PR libstdc++/68222 Hide safe iterator operators

[Jonathan Wakely]

On 18/08/18 22:31 +0200, François Dumont wrote:
>Here is the new proposal. It is indeed possible to keep _Safe_iterator 
>and just add a _Category template parameter to it.

While this is still a large patch (obviously, because it's changing a
lot!) I think this version is much easier to understand, and doesn't
add a whole new class unnecessarily. Thanks for updating it.

>I introduce a friend declaration to access container _Base nested 
>typedef from the safe iterator.
>
>I review the safe const_iterator constructor from safe iterator. I now 
>check if we are in the a const_iterator context so that compilers 
>don't even try to consider this constructor when we are in an iterator 
>context.

Nice.

>I adapted _Safe_local_iterator the same way to keep consistency with 
>_Safe_iterator and because I find the new design cleaner. It also 
>fixes the same problem I fixed on _Safe_iterator when checking it 
>iterator has been initialized using _MutableIterator() rather than 
>_Iterator().
>
>I stop overloading __get_distance for safe iterators or safe local 
>iterators, it was useless. I prefer to introduce similar functions as 
>members. Same for __get_distance_from_begin or __get_distance_to_end, 
>and I move code in safe_iterator.tcc.
>
>Tested under Linux x86_64 debug mode.
>
>Ok to commit ?

OK for trunk, thanks again.