Macro spec_tuple_impl

macro_rules! spec_tuple_impl {
    (
        (
            $ty_name:ident, $var_name:ident, $extend_ty_name: ident,
            $trait_name:ident, $default_fn_name:ident, $cnt:tt
        ),
    ) => { ... };
    (
        (
            $ty_name:ident, $var_name:ident, $extend_ty_name: ident,
            $trait_name:ident, $default_fn_name:ident, $cnt:tt
        ),
        $(
            (
                $ty_names:ident, $var_names:ident,  $extend_ty_names:ident,
                $trait_names:ident, $default_fn_names:ident, $cnts:tt
            ),
        )*
    ) => { ... };
    (
        $trait_name:ident, $default_fn_name:ident, #[$meta:meta]
        $(#[$doctext:meta])? => $(
            (
                $ty_names:ident, $var_names:ident, $extend_ty_names:ident, $cnts:tt
            ),
        )*
    ) => { ... };
}