Implement MethodImplementation for unsafe function pointers

Author: madsmtm

objc2/CHANGELOG.md

@@ -18,6 +18,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Consistently allow trailing commas in `msg_send!`.
 * Added `msg_send_bool!`, a less error-prone version of `msg_send!` for
   Objective-C methods that return `BOOL`.
+* Implemented `MethodImplementation` for `unsafe` function pointers.
 
 ### Changed
 * **BREAKING**: Changed signature of `Id::new` and `Id::retain` from

objc2/src/declare.rs

@@ -78,6 +78,10 @@ macro_rules! method_decl_impl {
     ($($t:ident),*) => (
         method_decl_impl!(-T, R, extern "C" fn(&T, Sel $(, $t)*) -> R, $($t),*);
         method_decl_impl!(-T, R, extern "C" fn(&mut T, Sel $(, $t)*) -> R, $($t),*);
+        method_decl_impl!(-T, R, unsafe extern "C" fn(*const T, Sel $(, $t)*) -> R, $($t),*);
+        method_decl_impl!(-T, R, unsafe extern "C" fn(*mut T, Sel $(, $t)*) -> R, $($t),*);
+        method_decl_impl!(-T, R, unsafe extern "C" fn(&T, Sel $(, $t)*) -> R, $($t),*);
+        method_decl_impl!(-T, R, unsafe extern "C" fn(&mut T, Sel $(, $t)*) -> R, $($t),*);
     );
 }