1 // ignore-tidy-filelength
2 //! Name resolution for lifetimes.
3 //!
4 //! Name resolution for lifetimes follows *much* simpler rules than the
5 //! full resolve. For example, lifetime names are never exported or
6 //! used between functions, and they operate in a purely top-down
7 //! way. Therefore, we break lifetime name resolution into a separate pass.
8
9 use crate::late::diagnostics::{ForLifetimeSpanType, MissingLifetimeSpot};
10 use rustc_ast::walk_list;
11 use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
12 use rustc_errors::{struct_span_err, Applicability, DiagnosticBuilder};
13 use rustc_hir as hir;
14 use rustc_hir::def::{DefKind, Res};
15 use rustc_hir::def_id::{DefIdMap, LocalDefId};
16 use rustc_hir::hir_id::ItemLocalId;
17 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
18 use rustc_hir::{GenericArg, GenericParam, LifetimeName, Node, ParamName, QPath};
19 use rustc_hir::{GenericParamKind, HirIdMap, HirIdSet, LifetimeParamKind};
20 use rustc_middle::hir::map::Map;
21 use rustc_middle::middle::resolve_lifetime::*;
22 use rustc_middle::ty::{self, DefIdTree, GenericParamDefKind, TyCtxt};
23 use rustc_middle::{bug, span_bug};
24 use rustc_session::lint;
25 use rustc_span::def_id::DefId;
26 use rustc_span::symbol::{kw, sym, Ident, Symbol};
27 use rustc_span::Span;
28 use std::borrow::Cow;
29 use std::cell::Cell;
30 use std::fmt;
31 use std::mem::take;
32
33 use tracing::{debug, span, Level};
34
35 // This counts the no of times a lifetime is used
36 #[derive(Clone, Copy, Debug)]
37 pub enum LifetimeUseSet<'tcx> {
38 One(&'tcx hir::Lifetime),
39 Many,
40 }
41
42 trait RegionExt {
early(hir_map: &Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (ParamName, Region)43 fn early(hir_map: &Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (ParamName, Region);
44
late(index: u32, hir_map: &Map<'_>, param: &GenericParam<'_>) -> (ParamName, Region)45 fn late(index: u32, hir_map: &Map<'_>, param: &GenericParam<'_>) -> (ParamName, Region);
46
late_anon(named_late_bound_vars: u32, index: &Cell<u32>) -> Region47 fn late_anon(named_late_bound_vars: u32, index: &Cell<u32>) -> Region;
48
id(&self) -> Option<DefId>49 fn id(&self) -> Option<DefId>;
50
shifted(self, amount: u32) -> Region51 fn shifted(self, amount: u32) -> Region;
52
shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region53 fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region;
54
subst<'a, L>(self, params: L, map: &NamedRegionMap) -> Option<Region> where L: Iterator<Item = &'a hir::Lifetime>55 fn subst<'a, L>(self, params: L, map: &NamedRegionMap) -> Option<Region>
56 where
57 L: Iterator<Item = &'a hir::Lifetime>;
58 }
59
60 impl RegionExt for Region {
early(hir_map: &Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (ParamName, Region)61 fn early(hir_map: &Map<'_>, index: &mut u32, param: &GenericParam<'_>) -> (ParamName, Region) {
62 let i = *index;
63 *index += 1;
64 let def_id = hir_map.local_def_id(param.hir_id);
65 let origin = LifetimeDefOrigin::from_param(param);
66 debug!("Region::early: index={} def_id={:?}", i, def_id);
67 (param.name.normalize_to_macros_2_0(), Region::EarlyBound(i, def_id.to_def_id(), origin))
68 }
69
late(idx: u32, hir_map: &Map<'_>, param: &GenericParam<'_>) -> (ParamName, Region)70 fn late(idx: u32, hir_map: &Map<'_>, param: &GenericParam<'_>) -> (ParamName, Region) {
71 let depth = ty::INNERMOST;
72 let def_id = hir_map.local_def_id(param.hir_id);
73 let origin = LifetimeDefOrigin::from_param(param);
74 debug!(
75 "Region::late: idx={:?}, param={:?} depth={:?} def_id={:?} origin={:?}",
76 idx, param, depth, def_id, origin,
77 );
78 (
79 param.name.normalize_to_macros_2_0(),
80 Region::LateBound(depth, idx, def_id.to_def_id(), origin),
81 )
82 }
83
late_anon(named_late_bound_vars: u32, index: &Cell<u32>) -> Region84 fn late_anon(named_late_bound_vars: u32, index: &Cell<u32>) -> Region {
85 let i = index.get();
86 index.set(i + 1);
87 let depth = ty::INNERMOST;
88 Region::LateBoundAnon(depth, named_late_bound_vars + i, i)
89 }
90
id(&self) -> Option<DefId>91 fn id(&self) -> Option<DefId> {
92 match *self {
93 Region::Static | Region::LateBoundAnon(..) => None,
94
95 Region::EarlyBound(_, id, _) | Region::LateBound(_, _, id, _) | Region::Free(_, id) => {
96 Some(id)
97 }
98 }
99 }
100
shifted(self, amount: u32) -> Region101 fn shifted(self, amount: u32) -> Region {
102 match self {
103 Region::LateBound(debruijn, idx, id, origin) => {
104 Region::LateBound(debruijn.shifted_in(amount), idx, id, origin)
105 }
106 Region::LateBoundAnon(debruijn, index, anon_index) => {
107 Region::LateBoundAnon(debruijn.shifted_in(amount), index, anon_index)
108 }
109 _ => self,
110 }
111 }
112
shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region113 fn shifted_out_to_binder(self, binder: ty::DebruijnIndex) -> Region {
114 match self {
115 Region::LateBound(debruijn, index, id, origin) => {
116 Region::LateBound(debruijn.shifted_out_to_binder(binder), index, id, origin)
117 }
118 Region::LateBoundAnon(debruijn, index, anon_index) => {
119 Region::LateBoundAnon(debruijn.shifted_out_to_binder(binder), index, anon_index)
120 }
121 _ => self,
122 }
123 }
124
subst<'a, L>(self, mut params: L, map: &NamedRegionMap) -> Option<Region> where L: Iterator<Item = &'a hir::Lifetime>,125 fn subst<'a, L>(self, mut params: L, map: &NamedRegionMap) -> Option<Region>
126 where
127 L: Iterator<Item = &'a hir::Lifetime>,
128 {
129 if let Region::EarlyBound(index, _, _) = self {
130 params.nth(index as usize).and_then(|lifetime| map.defs.get(&lifetime.hir_id).cloned())
131 } else {
132 Some(self)
133 }
134 }
135 }
136
137 /// Maps the id of each lifetime reference to the lifetime decl
138 /// that it corresponds to.
139 ///
140 /// FIXME. This struct gets converted to a `ResolveLifetimes` for
141 /// actual use. It has the same data, but indexed by `LocalDefId`. This
142 /// is silly.
143 #[derive(Debug, Default)]
144 struct NamedRegionMap {
145 // maps from every use of a named (not anonymous) lifetime to a
146 // `Region` describing how that region is bound
147 defs: HirIdMap<Region>,
148
149 // the set of lifetime def ids that are late-bound; a region can
150 // be late-bound if (a) it does NOT appear in a where-clause and
151 // (b) it DOES appear in the arguments.
152 late_bound: HirIdSet,
153
154 // Maps relevant hir items to the bound vars on them. These include:
155 // - function defs
156 // - function pointers
157 // - closures
158 // - trait refs
159 // - bound types (like `T` in `for<'a> T<'a>: Foo`)
160 late_bound_vars: HirIdMap<Vec<ty::BoundVariableKind>>,
161
162 // maps `PathSegment` `HirId`s to lifetime scopes.
163 scope_for_path: Option<FxHashMap<LocalDefId, FxHashMap<ItemLocalId, LifetimeScopeForPath>>>,
164 }
165
166 crate struct LifetimeContext<'a, 'tcx> {
167 crate tcx: TyCtxt<'tcx>,
168 map: &'a mut NamedRegionMap,
169 scope: ScopeRef<'a>,
170
171 /// Used to disallow the use of in-band lifetimes in `fn` or `Fn` syntax.
172 is_in_fn_syntax: bool,
173
174 is_in_const_generic: bool,
175
176 /// Indicates that we only care about the definition of a trait. This should
177 /// be false if the `Item` we are resolving lifetimes for is not a trait or
178 /// we eventually need lifetimes resolve for trait items.
179 trait_definition_only: bool,
180
181 /// List of labels in the function/method currently under analysis.
182 labels_in_fn: Vec<Ident>,
183
184 /// Cache for cross-crate per-definition object lifetime defaults.
185 xcrate_object_lifetime_defaults: DefIdMap<Vec<ObjectLifetimeDefault>>,
186
187 lifetime_uses: &'a mut DefIdMap<LifetimeUseSet<'tcx>>,
188
189 /// When encountering an undefined named lifetime, we will suggest introducing it in these
190 /// places.
191 crate missing_named_lifetime_spots: Vec<MissingLifetimeSpot<'tcx>>,
192 }
193
194 #[derive(Debug)]
195 enum Scope<'a> {
196 /// Declares lifetimes, and each can be early-bound or late-bound.
197 /// The `DebruijnIndex` of late-bound lifetimes starts at `1` and
198 /// it should be shifted by the number of `Binder`s in between the
199 /// declaration `Binder` and the location it's referenced from.
200 Binder {
201 /// We use an IndexMap here because we want these lifetimes in order
202 /// for diagnostics.
203 lifetimes: FxIndexMap<hir::ParamName, Region>,
204
205 /// if we extend this scope with another scope, what is the next index
206 /// we should use for an early-bound region?
207 next_early_index: u32,
208
209 /// Flag is set to true if, in this binder, `'_` would be
210 /// equivalent to a "single-use region". This is true on
211 /// impls, but not other kinds of items.
212 track_lifetime_uses: bool,
213
214 /// Whether or not this binder would serve as the parent
215 /// binder for opaque types introduced within. For example:
216 ///
217 /// ```text
218 /// fn foo<'a>() -> impl for<'b> Trait<Item = impl Trait2<'a>>
219 /// ```
220 ///
221 /// Here, the opaque types we create for the `impl Trait`
222 /// and `impl Trait2` references will both have the `foo` item
223 /// as their parent. When we get to `impl Trait2`, we find
224 /// that it is nested within the `for<>` binder -- this flag
225 /// allows us to skip that when looking for the parent binder
226 /// of the resulting opaque type.
227 opaque_type_parent: bool,
228
229 scope_type: BinderScopeType,
230
231 /// The late bound vars for a given item are stored by `HirId` to be
232 /// queried later. However, if we enter an elision scope, we have to
233 /// later append the elided bound vars to the list and need to know what
234 /// to append to.
235 hir_id: hir::HirId,
236
237 s: ScopeRef<'a>,
238 },
239
240 /// Lifetimes introduced by a fn are scoped to the call-site for that fn,
241 /// if this is a fn body, otherwise the original definitions are used.
242 /// Unspecified lifetimes are inferred, unless an elision scope is nested,
243 /// e.g., `(&T, fn(&T) -> &T);` becomes `(&'_ T, for<'a> fn(&'a T) -> &'a T)`.
244 Body {
245 id: hir::BodyId,
246 s: ScopeRef<'a>,
247 },
248
249 /// A scope which either determines unspecified lifetimes or errors
250 /// on them (e.g., due to ambiguity). For more details, see `Elide`.
251 Elision {
252 elide: Elide,
253 s: ScopeRef<'a>,
254 },
255
256 /// Use a specific lifetime (if `Some`) or leave it unset (to be
257 /// inferred in a function body or potentially error outside one),
258 /// for the default choice of lifetime in a trait object type.
259 ObjectLifetimeDefault {
260 lifetime: Option<Region>,
261 s: ScopeRef<'a>,
262 },
263
264 /// When we have nested trait refs, we concanetate late bound vars for inner
265 /// trait refs from outer ones. But we also need to include any HRTB
266 /// lifetimes encountered when identifying the trait that an associated type
267 /// is declared on.
268 Supertrait {
269 lifetimes: Vec<ty::BoundVariableKind>,
270 s: ScopeRef<'a>,
271 },
272
273 TraitRefBoundary {
274 s: ScopeRef<'a>,
275 },
276
277 Root,
278 }
279
280 #[derive(Copy, Clone, Debug)]
281 enum BinderScopeType {
282 /// Any non-concatenating binder scopes.
283 Normal,
284 /// Within a syntactic trait ref, there may be multiple poly trait refs that
285 /// are nested (under the `associcated_type_bounds` feature). The binders of
286 /// the innner poly trait refs are extended from the outer poly trait refs
287 /// and don't increase the late bound depth. If you had
288 /// `T: for<'a> Foo<Bar: for<'b> Baz<'a, 'b>>`, then the `for<'b>` scope
289 /// would be `Concatenating`. This also used in trait refs in where clauses
290 /// where we have two binders `for<> T: for<> Foo` (I've intentionally left
291 /// out any lifetimes because they aren't needed to show the two scopes).
292 /// The inner `for<>` has a scope of `Concatenating`.
293 Concatenating,
294 }
295
296 // A helper struct for debugging scopes without printing parent scopes
297 struct TruncatedScopeDebug<'a>(&'a Scope<'a>);
298
299 impl<'a> fmt::Debug for TruncatedScopeDebug<'a> {
fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result300 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
301 match self.0 {
302 Scope::Binder {
303 lifetimes,
304 next_early_index,
305 track_lifetime_uses,
306 opaque_type_parent,
307 scope_type,
308 hir_id,
309 s: _,
310 } => f
311 .debug_struct("Binder")
312 .field("lifetimes", lifetimes)
313 .field("next_early_index", next_early_index)
314 .field("track_lifetime_uses", track_lifetime_uses)
315 .field("opaque_type_parent", opaque_type_parent)
316 .field("scope_type", scope_type)
317 .field("hir_id", hir_id)
318 .field("s", &"..")
319 .finish(),
320 Scope::Body { id, s: _ } => {
321 f.debug_struct("Body").field("id", id).field("s", &"..").finish()
322 }
323 Scope::Elision { elide, s: _ } => {
324 f.debug_struct("Elision").field("elide", elide).field("s", &"..").finish()
325 }
326 Scope::ObjectLifetimeDefault { lifetime, s: _ } => f
327 .debug_struct("ObjectLifetimeDefault")
328 .field("lifetime", lifetime)
329 .field("s", &"..")
330 .finish(),
331 Scope::Supertrait { lifetimes, s: _ } => f
332 .debug_struct("Supertrait")
333 .field("lifetimes", lifetimes)
334 .field("s", &"..")
335 .finish(),
336 Scope::TraitRefBoundary { s: _ } => f.debug_struct("TraitRefBoundary").finish(),
337 Scope::Root => f.debug_struct("Root").finish(),
338 }
339 }
340 }
341
342 #[derive(Clone, Debug)]
343 enum Elide {
344 /// Use a fresh anonymous late-bound lifetime each time, by
345 /// incrementing the counter to generate sequential indices. All
346 /// anonymous lifetimes must start *after* named bound vars.
347 FreshLateAnon(u32, Cell<u32>),
348 /// Always use this one lifetime.
349 Exact(Region),
350 /// Less or more than one lifetime were found, error on unspecified.
351 Error(Vec<ElisionFailureInfo>),
352 /// Forbid lifetime elision inside of a larger scope where it would be
353 /// permitted. For example, in let position impl trait.
354 Forbid,
355 }
356
357 #[derive(Clone, Debug)]
358 crate struct ElisionFailureInfo {
359 /// Where we can find the argument pattern.
360 parent: Option<hir::BodyId>,
361 /// The index of the argument in the original definition.
362 index: usize,
363 lifetime_count: usize,
364 have_bound_regions: bool,
365 crate span: Span,
366 }
367
368 type ScopeRef<'a> = &'a Scope<'a>;
369
370 const ROOT_SCOPE: ScopeRef<'static> = &Scope::Root;
371
provide(providers: &mut ty::query::Providers)372 pub fn provide(providers: &mut ty::query::Providers) {
373 *providers = ty::query::Providers {
374 resolve_lifetimes_trait_definition,
375 resolve_lifetimes,
376
377 named_region_map: |tcx, id| resolve_lifetimes_for(tcx, id).defs.get(&id),
378 is_late_bound_map,
379 object_lifetime_defaults_map: |tcx, id| {
380 let hir_id = tcx.hir().local_def_id_to_hir_id(id);
381 match tcx.hir().find(hir_id) {
382 Some(Node::Item(item)) => compute_object_lifetime_defaults(tcx, item),
383 _ => None,
384 }
385 },
386 late_bound_vars_map: |tcx, id| resolve_lifetimes_for(tcx, id).late_bound_vars.get(&id),
387 lifetime_scope_map: |tcx, id| {
388 let item_id = item_for(tcx, id);
389 do_resolve(tcx, item_id, false, true).scope_for_path.unwrap().remove(&id)
390 },
391
392 ..*providers
393 };
394 }
395
396 /// Like `resolve_lifetimes`, but does not resolve lifetimes for trait items.
397 /// Also does not generate any diagnostics.
398 ///
399 /// This is ultimately a subset of the `resolve_lifetimes` work. It effectively
400 /// resolves lifetimes only within the trait "header" -- that is, the trait
401 /// and supertrait list. In contrast, `resolve_lifetimes` resolves all the
402 /// lifetimes within the trait and its items. There is room to refactor this,
403 /// for example to resolve lifetimes for each trait item in separate queries,
404 /// but it's convenient to do the entire trait at once because the lifetimes
405 /// from the trait definition are in scope within the trait items as well.
406 ///
407 /// The reason for this separate call is to resolve what would otherwise
408 /// be a cycle. Consider this example:
409 ///
410 /// ```rust
411 /// trait Base<'a> {
412 /// type BaseItem;
413 /// }
414 /// trait Sub<'b>: for<'a> Base<'a> {
415 /// type SubItem: Sub<BaseItem = &'b u32>;
416 /// }
417 /// ```
418 ///
419 /// When we resolve `Sub` and all its items, we also have to resolve `Sub<BaseItem = &'b u32>`.
420 /// To figure out the index of `'b`, we have to know about the supertraits
421 /// of `Sub` so that we can determine that the `for<'a>` will be in scope.
