token &Result, const char *CurPtr) {
    assert(CurPtr[-1] == '<' && CurPtr[0] == '#' && "Not a placeholder!");
    if (!PP || !PP->getPreprocessorOpts().LexEditorPlaceholders || LexingRawMode)
      return false;
    const char *End = findPlaceholderEnd(CurPtr + 1, BufferEnd);
    if (!End)
      return false;
    const char *Start = CurPtr - 1;
    if (!LangOpts.AllowEditorPlaceholders)
      Diag(Start, diag::err_placeholder_in_source);
    Result.startToken();
    FormTokenWithChars(Result, End, tok::raw_identifier);
    Result.setRawIdentifierData(Start);
    PP->LookUpIdentifierInfo(Result);
    Result.setFlag(Token::IsEditorPlaceholder);
    BufferPtr = End;
    return true;
  }
  
  bool Lexer::isCodeCompletionPoint(const char *CurPtr) const {
    if (PP && PP->isCodeCompletionEnabled()) {
      SourceLocation Loc = FileLoc.getLocWithOffset(CurPtr-BufferStart);
      return Loc == PP->getCodeCompletionLoc();
    }
  
    return false;
  }
  
  uint32_t Lexer::tryReadUCN(const char *&StartPtr, const char *SlashLoc,
                             Token *Result) {
    unsigned CharSize;
    char Kind = getCharAndSize(StartPtr, CharSize);
  
    unsigned NumHexDigits;
    if (Kind == 'u')
      NumHexDigits = 4;
    else if (Kind == 'U')
      NumHexDigits = 8;
    else
      return 0;
  
    if (!LangOpts.CPlusPlus && !LangOpts.C99) {
      if (Result && !isLexingRawMode())
        Diag(SlashLoc, diag::warn_ucn_not_valid_in_c89);
      return 0;
    }
  
    const char *CurPtr = StartPtr + CharSize;
    const char *KindLoc = &CurPtr[-1];
  
    uint32_t CodePoint = 0;
    for (unsigned i = 0; i < NumHexDigits; ++i) {
      char C = getCharAndSize(CurPtr, CharSize);
  
      unsigned Value = llvm::hexDigitValue(C);
      if (Value == -1U) {
        if (Result && !isLexingRawMode()) {
          if (i == 0) {
            Diag(BufferPtr, diag::warn_ucn_escape_no_digits)
              << StringRef(KindLoc, 1);
          } else {
            Diag(BufferPtr, diag::warn_ucn_escape_incomplete);
  
            // If the user wrote \U1234, suggest a fixit to \u.
            if (i == 4 && NumHexDigits == 8) {
              CharSourceRange URange = makeCharRange(*this, KindLoc, KindLoc + 1);
              Diag(KindLoc, diag::note_ucn_four_not_eight)
                << FixItHint::CreateReplacement(URange, "u");
            }
          }
        }
  
        return 0;
      }
  
      CodePoint <<= 4;
      CodePoint += Value;
  
      CurPtr += CharSize;
    }
  
    if (Result) {
      Result->setFlag(Token::HasUCN);
      if (CurPtr - StartPtr == (ptrdiff_t)NumHexDigits + 2)
        StartPtr = CurPtr;
      else
        while (StartPtr != CurPtr)
          (void)getAndAdvanceChar(StartPtr, *Result);
    } else {
      StartPtr = CurPtr;
    }
  
    // Don't apply C family restrictions to UCNs in assembly mode
    if (LangOpts.AsmPreprocessor)
      return CodePoint;
  
    // C99 6.4.3p2: A universal character name shall not specify a character whose
    //   short identifier is less than 00A0 other than 0024 ($), 0040 (@), or
    //   0060 (`), nor one in the range D800 through DFFF inclusive.)
    // C++11 [lex.charset]p2: If the hexadecimal value for a
    //   universal-character-name corresponds to a surrogate code point (in the
    //   range 0xD800-0xDFFF, inclusive), the program is ill-formed. Additionally,
    //   if the hexadecimal value for a universal-character-name outside the
    //   c-char-sequence, s-char-sequence, or r-char-sequence of a character or
    //   string literal corresponds to a control character (in either of the
    //   ranges 0x00-0x1F or 0x7F-0x9F, both inclusive) or to a character in the
    //   basic source character set, the program is ill-formed.
    if (CodePoint < 0xA0) {
      if (CodePoint == 0x24 || CodePoint == 0x40 || CodePoint == 0x60)
        return CodePoint;
  
