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;
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 pub struct InferCtxt<'a, 'tcx> {
243 pub tcx: TyCtxt<'tcx>,
245 /// The `DefId` of the item in whose context we are performing inference or typeck.
246 /// It is used to check whether an opaque type use is a defining use.
248 /// If it is `None`, we can't resolve opaque types here and need to bubble up
249 /// the obligation. This frequently happens for
250 /// short lived InferCtxt within queries. The opaque type obligations are forwarded
251 /// to the outside until the end up in an `InferCtxt` for typeck or borrowck.
252 pub defining_use_anchor: Option<LocalDefId>,
254 /// During type-checking/inference of a body, `in_progress_typeck_results`
255 /// contains a reference to the typeck results being built up, which are
256 /// used for reading closure kinds/signatures as they are inferred,
257 /// and for error reporting logic to read arbitrary node types.
258 pub in_progress_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
260 pub inner: RefCell<InferCtxtInner<'tcx>>,
262 /// If set, this flag causes us to skip the 'leak check' during
263 /// higher-ranked subtyping operations. This flag is a temporary one used
264 /// to manage the removal of the leak-check: for the time being, we still run the
265 /// leak-check, but we issue warnings. This flag can only be set to true
266 /// when entering a snapshot.
267 skip_leak_check: Cell<bool>,
269 /// Once region inference is done, the values for each variable.
270 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
272 /// Caches the results of trait selection. This cache is used
273 /// for things that have to do with the parameters in scope.
274 pub selection_cache: select::SelectionCache<'tcx>,
276 /// Caches the results of trait evaluation.
277 pub evaluation_cache: select::EvaluationCache<'tcx>,
279 /// the set of predicates on which errors have been reported, to
280 /// avoid reporting the same error twice.
281 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
283 pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
285 /// When an error occurs, we want to avoid reporting "derived"
286 /// errors that are due to this original failure. Normally, we
287 /// handle this with the `err_count_on_creation` count, which
288 /// basically just tracks how many errors were reported when we
289 /// started type-checking a fn and checks to see if any new errors
290 /// have been reported since then. Not great, but it works.
292 /// However, when errors originated in other passes -- notably
293 /// resolve -- this heuristic breaks down. Therefore, we have this
294 /// auxiliary flag that one can set whenever one creates a
295 /// type-error that is due to an error in a prior pass.
297 /// Don't read this flag directly, call `is_tainted_by_errors()`
298 /// and `set_tainted_by_errors()`.
299 tainted_by_errors_flag: Cell<bool>,
301 /// Track how many errors were reported when this infcx is created.
302 /// If the number of errors increases, that's also a sign (line
303 /// `tainted_by_errors`) to avoid reporting certain kinds of errors.
304 // FIXME(matthewjasper) Merge into `tainted_by_errors_flag`
305 err_count_on_creation: usize,
307 /// This flag is true while there is an active snapshot.
308 in_snapshot: Cell<bool>,
310 /// What is the innermost universe we have created? Starts out as
311 /// `UniverseIndex::root()` but grows from there as we enter
312 /// universal quantifiers.
314 /// N.B., at present, we exclude the universal quantifiers on the
315 /// item we are type-checking, and just consider those names as
316 /// part of the root universe. So this would only get incremented
317 /// when we enter into a higher-ranked (`for<..>`) type or trait
319 universe: Cell<ty::UniverseIndex>,
322 /// See the `error_reporting` module for more details.
323 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
324 pub enum ValuePairs<'tcx> {
325 Regions(ExpectedFound<ty::Region<'tcx>>),
326 Terms(ExpectedFound<ty::Term<'tcx>>),
327 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
328 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
331 impl<'tcx> ValuePairs<'tcx> {
332 pub fn ty(&self) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
333 if let ValuePairs::Terms(ExpectedFound {
334 expected: ty::Term::Ty(expected),
335 found: ty::Term::Ty(found),
338 Some((*expected, *found))
345 /// The trace designates the path through inference that we took to
346 /// encounter an error or subtyping constraint.
348 /// See the `error_reporting` module for more details.
349 #[derive(Clone, Debug)]
350 pub struct TypeTrace<'tcx> {
351 pub cause: ObligationCause<'tcx>,
352 pub values: ValuePairs<'tcx>,
355 /// The origin of a `r1 <= r2` constraint.
357 /// See `error_reporting` module for more details
358 #[derive(Clone, Debug)]
359 pub enum SubregionOrigin<'tcx> {
360 /// Arose from a subtyping relation
361 Subtype(Box<TypeTrace<'tcx>>),
363 /// When casting `&'a T` to an `&'b Trait` object,
364 /// relating `'a` to `'b`
365 RelateObjectBound(Span),
367 /// Some type parameter was instantiated with the given type,
368 /// and that type must outlive some region.
369 RelateParamBound(Span, Ty<'tcx>, Option<Span>),
371 /// The given region parameter was instantiated with a region
372 /// that must outlive some other region.
373 RelateRegionParamBound(Span),
375 /// Creating a pointer `b` to contents of another reference
378 /// Creating a pointer `b` to contents of an upvar
379 ReborrowUpvar(Span, ty::UpvarId),
381 /// Data with type `Ty<'tcx>` was borrowed
382 DataBorrowed(Ty<'tcx>, Span),
384 /// (&'a &'b T) where a >= b
385 ReferenceOutlivesReferent(Ty<'tcx>, Span),
387 /// Comparing the signature and requirements of an impl method against
388 /// the containing trait.