422 /// (This is because we -- currently at least -- flatten all the late-bound
423 /// lifetimes into a single binder.) This requires us to resolve the
424 /// *trait definition* of `Sub`; basically just enough lifetime information
425 /// to look at the supertraits.
426 #[tracing::instrument(level = "debug", skip(tcx))]
resolve_lifetimes_trait_definition( tcx: TyCtxt<'_>, local_def_id: LocalDefId, ) -> ResolveLifetimes427 fn resolve_lifetimes_trait_definition(
428 tcx: TyCtxt<'_>,
429 local_def_id: LocalDefId,
430 ) -> ResolveLifetimes {
431 convert_named_region_map(do_resolve(tcx, local_def_id, true, false))
432 }
433
434 /// Computes the `ResolveLifetimes` map that contains data for an entire `Item`.
435 /// You should not read the result of this query directly, but rather use
436 /// `named_region_map`, `is_late_bound_map`, etc.
437 #[tracing::instrument(level = "debug", skip(tcx))]
resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> ResolveLifetimes438 fn resolve_lifetimes(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> ResolveLifetimes {
439 convert_named_region_map(do_resolve(tcx, local_def_id, false, false))
440 }
441
do_resolve( tcx: TyCtxt<'_>, local_def_id: LocalDefId, trait_definition_only: bool, with_scope_for_path: bool, ) -> NamedRegionMap442 fn do_resolve(
443 tcx: TyCtxt<'_>,
444 local_def_id: LocalDefId,
445 trait_definition_only: bool,
446 with_scope_for_path: bool,
447 ) -> NamedRegionMap {
448 let item = tcx.hir().expect_item(tcx.hir().local_def_id_to_hir_id(local_def_id));
449 let mut named_region_map = NamedRegionMap {
450 defs: Default::default(),
451 late_bound: Default::default(),
452 late_bound_vars: Default::default(),
453 scope_for_path: with_scope_for_path.then(|| Default::default()),
454 };
455 let mut visitor = LifetimeContext {
456 tcx,
457 map: &mut named_region_map,
458 scope: ROOT_SCOPE,
459 is_in_fn_syntax: false,
460 is_in_const_generic: false,
461 trait_definition_only,
462 labels_in_fn: vec![],
463 xcrate_object_lifetime_defaults: Default::default(),
464 lifetime_uses: &mut Default::default(),
465 missing_named_lifetime_spots: vec![],
466 };
467 visitor.visit_item(item);
468
469 named_region_map
470 }
471
convert_named_region_map(named_region_map: NamedRegionMap) -> ResolveLifetimes472 fn convert_named_region_map(named_region_map: NamedRegionMap) -> ResolveLifetimes {
473 let mut rl = ResolveLifetimes::default();
474
475 for (hir_id, v) in named_region_map.defs {
476 let map = rl.defs.entry(hir_id.owner).or_default();
477 map.insert(hir_id.local_id, v);
478 }
479 for hir_id in named_region_map.late_bound {
480 let map = rl.late_bound.entry(hir_id.owner).or_default();
481 map.insert(hir_id.local_id);
482 }
483 for (hir_id, v) in named_region_map.late_bound_vars {
484 let map = rl.late_bound_vars.entry(hir_id.owner).or_default();
485 map.insert(hir_id.local_id, v);
486 }
487
488 debug!(?rl.defs);
489 rl
490 }
491
492 /// Given `any` owner (structs, traits, trait methods, etc.), does lifetime resolution.
493 /// There are two important things this does.
494 /// First, we have to resolve lifetimes for
495 /// the entire *`Item`* that contains this owner, because that's the largest "scope"
496 /// where we can have relevant lifetimes.
497 /// Second, if we are asking for lifetimes in a trait *definition*, we use `resolve_lifetimes_trait_definition`
498 /// instead of `resolve_lifetimes`, which does not descend into the trait items and does not emit diagnostics.
499 /// This allows us to avoid cycles. Importantly, if we ask for lifetimes for lifetimes that have an owner
500 /// other than the trait itself (like the trait methods or associated types), then we just use the regular
501 /// `resolve_lifetimes`.
resolve_lifetimes_for<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ResolveLifetimes502 fn resolve_lifetimes_for<'tcx>(tcx: TyCtxt<'tcx>, def_id: LocalDefId) -> &'tcx ResolveLifetimes {
503 let item_id = item_for(tcx, def_id);
504 if item_id == def_id {
505 let item = tcx.hir().item(hir::ItemId { def_id: item_id });
506 match item.kind {
507 hir::ItemKind::Trait(..) => tcx.resolve_lifetimes_trait_definition(item_id),
508 _ => tcx.resolve_lifetimes(item_id),
509 }
510 } else {
511 tcx.resolve_lifetimes(item_id)
512 }
513 }
514
515 /// Finds the `Item` that contains the given `LocalDefId`
item_for(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> LocalDefId516 fn item_for(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> LocalDefId {
517 let hir_id = tcx.hir().local_def_id_to_hir_id(local_def_id);
518 match tcx.hir().find(hir_id) {
519 Some(Node::Item(item)) => {
520 return item.def_id;
521 }
522 _ => {}
523 }
524 let item = {
525 let mut parent_iter = tcx.hir().parent_iter(hir_id);
526 loop {
527 let node = parent_iter.next().map(|n| n.1);
528 match node {
529 Some(hir::Node::Item(item)) => break item.def_id,
530 Some(hir::Node::Crate(_)) | None => bug!("Called `item_for` on an Item."),
531 _ => {}
532 }
533 }
534 };
535 item
536 }
537
is_late_bound_map<'tcx>( tcx: TyCtxt<'tcx>, def_id: LocalDefId, ) -> Option<(LocalDefId, &'tcx FxHashSet<ItemLocalId>)>538 fn is_late_bound_map<'tcx>(
539 tcx: TyCtxt<'tcx>,
540 def_id: LocalDefId,
541 ) -> Option<(LocalDefId, &'tcx FxHashSet<ItemLocalId>)> {
542 match tcx.def_kind(def_id) {
543 DefKind::AnonConst | DefKind::InlineConst => {
544 let mut def_id = tcx
545 .parent(def_id.to_def_id())
546 .unwrap_or_else(|| bug!("anon const or closure without a parent"));
547 // We search for the next outer anon const or fn here
548 // while skipping closures.
549 //
550 // Note that for `AnonConst` we still just recurse until we
551 // find a function body, but who cares :shrug:
552 while tcx.is_closure(def_id) {
553 def_id = tcx
554 .parent(def_id)
555 .unwrap_or_else(|| bug!("anon const or closure without a parent"));
556 }
557
558 tcx.is_late_bound_map(def_id.expect_local())
559 }
560 _ => resolve_lifetimes_for(tcx, def_id).late_bound.get(&def_id).map(|lt| (def_id, lt)),
561 }
562 }
563
564 /// In traits, there is an implicit `Self` type parameter which comes before the generics.
565 /// We have to account for this when computing the index of the other generic parameters.
566 /// This function returns whether there is such an implicit parameter defined on the given item.
sub_items_have_self_param(node: &hir::ItemKind<'_>) -> bool567 fn sub_items_have_self_param(node: &hir::ItemKind<'_>) -> bool {
568 matches!(*node, hir::ItemKind::Trait(..) | hir::ItemKind::TraitAlias(..))
569 }
570
late_region_as_bound_region<'tcx>(tcx: TyCtxt<'tcx>, region: &Region) -> ty::BoundVariableKind571 fn late_region_as_bound_region<'tcx>(tcx: TyCtxt<'tcx>, region: &Region) -> ty::BoundVariableKind {
572 match region {
573 Region::LateBound(_, _, def_id, _) => {
574 let name = tcx.hir().name(tcx.hir().local_def_id_to_hir_id(def_id.expect_local()));
575 ty::BoundVariableKind::Region(ty::BrNamed(*def_id, name))
576 }
577 Region::LateBoundAnon(_, _, anon_idx) => {
578 ty::BoundVariableKind::Region(ty::BrAnon(*anon_idx))
579 }
580 _ => bug!("{:?} is not a late region", region),
581 }
582 }
583
584 #[tracing::instrument(level = "debug")]
get_lifetime_scopes_for_path(mut scope: &Scope<'_>) -> LifetimeScopeForPath585 fn get_lifetime_scopes_for_path(mut scope: &Scope<'_>) -> LifetimeScopeForPath {
586 let mut available_lifetimes = vec![];
587 loop {
588 match scope {
589 Scope::Binder { lifetimes, s, .. } => {
590 available_lifetimes.extend(lifetimes.keys().filter_map(|p| match p {
591 hir::ParamName::Plain(ident) => Some(ident.name.to_string()),
592 _ => None,
593 }));
594 scope = s;
595 }
596 Scope::Body { s, .. } => {
597 scope = s;
598 }
599 Scope::Elision { elide, s } => {
600 if let Elide::Exact(_) = elide {
601 return LifetimeScopeForPath::Elided;
602 } else {
603 scope = s;
604 }
605 }
606 Scope::ObjectLifetimeDefault { s, .. } => {
607 scope = s;
608 }
609 Scope::Root => {
610 return LifetimeScopeForPath::NonElided(available_lifetimes);
611 }
612 Scope::Supertrait { s, .. } | Scope::TraitRefBoundary { s, .. } => {
613 scope = s;
614 }
615 }
616 }
617 }
618
619 impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
620 /// Returns the binders in scope and the type of `Binder` that should be created for a poly trait ref.
poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType)621 fn poly_trait_ref_binder_info(&mut self) -> (Vec<ty::BoundVariableKind>, BinderScopeType) {
622 let mut scope = self.scope;
623 let mut supertrait_lifetimes = vec![];
624 loop {
625 match scope {
626 Scope::Body { .. } | Scope::Root => {
627 break (vec![], BinderScopeType::Normal);
628 }
629
630 Scope::Elision { s, .. } | Scope::ObjectLifetimeDefault { s, .. } => {
631 scope = s;
632 }
633
634 Scope::Supertrait { s, lifetimes } => {
635 supertrait_lifetimes = lifetimes.clone();
636 scope = s;
637 }
638
639 Scope::TraitRefBoundary { .. } => {
640 // We should only see super trait lifetimes if there is a `Binder` above
641 assert!(supertrait_lifetimes.is_empty());
642 break (vec![], BinderScopeType::Normal);
643 }
644
645 Scope::Binder { hir_id, .. } => {
646 // Nested poly trait refs have the binders concatenated
647 let mut full_binders =
648 self.map.late_bound_vars.entry(*hir_id).or_default().clone();
649 full_binders.extend(supertrait_lifetimes.into_iter());
650 break (full_binders, BinderScopeType::Concatenating);
651 }
652 }
653 }
654 }
655 }
656 impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
657 type Map = Map<'tcx>;
658
nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map>659 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
660 NestedVisitorMap::All(self.tcx.hir())
661 }
662
663 // We want to nest trait/impl items in their parent, but nothing else.
visit_nested_item(&mut self, _: hir::ItemId)664 fn visit_nested_item(&mut self, _: hir::ItemId) {}
665
visit_trait_item_ref(&mut self, ii: &'tcx hir::TraitItemRef)666 fn visit_trait_item_ref(&mut self, ii: &'tcx hir::TraitItemRef) {
667 if !self.trait_definition_only {
668 intravisit::walk_trait_item_ref(self, ii)
669 }
670 }
671
visit_nested_body(&mut self, body: hir::BodyId)672 fn visit_nested_body(&mut self, body: hir::BodyId) {
673 // Each body has their own set of labels, save labels.
674 let saved = take(&mut self.labels_in_fn);
675 let body = self.tcx.hir().body(body);
676 extract_labels(self, body);
677 self.with(Scope::Body { id: body.id(), s: self.scope }, |_, this| {
678 this.visit_body(body);
679 });
680 self.labels_in_fn = saved;
681 }
682
visit_fn( &mut self, fk: intravisit::FnKind<'tcx>, fd: &'tcx hir::FnDecl<'tcx>, b: hir::BodyId, s: rustc_span::Span, hir_id: hir::HirId, )683 fn visit_fn(
684 &mut self,
685 fk: intravisit::FnKind<'tcx>,
686 fd: &'tcx hir::FnDecl<'tcx>,
687 b: hir::BodyId,
688 s: rustc_span::Span,
689 hir_id: hir::HirId,
690 ) {
691 let name = match fk {
692 intravisit::FnKind::ItemFn(id, _, _, _) => id.as_str(),
693 intravisit::FnKind::Method(id, _, _) => id.as_str(),
694 intravisit::FnKind::Closure => Symbol::intern("closure").as_str(),
695 };
696 let name: &str = &name;
697 let span = span!(Level::DEBUG, "visit_fn", name);
698 let _enter = span.enter();
699 match fk {
700 // Any `Binders` are handled elsewhere
701 intravisit::FnKind::ItemFn(..) | intravisit::FnKind::Method(..) => {
702 intravisit::walk_fn(self, fk, fd, b, s, hir_id)
703 }
704 intravisit::FnKind::Closure => {
705 self.map.late_bound_vars.insert(hir_id, vec![]);
706 let scope = Scope::Binder {
707 hir_id,
708 lifetimes: FxIndexMap::default(),
709 next_early_index: self.next_early_index(),
710 s: self.scope,
711 track_lifetime_uses: true,
712 opaque_type_parent: false,
713 scope_type: BinderScopeType::Normal,
714 };
715 self.with(scope, move |_old_scope, this| {
716 intravisit::walk_fn(this, fk, fd, b, s, hir_id)
717 });
718 }
719 }
720 }
721
visit_item(&mut self, item: &'tcx hir::Item<'tcx>)722 fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
723 match &item.kind {
724 hir::ItemKind::Impl(hir::Impl { of_trait, .. }) => {
725 if let Some(of_trait) = of_trait {
726 self.map.late_bound_vars.insert(of_trait.hir_ref_id, Vec::default());
727 }
728 }
729 _ => {}
730 }
731 match item.kind {
732 hir::ItemKind::Fn(ref sig, ref generics, _) => {
733 self.missing_named_lifetime_spots.push(generics.into());
734 self.visit_early_late(None, item.hir_id(), &sig.decl, generics, |this| {
735 intravisit::walk_item(this, item);
736 });
737 self.missing_named_lifetime_spots.pop();
738 }
739
740 hir::ItemKind::ExternCrate(_)
741 | hir::ItemKind::Use(..)
742 | hir::ItemKind::Macro(..)
743 | hir::ItemKind::Mod(..)
744 | hir::ItemKind::ForeignMod { .. }
745 | hir::ItemKind::GlobalAsm(..) => {
746 // These sorts of items have no lifetime parameters at all.
747 intravisit::walk_item(self, item);
748 }
749 hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => {
750 // No lifetime parameters, but implied 'static.
751 let scope = Scope::Elision { elide: Elide::Exact(Region::Static), s: ROOT_SCOPE };
752 self.with(scope, |_, this| intravisit::walk_item(this, item));
753 }
754 hir::ItemKind::OpaqueTy(hir::OpaqueTy { .. }) => {
755 // Opaque types are visited when we visit the
756 // `TyKind::OpaqueDef`, so that they have the lifetimes from
757 // their parent opaque_ty in scope.
758 //
759 // The core idea here is that since OpaqueTys are generated with the impl Trait as
760 // their owner, we can keep going until we find the Item that owns that. We then
761 // conservatively add all resolved lifetimes. Otherwise we run into problems in
762 // cases like `type Foo<'a> = impl Bar<As = impl Baz + 'a>`.
763 for (_hir_id, node) in
764 self.tcx.hir().parent_iter(self.tcx.hir().local_def_id_to_hir_id(item.def_id))
765 {
766 match node {
767 hir::Node::Item(parent_item) => {
768 let resolved_lifetimes: &ResolveLifetimes =
769 self.tcx.resolve_lifetimes(item_for(self.tcx, parent_item.def_id));
770 // We need to add *all* deps, since opaque tys may want them from *us*
771 for (&owner, defs) in resolved_lifetimes.defs.iter() {
772 defs.iter().for_each(|(&local_id, region)| {
773 self.map.defs.insert(hir::HirId { owner, local_id }, *region);
774 });
775 }
776 for (&owner, late_bound) in resolved_lifetimes.late_bound.iter() {
777 late_bound.iter().for_each(|&local_id| {
778 self.map.late_bound.insert(hir::HirId { owner, local_id });
779 });
780 }
781 for (&owner, late_bound_vars) in
782 resolved_lifetimes.late_bound_vars.iter()
783 {
784 late_bound_vars.iter().for_each(|(&local_id, late_bound_vars)| {
785 self.map.late_bound_vars.insert(
786 hir::HirId { owner, local_id },
787 late_bound_vars.clone(),
788 );
789 });
790 }
791 break;
792 }
793 hir::Node::Crate(_) => bug!("No Item about an OpaqueTy"),
794 _ => {}
795 }
796 }
797 }
798 hir::ItemKind::TyAlias(_, ref generics)
799 | hir::ItemKind::Enum(_, ref generics)
800 | hir::ItemKind::Struct(_, ref generics)
801 | hir::ItemKind::Union(_, ref generics)
802 | hir::ItemKind::Trait(_, _, ref generics, ..)
803 | hir::ItemKind::TraitAlias(ref generics, ..)
804 | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => {
805 self.missing_named_lifetime_spots.push(generics.into());
806
807 // Impls permit `'_` to be used and it is equivalent to "some fresh lifetime name".
808 // This is not true for other kinds of items.
809 let track_lifetime_uses = matches!(item.kind, hir::ItemKind::Impl { .. });
810 // These kinds of items have only early-bound lifetime parameters.
