code: function(){
      this.skipSpacesAndComments();
      if ('(' == this.peek().type) {
        var la = this.lookahead(2).type;
  
        if ('ident' == la || '{' == la) {
          return this.feature();
        } else {
          this.expect('(');
          var node = new nodes.Expression;
          node.push(new nodes.Literal('('));
          node.push(this.supportsCondition());
          this.expect(')')
          node.push(new nodes.Literal(')'));
          this.skipSpacesAndComments();
          return node;
        }
      }
    }
docs: ('(' supports condition ')')
  | feature