code: function foldLiterals(nodes) {
    return nodes.reduce(function(c, e) {
      if (e.type === 'Literal') {
        var last = c[c.length - 1];
        if (last && last.type === 'Literal') {
          c.pop();
          return c.concat(literal(last.value + e.value));
        }
      }
      return c.concat(e);
    }, [])
  }
docs: Fold adjacent string literals