use clippy_utils::diagnostics::span_lint;
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};
use rustc_hir::intravisit::{
- walk_fn_decl, walk_generic_param, walk_generics, walk_item, walk_param_bound, walk_poly_trait_ref, walk_ty,
- NestedVisitorMap, Visitor,
+ 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::FnRetTy::Return;
use rustc_hir::{
- BareFnTy, BodyId, FnDecl, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, ImplItem,
- ImplItemKind, Item, ItemKind, LangItem, Lifetime, LifetimeName, ParamName, PolyTraitRef, TraitBoundModifier,
- TraitFn, TraitItem, TraitItemKind, Ty, TyKind, WhereClause, WherePredicate,
+ BareFnTy, BodyId, FnDecl, GenericArg, GenericBound, GenericParam, GenericParamKind, Generics, Impl, ImplItem,
+ ImplItemKind, Item, ItemKind, LangItem, Lifetime, LifetimeName, ParamName, PolyTraitRef, PredicateOrigin,
+ TraitBoundModifier, TraitFn, TraitItem, TraitItemKind, Ty, TyKind, WherePredicate,
};
use rustc_lint::{LateContext, LateLintPass};
-use rustc_middle::hir::map::Map;
+use rustc_middle::hir::nested_filter as middle_nested_filter;
+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;
-use rustc_span::symbol::{kw, Symbol};
+use rustc_span::symbol::{kw, Ident, Symbol};
declare_clippy_lint! {
/// ### What it does
///
/// ### Example
/// ```rust
- /// // Bad: unnecessary lifetime annotations
+ /// // Unnecessary lifetime annotations
/// fn in_and_out<'a>(x: &'a u8, y: u8) -> &'a u8 {
/// x
/// }
+ /// ```
///
- /// // Good
+ /// Use instead:
+ /// ```rust
/// fn elided(x: &u8, y: u8) -> &u8 {
/// x
/// }
///
/// ### Example
/// ```rust
- /// // Bad: unnecessary lifetimes
+ /// // unnecessary lifetimes
/// fn unused_lifetime<'a>(x: u8) {
/// // ..
/// }
+ /// ```
///
- /// // Good
+ /// Use instead:
+ /// ```rust
/// fn no_lifetime(x: u8) {
/// // ...
/// }
impl<'tcx> LateLintPass<'tcx> for Lifetimes {
fn check_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx Item<'_>) {
- if let ItemKind::Fn(ref sig, ref generics, id) = item.kind {
- check_fn_inner(cx, sig.decl, Some(id), generics, item.span, true);
+ if let ItemKind::Fn(ref sig, generics, id) = item.kind {
+ check_fn_inner(cx, sig.decl, 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_);
+ }
}
}
fn check_impl_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx ImplItem<'_>) {
if let ImplItemKind::Fn(ref sig, id) = item.kind {
- let report_extra_lifetimes = trait_ref_of_method(cx, item.hir_id()).is_none();
+ let report_extra_lifetimes = trait_ref_of_method(cx, item.def_id).is_none();
check_fn_inner(
cx,
sig.decl,
Some(id),
- &item.generics,
+ None,
+ item.generics,
item.span,
report_extra_lifetimes,
);
fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
if let TraitItemKind::Fn(ref sig, ref body) = item.kind {
- let body = match *body {
- TraitFn::Required(_) => None,
- TraitFn::Provided(id) => Some(id),
+ let (body, trait_sig) = match *body {
+ TraitFn::Required(sig) => (None, Some(sig)),
+ TraitFn::Provided(id) => (Some(id), None),
};
- check_fn_inner(cx, sig.decl, body, &item.generics, item.span, true);
+ check_fn_inner(cx, sig.decl, body, trait_sig, item.generics, item.span, true);
}
}
}
enum RefLt {
Unnamed,
Static,
- Named(Symbol),
+ Named(LocalDefId),
}
fn check_fn_inner<'tcx>(
cx: &LateContext<'tcx>,
decl: &'tcx FnDecl<'_>,
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.where_clause) {
+ if span.from_expansion() || has_where_lifetimes(cx, generics) {
return;
}
.iter()
.filter(|param| matches!(param.kind, GenericParamKind::Type { .. }));
for typ in types {
- for bound in typ.bounds {
- let mut visitor = RefVisitor::new(cx);
- walk_param_bound(&mut visitor, bound);
- if visitor.lts.iter().any(|lt| matches!(lt, RefLt::Named(_))) {
- return;
+ for pred in generics.bounds_for_param(cx.tcx.hir().local_def_id(typ.hir_id)) {
+ if pred.origin == PredicateOrigin::WhereClause {
+ // has_where_lifetimes checked that this predicate contains no lifetime.