      // We don't use isLexingRawMode() here because we need to warn about bad
      // UCNs even when skipping preprocessing tokens in a #if block.
      if (Result && PP) {
        if (CodePoint < 0x20 || CodePoint >= 0x7F)
          Diag(BufferPtr, diag::err_ucn_control_character);
        else {
          char C = static_cast<char>(CodePoint);
          Diag(BufferPtr, diag::err_ucn_escape_basic_scs) << StringRef(&C, 1);
        }
      }
  
      return 0;
    } else if (CodePoint >= 0xD800 && CodePoint <= 0xDFFF) {
      // C++03 allows UCNs representing surrogate characters. C99 and C++11 don't.
      // We don't use isLexingRawMode() here because we need to diagnose bad
      // UCNs even when skipping preprocessing tokens in a #if block.
      if (Result && PP) {
        if (LangOpts.CPlusPlus && !LangOpts.CPlusPlus11)
          Diag(BufferPtr, diag::warn_ucn_escape_surrogate);
        else
          Diag(BufferPtr, diag::err_ucn_escape_invalid);
      }
      return 0;
    }
  
    return CodePoint;
  }
  
  bool Lexer::CheckUnicodeWhitespace(Token &Result, uint32_t C,
                                     const char *CurPtr) {
    static const llvm::sys::UnicodeCharSet UnicodeWhitespaceChars(
        UnicodeWhitespaceCharRanges);
    if (!isLexingRawMode() && !PP->isPreprocessedOutput() &&
        UnicodeWhitespaceChars.contains(C)) {
      Diag(BufferPtr, diag::ext_unicode_whitespace)
        << makeCharRange(*this, BufferPtr, CurPtr);
  
      Result.setFlag(Token::LeadingSpace);
      return true;
    }
    return false;
  }
  
  bool Lexer::LexUnicode(Token &Result, uint32_t C, const char *CurPtr) {
    if (isAllowedIDChar(C, LangOpts) && isAllowedInitiallyIDChar(C, LangOpts)) {
      if (!isLexingRawMode() && !ParsingPreprocessorDirective &&
          !PP->isPreprocessedOutput()) {
        maybeDiagnoseIDCharCompat(PP->getDiagnostics(), C,
                                  makeCharRange(*this, BufferPtr, CurPtr),
                                  /*IsFirst=*/true);
        maybeDiagnoseUTF8Homoglyph(PP->getDiagnostics(), C,
                                   makeCharRange(*this, BufferPtr, CurPtr));
      }
  
      MIOpt.ReadToken();
      return LexIdentifier(Result, CurPtr);
    }
  
    if (!isLexingRawMode() && !ParsingPreprocessorDirective &&
        !PP->isPreprocessedOutput() &&
        !isASCII(*BufferPtr) && !isAllowedIDChar(C, LangOpts)) {
      // Non-ASCII characters tend to creep into source code unintentionally.
      // Instead of letting the parser complain about the unknown token,
      // just drop the character.
      // Note that we can /only/ do this when the non-ASCII character is actually
      // spelled as Unicode, not written as a UCN. The standard requires that
      // we not throw away any possible preprocessor tokens, but there's a
      // loophole in the mapping of Unicode characters to basic character set
      // characters that allows us to map these particular characters to, say,
      // whitespace.
      Diag(BufferPtr, diag::err_non_ascii)
        << FixItHint::CreateRemoval(makeCharRange(*this, BufferPtr, CurPtr));
  
      BufferPtr = CurPtr;
      return false;
    }
  
    // Otherwise, we have an explicit UCN or a character that's unlikely to show
    // up by accident.
    MIOpt.ReadToken();
    FormTokenWithChars(Result, CurPtr, tok::unknown);
    return true;
  }
  
  void Lexer::PropagateLineStartLeadingSpaceInfo(Token &Result) {
    IsAtStartOfLine = Result.isAtStartOfLine();
    HasLeadingSpace = Result.hasLeadingSpace();
    HasLeadingEmptyMacro = Result.hasLeadingEmptyMacro();
    // Note that this doesn't affect IsAtPhysicalStartOfLine.
  }
  
  bool Lexer::Lex(Token &Result) {
    // Start a new token.
    Result.startToken();
  
