diff --git a/clippy_lints/src/lifetimes.rs b/clippy_lints/src/lifetimes.rs index ef9ac96ace5c..3cccc2cfe2aa 100644 --- a/clippy_lints/src/lifetimes.rs +++ b/clippy_lints/src/lifetimes.rs @@ -1,22 +1,21 @@ 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_errors::Applicability; use rustc_hir::intravisit::nested_filter::{self as hir_nested_filter, NestedFilter}; use rustc_hir::intravisit::{ - walk_fn_decl, walk_generic_arg, walk_generic_param, walk_generics, walk_impl_item_ref, walk_item, walk_param_bound, + walk_fn_decl, walk_generic_param, walk_generics, walk_impl_item_ref, walk_item, walk_param_bound, walk_poly_trait_ref, walk_trait_ref, walk_ty, Visitor, }; -use rustc_hir::lang_items; use rustc_hir::FnRetTy::Return; use rustc_hir::{ - BareFnTy, BodyId, FnDecl, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, Impl, ImplItem, - ImplItemKind, Item, ItemKind, Lifetime, LifetimeName, LifetimeParamKind, PolyTraitRef, PredicateOrigin, TraitFn, - TraitItem, TraitItemKind, Ty, TyKind, WherePredicate, + lang_items, BareFnTy, BodyId, FnDecl, FnSig, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, + Impl, ImplItem, ImplItemKind, Item, ItemKind, Lifetime, LifetimeName, LifetimeParamKind, Node, PolyTraitRef, + PredicateOrigin, TraitFn, TraitItem, TraitItemKind, Ty, TyKind, WherePredicate, }; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::hir::nested_filter as middle_nested_filter; use rustc_middle::lint::in_external_macro; -use rustc_middle::ty::TyCtxt; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::def_id::LocalDefId; use rustc_span::source_map::Span; @@ -35,8 +34,6 @@ declare_clippy_lint! { /// ### Known problems /// - We bail out if the function has a `where` clause where lifetimes /// are mentioned due to potential false positives. - /// - Lifetime bounds such as `impl Foo + 'a` and `T: 'a` must be elided with the - /// placeholder notation `'_` because the fully elided notation leaves the type bound to `'static`. /// /// ### Example /// ```rust @@ -94,7 +91,7 @@ declare_lint_pass!(Lifetimes => [NEEDLESS_LIFETIMES, EXTRA_UNUSED_LIFETIMES]); impl<'tcx> LateLintPass<'tcx> for Lifetimes { fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) { if let ItemKind::Fn(ref sig, generics, id) = item.kind { - check_fn_inner(cx, sig.decl, Some(id), None, generics, item.span, true); + check_fn_inner(cx, sig, Some(id), None, generics, item.span, true); } else if let ItemKind::Impl(impl_) = item.kind { if !item.span.from_expansion() { report_extra_impl_lifetimes(cx, impl_); @@ -107,7 +104,7 @@ impl<'tcx> LateLintPass<'tcx> for Lifetimes { let report_extra_lifetimes = trait_ref_of_method(cx, item.owner_id.def_id).is_none(); check_fn_inner( cx, - sig.decl, + sig, Some(id), None, item.generics, @@ -123,22 +120,14 @@ impl<'tcx> LateLintPass<'tcx> for Lifetimes { TraitFn::Required(sig) => (None, Some(sig)), TraitFn::Provided(id) => (Some(id), None), }; - check_fn_inner(cx, sig.decl, body, trait_sig, item.generics, item.span, true); + check_fn_inner(cx, sig, body, trait_sig, item.generics, item.span, true); } } } -/// The lifetime of a &-reference. -#[derive(PartialEq, Eq, Hash, Debug, Clone)] -enum RefLt { - Unnamed, - Static, - Named(LocalDefId), -} - fn check_fn_inner<'tcx>( cx: &LateContext<'tcx>, - decl: &'tcx FnDecl<'_>, + sig: &'tcx FnSig<'_>, body: Option, trait_sig: Option<&[Ident]>, generics: &'tcx Generics<'_>, @@ -164,7 +153,7 @@ fn check_fn_inner<'tcx>( for bound in pred.bounds { let mut visitor = RefVisitor::new(cx); walk_param_bound(&mut visitor, bound); - if visitor.lts.iter().any(|lt| matches!(lt, RefLt::Named(_))) { + if visitor.lts.iter().any(|lt| matches!(lt.res, LifetimeName::Param(_))) { return; } if let GenericBound::Trait(ref trait_ref, _) = *bound { @@ -191,12 +180,12 @@ fn check_fn_inner<'tcx>( } } - if let Some(elidable_lts) = could_use_elision(cx, decl, body, trait_sig, generics.params) { + if let Some((elidable_lts, usages)) = could_use_elision(cx, sig.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()) + .filter_map(|&def_id| cx.tcx.hir().get_by_def_id(def_id).ident()) .map(|ident| ident.to_string()) .collect::>() .join(", "); @@ -204,21 +193,99 @@ fn check_fn_inner<'tcx>( span_lint_and_then( cx, NEEDLESS_LIFETIMES, - span.with_hi(decl.output.span().hi()), + span.with_hi(sig.decl.output.span().hi()), &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 sig.header.is_async() { + // async functions have usages whose spans point at the lifetime declaration which messes up + // suggestions + return; + }; + + if let Some(suggestions) = elision_suggestions(cx, generics, &elidable_lts, &usages) { + diag.multipart_suggestion("elide the lifetimes", suggestions, Applicability::MachineApplicable); } }, ); } if report_extra_lifetimes { - self::report_extra_lifetimes(cx, decl, generics); + self::report_extra_lifetimes(cx, sig.decl, generics); } } +fn elision_suggestions( + cx: &LateContext<'_>, + generics: &Generics<'_>, + elidable_lts: &[LocalDefId], + usages: &[Lifetime], +) -> Option> { + let explicit_params = generics + .params + .iter() + .filter(|param| !param.is_elided_lifetime() && !param.is_impl_trait()) + .collect::>(); + + let mut suggestions = if elidable_lts.len() == explicit_params.len() { + // if all the params are elided remove the whole generic block + // + // fn x<'a>() {} + // ^^^^ + vec![(generics.span, String::new())] + } else { + elidable_lts + .iter() + .map(|&id| { + let pos = explicit_params.iter().position(|param| param.def_id == id)?; + let param = explicit_params.get(pos)?; + + let span = if let Some(next) = explicit_params.get(pos + 1) { + // fn x<'prev, 'a, 'next>() {} + // ^^^^ + param.span.until(next.span) + } else { + // `pos` should be at least 1 here, because the param in position 0 would either have a `next` + // param or would have taken the `elidable_lts.len() == explicit_params.len()` branch. + let prev = explicit_params.get(pos - 1)?; + + // fn x<'prev, 'a>() {} + // ^^^^ + param.span.with_lo(prev.span.hi()) + }; + + Some((span, String::new())) + }) + .collect::>>()? + }; + + suggestions.extend( + usages + .iter() + .filter(|usage| named_lifetime(usage).map_or(false, |id| elidable_lts.contains(&id))) + .map(|usage| { + match cx.tcx.hir().get_parent(usage.hir_id) { + Node::Ty(Ty { + kind: TyKind::Ref(..), .. + }) => { + // expand `&'a T` to `&'a T` + // ^^ ^^^ + let span = cx + .sess() + .source_map() + .span_extend_while(usage.ident.span, |ch| ch.is_ascii_whitespace()) + .unwrap_or(usage.ident.span); + + (span, String::new()) + }, + // `T<'a>` and `impl Foo + 'a` should be replaced by `'_` + _ => (usage.ident.span, String::from("'_")), + } + }), + ); + + Some(suggestions) +} + // elision doesn't work for explicit self types, see rust-lang/rust#69064 fn explicit_self_type<'tcx>(cx: &LateContext<'tcx>, func: &FnDecl<'tcx>, ident: Option) -> bool { if_chain! { @@ -238,13 +305,20 @@ fn explicit_self_type<'tcx>(cx: &LateContext<'tcx>, func: &FnDecl<'tcx>, ident: } } +fn named_lifetime(lt: &Lifetime) -> Option { + match lt.res { + LifetimeName::Param(id) if !lt.is_anonymous() => Some(id), + _ => None, + } +} + fn could_use_elision<'tcx>( cx: &LateContext<'tcx>, func: &'tcx FnDecl<'_>, body: Option, trait_sig: Option<&[Ident]>, named_generics: &'tcx [GenericParam<'_>], -) -> Option)>> { +) -> Option<(Vec, Vec)> { // 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 @@ -252,7 +326,7 @@ fn could_use_elision<'tcx>( // level of the current item. // check named LTs - let allowed_lts = allowed_lts_from(cx.tcx, named_generics); + let allowed_lts = allowed_lts_from(named_generics); // these will collect all the lifetimes for references in arg/return types let mut input_visitor = RefVisitor::new(cx); @@ -302,32 +376,24 @@ fn could_use_elision<'tcx>( // check for lifetimes from higher scopes for lt in input_lts.iter().chain(output_lts.iter()) { - if !allowed_lts.contains(lt) { + if let Some(id) = named_lifetime(lt) + && !allowed_lts.contains(&id) + { return None; } } // check for higher-ranked trait bounds if !input_visitor.nested_elision_site_lts.is_empty() || !output_visitor.nested_elision_site_lts.is_empty() { - let allowed_lts: FxHashSet<_> = allowed_lts - .iter() - .filter_map(|lt| match lt { - RefLt::Named(def_id) => Some(cx.tcx.item_name(def_id.to_def_id())), - _ => None, - }) - .collect(); + let allowed_lts: FxHashSet<_> = allowed_lts.iter().map(|id| cx.tcx.item_name(id.to_def_id())).collect(); 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 None; - } + if allowed_lts.contains(<.ident.name) { + 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 None; - } + if allowed_lts.contains(<.ident.name) { + return None; } } } @@ -339,15 +405,10 @@ fn could_use_elision<'tcx>( let elidable_lts = named_lifetime_occurrences(&input_lts) .into_iter() .filter_map(|(def_id, occurrences)| { - if occurrences == 1 && (input_lts.len() == 1 || !output_lts.contains(&RefLt::Named(def_id))) { - Some(( - def_id, - input_visitor - .lifetime_generic_arg_spans - .get(&def_id) - .or_else(|| output_visitor.lifetime_generic_arg_spans.get(&def_id)) - .copied(), - )) + if occurrences == 1 + && (input_lts.len() == 1 || !output_lts.iter().any(|lt| named_lifetime(lt) == Some(def_id))) + { + Some(def_id) } else { None } @@ -355,31 +416,34 @@ fn could_use_elision<'tcx>( .collect::>(); if elidable_lts.is_empty() { - None - } else { - Some(elidable_lts) + return None; } + + let usages = itertools::chain(input_lts, output_lts).collect(); + + Some((elidable_lts, usages)) } -fn allowed_lts_from(tcx: TyCtxt<'_>, named_generics: &[GenericParam<'_>]) -> FxHashSet { - let mut allowed_lts = FxHashSet::default(); - for par in named_generics.iter() { - if let GenericParamKind::Lifetime { .. } = par.kind { - allowed_lts.insert(RefLt::Named(tcx.hir().local_def_id(par.hir_id))); - } - } - allowed_lts.insert(RefLt::Unnamed); - allowed_lts.insert(RefLt::Static); - allowed_lts +fn allowed_lts_from(named_generics: &[GenericParam<'_>]) -> FxHashSet { + named_generics + .iter() + .filter_map(|par| { + if let GenericParamKind::Lifetime { .. } = par.kind { + Some(par.def_id) + } else { + None + } + }) + .collect() } /// Number of times each named lifetime occurs in the given slice. Returns a vector to preserve /// relative order. #[must_use] -fn named_lifetime_occurrences(lts: &[RefLt]) -> Vec<(LocalDefId, usize)> { +fn named_lifetime_occurrences(lts: &[Lifetime]) -> Vec<(LocalDefId, usize)> { let mut occurrences = Vec::new(); for lt in lts { - if let &RefLt::Named(curr_def_id) = lt { + if let Some(curr_def_id) = named_lifetime(lt) { if let Some(pair) = occurrences .iter_mut() .find(|(prev_def_id, _)| *prev_def_id == curr_def_id) @@ -393,12 +457,10 @@ fn named_lifetime_occurrences(lts: &[RefLt]) -> Vec<(LocalDefId, usize)> { occurrences } -/// A visitor usable for `rustc_front::visit::walk_ty()`. struct RefVisitor<'a, 'tcx> { cx: &'a LateContext<'tcx>, - lts: Vec, - lifetime_generic_arg_spans: FxHashMap, - nested_elision_site_lts: Vec, + lts: Vec, + nested_elision_site_lts: Vec, unelided_trait_object_lifetime: bool, } @@ -407,32 +469,16 @@ impl<'a, 'tcx> RefVisitor<'a, 'tcx> { Self { cx, lts: Vec::new(), - lifetime_generic_arg_spans: