Macro std::__thread_local_inner

macro_rules! __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)