1 //! See the Book for more information.
3 pub use self::freshen::TypeFreshener;
4 pub use self::LateBoundRegionConversionTime::*;
5 pub use self::RegionVariableOrigin::*;
6 pub use self::SubregionOrigin::*;
7 pub use self::ValuePairs::*;
9 use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
12 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
13 use rustc_data_structures::snapshot_vec as sv;
14 use rustc_data_structures::sync::Lrc;
15 use rustc_data_structures::undo_log::{Rollback, Snapshots, UndoLogs};
16 use rustc_data_structures::unify as ut;
17 use rustc_errors::DiagnosticBuilder;
19 use rustc_hir::def_id::{DefId, LocalDefId};
20 use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
21 use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
22 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
23 use rustc_middle::middle::region;
24 use rustc_middle::mir;
25 use rustc_middle::mir::interpret::ConstEvalResult;
26 use rustc_middle::traits::select;
27 use rustc_middle::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
28 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder};
29 use rustc_middle::ty::relate::RelateResult;
30 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
31 pub use rustc_middle::ty::IntVarValue;
32 use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
33 use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
34 use rustc_session::config::BorrowckMode;
35 use rustc_span::symbol::Symbol;
38 use std::cell::{Cell, Ref, RefCell};
39 use std::collections::BTreeMap;
41 use std::marker::PhantomData;
43 use self::combine::CombineFields;
44 use self::free_regions::RegionRelations;
45 use self::lexical_region_resolve::LexicalRegionResolutions;
46 use self::outlives::env::OutlivesEnvironment;
47 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
48 use self::region_constraints::{
49 RegionConstraintCollector, RegionConstraintStorage, RegionSnapshot,
51 use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
57 pub mod error_reporting;
64 mod lexical_region_resolve;
68 pub mod region_constraints;
71 pub mod type_variable;
73 use crate::infer::canonical::OriginalQueryValues;
74 pub use rustc_middle::infer::unify_key;
78 pub struct InferOk<'tcx, T> {
80 pub obligations: PredicateObligations<'tcx>,
82 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
84 pub type Bound<T> = Option<T>;
85 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
86 pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
88 /// How we should handle region solving.
90 /// This is used so that the region values inferred by HIR region solving are
91 /// not exposed, and so that we can avoid doing work in HIR typeck that MIR
92 /// typeck will also do.
93 #[derive(Copy, Clone, Debug)]
94 pub enum RegionckMode {
95 /// The default mode: report region errors, don't erase regions.
97 /// Erase the results of region after solving.
99 /// A flag that is used to suppress region errors, when we are doing
100 /// region checks that the NLL borrow checker will also do -- it might
102 suppress_errors: bool,
106 impl Default for RegionckMode {
107 fn default() -> Self {
113 pub fn suppressed(self) -> bool {
115 Self::Solve => false,
116 Self::Erase { suppress_errors } => suppress_errors,
120 /// Indicates that the MIR borrowck will repeat these region
121 /// checks, so we should ignore errors if NLL is (unconditionally)
123 pub fn for_item_body(tcx: TyCtxt<'_>) -> Self {
124 // FIXME(Centril): Once we actually remove `::Migrate` also make
125 // this always `true` and then proceed to eliminate the dead code.
126 match tcx.borrowck_mode() {
127 // If we're on Migrate mode, report AST region errors
128 BorrowckMode::Migrate => RegionckMode::Erase { suppress_errors: false },
130 // If we're on MIR, don't report AST region errors as they should be reported by NLL
131 BorrowckMode::Mir => RegionckMode::Erase { suppress_errors: true },
136 /// This type contains all the things within `InferCtxt` that sit within a
137 /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
138 /// operations are hot enough that we want only one call to `borrow_mut` per
139 /// call to `start_snapshot` and `rollback_to`.
140 pub struct InferCtxtInner<'tcx> {
141 /// Cache for projections. This cache is snapshotted along with the infcx.
143 /// Public so that `traits::project` can use it.
144 pub projection_cache: traits::ProjectionCacheStorage<'tcx>,
146 /// We instantiate `UnificationTable` with `bounds<Ty>` because the types
147 /// that might instantiate a general type variable have an order,
148 /// represented by its upper and lower bounds.
149 type_variables: type_variable::TypeVariableStorage<'tcx>,
150 undo_log: Logs<'tcx>,
152 /// Map from const parameter variable to the kind of const it represents.
153 const_unification_table: ut::UnificationStorage<ty::ConstVid<'tcx>>,
155 /// Map from integral variable to the kind of integer it represents.
156 int_unification_table: ut::UnificationStorage<ty::IntVid>,
158 /// Map from floating variable to the kind of float it represents.
159 float_unification_table: ut::UnificationStorage<ty::FloatVid>,
161 /// Tracks the set of region variables and the constraints between them.
162 /// This is initially `Some(_)` but when
163 /// `resolve_regions_and_report_errors` is invoked, this gets set to `None`
164 /// -- further attempts to perform unification, etc., may fail if new
165 /// region constraints would've been added.
166 region_constraints: Option<RegionConstraintStorage<'tcx>>,
168 /// A set of constraints that regionck must validate. Each
169 /// constraint has the form `T:'a`, meaning "some type `T` must
170 /// outlive the lifetime 'a". These constraints derive from
171 /// instantiated type parameters. So if you had a struct defined
174 /// struct Foo<T:'static> { ... }
176 /// then in some expression `let x = Foo { ... }` it will
177 /// instantiate the type parameter `T` with a fresh type `$0`. At
178 /// the same time, it will record a region obligation of
179 /// `$0:'static`. This will get checked later by regionck. (We
180 /// can't generally check these things right away because we have
181 /// to wait until types are resolved.)
183 /// These are stored in a map keyed to the id of the innermost
184 /// enclosing fn body / static initializer expression. This is
185 /// because the location where the obligation was incurred can be
186 /// relevant with respect to which sublifetime assumptions are in
187 /// place. The reason that we store under the fn-id, and not
188 /// something more fine-grained, is so that it is easier for
189 /// regionck to be sure that it has found *all* the region
190 /// obligations (otherwise, it's easy to fail to walk to a
191 /// particular node-id).
193 /// Before running `resolve_regions_and_report_errors`, the creator
194 /// of the inference context is expected to invoke
195 /// `process_region_obligations` (defined in `self::region_obligations`)
196 /// for each body-id in this map, which will process the
197 /// obligations within. This is expected to be done 'late enough'
198 /// that all type inference variables have been bound and so forth.
