message: Fix assert_assignable for array types
  Fixes
diff: @@ -828,6 +828,9 @@ pub(crate) fn assert_assignable<'tcx>(
  }
  }
  }
  + (ty::Array(a, _), ty::Array(b, _)) => {
  + assert_assignable(fx, *a, *b)
  + }
  _ => {
  assert_eq!(
  from_ty, to_ty,
  