    // Set up misc whitespace flags for LexTokenInternal.
    if (IsAtStartOfLine) {
      Result.setFlag(Token::StartOfLine);
      IsAtStartOfLine = false;
    }
  
    if (HasLeadingSpace) {
      Result.setFlag(Token::LeadingSpace);
      HasLeadingSpace = false;
    }
  
    if (HasLeadingEmptyMacro) {
      Result.setFlag(Token::LeadingEmptyMacro);
      HasLeadingEmptyMacro = false;
    }
  
    bool atPhysicalStartOfLine = IsAtPhysicalStartOfLine;
    IsAtPhysicalStartOfLine = false;
    bool isRawLex = isLexingRawMode();
    (void) isRawLex;
    bool returnedToken = LexTokenInternal(Result, atPhysicalStartOfLine);
    // (After the LexTokenInternal call, the lexer might be destroyed.)
    assert((returnedToken || !isRawLex) && "Raw lex must succeed");
    return returnedToken;
  }
  
  /// LexTokenInternal - This implements a simple C family lexer.  It is an
  /// extremely performance critical piece of code.  This assumes that the buffer
  /// has a null character at the end of the file.  This returns a preprocessing
  /// token, not a normal token, as such, it is an internal interface.  It assumes
  /// that the Flags of result have been cleared before calling this.
  bool Lexer::LexTokenInternal(Token &Result, bool TokAtPhysicalStartOfLine) {
  LexNextToken:
    // New token, can't need cleaning yet.
    Result.clearFlag(Token::NeedsCleaning);
    Result.setIdentifierInfo(nullptr);
  
    // CurPtr - Cache BufferPtr in an automatic variable.
    const char *CurPtr = BufferPtr;
  
    // Small amounts of horizontal whitespace is very common between tokens.
    if ((*CurPtr == ' ') || (*CurPtr == '\t')) {
      ++CurPtr;
      while ((*CurPtr == ' ') || (*CurPtr == '\t'))
        ++CurPtr;
  
      // If we are keeping whitespace and other tokens, just return what we just
      // skipped.  The next lexer invocation will return the token after the
      // whitespace.
      if (isKeepWhitespaceMode()) {
        FormTokenWithChars(Result, CurPtr, tok::unknown);
        // FIXME: The next token will not have LeadingSpace set.
        return true;
      }
  
      BufferPtr = CurPtr;
      Result.setFlag(Token::LeadingSpace);
    }
  
    unsigned SizeTmp, SizeTmp2;   // Temporaries for use in cases below.
  
    // Read a character, advancing over it.
    char Char = getAndAdvanceChar(CurPtr, Result);
    tok::TokenKind Kind;
  
    switch (Char) {
    case 0:  // Null.
      // Found end of file?
      if (CurPtr-1 == BufferEnd)
        return LexEndOfFile(Result, CurPtr-1);
  
      // Check if we are performing code completion.
      if (isCodeCompletionPoint(CurPtr-1)) {
        // Return the code-completion token.
        Result.startToken();
        FormTokenWithChars(Result, CurPtr, tok::code_completion);
        return true;
      }
  
      if (!isLexingRawMode())
        Diag(CurPtr-1, diag::null_in_file);
      Result.setFlag(Token::LeadingSpace);
      if (SkipWhitespace(Result, CurPtr, TokAtPhysicalStartOfLine))
        return true; // KeepWhitespaceMode
  
      // We know the lexer hasn't changed, so just try again with this lexer.
      // (We manually eliminate the tail call to avoid recursion.)
      goto LexNextToken;
  
    case 26:  // DOS & CP/M EOF: "^Z".
      // If we're in Microsoft extensions mode, treat this as end of file.
      if (LangOpts.MicrosoftExt) {
        if (!isLexingRawMode())
          Diag(CurPtr-1, diag::ext_ctrl_z_eof_microsoft);
        return LexEndOfFile(Result, CurPtr-1);
      }
  
      // If Microsoft extensions are disabled, this is just random garbage.
      Kind = tok::unknown;
      break;
  
    case '\r':
      if (CurPtr[0] == '\n')
        Char = getAndAdvanceChar(CurPtr, Result);
      LLVM_FALLTHROUGH;
    case '\n':
      // If we are inside a preprocessor directive and we see the end of line,
      // we know we are done with the directive, so return an EOD token.
      if (ParsingPreprocessorDirective) {
        // Done parsing the "line".
        ParsingPreprocessorDirective = false;
  
        // Restore comment saving mode, in case it was disabled for directive.
        if (PP)
          resetExtendedTokenMode();
  
        // Since we consumed a newline, we are back at the start of a line.
        IsAtStartOfLine = true;
        IsAtPhysicalStartOfLine = true;
  
        Kind = tok::eod;
        break;
      }
  
      // No leading whitespace seen so far.
      Result.clearFlag(Token::LeadingSpace);
  
      if (SkipWhitespace(Result, CurPtr, TokAtPhysicalStartOfLine))
        return true; // KeepWhitespaceMode
  
