1 // Copyright 2012-2013 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! Name resolution for lifetimes.
13 //! Name resolution for lifetimes follows MUCH simpler rules than the
14 //! full resolve. For example, lifetime names are never exported or
15 //! used between functions, and they operate in a purely top-down
16 //! way. Therefore we break lifetime name resolution into a separate pass.
21 use hir::def_id::DefId;
26 use std::mem::replace;
30 use syntax::symbol::keywords;
32 use errors::DiagnosticBuilder;
33 use util::nodemap::{NodeMap, NodeSet, FxHashSet, FxHashMap, DefIdMap};
34 use rustc_back::slice;
37 use hir::intravisit::{self, Visitor, NestedVisitorMap};
39 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
42 EarlyBound(/* index */ u32, /* lifetime decl */ ast::NodeId),
43 LateBound(ty::DebruijnIndex, /* lifetime decl */ ast::NodeId),
44 LateBoundAnon(ty::DebruijnIndex, /* anon index */ u32),
45 Free(region::CallSiteScopeData, /* lifetime decl */ ast::NodeId),
49 fn early(index: &mut u32, def: &hir::LifetimeDef) -> (ast::Name, Region) {
52 (def.lifetime.name, Region::EarlyBound(i, def.lifetime.id))
55 fn late(def: &hir::LifetimeDef) -> (ast::Name, Region) {
56 let depth = ty::DebruijnIndex::new(1);
57 (def.lifetime.name, Region::LateBound(depth, def.lifetime.id))
60 fn late_anon(index: &Cell<u32>) -> Region {
63 let depth = ty::DebruijnIndex::new(1);
64 Region::LateBoundAnon(depth, i)
67 fn id(&self) -> Option<ast::NodeId> {
70 Region::LateBoundAnon(..) => None,
72 Region::EarlyBound(_, id) |
73 Region::LateBound(_, id) |
74 Region::Free(_, id) => Some(id)
78 fn shifted(self, amount: u32) -> Region {
80 Region::LateBound(depth, id) => {
81 Region::LateBound(depth.shifted(amount), id)
83 Region::LateBoundAnon(depth, index) => {
84 Region::LateBoundAnon(depth.shifted(amount), index)
90 fn from_depth(self, depth: u32) -> Region {
92 Region::LateBound(debruijn, id) => {
93 Region::LateBound(ty::DebruijnIndex {
94 depth: debruijn.depth - (depth - 1)
97 Region::LateBoundAnon(debruijn, index) => {
98 Region::LateBoundAnon(ty::DebruijnIndex {
99 depth: debruijn.depth - (depth - 1)
106 fn subst(self, params: &[hir::Lifetime], map: &NamedRegionMap)
108 if let Region::EarlyBound(index, _) = self {
109 params.get(index as usize).and_then(|lifetime| {
110 map.defs.get(&lifetime.id).cloned()
118 /// A set containing, at most, one known element.
119 /// If two distinct values are inserted into a set, then it
120 /// becomes `Many`, which can be used to detect ambiguities.
121 #[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Debug)]
128 impl<T: PartialEq> Set1<T> {
129 pub fn insert(&mut self, value: T) {
130 if let Set1::Empty = *self {
131 *self = Set1::One(value);
134 if let Set1::One(ref old) = *self {
143 pub type ObjectLifetimeDefault = Set1<Region>;
145 // Maps the id of each lifetime reference to the lifetime decl
146 // that it corresponds to.
147 pub struct NamedRegionMap {
148 // maps from every use of a named (not anonymous) lifetime to a
149 // `Region` describing how that region is bound
150 pub defs: NodeMap<Region>,
152 // the set of lifetime def ids that are late-bound; a region can
153 // be late-bound if (a) it does NOT appear in a where-clause and
154 // (b) it DOES appear in the arguments.
155 pub late_bound: NodeSet,
157 // Contains the node-ids for lifetimes that were (incorrectly) categorized
158 // as late-bound, until #32330 was fixed.
159 pub issue_32330: NodeMap<ty::Issue32330>,
161 // For each type and trait definition, maps type parameters
162 // to the trait object lifetime defaults computed from them.
163 pub object_lifetime_defaults: NodeMap<Vec<ObjectLifetimeDefault>>,
166 struct LifetimeContext<'a, 'tcx: 'a> {
168 hir_map: &'a Map<'tcx>,
169 map: &'a mut NamedRegionMap,
171 // Deep breath. Our representation for poly trait refs contains a single
172 // binder and thus we only allow a single level of quantification. However,
173 // the syntax of Rust permits quantification in two places, e.g., `T: for <'a> Foo<'a>`
174 // and `for <'a, 'b> &'b T: Foo<'a>`. In order to get the de Bruijn indices
175 // correct when representing these constraints, we should only introduce one
176 // scope. However, we want to support both locations for the quantifier and
177 // during lifetime resolution we want precise information (so we can't
178 // desugar in an earlier phase).
180 // SO, if we encounter a quantifier at the outer scope, we set
181 // trait_ref_hack to true (and introduce a scope), and then if we encounter
182 // a quantifier at the inner scope, we error. If trait_ref_hack is false,
183 // then we introduce the scope at the inner quantifier.
186 trait_ref_hack: bool,
188 // List of labels in the function/method currently under analysis.
189 labels_in_fn: Vec<(ast::Name, Span)>,
191 // Cache for cross-crate per-definition object lifetime defaults.
192 xcrate_object_lifetime_defaults: DefIdMap<Vec<ObjectLifetimeDefault>>,
197 /// Declares lifetimes, and each can be early-bound or late-bound.
198 /// The `DebruijnIndex` of late-bound lifetimes starts at `1` and
199 /// it should be shifted by the number of `Binder`s in between the
200 /// declaration `Binder` and the location it's referenced from.
202 lifetimes: FxHashMap<ast::Name, Region>,
206 /// Lifetimes introduced by a fn are scoped to the call-site for that fn,
207 /// if this is a fn body, otherwise the original definitions are used.
208 /// Unspecified lifetimes are inferred, unless an elision scope is nested,
209 /// e.g. `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`.
