[libcxx-commits] [libcxx] [libc++] Implement LWG3749: `common_iterator` should handle integer-class difference types (PR #233606)

[Vishank Singh via libcxx-commits]

VishankSingh wrote:

> I just realized that libc++ doesn't consider any type to be an integer-class type. But other standard library implementations have integer-class types and may use libc++'s test suite.
> 
> Maybe it would be OK to keep the new test case without touching the product code. Also, we may alternatively consider LWG3749 "Nothing To Do" or "Complete" in LLVM 13 (in which `common_iterator` is implemented).

You're right that it doesn't do anything effectively, but not having the change would leave it slightly out of step with the wording. Given that it's is tiny and has no observable cost, I feel it's better to keep it. 
Happy to adjust if you (or Louis/Nikolas) prefer Nothing-To-Do/Complete-in-13 instead.

https://github.com/llvm/llvm-project/pull/233606