Macro generate_to_tokens

macro_rules! generate_to_tokens {
    (
        ($($arms:tt)*) $tokens:ident $name:ident {
            $(#[cfg $cfg_attr:tt])*
            $(#[doc $($doc_attr:tt)*])*
            $variant:ident,
            $($next:tt)*
        }
    ) => { ... };
    (
        ($($arms:tt)*) $tokens:ident $name:ident {
            $(#[cfg $cfg_attr:tt])*
            $(#[doc $($doc_attr:tt)*])*
            $variant:ident($member:ident),
            $($next:tt)*
        }
    ) => { ... };
    (($($arms:tt)*) $tokens:ident $name:ident {}) => { ... };
}