1 pub use self::freshen::TypeFreshener;
2 pub use self::lexical_region_resolve::RegionResolutionError;
3 pub use self::LateBoundRegionConversionTime::*;
4 pub use self::RegionVariableOrigin::*;
5 pub use self::SubregionOrigin::*;
6 pub use self::ValuePairs::*;
8 use self::opaque_types::OpaqueTypeStorage;
9 pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog};
11 use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
13 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
14 use rustc_data_structures::sync::Lrc;
15 use rustc_data_structures::undo_log::Rollback;
16 use rustc_data_structures::unify as ut;
17 use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed};
18 use rustc_hir::def_id::{DefId, LocalDefId};
19 use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues};
20 use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue};
21 use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
22 use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult};
23 use rustc_middle::traits::select;
24 use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind};
25 use rustc_middle::ty::error::{ExpectedFound, TypeError};
26 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
27 use rustc_middle::ty::relate::RelateResult;
28 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
29 use rustc_middle::ty::visit::TypeVisitable;
30 pub use rustc_middle::ty::IntVarValue;
31 use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
32 use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
33 use rustc_span::symbol::Symbol;
36 use std::cell::{Cell, Ref, RefCell};
39 use self::combine::CombineFields;
40 use self::free_regions::RegionRelations;
41 use self::lexical_region_resolve::LexicalRegionResolutions;
42 use self::outlives::env::OutlivesEnvironment;
43 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
44 use self::region_constraints::{
45 RegionConstraintCollector, RegionConstraintStorage, RegionSnapshot,
47 use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
53 pub mod error_reporting;
60 mod lexical_region_resolve;
66 pub mod region_constraints;
69 pub mod type_variable;
74 pub struct InferOk<'tcx, T> {
76 pub obligations: PredicateObligations<'tcx>,
78 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
80 pub type Bound<T> = Option<T>;
81 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
82 pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
84 pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
85 ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>,
88 /// This type contains all the things within `InferCtxt` that sit within a
89 /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
90 /// operations are hot enough that we want only one call to `borrow_mut` per
91 /// call to `start_snapshot` and `rollback_to`.
93 pub struct InferCtxtInner<'tcx> {
94 /// Cache for projections. This cache is snapshotted along with the infcx.
96 /// Public so that `traits::project` can use it.
97 pub projection_cache: traits::ProjectionCacheStorage<'tcx>,
99 /// We instantiate `UnificationTable` with `bounds<Ty>` because the types
100 /// that might instantiate a general type variable have an order,
101 /// represented by its upper and lower bounds.
102 type_variable_storage: type_variable::TypeVariableStorage<'tcx>,
104 /// Map from const parameter variable to the kind of const it represents.
105 const_unification_storage: ut::UnificationTableStorage<ty::ConstVid<'tcx>>,
107 /// Map from integral variable to the kind of integer it represents.
108 int_unification_storage: ut::UnificationTableStorage<ty::IntVid>,
110 /// Map from floating variable to the kind of float it represents.
111 float_unification_storage: ut::UnificationTableStorage<ty::FloatVid>,
113 /// Tracks the set of region variables and the constraints between them.
114 /// This is initially `Some(_)` but when
115 /// `resolve_regions_and_report_errors` is invoked, this gets set to `None`
116 /// -- further attempts to perform unification, etc., may fail if new
117 /// region constraints would've been added.
118 region_constraint_storage: Option<RegionConstraintStorage<'tcx>>,
120 /// A set of constraints that regionck must validate. Each
121 /// constraint has the form `T:'a`, meaning "some type `T` must
122 /// outlive the lifetime 'a". These constraints derive from
123 /// instantiated type parameters. So if you had a struct defined
125 /// ```ignore (illustrative)
126 /// struct Foo<T:'static> { ... }
128 /// then in some expression `let x = Foo { ... }` it will
129 /// instantiate the type parameter `T` with a fresh type `$0`. At
130 /// the same time, it will record a region obligation of
131 /// `$0:'static`. This will get checked later by regionck. (We
132 /// can't generally check these things right away because we have
133 /// to wait until types are resolved.)
135 /// These are stored in a map keyed to the id of the innermost
136 /// enclosing fn body / static initializer expression. This is
137 /// because the location where the obligation was incurred can be
138 /// relevant with respect to which sublifetime assumptions are in
139 /// place. The reason that we store under the fn-id, and not
140 /// something more fine-grained, is so that it is easier for
141 /// regionck to be sure that it has found *all* the region
142 /// obligations (otherwise, it's easy to fail to walk to a
143 /// particular node-id).
145 /// Before running `resolve_regions_and_report_errors`, the creator
146 /// of the inference context is expected to invoke
147 /// [`InferCtxt::process_registered_region_obligations`]
148 /// for each body-id in this map, which will process the
149 /// obligations within. This is expected to be done 'late enough'
150 /// that all type inference variables have been bound and so forth.
151 region_obligations: Vec<RegionObligation<'tcx>>,
153 undo_log: InferCtxtUndoLogs<'tcx>,
155 /// Caches for opaque type inference.
156 pub opaque_type_storage: OpaqueTypeStorage<'tcx>,
159 impl<'tcx> InferCtxtInner<'tcx> {
160 fn new() -> InferCtxtInner<'tcx> {
162 projection_cache: Default::default(),
163 type_variable_storage: type_variable::TypeVariableStorage::new(),
164 undo_log: InferCtxtUndoLogs::default(),
165 const_unification_storage: ut::UnificationTableStorage::new(),
166 int_unification_storage: ut::UnificationTableStorage::new(),
167 float_unification_storage: ut::UnificationTableStorage::new(),
168 region_constraint_storage: Some(RegionConstraintStorage::new()),
169 region_obligations: vec![],
170 opaque_type_storage: Default::default(),
175 pub fn region_obligations(&self) -> &[RegionObligation<'tcx>] {
176 &self.region_obligations
180 pub fn projection_cache(&mut self) -> traits::ProjectionCache<'_, 'tcx> {
181 self.projection_cache.with_log(&mut self.undo_log)
185 fn type_variables(&mut self) -> type_variable::TypeVariableTable<'_, 'tcx> {
186 self.type_variable_storage.with_log(&mut self.undo_log)
190 pub fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> {
191 self.opaque_type_storage.with_log(&mut self.undo_log)
195 fn int_unification_table(
197 ) -> ut::UnificationTable<
200 &mut ut::UnificationStorage<ty::IntVid>,
201 &mut InferCtxtUndoLogs<'tcx>,
204 self.int_unification_storage.with_log(&mut self.undo_log)
208 fn float_unification_table(
210 ) -> ut::UnificationTable<
213 &mut ut::UnificationStorage<ty::FloatVid>,
214 &mut InferCtxtUndoLogs<'tcx>,
217 self.float_unification_storage.with_log(&mut self.undo_log)
221 fn const_unification_table(
223 ) -> ut::UnificationTable<
226 &mut ut::UnificationStorage<ty::ConstVid<'tcx>>,
227 &mut InferCtxtUndoLogs<'tcx>,
230 self.const_unification_storage.with_log(&mut self.undo_log)
234 pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'_, 'tcx> {
235 self.region_constraint_storage
237 .expect("region constraints already solved")
238 .with_log(&mut self.undo_log)
242 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
243 pub enum DefiningAnchor {
244 /// `DefId` of the item.
246 /// When opaque types are not resolved, we `Bubble` up, meaning
247 /// return the opaque/hidden type pair from query, for caller of query to handle it.
