Macro digestible

macro_rules! digestible {
    ($ty:ident, verifying_keys) => { ... };
    ($ty:ident, public_keys) => { ... };
    ($ty:ident, secret_keys) => { ... };
    ($ty:ident, signing_keys) => { ... };
    ($ty:ident, $ec_field:tt, $pq_field:tt, $($pq_field_accessor:ident).+) => { ... };
}