199 pub region_obligations: Vec<(hir::HirId, RegionObligation<'tcx>)>,
202 impl<'tcx> InferCtxtInner<'tcx> {
203 fn new() -> InferCtxtInner<'tcx> {
205 projection_cache: Default::default(),
206 type_variables: type_variable::TypeVariableStorage::new(),
207 undo_log: Logs::default(),
208 const_unification_table: ut::UnificationStorage::new(),
209 int_unification_table: ut::UnificationStorage::new(),
210 float_unification_table: ut::UnificationStorage::new(),
211 region_constraints: Some(RegionConstraintStorage::new()),
212 region_obligations: vec![],
216 pub(crate) fn projection_cache(&mut self) -> traits::ProjectionCache<'tcx, '_> {
217 self.projection_cache.with_log(&mut self.undo_log)
220 fn type_variables(&mut self) -> type_variable::TypeVariableTable<'tcx, '_> {
221 self.type_variables.with_log(&mut self.undo_log)
224 fn int_unification_table(
226 ) -> ut::UnificationTable<
227 ut::InPlace<ty::IntVid, &mut ut::UnificationStorage<ty::IntVid>, &mut Logs<'tcx>>,
229 ut::UnificationTable::with_log(&mut self.int_unification_table, &mut self.undo_log)
232 fn float_unification_table(
234 ) -> ut::UnificationTable<
235 ut::InPlace<ty::FloatVid, &mut ut::UnificationStorage<ty::FloatVid>, &mut Logs<'tcx>>,
237 ut::UnificationTable::with_log(&mut self.float_unification_table, &mut self.undo_log)
240 fn const_unification_table(
242 ) -> ut::UnificationTable<
245 &mut ut::UnificationStorage<ty::ConstVid<'tcx>>,
249 ut::UnificationTable::with_log(&mut self.const_unification_table, &mut self.undo_log)
252 pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'tcx, '_> {
253 self.region_constraints
255 .expect("region constraints already solved")
256 .with_log(&mut self.undo_log)
260 pub struct Snapshot<'tcx> {
262 _marker: PhantomData<&'tcx ()>,
265 pub(crate) enum UndoLog<'tcx> {
266 TypeVariables(type_variable::UndoLog<'tcx>),
267 ConstUnificationTable(sv::UndoLog<ut::Delegate<ty::ConstVid<'tcx>>>),
268 IntUnificationTable(sv::UndoLog<ut::Delegate<ty::IntVid>>),
269 FloatUnificationTable(sv::UndoLog<ut::Delegate<ty::FloatVid>>),
270 RegionConstraintCollector(region_constraints::UndoLog<'tcx>),
271 RegionUnificationTable(sv::UndoLog<ut::Delegate<ty::RegionVid>>),
272 ProjectionCache(traits::UndoLog<'tcx>),
275 impl<'tcx> From<region_constraints::UndoLog<'tcx>> for UndoLog<'tcx> {
276 fn from(l: region_constraints::UndoLog<'tcx>) -> Self {
277 UndoLog::RegionConstraintCollector(l)
281 impl<'tcx> From<sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>> for UndoLog<'tcx> {
282 fn from(l: sv::UndoLog<ut::Delegate<type_variable::TyVidEqKey<'tcx>>>) -> Self {
283 UndoLog::TypeVariables(type_variable::UndoLog::EqRelation(l))
287 impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::TyVid>>> for UndoLog<'tcx> {
288 fn from(l: sv::UndoLog<ut::Delegate<ty::TyVid>>) -> Self {
289 UndoLog::TypeVariables(type_variable::UndoLog::SubRelation(l))
293 impl<'tcx> From<sv::UndoLog<type_variable::Delegate>> for UndoLog<'tcx> {
294 fn from(l: sv::UndoLog<type_variable::Delegate>) -> Self {
295 UndoLog::TypeVariables(type_variable::UndoLog::Values(l))
299 impl<'tcx> From<type_variable::Instantiate> for UndoLog<'tcx> {
300 fn from(l: type_variable::Instantiate) -> Self {
301 UndoLog::TypeVariables(type_variable::UndoLog::from(l))
305 impl From<type_variable::UndoLog<'tcx>> for UndoLog<'tcx> {
306 fn from(t: type_variable::UndoLog<'tcx>) -> Self {
307 Self::TypeVariables(t)
311 impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::ConstVid<'tcx>>>> for UndoLog<'tcx> {
312 fn from(l: sv::UndoLog<ut::Delegate<ty::ConstVid<'tcx>>>) -> Self {
313 Self::ConstUnificationTable(l)
317 impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::IntVid>>> for UndoLog<'tcx> {
318 fn from(l: sv::UndoLog<ut::Delegate<ty::IntVid>>) -> Self {
319 Self::IntUnificationTable(l)
323 impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::FloatVid>>> for UndoLog<'tcx> {
324 fn from(l: sv::UndoLog<ut::Delegate<ty::FloatVid>>) -> Self {
325 Self::FloatUnificationTable(l)
329 impl<'tcx> From<sv::UndoLog<ut::Delegate<ty::RegionVid>>> for UndoLog<'tcx> {
330 fn from(l: sv::UndoLog<ut::Delegate<ty::RegionVid>>) -> Self {
331 Self::RegionUnificationTable(l)
335 impl<'tcx> From<traits::UndoLog<'tcx>> for UndoLog<'tcx> {
336 fn from(l: traits::UndoLog<'tcx>) -> Self {
337 Self::ProjectionCache(l)
341 pub(crate) type UnificationTable<'a, 'tcx, T> =
342 ut::UnificationTable<ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut Logs<'tcx>>>;
344 struct RollbackView<'tcx, 'a> {
345 type_variables: type_variable::RollbackView<'tcx, 'a>,
346 const_unification_table: &'a mut ut::UnificationStorage<ty::ConstVid<'tcx>>,
347 int_unification_table: &'a mut ut::UnificationStorage<ty::IntVid>,
348 float_unification_table: &'a mut ut::UnificationStorage<ty::FloatVid>,
349 region_constraints: &'a mut RegionConstraintStorage<'tcx>,
350 projection_cache: &'a mut traits::ProjectionCacheStorage<'tcx>,
353 impl<'tcx> Rollback<UndoLog<'tcx>> for RollbackView<'tcx, '_> {
354 fn reverse(&mut self, undo: UndoLog<'tcx>) {
356 UndoLog::TypeVariables(undo) => self.type_variables.reverse(undo),
357 UndoLog::ConstUnificationTable(undo) => self.const_unification_table.reverse(undo),
358 UndoLog::IntUnificationTable(undo) => self.int_unification_table.reverse(undo),
359 UndoLog::FloatUnificationTable(undo) => self.float_unification_table.reverse(undo),
360 UndoLog::RegionConstraintCollector(undo) => self.region_constraints.reverse(undo),
361 UndoLog::RegionUnificationTable(undo) => {
362 self.region_constraints.unification_table.reverse(undo)
364 UndoLog::ProjectionCache(undo) => self.projection_cache.reverse(undo),
369 pub(crate) struct Logs<'tcx> {
370 logs: Vec<UndoLog<'tcx>>,
371 num_open_snapshots: usize,
374 impl Default for Logs<'_> {
375 fn default() -> Self {
376 Self { logs: Default::default(), num_open_snapshots: Default::default() }
380 impl<'tcx, T> UndoLogs<T> for Logs<'tcx>
382 UndoLog<'tcx>: From<T>,
384 fn num_open_snapshots(&self) -> usize {
385 self.num_open_snapshots
387 fn push(&mut self, undo: T) {
388 if self.in_snapshot() {
389 self.logs.push(undo.into())
392 fn clear(&mut self) {
394 self.num_open_snapshots = 0;
396 fn extend<J>(&mut self, undos: J)
399 J: IntoIterator<Item = T>,
401 if self.in_snapshot() {
402 self.logs.extend(undos.into_iter().map(UndoLog::from))
407 impl<'tcx> Snapshots<UndoLog<'tcx>> for Logs<'tcx> {
408 type Snapshot = Snapshot<'tcx>;
409 fn actions_since_snapshot(&self, snapshot: &Self::Snapshot) -> &[UndoLog<'tcx>] {
410 &self.logs[snapshot.undo_len..]
413 fn start_snapshot(&mut self) -> Self::Snapshot {
417 fn rollback_to(&mut self, values: &mut impl Rollback<UndoLog<'tcx>>, snapshot: Self::Snapshot) {
418 debug!("rollback_to({})", snapshot.undo_len);
419 self.assert_open_snapshot(&snapshot);
421 while self.logs.len() > snapshot.undo_len {
422 values.reverse(self.logs.pop().unwrap());
425 if self.num_open_snapshots == 1 {
426 // The root snapshot. It's safe to clear the undo log because
427 // there's no snapshot further out that we might need to roll back
429 assert!(snapshot.undo_len == 0);
433 self.num_open_snapshots -= 1;
436 fn commit(&mut self, snapshot: Self::Snapshot) {
437 debug!("commit({})", snapshot.undo_len);
439 if self.num_open_snapshots == 1 {
440 // The root snapshot. It's safe to clear the undo log because
441 // there's no snapshot further out that we might need to roll back
443 assert!(snapshot.undo_len == 0);
447 self.num_open_snapshots -= 1;
451 impl<'tcx> Logs<'tcx> {
452 pub(crate) fn region_constraints(
455 ) -> impl Iterator<Item = &'_ region_constraints::UndoLog<'tcx>> + Clone {
456 self.logs[after..].iter().filter_map(|log| match log {
457 UndoLog::RegionConstraintCollector(log) => Some(log),
462 fn assert_open_snapshot(&self, snapshot: &Snapshot<'tcx>) {
463 // Failures here may indicate a failure to follow a stack discipline.
