Implicit `this` in CoffeeScript

implicit_this.coffee

class Sprite

  @id: 0
  
  id: -1
  x:  0
  y:  0
  width:  0
  height: 0

  constructor: ->
    id = ++Sprite.id # ~> this.id = ++Sprite.id

  move: (x,y) ->
    this.x = x
    this.y = y
    # `this` is sometimes still useful/necessary (identical params/class body vars)

  getRect: -> 
    new Rectangle x, y, width, height
    # ~> new Rectangle this.x, this.y, this.width, this.height

  

Ruby also doesn't have "var", and does have "implicit this", and it works beautifully.

Interesting... Time for me to finally finish the pickaxe book :)

and you might yourself be subclassing from an external script that we're not compiling.

Great point. I'm accustomed to compilers that require all the source up front. That actually ties into #558 (debug support). One of the big challenges is what to do when CoffeeScript code calls buggy code from a precompiled CoffeeScript file. Since the compiler doesn't have access to the original CoffeeScript, the compiler can't show the original line of code responsible for the error (without an intermediary form like a source map).