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, TraitEngineExt};
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::mir::ConstraintCategory;
24 use rustc_middle::traits::select;
25 use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind};
26 use rustc_middle::ty::error::{ExpectedFound, TypeError};
27 use rustc_middle::ty::fold::BoundVarReplacerDelegate;
28 use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable};
29 use rustc_middle::ty::relate::RelateResult;
30 use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
31 use rustc_middle::ty::visit::TypeVisitable;
32 pub use rustc_middle::ty::IntVarValue;
33 use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
34 use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid};
35 use rustc_span::symbol::Symbol;
36 use rustc_span::{Span, DUMMY_SP};
38 use std::cell::{Cell, Ref, RefCell};
41 use self::combine::CombineFields;
42 use self::free_regions::RegionRelations;
43 use self::lexical_region_resolve::LexicalRegionResolutions;
44 use self::outlives::env::OutlivesEnvironment;
45 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
46 use self::region_constraints::{
47 RegionConstraintCollector, RegionConstraintStorage, RegionSnapshot,
49 use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
55 pub mod error_reporting;
62 mod lexical_region_resolve;
68 pub mod region_constraints;
71 pub mod type_variable;
76 pub struct InferOk<'tcx, T> {
78 pub obligations: PredicateObligations<'tcx>,
80 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
82 pub type Bound<T> = Option<T>;
83 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
84 pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
86 pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable<
87 ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>,
90 /// This type contains all the things within `InferCtxt` that sit within a
91 /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
92 /// operations are hot enough that we want only one call to `borrow_mut` per
93 /// call to `start_snapshot` and `rollback_to`.
95 pub struct InferCtxtInner<'tcx> {
96 /// Cache for projections. This cache is snapshotted along with the infcx.
98 /// Public so that `traits::project` can use it.
99 pub projection_cache: traits::ProjectionCacheStorage<'tcx>,
101 /// We instantiate `UnificationTable` with `bounds<Ty>` because the types
102 /// that might instantiate a general type variable have an order,
103 /// represented by its upper and lower bounds.
104 type_variable_storage: type_variable::TypeVariableStorage<'tcx>,
106 /// Map from const parameter variable to the kind of const it represents.
107 const_unification_storage: ut::UnificationTableStorage<ty::ConstVid<'tcx>>,
109 /// Map from integral variable to the kind of integer it represents.
110 int_unification_storage: ut::UnificationTableStorage<ty::IntVid>,
112 /// Map from floating variable to the kind of float it represents.
113 float_unification_storage: ut::UnificationTableStorage<ty::FloatVid>,
115 /// Tracks the set of region variables and the constraints between them.
116 /// This is initially `Some(_)` but when
117 /// `resolve_regions_and_report_errors` is invoked, this gets set to `None`
118 /// -- further attempts to perform unification, etc., may fail if new
119 /// region constraints would've been added.
120 region_constraint_storage: Option<RegionConstraintStorage<'tcx>>,
122 /// A set of constraints that regionck must validate. Each
123 /// constraint has the form `T:'a`, meaning "some type `T` must
124 /// outlive the lifetime 'a". These constraints derive from
125 /// instantiated type parameters. So if you had a struct defined
127 /// ```ignore (illustrative)
128 /// struct Foo<T:'static> { ... }
130 /// then in some expression `let x = Foo { ... }` it will
131 /// instantiate the type parameter `T` with a fresh type `$0`. At
132 /// the same time, it will record a region obligation of
133 /// `$0:'static`. This will get checked later by regionck. (We
134 /// can't generally check these things right away because we have
135 /// to wait until types are resolved.)
137 /// These are stored in a map keyed to the id of the innermost
138 /// enclosing fn body / static initializer expression. This is
139 /// because the location where the obligation was incurred can be
140 /// relevant with respect to which sublifetime assumptions are in
141 /// place. The reason that we store under the fn-id, and not
142 /// something more fine-grained, is so that it is easier for
143 /// regionck to be sure that it has found *all* the region
144 /// obligations (otherwise, it's easy to fail to walk to a
145 /// particular node-id).
147 /// Before running `resolve_regions_and_report_errors`, the creator
148 /// of the inference context is expected to invoke
149 /// [`InferCtxt::process_registered_region_obligations`]
150 /// for each body-id in this map, which will process the
151 /// obligations within. This is expected to be done 'late enough'
152 /// that all type inference variables have been bound and so forth.
153 region_obligations: Vec<RegionObligation<'tcx>>,
155 undo_log: InferCtxtUndoLogs<'tcx>,
157 /// Caches for opaque type inference.
158 pub opaque_type_storage: OpaqueTypeStorage<'tcx>,
161 impl<'tcx> InferCtxtInner<'tcx> {
162 fn new() -> InferCtxtInner<'tcx> {
164 projection_cache: Default::default(),
165 type_variable_storage: type_variable::TypeVariableStorage::new(),
166 undo_log: InferCtxtUndoLogs::default(),
167 const_unification_storage: ut::UnificationTableStorage::new(),
168 int_unification_storage: ut::UnificationTableStorage::new(),
169 float_unification_storage: ut::UnificationTableStorage::new(),
170 region_constraint_storage: Some(RegionConstraintStorage::new()),
171 region_obligations: vec![],
172 opaque_type_storage: Default::default(),
177 pub fn region_obligations(&self) -> &[RegionObligation<'tcx>] {
178 &self.region_obligations
182 pub fn projection_cache(&mut self) -> traits::ProjectionCache<'_, 'tcx> {
183 self.projection_cache.with_log(&mut self.undo_log)
187 fn type_variables(&mut self) -> type_variable::TypeVariableTable<'_, 'tcx> {
188 self.type_variable_storage.with_log(&mut self.undo_log)
192 pub fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> {
193 self.opaque_type_storage.with_log(&mut self.undo_log)
197 fn int_unification_table(
199 ) -> ut::UnificationTable<
202 &mut ut::UnificationStorage<ty::IntVid>,
203 &mut InferCtxtUndoLogs<'tcx>,
206 self.int_unification_storage.with_log(&mut self.undo_log)
210 fn float_unification_table(
212 ) -> ut::UnificationTable<
215 &mut ut::UnificationStorage<ty::FloatVid>,
216 &mut InferCtxtUndoLogs<'tcx>,
219 self.float_unification_storage.with_log(&mut self.undo_log)
223 fn const_unification_table(
225 ) -> ut::UnificationTable<
228 &mut ut::UnificationStorage<ty::ConstVid<'tcx>>,
229 &mut InferCtxtUndoLogs<'tcx>,
232 self.const_unification_storage.with_log(&mut self.undo_log)
236 pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'_, 'tcx> {
237 self.region_constraint_storage
239 .expect("region constraints already solved")
240 .with_log(&mut self.undo_log)
244 #[derive(Clone, Copy, Debug, PartialEq, Eq)]
245 pub enum DefiningAnchor {
246 /// `DefId` of the item.
248 /// When opaque types are not resolved, we `Bubble` up, meaning
249 /// return the opaque/hidden type pair from query, for caller of query to handle it.
