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.

4 files changed, 40 insertions, 31 deletions

diff --git a/tests/codegen/align-fn.rs b/tests/codegen/align-fn.rs
index fd572910c28..cbc24e2ae2e 100644
--- a/tests/codegen/align-fn.rs
+++ b/tests/codegen/align-fn.rs
@@ -3,11 +3,13 @@
 //@ ignore-wasm32 aligning functions is not currently supported on wasm (#143368)
 
 #![crate_type = "lib"]
+// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
+#![feature(rustc_attrs)]
 #![feature(fn_align)]
 
 // CHECK: align 16
 #[unsafe(no_mangle)]
-#[align(16)]
+#[rustc_align(16)]
 pub fn fn_align() {}
 
 pub struct A;
@@ -15,12 +17,12 @@ pub struct A;
 impl A {
     // CHECK: align 16
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     pub fn method_align(self) {}
 
     // CHECK: align 16
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     pub fn associated_fn() {}
 }
 
@@ -29,18 +31,18 @@ trait T: Sized {
 
     fn trait_method(self) {}
 
-    #[align(8)]
+    #[rustc_align(8)]
     fn trait_method_inherit_low(self);
 
-    #[align(32)]
+    #[rustc_align(32)]
     fn trait_method_inherit_high(self);
 
-    #[align(32)]
+    #[rustc_align(32)]
     fn trait_method_inherit_default(self) {}
 
-    #[align(4)]
-    #[align(128)]
-    #[align(8)]
+    #[rustc_align(4)]
+    #[rustc_align(128)]
+    #[rustc_align(8)]
     fn inherit_highest(self) {}
 }
 
@@ -48,27 +50,27 @@ impl T for A {
     // CHECK-LABEL: trait_fn
     // CHECK-SAME: align 16
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     fn trait_fn() {}
 
     // CHECK-LABEL: trait_method
     // CHECK-SAME: align 16
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     fn trait_method(self) {}
 
     // The prototype's align is ignored because the align here is higher.
     // CHECK-LABEL: trait_method_inherit_low
     // CHECK-SAME: align 16
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     fn trait_method_inherit_low(self) {}
 
     // The prototype's align is used because it is higher.
     // CHECK-LABEL: trait_method_inherit_high
     // CHECK-SAME: align 32
     #[unsafe(no_mangle)]
-    #[align(16)]
+    #[rustc_align(16)]
     fn trait_method_inherit_high(self) {}
 
     // The prototype's align inherited.
@@ -81,8 +83,8 @@ impl T for A {
     // CHECK-LABEL: inherit_highest
     // CHECK-SAME: align 128
     #[unsafe(no_mangle)]
-    #[align(32)]
-    #[align(64)]
+    #[rustc_align(32)]
+    #[rustc_align(64)]
     fn inherit_highest(self) {}
 }
 
@@ -90,7 +92,7 @@ trait HasDefaultImpl: Sized {
     // CHECK-LABEL: inherit_from_default_method
     // CHECK-LABEL: inherit_from_default_method
     // CHECK-SAME: align 32
-    #[align(32)]
+    #[rustc_align(32)]
     fn inherit_from_default_method(self) {}
 }
 
@@ -101,35 +103,35 @@ impl HasDefaultImpl for InstantiateDefaultMethods {}
 // CHECK-LABEL: align_specified_twice_1
 // CHECK-SAME: align 64
 #[unsafe(no_mangle)]
-#[align(32)]
-#[align(64)]
+#[rustc_align(32)]
+#[rustc_align(64)]
 pub fn align_specified_twice_1() {}
 
 // CHECK-LABEL: align_specified_twice_2
 // CHECK-SAME: align 128
 #[unsafe(no_mangle)]
-#[align(128)]
-#[align(32)]
+#[rustc_align(128)]
+#[rustc_align(32)]
 pub fn align_specified_twice_2() {}
 
