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Split needless_lifetime '_ suggestions into elidable_lifetime_names (#13960)

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Fixes https://github.com/rust-lang/rust-clippy/issues/13514

changelog: Added [`elidable_lifetime_names`] to `pedantic` (Split off
from [`needless_lifetime`] for suggestions with `'_`)
[#13960](https://github.com/rust-lang/rust-clippy/pull/13960)

changelog: Enhancement: [`needless_lifetime`] No longer lints for
elidable lifetimes `'_`, use [`elidable_lifetime_names`] to lint these.
[#13960](https://github.com/rust-lang/rust-clippy/pull/13960)
This commit is contained in:
Fridtjof Stoldt 2025-02-27 09:21:50 +00:00 • committed by GitHub
commit f50266a423
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GPG key ID: B5690EEEBB952194
14 changed files with 687 additions and 637 deletions
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1
clippy_lints/src/declared_lints.rs
View file

@ -274,6 +274,7 @@ pub static LINTS: &[&crate::LintInfo] = &[
crate::let_underscore::LET_UNDERSCORE_MUST_USE_INFO,
crate::let_underscore::LET_UNDERSCORE_UNTYPED_INFO,
crate::let_with_type_underscore::LET_WITH_TYPE_UNDERSCORE_INFO,
crate::lifetimes::ELIDABLE_LIFETIME_NAMES_INFO,
crate::lifetimes::EXTRA_UNUSED_LIFETIMES_INFO,
crate::lifetimes::NEEDLESS_LIFETIMES_INFO,
crate::lines_filter_map_ok::LINES_FILTER_MAP_OK_INFO,

110
clippy_lints/src/lifetimes.rs
View file

@ -38,8 +38,8 @@ declare_clippy_lint! {
/// them leads to more readable code.
///
/// ### Known problems
/// - We bail out if the function has a `where` clause where lifetimes
/// are mentioned due to potential false positives.
/// This lint ignores functions with `where` clauses that reference
/// lifetimes to prevent false positives.
///
/// ### Example
/// ```no_run
@ -62,6 +62,38 @@ declare_clippy_lint! {
would allow omitting them"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for lifetime annotations which can be replaced with anonymous lifetimes (`'_`).
///
/// ### Why is this bad?
/// The additional lifetimes can make the code look more complicated.
///
/// ### Known problems
/// This lint ignores functions with `where` clauses that reference
/// lifetimes to prevent false positives.
///
/// ### Example
/// ```no_run
/// # use std::str::Chars;
/// fn f<'a>(x: &'a str) -> Chars<'a> {
/// x.chars()
/// }
/// ```
///
/// Use instead:
/// ```no_run
/// # use std::str::Chars;
/// fn f(x: &str) -> Chars<'_> {
/// x.chars()
/// }
/// ```
#[clippy::version = "1.84.0"]
pub ELIDABLE_LIFETIME_NAMES,
pedantic,
"lifetime name that can be replaced with the anonymous lifetime"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for lifetimes in generics that are never used
@ -104,7 +136,11 @@ impl Lifetimes {
}
}
impl_lint_pass!(Lifetimes => [NEEDLESS_LIFETIMES, EXTRA_UNUSED_LIFETIMES]);
impl_lint_pass!(Lifetimes => [
NEEDLESS_LIFETIMES,
ELIDABLE_LIFETIME_NAMES,
EXTRA_UNUSED_LIFETIMES,
]);
impl<'tcx> LateLintPass<'tcx> for Lifetimes {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
@ -746,6 +782,15 @@ fn report_elidable_impl_lifetimes<'tcx>(
report_elidable_lifetimes(cx, impl_.generics, &elidable_lts, &usages, true);
}
#[derive(Copy, Clone)]
enum ElidableUsage {
/// Used in a ref (`&'a T`), can be removed
Ref(Span),
/// Used as a generic param (`T<'a>`) or an impl lifetime (`impl T + 'a`), can be replaced
/// with `'_`
Other(Span),
}
/// Generate diagnostic messages for elidable lifetimes.
fn report_elidable_lifetimes(
cx: &LateContext<'_>,
@ -763,9 +808,29 @@ fn report_elidable_lifetimes(
.collect::<Vec<_>>()
.join(", ");
let elidable_usages: Vec<ElidableUsage> = usages
.iter()
.filter(|usage| named_lifetime(usage).is_some_and(|id| elidable_lts.contains(&id)))
.map(|usage| match cx.tcx.parent_hir_node(usage.hir_id) {
Node::Ty(Ty {
kind: TyKind::Ref(..), ..
}) => ElidableUsage::Ref(usage.ident.span),
_ => ElidableUsage::Other(usage.ident.span),
})
.collect();
let lint = if elidable_usages
.iter()
.any(|usage| matches!(usage, ElidableUsage::Other(_)))
{
ELIDABLE_LIFETIME_NAMES
} else {
NEEDLESS_LIFETIMES
};
span_lint_and_then(
cx,
NEEDLESS_LIFETIMES,
lint,
elidable_lts
.iter()
.map(|&lt| cx.tcx.def_span(lt))
@ -785,7 +850,7 @@ fn report_elidable_lifetimes(
return;
}
if let Some(suggestions) = elision_suggestions(cx, generics, elidable_lts, usages) {
if let Some(suggestions) = elision_suggestions(cx, generics, elidable_lts, &elidable_usages) {
diag.multipart_suggestion("elide the lifetimes", suggestions, Applicability::MachineApplicable);
}
},
@ -796,7 +861,7 @@ fn elision_suggestions(
cx: &LateContext<'_>,
generics: &Generics<'_>,
elidable_lts: &[LocalDefId],
usages: &[Lifetime],
usages: &[ElidableUsage],
) -> Option<Vec<(Span, String)>> {
let explicit_params = generics
.params
@ -836,26 +901,21 @@ fn elision_suggestions(
.collect::<Option<Vec<_>>>()?
};
suggestions.extend(
usages
.iter()
.filter(|usage| named_lifetime(usage).is_some_and(|id| elidable_lts.contains(&id)))
.map(|usage| {
match cx.tcx.parent_hir_node(usage.hir_id) {
Node::Ty(Ty {
kind: TyKind::Ref(..), ..
}) => {
// expand `&'a T` to `&'a T`
// ^^ ^^^
let span = cx.sess().source_map().span_extend_while_whitespace(usage.ident.span);
suggestions.extend(usages.iter().map(|&usage| {
match usage {
ElidableUsage::Ref(span) => {
// expand `&'a T` to `&'a T`
// ^^ ^^^
let span = cx.sess().source_map().span_extend_while_whitespace(span);
(span, String::new())
},
// `T<'a>` and `impl Foo + 'a` should be replaced by `'_`
_ => (usage.ident.span, String::from("'_")),
}
}),
);
(span, String::new())
},
ElidableUsage::Other(span) => {
// `T<'a>` and `impl Foo + 'a` should be replaced by `'_`
(span, String::from("'_"))
},
}
}));
Some(suggestions)
}