visual studio - c++ template enable_if unable to match function definition to an existing declaration -

i trying define template member function template class outside of class leverage sfinae partially overload function. minimal example of trying is:

test.h:

template<typename t, size_t d> class test { public:     test(){}     ~test(){}      template<size_t w = d, typename = int*>     void do_something(test&); private:     t data[d]; };  #include <type_traits>  template<typename t, size_t d> template<size_t w, typename std::enable_if<w == 2, int>::type* = 0> inline void test<t, d>::do_something(test &) {     exit(2); }  template<typename t, size_t d> template<size_t w, typename std::enable_if<w == 3, int>::type* = 0> inline void test<t, d>::do_something(test &) {     exit(3); } 

main.cpp:

int main(int, char**) {     test<float, 2> t1;     test<float, 2> t2;     t1.do_something(t2);     return 0; } 

however code sample produces error: c2244 'test::do_something': unable match function definition existing declaration. if change

template<size_t w, typename std::enable_if<w == 2, int>::type* = 0> 

to

 template<size_t w, typename type> 

and remove other definition of do_something code compile no problem know enable_if problem. question is: how use enable_if achieve partial overload effect without defining function inside class?

should add compiling msvs 2015.

you have use std::enable_if in declaration:

template<typename t, std::size_t d> class test { public:     template<std::size_t w, typename std::enable_if<w == 2>::type* = nullptr>     void do_something(test<t, w> &);      template<std::size_t w, typename std::enable_if<w == 3>::type* = nullptr>     void do_something(test<t, w> &); };    template<typename t, std::size_t d> template<std::size_t w, typename std::enable_if<w == 2>::type*> void test<t, d>::do_something(test<t, w> &) {     std::cout << 1 << std::endl; }  template<typename t, std::size_t d> template<std::size_t w, typename std::enable_if<w == 3>::type*> void test<t, d>::do_something(test<t, w> &) {     std::cout << 2 << std::endl; } 

demo