Testing: `P2415R2_owning_view\test.cpp` does not test anything

[JMazurkiewicz]

Currently P2415R2_owning_view\test.cpp looks like this:

// [banner, headers]

struct instantiator {
    template <ranges::input_range R>
    static constexpr void call() {
        if constexpr (move_constructible<R>) {
            // [ALL TESTS]
        }
    }
};

int main() {
    STATIC_ASSERT((test_in<instantiator, int>(), true));
    test_in<instantiator, int>();
}

When we add extra constraint to instantiator::call, which is negation of the condition in if constexpr statement:

struct instantiator {
    template <ranges::input_range R>
        requires (!move_constructible<R>)
    static constexpr void call() {
        if constexpr (move_constructible<R>) {
            // [ALL TESTS]
        }
    }
};

The test still passes, which means that the // [ALL TESTS] part is never executed.