add array tests, cleanup, tidy, and bless

Author: RalfJung

tests/ui/derive.rs

@@ -1,7 +1,7 @@
-#![feature(untagged_unions)]
 #![allow(dead_code)]
 #![warn(clippy::expl_impl_clone_on_copy)]
 
+
 #[derive(Copy)]
 struct Qux;
 

tests/ui/no_effect.rs

@@ -4,7 +4,7 @@
 #![allow(path_statements)]
 #![allow(clippy::deref_addrof)]
 #![allow(clippy::redundant_field_names)]
-#![feature(untagged_unions)]
+
 
 struct Unit;
 struct Tuple(i32);