Nested scopes with lifetime bounds

[joshtriplett]

I'd like to be able to ask a Scope object for a nested scope whose lifetime is bounded by the lifetime of the outer scope. That would allow a scoped thread to spawn a more narrowly scoped inner thread that can borrow from the outer-scoped thread.

This could look like a method scope on Scope that creates a new Scope with an appropriately bounded lifetime.

[taiki-e]

It seems rust-lang/rust#94559 implements this.

EDIT: sorry, it seems I misunderstood the request.

[m-ou-se]

I think what @joshtriplett meant is starting an new smaller scope. The PR you mention just removes the need for the argument to the closure, but doesn't provide any new functionality.

@joshtriplett Why doesn't just starting a new crossbeam_utils::thread::scope with the existing function suffice? Does it need to be attached to the existing Scope? Do you have an example?

[joshtriplett]

When I posted the original request, I had a specific use case that motivated it, but it's been too long and I can no longer reconstruct the specific use case. I'm going to close this.

I'm looking forward to the new standard library scopes.