Add missing num_internals feature gate to coretests/benches

library/coretests/benches/lib.rs

@@ -8,7 +8,9 @@
 #![feature(iter_array_chunks)]
 #![feature(iter_next_chunk)]
 #![feature(iter_advance_by)]
+#![feature(num_internals)]
 #![feature(uint_gather_scatter_bits)]
+#![allow(internal_features)]
 
 extern crate test;