You can convert an rvalue of type cv1 T* where
cv1 is any combination of zero or more const or
volatile qualifications, to an rvalue of type cv2
T* if cv2 T* is more const or
volatile qualified than cv1 T*.
You can convert an rvalue of type pointer to member of a class X of cv1 T, to an rvalue of type pointer to member of a class X of cv2 T if cv2 T is more const or volatile qualified than cv1 T.
Related References