Class template argument deduction failed with derived class

Question

#include <utility>

template<class T1, class T2>
struct mypair : std::pair<T1, T2>
{ using std::pair<T1, T2>::pair; };

int main()
{
    (void)std::pair(2, 3); // It works
    (void)mypair(2, 3);    // It doesn't work
}

Is the above well formed?

Is it possible deduce the class template arguments in the second case if the constructors are being inherited? Are the constructors of std::pair participating in the creation of implicit deduction guides for mypair?

My compiler is g++ 7.2.0.

Answer 1

See Richard Smith's answer.

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A previous version of this answer had stated that the following should work

template <class T> struct B { B(T ) { } };
template <class T> struct D : B<T> { using B<T>::B; };

B b = 4; // okay, obviously
D d = 4; // expected: okay

But this isn't really viable, and wouldn't even be a good idea to work as I thought it would (we inherit the constructors but not the deduction guides?)