Auto merge of #47006 - bitshifter:stabilize-repr-align, r=eddyb

Stabilized `#[repr(align(x))]` attribute (RFC 1358)

Stabilzed `#[repr(align(x))]` with attr_literal syntax as proposed by @eddyb https://github.com/rust-lang/rust/issues/33626#issuecomment-348467804

src/test/ui/feature-gate-repr_align.rs

@@ -1,15 +0,0 @@
-// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-#![feature(attr_literals)]
-
-#[repr(align(64))] //~ error: the struct `#[repr(align(u16))]` attribute is experimental
-struct Foo(u64, u64);
-
-fn main() {}

src/test/ui/feature-gate-repr_align.stderr

@@ -1,10 +0,0 @@
-error[E0658]: the struct `#[repr(align(u16))]` attribute is experimental (see issue #33626)
-  --> $DIR/feature-gate-repr_align.rs:12:1
-   |
-12 | #[repr(align(64))] //~ error: the struct `#[repr(align(u16))]` attribute is experimental
-   | ^^^^^^^^^^^^^^^^^^
-   |
-   = help: add #![feature(repr_align)] to the crate attributes to enable
-
-error: aborting due to previous error
-

src/test/ui/print_type_sizes/repr-align.rs

@@ -18,8 +18,6 @@
 // It avoids using u64/i64 because on some targets that is only 4-byte
 // aligned (while on most it is 8-byte aligned) and so the resulting
 // padding and overall computed sizes can be quite different.
-#![feature(attr_literals)]
-#![feature(repr_align)]
 #![feature(start)]
 #![allow(dead_code)]
 

src/test/ui/span/gated-features-attr-spans.rs

@@ -10,7 +10,7 @@
 
 #![feature(attr_literals)]
 
-#[repr(align(16))] //~ ERROR is experimental
+#[repr(align(16))]
 struct Gem {
     mohs_hardness: u8,
     poofed: bool,

src/test/ui/span/gated-features-attr-spans.stderr

@@ -1,11 +1,3 @@
-error[E0658]: the struct `#[repr(align(u16))]` attribute is experimental (see issue #33626)
-  --> $DIR/gated-features-attr-spans.rs:13:1
-   |
-13 | #[repr(align(16))] //~ ERROR is experimental
-   | ^^^^^^^^^^^^^^^^^^
-   |
-   = help: add #![feature(repr_align)] to the crate attributes to enable
-
 error[E0658]: SIMD types are experimental and possibly buggy (see issue #27731)
   --> $DIR/gated-features-attr-spans.rs:20:1
    |
@@ -30,5 +22,5 @@ warning: `#[must_use]` on functions is experimental (see issue #43302)
    |
    = help: add #![feature(fn_must_use)] to the crate attributes to enable
 
-error: aborting due to 2 previous errors
+error: aborting due to previous error