      // We only saw whitespace, so just try again with this lexer.
      // (We manually eliminate the tail call to avoid recursion.)
      goto LexNextToken;
    case ' ':
    case '\t':
    case '\f':
    case '\v':
    SkipHorizontalWhitespace:
      Result.setFlag(Token::LeadingSpace);
      if (SkipWhitespace(Result, CurPtr, TokAtPhysicalStartOfLine))
        return true; // KeepWhitespaceMode
  
    SkipIgnoredUnits:
      CurPtr = BufferPtr;
  
      // If the next token is obviously a // or /* */ comment, skip it efficiently
      // too (without going through the big switch stmt).
      if (CurPtr[0] == '/' && CurPtr[1] == '/' && !inKeepCommentMode() &&
          LangOpts.LineComment &&
          (LangOpts.CPlusPlus || !LangOpts.TraditionalCPP)) {
        if (SkipLineComment(Result, CurPtr+2, TokAtPhysicalStartOfLine))
          return true; // There is a token to return.
        goto SkipIgnoredUnits;
      } else if (CurPtr[0] == '/' && CurPtr[1] == '*' && !inKeepCommentMode()) {
        if (SkipBlockComment(Result, CurPtr+2, TokAtPhysicalStartOfLine))
          return true; // There is a token to return.
        goto SkipIgnoredUnits;
      } else if (isHorizontalWhitespace(*CurPtr)) {
        goto SkipHorizontalWhitespace;
      }
      // We only saw whitespace, so just try again with this lexer.
      // (We manually eliminate the tail call to avoid recursion.)
      goto LexNextToken;
  
    // C99 6.4.4.1: Integer Constants.
    // C99 6.4.4.2: Floating Constants.
    case '0': case '1': case '2': case '3': case '4':
    case '5': case '6': case '7': case '8': case '9':
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
      return LexNumericConstant(Result, CurPtr);
  
    case 'u':   // Identifier (uber) or C11/C++11 UTF-8 or UTF-16 string literal
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
  
      if (LangOpts.CPlusPlus11 || LangOpts.C11) {
        Char = getCharAndSize(CurPtr, SizeTmp);
  
        // UTF-16 string literal
        if (Char == '"')
          return LexStringLiteral(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                                  tok::utf16_string_literal);
  
        // UTF-16 character constant
        if (Char == '\'')
          return LexCharConstant(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                                 tok::utf16_char_constant);
  
        // UTF-16 raw string literal
        if (Char == 'R' && LangOpts.CPlusPlus11 &&
            getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
          return LexRawStringLiteral(Result,
                                 ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                             SizeTmp2, Result),
                                 tok::utf16_string_literal);
  
        if (Char == '8') {
          char Char2 = getCharAndSize(CurPtr + SizeTmp, SizeTmp2);
  
          // UTF-8 string literal
          if (Char2 == '"')
            return LexStringLiteral(Result,
                                 ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                             SizeTmp2, Result),
                                 tok::utf8_string_literal);
          if (Char2 == '\'' && LangOpts.CPlusPlus17)
            return LexCharConstant(
                Result, ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                    SizeTmp2, Result),
                tok::utf8_char_constant);
  
          if (Char2 == 'R' && LangOpts.CPlusPlus11) {
            unsigned SizeTmp3;
            char Char3 = getCharAndSize(CurPtr + SizeTmp + SizeTmp2, SizeTmp3);
            // UTF-8 raw string literal
            if (Char3 == '"') {
              return LexRawStringLiteral(Result,
                     ConsumeChar(ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                             SizeTmp2, Result),
                                 SizeTmp3, Result),
                     tok::utf8_string_literal);
            }
          }
        }
      }
  
      // treat u like the start of an identifier.
      return LexIdentifier(Result, CurPtr);
  
    case 'U':   // Identifier (Uber) or C11/C++11 UTF-32 string literal
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
  
      if (LangOpts.CPlusPlus11 || LangOpts.C11) {
        Char = getCharAndSize(CurPtr, SizeTmp);
  
        // UTF-32 string literal
        if (Char == '"')
          return LexStringLiteral(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                                  tok::utf32_string_literal);
  
        // UTF-32 character constant
        if (Char == '\'')
          return LexCharConstant(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                                 tok::utf32_char_constant);
  
        // UTF-32 raw string literal
        if (Char == 'R' && LangOpts.CPlusPlus11 &&
            getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
          return LexRawStringLiteral(Result,
                                 ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                             SizeTmp2, Result),
                                 tok::utf32_string_literal);
      }
  