811 let mut index = if sub_items_have_self_param(&item.kind) {
812 1 // Self comes before lifetimes
813 } else {
814 0
815 };
816 let mut non_lifetime_count = 0;
817 let lifetimes = generics
818 .params
819 .iter()
820 .filter_map(|param| match param.kind {
821 GenericParamKind::Lifetime { .. } => {
822 Some(Region::early(&self.tcx.hir(), &mut index, param))
823 }
824 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
825 non_lifetime_count += 1;
826 None
827 }
828 })
829 .collect();
830 self.map.late_bound_vars.insert(item.hir_id(), vec![]);
831 let scope = Scope::Binder {
832 hir_id: item.hir_id(),
833 lifetimes,
834 next_early_index: index + non_lifetime_count,
835 opaque_type_parent: true,
836 track_lifetime_uses,
837 scope_type: BinderScopeType::Normal,
838 s: ROOT_SCOPE,
839 };
840 self.with(scope, |old_scope, this| {
841 this.check_lifetime_params(old_scope, &generics.params);
842 let scope = Scope::TraitRefBoundary { s: this.scope };
843 this.with(scope, |_, this| {
844 intravisit::walk_item(this, item);
845 });
846 });
847 self.missing_named_lifetime_spots.pop();
848 }
849 }
850 }
851
visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>)852 fn visit_foreign_item(&mut self, item: &'tcx hir::ForeignItem<'tcx>) {
853 match item.kind {
854 hir::ForeignItemKind::Fn(ref decl, _, ref generics) => {
855 self.visit_early_late(None, item.hir_id(), decl, generics, |this| {
856 intravisit::walk_foreign_item(this, item);
857 })
858 }
859 hir::ForeignItemKind::Static(..) => {
860 intravisit::walk_foreign_item(self, item);
861 }
862 hir::ForeignItemKind::Type => {
863 intravisit::walk_foreign_item(self, item);
864 }
865 }
866 }
867
868 #[tracing::instrument(level = "debug", skip(self))]
visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>)869 fn visit_ty(&mut self, ty: &'tcx hir::Ty<'tcx>) {
870 match ty.kind {
871 hir::TyKind::BareFn(ref c) => {
872 let next_early_index = self.next_early_index();
873 let was_in_fn_syntax = self.is_in_fn_syntax;
874 self.is_in_fn_syntax = true;
875 let lifetime_span: Option<Span> =
876 c.generic_params.iter().rev().find_map(|param| match param.kind {
877 GenericParamKind::Lifetime { .. } => Some(param.span),
878 _ => None,
879 });
880 let (span, span_type) = if let Some(span) = lifetime_span {
881 (span.shrink_to_hi(), ForLifetimeSpanType::TypeTail)
882 } else {
883 (ty.span.shrink_to_lo(), ForLifetimeSpanType::TypeEmpty)
884 };
885 self.missing_named_lifetime_spots
886 .push(MissingLifetimeSpot::HigherRanked { span, span_type });
887 let (lifetimes, binders): (FxIndexMap<hir::ParamName, Region>, Vec<_>) = c
888 .generic_params
889 .iter()
890 .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. }))
891 .enumerate()
892 .map(|(late_bound_idx, param)| {
893 let pair = Region::late(late_bound_idx as u32, &self.tcx.hir(), param);
894 let r = late_region_as_bound_region(self.tcx, &pair.1);
895 (pair, r)
896 })
897 .unzip();
898 self.map.late_bound_vars.insert(ty.hir_id, binders);
899 let scope = Scope::Binder {
900 hir_id: ty.hir_id,
901 lifetimes,
902 s: self.scope,
903 next_early_index,
904 track_lifetime_uses: true,
905 opaque_type_parent: false,
906 scope_type: BinderScopeType::Normal,
907 };
908 self.with(scope, |old_scope, this| {
909 // a bare fn has no bounds, so everything
910 // contained within is scoped within its binder.
911 this.check_lifetime_params(old_scope, &c.generic_params);
912 intravisit::walk_ty(this, ty);
913 });
914 self.missing_named_lifetime_spots.pop();
915 self.is_in_fn_syntax = was_in_fn_syntax;
916 }
917 hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
918 debug!(?bounds, ?lifetime, "TraitObject");
919 let scope = Scope::TraitRefBoundary { s: self.scope };
920 self.with(scope, |_, this| {
921 for bound in bounds {
922 this.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
923 }
924 });
925 match lifetime.name {
926 LifetimeName::Implicit => {
927 // For types like `dyn Foo`, we should
928 // generate a special form of elided.
929 span_bug!(ty.span, "object-lifetime-default expected, not implicit",);
930 }
931 LifetimeName::ImplicitObjectLifetimeDefault => {
932 // If the user does not write *anything*, we
933 // use the object lifetime defaulting
934 // rules. So e.g., `Box<dyn Debug>` becomes
935 // `Box<dyn Debug + 'static>`.
936 self.resolve_object_lifetime_default(lifetime)
937 }
938 LifetimeName::Underscore => {
939 // If the user writes `'_`, we use the *ordinary* elision
940 // rules. So the `'_` in e.g., `Box<dyn Debug + '_>` will be
941 // resolved the same as the `'_` in `&'_ Foo`.
942 //
943 // cc #48468
944 self.resolve_elided_lifetimes(&[lifetime])
945 }
946 LifetimeName::Param(_) | LifetimeName::Static => {
947 // If the user wrote an explicit name, use that.
948 self.visit_lifetime(lifetime);
949 }
950 LifetimeName::Error => {}
951 }
952 }
953 hir::TyKind::Rptr(ref lifetime_ref, ref mt) => {
954 self.visit_lifetime(lifetime_ref);
955 let scope = Scope::ObjectLifetimeDefault {
956 lifetime: self.map.defs.get(&lifetime_ref.hir_id).cloned(),
957 s: self.scope,
958 };
959 self.with(scope, |_, this| this.visit_ty(&mt.ty));
960 }
961 hir::TyKind::OpaqueDef(item_id, lifetimes) => {
962 // Resolve the lifetimes in the bounds to the lifetime defs in the generics.
963 // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to
964 // `type MyAnonTy<'b> = impl MyTrait<'b>;`
965 // ^ ^ this gets resolved in the scope of
966 // the opaque_ty generics
967 let opaque_ty = self.tcx.hir().item(item_id);
968 let (generics, bounds) = match opaque_ty.kind {
969 // Named opaque `impl Trait` types are reached via `TyKind::Path`.
970 // This arm is for `impl Trait` in the types of statics, constants and locals.
971 hir::ItemKind::OpaqueTy(hir::OpaqueTy { impl_trait_fn: None, .. }) => {
972 intravisit::walk_ty(self, ty);
973
974 // Elided lifetimes are not allowed in non-return
975 // position impl Trait
976 let scope = Scope::TraitRefBoundary { s: self.scope };
977 self.with(scope, |_, this| {
978 let scope = Scope::Elision { elide: Elide::Forbid, s: this.scope };
979 this.with(scope, |_, this| {
980 intravisit::walk_item(this, opaque_ty);
981 })
982 });
983
984 return;
985 }
986 // RPIT (return position impl trait)
987 hir::ItemKind::OpaqueTy(hir::OpaqueTy {
988 impl_trait_fn: Some(_),
989 ref generics,
990 bounds,
991 ..
992 }) => (generics, bounds),
993 ref i => bug!("`impl Trait` pointed to non-opaque type?? {:#?}", i),
994 };
995
996 // Resolve the lifetimes that are applied to the opaque type.
997 // These are resolved in the current scope.
998 // `fn foo<'a>() -> impl MyTrait<'a> { ... }` desugars to
999 // `fn foo<'a>() -> MyAnonTy<'a> { ... }`
1000 // ^ ^this gets resolved in the current scope
1001 for lifetime in lifetimes {
1002 if let hir::GenericArg::Lifetime(lifetime) = lifetime {
1003 self.visit_lifetime(lifetime);
1004
1005 // Check for predicates like `impl for<'a> Trait<impl OtherTrait<'a>>`
1006 // and ban them. Type variables instantiated inside binders aren't
1007 // well-supported at the moment, so this doesn't work.
1008 // In the future, this should be fixed and this error should be removed.
1009 let def = self.map.defs.get(&lifetime.hir_id).cloned();
1010 if let Some(Region::LateBound(_, _, def_id, _)) = def {
1011 if let Some(def_id) = def_id.as_local() {
1012 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
1013 // Ensure that the parent of the def is an item, not HRTB
1014 let parent_id = self.tcx.hir().get_parent_node(hir_id);
1015 // FIXME(cjgillot) Can this check be replaced by
1016 // `let parent_is_item = parent_id.is_owner();`?
1017 let parent_is_item =
1018 if let Some(parent_def_id) = parent_id.as_owner() {
1019 matches!(
1020 self.tcx.hir().krate().owners.get(parent_def_id),
1021 Some(Some(_)),
1022 )
1023 } else {
1024 false
1025 };
1026
1027 if !parent_is_item {
1028 if !self.trait_definition_only {
1029 struct_span_err!(
1030 self.tcx.sess,
1031 lifetime.span,
1032 E0657,
1033 "`impl Trait` can only capture lifetimes \
1034 bound at the fn or impl level"
1035 )
1036 .emit();
1037 }
1038 self.uninsert_lifetime_on_error(lifetime, def.unwrap());
1039 }
1040 }
1041 }
1042 }
1043 }
1044
1045 // We want to start our early-bound indices at the end of the parent scope,
1046 // not including any parent `impl Trait`s.
1047 let mut index = self.next_early_index_for_opaque_type();
1048 debug!(?index);
1049
1050 let mut elision = None;
1051 let mut lifetimes = FxIndexMap::default();
1052 let mut non_lifetime_count = 0;
1053 for param in generics.params {
1054 match param.kind {
1055 GenericParamKind::Lifetime { .. } => {
1056 let (name, reg) = Region::early(&self.tcx.hir(), &mut index, ¶m);
1057 let Region::EarlyBound(_, def_id, _) = reg else {
1058 bug!();
1059 };
1060 // We cannot predict what lifetimes are unused in opaque type.
1061 self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
1062 if let hir::ParamName::Plain(Ident {
1063 name: kw::UnderscoreLifetime,
1064 ..
1065 }) = name
1066 {
1067 // Pick the elided lifetime "definition" if one exists
1068 // and use it to make an elision scope.
1069 elision = Some(reg);
1070 } else {
1071 lifetimes.insert(name, reg);
1072 }
1073 }
1074 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1075 non_lifetime_count += 1;
1076 }
1077 }
1078 }
1079 let next_early_index = index + non_lifetime_count;
1080 self.map.late_bound_vars.insert(ty.hir_id, vec![]);
1081
1082 if let Some(elision_region) = elision {
1083 let scope =
1084 Scope::Elision { elide: Elide::Exact(elision_region), s: self.scope };
1085 self.with(scope, |_old_scope, this| {
1086 let scope = Scope::Binder {
1087 hir_id: ty.hir_id,
1088 lifetimes,
1089 next_early_index,
1090 s: this.scope,
1091 track_lifetime_uses: true,
1092 opaque_type_parent: false,
1093 scope_type: BinderScopeType::Normal,
1094 };
1095 this.with(scope, |_old_scope, this| {
1096 this.visit_generics(generics);
1097 let scope = Scope::TraitRefBoundary { s: this.scope };
1098 this.with(scope, |_, this| {
1099 for bound in bounds {
1100 this.visit_param_bound(bound);
1101 }
1102 })
1103 });
1104 });
1105 } else {
1106 let scope = Scope::Binder {
1107 hir_id: ty.hir_id,
1108 lifetimes,
1109 next_early_index,
1110 s: self.scope,
1111 track_lifetime_uses: true,
1112 opaque_type_parent: false,
1113 scope_type: BinderScopeType::Normal,
1114 };
1115 self.with(scope, |_old_scope, this| {
1116 let scope = Scope::TraitRefBoundary { s: this.scope };
1117 this.with(scope, |_, this| {
1118 this.visit_generics(generics);
1119 for bound in bounds {
1120 this.visit_param_bound(bound);
1121 }
1122 })
1123 });
1124 }
1125 }
1126 _ => intravisit::walk_ty(self, ty),
1127 }
1128 }
1129
visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>)1130 fn visit_trait_item(&mut self, trait_item: &'tcx hir::TraitItem<'tcx>) {
1131 use self::hir::TraitItemKind::*;
1132 match trait_item.kind {
1133 Fn(ref sig, _) => {
1134 self.missing_named_lifetime_spots.push((&trait_item.generics).into());
1135 let tcx = self.tcx;
1136 self.visit_early_late(
1137 Some(tcx.hir().get_parent_item(trait_item.hir_id())),
1138 trait_item.hir_id(),
1139 &sig.decl,
1140 &trait_item.generics,
1141 |this| intravisit::walk_trait_item(this, trait_item),
1142 );
1143 self.missing_named_lifetime_spots.pop();
1144 }
1145 Type(bounds, ref ty) => {
1146 self.missing_named_lifetime_spots.push((&trait_item.generics).into());
1147 let generics = &trait_item.generics;
1148 let mut index = self.next_early_index();
1149 debug!("visit_ty: index = {}", index);
1150 let mut non_lifetime_count = 0;
1151 let lifetimes = generics
1152 .params
1153 .iter()
1154 .filter_map(|param| match param.kind {
1155 GenericParamKind::Lifetime { .. } => {
1156 Some(Region::early(&self.tcx.hir(), &mut index, param))
1157 }
1158 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
1159 non_lifetime_count += 1;
1160 None
1161 }
1162 })
1163 .collect();
1164 self.map.late_bound_vars.insert(trait_item.hir_id(), vec![]);
1165 let scope = Scope::Binder {
1166 hir_id: trait_item.hir_id(),
1167 lifetimes,
1168 next_early_index: index + non_lifetime_count,
1169 s: self.scope,
1170 track_lifetime_uses: true,
1171 opaque_type_parent: true,
1172 scope_type: BinderScopeType::Normal,
1173 };
1174 self.with(scope, |old_scope, this| {
1175 this.check_lifetime_params(old_scope, &generics.params);
1176 let scope = Scope::TraitRefBoundary { s: this.scope };
1177 this.with(scope, |_, this| {
1178 this.visit_generics(generics);
1179 for bound in bounds {
1180 this.visit_param_bound(bound);
1181 }
1182 if let Some(ty) = ty {
1183 this.visit_ty(ty);
1184 }
1185 })
1186 });
1187 self.missing_named_lifetime_spots.pop();
1188 }
1189 Const(_, _) => {
1190 // Only methods and types support generics.
1191 assert!(trait_item.generics.params.is_empty());
1192 self.missing_named_lifetime_spots.push(MissingLifetimeSpot::Static);
1193 intravisit::walk_trait_item(self, trait_item);
1194 self.missing_named_lifetime_spots.pop();
1195 }
1196 }
1197 }
1198
visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>)1199 fn visit_impl_item(&mut self, impl_item: &'tcx hir::ImplItem<'tcx>) {
1200 use self::hir::ImplItemKind::*;
1201 match impl_item.kind {
1202 Fn(ref sig, _) => {
1203 self.missing_named_lifetime_spots.push((&impl_item.generics).into());
1204 let tcx = self.tcx;
1205 self.visit_early_late(
1206 Some(tcx.hir().get_parent_item(impl_item.hir_id())),
1207 impl_item.hir_id(),
1208 &sig.decl,
1209 &impl_item.generics,
1210 |this| intravisit::walk_impl_item(this, impl_item),
1211 );
1212 self.missing_named_lifetime_spots.pop();
1213 }
1214 TyAlias(ref ty) => {
1215 let generics = &impl_item.generics;
1216 self.missing_named_lifetime_spots.push(generics.into());
1217 let mut index = self.next_early_index();
1218 let mut non_lifetime_count = 0;
1219 debug!("visit_ty: index = {}", index);
1220 let lifetimes: FxIndexMap<hir::ParamName, Region> = generics
1221 .params
1222 .iter()
1223 .filter_map(|param| match param.kind {
1224 GenericParamKind::Lifetime { .. } => {
1225 Some(Region::early(&self.tcx.hir(), &mut index, param))
1226 }
1227 GenericParamKind::Const { .. } | GenericParamKind::Type { .. } => {
1228 non_lifetime_count += 1;
1229 None
1230 }
1231 })
1232 .collect();
1233 self.map.late_bound_vars.insert(ty.hir_id, vec![]);
1234 let scope = Scope::Binder {
1235 hir_id: ty.hir_id,
1236 lifetimes,
1237 next_early_index: index + non_lifetime_count,
1238 s: self.scope,
1239 track_lifetime_uses: true,
1240 opaque_type_parent: true,
1241 scope_type: BinderScopeType::Normal,
1242 };
1243 self.with(scope, |old_scope, this| {
1244 this.check_lifetime_params(old_scope, &generics.params);
1245 let scope = Scope::TraitRefBoundary { s: this.scope };
1246 this.with(scope, |_, this| {
1247 this.visit_generics(generics);
1248 this.visit_ty(ty);
1249 })
1250 });
1251 self.missing_named_lifetime_spots.pop();
1252 }
1253 Const(_, _) => {
1254 // Only methods and types support generics.
1255 assert!(impl_item.generics.params.is_empty());
1256 self.missing_named_lifetime_spots.push(MissingLifetimeSpot::Static);
1257 intravisit::walk_impl_item(self, impl_item);
1258 self.missing_named_lifetime_spots.pop();
1259 }
1260 }
1261 }
1262
1263 #[tracing::instrument(level = "debug", skip(self))]
visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime)1264 fn visit_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
1265 if lifetime_ref.is_elided() {
1266 self.resolve_elided_lifetimes(&[lifetime_ref]);
1267 return;
1268 }
1269 if lifetime_ref.is_static() {
1270 self.insert_lifetime(lifetime_ref, Region::Static);
1271 return;
1272 }
1273 if self.is_in_const_generic && lifetime_ref.name != LifetimeName::Error {
1274 self.emit_non_static_lt_in_const_generic_error(lifetime_ref);
1275 return;
1276 }
1277 self.resolve_lifetime_ref(lifetime_ref);
1278 }
1279
visit_assoc_type_binding(&mut self, type_binding: &'tcx hir::TypeBinding<'_>)1280 fn visit_assoc_type_binding(&mut self, type_binding: &'tcx hir::TypeBinding<'_>) {
1281 let scope = self.scope;
1282 if let Some(scope_for_path) = self.map.scope_for_path.as_mut() {
1283 // We add lifetime scope information for `Ident`s in associated type bindings and use
1284 // the `HirId` of the type binding as the key in `LifetimeMap`
1285 let lifetime_scope = get_lifetime_scopes_for_path(scope);
1286 let map = scope_for_path.entry(type_binding.hir_id.owner).or_default();
1287 map.insert(type_binding.hir_id.local_id, lifetime_scope);
1288 }
1289 hir::intravisit::walk_assoc_type_binding(self, type_binding);
1290 }
1291
visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId)1292 fn visit_path(&mut self, path: &'tcx hir::Path<'tcx>, _: hir::HirId) {
1293 for (i, segment) in path.segments.iter().enumerate() {
1294 let depth = path.segments.len() - i - 1;
1295 if let Some(ref args) = segment.args {
1296 self.visit_segment_args(path.res, depth, args);
1297 }
1298
1299 let scope = self.scope;
1300 if let Some(scope_for_path) = self.map.scope_for_path.as_mut() {
1301 // Add lifetime scope information to path segment. Note we cannot call `visit_path_segment`
1302 // here because that call would yield to resolution problems due to `walk_path_segment`
1303 // being called, which processes the path segments generic args, which we have already
1304 // processed using `visit_segment_args`.
