[Bug libstdc++/68190] iterator mix up with set::find and heterogenous lookup

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68190

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2015-11-02
     Ever confirmed|0                           |1

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
Started with r219888, which implements N3657.

The bug depends on LWG 103 only insofar as it wouldn't happen
if const_iterator and iterator were different in the set and
multiset case.

The problem is that the auto return type of find doesn't know that 
const_iterator and iterator are the same in this case and returns
std::_Rb_tree_iterator instead of std::_Rb_tree_const_iterator

693       iterator                                                              
694       find(const key_type& __x)                                             
695       { return _M_t.find(__x); }                                            
696                                                                             
697       const_iterator                                                        
698       find(const key_type& __x) const                                       
699       { return _M_t.find(__x); }                                            
700                                                                             
701 #if __cplusplus > 201103L                                                   
702       template<typename _Kt>                                                
703         auto                                                                
704         find(const _Kt& __x) -> decltype(_M_t._M_find_tr(__x))              
705         { return _M_t._M_find_tr(__x); }                                    
706                                                                             
707       template<typename _Kt>                                                
708         auto                                                                
709         find(const _Kt& __x) const -> decltype(_M_t._M_find_tr(__x))        
710         
711 #endif