rust/tests/ui/feature-gates/feature-gate-fn_align.rs
Jieyou Xu 69b71e4410
Mitigate #[align] name resolution ambiguity regression with a rename
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.
2025-07-19 01:42:30 +08:00

17 lines
437 B
Rust

#![crate_type = "lib"]
// ignore-tidy-linelength
// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
#[rustc_align(16)]
//~^ ERROR the `#[rustc_align]` attribute is an experimental feature
fn requires_alignment() {}
trait MyTrait {
#[rustc_align]
//~^ ERROR the `#[rustc_align]` attribute is an experimental feature
//~| ERROR malformed `rustc_align` attribute input
fn myfun();
}