iread_n_const: unwrap->expect

src/rstd/inlining.rs

@@ -26,7 +26,11 @@ pub trait InliningExt<E>: Inlining {
         self,
         err: impl FnOnce(&[u8]) -> E,
     ) -> Result<([u8; N], Self), E> {
-        self.iread_n(N, |slice| slice.try_into().unwrap(), err)
+        self.iread_n(
+            N,
+            |slice| slice.try_into().expect("iread_n wrong length."),
+            err,
+        )
     }
 }