Macro jumpy::impl_system_param

macro_rules! impl_system_param {
    (
        $( #[$m:meta] )*
        pub struct $t:ident<'a> {
            $(
                $( #[$attrs:meta] )*
                $f_name:ident: $f_ty:ty
            ),*
            $(,)?
        }
    ) => { ... };
}

Macro to “derive” ( not really a derive macro ) SystemParam for a struct.