<iterator>: The issue of std::common_iterator::iterator_­category

[hewillk]

The standard explains the definition of iterator_category of common_iterator in [iterators.common#common.iter.types-1.2]: "iterator_­category denotes forward_­iterator_­tag if the qualified-id iterator_­traits<I>​::​iterator_­category is valid and denotes a type that models derived_­from<forward_­iterator_­tag>; otherwise it denotes input_­iterator_­tag."
However, the MSVC's implementation is as follows:

STL/stl/inc/iterator

Lines 1034 to 1035 in bd7adb4

	using iterator_category =
	conditional_t<derived_from<_Iter_cat_t<_Iter>, forward_iterator_tag>, forward_iterator_tag, input_iterator_tag>;

This does not check the validity of iterator_traits<I>​::​iterator_category.

[cpplearner]

IIUC this will be fixed by #2059

[hewillk]

IIUC this will be fixed by #2059

@cpplearner
Thank you for pointing it out for me. I just found out that @CaseyCarter has already implemented it.