389 CompareImplMethodObligation {
391 impl_item_def_id: LocalDefId,
392 trait_item_def_id: DefId,
395 /// Comparing the signature and requirements of an impl associated type
396 /// against the containing trait
397 CompareImplTypeObligation { span: Span, impl_item_def_id: LocalDefId, trait_item_def_id: DefId },
399 /// Checking that the bounds of a trait's associated type hold for a given impl
400 CheckAssociatedTypeBounds {
401 parent: Box<SubregionOrigin<'tcx>>,
402 impl_item_def_id: LocalDefId,
403 trait_item_def_id: DefId,
407 // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
408 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
409 static_assert_size!(SubregionOrigin<'_>, 32);
411 /// Times when we replace late-bound regions with variables:
412 #[derive(Clone, Copy, Debug)]
413 pub enum LateBoundRegionConversionTime {
414 /// when a fn is called
417 /// when two higher-ranked types are compared
420 /// when projecting an associated type
421 AssocTypeProjection(DefId),
424 /// Reasons to create a region inference variable
426 /// See `error_reporting` module for more details
427 #[derive(Copy, Clone, Debug)]
428 pub enum RegionVariableOrigin {
429 /// Region variables created for ill-categorized reasons,
430 /// mostly indicates places in need of refactoring
433 /// Regions created by a `&P` or `[...]` pattern
436 /// Regions created by `&` operator
439 /// Regions created as part of an autoref of a method receiver
442 /// Regions created as part of an automatic coercion
445 /// Region variables created as the values for early-bound regions
446 EarlyBoundRegion(Span, Symbol),
448 /// Region variables created for bound regions
449 /// in a function or method that is called
450 LateBoundRegion(Span, ty::BoundRegionKind, LateBoundRegionConversionTime),
452 UpvarRegion(ty::UpvarId, Span),
454 /// This origin is used for the inference variables that we create
455 /// during NLL region processing.
456 Nll(NllRegionVariableOrigin),
459 #[derive(Copy, Clone, Debug)]
460 pub enum NllRegionVariableOrigin {
461 /// During NLL region processing, we create variables for free
462 /// regions that we encounter in the function signature and
463 /// elsewhere. This origin indices we've got one of those.
466 /// "Universal" instantiation of a higher-ranked region (e.g.,
467 /// from a `for<'a> T` binder). Meant to represent "any region".
468 Placeholder(ty::PlaceholderRegion),
471 /// If this is true, then this variable was created to represent a lifetime
472 /// bound in a `for` binder. For example, it might have been created to
473 /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
474 /// Such variables are created when we are trying to figure out if there
475 /// is any valid instantiation of `'a` that could fit into some scenario.
477 /// This is used to inform error reporting: in the case that we are trying to
478 /// determine whether there is any valid instantiation of a `'a` variable that meets
479 /// some constraint C, we want to blame the "source" of that `for` type,
480 /// rather than blaming the source of the constraint C.
485 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
486 #[derive(Copy, Clone, Debug)]
487 pub enum FixupError<'tcx> {
488 UnresolvedIntTy(IntVid),
489 UnresolvedFloatTy(FloatVid),
491 UnresolvedConst(ConstVid<'tcx>),
494 /// See the `region_obligations` field for more information.
496 pub struct RegionObligation<'tcx> {
497 pub sub_region: ty::Region<'tcx>,
498 pub sup_type: Ty<'tcx>,
499 pub origin: SubregionOrigin<'tcx>,
502 impl<'tcx> fmt::Display for FixupError<'tcx> {
503 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
504 use self::FixupError::*;
507 UnresolvedIntTy(_) => write!(
509 "cannot determine the type of this integer; \
510 add a suffix to specify the type explicitly"
512 UnresolvedFloatTy(_) => write!(
514 "cannot determine the type of this number; \
515 add a suffix to specify the type explicitly"
517 UnresolvedTy(_) => write!(f, "unconstrained type"),
518 UnresolvedConst(_) => write!(f, "unconstrained const value"),
523 /// A temporary returned by `tcx.infer_ctxt()`. This is necessary
524 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
525 /// without using `Rc` or something similar.
526 pub struct InferCtxtBuilder<'tcx> {
528 fresh_typeck_results: Option<RefCell<ty::TypeckResults<'tcx>>>,
529 defining_use_anchor: Option<LocalDefId>,
532 pub trait TyCtxtInferExt<'tcx> {
533 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>;
536 impl<'tcx> TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
537 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
538 InferCtxtBuilder { tcx: self, defining_use_anchor: None, fresh_typeck_results: None }
542 impl<'tcx> InferCtxtBuilder<'tcx> {
543 /// Used only by `rustc_typeck` during body type-checking/inference,
544 /// will initialize `in_progress_typeck_results` with fresh `TypeckResults`.
545 /// Will also change the scope for opaque type defining use checks to the given owner.
546 pub fn with_fresh_in_progress_typeck_results(mut self, table_owner: LocalDefId) -> Self {
547 self.fresh_typeck_results = Some(RefCell::new(ty::TypeckResults::new(table_owner)));
548 self.with_opaque_type_inference(table_owner)
551 /// Whenever the `InferCtxt` should be able to handle defining uses of opaque types,
552 /// you need to call this function. Otherwise the opaque type will be treated opaquely.
554 /// It is only meant to be called in two places, for typeck
555 /// (via `with_fresh_in_progress_typeck_results`) and for the inference context used
557 pub fn with_opaque_type_inference(mut self, defining_use_anchor: LocalDefId) -> Self {
558 self.defining_use_anchor = Some(defining_use_anchor);
562 /// Given a canonical value `C` as a starting point, create an
563 /// inference context that contains each of the bound values
564 /// within instantiated as a fresh variable. The `f` closure is
565 /// invoked with the new infcx, along with the instantiated value
566 /// `V` and a substitution `S`. This substitution `S` maps from
567 /// the bound values in `C` to their instantiated values in `V`
568 /// (in other words, `S(C) = V`).
569 pub fn enter_with_canonical<T, R>(
572 canonical: &Canonical<'tcx, T>,
573 f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
576 T: TypeFoldable<'tcx>,
580 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
581 f(infcx, value, subst)
585 pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R {
586 let InferCtxtBuilder { tcx, defining_use_anchor, ref fresh_typeck_results } = *self;
587 let in_progress_typeck_results = fresh_typeck_results.as_ref();
591 in_progress_typeck_results,
592 inner: RefCell::new(InferCtxtInner::new()),
593 lexical_region_resolutions: RefCell::new(None),
594 selection_cache: Default::default(),
595 evaluation_cache: Default::default(),
596 reported_trait_errors: Default::default(),
597 reported_closure_mismatch: Default::default(),
598 tainted_by_errors_flag: Cell::new(false),
599 err_count_on_creation: tcx.sess.err_count(),
600 in_snapshot: Cell::new(false),
601 skip_leak_check: Cell::new(false),
602 universe: Cell::new(ty::UniverseIndex::ROOT),
607 impl<'tcx, T> InferOk<'tcx, T> {
608 pub fn unit(self) -> InferOk<'tcx, ()> {
609 InferOk { value: (), obligations: self.obligations }
612 /// Extracts `value`, registering any obligations into `fulfill_cx`.