249 /// Used to catch type mismatch errors when handling opaque types.
253 pub struct InferCtxt<'a, 'tcx> {
254 pub tcx: TyCtxt<'tcx>,
256 /// The `DefId` of the item in whose context we are performing inference or typeck.
257 /// It is used to check whether an opaque type use is a defining use.
259 /// If it is `DefiningAnchor::Bubble`, we can't resolve opaque types here and need to bubble up
260 /// the obligation. This frequently happens for
261 /// short lived InferCtxt within queries. The opaque type obligations are forwarded
262 /// to the outside until the end up in an `InferCtxt` for typeck or borrowck.
264 /// It is default value is `DefiningAnchor::Error`, this way it is easier to catch errors that
265 /// might come up during inference or typeck.
266 pub defining_use_anchor: DefiningAnchor,
268 /// Whether this inference context should care about region obligations in
269 /// the root universe. Most notably, this is used during hir typeck as region
270 /// solving is left to borrowck instead.
271 pub considering_regions: bool,
273 /// During type-checking/inference of a body, `in_progress_typeck_results`
274 /// contains a reference to the typeck results being built up, which are
275 /// used for reading closure kinds/signatures as they are inferred,
276 /// and for error reporting logic to read arbitrary node types.
277 pub in_progress_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
279 pub inner: RefCell<InferCtxtInner<'tcx>>,
281 /// If set, this flag causes us to skip the 'leak check' during
282 /// higher-ranked subtyping operations. This flag is a temporary one used
283 /// to manage the removal of the leak-check: for the time being, we still run the
284 /// leak-check, but we issue warnings. This flag can only be set to true
285 /// when entering a snapshot.
286 skip_leak_check: Cell<bool>,
288 /// Once region inference is done, the values for each variable.
289 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
291 /// Caches the results of trait selection. This cache is used
292 /// for things that have to do with the parameters in scope.
293 pub selection_cache: select::SelectionCache<'tcx>,
295 /// Caches the results of trait evaluation.
296 pub evaluation_cache: select::EvaluationCache<'tcx>,
298 /// the set of predicates on which errors have been reported, to
299 /// avoid reporting the same error twice.
300 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
302 pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
304 /// When an error occurs, we want to avoid reporting "derived"
305 /// errors that are due to this original failure. Normally, we
306 /// handle this with the `err_count_on_creation` count, which
307 /// basically just tracks how many errors were reported when we
308 /// started type-checking a fn and checks to see if any new errors
309 /// have been reported since then. Not great, but it works.
311 /// However, when errors originated in other passes -- notably
312 /// resolve -- this heuristic breaks down. Therefore, we have this
313 /// auxiliary flag that one can set whenever one creates a
314 /// type-error that is due to an error in a prior pass.
316 /// Don't read this flag directly, call `is_tainted_by_errors()`
317 /// and `set_tainted_by_errors()`.
318 tainted_by_errors_flag: Cell<bool>,
320 /// Track how many errors were reported when this infcx is created.
321 /// If the number of errors increases, that's also a sign (line
322 /// `tainted_by_errors`) to avoid reporting certain kinds of errors.
323 // FIXME(matthewjasper) Merge into `tainted_by_errors_flag`
324 err_count_on_creation: usize,
326 /// This flag is true while there is an active snapshot.
327 in_snapshot: Cell<bool>,
329 /// What is the innermost universe we have created? Starts out as
330 /// `UniverseIndex::root()` but grows from there as we enter
331 /// universal quantifiers.
333 /// N.B., at present, we exclude the universal quantifiers on the
334 /// item we are type-checking, and just consider those names as
335 /// part of the root universe. So this would only get incremented
336 /// when we enter into a higher-ranked (`for<..>`) type or trait
338 universe: Cell<ty::UniverseIndex>,
341 /// See the `error_reporting` module for more details.
342 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
343 pub enum ValuePairs<'tcx> {
344 Regions(ExpectedFound<ty::Region<'tcx>>),
345 Terms(ExpectedFound<ty::Term<'tcx>>),
346 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
347 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
350 impl<'tcx> ValuePairs<'tcx> {
351 pub fn ty(&self) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
352 if let ValuePairs::Terms(ExpectedFound {
353 expected: ty::Term::Ty(expected),
354 found: ty::Term::Ty(found),
357 Some((*expected, *found))
364 /// The trace designates the path through inference that we took to
365 /// encounter an error or subtyping constraint.
367 /// See the `error_reporting` module for more details.
368 #[derive(Clone, Debug)]
369 pub struct TypeTrace<'tcx> {
370 pub cause: ObligationCause<'tcx>,
371 pub values: ValuePairs<'tcx>,
374 /// The origin of a `r1 <= r2` constraint.
376 /// See `error_reporting` module for more details
377 #[derive(Clone, Debug)]
378 pub enum SubregionOrigin<'tcx> {
379 /// Arose from a subtyping relation
380 Subtype(Box<TypeTrace<'tcx>>),
382 /// When casting `&'a T` to an `&'b Trait` object,
383 /// relating `'a` to `'b`
384 RelateObjectBound(Span),
386 /// Some type parameter was instantiated with the given type,
387 /// and that type must outlive some region.
388 RelateParamBound(Span, Ty<'tcx>, Option<Span>),
390 /// The given region parameter was instantiated with a region
391 /// that must outlive some other region.
392 RelateRegionParamBound(Span),
394 /// Creating a pointer `b` to contents of another reference
397 /// Creating a pointer `b` to contents of an upvar
398 ReborrowUpvar(Span, ty::UpvarId),
400 /// Data with type `Ty<'tcx>` was borrowed
401 DataBorrowed(Ty<'tcx>, Span),
403 /// (&'a &'b T) where a >= b
404 ReferenceOutlivesReferent(Ty<'tcx>, Span),
406 /// Comparing the signature and requirements of an impl method against
407 /// the containing trait.
408 CompareImplItemObligation { span: Span, impl_item_def_id: LocalDefId, trait_item_def_id: DefId },
410 /// Checking that the bounds of a trait's associated type hold for a given impl
411 CheckAssociatedTypeBounds {
412 parent: Box<SubregionOrigin<'tcx>>,
413 impl_item_def_id: LocalDefId,
414 trait_item_def_id: DefId,
418 // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
419 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
420 static_assert_size!(SubregionOrigin<'_>, 32);
422 /// Times when we replace late-bound regions with variables:
423 #[derive(Clone, Copy, Debug)]
424 pub enum LateBoundRegionConversionTime {
425 /// when a fn is called
428 /// when two higher-ranked types are compared
431 /// when projecting an associated type
432 AssocTypeProjection(DefId),
435 /// Reasons to create a region inference variable
437 /// See `error_reporting` module for more details
438 #[derive(Copy, Clone, Debug)]
439 pub enum RegionVariableOrigin {
440 /// Region variables created for ill-categorized reasons,
441 /// mostly indicates places in need of refactoring
444 /// Regions created by a `&P` or `[...]` pattern
447 /// Regions created by `&` operator
450 /// Regions created as part of an autoref of a method receiver
453 /// Regions created as part of an automatic coercion
456 /// Region variables created as the values for early-bound regions
457 EarlyBoundRegion(Span, Symbol),
459 /// Region variables created for bound regions
460 /// in a function or method that is called
461 LateBoundRegion(Span, ty::BoundRegionKind, LateBoundRegionConversionTime),
463 UpvarRegion(ty::UpvarId, Span),
465 /// This origin is used for the inference variables that we create
466 /// during NLL region processing.
