}{
		{&N1{}, "*gob.N1"},
		{N2{}, "encoding/gob.N2"},
	}

	for _, tc := range testCases {
		Register(tc.t)

		tct := reflect.TypeOf(tc.t)
		ct, _ := nameToConcreteType.Load(tc.name)
		if ct != tct {
			t.Errorf("nameToConcreteType[%q] = %v, want %v", tc.name, ct, tct)
		}
		// concreteTypeToName is keyed off the base type.
		if tct.Kind() == reflect.Pointer {
			tct = tct.Elem()
		}

	if t, dup := nameToConcreteType.LoadOrStore(name, reflect.TypeOf(value)); dup && t != ut.user {
		panic(fmt.Sprintf("gob: registering duplicate types for %q: %s != %s", name, t, ut.user))
	}

	// but the flattened type in the type table, since that's what decode needs.
	if n, dup := concreteTypeToName.LoadOrStore(ut.base, name); dup && n != name {
		nameToConcreteType.Delete(name)

		value.SetZero()
		return
	}
	if len(name) > 1024 {
		errorf("name too long (%d bytes): %.20q...", len(name), name)
	}
	// The concrete type must be registered.
	typi, ok := nameToConcreteType.Load(string(name))
	if !ok {
		errorf("name not registered for interface: %q", name)
	}
	typ := typi.(reflect.Type)

	// Read the type id of the concrete value.
	concreteId := dec.decodeTypeSequence(true)