613 pub fn into_value_registering_obligations(
615 infcx: &InferCtxt<'_, 'tcx>,
616 fulfill_cx: &mut dyn TraitEngine<'tcx>,
618 let InferOk { value, obligations } = self;
619 for obligation in obligations {
620 fulfill_cx.register_predicate_obligation(infcx, obligation);
626 impl<'tcx> InferOk<'tcx, ()> {
627 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
632 #[must_use = "once you start a snapshot, you should always consume it"]
633 pub struct CombinedSnapshot<'a, 'tcx> {
634 undo_snapshot: Snapshot<'tcx>,
635 region_constraints_snapshot: RegionSnapshot,
636 universe: ty::UniverseIndex,
637 was_in_snapshot: bool,
638 _in_progress_typeck_results: Option<Ref<'a, ty::TypeckResults<'tcx>>>,
641 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
642 /// calls `tcx.try_unify_abstract_consts` after
643 /// canonicalizing the consts.
644 #[instrument(skip(self), level = "debug")]
645 pub fn try_unify_abstract_consts(
647 a: ty::Unevaluated<'tcx, ()>,
648 b: ty::Unevaluated<'tcx, ()>,
649 param_env: ty::ParamEnv<'tcx>,
651 // Reject any attempt to unify two unevaluated constants that contain inference
652 // variables, since inference variables in queries lead to ICEs.
653 if a.substs.has_infer_types_or_consts()
654 || b.substs.has_infer_types_or_consts()
655 || param_env.has_infer_types_or_consts()
657 debug!("a or b or param_env contain infer vars in its substs -> cannot unify");
661 let param_env_and = param_env.and((a, b));
662 let erased = self.tcx.erase_regions(param_env_and);
663 debug!("after erase_regions: {:?}", erased);
665 self.tcx.try_unify_abstract_consts(erased)
668 pub fn is_in_snapshot(&self) -> bool {
669 self.in_snapshot.get()
672 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
673 t.fold_with(&mut self.freshener())
676 /// Returns the origin of the type variable identified by `vid`, or `None`
677 /// if this is not a type variable.
679 /// No attempt is made to resolve `ty`.
680 pub fn type_var_origin(&'a self, ty: Ty<'tcx>) -> Option<TypeVariableOrigin> {
682 ty::Infer(ty::TyVar(vid)) => {
683 Some(*self.inner.borrow_mut().type_variables().var_origin(vid))
689 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
690 freshen::TypeFreshener::new(self, false)
693 /// Like `freshener`, but does not replace `'static` regions.
694 pub fn freshener_keep_static<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
695 freshen::TypeFreshener::new(self, true)
698 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
699 let mut inner = self.inner.borrow_mut();
700 let mut vars: Vec<Ty<'_>> = inner
702 .unsolved_variables()
704 .map(|t| self.tcx.mk_ty_var(t))
707 (0..inner.int_unification_table().len())
708 .map(|i| ty::IntVid { index: i as u32 })
709 .filter(|&vid| inner.int_unification_table().probe_value(vid).is_none())
710 .map(|v| self.tcx.mk_int_var(v)),
713 (0..inner.float_unification_table().len())
714 .map(|i| ty::FloatVid { index: i as u32 })
715 .filter(|&vid| inner.float_unification_table().probe_value(vid).is_none())
716 .map(|v| self.tcx.mk_float_var(v)),
723 trace: TypeTrace<'tcx>,
724 param_env: ty::ParamEnv<'tcx>,
725 define_opaque_types: bool,
726 ) -> CombineFields<'a, 'tcx> {
732 obligations: PredicateObligations::new(),
737 /// Clear the "currently in a snapshot" flag, invoke the closure,
738 /// then restore the flag to its original value. This flag is a
739 /// debugging measure designed to detect cases where we start a
740 /// snapshot, create type variables, and register obligations
741 /// which may involve those type variables in the fulfillment cx,
742 /// potentially leaving "dangling type variables" behind.
743 /// In such cases, an assertion will fail when attempting to
744 /// register obligations, within a snapshot. Very useful, much
745 /// better than grovelling through megabytes of `RUSTC_LOG` output.
747 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
748 /// sometimes create a "mini-fulfilment-cx" in which we enroll
749 /// obligations. As long as this fulfillment cx is fully drained
750 /// before we return, this is not a problem, as there won't be any
751 /// escaping obligations in the main cx. In those cases, you can
752 /// use this function.
753 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
755 F: FnOnce(&Self) -> R,
757 let flag = self.in_snapshot.replace(false);
758 let result = func(self);
759 self.in_snapshot.set(flag);
763 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
764 debug!("start_snapshot()");
766 let in_snapshot = self.in_snapshot.replace(true);
768 let mut inner = self.inner.borrow_mut();
771 undo_snapshot: inner.undo_log.start_snapshot(),
772 region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
773 universe: self.universe(),
774 was_in_snapshot: in_snapshot,
775 // Borrow typeck results "in progress" (i.e., during typeck)
776 // to ban writes from within a snapshot to them.
777 _in_progress_typeck_results: self
778 .in_progress_typeck_results
779 .map(|typeck_results| typeck_results.borrow()),
783 #[instrument(skip(self, snapshot), level = "debug")]
784 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
785 let CombinedSnapshot {
787 region_constraints_snapshot,
790 _in_progress_typeck_results,
793 self.in_snapshot.set(was_in_snapshot);
794 self.universe.set(universe);
796 let mut inner = self.inner.borrow_mut();
797 inner.rollback_to(undo_snapshot);
798 inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
801 #[instrument(skip(self, snapshot), level = "debug")]
802 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
803 let CombinedSnapshot {
805 region_constraints_snapshot: _,
808 _in_progress_typeck_results,
811 self.in_snapshot.set(was_in_snapshot);
813 self.inner.borrow_mut().commit(undo_snapshot);
816 /// Executes `f` and commit the bindings.
817 #[instrument(skip(self, f), level = "debug")]
818 pub fn commit_unconditionally<R, F>(&self, f: F) -> R
820 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
822 let snapshot = self.start_snapshot();
823 let r = f(&snapshot);
824 self.commit_from(snapshot);
828 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
829 #[instrument(skip(self, f), level = "debug")]
830 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
832 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
834 let snapshot = self.start_snapshot();
835 let r = f(&snapshot);
836 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
839 self.commit_from(snapshot);
842 self.rollback_to("commit_if_ok -- error", snapshot);
848 /// Execute `f` then unroll any bindings it creates.
