VS2017 unable to match function definition.

test_delaunay_3.cpp

struct Point {};



namespace CGAL {

struct GT {
  struct Point_3 {};
};

  
template <class Gt, class Location_policy = int>
struct DEL_3;
  

template < class Gt>
struct DEL_3<Gt, int>
{
  typedef typename Gt::Point_3       Point;
  
  void
  side_of_oriented_sphere(const Point &p0) const;

};
  

template < class Gt>
void
DEL_3<Gt,int>::
side_of_oriented_sphere(const Point &p0) const
{}

} // namspace CGAL


int main()
{
  CGAL::DEL_3<CGAL::GT> del;
  return 0;
}

/*
$ cl.exe -permissive- test_delaunay_3.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.14.26429.4 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

test_delaunay_3.cpp
test_delaunay_3.cpp(33): error C2244: 'CGAL::DEL_3<Gt,int>::side_of_oriented_sphere': unable to match function definition to an existing declaration
test_delaunay_3.cpp(32): note: see declaration of 'CGAL::DEL_3<Gt,int>::side_of_oriented_sphere'
test_delaunay_3.cpp(33): note: definition
test_delaunay_3.cpp(33): note: 'void CGAL::DEL_3<Gt,int>::side_of_oriented_sphere(const Point &) const'
test_delaunay_3.cpp(33): note: existing declarations
test_delaunay_3.cpp(33): note: 'void CGAL::DEL_3<Gt,int>::side_of_oriented_sphere(const Gt::Point_3 &) const'
*/