pub type lua_Writer = Option<extern "C" fn(L: *mut lua_State, p: *const c_void, sz: size_t, ud: *mut c_void) -> c_int>;
enum lua_Writer { None, Some(extern "C" fn(*mut lua_State, *const c_void, usize, *mut c_void) -> i32), }
No value.
Some value of type T.
T