Better call block features will be introduced in Android P.
According to XDA developers, a new feature can be introduced in Android P Call Dialer. With this new feature, you can block incoming calls from all the numbers that are not safe in your phone. With this feature you will also be able to block calls from private numbers,pay phone, phone numbers and the numbers which don't have caller ID information.
This new feature will be disable after you call your emergency because the Local Emergency Call Center can call you with anonymous number after the emergency call.
This feature is actually included in Android, but it may be possible to see it in Android P.