rust-lang / rust-lang/rust-clippy
suggest `filter`, `map` instead of `if let Some(..) { Some() } else { None }` on Options?
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Description
What it does
I was looking at some rustc code and noticed some if let Some(..) code where we would map back to Some(x) or None in the end and wondered if it would make sense to use filter and map here instead
Lint Name
not sure
Category
pedantic
Advantage
Code is shorter but I am not sure if its easier to understand
Drawbacks
Not sure if readability is actually improved.
Example
fn main() {
let s = String::from("opt-level=2");
let i = 42; // whatever
let z = if let Some("opt-level") = s.split('=').next() { Some(i) } else { None };
dbg!(z);
}
Could be written as:
fn main() {
let s = String::from("opt-level=2");
let i = 42; // whatever
let z = s.split('=').next().filter(|x| x == &"opt-level").map(|x| i);
dbg!(z);
}
(we have an Option here so we can filter to None instead of if let .. else { None } and we can map(|x| i) instead of if let .. { Some(i) })
I think the second example looks a bit more streamlined and might be easier to understand it doesn't have all the if let else control flow, on the other hand, the explicit control flow might make the code better to understand as well (explicit is better than implicit etc..)
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.
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- Open a pull request that references the issue number.
Research direction
No source file, test, or lint entry point is identified. Start by comparing the two Rust examples and determining whether this transformation should be a Clippy lint, including its scope and readability tradeoffs; done requires a decided lint design and corresponding implementation and tests.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100