var _ I = &S{}

type CloningMap[K comparable, V any] struct {
	inner map[K]V
}

func (cm CloningMap[K, V]) With(key K, value V) CloningMap[K, V] {
	result := CloneBad(cm.inner)
	result[key] = value
	return CloningMap[K, V]{result}
}

func CloneBad[M ~map[K]V, K comparable, V any](m M) M {
	r := make(M, len(m))
	for k, v := range m {
		r[k] = v
	}
	return r
}

func main() {
	s1 := &S{"one"}