215 /// A scope which either determines unspecified lifetimes or errors
216 /// on them (e.g. due to ambiguity). For more details, see `Elide`.
222 /// Use a specific lifetime (if `Some`) or leave it unset (to be
223 /// inferred in a function body or potentially error outside one),
224 /// for the default choice of lifetime in a trait object type.
225 ObjectLifetimeDefault {
226 lifetime: Option<Region>,
233 #[derive(Clone, Debug)]
235 /// Use a fresh anonymous late-bound lifetime each time, by
236 /// incrementing the counter to generate sequential indices.
237 FreshLateAnon(Cell<u32>),
238 /// Always use this one lifetime.
240 /// Less or more than one lifetime were found, error on unspecified.
241 Error(Vec<ElisionFailureInfo>)
244 #[derive(Clone, Debug)]
245 struct ElisionFailureInfo {
246 /// Where we can find the argument pattern.
247 parent: Option<hir::BodyId>,
248 /// The index of the argument in the original definition.
250 lifetime_count: usize,
251 have_bound_regions: bool
254 type ScopeRef<'a> = &'a Scope<'a>;
256 const ROOT_SCOPE: ScopeRef<'static> = &Scope::Root;
258 pub fn krate(sess: &Session,
260 -> Result<NamedRegionMap, usize> {
261 let krate = hir_map.krate();
262 let mut map = NamedRegionMap {
264 late_bound: NodeSet(),
265 issue_32330: NodeMap(),
266 object_lifetime_defaults: compute_object_lifetime_defaults(sess, hir_map),
268 sess.track_errors(|| {
269 let mut visitor = LifetimeContext {
274 trait_ref_hack: false,
275 labels_in_fn: vec![],
276 xcrate_object_lifetime_defaults: DefIdMap(),
278 for (_, item) in &krate.items {
279 visitor.visit_item(item);
285 impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
286 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
287 NestedVisitorMap::All(self.hir_map)
290 // We want to nest trait/impl items in their parent, but nothing else.
291 fn visit_nested_item(&mut self, _: hir::ItemId) {}
293 fn visit_nested_body(&mut self, body: hir::BodyId) {
294 // Each body has their own set of labels, save labels.
295 let saved = replace(&mut self.labels_in_fn, vec![]);
296 let body = self.hir_map.body(body);
297 extract_labels(self, body);
298 self.with(Scope::Body { id: body.id(), s: self.scope }, |_, this| {
299 this.visit_body(body);
301 replace(&mut self.labels_in_fn, saved);
304 fn visit_item(&mut self, item: &'tcx hir::Item) {
306 hir::ItemFn(ref decl, _, _, _, ref generics, _) => {
307 self.visit_early_late(item.id, None, decl, generics, |this| {
308 intravisit::walk_item(this, item);
311 hir::ItemExternCrate(_) |
314 hir::ItemDefaultImpl(..) |
315 hir::ItemForeignMod(..) |
316 hir::ItemGlobalAsm(..) => {
317 // These sorts of items have no lifetime parameters at all.
318 intravisit::walk_item(self, item);
320 hir::ItemStatic(..) |
321 hir::ItemConst(..) => {
322 // No lifetime parameters, but implied 'static.
323 let scope = Scope::Elision {
324 elide: Elide::Exact(Region::Static),
327 self.with(scope, |_, this| intravisit::walk_item(this, item));
329 hir::ItemTy(_, ref generics) |
330 hir::ItemEnum(_, ref generics) |
331 hir::ItemStruct(_, ref generics) |
332 hir::ItemUnion(_, ref generics) |
333 hir::ItemTrait(_, ref generics, ..) |
334 hir::ItemImpl(_, _, _, ref generics, ..) => {
335 // These kinds of items have only early bound lifetime parameters.
336 let mut index = if let hir::ItemTrait(..) = item.node {
337 1 // Self comes before lifetimes
341 let lifetimes = generics.lifetimes.iter().map(|def| {
342 Region::early(&mut index, def)
344 let scope = Scope::Binder {
345 lifetimes: lifetimes,
348 self.with(scope, |old_scope, this| {
349 this.check_lifetime_defs(old_scope, &generics.lifetimes);
350 intravisit::walk_item(this, item);
356 fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem) {
358 hir::ForeignItemFn(ref decl, _, ref generics) => {
359 self.visit_early_late(item.id, None, decl, generics, |this| {
360 intravisit::walk_foreign_item(this, item);
363 hir::ForeignItemStatic(..) => {
364 intravisit::walk_foreign_item(self, item);
369 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
371 hir::TyBareFn(ref c) => {
372 let scope = Scope::Binder {
373 lifetimes: c.lifetimes.iter().map(Region::late).collect(),
376 self.with(scope, |old_scope, this| {
377 // a bare fn has no bounds, so everything
378 // contained within is scoped within its binder.
