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.
18 pub use self::DefRegion::*;
19 use self::ScopeChain::*;
21 use dep_graph::DepNode;
25 use hir::def_id::DefId;
28 use std::mem::replace;
30 use syntax::symbol::keywords;
32 use util::nodemap::NodeMap;
34 use rustc_data_structures::fx::FxHashSet;
36 use hir::print::lifetime_to_string;
37 use hir::intravisit::{self, Visitor, FnKind, NestedVisitorMap};
39 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Debug)]
42 DefEarlyBoundRegion(/* index */ u32,
43 /* lifetime decl */ ast::NodeId),
44 DefLateBoundRegion(ty::DebruijnIndex,
45 /* lifetime decl */ ast::NodeId),
46 DefFreeRegion(region::CallSiteScopeData,
47 /* lifetime decl */ ast::NodeId),
50 // Maps the id of each lifetime reference to the lifetime decl
51 // that it corresponds to.
52 pub struct NamedRegionMap {
53 // maps from every use of a named (not anonymous) lifetime to a
54 // `DefRegion` describing how that region is bound
55 pub defs: NodeMap<DefRegion>,
57 // the set of lifetime def ids that are late-bound; late-bound ids
58 // are named regions appearing in fn arguments that do not appear
60 pub late_bound: NodeMap<ty::Issue32330>,
63 struct LifetimeContext<'a, 'tcx: 'a> {
65 hir_map: &'a Map<'tcx>,
66 map: &'a mut NamedRegionMap,
68 // Deep breath. Our representation for poly trait refs contains a single
69 // binder and thus we only allow a single level of quantification. However,
70 // the syntax of Rust permits quantification in two places, e.g., `T: for <'a> Foo<'a>`
71 // and `for <'a, 'b> &'b T: Foo<'a>`. In order to get the de Bruijn indices
72 // correct when representing these constraints, we should only introduce one
73 // scope. However, we want to support both locations for the quantifier and
74 // during lifetime resolution we want precise information (so we can't
75 // desugar in an earlier phase).
77 // SO, if we encounter a quantifier at the outer scope, we set
78 // trait_ref_hack to true (and introduce a scope), and then if we encounter
79 // a quantifier at the inner scope, we error. If trait_ref_hack is false,
80 // then we introduce the scope at the inner quantifier.
85 // List of labels in the function/method currently under analysis.
86 labels_in_fn: Vec<(ast::Name, Span)>,
89 #[derive(PartialEq, Debug)]
91 /// EarlyScope(['a, 'b, ...], start, s) extends s with early-bound
92 /// lifetimes, with consecutive parameter indices from `start`.
93 /// That is, 'a has index `start`, 'b has index `start + 1`, etc.
94 /// Indices before `start` correspond to other generic parameters
95 /// of a parent item (trait/impl of a method), or `Self` in traits.
96 EarlyScope(&'a [hir::LifetimeDef], u32, Scope<'a>),
97 /// LateScope(['a, 'b, ...], s) extends s with late-bound
98 /// lifetimes introduced by the declaration binder_id.
99 LateScope(&'a [hir::LifetimeDef], Scope<'a>),
101 /// lifetimes introduced by a fn are scoped to the call-site for that fn.
102 FnScope { fn_id: ast::NodeId, body_id: ast::NodeId, s: Scope<'a> },
106 type Scope<'a> = &'a ScopeChain<'a>;
108 static ROOT_SCOPE: ScopeChain<'static> = RootScope;
110 pub fn krate(sess: &Session,
112 -> Result<NamedRegionMap, usize> {
113 let _task = hir_map.dep_graph.in_task(DepNode::ResolveLifetimes);
114 let krate = hir_map.krate();
115 let mut map = NamedRegionMap {
117 late_bound: NodeMap(),
119 sess.track_errors(|| {
120 intravisit::walk_crate(&mut LifetimeContext {
125 trait_ref_hack: false,
126 labels_in_fn: vec![],
132 impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
133 // Override the nested functions -- lifetimes follow lexical scope,
134 // so it's convenient to walk the tree in lexical order.
135 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
136 NestedVisitorMap::All(&self.hir_map)
139 fn visit_item(&mut self, item: &'tcx hir::Item) {
140 // Save labels for nested items.