1305 let lifetime_scope = get_lifetime_scopes_for_path(scope);
1306 if let Some(hir_id) = segment.hir_id {
1307 let map = scope_for_path.entry(hir_id.owner).or_default();
1308 map.insert(hir_id.local_id, lifetime_scope);
1309 }
1310 }
1311 }
1312 }
1313
visit_path_segment(&mut self, path_span: Span, path_segment: &'tcx hir::PathSegment<'tcx>)1314 fn visit_path_segment(&mut self, path_span: Span, path_segment: &'tcx hir::PathSegment<'tcx>) {
1315 let scope = self.scope;
1316 if let Some(scope_for_path) = self.map.scope_for_path.as_mut() {
1317 let lifetime_scope = get_lifetime_scopes_for_path(scope);
1318 if let Some(hir_id) = path_segment.hir_id {
1319 let map = scope_for_path.entry(hir_id.owner).or_default();
1320 map.insert(hir_id.local_id, lifetime_scope);
1321 }
1322 }
1323
1324 intravisit::walk_path_segment(self, path_span, path_segment);
1325 }
1326
visit_fn_decl(&mut self, fd: &'tcx hir::FnDecl<'tcx>)1327 fn visit_fn_decl(&mut self, fd: &'tcx hir::FnDecl<'tcx>) {
1328 let output = match fd.output {
1329 hir::FnRetTy::DefaultReturn(_) => None,
1330 hir::FnRetTy::Return(ref ty) => Some(&**ty),
1331 };
1332 self.visit_fn_like_elision(&fd.inputs, output);
1333 }
1334
visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>)1335 fn visit_generics(&mut self, generics: &'tcx hir::Generics<'tcx>) {
1336 if !self.trait_definition_only {
1337 check_mixed_explicit_and_in_band_defs(self.tcx, &generics.params);
1338 }
1339 let scope = Scope::TraitRefBoundary { s: self.scope };
1340 self.with(scope, |_, this| {
1341 for param in generics.params {
1342 match param.kind {
1343 GenericParamKind::Lifetime { .. } => {}
1344 GenericParamKind::Type { ref default, .. } => {
1345 walk_list!(this, visit_param_bound, param.bounds);
1346 if let Some(ref ty) = default {
1347 this.visit_ty(&ty);
1348 }
1349 }
1350 GenericParamKind::Const { ref ty, .. } => {
1351 let was_in_const_generic = this.is_in_const_generic;
1352 this.is_in_const_generic = true;
1353 walk_list!(this, visit_param_bound, param.bounds);
1354 this.visit_ty(&ty);
1355 this.is_in_const_generic = was_in_const_generic;
1356 }
1357 }
1358 }
1359 for predicate in generics.where_clause.predicates {
1360 match predicate {
1361 &hir::WherePredicate::BoundPredicate(hir::WhereBoundPredicate {
1362 ref bounded_ty,
1363 bounds,
1364 ref bound_generic_params,
1365 ..
1366 }) => {
1367 let (lifetimes, binders): (FxIndexMap<hir::ParamName, Region>, Vec<_>) =
1368 bound_generic_params
1369 .iter()
1370 .filter(|param| {
1371 matches!(param.kind, GenericParamKind::Lifetime { .. })
1372 })
1373 .enumerate()
1374 .map(|(late_bound_idx, param)| {
1375 let pair =
1376 Region::late(late_bound_idx as u32, &this.tcx.hir(), param);
1377 let r = late_region_as_bound_region(this.tcx, &pair.1);
1378 (pair, r)
1379 })
1380 .unzip();
1381 this.map.late_bound_vars.insert(bounded_ty.hir_id, binders.clone());
1382 let next_early_index = this.next_early_index();
1383 // Even if there are no lifetimes defined here, we still wrap it in a binder
1384 // scope. If there happens to be a nested poly trait ref (an error), that
1385 // will be `Concatenating` anyways, so we don't have to worry about the depth
1386 // being wrong.
1387 let scope = Scope::Binder {
1388 hir_id: bounded_ty.hir_id,
1389 lifetimes,
1390 s: this.scope,
1391 next_early_index,
1392 track_lifetime_uses: true,
1393 opaque_type_parent: false,
1394 scope_type: BinderScopeType::Normal,
1395 };
1396 this.with(scope, |old_scope, this| {
1397 this.check_lifetime_params(old_scope, &bound_generic_params);
1398 this.visit_ty(&bounded_ty);
1399 walk_list!(this, visit_param_bound, bounds);
1400 })
1401 }
1402 &hir::WherePredicate::RegionPredicate(hir::WhereRegionPredicate {
1403 ref lifetime,
1404 bounds,
1405 ..
1406 }) => {
1407 this.visit_lifetime(lifetime);
1408 walk_list!(this, visit_param_bound, bounds);
1409 }
1410 &hir::WherePredicate::EqPredicate(hir::WhereEqPredicate {
1411 ref lhs_ty,
1412 ref rhs_ty,
1413 ..
1414 }) => {
1415 this.visit_ty(lhs_ty);
1416 this.visit_ty(rhs_ty);
1417 }
1418 }
1419 }
1420 })
1421 }
1422
visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>)1423 fn visit_param_bound(&mut self, bound: &'tcx hir::GenericBound<'tcx>) {
1424 match bound {
1425 hir::GenericBound::LangItemTrait(_, _, hir_id, _) => {
1426 // FIXME(jackh726): This is pretty weird. `LangItemTrait` doesn't go
1427 // through the regular poly trait ref code, so we don't get another
1428 // chance to introduce a binder. For now, I'm keeping the existing logic
1429 // of "if there isn't a Binder scope above us, add one", but I
1430 // imagine there's a better way to go about this.
1431 let (binders, scope_type) = self.poly_trait_ref_binder_info();
1432
1433 self.map.late_bound_vars.insert(*hir_id, binders);
1434 let scope = Scope::Binder {
1435 hir_id: *hir_id,
1436 lifetimes: FxIndexMap::default(),
1437 s: self.scope,
1438 next_early_index: self.next_early_index(),
1439 track_lifetime_uses: true,
1440 opaque_type_parent: false,
1441 scope_type,
1442 };
1443 self.with(scope, |_, this| {
1444 intravisit::walk_param_bound(this, bound);
1445 });
1446 }
1447 _ => intravisit::walk_param_bound(self, bound),
1448 }
1449 }
1450
visit_poly_trait_ref( &mut self, trait_ref: &'tcx hir::PolyTraitRef<'tcx>, _modifier: hir::TraitBoundModifier, )1451 fn visit_poly_trait_ref(
1452 &mut self,
1453 trait_ref: &'tcx hir::PolyTraitRef<'tcx>,
1454 _modifier: hir::TraitBoundModifier,
1455 ) {
1456 debug!("visit_poly_trait_ref(trait_ref={:?})", trait_ref);
1457
1458 let should_pop_missing_lt = self.is_trait_ref_fn_scope(trait_ref);
1459
1460 let next_early_index = self.next_early_index();
1461 let (mut binders, scope_type) = self.poly_trait_ref_binder_info();
1462
1463 let initial_bound_vars = binders.len() as u32;
1464 let mut lifetimes: FxIndexMap<hir::ParamName, Region> = FxIndexMap::default();
1465 let binders_iter = trait_ref
1466 .bound_generic_params
1467 .iter()
1468 .filter(|param| matches!(param.kind, GenericParamKind::Lifetime { .. }))
1469 .enumerate()
1470 .map(|(late_bound_idx, param)| {
1471 let pair = Region::late(
1472 initial_bound_vars + late_bound_idx as u32,
1473 &self.tcx.hir(),
1474 param,
1475 );
1476 let r = late_region_as_bound_region(self.tcx, &pair.1);
1477 lifetimes.insert(pair.0, pair.1);
1478 r
1479 });
1480 binders.extend(binders_iter);
1481
1482 debug!(?binders);
1483 self.map.late_bound_vars.insert(trait_ref.trait_ref.hir_ref_id, binders);
1484
1485 // Always introduce a scope here, even if this is in a where clause and
1486 // we introduced the binders around the bounded Ty. In that case, we
1487 // just reuse the concatenation functionality also present in nested trait
1488 // refs.
1489 let scope = Scope::Binder {
1490 hir_id: trait_ref.trait_ref.hir_ref_id,
1491 lifetimes,
1492 s: self.scope,
1493 next_early_index,
1494 track_lifetime_uses: true,
1495 opaque_type_parent: false,
1496 scope_type,
1497 };
1498 self.with(scope, |old_scope, this| {
1499 this.check_lifetime_params(old_scope, &trait_ref.bound_generic_params);
1500 walk_list!(this, visit_generic_param, trait_ref.bound_generic_params);
1501 this.visit_trait_ref(&trait_ref.trait_ref);
1502 });
1503
1504 if should_pop_missing_lt {
1505 self.missing_named_lifetime_spots.pop();
1506 }
1507 }
1508 }
1509
1510 #[derive(Copy, Clone, PartialEq)]
1511 enum ShadowKind {
1512 Label,
1513 Lifetime,
1514 }
1515 struct Original {
1516 kind: ShadowKind,
1517 span: Span,
1518 }
1519 struct Shadower {
1520 kind: ShadowKind,
1521 span: Span,
1522 }
1523
original_label(span: Span) -> Original1524 fn original_label(span: Span) -> Original {
1525 Original { kind: ShadowKind::Label, span }
1526 }
shadower_label(span: Span) -> Shadower1527 fn shadower_label(span: Span) -> Shadower {
1528 Shadower { kind: ShadowKind::Label, span }
1529 }
original_lifetime(span: Span) -> Original1530 fn original_lifetime(span: Span) -> Original {
1531 Original { kind: ShadowKind::Lifetime, span }
1532 }
shadower_lifetime(param: &hir::GenericParam<'_>) -> Shadower1533 fn shadower_lifetime(param: &hir::GenericParam<'_>) -> Shadower {
1534 Shadower { kind: ShadowKind::Lifetime, span: param.span }
1535 }
1536
1537 impl ShadowKind {
desc(&self) -> &'static str1538 fn desc(&self) -> &'static str {
1539 match *self {
1540 ShadowKind::Label => "label",
1541 ShadowKind::Lifetime => "lifetime",
1542 }
1543 }
1544 }
1545
check_mixed_explicit_and_in_band_defs(tcx: TyCtxt<'_>, params: &[hir::GenericParam<'_>])1546 fn check_mixed_explicit_and_in_band_defs(tcx: TyCtxt<'_>, params: &[hir::GenericParam<'_>]) {
1547 let lifetime_params: Vec<_> = params
1548 .iter()
1549 .filter_map(|param| match param.kind {
1550 GenericParamKind::Lifetime { kind, .. } => Some((kind, param.span)),
1551 _ => None,
1552 })
1553 .collect();
1554 let explicit = lifetime_params.iter().find(|(kind, _)| *kind == LifetimeParamKind::Explicit);
1555 let in_band = lifetime_params.iter().find(|(kind, _)| *kind == LifetimeParamKind::InBand);
1556
1557 if let (Some((_, explicit_span)), Some((_, in_band_span))) = (explicit, in_band) {
1558 struct_span_err!(
1559 tcx.sess,
1560 *in_band_span,
1561 E0688,
1562 "cannot mix in-band and explicit lifetime definitions"
1563 )
1564 .span_label(*in_band_span, "in-band lifetime definition here")
1565 .span_label(*explicit_span, "explicit lifetime definition here")
1566 .emit();
1567 }
1568 }
1569
signal_shadowing_problem(tcx: TyCtxt<'_>, name: Symbol, orig: Original, shadower: Shadower)1570 fn signal_shadowing_problem(tcx: TyCtxt<'_>, name: Symbol, orig: Original, shadower: Shadower) {
1571 let mut err = if let (ShadowKind::Lifetime, ShadowKind::Lifetime) = (orig.kind, shadower.kind) {
1572 // lifetime/lifetime shadowing is an error
1573 struct_span_err!(
1574 tcx.sess,
1575 shadower.span,
1576 E0496,
1577 "{} name `{}` shadows a \
1578 {} name that is already in scope",
1579 shadower.kind.desc(),
1580 name,
1581 orig.kind.desc()
1582 )
1583 } else {
1584 // shadowing involving a label is only a warning, due to issues with
1585 // labels and lifetimes not being macro-hygienic.
1586 tcx.sess.struct_span_warn(
1587 shadower.span,
1588 &format!(
1589 "{} name `{}` shadows a \
1590 {} name that is already in scope",
1591 shadower.kind.desc(),
1592 name,
1593 orig.kind.desc()
1594 ),
1595 )
1596 };
1597 err.span_label(orig.span, "first declared here");
1598 err.span_label(shadower.span, format!("{} `{}` already in scope", orig.kind.desc(), name));
1599 err.emit();
1600 }
1601
1602 // Adds all labels in `b` to `ctxt.labels_in_fn`, signalling a warning
1603 // if one of the label shadows a lifetime or another label.
extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body<'_>)1604 fn extract_labels(ctxt: &mut LifetimeContext<'_, '_>, body: &hir::Body<'_>) {
1605 struct GatherLabels<'a, 'tcx> {
1606 tcx: TyCtxt<'tcx>,
1607 scope: ScopeRef<'a>,
1608 labels_in_fn: &'a mut Vec<Ident>,
1609 }
1610
1611 let mut gather =
1612 GatherLabels { tcx: ctxt.tcx, scope: ctxt.scope, labels_in_fn: &mut ctxt.labels_in_fn };
1613 gather.visit_body(body);
1614
1615 impl<'v, 'a, 'tcx> Visitor<'v> for GatherLabels<'a, 'tcx> {
1616 type Map = intravisit::ErasedMap<'v>;
1617
1618 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
1619 NestedVisitorMap::None
1620 }
1621
1622 fn visit_expr(&mut self, ex: &hir::Expr<'_>) {
1623 if let Some(label) = expression_label(ex) {
1624 for prior_label in &self.labels_in_fn[..] {
1625 // FIXME (#24278): non-hygienic comparison
1626 if label.name == prior_label.name {
1627 signal_shadowing_problem(
1628 self.tcx,
1629 label.name,
1630 original_label(prior_label.span),
1631 shadower_label(label.span),
1632 );
1633 }
1634 }
1635
1636 check_if_label_shadows_lifetime(self.tcx, self.scope, label);
1637
1638 self.labels_in_fn.push(label);
1639 }
1640 intravisit::walk_expr(self, ex)
1641 }
1642 }
1643
1644 fn expression_label(ex: &hir::Expr<'_>) -> Option<Ident> {
1645 match ex.kind {
1646 hir::ExprKind::Loop(_, Some(label), ..) => Some(label.ident),
1647 hir::ExprKind::Block(_, Some(label)) => Some(label.ident),
1648 _ => None,
1649 }
1650 }
1651
1652 fn check_if_label_shadows_lifetime(tcx: TyCtxt<'_>, mut scope: ScopeRef<'_>, label: Ident) {
1653 loop {
1654 match *scope {
1655 Scope::Body { s, .. }
1656 | Scope::Elision { s, .. }
1657 | Scope::ObjectLifetimeDefault { s, .. }
1658 | Scope::Supertrait { s, .. }
1659 | Scope::TraitRefBoundary { s, .. } => {
1660 scope = s;
1661 }
1662
1663 Scope::Root => {
1664 return;
1665 }
1666
1667 Scope::Binder { ref lifetimes, s, .. } => {
1668 // FIXME (#24278): non-hygienic comparison
1669 if let Some(def) =
1670 lifetimes.get(&hir::ParamName::Plain(label.normalize_to_macros_2_0()))
1671 {
1672 let hir_id =
1673 tcx.hir().local_def_id_to_hir_id(def.id().unwrap().expect_local());
1674
1675 signal_shadowing_problem(
1676 tcx,
1677 label.name,
1678 original_lifetime(tcx.hir().span(hir_id)),
1679 shadower_label(label.span),
1680 );
1681 return;
1682 }
1683 scope = s;
1684 }
1685 }
1686 }
1687 }
1688 }
1689
compute_object_lifetime_defaults( tcx: TyCtxt<'_>, item: &hir::Item<'_>, ) -> Option<Vec<ObjectLifetimeDefault>>1690 fn compute_object_lifetime_defaults(
1691 tcx: TyCtxt<'_>,
1692 item: &hir::Item<'_>,
1693 ) -> Option<Vec<ObjectLifetimeDefault>> {
1694 match item.kind {
1695 hir::ItemKind::Struct(_, ref generics)
1696 | hir::ItemKind::Union(_, ref generics)
1697 | hir::ItemKind::Enum(_, ref generics)
1698 | hir::ItemKind::OpaqueTy(hir::OpaqueTy { ref generics, impl_trait_fn: None, .. })
1699 | hir::ItemKind::TyAlias(_, ref generics)
1700 | hir::ItemKind::Trait(_, _, ref generics, ..) => {
1701 let result = object_lifetime_defaults_for_item(tcx, generics);
1702
1703 // Debugging aid.
