Rollup merge of #146178 - folkertdev:static-align, r=jdonszelmann,ralfjung,traviscross

Implement `#[rustc_align_static(N)]` on `static`s

Tracking issue: https://github.com/rust-lang/rust/issues/146177

```rust
#![feature(static_align)]

#[rustc_align_static(64)]
static SO_ALIGNED: u64 = 0;
```

We need a different attribute than `rustc_align` because unstable attributes are tied to their feature (we can't have two unstable features use the same unstable attribute). Otherwise this uses all of the same infrastructure as `#[rustc_align]`.

r? `@traviscross`

1 files changed, 7 insertions, 1 deletions

diff --git a/compiler/rustc_passes/src/check_attr.rs b/compiler/rustc_passes/src/check_attr.rs
index 487bdd2a888..38a6b4b16c9 100644
--- a/compiler/rustc_passes/src/check_attr.rs
+++ b/compiler/rustc_passes/src/check_attr.rs
@@ -1606,12 +1606,18 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 ReprAttr::ReprAlign(align) => {
                     match target {
                         Target::Struct | Target::Union | Target::Enum => {}
-                        Target::Fn | Target::Method(_) => {
+                        Target::Fn | Target::Method(_) if self.tcx.features().fn_align() => {
                             self.dcx().emit_err(errors::ReprAlignShouldBeAlign {
                                 span: *repr_span,
                                 item: target.plural_name(),
                             });
                         }
+                        Target::Static if self.tcx.features().static_align() => {
+                            self.dcx().emit_err(errors::ReprAlignShouldBeAlignStatic {
+                                span: *repr_span,
+                                item: target.plural_name(),
+                            });
+                        }
                         _ => {
                             self.dcx().emit_err(errors::AttrApplication::StructEnumUnion {
                                 hint_span: *repr_span,