On 24 Apr 2025 13:55, Ville Voutilainen wrote:
> On Thu, 24 Apr 2025 at 13:48, Andrey Semashev via Std-Proposals
> <std-proposals_at_[hidden]> wrote:
>>> No, a moved-from std::list also needs to support all operations that
>>> have no preconditions, such as size() and empty() and begin() and end().
>>
>> Well, likewise, citation needed. As far as I know, the standard doesn't
>> formally define requirements on the moved-from objects.
>
> Yes, it does. Your citation is [defns.valid]:
>
> 〈library〉 value of an object that is not specified except that the
> object’s invariants are met and operations on
> the object behave as specified for its type
> [Example 1 : If an object x of type std::vector<int> is in a valid but
> unspecified state, x.empty() can be called
> unconditionally, and x.front() can be called only if x.empty() returns
> false. — end example]

Ok, so the standard library makes extra guarantees about the types it
provides. It harms e.g. std::list and I don't agree with this approach,
but fine.

It doesn't make a general rule about moved-from objects, including not
provided by the standard library. And it doesn't invalidate what I said
in my post or undermine the usefulness of the proposal.