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.

1 files changed, 20 insertions, 15 deletions

diff --git a/tests/ui/attributes/malformed-fn-align.rs b/tests/ui/attributes/malformed-fn-align.rs
index e06e6116842..cf143b28e54 100644
--- a/tests/ui/attributes/malformed-fn-align.rs
+++ b/tests/ui/attributes/malformed-fn-align.rs
@@ -1,49 +1,54 @@
+// ignore-tidy-linelength
+
+// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
+#![feature(rustc_attrs)]
 #![feature(fn_align)]
+
 #![crate_type = "lib"]
 
 trait MyTrait {
-    #[align] //~ ERROR malformed `align` attribute input
+    #[rustc_align] //~ ERROR malformed `rustc_align` attribute input
     fn myfun1();
 
-    #[align(1, 2)] //~ ERROR malformed `align` attribute input
+    #[rustc_align(1, 2)] //~ ERROR malformed `rustc_align` attribute input
     fn myfun2();
 }
 
-#[align = 16] //~ ERROR malformed `align` attribute input
+#[rustc_align = 16] //~ ERROR malformed `rustc_align` attribute input
 fn f1() {}
 
-#[align("hello")] //~ ERROR invalid alignment value: not an unsuffixed integer
+#[rustc_align("hello")] //~ ERROR invalid alignment value: not an unsuffixed integer
 fn f2() {}
 
-#[align(0)] //~ ERROR invalid alignment value: not a power of two
+#[rustc_align(0)] //~ ERROR invalid alignment value: not a power of two
 fn f3() {}
 
 #[repr(align(16))] //~ ERROR `#[repr(align(...))]` is not supported on function items
 fn f4() {}
 
-#[align(-1)] //~ ERROR expected unsuffixed literal, found `-`
+#[rustc_align(-1)] //~ ERROR expected unsuffixed literal, found `-`
 fn f5() {}
 
-#[align(3)] //~ ERROR invalid alignment value: not a power of two
+#[rustc_align(3)] //~ ERROR invalid alignment value: not a power of two
 fn f6() {}
 
-#[align(4usize)] //~ ERROR invalid alignment value: not an unsuffixed integer [E0589]
+#[rustc_align(4usize)] //~ ERROR invalid alignment value: not an unsuffixed integer [E0589]
 //~^ ERROR suffixed literals are not allowed in attributes
 fn f7() {}
 
-#[align(16)]
-#[align(3)] //~ ERROR invalid alignment value: not a power of two
-#[align(16)]
+#[rustc_align(16)]
+#[rustc_align(3)] //~ ERROR invalid alignment value: not a power of two
+#[rustc_align(16)]
 fn f8() {}
 
-#[align(16)] //~ ERROR `#[align(...)]` is not supported on struct items
+#[rustc_align(16)] //~ ERROR `#[rustc_align(...)]` is not supported on struct items
 struct S1;
 
-#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+#[rustc_align(32)] //~ ERROR `#[rustc_align(...)]` should be applied to a function item
 const FOO: i32 = 42;
 
-#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+#[rustc_align(32)] //~ ERROR `#[rustc_align(...)]` should be applied to a function item
 mod test {}
 
-#[align(32)] //~ ERROR `#[align(...)]` should be applied to a function item
+#[rustc_align(32)] //~ ERROR `#[rustc_align(...)]` should be applied to a function item
 use ::std::iter;