Macro native_op 

macro_rules! native_op {
    ($name:ident, $fn_title:tt, [$($arg:ident),* $(,)?] $(, $ctx:ident)? , $body:block) => { ... };
    (@bind_ctx $native_ctx:ident, $ctx:ident) => { ... };
    (@bind_ctx $native_ctx:ident) => { ... };
    (@define_titles $env:ident, $val:ident, [$($title:expr),+ $(,)?]) => { ... };
    (@define_titles $env:ident, $val:ident, $title:expr) => { ... };
    (@define_help $env:ident, $kind:expr, $msg:expr, [$($title:expr),+ $(,)?]) => { ... };
    (@define_help $env:ident, $kind:expr, $msg:expr, $title:expr) => { ... };
}