`#![feature(pub_macro_rules)]`
feature: public_private_dependencies
`#![feature(raw_ref_op)]`
`#![feature(re_rebalance_coherence)]`
`#![feature(refine)]`; RFC #3245
`#![feature(register_tool)]`
`#![feature(relaxed_struct_unsize)]`
`#![feature(reserved_prefixes)]`
`#![feature(return_position_impl_trait_in_trait)]`
`#[feature(return_type_notation)]`
`#![feature(rust_cold_cc)]`
`#![feature(rust_2018_preview)]`
Internal rustc attributes gated on the `#[rustc_attrs]` feature gate.
`#![feature(shorter_tail_lifetimes)]`
`#![feature(sleep_until)]`
`#![feature(slice_patterns)]`
`#![feature(specialization)]`
`#![feature(staged_api)]`
`#![feature(stdarch_aarch64_mte)]`
`#![feature(stdarch_x86_avx512)]`
`#![feature(stmt_expr_attributes)]`
`#![feature(struct_target_features)]`
`#![feature(supertrait_item_shadowing)]`
`#![feature(target_modifiers)]`
`#![feature(thread_local)]`
`#![feature(thread_spawn_hook)]`