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Auto merge of #11647 - flip1995:needless-pass-by-ref-mut-pub-api, r=xFrednet

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Honor `avoid-breaking-exported-api` in `needless_pass_by_ref_mut`

Until now, the lint only emitted a warning, when breaking public API. Now it doesn't lint at all when the config value is not set to `false`, bringing it in line with the other lints using this config value.

Also ensures that this config value is documented in the lint.

changelog: none
(I don't think a changelog is necessary, since this lint is in `nursery`)

---

Fixes https://github.com/rust-lang/rust-clippy/issues/11374

cc `@GuillaumeGomez`

Marking as draft: Does this lint even break public API? If I change a function signature from `fn foo(x: &mut T)` to `fn foo(x: &T)`, I can still call it with `foo(&mut x)`. The only "breaking" thing is that the `clippy::unnecessary_mut_passed` lint will complain that `&mut` at the callsite is not necessary, possibly trickling down to the crate user having to remote a `mut` from a variable. [Playground](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=058165a7663902e84af1d23e35c10d66).

Are there examples where this actually breaks public API, that I'm missing?
This commit is contained in:
bors 2024-07-03 07:55:05 +00:00
commit 918ae1bec4
12 changed files with 86 additions and 54 deletions
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11
clippy_lints/src/needless_pass_by_ref_mut.rs
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@ -27,7 +27,7 @@ declare_clippy_lint! {
/// Check if a `&mut` function argument is actually used mutably.
///
/// Be careful if the function is publicly reexported as it would break compatibility with
/// users of this function.
/// users of this function, when the users pass this function as an argument.
///
/// ### Why is this bad?
/// Less `mut` means less fights with the borrow checker. It can also lead to more
@ -138,6 +138,10 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
return;
}
if self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(fn_def_id) {
return;
}
let hir_id = cx.tcx.local_def_id_to_hir_id(fn_def_id);
let is_async = match kind {
FnKind::ItemFn(.., header) => {
@ -262,9 +266,6 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
.iter()
.filter(|(def_id, _)| !self.used_fn_def_ids.contains(def_id))
{
let show_semver_warning =
self.avoid_breaking_exported_api && cx.effective_visibilities.is_exported(*fn_def_id);
let mut is_cfged = None;
for input in unused {
// If the argument is never used mutably, we emit the warning.
@ -284,7 +285,7 @@ impl<'tcx> LateLintPass<'tcx> for NeedlessPassByRefMut<'tcx> {
format!("&{}", snippet(cx, cx.tcx.hir().span(inner_ty.ty.hir_id), "_"),),
Applicability::Unspecified,
);
if show_semver_warning {
if cx.effective_visibilities.is_exported(*fn_def_id) {
diag.warn("changing this function will impact semver compatibility");
}
if *is_cfged {