anchor.diff:       * @return {@code true} iff the lexer can match a regex literal.
        */
       private boolean isRegexPossible() {
  +                                       
           if (this.lastToken == null) {
               // No token has been produced yet: at the start of the input,
               // no division is possible, so a regex literal _is_ possible.
               return true;
           }
  +        
           switch (this.lastToken.getType()) {
               case Identifier:
               case NullLiteral:
  
positive.code:      */
      @Override
      public Token nextToken() {
          Token next = super.nextToken();
          if (next.getChannel() == Token.DEFAULT_CHANNEL) {
              lastToken = next;
          }
          return next;
      }
  
  
negative.code:         int possibleIndexEosToken = this.getCurrentToken().getTokenIndex() - 1;
          Token ahead = _input.get(possibleIndexEosToken);
  
          if (ahead.getChannel() != Lexer.HIDDEN) {
              // We're only interested in tokens on the HIDDEN channel.
              return false;
          }
  
          // Get the token's text and type.
          String text = ahead.getText();
          int type = ahead.getType();
  
          // Check if the token is, or contains a line terminator.
          return (type == MultiLineComment && (text.contains("\r") || text.contains("\n"))) ||
  