text: //===- ASTDiffInternal.h --------------------------------------*- 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
  //
  //===----------------------------------------------------------------------===//
  
  #ifndef LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFFINTERNAL_H
  #define LLVM_CLANG_TOOLING_ASTDIFF_ASTDIFFINTERNAL_H
  
  #include "clang/AST/ASTTypeTraits.h"
  
  namespace clang {
  namespace diff {
  
  using DynTypedNode = DynTypedNode;
  
  /// Within a tree, this identifies a node by its preorder offset.
  struct NodeId {
  private:
    static constexpr int InvalidNodeId = -1;
  
  public:
    int Id;
  
    NodeId() : Id(InvalidNodeId) {}
    NodeId(int Id) : Id(Id) {}
  
    operator int() const { return Id; }
    NodeId &operator++() { return ++Id, *this; }
    NodeId &operator--() { return --Id, *this; }
    // Support defining iterators on NodeId.
    NodeId &operator*() { return *this; }
  
    bool isValid() const { return Id != InvalidNodeId; }
    bool isInvalid() const { return Id == InvalidNodeId; }
  };
  
  } // end namespace diff
  } // end namespace clang
  #endif
  