[libcxx] Portability fix: unordered_set and unordered_multiset iterators are not required to be the same.

[amakc11]

Summary

The unordered_set and unordered_multiset iterators are specified in the standard as follows:

using iterator             = implementation-defined; // see [container.requirements]
using const_iterator       = implementation-defined; // see [container.requirements]
using local_iterator       = implementation-defined; // see [container.requirements]
using const_local_iterator = implementation-defined; // see [container.requirements]

The pairs iterator/const_iterator and local_iterator/const_local_iterator are not required to be the same. The reasonable requirement would be that iterator can convert to const_iterator and local_iterator can convert to const_local_iterator. This patch weakens the check and makes the test more portable.

[amakc11]

ping

[ldionne]

Just to confirm, are you OK with this being committed under the new LLVM license? See http://lists.llvm.org/pipermail/llvm-dev/2019-January/129069.html for details.

[amakc11]

Yes, I am. The same is true for all other my patches awaiting review.

[ldionne]

Thanks. Committed as r352083.

test/std/containers/unord/iterator_difference_type.pass.cpp

typedef typename Map::difference_type Diff;
     static_assert((std::is_same<typename It::pointer, CPtrT>::value), "");
     static_assert((std::is_same<typename It::difference_type, Diff>::value), "");
   }
 }
 
 
 template <class Set, class ValueTp, class CPtrT>
 void testUnorderedSet() {
-  static_assert((std::is_same<typename Set::iterator,
+  static_assert((std::is_convertible<typename Set::iterator,
                                      typename Set::const_iterator>::value), "");
-  static_assert((std::is_same<typename Set::local_iterator,
+  static_assert((std::is_convertible<typename Set::local_iterator,
                                      typename Set::const_local_iterator>::value), "");
   typedef typename Set::difference_type Diff;
   {
     typedef typename Set::iterator It;
     static_assert((std::is_same<typename It::value_type, ValueTp>::value), "");
     static_assert((std::is_same<typename It::reference, ValueTp const&>::value), "");
     static_assert((std::is_same<typename It::pointer, CPtrT>::value), "");
     static_assert((std::is_same<typename It::difference_type, Diff>::value), "");