379 this.check_lifetime_defs(old_scope, &c.lifetimes);
380 intravisit::walk_ty(this, ty);
383 hir::TyTraitObject(ref bounds, ref lifetime) => {
384 for bound in bounds {
385 self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
387 if lifetime.is_elided() {
388 self.resolve_object_lifetime_default(lifetime)
390 self.visit_lifetime(lifetime);
393 hir::TyRptr(ref lifetime_ref, ref mt) => {
394 self.visit_lifetime(lifetime_ref);
395 let scope = Scope::ObjectLifetimeDefault {
396 lifetime: self.map.defs.get(&lifetime_ref.id).cloned(),
399 self.with(scope, |_, this| this.visit_ty(&mt.ty));
402 intravisit::walk_ty(self, ty)
407 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
408 if let hir::TraitItemKind::Method(ref sig, _) = trait_item.node {
409 self.visit_early_late(
411 Some(self.hir_map.get_parent(trait_item.id)),
412 &sig.decl, &sig.generics,
413 |this| intravisit::walk_trait_item(this, trait_item))
415 intravisit::walk_trait_item(self, trait_item);
419 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem) {
420 if let hir::ImplItemKind::Method(ref sig, _) = impl_item.node {
421 self.visit_early_late(
423 Some(self.hir_map.get_parent(impl_item.id)),
424 &sig.decl, &sig.generics,
425 |this| intravisit::walk_impl_item(this, impl_item))
427 intravisit::walk_impl_item(self, impl_item);
431 fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
432 if lifetime_ref.is_elided() {
433 self.resolve_elided_lifetimes(slice::ref_slice(lifetime_ref));
436 if lifetime_ref.is_static() {
437 self.insert_lifetime(lifetime_ref, Region::Static);
440 self.resolve_lifetime_ref(lifetime_ref);
443 fn visit_path(&mut self, path: &'tcx hir::Path, _: ast::NodeId) {
444 for (i, segment) in path.segments.iter().enumerate() {
445 let depth = path.segments.len() - i - 1;
446 self.visit_segment_parameters(path.def, depth, &segment.parameters);
450 fn visit_fn_decl(&mut self, fd: &'tcx hir::FnDecl) {
451 let output = match fd.output {
452 hir::DefaultReturn(_) => None,
453 hir::Return(ref ty) => Some(ty)
455 self.visit_fn_like_elision(&fd.inputs, output);
458 fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
459 for ty_param in generics.ty_params.iter() {
460 walk_list!(self, visit_ty_param_bound, &ty_param.bounds);
461 if let Some(ref ty) = ty_param.default {
465 for predicate in &generics.where_clause.predicates {
467 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate{ ref bounded_ty,
471 if !bound_lifetimes.is_empty() {
472 self.trait_ref_hack = true;
473 let scope = Scope::Binder {
474 lifetimes: bound_lifetimes.iter().map(Region::late).collect(),
477 let result = self.with(scope, |old_scope, this| {
478 this.check_lifetime_defs(old_scope, bound_lifetimes);
479 this.visit_ty(&bounded_ty);
480 walk_list!(this, visit_ty_param_bound, bounds);
482 self.trait_ref_hack = false;
485 self.visit_ty(&bounded_ty);
486 walk_list!(self, visit_ty_param_bound, bounds);
489 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
493 self.visit_lifetime(lifetime);
494 for bound in bounds {
495 self.visit_lifetime(bound);
498 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ref lhs_ty,
501 self.visit_ty(lhs_ty);
502 self.visit_ty(rhs_ty);
508 fn visit_poly_trait_ref(&mut self,
509 trait_ref: &'tcx hir::PolyTraitRef,
510 _modifier: hir::TraitBoundModifier) {
511 debug!("visit_poly_trait_ref trait_ref={:?}", trait_ref);
513 if !self.trait_ref_hack || !trait_ref.bound_lifetimes.is_empty() {
514 if self.trait_ref_hack {
515 span_err!(self.sess, trait_ref.span, E0316,
516 "nested quantification of lifetimes");
518 let scope = Scope::Binder {
519 lifetimes: trait_ref.bound_lifetimes.iter().map(Region::late).collect(),
522 self.with(scope, |old_scope, this| {
523 this.check_lifetime_defs(old_scope, &trait_ref.bound_lifetimes);
524 for lifetime in &trait_ref.bound_lifetimes {
525 this.visit_lifetime_def(lifetime);
527 this.visit_trait_ref(&trait_ref.trait_ref)
530 self.visit_trait_ref(&trait_ref.trait_ref)
535 #[derive(Copy, Clone, PartialEq)]
536 enum ShadowKind { Label, Lifetime }
537 struct Original { kind: ShadowKind, span: Span }
538 struct Shadower { kind: ShadowKind, span: Span }
540 fn original_label(span: Span) -> Original {
541 Original { kind: ShadowKind::Label, span: span }
543 fn shadower_label(span: Span) -> Shadower {
544 Shadower { kind: ShadowKind::Label, span: span }
546 fn original_lifetime(span: Span) -> Original {
547 Original { kind: ShadowKind::Lifetime, span: span }
549 fn shadower_lifetime(l: &hir::Lifetime) -> Shadower {
550 Shadower { kind: ShadowKind::Lifetime, span: l.span }
554 fn desc(&self) -> &'static str {
556 ShadowKind::Label => "label",
557 ShadowKind::Lifetime => "lifetime",
562 fn signal_shadowing_problem(sess: &Session, name: ast::Name, orig: Original, shadower: Shadower) {
563 let mut err = if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
564 // lifetime/lifetime shadowing is an error
565 struct_span_err!(sess, shadower.span, E0496,
566 "{} name `{}` shadows a \
567 {} name that is already in scope",
568 shadower.kind.desc(), name, orig.kind.desc())
570 // shadowing involving a label is only a warning, due to issues with
571 // labels and lifetimes not being macro-hygienic.
572 sess.struct_span_warn(shadower.span,
573 &format!("{} name `{}` shadows a \
574 {} name that is already in scope",
575 shadower.kind.desc(), name, orig.kind.desc()))
577 err.span_label(orig.span, &"first declared here");
578 err.span_label(shadower.span,
579 &format!("lifetime {} already in scope", name));
583 // Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
584 // if one of the label shadows a lifetime or another label.