1704 let attrs = tcx.hir().attrs(item.hir_id());
1705 if tcx.sess.contains_name(attrs, sym::rustc_object_lifetime_default) {
1706 let object_lifetime_default_reprs: String = result
1707 .iter()
1708 .map(|set| match *set {
1709 Set1::Empty => "BaseDefault".into(),
1710 Set1::One(Region::Static) => "'static".into(),
1711 Set1::One(Region::EarlyBound(mut i, _, _)) => generics
1712 .params
1713 .iter()
1714 .find_map(|param| match param.kind {
1715 GenericParamKind::Lifetime { .. } => {
1716 if i == 0 {
1717 return Some(param.name.ident().to_string().into());
1718 }
1719 i -= 1;
1720 None
1721 }
1722 _ => None,
1723 })
1724 .unwrap(),
1725 Set1::One(_) => bug!(),
1726 Set1::Many => "Ambiguous".into(),
1727 })
1728 .collect::<Vec<Cow<'static, str>>>()
1729 .join(",");
1730 tcx.sess.span_err(item.span, &object_lifetime_default_reprs);
1731 }
1732
1733 Some(result)
1734 }
1735 _ => None,
1736 }
1737 }
1738
1739 /// Scan the bounds and where-clauses on parameters to extract bounds
1740 /// of the form `T:'a` so as to determine the `ObjectLifetimeDefault`
1741 /// for each type parameter.
object_lifetime_defaults_for_item( tcx: TyCtxt<'_>, generics: &hir::Generics<'_>, ) -> Vec<ObjectLifetimeDefault>1742 fn object_lifetime_defaults_for_item(
1743 tcx: TyCtxt<'_>,
1744 generics: &hir::Generics<'_>,
1745 ) -> Vec<ObjectLifetimeDefault> {
1746 fn add_bounds(set: &mut Set1<hir::LifetimeName>, bounds: &[hir::GenericBound<'_>]) {
1747 for bound in bounds {
1748 if let hir::GenericBound::Outlives(ref lifetime) = *bound {
1749 set.insert(lifetime.name.normalize_to_macros_2_0());
1750 }
1751 }
1752 }
1753
1754 generics
1755 .params
1756 .iter()
1757 .filter_map(|param| match param.kind {
1758 GenericParamKind::Lifetime { .. } => None,
1759 GenericParamKind::Type { .. } => {
1760 let mut set = Set1::Empty;
1761
1762 add_bounds(&mut set, ¶m.bounds);
1763
1764 let param_def_id = tcx.hir().local_def_id(param.hir_id);
1765 for predicate in generics.where_clause.predicates {
1766 // Look for `type: ...` where clauses.
1767 let data = match *predicate {
1768 hir::WherePredicate::BoundPredicate(ref data) => data,
1769 _ => continue,
1770 };
1771
1772 // Ignore `for<'a> type: ...` as they can change what
1773 // lifetimes mean (although we could "just" handle it).
1774 if !data.bound_generic_params.is_empty() {
1775 continue;
1776 }
1777
1778 let res = match data.bounded_ty.kind {
1779 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => path.res,
1780 _ => continue,
1781 };
1782
1783 if res == Res::Def(DefKind::TyParam, param_def_id.to_def_id()) {
1784 add_bounds(&mut set, &data.bounds);
1785 }
1786 }
1787
1788 Some(match set {
1789 Set1::Empty => Set1::Empty,
1790 Set1::One(name) => {
1791 if name == hir::LifetimeName::Static {
1792 Set1::One(Region::Static)
1793 } else {
1794 generics
1795 .params
1796 .iter()
1797 .filter_map(|param| match param.kind {
1798 GenericParamKind::Lifetime { .. } => Some((
1799 param.hir_id,
1800 hir::LifetimeName::Param(param.name),
1801 LifetimeDefOrigin::from_param(param),
1802 )),
1803 _ => None,
1804 })
1805 .enumerate()
1806 .find(|&(_, (_, lt_name, _))| lt_name == name)
1807 .map_or(Set1::Many, |(i, (id, _, origin))| {
1808 let def_id = tcx.hir().local_def_id(id);
1809 Set1::One(Region::EarlyBound(
1810 i as u32,
1811 def_id.to_def_id(),
1812 origin,
1813 ))
1814 })
1815 }
1816 }
1817 Set1::Many => Set1::Many,
1818 })
1819 }
1820 GenericParamKind::Const { .. } => {
1821 // Generic consts don't impose any constraints.
1822 //
1823 // We still store a dummy value here to allow generic parameters
1824 // in an arbitrary order.
1825 Some(Set1::Empty)
1826 }
1827 })
1828 .collect()
1829 }
1830
1831 impl<'a, 'tcx> LifetimeContext<'a, 'tcx> {
with<F>(&mut self, wrap_scope: Scope<'_>, f: F) where F: for<'b> FnOnce(ScopeRef<'_>, &mut LifetimeContext<'b, 'tcx>),1832 fn with<F>(&mut self, wrap_scope: Scope<'_>, f: F)
1833 where
1834 F: for<'b> FnOnce(ScopeRef<'_>, &mut LifetimeContext<'b, 'tcx>),
1835 {
1836 let LifetimeContext { tcx, map, lifetime_uses, .. } = self;
1837 let labels_in_fn = take(&mut self.labels_in_fn);
1838 let xcrate_object_lifetime_defaults = take(&mut self.xcrate_object_lifetime_defaults);
1839 let missing_named_lifetime_spots = take(&mut self.missing_named_lifetime_spots);
1840 let mut this = LifetimeContext {
1841 tcx: *tcx,
1842 map,
1843 scope: &wrap_scope,
1844 is_in_fn_syntax: self.is_in_fn_syntax,
1845 is_in_const_generic: self.is_in_const_generic,
1846 trait_definition_only: self.trait_definition_only,
1847 labels_in_fn,
1848 xcrate_object_lifetime_defaults,
1849 lifetime_uses,
1850 missing_named_lifetime_spots,
1851 };
1852 let span = tracing::debug_span!("scope", scope = ?TruncatedScopeDebug(&this.scope));
1853 {
1854 let _enter = span.enter();
1855 f(self.scope, &mut this);
1856 if !self.trait_definition_only {
1857 this.check_uses_for_lifetimes_defined_by_scope();
1858 }
1859 }
1860 self.labels_in_fn = this.labels_in_fn;
1861 self.xcrate_object_lifetime_defaults = this.xcrate_object_lifetime_defaults;
1862 self.missing_named_lifetime_spots = this.missing_named_lifetime_spots;
1863 }
1864
1865 /// helper method to determine the span to remove when suggesting the
1866 /// deletion of a lifetime
lifetime_deletion_span(&self, name: Ident, generics: &hir::Generics<'_>) -> Option<Span>1867 fn lifetime_deletion_span(&self, name: Ident, generics: &hir::Generics<'_>) -> Option<Span> {
1868 generics.params.iter().enumerate().find_map(|(i, param)| {
1869 if param.name.ident() == name {
1870 let in_band = matches!(
1871 param.kind,
1872 hir::GenericParamKind::Lifetime { kind: hir::LifetimeParamKind::InBand }
1873 );
1874 if in_band {
1875 Some(param.span)
1876 } else if generics.params.len() == 1 {
1877 // if sole lifetime, remove the entire `<>` brackets
1878 Some(generics.span)
1879 } else {
1880 // if removing within `<>` brackets, we also want to
1881 // delete a leading or trailing comma as appropriate
1882 if i >= generics.params.len() - 1 {
1883 Some(generics.params[i - 1].span.shrink_to_hi().to(param.span))
1884 } else {
1885 Some(param.span.to(generics.params[i + 1].span.shrink_to_lo()))
1886 }
1887 }
1888 } else {
1889 None
1890 }
1891 })
1892 }
1893
1894 // helper method to issue suggestions from `fn rah<'a>(&'a T)` to `fn rah(&T)`
1895 // or from `fn rah<'a>(T<'a>)` to `fn rah(T<'_>)`
suggest_eliding_single_use_lifetime( &self, err: &mut DiagnosticBuilder<'_>, def_id: DefId, lifetime: &hir::Lifetime, )1896 fn suggest_eliding_single_use_lifetime(
1897 &self,
1898 err: &mut DiagnosticBuilder<'_>,
1899 def_id: DefId,
1900 lifetime: &hir::Lifetime,
1901 ) {
1902 let name = lifetime.name.ident();
1903 let remove_decl = self
1904 .tcx
1905 .parent(def_id)
1906 .and_then(|parent_def_id| self.tcx.hir().get_generics(parent_def_id))
1907 .and_then(|generics| self.lifetime_deletion_span(name, generics));
1908
1909 let mut remove_use = None;
1910 let mut elide_use = None;
1911 let mut find_arg_use_span = |inputs: &[hir::Ty<'_>]| {
1912 for input in inputs {
1913 match input.kind {
1914 hir::TyKind::Rptr(lt, _) => {
1915 if lt.name.ident() == name {
1916 // include the trailing whitespace between the lifetime and type names
1917 let lt_through_ty_span = lifetime.span.to(input.span.shrink_to_hi());
1918 remove_use = Some(
1919 self.tcx
1920 .sess
1921 .source_map()
1922 .span_until_non_whitespace(lt_through_ty_span),
1923 );
1924 break;
1925 }
1926 }
1927 hir::TyKind::Path(QPath::Resolved(_, path)) => {
1928 let last_segment = &path.segments[path.segments.len() - 1];
1929 let generics = last_segment.args();
1930 for arg in generics.args.iter() {
1931 if let GenericArg::Lifetime(lt) = arg {
1932 if lt.name.ident() == name {
1933 elide_use = Some(lt.span);
1934 break;
1935 }
1936 }
1937 }
1938 break;
1939 }
1940 _ => {}
1941 }
1942 }
1943 };
1944 if let Node::Lifetime(hir_lifetime) = self.tcx.hir().get(lifetime.hir_id) {
1945 if let Some(parent) =
1946 self.tcx.hir().find(self.tcx.hir().get_parent_item(hir_lifetime.hir_id))
1947 {
1948 match parent {
1949 Node::Item(item) => {
1950 if let hir::ItemKind::Fn(sig, _, _) = &item.kind {
1951 find_arg_use_span(sig.decl.inputs);
1952 }
1953 }
1954 Node::ImplItem(impl_item) => {
1955 if let hir::ImplItemKind::Fn(sig, _) = &impl_item.kind {
1956 find_arg_use_span(sig.decl.inputs);
1957 }
1958 }
1959 _ => {}
1960 }
1961 }
1962 }
1963
1964 let msg = "elide the single-use lifetime";
1965 match (remove_decl, remove_use, elide_use) {
1966 (Some(decl_span), Some(use_span), None) => {
1967 // if both declaration and use deletion spans start at the same
1968 // place ("start at" because the latter includes trailing
1969 // whitespace), then this is an in-band lifetime
1970 if decl_span.shrink_to_lo() == use_span.shrink_to_lo() {
1971 err.span_suggestion(
1972 use_span,
1973 msg,
1974 String::new(),
1975 Applicability::MachineApplicable,
1976 );
1977 } else {
1978 err.multipart_suggestion(
1979 msg,
1980 vec![(decl_span, String::new()), (use_span, String::new())],
1981 Applicability::MachineApplicable,
1982 );
1983 }
1984 }
1985 (Some(decl_span), None, Some(use_span)) => {
1986 err.multipart_suggestion(
1987 msg,
1988 vec![(decl_span, String::new()), (use_span, "'_".to_owned())],
1989 Applicability::MachineApplicable,
1990 );
1991 }
1992 _ => {}
1993 }
1994 }
1995
check_uses_for_lifetimes_defined_by_scope(&mut self)1996 fn check_uses_for_lifetimes_defined_by_scope(&mut self) {
1997 let defined_by = match self.scope {
1998 Scope::Binder { lifetimes, .. } => lifetimes,
1999 _ => {
2000 debug!("check_uses_for_lifetimes_defined_by_scope: not in a binder scope");
2001 return;
2002 }
2003 };
2004
2005 let mut def_ids: Vec<_> = defined_by
2006 .values()
2007 .flat_map(|region| match region {
2008 Region::EarlyBound(_, def_id, _)
2009 | Region::LateBound(_, _, def_id, _)
2010 | Region::Free(_, def_id) => Some(*def_id),
2011
2012 Region::LateBoundAnon(..) | Region::Static => None,
2013 })
2014 .collect();
2015
2016 // ensure that we issue lints in a repeatable order
2017 def_ids.sort_by_cached_key(|&def_id| self.tcx.def_path_hash(def_id));
2018
2019 'lifetimes: for def_id in def_ids {
2020 debug!("check_uses_for_lifetimes_defined_by_scope: def_id = {:?}", def_id);
2021
2022 let lifetimeuseset = self.lifetime_uses.remove(&def_id);
2023
2024 debug!(
2025 "check_uses_for_lifetimes_defined_by_scope: lifetimeuseset = {:?}",
2026 lifetimeuseset
2027 );
2028
2029 match lifetimeuseset {
2030 Some(LifetimeUseSet::One(lifetime)) => {
2031 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2032 debug!("hir id first={:?}", hir_id);
2033 if let Some((id, span, name)) = match self.tcx.hir().get(hir_id) {
2034 Node::Lifetime(hir_lifetime) => Some((
2035 hir_lifetime.hir_id,
2036 hir_lifetime.span,
2037 hir_lifetime.name.ident(),
2038 )),
2039 Node::GenericParam(param) => {
2040 Some((param.hir_id, param.span, param.name.ident()))
2041 }
2042 _ => None,
2043 } {
2044 debug!("id = {:?} span = {:?} name = {:?}", id, span, name);
2045 if name.name == kw::UnderscoreLifetime {
2046 continue;
2047 }
2048
2049 if let Some(parent_def_id) = self.tcx.parent(def_id) {
2050 if let Some(def_id) = parent_def_id.as_local() {
2051 let parent_hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2052 // lifetimes in `derive` expansions don't count (Issue #53738)
2053 if self
2054 .tcx
2055 .hir()
2056 .attrs(parent_hir_id)
2057 .iter()
2058 .any(|attr| attr.has_name(sym::automatically_derived))
2059 {
2060 continue;
2061 }
2062
2063 // opaque types generated when desugaring an async function can have a single
2064 // use lifetime even if it is explicitly denied (Issue #77175)
2065 if let hir::Node::Item(hir::Item {
2066 kind: hir::ItemKind::OpaqueTy(ref opaque),
2067 ..
2068 }) = self.tcx.hir().get(parent_hir_id)
2069 {
2070 if opaque.origin != hir::OpaqueTyOrigin::AsyncFn {
2071 continue 'lifetimes;
2072 }
2073 // We want to do this only if the liftime identifier is already defined
2074 // in the async function that generated this. Otherwise it could be
2075 // an opaque type defined by the developer and we still want this
2076 // lint to fail compilation
2077 for p in opaque.generics.params {
2078 if defined_by.contains_key(&p.name) {
2079 continue 'lifetimes;
2080 }
2081 }
2082 }
2083 }
2084 }
2085
2086 self.tcx.struct_span_lint_hir(
2087 lint::builtin::SINGLE_USE_LIFETIMES,
2088 id,
2089 span,
2090 |lint| {
2091 let mut err = lint.build(&format!(
2092 "lifetime parameter `{}` only used once",
2093 name
2094 ));
2095 if span == lifetime.span {
2096 // spans are the same for in-band lifetime declarations
2097 err.span_label(span, "this lifetime is only used here");
2098 } else {
2099 err.span_label(span, "this lifetime...");
2100 err.span_label(lifetime.span, "...is used only here");
2101 }
2102 self.suggest_eliding_single_use_lifetime(
2103 &mut err, def_id, lifetime,
2104 );
2105 err.emit();
2106 },
2107 );
2108 }
2109 }
2110 Some(LifetimeUseSet::Many) => {
2111 debug!("not one use lifetime");
2112 }
2113 None => {
2114 let hir_id = self.tcx.hir().local_def_id_to_hir_id(def_id.expect_local());
2115 if let Some((id, span, name)) = match self.tcx.hir().get(hir_id) {
2116 Node::Lifetime(hir_lifetime) => Some((
2117 hir_lifetime.hir_id,
2118 hir_lifetime.span,
2119 hir_lifetime.name.ident(),
2120 )),
2121 Node::GenericParam(param) => {
2122 Some((param.hir_id, param.span, param.name.ident()))
2123 }
2124 _ => None,
2125 } {
2126 debug!("id ={:?} span = {:?} name = {:?}", id, span, name);
2127 self.tcx.struct_span_lint_hir(
2128 lint::builtin::UNUSED_LIFETIMES,
2129 id,
2130 span,
2131 |lint| {
2132 let mut err = lint
2133 .build(&format!("lifetime parameter `{}` never used", name));
2134 if let Some(parent_def_id) = self.tcx.parent(def_id) {
2135 if let Some(generics) =
2136 self.tcx.hir().get_generics(parent_def_id)
2137 {
2138 let unused_lt_span =
2139 self.lifetime_deletion_span(name, generics);
2140 if let Some(span) = unused_lt_span {
2141 err.span_suggestion(
2142 span,
2143 "elide the unused lifetime",
2144 String::new(),
2145 Applicability::MachineApplicable,
2146 );
2147 }
2148 }
2149 }
2150 err.emit();
2151 },
2152 );
2153 }
2154 }
2155 }
2156 }
2157 }
2158
2159 /// Visits self by adding a scope and handling recursive walk over the contents with `walk`.
2160 ///
2161 /// Handles visiting fns and methods. These are a bit complicated because we must distinguish
2162 /// early- vs late-bound lifetime parameters. We do this by checking which lifetimes appear
2163 /// within type bounds; those are early bound lifetimes, and the rest are late bound.
2164 ///
2165 /// For example:
2166 ///
2167 /// fn foo<'a,'b,'c,T:Trait<'b>>(...)
2168 ///
2169 /// Here `'a` and `'c` are late bound but `'b` is early bound. Note that early- and late-bound
2170 /// lifetimes may be interspersed together.
2171 ///
2172 /// If early bound lifetimes are present, we separate them into their own list (and likewise
2173 /// for late bound). They will be numbered sequentially, starting from the lowest index that is
2174 /// already in scope (for a fn item, that will be 0, but for a method it might not be). Late
2175 /// bound lifetimes are resolved by name and associated with a binder ID (`binder_id`), so the
2176 /// ordering is not important there.
visit_early_late<F>( &mut self, parent_id: Option<hir::HirId>, hir_id: hir::HirId, decl: &'tcx hir::FnDecl<'tcx>, generics: &'tcx hir::Generics<'tcx>, walk: F, ) where F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),2177 fn visit_early_late<F>(
2178 &mut self,
2179 parent_id: Option<hir::HirId>,
2180 hir_id: hir::HirId,
2181 decl: &'tcx hir::FnDecl<'tcx>,
2182 generics: &'tcx hir::Generics<'tcx>,
2183 walk: F,
2184 ) where
2185 F: for<'b, 'c> FnOnce(&'b mut LifetimeContext<'c, 'tcx>),
2186 {
2187 insert_late_bound_lifetimes(self.map, decl, generics);
2188
2189 // Find the start of nested early scopes, e.g., in methods.
