X-Git-Url: https://git.lizzy.rs/?a=blobdiff_plain;f=src%2Ftools%2Fclippy%2Fclippy_lints%2Fsrc%2Flifetimes.rs;h=d7043e7bd8f713ce010fc84c48ef2f70fb48ace2;hb=6b8d25ecda4cbc7266bd1499466dfc5737c9fbdf;hp=4df6827d77f94027551ba7663b1cace0af537c88;hpb=9a74fb726ec40be398c55bce66c6d0b1a91d106c;p=rust.git diff --git a/src/tools/clippy/clippy_lints/src/lifetimes.rs b/src/tools/clippy/clippy_lints/src/lifetimes.rs index 4df6827d77f..d7043e7bd8f 100644 --- a/src/tools/clippy/clippy_lints/src/lifetimes.rs +++ b/src/tools/clippy/clippy_lints/src/lifetimes.rs @@ -1,21 +1,22 @@ +use crate::utils::paths; +use crate::utils::{get_trait_def_id, in_macro, span_lint, trait_ref_of_method}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; -use rustc_hir::def::{DefKind, Res}; use rustc_hir::intravisit::{ - walk_fn_decl, walk_generic_param, walk_generics, walk_param_bound, walk_ty, NestedVisitorMap, Visitor, + walk_fn_decl, walk_generic_param, walk_generics, walk_item, walk_param_bound, walk_poly_trait_ref, walk_ty, + NestedVisitorMap, Visitor, }; use rustc_hir::FnRetTy::Return; use rustc_hir::{ - BodyId, FnDecl, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, ImplItem, ImplItemKind, Item, - ItemKind, Lifetime, LifetimeName, ParamName, QPath, TraitBoundModifier, TraitFn, TraitItem, TraitItemKind, Ty, - TyKind, WhereClause, WherePredicate, + BareFnTy, BodyId, FnDecl, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, ImplItem, + ImplItemKind, Item, ItemKind, Lifetime, LifetimeName, ParamName, PolyTraitRef, TraitBoundModifier, TraitFn, + TraitItem, TraitItemKind, Ty, TyKind, WhereClause, WherePredicate, }; use rustc_lint::{LateContext, LateLintPass}; use rustc_middle::hir::map::Map; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; use rustc_span::symbol::{kw, Symbol}; - -use crate::utils::{in_macro, last_path_segment, span_lint, trait_ref_of_method}; +use std::iter::FromIterator; declare_clippy_lint! { /// **What it does:** Checks for lifetime annotations which can be removed by @@ -25,8 +26,11 @@ /// complicated, while there is nothing out of the ordinary going on. Removing /// them leads to more readable code. /// - /// **Known problems:** Potential false negatives: we bail out if the function - /// has a `where` clause where lifetimes are mentioned. + /// **Known problems:** + /// - We bail out if the function has a `where` clause where lifetimes + /// are mentioned due to potenial 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 @@ -108,7 +112,7 @@ fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_> } /// The lifetime of a &-reference. -#[derive(PartialEq, Eq, Hash, Debug)] +#[derive(PartialEq, Eq, Hash, Debug, Clone)] enum RefLt { Unnamed, Static, @@ -127,7 +131,6 @@ fn check_fn_inner<'tcx>( return; } - let mut bounds_lts = Vec::new(); let types = generics .params .iter() @@ -156,13 +159,12 @@ fn check_fn_inner<'tcx>( if bound.name != LifetimeName::Static && !bound.is_elided() { return; } - bounds_lts.push(bound); } } } } } - if could_use_elision(cx, decl, body, &generics.params, bounds_lts) { + if could_use_elision(cx, decl, body, &generics.params) { span_lint( cx, NEEDLESS_LIFETIMES, @@ -181,7 +183,6 @@ fn could_use_elision<'tcx>( func: &'tcx FnDecl<'_>, body: Option, named_generics: &'tcx [GenericParam<'_>], - bounds_lts: Vec<&'tcx Lifetime>, ) -> bool { // There are two scenarios where elision works: // * no output references, all input references have different LT @@ -204,15 +205,31 @@ fn could_use_elision<'tcx>( if let Return(ref ty) = func.output { output_visitor.visit_ty(ty); } + for lt in named_generics { + input_visitor.visit_generic_param(lt) + } + + if input_visitor.abort() || output_visitor.abort() { + return false; + } - let input_lts = match input_visitor.into_vec() { - Some(lts) => lts_from_bounds(lts, bounds_lts.into_iter()), - None => return false, - }; - let output_lts = match output_visitor.into_vec() { - Some(val) => val, - None => return false, - }; + if allowed_lts + .intersection(&FxHashSet::from_iter( + input_visitor + .nested_elision_site_lts + .iter() + .chain(output_visitor.nested_elision_site_lts.iter()) + .cloned() + .filter(|v| matches!