closure iterator assertionError on nested for loop

[nitely]

The following code throws an assertion error:

iterator myiterclosure(cps: seq[int]): int {.closure.} =
  echo cps
  for cp in cps:
    echo "loop"
    var dcps: seq[int] = @[1,2]
    for dcp in dcps:
      yield dcp
    echo cps
  echo "end"

var myseqnum = @[1,2,3,4,5]
for myI in myiterclosure(myseqnum):
  echo myI

$ nim --run c some
@[1, 2, 3, 4, 5]
loop
1
2
@[1, 2, 3, 4, 5]
Traceback (most recent call last)
mybuggyiterator.nim(13)  mybuggyiterator
system.nim(3772)         myiterclosure
system.nim(3741)         failedAssertImpl
system.nim(3733)         raiseAssert
system.nim(2799)         sysFatal
Error: unhandled exception: len(a) == L seq modified while iterating over it [AssertionError]

Tried on devel

Edit: works if I remove the inner loop.

[nitely]

Nevermind, I've been bitten by #2563 . The behaviour is well explained in the manual