I can imagine an alternate universe in which you cannot do:

1. Create future A.

2. Poll future A at least once but not provably poll it to completion and also not drop it. This includes selecting it.

3. Pause yourself by awaiting anything that does not involve continuing to poll A.

I’m struggling a bit to imagine the scenario in which it makes sense to pause a coroutine that you depend on in the middle like this. But I also don’t immediately see a way to change a language like Rust to reliably prevent doing this without massively breaking changes. See my other comment :)