467 Nll(NllRegionVariableOrigin),
470 #[derive(Copy, Clone, Debug)]
471 pub enum NllRegionVariableOrigin {
472 /// During NLL region processing, we create variables for free
473 /// regions that we encounter in the function signature and
474 /// elsewhere. This origin indices we've got one of those.
477 /// "Universal" instantiation of a higher-ranked region (e.g.,
478 /// from a `for<'a> T` binder). Meant to represent "any region".
479 Placeholder(ty::PlaceholderRegion),
482 /// If this is true, then this variable was created to represent a lifetime
483 /// bound in a `for` binder. For example, it might have been created to
484 /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
485 /// Such variables are created when we are trying to figure out if there
486 /// is any valid instantiation of `'a` that could fit into some scenario.
488 /// This is used to inform error reporting: in the case that we are trying to
489 /// determine whether there is any valid instantiation of a `'a` variable that meets
490 /// some constraint C, we want to blame the "source" of that `for` type,
491 /// rather than blaming the source of the constraint C.
496 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
497 #[derive(Copy, Clone, Debug)]
498 pub enum FixupError<'tcx> {
499 UnresolvedIntTy(IntVid),
500 UnresolvedFloatTy(FloatVid),
502 UnresolvedConst(ConstVid<'tcx>),
505 /// See the `region_obligations` field for more information.
507 pub struct RegionObligation<'tcx> {
508 pub sub_region: ty::Region<'tcx>,
509 pub sup_type: Ty<'tcx>,
510 pub origin: SubregionOrigin<'tcx>,
513 impl<'tcx> fmt::Display for FixupError<'tcx> {
514 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
515 use self::FixupError::*;
518 UnresolvedIntTy(_) => write!(
520 "cannot determine the type of this integer; \
521 add a suffix to specify the type explicitly"
523 UnresolvedFloatTy(_) => write!(
525 "cannot determine the type of this number; \
526 add a suffix to specify the type explicitly"
528 UnresolvedTy(_) => write!(f, "unconstrained type"),
529 UnresolvedConst(_) => write!(f, "unconstrained const value"),
534 /// A temporary returned by `tcx.infer_ctxt()`. This is necessary
535 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
536 /// without using `Rc` or something similar.
537 pub struct InferCtxtBuilder<'tcx> {
539 defining_use_anchor: DefiningAnchor,
540 considering_regions: bool,
541 fresh_typeck_results: Option<RefCell<ty::TypeckResults<'tcx>>>,
544 pub trait TyCtxtInferExt<'tcx> {
545 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>;
548 impl<'tcx> TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
549 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
552 defining_use_anchor: DefiningAnchor::Error,
553 considering_regions: true,
554 fresh_typeck_results: None,
559 impl<'tcx> InferCtxtBuilder<'tcx> {
560 /// Used only by `rustc_typeck` during body type-checking/inference,
561 /// will initialize `in_progress_typeck_results` with fresh `TypeckResults`.
562 /// Will also change the scope for opaque type defining use checks to the given owner.
563 pub fn with_fresh_in_progress_typeck_results(mut self, table_owner: LocalDefId) -> Self {
564 self.fresh_typeck_results = Some(RefCell::new(ty::TypeckResults::new(table_owner)));
565 self.with_opaque_type_inference(DefiningAnchor::Bind(table_owner))
568 /// Whenever the `InferCtxt` should be able to handle defining uses of opaque types,
569 /// you need to call this function. Otherwise the opaque type will be treated opaquely.
571 /// It is only meant to be called in two places, for typeck
572 /// (via `with_fresh_in_progress_typeck_results`) and for the inference context used
574 pub fn with_opaque_type_inference(mut self, defining_use_anchor: DefiningAnchor) -> Self {
575 self.defining_use_anchor = defining_use_anchor;
579 pub fn ignoring_regions(mut self) -> Self {
580 self.considering_regions = false;
584 /// Given a canonical value `C` as a starting point, create an
585 /// inference context that contains each of the bound values
586 /// within instantiated as a fresh variable. The `f` closure is
587 /// invoked with the new infcx, along with the instantiated value
588 /// `V` and a substitution `S`. This substitution `S` maps from
589 /// the bound values in `C` to their instantiated values in `V`
590 /// (in other words, `S(C) = V`).
591 pub fn enter_with_canonical<T, R>(
594 canonical: &Canonical<'tcx, T>,
595 f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
598 T: TypeFoldable<'tcx>,
602 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
603 f(infcx, value, subst)
607 pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R {
608 let InferCtxtBuilder {
612 ref fresh_typeck_results,
614 let in_progress_typeck_results = fresh_typeck_results.as_ref();
619 in_progress_typeck_results,
620 inner: RefCell::new(InferCtxtInner::new()),
621 lexical_region_resolutions: RefCell::new(None),
622 selection_cache: Default::default(),
623 evaluation_cache: Default::default(),
624 reported_trait_errors: Default::default(),
625 reported_closure_mismatch: Default::default(),
626 tainted_by_errors_flag: Cell::new(false),
627 err_count_on_creation: tcx.sess.err_count(),
628 in_snapshot: Cell::new(false),
629 skip_leak_check: Cell::new(false),
630 universe: Cell::new(ty::UniverseIndex::ROOT),
635 impl<'tcx, T> InferOk<'tcx, T> {
636 pub fn unit(self) -> InferOk<'tcx, ()> {
637 InferOk { value: (), obligations: self.obligations }
640 /// Extracts `value`, registering any obligations into `fulfill_cx`.
641 pub fn into_value_registering_obligations(
643 infcx: &InferCtxt<'_, 'tcx>,
644 fulfill_cx: &mut dyn TraitEngine<'tcx>,
646 let InferOk { value, obligations } = self;
647 for obligation in obligations {
648 fulfill_cx.register_predicate_obligation(infcx, obligation);
654 impl<'tcx> InferOk<'tcx, ()> {
655 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
660 #[must_use = "once you start a snapshot, you should always consume it"]
661 pub struct CombinedSnapshot<'a, 'tcx> {
662 undo_snapshot: Snapshot<'tcx>,
663 region_constraints_snapshot: RegionSnapshot,
664 universe: ty::UniverseIndex,
665 was_in_snapshot: bool,
666 _in_progress_typeck_results: Option<Ref<'a, ty::TypeckResults<'tcx>>>,
669 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
670 /// calls `tcx.try_unify_abstract_consts` after
671 /// canonicalizing the consts.
672 #[instrument(skip(self), level = "debug")]
673 pub fn try_unify_abstract_consts(
675 a: ty::Unevaluated<'tcx, ()>,
676 b: ty::Unevaluated<'tcx, ()>,
677 param_env: ty::ParamEnv<'tcx>,
679 // Reject any attempt to unify two unevaluated constants that contain inference
680 // variables, since inference variables in queries lead to ICEs.
681 if a.substs.has_infer_types_or_consts()
682 || b.substs.has_infer_types_or_consts()
683 || param_env.has_infer_types_or_consts()
685 debug!("a or b or param_env contain infer vars in its substs -> cannot unify");
689 let param_env_and = param_env.and((a, b));
690 let erased = self.tcx.erase_regions(param_env_and);
691 debug!("after erase_regions: {:?}", erased);
693 self.tcx.try_unify_abstract_consts(erased)
696 pub fn is_in_snapshot(&self) -> bool {
697 self.in_snapshot.get()
700 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
701 t.fold_with(&mut self.freshener())
704 /// Returns the origin of the type variable identified by `vid`, or `None`
705 /// if this is not a type variable.
