`std::rc::try_unwrap()` should only consider the strong refcount

[abonander]

From this reddit thread.

std::rc::try_unwrap() returns Err if the Rc is not unique, which includes weak references. This fails intuition as the logic is the same as when the last Rc is dropped, which only considers strong references when deciding whether to drop the contained value, except it keeps the contained value from being destroyed. I fail to see how it is unsafe to unwrap when only weak references remain.

[SimonSapin]

This is fixed in #27837 and can be closed.