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Improve needless_lifetimes

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This commit is contained in:
Samuel Moelius 2022-10-28 13:17:36 -04:00
parent 43268141da
commit e9216d836c
3 changed files with 168 additions and 60 deletions
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118
clippy_lints/src/lifetimes.rs
View File

@ -1,4 +1,4 @@
use clippy_utils::diagnostics::span_lint;
use clippy_utils::diagnostics::{span_lint, span_lint_and_then};
use clippy_utils::trait_ref_of_method;
use rustc_data_structures::fx::{FxHashMap, FxHashSet};
use rustc_hir::intravisit::nested_filter::{self as hir_nested_filter, NestedFilter};
@ -151,6 +151,7 @@ fn check_fn_inner<'tcx>(
.params
.iter()
.filter(|param| matches!(param.kind, GenericParamKind::Type { .. }));
for typ in types {
for pred in generics.bounds_for_param(cx.tcx.hir().local_def_id(typ.hir_id)) {
if pred.origin == PredicateOrigin::WhereClause {
@ -187,15 +188,30 @@ fn check_fn_inner<'tcx>(
}
}
}
if could_use_elision(cx, decl, body, trait_sig, generics.params) {
span_lint(
if let Some(elidable_lts) = could_use_elision(cx, decl, body, trait_sig, generics.params) {
let lts = elidable_lts
.iter()
// In principle, the result of the call to `Node::ident` could be `unwrap`ped, as `DefId` should refer to a
// `Node::GenericParam`.
.filter_map(|&(def_id, _)| cx.tcx.hir().get_by_def_id(def_id).ident())
.map(|ident| ident.to_string())
.collect::<Vec<_>>()
.join(", ");
span_lint_and_then(
cx,
NEEDLESS_LIFETIMES,
span.with_hi(decl.output.span().hi()),
"explicit lifetimes given in parameter types where they could be elided \
(or replaced with `'_` if needed by type declaration)",
&format!("the following explicit lifetimes could be elided: {lts}"),
|diag| {
if let Some(span) = elidable_lts.iter().find_map(|&(_, span)| span) {
diag.span_help(span, "replace with `'_` in generic arguments such as here");
}
},
);
}
if report_extra_lifetimes {
self::report_extra_lifetimes(cx, decl, generics);
}
@ -220,13 +236,14 @@ fn explicit_self_type<'tcx>(cx: &LateContext<'tcx>, func: &FnDecl<'tcx>, ident:
}
}
#[expect(clippy::too_many_lines)]
fn could_use_elision<'tcx>(
cx: &LateContext<'tcx>,
func: &'tcx FnDecl<'_>,
body: Option<BodyId>,
trait_sig: Option<&[Ident]>,
named_generics: &'tcx [GenericParam<'_>],
) -> bool {
) -> Option<Vec<(LocalDefId, Option<Span>)>> {
// There are two scenarios where elision works:
// * no output references, all input references have different LT
// * output references, exactly one input reference with same LT
@ -253,7 +270,7 @@ fn could_use_elision<'tcx>(
}
if input_visitor.abort() || output_visitor.abort() {
return false;
return None;
}
let input_lts = input_visitor.lts;
@ -261,7 +278,7 @@ fn could_use_elision<'tcx>(
if let Some(trait_sig) = trait_sig {
if explicit_self_type(cx, func, trait_sig.first().copied()) {
return false;
return None;
}
}
@ -270,7 +287,7 @@ fn could_use_elision<'tcx>(
let first_ident = body.params.first().and_then(|param| param.pat.simple_ident());
if explicit_self_type(cx, func, first_ident) {
return false;
return None;
}
let mut checker = BodyLifetimeChecker {
@ -278,14 +295,14 @@ fn could_use_elision<'tcx>(
};
checker.visit_expr(body.value);
if checker.lifetimes_used_in_body {
return false;
return None;
}
}
// check for lifetimes from higher scopes
for lt in input_lts.iter().chain(output_lts.iter()) {
if !allowed_lts.contains(lt) {
return false;
return None;
}
}
@ -301,14 +318,14 @@ fn could_use_elision<'tcx>(
for lt in input_visitor.nested_elision_site_lts {
if let RefLt::Named(def_id) = lt {
if allowed_lts.contains(&cx.tcx.item_name(def_id.to_def_id())) {
return false;
return None;
}
}
}
for lt in output_visitor.nested_elision_site_lts {
if let RefLt::Named(def_id) = lt {
if allowed_lts.contains(&cx.tcx.item_name(def_id.to_def_id())) {