      // treat U like the start of an identifier.
      return LexIdentifier(Result, CurPtr);
  
    case 'R': // Identifier or C++0x raw string literal
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
  
      if (LangOpts.CPlusPlus11) {
        Char = getCharAndSize(CurPtr, SizeTmp);
  
        if (Char == '"')
          return LexRawStringLiteral(Result,
                                     ConsumeChar(CurPtr, SizeTmp, Result),
                                     tok::string_literal);
      }
  
      // treat R like the start of an identifier.
      return LexIdentifier(Result, CurPtr);
  
    case 'L':   // Identifier (Loony) or wide literal (L'x' or L"xyz").
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
      Char = getCharAndSize(CurPtr, SizeTmp);
  
      // Wide string literal.
      if (Char == '"')
        return LexStringLiteral(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                                tok::wide_string_literal);
  
      // Wide raw string literal.
      if (LangOpts.CPlusPlus11 && Char == 'R' &&
          getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == '"')
        return LexRawStringLiteral(Result,
                                 ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                             SizeTmp2, Result),
                                 tok::wide_string_literal);
  
      // Wide character constant.
      if (Char == '\'')
        return LexCharConstant(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                               tok::wide_char_constant);
      // FALL THROUGH, treating L like the start of an identifier.
      LLVM_FALLTHROUGH;
  
    // C99 6.4.2: Identifiers.
    case 'A': case 'B': case 'C': case 'D': case 'E': case 'F': case 'G':
    case 'H': case 'I': case 'J': case 'K':    /*'L'*/case 'M': case 'N':
    case 'O': case 'P': case 'Q':    /*'R'*/case 'S': case 'T':    /*'U'*/
    case 'V': case 'W': case 'X': case 'Y': case 'Z':
    case 'a': case 'b': case 'c': case 'd': case 'e': case 'f': case 'g':
    case 'h': case 'i': case 'j': case 'k': case 'l': case 'm': case 'n':
    case 'o': case 'p': case 'q': case 'r': case 's': case 't':    /*'u'*/
    case 'v': case 'w': case 'x': case 'y': case 'z':
    case '_':
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
      return LexIdentifier(Result, CurPtr);
  
    case '$':   // $ in identifiers.
      if (LangOpts.DollarIdents) {
        if (!isLexingRawMode())
          Diag(CurPtr-1, diag::ext_dollar_in_identifier);
        // Notify MIOpt that we read a non-whitespace/non-comment token.
        MIOpt.ReadToken();
        return LexIdentifier(Result, CurPtr);
      }
  
      Kind = tok::unknown;
      break;
  
    // C99 6.4.4: Character Constants.
    case '\'':
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
      return LexCharConstant(Result, CurPtr, tok::char_constant);
  
    // C99 6.4.5: String Literals.
    case '"':
      // Notify MIOpt that we read a non-whitespace/non-comment token.
      MIOpt.ReadToken();
      return LexStringLiteral(Result, CurPtr, tok::string_literal);
  
    // C99 6.4.6: Punctuators.
    case '?':
      Kind = tok::question;
      break;
    case '[':
      Kind = tok::l_square;
      break;
    case ']':
      Kind = tok::r_square;
      break;
    case '(':
      Kind = tok::l_paren;
      break;
    case ')':
      Kind = tok::r_paren;
      break;
    case '{':
      Kind = tok::l_brace;
      break;
    case '}':
      Kind = tok::r_brace;
      break;
    case '.':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char >= '0' && Char <= '9') {
        // Notify MIOpt that we read a non-whitespace/non-comment token.
        MIOpt.ReadToken();
  