849 #[instrument(skip(self, f), level = "debug")]
850 pub fn probe<R, F>(&self, f: F) -> R
852 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
854 let snapshot = self.start_snapshot();
855 let r = f(&snapshot);
856 self.rollback_to("probe", snapshot);
860 /// If `should_skip` is true, then execute `f` then unroll any bindings it creates.
861 #[instrument(skip(self, f), level = "debug")]
862 pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R
864 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
866 let snapshot = self.start_snapshot();
867 let was_skip_leak_check = self.skip_leak_check.get();
869 self.skip_leak_check.set(true);
871 let r = f(&snapshot);
872 self.rollback_to("probe", snapshot);
873 self.skip_leak_check.set(was_skip_leak_check);
877 /// Scan the constraints produced since `snapshot` began and returns:
879 /// - `None` -- if none of them involve "region outlives" constraints
880 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
881 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
882 pub fn region_constraints_added_in_snapshot(
884 snapshot: &CombinedSnapshot<'a, 'tcx>,
888 .unwrap_region_constraints()
889 .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
892 pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'a, 'tcx>) -> bool {
893 self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot)
896 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
897 self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
900 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
902 T: at::ToTrace<'tcx>,
904 let origin = &ObligationCause::dummy();
906 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
907 // Ignore obligations, since we are unrolling
908 // everything anyway.
913 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
915 T: at::ToTrace<'tcx>,
917 let origin = &ObligationCause::dummy();
919 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
920 // Ignore obligations, since we are unrolling
921 // everything anyway.
926 #[instrument(skip(self), level = "debug")]
929 origin: SubregionOrigin<'tcx>,
933 self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
936 /// Require that the region `r` be equal to one of the regions in
937 /// the set `regions`.
938 #[instrument(skip(self), level = "debug")]
939 pub fn member_constraint(
941 opaque_type_def_id: LocalDefId,
942 definition_span: Span,
944 region: ty::Region<'tcx>,
945 in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
947 self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
956 /// Processes a `Coerce` predicate from the fulfillment context.
957 /// This is NOT the preferred way to handle coercion, which is to
958 /// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`).
960 /// This method here is actually a fallback that winds up being
961 /// invoked when `FnCtxt::coerce` encounters unresolved type variables
962 /// and records a coercion predicate. Presently, this method is equivalent
963 /// to `subtype_predicate` -- that is, "coercing" `a` to `b` winds up
964 /// actually requiring `a <: b`. This is of course a valid coercion,
965 /// but it's not as flexible as `FnCtxt::coerce` would be.
967 /// (We may refactor this in the future, but there are a number of
968 /// practical obstacles. Among other things, `FnCtxt::coerce` presently
969 /// records adjustments that are required on the HIR in order to perform
970 /// the coercion, and we don't currently have a way to manage that.)
971 pub fn coerce_predicate(
973 cause: &ObligationCause<'tcx>,
974 param_env: ty::ParamEnv<'tcx>,
975 predicate: ty::PolyCoercePredicate<'tcx>,
976 ) -> Option<InferResult<'tcx, ()>> {
977 let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
978 a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
982 self.subtype_predicate(cause, param_env, subtype_predicate)
985 pub fn subtype_predicate(
987 cause: &ObligationCause<'tcx>,
988 param_env: ty::ParamEnv<'tcx>,
989 predicate: ty::PolySubtypePredicate<'tcx>,
990 ) -> Option<InferResult<'tcx, ()>> {
991 // Check for two unresolved inference variables, in which case we can
992 // make no progress. This is partly a micro-optimization, but it's
993 // also an opportunity to "sub-unify" the variables. This isn't
994 // *necessary* to prevent cycles, because they would eventually be sub-unified
995 // anyhow during generalization, but it helps with diagnostics (we can detect
996 // earlier that they are sub-unified).
998 // Note that we can just skip the binders here because
999 // type variables can't (at present, at
1000 // least) capture any of the things bound by this binder.
1002 // Note that this sub here is not just for diagnostics - it has semantic
1004 let r_a = self.shallow_resolve(predicate.skip_binder().a);
1005 let r_b = self.shallow_resolve(predicate.skip_binder().b);
1006 match (r_a.kind(), r_b.kind()) {
1007 (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
1008 self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
1014 Some(self.commit_if_ok(|_snapshot| {
1015 let ty::SubtypePredicate { a_is_expected, a, b } =
1016 self.replace_bound_vars_with_placeholders(predicate);
1018 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
1024 pub fn region_outlives_predicate(
1026 cause: &traits::ObligationCause<'tcx>,
1027 predicate: ty::PolyRegionOutlivesPredicate<'tcx>,
1028 ) -> UnitResult<'tcx> {
1029 self.commit_if_ok(|_snapshot| {
1030 let ty::OutlivesPredicate(r_a, r_b) =
1031 self.replace_bound_vars_with_placeholders(predicate);
1032 let origin = SubregionOrigin::from_obligation_cause(cause, || {
1033 RelateRegionParamBound(cause.span)
1035 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1040 /// Number of type variables created so far.
1041 pub fn num_ty_vars(&self) -> usize {
1042 self.inner.borrow_mut().type_variables().num_vars()
1045 pub fn next_ty_var_id(&self, origin: TypeVariableOrigin) -> TyVid {
1046 self.inner.borrow_mut().type_variables().new_var(self.universe(), origin)
1049 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1050 self.tcx.mk_ty_var(self.next_ty_var_id(origin))
1053 pub fn next_ty_var_id_in_universe(
1055 origin: TypeVariableOrigin,
1056 universe: ty::UniverseIndex,
1058 self.inner.borrow_mut().type_variables().new_var(universe, origin)
1061 pub fn next_ty_var_in_universe(
1063 origin: TypeVariableOrigin,
1064 universe: ty::UniverseIndex,
1066 let vid = self.next_ty_var_id_in_universe(origin, universe);
1067 self.tcx.mk_ty_var(vid)
1070 pub fn next_const_var(&self, ty: Ty<'tcx>, origin: ConstVariableOrigin) -> ty::Const<'tcx> {
1071 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1074 pub fn next_const_var_in_universe(
1077 origin: ConstVariableOrigin,
1078 universe: ty::UniverseIndex,
1079 ) -> ty::Const<'tcx> {
1083 .const_unification_table()
1084 .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
1085 self.tcx.mk_const_var(vid, ty)
1088 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1089 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1091 val: ConstVariableValue::Unknown { universe: self.universe() },
1095 fn next_int_var_id(&self) -> IntVid {
1096 self.inner.borrow_mut().int_unification_table().new_key(None)
1099 pub fn next_int_var(&self) -> Ty<'tcx> {
1100 self.tcx.mk_int_var(self.next_int_var_id())
1103 fn next_float_var_id(&self) -> FloatVid {
1104 self.inner.borrow_mut().float_unification_table().new_key(None)
1107 pub fn next_float_var(&self) -> Ty<'tcx> {
1108 self.tcx.mk_float_var(self.next_float_var_id())
1111 /// Creates a fresh region variable with the next available index.
