The async pragma doesn't work properly with a nested proc inside a generic function

[zah]

The following example fails to compile with the the error

example.nim(9, 11) Error: undeclared identifier: 'await'

Example

import
  asyncdispatch

type
  AsyncProc = proc(): Future[void]

proc makeCallback[T](v: T): AsyncProc =
  result = proc() {.async.} =
    await sleepAsync(100)
  
let c = makeCallback(10)

The problem manifests only when the makeCallback proc is generic. At the moment, it's possible to work-around the issue by manually simulating the low-level mechanics of await:

proc makeCallback[T](v: T): AsyncProc =
  result = proc() {.async.} =
    var future = sleepAsync(100)
    yield future
    if future.failed: ...

Additional Information

$ nim -v
Nim Compiler Version 0.19.9 [Linux: amd64]
git hash: b9f8528db675927aacc6443ae3a363711bb41945
active boot switches: -d:release

[mratsim]

Sounds like another case of #8677 - generics early symbol resolution issue

[ringabout]

same issue as #15804
And fixed by #15820