[SuperV1234]

It is kind of weird at first but the reason is that `std::vector` requires heap allocation and transient allocations are not allowed in `constexpr` contexts. The purpose of `std::define_static_array` is to promote the storage of the vector to static storage to eliminate the transient allocation issue, and so that the `template for` can work properly with it.

See wg21.link/P3491

[mort96]

Is there a reason why `std::meta::enumerators_of`, a reflection feature that's surely almost exclusively going to be used in constexpr contexts, returns a value which doesn't work in constexpr contexts?

[SuperV1234]

It works generally, but not with expansion statements. See section 3.2 here: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2025/p13...

It seems that this is being worked on, and eventually the `define_static_array` won't be needed anymore

[mort96]

Just another example where C++ language features are incompatible with each other, to be fixed "in a later version" which may or may not happen. There are so many of those in C++. I desperately wish they'd just do it properly initially.

[pjmlp]

Me too, unfortunately the old guard sees no value in implementation before standardisation for each single feature.

So it is as it is, plenty of software in C++ isn't going to be rewriten into something else.

Maybe someone can do a Claude rewrite from LLVM into something else. /s