needless_collect doesn't take into account side-effects #8055
Description
Summary
needless_collect does not take into account side effects of the iterator, and so spuriously reports a necessary collect as needless.
Lint Name
needless_collect
Reproducer
I tried this code:
pub fn filter(v: impl IntoIterator<Item = i32>) -> Result<impl Iterator<Item = i32>, usize> {
let mut zeros = 0;
let res: Vec<_> = v
.into_iter()
.filter(|i| {
if *i == 0 {
zeros += 1
};
*i != 0
})
.collect();
if zeros != 0 {
return Err(zeros);
}
Ok(res.into_iter())
}I saw this happen:
warning: avoid using `collect()` when not needed
--> src/lib.rs:12:10
|
12 | .collect();
| ^^^^^^^
...
17 | Ok(res.into_iter())
| --------------- the iterator could be used here instead
|
= note: `#[warn(clippy::needless_collect)]` on by default
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_collect
help: use the original Iterator instead of collecting it and then producing a new one
|
4 ~
5 |
6 | if zeros != 0 {
7 | return Err(zeros);
8 | }
9 ~ Ok(v
...
I expected to see this happen: no warning
Version
rustc 1.56.1 (59eed8a2a 2021-11-01)
binary: rustc
commit-hash: 59eed8a2aac0230a8b53e89d4e99d55912ba6b35
commit-date: 2021-11-01
host: x86_64-unknown-linux-gnu
release: 1.56.1
LLVM version: 13.0.0
Additional Labels
No response