1112 /// The variable will be created in the maximum universe created
1113 /// thus far, allowing it to name any region created thus far.
1114 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1115 self.next_region_var_in_universe(origin, self.universe())
1118 /// Creates a fresh region variable with the next available index
1119 /// in the given universe; typically, you can use
1120 /// `next_region_var` and just use the maximal universe.
1121 pub fn next_region_var_in_universe(
1123 origin: RegionVariableOrigin,
1124 universe: ty::UniverseIndex,
1125 ) -> ty::Region<'tcx> {
1127 self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
1128 self.tcx.mk_region(ty::ReVar(region_var))
1131 /// Return the universe that the region `r` was created in. For
1132 /// most regions (e.g., `'static`, named regions from the user,
1133 /// etc) this is the root universe U0. For inference variables or
1134 /// placeholders, however, it will return the universe which which
1135 /// they are associated.
1136 pub fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
1137 self.inner.borrow_mut().unwrap_region_constraints().universe(r)
1140 /// Number of region variables created so far.
1141 pub fn num_region_vars(&self) -> usize {
1142 self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
1145 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1146 pub fn next_nll_region_var(&self, origin: NllRegionVariableOrigin) -> ty::Region<'tcx> {
1147 self.next_region_var(RegionVariableOrigin::Nll(origin))
1150 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1151 pub fn next_nll_region_var_in_universe(
1153 origin: NllRegionVariableOrigin,
1154 universe: ty::UniverseIndex,
1155 ) -> ty::Region<'tcx> {
1156 self.next_region_var_in_universe(RegionVariableOrigin::Nll(origin), universe)
1159 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
1161 GenericParamDefKind::Lifetime => {
1162 // Create a region inference variable for the given
1163 // region parameter definition.
1164 self.next_region_var(EarlyBoundRegion(span, param.name)).into()
1166 GenericParamDefKind::Type { .. } => {
1167 // Create a type inference variable for the given
1168 // type parameter definition. The substitutions are
1169 // for actual parameters that may be referred to by
1170 // the default of this type parameter, if it exists.
1171 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1172 // used in a path such as `Foo::<T, U>::new()` will
1173 // use an inference variable for `C` with `[T, U]`
1174 // as the substitutions for the default, `(T, U)`.
1175 let ty_var_id = self.inner.borrow_mut().type_variables().new_var(
1177 TypeVariableOrigin {
1178 kind: TypeVariableOriginKind::TypeParameterDefinition(
1186 self.tcx.mk_ty_var(ty_var_id).into()
1188 GenericParamDefKind::Const { .. } => {
1189 let origin = ConstVariableOrigin {
1190 kind: ConstVariableOriginKind::ConstParameterDefinition(
1197 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1199 val: ConstVariableValue::Unknown { universe: self.universe() },
1201 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1206 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1207 /// type/region parameter to a fresh inference variable.
1208 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1209 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1212 /// Returns `true` if errors have been reported since this infcx was
1213 /// created. This is sometimes used as a heuristic to skip
1214 /// reporting errors that often occur as a result of earlier
1215 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1216 /// inference variables, regionck errors).
1217 pub fn is_tainted_by_errors(&self) -> bool {
1219 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1220 tainted_by_errors_flag={})",
1221 self.tcx.sess.err_count(),
1222 self.err_count_on_creation,
1223 self.tainted_by_errors_flag.get()
1226 if self.tcx.sess.err_count() > self.err_count_on_creation {
1227 return true; // errors reported since this infcx was made
1229 self.tainted_by_errors_flag.get()
1232 /// Set the "tainted by errors" flag to true. We call this when we
1233 /// observe an error from a prior pass.
1234 pub fn set_tainted_by_errors(&self) {
1235 debug!("set_tainted_by_errors()");
1236 self.tainted_by_errors_flag.set(true)
1239 pub fn skip_region_resolution(&self) {
1240 let (var_infos, _) = {
1241 let mut inner = self.inner.borrow_mut();
1242 let inner = &mut *inner;
1243 // Note: `inner.region_obligations` may not be empty, because we
1244 // didn't necessarily call `process_registered_region_obligations`.
1245 // This is okay, because that doesn't introduce new vars.
1247 .region_constraint_storage
1249 .expect("regions already resolved")
1250 .with_log(&mut inner.undo_log)
1251 .into_infos_and_data()
1254 let lexical_region_resolutions = LexicalRegionResolutions {
1255 values: rustc_index::vec::IndexVec::from_elem_n(
1256 crate::infer::lexical_region_resolve::VarValue::Value(self.tcx.lifetimes.re_erased),
1261 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1262 assert!(old_value.is_none());
1265 /// Process the region constraints and return any any errors that
1266 /// result. After this, no more unification operations should be
1267 /// done -- or the compiler will panic -- but it is legal to use
1268 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1269 pub fn resolve_regions(
1271 outlives_env: &OutlivesEnvironment<'tcx>,
1272 ) -> Vec<RegionResolutionError<'tcx>> {
1273 let (var_infos, data) = {
1274 let mut inner = self.inner.borrow_mut();
1275 let inner = &mut *inner;
1277 self.is_tainted_by_errors() || inner.region_obligations.is_empty(),
1278 "region_obligations not empty: {:#?}",
1279 inner.region_obligations
1282 .region_constraint_storage
1284 .expect("regions already resolved")
1285 .with_log(&mut inner.undo_log)
1286 .into_infos_and_data()
1289 let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map());
1291 let (lexical_region_resolutions, errors) =
1292 lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data);
1294 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1295 assert!(old_value.is_none());
1300 /// Process the region constraints and report any errors that
1301 /// result. After this, no more unification operations should be
1302 /// done -- or the compiler will panic -- but it is legal to use
1303 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1304 pub fn resolve_regions_and_report_errors(
1306 generic_param_scope: LocalDefId,
1307 outlives_env: &OutlivesEnvironment<'tcx>,
1309 let errors = self.resolve_regions(outlives_env);
1311 if !self.is_tainted_by_errors() {
1312 // As a heuristic, just skip reporting region errors
1313 // altogether if other errors have been reported while
1314 // this infcx was in use. This is totally hokey but
1315 // otherwise we have a hard time separating legit region
1316 // errors from silly ones.
