Design meeting: Solution for `NoCell` and `no_std`

[traviscross]

Summary

Let's discuss the solution for NoCell with no_std as discussed here:

• core::marker::NoCell in bounds (previously known an Freeze) rfcs#3633 (comment)

cc @p-avital

About this issue

This issue corresponds to a lang-team design meeting proposal. It corresponds to a possible topic of discussion that may be scheduled for deeper discussion during one of our design meetings.

[traviscross]

We scheduled for 2025-07-23 to see about unblocking NoCell by coming up with a solution to the problem of how to express the propagation of auto traits for owned types with PhantomData<_> in no_std cases where Box<T> isn't available.