Fix Id's UnwindSafe impl for upcoming changes to the compiler

See rust-lang/rust#93367

objc2-foundation/src/array.rs

@@ -43,19 +43,10 @@ unsafe impl<T: Send> Send for NSArray<T, Owned> {}
 
 object! {
     // TODO: Ensure that this deref to NSArray is safe!
-    unsafe pub struct NSMutableArray<T, O: Ownership>: NSArray<T, O> {
-        item: PhantomData<Id<T, O>>,
-    }
+    // This "inherits" NSArray, and has the same `Send`/`Sync` impls as that.
+    unsafe pub struct NSMutableArray<T, O: Ownership>: NSArray<T, O> {}
 }
 
-// SAFETY: Same as NSArray.
-//
-// TODO: Properly verify this
-unsafe impl<T: Sync + Send> Sync for NSMutableArray<T, Shared> {}
-unsafe impl<T: Sync + Send> Send for NSMutableArray<T, Shared> {}
-unsafe impl<T: Sync> Sync for NSMutableArray<T, Owned> {}
-unsafe impl<T: Send> Send for NSMutableArray<T, Owned> {}
-
 unsafe fn from_refs<T: Message + ?Sized>(cls: &Class, refs: &[&T]) -> NonNull<Object> {
     let obj: *mut Object = unsafe { msg_send![cls, alloc] };
     let obj: *mut Object = unsafe {

objc2/src/rc/id.rs

@@ -2,8 +2,8 @@ use core::fmt;
 use core::marker::PhantomData;
 use core::mem::ManuallyDrop;
 use core::ops::{Deref, DerefMut};
+use core::panic::{RefUnwindSafe, UnwindSafe};
 use core::ptr::NonNull;
-use std::panic::{RefUnwindSafe, UnwindSafe};
 
 use super::AutoreleasePool;
 use super::{Owned, Ownership, Shared};
@@ -117,6 +117,11 @@ pub struct Id<T: ?Sized, O: Ownership> {
     item: PhantomData<T>,
     /// To prevent warnings about unused type parameters.
     own: PhantomData<O>,
+    /// Marks the type as !UnwindSafe. Later on we'll re-enable this.
+    ///
+    /// See <https://github.com/rust-lang/rust/issues/93367> for why this is
+    /// required.
+    notunwindsafe: PhantomData<&'static mut ()>,
 }
 
 impl<T: Message + ?Sized, O: Ownership> Id<T, O> {
@@ -171,6 +176,7 @@ impl<T: Message + ?Sized, O: Ownership> Id<T, O> {
             ptr,
             item: PhantomData,
             own: PhantomData,
+            notunwindsafe: PhantomData,
         }
     }