1317 self.report_region_errors(generic_param_scope, &errors);
1321 /// Obtains (and clears) the current set of region
1322 /// constraints. The inference context is still usable: further
1323 /// unifications will simply add new constraints.
1325 /// This method is not meant to be used with normal lexical region
1326 /// resolution. Rather, it is used in the NLL mode as a kind of
1327 /// interim hack: basically we run normal type-check and generate
1328 /// region constraints as normal, but then we take them and
1329 /// translate them into the form that the NLL solver
1330 /// understands. See the NLL module for mode details.
1331 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1333 self.inner.borrow().region_obligations.is_empty(),
1334 "region_obligations not empty: {:#?}",
1335 self.inner.borrow().region_obligations
1338 self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data()
1341 /// Gives temporary access to the region constraint data.
1342 pub fn with_region_constraints<R>(
1344 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1346 let mut inner = self.inner.borrow_mut();
1347 op(inner.unwrap_region_constraints().data())
1350 pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin {
1351 let mut inner = self.inner.borrow_mut();
1352 let inner = &mut *inner;
1354 .region_constraint_storage
1356 .expect("regions already resolved")
1357 .with_log(&mut inner.undo_log)
1361 /// Takes ownership of the list of variable regions. This implies
1362 /// that all the region constraints have already been taken, and
1363 /// hence that `resolve_regions_and_report_errors` can never be
1364 /// called. This is used only during NLL processing to "hand off" ownership
1365 /// of the set of region variables into the NLL region context.
1366 pub fn take_region_var_origins(&self) -> VarInfos {
1367 let mut inner = self.inner.borrow_mut();
1368 let (var_infos, data) = inner
1369 .region_constraint_storage
1371 .expect("regions already resolved")
1372 .with_log(&mut inner.undo_log)
1373 .into_infos_and_data();
1374 assert!(data.is_empty());
1378 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1379 self.resolve_vars_if_possible(t).to_string()
1382 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1383 /// universe index of `TyVar(vid)`.
1384 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1385 use self::type_variable::TypeVariableValue;
1387 match self.inner.borrow_mut().type_variables().probe(vid) {
1388 TypeVariableValue::Known { value } => Ok(value),
1389 TypeVariableValue::Unknown { universe } => Err(universe),
1393 /// Resolve any type variables found in `value` -- but only one
1394 /// level. So, if the variable `?X` is bound to some type
1395 /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
1396 /// itself be bound to a type).
1398 /// Useful when you only need to inspect the outermost level of
1399 /// the type and don't care about nested types (or perhaps you
1400 /// will be resolving them as well, e.g. in a loop).
1401 pub fn shallow_resolve<T>(&self, value: T) -> T
1403 T: TypeFoldable<'tcx>,
1405 value.fold_with(&mut ShallowResolver { infcx: self })
1408 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1409 self.inner.borrow_mut().type_variables().root_var(var)
1412 /// Where possible, replaces type/const variables in
1413 /// `value` with their final value. Note that region variables
1414 /// are unaffected. If a type/const variable has not been unified, it
1415 /// is left as is. This is an idempotent operation that does
1416 /// not affect inference state in any way and so you can do it
1418 pub fn resolve_vars_if_possible<T>(&self, value: T) -> T
1420 T: TypeFoldable<'tcx>,
1422 if !value.needs_infer() {
1423 return value; // Avoid duplicated subst-folding.
1425 let mut r = resolve::OpportunisticVarResolver::new(self);
1426 value.fold_with(&mut r)
1429 pub fn resolve_numeric_literals_with_default<T>(&self, value: T) -> T
1431 T: TypeFoldable<'tcx>,
1433 if !value.needs_infer() {
1434 return value; // Avoid duplicated subst-folding.
1436 let mut r = InferenceLiteralEraser { tcx: self.tcx };
1437 value.fold_with(&mut r)
1440 /// Returns the first unresolved variable contained in `T`. In the
1441 /// process of visiting `T`, this will resolve (where possible)
1442 /// type variables in `T`, but it never constructs the final,
1443 /// resolved type, so it's more efficient than
1444 /// `resolve_vars_if_possible()`.
1445 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1447 T: TypeVisitable<'tcx>,
1449 value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value()
1452 pub fn probe_const_var(
1454 vid: ty::ConstVid<'tcx>,
1455 ) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
1456 match self.inner.borrow_mut().const_unification_table().probe_value(vid).val {
1457 ConstVariableValue::Known { value } => Ok(value),
1458 ConstVariableValue::Unknown { universe } => Err(universe),
1462 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: T) -> FixupResult<'tcx, T> {
1464 * Attempts to resolve all type/region/const variables in
1465 * `value`. Region inference must have been run already (e.g.,
1466 * by calling `resolve_regions_and_report_errors`). If some
1467 * variable was never unified, an `Err` results.
1469 * This method is idempotent, but it not typically not invoked
1470 * except during the writeback phase.
1473 resolve::fully_resolve(self, value)
1476 // [Note-Type-error-reporting]
1477 // An invariant is that anytime the expected or actual type is Error (the special
1478 // error type, meaning that an error occurred when typechecking this expression),
1479 // this is a derived error. The error cascaded from another error (that was already
1480 // reported), so it's not useful to display it to the user.
1481 // The following methods implement this logic.
