/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

module antlr.v4.runtime.tree.ParseTreeVisitor;

/**
 * This interface defines the basic notion of a parse tree visitor. Generated
 * visitors implement this interface and the {@code XVisitor} interface for
 * grammar {@code X}.
 *
 *  @param <T> The return type of the visit operation. Use {@link Void} for
 *  operations with no return type.
 */
interface ParseTreeVisitor(T)
{

    /**
     * Visit a parse tree, and return a user-defined result of the operation.
     *
     *  @param tree The {@link ParseTree} to visit.
     *  @return The result of visiting the parse tree.
     */
    public T visit(ParseTree tree);

    /**
     * Visit the children of a node, and return a user-defined result of the
     * operation.
     *
     *  @param node The {@link RuleNode} whose children should be visited.
     *  @return The result of visiting the children of the node.
     */
    public T visitChildren(RuleNode node);

    /**
     * Visit a terminal node, and return a user-defined result of the operation.
     *
     *  @param node The {@link TerminalNode} to visit.
     *  @return The result of visiting the node.
     */
    public T visitTerminal(TerminalNode node);

    /**
     * Visit an error node, and return a user-defined result of the operation.
     *
     *  @param node The {@link ErrorNode} to visit.
     *  @return The result of visiting the node.
     */
    public T visitErrorNode(ErrorNode node);

}