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81 lines
2.6 KiB
C++
81 lines
2.6 KiB
C++
//===--- ASTWalker.h - Class for walking the AST ----------------*- C++ -*-===//
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//
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// This source file is part of the Swift.org open source project
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//
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// Copyright (c) 2014 - 2015 Apple Inc. and the Swift project authors
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// Licensed under Apache License v2.0 with Runtime Library Exception
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//
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// See http://swift.org/LICENSE.txt for license information
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// See http://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
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//
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//===----------------------------------------------------------------------===//
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#ifndef SWIFT_AST_ASTWALKER_H
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#define SWIFT_AST_ASTWALKER_H
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#include "llvm/ADT/PointerUnion.h"
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namespace swift {
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class Decl;
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class Expr;
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class Stmt;
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/// \brief An abstract class used to traverse an AST.
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class ASTWalker {
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public:
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/// \brief The parent of the node we are visiting.
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llvm::PointerUnion<Expr *, Stmt *> Parent;
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/// This method is called when first visiting an expression,
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/// before walking into its children. If it returns false, the
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/// subtree is ignored.
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///
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/// The default implementation always returns true.
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virtual bool walkToExprPre(Expr *E) { return true; }
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/// This method is called after visiting an expression's children.
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/// If it returns null, the walk is terminated; otherwise, the
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/// returned expression is spliced in where the old expression
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/// previously appeared.
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///
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/// The default implementation always returns its argument.
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virtual Expr *walkToExprPost(Expr *E) { return E; }
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/// This method is called when first visiting a statement, before
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/// walking into its children. If it returns false, the subtree is
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/// ignored.
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///
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/// The default implementation always returns true.
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virtual bool walkToStmtPre(Stmt *S) { return true; }
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/// This method is called after visiting a statement's children. If
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/// it returns null, the walk is terminated; otherwise, the returned
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/// statement is spliced in where the old statement previously
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/// appeared.
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///
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/// The default implementation always returns its argument.
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virtual Stmt *walkToStmtPost(Stmt *S) { return S; }
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/// walkToDeclPre - This method is called when first visiting a decl, before
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/// walking into its children. If it returns false, the subtree is skipped.
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virtual bool walkToDeclPre(Decl *D) { return true; }
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/// walkToDeclPost - This method is called after visiting the children of a
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/// decl. If it returns false, the remaining traversal is terminated and
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/// returns failure.
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virtual bool walkToDeclPost(Decl *D) { return true; }
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protected:
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ASTWalker() = default;
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ASTWalker(const ASTWalker &) = default;
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virtual ~ASTWalker() {}
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virtual void anchor();
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};
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} // end namespace swift
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#endif
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