anchor.diff:          rest: rest, keywordRest: keywordRest);
     }
   
  -  Expression _expression({bool until(), String untilName}) {
  +  Expression _expression({bool until()}) {
       if (until != null && until()) scanner.error("Expected expression.");
   
       List<Expression> commaExpressions;
  
positive.code:   }
  
    Expression _expressionUntilComma() =>
        _expression(until: () => scanner.peekChar() == $comma, untilName: '","');
  
    // non-list expression
    Expression _singleExpression() {
  
negative.code:       case $7:
        case $8:
        case $9:
          return _number();
          break;
  
  