251 /// Used to catch type mismatch errors when handling opaque types.
255 pub struct InferCtxt<'a, 'tcx> {
256 pub tcx: TyCtxt<'tcx>,
258 /// The `DefId` of the item in whose context we are performing inference or typeck.
259 /// It is used to check whether an opaque type use is a defining use.
261 /// If it is `DefiningAnchor::Bubble`, we can't resolve opaque types here and need to bubble up
262 /// the obligation. This frequently happens for
263 /// short lived InferCtxt within queries. The opaque type obligations are forwarded
264 /// to the outside until the end up in an `InferCtxt` for typeck or borrowck.
266 /// It is default value is `DefiningAnchor::Error`, this way it is easier to catch errors that
267 /// might come up during inference or typeck.
268 pub defining_use_anchor: DefiningAnchor,
270 /// Whether this inference context should care about region obligations in
271 /// the root universe. Most notably, this is used during hir typeck as region
272 /// solving is left to borrowck instead.
273 pub considering_regions: bool,
275 /// During type-checking/inference of a body, `in_progress_typeck_results`
276 /// contains a reference to the typeck results being built up, which are
277 /// used for reading closure kinds/signatures as they are inferred,
278 /// and for error reporting logic to read arbitrary node types.
279 pub in_progress_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>,
281 pub inner: RefCell<InferCtxtInner<'tcx>>,
283 /// If set, this flag causes us to skip the 'leak check' during
284 /// higher-ranked subtyping operations. This flag is a temporary one used
285 /// to manage the removal of the leak-check: for the time being, we still run the
286 /// leak-check, but we issue warnings. This flag can only be set to true
287 /// when entering a snapshot.
288 skip_leak_check: Cell<bool>,
290 /// Once region inference is done, the values for each variable.
291 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
293 /// Caches the results of trait selection. This cache is used
294 /// for things that have to do with the parameters in scope.
295 pub selection_cache: select::SelectionCache<'tcx>,
297 /// Caches the results of trait evaluation.
298 pub evaluation_cache: select::EvaluationCache<'tcx>,
300 /// the set of predicates on which errors have been reported, to
301 /// avoid reporting the same error twice.
302 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
304 pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
306 /// When an error occurs, we want to avoid reporting "derived"
307 /// errors that are due to this original failure. Normally, we
308 /// handle this with the `err_count_on_creation` count, which
309 /// basically just tracks how many errors were reported when we
310 /// started type-checking a fn and checks to see if any new errors
311 /// have been reported since then. Not great, but it works.
313 /// However, when errors originated in other passes -- notably
314 /// resolve -- this heuristic breaks down. Therefore, we have this
315 /// auxiliary flag that one can set whenever one creates a
316 /// type-error that is due to an error in a prior pass.
318 /// Don't read this flag directly, call `is_tainted_by_errors()`
319 /// and `set_tainted_by_errors()`.
320 tainted_by_errors: Cell<Option<ErrorGuaranteed>>,
322 /// Track how many errors were reported when this infcx is created.
323 /// If the number of errors increases, that's also a sign (line
324 /// `tainted_by_errors`) to avoid reporting certain kinds of errors.
325 // FIXME(matthewjasper) Merge into `tainted_by_errors`
326 err_count_on_creation: usize,
328 /// This flag is true while there is an active snapshot.
329 in_snapshot: Cell<bool>,
331 /// What is the innermost universe we have created? Starts out as
332 /// `UniverseIndex::root()` but grows from there as we enter
333 /// universal quantifiers.
335 /// N.B., at present, we exclude the universal quantifiers on the
336 /// item we are type-checking, and just consider those names as
337 /// part of the root universe. So this would only get incremented
338 /// when we enter into a higher-ranked (`for<..>`) type or trait
340 universe: Cell<ty::UniverseIndex>,
342 normalize_fn_sig_for_diagnostic:
343 Option<Lrc<dyn Fn(&InferCtxt<'_, 'tcx>, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>>,
346 /// See the `error_reporting` module for more details.
347 #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)]
348 pub enum ValuePairs<'tcx> {
349 Regions(ExpectedFound<ty::Region<'tcx>>),
350 Terms(ExpectedFound<ty::Term<'tcx>>),
351 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
352 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
355 impl<'tcx> ValuePairs<'tcx> {
356 pub fn ty(&self) -> Option<(Ty<'tcx>, Ty<'tcx>)> {
357 if let ValuePairs::Terms(ExpectedFound { expected, found }) = self
358 && let Some(expected) = expected.ty()
359 && let Some(found) = found.ty()
361 Some((expected, found))
368 /// The trace designates the path through inference that we took to
369 /// encounter an error or subtyping constraint.
371 /// See the `error_reporting` module for more details.
372 #[derive(Clone, Debug)]
373 pub struct TypeTrace<'tcx> {
374 pub cause: ObligationCause<'tcx>,
375 pub values: ValuePairs<'tcx>,
378 /// The origin of a `r1 <= r2` constraint.
380 /// See `error_reporting` module for more details
381 #[derive(Clone, Debug)]
382 pub enum SubregionOrigin<'tcx> {
383 /// Arose from a subtyping relation
384 Subtype(Box<TypeTrace<'tcx>>),
386 /// When casting `&'a T` to an `&'b Trait` object,
387 /// relating `'a` to `'b`
388 RelateObjectBound(Span),
390 /// Some type parameter was instantiated with the given type,
391 /// and that type must outlive some region.
392 RelateParamBound(Span, Ty<'tcx>, Option<Span>),
394 /// The given region parameter was instantiated with a region
395 /// that must outlive some other region.
396 RelateRegionParamBound(Span),
398 /// Creating a pointer `b` to contents of another reference
401 /// Creating a pointer `b` to contents of an upvar
402 ReborrowUpvar(Span, ty::UpvarId),
404 /// Data with type `Ty<'tcx>` was borrowed
405 DataBorrowed(Ty<'tcx>, Span),
407 /// (&'a &'b T) where a >= b
408 ReferenceOutlivesReferent(Ty<'tcx>, Span),
410 /// Comparing the signature and requirements of an impl method against
411 /// the containing trait.
