[iterator.concept.winc]/12:

For any two integer-like types I1 and I2, at least one of which is an integer-class type, common_­type_­t<I1, I2> denotes an integer-class type whose width is not less than that of I1 or I2. If both I1 and I2 are signed-integer-like types, then common_­type_­t<I1, I2> is also a signed-integer-like type.

[iterator.concept.winc]/13:

For any two integer-like types I1 and I2, at least one of which is an integer-class type, common_­type_­t<I1, I2> denotes an integer-like type whose width is not less than that of I1 or I2. If both I1 and I2 are signed-integer-like types, then common_­type_­t<I1, I2> is also a signed-integer-like type.

These are nearly identical, except that /12 says "common_­type_­t<I1, I2> denotes an integer-class type" while /13 says "common_­type_­t<I1, I2> denotes an integer-like type". Note that "integer-like type" is defined as "integral or integer-class type" in this section.

I believe that /13 is not needed, as it only specifies a weaker form of the previous paragraph.

/12 was added by P2393R1 Cleaning up integer-class types. /13 was added by P2321R2 zip.

cc @timsong-cpp