Can't call closure iterator from inside an async function

[kayabaNerve]

Function echo outputs the wrong string.

Example

iterator x(): int {.closure.} =
  discard

proc y() {.async.} =
  for z in x():
    discard

waitFor y()

Current Output

/usercode/in.nim(7, 7) Error: internal error: expr: var not init x_17965377
No stack traceback available
To create a stacktrace, rerun compilation with './koch temp c <file>', see https://nim-lang.github.io/Nim/intern.html#debugging-the-compiler for details

Expected Output

Additional Information

Present since at least Nim 1.2.4, is present in latest (1.4.2). Instead of calling x, using var foo = x and then calling foo causes a codegen error.

Hint: used config file '/playground/nim/config/nim.cfg' [Conf]
Hint: used config file '/playground/nim/config/config.nims' [Conf]
..................................
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_assertions.nim.c.o /usercode/nimcache/stdlib_assertions.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_dollars.nim.c.o /usercode/nimcache/stdlib_dollars.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_system.nim.c.o /usercode/nimcache/stdlib_system.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_math.nim.c.o /usercode/nimcache/stdlib_math.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_strutils.nim.c.o /usercode/nimcache/stdlib_strutils.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_options.nim.c.o /usercode/nimcache/stdlib_options.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_times.nim.c.o /usercode/nimcache/stdlib_times.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_os.nim.c.o /usercode/nimcache/stdlib_os.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_heapqueue.nim.c.o /usercode/nimcache/stdlib_heapqueue.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_deques.nim.c.o /usercode/nimcache/stdlib_deques.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_cstrutils.nim.c.o /usercode/nimcache/stdlib_cstrutils.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_asyncfutures.nim.c.o /usercode/nimcache/stdlib_asyncfutures.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_monotimes.nim.c.o /usercode/nimcache/stdlib_monotimes.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_nativesockets.nim.c.o /usercode/nimcache/stdlib_nativesockets.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_selectors.nim.c.o /usercode/nimcache/stdlib_selectors.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/stdlib_asyncdispatch.nim.c.o /usercode/nimcache/stdlib_asyncdispatch.nim.c [Exec]
Hint: gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/@min.nim.c.o /usercode/nimcache/@min.nim.c [Exec]
/usercode/nimcache/@min.nim.c: In function 'yIter__aqJRG7LPaI9c3tRfsLoZqKA':
/usercode/nimcache/@min.nim.c:562:77: error: request for member 'ClE_0' in something not a structure or union
     asgnRef((void**) (&(*colonenvP_).foo1.ClE_0), x__ekSWG86elE9byusFc3hPHFw.ClE_0);
                                                                             ^
/usercode/nimcache/@min.nim.c:563:58: error: request for member 'ClP_0' in something not a structure or union
     (*colonenvP_).foo1.ClP_0 = x__ekSWG86elE9byusFc3hPHFw.ClP_0;
                                                          ^
Error: execution of an external program failed: 'gcc -c  -w -fmax-errors=3   -I/playground/nim/lib -I/usercode -o /usercode/nimcache/@min.nim.c.o /usercode/nimcache/@min.nim.c'

[metagn]

This gives the same var not init error:

iterator x(): int {.closure.} =
  discard

proc y() =
  iterator z(): int {.closure.} =
    for a in x():
      yield a

  let foo = z

y()

/usercode/in.nim(6, 9) Error: internal error: expr: var not init x_4602093