Why void_t doesnt work in SFINAE but enable_if does

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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<typename... Ts> struct make_void { typedef void type;};
template<typename... Ts> using void_t = typename make_void<Ts...>::type;

(from cppreference)

live example on wandbox

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