        return LexNumericConstant(Result, ConsumeChar(CurPtr, SizeTmp, Result));
      } else if (LangOpts.CPlusPlus && Char == '*') {
        Kind = tok::periodstar;
        CurPtr += SizeTmp;
      } else if (Char == '.' &&
                 getCharAndSize(CurPtr+SizeTmp, SizeTmp2) == '.') {
        Kind = tok::ellipsis;
        CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                             SizeTmp2, Result);
      } else {
        Kind = tok::period;
      }
      break;
    case '&':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '&') {
        Kind = tok::ampamp;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if (Char == '=') {
        Kind = tok::ampequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::amp;
      }
      break;
    case '*':
      if (getCharAndSize(CurPtr, SizeTmp) == '=') {
        Kind = tok::starequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::star;
      }
      break;
    case '+':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '+') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::plusplus;
      } else if (Char == '=') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::plusequal;
      } else {
        Kind = tok::plus;
      }
      break;
    case '-':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '-') {      // --
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::minusminus;
      } else if (Char == '>' && LangOpts.CPlusPlus &&
                 getCharAndSize(CurPtr+SizeTmp, SizeTmp2) == '*') {  // C++ ->*
        CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                             SizeTmp2, Result);
        Kind = tok::arrowstar;
      } else if (Char == '>') {   // ->
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::arrow;
      } else if (Char == '=') {   // -=
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::minusequal;
      } else {
        Kind = tok::minus;
      }
      break;
    case '~':
      Kind = tok::tilde;
      break;
    case '!':
      if (getCharAndSize(CurPtr, SizeTmp) == '=') {
        Kind = tok::exclaimequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::exclaim;
      }
      break;
    case '/':
      // 6.4.9: Comments
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '/') {         // Line comment.
        // Even if Line comments are disabled (e.g. in C89 mode), we generally
        // want to lex this as a comment.  There is one problem with this though,
        // that in one particular corner case, this can change the behavior of the
        // resultant program.  For example, In  "foo //**/ bar", C89 would lex
        // this as "foo / bar" and languages with Line comments would lex it as
        // "foo".  Check to see if the character after the second slash is a '*'.
        // If so, we will lex that as a "/" instead of the start of a comment.
        // However, we never do this if we are just preprocessing.
        bool TreatAsComment = LangOpts.LineComment &&
                              (LangOpts.CPlusPlus || !LangOpts.TraditionalCPP);
        if (!TreatAsComment)
          if (!(PP && PP->isPreprocessedOutput()))
            TreatAsComment = getCharAndSize(CurPtr+SizeTmp, SizeTmp2) != '*';
  
        if (TreatAsComment) {
          if (SkipLineComment(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                              TokAtPhysicalStartOfLine))
            return true; // There is a token to return.
  
          // It is common for the tokens immediately after a // comment to be
          // whitespace (indentation for the next line).  Instead of going through
          // the big switch, handle it efficiently now.
          goto SkipIgnoredUnits;
        }
      }
  
      if (Char == '*') {  // /**/ comment.
        if (SkipBlockComment(Result, ConsumeChar(CurPtr, SizeTmp, Result),
                             TokAtPhysicalStartOfLine))
          return true; // There is a token to return.
  
        // We only saw whitespace, so just try again with this lexer.
        // (We manually eliminate the tail call to avoid recursion.)
        goto LexNextToken;
      }
  
      if (Char == '=') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::slashequal;
      } else {
        Kind = tok::slash;
      }
      break;
    case '%':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '=') {
        Kind = tok::percentequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if (LangOpts.Digraphs && Char == '>') {
        Kind = tok::r_brace;                             // '%>' -> '}'
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if (LangOpts.Digraphs && Char == ':') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Char = getCharAndSize(CurPtr, SizeTmp);
        if (Char == '%' && getCharAndSize(CurPtr+SizeTmp, SizeTmp2) == ':') {
          Kind = tok::hashhash;                          // '%:%:' -> '##'
          CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                               SizeTmp2, Result);
        } else if (Char == '@' && LangOpts.MicrosoftExt) {// %:@ -> #@ -> Charize
          CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
          if (!isLexingRawMode())
            Diag(BufferPtr, diag::ext_charize_microsoft);
          Kind = tok::hashat;
        } else {                                         // '%:' -> '#'
          // We parsed a # character.  If this occurs at the start of the line,
          // it's actually the start of a preprocessing directive.  Callback to
          // the preprocessor to handle it.
          // TODO: -fpreprocessed mode??
          if (TokAtPhysicalStartOfLine && !LexingRawMode && !Is_PragmaLexer)
            goto HandleDirective;
  
