Don't special-case `!` in stability checks anymore by GrigorenkoPV · Pull Request #162162 · rust-lang/rust

GrigorenkoPV · 2026-09-01T21:49:42Z

Two instances of special-casing:

one for !, added in Warn for #[unstable] on trait impls when it has no effect. #76538 (nearly 6 years ago, Rust v1.48), back when ! was unstable,
one for fn() -> ! in Allow #[unstable] impls for fn() with unstable abi. #103239 (nearly 4 years ago, Rust v1.66), because -> ! was allowed on stable even with ! being unstable.

Since then, in #103239 (just a week ago, on track to be part of Rust v1.100), ! was stabilized, so the first check became wrong and the second became redundant. Let's remove them.

Fixes #162116.

rustbot · 2026-09-01T21:49:47Z

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WaffleLapkin

r=me with green ci

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mejrs

I now realize impls for function pointers

#[unstable(feature = "b", issue = "none")]
impl Trait for fn(!) {}

also emit no diagnostic, can you add a test for it?

I think this works correctly but it's untested, can you add one as well?

#[unstable(feature = "b", issue = "none")]
impl Trait for fn(UnstableType) {}

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rustbot · 2026-09-01T22:08:44Z

Reminder, once the PR becomes ready for a review, use @rustbot ready.

Co-authored-by: mejrs <59372212+mejrs@users.noreply.github.com>

GrigorenkoPV · 2026-09-01T22:27:53Z

@rustbot ready

mejrs

Thanks!

@bors r=mejrs,WaffleLapkin

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rust-bors · 2026-09-02T08:34:37Z

📌 Commit 3cc3682 has been approved by mejrs,WaffleLapkin

It is now in the queue for this repository.

…,WaffleLapkin Don't special-case `!` in stability checks anymore Two instances of special-casing: - one for `!`, added in rust-lang#76538 (nearly 6 years ago, Rust v1.48), back when `!` was unstable, - one for `fn() -> !` in rust-lang#103239 (nearly 4 years ago, Rust v1.66), because `-> !` was allowed on stable even with `!` being unstable. Since then, in rust-lang#103239 (just a week ago, on track to be part of Rust v1.100), `!` was stabilized, so the first check became wrong and the second became redundant. Let's remove them. Fixes rust-lang#162116.

…uwer Rollup of 23 pull requests Successful merges: - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

…,WaffleLapkin Don't special-case `!` in stability checks anymore Two instances of special-casing: - one for `!`, added in rust-lang#76538 (nearly 6 years ago, Rust v1.48), back when `!` was unstable, - one for `fn() -> !` in rust-lang#103239 (nearly 4 years ago, Rust v1.66), because `-> !` was allowed on stable even with `!` being unstable. Since then, in rust-lang#103239 (just a week ago, on track to be part of Rust v1.100), `!` was stabilized, so the first check became wrong and the second became redundant. Let's remove them. Fixes rust-lang#162116.

Rollup of 23 pull requests Successful merges: - #157808 (sanitizers: Implement support for the sanitize ignorelist) - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162199 (docs(time): clarify exact seconds for hour and minute)

…,WaffleLapkin Don't special-case `!` in stability checks anymore Two instances of special-casing: - one for `!`, added in rust-lang#76538 (nearly 6 years ago, Rust v1.48), back when `!` was unstable, - one for `fn() -> !` in rust-lang#103239 (nearly 4 years ago, Rust v1.66), because `-> !` was allowed on stable even with `!` being unstable. Since then, in rust-lang#103239 (just a week ago, on track to be part of Rust v1.100), `!` was stabilized, so the first check became wrong and the second became redundant. Let's remove them. Fixes rust-lang#162116.

