Macro nightly_crimes::nightly_crimes

macro_rules! nightly_crimes {
    (
        #![feature($($a:ident),* $(,)?)]
        #![feature($($b:ident),* $(,)?)]
        $($code:tt)*
    ) => { ... };
    (
        #![feature($($feature:ident),* $(,)?)]
        $($code:tt)*
    ) => { ... };
}