Regression from `version-1-6` to `version-2-0`/`version-2-2`/`devel` with mutually recursive functions and `Error: n(t) can raise an unlisted exception: Exception`

[tersec]

Nim Version

Builds and runs:

Nim Compiler Version 1.6.21 [Linux: amd64]
Compiled at 2025-03-10
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: ec324ad0736c3e0cfa26b64d6631b15693633a6f
active boot switches: -d:release

Does not bulid:

Nim Compiler Version 2.0.15 [Linux: amd64]
Compiled at 2025-03-10
Copyright (c) 2006-2023 by Andreas Rumpf

git hash: 41637db18f6a82df4a92f2e00a780e5815d17028
active boot switches: -d:release

Nim Compiler Version 2.2.3 [Linux: amd64]
Compiled at 2025-03-10
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: 9cf0d07b9e1e21ecbee8796bda7d3cedb9196dc9
active boot switches: -d:release

Nim Compiler Version 2.3.1 [Linux: amd64]
Compiled at 2025-03-10
Copyright (c) 2006-2025 by Andreas Rumpf

git hash: f8294ce06e61752d15624e0422c5296292ef5467
active boot switches: -d:release

Description

proc n(d: var int)

proc s(p: int|int) {.raises: [CatchableError].} =
  var t: int
  if false: n(t)

proc n(d: var int) = s(0)

Current Output

/tmp/w.nim(7, 23) template/generic instantiation of `s` from here
/tmp/w.nim(3, 30) template/generic instantiation from here
/tmp/w.nim(5, 14) Error: n(t) can raise an unlisted exception: Exception

Expected Output

Known Workarounds

No response

Additional Information

No response

[metagn]

!nim c

proc n(d: var int)

proc s(p: int|int) {.raises: [CatchableError].} =
  var t: int
  if false: n(t)

proc n(d: var int) = s(0)

[github-actions]

🐧 Linux bisect by @metagn (collaborator)

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 👎 FAIL

Output

Filesize 0 (0 bytes)
Duration

1.6.20 👍 OK

Output

Filesize 95.50 Kb (97,792 bytes)
Duration

1.4.8 👍 OK

Output

Filesize 91.16 Kb (93,344 bytes)
Duration

1.2.18 👍 OK

Output

Filesize 86.88 Kb (88,968 bytes)
Duration

1.0.10 👍 OK

Output

Filesize 81.98 Kb (83,952 bytes)
Duration

#1e15f975b ➡️ 🐛

Diagnostics

ringabout introduced a bug at 2022-10-15 20:07:40 +0800 on commit #1e15f975b with message:

The bug is in the files:

The bug can be in the commits:

• #c0824b9b8
• #b7f175795
• #2102e3b02
• #081dfea74
• #0bacdf5fd
• #619d6c318
• #ed26156c9
• #1e15f975b
• #0510a2be0
• #57574eaf3

(Diagnostics sometimes off-by-one).

Stats

• GCC 13.3.0
• Clang 18.1.3
• NodeJS 18.3
• Created 2025-03-11T09:49:24Z
• 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 23 mins bisecting 2809 commits at 119 commits per second

[ringabout]

It seems to be an issue of strictEffects

[metagn]

Probably specifically because of these lines:

Nim/compiler/sempass2.nim

Lines 1036 to 1038 in 850f327

	if laxEffects notin tracked.c.config.legacyFeatures and a.kind == nkSym and
	a.sym.kind in routineKinds:
	propagateEffects(tracked, n, a.sym)

By the time s is getting instantiated, n is no longer marked as a forward proc but still does not have a built effect list. Previously, without strictEffects, this case would just be ignored. So this now fails because strictEffects is always enabled, it should work with --legacy:laxEffects. Given that this works as expected though, maybe there is a fix here unlike #24766:

proc n() =
  if false:
    n()

proc foo() {.raises: [CatchableError].} =
  n()