141 let saved_labels_in_fn = replace(&mut self.labels_in_fn, vec![]);
143 // Items always introduce a new root scope
144 self.with(RootScope, |_, this| {
147 // Fn lifetimes get added in visit_fn below:
148 intravisit::walk_item(this, item);
150 hir::ItemExternCrate(_) |
153 hir::ItemDefaultImpl(..) |
154 hir::ItemForeignMod(..) |
155 hir::ItemStatic(..) |
156 hir::ItemConst(..) => {
157 // These sorts of items have no lifetime parameters at all.
158 intravisit::walk_item(this, item);
160 hir::ItemTy(_, ref generics) |
161 hir::ItemEnum(_, ref generics) |
162 hir::ItemStruct(_, ref generics) |
163 hir::ItemUnion(_, ref generics) |
164 hir::ItemTrait(_, ref generics, ..) |
165 hir::ItemImpl(_, _, ref generics, ..) => {
166 // These kinds of items have only early bound lifetime parameters.
167 let lifetimes = &generics.lifetimes;
168 let start = if let hir::ItemTrait(..) = item.node {
169 1 // Self comes before lifetimes
173 this.with(EarlyScope(lifetimes, start, &ROOT_SCOPE), |old_scope, this| {
174 this.check_lifetime_defs(old_scope, lifetimes);
175 intravisit::walk_item(this, item);
181 // Done traversing the item; remove any labels it created
182 self.labels_in_fn = saved_labels_in_fn;
185 fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem) {
186 // Items save/restore the set of labels. This way inner items
187 // can freely reuse names, be they loop labels or lifetimes.
188 let saved = replace(&mut self.labels_in_fn, vec![]);
190 // Items always introduce a new root scope
191 self.with(RootScope, |_, this| {
193 hir::ForeignItemFn(ref decl, ref generics) => {
194 this.visit_early_late(item.id, decl, generics, |this| {
195 intravisit::walk_foreign_item(this, item);
198 hir::ForeignItemStatic(..) => {
199 intravisit::walk_foreign_item(this, item);
204 // Done traversing the item; restore saved set of labels.
205 replace(&mut self.labels_in_fn, saved);
208 fn visit_fn(&mut self, fk: FnKind<'tcx>, decl: &'tcx hir::FnDecl,
209 b: hir::ExprId, s: Span, fn_id: ast::NodeId) {
211 FnKind::ItemFn(_, generics, ..) => {
212 self.visit_early_late(fn_id,decl, generics, |this| {
213 this.add_scope_and_walk_fn(fk, decl, b, s, fn_id)
216 FnKind::Method(_, sig, ..) => {
217 self.visit_early_late(
221 |this| this.add_scope_and_walk_fn(fk, decl, b, s, fn_id));
223 FnKind::Closure(_) => {
224 // Closures have their own set of labels, save labels just
225 // like for foreign items above.
226 let saved = replace(&mut self.labels_in_fn, vec![]);
227 let result = self.add_scope_and_walk_fn(fk, decl, b, s, fn_id);
228 replace(&mut self.labels_in_fn, saved);
234 fn visit_ty(&mut self, ty: &'tcx hir::Ty) {
236 hir::TyBareFn(ref c) => {
237 self.with(LateScope(&c.lifetimes, self.scope), |old_scope, this| {
238 // a bare fn has no bounds, so everything
239 // contained within is scoped within its binder.
240 this.check_lifetime_defs(old_scope, &c.lifetimes);
241 intravisit::walk_ty(this, ty);
244 hir::TyPath(hir::QPath::Resolved(None, ref path)) => {
245 // if this path references a trait, then this will resolve to
246 // a trait ref, which introduces a binding scope.
249 self.with(LateScope(&[], self.scope), |_, this| {
250 this.visit_path(path, ty.id);
254 intravisit::walk_ty(self, ty);
259 intravisit::walk_ty(self, ty)
264 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem) {
265 // We reset the labels on every trait item, so that different
266 // methods in an impl can reuse label names.