1482 // They check if either the actual or expected type is Error, and don't print the error
1483 // in this case. The typechecker should only ever report type errors involving mismatched
1484 // types using one of these methods, and should not call span_err directly for such
1487 pub fn type_error_struct_with_diag<M>(
1491 actual_ty: Ty<'tcx>,
1492 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>
1494 M: FnOnce(String) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
1496 let actual_ty = self.resolve_vars_if_possible(actual_ty);
1497 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1499 let mut err = mk_diag(self.ty_to_string(actual_ty));
1501 // Don't report an error if actual type is `Error`.
1502 if actual_ty.references_error() {
1503 err.downgrade_to_delayed_bug();
1509 pub fn report_mismatched_types(
1511 cause: &ObligationCause<'tcx>,
1514 err: TypeError<'tcx>,
1515 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1516 let trace = TypeTrace::types(cause, true, expected, actual);
1517 self.report_and_explain_type_error(trace, &err)
1520 pub fn report_mismatched_consts(
1522 cause: &ObligationCause<'tcx>,
1523 expected: ty::Const<'tcx>,
1524 actual: ty::Const<'tcx>,
1525 err: TypeError<'tcx>,
1526 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1527 let trace = TypeTrace::consts(cause, true, expected, actual);
1528 self.report_and_explain_type_error(trace, &err)
1531 pub fn replace_bound_vars_with_fresh_vars<T>(
1534 lbrct: LateBoundRegionConversionTime,
1535 value: ty::Binder<'tcx, T>,
1538 T: TypeFoldable<'tcx> + Copy,
1540 if let Some(inner) = value.no_bound_vars() {
1544 let mut region_map = FxHashMap::default();
1545 let fld_r = |br: ty::BoundRegion| {
1548 .or_insert_with(|| self.next_region_var(LateBoundRegion(span, br.kind, lbrct)))
1551 let mut ty_map = FxHashMap::default();
1552 let fld_t = |bt: ty::BoundTy| {
1553 *ty_map.entry(bt).or_insert_with(|| {
1554 self.next_ty_var(TypeVariableOrigin {
1555 kind: TypeVariableOriginKind::MiscVariable,
1560 let mut ct_map = FxHashMap::default();
1561 let fld_c = |bc: ty::BoundVar, ty| {
1562 *ct_map.entry(bc).or_insert_with(|| {
1563 self.next_const_var(
1565 ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span },
1569 self.tcx.replace_bound_vars_uncached(value, fld_r, fld_t, fld_c)
1572 /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
1573 pub fn verify_generic_bound(
1575 origin: SubregionOrigin<'tcx>,
1576 kind: GenericKind<'tcx>,
1577 a: ty::Region<'tcx>,
1578 bound: VerifyBound<'tcx>,
1580 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1584 .unwrap_region_constraints()
1585 .verify_generic_bound(origin, kind, a, bound);
1588 /// Obtains the latest type of the given closure; this may be a
1589 /// closure in the current function, in which case its
1590 /// `ClosureKind` may not yet be known.
1591 pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
1592 let closure_kind_ty = closure_substs.as_closure().kind_ty();
1593 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1594 closure_kind_ty.to_opt_closure_kind()
1597 /// Clears the selection, evaluation, and projection caches. This is useful when
1598 /// repeatedly attempting to select an `Obligation` while changing only
1599 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1600 pub fn clear_caches(&self) {
1601 self.selection_cache.clear();
1602 self.evaluation_cache.clear();
1603 self.inner.borrow_mut().projection_cache().clear();
1606 pub fn universe(&self) -> ty::UniverseIndex {
1610 /// Creates and return a fresh universe that extends all previous
1611 /// universes. Updates `self.universe` to that new universe.
1612 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1613 let u = self.universe.get().next_universe();
1614 self.universe.set(u);
1618 pub fn try_const_eval_resolve(
1620 param_env: ty::ParamEnv<'tcx>,
1621 unevaluated: ty::Unevaluated<'tcx>,
1624 ) -> Result<ty::Const<'tcx>, ErrorHandled> {
1625 match self.const_eval_resolve(param_env, unevaluated, span) {
1626 Ok(Some(val)) => Ok(ty::Const::from_value(self.tcx, val, ty)),
1629 let def_id = unevaluated.def.did;
1631 tcx.def_span(def_id),
1632 "unable to construct a constant value for the unevaluated constant {:?}",
1636 Err(err) => Err(err),
1640 /// Resolves and evaluates a constant.
1642 /// The constant can be located on a trait like `<A as B>::C`, in which case the given
1643 /// substitutions and environment are used to resolve the constant. Alternatively if the
1644 /// constant has generic parameters in scope the substitutions are used to evaluate the value of
1645 /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
1646 /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
1647 /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
1650 /// This handles inferences variables within both `param_env` and `substs` by
1651 /// performing the operation on their respective canonical forms.
1652 #[instrument(skip(self), level = "debug")]
1653 pub fn const_eval_resolve(
1655 param_env: ty::ParamEnv<'tcx>,
1656 unevaluated: ty::Unevaluated<'tcx>,
1658 ) -> EvalToValTreeResult<'tcx> {
1659 let mut substs = self.resolve_vars_if_possible(unevaluated.substs);
1662 // Postpone the evaluation of constants whose substs depend on inference
1664 if substs.has_infer_types_or_consts() {
1665 let ac = AbstractConst::new(self.tcx, unevaluated.shrink());
1666 if let Ok(None) = ac {
1667 substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
1669 return Err(ErrorHandled::TooGeneric);
1673 let param_env_erased = self.tcx.erase_regions(param_env);
1674 let substs_erased = self.tcx.erase_regions(substs);
1675 debug!(?param_env_erased);
1676 debug!(?substs_erased);
1678 let unevaluated = ty::Unevaluated {
1679 def: unevaluated.def,
1680 substs: substs_erased,
1681 promoted: unevaluated.promoted,
1684 // The return value is the evaluated value which doesn't contain any reference to inference
1685 // variables, thus we don't need to substitute back the original values.
1686 self.tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
1689 /// `ty_or_const_infer_var_changed` is equivalent to one of these two:
1690 /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
1691 /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
1693 /// However, `ty_or_const_infer_var_changed` is more efficient. It's always
1694 /// inlined, despite being large, because it has only two call sites that
1695 /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
1696 /// inference variables), and it handles both `Ty` and `ty::Const` without
1697 /// having to resort to storing full `GenericArg`s in `stalled_on`.
