Test failures all should get green after #25679.

Very nice, specially that things compose and don't have to be materialized!

1. Can closure iterators be supported as well out of the box via some standard helper? feels like a pretty sad omission
2. does the whole thing evaluate to an iterator itself, ie does for x in (-25..25).items.mapIt(it * 10 div 7): echo x work?

Thanks!

1. Can closure iterators be supported as well out of the box via some standard helper? feels like a pretty sad omission

Well, it's a language omission first (iterator (): T isnot iterable[T]) and I don't think it doable now without instantiating an inline iterator that uses the closure first.

This works:

  let infinite = iterator(): int =
     while true: yield 1

  template asIterable[T](it: iterator(): T {.closure.}): untyped =
    iterator wrap(): T =
      for x in it():
        yield x
    wrap()

  var sum = 0
  for i in infinite.asIterable().take(3):
    sum.inc i

  doAssert sum == 3

We could provide such template in the module, but it's a hack and we should just make iterator {.closure.} satisfy iterable[T].

2. does the whole thing evaluate to an iterator itself, ie  does `for x in (-25..25).items.mapIt(it * 10 div 7): echo x` work?

Absolutely! Otherwise, the templates wouldn't compose. Added a test case for the chain in the regular iterator context (the for loop).