585 fn extract_labels(ctxt: &mut LifetimeContext, body: &hir::Body) {
586 struct GatherLabels<'a, 'tcx: 'a> {
588 hir_map: &'a Map<'tcx>,
590 labels_in_fn: &'a mut Vec<(ast::Name, Span)>,
593 let mut gather = GatherLabels {
595 hir_map: ctxt.hir_map,
597 labels_in_fn: &mut ctxt.labels_in_fn,
599 gather.visit_body(body);
601 impl<'v, 'a, 'tcx> Visitor<'v> for GatherLabels<'a, 'tcx> {
602 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
603 NestedVisitorMap::None
606 fn visit_expr(&mut self, ex: &hir::Expr) {
607 if let Some((label, label_span)) = expression_label(ex) {
608 for &(prior, prior_span) in &self.labels_in_fn[..] {
609 // FIXME (#24278): non-hygienic comparison
611 signal_shadowing_problem(self.sess,
613 original_label(prior_span),
614 shadower_label(label_span));
618 check_if_label_shadows_lifetime(self.sess,
624 self.labels_in_fn.push((label, label_span));
626 intravisit::walk_expr(self, ex)
630 fn expression_label(ex: &hir::Expr) -> Option<(ast::Name, Span)> {
632 hir::ExprWhile(.., Some(label)) |
633 hir::ExprLoop(_, Some(label), _) => Some((label.node, label.span)),
638 fn check_if_label_shadows_lifetime<'a>(sess: &'a Session,
640 mut scope: ScopeRef<'a>,
645 Scope::Body { s, .. } |
646 Scope::Elision { s, .. } |
647 Scope::ObjectLifetimeDefault { s, .. } => { scope = s; }
649 Scope::Root => { return; }
651 Scope::Binder { ref lifetimes, s } => {
652 // FIXME (#24278): non-hygienic comparison
653 if let Some(def) = lifetimes.get(&label) {
654 signal_shadowing_problem(
657 original_lifetime(hir_map.span(def.id().unwrap())),
658 shadower_label(label_span));
668 fn compute_object_lifetime_defaults(sess: &Session, hir_map: &Map)
669 -> NodeMap<Vec<ObjectLifetimeDefault>> {
670 let mut map = NodeMap();
671 for item in hir_map.krate().items.values() {
673 hir::ItemStruct(_, ref generics) |
674 hir::ItemUnion(_, ref generics) |
675 hir::ItemEnum(_, ref generics) |
676 hir::ItemTy(_, ref generics) |
677 hir::ItemTrait(_, ref generics, ..) => {
678 let result = object_lifetime_defaults_for_item(hir_map, generics);
681 if attr::contains_name(&item.attrs, "rustc_object_lifetime_default") {
682 let object_lifetime_default_reprs: String =
683 result.iter().map(|set| {
685 Set1::Empty => "BaseDefault".to_string(),
686 Set1::One(Region::Static) => "'static".to_string(),
687 Set1::One(Region::EarlyBound(i, _)) => {
688 generics.lifetimes[i as usize].lifetime.name.to_string()
690 Set1::One(_) => bug!(),
691 Set1::Many => "Ambiguous".to_string(),
693 }).collect::<Vec<String>>().join(",");
694 sess.span_err(item.span, &object_lifetime_default_reprs);
697 map.insert(item.id, result);
705 /// Scan the bounds and where-clauses on parameters to extract bounds
706 /// of the form `T:'a` so as to determine the `ObjectLifetimeDefault`
707 /// for each type parameter.
708 fn object_lifetime_defaults_for_item(hir_map: &Map, generics: &hir::Generics)
709 -> Vec<ObjectLifetimeDefault> {
710 fn add_bounds(set: &mut Set1<ast::Name>, bounds: &[hir::TyParamBound]) {
711 for bound in bounds {
712 if let hir::RegionTyParamBound(ref lifetime) = *bound {
713 set.insert(lifetime.name);
718 generics.ty_params.iter().map(|param| {
719 let mut set = Set1::Empty;
721 add_bounds(&mut set, ¶m.bounds);
723 let param_def_id = hir_map.local_def_id(param.id);
724 for predicate in &generics.where_clause.predicates {
725 // Look for `type: ...` where clauses.
726 let data = match *predicate {
727 hir::WherePredicate::BoundPredicate(ref data) => data,
731 // Ignore `for<'a> type: ...` as they can change what
732 // lifetimes mean (although we could "just" handle it).
733 if !data.bound_lifetimes.is_empty() {
737 let def = match data.bounded_ty.node {
738 hir::TyPath(hir::QPath::Resolved(None, ref path)) => path.def,
742 if def == Def::TyParam(param_def_id) {
743 add_bounds(&mut set, &data.bounds);
748 Set1::Empty => Set1::Empty,
750 if name == keywords::StaticLifetime.name() {
751 Set1::One(Region::Static)
753 generics.lifetimes.iter().enumerate().find(|&(_, def)| {
754 def.lifetime.name == name
755 }).map_or(Set1::Many, |(i, def)| {
756 Set1::One(Region::EarlyBound(i as u32, def.lifetime.id))
760 Set1::Many => Set1::Many
765 impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
766 // FIXME(#37666) this works around a limitation in the region inferencer
767 fn hack<F>(&mut self, f: F) where
768 F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>),
773 fn with<F>(&mut self, wrap_scope: Scope, f: F) where
774 F: for<'b> FnOnce(ScopeRef, &mut LifetimeContext<'b, 'tcx>),
776 let LifetimeContext {sess, hir_map, ref mut map, ..} = *self;
777 let labels_in_fn = replace(&mut self.labels_in_fn, vec![]);
778 let xcrate_object_lifetime_defaults =
779 replace(&mut self.xcrate_object_lifetime_defaults, DefIdMap());
780 let mut this = LifetimeContext {
785 trait_ref_hack: self.trait_ref_hack,
786 labels_in_fn: labels_in_fn,
787 xcrate_object_lifetime_defaults: xcrate_object_lifetime_defaults,
789 debug!("entering scope {:?}", this.scope);
790 f(self.scope, &mut this);
791 debug!("exiting scope {:?}", this.scope);
792 self.labels_in_fn = this.labels_in_fn;
793 self.xcrate_object_lifetime_defaults = this.xcrate_object_lifetime_defaults;
796 /// Visits self by adding a scope and handling recursive walk over the contents with `walk`.
798 /// Handles visiting fns and methods. These are a bit complicated because we must distinguish
799 /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear
800 /// within type bounds; those are early bound lifetimes, and the rest are late bound.
804 /// fn foo<'a,'b,'c,T:Trait<'b>>(...)
806 /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound
807 /// lifetimes may be interspersed together.
809 /// If early bound lifetimes are present, we separate them into their own list (and likewise
810 /// for late bound). They will be numbered sequentially, starting from the lowest index that is
811 /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late
812 /// bound lifetimes are resolved by name and associated with a binder id (`binder_id`), so the
813 /// ordering is not important there.
814 fn visit_early_late<F>(&mut self,
816 parent_id: Option<ast::NodeId>,
817 decl: &'tcx hir::FnDecl,
818 generics: &'tcx hir::Generics,
820 F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
822 let fn_def_id = self.hir_map.local_def_id(fn_id);
823 insert_late_bound_lifetimes(self.map,
828 // Find the start of nested early scopes, e.g. in methods.
