VM error when passing object field ref to `proc(var T): var T`

[nitely]

Nim Version

Nim Compiler Version 2.3.1 [Linux: amd64]
Compiled at 2025-09-25
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: 9f74712
active boot switches: -d:release

Description

It used to work in Nim 2.0.8.

iterator it(x: var int): var int =
  yield x

proc it(x: var int): var int =
  x

proc main() =
  type Obj = object
    field: ref int
  var obj = Obj(field: new(int))
  obj.field[] = 123
  echo it(obj.field[]) # fails
  for x in it(obj.field[]): # fails
    echo x

static:
  main()

Current Output

Error: attempt to access a nil address kind: rkInt

Expected Output

123
123

Known Workarounds

No response

Additional Information

The iterator issue was found when using nim-stew.

[ringabout]

!nim c

iterator it(x: var int): var int =
  yield x

proc it(x: var int): var int =
  x

proc main() =
  type Obj = object
    field: ref int
  var obj = Obj(field: new(int))
  obj.field[] = 123
  echo it(obj.field[]) # fails
  for x in it(obj.field[]): # fails
    echo x

static:
  main()

[github-actions]

🐧 Linux bisect by @ringabout (member)

devel 👎 FAIL

Output

Filesize 0 (0 bytes)
Duration

stable 👎 FAIL

Output

Filesize 0 (0 bytes)
Duration

2.2.2 👎 FAIL

Output

Filesize 0 (0 bytes)
Duration

2.0.0 👍 OK

Output

Filesize 90.64 Kb (92,816 bytes)
Duration

1.6.20 👎 FAIL

Output

Filesize 90.64 Kb (92,816 bytes)
Duration

1.4.8 👎 FAIL

Output

Filesize 90.64 Kb (92,816 bytes)
Duration

1.2.18 👎 FAIL

Output

Filesize 90.64 Kb (92,816 bytes)
Duration

1.0.10 👎 FAIL

Output

Filesize 90.64 Kb (92,816 bytes)
Duration

#aa90d00ca ➡️ 🐛

Diagnostics

ringabout introduced a bug at 2024-10-26 04:36:19 +0800 on commit #aa90d00ca with message:

The bug is in the files:

The bug can be in the commits:

• #efd603eb2
• #79ce3fe6b
• #aa90d00ca
• #2af602a5c
• #d303c289f

(Diagnostics sometimes off-by-one).

Stats

• GCC 13.3.0
• Clang 18.1.3
• NodeJS 19.5
• Created 2025-10-08T12:22:42Z
• Comments 1
• Commands nim c --run -d:nimDebug -d:nimDebugDlOpen -d:ssl -d:nimDisableCertificateValidation --forceBuild:on --colors:off --verbosity:0 --hints:off --lineTrace:off --nimcache:/home/runner/work/Nim/Nim --out:/home/runner/work/Nim/Nim/temp /home/runner/work/Nim/Nim/temp.nim

🤖 Bug found in 59 mins bisecting 1382 commits at 23 commits per second

[ringabout]

half regression it seems