Remove AsMut and BorrowMut implementations

Part of #563

crates/objc2/CHANGELOG.md

@@ -49,6 +49,8 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * **BREAKING**: Disallow `&mut` message receivers (except in the special case
   when the object is `AnyObject`, for better backwards compatibility with
   `objc`).
+* **BREAKING**: Removed `AsMut` and `BorrowMut` implementations in
+  `extern_class!` and `declare_class!`.
 
 ### Fixed
 * Remove an incorrect assertion when adding protocols to classes in an unexpected

crates/objc2/src/__macro_helpers/mod.rs

@@ -1,6 +1,6 @@
-pub use core::borrow::{Borrow, BorrowMut};
+pub use core::borrow::Borrow;
 pub use core::cell::UnsafeCell;
-pub use core::convert::{AsMut, AsRef};
+pub use core::convert::AsRef;
 pub use core::marker::{PhantomData, Sized};
 pub use core::mem::{size_of, ManuallyDrop, MaybeUninit};
 pub use core::ops::{Deref, DerefMut};

crates/objc2/src/macros/extern_class.rs

@@ -24,9 +24,7 @@
 /// - [`Deref<Target = $superclass>`][core::ops::Deref]
 /// - [`DerefMut`][core::ops::DerefMut]
 /// - [`AsRef<$inheritance_chain>`][AsRef]
-/// - [`AsMut<$inheritance_chain>`][AsMut]
 /// - [`Borrow<$inheritance_chain>`][core::borrow::Borrow]
-/// - [`BorrowMut<$inheritance_chain>`][core::borrow::BorrowMut]
 ///
 /// The macro allows specifying zero-sized fields like [`PhantomData`] on the
 /// struct.
@@ -262,15 +260,13 @@ macro_rules! __impl_as_ref_borrow {
     {
         impl ($($t:tt)*) for $for:ty {
             fn as_ref($($self:tt)*) $ref:block
-            fn as_mut($($self_mut:tt)*) $mut:block
         }
 
         ()
     } => {};
     {
         impl ($($t:tt)*) for $for:ty {
             fn as_ref($($self:tt)*) $ref:block
-            fn as_mut($($self_mut:tt)*) $mut:block
         }
 
         ($item:ty, $($tail:ty,)*)
@@ -280,13 +276,8 @@ macro_rules! __impl_as_ref_borrow {
             fn as_ref($($self)*) -> &$item $ref
         }
 
-        impl<$($t)*> $crate::__macro_helpers::AsMut<$item> for $for {
-            #[inline]
-            fn as_mut($($self_mut)*) -> &mut $item $mut
-        }
-
-        // Borrow and BorrowMut are correct, since subclasses behaves
-        // identical to the class they inherit (message sending doesn't care).
+        // Borrow is correct, since subclasses behaves identical to the class
+        // they inherit (message sending doesn't care).
         //
         // In particular, `Eq`, `Ord` and `Hash` all give the same results
         // after borrow.
@@ -296,15 +287,9 @@ macro_rules! __impl_as_ref_borrow {
             fn borrow($($self)*) -> &$item $ref
         }
 
-        impl<$($t)*> $crate::__macro_helpers::BorrowMut<$item> for $for {
-            #[inline]
-            fn borrow_mut($($self_mut)*) -> &mut $item $mut
-        }
-
         $crate::__impl_as_ref_borrow! {
             impl ($($t)*) for $for {
                 fn as_ref($($self)*) $ref
-                fn as_mut($($self_mut)*) $mut
             }
 
             ($($tail,)*)
@@ -478,14 +463,6 @@ macro_rules! __extern_class_impl_traits {
             }
         }
 
-        $(#[$impl_m])*
-        impl<$($t)*> $crate::__macro_helpers::AsMut<Self> for $for {
-            #[inline]
-            fn as_mut(&mut self) -> &mut Self {
-                self
-            }
-        }
-
         // Assume the meta attributes are all `cfg` attributes
         $(#[$impl_m])*
         $crate::__impl_as_ref_borrow! {
@@ -494,10 +471,6 @@ macro_rules! __extern_class_impl_traits {
                     // Triggers Deref coercion depending on return type
                     &*self
                 }
-                fn as_mut(&mut self) {
-                    // Triggers Deref coercion depending on return type
-                    &mut *self
-                }
             }
 
             ($superclass, $($inheritance_rest,)*)

crates/objc2/src/rc/id_forwarding_impls.rs

@@ -137,27 +137,13 @@ impl<T: ?Sized> borrow::Borrow<T> for Retained<T> {
     }
 }
 
-impl<T: ?Sized + IsMutable> borrow::BorrowMut<T> for Retained<T> {
-    fn borrow_mut(&mut self) -> &mut T {
-        // Auto-derefs
-        self
-    }
-}
-
 impl<T: ?Sized> AsRef<T> for Retained<T> {
     fn as_ref(&self) -> &T {
         // Auto-derefs
         self
     }
 }
 
-impl<T: ?Sized + IsMutable> AsMut<T> for Retained<T> {
-    fn as_mut(&mut self) -> &mut T {
-        // Auto-derefs
-        self
-    }
-}
-
 impl<T: Error + ?Sized> Error for Retained<T> {
     fn source(&self) -> Option<&(dyn Error + 'static)> {
         (**self).source()

crates/objc2/src/runtime/nsobject.rs

@@ -506,20 +506,15 @@ mod tests {
 
     #[test]
     fn test_as_ref_borrow() {
-        use core::borrow::{Borrow, BorrowMut};
+        use core::borrow::Borrow;
 
         fn impls_as_ref<T: AsRef<U> + Borrow<U> + ?Sized, U: ?Sized>(_: &T) {}
-        fn impls_as_mut<T: AsMut<U> + BorrowMut<U> + ?Sized, U: ?Sized>(_: &mut T) {}
 
-        let mut obj = NSObjectMutable::new();
+        let obj = NSObjectMutable::new();
         impls_as_ref::<Retained<NSObjectMutable>, NSObjectMutable>(&obj);
-        impls_as_mut::<Retained<NSObjectMutable>, NSObjectMutable>(&mut obj);
         impls_as_ref::<NSObjectMutable, NSObjectMutable>(&obj);
-        impls_as_mut::<NSObjectMutable, NSObjectMutable>(&mut obj);
         impls_as_ref::<NSObject, NSObject>(&obj);
-        impls_as_mut::<NSObject, NSObject>(&mut obj);
         impls_as_ref::<NSObject, AnyObject>(&obj);
-        impls_as_mut::<NSObject, AnyObject>(&mut obj);
 
         let obj = NSObject::new();
         impls_as_ref::<Retained<NSObject>, NSObject>(&obj);

crates/objc2/src/runtime/protocol_object.rs

@@ -203,17 +203,7 @@ where
     }
 }
 
-impl<P: ?Sized, T> AsMut<ProtocolObject<T>> for ProtocolObject<P>
-where
-    T: ?Sized + ImplementedBy<ProtocolObject<P>>,
-{
-    #[inline]
-    fn as_mut(&mut self) -> &mut ProtocolObject<T> {
-        ProtocolObject::from_mut(self)
-    }
-}
-
-// TODO: Maybe implement Borrow + BorrowMut?
+// TODO: Maybe implement Borrow?
 
 #[cfg(test)]
 #[allow(clippy::missing_safety_doc)]