Generic sequence of proc type mismatch

[nitely]

Description

type Callback = proc(s: string): int

proc foobar(s: string): int =
  result = s.len

proc foo[B](b:B) =
  echo b("foo")

proc bar[B](a: seq[B]) =
  for x in items a:
    echo x("foo")

proc main() =
  foo[Callback](foobar)
  bar(@[foobar]) 
  bar[Callback](@[foobar])  # Error: type mismatch
main()

Nim Version

Nim Compiler Version 2.1.1 [Linux: amd64] Compiled at 2024-06-20 Copyright (c) 2006-2024 by Andreas Rumpf

git hash: 646bd99d461469f08e656f92ae278d6695b35778 active boot switches: -d:release

Current Output

bug.nim(16, 16) Error: type mismatch: got <seq[proc (s: string): int{.noSideEffect, gcsafe.}]>
but expected one of:
proc (a: seq[Callback])

Expected Output

3
3
3

Possible Solution

No response

Additional Information

I found it while trying to make a table of [string, proc] type with initial data.

[nitely]

workaround:

type Callback = proc(s: string): int

proc foobar(s: string): int =
  result = s.len

proc foo[B](b:B) =
  echo b("foo")

proc bar[B](a: seq[B]) =
  for x in items a:
    echo x("foo")

proc main() =
  foo[Callback](foobar)
  bar(@[foobar])
  bar[Callback](@[foobar.Callback])
main()

[nitely]

mmh pretty sure this is an inference limitation that won't get fixed.

[beef331]

Not really inference as much as Callback gets noSideEffect the following is "more correct"

type Callback = proc(s: string): int {.nimcall.} # or {.closure.}`