Macro vtable_for_trait 

macro_rules! vtable_for_trait {
    {
        $trait_vis:vis trait $trait_name:ident {
            $(fn $method_name:ident(& $(mut $(@$self_mut:tt)?)? self $(, $param_name:ident : $param_type:ty)* $(,)?) $(-> $return_type:ty)?;)*
        }

        $vtable_vis:vis vtable $vtable_name:ident;
    } => { ... };
}