+ continue;
}
- if let GenericBound::Trait(ref trait_ref, _) = *bound {
- let params = &trait_ref
- .trait_ref
- .path
- .segments
- .last()
- .expect("a path must have at least one segment")
- .args;
- if let Some(params) = *params {
- let lifetimes = params.args.iter().filter_map(|arg| match arg {
- GenericArg::Lifetime(lt) => Some(lt),
- _ => None,
- });
- for bound in lifetimes {
- if bound.name != LifetimeName::Static && !bound.is_elided() {
- return;
+
+ 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(_))) {
+ return;
+ }
+ if let GenericBound::Trait(ref trait_ref, _) = *bound {
+ let params = &trait_ref
+ .trait_ref
+ .path
+ .segments
+ .last()
+ .expect("a path must have at least one segment")
+ .args;
+ if let Some(params) = *params {
+ let lifetimes = params.args.iter().filter_map(|arg| match arg {
+ GenericArg::Lifetime(lt) => Some(lt),
+ _ => None,
+ });
+ for bound in lifetimes {
+ if bound.name != LifetimeName::Static && !bound.is_elided() {
+ return;
+ }
}
}
}
}
}
}
- if could_use_elision(cx, decl, body, generics.params) {
+ if could_use_elision(cx, decl, body, trait_sig, generics.params) {
span_lint(
cx,
NEEDLESS_LIFETIMES,
}
}
+// 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! {
+ if let Some(ident) = ident;
+ if ident.name == kw::SelfLower;
+ if !func.implicit_self.has_implicit_self();
+
+ if let Some(self_ty) = func.inputs.first();
+ then {
+ let mut visitor = RefVisitor::new(cx);
+ visitor.visit_ty(self_ty);
+
+ !visitor.all_lts().is_empty()
+ } else {
+ false
+ }
+ }
+}
+
fn could_use_elision<'tcx>(
cx: &LateContext<'tcx>,
func: &'tcx FnDecl<'_>,
body: Option<BodyId>,
+ trait_sig: Option<&[Ident]>,
named_generics: &'tcx [GenericParam<'_>],
) -> bool {
// There are two scenarios where elision works:
// level of the current item.
// check named LTs
- let allowed_lts = allowed_lts_from(named_generics);
+ let allowed_lts = allowed_lts_from(cx.tcx, named_generics);
// these will collect all the lifetimes for references in arg/return types
let mut input_visitor = RefVisitor::new(cx);
return false;
}
- if allowed_lts
- .intersection(
- &input_visitor
- .nested_elision_site_lts
- .iter()
- .chain(output_visitor.nested_elision_site_lts.iter())
- .cloned()
- .filter(|v| matches!(v, RefLt::Named(_)))
- .collect(),
- )
- .next()
- .is_some()
- {
- return false;
- }
-
let input_lts = input_visitor.lts;
let output_lts = output_visitor.lts;
+ if let Some(trait_sig) = trait_sig {
+ if explicit_self_type(cx, func, trait_sig.first().copied()) {
+ return false;
+ }
+ }
+
if let Some(body_id) = body {
+ let body = cx.tcx.hir().body(body_id);
+
+ let first_ident = body.params.first().and_then(|param| param.pat.simple_ident());
+ if explicit_self_type(cx, func, first_ident) {
+ return false;
+ }
+
let mut checker = BodyLifetimeChecker {
lifetimes_used_in_body: false,
};
- checker.visit_expr(&cx.tcx.hir().body(body_id).value);
+ checker.visit_expr(&body.value);
if checker.lifetimes_used_in_body {
return false;
}
}
}
+ // 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();
+ 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;
+ }
+ }
+ }
+ 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;
+ }
+ }
+ }
+ }
+
// no input lifetimes? easy case!
if input_lts.is_empty() {
false
}
}
-fn allowed_lts_from(named_generics: &[GenericParam<'_>]) -> FxHashSet<RefLt> {
+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 {
- if par.bounds.is_empty() {
- allowed_lts.insert(RefLt::Named(par.name.ident().name));
- }
+ allowed_lts.insert(RefLt::Named(tcx.hir().local_def_id(par.hir_id)));
}
}
allowed_lts.insert(RefLt::Unnamed);
if let Some(ref lt) = *lifetime {
if lt.name == LifetimeName::Static {
self.lts.push(RefLt::Static);
- } else if let LifetimeName::Param(ParamName::Fresh(_)) = lt.name {
+ } else if let LifetimeName::Param(_, ParamName::Fresh) = lt.name {
// Fresh lifetimes generated should be ignored.
