Improve zero sized panic message

Author: dtolnay

src/distributed_slice.rs

@@ -163,7 +163,9 @@ impl<T> DistributedSlice<[T]> {
         dupcheck_start: *const (),
         dupcheck_stop: *const (),
     ) -> Self {
-        assert!(mem::size_of::<T>() > 0);
+        if mem::size_of::<T>() == 0 {
+            panic!("#[distributed_slice] requires that the slice element type has nonzero size");
+        }
 
         DistributedSlice {
             name,

tests/ui/zerosized.stderr

@@ -1,4 +1,4 @@
-error[E0080]: evaluation panicked: assertion failed: mem::size_of::<T>() > 0
+error[E0080]: evaluation panicked: #[distributed_slice] requires that the slice element type has nonzero size
  --> tests/ui/zerosized.rs:7:1
   |
 7 | #[distributed_slice]