707 /// No attempt is made to resolve `ty`.
708 pub fn type_var_origin(&'a self, ty: Ty<'tcx>) -> Option<TypeVariableOrigin> {
710 ty::Infer(ty::TyVar(vid)) => {
711 Some(*self.inner.borrow_mut().type_variables().var_origin(vid))
717 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
718 freshen::TypeFreshener::new(self, false)
721 /// Like `freshener`, but does not replace `'static` regions.
722 pub fn freshener_keep_static<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
723 freshen::TypeFreshener::new(self, true)
726 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
727 let mut inner = self.inner.borrow_mut();
728 let mut vars: Vec<Ty<'_>> = inner
730 .unsolved_variables()
732 .map(|t| self.tcx.mk_ty_var(t))
735 (0..inner.int_unification_table().len())
736 .map(|i| ty::IntVid { index: i as u32 })
737 .filter(|&vid| inner.int_unification_table().probe_value(vid).is_none())
738 .map(|v| self.tcx.mk_int_var(v)),
741 (0..inner.float_unification_table().len())
742 .map(|i| ty::FloatVid { index: i as u32 })
743 .filter(|&vid| inner.float_unification_table().probe_value(vid).is_none())
744 .map(|v| self.tcx.mk_float_var(v)),
751 trace: TypeTrace<'tcx>,
752 param_env: ty::ParamEnv<'tcx>,
753 define_opaque_types: bool,
754 ) -> CombineFields<'a, 'tcx> {
760 obligations: PredicateObligations::new(),
765 /// Clear the "currently in a snapshot" flag, invoke the closure,
766 /// then restore the flag to its original value. This flag is a
767 /// debugging measure designed to detect cases where we start a
768 /// snapshot, create type variables, and register obligations
769 /// which may involve those type variables in the fulfillment cx,
770 /// potentially leaving "dangling type variables" behind.
771 /// In such cases, an assertion will fail when attempting to
772 /// register obligations, within a snapshot. Very useful, much
773 /// better than grovelling through megabytes of `RUSTC_LOG` output.
775 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
776 /// sometimes create a "mini-fulfilment-cx" in which we enroll
777 /// obligations. As long as this fulfillment cx is fully drained
778 /// before we return, this is not a problem, as there won't be any
779 /// escaping obligations in the main cx. In those cases, you can
780 /// use this function.
781 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
783 F: FnOnce(&Self) -> R,
785 let flag = self.in_snapshot.replace(false);
786 let result = func(self);
787 self.in_snapshot.set(flag);
791 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
792 debug!("start_snapshot()");
794 let in_snapshot = self.in_snapshot.replace(true);
796 let mut inner = self.inner.borrow_mut();
799 undo_snapshot: inner.undo_log.start_snapshot(),
800 region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
801 universe: self.universe(),
802 was_in_snapshot: in_snapshot,
803 // Borrow typeck results "in progress" (i.e., during typeck)
804 // to ban writes from within a snapshot to them.
805 _in_progress_typeck_results: self
806 .in_progress_typeck_results
807 .map(|typeck_results| typeck_results.borrow()),
811 #[instrument(skip(self, snapshot), level = "debug")]
812 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
813 let CombinedSnapshot {
815 region_constraints_snapshot,
818 _in_progress_typeck_results,
821 self.in_snapshot.set(was_in_snapshot);
822 self.universe.set(universe);
824 let mut inner = self.inner.borrow_mut();
825 inner.rollback_to(undo_snapshot);
826 inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
829 #[instrument(skip(self, snapshot), level = "debug")]
830 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
831 let CombinedSnapshot {
833 region_constraints_snapshot: _,
836 _in_progress_typeck_results,
839 self.in_snapshot.set(was_in_snapshot);
841 self.inner.borrow_mut().commit(undo_snapshot);
844 /// Executes `f` and commit the bindings.
845 #[instrument(skip(self, f), level = "debug")]
846 pub fn commit_unconditionally<R, F>(&self, f: F) -> R
848 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
850 let snapshot = self.start_snapshot();
851 let r = f(&snapshot);
852 self.commit_from(snapshot);
856 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
857 #[instrument(skip(self, f), level = "debug")]
858 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
860 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
862 let snapshot = self.start_snapshot();
863 let r = f(&snapshot);
864 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
867 self.commit_from(snapshot);
870 self.rollback_to("commit_if_ok -- error", snapshot);
876 /// Execute `f` then unroll any bindings it creates.
877 #[instrument(skip(self, f), level = "debug")]
878 pub fn probe<R, F>(&self, f: F) -> R
880 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
882 let snapshot = self.start_snapshot();
883 let r = f(&snapshot);
884 self.rollback_to("probe", snapshot);
888 /// If `should_skip` is true, then execute `f` then unroll any bindings it creates.
889 #[instrument(skip(self, f), level = "debug")]
890 pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R
892 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
894 let snapshot = self.start_snapshot();
895 let was_skip_leak_check = self.skip_leak_check.get();
897 self.skip_leak_check.set(true);
899 let r = f(&snapshot);
900 self.rollback_to("probe", snapshot);
901 self.skip_leak_check.set(was_skip_leak_check);
905 /// Scan the constraints produced since `snapshot` began and returns:
907 /// - `None` -- if none of them involve "region outlives" constraints
908 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
909 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
910 pub fn region_constraints_added_in_snapshot(
912 snapshot: &CombinedSnapshot<'a, 'tcx>,
916 .unwrap_region_constraints()
917 .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
920 pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'a, 'tcx>) -> bool {
921 self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot)
924 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
925 self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
928 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
930 T: at::ToTrace<'tcx>,
932 let origin = &ObligationCause::dummy();
934 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
935 // Ignore obligations, since we are unrolling
936 // everything anyway.
941 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
943 T: at::ToTrace<'tcx>,
945 let origin = &ObligationCause::dummy();
947 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
948 // Ignore obligations, since we are unrolling
949 // everything anyway.
954 #[instrument(skip(self), level = "debug")]
957 origin: SubregionOrigin<'tcx>,
961 self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
964 /// Require that the region `r` be equal to one of the regions in
965 /// the set `regions`.
966 #[instrument(skip(self), level = "debug")]
967 pub fn member_constraint(
969 opaque_type_def_id: LocalDefId,
970 definition_span: Span,
972 region: ty::Region<'tcx>,
973 in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
975 self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
984 /// Processes a `Coerce` predicate from the fulfillment context.
985 /// This is NOT the preferred way to handle coercion, which is to
986 /// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`).
988 /// This method here is actually a fallback that winds up being
989 /// invoked when `FnCtxt::coerce` encounters unresolved type variables
990 /// and records a coercion predicate. Presently, this method is equivalent
991 /// to `subtype_predicate` -- that is, "coercing" `a` to `b` winds up
992 /// actually requiring `a <: b`. This is of course a valid coercion,
993 /// but it's not as flexible as `FnCtxt::coerce` would be.
995 /// (We may refactor this in the future, but there are a number of
996 /// practical obstacles. Among other things, `FnCtxt::coerce` presently
997 /// records adjustments that are required on the HIR in order to perform
998 /// the coercion, and we don't currently have a way to manage that.)
