if !ok {
			t.Errorf("e2t_ssa(s) panic type %T", e)
		}
		want := "interface conversion: interface {} is *main.S, not *main.U"
		if err.Error() != want {
			t.Errorf("e2t_ssa(s) wrong error, want '%s', got '%s'", want, err.Error())
		}
	}()
	got = e2t_ssa(s)
	t.Errorf("e2t_ssa(s) should panic")

}

func testAssertI2TOk(t *testing.T) {
	if got := i2t_ssa(u); got != u {
		t.Errorf("i2t_ssa(u)=%v want %v", got, u)
	}
}