Reusing data member storage via placement new during enclosing object's lifetime

Question

This is a follow-up to my previous question where I seem to have made the problem more involved than I had originally intended. (See discussions in question and answer comme

Answer 1

If a is destroyed (whether by delete or by falling out of scope), then t.~T() is called, which is UB if t isn't actually a T (by not calling destruct).

This doesn't apply if

• the destructor of T is trivial, or
• for delete U is derived from T, or
• you're using a destroying delete

After destruct is called you are not allowed to use t if T has const or reference members (until C++20).

Apart from that there is no restriction on what you do with the class as written as far as I can see.