anchor.diff:        var first = _expressionUntilComma();
         if (scanner.scanChar($colon)) {
           whitespace();
  -        _inParentheses = false;
           return _map(first, start);
         }
   
  
positive.code: 
    /// Consumes an argument invocation.
    ArgumentInvocation _argumentInvocation() {
      var start = scanner.state;
      scanner.expectChar($lparen);
      whitespace();
  
negative.code:     }
      scanner.expectChar($rparen);
  
      _inParentheses = wasInParentheses;
      return new ArgumentInvocation(positional, named, scanner.spanFrom(start),
          rest: rest, keywordRest: keywordRest);
    }
  