make target an associated type

packages/signals/src/copy_value.rs

@@ -204,14 +204,18 @@ impl<T: 'static, S: Storage<T>> CopyValue<T, S> {
     }
 }
 
-impl<T: 'static, S: Storage<T>> Readable<T> for CopyValue<T, S> {
+impl<T: 'static, S: Storage<T>> Readable for CopyValue<T, S> {
+    type Target = T;
     type Ref<R: ?Sized + 'static> = S::Ref<R>;
 
-    fn map_ref<I, U: ?Sized, F: FnOnce(&I) -> &U>(ref_: Self::Ref<I>, f: F) -> Self::Ref<U> {
+    fn map_ref<I: ?Sized, U: ?Sized, F: FnOnce(&I) -> &U>(
+        ref_: Self::Ref<I>,
+        f: F,
+    ) -> Self::Ref<U> {
         S::map(ref_, f)
     }
 
-    fn try_map_ref<I, U: ?Sized, F: FnOnce(&I) -> Option<&U>>(
+    fn try_map_ref<I: ?Sized, U: ?Sized, F: FnOnce(&I) -> Option<&U>>(
         ref_: Self::Ref<I>,
         f: F,
     ) -> Option<Self::Ref<U>> {
@@ -227,17 +231,17 @@ impl<T: 'static, S: Storage<T>> Readable<T> for CopyValue<T, S> {
     }
 }
 
-impl<T: 'static, S: Storage<T>> Writable<T> for CopyValue<T, S> {
+impl<T: 'static, S: Storage<T>> Writable for CopyValue<T, S> {
     type Mut<R: ?Sized + 'static> = S::Mut<R>;
 
-    fn map_mut<I, U: ?Sized, F: FnOnce(&mut I) -> &mut U>(
+    fn map_mut<I: ?Sized, U: ?Sized, F: FnOnce(&mut I) -> &mut U>(
         mut_: Self::Mut<I>,
         f: F,
     ) -> Self::Mut<U> {
         S::map_mut(mut_, f)
     }
 
-    fn try_map_mut<I, U: ?Sized, F: FnOnce(&mut I) -> Option<&mut U>>(
+    fn try_map_mut<I: ?Sized, U: ?Sized, F: FnOnce(&mut I) -> Option<&mut U>>(
         mut_: Self::Mut<I>,
         f: F,
     ) -> Option<Self::Mut<U>> {