Closure iterator with inner iterator causes infinite loop

[auxym]

The following program runs infinitely:

Example

iterator count2(): int {.closure.} =
  var x = 1
  yield x
  inc x
  yield x

iterator iterinvoke[T](iter: iterator(): T {.closure.}): T {.closure.} =
  for x in iter(): yield x

for e in iterinvoke(count2): echo e

Current Output

1 is echo'd infinitely, seems like the inner iterator is not advanced.

Expected Output

1
2
<program ends>

Possible Solution

Removing {.closure.} from the iterinvoke definition does not trigger the infinite loop behavior.

Additional Information

@Araq let me know on IRC that this was an old bug that was fixed in the past, though I did not find the issue from a quick search.

$ nim -v
Nim Compiler Version 1.1.1 [Linux: amd64]

Installed from choosenim devel on 2019-12-07, but I also got the same issue with 1.0.4 release.

[cooldome]

This how it works

iterator count2(): int {.closure.} =
  var x = 1
  yield x
  inc x
  yield x

iterator iterinvoke[T](iter: iterator(): T {.closure.}): T {.closure.} =
  let t = iter
  for x in t(): yield x

for e in iterinvoke(count2): echo e

[pmetras]

Some problem as #12944