template<typename T, typename = void>
struct has_value_type
{
   static constexpr bool value = false;
};

template<typename T>
struct has_value_type< T, std::void_t<typename T::value_type> >
{
   static constexpr bool value = false;
};

template<typename T>
constexpr bool has_value_type_v = has_value_type::value;


template<typename T>
struct Foo
{
   using type = T;
};

template<typename Container,
        std::enable_if_t< has_value_type_v, int > = 0
>
Foo(Container&&) -> Foo< typename std::decay_t<Container&&>::value_type >;

template<typename Functor,
        std::enable_if_t< !has_value_type_v, int > = 0
>
Foo(Functor&&) -> Foo< std::invoke_result_t<Functor&&> >;

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