Fibers bug with IIFE in parentheses

[aseemk]

This source JS compiles fine:

(function() {
    async(_);
})();

But if you wrap it in parentheses, it doesn't under fibers mode (streamline 0.10.2):

((function() {
    async(_);
})());

The error and stack trace:

Error: Function contains async calls but does not have _ parameter on line 2
    <<< async stack >>>
    at Node.Walker.call (/path/to/streamline/lib/fibers/transform.js:356:36)
    at walk (/path/to/streamline/lib/fibers/walker.js:222:21)
    at Node.Walker.semicolon (/path/to/streamline/lib/fibers/transform.js:525:18)
    at walk (/path/to/streamline/lib/fibers/walker.js:169:21)
    at Array.map (native)
    at Node.Walker.function (/path/to/streamline/lib/fibers/transform.js:330:9)
    at walk (/path/to/streamline/lib/fibers/walker.js:30:21)
    at Node.Walker.call (/path/to/streamline/lib/fibers/transform.js:441:5)
    at walk (/path/to/streamline/lib/fibers/walker.js:222:21)
    at Node.Walker.semicolon (/path/to/streamline/lib/fibers/transform.js:525:18)
    at exports_loadFile__2 (/path/to/streamline/lib/callbacks/compile.js:190:9)
    at _compile (/path/to/streamline/lib/callbacks/compile.js:273:4)
    at __1 (/path/to/streamline/lib/callbacks/compile.js:306:2)
    at value__1 (/path/to/streamline/lib/callbacks/builtins.js:131:28)
    at exports_compile__3 (/path/to/streamline/lib/callbacks/compile.js:305:1)
    <<< raw stack >>>
    at Node.Walker.call (/path/to/streamline/lib/fibers/transform.js:356:36)
    at walk (/path/to/streamline/lib/fibers/walker.js:222:21)
    at Node.Walker.semicolon (/path/to/streamline/lib/fibers/transform.js:525:18)
    at walk (/path/to/streamline/lib/fibers/walker.js:169:21)
    at Array.map (native)
    at Node.Walker.function (/path/to/streamline/lib/fibers/transform.js:330:9)
    at walk (/path/to/streamline/lib/fibers/walker.js:30:21)
    at Node.Walker.call (/path/to/streamline/lib/fibers/transform.js:441:5)
    at walk (/path/to/streamline/lib/fibers/walker.js:222:21)
    at Node.Walker.semicolon (/path/to/streamline/lib/fibers/transform.js:525:18)

It compiles fine in callbacks mode.

—

That's the tiniest repro I could arrive at; my actual use case is something like this CoffeeScript:

# get the first URL from a list of URLs (fetched async'ly)
# that matches a given regex:
[url] = (url for url in getURLs _ when url.match regex)

Compiled JS:

// Generated by CoffeeScript 1.6.3
var url;

url = ((function() {
  var _i, _len, _ref, _results;
  _ref = getURLs(_);
  _results = [];
  for (_i = 0, _len = _ref.length; _i < _len; _i++) {
    url = _ref[_i];
    if (url.match(regex)) {
      _results.push(url);
    }
  }
  return _results;
})())[0];

Notice the parentheses around the IIFE.