Function get_rust_try_fn

fn get_rust_try_fn<'a, 'll, 'tcx>(
    cx: &'a GenericCx<'ll, FullCx<'ll, 'tcx>>,
    codegen: &mut dyn FnMut(GenericBuilder<'a, 'll, FullCx<'ll, 'tcx>>),
) -> (&'ll Type, &'ll Value)