999 pub fn coerce_predicate(
1001 cause: &ObligationCause<'tcx>,
1002 param_env: ty::ParamEnv<'tcx>,
1003 predicate: ty::PolyCoercePredicate<'tcx>,
1004 ) -> Option<InferResult<'tcx, ()>> {
1005 let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
1006 a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
1010 self.subtype_predicate(cause, param_env, subtype_predicate)
1013 pub fn subtype_predicate(
1015 cause: &ObligationCause<'tcx>,
1016 param_env: ty::ParamEnv<'tcx>,
1017 predicate: ty::PolySubtypePredicate<'tcx>,
1018 ) -> Option<InferResult<'tcx, ()>> {
1019 // Check for two unresolved inference variables, in which case we can
1020 // make no progress. This is partly a micro-optimization, but it's
1021 // also an opportunity to "sub-unify" the variables. This isn't
1022 // *necessary* to prevent cycles, because they would eventually be sub-unified
1023 // anyhow during generalization, but it helps with diagnostics (we can detect
1024 // earlier that they are sub-unified).
1026 // Note that we can just skip the binders here because
1027 // type variables can't (at present, at
1028 // least) capture any of the things bound by this binder.
1030 // Note that this sub here is not just for diagnostics - it has semantic
1032 let r_a = self.shallow_resolve(predicate.skip_binder().a);
1033 let r_b = self.shallow_resolve(predicate.skip_binder().b);
1034 match (r_a.kind(), r_b.kind()) {
1035 (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
1036 self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
1042 Some(self.commit_if_ok(|_snapshot| {
1043 let ty::SubtypePredicate { a_is_expected, a, b } =
1044 self.replace_bound_vars_with_placeholders(predicate);
1046 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
1052 pub fn region_outlives_predicate(
1054 cause: &traits::ObligationCause<'tcx>,
1055 predicate: ty::PolyRegionOutlivesPredicate<'tcx>,
1057 let ty::OutlivesPredicate(r_a, r_b) = self.replace_bound_vars_with_placeholders(predicate);
1059 SubregionOrigin::from_obligation_cause(cause, || RelateRegionParamBound(cause.span));
1060 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1063 /// Number of type variables created so far.
1064 pub fn num_ty_vars(&self) -> usize {
1065 self.inner.borrow_mut().type_variables().num_vars()
1068 pub fn next_ty_var_id(&self, origin: TypeVariableOrigin) -> TyVid {
1069 self.inner.borrow_mut().type_variables().new_var(self.universe(), origin)
1072 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1073 self.tcx.mk_ty_var(self.next_ty_var_id(origin))
1076 pub fn next_ty_var_id_in_universe(
1078 origin: TypeVariableOrigin,
1079 universe: ty::UniverseIndex,
1081 self.inner.borrow_mut().type_variables().new_var(universe, origin)
1084 pub fn next_ty_var_in_universe(
1086 origin: TypeVariableOrigin,
1087 universe: ty::UniverseIndex,
1089 let vid = self.next_ty_var_id_in_universe(origin, universe);
1090 self.tcx.mk_ty_var(vid)
1093 pub fn next_const_var(&self, ty: Ty<'tcx>, origin: ConstVariableOrigin) -> ty::Const<'tcx> {
1094 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1097 pub fn next_const_var_in_universe(
1100 origin: ConstVariableOrigin,
1101 universe: ty::UniverseIndex,
1102 ) -> ty::Const<'tcx> {
1106 .const_unification_table()
1107 .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
1108 self.tcx.mk_const_var(vid, ty)
1111 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1112 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1114 val: ConstVariableValue::Unknown { universe: self.universe() },
1118 fn next_int_var_id(&self) -> IntVid {
1119 self.inner.borrow_mut().int_unification_table().new_key(None)
1122 pub fn next_int_var(&self) -> Ty<'tcx> {
1123 self.tcx.mk_int_var(self.next_int_var_id())
1126 fn next_float_var_id(&self) -> FloatVid {
1127 self.inner.borrow_mut().float_unification_table().new_key(None)
1130 pub fn next_float_var(&self) -> Ty<'tcx> {
1131 self.tcx.mk_float_var(self.next_float_var_id())
1134 /// Creates a fresh region variable with the next available index.
1135 /// The variable will be created in the maximum universe created
1136 /// thus far, allowing it to name any region created thus far.
1137 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1138 self.next_region_var_in_universe(origin, self.universe())
1141 /// Creates a fresh region variable with the next available index
1142 /// in the given universe; typically, you can use
1143 /// `next_region_var` and just use the maximal universe.
1144 pub fn next_region_var_in_universe(
1146 origin: RegionVariableOrigin,
1147 universe: ty::UniverseIndex,
1148 ) -> ty::Region<'tcx> {
1150 self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
1151 self.tcx.mk_region(ty::ReVar(region_var))
1154 /// Return the universe that the region `r` was created in. For
1155 /// most regions (e.g., `'static`, named regions from the user,
1156 /// etc) this is the root universe U0. For inference variables or
1157 /// placeholders, however, it will return the universe which which
1158 /// they are associated.
1159 pub fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
1160 self.inner.borrow_mut().unwrap_region_constraints().universe(r)
1163 /// Number of region variables created so far.
1164 pub fn num_region_vars(&self) -> usize {
1165 self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
1168 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1169 pub fn next_nll_region_var(&self, origin: NllRegionVariableOrigin) -> ty::Region<'tcx> {
1170 self.next_region_var(RegionVariableOrigin::Nll(origin))
1173 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1174 pub fn next_nll_region_var_in_universe(
1176 origin: NllRegionVariableOrigin,
1177 universe: ty::UniverseIndex,
1178 ) -> ty::Region<'tcx> {
1179 self.next_region_var_in_universe(RegionVariableOrigin::Nll(origin), universe)
1182 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
1184 GenericParamDefKind::Lifetime => {
1185 // Create a region inference variable for the given
1186 // region parameter definition.
1187 self.next_region_var(EarlyBoundRegion(span, param.name)).into()
1189 GenericParamDefKind::Type { .. } => {
1190 // Create a type inference variable for the given
1191 // type parameter definition. The substitutions are
1192 // for actual parameters that may be referred to by
1193 // the default of this type parameter, if it exists.
1194 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1195 // used in a path such as `Foo::<T, U>::new()` will
1196 // use an inference variable for `C` with `[T, U]`
1197 // as the substitutions for the default, `(T, U)`.
1198 let ty_var_id = self.inner.borrow_mut().type_variables().new_var(
1200 TypeVariableOrigin {
1201 kind: TypeVariableOriginKind::TypeParameterDefinition(
1209 self.tcx.mk_ty_var(ty_var_id).into()
1211 GenericParamDefKind::Const { .. } => {
1212 let origin = ConstVariableOrigin {
1213 kind: ConstVariableOriginKind::ConstParameterDefinition(
1220 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1222 val: ConstVariableValue::Unknown { universe: self.universe() },
1224 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1229 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1230 /// type/region parameter to a fresh inference variable.
1231 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1232 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1235 /// Returns `true` if errors have been reported since this infcx was
1236 /// created. This is sometimes used as a heuristic to skip
1237 /// reporting errors that often occur as a result of earlier
1238 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1239 /// inference variables, regionck errors).
1240 pub fn is_tainted_by_errors(&self) -> bool {
1242 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1243 tainted_by_errors_flag={})",
1244 self.tcx.sess.err_count(),
1245 self.err_count_on_creation,
1246 self.tainted_by_errors_flag.get()
1249 if self.tcx.sess.err_count() > self.err_count_on_creation {
1250 return true; // errors reported since this infcx was made
1252 self.tainted_by_errors_flag.get()
1255 /// Set the "tainted by errors" flag to true. We call this when we
1256 /// observe an error from a prior pass.
