library: add {Pointee,Meta}Sized to next prelude

Its strange to have to import sizedness traits, so add them to the
prelude in the next edition.

Author: davidtwco

library/core/src/prelude/mod.rs

@@ -92,4 +92,8 @@ pub mod rust_future {
     #[stable(feature = "prelude_2024", since = "1.85.0")]
     #[doc(no_inline)]
     pub use crate::future::{Future, IntoFuture};
+
+    #[unstable(feature = "prelude_next", issue = "none")]
+    #[doc(no_inline)]
+    pub use crate::marker::{MetaSized, PointeeSized};
 }

tests/ui/sized-hierarchy/extern-type-behind-ptr.rs

@@ -1,7 +1,7 @@
 //@ check-pass
 #![feature(extern_types, sized_hierarchy)]
 
-use std::marker::{MetaSized, PointeeSized};
+use std::marker::PointeeSized;
 
 pub fn hash<T: PointeeSized>(_: *const T) {
     unimplemented!();

tests/ui/sized-hierarchy/prelude.e2024.stderr

@@ -0,0 +1,25 @@
+error[E0405]: cannot find trait `MetaSized` in this scope
+  --> $DIR/prelude.rs:10:21
+   |
+LL | pub fn metasized<T: MetaSized>() {}
+   |                     ^^^^^^^^^ not found in this scope
+   |
+help: consider importing this trait
+   |
+LL + use std::marker::MetaSized;
+   |
+
+error[E0405]: cannot find trait `PointeeSized` in this scope
+  --> $DIR/prelude.rs:12:24
+   |
+LL | pub fn pointeesized<T: PointeeSized>() {}
+   |                        ^^^^^^^^^^^^ not found in this scope
+   |
+help: consider importing this trait
+   |
+LL + use std::marker::PointeeSized;
+   |
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0405`.

tests/ui/sized-hierarchy/prelude.rs

@@ -0,0 +1,13 @@
+//@ compile-flags: --crate-type=lib
+//@ revisions: e2024 future
+//@[e2024] edition: 2024
+//@[e2024] check-fail
+//@[future] compile-flags: -Zunstable-options
+//@[future] edition: future
+//@[future] check-pass
+#![feature(sized_hierarchy)]
+
+pub fn metasized<T: MetaSized>() {}
+//[e2024]~^ ERROR cannot find trait `MetaSized` in this scope
+pub fn pointeesized<T: PointeeSized>() {}
+//[e2024]~^ ERROR cannot find trait `PointeeSized` in this scope