rust-lang / rust-lang/rust-clippy
Spot always false "else if" branches with str::contains
Open
Nobody has claimed this yet.
A-lint
E-hard
L-correctness
T-middle
- Dominant language
- Rust
- Stars
- 13.5k
- Forks
- 2.2k
- Avg merge
- 2d 10h
- Merged PRs (30d)
- 32
Description
I'd like Clippy to spot cases like this (similar to #1596) the first string is a substring of the second, so the result 2 can't be produced:
fn foo5(txt: &str) -> u32 {
if txt.contains("ban") { 1 }
else if txt.contains("bana") { 2 }
else { 3 }
}
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 locating Clippy's existing lints for str::contains and the tests that exercise similar always-false branches, then compare them with the Rust example in this issue. Done means the example is diagnosed for the substring ordering case and the relevant lint tests cover the behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- tooling
- Issue type
- Feature
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100