lib/parser.js
function() {
    var node = this.unary();
    if (this.accept('is defined')) {
      if (!node) this.error('illegal unary "is defined", missing left-hand operand');
      node = new nodes.BinOp('is defined', node);
    }
    return node;
  }
function() {
    var node = this.unary();
    if (this.accept('is defined')) {
      if (!node) this.error('illegal unary "is defined", missing left-hand operand');
      node = new nodes.BinOp('is defined', node);
    }
    return node;
  }
function ( ) { var node = this . unary ( ) ; if ( this . accept ( 'is defined' ) ) { if ( ! node ) this . error ( 'illegal unary "is defined", missing left-hand operand' ) ; node = new nodes . BinOp ( 'is defined' , node ) ; } return node ; }
unary 'is defined'
| unary
unary is defined | unary