464 assert!(self.logs.len() >= snapshot.undo_len);
465 assert!(self.num_open_snapshots > 0);
469 pub struct InferCtxt<'a, 'tcx> {
470 pub tcx: TyCtxt<'tcx>,
472 /// During type-checking/inference of a body, `in_progress_tables`
473 /// contains a reference to the tables being built up, which are
474 /// used for reading closure kinds/signatures as they are inferred,
475 /// and for error reporting logic to read arbitrary node types.
476 pub in_progress_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
478 pub inner: RefCell<InferCtxtInner<'tcx>>,
480 /// If set, this flag causes us to skip the 'leak check' during
481 /// higher-ranked subtyping operations. This flag is a temporary one used
482 /// to manage the removal of the leak-check: for the time being, we still run the
483 /// leak-check, but we issue warnings. This flag can only be set to true
484 /// when entering a snapshot.
485 skip_leak_check: Cell<bool>,
487 /// Once region inference is done, the values for each variable.
488 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
490 /// Caches the results of trait selection. This cache is used
491 /// for things that have to do with the parameters in scope.
492 pub selection_cache: select::SelectionCache<'tcx>,
494 /// Caches the results of trait evaluation.
495 pub evaluation_cache: select::EvaluationCache<'tcx>,
497 /// the set of predicates on which errors have been reported, to
498 /// avoid reporting the same error twice.
499 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
501 pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
503 /// When an error occurs, we want to avoid reporting "derived"
504 /// errors that are due to this original failure. Normally, we
505 /// handle this with the `err_count_on_creation` count, which
506 /// basically just tracks how many errors were reported when we
507 /// started type-checking a fn and checks to see if any new errors
508 /// have been reported since then. Not great, but it works.
510 /// However, when errors originated in other passes -- notably
511 /// resolve -- this heuristic breaks down. Therefore, we have this
512 /// auxiliary flag that one can set whenever one creates a
513 /// type-error that is due to an error in a prior pass.
515 /// Don't read this flag directly, call `is_tainted_by_errors()`
516 /// and `set_tainted_by_errors()`.
517 tainted_by_errors_flag: Cell<bool>,
519 /// Track how many errors were reported when this infcx is created.
520 /// If the number of errors increases, that's also a sign (line
521 /// `tained_by_errors`) to avoid reporting certain kinds of errors.
522 // FIXME(matthewjasper) Merge into `tainted_by_errors_flag`
523 err_count_on_creation: usize,
525 /// This flag is true while there is an active snapshot.
526 in_snapshot: Cell<bool>,
528 /// What is the innermost universe we have created? Starts out as
529 /// `UniverseIndex::root()` but grows from there as we enter
530 /// universal quantifiers.
532 /// N.B., at present, we exclude the universal quantifiers on the
533 /// item we are type-checking, and just consider those names as
534 /// part of the root universe. So this would only get incremented
535 /// when we enter into a higher-ranked (`for<..>`) type or trait
537 universe: Cell<ty::UniverseIndex>,
540 /// A map returned by `replace_bound_vars_with_placeholders()`
541 /// indicating the placeholder region that each late-bound region was
543 pub type PlaceholderMap<'tcx> = BTreeMap<ty::BoundRegion, ty::Region<'tcx>>;
545 /// See the `error_reporting` module for more details.
546 #[derive(Clone, Debug, PartialEq, Eq, TypeFoldable)]
547 pub enum ValuePairs<'tcx> {
548 Types(ExpectedFound<Ty<'tcx>>),
549 Regions(ExpectedFound<ty::Region<'tcx>>),
550 Consts(ExpectedFound<&'tcx ty::Const<'tcx>>),
551 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
552 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
555 /// The trace designates the path through inference that we took to
556 /// encounter an error or subtyping constraint.
558 /// See the `error_reporting` module for more details.
559 #[derive(Clone, Debug)]
560 pub struct TypeTrace<'tcx> {
561 cause: ObligationCause<'tcx>,
562 values: ValuePairs<'tcx>,
565 /// The origin of a `r1 <= r2` constraint.
567 /// See `error_reporting` module for more details
568 #[derive(Clone, Debug)]
569 pub enum SubregionOrigin<'tcx> {
570 /// Arose from a subtyping relation
571 Subtype(Box<TypeTrace<'tcx>>),
573 /// Stack-allocated closures cannot outlive innermost loop
574 /// or function so as to ensure we only require finite stack
575 InfStackClosure(Span),
577 /// Invocation of closure must be within its lifetime
580 /// Dereference of reference must be within its lifetime
583 /// Closure bound must not outlive captured variables
584 ClosureCapture(Span, hir::HirId),
586 /// Index into slice must be within its lifetime
589 /// When casting `&'a T` to an `&'b Trait` object,
590 /// relating `'a` to `'b`
591 RelateObjectBound(Span),
593 /// Some type parameter was instantiated with the given type,
594 /// and that type must outlive some region.
595 RelateParamBound(Span, Ty<'tcx>),
597 /// The given region parameter was instantiated with a region
598 /// that must outlive some other region.
599 RelateRegionParamBound(Span),
601 /// A bound placed on type parameters that states that must outlive
602 /// the moment of their instantiation.
603 RelateDefaultParamBound(Span, Ty<'tcx>),
605 /// Creating a pointer `b` to contents of another reference
608 /// Creating a pointer `b` to contents of an upvar
609 ReborrowUpvar(Span, ty::UpvarId),
611 /// Data with type `Ty<'tcx>` was borrowed
612 DataBorrowed(Ty<'tcx>, Span),
614 /// (&'a &'b T) where a >= b
615 ReferenceOutlivesReferent(Ty<'tcx>, Span),
617 /// Type or region parameters must be in scope.
618 ParameterInScope(ParameterOrigin, Span),
620 /// The type T of an expression E must outlive the lifetime for E.
621 ExprTypeIsNotInScope(Ty<'tcx>, Span),
623 /// A `ref b` whose region does not enclose the decl site
624 BindingTypeIsNotValidAtDecl(Span),
626 /// Regions appearing in a method receiver must outlive method call
629 /// Regions appearing in a function argument must outlive func call
632 /// Region in return type of invoked fn must enclose call
635 /// Operands must be in scope
638 /// Region resulting from a `&` expr must enclose the `&` expr
641 /// An auto-borrow that does not enclose the expr where it occurs
644 /// Region constraint arriving from destructor safety
645 SafeDestructor(Span),
647 /// Comparing the signature and requirements of an impl method against
648 /// the containing trait.
649 CompareImplMethodObligation {
651 item_name: ast::Name,
652 impl_item_def_id: DefId,
653 trait_item_def_id: DefId,
657 // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
658 #[cfg(target_arch = "x86_64")]
659 static_assert_size!(SubregionOrigin<'_>, 32);
661 /// Places that type/region parameters can appear.
662 #[derive(Clone, Copy, Debug)]
663 pub enum ParameterOrigin {
665 MethodCall, // foo.bar() <-- parameters on impl providing bar()
666 OverloadedOperator, // a + b when overloaded
667 OverloadedDeref, // *a when overloaded
670 /// Times when we replace late-bound regions with variables:
671 #[derive(Clone, Copy, Debug)]
672 pub enum LateBoundRegionConversionTime {
673 /// when a fn is called
676 /// when two higher-ranked types are compared
679 /// when projecting an associated type
680 AssocTypeProjection(DefId),
683 /// Reasons to create a region inference variable
685 /// See `error_reporting` module for more details
686 #[derive(Copy, Clone, Debug)]
687 pub enum RegionVariableOrigin {
688 /// Region variables created for ill-categorized reasons,
689 /// mostly indicates places in need of refactoring
692 /// Regions created by a `&P` or `[...]` pattern
695 /// Regions created by `&` operator
698 /// Regions created as part of an autoref of a method receiver
701 /// Regions created as part of an automatic coercion
704 /// Region variables created as the values for early-bound regions
705 EarlyBoundRegion(Span, Symbol),
707 /// Region variables created for bound regions
708 /// in a function or method that is called
709 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
711 UpvarRegion(ty::UpvarId, Span),
713 BoundRegionInCoherence(ast::Name),
715 /// This origin is used for the inference variables that we create
716 /// during NLL region processing.