Rollup of 29 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161847 (Preserve visibility in nested macro import suggestions) - #161951 (Windows: add fallback if `canonicalize` fails) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm) - #162173 (fix supposedly unreachable `bug!` being reachable) - #162180 (remove outdated next-solver FIXMEs) - #162191 (core: mark float `ClampBounds` methods as `#[inline]`) - #162195 (docs(time): clarify exact seconds for week and day) - #162199 (docs(time): clarify exact seconds for hour and minute)

…uwer Rollup of 25 pull requests Successful merges: - #161694 (add `Complex` ABI run-make test) - #162014 (Move more `rustdoc-html` tests using `--test` into the right folder) - #162164 (Revert "Implement Debug for C-like enums with a concatenated string") - #160564 (volatile: allow accesses to non-AM memory to trap) - #161579 (suggest calling a fn item used as the iterator of a `for` loop) - #162044 (coverage: Resolve spans to file-coordinates in a separate step) - #162120 (Introduce `PerOwnerLoweringState`) - #162132 (std: improve safety documentation in UNIX stack overflow code) - #162151 (Test itanium mangling of `f16` and `f128`) - #162162 (Don't special-case `!` in stability checks anymore) - #162181 (Remove wrong UnusedBraces lint for iterator loop in edition 2024 ) - #162187 (Rename `thir::ExprKind::Use` to `ValueExpr`) - #158401 (mgca: Don't ICE when evaluating ValTrees that contain error constants) - #159873 (fuchsia: Add safestack as a supported sanitizer for x86_64 fuchsia) - #161135 (Add `f16` and `f128` inline ASM support for PowerPC) - #161847 (Preserve visibility in nested macro import suggestions) - #161972 (Improve tests for `#[track_caller]` in async) - #162008 (Render the `box` pattern removal diagnostic more actionable & remove `box` expression recovery) - #162065 (std: don't reference `libc::O_NOFOLLOW` on VxWorks in `set_perm_nofollow`) - #162076 (docs(num): clarify conditions under which error occurs in `impl TryFrom<int> for int`) - #162111 (Update mailmap for Will Crichton and Petr Hosek) - #162152 (Revert "retrieve supported GCC targets from the sysroot") - #162153 (Prefer `LLVMGetVersion` for runtime info) - #162168 (fix ICE in project_goals/inherent) - #162171 (Explain LoongArch f16 NaN-boxing in inline asm)

Rollup merge of #162162 - GrigorenkoPV:never-is-now, r=mejrs,WaffleLapkin Don't special-case `!` in stability checks anymore Two instances of special-casing: - one for `!`, added in #76538 (nearly 6 years ago, Rust v1.48), back when `!` was unstable, - one for `fn() -> !` in #103239 (nearly 4 years ago, Rust v1.66), because `-> !` was allowed on stable even with `!` being unstable. Since then, in #103239 (just a week ago, on track to be part of Rust v1.100), `!` was stabilized, so the first check became wrong and the second became redundant. Let's remove them. Fixes #162116.

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Sep 1, 2026

rustbot assigned mejrs Sep 1, 2026

GrigorenkoPV changed the title ~~Don't special-case ! in stability checks~~ Don't special-case ! in stability checks anymore Sep 1, 2026

WaffleLapkin approved these changes Sep 1, 2026

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WaffleLapkin self-assigned this Sep 1, 2026

mejrs requested changes Sep 1, 2026

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rustbot added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 1, 2026

GrigorenkoPV and others added 2 commits September 2, 2026 01:26

ineffective_unstable_trait_impl: add tests for fn(!) & fn(UnstableT)

fa8bb67

Co-authored-by: mejrs <59372212+mejrs@users.noreply.github.com>

Don't special-case ! in stability checks

3cc3682

GrigorenkoPV force-pushed the never-is-now branch from bdfc5ad to 3cc3682 Compare September 1, 2026 22:27

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Sep 1, 2026

GrigorenkoPV requested a review from mejrs September 1, 2026 22:32

mejrs approved these changes Sep 2, 2026

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rust-bors Bot added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 2, 2026

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Rollup of 16 pull requests #162184

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Rollup of 29 pull requests #162221

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Rollup of 25 pull requests #162229

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rust-bors Bot merged commit 04abbba into rust-lang:main Sep 3, 2026
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rustbot added this to the 1.100.0 milestone Sep 3, 2026

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Don't special-case `!` in stability checks anymore - #162162

Don't special-case `!` in stability checks anymore#162162
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