1257 pub fn set_tainted_by_errors(&self) {
1258 debug!("set_tainted_by_errors()");
1259 self.tainted_by_errors_flag.set(true)
1262 pub fn skip_region_resolution(&self) {
1263 let (var_infos, _) = {
1264 let mut inner = self.inner.borrow_mut();
1265 let inner = &mut *inner;
1266 // Note: `inner.region_obligations` may not be empty, because we
1267 // didn't necessarily call `process_registered_region_obligations`.
1268 // This is okay, because that doesn't introduce new vars.
1270 .region_constraint_storage
1272 .expect("regions already resolved")
1273 .with_log(&mut inner.undo_log)
1274 .into_infos_and_data()
1277 let lexical_region_resolutions = LexicalRegionResolutions {
1278 values: rustc_index::vec::IndexVec::from_elem_n(
1279 crate::infer::lexical_region_resolve::VarValue::Value(self.tcx.lifetimes.re_erased),
1284 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1285 assert!(old_value.is_none());
1288 /// Process the region constraints and return any any errors that
1289 /// result. After this, no more unification operations should be
1290 /// done -- or the compiler will panic -- but it is legal to use
1291 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1292 pub fn resolve_regions(
1294 outlives_env: &OutlivesEnvironment<'tcx>,
1295 ) -> Vec<RegionResolutionError<'tcx>> {
1296 let (var_infos, data) = {
1297 let mut inner = self.inner.borrow_mut();
1298 let inner = &mut *inner;
1300 self.is_tainted_by_errors() || inner.region_obligations.is_empty(),
1301 "region_obligations not empty: {:#?}",
1302 inner.region_obligations
1305 .region_constraint_storage
1307 .expect("regions already resolved")
1308 .with_log(&mut inner.undo_log)
1309 .into_infos_and_data()
1312 let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map());
1314 let (lexical_region_resolutions, errors) =
1315 lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data);
1317 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1318 assert!(old_value.is_none());
1323 /// Process the region constraints and report any errors that
1324 /// result. After this, no more unification operations should be
1325 /// done -- or the compiler will panic -- but it is legal to use
1326 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1327 pub fn resolve_regions_and_report_errors(
1329 generic_param_scope: LocalDefId,
1330 outlives_env: &OutlivesEnvironment<'tcx>,
1332 let errors = self.resolve_regions(outlives_env);
1334 if !self.is_tainted_by_errors() {
1335 // As a heuristic, just skip reporting region errors
1336 // altogether if other errors have been reported while
1337 // this infcx was in use. This is totally hokey but
1338 // otherwise we have a hard time separating legit region
1339 // errors from silly ones.
1340 self.report_region_errors(generic_param_scope, &errors);
1344 /// Obtains (and clears) the current set of region
1345 /// constraints. The inference context is still usable: further
1346 /// unifications will simply add new constraints.
1348 /// This method is not meant to be used with normal lexical region
1349 /// resolution. Rather, it is used in the NLL mode as a kind of
1350 /// interim hack: basically we run normal type-check and generate
1351 /// region constraints as normal, but then we take them and
1352 /// translate them into the form that the NLL solver
1353 /// understands. See the NLL module for mode details.
1354 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1356 self.inner.borrow().region_obligations.is_empty(),
1357 "region_obligations not empty: {:#?}",
1358 self.inner.borrow().region_obligations
1361 self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data()
1364 /// Gives temporary access to the region constraint data.
1365 pub fn with_region_constraints<R>(
1367 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1369 let mut inner = self.inner.borrow_mut();
1370 op(inner.unwrap_region_constraints().data())
1373 pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin {
1374 let mut inner = self.inner.borrow_mut();
1375 let inner = &mut *inner;
1377 .region_constraint_storage
1379 .expect("regions already resolved")
1380 .with_log(&mut inner.undo_log)
1384 /// Takes ownership of the list of variable regions. This implies
1385 /// that all the region constraints have already been taken, and
1386 /// hence that `resolve_regions_and_report_errors` can never be
1387 /// called. This is used only during NLL processing to "hand off" ownership
1388 /// of the set of region variables into the NLL region context.
1389 pub fn take_region_var_origins(&self) -> VarInfos {
1390 let mut inner = self.inner.borrow_mut();
1391 let (var_infos, data) = inner
1392 .region_constraint_storage
1394 .expect("regions already resolved")
1395 .with_log(&mut inner.undo_log)
1396 .into_infos_and_data();
1397 assert!(data.is_empty());
1401 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1402 self.resolve_vars_if_possible(t).to_string()
1405 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1406 /// universe index of `TyVar(vid)`.
1407 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1408 use self::type_variable::TypeVariableValue;
1410 match self.inner.borrow_mut().type_variables().probe(vid) {
1411 TypeVariableValue::Known { value } => Ok(value),
1412 TypeVariableValue::Unknown { universe } => Err(universe),
1416 /// Resolve any type variables found in `value` -- but only one
1417 /// level. So, if the variable `?X` is bound to some type
1418 /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
1419 /// itself be bound to a type).
1421 /// Useful when you only need to inspect the outermost level of
1422 /// the type and don't care about nested types (or perhaps you
1423 /// will be resolving them as well, e.g. in a loop).
1424 pub fn shallow_resolve<T>(&self, value: T) -> T
1426 T: TypeFoldable<'tcx>,
1428 value.fold_with(&mut ShallowResolver { infcx: self })
1431 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1432 self.inner.borrow_mut().type_variables().root_var(var)
1435 /// Where possible, replaces type/const variables in
1436 /// `value` with their final value. Note that region variables
1437 /// are unaffected. If a type/const variable has not been unified, it
1438 /// is left as is. This is an idempotent operation that does
1439 /// not affect inference state in any way and so you can do it
1441 pub fn resolve_vars_if_possible<T>(&self, value: T) -> T
1443 T: TypeFoldable<'tcx>,
1445 if !value.needs_infer() {
1446 return value; // Avoid duplicated subst-folding.
1448 let mut r = resolve::OpportunisticVarResolver::new(self);
1449 value.fold_with(&mut r)
1452 pub fn resolve_numeric_literals_with_default<T>(&self, value: T) -> T
1454 T: TypeFoldable<'tcx>,
1456 if !value.needs_infer() {
1457 return value; // Avoid duplicated subst-folding.
1459 let mut r = InferenceLiteralEraser { tcx: self.tcx };
1460 value.fold_with(&mut r)
1463 /// Returns the first unresolved variable contained in `T`. In the
1464 /// process of visiting `T`, this will resolve (where possible)
1465 /// type variables in `T`, but it never constructs the final,
1466 /// resolved type, so it's more efficient than
1467 /// `resolve_vars_if_possible()`.
1468 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1470 T: TypeVisitable<'tcx>,
1472 value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value()
1475 pub fn probe_const_var(
1477 vid: ty::ConstVid<'tcx>,
1478 ) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
1479 match self.inner.borrow_mut().const_unification_table().probe_value(vid).val {
1480 ConstVariableValue::Known { value } => Ok(value),
1481 ConstVariableValue::Unknown { universe } => Err(universe),
1485 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: T) -> FixupResult<'tcx, T> {
1487 * Attempts to resolve all type/region/const variables in
1488 * `value`. Region inference must have been run already (e.g.,
1489 * by calling `resolve_regions_and_report_errors`). If some
1490 * variable was never unified, an `Err` results.
