Macro assert_impl 

macro_rules! assert_impl {
    (impl $(<$($a:ident),*>)? $tr:ident$(<$($tra:ident),*>)? for $ty:ty where $($w:tt)*) => { ... };
    (impl $(<$($a:ident),*>)? $tr:ident$(<$($tra:ident),*>)? for $ty:ty {}) => { ... };
}

object_rainbow::assert_impl!(
    impl<T> Send for std::sync::Arc<T>
    where
        T: Send + Sync,
    {}
);
object_rainbow::assert_impl!(
    impl<T> Sync for std::sync::Arc<T>
    where
        T: Send + Sync,
    {}
);