1699 pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
1701 TyOrConstInferVar::Ty(v) => {
1702 use self::type_variable::TypeVariableValue;
1704 // If `inlined_probe` returns a `Known` value, it never equals
1705 // `ty::Infer(ty::TyVar(v))`.
1706 match self.inner.borrow_mut().type_variables().inlined_probe(v) {
1707 TypeVariableValue::Unknown { .. } => false,
1708 TypeVariableValue::Known { .. } => true,
1712 TyOrConstInferVar::TyInt(v) => {
1713 // If `inlined_probe_value` returns a value it's always a
1714 // `ty::Int(_)` or `ty::UInt(_)`, which never matches a
1716 self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_some()
1719 TyOrConstInferVar::TyFloat(v) => {
1720 // If `probe_value` returns a value it's always a
1721 // `ty::Float(_)`, which never matches a `ty::Infer(_)`.
1723 // Not `inlined_probe_value(v)` because this call site is colder.
1724 self.inner.borrow_mut().float_unification_table().probe_value(v).is_some()
1727 TyOrConstInferVar::Const(v) => {
1728 // If `probe_value` returns a `Known` value, it never equals
1729 // `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
1731 // Not `inlined_probe_value(v)` because this call site is colder.
1732 match self.inner.borrow_mut().const_unification_table().probe_value(v).val {
1733 ConstVariableValue::Unknown { .. } => false,
1734 ConstVariableValue::Known { .. } => true,
1741 /// Helper for `ty_or_const_infer_var_changed` (see comment on that), currently
1742 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
1743 #[derive(Copy, Clone, Debug)]
1744 pub enum TyOrConstInferVar<'tcx> {
1745 /// Equivalent to `ty::Infer(ty::TyVar(_))`.
1747 /// Equivalent to `ty::Infer(ty::IntVar(_))`.
1749 /// Equivalent to `ty::Infer(ty::FloatVar(_))`.
1752 /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
1753 Const(ConstVid<'tcx>),
1756 impl<'tcx> TyOrConstInferVar<'tcx> {
1757 /// Tries to extract an inference variable from a type or a constant, returns `None`
1758 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
1759 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1760 pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
1761 match arg.unpack() {
1762 GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
1763 GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
1764 GenericArgKind::Lifetime(_) => None,
1768 /// Tries to extract an inference variable from a type, returns `None`
1769 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
1770 pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
1772 ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
1773 ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
1774 ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
1779 /// Tries to extract an inference variable from a constant, returns `None`
1780 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1781 pub fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
1783 ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
1789 /// Replace `{integer}` with `i32` and `{float}` with `f64`.
1790 /// Used only for diagnostics.
1791 struct InferenceLiteralEraser<'tcx> {
1795 impl<'tcx> TypeFolder<'tcx> for InferenceLiteralEraser<'tcx> {
1796 fn tcx(&self) -> TyCtxt<'tcx> {
1800 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1802 ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32,
1803 ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64,
1804 _ => ty.super_fold_with(self),
1809 struct ShallowResolver<'a, 'tcx> {
1810 infcx: &'a InferCtxt<'a, 'tcx>,
1813 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
1814 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1818 /// If `ty` is a type variable of some kind, resolve it one level
1819 /// (but do not resolve types found in the result). If `typ` is
1820 /// not a type variable, just return it unmodified.
1821 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1823 ty::Infer(ty::TyVar(v)) => {
1824 // Not entirely obvious: if `typ` is a type variable,
1825 // it can be resolved to an int/float variable, which
1826 // can then be recursively resolved, hence the
1827 // recursion. Note though that we prevent type
1828 // variables from unifying to other type variables
1829 // directly (though they may be embedded
1830 // structurally), and we prevent cycles in any case,
1831 // so this recursion should always be of very limited
1834 // Note: if these two lines are combined into one we get
1835 // dynamic borrow errors on `self.inner`.
1836 let known = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
1837 known.map_or(ty, |t| self.fold_ty(t))
1840 ty::Infer(ty::IntVar(v)) => self
1844 .int_unification_table()
1846 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1848 ty::Infer(ty::FloatVar(v)) => self
1852 .float_unification_table()
1854 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1860 fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
1861 if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() {
1865 .const_unification_table()
1876 impl<'tcx> TypeTrace<'tcx> {
1877 pub fn span(&self) -> Span {
1882 cause: &ObligationCause<'tcx>,
1883 a_is_expected: bool,
1886 ) -> TypeTrace<'tcx> {
1888 cause: cause.clone(),
1889 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1894 cause: &ObligationCause<'tcx>,
1895 a_is_expected: bool,
1898 ) -> TypeTrace<'tcx> {
1900 cause: cause.clone(),
1901 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1906 impl<'tcx> SubregionOrigin<'tcx> {
1907 pub fn span(&self) -> Span {
1909 Subtype(ref a) => a.span(),
1910 RelateObjectBound(a) => a,
1911 RelateParamBound(a, ..) => a,
1912 RelateRegionParamBound(a) => a,
1914 ReborrowUpvar(a, _) => a,
1915 DataBorrowed(_, a) => a,
1916 ReferenceOutlivesReferent(_, a) => a,
1917 CompareImplMethodObligation { span, .. } => span,
1918 CompareImplTypeObligation { span, .. } => span,
1919 CheckAssociatedTypeBounds { ref parent, .. } => parent.span(),
1923 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
1925 F: FnOnce() -> Self,
1927 match *cause.code() {
1928 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
1929 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
1932 traits::ObligationCauseCode::CompareImplMethodObligation {
1935 } => SubregionOrigin::CompareImplMethodObligation {
1941 traits::ObligationCauseCode::CompareImplTypeObligation {
1944 } => SubregionOrigin::CompareImplTypeObligation {
1950 traits::ObligationCauseCode::CheckAssociatedTypeBounds {
1953 } => SubregionOrigin::CheckAssociatedTypeBounds {
1956 parent: Box::new(default()),
1964 impl RegionVariableOrigin {
1965 pub fn span(&self) -> Span {
1972 | EarlyBoundRegion(a, ..)
1973 | LateBoundRegion(a, ..)
1974 | UpvarRegion(_, a) => a,
1975 Nll(..) => bug!("NLL variable used with `span`"),
1980 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
1981 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1984 "RegionObligation(sub_region={:?}, sup_type={:?})",
1985 self.sub_region, self.sup_type