412 CompareImplItemObligation {
414 impl_item_def_id: LocalDefId,
415 trait_item_def_id: DefId,
418 /// Checking that the bounds of a trait's associated type hold for a given impl
419 CheckAssociatedTypeBounds {
420 parent: Box<SubregionOrigin<'tcx>>,
421 impl_item_def_id: LocalDefId,
422 trait_item_def_id: DefId,
425 AscribeUserTypeProvePredicate(Span),
428 // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
429 #[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
430 static_assert_size!(SubregionOrigin<'_>, 32);
432 impl<'tcx> SubregionOrigin<'tcx> {
433 pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> {
435 Self::Subtype(type_trace) => type_trace.cause.to_constraint_category(),
436 Self::AscribeUserTypeProvePredicate(span) => ConstraintCategory::Predicate(*span),
437 _ => ConstraintCategory::BoringNoLocation,
442 /// Times when we replace late-bound regions with variables:
443 #[derive(Clone, Copy, Debug)]
444 pub enum LateBoundRegionConversionTime {
445 /// when a fn is called
448 /// when two higher-ranked types are compared
451 /// when projecting an associated type
452 AssocTypeProjection(DefId),
455 /// Reasons to create a region inference variable
457 /// See `error_reporting` module for more details
458 #[derive(Copy, Clone, Debug)]
459 pub enum RegionVariableOrigin {
460 /// Region variables created for ill-categorized reasons,
461 /// mostly indicates places in need of refactoring
464 /// Regions created by a `&P` or `[...]` pattern
467 /// Regions created by `&` operator
470 /// Regions created as part of an autoref of a method receiver
473 /// Regions created as part of an automatic coercion
476 /// Region variables created as the values for early-bound regions
477 EarlyBoundRegion(Span, Symbol),
479 /// Region variables created for bound regions
480 /// in a function or method that is called
481 LateBoundRegion(Span, ty::BoundRegionKind, LateBoundRegionConversionTime),
483 UpvarRegion(ty::UpvarId, Span),
485 /// This origin is used for the inference variables that we create
486 /// during NLL region processing.
487 Nll(NllRegionVariableOrigin),
490 #[derive(Copy, Clone, Debug)]
491 pub enum NllRegionVariableOrigin {
492 /// During NLL region processing, we create variables for free
493 /// regions that we encounter in the function signature and
494 /// elsewhere. This origin indices we've got one of those.
497 /// "Universal" instantiation of a higher-ranked region (e.g.,
498 /// from a `for<'a> T` binder). Meant to represent "any region".
499 Placeholder(ty::PlaceholderRegion),
502 /// If this is true, then this variable was created to represent a lifetime
503 /// bound in a `for` binder. For example, it might have been created to
504 /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
505 /// Such variables are created when we are trying to figure out if there
506 /// is any valid instantiation of `'a` that could fit into some scenario.
508 /// This is used to inform error reporting: in the case that we are trying to
509 /// determine whether there is any valid instantiation of a `'a` variable that meets
510 /// some constraint C, we want to blame the "source" of that `for` type,
511 /// rather than blaming the source of the constraint C.
516 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
517 #[derive(Copy, Clone, Debug)]
518 pub enum FixupError<'tcx> {
519 UnresolvedIntTy(IntVid),
520 UnresolvedFloatTy(FloatVid),
522 UnresolvedConst(ConstVid<'tcx>),
525 /// See the `region_obligations` field for more information.
526 #[derive(Clone, Debug)]
527 pub struct RegionObligation<'tcx> {
528 pub sub_region: ty::Region<'tcx>,
529 pub sup_type: Ty<'tcx>,
530 pub origin: SubregionOrigin<'tcx>,
533 impl<'tcx> fmt::Display for FixupError<'tcx> {
534 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
535 use self::FixupError::*;
538 UnresolvedIntTy(_) => write!(
540 "cannot determine the type of this integer; \
541 add a suffix to specify the type explicitly"
543 UnresolvedFloatTy(_) => write!(
545 "cannot determine the type of this number; \
546 add a suffix to specify the type explicitly"
548 UnresolvedTy(_) => write!(f, "unconstrained type"),
549 UnresolvedConst(_) => write!(f, "unconstrained const value"),
554 /// A temporary returned by `tcx.infer_ctxt()`. This is necessary
555 /// for multiple `InferCtxt` to share the same `in_progress_typeck_results`
556 /// without using `Rc` or something similar.
557 pub struct InferCtxtBuilder<'tcx> {
559 defining_use_anchor: DefiningAnchor,
560 considering_regions: bool,
561 fresh_typeck_results: Option<RefCell<ty::TypeckResults<'tcx>>>,
562 normalize_fn_sig_for_diagnostic:
563 Option<Lrc<dyn Fn(&InferCtxt<'_, 'tcx>, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>>,
566 pub trait TyCtxtInferExt<'tcx> {
567 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>;
570 impl<'tcx> TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
571 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
574 defining_use_anchor: DefiningAnchor::Error,
575 considering_regions: true,
576 fresh_typeck_results: None,
577 normalize_fn_sig_for_diagnostic: None,
582 impl<'tcx> InferCtxtBuilder<'tcx> {
583 /// Used only by `rustc_typeck` during body type-checking/inference,
584 /// will initialize `in_progress_typeck_results` with fresh `TypeckResults`.
585 /// Will also change the scope for opaque type defining use checks to the given owner.
586 pub fn with_fresh_in_progress_typeck_results(mut self, table_owner: LocalDefId) -> Self {
587 self.fresh_typeck_results = Some(RefCell::new(ty::TypeckResults::new(table_owner)));
588 self.with_opaque_type_inference(DefiningAnchor::Bind(table_owner))
591 /// Whenever the `InferCtxt` should be able to handle defining uses of opaque types,
592 /// you need to call this function. Otherwise the opaque type will be treated opaquely.
594 /// It is only meant to be called in two places, for typeck
595 /// (via `with_fresh_in_progress_typeck_results`) and for the inference context used
597 pub fn with_opaque_type_inference(mut self, defining_use_anchor: DefiningAnchor) -> Self {
598 self.defining_use_anchor = defining_use_anchor;
602 pub fn ignoring_regions(mut self) -> Self {
603 self.considering_regions = false;
607 pub fn with_normalize_fn_sig_for_diagnostic(
609 fun: Lrc<dyn Fn(&InferCtxt<'_, 'tcx>, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>,
611 self.normalize_fn_sig_for_diagnostic = Some(fun);
615 /// Given a canonical value `C` as a starting point, create an
616 /// inference context that contains each of the bound values
617 /// within instantiated as a fresh variable. The `f` closure is
618 /// invoked with the new infcx, along with the instantiated value
619 /// `V` and a substitution `S`. This substitution `S` maps from
620 /// the bound values in `C` to their instantiated values in `V`
621 /// (in other words, `S(C) = V`).
622 pub fn enter_with_canonical<T, R>(
625 canonical: &Canonical<'tcx, T>,
626 f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
629 T: TypeFoldable<'tcx>,
633 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
634 f(infcx, value, subst)
638 pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R {
639 let InferCtxtBuilder {
643 ref fresh_typeck_results,
644 ref normalize_fn_sig_for_diagnostic,
646 let in_progress_typeck_results = fresh_typeck_results.as_ref();
651 in_progress_typeck_results,
652 inner: RefCell::new(InferCtxtInner::new()),
653 lexical_region_resolutions: RefCell::new(None),
654 selection_cache: Default::default(),
655 evaluation_cache: Default::default(),
656 reported_trait_errors: Default::default(),
657 reported_closure_mismatch: Default::default(),
658 tainted_by_errors: Cell::new(None),
659 err_count_on_creation: tcx.sess.err_count(),
660 in_snapshot: Cell::new(false),
661 skip_leak_check: Cell::new(false),
662 universe: Cell::new(ty::UniverseIndex::ROOT),
663 normalize_fn_sig_for_diagnostic: normalize_fn_sig_for_diagnostic
670 impl<'tcx, T> InferOk<'tcx, T> {
671 pub fn unit(self) -> InferOk<'tcx, ()> {
672 InferOk { value: (), obligations: self.obligations }
675 /// Extracts `value`, registering any obligations into `fulfill_cx`.
