rust-lang / rust-lang/rust-clippy
`or_fun_call` isn't always a performance lint
Nobody has claimed this yet.
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Description
Replacing .unwrap_or(Vec::new()) with .unwrap_or_default() doesn't do anything for performance, they produce identical machine code with optimizations: https://rust.godbolt.org/z/hzTdazGqW.
Perhaps the lint category could be changed or it could be changed to not detect cases where it's not actually a performance warning?
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 with the or_fun_call lint and reproduce the .unwrap_or(Vec::new()) versus .unwrap_or_default() example using the linked Godbolt case. Inspect the lint's existing tests and diagnostic classification; done when equivalent optimized code is no longer reported as a performance warning, with a regression test covering the case.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Bug
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100