[Bug c++/67727] New: [concepts] parameterized constraint not being checked for unused variables

[ryan.burn at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67727

            Bug ID: 67727
           Summary: [concepts] parameterized constraint not being checked
                    for unused variables
           Product: gcc
           Version: 6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: ryan.burn at gmail dot com
  Target Milestone: ---

The following code prints 1 1, but according to 

http://stackoverflow.com/questions/32801326/in-requires-parameter-lists-can-you-introduce-types-that-result-in-substitution

should print 1 0

/////////////////////////////////////////////////////////////////////////
#include <iterator>                                                             
#include <iostream>                                                             

template <class Iter>                                                           
concept bool Iterator =                                                         
    requires(Iter i, typename std::iterator_traits<Iter>::value_type val,       
             typename std::iterator_traits<Iter>::reference ref) {              
  ++i;                                                                          
};                                                                              

int main() {                                                                    
  std::cout << Iterator<int*> << "\n"; // prints 1                              
  std::cout << Iterator<int> << "\n"; // prints 1                               
  return 0;                                                                     
}
/////////////////////////////////////////////////////////////////////////