Reserved keywords as parameters maybe clobbered

[josh]

I was looking at some of the strict tests added in 66eb186 (by @geraldalewis) and noticed some are generating invalid output. The test only checks if the code can be generated but not evaluated.

There was two different types of errors.

(@case, _case) ->

generates

(function(_case, _case) {
  this["case"] = _case;
});

So theres a bug in the variable renaming here.

The second is a little worse.

(@case, _case...) ->

generates

var __slice = [].slice;

(function() {
  var case, _case;
  _case = arguments[0], _case = 2 <= arguments.length ? __slice.call(arguments, 1) : [];
  this["case"] = _case;
});

An unused and reversed local is created for case.

I haven't looked into a fix yet, but I figured I'd open an patch with tests and maybe someone much more familiar will know what to do.

[michaelficarra]

This seems like just another duplicate of #1574 to me (which is basically a dupe of #1500). Needs two-pass variable naming. Also related: we have an open issue to disallow referencing @-params by the locals used in their compilation (e.g. (@a) -> a), but I can't find it right now.

[josh]

Should I close this out in favor of the existing issues or leave open because it has tests?

[vendethiel]

I'd say leave it open because it has tests.

[jashkenas]

Should we merge the failing tests now? Or add to this PR first?

[michaelficarra]

Let's not merge failing tests. I've had problems with that in the past. Either the fix never comes and your build will fail forever or the tests won't actually be what you wanted (and you won't know this until you have an implementation).

[jashkenas]

Words of wisdom.

[vendethiel]

Well, these could be "negative tests" so we'd know when we fix these, or "TODO" (skipped tests) (e.g. which would not be run in usual run, but could be run with a special command)

[lydell]

Mocha lets you mark tests as pending. It then reports X passed, Y failed and Z pending. FYI.

[lydell]

This was included in #3784.