1492 * This method is idempotent, but it not typically not invoked
1493 * except during the writeback phase.
1496 resolve::fully_resolve(self, value)
1499 // [Note-Type-error-reporting]
1500 // An invariant is that anytime the expected or actual type is Error (the special
1501 // error type, meaning that an error occurred when typechecking this expression),
1502 // this is a derived error. The error cascaded from another error (that was already
1503 // reported), so it's not useful to display it to the user.
1504 // The following methods implement this logic.
1505 // They check if either the actual or expected type is Error, and don't print the error
1506 // in this case. The typechecker should only ever report type errors involving mismatched
1507 // types using one of these methods, and should not call span_err directly for such
1510 pub fn type_error_struct_with_diag<M>(
1514 actual_ty: Ty<'tcx>,
1515 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>
1517 M: FnOnce(String) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
1519 let actual_ty = self.resolve_vars_if_possible(actual_ty);
1520 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1522 let mut err = mk_diag(self.ty_to_string(actual_ty));
1524 // Don't report an error if actual type is `Error`.
1525 if actual_ty.references_error() {
1526 err.downgrade_to_delayed_bug();
1532 pub fn report_mismatched_types(
1534 cause: &ObligationCause<'tcx>,
1537 err: TypeError<'tcx>,
1538 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1539 let trace = TypeTrace::types(cause, true, expected, actual);
1540 self.report_and_explain_type_error(trace, &err)
1543 pub fn report_mismatched_consts(
1545 cause: &ObligationCause<'tcx>,
1546 expected: ty::Const<'tcx>,
1547 actual: ty::Const<'tcx>,
1548 err: TypeError<'tcx>,
1549 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1550 let trace = TypeTrace::consts(cause, true, expected, actual);
1551 self.report_and_explain_type_error(trace, &err)
1554 pub fn replace_bound_vars_with_fresh_vars<T>(
1557 lbrct: LateBoundRegionConversionTime,
1558 value: ty::Binder<'tcx, T>,
1561 T: TypeFoldable<'tcx> + Copy,
1563 if let Some(inner) = value.no_bound_vars() {
1567 let mut region_map = FxHashMap::default();
1568 let fld_r = |br: ty::BoundRegion| {
1571 .or_insert_with(|| self.next_region_var(LateBoundRegion(span, br.kind, lbrct)))
1574 let mut ty_map = FxHashMap::default();
1575 let fld_t = |bt: ty::BoundTy| {
1576 *ty_map.entry(bt).or_insert_with(|| {
1577 self.next_ty_var(TypeVariableOrigin {
1578 kind: TypeVariableOriginKind::MiscVariable,
1583 let mut ct_map = FxHashMap::default();
1584 let fld_c = |bc: ty::BoundVar, ty| {
1585 *ct_map.entry(bc).or_insert_with(|| {
1586 self.next_const_var(
1588 ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span },
1592 self.tcx.replace_bound_vars_uncached(value, fld_r, fld_t, fld_c)
1595 /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
1596 pub fn verify_generic_bound(
1598 origin: SubregionOrigin<'tcx>,
1599 kind: GenericKind<'tcx>,
1600 a: ty::Region<'tcx>,
1601 bound: VerifyBound<'tcx>,
1603 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1607 .unwrap_region_constraints()
1608 .verify_generic_bound(origin, kind, a, bound);
1611 /// Obtains the latest type of the given closure; this may be a
1612 /// closure in the current function, in which case its
1613 /// `ClosureKind` may not yet be known.
1614 pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
1615 let closure_kind_ty = closure_substs.as_closure().kind_ty();
1616 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1617 closure_kind_ty.to_opt_closure_kind()
1620 /// Clears the selection, evaluation, and projection caches. This is useful when
1621 /// repeatedly attempting to select an `Obligation` while changing only
1622 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1623 pub fn clear_caches(&self) {
1624 self.selection_cache.clear();
1625 self.evaluation_cache.clear();
1626 self.inner.borrow_mut().projection_cache().clear();
1629 pub fn universe(&self) -> ty::UniverseIndex {
1633 /// Creates and return a fresh universe that extends all previous
1634 /// universes. Updates `self.universe` to that new universe.
1635 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1636 let u = self.universe.get().next_universe();
1637 self.universe.set(u);
1641 pub fn try_const_eval_resolve(
1643 param_env: ty::ParamEnv<'tcx>,
1644 unevaluated: ty::Unevaluated<'tcx>,
1647 ) -> Result<ty::Const<'tcx>, ErrorHandled> {
1648 match self.const_eval_resolve(param_env, unevaluated, span) {
1649 Ok(Some(val)) => Ok(ty::Const::from_value(self.tcx, val, ty)),
1652 let def_id = unevaluated.def.did;
1654 tcx.def_span(def_id),
1655 "unable to construct a constant value for the unevaluated constant {:?}",
1659 Err(err) => Err(err),
1663 /// Resolves and evaluates a constant.
1665 /// The constant can be located on a trait like `<A as B>::C`, in which case the given
1666 /// substitutions and environment are used to resolve the constant. Alternatively if the
1667 /// constant has generic parameters in scope the substitutions are used to evaluate the value of
1668 /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
1669 /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
1670 /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
1673 /// This handles inferences variables within both `param_env` and `substs` by
1674 /// performing the operation on their respective canonical forms.
1675 #[instrument(skip(self), level = "debug")]
1676 pub fn const_eval_resolve(
1678 mut param_env: ty::ParamEnv<'tcx>,
1679 unevaluated: ty::Unevaluated<'tcx>,
1681 ) -> EvalToValTreeResult<'tcx> {
1682 let mut substs = self.resolve_vars_if_possible(unevaluated.substs);
1685 // Postpone the evaluation of constants whose substs depend on inference
1687 if substs.has_infer_types_or_consts() {
1688 let ac = AbstractConst::new(self.tcx, unevaluated.shrink());
1691 substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
1692 param_env = self.tcx.param_env(unevaluated.def.did);
1695 if ct.unify_failure_kind(self.tcx) == FailureKind::Concrete {
1696 substs = replace_param_and_infer_substs_with_placeholder(self.tcx, substs);
1698 return Err(ErrorHandled::TooGeneric);
1701 Err(guar) => return Err(ErrorHandled::Reported(guar)),
1705 let param_env_erased = self.tcx.erase_regions(param_env);
1706 let substs_erased = self.tcx.erase_regions(substs);
1707 debug!(?param_env_erased);
1708 debug!(?substs_erased);
1710 let unevaluated = ty::Unevaluated {
1711 def: unevaluated.def,
1712 substs: substs_erased,
1713 promoted: unevaluated.promoted,
1716 // The return value is the evaluated value which doesn't contain any reference to inference
1717 // variables, thus we don't need to substitute back the original values.
1718 self.tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
1721 /// `ty_or_const_infer_var_changed` is equivalent to one of these two:
1722 /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
1723 /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
1725 /// However, `ty_or_const_infer_var_changed` is more efficient. It's always
1726 /// inlined, despite being large, because it has only two call sites that
1727 /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
1728 /// inference variables), and it handles both `Ty` and `ty::Const` without
1729 /// having to resort to storing full `GenericArg`s in `stalled_on`.