676 pub fn into_value_registering_obligations(
678 infcx: &InferCtxt<'_, 'tcx>,
679 fulfill_cx: &mut dyn TraitEngine<'tcx>,
681 let InferOk { value, obligations } = self;
682 fulfill_cx.register_predicate_obligations(infcx, obligations);
687 impl<'tcx> InferOk<'tcx, ()> {
688 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
693 #[must_use = "once you start a snapshot, you should always consume it"]
694 pub struct CombinedSnapshot<'a, 'tcx> {
695 undo_snapshot: Snapshot<'tcx>,
696 region_constraints_snapshot: RegionSnapshot,
697 universe: ty::UniverseIndex,
698 was_in_snapshot: bool,
699 _in_progress_typeck_results: Option<Ref<'a, ty::TypeckResults<'tcx>>>,
702 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
703 /// calls `tcx.try_unify_abstract_consts` after
704 /// canonicalizing the consts.
705 #[instrument(skip(self), level = "debug")]
706 pub fn try_unify_abstract_consts(
708 a: ty::UnevaluatedConst<'tcx>,
709 b: ty::UnevaluatedConst<'tcx>,
710 param_env: ty::ParamEnv<'tcx>,
712 // Reject any attempt to unify two unevaluated constants that contain inference
713 // variables, since inference variables in queries lead to ICEs.
714 if a.substs.has_infer_types_or_consts()
715 || b.substs.has_infer_types_or_consts()
716 || param_env.has_infer_types_or_consts()
718 debug!("a or b or param_env contain infer vars in its substs -> cannot unify");
722 let param_env_and = param_env.and((a, b));
723 let erased = self.tcx.erase_regions(param_env_and);
724 debug!("after erase_regions: {:?}", erased);
726 self.tcx.try_unify_abstract_consts(erased)
729 pub fn is_in_snapshot(&self) -> bool {
730 self.in_snapshot.get()
733 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
734 t.fold_with(&mut self.freshener())
737 /// Returns the origin of the type variable identified by `vid`, or `None`
738 /// if this is not a type variable.
740 /// No attempt is made to resolve `ty`.
741 pub fn type_var_origin(&'a self, ty: Ty<'tcx>) -> Option<TypeVariableOrigin> {
743 ty::Infer(ty::TyVar(vid)) => {
744 Some(*self.inner.borrow_mut().type_variables().var_origin(vid))
750 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
751 freshen::TypeFreshener::new(self, false)
754 /// Like `freshener`, but does not replace `'static` regions.
755 pub fn freshener_keep_static<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
756 freshen::TypeFreshener::new(self, true)
759 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
760 let mut inner = self.inner.borrow_mut();
761 let mut vars: Vec<Ty<'_>> = inner
763 .unsolved_variables()
765 .map(|t| self.tcx.mk_ty_var(t))
768 (0..inner.int_unification_table().len())
769 .map(|i| ty::IntVid { index: i as u32 })
770 .filter(|&vid| inner.int_unification_table().probe_value(vid).is_none())
771 .map(|v| self.tcx.mk_int_var(v)),
774 (0..inner.float_unification_table().len())
775 .map(|i| ty::FloatVid { index: i as u32 })
776 .filter(|&vid| inner.float_unification_table().probe_value(vid).is_none())
777 .map(|v| self.tcx.mk_float_var(v)),
784 trace: TypeTrace<'tcx>,
785 param_env: ty::ParamEnv<'tcx>,
786 define_opaque_types: bool,
787 ) -> CombineFields<'a, 'tcx> {
793 obligations: PredicateObligations::new(),
798 /// Clear the "currently in a snapshot" flag, invoke the closure,
799 /// then restore the flag to its original value. This flag is a
800 /// debugging measure designed to detect cases where we start a
801 /// snapshot, create type variables, and register obligations
802 /// which may involve those type variables in the fulfillment cx,
803 /// potentially leaving "dangling type variables" behind.
804 /// In such cases, an assertion will fail when attempting to
805 /// register obligations, within a snapshot. Very useful, much
806 /// better than grovelling through megabytes of `RUSTC_LOG` output.
808 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
809 /// sometimes create a "mini-fulfilment-cx" in which we enroll
810 /// obligations. As long as this fulfillment cx is fully drained
811 /// before we return, this is not a problem, as there won't be any
812 /// escaping obligations in the main cx. In those cases, you can
813 /// use this function.
814 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
816 F: FnOnce(&Self) -> R,
818 let flag = self.in_snapshot.replace(false);
819 let result = func(self);
820 self.in_snapshot.set(flag);
824 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
825 debug!("start_snapshot()");
827 let in_snapshot = self.in_snapshot.replace(true);
829 let mut inner = self.inner.borrow_mut();
832 undo_snapshot: inner.undo_log.start_snapshot(),
833 region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
834 universe: self.universe(),
835 was_in_snapshot: in_snapshot,
836 // Borrow typeck results "in progress" (i.e., during typeck)
837 // to ban writes from within a snapshot to them.
838 _in_progress_typeck_results: self
839 .in_progress_typeck_results
840 .map(|typeck_results| typeck_results.borrow()),
844 #[instrument(skip(self, snapshot), level = "debug")]
845 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
846 let CombinedSnapshot {
848 region_constraints_snapshot,
851 _in_progress_typeck_results,
854 self.in_snapshot.set(was_in_snapshot);
855 self.universe.set(universe);
857 let mut inner = self.inner.borrow_mut();
858 inner.rollback_to(undo_snapshot);
859 inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
862 #[instrument(skip(self, snapshot), level = "debug")]
863 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
864 let CombinedSnapshot {
866 region_constraints_snapshot: _,
869 _in_progress_typeck_results,
872 self.in_snapshot.set(was_in_snapshot);
874 self.inner.borrow_mut().commit(undo_snapshot);
877 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
878 #[instrument(skip(self, f), level = "debug")]
879 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
881 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
883 let snapshot = self.start_snapshot();
884 let r = f(&snapshot);
885 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
888 self.commit_from(snapshot);
891 self.rollback_to("commit_if_ok -- error", snapshot);
897 /// Execute `f` then unroll any bindings it creates.
898 #[instrument(skip(self, f), level = "debug")]
899 pub fn probe<R, F>(&self, f: F) -> R
901 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
903 let snapshot = self.start_snapshot();
904 let r = f(&snapshot);
905 self.rollback_to("probe", snapshot);
909 /// If `should_skip` is true, then execute `f` then unroll any bindings it creates.