830 if let Some(parent_id) = parent_id {
831 let parent = self.hir_map.expect_item(parent_id);
832 if let hir::ItemTrait(..) = parent.node {
833 index += 1; // Self comes first.
836 hir::ItemTrait(_, ref generics, ..) |
837 hir::ItemImpl(_, _, _, ref generics, ..) => {
838 index += (generics.lifetimes.len() + generics.ty_params.len()) as u32;
844 let lifetimes = generics.lifetimes.iter().map(|def| {
845 if self.map.late_bound.contains(&def.lifetime.id) {
848 Region::early(&mut index, def)
852 let scope = Scope::Binder {
853 lifetimes: lifetimes,
856 self.with(scope, move |old_scope, this| {
857 this.check_lifetime_defs(old_scope, &generics.lifetimes);
858 this.hack(walk); // FIXME(#37666) workaround in place of `walk(this)`
862 fn resolve_lifetime_ref(&mut self, lifetime_ref: &hir::Lifetime) {
863 // Walk up the scope chain, tracking the number of fn scopes
864 // that we pass through, until we find a lifetime with the
865 // given name or we run out of scopes.
867 let mut late_depth = 0;
868 let mut scope = self.scope;
869 let mut outermost_body = None;
872 Scope::Body { id, s } => {
873 outermost_body = Some(id);
881 Scope::Binder { ref lifetimes, s } => {
882 if let Some(&def) = lifetimes.get(&lifetime_ref.name) {
883 break Some(def.shifted(late_depth));
890 Scope::Elision { s, .. } |
891 Scope::ObjectLifetimeDefault { s, .. } => {
897 if let Some(mut def) = result {
898 if let Some(body_id) = outermost_body {
899 let fn_id = self.hir_map.body_owner(body_id);
900 let scope_data = region::CallSiteScopeData {
901 fn_id: fn_id, body_id: body_id.node_id
903 match self.hir_map.get(fn_id) {
904 hir::map::NodeItem(&hir::Item {
905 node: hir::ItemFn(..), ..
907 hir::map::NodeTraitItem(&hir::TraitItem {
908 node: hir::TraitItemKind::Method(..), ..
910 hir::map::NodeImplItem(&hir::ImplItem {
911 node: hir::ImplItemKind::Method(..), ..
913 def = Region::Free(scope_data, def.id().unwrap());
918 self.insert_lifetime(lifetime_ref, def);
920 struct_span_err!(self.sess, lifetime_ref.span, E0261,
921 "use of undeclared lifetime name `{}`", lifetime_ref.name)
922 .span_label(lifetime_ref.span, &format!("undeclared lifetime"))
927 fn visit_segment_parameters(&mut self,
930 params: &'tcx hir::PathParameters) {
931 let data = match *params {
932 hir::ParenthesizedParameters(ref data) => {
933 self.visit_fn_like_elision(&data.inputs, data.output.as_ref());
936 hir::AngleBracketedParameters(ref data) => data
939 if data.lifetimes.iter().all(|l| l.is_elided()) {
940 self.resolve_elided_lifetimes(&data.lifetimes);
942 for l in &data.lifetimes { self.visit_lifetime(l); }
945 // Figure out if this is a type/trait segment,
946 // which requires object lifetime defaults.
947 let parent_def_id = |this: &mut Self, def_id: DefId| {
948 let def_key = if def_id.is_local() {
949 this.hir_map.def_key(def_id)
951 this.sess.cstore.def_key(def_id)
955 index: def_key.parent.expect("missing parent")
958 let type_def_id = match def {
959 Def::AssociatedTy(def_id) if depth == 1 => {
960 Some(parent_def_id(self, def_id))
962 Def::Variant(def_id) if depth == 0 => {
963 Some(parent_def_id(self, def_id))
965 Def::Struct(def_id) |
968 Def::TyAlias(def_id) |
969 Def::Trait(def_id) if depth == 0 => Some(def_id),
973 let object_lifetime_defaults = type_def_id.map_or(vec![], |def_id| {
975 let mut scope = self.scope;
978 Scope::Root => break false,
980 Scope::Body { .. } => break true,
982 Scope::Binder { s, .. } |
983 Scope::Elision { s, .. } |
984 Scope::ObjectLifetimeDefault { s, .. } => {
992 let unsubst = if let Some(id) = self.hir_map.as_local_node_id(def_id) {
993 &map.object_lifetime_defaults[&id]
995 let cstore = &self.sess.cstore;
996 self.xcrate_object_lifetime_defaults.entry(def_id).or_insert_with(|| {
997 cstore.item_generics_cloned(def_id).types.into_iter().map(|def| {
998 def.object_lifetime_default
1002 unsubst.iter().map(|set| {
1008 Some(Region::Static)
1011 Set1::One(r) => r.subst(&data.lifetimes, map),
1017 for (i, ty) in data.types.iter().enumerate() {
1018 if let Some(<) = object_lifetime_defaults.get(i) {
1019 let scope = Scope::ObjectLifetimeDefault {
1023 self.with(scope, |_, this| this.visit_ty(ty));
1029 for b in &data.bindings { self.visit_assoc_type_binding(b); }
1032 fn visit_fn_like_elision(&mut self, inputs: &'tcx [P<hir::Ty>],
1033 output: Option<&'tcx P<hir::Ty>>) {
1034 let mut arg_elide = Elide::FreshLateAnon(Cell::new(0));
1035 let arg_scope = Scope::Elision {
1036 elide: arg_elide.clone(),
1039 self.with(arg_scope, |_, this| {
1040 for input in inputs {
1041 this.visit_ty(input);
1044 Scope::Elision { ref elide, .. } => {
1045 arg_elide = elide.clone();
1051 let output = match output {
1056 // Figure out if there's a body we can get argument names from,
1057 // and whether there's a `self` argument (treated specially).
1058 let mut assoc_item_kind = None;
1059 let mut impl_self = None;
1060 let parent = self.hir_map.get_parent_node(output.id);
1061 let body = match self.hir_map.get(parent) {
1062 // `fn` definitions and methods.
1063 hir::map::NodeItem(&hir::Item {
1064 node: hir::ItemFn(.., body), ..
