Macro thread_local_inner

#[doc(hidden)] pub macro thread_local_inner {
    (@key $t:ty, const $init:expr) => { ... },
    (@key $t:ty, $init:expr) => { ... },
    ($(#[$attr:meta])* $vis:vis $name:ident, $t:ty, $($init:tt)*) => { ... },
}

🔬This is a nightly-only experimental API. (thread_local_internals)