optimal-compute-core: fix blanket-implementation of ComputationFn f…

…or `Box`

optimal-compute-core/src/lib.rs

@@ -475,11 +475,21 @@ where
 ///
 /// Most computations should implement this,
 /// even if they represent a function with zero arguments.
-#[blanket(derive(Ref, Mut, Box, Rc, Arc, Cow))]
+#[blanket(derive(Ref, Mut, Rc, Arc, Cow))]
 pub trait ComputationFn: Computation {
     fn args(&self) -> Args;
 }
 
+// `blanket` version `0.4.0` derives this without `?Sized`.
+impl<T> ComputationFn for Box<T>
+where
+    T: ComputationFn + ?Sized,
+{
+    fn args(&self) -> Args {
+        (*(*self)).args()
+    }
+}
+
 #[derive(Clone, Copy, Debug)]
 pub struct Val<Dim, A>
 where