[Bug c++/107862] Returning an std::vector from a lambda fails to be constexpr, while a custom class with allocated storage works

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107862

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I don't think this is valid code.
In the function dynamic_data_to_array you have:
    std::array<VT, test.size()> data;

But test.size() is not a constexpr unless test is a constexpr. making test a
constexpr does not work as it has dynamic allocation

In your Test struct you have:
    constexpr unsigned size() const { return 1; }

So it is always a constexpr ...

Note clang also rejects this code for the same reason as GCC even with libc++.