Compiler Explorer - C++ (x86 msvc v19.50 VS18.2)

struct A {}; struct convertible { operator A&() const { static A a; return a; } }; template<typename From, typename To> constexpr bool test1() { return requires(From f) { f.operator To&(); }; } template<typename From, typename To> constexpr bool test2() { static_assert(requires(From f) { f.operator To&(); }); return true; } static_assert(test1<convertible, A>()); static_assert(test2<convertible, A>());