1067 hir::map::NodeTraitItem(&hir::TraitItem {
1068 node: hir::TraitItemKind::Method(_, ref m), ..
1070 match self.hir_map.expect_item(self.hir_map.get_parent(parent)).node {
1071 hir::ItemTrait(.., ref trait_items) => {
1072 assoc_item_kind = trait_items.iter().find(|ti| ti.id.node_id == parent)
1078 hir::TraitMethod::Required(_) => None,
1079 hir::TraitMethod::Provided(body) => Some(body),
1083 hir::map::NodeImplItem(&hir::ImplItem {
1084 node: hir::ImplItemKind::Method(_, body), ..
1086 match self.hir_map.expect_item(self.hir_map.get_parent(parent)).node {
1087 hir::ItemImpl(.., ref self_ty, ref impl_items) => {
1088 impl_self = Some(self_ty);
1089 assoc_item_kind = impl_items.iter().find(|ii| ii.id.node_id == parent)
1097 // `fn(...) -> R` and `Trait(...) -> R` (both types and bounds).
1098 hir::map::NodeTy(_) | hir::map::NodeTraitRef(_) => None,
1100 // Foreign `fn` decls are terrible because we messed up,
1101 // and their return types get argument type elision.
1102 // And now too much code out there is abusing this rule.
1103 hir::map::NodeForeignItem(_) => {
1104 let arg_scope = Scope::Elision {
1108 self.with(arg_scope, |_, this| this.visit_ty(output));
1112 // Everything else (only closures?) doesn't
1113 // actually enjoy elision in return types.
1115 self.visit_ty(output);
1120 let has_self = match assoc_item_kind {
1121 Some(hir::AssociatedItemKind::Method { has_self }) => has_self,
1125 // In accordance with the rules for lifetime elision, we can determine
1126 // what region to use for elision in the output type in two ways.
1127 // First (determined here), if `self` is by-reference, then the
1128 // implied output region is the region of the self parameter.
1130 // Look for `self: &'a Self` - also desugared from `&'a self`,
1131 // and if that matches, use it for elision and return early.
1132 let is_self_ty = |def: Def| {
1133 if let Def::SelfTy(..) = def {
1137 // Can't always rely on literal (or implied) `Self` due
1138 // to the way elision rules were originally specified.
1139 let impl_self = impl_self.map(|ty| &ty.node);
1140 if let Some(&hir::TyPath(hir::QPath::Resolved(None, ref path))) = impl_self {
1142 // Whitelist the types that unambiguously always
1143 // result in the same type constructor being used
1144 // (it can't differ between `Self` and `self`).
1148 Def::PrimTy(_) => return def == path.def,
1156 if let hir::TyRptr(lifetime_ref, ref mt) = inputs[0].node {
1157 if let hir::TyPath(hir::QPath::Resolved(None, ref path)) = mt.ty.node {
1158 if is_self_ty(path.def) {
1159 if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.id) {
1160 let scope = Scope::Elision {
1161 elide: Elide::Exact(lifetime),
1164 self.with(scope, |_, this| this.visit_ty(output));
1172 // Second, if there was exactly one lifetime (either a substitution or a
1173 // reference) in the arguments, then any anonymous regions in the output
1174 // have that lifetime.
1175 let mut possible_implied_output_region = None;
1176 let mut lifetime_count = 0;
1177 let arg_lifetimes = inputs.iter().enumerate().skip(has_self as usize).map(|(i, input)| {
1178 let mut gather = GatherLifetimes {
1181 have_bound_regions: false,
1182 lifetimes: FxHashSet()
1184 gather.visit_ty(input);
1186 lifetime_count += gather.lifetimes.len();
1188 if lifetime_count == 1 && gather.lifetimes.len() == 1 {
1189 // there's a chance that the unique lifetime of this
1190 // iteration will be the appropriate lifetime for output
1191 // parameters, so lets store it.
1192 possible_implied_output_region = gather.lifetimes.iter().cloned().next();
1195 ElisionFailureInfo {
1198 lifetime_count: gather.lifetimes.len(),
1199 have_bound_regions: gather.have_bound_regions
1203 let elide = if lifetime_count == 1 {
1204 Elide::Exact(possible_implied_output_region.unwrap())
1206 Elide::Error(arg_lifetimes)
1209 let scope = Scope::Elision {
1213 self.with(scope, |_, this| this.visit_ty(output));
1215 struct GatherLifetimes<'a> {
1216 map: &'a NamedRegionMap,
1218 have_bound_regions: bool,
1219 lifetimes: FxHashSet<Region>,
1222 impl<'v, 'a> Visitor<'v> for GatherLifetimes<'a> {
1223 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
1224 NestedVisitorMap::None
1227 fn visit_ty(&mut self, ty: &hir::Ty) {
1228 if let hir::TyBareFn(_) = ty.node {
1229 self.binder_depth += 1;
1231 if let hir::TyTraitObject(ref bounds, ref lifetime) = ty.node {
1232 for bound in bounds {
1233 self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
1236 // Stay on the safe side and don't include the object
1237 // lifetime default (which may not end up being used).
1238 if !lifetime.is_elided() {
1239 self.visit_lifetime(lifetime);
1242 intravisit::walk_ty(self, ty);
1244 if let hir::TyBareFn(_) = ty.node {
1245 self.binder_depth -= 1;
1249 fn visit_poly_trait_ref(&mut self,
1250 trait_ref: &hir::PolyTraitRef,
1251 modifier: hir::TraitBoundModifier) {
1252 self.binder_depth += 1;
1253 intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
1254 self.binder_depth -= 1;
1257 fn visit_lifetime_def(&mut self, lifetime_def: &hir::LifetimeDef) {
1258 for l in &lifetime_def.bounds { self.visit_lifetime(l); }
1261 fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
1262 if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.id) {
1264 Region::LateBound(debruijn, _) |
1265 Region::LateBoundAnon(debruijn, _)
1266 if debruijn.depth < self.binder_depth => {
1267 self.have_bound_regions = true;
1270 self.lifetimes.insert(lifetime.from_depth(self.binder_depth));
1279 fn resolve_elided_lifetimes(&mut self, lifetime_refs: &[hir::Lifetime]) {
1280 if lifetime_refs.is_empty() {
1284 let span = lifetime_refs[0].span;
1285 let mut late_depth = 0;
1286 let mut scope = self.scope;
1289 // Do not assign any resolution, it will be inferred.