267 let saved = replace(&mut self.labels_in_fn, vec![]);
269 if let hir::MethodTraitItem(ref sig, None) = trait_item.node {
270 self.visit_early_late(
272 &sig.decl, &sig.generics,
273 |this| intravisit::walk_trait_item(this, trait_item))
275 intravisit::walk_trait_item(self, trait_item);
278 replace(&mut self.labels_in_fn, saved);
281 fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
282 if lifetime_ref.name == keywords::StaticLifetime.name() {
283 self.insert_lifetime(lifetime_ref, DefStaticRegion);
286 self.resolve_lifetime_ref(lifetime_ref);
289 fn visit_generics(&mut self, generics: &'tcx hir::Generics) {
290 for ty_param in generics.ty_params.iter() {
291 walk_list!(self, visit_ty_param_bound, &ty_param.bounds);
292 if let Some(ref ty) = ty_param.default {
296 for predicate in &generics.where_clause.predicates {
298 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate{ ref bounded_ty,
302 if !bound_lifetimes.is_empty() {
303 self.trait_ref_hack = true;
304 let result = self.with(LateScope(bound_lifetimes, self.scope),
306 this.check_lifetime_defs(old_scope, bound_lifetimes);
307 this.visit_ty(&bounded_ty);
308 walk_list!(this, visit_ty_param_bound, bounds);
310 self.trait_ref_hack = false;
313 self.visit_ty(&bounded_ty);
314 walk_list!(self, visit_ty_param_bound, bounds);
317 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate{ref lifetime,
321 self.visit_lifetime(lifetime);
322 for bound in bounds {
323 self.visit_lifetime(bound);
326 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate{ id,
330 self.visit_path(path, id);
337 fn visit_poly_trait_ref(&mut self,
338 trait_ref: &'tcx hir::PolyTraitRef,
339 _modifier: &'tcx hir::TraitBoundModifier) {
340 debug!("visit_poly_trait_ref trait_ref={:?}", trait_ref);
342 if !self.trait_ref_hack || !trait_ref.bound_lifetimes.is_empty() {
343 if self.trait_ref_hack {
344 span_err!(self.sess, trait_ref.span, E0316,
345 "nested quantification of lifetimes");
347 self.with(LateScope(&trait_ref.bound_lifetimes, self.scope), |old_scope, this| {
348 this.check_lifetime_defs(old_scope, &trait_ref.bound_lifetimes);
349 for lifetime in &trait_ref.bound_lifetimes {
350 this.visit_lifetime_def(lifetime);
352 intravisit::walk_path(this, &trait_ref.trait_ref.path)
355 self.visit_trait_ref(&trait_ref.trait_ref)
360 #[derive(Copy, Clone, PartialEq)]
361 enum ShadowKind { Label, Lifetime }
362 struct Original { kind: ShadowKind, span: Span }
363 struct Shadower { kind: ShadowKind, span: Span }
365 fn original_label(span: Span) -> Original {
366 Original { kind: ShadowKind::Label, span: span }
368 fn shadower_label(span: Span) -> Shadower {
369 Shadower { kind: ShadowKind::Label, span: span }
371 fn original_lifetime(l: &hir::Lifetime) -> Original {
372 Original { kind: ShadowKind::Lifetime, span: l.span }
374 fn shadower_lifetime(l: &hir::Lifetime) -> Shadower {
375 Shadower { kind: ShadowKind::Lifetime, span: l.span }
379 fn desc(&self) -> &'static str {
381 ShadowKind::Label => "label",
382 ShadowKind::Lifetime => "lifetime",
387 fn signal_shadowing_problem(sess: &Session, name: ast::Name, orig: Original, shadower: Shadower) {
388 let mut err = if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
389 // lifetime/lifetime shadowing is an error
390 struct_span_err!(sess, shadower.span, E0496,
391 "{} name `{}` shadows a \
392 {} name that is already in scope",
393 shadower.kind.desc(), name, orig.kind.desc())
395 // shadowing involving a label is only a warning, due to issues with
396 // labels and lifetimes not being macro-hygienic.
397 sess.struct_span_warn(shadower.span,
398 &format!("{} name `{}` shadows a \
399 {} name that is already in scope",
400 shadower.kind.desc(), name, orig.kind.desc()))
402 err.span_label(orig.span, &"first declared here");
403 err.span_label(shadower.span,
404 &format!("lifetime {} already in scope", name));
408 // Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
409 // if one of the label shadows a lifetime or another label.