return false;
return None;
}
}
}
@ -316,32 +333,47 @@ fn could_use_elision<'tcx>(
// no input lifetimes? easy case!
if input_lts.is_empty() {
false
None
} else if output_lts.is_empty() {
// no output lifetimes, check distinctness of input lifetimes
// only unnamed and static, ok
let unnamed_and_static = input_lts.iter().all(|lt| *lt == RefLt::Unnamed || *lt == RefLt::Static);
if unnamed_and_static {
return false;
return None;
}
// we have no output reference, so we can elide explicit lifetimes that occur at most once
let elidable_lts = named_lifetime_occurrences(&input_lts)
.into_iter()
.filter_map(|(def_id, occurrences)| {
if occurrences <= 1 {
Some((def_id, input_visitor.sample_generic_arg_span.get(&def_id).copied()))
} else {
None
}
})
.collect::<Vec<_>>();
if elidable_lts.is_empty() {
None
} else {
Some(elidable_lts)
}
// we have no output reference, so we only need all distinct lifetimes
input_lts.len() == unique_lifetimes(&input_lts)
} else {
// we have output references, so we need one input reference,
// and all output lifetimes must be the same
if unique_lifetimes(&output_lts) > 1 {
return false;
}
if input_lts.len() == 1 {
match (&input_lts[0], &output_lts[0]) {
(&RefLt::Named(n1), &RefLt::Named(n2)) if n1 == n2 => true,
(&RefLt::Named(_), &RefLt::Unnamed) => true,
_ => false, /* already elided, different named lifetimes
(&RefLt::Named(n1), &RefLt::Named(n2)) if n1 == n2 => {
Some(vec![(n1, input_visitor.sample_generic_arg_span.get(&n1).copied())])
},
(&RefLt::Named(n), &RefLt::Unnamed) => {
Some(vec![(n, input_visitor.sample_generic_arg_span.get(&n).copied())])
},
_ => None, /* already elided, different named lifetimes
* or something static going on */
}
} else {
false
None
}
}
}
@ -358,10 +390,24 @@ fn allowed_lts_from(tcx: TyCtxt<'_>, named_generics: &[GenericParam<'_>]) -> FxH
allowed_lts
}
/// Number of unique lifetimes in the given vector.
/// Number of times each named lifetime occurs in the given slice. Returns a vector to preserve
/// relative order.
#[must_use]
fn unique_lifetimes(lts: &[RefLt]) -> usize {
lts.iter().collect::<FxHashSet<_>>().len()
fn named_lifetime_occurrences(lts: &[RefLt]) -> Vec<(LocalDefId, usize)> {
let mut occurrences = Vec::new();
for lt in lts {
if let &RefLt::Named(curr_def_id) = lt {
if let Some(i) = occurrences
.iter()
.position(|&(prev_def_id, _)| prev_def_id == curr_def_id)
{
occurrences[i].1 += 1;
} else {
occurrences.push((curr_def_id, 1));
}
}
}
occurrences
}
const CLOSURE_TRAIT_BOUNDS: [LangItem; 3] = [LangItem::Fn, LangItem::FnMut, LangItem::FnOnce];
@ -370,6 +416,7 @@ fn unique_lifetimes(lts: &[RefLt]) -> usize {
struct RefVisitor<'a, 'tcx> {
cx: &'a LateContext<'tcx>,
lts: Vec<RefLt>,
sample_generic_arg_span: FxHashMap<LocalDefId, Span>,
nested_elision_site_lts: Vec<RefLt>,
unelided_trait_object_lifetime: bool,
}
@ -379,6 +426,7 @@ fn new(cx: &'a LateContext<'tcx>) -> Self {
Self {
cx,
lts: Vec::new(),
sample_generic_arg_span: FxHashMap::default(),
nested_elision_site_lts: Vec::new(),
unelided_trait_object_lifetime: false,
}
@ -472,6 +520,22 @@ fn visit_ty(&mut self, ty: &'tcx Ty<'_>) {
_ => walk_ty(self, ty),
}
}
fn visit_generic_arg(&mut self, generic_arg: &'tcx GenericArg<'tcx>) {
if let GenericArg::Lifetime(l) = generic_arg
&& let LifetimeName::Param(def_id, _) = l.name
{
self.sample_generic_arg_span.entry(def_id).or_insert(l.span);
}
// Replace with `walk_generic_arg` if/when https://github.com/rust-lang/rust/pull/103692 lands.
// walk_generic_arg(self, generic_arg);
match generic_arg {
GenericArg::Lifetime(lt) => self.visit_lifetime(lt),
GenericArg::Type(ty) => self.visit_ty(ty),
GenericArg::Const(ct) => self.visit_anon_const(&ct.value),
GenericArg::Infer(inf) => self.visit_infer(inf),
}
}
}
/// Are any lifetimes mentioned in the `where` clause? If so, we don't try to

