asyncjs: declaring .async proc inside an .async proc gives CT error

[timotheecour]

Example

import std/asyncjs
proc fn1(n: int): Future[int] {.async.} = return n
proc main2() =
  proc fn2(n: int): Future[int] {.async.} = return n
proc main3(a: auto) =
  proc fn3(n: int): Future[int] {.async.} = return n
proc main4() {.async.} =
  proc fn4(n: int): Future[int] {.async.} = return n # xxx bug: uncomment this and it works
  discard

Current Output

/Users/timothee/git_clone/nim/timn/tests/nim/all/t11907.nim(11, 1) template/generic instantiation from here
/Users/timothee/git_clone/nim/timn/tests/nim/all/t11907.nim(12, 52) Error: type mismatch:
 got 'Future[Future[system.int]]' for 'jsResolve(jsResolve(n))' [ref declared in /Users/timothee/git_clone/nim/Nim_devel/lib/js/asyncjs.nim(68, 3)]
 but expected 'Future[system.int]' [ref declared in /Users/timothee/git_clone/nim/Nim_devel/lib/js/asyncjs.nim(68, 3)]
    proc fn4(n: int): Future[int] {.async.} = return n

Expected Output

works

Additional Information

• 1.5.1 a4e6b24
• looks similar to async proc inside a generic proc gives CT error #16786 but definitely a different issue
• prevents using (a: int) {.async.} => await ... anonymous procs inside an async proc which would be useful sugar for the new asyncjs.then (asyncjs: add then, catch for promise pipelining #16871)