rust-lang / rust-lang/rust-clippy
int_plus_one changes program behavior in regards of overflows
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C-bug
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Description
Summary
int_plus_one suggestions prevent overflows from happening because it removes a potential case where we could run into T::max() + 1
Reproducer
I tried this code:
fn main() {
dbg!(comp(254));
dbg!(comp(255)); // overflow/panic
dbg!(comp_clippyfixed(254));
dbg!(comp_clippyfixed(255)); // no panic
}
fn comp(x: u8) -> bool {
1 >= x + 1
}
fn comp_clippyfixed(x: u8) -> bool {
1 > x
}
Version
rustc 1.64.0-nightly (0f4bcadb4 2022-07-30)
binary: rustc
commit-hash: 0f4bcadb46006bc484dad85616b484f93879ca4e
commit-date: 2022-07-30
host: x86_64-unknown-linux-gnu
release: 1.64.0-nightly
LLVM version: 14.0.6
Additional Labels
No response
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 int_plus_one lint and reproduce the behavior using the supplied comp and comp_clippyfixed examples with u8 values 254 and 255. Investigate how the suggestion changes overflow behavior; done means the lint no longer changes the program's overflow behavior and the regression is covered.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- devtools
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 38/100