410 fn extract_labels(ctxt: &mut LifetimeContext, b: hir::ExprId) {
411 struct GatherLabels<'a> {
414 labels_in_fn: &'a mut Vec<(ast::Name, Span)>,
417 let mut gather = GatherLabels {
420 labels_in_fn: &mut ctxt.labels_in_fn,
422 gather.visit_expr(ctxt.hir_map.expr(b));
425 impl<'v, 'a> Visitor<'v> for GatherLabels<'a> {
426 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
427 NestedVisitorMap::None
430 fn visit_expr(&mut self, ex: &'v hir::Expr) {
431 // do not recurse into closures defined in the block
432 // since they are treated as separate fns from the POV of
434 if let hir::ExprClosure(..) = ex.node {
437 if let Some((label, label_span)) = expression_label(ex) {
438 for &(prior, prior_span) in &self.labels_in_fn[..] {
439 // FIXME (#24278): non-hygienic comparison
441 signal_shadowing_problem(self.sess,
443 original_label(prior_span),
444 shadower_label(label_span));
448 check_if_label_shadows_lifetime(self.sess,
453 self.labels_in_fn.push((label, label_span));
455 intravisit::walk_expr(self, ex)
458 fn visit_item(&mut self, _: &hir::Item) {
459 // do not recurse into items defined in the block
463 fn expression_label(ex: &hir::Expr) -> Option<(ast::Name, Span)> {
465 hir::ExprWhile(.., Some(label)) |
466 hir::ExprLoop(_, Some(label), _) => Some((label.node, label.span)),
471 fn check_if_label_shadows_lifetime<'a>(sess: &'a Session,
472 mut scope: Scope<'a>,
477 FnScope { s, .. } => { scope = s; }
478 RootScope => { return; }
480 EarlyScope(lifetimes, _, s) |
481 LateScope(lifetimes, s) => {
482 for lifetime_def in lifetimes {
483 // FIXME (#24278): non-hygienic comparison
484 if label == lifetime_def.lifetime.name {
485 signal_shadowing_problem(
488 original_lifetime(&lifetime_def.lifetime),
489 shadower_label(label_span));
500 impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
501 fn add_scope_and_walk_fn(&mut self,
503 fd: &'tcx hir::FnDecl,
506 fn_id: ast::NodeId) {
508 FnKind::ItemFn(_, generics, ..) => {
509 intravisit::walk_fn_decl(self, fd);
510 self.visit_generics(generics);
512 FnKind::Method(_, sig, ..) => {
513 intravisit::walk_fn_decl(self, fd);
514 self.visit_generics(&sig.generics);
516 FnKind::Closure(_) => {
517 intravisit::walk_fn_decl(self, fd);
521 // After inpsecting the decl, add all labels from the body to
522 // `self.labels_in_fn`.
523 extract_labels(self, fb);
525 self.with(FnScope { fn_id: fn_id, body_id: fb.node_id(), s: self.scope },
526 |_old_scope, this| this.visit_body(fb))
529 // FIXME(#37666) this works around a limitation in the region inferencer
530 fn hack<F>(&mut self, f: F) where
531 F: for<'b> FnOnce(&mut LifetimeContext<'b, 'tcx>),
536 fn with<F>(&mut self, wrap_scope: ScopeChain, f: F) where
537 F: for<'b> FnOnce(Scope, &mut LifetimeContext<'b, 'tcx>),
539 let LifetimeContext {sess, hir_map, ref mut map, ..} = *self;
540 let mut this = LifetimeContext {
545 trait_ref_hack: self.trait_ref_hack,
546 labels_in_fn: self.labels_in_fn.clone(),
548 debug!("entering scope {:?}", this.scope);
549 f(self.scope, &mut this);
550 debug!("exiting scope {:?}", this.scope);
553 /// Visits self by adding a scope and handling recursive walk over the contents with `walk`.
555 /// Handles visiting fns and methods. These are a bit complicated because we must distinguish
556 /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear
557 /// within type bounds; those are early bound lifetimes, and the rest are late bound.
561 /// fn foo<'a,'b,'c,T:Trait<'b>>(...)
563 /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound
564 /// lifetimes may be interspersed together.
