llvm/clang/include/clang/Tooling/Syntax/Tree.h

//===- Tree.h - structure of the syntax tree ------------------*- 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
//
//===----------------------------------------------------------------------===//
// Defines the basic structure of the syntax tree. There are two kinds of nodes:
//   - leaf nodes correspond to tokens,
//   - tree nodes correspond to language grammar constructs.
//
// The tree is initially built from an AST. Each node of a newly built tree
// covers a continuous subrange of expanded tokens (i.e. tokens after
// preprocessing), the specific tokens coverered are stored in the leaf nodes of
// a tree. A post-order traversal of a tree will visit leaf nodes in an order
// corresponding the original order of expanded tokens.
//
// This is still work in progress and highly experimental, we leave room for
// ourselves to completely change the design and/or implementation.
//===----------------------------------------------------------------------===//
#ifndef LLVM_CLANG_TOOLING_SYNTAX_TREE_H
#define LLVM_CLANG_TOOLING_SYNTAX_TREE_H

#include "clang/Basic/TokenKinds.h"
#include "clang/Tooling/Syntax/TokenManager.h"
#include "llvm/ADT/iterator.h"
#include "llvm/Support/Allocator.h"
#include <cstdint>
#include <vector>

namespace clang {
namespace syntax {

/// A memory arena for syntax trees.
// FIXME: use BumpPtrAllocator directly.
class Arena { … };

class Tree;
class TreeBuilder;
class FactoryImpl;
class MutationsImpl;

enum class NodeKind : uint16_t;
enum class NodeRole : uint8_t;

/// A node in a syntax tree. Each node is either a Leaf (representing tokens) or
/// a Tree (representing language constructrs).
class Node { … };

/// A leaf node points to a single token.
// FIXME: add TokenKind field (borrow some bits from the Node::kind).
class Leaf final : public Node { … };

/// A node that has children and represents a syntactic language construct.
class Tree : public Node { … };

/// A list of Elements separated or terminated by a fixed token.
///
/// This type models the following grammar construct:
/// delimited-list(element, delimiter, termination, canBeEmpty)
class List : public Tree { … };

} // namespace syntax
} // namespace clang

#endif