Auto merge of #122045 - matthiaskrgr:rollup-5l3vpn7, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #121065 (Add basic i18n guidance for `Display`)
 - #121744 (Stop using Bubble in coherence and instead emulate it with an intercrate check)
 - #121829 (Dummy tweaks (attempt 2))
 - #121857 (Implement async closure signature deduction)
 - #121894 (const_eval_select: make it safe but be careful with what we expose on stable for now)
 - #122014 (Change some attributes to only_local.)
 - #122016 (will_wake tests fail on Miri and that is expected)
 - #122018 (only set noalias on Box with the global allocator)
 - #122028 (Remove some dead code)

r? `@ghost`
`@rustbot` modify labels: rollup

2 files changed, 6 insertions, 0 deletions

diff --git a/library/alloc/src/alloc.rs b/library/alloc/src/alloc.rs
index 0b142939755..a5d28aa5252 100644
--- a/library/alloc/src/alloc.rs
+++ b/library/alloc/src/alloc.rs
@@ -50,6 +50,8 @@ extern "Rust" {
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Copy, Clone, Default, Debug)]
 #[cfg(not(test))]
+// the compiler needs to know when a Box uses the global allocator vs a custom one
+#[cfg_attr(not(bootstrap), lang = "global_alloc_ty")]
 pub struct Global;
 
 #[cfg(test)]
@@ -385,6 +387,7 @@ pub const fn handle_alloc_error(layout: Layout) -> ! {
     }
 
     #[cfg(not(feature = "panic_immediate_abort"))]
+    #[cfg_attr(not(bootstrap), allow(unused_unsafe))] // on bootstrap bump, remove unsafe block
     unsafe {
         core::intrinsics::const_eval_select((layout,), ct_error, rt_error)
     }
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index b202d9250d5..2736e5ee6c5 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -2062,6 +2062,9 @@ impl<Args: Tuple, F: AsyncFn<Args> + ?Sized, A: Allocator> AsyncFn<Args> for Box
 #[unstable(feature = "coerce_unsized", issue = "18598")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized, A: Allocator> CoerceUnsized<Box<U, A>> for Box<T, A> {}
 
+// It is quite crucial that we only allow the `Global` allocator here.
+// Handling arbitrary custom allocators (which can affect the `Box` layout heavily!)
+// would need a lot of codegen and interpreter adjustments.
 #[unstable(feature = "dispatch_from_dyn", issue = "none")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> DispatchFromDyn<Box<U>> for Box<T, Global> {}