FxHashMap::default(), nested_elision_site_lts: Vec::new(), unelided_trait_object_lifetime: false, } } - fn record(&mut self, lifetime: &Option) { - if let Some(ref lt) = *lifetime { - if lt.is_static() { - self.lts.push(RefLt::Static); - } else if lt.is_anonymous() { - // Fresh lifetimes generated should be ignored. - self.lts.push(RefLt::Unnamed); - } else if let LifetimeName::Param(def_id) = lt.res { - self.lts.push(RefLt::Named(def_id)); - } - } else { - self.lts.push(RefLt::Unnamed); - } - } - - fn all_lts(&self) -> Vec { + fn all_lts(&self) -> Vec { self.lts .iter() .chain(self.nested_elision_site_lts.iter()) - .cloned() + .copied() .collect::>() } @@ -444,7 +490,7 @@ impl<'a, 'tcx> RefVisitor<'a, 'tcx> { impl<'a, 'tcx> Visitor<'tcx> for RefVisitor<'a, 'tcx> { // for lifetimes as parameters of generics fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) { - self.record(&Some(*lifetime)); + self.lts.push(*lifetime); } fn visit_poly_trait_ref(&mut self, poly_tref: &'tcx PolyTraitRef<'tcx>) { @@ -469,11 +515,7 @@ impl<'a, 'tcx> Visitor<'tcx> for RefVisitor<'a, 'tcx> { walk_item(self, item); self.lts.truncate(len); self.lts.extend(bounds.iter().filter_map(|bound| match bound { - GenericArg::Lifetime(l) => Some(if let LifetimeName::Param(def_id) = l.res { - RefLt::Named(def_id) - } else { - RefLt::Unnamed - }), + GenericArg::Lifetime(&l) => Some(l), _ => None, })); }, @@ -493,13 +535,6 @@ impl<'a, 'tcx> Visitor<'tcx> for RefVisitor<'a, 'tcx> { _ => 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.res { - self.lifetime_generic_arg_spans.entry(def_id).or_insert(l.ident.span); - } - walk_generic_arg(self, generic_arg); - } } /// Are any lifetimes mentioned in the `where` clause? If so, we don't try to @@ -517,14 +552,18 @@ fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, generics: &'tcx Generics<'_ return true; } // if the bounds define new lifetimes, they are fine to occur - let allowed_lts = allowed_lts_from(cx.tcx, pred.bound_generic_params); + let allowed_lts = allowed_lts_from(pred.bound_generic_params); // now walk the bounds for bound in pred.bounds.iter() { walk_param_bound(&mut visitor, bound); } // and check that all lifetimes are allowed - if visitor.all_lts().iter().any(|it| !allowed_lts.contains(it)) { - return true; + for lt in visitor.all_lts() { + if let Some(id) = named_lifetime(<) + && !allowed_lts.contains(&id) + { + return true; + } } }, WherePredicate::EqPredicate(ref pred) => { diff --git a/tests/ui/crashes/ice-2774.stderr b/tests/ui/crashes/ice-2774.stderr index 1f26c7f4db65..c5ea0b16d1be 100644 --- a/tests/ui/crashes/ice-2774.stderr +++ b/tests/ui/crashes/ice-2774.stderr @@ -5,6 +5,11 @@ LL | pub fn add_barfoos_to_foos<'a>(bars: &HashSet<&'a Bar>) { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: `-D clippy::needless-lifetimes` implied by `-D warnings` +help: elide the lifetimes + | +LL - pub fn add_barfoos_to_foos<'a>(bars: &HashSet<&'a Bar>) { +LL + pub fn add_barfoos_to_foos(bars: &HashSet<&Bar>) { + | error: aborting due to previous error diff --git a/tests/ui/crashes/needless_lifetimes_impl_trait.stderr b/tests/ui/crashes/needless_lifetimes_impl_trait.stderr index 875d5ab4f21c..0b0e0ad2684a 100644 --- a/tests/ui/crashes/needless_lifetimes_impl_trait.stderr +++ b/tests/ui/crashes/needless_lifetimes_impl_trait.stderr @@ -9,6 +9,11 @@ note: the lint level is defined here | LL | #![deny(clippy::needless_lifetimes)] | ^^^^^^^^^^^^^^^^^^^^^^^^^^ +help: elide the lifetimes + | +LL - fn baz<'a>(&'a self) -> impl Foo + 'a { +LL + fn baz(&self) -> impl Foo + '_ { + | error: aborting due to previous error diff --git a/tests/ui/needless_lifetimes.fixed b/tests/ui/needless_lifetimes.fixed new file mode 100644 index 000000000000..270cd1afc679 --- /dev/null +++ b/tests/ui/needless_lifetimes.fixed @@ -0,0 +1,537 @@ +// run-rustfix +// aux-build:macro_rules.rs + +#![warn(clippy::needless_lifetimes)] +#![allow( + unused, + clippy::boxed_local, + clippy::needless_pass_by_value, + clippy::unnecessary_wraps, + dyn_drop, + clippy::get_first +)] + +#[macro_use] +extern crate macro_rules; + +fn distinct_lifetimes(_x: &u8, _y: &u8, _z: u8) {} + +fn distinct_and_static(_x: &u8, _y: &u8, _z: &'static u8) {} + +// No error; same lifetime on two params. +fn same_lifetime_on_input<'a>(_x: &'a u8, _y: &'a u8) {} + +// No error; static involved. +fn only_static_on_input(_x: &u8, _y: &u8, _z: &'static u8) {} + +fn mut_and_static_input(_x: &mut u8, _y: &'static str) {} + +fn in_and_out(x: &u8, _y: u8) -> &u8 { + x +} + +// No error; multiple input refs. +fn multiple_in_and_out_1<'a>(x: &'a u8, _y: &'a u8) -> &'a u8 { + x +} + +// Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: +// fn multiple_in_and_out_2a<'a>(x: &'a u8, _y: &u8) -> &'a u8 +// ^^^ +fn multiple_in_and_out_2a<'a>(x: &'a u8, _y: &u8) -> &'a u8 { + x +} + +// Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: +// fn multiple_in_and_out_2b<'b>(_x: &u8, y: &'b u8) -> &'b u8 +// ^^^ +fn multiple_in_and_out_2b<'b>(_x: &u8, y: &'b u8) -> &'b u8 { + y +} + +// No error; multiple input refs +async fn func<'a>(args: &[&'a str]) -> Option<&'a str> { + args.get(0).cloned() +} + +// No error; static involved. +fn in_static_and_out<'a>(x: &'a u8, _y: &'static u8) -> &'a u8 { + x +} + +// Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: +// fn deep_reference_1a<'a>(x: &'a u8, _y: &u8) -> Result<&'a u8, ()> +// ^^^ +fn deep_reference_1a<'a>(x: &'a u8, _y: &u8) -> Result<&'a u8, ()> { + Ok(x) +} + +// Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: +// fn deep_reference_1b<'b>(_x: &u8, y: &'b u8) -> Result<&'b u8, ()> +// ^^^ +fn deep_reference_1b<'b>(_x: &u8, y: &'b u8) -> Result<&'b u8, ()> { + Ok(y) +} + +// No error; two input refs. +fn deep_reference_2<'a>(x: Result<&'a u8, &'a u8>) -> &'a u8 { + x.unwrap() +} + +fn deep_reference_3(x: &u8, _y: u8) -> Result<&u8, ()> { + Ok(x) +} + +// Where-clause, but without lifetimes. +fn where_clause_without_lt(x: &u8, _y: u8) -> Result<&u8, ()> +where + T: Copy, +{ + Ok(x) +} + +type Ref<'r> = &'r u8; + +// No error; same lifetime on two params. +fn lifetime_param_1<'a>(_x: Ref<'a>, _y: &'a u8) {} + +fn lifetime_param_2(_x: Ref<'_>, _y: &u8) {} + +// No error; bounded lifetime. +fn lifetime_param_3<'a, 'b: 'a>(_x: Ref<'a>, _y: &'b u8) {} + +// No error; bounded lifetime. +fn lifetime_param_4<'a, 'b>(_x: Ref<'a>, _y: &'b u8) +where + 'b: 'a, +{ +} + +struct Lt<'a, I: 'static> { + x: &'a I, +} + +// No error; fn bound references `'a`. +fn fn_bound<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I> +where + F: Fn(Lt<'a, I>) -> Lt<'a, I>, +{ + unreachable!() +} + +fn fn_bound_2(_m: Lt<'_, I>, _f: F) -> Lt<'_, I> +where + for<'x> F: Fn(Lt<'x, I>) -> Lt<'x, I>, +{ + unreachable!() +} + +// No error; see below. +fn fn_bound_3<'a, F: FnOnce(&'a i32)>(x: &'a i32, f: F) { + f(x); +} + +fn fn_bound_3_cannot_elide() { + let x = 42; + let p = &x; + let mut q = &x; + // This will fail if we elide lifetimes of `fn_bound_3`. + fn_bound_3(p, |y| q = y); +} + +// No error; multiple input refs. +fn fn_bound_4<'a, F: FnOnce() -> &'a ()>(cond: bool, x: &'a (), f: F) -> &'a () { + if cond { x } else { f() } +} + +struct X { + x: u8, +} + +impl X { + fn self_and_out(&self) -> &u8 { + &self.x + } + + // Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: + // fn self_and_in_out_1<'s>(&'s self, _x: &u8) -> &'s u8 + // ^^^ + fn self_and_in_out_1<'s>(&'s self, _x: &u8) -> &'s u8 { + &self.x + } + + // Error; multiple input refs, but the output lifetime is not elided, i.e., the following is valid: + // fn self_and_in_out_2<'t>(&self, x: &'t u8) -> &'t u8 + // ^^^^^ + fn self_and_in_out_2<'t>(&self, x: &'t u8) -> &'t u8 { + x + } + + fn distinct_self_and_in(&self, _x: &u8) {} + + // No error; same lifetimes on two params. + fn self_and_same_in<'s>(&'s self, _x: &'s u8) {} +} + +struct Foo<'a>(&'a u8); + +impl<'a> Foo<'a> { + // No error; lifetime `'a` not defined in method. + fn self_shared_lifetime(&self, _: &'a u8) {} + // No error; bounds exist. + fn self_bound_lifetime<'b: 'a>(&self, _: &'b u8) {} +} + +fn already_elided<'a>(_: &u8, _: &'a u8) -> &'a u8 { + unimplemented!() +} + +fn struct_with_lt(_foo: Foo<'_>) -> &str { + unimplemented!() +} + +// No warning; two input lifetimes (named on the reference, anonymous on `Foo`). +fn struct_with_lt2<'a>(_foo: &'a Foo) -> &'a str { + unimplemented!() +} + +// No warning; two input lifetimes (anonymous on the reference, named on `Foo`). +fn struct_with_lt3<'a>(_foo: &Foo<'a>) -> &'a str { + unimplemented!() +} + +// Warning; two input lifetimes, but the output lifetime is not elided, i.e., the following is +// valid: +// fn struct_with_lt4a<'a>(_foo: &'a Foo<'_>) -> &'a str +// ^^ +fn struct_with_lt4a<'a>(_foo: &'a Foo<'_>) -> &'a str { + unimplemented!() +} + +// Warning; two input lifetimes, but the output lifetime is not elided, i.e., the following is +// valid: +// fn struct_with_lt4b<'b>(_foo: &Foo<'b>) -> &'b str +// ^^^^ +fn struct_with_lt4b<'b>(_foo: &Foo<'b>) -> &'b str { + unimplemented!() +} + +trait WithLifetime<'a> {} + +type WithLifetimeAlias<'a> = dyn WithLifetime<'a>; + +// Should not warn because it won't build without the lifetime. +fn trait_obj_elided<'a>(_arg: &'a dyn WithLifetime) -> &'a str { + unimplemented!() +} + +// Should warn because there is no lifetime on `Drop`, so this would be +// unambiguous if we elided the lifetime. +fn trait_obj_elided2(_arg: &dyn Drop) -> &str { + unimplemented!() +} + +type FooAlias<'a> = Foo<'a>; + +fn alias_with_lt(_foo: FooAlias<'_>) -> &str { + unimplemented!() +} + +// No warning; two input lifetimes (named on the reference, anonymous on `FooAlias`). +fn alias_with_lt2<'a>(_foo: &'a FooAlias) -> &'a str { + unimplemented!() +} + +// No warning; two input lifetimes (anonymous on the reference, named on `FooAlias`). +fn alias_with_lt3<'a>(_foo: &FooAlias<'a>) -> &'a str { + unimplemented!() +} + +// Warning; two input lifetimes, but the output lifetime is not elided, i.e., the following is +// valid: +// fn alias_with_lt4a<'a>(_foo: &'a FooAlias<'_>) -> &'a str +// ^^ +fn alias_with_lt4a<'a>(_foo: &'a FooAlias<'_>) -> &'a str { + unimplemented!() +} + +// Warning; two input lifetimes, but the output lifetime is not elided, i.e., the following is +// valid: +// fn alias_with_lt4b<'b>(_foo: &FooAlias<'b>) -> &'b str +// ^^^^^^^^^ +fn alias_with_lt4b<'b>(_foo: &FooAlias<'b>) -> &'b str { + unimplemented!() +} + +fn named_input_elided_output(_arg: &str) -> &str { + unimplemented!() +} + +fn elided_input_named_output<'a>(_arg: &str) -> &'a str { + unimplemented!() +} + +fn trait_bound_ok>(_: &u8, _: T) { + unimplemented!() +} +fn trait_bound<'a, T: WithLifetime<'a>>(_: &'a u8, _: T) { + unimplemented!() +} + +// Don't warn on these; see issue #292. +fn trait_bound_bug<'a, T: WithLifetime<'a>>() { + unimplemented!() +} + +// See issue #740. +struct Test { + vec: Vec, +} + +impl Test { + fn iter<'a>(&'a self) -> Box + 'a> { + unimplemented!() + } +} + +trait LintContext<'a> {} + +fn f<'a, T: LintContext<'a>>(_: &T) {} + +fn test<'a>(x: &'a [u8]) -> u8 { + let y: &'a u8 = &x[5]; + *y +} + +// Issue #3284: give hint regarding lifetime in return type. +struct Cow<'a> { + x: &'a str, +} +fn out_return_type_lts(e: &str) -> Cow<'_> { + unimplemented!