[ 2022-08-23; Reflector poll ]

Set priority to 3 after reflector poll.

"I think common_iterator should reject iterators with integer-class difference types since it can't possibly achieve the design intent of adapting them to Cpp17Iterators, so this issue should only affect counted_iterator."

"If the difference types of I and I2 are different then the operator- can't be used to model sized_sentinel_for, since i - i2 and i2 - i would have different types. Providing operator- under such circumstances seems to be of dubious value."