> On 30 Apr 2025, at 19:11, Ville Voutilainen <ville.voutilainen_at_[hidden]> wrote:
>
> On Wed, 30 Apr 2025 at 20:04, Hans Åberg via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
>>
>> This is a rather long video. Do you have something more succinct?
>
> A std::polymorphic<B>, when initialized with an in-place value of D,
> type-erases the D but copies of the std::polymorphic copy a D.

If that is enough for building my type val<A>, that is all I need. The example you gave looks right for that purpose.