Re: [boost] [variant] Heads-up!

On Mon, Apr 29, 2019 at 4:50 PM Steven Watanabe wrote:

AMDG

On 4/29/19 2:28 PM, Matt Calabrese wrote:

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On Mon, Apr 29, 2019 at 4:23 PM Matt Calabrese wrote:

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<snip> Stressing that, as Steven points out, this wouldn't violate the never-empty guarantee *if* after stealing you were able to default-construct something on the right-hand side and update the discriminator accordingly

Continuing on this thought, you don't necessarily have to default-construct on the right-hand side to satisfy the never-empty guarantee here. If the left-hand side also happens to currently contain a recursive_wrapper, or something that is nothrow-move-constructible, it can be moved into or swapped with rhs.

That's true, but it doesn't help much, because it only applies to assignment, not construction.

True. And noexcept-ness, in practice, often ends up more being more frequently needed for construction than for assignment anyway. Or at least that's been my personal experience, anyway. -- -Matt Calabrese