910 #[instrument(skip(self, f), level = "debug")]
911 pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R
913 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
915 let snapshot = self.start_snapshot();
916 let was_skip_leak_check = self.skip_leak_check.get();
918 self.skip_leak_check.set(true);
920 let r = f(&snapshot);
921 self.rollback_to("probe", snapshot);
922 self.skip_leak_check.set(was_skip_leak_check);
926 /// Scan the constraints produced since `snapshot` began and returns:
928 /// - `None` -- if none of them involve "region outlives" constraints
929 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
930 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
931 pub fn region_constraints_added_in_snapshot(
933 snapshot: &CombinedSnapshot<'a, 'tcx>,
937 .unwrap_region_constraints()
938 .region_constraints_added_in_snapshot(&snapshot.undo_snapshot)
941 pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'a, 'tcx>) -> bool {
942 self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot)
945 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
946 self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
949 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
951 T: at::ToTrace<'tcx>,
953 let origin = &ObligationCause::dummy();
955 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
956 // Ignore obligations, since we are unrolling
957 // everything anyway.
962 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
964 T: at::ToTrace<'tcx>,
966 let origin = &ObligationCause::dummy();
968 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
969 // Ignore obligations, since we are unrolling
970 // everything anyway.
975 #[instrument(skip(self), level = "debug")]
978 origin: SubregionOrigin<'tcx>,
982 self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
985 /// Require that the region `r` be equal to one of the regions in
986 /// the set `regions`.
987 #[instrument(skip(self), level = "debug")]
988 pub fn member_constraint(
990 key: ty::OpaqueTypeKey<'tcx>,
991 definition_span: Span,
993 region: ty::Region<'tcx>,
994 in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
996 self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
1005 /// Processes a `Coerce` predicate from the fulfillment context.
1006 /// This is NOT the preferred way to handle coercion, which is to
1007 /// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`).
1009 /// This method here is actually a fallback that winds up being
1010 /// invoked when `FnCtxt::coerce` encounters unresolved type variables
1011 /// and records a coercion predicate. Presently, this method is equivalent
1012 /// to `subtype_predicate` -- that is, "coercing" `a` to `b` winds up
1013 /// actually requiring `a <: b`. This is of course a valid coercion,
1014 /// but it's not as flexible as `FnCtxt::coerce` would be.
1016 /// (We may refactor this in the future, but there are a number of
1017 /// practical obstacles. Among other things, `FnCtxt::coerce` presently
1018 /// records adjustments that are required on the HIR in order to perform
1019 /// the coercion, and we don't currently have a way to manage that.)
1020 pub fn coerce_predicate(
1022 cause: &ObligationCause<'tcx>,
1023 param_env: ty::ParamEnv<'tcx>,
1024 predicate: ty::PolyCoercePredicate<'tcx>,
1025 ) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
1026 let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate {
1027 a_is_expected: false, // when coercing from `a` to `b`, `b` is expected
1031 self.subtype_predicate(cause, param_env, subtype_predicate)
1034 pub fn subtype_predicate(
1036 cause: &ObligationCause<'tcx>,
1037 param_env: ty::ParamEnv<'tcx>,
1038 predicate: ty::PolySubtypePredicate<'tcx>,
1039 ) -> Result<InferResult<'tcx, ()>, (TyVid, TyVid)> {
1040 // Check for two unresolved inference variables, in which case we can
1041 // make no progress. This is partly a micro-optimization, but it's
1042 // also an opportunity to "sub-unify" the variables. This isn't
1043 // *necessary* to prevent cycles, because they would eventually be sub-unified
1044 // anyhow during generalization, but it helps with diagnostics (we can detect
1045 // earlier that they are sub-unified).
1047 // Note that we can just skip the binders here because
1048 // type variables can't (at present, at
1049 // least) capture any of the things bound by this binder.
1051 // Note that this sub here is not just for diagnostics - it has semantic
1053 let r_a = self.shallow_resolve(predicate.skip_binder().a);
1054 let r_b = self.shallow_resolve(predicate.skip_binder().b);
1055 match (r_a.kind(), r_b.kind()) {
1056 (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => {
1057 self.inner.borrow_mut().type_variables().sub(a_vid, b_vid);
1058 return Err((a_vid, b_vid));
1063 Ok(self.commit_if_ok(|_snapshot| {
1064 let ty::SubtypePredicate { a_is_expected, a, b } =
1065 self.replace_bound_vars_with_placeholders(predicate);
1067 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
1073 pub fn region_outlives_predicate(
1075 cause: &traits::ObligationCause<'tcx>,
1076 predicate: ty::PolyRegionOutlivesPredicate<'tcx>,
1078 let ty::OutlivesPredicate(r_a, r_b) = self.replace_bound_vars_with_placeholders(predicate);
1080 SubregionOrigin::from_obligation_cause(cause, || RelateRegionParamBound(cause.span));
1081 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1084 /// Number of type variables created so far.
1085 pub fn num_ty_vars(&self) -> usize {
1086 self.inner.borrow_mut().type_variables().num_vars()
1089 pub fn next_ty_var_id(&self, origin: TypeVariableOrigin) -> TyVid {
1090 self.inner.borrow_mut().type_variables().new_var(self.universe(), origin)
1093 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1094 self.tcx.mk_ty_var(self.next_ty_var_id(origin))
1097 pub fn next_ty_var_id_in_universe(
1099 origin: TypeVariableOrigin,
1100 universe: ty::UniverseIndex,
1102 self.inner.borrow_mut().type_variables().new_var(universe, origin)
1105 pub fn next_ty_var_in_universe(
1107 origin: TypeVariableOrigin,
1108 universe: ty::UniverseIndex,
1110 let vid = self.next_ty_var_id_in_universe(origin, universe);
1111 self.tcx.mk_ty_var(vid)
1114 pub fn next_const_var(&self, ty: Ty<'tcx>, origin: ConstVariableOrigin) -> ty::Const<'tcx> {
1115 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1118 pub fn next_const_var_in_universe(
1121 origin: ConstVariableOrigin,
1122 universe: ty::UniverseIndex,
1123 ) -> ty::Const<'tcx> {
1127 .const_unification_table()
1128 .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
1129 self.tcx.mk_const_var(vid, ty)
1132 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1133 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1135 val: ConstVariableValue::Unknown { universe: self.universe() },
1139 fn next_int_var_id(&self) -> IntVid {
1140 self.inner.borrow_mut().int_unification_table().new_key(None)
1143 pub fn next_int_var(&self) -> Ty<'tcx> {
1144 self.tcx.mk_int_var(self.next_int_var_id())
1147 fn next_float_var_id(&self) -> FloatVid {
1148 self.inner.borrow_mut().float_unification_table().new_key(None)
1151 pub fn next_float_var(&self) -> Ty<'tcx> {
1152 self.tcx.mk_float_var(self.next_float_var_id())
1155 /// Creates a fresh region variable with the next available index.
1156 /// The variable will be created in the maximum universe created
1157 /// thus far, allowing it to name any region created thus far.
1158 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1159 self.next_region_var_in_universe(origin, self.universe())
1162 /// Creates a fresh region variable with the next available index
1163 /// in the given universe; typically, you can use
1164 /// `next_region_var` and just use the maximal universe.