1731 pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
1733 TyOrConstInferVar::Ty(v) => {
1734 use self::type_variable::TypeVariableValue;
1736 // If `inlined_probe` returns a `Known` value, it never equals
1737 // `ty::Infer(ty::TyVar(v))`.
1738 match self.inner.borrow_mut().type_variables().inlined_probe(v) {
1739 TypeVariableValue::Unknown { .. } => false,
1740 TypeVariableValue::Known { .. } => true,
1744 TyOrConstInferVar::TyInt(v) => {
1745 // If `inlined_probe_value` returns a value it's always a
1746 // `ty::Int(_)` or `ty::UInt(_)`, which never matches a
1748 self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_some()
1751 TyOrConstInferVar::TyFloat(v) => {
1752 // If `probe_value` returns a value it's always a
1753 // `ty::Float(_)`, which never matches a `ty::Infer(_)`.
1755 // Not `inlined_probe_value(v)` because this call site is colder.
1756 self.inner.borrow_mut().float_unification_table().probe_value(v).is_some()
1759 TyOrConstInferVar::Const(v) => {
1760 // If `probe_value` returns a `Known` value, it never equals
1761 // `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
1763 // Not `inlined_probe_value(v)` because this call site is colder.
1764 match self.inner.borrow_mut().const_unification_table().probe_value(v).val {
1765 ConstVariableValue::Unknown { .. } => false,
1766 ConstVariableValue::Known { .. } => true,
1773 /// Helper for `ty_or_const_infer_var_changed` (see comment on that), currently
1774 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
1775 #[derive(Copy, Clone, Debug)]
1776 pub enum TyOrConstInferVar<'tcx> {
1777 /// Equivalent to `ty::Infer(ty::TyVar(_))`.
1779 /// Equivalent to `ty::Infer(ty::IntVar(_))`.
1781 /// Equivalent to `ty::Infer(ty::FloatVar(_))`.
1784 /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
1785 Const(ConstVid<'tcx>),
1788 impl<'tcx> TyOrConstInferVar<'tcx> {
1789 /// Tries to extract an inference variable from a type or a constant, returns `None`
1790 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
1791 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1792 pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
1793 match arg.unpack() {
1794 GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
1795 GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
1796 GenericArgKind::Lifetime(_) => None,
1800 /// Tries to extract an inference variable from a type, returns `None`
1801 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
1802 pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
1804 ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
1805 ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
1806 ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
1811 /// Tries to extract an inference variable from a constant, returns `None`
1812 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1813 pub fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
1815 ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
1821 /// Replace `{integer}` with `i32` and `{float}` with `f64`.
1822 /// Used only for diagnostics.
1823 struct InferenceLiteralEraser<'tcx> {
1827 impl<'tcx> TypeFolder<'tcx> for InferenceLiteralEraser<'tcx> {
1828 fn tcx(&self) -> TyCtxt<'tcx> {
1832 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1834 ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32,
1835 ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64,
1836 _ => ty.super_fold_with(self),
1841 struct ShallowResolver<'a, 'tcx> {
1842 infcx: &'a InferCtxt<'a, 'tcx>,
1845 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
1846 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1850 /// If `ty` is a type variable of some kind, resolve it one level
1851 /// (but do not resolve types found in the result). If `typ` is
1852 /// not a type variable, just return it unmodified.
1853 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1855 ty::Infer(ty::TyVar(v)) => {
1856 // Not entirely obvious: if `typ` is a type variable,
1857 // it can be resolved to an int/float variable, which
1858 // can then be recursively resolved, hence the
1859 // recursion. Note though that we prevent type
1860 // variables from unifying to other type variables
1861 // directly (though they may be embedded
1862 // structurally), and we prevent cycles in any case,
1863 // so this recursion should always be of very limited
1866 // Note: if these two lines are combined into one we get
1867 // dynamic borrow errors on `self.inner`.
1868 let known = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
1869 known.map_or(ty, |t| self.fold_ty(t))
1872 ty::Infer(ty::IntVar(v)) => self
1876 .int_unification_table()
1878 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1880 ty::Infer(ty::FloatVar(v)) => self
1884 .float_unification_table()
1886 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1892 fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
1893 if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() {
1897 .const_unification_table()
1908 impl<'tcx> TypeTrace<'tcx> {
1909 pub fn span(&self) -> Span {
1914 cause: &ObligationCause<'tcx>,
1915 a_is_expected: bool,
1918 ) -> TypeTrace<'tcx> {
1920 cause: cause.clone(),
1921 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1926 cause: &ObligationCause<'tcx>,
1927 a_is_expected: bool,
1930 ) -> TypeTrace<'tcx> {
1932 cause: cause.clone(),
1933 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1938 impl<'tcx> SubregionOrigin<'tcx> {
1939 pub fn span(&self) -> Span {
1941 Subtype(ref a) => a.span(),
1942 RelateObjectBound(a) => a,
1943 RelateParamBound(a, ..) => a,
1944 RelateRegionParamBound(a) => a,
1946 ReborrowUpvar(a, _) => a,
1947 DataBorrowed(_, a) => a,
1948 ReferenceOutlivesReferent(_, a) => a,
1949 CompareImplItemObligation { span, .. } => span,
1950 CheckAssociatedTypeBounds { ref parent, .. } => parent.span(),
1954 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
1956 F: FnOnce() -> Self,
1958 match *cause.code() {
1959 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
1960 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
1963 traits::ObligationCauseCode::CompareImplItemObligation {
1967 } => SubregionOrigin::CompareImplItemObligation {
1973 traits::ObligationCauseCode::CheckAssociatedTypeBounds {
1976 } => SubregionOrigin::CheckAssociatedTypeBounds {
1979 parent: Box::new(default()),
1987 impl RegionVariableOrigin {
1988 pub fn span(&self) -> Span {
1995 | EarlyBoundRegion(a, ..)
1996 | LateBoundRegion(a, ..)
1997 | UpvarRegion(_, a) => a,
1998 Nll(..) => bug!("NLL variable used with `span`"),
2003 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
2004 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
2007 "RegionObligation(sub_region={:?}, sup_type={:?})",
2008 self.sub_region, self.sup_type
2013 /// Replaces substs that reference param or infer variables with suitable
2014 /// placeholders. This function is meant to remove these param and infer
2015 /// substs when they're not actually needed to evaluate a constant.
2016 fn replace_param_and_infer_substs_with_placeholder<'tcx>(
2018 substs: SubstsRef<'tcx>,
2019 ) -> SubstsRef<'tcx> {
2020 tcx.mk_substs(substs.iter().enumerate().map(|(idx, arg)| {
2021 match arg.unpack() {
2022 GenericArgKind::Type(_)
2023 if arg.has_param_types_or_consts() || arg.has_infer_types_or_consts() =>
2025 tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
2026 universe: ty::UniverseIndex::ROOT,
2027 name: ty::BoundVar::from_usize(idx),
2031 GenericArgKind::Const(ct)
2032 if ct.has_infer_types_or_consts() || ct.has_param_types_or_consts() =>
2035 // If the type references param or infer, replace that too...
2036 if ty.has_param_types_or_consts() || ty.has_infer_types_or_consts() {
2037 bug!("const `{ct}`'s type should not reference params or types");
2039 tcx.mk_const(ty::ConstS {
2041 kind: ty::ConstKind::Placeholder(ty::PlaceholderConst {
2042 universe: ty::UniverseIndex::ROOT,
2043 name: ty::BoundConst { ty, var: ty::BoundVar::from_usize(idx) },