717 NLL(NLLRegionVariableOrigin),
720 #[derive(Copy, Clone, Debug)]
721 pub enum NLLRegionVariableOrigin {
722 /// During NLL region processing, we create variables for free
723 /// regions that we encounter in the function signature and
724 /// elsewhere. This origin indices we've got one of those.
727 /// "Universal" instantiation of a higher-ranked region (e.g.,
728 /// from a `for<'a> T` binder). Meant to represent "any region".
729 Placeholder(ty::PlaceholderRegion),
731 /// The variable we create to represent `'empty(U0)`.
735 /// If this is true, then this variable was created to represent a lifetime
736 /// bound in a `for` binder. For example, it might have been created to
737 /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
738 /// Such variables are created when we are trying to figure out if there
739 /// is any valid instantiation of `'a` that could fit into some scenario.
741 /// This is used to inform error reporting: in the case that we are trying to
742 /// determine whether there is any valid instantiation of a `'a` variable that meets
743 /// some constraint C, we want to blame the "source" of that `for` type,
744 /// rather than blaming the source of the constraint C.
749 impl NLLRegionVariableOrigin {
750 pub fn is_universal(self) -> bool {
752 NLLRegionVariableOrigin::FreeRegion => true,
753 NLLRegionVariableOrigin::Placeholder(..) => true,
754 NLLRegionVariableOrigin::Existential { .. } => false,
755 NLLRegionVariableOrigin::RootEmptyRegion => false,
759 pub fn is_existential(self) -> bool {
764 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
765 #[derive(Copy, Clone, Debug)]
766 pub enum FixupError<'tcx> {
767 UnresolvedIntTy(IntVid),
768 UnresolvedFloatTy(FloatVid),
770 UnresolvedConst(ConstVid<'tcx>),
773 /// See the `region_obligations` field for more information.
775 pub struct RegionObligation<'tcx> {
776 pub sub_region: ty::Region<'tcx>,
777 pub sup_type: Ty<'tcx>,
778 pub origin: SubregionOrigin<'tcx>,
781 impl<'tcx> fmt::Display for FixupError<'tcx> {
782 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
783 use self::FixupError::*;
786 UnresolvedIntTy(_) => write!(
788 "cannot determine the type of this integer; \
789 add a suffix to specify the type explicitly"
791 UnresolvedFloatTy(_) => write!(
793 "cannot determine the type of this number; \
794 add a suffix to specify the type explicitly"
796 UnresolvedTy(_) => write!(f, "unconstrained type"),
797 UnresolvedConst(_) => write!(f, "unconstrained const value"),
802 /// Helper type of a temporary returned by `tcx.infer_ctxt()`.
803 /// Necessary because we can't write the following bound:
804 /// `F: for<'b, 'tcx> where 'tcx FnOnce(InferCtxt<'b, 'tcx>)`.
805 pub struct InferCtxtBuilder<'tcx> {
806 global_tcx: TyCtxt<'tcx>,
807 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
810 pub trait TyCtxtInferExt<'tcx> {
811 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>;
814 impl TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
815 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
816 InferCtxtBuilder { global_tcx: self, fresh_tables: None }
820 impl<'tcx> InferCtxtBuilder<'tcx> {
821 /// Used only by `rustc_typeck` during body type-checking/inference,
822 /// will initialize `in_progress_tables` with fresh `TypeckTables`.
823 pub fn with_fresh_in_progress_tables(mut self, table_owner: LocalDefId) -> Self {
824 self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
828 /// Given a canonical value `C` as a starting point, create an
829 /// inference context that contains each of the bound values
830 /// within instantiated as a fresh variable. The `f` closure is
831 /// invoked with the new infcx, along with the instantiated value
832 /// `V` and a substitution `S`. This substitution `S` maps from
833 /// the bound values in `C` to their instantiated values in `V`
834 /// (in other words, `S(C) = V`).
835 pub fn enter_with_canonical<T, R>(
838 canonical: &Canonical<'tcx, T>,
839 f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
842 T: TypeFoldable<'tcx>,
846 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
847 f(infcx, value, subst)
851 pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R {
852 let InferCtxtBuilder { global_tcx, ref fresh_tables } = *self;
853 let in_progress_tables = fresh_tables.as_ref();
854 global_tcx.enter_local(|tcx| {
858 inner: RefCell::new(InferCtxtInner::new()),
859 lexical_region_resolutions: RefCell::new(None),
860 selection_cache: Default::default(),
861 evaluation_cache: Default::default(),
862 reported_trait_errors: Default::default(),
863 reported_closure_mismatch: Default::default(),
864 tainted_by_errors_flag: Cell::new(false),
865 err_count_on_creation: tcx.sess.err_count(),
866 in_snapshot: Cell::new(false),
867 skip_leak_check: Cell::new(false),
868 universe: Cell::new(ty::UniverseIndex::ROOT),
874 impl<'tcx, T> InferOk<'tcx, T> {
875 pub fn unit(self) -> InferOk<'tcx, ()> {
876 InferOk { value: (), obligations: self.obligations }
879 /// Extracts `value`, registering any obligations into `fulfill_cx`.
880 pub fn into_value_registering_obligations(
882 infcx: &InferCtxt<'_, 'tcx>,
883 fulfill_cx: &mut dyn TraitEngine<'tcx>,
885 let InferOk { value, obligations } = self;
886 for obligation in obligations {
887 fulfill_cx.register_predicate_obligation(infcx, obligation);
893 impl<'tcx> InferOk<'tcx, ()> {
894 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
899 #[must_use = "once you start a snapshot, you should always consume it"]
900 pub struct CombinedSnapshot<'a, 'tcx> {
901 undo_snapshot: Snapshot<'tcx>,
902 type_snapshot: type_variable::Snapshot<'tcx>,
903 const_snapshot: usize,
905 float_snapshot: usize,
906 region_constraints_snapshot: RegionSnapshot,
907 region_obligations_snapshot: usize,
908 universe: ty::UniverseIndex,
909 was_in_snapshot: bool,
910 was_skip_leak_check: bool,
911 _in_progress_tables: Option<Ref<'a, ty::TypeckTables<'tcx>>>,
914 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
915 pub fn is_in_snapshot(&self) -> bool {
916 self.in_snapshot.get()
919 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
920 t.fold_with(&mut self.freshener())
923 pub fn type_var_diverges(&'a self, ty: Ty<'_>) -> bool {
925 ty::Infer(ty::TyVar(vid)) => self.inner.borrow_mut().type_variables().var_diverges(vid),
930 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
931 freshen::TypeFreshener::new(self)
934 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty<'_>) -> UnconstrainedNumeric {
935 use rustc_middle::ty::error::UnconstrainedNumeric::Neither;
936 use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
938 ty::Infer(ty::IntVar(vid)) => {
939 if self.inner.borrow_mut().int_unification_table().probe_value(vid).is_some() {
945 ty::Infer(ty::FloatVar(vid)) => {
946 if self.inner.borrow_mut().float_unification_table().probe_value(vid).is_some() {
956 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
957 let mut inner = self.inner.borrow_mut();
958 // FIXME(const_generics): should there be an equivalent function for const variables?
