gather use cases

[yoshuawuyts]

• mock the time source for testing in an async code base
• mark a thread as being "the UI thread" #7

[matthunz]

If we can nest contexts (as in set them in a child context and pop them off when we get to a sibling function) this would be great for function scope!

For example how Jetpack Compose use's a RowScope in UI

[NobodyXu]

One example that I heard of (but not used) is passing around tokens of ghost-cell, singleton cell, combined with capability, writing code that need multiple aliases but not active at the same time will be much easier to write.

I also heard that one single-thread async runtime also passes ghost-cell token to future so that multiple fut can store alias to the same variable but without using RefCell/Rc.

This also sounds very useful since future by its very nature, relinquishes the alias when pending.

This could be also useful for generators in general to avoid RefCell/Rc.