diff options
Diffstat (limited to 'src/tools/clippy/clippy_lints/src/lifetimes.rs')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/lifetimes.rs | 268 |
1 files changed, 158 insertions, 110 deletions
diff --git a/src/tools/clippy/clippy_lints/src/lifetimes.rs b/src/tools/clippy/clippy_lints/src/lifetimes.rs index 7cf1a6b80..986ffcad8 100644 --- a/src/tools/clippy/clippy_lints/src/lifetimes.rs +++ b/src/tools/clippy/clippy_lints/src/lifetimes.rs @@ -1,21 +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}; +use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::hir::nested_filter as middle_nested_filter; -use rustc_middle::ty::TyCtxt; +use rustc_middle::lint::in_external_macro; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::def_id::LocalDefId; use rustc_span::source_map::Span; @@ -34,8 +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 @@ -93,7 +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_); @@ -106,7 +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, @@ -122,29 +120,21 @@ 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<BodyId>, trait_sig: Option<&[Ident]>, generics: &'tcx Generics<'_>, span: Span, report_extra_lifetimes: bool, ) { - if span.from_expansion() || has_where_lifetimes(cx, generics) { + if in_external_macro(cx.sess(), span) || has_where_lifetimes(cx, generics) { return; } @@ -154,7 +144,11 @@ fn check_fn_inner<'tcx>( .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 !typ.span.eq_ctxt(span) { + return; + } + + for pred in generics.bounds_for_param(typ.def_id) { if pred.origin == PredicateOrigin::WhereClause { // has_where_lifetimes checked that this predicate contains no lifetime. continue; @@ -163,7 +157,7 @@ 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 { @@ -190,12 +184,16 @@ 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) { + if usages.iter().any(|usage| !usage.ident.span.eq_ctxt(span)) { + return; + } + 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::<Vec<_>>() .join(", "); @@ -203,21 +201,99 @@ 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<Vec<(Span, String)>> { + let explicit_params = generics + .params + .iter() + .filter(|param| !param.is_elided_lifetime() && !param.is_impl_trait()) + .collect::<Vec<_>>(); + + 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::<Option<Vec<_>>>()? + }; + + 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<Ident>) -> bool { if_chain! { @@ -237,13 +313,20 @@ fn explicit_self_type<'tcx>(cx: &LateContext<'tcx>, func: &FnDecl<'tcx>, ident: } } +fn named_lifetime(lt: &Lifetime) -> Option<LocalDefId> { + 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<BodyId>, trait_sig: Option<&[Ident]>, named_generics: &'tcx [GenericParam<'_>], -) -> Option<Vec<(LocalDefId, Option<Span>)>> { +) -> Option<(Vec<LocalDefId>, Vec<Lifetime>)> { // 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 @@ -251,7 +334,7 @@ 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); @@ -301,32 +384,24 @@ 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; } } } @@ -338,15 +413,10 @@ 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 } @@ -354,31 +424,34 @@ fn could_use_elision<'tcx>( .collect::<Vec<_>>(); 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<RefLt> { - 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<LocalDefId> { + 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) @@ -392,12 +465,10 @@ 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<RefLt>, - lifetime_generic_arg_spans: FxHashMap<LocalDefId, Span>, - nested_elision_site_lts: Vec<RefLt>, + lts: Vec<Lifetime>, + nested_elision_site_lts: Vec<Lifetime>, unelided_trait_object_lifetime: bool, } @@ -406,32 +477,16 @@ 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<Lifetime>) { - 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<RefLt> { + fn all_lts(&self) -> Vec<Lifetime> { self.lts .iter() .chain(self.nested_elision_site_lts.iter()) - .cloned() + .copied() .collect::<Vec<_>>() } @@ -443,7 +498,7 @@ 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>) { @@ -468,11 +523,7 @@ 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, })); }, @@ -492,13 +543,6 @@ 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 @@ -516,14 +560,18 @@ 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) => { |