#![feature(exhaustive_patterns)]
#![feature(get_mut_unchecked)]
#![feature(if_let_guard)]
-#![feature(map_first_last)]
#![feature(negative_impls)]
#![feature(never_type)]
#![feature(extern_types)]
#![feature(type_alias_impl_trait)]
#![feature(associated_type_bounds)]
#![feature(rustc_attrs)]
-#![feature(half_open_range_patterns)]
+#![cfg_attr(bootstrap, feature(half_open_range_patterns))]
#![feature(control_flow_enum)]
#![feature(associated_type_defaults)]
#![feature(trusted_step)]