TokenConcatenation.h

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//===--- TokenConcatenation.h - Token Concatenation Avoidance ---*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the TokenConcatenation class.
//
//===----------------------------------------------------------------------===//
 
#ifndef LLVM_CLANG_LEX_TOKENCONCATENATION_H
#define LLVM_CLANG_LEX_TOKENCONCATENATION_H
 
#include "clang/Basic/TokenKinds.h"
 
namespace clang {
  class Preprocessor;
  class Token;
 
  /// TokenConcatenation class, which answers the question of
  ///   "Is it safe to emit two tokens without a whitespace between them, or
  ///    would that cause implicit concatenation of the tokens?"
  ///
  /// For example, it emitting two identifiers "foo" and "bar" next to each
  /// other would cause the lexer to produce one "foobar" token.  Emitting "1"
  /// and ")" next to each other is safe.
  ///
  class TokenConcatenation {
    const Preprocessor &PP;
 
    enum AvoidConcatInfo {
      /// By default, a token never needs to avoid concatenation.  Most tokens
      /// (e.g. ',', ')', etc) don't cause a problem when concatenated.
      aci_never_avoid_concat = 0,
 
      /// aci_custom_firstchar - AvoidConcat contains custom code to handle this
      /// token's requirements, and it needs to know the first character of the
      /// token.
      aci_custom_firstchar = 1,
 
      /// aci_custom - AvoidConcat contains custom code to handle this token's
      /// requirements, but it doesn't need to know the first character of the
      /// token.
      aci_custom = 2,
 
      /// aci_avoid_equal - Many tokens cannot be safely followed by an '='
      /// character.  For example, "<<" turns into "<<=" when followed by an =.
      aci_avoid_equal = 4
    };
 
    /// TokenInfo - This array contains information for each token on what
    /// action to take when avoiding concatenation of tokens in the AvoidConcat
    /// method.
    char TokenInfo[tok::NUM_TOKENS];
  public:
    TokenConcatenation(const Preprocessor &PP);
 
    bool AvoidConcat(const Token &PrevPrevTok,
                     const Token &PrevTok,
                     const Token &Tok) const;
 
  private:
    /// IsIdentifierStringPrefix - Return true if the spelling of the token
    /// is literally 'L', 'u', 'U', or 'u8'.
    bool IsIdentifierStringPrefix(const Token &Tok) const;
  };
  } // end clang namespace
 
#endif