1290 Scope::Body { .. } => return,
1292 Scope::Root => break None,
1294 Scope::Binder { s, .. } => {
1299 Scope::Elision { ref elide, .. } => {
1300 let lifetime = match *elide {
1301 Elide::FreshLateAnon(ref counter) => {
1302 for lifetime_ref in lifetime_refs {
1303 let lifetime = Region::late_anon(counter).shifted(late_depth);
1304 self.insert_lifetime(lifetime_ref, lifetime);
1308 Elide::Exact(l) => l.shifted(late_depth),
1309 Elide::Error(ref e) => break Some(e)
1311 for lifetime_ref in lifetime_refs {
1312 self.insert_lifetime(lifetime_ref, lifetime);
1317 Scope::ObjectLifetimeDefault { s, .. } => {
1323 let mut err = struct_span_err!(self.sess, span, E0106,
1324 "missing lifetime specifier{}",
1325 if lifetime_refs.len() > 1 { "s" } else { "" });
1326 let msg = if lifetime_refs.len() > 1 {
1327 format!("expected {} lifetime parameters", lifetime_refs.len())
1329 format!("expected lifetime parameter")
1331 err.span_label(span, &msg);
1333 if let Some(params) = error {
1334 if lifetime_refs.len() == 1 {
1335 self.report_elision_failure(&mut err, params);
1341 fn report_elision_failure(&mut self,
1342 db: &mut DiagnosticBuilder,
1343 params: &[ElisionFailureInfo]) {
1344 let mut m = String::new();
1345 let len = params.len();
1347 let elided_params: Vec<_> = params.iter().cloned()
1348 .filter(|info| info.lifetime_count > 0)
1351 let elided_len = elided_params.len();
1353 for (i, info) in elided_params.into_iter().enumerate() {
1354 let ElisionFailureInfo {
1355 parent, index, lifetime_count: n, have_bound_regions
1358 let help_name = if let Some(body) = parent {
1359 let arg = &self.hir_map.body(body).arguments[index];
1360 format!("`{}`", self.hir_map.node_to_pretty_string(arg.pat.id))
1362 format!("argument {}", index + 1)
1365 m.push_str(&(if n == 1 {
1368 format!("one of {}'s {} elided {}lifetimes", help_name, n,
1369 if have_bound_regions { "free " } else { "" } )
1372 if elided_len == 2 && i == 0 {
1374 } else if i + 2 == elided_len {
1375 m.push_str(", or ");
1376 } else if i != elided_len - 1 {
1384 "this function's return type contains a borrowed value, but \
1385 there is no value for it to be borrowed from");
1387 "consider giving it a 'static lifetime");
1388 } else if elided_len == 0 {
1390 "this function's return type contains a borrowed value with \
1391 an elided lifetime, but the lifetime cannot be derived from \
1394 "consider giving it an explicit bounded or 'static \
1396 } else if elided_len == 1 {
1398 "this function's return type contains a borrowed value, but \
1399 the signature does not say which {} it is borrowed from",
1403 "this function's return type contains a borrowed value, but \
1404 the signature does not say whether it is borrowed from {}",
1409 fn resolve_object_lifetime_default(&mut self, lifetime_ref: &hir::Lifetime) {
1410 let mut late_depth = 0;
1411 let mut scope = self.scope;
1412 let lifetime = loop {
1414 Scope::Binder { s, .. } => {
1420 Scope::Elision { .. } => break Region::Static,
1422 Scope::Body { .. } |
1423 Scope::ObjectLifetimeDefault { lifetime: None, .. } => return,
1425 Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l
1428 self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth));
1431 fn check_lifetime_defs(&mut self, old_scope: ScopeRef, lifetimes: &[hir::LifetimeDef]) {
1432 for i in 0..lifetimes.len() {
1433 let lifetime_i = &lifetimes[i];
1435 for lifetime in lifetimes {
1436 if lifetime.lifetime.is_static() {
1437 let lifetime = lifetime.lifetime;
1438 let mut err = struct_span_err!(self.sess, lifetime.span, E0262,
1439 "invalid lifetime parameter name: `{}`", lifetime.name);
1440 err.span_label(lifetime.span,
1441 &format!("{} is a reserved lifetime name", lifetime.name));
1446 // It is a hard error to shadow a lifetime within the same scope.
1447 for j in i + 1..lifetimes.len() {
1448 let lifetime_j = &lifetimes[j];
1450 if lifetime_i.lifetime.name == lifetime_j.lifetime.name {
1451 struct_span_err!(self.sess, lifetime_j.lifetime.span, E0263,
1452 "lifetime name `{}` declared twice in the same scope",
1453 lifetime_j.lifetime.name)
1454 .span_label(lifetime_j.lifetime.span,
1455 &format!("declared twice"))
1456 .span_label(lifetime_i.lifetime.span,
1457 &format!("previous declaration here"))
1462 // It is a soft error to shadow a lifetime within a parent scope.
