Macro yarnn::sequential_type_ctx_impl

macro_rules! sequential_type_ctx_impl {
    ($t:ty {$($xx:tt)*}) => { ... };
    ($t:ty {$($xx:tt)*}, $($tt:tt)*) => { ... };
    ($t:ty) => { ... };
    ($t:ty, $($tt:tt)*) => { ... };
}