On 3/13/25 20:36, Giuseppe D'Angelo via Std-Discussion wrote:
> Concretely speaking, this requirement was introduced to allow
> erasure/insertion in the middle of a std::vector to use (trivial)
> relocation instead of assignment. In such a scenario both the extra
> properties I described above hold.

There's another quirk, which also doesn't affect moving stuff around in
a vector, but affects the general definitions: some types are not
replaceable, but *are* replace-relocatable. For example, an std::list
that allocates its sentinel node (list2 in the paper), whose move
constructor can throw.

You can't replace move-assignment with destruction + move-construction,
because if the constructor throws you end up with a dead list. However,
you *can* replace move-assignment + destruction (of the source) with
destruction (of the destination) + (trivial) relocation.