Proposed resolution:

Adopt the proposed resolution in N2409.

[ John adds: ]

I think either could be implemented? Although an input iterator would probably require an internal copy of the string being made.

I have no strong feelings either way, although I think my original intent was InputIterator.

Looking at N2284, [re.regex], p3 basic_regex class template synopsis shows this constructor:

template <class InputIterator>
     basic_regex(InputIterator first, InputIterator last, 
                 flag_type f = regex_constants::ECMAScript);

In [re.regex.construct], p15, the constructor appears with this signature:

template <class ForwardIterator>
     basic_regex(ForwardIterator first, ForwardIterator last, 
                 flag_type f = regex_constants::ECMAScript);

ForwardIterator is probably correct, so the synopsis is wrong.