Macro enum_derive::NextVariant

macro_rules! NextVariant {
    (
        @expand ($($pub_:tt)*) $name:ident ()
    ) => { ... };
    (
        @expand ($($pub_:tt)*) $name:ident ($($var_names:ident),*)
    ) => { ... };
    (
        @arms ($name:ident, $self_:expr), ($a:ident) -> ($($body:tt)*)
    ) => { ... };
    (
        @arms ($name:ident, $self_:expr), ($a:ident $b:ident $($rest:tt)*) -> ($($body:tt)*)
    ) => { ... };
    (() pub enum $name:ident { $($body:tt)* }) => { ... };
    (() enum $name:ident { $($body:tt)* }) => { ... };
}