Macro java_bindgen::signature_by_type

macro_rules! signature_by_type {
    ( => ) => { ... };
    ( => $_return:tt) => { ... };
    ( $a1:tt => $_return:tt) => { ... };
    ( $a1:tt => ) => { ... };
    ($a1:tt , $($arg:ty),* => $_return:ty) => { ... };
    ($a1:tt , $($arg:tt),* => ) => { ... };
}