1165 pub fn next_region_var_in_universe(
1167 origin: RegionVariableOrigin,
1168 universe: ty::UniverseIndex,
1169 ) -> ty::Region<'tcx> {
1171 self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
1172 self.tcx.mk_region(ty::ReVar(region_var))
1175 /// Return the universe that the region `r` was created in. For
1176 /// most regions (e.g., `'static`, named regions from the user,
1177 /// etc) this is the root universe U0. For inference variables or
1178 /// placeholders, however, it will return the universe which which
1179 /// they are associated.
1180 pub fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
1181 self.inner.borrow_mut().unwrap_region_constraints().universe(r)
1184 /// Number of region variables created so far.
1185 pub fn num_region_vars(&self) -> usize {
1186 self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
1189 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1190 pub fn next_nll_region_var(&self, origin: NllRegionVariableOrigin) -> ty::Region<'tcx> {
1191 self.next_region_var(RegionVariableOrigin::Nll(origin))
1194 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1195 pub fn next_nll_region_var_in_universe(
1197 origin: NllRegionVariableOrigin,
1198 universe: ty::UniverseIndex,
1199 ) -> ty::Region<'tcx> {
1200 self.next_region_var_in_universe(RegionVariableOrigin::Nll(origin), universe)
1203 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
1205 GenericParamDefKind::Lifetime => {
1206 // Create a region inference variable for the given
1207 // region parameter definition.
1208 self.next_region_var(EarlyBoundRegion(span, param.name)).into()
1210 GenericParamDefKind::Type { .. } => {
1211 // Create a type inference variable for the given
1212 // type parameter definition. The substitutions are
1213 // for actual parameters that may be referred to by
1214 // the default of this type parameter, if it exists.
1215 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1216 // used in a path such as `Foo::<T, U>::new()` will
1217 // use an inference variable for `C` with `[T, U]`
1218 // as the substitutions for the default, `(T, U)`.
1219 let ty_var_id = self.inner.borrow_mut().type_variables().new_var(
1221 TypeVariableOrigin {
1222 kind: TypeVariableOriginKind::TypeParameterDefinition(
1230 self.tcx.mk_ty_var(ty_var_id).into()
1232 GenericParamDefKind::Const { .. } => {
1233 let origin = ConstVariableOrigin {
1234 kind: ConstVariableOriginKind::ConstParameterDefinition(
1241 self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue {
1243 val: ConstVariableValue::Unknown { universe: self.universe() },
1245 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1250 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1251 /// type/region parameter to a fresh inference variable.
1252 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1253 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1256 /// Returns `true` if errors have been reported since this infcx was
1257 /// created. This is sometimes used as a heuristic to skip
1258 /// reporting errors that often occur as a result of earlier
1259 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1260 /// inference variables, regionck errors).
1261 pub fn is_tainted_by_errors(&self) -> bool {
1263 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1264 tainted_by_errors={})",
1265 self.tcx.sess.err_count(),
1266 self.err_count_on_creation,
1267 self.tainted_by_errors.get().is_some()
1270 if self.tcx.sess.err_count() > self.err_count_on_creation {
1271 return true; // errors reported since this infcx was made
1273 self.tainted_by_errors.get().is_some()
1276 /// Set the "tainted by errors" flag to true. We call this when we
1277 /// observe an error from a prior pass.
1278 pub fn set_tainted_by_errors(&self) {
1279 debug!("set_tainted_by_errors()");
1280 self.tainted_by_errors.set(Some(
1281 self.tcx.sess.delay_span_bug(DUMMY_SP, "`InferCtxt` incorrectly tainted by errors"),
1285 pub fn skip_region_resolution(&self) {
1286 let (var_infos, _) = {
1287 let mut inner = self.inner.borrow_mut();
1288 let inner = &mut *inner;
1289 // Note: `inner.region_obligations` may not be empty, because we
1290 // didn't necessarily call `process_registered_region_obligations`.
1291 // This is okay, because that doesn't introduce new vars.
1293 .region_constraint_storage
1295 .expect("regions already resolved")
1296 .with_log(&mut inner.undo_log)
1297 .into_infos_and_data()
1300 let lexical_region_resolutions = LexicalRegionResolutions {
1301 values: rustc_index::vec::IndexVec::from_elem_n(
1302 crate::infer::lexical_region_resolve::VarValue::Value(self.tcx.lifetimes.re_erased),
1307 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1308 assert!(old_value.is_none());
1311 /// Process the region constraints and return any any errors that
1312 /// result. After this, no more unification operations should be
1313 /// done -- or the compiler will panic -- but it is legal to use
1314 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1315 pub fn resolve_regions(
1317 outlives_env: &OutlivesEnvironment<'tcx>,
1318 ) -> Vec<RegionResolutionError<'tcx>> {
1319 let (var_infos, data) = {
1320 let mut inner = self.inner.borrow_mut();
1321 let inner = &mut *inner;
1323 self.is_tainted_by_errors() || inner.region_obligations.is_empty(),
1324 "region_obligations not empty: {:#?}",
1325 inner.region_obligations
1328 .region_constraint_storage
1330 .expect("regions already resolved")
1331 .with_log(&mut inner.undo_log)
1332 .into_infos_and_data()
1335 let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map());
1337 let (lexical_region_resolutions, errors) =
1338 lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data);
1340 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1341 assert!(old_value.is_none());
1346 /// Process the region constraints and report any errors that
1347 /// result. After this, no more unification operations should be
1348 /// done -- or the compiler will panic -- but it is legal to use
1349 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1351 /// Make sure to call [`InferCtxt::process_registered_region_obligations`]
1352 /// first, or preferably use [`InferCtxt::check_region_obligations_and_report_errors`]
1353 /// to do both of these operations together.
1354 pub fn resolve_regions_and_report_errors(
1356 generic_param_scope: LocalDefId,
1357 outlives_env: &OutlivesEnvironment<'tcx>,
1359 let errors = self.resolve_regions(outlives_env);
1361 if !self.is_tainted_by_errors() {
1362 // As a heuristic, just skip reporting region errors
1363 // altogether if other errors have been reported while
1364 // this infcx was in use. This is totally hokey but
1365 // otherwise we have a hard time separating legit region
1366 // errors from silly ones.
1367 self.report_region_errors(generic_param_scope, &errors);
1371 /// Obtains (and clears) the current set of region
1372 /// constraints. The inference context is still usable: further
1373 /// unifications will simply add new constraints.
1375 /// This method is not meant to be used with normal lexical region
1376 /// resolution. Rather, it is used in the NLL mode as a kind of
1377 /// interim hack: basically we run normal type-check and generate
1378 /// region constraints as normal, but then we take them and
1379 /// translate them into the form that the NLL solver
1380 /// understands. See the NLL module for mode details.
1381 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1383 self.inner.borrow().region_obligations.is_empty(),
1384 "region_obligations not empty: {:#?}",
1385 self.inner.borrow().region_obligations
1388 self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data()
1391 /// Gives temporary access to the region constraint data.
