code: function() {
      if (this.isSelectorToken(1)) {
        if ('{' == this.peek().type) {
          // unclosed, must be a block
          if (!this.lineContains('}')) return;
          // check if ':' is within the braces.
          // though not required by Stylus, chances
          // are if someone is using {} they will
          // use CSS-style props, helping us with
          // the ambiguity in this case
          var i = 0
            , la;
          while (la = this.lookahead(++i)) {
            if ('}' == la.type) {
              // Check empty block.
              if (i == 2 || (i == 3 && this.lookahead(i - 1).type == 'space'))
                return;
              break;
            }
            if (':' == la.type) return;
          }
        }
        return this.next();
      }
    }
docs: Valid selector tokens.