anchor.diff:      Token hashToken = token;
       listener.beginLiteralSymbol(hashToken);
       token = token.next;
  -    // TODO(brianwilkerson) Should this use `token.isUserDefinableOperator`?
  -    if (isUserDefinableOperator(token.stringValue)) {
  +    if (token.isUserDefinableOperator) {
         listener.handleOperator(token);
         listener.endLiteralSymbol(hashToken, 1);
         return token.next;
  
positive.code: 
    Token parseOperatorName(Token token) {
      assert(optional('operator', token));
      if (isUserDefinableOperator(token.next.stringValue)) {
        Token operator = token;
        token = token.next;
        listener.handleOperatorName(operator, token);
  
negative.code:         SyntheticStringToken,
          SyntheticToken,
          TokenType;
  
  import '../scanner/token_constants.dart'
      show
  