pub fn variant_emplace() {
// C++ `Variant::emplace<T, Args...>` is a low-level memory-management
// operation that replaces the active alternative in a `std::variant`-like
// storage.
//
// In this Rust port, `VariantN` enums are safe, type-safe tagged unions.
// Reassignment is handled by standard assignment (e.g., `*v = VariantN::V<pos>(T::from(args))`),
// which automatically drops the old value and initializes the new one.
// A direct translation of the C++ placement-new/type-id-table logic is
// unnecessary and unsafe in Rust.
}