Why void_t doesnt work in SFINAE but enable_if does

Question

I was trying to understand how SFINAE works and I was experimenting with this code

#include 

struct One { 
  using x = int;          


        

Answer 1

This seems to be related to CWG issue #1980 (credits to T.C. for correcting me).

As a workaround you can define void_t as:

template struct make_void { typedef void type;};
template using void_t = typename make_void::type;

(from cppreference)

live example on wandbox