CS2 Discussion: Output: Remove unnecessary polyfills

[coffeescriptbot]

From @GeoffreyBooth on 2016-12-15 06:39

See #2562, to take just one example. CoffeeScript 2 can assume that browsers have indexOf, includes and other modern prototype methods. We can streamline our output by using them.

[coffeescriptbot]

From @connec on 2016-12-15 14:45

Heh, I was just about to make the same issue after reading #4268 😄

I just had a quick glance and I think the only non-shortcut ones we will need are modulo and, possibly, extend:

UTILITIES =
  # `extend` has been replaced by ES inheritance for class declaration, but can still
  # appear standalone, e.g. `A extends B` is valid CS. We could drop standalone `extends`
  # and eliminate this helper.
  extend: (o) -> ...

  # We can probably rely on the existence of `Function#bind` in modern environments, so
  # this could become a shortcut (call-sites need to change to use `utility(...).call`).
  bind: -> '(() => {}).bind'

  # We can certainly rely on the existence of `Array#indexOf`.
  indexOf: -> '[].indexOf'

  # This is still needed.
  modulo: -> 'function(a, b) { return (+a % (b = +b) + b) % b; }'

  # These are already just shortcuts and should probably remain.
  hasProp: -> '{}.hasOwnProperty'
  slice  : -> '[].slice'