8
tests/ui/needless_lifetimes.rs
View File

@ -419,4 +419,12 @@ fn lifetime_elsewhere_provided<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
}
}
mod false_negative {
#![allow(unused)]
fn foo<'a>(x: &'a u8, y: &'_ u8) {}
fn bar<'a>(x: &'a u8, y: &'_ u8, z: &'_ u8) {}
}
fn main() {}

100
tests/ui/needless_lifetimes.stderr
View File

@ -1,4 +1,4 @@
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a, 'b
--> $DIR/needless_lifetimes.rs:11:1
|
LL | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
@ -6,185 +6,221 @@ LL | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {}
|
= note: `-D clippy::needless-lifetimes` implied by `-D warnings`
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a, 'b
--> $DIR/needless_lifetimes.rs:13:1
|
LL | fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:23:1
|
LL | fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:57:1
|
LL | fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:62:1
|
LL | fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()>
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a, 'b
--> $DIR/needless_lifetimes.rs:74:1
|
LL | fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: replace with `'_` in generic arguments such as here
--> $DIR/needless_lifetimes.rs:74:37
|
LL | fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {}
| ^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:98:1
|
LL | fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: replace with `'_` in generic arguments such as here
--> $DIR/needless_lifetimes.rs:98:32
|
LL | fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I>
| ^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 's
--> $DIR/needless_lifetimes.rs:128:5
|
LL | fn self_and_out<'s>(&'s self) -> &'s u8 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 's, 't
--> $DIR/needless_lifetimes.rs:137:5
|
LL | fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:156:1
|
LL | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: replace with `'_` in generic arguments such as here
--> $DIR/needless_lifetimes.rs:156:33
|
LL | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str {
| ^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:186:1
|
LL | fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:192:1
|
LL | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
help: replace with `'_` in generic arguments such as here
--> $DIR/needless_lifetimes.rs:192:37
|
LL | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str {
| ^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:211:1
|
LL | fn named_input_elided_output<'a>(_arg: &'a str) -> &str {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:219:1
|
LL | fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:255:1
|
LL | fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:262:9
|
LL | fn needless_lt<'a>(x: &'a u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:266:9
|
LL | fn needless_lt<'a>(_x: &'a u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:279:9
|
LL | fn baz<'a>(&'a self) -> impl Foo + 'a {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:311:5
|
LL | fn impl_trait_elidable_nested_anonymous_lifetimes<'a>(i: &'a i32, f: impl Fn(&i32) -> &i32) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:320:5
|
LL | fn generics_elidable<'a, T: Fn(&i32) -> &i32>(i: &'a i32, f: T) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:332:5
|
LL | fn where_clause_elidadable<'a, T>(i: &'a i32, f: T) -> &'a i32
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:347:5
|
LL | fn pointer_fn_elidable<'a>(i: &'a i32, f: fn(&i32) -> &i32) -> &'a i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:360:5
|
LL | fn nested_fn_pointer_3<'a>(_: &'a i32) -> fn(fn(&i32) -> &i32) -> i32 {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:363:5
|
LL | fn nested_fn_pointer_4<'a>(_: &'a i32) -> impl Fn(fn(&i32)) {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:385:9
|
LL | fn implicit<'a>(&'a self) -> &'a () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:388:9
|
LL | fn implicit_mut<'a>(&'a mut self) -> &'a () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:399:9
|
LL | fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:405:9
|
LL | fn implicit<'a>(&'a self) -> &'a ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:406:9
|
LL | fn implicit_provided<'a>(&'a self) -> &'a () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:415:9
|
LL | fn lifetime_elsewhere<'a>(self: Box<Self>, here: &'a ()) -> &'a ();
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: explicit lifetimes given in parameter types where they could be elided (or replaced with `'_` if needed by type declaration)
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:416:9
|
LL | fn lifetime_elsewhere_provided<'a>(self: Box<Self>, here: &'a ()) -> &'a () {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 31 previous errors
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:425:5
|
LL | fn foo<'a>(x: &'a u8, y: &'_ u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: the following explicit lifetimes could be elided: 'a
--> $DIR/needless_lifetimes.rs:427:5
|
LL | fn bar<'a>(x: &'a u8, y: &'_ u8, z: &'_ u8) {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
error: aborting due to 33 previous errors