          Kind = tok::hash;
        }
      } else {
        Kind = tok::percent;
      }
      break;
    case '<':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (ParsingFilename) {
        return LexAngledStringLiteral(Result, CurPtr);
      } else if (Char == '<') {
        char After = getCharAndSize(CurPtr+SizeTmp, SizeTmp2);
        if (After == '=') {
          Kind = tok::lesslessequal;
          CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                               SizeTmp2, Result);
        } else if (After == '<' && IsStartOfConflictMarker(CurPtr-1)) {
          // If this is actually a '<<<<<<<' version control conflict marker,
          // recognize it as such and recover nicely.
          goto LexNextToken;
        } else if (After == '<' && HandleEndOfConflictMarker(CurPtr-1)) {
          // If this is '<<<<' and we're in a Perforce-style conflict marker,
          // ignore it.
          goto LexNextToken;
        } else if (LangOpts.CUDA && After == '<') {
          Kind = tok::lesslessless;
          CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                               SizeTmp2, Result);
        } else {
          CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
          Kind = tok::lessless;
        }
      } else if (Char == '=') {
        char After = getCharAndSize(CurPtr+SizeTmp, SizeTmp2);
        if (After == '>') {
          if (getLangOpts().CPlusPlus2a) {
            if (!isLexingRawMode())
              Diag(BufferPtr, diag::warn_cxx17_compat_spaceship);
            CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                                 SizeTmp2, Result);
            Kind = tok::spaceship;
            break;
          }
          // Suggest adding a space between the '<=' and the '>' to avoid a
          // change in semantics if this turns up in C++ <=17 mode.
          if (getLangOpts().CPlusPlus && !isLexingRawMode()) {
            Diag(BufferPtr, diag::warn_cxx2a_compat_spaceship)
              << FixItHint::CreateInsertion(
                     getSourceLocation(CurPtr + SizeTmp, SizeTmp2), " ");
          }
        }
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::lessequal;
      } else if (LangOpts.Digraphs && Char == ':') {     // '<:' -> '['
        if (LangOpts.CPlusPlus11 &&
            getCharAndSize(CurPtr + SizeTmp, SizeTmp2) == ':') {
          // C++0x [lex.pptoken]p3:
          //  Otherwise, if the next three characters are <:: and the subsequent
          //  character is neither : nor >, the < is treated as a preprocessor
          //  token by itself and not as the first character of the alternative
          //  token <:.
          unsigned SizeTmp3;
          char After = getCharAndSize(CurPtr + SizeTmp + SizeTmp2, SizeTmp3);
          if (After != ':' && After != '>') {
            Kind = tok::less;
            if (!isLexingRawMode())
              Diag(BufferPtr, diag::warn_cxx98_compat_less_colon_colon);
            break;
          }
        }
  
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::l_square;
      } else if (LangOpts.Digraphs && Char == '%') {     // '<%' -> '{'
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::l_brace;
      } else if (Char == '#' && /*Not a trigraph*/ SizeTmp == 1 &&
                 lexEditorPlaceholder(Result, CurPtr)) {
        return true;
      } else {
        Kind = tok::less;
      }
      break;
    case '>':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '=') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::greaterequal;
      } else if (Char == '>') {
        char After = getCharAndSize(CurPtr+SizeTmp, SizeTmp2);
        if (After == '=') {
          CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                               SizeTmp2, Result);
          Kind = tok::greatergreaterequal;
        } else if (After == '>' && IsStartOfConflictMarker(CurPtr-1)) {
          // If this is actually a '>>>>' conflict marker, recognize it as such
          // and recover nicely.
          goto LexNextToken;
        } else if (After == '>' && HandleEndOfConflictMarker(CurPtr-1)) {
          // If this is '>>>>>>>' and we're in a conflict marker, ignore it.
          goto LexNextToken;
        } else if (LangOpts.CUDA && After == '>') {
          Kind = tok::greatergreatergreater;
          CurPtr = ConsumeChar(ConsumeChar(CurPtr, SizeTmp, Result),
                               SizeTmp2, Result);
        } else {
          CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
          Kind = tok::greatergreater;
        }
      } else {
        Kind = tok::greater;
      }
      break;
    case '^':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '=') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::caretequal;
      } else if (LangOpts.OpenCL && Char == '^') {
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
        Kind = tok::caretcaret;
      } else {
        Kind = tok::caret;
      }
      break;
    case '|':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '=') {
        Kind = tok::pipeequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if (Char == '|') {
        // If this is '|||||||' and we're in a conflict marker, ignore it.
        if (CurPtr[1] == '|' && HandleEndOfConflictMarker(CurPtr-1))
          goto LexNextToken;
        Kind = tok::pipepipe;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::pipe;
      }
      break;
    case ':':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (LangOpts.Digraphs && Char == '>') {
        Kind = tok::r_square; // ':>' -> ']'
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if ((LangOpts.CPlusPlus ||
                  LangOpts.DoubleSquareBracketAttributes) &&
                 Char == ':') {
        Kind = tok::coloncolon;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::colon;
      }
      break;
    case ';':
      Kind = tok::semi;
      break;
    case '=':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '=') {
        // If this is '====' and we're in a conflict marker, ignore it.
        if (CurPtr[1] == '=' && HandleEndOfConflictMarker(CurPtr-1))
          goto LexNextToken;
  