566 /// If early bound lifetimes are present, we separate them into their own list (and likewise
567 /// for late bound). They will be numbered sequentially, starting from the lowest index that is
568 /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late
569 /// bound lifetimes are resolved by name and associated with a binder id (`binder_id`), so the
570 /// ordering is not important there.
571 fn visit_early_late<F>(&mut self,
573 decl: &'tcx hir::FnDecl,
574 generics: &'tcx hir::Generics,
576 F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
578 let fn_def_id = self.hir_map.local_def_id(fn_id);
579 insert_late_bound_lifetimes(self.map,
584 let (late, early): (Vec<_>, _) =
588 .partition(|l| self.map.late_bound.contains_key(&l.lifetime.id));
590 // Find the start of nested early scopes, e.g. in methods.
592 if let EarlyScope(..) = *self.scope {
593 let parent = self.hir_map.expect_item(self.hir_map.get_parent(fn_id));
594 if let hir::ItemTrait(..) = parent.node {
595 start += 1; // Self comes first.
598 hir::ItemTrait(_, ref generics, ..) |
599 hir::ItemImpl(_, _, ref generics, ..) => {
600 start += generics.lifetimes.len() + generics.ty_params.len();
606 self.with(EarlyScope(&early, start as u32, self.scope), move |old_scope, this| {
607 this.with(LateScope(&late, this.scope), move |_, this| {
608 this.check_lifetime_defs(old_scope, &generics.lifetimes);
609 this.hack(walk); // FIXME(#37666) workaround in place of `walk(this)`
614 fn resolve_lifetime_ref(&mut self, lifetime_ref: &hir::Lifetime) {
615 // Walk up the scope chain, tracking the number of fn scopes
616 // that we pass through, until we find a lifetime with the
617 // given name or we run out of scopes. If we encounter a code
618 // block, then the lifetime is not bound but free, so switch
619 // over to `resolve_free_lifetime_ref()` to complete the
621 let mut late_depth = 0;
622 let mut scope = self.scope;
625 FnScope {fn_id, body_id, s } => {
626 return self.resolve_free_lifetime_ref(
627 region::CallSiteScopeData { fn_id: fn_id, body_id: body_id },
636 EarlyScope(lifetimes, start, s) => {
637 match search_lifetimes(lifetimes, lifetime_ref) {
638 Some((index, lifetime_def)) => {
639 let decl_id = lifetime_def.id;
640 let def = DefEarlyBoundRegion(start + index, decl_id);
641 self.insert_lifetime(lifetime_ref, def);
650 LateScope(lifetimes, s) => {
651 match search_lifetimes(lifetimes, lifetime_ref) {
652 Some((_index, lifetime_def)) => {
653 let decl_id = lifetime_def.id;
654 let debruijn = ty::DebruijnIndex::new(late_depth + 1);
655 let def = DefLateBoundRegion(debruijn, decl_id);
656 self.insert_lifetime(lifetime_ref, def);
669 self.unresolved_lifetime_ref(lifetime_ref);
672 fn resolve_free_lifetime_ref(&mut self,
673 scope_data: region::CallSiteScopeData,
674 lifetime_ref: &hir::Lifetime,
676 debug!("resolve_free_lifetime_ref \
677 scope_data: {:?} lifetime_ref: {:?} scope: {:?}",
678 scope_data, lifetime_ref, scope);
680 // Walk up the scope chain, tracking the outermost free scope,
681 // until we encounter a scope that contains the named lifetime
682 // or we run out of scopes.
