pub type PFNGLVERTEXATTRIB2SNVPROC = Option<unsafe extern "C" fn(index: GLuint, x: GLshort, y: GLshort)>;
enum PFNGLVERTEXATTRIB2SNVPROC { None, Some(unsafe extern "C" fn(_: u32, _: i16, _: i16)), }
No value.
Some value of type T.
T