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/*
 * 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.
 */

package org.antlr.v4.runtime;

import org.antlr.v4.runtime.misc.ParseCancellationException;

/**
 * This implementation of {@link ANTLRErrorStrategy} responds to syntax errors
 * by immediately canceling the parse operation with a
 * {@link ParseCancellationException}. The implementation ensures that the
 * {@link ParserRuleContext#exception} field is set for all parse tree nodes
 * that were not completed prior to encountering the error.
 *
 * 

* This error strategy is useful in the following scenarios.

* *
    *
  • Two-stage parsing: This error strategy allows the first * stage of two-stage parsing to immediately terminate if an error is * encountered, and immediately fall back to the second stage. In addition to * avoiding wasted work by attempting to recover from errors here, the empty * implementation of {@link BailErrorStrategy#sync} improves the performance of * the first stage.
  • *
  • Silent validation: When syntax errors are not being * reported or logged, and the parse result is simply ignored if errors occur, * the {@link BailErrorStrategy} avoids wasting work on recovering from errors * when the result will be ignored either way.
  • *
* *

* {@code myparser.setErrorHandler(new BailErrorStrategy());}

* * @see Parser#setErrorHandler(ANTLRErrorStrategy) */ public class BailErrorStrategy extends DefaultErrorStrategy { /** Instead of recovering from exception {@code e}, re-throw it wrapped * in a {@link ParseCancellationException} so it is not caught by the * rule function catches. Use {@link Exception#getCause()} to get the * original {@link RecognitionException}. */ @Override public void recover(Parser recognizer, RecognitionException e) { for (ParserRuleContext context = recognizer.getContext(); context != null; context = context.getParent()) { context.exception = e; } throw new ParseCancellationException(e); } /** Make sure we don't attempt to recover inline; if the parser * successfully recovers, it won't throw an exception. */ @Override public Token recoverInline(Parser recognizer) throws RecognitionException { InputMismatchException e = new InputMismatchException(recognizer); for (ParserRuleContext context = recognizer.getContext(); context != null; context = context.getParent()) { context.exception = e; } throw new ParseCancellationException(e); } /** Make sure we don't attempt to recover from problems in subrules. */ @Override public void sync(Parser recognizer) { } }




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