Summary

Code using catch_unwind is not typically prepared to handle an object that panics in its Drop impl. Even the standard library has had various bugs in this regard, and if the standard library doesn't consistently get it right, we can hardly expect others to do so.

This came up in @rust-lang/libs discussion.

We discussed various ways to handle this, including potential tweaks to panic_any or catch_unwind to add special handling of types that implement Drop, but on balance we felt like it would be preferable to decide at the language level to generally not allow unwind from Drop impls. (We may not be able to universally prohibit this, but we could work towards transitioning there.)

Background reading

rust-lang/rust#86027

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.