683 let mut scope_data = scope_data;
684 let mut scope = scope;
685 let mut search_result = None;
687 debug!("resolve_free_lifetime_ref \
688 scope_data: {:?} scope: {:?} search_result: {:?}",
689 scope_data, scope, search_result);
691 FnScope { fn_id, body_id, s } => {
692 scope_data = region::CallSiteScopeData {
693 fn_id: fn_id, body_id: body_id
702 EarlyScope(lifetimes, _, s) |
703 LateScope(lifetimes, s) => {
704 search_result = search_lifetimes(lifetimes, lifetime_ref);
705 if search_result.is_some() {
713 match search_result {
714 Some((_depth, lifetime)) => {
715 let def = DefFreeRegion(scope_data, lifetime.id);
716 self.insert_lifetime(lifetime_ref, def);
720 self.unresolved_lifetime_ref(lifetime_ref);
726 fn unresolved_lifetime_ref(&self, lifetime_ref: &hir::Lifetime) {
727 struct_span_err!(self.sess, lifetime_ref.span, E0261,
728 "use of undeclared lifetime name `{}`", lifetime_ref.name)
729 .span_label(lifetime_ref.span, &format!("undeclared lifetime"))
733 fn check_lifetime_defs(&mut self, old_scope: Scope, lifetimes: &[hir::LifetimeDef]) {
734 for i in 0..lifetimes.len() {
735 let lifetime_i = &lifetimes[i];
737 for lifetime in lifetimes {
738 if lifetime.lifetime.name == keywords::StaticLifetime.name() {
739 let lifetime = lifetime.lifetime;
740 let mut err = struct_span_err!(self.sess, lifetime.span, E0262,
741 "invalid lifetime parameter name: `{}`", lifetime.name);
742 err.span_label(lifetime.span,
743 &format!("{} is a reserved lifetime name", lifetime.name));
748 // It is a hard error to shadow a lifetime within the same scope.
749 for j in i + 1..lifetimes.len() {
750 let lifetime_j = &lifetimes[j];
752 if lifetime_i.lifetime.name == lifetime_j.lifetime.name {
753 struct_span_err!(self.sess, lifetime_j.lifetime.span, E0263,
754 "lifetime name `{}` declared twice in the same scope",
755 lifetime_j.lifetime.name)
756 .span_label(lifetime_j.lifetime.span,
757 &format!("declared twice"))
758 .span_label(lifetime_i.lifetime.span,
759 &format!("previous declaration here"))
764 // It is a soft error to shadow a lifetime within a parent scope.
765 self.check_lifetime_def_for_shadowing(old_scope, &lifetime_i.lifetime);
767 for bound in &lifetime_i.bounds {
768 self.resolve_lifetime_ref(bound);
773 fn check_lifetime_def_for_shadowing(&self,
774 mut old_scope: Scope,
775 lifetime: &hir::Lifetime)
777 for &(label, label_span) in &self.labels_in_fn {
778 // FIXME (#24278): non-hygienic comparison
779 if lifetime.name == label {
780 signal_shadowing_problem(self.sess,
782 original_label(label_span),
783 shadower_lifetime(&lifetime));
790 FnScope { s, .. } => {
798 EarlyScope(lifetimes, _, s) |
799 LateScope(lifetimes, s) => {
800 if let Some((_, lifetime_def)) = search_lifetimes(lifetimes, lifetime) {
801 signal_shadowing_problem(
804 original_lifetime(&lifetime_def),
805 shadower_lifetime(&lifetime));
815 fn insert_lifetime(&mut self,
816 lifetime_ref: &hir::Lifetime,
818 if lifetime_ref.id == ast::DUMMY_NODE_ID {
819 span_bug!(lifetime_ref.span,
820 "lifetime reference not renumbered, \
821 probably a bug in syntax::fold");
824 debug!("lifetime_ref={:?} id={:?} resolved to {:?} span={:?}",
825 lifetime_to_string(lifetime_ref),
828 self.sess.codemap().span_to_string(lifetime_ref.span));
829 self.map.defs.insert(lifetime_ref.id, def);
833 fn search_lifetimes<'a>(lifetimes: &'a [hir::LifetimeDef],
834 lifetime_ref: &hir::Lifetime)
835 -> Option<(u32, &'a hir::Lifetime)> {
836 for (i, lifetime_decl) in lifetimes.iter().enumerate() {
837 if lifetime_decl.lifetime.name == lifetime_ref.name {
838 return Some((i as u32, &lifetime_decl.lifetime));
844 ///////////////////////////////////////////////////////////////////////////
846 /// Detects late-bound lifetimes and inserts them into
847 /// `map.late_bound`.
849 /// A region declared on a fn is **late-bound** if:
850 /// - it is constrained by an argument type;
851 /// - it does not appear in a where-clause.
853 /// "Constrained" basically means that it appears in any type but
854 /// not amongst the inputs to a projection. In other words, `<&'a
855 /// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`.
