Coco to LiveScript migration

Question

I am migrating a small script from coco to LiveScript:

D = (obj, l = 20) ->
  if (l > 0)
    new
      @[k] = (try D(v, l - 1) catch (e) e) for k, v in obj
  else
    obj

This code, which is valid in coco, does not compile in LiveScript:

Parse error on line 4: Unexpected 'FOR'

I was trying to modify that code the following way (for LiveScript):

D = (obj, l = 20) ->
  if (l > 0)
    new
      for k, v of obj
        @[k] = (try D(v, l - 1) catch (e) e)
  else
    obj

But still it does not compile:

invalid assign on line 5

How to rewrite this coco script into LiveScript? (Not in the plain JavaScript way -- without using a temporary variable.)

Answer 1

Just FYI, LiveScript has object comprehensions

D = (obj, l = 20) ->
  if l > 0
    {[k, try D(v, l - 1) catch => e] for k, v of obj}
  else
    obj

so, the answer is that catch (e) e is not valid in LS because LS allowed expressions as catchee for destructuring (catch {msg}) which means you must pass it a block catch => e (the e is implicit, but you can make it explicit : catch e => e).