Stage-step cfgs

Author: Mark-Simulacrum

library/core/src/lib.rs

@@ -171,7 +171,6 @@
 #![feature(const_precise_live_drops)]
 #![feature(const_refs_to_cell)]
 #![feature(decl_macro)]
-#![cfg_attr(bootstrap, feature(derive_default_enum))]
 #![feature(deprecated_suggestion)]
 #![feature(doc_cfg)]
 #![feature(doc_notable_trait)]

library/core/src/slice/mod.rs

@@ -4016,7 +4016,6 @@ impl<T> [T] {
     }
 }
 
-#[cfg(not(bootstrap))]
 impl<T, const N: usize> [[T; N]] {
     /// Takes a `&[[T; N]]`, and flattens it to a `&[T]`.
     ///

library/core/tests/slice.rs

@@ -2518,15 +2518,13 @@ fn test_slice_from_ptr_range() {
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 #[should_panic = "slice len overflow"]
 fn test_flatten_size_overflow() {
     let x = &[[(); usize::MAX]; 2][..];
     let _ = x.flatten();
 }
 
 #[test]
-#[cfg(not(bootstrap))]
 #[should_panic = "slice len overflow"]
 fn test_flatten_mut_size_overflow() {
     let x = &mut [[(); usize::MAX]; 2][..];