(v, RefLt::Named(_))), + )) + .next() + .is_some() + { + return false; + } + + let input_lts = input_visitor.lts; + let output_lts = output_visitor.lts; if let Some(body_id) = body { let mut checker = BodyLifetimeChecker { @@ -277,27 +294,20 @@ fn allowed_lts_from(named_generics: &[GenericParam<'_>]) -> FxHashSet { allowed_lts } -fn lts_from_bounds<'a, T: Iterator>(mut vec: Vec, bounds_lts: T) -> Vec { - for lt in bounds_lts { - if lt.name != LifetimeName::Static { - vec.push(RefLt::Named(lt.name.ident().name)); - } - } - - vec -} - /// Number of unique lifetimes in the given vector. #[must_use] fn unique_lifetimes(lts: &[RefLt]) -> usize { lts.iter().collect::>().len() } +const CLOSURE_TRAIT_BOUNDS: [&[&str]; 3] = [&paths::FN, &paths::FN_MUT, &paths::FN_ONCE]; + /// A visitor usable for `rustc_front::visit::walk_ty()`. struct RefVisitor<'a, 'tcx> { cx: &'a LateContext<'tcx>, lts: Vec, - abort: bool, + nested_elision_site_lts: Vec, + unelided_trait_object_lifetime: bool, } impl<'a, 'tcx> RefVisitor<'a, 'tcx> { @@ -305,7 +315,8 @@ fn new(cx: &'a LateContext<'tcx>) -> Self { Self { cx, lts: Vec::new(), - abort: false, + nested_elision_site_lts: Vec::new(), + unelided_trait_object_lifetime: false, } } @@ -325,40 +336,16 @@ fn record(&mut self, lifetime: &Option) { } } - fn into_vec(self) -> Option> { - if self.abort { - None - } else { - Some(self.lts) - } + fn all_lts(&self) -> Vec { + self.lts + .iter() + .chain(self.nested_elision_site_lts.iter()) + .cloned() + .collect::>() } - fn collect_anonymous_lifetimes(&mut self, qpath: &QPath<'_>, ty: &Ty<'_>) { - if let Some(ref last_path_segment) = last_path_segment(qpath).args { - if !last_path_segment.parenthesized - && !last_path_segment - .args - .iter() - .any(|arg| matches!(arg, GenericArg::Lifetime(_))) - { - let hir_id = ty.hir_id; - match self.cx.qpath_res(qpath, hir_id) { - Res::Def(DefKind::TyAlias | DefKind::Struct, def_id) => { - let generics = self.cx.tcx.generics_of(def_id); - for _ in generics.params.as_slice() { - self.record(&None); - } - }, - Res::Def(DefKind::Trait, def_id) => { - let trait_def = self.cx.tcx.trait_def(def_id); - for _ in &self.cx.tcx.generics_of(trait_def.def_id).params { - self.record(&None); - } - }, - _ => (), - } - } - } + fn abort(&self) -> bool { + self.unelided_trait_object_lifetime } } @@ -370,30 +357,37 @@ fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) { self.record(&Some(*lifetime)); } + fn visit_poly_trait_ref(&mut self, poly_tref: &'tcx PolyTraitRef<'tcx>, tbm: TraitBoundModifier) { + let trait_ref = &poly_tref.trait_ref; + if CLOSURE_TRAIT_BOUNDS + .iter() + .any(|trait_path| trait_ref.trait_def_id() == get_trait_def_id(self.cx, trait_path)) + { + let mut sub_visitor = RefVisitor::new(self.cx); + sub_visitor.visit_trait_ref(trait_ref); + self.nested_elision_site_lts.append(&mut sub_visitor.all_lts()); + } else { + walk_poly_trait_ref(self, poly_tref, tbm); + } + } + fn visit_ty(&mut self, ty: &'tcx Ty<'_>) { match ty.kind { - TyKind::Rptr(ref lt, _) if lt.is_elided() => { - self.record(&None); - }, - TyKind::Path(ref path) => { - self.collect_anonymous_lifetimes(path, ty); - }, TyKind::OpaqueDef(item, _) => { let map = self.cx.tcx.hir(); - if let ItemKind::OpaqueTy(ref exist_ty) = map.expect_item(item.id).kind { - for bound in exist_ty.bounds { - if let GenericBound::Outlives(_) = *bound { - self.record(&None); - } - } - } else { - unreachable!() - } + let item = map.expect_item(item.id); + walk_item(self, item); walk_ty(self, ty); }, + TyKind::BareFn(&BareFnTy { decl, .. }) => { + let mut sub_visitor = RefVisitor::new(self.cx); + sub_visitor.visit_fn_decl(decl); + self.nested_elision_site_lts.append(&mut sub_visitor.all_lts()); + return; + }, TyKind::TraitObject(bounds, ref lt) => { if !lt.is_elided() { - self.abort = true; + self.unelided_trait_object_lifetime = true; } for bound in bounds { self.visit_poly_trait_ref(bound, TraitBoundModifier::None); @@ -430,16 +424,7 @@ fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, where_clause: &'tcx WhereCl walk_param_bound(&mut visitor, bound); } // and check that all lifetimes are allowed - match visitor.into_vec() { - None => return false, - Some(lts) => { - for lt in lts { - if !allowed_lts.contains(<) { - return true; - } - } - }, - } + return visitor.all_lts().iter().any(|it| !allowed_lts.contains(it)); }, WherePredicate::EqPredicate(ref pred) => { let mut visitor = RefVisitor::new(cx);