856 fn insert_late_bound_lifetimes(map: &mut NamedRegionMap,
859 generics: &hir::Generics) {
860 debug!("insert_late_bound_lifetimes(decl={:?}, generics={:?})", decl, generics);
862 let mut constrained_by_input = ConstrainedCollector { regions: FxHashSet() };
863 for arg in &decl.inputs {
864 constrained_by_input.visit_ty(&arg.ty);
867 let mut appears_in_output = AllCollector {
868 regions: FxHashSet(),
871 intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output);
873 debug!("insert_late_bound_lifetimes: constrained_by_input={:?}",
874 constrained_by_input.regions);
876 // Walk the lifetimes that appear in where clauses.
878 // Subtle point: because we disallow nested bindings, we can just
879 // ignore binders here and scrape up all names we see.
880 let mut appears_in_where_clause = AllCollector {
881 regions: FxHashSet(),
884 for ty_param in generics.ty_params.iter() {
885 walk_list!(&mut appears_in_where_clause,
886 visit_ty_param_bound,
889 walk_list!(&mut appears_in_where_clause,
890 visit_where_predicate,
891 &generics.where_clause.predicates);
892 for lifetime_def in &generics.lifetimes {
893 if !lifetime_def.bounds.is_empty() {
894 // `'a: 'b` means both `'a` and `'b` are referenced
895 appears_in_where_clause.visit_lifetime_def(lifetime_def);
899 debug!("insert_late_bound_lifetimes: appears_in_where_clause={:?}",
900 appears_in_where_clause.regions);
902 // Late bound regions are those that:
903 // - appear in the inputs
904 // - do not appear in the where-clauses
905 // - are not implicitly captured by `impl Trait`
906 for lifetime in &generics.lifetimes {
907 let name = lifetime.lifetime.name;
909 // appears in the where clauses? early-bound.
910 if appears_in_where_clause.regions.contains(&name) { continue; }
912 // any `impl Trait` in the return type? early-bound.
913 if appears_in_output.impl_trait { continue; }
915 // does not appear in the inputs, but appears in the return
916 // type? eventually this will be early-bound, but for now we
917 // just mark it so we can issue warnings.
918 let constrained_by_input = constrained_by_input.regions.contains(&name);
919 let appears_in_output = appears_in_output.regions.contains(&name);
920 let will_change = !constrained_by_input && appears_in_output;
921 let issue_32330 = if will_change {
922 ty::Issue32330::WillChange {
923 fn_def_id: fn_def_id,
927 ty::Issue32330::WontChange
930 debug!("insert_late_bound_lifetimes: \
931 lifetime {:?} with id {:?} is late-bound ({:?}",
932 lifetime.lifetime.name, lifetime.lifetime.id, issue_32330);
934 let prev = map.late_bound.insert(lifetime.lifetime.id, issue_32330);
935 assert!(prev.is_none(), "visited lifetime {:?} twice", lifetime.lifetime.id);
940 struct ConstrainedCollector {
941 regions: FxHashSet<ast::Name>,
944 impl<'v> Visitor<'v> for ConstrainedCollector {
945 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
946 NestedVisitorMap::None
949 fn visit_ty(&mut self, ty: &'v hir::Ty) {
951 hir::TyPath(hir::QPath::Resolved(Some(_), _)) |
952 hir::TyPath(hir::QPath::TypeRelative(..)) => {
953 // ignore lifetimes appearing in associated type
954 // projections, as they are not *constrained*
958 hir::TyPath(hir::QPath::Resolved(None, ref path)) => {
959 // consider only the lifetimes on the final
960 // segment; I am not sure it's even currently
961 // valid to have them elsewhere, but even if it
962 // is, those would be potentially inputs to
964 if let Some(last_segment) = path.segments.last() {
965 self.visit_path_segment(path.span, last_segment);
970 intravisit::walk_ty(self, ty);
975 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
976 self.regions.insert(lifetime_ref.name);
980 struct AllCollector {
981 regions: FxHashSet<ast::Name>,
985 impl<'v> Visitor<'v> for AllCollector {
986 fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
987 NestedVisitorMap::None
990 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
991 self.regions.insert(lifetime_ref.name);
994 fn visit_ty(&mut self, ty: &hir::Ty) {
995 if let hir::TyImplTrait(_) = ty.node {
996 self.impl_trait = true;
998 intravisit::walk_ty(self, ty);