Implement RefEncode for Protocol

Author: madsmtm

objc2/CHANGELOG.md

@@ -10,6 +10,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 * Export `objc-sys` as `ffi` module.
 * Added common trait impls on `rc::Owned` and `rc::Shared` (useful in generic
   contexts).
+* Implement `RefEncode` for `runtime::Protocol`.
 
 ### Changed
 * Deprecated `runtime::BOOL`, `runtime::YES` and `runtime::NO`. Use the

objc2/src/runtime.rs

@@ -472,6 +472,11 @@ impl PartialEq for Protocol {
     }
 }
 
+unsafe impl RefEncode for Protocol {
+    // Protocol is an object internally
+    const ENCODING_REF: Encoding<'static> = Encoding::Object;
+}
+
 impl Eq for Protocol {}
 
 impl fmt::Debug for Protocol {
@@ -697,12 +702,16 @@ mod tests {
 
     #[test]
     fn test_encode() {
-        assert_eq!(<&Object>::ENCODING.to_string(), "@");
-        assert_eq!(<*mut Object>::ENCODING.to_string(), "@");
-        assert_eq!(<&Class>::ENCODING.to_string(), "#");
-        assert_eq!(Sel::ENCODING.to_string(), ":");
-        assert_eq!(Imp::ENCODING.to_string(), "^?");
-        assert_eq!(<Option<Imp>>::ENCODING.to_string(), "^?");
+        fn assert_enc<T: Encode>(expected: &str) {
+            assert_eq!(&T::ENCODING.to_string(), expected);
+        }
+        assert_enc::<&Object>("@");
+        assert_enc::<*mut Object>("@");
+        assert_enc::<&Class>("#");
+        assert_enc::<Sel>(":");
+        assert_enc::<Imp>("^?");
+        assert_enc::<Option<Imp>>("^?");
+        assert_enc::<&Protocol>("@");
     }
 
     #[test]