Added to_array

[anarthal]

No description provided.

[pdimov]

1. the static asserts don't actually test what the code requires. The array elements are of type remove_cv_t<T>, not T, so the conditions being asserted should be is_constructible<remove_cv_t<T>, T&> and is_constructible<remove_cv_t<T>, T&&> respectively.
2. documentation
3. the tests should test const input elements, e.g. int const, std::vector<int> const.
4. the constexpr tests should still check that the result is correct (at runtime).

[anarthal]

Regarding 1. cppreference it states it as I wrote it - is it a defect in cppreference?

[pdimov]

cppreference correctly reflects what the standard says in https://eel.is/c++draft/array.creation, but I think that this is a defect in the standard. I'll ask.

[pdimov]

Please add lvalue tests for const int and l/rvalue tests for const.

Also, let's use the correct is_constructible<remove_cv_t<T>, T&> in both code and docs, regardless of what the standard says.

[pdimov]

No, sorry. The array elements being constructed are of type remove_cv_t<T>. The arguments are of type T& or T&& respectively. Ergo, the conditions are is_constructible<remove_cv_t<T>, T&> and is_constructible<remove_cv_t<T>, T&&>, respectively.

[anarthal]

Long day yesterday. Should be fixed now. If I've understood this correctly, using remove_cvref_t doesn't make sense because C arrays can't contain references, and thus remove_cv_t is more accurate.

I've left the multi-dimensional checking condition as is_array<T> because is_array<const/volatile int[N]> is also true.