        Kind = tok::equalequal;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        Kind = tok::equal;
      }
      break;
    case ',':
      Kind = tok::comma;
      break;
    case '#':
      Char = getCharAndSize(CurPtr, SizeTmp);
      if (Char == '#') {
        Kind = tok::hashhash;
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else if (Char == '@' && LangOpts.MicrosoftExt) {  // #@ -> Charize
        Kind = tok::hashat;
        if (!isLexingRawMode())
          Diag(BufferPtr, diag::ext_charize_microsoft);
        CurPtr = ConsumeChar(CurPtr, SizeTmp, Result);
      } else {
        // We parsed a # character.  If this occurs at the start of the line,
        // it's actually the start of a preprocessing directive.  Callback to
        // the preprocessor to handle it.
        // TODO: -fpreprocessed mode??
        if (TokAtPhysicalStartOfLine && !LexingRawMode && !Is_PragmaLexer)
          goto HandleDirective;
  
        Kind = tok::hash;
      }
      break;
  
    case '@':
      // Objective C support.
      if (CurPtr[-1] == '@' && LangOpts.ObjC)
        Kind = tok::at;
      else
        Kind = tok::unknown;
      break;
  
    // UCNs (C99 6.4.3, C++11 [lex.charset]p2)
    case '\\':
      if (!LangOpts.AsmPreprocessor) {
        if (uint32_t CodePoint = tryReadUCN(CurPtr, BufferPtr, &Result)) {
          if (CheckUnicodeWhitespace(Result, CodePoint, CurPtr)) {
            if (SkipWhitespace(Result, CurPtr, TokAtPhysicalStartOfLine))
              return true; // KeepWhitespaceMode
  
            // We only saw whitespace, so just try again with this lexer.
            // (We manually eliminate the tail call to avoid recursion.)
            goto LexNextToken;
          }
  
          return LexUnicode(Result, CodePoint, CurPtr);
        }
      }
  
      Kind = tok::unknown;
      break;
  
    default: {
      if (isASCII(Char)) {
        Kind = tok::unknown;
        break;
      }
  
      llvm::UTF32 CodePoint;
  
      // We can't just reset CurPtr to BufferPtr because BufferPtr may point to
      // an escaped newline.
      --CurPtr;
      llvm::ConversionResult Status =
          llvm::convertUTF8Sequence((const llvm::UTF8 **)&CurPtr,
                                    (const llvm::UTF8 *)BufferEnd,
                                    &CodePoint,
                                    llvm::strictConversion);
      if (Status == llvm::conversionOK) {
        if (CheckUnicodeWhitespace(Result, CodePoint, CurPtr)) {
          if (SkipWhitespace(Result, CurPtr, TokAtPhysicalStartOfLine))
            return true; // KeepWhitespaceMode
  
          // We only saw whitespace, so just try again with this lexer.
          // (We manually eliminate the tail call to avoid recursion.)
          goto LexNextToken;
        }
        return LexUnicode(Result, CodePoint, CurPtr);
      }
  
      if (isLexingRawMode() || ParsingPreprocessorDirective ||
          PP->isPreprocessedOutput()) {
        ++CurPtr;
        Kind = tok::unknown;
        break;
      }
  
      // Non-ASCII characters tend to creep into source code unintentionally.
      // Instead of letting the parser complain about the unknown token,
      // just diagnose the invalid UTF-8, then drop the character.
      Diag(CurPtr, diag::err_invalid_utf8);
  
      BufferPtr = CurPtr+1;
      // We're pretending the character didn't exist, so just try again with
      // this lexer.
      // (We manually eliminate the tail call to avoid recursion.)
      goto LexNextToken;
    }
    }
  
    // Notify MIOpt that we read a non-whitespace/non-comment token.
    MIOpt.ReadToken();
  
    // Update the location of token as well as BufferPtr.
    FormTokenWithChars(Result, CurPtr, Kind);
    return true;
  
  HandleDirective:
    // We parsed a # character and it's the start of a preprocessing directive.
  
    FormTokenWithChars(Result, CurPtr, tok::hash);
    PP->HandleDirective(Result);
  
    if (PP->hadModuleLoaderFatalFailure()) {
      // With a fatal failure in the module loader, we abort parsing.
      assert(Result.is(tok::eof) && "Preprocessor did not set tok:eof");
      return true;
    }
  
    // We parsed the directive; lex a token with the new state.
    return false;
  }
  