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Mitigate #[align] name resolution ambiguity regression with a rename

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From `#[align]` -> `#[rustc_align]`. Attributes starting with `rustc`
are always perma-unstable and feature-gated by `feature(rustc_attrs)`.

See regression RUST-143834.

For the underlying problem where even introducing new feature-gated
unstable built-in attributes can break user code such as

```rs
macro_rules! align {
    () => {
        /* .. */
    };
}

pub(crate) use align; // `use` here becomes ambiguous
```

refer to RUST-134963.

Since the `#[align]` attribute is still feature-gated by
`feature(fn_align)`, we can rename it as a mitigation. Note that
`#[rustc_align]` will obviously mean that current unstable user code
using `feature(fn_aling)` will need additionally `feature(rustc_attrs)`,
but this is a short-term mitigation to buy time, and is expected to be
changed to a better name with less collision potential.

See
<https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bweekly.5D.202025-07-17/near/529290371>
where mitigation options were considered.
This commit is contained in:
Jieyou Xu
2025-07-18 00:10:46 +08:00
parent b2e94bf020
commit 69b71e4410
25 changed files with 270 additions and 255 deletions
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3
compiler/rustc_feature/src/builtin_attrs.rs
View File

@@ -490,7 +490,8 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
),
ungated!(no_link, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),
ungated!(repr, Normal, template!(List: "C"), DuplicatesOk, EncodeCrossCrate::No),
gated!(align, Normal, template!(List: "alignment"), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(align)),
// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
gated!(rustc_align, Normal, template!(List: "alignment"), DuplicatesOk, EncodeCrossCrate::No, fn_align, experimental!(rustc_align)),
ungated!(unsafe(Edition2024) export_name, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
ungated!(unsafe(Edition2024) link_section, Normal, template!(NameValueStr: "name"), FutureWarnPreceding, EncodeCrossCrate::No),
ungated!(unsafe(Edition2024) no_mangle, Normal, template!(Word), WarnFollowing, EncodeCrossCrate::No),