singleTokenInsertion method

bool singleTokenInsertion(Parser recognizer)

This method implements the single-token insertion inline error recovery strategy. It is called by {@link #recoverInline} if the single-token deletion strategy fails to recover from the mismatched input. If this method returns true, recognizer will be in error recovery mode.

This method determines whether or not single-token insertion is viable by checking if the {@code LA(1)} input symbol could be successfully matched if it were instead the {@code LA(2)} symbol. If this method returns [true], the caller is responsible for creating and inserting a token with the correct type to produce this behavior.

@param recognizer the parser instance @return true if single-token insertion is a viable recovery strategy for the current mismatched input, otherwise false

Implementation

bool singleTokenInsertion(Parser recognizer) {
  final currentSymbolType = recognizer.inputStream.LA(1)!;
  // if current token is consistent with what could come after current
  // ATN state, then we know we're missing a token; error recovery
  // is free to conjure up and insert the missing token
  final currentState = recognizer.interpreter!.atn.states[recognizer.state]!;
  final next = currentState.transition(0).target;
  final atn = recognizer.interpreter!.atn;
  final expectingAtLL2 = atn.nextTokens(next, recognizer.context);
//		System.out.println("LT(2) set="+expectingAtLL2.toString(recognizer.getTokenNames()));
  if (expectingAtLL2.contains(currentSymbolType)) {
    reportMissingToken(recognizer);
    return true;
  }
  return false;
}