The Rust Closure Pitfall That Silently Corrupted Our Metrics: A Debugging Saga(medium.com)
medium.com
The Rust Closure Pitfall That Silently Corrupted Our Metrics: A Debugging Saga
https://medium.com/towardsdev/the-case-of-the-missing-metrics-a-rust-closure-mystery-e8e51c8ab484
2 comments
Key takeaways:
Rust 2021's closure minimal capture breaks RAII patterns when only Copy-type fields are used in structs with Drop impl.
Even with impl Drop, closures may capture Copy fields instead of the whole struct — a surprising edge case.
Fix requires explicit ownership transfer via let stats = self.stats to override closure's partial capture.
Fun fact is, the behavior used to be what the author expected: |thing| thing.field would capture the entire thing, not just the field.
This also used to be really annoying, so they changed it.
The 2021 Rust edition introduced partial capturing [1]. This greatly increased ergonomics, but it seems it has a hidden cost too. Unfortunate.
[1] https://doc.rust-lang.org/edition-guide/rust-2021/disjoint-c...