960 let mut vars: Vec<Ty<'_>> = inner
962 .unsolved_variables()
964 .map(|t| self.tcx.mk_ty_var(t))
967 (0..inner.int_unification_table().len())
968 .map(|i| ty::IntVid { index: i as u32 })
969 .filter(|&vid| inner.int_unification_table().probe_value(vid).is_none())
970 .map(|v| self.tcx.mk_int_var(v)),
973 (0..inner.float_unification_table().len())
974 .map(|i| ty::FloatVid { index: i as u32 })
975 .filter(|&vid| inner.float_unification_table().probe_value(vid).is_none())
976 .map(|v| self.tcx.mk_float_var(v)),
983 trace: TypeTrace<'tcx>,
984 param_env: ty::ParamEnv<'tcx>,
985 ) -> CombineFields<'a, 'tcx> {
991 obligations: PredicateObligations::new(),
995 /// Clear the "currently in a snapshot" flag, invoke the closure,
996 /// then restore the flag to its original value. This flag is a
997 /// debugging measure designed to detect cases where we start a
998 /// snapshot, create type variables, and register obligations
999 /// which may involve those type variables in the fulfillment cx,
1000 /// potentially leaving "dangling type variables" behind.
1001 /// In such cases, an assertion will fail when attempting to
1002 /// register obligations, within a snapshot. Very useful, much
1003 /// better than grovelling through megabytes of `RUSTC_LOG` output.
1005 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
1006 /// sometimes create a "mini-fulfilment-cx" in which we enroll
1007 /// obligations. As long as this fulfillment cx is fully drained
1008 /// before we return, this is not a problem, as there won't be any
1009 /// escaping obligations in the main cx. In those cases, you can
1010 /// use this function.
1011 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
1013 F: FnOnce(&Self) -> R,
1015 let flag = self.in_snapshot.replace(false);
1016 let result = func(self);
1017 self.in_snapshot.set(flag);
1021 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
1022 debug!("start_snapshot()");
1024 let in_snapshot = self.in_snapshot.replace(true);
1026 let mut inner = self.inner.borrow_mut();
1028 inner.undo_log.num_open_snapshots += 1;
1029 let undo_snapshot = Snapshot { undo_len: inner.undo_log.logs.len(), _marker: PhantomData };
1032 type_snapshot: inner.type_variables().snapshot(),
1033 const_snapshot: inner.const_unification_table().len(),
1034 int_snapshot: inner.int_unification_table().len(),
1035 float_snapshot: inner.float_unification_table().len(),
1036 region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
1037 region_obligations_snapshot: inner.region_obligations.len(),
1038 universe: self.universe(),
1039 was_in_snapshot: in_snapshot,
1040 was_skip_leak_check: self.skip_leak_check.get(),
1041 // Borrow tables "in progress" (i.e., during typeck)
1042 // to ban writes from within a snapshot to them.
1043 _in_progress_tables: self.in_progress_tables.map(|tables| tables.borrow()),
1047 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
1048 debug!("rollback_to(cause={})", cause);
1049 let CombinedSnapshot {
1055 region_constraints_snapshot: _,
1056 region_obligations_snapshot,
1059 was_skip_leak_check,
1060 _in_progress_tables,
1063 self.in_snapshot.set(was_in_snapshot);
1064 self.universe.set(universe);
1065 self.skip_leak_check.set(was_skip_leak_check);
1067 let mut inner = self.inner.borrow_mut();
1068 let inner = &mut *inner;
1069 let InferCtxtInner {
1071 const_unification_table,
1072 int_unification_table,
1073 float_unification_table,
1078 inner.undo_log.rollback_to(
1080 type_variables: type_variable::RollbackView::from(type_variables),
1081 const_unification_table,
1082 int_unification_table,
1083 float_unification_table,
1084 region_constraints: region_constraints.as_mut().unwrap(),
1089 inner.region_obligations.truncate(region_obligations_snapshot);
1092 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
1093 debug!("commit_from()");
1094 let CombinedSnapshot {
1100 region_constraints_snapshot: _,
1101 region_obligations_snapshot: _,
1104 was_skip_leak_check,
1105 _in_progress_tables,
1108 self.in_snapshot.set(was_in_snapshot);
1109 self.skip_leak_check.set(was_skip_leak_check);
1111 let mut inner = self.inner.borrow_mut();
1112 inner.undo_log.commit(undo_snapshot);
1115 /// Executes `f` and commit the bindings.
1116 pub fn commit_unconditionally<R, F>(&self, f: F) -> R
1118 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
1120 debug!("commit_unconditionally()");
1121 let snapshot = self.start_snapshot();
1122 let r = f(&snapshot);
1123 self.commit_from(snapshot);
1127 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
1128 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
1130 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
1132 debug!("commit_if_ok()");
1133 let snapshot = self.start_snapshot();
1134 let r = f(&snapshot);
1135 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
1138 self.commit_from(snapshot);
1141 self.rollback_to("commit_if_ok -- error", snapshot);
1147 /// Execute `f` then unroll any bindings it creates.
1148 pub fn probe<R, F>(&self, f: F) -> R
1150 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
1153 let snapshot = self.start_snapshot();
1154 let r = f(&snapshot);
1155 self.rollback_to("probe", snapshot);
1159 /// If `should_skip` is true, then execute `f` then unroll any bindings it creates.
1160 pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R
1162 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
1165 let snapshot = self.start_snapshot();
1166 let skip_leak_check = should_skip || self.skip_leak_check.get();
1167 self.skip_leak_check.set(skip_leak_check);
1168 let r = f(&snapshot);
1169 self.rollback_to("probe", snapshot);
1173 /// Scan the constraints produced since `snapshot` began and returns:
1175 /// - `None` -- if none of them involve "region outlives" constraints
1176 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
1177 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
1178 pub fn region_constraints_added_in_snapshot(
1180 snapshot: &CombinedSnapshot<'a, 'tcx>,
1184 .unwrap_region_constraints()
1185 .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
1188 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
1189 self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
1192 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
1194 T: at::ToTrace<'tcx>,
1196 let origin = &ObligationCause::dummy();
1198 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
1199 // Ignore obligations, since we are unrolling
1200 // everything anyway.
1205 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
1207 T: at::ToTrace<'tcx>,
1209 let origin = &ObligationCause::dummy();
1211 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
1212 // Ignore obligations, since we are unrolling
1213 // everything anyway.
1220 origin: SubregionOrigin<'tcx>,
1221 a: ty::Region<'tcx>,
1222 b: ty::Region<'tcx>,
1224 debug!("sub_regions({:?} <: {:?})", a, b);
1225 self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
1228 /// Require that the region `r` be equal to one of the regions in
1229 /// the set `regions`.
1230 pub fn member_constraint(
1232 opaque_type_def_id: DefId,
1233 definition_span: Span,
1234 hidden_ty: Ty<'tcx>,
1235 region: ty::Region<'tcx>,
1236 in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
1238 debug!("member_constraint({:?} <: {:?})", region, in_regions);
1239 self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
1248 pub fn subtype_predicate(
1250 cause: &ObligationCause<'tcx>,
1251 param_env: ty::ParamEnv<'tcx>,
1252 predicate: &ty::PolySubtypePredicate<'tcx>,
1253 ) -> Option<InferResult<'tcx, ()>> {
1254 // Subtle: it's ok to skip the binder here and resolve because
1255 // `shallow_resolve` just ignores anything that is not a type
1256 // variable, and because type variable's can't (at present, at
1257 // least) capture any of the things bound by this binder.
1259 // NOTE(nmatsakis): really, there is no *particular* reason to do this
1260 // `shallow_resolve` here except as a micro-optimization.
1261 // Naturally I could not resist.
1262 let two_unbound_type_vars = {
1263 let a = self.shallow_resolve(predicate.skip_binder().a);
1264 let b = self.shallow_resolve(predicate.skip_binder().b);
1265 a.is_ty_var() && b.is_ty_var()
1268 if two_unbound_type_vars {
1269 // Two unbound type variables? Can't make progress.