1463 self.check_lifetime_def_for_shadowing(old_scope, &lifetime_i.lifetime);
1465 for bound in &lifetime_i.bounds {
1466 if !bound.is_static() {
1467 self.resolve_lifetime_ref(bound);
1469 self.insert_lifetime(bound, Region::Static);
1470 self.sess.struct_span_warn(lifetime_i.lifetime.span.to(bound.span),
1471 &format!("unnecessary lifetime parameter `{}`", lifetime_i.lifetime.name))
1472 .help(&format!("you can use the `'static` lifetime directly, in place \
1473 of `{}`", lifetime_i.lifetime.name))
1480 fn check_lifetime_def_for_shadowing(&self,
1481 mut old_scope: ScopeRef,
1482 lifetime: &hir::Lifetime)
1484 for &(label, label_span) in &self.labels_in_fn {
1485 // FIXME (#24278): non-hygienic comparison
1486 if lifetime.name == label {
1487 signal_shadowing_problem(self.sess,
1489 original_label(label_span),
1490 shadower_lifetime(&lifetime));
1497 Scope::Body { s, .. } |
1498 Scope::Elision { s, .. } |
1499 Scope::ObjectLifetimeDefault { s, .. } => {
1507 Scope::Binder { ref lifetimes, s } => {
1508 if let Some(&def) = lifetimes.get(&lifetime.name) {
1509 signal_shadowing_problem(
1512 original_lifetime(self.hir_map.span(def.id().unwrap())),
1513 shadower_lifetime(&lifetime));
1523 fn insert_lifetime(&mut self,
1524 lifetime_ref: &hir::Lifetime,
1526 if lifetime_ref.id == ast::DUMMY_NODE_ID {
1527 span_bug!(lifetime_ref.span,
1528 "lifetime reference not renumbered, \
1529 probably a bug in syntax::fold");
1532 debug!("{} resolved to {:?} span={:?}",
1533 self.hir_map.node_to_string(lifetime_ref.id),
1535 self.sess.codemap().span_to_string(lifetime_ref.span));
1536 self.map.defs.insert(lifetime_ref.id, def);
1540 ///////////////////////////////////////////////////////////////////////////
1542 /// Detects late-bound lifetimes and inserts them into
1543 /// `map.late_bound`.
1545 /// A region declared on a fn is **late-bound** if:
1546 /// - it is constrained by an argument type;
1547 /// - it does not appear in a where-clause.
1549 /// "Constrained" basically means that it appears in any type but
1550 /// not amongst the inputs to a projection. In other words, `<&'a
1551 /// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`.
1552 fn insert_late_bound_lifetimes(map: &mut NamedRegionMap,
1555 generics: &hir::Generics) {
1556 debug!("insert_late_bound_lifetimes(decl={:?}, generics={:?})", decl, generics);
1558 let mut constrained_by_input = ConstrainedCollector { regions: FxHashSet() };
1559 for arg_ty in &decl.inputs {
1560 constrained_by_input.visit_ty(arg_ty);
1563 let mut appears_in_output = AllCollector {
1564 regions: FxHashSet(),
1567 intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output);
1569 debug!("insert_late_bound_lifetimes: constrained_by_input={:?}",
1570 constrained_by_input.regions);
1572 // Walk the lifetimes that appear in where clauses.
1574 // Subtle point: because we disallow nested bindings, we can just
1575 // ignore binders here and scrape up all names we see.
1576 let mut appears_in_where_clause = AllCollector {
1577 regions: FxHashSet(),
1580 for ty_param in generics.ty_params.iter() {
1581 walk_list!(&mut appears_in_where_clause,
1582 visit_ty_param_bound,
1585 walk_list!(&mut appears_in_where_clause,
1586 visit_where_predicate,
1587 &generics.where_clause.predicates);
1588 for lifetime_def in &generics.lifetimes {
1589 if !lifetime_def.bounds.is_empty() {
1590 // `'a: 'b` means both `'a` and `'b` are referenced
1591 appears_in_where_clause.visit_lifetime_def(lifetime_def);
1595 debug!("insert_late_bound_lifetimes: appears_in_where_clause={:?}",
1596 appears_in_where_clause.regions);
1598 // Late bound regions are those that:
1599 // - appear in the inputs
1600 // - do not appear in the where-clauses
1601 // - are not implicitly captured by `impl Trait`
1602 for lifetime in &generics.lifetimes {
1603 let name = lifetime.lifetime.name;
1605 // appears in the where clauses? early-bound.
1606 if appears_in_where_clause.regions.contains(&name) { continue; }
1608 // any `impl Trait` in the return type? early-bound.
1609 if appears_in_output.impl_trait { continue; }
1611 // does not appear in the inputs, but appears in the return
1612 // type? eventually this will be early-bound, but for now we
1613 // just mark it so we can issue warnings.
1614 let constrained_by_input = constrained_by_input.regions.contains(&name);
1615 let appears_in_output = appears_in_output.regions.contains(&name);
1616 if !constrained_by_input && appears_in_output {
1617 debug!("inserting issue_32330 entry for {:?}, {:?} on {:?}",
1618 lifetime.lifetime.id,
1621 map.issue_32330.insert(
1622 lifetime.lifetime.id,
1624 fn_def_id: fn_def_id,
1630 debug!("insert_late_bound_lifetimes: \
1631 lifetime {:?} with id {:?} is late-bound",
1632 lifetime.lifetime.name, lifetime.lifetime.id);
1634 let inserted = map.late_bound.insert(lifetime.lifetime.id);
1635 assert!(inserted, "visited lifetime {:?} twice", lifetime.lifetime.id);
1640 struct ConstrainedCollector {
1641 regions: FxHashSet<ast::Name>,
1644 impl<'v> Visitor<'v> for ConstrainedCollector {
1645 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
1646 NestedVisitorMap::None
1649 fn visit_ty(&mut self, ty: &'v hir::Ty) {
1651 hir::TyPath(hir::QPath::Resolved(Some(_), _)) |
1652 hir::TyPath(hir::QPath::TypeRelative(..)) => {
1653 // ignore lifetimes appearing in associated type
1654 // projections, as they are not *constrained*
1658 hir::TyPath(hir::QPath::Resolved(None, ref path)) => {
1659 // consider only the lifetimes on the final
1660 // segment; I am not sure it's even currently
1661 // valid to have them elsewhere, but even if it
1662 // is, those would be potentially inputs to
1664 if let Some(last_segment) = path.segments.last() {
1665 self.visit_path_segment(path.span, last_segment);
1670 intravisit::walk_ty(self, ty);
1675 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
1676 self.regions.insert(lifetime_ref.name);
1680 struct AllCollector {
1681 regions: FxHashSet<ast::Name>,
1685 impl<'v> Visitor<'v> for AllCollector {
1686 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
1687 NestedVisitorMap::None
1690 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
1691 self.regions.insert(lifetime_ref.name);
1694 fn visit_ty(&mut self, ty: &hir::Ty) {
1695 if let hir::TyImplTrait(_) = ty.node {
1696 self.impl_trait = true;
1698 intravisit::walk_ty(self, ty);