 // CHECK-LABEL: align_specified_twice_3
 // CHECK-SAME: align 256
 #[unsafe(no_mangle)]
-#[align(32)]
-#[align(256)]
+#[rustc_align(32)]
+#[rustc_align(256)]
 pub fn align_specified_twice_3() {}
 
 const _: () = {
     // CHECK-LABEL: align_unmangled
     // CHECK-SAME: align 256
     #[unsafe(no_mangle)]
-    #[align(32)]
-    #[align(256)]
+    #[rustc_align(32)]
+    #[rustc_align(256)]
     extern "C" fn align_unmangled() {}
 };
 
 unsafe extern "C" {
-    #[align(256)]
+    #[rustc_align(256)]
     fn align_unmangled();
 }
 
@@ -137,5 +139,5 @@ unsafe extern "C" {
 // CHECK-LABEL: async_align
 // CHECK-SAME: align 64
 #[unsafe(no_mangle)]
-#[align(64)]
+#[rustc_align(64)]
 pub async fn async_align() {}
diff --git a/tests/codegen/min-function-alignment.rs b/tests/codegen/min-function-alignment.rs
index 6a3843b0f4f..ea5f957e81f 100644
--- a/tests/codegen/min-function-alignment.rs
+++ b/tests/codegen/min-function-alignment.rs
@@ -5,6 +5,8 @@
 //@ ignore-wasm32 aligning functions is not currently supported on wasm (#143368)
 
 #![crate_type = "lib"]
+// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
+#![feature(rustc_attrs)]
 #![feature(fn_align)]
 
 // Functions without explicit alignment use the global minimum.
@@ -21,7 +23,7 @@ pub fn no_explicit_align() {}
 // align16: align 16
 // align1024: align 1024
 #[no_mangle]
-#[align(8)]
+#[rustc_align(8)]
 pub fn lower_align() {}
 
 // the higher value of min-function-alignment and the align attribute wins out
@@ -30,7 +32,7 @@ pub fn lower_align() {}
 // align16: align 32
 // align1024: align 1024
 #[no_mangle]
-#[align(32)]
+#[rustc_align(32)]
 pub fn higher_align() {}
 
 // cold functions follow the same rules as other functions
diff --git a/tests/codegen/naked-fn/aligned.rs b/tests/codegen/naked-fn/aligned.rs
index 2648b0213ca..d7281c4219a 100644
--- a/tests/codegen/naked-fn/aligned.rs
+++ b/tests/codegen/naked-fn/aligned.rs
@@ -4,12 +4,15 @@
 //@ ignore-wasm32 aligning functions is not currently supported on wasm (#143368)
 
 #![crate_type = "lib"]
+// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
+#![feature(rustc_attrs)]
 #![feature(fn_align)]
+
 use std::arch::naked_asm;
 
 // CHECK: .balign 16
 // CHECK-LABEL: naked_empty:
-#[align(16)]
+#[rustc_align(16)]
 #[no_mangle]
 #[unsafe(naked)]
 pub extern "C" fn naked_empty() {
diff --git a/tests/codegen/naked-fn/min-function-alignment.rs b/tests/codegen/naked-fn/min-function-alignment.rs
index 4ebaacd3eff..406e9334fa5 100644
--- a/tests/codegen/naked-fn/min-function-alignment.rs
+++ b/tests/codegen/naked-fn/min-function-alignment.rs
@@ -3,6 +3,8 @@
 //@ ignore-arm no "ret" mnemonic
 //@ ignore-wasm32 aligning functions is not currently supported on wasm (#143368)
 
+// FIXME(#82232, #143834): temporarily renamed to mitigate `#[align]` nameres ambiguity
+#![feature(rustc_attrs)]
 #![feature(fn_align)]
 #![crate_type = "lib"]
 
@@ -17,7 +19,7 @@ pub extern "C" fn naked_no_explicit_align() {
 
 // CHECK: .balign 16
 #[no_mangle]
-#[align(8)]
+#[rustc_align(8)]
 #[unsafe(naked)]
 pub extern "C" fn naked_lower_align() {
     core::arch::naked_asm!("ret")
@@ -25,7 +27,7 @@ pub extern "C" fn naked_lower_align() {
 
 // CHECK: .balign 32
 #[no_mangle]
-#[align(32)]
+#[rustc_align(32)]
 #[unsafe(naked)]
 pub extern "C" fn naked_higher_align() {
     core::arch::naked_asm!("ret")