2190 let mut next_early_index = 0;
2191 if let Some(parent_id) = parent_id {
2192 let parent = self.tcx.hir().expect_item(parent_id);
2193 if sub_items_have_self_param(&parent.kind) {
2194 next_early_index += 1; // Self comes before lifetimes
2195 }
2196 match parent.kind {
2197 hir::ItemKind::Trait(_, _, ref generics, ..)
2198 | hir::ItemKind::Impl(hir::Impl { ref generics, .. }) => {
2199 next_early_index += generics.params.len() as u32;
2200 }
2201 _ => {}
2202 }
2203 }
2204
2205 let mut non_lifetime_count = 0;
2206 let mut named_late_bound_vars = 0;
2207 let lifetimes: FxIndexMap<hir::ParamName, Region> = generics
2208 .params
2209 .iter()
2210 .filter_map(|param| match param.kind {
2211 GenericParamKind::Lifetime { .. } => {
2212 if self.map.late_bound.contains(¶m.hir_id) {
2213 let late_bound_idx = named_late_bound_vars;
2214 named_late_bound_vars += 1;
2215 Some(Region::late(late_bound_idx, &self.tcx.hir(), param))
2216 } else {
2217 Some(Region::early(&self.tcx.hir(), &mut next_early_index, param))
2218 }
2219 }
2220 GenericParamKind::Type { .. } | GenericParamKind::Const { .. } => {
2221 non_lifetime_count += 1;
2222 None
2223 }
2224 })
2225 .collect();
2226 let next_early_index = next_early_index + non_lifetime_count;
2227
2228 let binders: Vec<_> = generics
2229 .params
2230 .iter()
2231 .filter(|param| {
2232 matches!(param.kind, GenericParamKind::Lifetime { .. })
2233 && self.map.late_bound.contains(¶m.hir_id)
2234 })
2235 .enumerate()
2236 .map(|(late_bound_idx, param)| {
2237 let pair = Region::late(late_bound_idx as u32, &self.tcx.hir(), param);
2238 late_region_as_bound_region(self.tcx, &pair.1)
2239 })
2240 .collect();
2241 self.map.late_bound_vars.insert(hir_id, binders);
2242 let scope = Scope::Binder {
2243 hir_id,
2244 lifetimes,
2245 next_early_index,
2246 s: self.scope,
2247 opaque_type_parent: true,
2248 track_lifetime_uses: false,
2249 scope_type: BinderScopeType::Normal,
2250 };
2251 self.with(scope, move |old_scope, this| {
2252 this.check_lifetime_params(old_scope, &generics.params);
2253 walk(this);
2254 });
2255 }
2256
next_early_index_helper(&self, only_opaque_type_parent: bool) -> u322257 fn next_early_index_helper(&self, only_opaque_type_parent: bool) -> u32 {
2258 let mut scope = self.scope;
2259 loop {
2260 match *scope {
2261 Scope::Root => return 0,
2262
2263 Scope::Binder { next_early_index, opaque_type_parent, .. }
2264 if (!only_opaque_type_parent || opaque_type_parent) =>
2265 {
2266 return next_early_index;
2267 }
2268
2269 Scope::Binder { s, .. }
2270 | Scope::Body { s, .. }
2271 | Scope::Elision { s, .. }
2272 | Scope::ObjectLifetimeDefault { s, .. }
2273 | Scope::Supertrait { s, .. }
2274 | Scope::TraitRefBoundary { s, .. } => scope = s,
2275 }
2276 }
2277 }
2278
2279 /// Returns the next index one would use for an early-bound-region
2280 /// if extending the current scope.
next_early_index(&self) -> u322281 fn next_early_index(&self) -> u32 {
2282 self.next_early_index_helper(true)
2283 }
2284
2285 /// Returns the next index one would use for an `impl Trait` that
2286 /// is being converted into an opaque type alias `impl Trait`. This will be the
2287 /// next early index from the enclosing item, for the most
2288 /// part. See the `opaque_type_parent` field for more info.
next_early_index_for_opaque_type(&self) -> u322289 fn next_early_index_for_opaque_type(&self) -> u32 {
2290 self.next_early_index_helper(false)
2291 }
2292
resolve_lifetime_ref(&mut self, lifetime_ref: &'tcx hir::Lifetime)2293 fn resolve_lifetime_ref(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
2294 debug!("resolve_lifetime_ref(lifetime_ref={:?})", lifetime_ref);
2295
2296 // If we've already reported an error, just ignore `lifetime_ref`.
2297 if let LifetimeName::Error = lifetime_ref.name {
2298 return;
2299 }
2300
2301 // Walk up the scope chain, tracking the number of fn scopes
2302 // that we pass through, until we find a lifetime with the
2303 // given name or we run out of scopes.
2304 // search.
2305 let mut late_depth = 0;
2306 let mut scope = self.scope;
2307 let mut outermost_body = None;
2308 let result = loop {
2309 match *scope {
2310 Scope::Body { id, s } => {
2311 // Non-static lifetimes are prohibited in anonymous constants without
2312 // `generic_const_exprs`.
2313 self.maybe_emit_forbidden_non_static_lifetime_error(id, lifetime_ref);
2314
2315 outermost_body = Some(id);
2316 scope = s;
2317 }
2318
2319 Scope::Root => {
2320 break None;
2321 }
2322
2323 Scope::Binder { ref lifetimes, scope_type, s, .. } => {
2324 match lifetime_ref.name {
2325 LifetimeName::Param(param_name) => {
2326 if let Some(&def) = lifetimes.get(¶m_name.normalize_to_macros_2_0())
2327 {
2328 break Some(def.shifted(late_depth));
2329 }
2330 }
2331 _ => bug!("expected LifetimeName::Param"),
2332 }
2333 match scope_type {
2334 BinderScopeType::Normal => late_depth += 1,
2335 BinderScopeType::Concatenating => {}
2336 }
2337 scope = s;
2338 }
2339
2340 Scope::Elision { s, .. }
2341 | Scope::ObjectLifetimeDefault { s, .. }
2342 | Scope::Supertrait { s, .. }
2343 | Scope::TraitRefBoundary { s, .. } => {
2344 scope = s;
2345 }
2346 }
2347 };
2348
2349 if let Some(mut def) = result {
2350 if let Region::EarlyBound(..) = def {
2351 // Do not free early-bound regions, only late-bound ones.
2352 } else if let Some(body_id) = outermost_body {
2353 let fn_id = self.tcx.hir().body_owner(body_id);
2354 match self.tcx.hir().get(fn_id) {
2355 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(..), .. })
2356 | Node::TraitItem(&hir::TraitItem {
2357 kind: hir::TraitItemKind::Fn(..), ..
2358 })
2359 | Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(..), .. }) => {
2360 let scope = self.tcx.hir().local_def_id(fn_id);
2361 def = Region::Free(scope.to_def_id(), def.id().unwrap());
2362 }
2363 _ => {}
2364 }
2365 }
2366
2367 // Check for fn-syntax conflicts with in-band lifetime definitions
2368 if !self.trait_definition_only && self.is_in_fn_syntax {
2369 match def {
2370 Region::EarlyBound(_, _, LifetimeDefOrigin::InBand)
2371 | Region::LateBound(_, _, _, LifetimeDefOrigin::InBand) => {
2372 struct_span_err!(
2373 self.tcx.sess,
2374 lifetime_ref.span,
2375 E0687,
2376 "lifetimes used in `fn` or `Fn` syntax must be \
2377 explicitly declared using `<...>` binders"
2378 )
2379 .span_label(lifetime_ref.span, "in-band lifetime definition")
2380 .emit();
2381 }
2382
2383 Region::Static
2384 | Region::EarlyBound(
2385 _,
2386 _,
2387 LifetimeDefOrigin::ExplicitOrElided | LifetimeDefOrigin::Error,
2388 )
2389 | Region::LateBound(
2390 _,
2391 _,
2392 _,
2393 LifetimeDefOrigin::ExplicitOrElided | LifetimeDefOrigin::Error,
2394 )
2395 | Region::LateBoundAnon(..)
2396 | Region::Free(..) => {}
2397 }
2398 }
2399
2400 self.insert_lifetime(lifetime_ref, def);
2401 } else {
2402 self.emit_undeclared_lifetime_error(lifetime_ref);
2403 }
2404 }
2405
visit_segment_args( &mut self, res: Res, depth: usize, generic_args: &'tcx hir::GenericArgs<'tcx>, )2406 fn visit_segment_args(
2407 &mut self,
2408 res: Res,
2409 depth: usize,
2410 generic_args: &'tcx hir::GenericArgs<'tcx>,
2411 ) {
2412 debug!(
2413 "visit_segment_args(res={:?}, depth={:?}, generic_args={:?})",
2414 res, depth, generic_args,
2415 );
2416
2417 if generic_args.parenthesized {
2418 let was_in_fn_syntax = self.is_in_fn_syntax;
2419 self.is_in_fn_syntax = true;
2420 self.visit_fn_like_elision(generic_args.inputs(), Some(generic_args.bindings[0].ty()));
2421 self.is_in_fn_syntax = was_in_fn_syntax;
2422 return;
2423 }
2424
2425 let mut elide_lifetimes = true;
2426 let lifetimes: Vec<_> = generic_args
2427 .args
2428 .iter()
2429 .filter_map(|arg| match arg {
2430 hir::GenericArg::Lifetime(lt) => {
2431 if !lt.is_elided() {
2432 elide_lifetimes = false;
2433 }
2434 Some(lt)
2435 }
2436 _ => None,
2437 })
2438 .collect();
2439 // We short-circuit here if all are elided in order to pluralize
2440 // possible errors
2441 if elide_lifetimes {
2442 self.resolve_elided_lifetimes(&lifetimes);
2443 } else {
2444 lifetimes.iter().for_each(|lt| self.visit_lifetime(lt));
2445 }
2446
2447 // Figure out if this is a type/trait segment,
2448 // which requires object lifetime defaults.
2449 let parent_def_id = |this: &mut Self, def_id: DefId| {
2450 let def_key = this.tcx.def_key(def_id);
2451 DefId { krate: def_id.krate, index: def_key.parent.expect("missing parent") }
2452 };
2453 let type_def_id = match res {
2454 Res::Def(DefKind::AssocTy, def_id) if depth == 1 => Some(parent_def_id(self, def_id)),
2455 Res::Def(DefKind::Variant, def_id) if depth == 0 => Some(parent_def_id(self, def_id)),
2456 Res::Def(
2457 DefKind::Struct
2458 | DefKind::Union
2459 | DefKind::Enum
2460 | DefKind::TyAlias
2461 | DefKind::Trait,
2462 def_id,
2463 ) if depth == 0 => Some(def_id),
2464 _ => None,
2465 };
2466
2467 debug!("visit_segment_args: type_def_id={:?}", type_def_id);
2468
2469 // Compute a vector of defaults, one for each type parameter,
2470 // per the rules given in RFCs 599 and 1156. Example:
2471 //
2472 // ```rust
2473 // struct Foo<'a, T: 'a, U> { }
2474 // ```
2475 //
2476 // If you have `Foo<'x, dyn Bar, dyn Baz>`, we want to default
2477 // `dyn Bar` to `dyn Bar + 'x` (because of the `T: 'a` bound)
2478 // and `dyn Baz` to `dyn Baz + 'static` (because there is no
2479 // such bound).
2480 //
2481 // Therefore, we would compute `object_lifetime_defaults` to a
2482 // vector like `['x, 'static]`. Note that the vector only
2483 // includes type parameters.
2484 let object_lifetime_defaults = type_def_id.map_or_else(Vec::new, |def_id| {
2485 let in_body = {
2486 let mut scope = self.scope;
2487 loop {
2488 match *scope {
2489 Scope::Root => break false,
2490
2491 Scope::Body { .. } => break true,
2492
2493 Scope::Binder { s, .. }
2494 | Scope::Elision { s, .. }
2495 | Scope::ObjectLifetimeDefault { s, .. }
2496 | Scope::Supertrait { s, .. }
2497 | Scope::TraitRefBoundary { s, .. } => {
2498 scope = s;
2499 }
2500 }
2501 }
2502 };
2503
2504 let map = &self.map;
2505 let set_to_region = |set: &ObjectLifetimeDefault| match *set {
2506 Set1::Empty => {
2507 if in_body {
2508 None
2509 } else {
2510 Some(Region::Static)
2511 }
2512 }
2513 Set1::One(r) => {
2514 let lifetimes = generic_args.args.iter().filter_map(|arg| match arg {
2515 GenericArg::Lifetime(lt) => Some(lt),
2516 _ => None,
2517 });
2518 r.subst(lifetimes, map)
2519 }
2520 Set1::Many => None,
2521 };
2522 if let Some(def_id) = def_id.as_local() {
2523 let id = self.tcx.hir().local_def_id_to_hir_id(def_id);
2524 self.tcx.object_lifetime_defaults(id).unwrap().iter().map(set_to_region).collect()
2525 } else {
2526 let tcx = self.tcx;
2527 self.xcrate_object_lifetime_defaults
2528 .entry(def_id)
2529 .or_insert_with(|| {
2530 tcx.generics_of(def_id)
2531 .params
2532 .iter()
2533 .filter_map(|param| match param.kind {
2534 GenericParamDefKind::Type { object_lifetime_default, .. } => {
2535 Some(object_lifetime_default)
2536 }
2537 GenericParamDefKind::Lifetime
2538 | GenericParamDefKind::Const { .. } => None,
2539 })
2540 .collect()
2541 })
2542 .iter()
2543 .map(set_to_region)
2544 .collect()
2545 }
2546 });
2547
2548 debug!("visit_segment_args: object_lifetime_defaults={:?}", object_lifetime_defaults);
2549
2550 let mut i = 0;
2551 for arg in generic_args.args {
2552 match arg {
2553 GenericArg::Lifetime(_) => {}
2554 GenericArg::Type(ty) => {
2555 if let Some(<) = object_lifetime_defaults.get(i) {
2556 let scope = Scope::ObjectLifetimeDefault { lifetime: lt, s: self.scope };
2557 self.with(scope, |_, this| this.visit_ty(ty));
2558 } else {
2559 self.visit_ty(ty);
2560 }
2561 i += 1;
2562 }
2563 GenericArg::Const(ct) => {
2564 self.visit_anon_const(&ct.value);
2565 }
2566 GenericArg::Infer(inf) => {
2567 self.visit_id(inf.hir_id);
2568 if inf.kind.is_type() {
2569 i += 1;
2570 }
2571 }
2572 }
2573 }
2574
2575 // Hack: when resolving the type `XX` in binding like `dyn
2576 // Foo<'b, Item = XX>`, the current object-lifetime default
2577 // would be to examine the trait `Foo` to check whether it has
2578 // a lifetime bound declared on `Item`. e.g., if `Foo` is
2579 // declared like so, then the default object lifetime bound in
2580 // `XX` should be `'b`:
2581 //
2582 // ```rust
2583 // trait Foo<'a> {
2584 // type Item: 'a;
2585 // }
2586 // ```
2587 //
2588 // but if we just have `type Item;`, then it would be
2589 // `'static`. However, we don't get all of this logic correct.
2590 //
2591 // Instead, we do something hacky: if there are no lifetime parameters
2592 // to the trait, then we simply use a default object lifetime
2593 // bound of `'static`, because there is no other possibility. On the other hand,
2594 // if there ARE lifetime parameters, then we require the user to give an
2595 // explicit bound for now.
2596 //
2597 // This is intended to leave room for us to implement the
2598 // correct behavior in the future.
2599 let has_lifetime_parameter =
2600 generic_args.args.iter().any(|arg| matches!(arg, GenericArg::Lifetime(_)));
2601
2602 // Resolve lifetimes found in the bindings, so either in the type `XX` in `Item = XX` or
2603 // in the trait ref `YY<...>` in `Item: YY<...>`.
2604 for binding in generic_args.bindings {
2605 let scope = Scope::ObjectLifetimeDefault {
2606 lifetime: if has_lifetime_parameter { None } else { Some(Region::Static) },
2607 s: self.scope,
2608 };
2609 if let Some(type_def_id) = type_def_id {
2610 let lifetimes = LifetimeContext::supertrait_hrtb_lifetimes(
2611 self.tcx,
2612 type_def_id,
2613 binding.ident,
2614 );
2615 self.with(scope, |_, this| {
2616 let scope = Scope::Supertrait {
2617 lifetimes: lifetimes.unwrap_or_default(),
2618 s: this.scope,
2619 };
2620 this.with(scope, |_, this| this.visit_assoc_type_binding(binding));
2621 });
2622 } else {
2623 self.with(scope, |_, this| this.visit_assoc_type_binding(binding));
2624 }
2625 }
2626 }
2627
2628 /// Returns all the late-bound vars that come into scope from supertrait HRTBs, based on the
2629 /// associated type name and starting trait.
2630 /// For example, imagine we have
2631 /// ```rust
2632 /// trait Foo<'a, 'b> {
2633 /// type As;
2634 /// }
2635 /// trait Bar<'b>: for<'a> Foo<'a, 'b> {}
2636 /// trait Bar: for<'b> Bar<'b> {}
2637 /// ```
2638 /// In this case, if we wanted to the supertrait HRTB lifetimes for `As` on
2639 /// the starting trait `Bar`, we would return `Some(['b, 'a])`.
supertrait_hrtb_lifetimes( tcx: TyCtxt<'tcx>, def_id: DefId, assoc_name: Ident, ) -> Option<Vec<ty::BoundVariableKind>>2640 fn supertrait_hrtb_lifetimes(
2641 tcx: TyCtxt<'tcx>,
2642 def_id: DefId,
2643 assoc_name: Ident,
2644 ) -> Option<Vec<ty::BoundVariableKind>> {
2645 let trait_defines_associated_type_named = |trait_def_id: DefId| {
2646 tcx.associated_items(trait_def_id)
2647 .find_by_name_and_kind(tcx, assoc_name, ty::AssocKind::Type, trait_def_id)
2648 .is_some()
2649 };
2650
2651 use smallvec::{smallvec, SmallVec};
2652 let mut stack: SmallVec<[(DefId, SmallVec<[ty::BoundVariableKind; 8]>); 8]> =
2653 smallvec![(def_id, smallvec![])];
2654 let mut visited: FxHashSet<DefId> = FxHashSet::default();
2655 loop {
2656 let (def_id, bound_vars) = match stack.pop() {
2657 Some(next) => next,
2658 None => break None,
2659 };
2660 // See issue #83753. If someone writes an associated type on a non-trait, just treat it as
2661 // there being no supertrait HRTBs.
