Proposed Fix for LWG 2059: C++0x ambiguity problem with map::erase

[mclow.lists]

Summary

http://www.open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#2059

[EricWF]

Why were no erase methods added for set, multiset, unordered_set, and unordered_multiset?

[EricWF]

In D9408#164597, @EricWF wrote:

Why were no erase methods added for set, multiset, unordered_set, and unordered_multiset?

Because const_iterator and iterator are the same type.

This patch LGTM but I would remove the __cplusplus >= 201402L blocks around the tests since the fix is applied in all standard versions.

[mclow.lists]

Committed as r236950

include/map

     void insert(initializer_list<value_type> il);
 
     iterator  erase(const_iterator position);
+    iterator  erase(iterator position); // C++14
     size_type erase(const key_type& k);
     iterator  erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     void insert(initializer_list<value_type> il);
 
     iterator  erase(const_iterator position);
+    iterator  erase(iterator position); // C++14
     size_type erase(const key_type& k);
     iterator  erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __tree_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
+    iterator erase(iterator __p)       {return __tree_.erase(__p.__i_);}
+    _LIBCPP_INLINE_VISIBILITY
     size_type erase(const key_type& __k)
         {return __tree_.__erase_unique(__k);}
     _LIBCPP_INLINE_VISIBILITY

     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __tree_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
+    iterator erase(iterator __p)       {return __tree_.erase(__p.__i_);}
+    _LIBCPP_INLINE_VISIBILITY
     size_type erase(const key_type& __k) {return __tree_.__erase_multi(__k);}
     _LIBCPP_INLINE_VISIBILITY
     iterator  erase(const_iterator __f, const_iterator __l)

include/set

     void insert(initializer_list<value_type> il);
 
     iterator  erase(const_iterator position);
+    iterator  erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator  erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     void insert(initializer_list<value_type> il);
 
     iterator  erase(const_iterator position);
+    iterator  erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator  erase(const_iterator first, const_iterator last);
     void clear() noexcept;

include/unordered_map

     void insert(initializer_list<value_type>);
 
     iterator erase(const_iterator position);
+    iterator erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     void insert(initializer_list<value_type>);
 
     iterator erase(const_iterator position);
+    iterator erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __table_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
+    iterator erase(iterator __p)       {return __table_.erase(__p.__i_);}
+    _LIBCPP_INLINE_VISIBILITY
     size_type erase(const key_type& __k) {return __table_.__erase_unique(__k);}
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __first, const_iterator __last)

     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __table_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
+    iterator erase(iterator __p)       {return __table_.erase(__p.__i_);}
+    _LIBCPP_INLINE_VISIBILITY
     size_type erase(const key_type& __k) {return __table_.__erase_multi(__k);}
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __first, const_iterator __last)

include/unordered_set

     void insert(initializer_list<value_type>);
 
     iterator erase(const_iterator position);
+    iterator erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator erase(const_iterator first, const_iterator last);
     void clear() noexcept;

     void insert(initializer_list<value_type>);
 
     iterator erase(const_iterator position);
+    iterator erase(iterator position);  // C++14
     size_type erase(const key_type& k);
     iterator erase(const_iterator first, const_iterator last);
     void clear() noexcept;

test/std/containers/associative/map/map.modifiers/erase_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator<(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+
 int main()
 {
     {

         assert(i == m.end());
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::map<T, int> C;
+        typedef C::iterator I;
+
+        C c;
+        T a{0};
+        I it = c.find(a);
+        if (it != c.end())
+            c.erase(it);
+    }
+#endif
 }

test/std/containers/associative/multimap/multimap.modifiers/erase_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator<(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+
 int main()
 {
     {

         assert(i == m.end());
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::multimap<T, int> C;
+        typedef C::iterator I;
+
+        C c;
+        T a{0};
+        I it = c.find(a);
+        if (it != c.end())
+            c.erase(it);
+    }
+#endif
 }

test/std/containers/associative/multiset/erase_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator<(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+
 int main()
 {
     {

         assert(i == m.end());
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::multiset<T> C;
+        typedef C::iterator I;
+
+        C c;
+        T a{0};
+        I it = c.find(a);
+        if (it != c.end())
+            c.erase(it);
+    }
+#endif
 }

test/std/containers/associative/set/erase_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator<(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+
 int main()
 {
     {

         assert(i == m.end());
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::set<T> C;
+        typedef C::iterator I;
+
+        C c;
+        T a{0};
+        I it = c.find(a);
+        if (it != c.end())
+            c.erase(it);
+    }
+#endif
 }

test/std/containers/unord/unord.map/unorder.map.modifiers/erase_const_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator==(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+struct Hash { size_t operator() (const TemplateConstructor &) const { return 0; } };
+
 int main()
 {
     {

         assert(c.at(4) == "four");
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::unordered_map<T, int, Hash> C;
+        typedef C::iterator I;
+
+        C m;
+        T a{0};
+        I it = m.find(a);
+        if (it != m.end())
+            m.erase(it);
+    }
+#endif
 }

test/std/containers/unord/unord.multimap/unord.multimap.modifiers/erase_const_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator==(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+struct Hash { size_t operator() (const TemplateConstructor &) const { return 0; } };
+
 int main()
 {
     {

         assert(std::distance(c.cbegin(), c.cend()) == c.size());
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::unordered_multimap<T, int, Hash> C;
+        typedef C::iterator I;
+
+        C m;
+        T a{0};
+        I it = m.find(a);
+        if (it != m.end())
+            m.erase(it);
+    }
+#endif
 }

test/std/containers/unord/unord.multiset/erase_const_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator==(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+struct Hash { size_t operator() (const TemplateConstructor &) const { return 0; } };
+
 int main()
 {
     {

         assert(c.count(4) == 1);
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::unordered_set<T, Hash> C;
+        typedef C::iterator I;
+
+        C m;
+        T a{0};
+        I it = m.find(a);
+        if (it != m.end())
+            m.erase(it);
+    }
+#endif
 }

test/std/containers/unord/unord.set/erase_const_iter.pass.cpp

 
 #include "min_allocator.h"
 
+struct TemplateConstructor
+{
+    template<typename T>
+    TemplateConstructor (const T&) {}
+};
+
+bool operator==(const TemplateConstructor&, const TemplateConstructor&) { return false; }
+struct Hash { size_t operator() (const TemplateConstructor &) const { return 0; } };
+
 int main()
 {
     {

         assert(c.count(4) == 1);
     }
 #endif
+#if __cplusplus >= 201402L
+    {
+    //  This is LWG #2059
+        typedef TemplateConstructor T;
+        typedef std::unordered_set<T, Hash> C;
+        typedef C::iterator I;
+
+        C m;
+        T a{0};
+        I it = m.find(a);
+        if (it != m.end())
+            m.erase(it);
+    }
+#endif
 }