rust-lang / rust-lang/rust-clippy
Lint against collect()ing from FromIterator::Option/Result
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- Dominant language
- Rust
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Description
Using collect() on Option/Result::FromIterator doesn't reserve any capacity, which results in bad performance. It might be a good idea to advise to switch to a Collection::with_capacity + extend()/pushing in a loop, because the most often case of collecting into an Option/Result is that the resulting collection is not empty.
See https://github.com/rust-lang/rust/pull/52910 for a related discussion.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start by reviewing the related discussion in rust-lang/rust pull request 52910 and the existing Clippy lint patterns for collecting into Option or Result. Define the lint's target and diagnostic, then verify that it consistently identifies the performance case and gives actionable guidance.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100