Fix bug 20740 - std::set/std::map don't support heterogeneous lookup for count(). Thanks to Jim Porter for the bug report

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@216353 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/map b/include/map
index 5534e40..5c3969a 100644
--- a/include/map
+++ b/include/map
@@ -159,7 +159,7 @@
     template<typename K>
         const_iterator find(const K& x) const;  // C++14
     template<typename K>
-      size_type count(const K& x) const;
+      size_type count(const K& x) const;        // C++14
 
     size_type      count(const key_type& k) const;
           iterator lower_bound(const key_type& k);
@@ -353,7 +353,7 @@
     template<typename K>
         const_iterator find(const K& x) const;  // C++14
     template<typename K>
-      size_type count(const K& x) const;
+      size_type count(const K& x) const;        // C++14
 
     size_type      count(const key_type& k) const;
           iterator lower_bound(const key_type& k);
@@ -1104,6 +1104,12 @@
     _LIBCPP_INLINE_VISIBILITY
     size_type      count(const key_type& __k) const
         {return __tree_.__count_unique(__k);}
+#if _LIBCPP_STD_VER > 11
+    template <typename _K2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename enable_if<__is_transparent<_Compare, _K2>::value,size_type>::type
+    count(const _K2& __k)                  {return __tree_.__count_unique(__k);}
+#endif
     _LIBCPP_INLINE_VISIBILITY
     iterator lower_bound(const key_type& __k)
         {return __tree_.lower_bound(__k);}
@@ -1834,6 +1840,12 @@
     _LIBCPP_INLINE_VISIBILITY
     size_type      count(const key_type& __k) const
         {return __tree_.__count_multi(__k);}
+#if _LIBCPP_STD_VER > 11
+    template <typename _K2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename enable_if<__is_transparent<_Compare, _K2>::value,size_type>::type
+    count(const _K2& __k)                   {return __tree_.__count_multi(__k);}
+#endif
     _LIBCPP_INLINE_VISIBILITY
     iterator lower_bound(const key_type& __k)
         {return __tree_.lower_bound(__k);}
diff --git a/include/set b/include/set
index b9e776d..22d794d 100644
--- a/include/set
+++ b/include/set
@@ -663,6 +663,12 @@
     _LIBCPP_INLINE_VISIBILITY
     size_type      count(const key_type& __k) const
         {return __tree_.__count_unique(__k);}
+#if _LIBCPP_STD_VER > 11
+    template <typename _K2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename enable_if<__is_transparent<_Compare, _K2>::value,size_type>::type
+    count(const _K2& __k)                  {return __tree_.__count_unique(__k);}
+#endif
     _LIBCPP_INLINE_VISIBILITY
     iterator lower_bound(const key_type& __k)
         {return __tree_.lower_bound(__k);}
@@ -1066,6 +1072,12 @@
     _LIBCPP_INLINE_VISIBILITY
     size_type      count(const key_type& __k) const
         {return __tree_.__count_multi(__k);}
+#if _LIBCPP_STD_VER > 11
+    template <typename _K2>
+    _LIBCPP_INLINE_VISIBILITY
+    typename enable_if<__is_transparent<_Compare, _K2>::value,size_type>::type
+    count(const _K2& __k)                  {return __tree_.__count_multi(__k);}
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     iterator lower_bound(const key_type& __k)