() +} + +// Make sure we still warn on implementations +mod issue4291 { + trait BadTrait { + fn needless_lt(x: &u8) {} + } + + impl BadTrait for () { + fn needless_lt(_x: &u8) {} + } +} + +mod issue2944 { + trait Foo {} + struct Bar; + struct Baz<'a> { + bar: &'a Bar, + } + + impl<'a> Foo for Baz<'a> {} + impl Bar { + fn baz(&self) -> impl Foo + '_ { + Baz { bar: self } + } + } +} + +mod nested_elision_sites { + // issue #issue2944 + + // closure trait bounds subject to nested elision + // don't lint because they refer to outer lifetimes + fn trait_fn<'a>(i: &'a i32) -> impl Fn() -> &'a i32 { + move || i + } + fn trait_fn_mut<'a>(i: &'a i32) -> impl FnMut() -> &'a i32 { + move || i + } + fn trait_fn_once<'a>(i: &'a i32) -> impl FnOnce() -> &'a i32 { + move || i + } + + // don't lint + fn impl_trait_in_input_position<'a>(f: impl Fn() -> &'a i32) -> &'a i32 { + f() + } + fn impl_trait_in_output_position<'a>(i: &'a i32) -> impl Fn() -> &'a i32 { + move || i + } + // lint + fn impl_trait_elidable_nested_named_lifetimes<'a>(i: &'a i32, f: impl for<'b> Fn(&'b i32) -> &'b i32) -> &'a i32 { + f(i) + } + fn impl_trait_elidable_nested_anonymous_lifetimes(i: &i32, f: impl Fn(&i32) -> &i32) -> &i32 { + f(i) + } + + // don't lint + fn generics_not_elidable<'a, T: Fn() -> &'a i32>(f: T) -> &'a i32 { + f() + } + // lint + fn generics_elidable &i32>(i: &i32, f: T) -> &i32 { + f(i) + } + + // don't lint + fn where_clause_not_elidable<'a, T>(f: T) -> &'a i32 + where + T: Fn() -> &'a i32, + { + f() + } + // lint + fn where_clause_elidadable(i: &i32, f: T) -> &i32 + where + T: Fn(&i32) -> &i32, + { + f(i) + } + + // don't lint + fn pointer_fn_in_input_position<'a>(f: fn(&'a i32) -> &'a i32, i: &'a i32) -> &'a i32 { + f(i) + } + fn pointer_fn_in_output_position<'a>(_: &'a i32) -> fn(&'a i32) -> &'a i32 { + |i| i + } + // lint + fn pointer_fn_elidable(i: &i32, f: fn(&i32) -> &i32) -> &i32 { + f(i) + } + + // don't lint + fn nested_fn_pointer_1<'a>(_: &'a i32) -> fn(fn(&'a i32) -> &'a i32) -> i32 { + |f| 42 + } + fn nested_fn_pointer_2<'a>(_: &'a i32) -> impl Fn(fn(&'a i32)) { + |f| () + } + + // lint + fn nested_fn_pointer_3(_: &i32) -> fn(fn(&i32) -> &i32) -> i32 { + |f| 42 + } + fn nested_fn_pointer_4(_: &i32) -> impl Fn(fn(&i32)) { + |f| () + } +} + +mod issue6159 { + use std::ops::Deref; + pub fn apply_deref<'a, T, F, R>(x: &'a T, f: F) -> R + where + T: Deref, + F: FnOnce(&'a T::Target) -> R, + { + f(x.deref()) + } +} + +mod issue7296 { + use std::rc::Rc; + use std::sync::Arc; + + struct Foo; + impl Foo { + fn implicit(&self) -> &() { + &() + } + fn implicit_mut(&mut self) -> &() { + &() + } + + fn explicit<'a>(self: &'a Arc) -> &'a () { + &() + } + fn explicit_mut<'a>(self: &'a mut Rc) -> &'a () { + &() + } + + fn lifetime_elsewhere(self: Box, here: &()) -> &() { + &() + } + } + + trait Bar { + fn implicit(&self) -> &(); + fn implicit_provided(&self) -> &() { + &() + } + + fn explicit<'a>(self: &'a Arc) -> &'a (); + fn explicit_provided<'a>(self: &'a Arc) -> &'a () { + &() + } + + fn lifetime_elsewhere(self: Box, here: &()) -> &(); + fn lifetime_elsewhere_provided(self: Box, here: &()) -> &() { + &() + } + } +} + +mod pr_9743_false_negative_fix { + #![allow(unused)] + + fn foo(x: &u8, y: &'_ u8) {} + + fn bar(x: &u8, y: &'_ u8, z: &'_ u8) {} +} + +mod pr_9743_output_lifetime_checks { + #![allow(unused)] + + // lint: only one input + fn one_input(x: &u8) -> &u8 { + unimplemented!() + } + + // lint: multiple inputs, output would not be elided + fn multiple_inputs_output_not_elided<'b>(x: &u8, y: &'b u8, z: &'b u8) -> &'b u8 { + unimplemented!() + } + + // don't lint: multiple inputs, output would be elided (which would create an ambiguity) + fn multiple_inputs_output_would_be_elided<'a, 'b>(x: &'a u8, y: &'b u8, z: &'b u8) -> &'a u8 { + unimplemented!() + } +} + +mod in_macro { + macro_rules! local_one_input_macro { + () => { + fn one_input(x: &u8) -> &u8 { + unimplemented!() + } + }; + } + + // lint local macro expands to function with needless lifetimes + local_one_input_macro!(); + + // no lint on external macro + macro_rules::needless_lifetime!(); +} + +mod issue5787 { + use std::sync::MutexGuard; + + struct Foo; + + impl Foo { + // doesn't get linted without async + pub async fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> MutexGuard<'a, T> { + guard + } + } + + async fn foo<'a>(_x: &i32, y: &'a str) -> &'a str { + y + } +} + +fn main() {} diff --git a/tests/ui/needless_lifetimes.rs b/tests/ui/needless_lifetimes.rs index 78493c6d0672..5d4dc971b8d2 100644 --- a/tests/ui/needless_lifetimes.rs +++ b/tests/ui/needless_lifetimes.rs @@ -1,7 +1,9 @@ +// run-rustfix // aux-build:macro_rules.rs + #![warn(clippy::needless_lifetimes)] #![allow( - dead_code, + unused, clippy::boxed_local, clippy::needless_pass_by_value, clippy::unnecessary_wraps, @@ -515,4 +517,21 @@ mod in_macro { macro_rules::needless_lifetime!