c++ - Is it possible to put constraints on type alias with concept?

Question

It is fairly straightforward with SFINAE:

using Integral = std::enable_if_t<std::is_integral_v<Foo>>;

I want the syntax something like:

#include <iterator>
using iterator = std::bidirectional_iterator ContainerIterator;

which is not supported.

The workaround is to use a type-checking class:

template <std::bidirectional_iterator T>
struct CheckContainerIterator {
  using type = T;
};

using iterator = CheckContainerIterator<ContainerIterator>::type;

Is there a more concise way of achieving this?

The reason being is that the SFINAE version of bidirectional_iterator does not seem to present in the standard. So I either have to implement it or use the type-checking class.

question from:https://stackoverflow.com/questions/65848102/is-it-possible-to-put-constraints-on-type-alias-with-concept

Answer 1

Waitting for answers