macro_rules! resource_path {
    ( ( relative_to_crate, None ) ) => { ... };
    ( ( relative_to_cwd, None ) ) => { ... };
    ( None ) => { ... };
    ( ( relative_to_crate, Some ( $_path : literal ) ) ) => { ... };
    ( ( relative_to_cwd, Some ( $_path : literal ) ) ) => { ... };
    ( Some ( $_path : literal ) ) => { ... };
    ( ( relative_to_crate, $_path : literal ) ) => { ... };
    ( ( relative_to_cwd, $_path : literal ) ) => { ... };
    ( $_path : literal ) => { ... };
}