1 files changed, 67 insertions, 6 deletions
diff --git a/library/core/src/marker.rs b/library/core/src/marker.rs
index 1326fc9ab..520ae0edb 100644
--- a/library/core/src/marker.rs
+++ b/library/core/src/marker.rs
@@ -97,6 +97,7 @@ unsafe impl<T: Sync + ?Sized> Send for &T {}
 #[fundamental] // for Default, for example, which requires that `[T]: !Default` be evaluatable
 #[rustc_specialization_trait]
 #[rustc_deny_explicit_impl]
+#[cfg_attr(not(bootstrap), rustc_coinductive)]
 pub trait Sized {
     // Empty.
 }
@@ -469,6 +470,62 @@ pub macro Copy($item:item) {
 #[cfg_attr(not(test), rustc_diagnostic_item = "Sync")]
 #[lang = "sync"]
 #[rustc_on_unimplemented(
+    on(
+        _Self = "std::cell::OnceCell<T>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::OnceLock` instead"
+    ),
+    on(
+        _Self = "std::cell::Cell<u8>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU8` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<u16>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU16` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<u32>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU32` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<u64>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicU64` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<usize>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicUsize` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<i8>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI8` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<i16>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI16` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<i32>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI32` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<i64>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicI64` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<isize>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicIsize` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<bool>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` or `std::sync::atomic::AtomicBool` instead",
+    ),
+    on(
+        _Self = "std::cell::Cell<T>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock`",
+    ),
+    on(
+        _Self = "std::cell::RefCell<T>",
+        note = "if you want to do aliasing and mutation between multiple threads, use `std::sync::RwLock` instead",
+    ),
     message = "`{Self}` cannot be shared between threads safely",
     label = "`{Self}` cannot be shared between threads safely"
 )]
@@ -815,14 +872,18 @@ pub trait Destruct {}
 #[rustc_deny_explicit_impl]
 pub trait Tuple {}
 
-/// A marker for things
-#[unstable(feature = "pointer_sized_trait", issue = "none")]
-#[lang = "pointer_sized"]
+/// A marker for pointer-like types.
+///
+/// All types that have the same size and alignment as a `usize` or
+/// `*const ()` automatically implement this trait.
+#[unstable(feature = "pointer_like_trait", issue = "none")]
+#[cfg_attr(bootstrap, lang = "pointer_sized")]
+#[cfg_attr(not(bootstrap), lang = "pointer_like")]
 #[rustc_on_unimplemented(
-    message = "`{Self}` needs to be a pointer-sized type",
-    label = "`{Self}` needs to be a pointer-sized type"
+    message = "`{Self}` needs to have the same alignment and size as a pointer",
+    label = "`{Self}` needs to be a pointer-like type"
 )]
-pub trait PointerSized {}
+pub trait PointerLike {}
 
 /// Implementations of `Copy` for primitive types.
 ///