fn Rav1dPictureDataComponentInner::wrap_buf: Attempt to add lifetimes

[kkysen]

I'm struggling to figure out the lifetimes here, even though I think they should work. The 'buf lifetime, i.e. the lifetime of Rav1dPictureDataComponentInner::buf, should outlive 'a, where 'a is in &'a Rav1dPictureDataComponent<'buf> when stored in Rav1dPictureDataComponentOffset::data. But things aren't working out. Can anyone else help and figure this out?

[rinon]

It's not that it needs to outlive 'a there, it's that you're assigning a Rav1dPictureComponent<'buf> and a Rav1dPictureComponent<'static> to the same variable, so the lifetimes in those two types must match (because DisjointMut is invariant).

Sorry I don't have a solution tonight, gonna get to bed, but I'll think on it.

[kkysen]

It's not that it needs to outlive 'a there, it's that you're assigning a Rav1dPictureComponent<'buf> and a Rav1dPictureComponent<'static> to the same variable, so the lifetimes in those two types must match (because DisjointMut is invariant).

Sorry I don't have a solution tonight, gonna get to bed, but I'll think on it.

Yeah, I realized that. But I don't know how to make the lifetimes exactly the same, or how to not have the lifetime be invariant. But as far as I can tell, the UnsafeCell<T> forces it to be invariant since &mut Ts can be made from it and &mut T is invariant over T. That's my current understanding at least.