Re: [boost] variant2 never empty guarantees (was: Re: Outcome/expected/etc/etc/etc)

Subject: Re: [boost] variant2 never empty guarantees (was: Re: Outcome/expected/etc/etc/etc)
From: Peter Dimov (lists_at_[hidden])
Date: 2017-06-07 14:28:12

Gottlob Frege wrote:

> Agreed.  But I don't see much value in the never-empty guarantee if it 
> doesn't give you the strong guarantee.

I'm not sure I understand this fully; could you please explain from what 
expressions, and under what conditions, you expect the strong guarantee?

    variant<X, Y> v1, v2;
    X x;

    v1= v2; // do you expect strong guarantee here?
    v1 = std::move(v2); // here?
    v1 = x; // here?
    v1 = std::move(x); // here?
    v1.emplace<X>(); // here?