(); } +mod issue5787 { + use std::sync::MutexGuard; + + struct Foo; + + impl Foo { + // doesn't get linted without async + pub async fn wait<'a, T>(&self, guard: MutexGuard<'a, T>) -> MutexGuard<'a, T> { + guard + } + } + + async fn foo<'a>(_x: &i32, y: &'a str) -> &'a str { + y + } +} + fn main() {} diff --git a/tests/ui/needless_lifetimes.stderr b/tests/ui/needless_lifetimes.stderr index 9d02626956e0..afe637ac3888 100644 --- a/tests/ui/needless_lifetimes.stderr +++ b/tests/ui/needless_lifetimes.stderr @@ -1,319 +1,546 @@ error: the following explicit lifetimes could be elided: 'a, 'b - --> $DIR/needless_lifetimes.rs:15:1 + --> $DIR/needless_lifetimes.rs:17:1 | LL | fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | = note: `-D clippy::needless-lifetimes` implied by `-D warnings` +help: elide the lifetimes + | +LL - fn distinct_lifetimes<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: u8) {} +LL + fn distinct_lifetimes(_x: &u8, _y: &u8, _z: u8) {} + | error: the following explicit lifetimes could be elided: 'a, 'b - --> $DIR/needless_lifetimes.rs:17:1 + --> $DIR/needless_lifetimes.rs:19:1 | LL | fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn distinct_and_static<'a, 'b>(_x: &'a u8, _y: &'b u8, _z: &'static u8) {} +LL + fn distinct_and_static(_x: &u8, _y: &u8, _z: &'static u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:27:1 + --> $DIR/needless_lifetimes.rs:29:1 | LL | fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn in_and_out<'a>(x: &'a u8, _y: u8) -> &'a u8 { +LL + fn in_and_out(x: &u8, _y: u8) -> &u8 { + | error: the following explicit lifetimes could be elided: 'b - --> $DIR/needless_lifetimes.rs:39:1 + --> $DIR/needless_lifetimes.rs:41:1 | LL | fn multiple_in_and_out_2a<'a, 'b>(x: &'a u8, _y: &'b u8) -> &'a u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn multiple_in_and_out_2a<'a, 'b>(x: &'a u8, _y: &'b u8) -> &'a u8 { +LL + fn multiple_in_and_out_2a<'a>(x: &'a u8, _y: &u8) -> &'a u8 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:46:1 + --> $DIR/needless_lifetimes.rs:48:1 | LL | fn multiple_in_and_out_2b<'a, 'b>(_x: &'a u8, y: &'b u8) -> &'b u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn multiple_in_and_out_2b<'a, 'b>(_x: &'a u8, y: &'b u8) -> &'b u8 { +LL + fn multiple_in_and_out_2b<'b>(_x: &u8, y: &'b u8) -> &'b u8 { + | error: the following explicit lifetimes could be elided: 'b - --> $DIR/needless_lifetimes.rs:63:1 + --> $DIR/needless_lifetimes.rs:65:1 | LL | fn deep_reference_1a<'a, 'b>(x: &'a u8, _y: &'b u8) -> Result<&'a u8, ()> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn deep_reference_1a<'a, 'b>(x: &'a u8, _y: &'b u8) -> Result<&'a u8, ()> { +LL + fn deep_reference_1a<'a>(x: &'a u8, _y: &u8) -> Result<&'a u8, ()> { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:70:1 + --> $DIR/needless_lifetimes.rs:72:1 | LL | fn deep_reference_1b<'a, 'b>(_x: &'a u8, y: &'b u8) -> Result<&'b u8, ()> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn deep_reference_1b<'a, 'b>(_x: &'a u8, y: &'b u8) -> Result<&'b u8, ()> { +LL + fn deep_reference_1b<'b>(_x: &u8, y: &'b u8) -> Result<&'b u8, ()> { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:79:1 + --> $DIR/needless_lifetimes.rs:81:1 | LL | fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn deep_reference_3<'a>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> { +LL + fn deep_reference_3(x: &u8, _y: u8) -> Result<&u8, ()> { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:84:1 + --> $DIR/needless_lifetimes.rs:86:1 | LL | fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn where_clause_without_lt<'a, T>(x: &'a u8, _y: u8) -> Result<&'a u8, ()> +LL + fn where_clause_without_lt(x: &u8, _y: u8) -> Result<&u8, ()> + | error: the following explicit lifetimes could be elided: 'a, 'b - --> $DIR/needless_lifetimes.rs:96:1 + --> $DIR/needless_lifetimes.rs:98:1 | 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:96:37 +help: elide the lifetimes + | +LL - fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {} +LL + fn lifetime_param_2(_x: Ref<'_>, _y: &u8) {} | -LL | fn lifetime_param_2<'a, 'b>(_x: Ref<'a>, _y: &'b u8) {} - | ^^ error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:120:1 + --> $DIR/needless_lifetimes.rs:122:1 | 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:120:32 +help: elide the lifetimes + | +LL - fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I> +LL + fn fn_bound_2(_m: Lt<'_, I>, _f: F) -> Lt<'_, I> | -LL | fn fn_bound_2<'a, F, I>(_m: Lt<'a, I>, _f: F) -> Lt<'a, I> - | ^^ error: the following explicit lifetimes could be elided: 's - --> $DIR/needless_lifetimes.rs:150:5 + --> $DIR/needless_lifetimes.rs:152:5 | LL | fn self_and_out<'s>(&'s self) -> &'s u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn self_and_out<'s>(&'s self) -> &'s u8 { +LL + fn self_and_out(&self) -> &u8 { + | error: the following explicit lifetimes could be elided: 't - --> $DIR/needless_lifetimes.rs:157:5 + --> $DIR/needless_lifetimes.rs:159:5 | LL | fn self_and_in_out_1<'s, 't>(&'s self, _x: &'t u8) -> &'s u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn self_and_in_out_1<'s, 't>(&'s self, _x: &'t u8) -> &'s u8 { +LL + fn self_and_in_out_1<'s>(&'s self, _x: &u8) -> &'s u8 { + | error: the following explicit lifetimes could be elided: 's - --> $DIR/needless_lifetimes.rs:164:5 + --> $DIR/needless_lifetimes.rs:166:5 | LL | fn self_and_in_out_2<'s, 't>(&'s self, x: &'t u8) -> &'t u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn self_and_in_out_2<'s, 't>(&'s self, x: &'t u8) -> &'t u8 { +LL + fn self_and_in_out_2<'t>(&self, x: &'t u8) -> &'t u8 { + | error: the following explicit lifetimes could be elided: 's, 't - --> $DIR/needless_lifetimes.rs:168:5 + --> $DIR/needless_lifetimes.rs:170:5 | LL | fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn distinct_self_and_in<'s, 't>(&'s self, _x: &'t u8) {} +LL + fn distinct_self_and_in(&self, _x: &u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:187:1 + --> $DIR/needless_lifetimes.rs:189:1 | LL | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -help: replace with `'_` in generic arguments