1273 Some(self.commit_if_ok(|snapshot| {
1274 let (ty::SubtypePredicate { a_is_expected, a, b }, placeholder_map) =
1275 self.replace_bound_vars_with_placeholders(predicate);
1277 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
1279 self.leak_check(false, &placeholder_map, snapshot)?;
1285 pub fn region_outlives_predicate(
1287 cause: &traits::ObligationCause<'tcx>,
1288 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>,
1289 ) -> UnitResult<'tcx> {
1290 self.commit_if_ok(|snapshot| {
1291 let (ty::OutlivesPredicate(r_a, r_b), placeholder_map) =
1292 self.replace_bound_vars_with_placeholders(predicate);
1293 let origin = SubregionOrigin::from_obligation_cause(cause, || {
1294 RelateRegionParamBound(cause.span)
1296 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1297 self.leak_check(false, &placeholder_map, snapshot)?;
1302 pub fn next_ty_var_id(&self, diverging: bool, origin: TypeVariableOrigin) -> TyVid {
1303 self.inner.borrow_mut().type_variables().new_var(self.universe(), diverging, origin)
1306 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1307 self.tcx.mk_ty_var(self.next_ty_var_id(false, origin))
1310 pub fn next_ty_var_in_universe(
1312 origin: TypeVariableOrigin,
1313 universe: ty::UniverseIndex,
1315 let vid = self.inner.borrow_mut().type_variables().new_var(universe, false, origin);
1316 self.tcx.mk_ty_var(vid)
1319 pub fn next_diverging_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1320 self.tcx.mk_ty_var(self.next_ty_var_id(true, origin))
1323 pub fn next_const_var(
1326 origin: ConstVariableOrigin,
1327 ) -> &'tcx ty::Const<'tcx> {
1328 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1331 pub fn next_const_var_in_universe(
1334 origin: ConstVariableOrigin,
1335 universe: ty::UniverseIndex,
1336 ) -> &'tcx ty::Const<'tcx> {
1340 .const_unification_table()
1341 .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
1342 self.tcx.mk_const_var(vid, ty)
1345 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1346 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1348 val: ConstVariableValue::Unknown { universe: self.universe() },
1352 fn next_int_var_id(&self) -> IntVid {
1353 self.inner.borrow_mut().int_unification_table().new_key(None)
1356 pub fn next_int_var(&self) -> Ty<'tcx> {
1357 self.tcx.mk_int_var(self.next_int_var_id())
1360 fn next_float_var_id(&self) -> FloatVid {
1361 self.inner.borrow_mut().float_unification_table().new_key(None)
1364 pub fn next_float_var(&self) -> Ty<'tcx> {
1365 self.tcx.mk_float_var(self.next_float_var_id())
1368 /// Creates a fresh region variable with the next available index.
1369 /// The variable will be created in the maximum universe created
1370 /// thus far, allowing it to name any region created thus far.
1371 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1372 self.next_region_var_in_universe(origin, self.universe())
1375 /// Creates a fresh region variable with the next available index
1376 /// in the given universe; typically, you can use
1377 /// `next_region_var` and just use the maximal universe.
1378 pub fn next_region_var_in_universe(
1380 origin: RegionVariableOrigin,
1381 universe: ty::UniverseIndex,
1382 ) -> ty::Region<'tcx> {
1384 self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
1385 self.tcx.mk_region(ty::ReVar(region_var))
1388 /// Return the universe that the region `r` was created in. For
1389 /// most regions (e.g., `'static`, named regions from the user,
1390 /// etc) this is the root universe U0. For inference variables or
1391 /// placeholders, however, it will return the universe which which
1392 /// they are associated.
1393 fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
1394 self.inner.borrow_mut().unwrap_region_constraints().universe(r)
1397 /// Number of region variables created so far.
1398 pub fn num_region_vars(&self) -> usize {
1399 self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
1402 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1403 pub fn next_nll_region_var(&self, origin: NLLRegionVariableOrigin) -> ty::Region<'tcx> {
1404 self.next_region_var(RegionVariableOrigin::NLL(origin))
1407 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1408 pub fn next_nll_region_var_in_universe(
1410 origin: NLLRegionVariableOrigin,
1411 universe: ty::UniverseIndex,
1412 ) -> ty::Region<'tcx> {
1413 self.next_region_var_in_universe(RegionVariableOrigin::NLL(origin), universe)
1416 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
1418 GenericParamDefKind::Lifetime => {
1419 // Create a region inference variable for the given
1420 // region parameter definition.
1421 self.next_region_var(EarlyBoundRegion(span, param.name)).into()
1423 GenericParamDefKind::Type { .. } => {
1424 // Create a type inference variable for the given
1425 // type parameter definition. The substitutions are
1426 // for actual parameters that may be referred to by
1427 // the default of this type parameter, if it exists.
1428 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1429 // used in a path such as `Foo::<T, U>::new()` will
1430 // use an inference variable for `C` with `[T, U]`
1431 // as the substitutions for the default, `(T, U)`.
1432 let ty_var_id = self.inner.borrow_mut().type_variables().new_var(
1435 TypeVariableOrigin {
1436 kind: TypeVariableOriginKind::TypeParameterDefinition(
1444 self.tcx.mk_ty_var(ty_var_id).into()
1446 GenericParamDefKind::Const { .. } => {
1447 let origin = ConstVariableOrigin {
1448 kind: ConstVariableOriginKind::ConstParameterDefinition(param.name),
1452 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1454 val: ConstVariableValue::Unknown { universe: self.universe() },
1456 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1461 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1462 /// type/region parameter to a fresh inference variable.
1463 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1464 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1467 /// Returns `true` if errors have been reported since this infcx was
1468 /// created. This is sometimes used as a heuristic to skip
1469 /// reporting errors that often occur as a result of earlier
1470 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1471 /// inference variables, regionck errors).
1472 pub fn is_tainted_by_errors(&self) -> bool {
1474 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1475 tainted_by_errors_flag={})",
1476 self.tcx.sess.err_count(),
1477 self.err_count_on_creation,
1478 self.tainted_by_errors_flag.get()
1481 if self.tcx.sess.err_count() > self.err_count_on_creation {
1482 return true; // errors reported since this infcx was made
1484 self.tainted_by_errors_flag.get()
1487 /// Set the "tainted by errors" flag to true. We call this when we
1488 /// observe an error from a prior pass.
1489 pub fn set_tainted_by_errors(&self) {
1490 debug!("set_tainted_by_errors()");
1491 self.tainted_by_errors_flag.set(true)
1494 /// Process the region constraints and report any errors that
1495 /// result. After this, no more unification operations should be
1496 /// done -- or the compiler will panic -- but it is legal to use
1497 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1498 pub fn resolve_regions_and_report_errors(
1500 region_context: DefId,
1501 region_map: ®ion::ScopeTree,
1502 outlives_env: &OutlivesEnvironment<'tcx>,
1506 self.is_tainted_by_errors() || self.inner.borrow().region_obligations.is_empty(),
1507 "region_obligations not empty: {:#?}",
1508 self.inner.borrow().region_obligations
1510 let (var_infos, data) = self
1515 .expect("regions already resolved")
1516 .with_log(&mut inner.undo_log)
1517 .into_infos_and_data();
1519 let region_rels = &RegionRelations::new(
1523 outlives_env.free_region_map(),
1526 let (lexical_region_resolutions, errors) =
1527 lexical_region_resolve::resolve(region_rels, var_infos, data, mode);
1529 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1530 assert!(old_value.is_none());
1532 if !self.is_tainted_by_errors() {
1533 // As a heuristic, just skip reporting region errors
1534 // altogether if other errors have been reported while
1535 // this infcx was in use. This is totally hokey but
1536 // otherwise we have a hard time separating legit region
1537 // errors from silly ones.
1538 self.report_region_errors(region_map, &errors);
1542 /// Obtains (and clears) the current set of region
1543 /// constraints. The inference context is still usable: further
1544 /// unifications will simply add new constraints.
