#include <utility>

struct Vertex{};

typedef std::pair<int,int> Facet;

struct Simplex {
  operator Vertex() { return Vertex();}
  operator Facet() { return std::make_pair(1,1);}
};

int main()
{
  Vertex v;
  Facet f;
  Simplex s;

  v = s;
  f = s;  //  	pair& operator=(const volatile pair&) = delete;

  return 0;
}

/*

[ 50%] Building CXX object CMakeFiles/simplex.dir/simplex.cpp.obj
simplex.cpp
C:\cgal\git\Skin_surface_3\examples\Skin_surface_3\simplex.cpp(20): error C2679: binary '=': no operator found which takes a right-hand operand of type 'Simplex' (or there is no acceptable conversion)
c:\Program Files (x86)\Microsoft Visual Studio\2017\Professional\VC\Tools\MSVC\14.16.27023\include\utility(276): note: could be 'std::pair<int,int> &std::pair<int,int>::operator =(volatile const std::pair<int,int> &)'
C:\cgal\git\Skin_surface_3\examples\Skin_surface_3\simplex.cpp(20): note: while trying to match the argument list '(Facet, Simplex)'

*/