such as here - --> $DIR/needless_lifetimes.rs:187:33 +help: elide the lifetimes + | +LL - fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str { +LL + fn struct_with_lt(_foo: Foo<'_>) -> &str { | -LL | fn struct_with_lt<'a>(_foo: Foo<'a>) -> &'a str { - | ^^ error: the following explicit lifetimes could be elided: 'b - --> $DIR/needless_lifetimes.rs:205:1 + --> $DIR/needless_lifetimes.rs:207:1 | LL | fn struct_with_lt4a<'a, 'b>(_foo: &'a Foo<'b>) -> &'a str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -help: replace with `'_` in generic arguments such as here - --> $DIR/needless_lifetimes.rs:205:43 +help: elide the lifetimes + | +LL - fn struct_with_lt4a<'a, 'b>(_foo: &'a Foo<'b>) -> &'a str { +LL + fn struct_with_lt4a<'a>(_foo: &'a Foo<'_>) -> &'a str { | -LL | fn struct_with_lt4a<'a, 'b>(_foo: &'a Foo<'b>) -> &'a str { - | ^^ error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:213:1 + --> $DIR/needless_lifetimes.rs:215:1 | LL | fn struct_with_lt4b<'a, 'b>(_foo: &'a Foo<'b>) -> &'b str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn struct_with_lt4b<'a, 'b>(_foo: &'a Foo<'b>) -> &'b str { +LL + fn struct_with_lt4b<'b>(_foo: &Foo<'b>) -> &'b str { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:228:1 + --> $DIR/needless_lifetimes.rs:230:1 | LL | fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn trait_obj_elided2<'a>(_arg: &'a dyn Drop) -> &'a str { +LL + fn trait_obj_elided2(_arg: &dyn Drop) -> &str { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:234:1 + --> $DIR/needless_lifetimes.rs:236:1 | LL | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -help: replace with `'_` in generic arguments such as here - --> $DIR/needless_lifetimes.rs:234:37 +help: elide the lifetimes + | +LL - fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str { +LL + fn alias_with_lt(_foo: FooAlias<'_>) -> &str { | -LL | fn alias_with_lt<'a>(_foo: FooAlias<'a>) -> &'a str { - | ^^ error: the following explicit lifetimes could be elided: 'b - --> $DIR/needless_lifetimes.rs:252:1 + --> $DIR/needless_lifetimes.rs:254:1 | LL | fn alias_with_lt4a<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'a str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -help: replace with `'_` in generic arguments such as here - --> $DIR/needless_lifetimes.rs:252:47 +help: elide the lifetimes + | +LL - fn alias_with_lt4a<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'a str { +LL + fn alias_with_lt4a<'a>(_foo: &'a FooAlias<'_>) -> &'a str { | -LL | fn alias_with_lt4a<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'a str { - | ^^ error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:260:1 + --> $DIR/needless_lifetimes.rs:262:1 | LL | fn alias_with_lt4b<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'b str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn alias_with_lt4b<'a, 'b>(_foo: &'a FooAlias<'b>) -> &'b str { +LL + fn alias_with_lt4b<'b>(_foo: &FooAlias<'b>) -> &'b str { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:264:1 + --> $DIR/needless_lifetimes.rs:266:1 | LL | fn named_input_elided_output<'a>(_arg: &'a str) -> &str { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn named_input_elided_output<'a>(_arg: &'a str) -> &str { +LL + fn named_input_elided_output(_arg: &str) -> &str { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:272:1 + --> $DIR/needless_lifetimes.rs:274:1 | LL | fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn trait_bound_ok<'a, T: WithLifetime<'static>>(_: &'a u8, _: T) { +LL + fn trait_bound_ok>(_: &u8, _: T) { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:308:1 + --> $DIR/needless_lifetimes.rs:310:1 | LL | fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | -help: replace with `'_` in generic arguments such as here - --> $DIR/needless_lifetimes.rs:308:47 +help: elide the lifetimes + | +LL - fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> { +LL + fn out_return_type_lts(e: &str) -> Cow<'_> { | -LL | fn out_return_type_lts<'a>(e: &'a str) -> Cow<'a> { - | ^^ error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:315:9 + --> $DIR/needless_lifetimes.rs:317:9 | LL | fn needless_lt<'a>(x: &'a u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn needless_lt<'a>(x: &'a u8) {} +LL + fn needless_lt(x: &u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:319:9 + --> $DIR/needless_lifetimes.rs:321:9 | LL | fn needless_lt<'a>(_x: &'a u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn needless_lt<'a>(_x: &'a u8) {} +LL + fn needless_lt(_x: &u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:332:9 + --> $DIR/needless_lifetimes.rs:334:9 | LL | fn baz<'a>(&'a self) -> impl Foo + 'a { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn baz<'a>(&'a self) -> impl Foo + 'a { +LL + fn baz(&self) -> impl Foo + '_ { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:364:5 + --> $DIR/needless_lifetimes.rs:366:5 | LL | fn impl_trait_elidable_nested_anonymous_lifetimes<'a>(i: &'a i32, f: impl Fn(&i32) -> &i32) -> &'a i32 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn impl_trait_elidable_nested_anonymous_lifetimes<'a>(i: &'a i32, f: impl Fn(&i32) -> &i32) -> &'a i32 { +LL + fn impl_trait_elidable_nested_anonymous_lifetimes(i: &i32, f: impl Fn(&i32) -> &i32) -> &i32 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:373:5 + --> $DIR/needless_lifetimes.rs:375:5 | LL | fn generics_elidable<'a, T: Fn(&i32) -> &i32>(i: &'a i32, f: T) -> &'a i32 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn generics_elidable<'a, T: Fn(&i32) -> &i32>(i: &'a i32, f: T) -> &'a i32 { +LL + fn generics_elidable &i32>(i: &i32, f: T) -> &i32 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:385:5 + --> $DIR/needless_lifetimes.rs:387:5 | LL | fn where_clause_elidadable<'a, T>(i: &'a i32, f: T) -> &'a i32 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn where_clause_elidadable<'a, T>(i: &'a i32, f: T) -> &'a i32 +LL + fn where_clause_elidadable(i: &i32, f: T) -> &i32 + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:400:5 + --> $DIR/needless_lifetimes.rs:402:5 | LL | fn pointer_fn_elidable<'a>(i: &'a i32, f: fn(&i32) -> &i32) -> &'a i32 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn pointer_fn_elidable<'a>(i: &'a i32, f: fn(&i32) -> &i32) -> &'a i32 { +LL + fn pointer_fn_elidable(i: &i32, f: fn(&i32) -> &i32) -> &i32 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:413:5 + --> $DIR/needless_lifetimes.rs:415:5 | LL | fn nested_fn_pointer_3<'a>(_: &'a i32) -> fn(fn(&i32) -> &i32) -> i32 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn nested_fn_pointer_3<'a>(_: &'a i32) -> fn(fn(&i32) -> &i32) -> i32 { +LL + fn nested_fn_pointer_3(_: &i32) -> fn(fn(&i32) -> &i32) -> i32 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:416:5 + --> $DIR/needless_lifetimes.rs:418:5 | LL | fn nested_fn_pointer_4<'a>(_: &'a i32) -> impl Fn(fn(&i32)) { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn nested_fn_pointer_4<'a>(_: &'a i32) -> impl Fn(fn(&i32)) { +LL + fn nested_fn_pointer_4(_: &i32) -> impl Fn(fn(&i32)) { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:438:9 + --> $DIR/needless_lifetimes.rs:440:9 | LL | fn implicit<'a>(&'a self) -> &'a () { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn implicit<'a>(&'a self) -> &'a () { +LL + fn implicit(&self) -> &() { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:441:9 + --> $DIR/needless_lifetimes.rs:443:9 | LL | fn implicit_mut<'a>(&'a mut self) -> &'a () { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn implicit_mut<'a>(&'a mut self) -> &'a () { +LL + fn implicit_mut(&mut self) -> &() { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:452:9 + --> $DIR/needless_lifetimes.rs:454:9 | LL | fn lifetime_elsewhere<'a>(self: Box, here: &'a ()) -> &'a () { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn lifetime_elsewhere<'a>(self: Box, here: &'a ()) -> &'a () { +LL + fn lifetime_elsewhere(self: Box, here: &()) -> &() { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:458:9 + --> $DIR/needless_lifetimes.rs:460:9 | LL | fn implicit<'a>(&'a self) -> &'a (); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn implicit<'a>(&'a self) -> &'a (); +LL + fn implicit(&self) -> &(); + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:459:9 + --> $DIR/needless_lifetimes.rs:461:9 | LL | fn implicit_provided<'a>(&'a self) -> &'a () { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn implicit_provided<'a>(&'a self) -> &'a () { +LL + fn implicit_provided(&self) -> &() { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:468:9 + --> $DIR/needless_lifetimes.rs:470:9 | LL | fn lifetime_elsewhere<'a>(self: Box, here: &'a ()) -> &'a (); | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn lifetime_elsewhere<'a>(self: Box, here: &'a ()) -> &'a (); +LL + fn lifetime_elsewhere(self: Box, here: &()) -> &(); + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:469:9 + --> $DIR/needless_lifetimes.rs:471:9 | LL | fn lifetime_elsewhere_provided<'a>(self: Box, here: &'a ()) -> &'a () { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn lifetime_elsewhere_provided<'a>(self: Box, here: &'a ()) -> &'a () { +LL + fn lifetime_elsewhere_provided(self: Box, here: &()) -> &() { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:478:5 + --> $DIR/needless_lifetimes.rs:480:5 | LL | fn foo<'a>(x: &'a u8, y: &'_ u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn foo<'a>(x: &'a u8, y: &'_ u8) {} +LL + fn foo(x: &u8, y: &'_ u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:480:5 + --> $DIR/needless_lifetimes.rs:482:5 | LL | fn bar<'a>(x: &'a u8, y: &'_ u8, z: &'_ u8) {} | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn bar<'a>(x: &'a u8, y: &'_ u8, z: &'_ u8) {} +LL + fn bar(x: &u8, y: &'_ u8, z: &'_ u8) {} + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:487:5 + --> $DIR/needless_lifetimes.rs:489:5 | LL | fn one_input<'a>(x: &'a u8) -> &'a u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn one_input<'a>(x: &'a u8) -> &'a u8 { +LL + fn one_input(x: &u8) -> &u8 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:492:5 + --> $DIR/needless_lifetimes.rs:494:5 | LL | fn multiple_inputs_output_not_elided<'a, 'b>(x: &'a u8, y: &'b u8, z: &'b u8) -> &'b u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ + | +help: elide the lifetimes + | +LL - fn multiple_inputs_output_not_elided<'a, 'b>(x: &'a u8, y: &'b u8, z: &'b u8) -> &'b u8 { +LL + fn multiple_inputs_output_not_elided<'b>(x: &u8, y: &'b u8, z: &'b u8) -> &'b u8 { + | error: the following explicit lifetimes could be elided: 'a - --> $DIR/needless_lifetimes.rs:505:13 + --> $DIR/needless_lifetimes.rs:507:13 | LL | fn one_input<'a>(x: &'a u8) -> &'a u8 { | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ @@ -322,6 +549,11 @@ LL | local_one_input_macro!(); | ------------------------ in this macro invocation | = note: this error originates in the macro `local_one_input_macro` (in Nightly builds, run with -Z macro-backtrace for more info) +help: elide the lifetimes + | +LL - fn one_input<'a>(x: &'a u8) -> &'a u8 { +LL + fn one_input(x: &u8) -> &u8 { + | error: aborting due to 46 previous errors