1546 /// This method is not meant to be used with normal lexical region
1547 /// resolution. Rather, it is used in the NLL mode as a kind of
1548 /// interim hack: basically we run normal type-check and generate
1549 /// region constraints as normal, but then we take them and
1550 /// translate them into the form that the NLL solver
1551 /// understands. See the NLL module for mode details.
1552 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1554 self.inner.borrow().region_obligations.is_empty(),
1555 "region_obligations not empty: {:#?}",
1556 self.inner.borrow().region_obligations
1559 self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data()
1562 /// Gives temporary access to the region constraint data.
1563 #[allow(non_camel_case_types)] // bug with impl trait
1564 pub fn with_region_constraints<R>(
1566 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1568 let mut inner = self.inner.borrow_mut();
1569 op(inner.unwrap_region_constraints().data())
1572 /// Takes ownership of the list of variable regions. This implies
1573 /// that all the region constraints have already been taken, and
1574 /// hence that `resolve_regions_and_report_errors` can never be
1575 /// called. This is used only during NLL processing to "hand off" ownership
1576 /// of the set of region variables into the NLL region context.
1577 pub fn take_region_var_origins(&self) -> VarInfos {
1578 let mut inner = self.inner.borrow_mut();
1579 let (var_infos, data) = inner
1582 .expect("regions already resolved")
1583 .with_log(&mut inner.undo_log)
1584 .into_infos_and_data();
1585 assert!(data.is_empty());
1589 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1590 self.resolve_vars_if_possible(&t).to_string()
1593 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1594 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1595 format!("({})", tstrs.join(", "))
1598 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1599 self.resolve_vars_if_possible(t).print_only_trait_path().to_string()
1602 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1603 /// universe index of `TyVar(vid)`.
1604 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1605 use self::type_variable::TypeVariableValue;
1607 match self.inner.borrow_mut().type_variables().probe(vid) {
1608 TypeVariableValue::Known { value } => Ok(value),
1609 TypeVariableValue::Unknown { universe } => Err(universe),
1613 /// Resolve any type variables found in `value` -- but only one
1614 /// level. So, if the variable `?X` is bound to some type
1615 /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
1616 /// itself be bound to a type).
1618 /// Useful when you only need to inspect the outermost level of
1619 /// the type and don't care about nested types (or perhaps you
1620 /// will be resolving them as well, e.g. in a loop).
1621 pub fn shallow_resolve<T>(&self, value: T) -> T
1623 T: TypeFoldable<'tcx>,
1625 value.fold_with(&mut ShallowResolver { infcx: self })
1628 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1629 self.inner.borrow_mut().type_variables().root_var(var)
1632 /// Where possible, replaces type/const variables in
1633 /// `value` with their final value. Note that region variables
1634 /// are unaffected. If a type/const variable has not been unified, it
1635 /// is left as is. This is an idempotent operation that does
1636 /// not affect inference state in any way and so you can do it
1638 pub fn resolve_vars_if_possible<T>(&self, value: &T) -> T
1640 T: TypeFoldable<'tcx>,
1642 if !value.needs_infer() {
1643 return value.clone(); // Avoid duplicated subst-folding.
1645 let mut r = resolve::OpportunisticVarResolver::new(self);
1646 value.fold_with(&mut r)
1649 /// Returns the first unresolved variable contained in `T`. In the
1650 /// process of visiting `T`, this will resolve (where possible)
1651 /// type variables in `T`, but it never constructs the final,
1652 /// resolved type, so it's more efficient than
1653 /// `resolve_vars_if_possible()`.
1654 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1656 T: TypeFoldable<'tcx>,
1658 let mut r = resolve::UnresolvedTypeFinder::new(self);
1659 value.visit_with(&mut r);
1663 pub fn probe_const_var(
1665 vid: ty::ConstVid<'tcx>,
1666 ) -> Result<&'tcx ty::Const<'tcx>, ty::UniverseIndex> {
1667 match self.inner.borrow_mut().const_unification_table().probe_value(vid).val {
1668 ConstVariableValue::Known { value } => Ok(value),
1669 ConstVariableValue::Unknown { universe } => Err(universe),
1673 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<'tcx, T> {
1675 * Attempts to resolve all type/region/const variables in
1676 * `value`. Region inference must have been run already (e.g.,
1677 * by calling `resolve_regions_and_report_errors`). If some
1678 * variable was never unified, an `Err` results.
1680 * This method is idempotent, but it not typically not invoked
1681 * except during the writeback phase.
1684 resolve::fully_resolve(self, value)
1687 // [Note-Type-error-reporting]
1688 // An invariant is that anytime the expected or actual type is Error (the special
1689 // error type, meaning that an error occurred when typechecking this expression),
1690 // this is a derived error. The error cascaded from another error (that was already
1691 // reported), so it's not useful to display it to the user.
1692 // The following methods implement this logic.
1693 // They check if either the actual or expected type is Error, and don't print the error
1694 // in this case. The typechecker should only ever report type errors involving mismatched
1695 // types using one of these methods, and should not call span_err directly for such
1698 pub fn type_error_struct_with_diag<M>(
1702 actual_ty: Ty<'tcx>,
1703 ) -> DiagnosticBuilder<'tcx>
1705 M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1707 let actual_ty = self.resolve_vars_if_possible(&actual_ty);
1708 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1710 // Don't report an error if actual type is `Error`.
1711 if actual_ty.references_error() {
1712 return self.tcx.sess.diagnostic().struct_dummy();
1715 mk_diag(self.ty_to_string(actual_ty))
1718 pub fn report_mismatched_types(
1720 cause: &ObligationCause<'tcx>,
1723 err: TypeError<'tcx>,
1724 ) -> DiagnosticBuilder<'tcx> {
1725 let trace = TypeTrace::types(cause, true, expected, actual);
1726 self.report_and_explain_type_error(trace, &err)
1729 pub fn replace_bound_vars_with_fresh_vars<T>(
1732 lbrct: LateBoundRegionConversionTime,
1733 value: &ty::Binder<T>,
1734 ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
1736 T: TypeFoldable<'tcx>,
1738 let fld_r = |br| self.next_region_var(LateBoundRegion(span, br, lbrct));
1740 self.next_ty_var(TypeVariableOrigin {
1741 kind: TypeVariableOriginKind::MiscVariable,
1745 let fld_c = |_, ty| {
1746 self.next_const_var(
1748 ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span },
1751 self.tcx.replace_bound_vars(value, fld_r, fld_t, fld_c)
1754 /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
1755 pub fn verify_generic_bound(
1757 origin: SubregionOrigin<'tcx>,
1758 kind: GenericKind<'tcx>,
1759 a: ty::Region<'tcx>,
1760 bound: VerifyBound<'tcx>,
1762 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1766 .unwrap_region_constraints()
1767 .verify_generic_bound(origin, kind, a, bound);
1770 /// Obtains the latest type of the given closure; this may be a
1771 /// closure in the current function, in which case its
1772 /// `ClosureKind` may not yet be known.
1773 pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
1774 let closure_kind_ty = closure_substs.as_closure().kind_ty();
1775 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1776 closure_kind_ty.to_opt_closure_kind()
1779 /// Clears the selection, evaluation, and projection caches. This is useful when
1780 /// repeatedly attempting to select an `Obligation` while changing only
1781 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1782 pub fn clear_caches(&self) {
1783 self.selection_cache.clear();
1784 self.evaluation_cache.clear();
1785 self.inner.borrow_mut().projection_cache().clear();
1788 fn universe(&self) -> ty::UniverseIndex {
1792 /// Creates and return a fresh universe that extends all previous
1793 /// universes. Updates `self.universe` to that new universe.
1794 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1795 let u = self.universe.get().next_universe();
1796 self.universe.set(u);
1800 /// Resolves and evaluates a constant.
1802 /// The constant can be located on a trait like `<A as B>::C`, in which case the given
1803 /// substitutions and environment are used to resolve the constant. Alternatively if the
1804 /// constant has generic parameters in scope the substitutions are used to evaluate the value of
1805 /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
1806 /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
1807 /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
1810 /// This handles inferences variables within both `param_env` and `substs` by
1811 /// performing the operation on their respective canonical forms.