1392 pub fn with_region_constraints<R>(
1394 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1396 let mut inner = self.inner.borrow_mut();
1397 op(inner.unwrap_region_constraints().data())
1400 pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin {
1401 let mut inner = self.inner.borrow_mut();
1402 let inner = &mut *inner;
1404 .region_constraint_storage
1406 .expect("regions already resolved")
1407 .with_log(&mut inner.undo_log)
1411 /// Takes ownership of the list of variable regions. This implies
1412 /// that all the region constraints have already been taken, and
1413 /// hence that `resolve_regions_and_report_errors` can never be
1414 /// called. This is used only during NLL processing to "hand off" ownership
1415 /// of the set of region variables into the NLL region context.
1416 pub fn take_region_var_origins(&self) -> VarInfos {
1417 let mut inner = self.inner.borrow_mut();
1418 let (var_infos, data) = inner
1419 .region_constraint_storage
1421 .expect("regions already resolved")
1422 .with_log(&mut inner.undo_log)
1423 .into_infos_and_data();
1424 assert!(data.is_empty());
1428 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1429 self.resolve_vars_if_possible(t).to_string()
1432 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1433 /// universe index of `TyVar(vid)`.
1434 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1435 use self::type_variable::TypeVariableValue;
1437 match self.inner.borrow_mut().type_variables().probe(vid) {
1438 TypeVariableValue::Known { value } => Ok(value),
1439 TypeVariableValue::Unknown { universe } => Err(universe),
1443 /// Resolve any type variables found in `value` -- but only one
1444 /// level. So, if the variable `?X` is bound to some type
1445 /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
1446 /// itself be bound to a type).
1448 /// Useful when you only need to inspect the outermost level of
1449 /// the type and don't care about nested types (or perhaps you
1450 /// will be resolving them as well, e.g. in a loop).
1451 pub fn shallow_resolve<T>(&self, value: T) -> T
1453 T: TypeFoldable<'tcx>,
1455 value.fold_with(&mut ShallowResolver { infcx: self })
1458 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1459 self.inner.borrow_mut().type_variables().root_var(var)
1462 /// Where possible, replaces type/const variables in
1463 /// `value` with their final value. Note that region variables
1464 /// are unaffected. If a type/const variable has not been unified, it
1465 /// is left as is. This is an idempotent operation that does
1466 /// not affect inference state in any way and so you can do it
1468 pub fn resolve_vars_if_possible<T>(&self, value: T) -> T
1470 T: TypeFoldable<'tcx>,
1472 if !value.needs_infer() {
1473 return value; // Avoid duplicated subst-folding.
1475 let mut r = resolve::OpportunisticVarResolver::new(self);
1476 value.fold_with(&mut r)
1479 pub fn resolve_numeric_literals_with_default<T>(&self, value: T) -> T
1481 T: TypeFoldable<'tcx>,
1483 if !value.needs_infer() {
1484 return value; // Avoid duplicated subst-folding.
1486 let mut r = InferenceLiteralEraser { tcx: self.tcx };
1487 value.fold_with(&mut r)
1490 /// Returns the first unresolved variable contained in `T`. In the
1491 /// process of visiting `T`, this will resolve (where possible)
1492 /// type variables in `T`, but it never constructs the final,
1493 /// resolved type, so it's more efficient than
1494 /// `resolve_vars_if_possible()`.
1495 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1497 T: TypeVisitable<'tcx>,
1499 value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value()
1502 pub fn probe_const_var(
1504 vid: ty::ConstVid<'tcx>,
1505 ) -> Result<ty::Const<'tcx>, ty::UniverseIndex> {
1506 match self.inner.borrow_mut().const_unification_table().probe_value(vid).val {
1507 ConstVariableValue::Known { value } => Ok(value),
1508 ConstVariableValue::Unknown { universe } => Err(universe),
1512 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: T) -> FixupResult<'tcx, T> {
1514 * Attempts to resolve all type/region/const variables in
1515 * `value`. Region inference must have been run already (e.g.,
1516 * by calling `resolve_regions_and_report_errors`). If some
1517 * variable was never unified, an `Err` results.
1519 * This method is idempotent, but it not typically not invoked
1520 * except during the writeback phase.
1523 resolve::fully_resolve(self, value)
1526 // [Note-Type-error-reporting]
1527 // An invariant is that anytime the expected or actual type is Error (the special
1528 // error type, meaning that an error occurred when typechecking this expression),
1529 // this is a derived error. The error cascaded from another error (that was already
1530 // reported), so it's not useful to display it to the user.
1531 // The following methods implement this logic.
1532 // They check if either the actual or expected type is Error, and don't print the error
1533 // in this case. The typechecker should only ever report type errors involving mismatched
1534 // types using one of these methods, and should not call span_err directly for such
1537 pub fn type_error_struct_with_diag<M>(
1541 actual_ty: Ty<'tcx>,
1542 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>
1544 M: FnOnce(String) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>,
1546 let actual_ty = self.resolve_vars_if_possible(actual_ty);
1547 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1549 let mut err = mk_diag(self.ty_to_string(actual_ty));
1551 // Don't report an error if actual type is `Error`.
1552 if actual_ty.references_error() {
1553 err.downgrade_to_delayed_bug();
1559 pub fn report_mismatched_types(
1561 cause: &ObligationCause<'tcx>,
1564 err: TypeError<'tcx>,
1565 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1566 self.report_and_explain_type_error(TypeTrace::types(cause, true, expected, actual), err)
1569 pub fn report_mismatched_consts(
1571 cause: &ObligationCause<'tcx>,
1572 expected: ty::Const<'tcx>,
1573 actual: ty::Const<'tcx>,
1574 err: TypeError<'tcx>,
1575 ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> {
1576 self.report_and_explain_type_error(TypeTrace::consts(cause, true, expected, actual), err)
1579 pub fn replace_bound_vars_with_fresh_vars<T>(
1582 lbrct: LateBoundRegionConversionTime,
1583 value: ty::Binder<'tcx, T>,
1586 T: TypeFoldable<'tcx> + Copy,
1588 if let Some(inner) = value.no_bound_vars() {
1592 struct ToFreshVars<'a, 'tcx> {
1593 infcx: &'a InferCtxt<'a, 'tcx>,
1595 lbrct: LateBoundRegionConversionTime,
1596 map: FxHashMap<ty::BoundVar, ty::GenericArg<'tcx>>,
1599 impl<'tcx> BoundVarReplacerDelegate<'tcx> for ToFreshVars<'_, 'tcx> {
1600 fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> {
1603 .or_insert_with(|| {
1605 .next_region_var(LateBoundRegion(self.span, br.kind, self.lbrct))
1610 fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> {
1613 .or_insert_with(|| {
1615 .next_ty_var(TypeVariableOrigin {
1616 kind: TypeVariableOriginKind::MiscVariable,
1623 fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> {
1626 .or_insert_with(|| {
1630 ConstVariableOrigin {
1631 kind: ConstVariableOriginKind::MiscVariable,
1640 let delegate = ToFreshVars { infcx: self, span, lbrct, map: Default::default() };
1641 self.tcx.replace_bound_vars_uncached(value, delegate)
1644 /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method.