2662 match tcx.def_kind(def_id) {
2663 DefKind::Trait | DefKind::TraitAlias | DefKind::Impl => {}
2664 _ => break None,
2665 }
2666
2667 if trait_defines_associated_type_named(def_id) {
2668 break Some(bound_vars.into_iter().collect());
2669 }
2670 let predicates =
2671 tcx.super_predicates_that_define_assoc_type((def_id, Some(assoc_name)));
2672 let obligations = predicates.predicates.iter().filter_map(|&(pred, _)| {
2673 let bound_predicate = pred.kind();
2674 match bound_predicate.skip_binder() {
2675 ty::PredicateKind::Trait(data) => {
2676 // The order here needs to match what we would get from `subst_supertrait`
2677 let pred_bound_vars = bound_predicate.bound_vars();
2678 let mut all_bound_vars = bound_vars.clone();
2679 all_bound_vars.extend(pred_bound_vars.iter());
2680 let super_def_id = data.trait_ref.def_id;
2681 Some((super_def_id, all_bound_vars))
2682 }
2683 _ => None,
2684 }
2685 });
2686
2687 let obligations = obligations.filter(|o| visited.insert(o.0));
2688 stack.extend(obligations);
2689 }
2690 }
2691
2692 #[tracing::instrument(level = "debug", skip(self))]
visit_fn_like_elision( &mut self, inputs: &'tcx [hir::Ty<'tcx>], output: Option<&'tcx hir::Ty<'tcx>>, )2693 fn visit_fn_like_elision(
2694 &mut self,
2695 inputs: &'tcx [hir::Ty<'tcx>],
2696 output: Option<&'tcx hir::Ty<'tcx>>,
2697 ) {
2698 debug!("visit_fn_like_elision: enter");
2699 let mut scope = &*self.scope;
2700 let hir_id = loop {
2701 match scope {
2702 Scope::Binder { hir_id, .. } => {
2703 break *hir_id;
2704 }
2705 Scope::ObjectLifetimeDefault { ref s, .. }
2706 | Scope::Elision { ref s, .. }
2707 | Scope::Supertrait { ref s, .. }
2708 | Scope::TraitRefBoundary { ref s, .. } => {
2709 scope = *s;
2710 }
2711 Scope::Root | Scope::Body { .. } => {
2712 // See issues #83907 and #83693. Just bail out from looking inside.
2713 self.tcx.sess.delay_span_bug(
2714 rustc_span::DUMMY_SP,
2715 "In fn_like_elision without appropriate scope above",
2716 );
2717 return;
2718 }
2719 }
2720 };
2721 // While not strictly necessary, we gather anon lifetimes *before* actually
2722 // visiting the argument types.
2723 let mut gather = GatherAnonLifetimes { anon_count: 0 };
2724 for input in inputs {
2725 gather.visit_ty(input);
2726 }
2727 trace!(?gather.anon_count);
2728 let late_bound_vars = self.map.late_bound_vars.entry(hir_id).or_default();
2729 let named_late_bound_vars = late_bound_vars.len() as u32;
2730 late_bound_vars.extend(
2731 (0..gather.anon_count).map(|var| ty::BoundVariableKind::Region(ty::BrAnon(var))),
2732 );
2733 let arg_scope = Scope::Elision {
2734 elide: Elide::FreshLateAnon(named_late_bound_vars, Cell::new(0)),
2735 s: self.scope,
2736 };
2737 self.with(arg_scope, |_, this| {
2738 for input in inputs {
2739 this.visit_ty(input);
2740 }
2741 });
2742
2743 let output = match output {
2744 Some(ty) => ty,
2745 None => return,
2746 };
2747
2748 debug!("determine output");
2749
2750 // Figure out if there's a body we can get argument names from,
2751 // and whether there's a `self` argument (treated specially).
2752 let mut assoc_item_kind = None;
2753 let mut impl_self = None;
2754 let parent = self.tcx.hir().get_parent_node(output.hir_id);
2755 let body = match self.tcx.hir().get(parent) {
2756 // `fn` definitions and methods.
2757 Node::Item(&hir::Item { kind: hir::ItemKind::Fn(.., body), .. }) => Some(body),
2758
2759 Node::TraitItem(&hir::TraitItem { kind: hir::TraitItemKind::Fn(_, ref m), .. }) => {
2760 if let hir::ItemKind::Trait(.., ref trait_items) =
2761 self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(parent)).kind
2762 {
2763 assoc_item_kind =
2764 trait_items.iter().find(|ti| ti.id.hir_id() == parent).map(|ti| ti.kind);
2765 }
2766 match *m {
2767 hir::TraitFn::Required(_) => None,
2768 hir::TraitFn::Provided(body) => Some(body),
2769 }
2770 }
2771
2772 Node::ImplItem(&hir::ImplItem { kind: hir::ImplItemKind::Fn(_, body), .. }) => {
2773 if let hir::ItemKind::Impl(hir::Impl { ref self_ty, ref items, .. }) =
2774 self.tcx.hir().expect_item(self.tcx.hir().get_parent_item(parent)).kind
2775 {
2776 impl_self = Some(self_ty);
2777 assoc_item_kind =
2778 items.iter().find(|ii| ii.id.hir_id() == parent).map(|ii| ii.kind);
2779 }
2780 Some(body)
2781 }
2782
2783 // Foreign functions, `fn(...) -> R` and `Trait(...) -> R` (both types and bounds).
2784 Node::ForeignItem(_) | Node::Ty(_) | Node::TraitRef(_) => None,
2785 // Everything else (only closures?) doesn't
2786 // actually enjoy elision in return types.
2787 _ => {
2788 self.visit_ty(output);
2789 return;
2790 }
2791 };
2792
2793 let has_self = match assoc_item_kind {
2794 Some(hir::AssocItemKind::Fn { has_self }) => has_self,
2795 _ => false,
2796 };
2797
2798 // In accordance with the rules for lifetime elision, we can determine
2799 // what region to use for elision in the output type in two ways.
2800 // First (determined here), if `self` is by-reference, then the
2801 // implied output region is the region of the self parameter.
2802 if has_self {
2803 struct SelfVisitor<'a> {
2804 map: &'a NamedRegionMap,
2805 impl_self: Option<&'a hir::TyKind<'a>>,
2806 lifetime: Set1<Region>,
2807 }
2808
2809 impl SelfVisitor<'_> {
2810 // Look for `self: &'a Self` - also desugared from `&'a self`,
2811 // and if that matches, use it for elision and return early.
2812 fn is_self_ty(&self, res: Res) -> bool {
2813 if let Res::SelfTy(..) = res {
2814 return true;
2815 }
2816
2817 // Can't always rely on literal (or implied) `Self` due
2818 // to the way elision rules were originally specified.
2819 if let Some(&hir::TyKind::Path(hir::QPath::Resolved(None, ref path))) =
2820 self.impl_self
2821 {
2822 match path.res {
2823 // Permit the types that unambiguously always
2824 // result in the same type constructor being used
2825 // (it can't differ between `Self` and `self`).
2826 Res::Def(DefKind::Struct | DefKind::Union | DefKind::Enum, _)
2827 | Res::PrimTy(_) => return res == path.res,
2828 _ => {}
2829 }
2830 }
2831
2832 false
2833 }
2834 }
2835
2836 impl<'a> Visitor<'a> for SelfVisitor<'a> {
2837 type Map = intravisit::ErasedMap<'a>;
2838
2839 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
2840 NestedVisitorMap::None
2841 }
2842
2843 fn visit_ty(&mut self, ty: &'a hir::Ty<'a>) {
2844 if let hir::TyKind::Rptr(lifetime_ref, ref mt) = ty.kind {
2845 if let hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) = mt.ty.kind
2846 {
2847 if self.is_self_ty(path.res) {
2848 if let Some(lifetime) = self.map.defs.get(&lifetime_ref.hir_id) {
2849 self.lifetime.insert(*lifetime);
2850 }
2851 }
2852 }
2853 }
2854 intravisit::walk_ty(self, ty)
2855 }
2856 }
2857
2858 let mut visitor = SelfVisitor {
2859 map: self.map,
2860 impl_self: impl_self.map(|ty| &ty.kind),
2861 lifetime: Set1::Empty,
2862 };
2863 visitor.visit_ty(&inputs[0]);
2864 if let Set1::One(lifetime) = visitor.lifetime {
2865 let scope = Scope::Elision { elide: Elide::Exact(lifetime), s: self.scope };
2866 self.with(scope, |_, this| this.visit_ty(output));
2867 return;
2868 }
2869 }
2870
2871 // Second, if there was exactly one lifetime (either a substitution or a
2872 // reference) in the arguments, then any anonymous regions in the output
2873 // have that lifetime.
2874 let mut possible_implied_output_region = None;
2875 let mut lifetime_count = 0;
2876 let arg_lifetimes = inputs
2877 .iter()
2878 .enumerate()
2879 .skip(has_self as usize)
2880 .map(|(i, input)| {
2881 let mut gather = GatherLifetimes {
2882 map: self.map,
2883 outer_index: ty::INNERMOST,
2884 have_bound_regions: false,
2885 lifetimes: Default::default(),
2886 };
2887 gather.visit_ty(input);
2888
2889 lifetime_count += gather.lifetimes.len();
2890
2891 if lifetime_count == 1 && gather.lifetimes.len() == 1 {
2892 // there's a chance that the unique lifetime of this
2893 // iteration will be the appropriate lifetime for output
2894 // parameters, so lets store it.
2895 possible_implied_output_region = gather.lifetimes.iter().cloned().next();
2896 }
2897
2898 ElisionFailureInfo {
2899 parent: body,
2900 index: i,
2901 lifetime_count: gather.lifetimes.len(),
2902 have_bound_regions: gather.have_bound_regions,
2903 span: input.span,
2904 }
2905 })
2906 .collect();
2907
2908 let elide = if lifetime_count == 1 {
2909 Elide::Exact(possible_implied_output_region.unwrap())
2910 } else {
2911 Elide::Error(arg_lifetimes)
2912 };
2913
2914 debug!(?elide);
2915
2916 let scope = Scope::Elision { elide, s: self.scope };
2917 self.with(scope, |_, this| this.visit_ty(output));
2918
2919 struct GatherLifetimes<'a> {
2920 map: &'a NamedRegionMap,
2921 outer_index: ty::DebruijnIndex,
2922 have_bound_regions: bool,
2923 lifetimes: FxHashSet<Region>,
2924 }
2925
2926 impl<'v, 'a> Visitor<'v> for GatherLifetimes<'a> {
2927 type Map = intravisit::ErasedMap<'v>;
2928
2929 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
2930 NestedVisitorMap::None
2931 }
2932
2933 fn visit_ty(&mut self, ty: &hir::Ty<'_>) {
2934 if let hir::TyKind::BareFn(_) = ty.kind {
2935 self.outer_index.shift_in(1);
2936 }
2937 match ty.kind {
2938 hir::TyKind::TraitObject(bounds, ref lifetime, _) => {
2939 for bound in bounds {
2940 self.visit_poly_trait_ref(bound, hir::TraitBoundModifier::None);
2941 }
2942
2943 // Stay on the safe side and don't include the object
2944 // lifetime default (which may not end up being used).
2945 if !lifetime.is_elided() {
2946 self.visit_lifetime(lifetime);
2947 }
2948 }
2949 _ => {
2950 intravisit::walk_ty(self, ty);
2951 }
2952 }
2953 if let hir::TyKind::BareFn(_) = ty.kind {
2954 self.outer_index.shift_out(1);
2955 }
2956 }
2957
2958 fn visit_generic_param(&mut self, param: &hir::GenericParam<'_>) {
2959 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
2960 // FIXME(eddyb) Do we want this? It only makes a difference
2961 // if this `for<'a>` lifetime parameter is never used.
2962 self.have_bound_regions = true;
2963 }
2964
2965 intravisit::walk_generic_param(self, param);
2966 }
2967
2968 fn visit_poly_trait_ref(
2969 &mut self,
2970 trait_ref: &hir::PolyTraitRef<'_>,
2971 modifier: hir::TraitBoundModifier,
2972 ) {
2973 self.outer_index.shift_in(1);
2974 intravisit::walk_poly_trait_ref(self, trait_ref, modifier);
2975 self.outer_index.shift_out(1);
2976 }
2977
2978 fn visit_param_bound(&mut self, bound: &hir::GenericBound<'_>) {
2979 if let hir::GenericBound::LangItemTrait { .. } = bound {
2980 self.outer_index.shift_in(1);
2981 intravisit::walk_param_bound(self, bound);
2982 self.outer_index.shift_out(1);
2983 } else {
2984 intravisit::walk_param_bound(self, bound);
2985 }
2986 }
2987
2988 fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
2989 if let Some(&lifetime) = self.map.defs.get(&lifetime_ref.hir_id) {
2990 match lifetime {
2991 Region::LateBound(debruijn, _, _, _)
2992 | Region::LateBoundAnon(debruijn, _, _)
2993 if debruijn < self.outer_index =>
2994 {
2995 self.have_bound_regions = true;
2996 }
2997 _ => {
2998 // FIXME(jackh726): nested trait refs?
2999 self.lifetimes.insert(lifetime.shifted_out_to_binder(self.outer_index));
3000 }
3001 }
3002 }
3003 }
3004 }
3005
3006 struct GatherAnonLifetimes {
3007 anon_count: u32,
3008 }
3009 impl<'v> Visitor<'v> for GatherAnonLifetimes {
3010 type Map = intravisit::ErasedMap<'v>;
3011
3012 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
3013 NestedVisitorMap::None
3014 }
3015
3016 #[instrument(skip(self), level = "trace")]
3017 fn visit_ty(&mut self, ty: &hir::Ty<'_>) {
3018 // If we enter a `BareFn`, then we enter a *new* binding scope
3019 if let hir::TyKind::BareFn(_) = ty.kind {
3020 return;
3021 }
3022 intravisit::walk_ty(self, ty);
3023 }
3024
3025 fn visit_generic_args(
3026 &mut self,
3027 path_span: Span,
3028 generic_args: &'v hir::GenericArgs<'v>,
3029 ) {
3030 // parenthesized args enter a new elison scope
3031 if generic_args.parenthesized {
3032 return;
3033 }
3034 intravisit::walk_generic_args(self, path_span, generic_args)
3035 }
3036
3037 #[instrument(skip(self), level = "trace")]
3038 fn visit_lifetime(&mut self, lifetime_ref: &hir::Lifetime) {
3039 if lifetime_ref.is_elided() {
3040 self.anon_count += 1;
3041 }
3042 }
3043 }
3044 }
3045
resolve_elided_lifetimes(&mut self, lifetime_refs: &[&'tcx hir::Lifetime])3046 fn resolve_elided_lifetimes(&mut self, lifetime_refs: &[&'tcx hir::Lifetime]) {
3047 debug!("resolve_elided_lifetimes(lifetime_refs={:?})", lifetime_refs);
3048
3049 if lifetime_refs.is_empty() {
3050 return;
3051 }
3052
3053 let mut late_depth = 0;
3054 let mut scope = self.scope;
3055 let mut lifetime_names = FxHashSet::default();
3056 let mut lifetime_spans = vec![];
3057 let error = loop {
3058 match *scope {
3059 // Do not assign any resolution, it will be inferred.
3060 Scope::Body { .. } => return,
3061
3062 Scope::Root => break None,
3063
3064 Scope::Binder { s, ref lifetimes, scope_type, .. } => {
3065 // collect named lifetimes for suggestions
3066 for name in lifetimes.keys() {
3067 if let hir::ParamName::Plain(name) = name {
3068 lifetime_names.insert(name.name);
3069 lifetime_spans.push(name.span);
3070 }
3071 }
3072 match scope_type {
3073 BinderScopeType::Normal => late_depth += 1,
3074 BinderScopeType::Concatenating => {}
3075 }
3076 scope = s;
3077 }
3078
3079 Scope::Elision { ref elide, ref s, .. } => {
3080 let lifetime = match *elide {
3081 Elide::FreshLateAnon(named_late_bound_vars, ref counter) => {
3082 for lifetime_ref in lifetime_refs {
3083 let lifetime = Region::late_anon(named_late_bound_vars, counter)
3084 .shifted(late_depth);
3085
3086 self.insert_lifetime(lifetime_ref, lifetime);
3087 }
3088 return;
3089 }
3090 Elide::Exact(l) => l.shifted(late_depth),
3091 Elide::Error(ref e) => {
3092 let mut scope = s;
3093 loop {
3094 match scope {
3095 Scope::Binder { ref lifetimes, s, .. } => {
3096 // Collect named lifetimes for suggestions.
3097 for name in lifetimes.keys() {
3098 if let hir::ParamName::Plain(name) = name {
3099 lifetime_names.insert(name.name);
3100 lifetime_spans.push(name.span);
3101 }
3102 }
3103 scope = s;
3104 }
3105 Scope::ObjectLifetimeDefault { ref s, .. }
3106 | Scope::Elision { ref s, .. }
3107 | Scope::TraitRefBoundary { ref s, .. } => {
3108 scope = s;
3109 }
3110 _ => break,
3111 }
3112 }
3113 break Some(&e[..]);
3114 }
3115 Elide::Forbid => break None,
3116 };
3117 for lifetime_ref in lifetime_refs {
3118 self.insert_lifetime(lifetime_ref, lifetime);
3119 }
3120 return;
3121 }
3122
3123 Scope::ObjectLifetimeDefault { s, .. }
3124 | Scope::Supertrait { s, .. }
3125 | Scope::TraitRefBoundary { s, .. } => {
3126 scope = s;
3127 }
3128 }
3129 };
3130
3131 // If we specifically need the `scope_for_path` map, then we're in the
3132 // diagnostic pass and we don't want to emit more errors.
3133 if self.map.scope_for_path.is_some() {
3134 self.tcx.sess.delay_span_bug(
3135 rustc_span::DUMMY_SP,
3136 "Encountered unexpected errors during diagnostics related part",
3137 );
3138 return;
3139 }
3140
3141 let mut spans: Vec<_> = lifetime_refs.iter().map(|lt| lt.span).collect();
3142 spans.sort();
3143 let mut spans_dedup = spans.clone();
3144 spans_dedup.dedup();
3145 let spans_with_counts: Vec<_> = spans_dedup
3146 .into_iter()
3147 .map(|sp| (sp, spans.iter().filter(|nsp| *nsp == &sp).count()))
3148 .collect();
3149
3150 let mut err = self.report_missing_lifetime_specifiers(spans.clone(), lifetime_refs.len());
3151
3152 if let Some(params) = error {
3153 // If there's no lifetime available, suggest `'static`.