1812 pub fn const_eval_resolve(
1814 param_env: ty::ParamEnv<'tcx>,
1816 substs: SubstsRef<'tcx>,
1817 promoted: Option<mir::Promoted>,
1819 ) -> ConstEvalResult<'tcx> {
1820 let mut original_values = OriginalQueryValues::default();
1821 let canonical = self.canonicalize_query(&(param_env, substs), &mut original_values);
1823 let (param_env, substs) = canonical.value;
1824 // The return value is the evaluated value which doesn't contain any reference to inference
1825 // variables, thus we don't need to substitute back the original values.
1826 self.tcx.const_eval_resolve(param_env, def_id, substs, promoted, span)
1829 /// If `typ` is a type variable of some kind, resolve it one level
1830 /// (but do not resolve types found in the result). If `typ` is
1831 /// not a type variable, just return it unmodified.
1832 // FIXME(eddyb) inline into `ShallowResolver::visit_ty`.
1833 fn shallow_resolve_ty(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1835 ty::Infer(ty::TyVar(v)) => {
1836 // Not entirely obvious: if `typ` is a type variable,
1837 // it can be resolved to an int/float variable, which
1838 // can then be recursively resolved, hence the
1839 // recursion. Note though that we prevent type
1840 // variables from unifying to other type variables
1841 // directly (though they may be embedded
1842 // structurally), and we prevent cycles in any case,
1843 // so this recursion should always be of very limited
1846 // Note: if these two lines are combined into one we get
1847 // dynamic borrow errors on `self.inner`.
1848 let known = self.inner.borrow_mut().type_variables().probe(v).known();
1849 known.map(|t| self.shallow_resolve_ty(t)).unwrap_or(typ)
1852 ty::Infer(ty::IntVar(v)) => self
1855 .int_unification_table()
1857 .map(|v| v.to_type(self.tcx))
1860 ty::Infer(ty::FloatVar(v)) => self
1863 .float_unification_table()
1865 .map(|v| v.to_type(self.tcx))
1872 /// `ty_or_const_infer_var_changed` is equivalent to one of these two:
1873 /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
1874 /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
1876 /// However, `ty_or_const_infer_var_changed` is more efficient. It's always
1877 /// inlined, despite being large, because it has only two call sites that
1878 /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
1879 /// inference variables), and it handles both `Ty` and `ty::Const` without
1880 /// having to resort to storing full `GenericArg`s in `stalled_on`.
1882 pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
1884 TyOrConstInferVar::Ty(v) => {
1885 use self::type_variable::TypeVariableValue;
1887 // If `inlined_probe` returns a `Known` value, it never equals
1888 // `ty::Infer(ty::TyVar(v))`.
1889 match self.inner.borrow_mut().type_variables().inlined_probe(v) {
1890 TypeVariableValue::Unknown { .. } => false,
1891 TypeVariableValue::Known { .. } => true,
1895 TyOrConstInferVar::TyInt(v) => {
1896 // If `inlined_probe_value` returns a value it's always a
1897 // `ty::Int(_)` or `ty::UInt(_)`, which never matches a
1899 self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_some()
1902 TyOrConstInferVar::TyFloat(v) => {
1903 // If `probe_value` returns a value it's always a
1904 // `ty::Float(_)`, which never matches a `ty::Infer(_)`.
1906 // Not `inlined_probe_value(v)` because this call site is colder.
1907 self.inner.borrow_mut().float_unification_table().probe_value(v).is_some()
1910 TyOrConstInferVar::Const(v) => {
1911 // If `probe_value` returns a `Known` value, it never equals
1912 // `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
1914 // Not `inlined_probe_value(v)` because this call site is colder.
1915 match self.inner.borrow_mut().const_unification_table.probe_value(v).val {
1916 ConstVariableValue::Unknown { .. } => false,
1917 ConstVariableValue::Known { .. } => true,
1924 /// Helper for `ty_or_const_infer_var_changed` (see comment on that), currently
1925 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
1926 #[derive(Copy, Clone, Debug)]
1927 pub enum TyOrConstInferVar<'tcx> {
1928 /// Equivalent to `ty::Infer(ty::TyVar(_))`.
1930 /// Equivalent to `ty::Infer(ty::IntVar(_))`.
1932 /// Equivalent to `ty::Infer(ty::FloatVar(_))`.
1935 /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
1936 Const(ConstVid<'tcx>),
1939 impl TyOrConstInferVar<'tcx> {
1940 /// Tries to extract an inference variable from a type or a constant, returns `None`
1941 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
1942 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1943 pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
1944 match arg.unpack() {
1945 GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
1946 GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
1947 GenericArgKind::Lifetime(_) => None,
1951 /// Tries to extract an inference variable from a type, returns `None`
1952 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
1953 pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
1955 ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
1956 ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
1957 ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
1962 /// Tries to extract an inference variable from a constant, returns `None`
1963 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1964 pub fn maybe_from_const(ct: &'tcx ty::Const<'tcx>) -> Option<Self> {
1966 ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
1972 struct ShallowResolver<'a, 'tcx> {
1973 infcx: &'a InferCtxt<'a, 'tcx>,
1976 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
1977 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1981 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1982 self.infcx.shallow_resolve_ty(ty)
1985 fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
1986 if let ty::Const { val: ty::ConstKind::Infer(InferConst::Var(vid)), .. } = ct {
1990 .const_unification_table()
2001 impl<'tcx> TypeTrace<'tcx> {
2002 pub fn span(&self) -> Span {
2007 cause: &ObligationCause<'tcx>,
2008 a_is_expected: bool,
2011 ) -> TypeTrace<'tcx> {
2012 TypeTrace { cause: cause.clone(), values: Types(ExpectedFound::new(a_is_expected, a, b)) }
2015 pub fn dummy(tcx: TyCtxt<'tcx>) -> TypeTrace<'tcx> {
2017 cause: ObligationCause::dummy(),
2018 values: Types(ExpectedFound { expected: tcx.types.err, found: tcx.types.err }),
2023 impl<'tcx> SubregionOrigin<'tcx> {
2024 pub fn span(&self) -> Span {
2026 Subtype(ref a) => a.span(),
2027 InfStackClosure(a) => a,
2028 InvokeClosure(a) => a,
2029 DerefPointer(a) => a,
2030 ClosureCapture(a, _) => a,
2032 RelateObjectBound(a) => a,
2033 RelateParamBound(a, _) => a,
2034 RelateRegionParamBound(a) => a,
2035 RelateDefaultParamBound(a, _) => a,
2037 ReborrowUpvar(a, _) => a,
2038 DataBorrowed(_, a) => a,
2039 ReferenceOutlivesReferent(_, a) => a,
2040 ParameterInScope(_, a) => a,
2041 ExprTypeIsNotInScope(_, a) => a,
2042 BindingTypeIsNotValidAtDecl(a) => a,
2049 SafeDestructor(a) => a,
2050 CompareImplMethodObligation { span, .. } => span,
2054 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
2056 F: FnOnce() -> Self,
2059 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
2060 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
2063 traits::ObligationCauseCode::CompareImplMethodObligation {
2067 } => SubregionOrigin::CompareImplMethodObligation {
2079 impl RegionVariableOrigin {
2080 pub fn span(&self) -> Span {
2082 MiscVariable(a) => a,
2083 PatternRegion(a) => a,
2084 AddrOfRegion(a) => a,
2087 EarlyBoundRegion(a, ..) => a,
2088 LateBoundRegion(a, ..) => a,
2089 BoundRegionInCoherence(_) => rustc_span::DUMMY_SP,
2090 UpvarRegion(_, a) => a,
2091 NLL(..) => bug!("NLL variable used with `span`"),
2096 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
2097 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2100 "RegionObligation(sub_region={:?}, sup_type={:?})",
2101 self.sub_region, self.sup_type