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don't suggest to use cloned for Cow in unnecessary_to_owned #13853

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don't suggest to use cloned for Cow in unnecessary_to_owned #13853

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13 changes: 13 additions & 0 deletions clippy_lints/src/methods/unnecessary_to_owned.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -221,6 +221,19 @@ fn check_into_iter_call_arg(
if unnecessary_iter_cloned::check_for_loop_iter(cx, parent, method_name, receiver, true) {
return true;
}
if is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(receiver), sym::Cow) {
span_lint_and_sugg(
cx,
UNNECESSARY_TO_OWNED,
parent.span,
format!("unnecessary use of `{method_name}.into_iter()`"),
"use",
format!("{receiver_snippet}.{method_name}()"),
Applicability::MaybeIncorrect,
);
return true;
}

let cloned_or_copied = if is_copy(cx, item_ty) && msrv.meets(msrvs::ITERATOR_COPIED) {
"copied"
} else {
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6 changes: 6 additions & 0 deletions tests/ui/unnecessary_to_owned.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -587,3 +587,9 @@ fn borrow_checks() {
HashSet::<i32>::new().foo::<&str>(&"".to_owned());
HashSet::<String>::new().get(&1.to_string());
}

fn issue13624() -> impl IntoIterator {
let cow: Cow<'_, Vec<String>> = Cow::Owned(vec![String::from("foo")]);

cow.into_owned().into_iter()
}
8 changes: 7 additions & 1 deletion tests/ui/unnecessary_to_owned.stderr
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Original file line number Diff line number Diff line change
Expand Up @@ -589,5 +589,11 @@ error: unnecessary use of `to_vec`
LL | s.remove(&(&["b"]).to_vec());
| ^^^^^^^^^^^^^^^^^^ help: replace it with: `(&["b"]).as_slice()`

error: aborting due to 88 previous errors
error: unnecessary use of `into_owned.into_iter()`
--> tests/ui/unnecessary_to_owned.rs:594:5
|
LL | cow.into_owned().into_iter()
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use: `cow.into_owned()`
Comment on lines +595 to +596
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The suggestion works in this specific case, but it doesn't seem like it would work in the general case if the iterator is later used as part of another expression, e.g. for cow.into_owned().into_iter().map(...).collect() the .into_iter() is required. Tbh I don't think we can really suggest anything here for Cow::into_owned and we probably should just not lint at all here?


error: aborting due to 89 previous errors

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