Any variables generated by CoffeeScript are now made sure to be named to
something not present in the source code being compiled. This way you can no
longer interfere with them, either on purpose or by mistake. (#1500, #1574)
For example, `({a}, _arg) ->` now compiles correctly. (#1574)
As opposed to the somewhat complex implementations discussed in #1500, this
commit takes a very simple approach by saving all used variables names using a
single pass over the token stream. Any generated variables are then made sure
not to exist in that list.
`(@a) -> a` used to be equivalent to `(@a) -> @a`, but now throws a runtime
`ReferenceError` instead (unless `a` exists in an upper scope of course). (#3318)
`(@a) ->` used to compile to `(function(a) { this.a = a; })`. Now it compiles to
`(function(_at_a) { this.a = _at_a; })`. (But you cannot access `_at_a` either,
of course.)
Because of the above, `(@a, a) ->` is now valid; `@a` and `a` are not duplicate
parameters.
Duplicate this-parameters with a reserved word, such as `(@case, @case) ->`,
used to compile but now throws, just like regular duplicate parameters.
These are the modifications I had to do in order to get source maps working
in 27.0.1425.2 (Official Build 185250) canary. I haven't tested other
browsers.
I first looked at the V3 spec and a few examples, and I saw that the
`source` key of the source map should be called `sources`.
After doing the `source` to `sources` change, the coffee source and for
some odd reason the javascript file would not show up in the browser
dev tools (it was being fetched but not evaluated).
To fix this, I had to add the coffee source to the `sources` list in the
source map file.
Jeremy Ashkenas