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Auto merge of #10913 - y21:issue10033, r=Manishearth,Centri3

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[`unnecessary_to_owned`]: check that the adjusted type matches target

Fixes #10033.

Before this change, the lint would assume that removing the `.to_string()` in `f(&x.to_string())` would be ok if x is of some type that implements `Deref<Target = str>` and `f` takes a `&str`.
This turns out to not actually be ok if the `to_string` call is some method that exists on `x` directly, which happens if it implements `Display`/`ToString` itself.

changelog: [`unnecessary_to_owned`]: only lint if the adjusted receiver type actually matches
This commit is contained in:
bors 2023-06-09 08:52:44 +00:00
commit 05de787089
3 changed files with 71 additions and 0 deletions
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5
clippy_lints/src/methods/unnecessary_to_owned.rs
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@ -144,6 +144,11 @@ fn check_addr_of_expr(
if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
if implements_trait(cx, receiver_ty, deref_trait_id, &[]);
if cx.get_associated_type(receiver_ty, deref_trait_id, "Target") == Some(target_ty);
// Make sure that it's actually calling the right `.to_string()`, (#10033)
// *or* this is a `Cow::into_owned()` call (which would be the wrong into_owned receiver (str != Cow)
// but that's ok for Cow::into_owned specifically)
if cx.typeck_results().expr_ty_adjusted(receiver).peel_refs() == target_ty
|| is_cow_into_owned(cx, method_name, method_def_id);
then {
if n_receiver_refs > 0 {
span_lint_and_sugg(