3154 if self.report_elision_failure(&mut err, params) && lifetime_names.is_empty() {
3155 lifetime_names.insert(kw::StaticLifetime);
3156 }
3157 }
3158
3159 self.add_missing_lifetime_specifiers_label(
3160 &mut err,
3161 spans_with_counts,
3162 &lifetime_names,
3163 lifetime_spans,
3164 error.unwrap_or(&[]),
3165 );
3166 err.emit();
3167 }
3168
report_elision_failure( &mut self, db: &mut DiagnosticBuilder<'_>, params: &[ElisionFailureInfo], ) -> bool3169 fn report_elision_failure(
3170 &mut self,
3171 db: &mut DiagnosticBuilder<'_>,
3172 params: &[ElisionFailureInfo],
3173 ) -> bool /* add `'static` lifetime to lifetime list */ {
3174 let mut m = String::new();
3175 let len = params.len();
3176
3177 let elided_params: Vec<_> =
3178 params.iter().cloned().filter(|info| info.lifetime_count > 0).collect();
3179
3180 let elided_len = elided_params.len();
3181
3182 for (i, info) in elided_params.into_iter().enumerate() {
3183 let ElisionFailureInfo { parent, index, lifetime_count: n, have_bound_regions, span } =
3184 info;
3185
3186 db.span_label(span, "");
3187 let help_name = if let Some(ident) =
3188 parent.and_then(|body| self.tcx.hir().body(body).params[index].pat.simple_ident())
3189 {
3190 format!("`{}`", ident)
3191 } else {
3192 format!("argument {}", index + 1)
3193 };
3194
3195 m.push_str(
3196 &(if n == 1 {
3197 help_name
3198 } else {
3199 format!(
3200 "one of {}'s {} {}lifetimes",
3201 help_name,
3202 n,
3203 if have_bound_regions { "free " } else { "" }
3204 )
3205 })[..],
3206 );
3207
3208 if elided_len == 2 && i == 0 {
3209 m.push_str(" or ");
3210 } else if i + 2 == elided_len {
3211 m.push_str(", or ");
3212 } else if i != elided_len - 1 {
3213 m.push_str(", ");
3214 }
3215 }
3216
3217 if len == 0 {
3218 db.help(
3219 "this function's return type contains a borrowed value, \
3220 but there is no value for it to be borrowed from",
3221 );
3222 true
3223 } else if elided_len == 0 {
3224 db.help(
3225 "this function's return type contains a borrowed value with \
3226 an elided lifetime, but the lifetime cannot be derived from \
3227 the arguments",
3228 );
3229 true
3230 } else if elided_len == 1 {
3231 db.help(&format!(
3232 "this function's return type contains a borrowed value, \
3233 but the signature does not say which {} it is borrowed from",
3234 m
3235 ));
3236 false
3237 } else {
3238 db.help(&format!(
3239 "this function's return type contains a borrowed value, \
3240 but the signature does not say whether it is borrowed from {}",
3241 m
3242 ));
3243 false
3244 }
3245 }
3246
resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime)3247 fn resolve_object_lifetime_default(&mut self, lifetime_ref: &'tcx hir::Lifetime) {
3248 debug!("resolve_object_lifetime_default(lifetime_ref={:?})", lifetime_ref);
3249 let mut late_depth = 0;
3250 let mut scope = self.scope;
3251 let lifetime = loop {
3252 match *scope {
3253 Scope::Binder { s, scope_type, .. } => {
3254 match scope_type {
3255 BinderScopeType::Normal => late_depth += 1,
3256 BinderScopeType::Concatenating => {}
3257 }
3258 scope = s;
3259 }
3260
3261 Scope::Root | Scope::Elision { .. } => break Region::Static,
3262
3263 Scope::Body { .. } | Scope::ObjectLifetimeDefault { lifetime: None, .. } => return,
3264
3265 Scope::ObjectLifetimeDefault { lifetime: Some(l), .. } => break l,
3266
3267 Scope::Supertrait { s, .. } | Scope::TraitRefBoundary { s, .. } => {
3268 scope = s;
3269 }
3270 }
3271 };
3272 self.insert_lifetime(lifetime_ref, lifetime.shifted(late_depth));
3273 }
3274
check_lifetime_params( &mut self, old_scope: ScopeRef<'_>, params: &'tcx [hir::GenericParam<'tcx>], )3275 fn check_lifetime_params(
3276 &mut self,
3277 old_scope: ScopeRef<'_>,
3278 params: &'tcx [hir::GenericParam<'tcx>],
3279 ) {
3280 let lifetimes: Vec<_> = params
3281 .iter()
3282 .filter_map(|param| match param.kind {
3283 GenericParamKind::Lifetime { .. } => {
3284 Some((param, param.name.normalize_to_macros_2_0()))
3285 }
3286 _ => None,
3287 })
3288 .collect();
3289 for (i, (lifetime_i, lifetime_i_name)) in lifetimes.iter().enumerate() {
3290 if let hir::ParamName::Plain(_) = lifetime_i_name {
3291 let name = lifetime_i_name.ident().name;
3292 if name == kw::UnderscoreLifetime || name == kw::StaticLifetime {
3293 let mut err = struct_span_err!(
3294 self.tcx.sess,
3295 lifetime_i.span,
3296 E0262,
3297 "invalid lifetime parameter name: `{}`",
3298 lifetime_i.name.ident(),
3299 );
3300 err.span_label(
3301 lifetime_i.span,
3302 format!("{} is a reserved lifetime name", name),
3303 );
3304 err.emit();
3305 }
3306 }
3307
3308 // It is a hard error to shadow a lifetime within the same scope.
3309 for (lifetime_j, lifetime_j_name) in lifetimes.iter().skip(i + 1) {
3310 if lifetime_i_name == lifetime_j_name {
3311 struct_span_err!(
3312 self.tcx.sess,
3313 lifetime_j.span,
3314 E0263,
3315 "lifetime name `{}` declared twice in the same scope",
3316 lifetime_j.name.ident()
3317 )
3318 .span_label(lifetime_j.span, "declared twice")
3319 .span_label(lifetime_i.span, "previous declaration here")
3320 .emit();
3321 }
3322 }
3323
3324 // It is a soft error to shadow a lifetime within a parent scope.
3325 self.check_lifetime_param_for_shadowing(old_scope, &lifetime_i);
3326
3327 for bound in lifetime_i.bounds {
3328 match bound {
3329 hir::GenericBound::Outlives(ref lt) => match lt.name {
3330 hir::LifetimeName::Underscore => self.tcx.sess.delay_span_bug(
3331 lt.span,
3332 "use of `'_` in illegal place, but not caught by lowering",
3333 ),
3334 hir::LifetimeName::Static => {
3335 self.insert_lifetime(lt, Region::Static);
3336 self.tcx
3337 .sess
3338 .struct_span_warn(
3339 lifetime_i.span.to(lt.span),
3340 &format!(
3341 "unnecessary lifetime parameter `{}`",
3342 lifetime_i.name.ident(),
3343 ),
3344 )
3345 .help(&format!(
3346 "you can use the `'static` lifetime directly, in place of `{}`",
3347 lifetime_i.name.ident(),
3348 ))
3349 .emit();
3350 }
3351 hir::LifetimeName::Param(_) | hir::LifetimeName::Implicit => {
3352 self.resolve_lifetime_ref(lt);
3353 }
3354 hir::LifetimeName::ImplicitObjectLifetimeDefault => {
3355 self.tcx.sess.delay_span_bug(
3356 lt.span,
3357 "lowering generated `ImplicitObjectLifetimeDefault` \
3358 outside of an object type",
3359 )
3360 }
3361 hir::LifetimeName::Error => {
3362 // No need to do anything, error already reported.
3363 }
3364 },
3365 _ => bug!(),
3366 }
3367 }
3368 }
3369 }
3370
check_lifetime_param_for_shadowing( &self, mut old_scope: ScopeRef<'_>, param: &'tcx hir::GenericParam<'tcx>, )3371 fn check_lifetime_param_for_shadowing(
3372 &self,
3373 mut old_scope: ScopeRef<'_>,
3374 param: &'tcx hir::GenericParam<'tcx>,
3375 ) {
3376 for label in &self.labels_in_fn {
3377 // FIXME (#24278): non-hygienic comparison
3378 if param.name.ident().name == label.name {
3379 signal_shadowing_problem(
3380 self.tcx,
3381 label.name,
3382 original_label(label.span),
3383 shadower_lifetime(¶m),
3384 );
3385 return;
3386 }
3387 }
3388
3389 loop {
3390 match *old_scope {
3391 Scope::Body { s, .. }
3392 | Scope::Elision { s, .. }
3393 | Scope::ObjectLifetimeDefault { s, .. }
3394 | Scope::Supertrait { s, .. }
3395 | Scope::TraitRefBoundary { s, .. } => {
3396 old_scope = s;
3397 }
3398
3399 Scope::Root => {
3400 return;
3401 }
3402
3403 Scope::Binder { ref lifetimes, s, .. } => {
3404 if let Some(&def) = lifetimes.get(¶m.name.normalize_to_macros_2_0()) {
3405 let hir_id =
3406 self.tcx.hir().local_def_id_to_hir_id(def.id().unwrap().expect_local());
3407
3408 signal_shadowing_problem(
3409 self.tcx,
3410 param.name.ident().name,
3411 original_lifetime(self.tcx.hir().span(hir_id)),
3412 shadower_lifetime(¶m),
3413 );
3414 return;
3415 }
3416
3417 old_scope = s;
3418 }
3419 }
3420 }
3421 }
3422
3423 /// Returns `true` if, in the current scope, replacing `'_` would be
3424 /// equivalent to a single-use lifetime.
track_lifetime_uses(&self) -> bool3425 fn track_lifetime_uses(&self) -> bool {
3426 let mut scope = self.scope;
3427 loop {
3428 match *scope {
3429 Scope::Root => break false,
3430
3431 // Inside of items, it depends on the kind of item.
3432 Scope::Binder { track_lifetime_uses, .. } => break track_lifetime_uses,
3433
3434 // Inside a body, `'_` will use an inference variable,
3435 // should be fine.
3436 Scope::Body { .. } => break true,
3437
3438 // A lifetime only used in a fn argument could as well
3439 // be replaced with `'_`, as that would generate a
3440 // fresh name, too.
3441 Scope::Elision { elide: Elide::FreshLateAnon(..), .. } => break true,
3442
3443 // In the return type or other such place, `'_` is not
3444 // going to make a fresh name, so we cannot
3445 // necessarily replace a single-use lifetime with
3446 // `'_`.
3447 Scope::Elision {
3448 elide: Elide::Exact(_) | Elide::Error(_) | Elide::Forbid, ..
3449 } => break false,
3450
3451 Scope::ObjectLifetimeDefault { s, .. }
3452 | Scope::Supertrait { s, .. }
3453 | Scope::TraitRefBoundary { s, .. } => scope = s,
3454 }
3455 }
3456 }
3457
3458 #[tracing::instrument(level = "debug", skip(self))]
insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region)3459 fn insert_lifetime(&mut self, lifetime_ref: &'tcx hir::Lifetime, def: Region) {
3460 debug!(
3461 node = ?self.tcx.hir().node_to_string(lifetime_ref.hir_id),
3462 span = ?self.tcx.sess.source_map().span_to_diagnostic_string(lifetime_ref.span)
3463 );
3464 self.map.defs.insert(lifetime_ref.hir_id, def);
3465
3466 match def {
3467 Region::LateBoundAnon(..) | Region::Static => {
3468 // These are anonymous lifetimes or lifetimes that are not declared.
3469 }
3470
3471 Region::Free(_, def_id)
3472 | Region::LateBound(_, _, def_id, _)
3473 | Region::EarlyBound(_, def_id, _) => {
3474 // A lifetime declared by the user.
3475 let track_lifetime_uses = self.track_lifetime_uses();
3476 debug!(?track_lifetime_uses);
3477 if track_lifetime_uses && !self.lifetime_uses.contains_key(&def_id) {
3478 debug!("first use of {:?}", def_id);
3479 self.lifetime_uses.insert(def_id, LifetimeUseSet::One(lifetime_ref));
3480 } else {
3481 debug!("many uses of {:?}", def_id);
3482 self.lifetime_uses.insert(def_id, LifetimeUseSet::Many);
3483 }
3484 }
3485 }
3486 }
3487
3488 /// Sometimes we resolve a lifetime, but later find that it is an
3489 /// error (esp. around impl trait). In that case, we remove the
3490 /// entry into `map.defs` so as not to confuse later code.
uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region)3491 fn uninsert_lifetime_on_error(&mut self, lifetime_ref: &'tcx hir::Lifetime, bad_def: Region) {
3492 let old_value = self.map.defs.remove(&lifetime_ref.hir_id);
3493 assert_eq!(old_value, Some(bad_def));
3494 }
3495 }
3496
3497 /// Detects late-bound lifetimes and inserts them into
3498 /// `map.late_bound`.
3499 ///
3500 /// A region declared on a fn is **late-bound** if:
3501 /// - it is constrained by an argument type;
3502 /// - it does not appear in a where-clause.
3503 ///
3504 /// "Constrained" basically means that it appears in any type but
3505 /// not amongst the inputs to a projection. In other words, `<&'a
3506 /// T as Trait<''b>>::Foo` does not constrain `'a` or `'b`.
3507 #[tracing::instrument(level = "debug", skip(map))]
insert_late_bound_lifetimes( map: &mut NamedRegionMap, decl: &hir::FnDecl<'_>, generics: &hir::Generics<'_>, )3508 fn insert_late_bound_lifetimes(
3509 map: &mut NamedRegionMap,
3510 decl: &hir::FnDecl<'_>,
3511 generics: &hir::Generics<'_>,
3512 ) {
3513 let mut constrained_by_input = ConstrainedCollector::default();
3514 for arg_ty in decl.inputs {
3515 constrained_by_input.visit_ty(arg_ty);
3516 }
3517
3518 let mut appears_in_output = AllCollector::default();
3519 intravisit::walk_fn_ret_ty(&mut appears_in_output, &decl.output);
3520
3521 debug!(?constrained_by_input.regions);
3522
3523 // Walk the lifetimes that appear in where clauses.
3524 //
3525 // Subtle point: because we disallow nested bindings, we can just
3526 // ignore binders here and scrape up all names we see.
3527 let mut appears_in_where_clause = AllCollector::default();
3528 appears_in_where_clause.visit_generics(generics);
3529
3530 for param in generics.params {
3531 if let hir::GenericParamKind::Lifetime { .. } = param.kind {
3532 if !param.bounds.is_empty() {
3533 // `'a: 'b` means both `'a` and `'b` are referenced
3534 appears_in_where_clause
3535 .regions
3536 .insert(hir::LifetimeName::Param(param.name.normalize_to_macros_2_0()));
3537 }
3538 }
3539 }
3540
3541 debug!(?appears_in_where_clause.regions);
3542
3543 // Late bound regions are those that:
3544 // - appear in the inputs
3545 // - do not appear in the where-clauses
3546 // - are not implicitly captured by `impl Trait`
3547 for param in generics.params {
3548 match param.kind {
3549 hir::GenericParamKind::Lifetime { .. } => { /* fall through */ }
3550
3551 // Neither types nor consts are late-bound.
3552 hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => continue,
3553 }
3554
3555 let lt_name = hir::LifetimeName::Param(param.name.normalize_to_macros_2_0());
3556 // appears in the where clauses? early-bound.
3557 if appears_in_where_clause.regions.contains(<_name) {
3558 continue;
3559 }
3560
3561 // does not appear in the inputs, but appears in the return type? early-bound.
3562 if !constrained_by_input.regions.contains(<_name)
3563 && appears_in_output.regions.contains(<_name)
3564 {
3565 continue;
3566 }
3567
3568 debug!("lifetime {:?} with id {:?} is late-bound", param.name.ident(), param.hir_id);
3569
3570 let inserted = map.late_bound.insert(param.hir_id);
3571 assert!(inserted, "visited lifetime {:?} twice", param.hir_id);
3572 }
3573
3574 return;
3575
3576 #[derive(Default)]
3577 struct ConstrainedCollector {
3578 regions: FxHashSet<hir::LifetimeName>,
3579 }
3580
3581 impl<'v> Visitor<'v> for ConstrainedCollector {
3582 type Map = intravisit::ErasedMap<'v>;
3583
3584 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
3585 NestedVisitorMap::None
3586 }
3587
3588 fn visit_ty(&mut self, ty: &'v hir::Ty<'v>) {
3589 match ty.kind {
3590 hir::TyKind::Path(
3591 hir::QPath::Resolved(Some(_), _) | hir::QPath::TypeRelative(..),
3592 ) => {
3593 // ignore lifetimes appearing in associated type
3594 // projections, as they are not *constrained*
3595 // (defined above)
3596 }
3597
3598 hir::TyKind::Path(hir::QPath::Resolved(None, ref path)) => {
3599 // consider only the lifetimes on the final
3600 // segment; I am not sure it's even currently
3601 // valid to have them elsewhere, but even if it
3602 // is, those would be potentially inputs to
3603 // projections
3604 if let Some(last_segment) = path.segments.last() {
3605 self.visit_path_segment(path.span, last_segment);
3606 }
3607 }
3608
3609 _ => {
3610 intravisit::walk_ty(self, ty);
3611 }
3612 }
3613 }
3614
3615 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
3616 self.regions.insert(lifetime_ref.name.normalize_to_macros_2_0());
3617 }
3618 }
3619
3620 #[derive(Default)]
3621 struct AllCollector {
3622 regions: FxHashSet<hir::LifetimeName>,
3623 }
3624
3625 impl<'v> Visitor<'v> for AllCollector {
3626 type Map = intravisit::ErasedMap<'v>;
3627
3628 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
3629 NestedVisitorMap::None
3630 }
3631
3632 fn visit_lifetime(&mut self, lifetime_ref: &'v hir::Lifetime) {
3633 self.regions.insert(lifetime_ref.name.normalize_to_macros_2_0());
3634 }
3635 }
3636 }
3637