Static async fn in traits
`#![feature(async_fn_traits)]`
`#![feature(async_for_loop)]`
`#![feature(auto_traits)]`
`#![feature(bindings_after_at)]`
`#![feature(box_patterns)]`
`#![feature(bufreader_peek)]`
`#![feature(c_str_literals)]`
`#![feature(c_variadic)]`
`#![feature(cfg_accessible)]`
`#![feature(cfg_version)]`
`#![feature(closure_lifetime_binder)]`
`#![feature(cmse_nonsecure_entry)]`
The `CoerceUnsized` trait
`#![feature(collapse_debuginfo)]`
`#![feature(const_async_blocks)]`
`#![feature(const_closures)]`
`#![feature(const_extern_fn)]`
`#![feature(const_generics_defaults)]`
`#![feature(const_generics)]`
`#![feature(const_mut_refs)]`
`#[feature(const_refs_to_cell)]`
`#![feature(const_refs_to_static)]`
`#![feature(const_trait_impl)]`