#![feature(decl_macro)]
#![feature(drain_filter)]
#![feature(generators)]
-#![cfg_attr(bootstrap, feature(generic_associated_types))]
#![feature(iter_from_generator)]
#![feature(let_chains)]
-#![cfg_attr(bootstrap, feature(let_else))]
#![feature(once_cell)]
#![feature(proc_macro_internals)]
#![feature(macro_metavar_expr)]