pub type dAABBTestFn = Option<unsafe extern "C" fn(o1: dGeomID, o2: dGeomID, aabb: *mut f64) -> c_int>;
pub enum dAABBTestFn { None, Some(unsafe extern "C" fn(*mut dxGeom, *mut dxGeom, *mut f64) -> i32), }
No value.
Some value of type T.
T