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needless_collect: avoid warning if non-iterator methods are used

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It can make sense to `collect()` an iterator and then immediately
iterate over it if the iterator has special methods that you need.
For example, the Map iterator doesn't implement Clone, but the
collection iterator might. Or the collection iterator might
support slicing.
This commit is contained in:
Michael Howell 2025-02-04 13:01:32 -07:00
parent 75e3a2e905
commit c012693961
3 changed files with 93 additions and 6 deletions
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14
tests/ui/needless_collect.fixed
View file

@ -73,6 +73,20 @@ fn main() {
let mut out = vec![];
values.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>();
let _y = values.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>(); // this is fine
// Don't write a warning if we call `clone()` on the iterator
// https://github.com/rust-lang/rust-clippy/issues/13430
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let _cloned = my_collection.into_iter().clone();
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let my_iter = my_collection.into_iter();
let _cloned = my_iter.clone();
// Same for `as_slice()`, for same reason.
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let _sliced = my_collection.into_iter().as_slice();
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let my_iter = my_collection.into_iter();
let _sliced = my_iter.as_slice();
}
fn foo(_: impl IntoIterator<Item = usize>) {}

14
tests/ui/needless_collect.rs
View file

@ -73,6 +73,20 @@ fn main() {
let mut out = vec![];
values.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>();
let _y = values.iter().cloned().map(|x| out.push(x)).collect::<Vec<_>>(); // this is fine
// Don't write a warning if we call `clone()` on the iterator
// https://github.com/rust-lang/rust-clippy/issues/13430
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let _cloned = my_collection.into_iter().clone();
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let my_iter = my_collection.into_iter();
let _cloned = my_iter.clone();
// Same for `as_slice()`, for same reason.
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let _sliced = my_collection.into_iter().as_slice();
let my_collection: Vec<()> = vec![()].into_iter().map(|()| {}).collect();
let my_iter = my_collection.into_iter();
let _sliced = my_iter.as_slice();
}
fn foo(_: impl IntoIterator<Item = usize>) {}