+ self.lts.push(RefLt::Unnamed);
} else if lt.is_elided() {
self.lts.push(RefLt::Unnamed);
+ } else if let LifetimeName::Param(def_id, _) = lt.name {
+ self.lts.push(RefLt::Named(def_id));
} else {
- self.lts.push(RefLt::Named(lt.name.ident().name));
+ self.lts.push(RefLt::Unnamed);
}
} else {
self.lts.push(RefLt::Unnamed);
}
impl<'a, 'tcx> Visitor<'tcx> for RefVisitor<'a, 'tcx> {
- type Map = Map<'tcx>;
-
// for lifetimes as parameters of generics
fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) {
self.record(&Some(*lifetime));
TyKind::OpaqueDef(item, bounds) => {
let map = self.cx.tcx.hir();
let item = map.item(item);
+ let len = self.lts.len();
walk_item(self, item);
- walk_ty(self, ty);
+ self.lts.truncate(len);
self.lts.extend(bounds.iter().filter_map(|bound| match bound {
- GenericArg::Lifetime(l) => Some(RefLt::Named(l.name.ident().name)),
+ GenericArg::Lifetime(l) => Some(if let LifetimeName::Param(def_id, _) = l.name {
+ RefLt::Named(def_id)
+ } else {
+ RefLt::Unnamed
+ }),
_ => None,
}));
},
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() {
for bound in bounds {
self.visit_poly_trait_ref(bound, TraitBoundModifier::None);
}
- return;
},
- _ => (),
+ _ => walk_ty(self, ty),
}
- walk_ty(self, ty);
- }
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
}
}
/// Are any lifetimes mentioned in the `where` clause? If so, we don't try to
/// reason about elision.
-fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, where_clause: &'tcx WhereClause<'_>) -> bool {
- for predicate in where_clause.predicates {
+fn has_where_lifetimes<'tcx>(cx: &LateContext<'tcx>, generics: &'tcx Generics<'_>) -> bool {
+ for predicate in generics.predicates {
match *predicate {
WherePredicate::RegionPredicate(..) => return true,
WherePredicate::BoundPredicate(ref pred) => {
return true;
}
// if the bounds define new lifetimes, they are fine to occur
- let allowed_lts = allowed_lts_from(pred.bound_generic_params);
+ let allowed_lts = allowed_lts_from(cx.tcx, pred.bound_generic_params);
// now walk the bounds
for bound in pred.bounds.iter() {
walk_param_bound(&mut visitor, bound);
false
}
-struct LifetimeChecker {
+struct LifetimeChecker<'cx, 'tcx, F> {
+ cx: &'cx LateContext<'tcx>,
map: FxHashMap<Symbol, Span>,
+ phantom: std::marker::PhantomData<F>,
}
-impl<'tcx> Visitor<'tcx> for LifetimeChecker {
- type Map = Map<'tcx>;
+impl<'cx, 'tcx, F> LifetimeChecker<'cx, 'tcx, F> {
+ fn new(cx: &'cx LateContext<'tcx>, map: FxHashMap<Symbol, Span>) -> LifetimeChecker<'cx, 'tcx, F> {
+ Self {
+ cx,
+ map,
+ phantom: std::marker::PhantomData,
+ }
+ }
+}
+
+impl<'cx, 'tcx, F> Visitor<'tcx> for LifetimeChecker<'cx, 'tcx, F>
+where
+ F: NestedFilter<'tcx>,
+{
+ type Map = rustc_middle::hir::map::Map<'tcx>;
+ type NestedFilter = F;
// for lifetimes as parameters of generics
fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) {
walk_generic_param(self, param);
}
}
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
+
+ fn nested_visit_map(&mut self) -> Self::Map {
+ self.cx.tcx.hir()
}
}
_ => None,
})
.collect();
- let mut checker = LifetimeChecker { map: hs };
+ let mut checker = LifetimeChecker::<hir_nested_filter::None>::new(cx, hs);
walk_generics(&mut checker, generics);
walk_fn_decl(&mut checker, func);
}
}
+fn report_extra_impl_lifetimes<'tcx>(cx: &LateContext<'tcx>, impl_: &'tcx Impl<'_>) {
+ let hs = impl_
+ .generics
+ .params
+ .iter()
+ .filter_map(|par| match par.kind {
+ GenericParamKind::Lifetime { .. } => Some((par.name.ident().name, par.span)),
+ _ => None,
+ })
+ .collect();
+ let mut checker = LifetimeChecker::<middle_nested_filter::All>::new(cx, hs);
+
+ walk_generics(&mut checker, impl_.generics);
+ if let Some(ref trait_ref) = impl_.of_trait {
+ walk_trait_ref(&mut checker, trait_ref);
+ }
+ walk_ty(&mut checker, impl_.self_ty);
+ for item in impl_.items {
+ walk_impl_item_ref(&mut checker, item);
+ }
+
+ for &v in checker.map.values() {
+ span_lint(cx, EXTRA_UNUSED_LIFETIMES, v, "this lifetime isn't used in the impl");
+ }
+}
+
struct BodyLifetimeChecker {
lifetimes_used_in_body: bool,
}
impl<'tcx> Visitor<'tcx> for BodyLifetimeChecker {
- type Map = Map<'tcx>;
-
// for lifetimes as parameters of generics
fn visit_lifetime(&mut self, lifetime: &'tcx Lifetime) {
- if lifetime.name.ident().name != kw::Empty && lifetime.name.ident().name != kw::StaticLifetime {
+ if lifetime.name.ident().name != kw::UnderscoreLifetime && lifetime.name.ident().name != kw::StaticLifetime {
self.lifetimes_used_in_body = true;
}
}
-
- fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
- NestedVisitorMap::None
- }
}
projects / rust.git / blobdiff