1645 pub fn verify_generic_bound(
1647 origin: SubregionOrigin<'tcx>,
1648 kind: GenericKind<'tcx>,
1649 a: ty::Region<'tcx>,
1650 bound: VerifyBound<'tcx>,
1652 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1656 .unwrap_region_constraints()
1657 .verify_generic_bound(origin, kind, a, bound);
1660 /// Obtains the latest type of the given closure; this may be a
1661 /// closure in the current function, in which case its
1662 /// `ClosureKind` may not yet be known.
1663 pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
1664 let closure_kind_ty = closure_substs.as_closure().kind_ty();
1665 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1666 closure_kind_ty.to_opt_closure_kind()
1669 /// Clears the selection, evaluation, and projection caches. This is useful when
1670 /// repeatedly attempting to select an `Obligation` while changing only
1671 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1672 pub fn clear_caches(&self) {
1673 self.selection_cache.clear();
1674 self.evaluation_cache.clear();
1675 self.inner.borrow_mut().projection_cache().clear();
1678 pub fn universe(&self) -> ty::UniverseIndex {
1682 /// Creates and return a fresh universe that extends all previous
1683 /// universes. Updates `self.universe` to that new universe.
1684 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1685 let u = self.universe.get().next_universe();
1686 self.universe.set(u);
1690 pub fn try_const_eval_resolve(
1692 param_env: ty::ParamEnv<'tcx>,
1693 unevaluated: ty::UnevaluatedConst<'tcx>,
1696 ) -> Result<ty::Const<'tcx>, ErrorHandled> {
1697 match self.const_eval_resolve(param_env, unevaluated, span) {
1698 Ok(Some(val)) => Ok(ty::Const::from_value(self.tcx, val, ty)),
1701 let def_id = unevaluated.def.did;
1703 tcx.def_span(def_id),
1704 "unable to construct a constant value for the unevaluated constant {:?}",
1708 Err(err) => Err(err),
1712 /// Resolves and evaluates a constant.
1714 /// The constant can be located on a trait like `<A as B>::C`, in which case the given
1715 /// substitutions and environment are used to resolve the constant. Alternatively if the
1716 /// constant has generic parameters in scope the substitutions are used to evaluate the value of
1717 /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
1718 /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
1719 /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
1722 /// This handles inferences variables within both `param_env` and `substs` by
1723 /// performing the operation on their respective canonical forms.
1724 #[instrument(skip(self), level = "debug")]
1725 pub fn const_eval_resolve(
1727 mut param_env: ty::ParamEnv<'tcx>,
1728 unevaluated: ty::UnevaluatedConst<'tcx>,
1730 ) -> EvalToValTreeResult<'tcx> {
1731 let mut substs = self.resolve_vars_if_possible(unevaluated.substs);
1734 // Postpone the evaluation of constants whose substs depend on inference
1736 if substs.has_infer_types_or_consts() {
1737 let ac = AbstractConst::new(self.tcx, unevaluated);
1740 substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did);
1741 param_env = self.tcx.param_env(unevaluated.def.did);
1744 if ct.unify_failure_kind(self.tcx) == FailureKind::Concrete {
1745 substs = replace_param_and_infer_substs_with_placeholder(self.tcx, substs);
1747 return Err(ErrorHandled::TooGeneric);
1750 Err(guar) => return Err(ErrorHandled::Reported(guar)),
1754 let param_env_erased = self.tcx.erase_regions(param_env);
1755 let substs_erased = self.tcx.erase_regions(substs);
1756 debug!(?param_env_erased);
1757 debug!(?substs_erased);
1759 let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, substs: substs_erased };
1761 // The return value is the evaluated value which doesn't contain any reference to inference
1762 // variables, thus we don't need to substitute back the original values.
1763 self.tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span)
1766 /// `ty_or_const_infer_var_changed` is equivalent to one of these two:
1767 /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
1768 /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
1770 /// However, `ty_or_const_infer_var_changed` is more efficient. It's always
1771 /// inlined, despite being large, because it has only two call sites that
1772 /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
1773 /// inference variables), and it handles both `Ty` and `ty::Const` without
1774 /// having to resort to storing full `GenericArg`s in `stalled_on`.
1776 pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
1778 TyOrConstInferVar::Ty(v) => {
1779 use self::type_variable::TypeVariableValue;
1781 // If `inlined_probe` returns a `Known` value, it never equals
1782 // `ty::Infer(ty::TyVar(v))`.
1783 match self.inner.borrow_mut().type_variables().inlined_probe(v) {
1784 TypeVariableValue::Unknown { .. } => false,
1785 TypeVariableValue::Known { .. } => true,
1789 TyOrConstInferVar::TyInt(v) => {
1790 // If `inlined_probe_value` returns a value it's always a
1791 // `ty::Int(_)` or `ty::UInt(_)`, which never matches a
1793 self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_some()
1796 TyOrConstInferVar::TyFloat(v) => {
1797 // If `probe_value` returns a value it's always a
1798 // `ty::Float(_)`, which never matches a `ty::Infer(_)`.
1800 // Not `inlined_probe_value(v)` because this call site is colder.
1801 self.inner.borrow_mut().float_unification_table().probe_value(v).is_some()
1804 TyOrConstInferVar::Const(v) => {
1805 // If `probe_value` returns a `Known` value, it never equals
1806 // `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
1808 // Not `inlined_probe_value(v)` because this call site is colder.
1809 match self.inner.borrow_mut().const_unification_table().probe_value(v).val {
1810 ConstVariableValue::Unknown { .. } => false,
1811 ConstVariableValue::Known { .. } => true,
1818 /// Helper for `ty_or_const_infer_var_changed` (see comment on that), currently
1819 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
1820 #[derive(Copy, Clone, Debug)]
1821 pub enum TyOrConstInferVar<'tcx> {
1822 /// Equivalent to `ty::Infer(ty::TyVar(_))`.
1824 /// Equivalent to `ty::Infer(ty::IntVar(_))`.
1826 /// Equivalent to `ty::Infer(ty::FloatVar(_))`.
1829 /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
1830 Const(ConstVid<'tcx>),
1833 impl<'tcx> TyOrConstInferVar<'tcx> {
1834 /// Tries to extract an inference variable from a type or a constant, returns `None`
1835 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
1836 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1837 pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
1838 match arg.unpack() {
1839 GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
1840 GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
1841 GenericArgKind::Lifetime(_) => None,
1845 /// Tries to extract an inference variable from a type, returns `None`
1846 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
1847 fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
1849 ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
1850 ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
1851 ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
1856 /// Tries to extract an inference variable from a constant, returns `None`
1857 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1858 fn maybe_from_const(ct: ty::Const<'tcx>) -> Option<Self> {
1860 ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
1866 /// Replace `{integer}` with `i32` and `{float}` with `f64`.
1867 /// Used only for diagnostics.
1868 struct InferenceLiteralEraser<'tcx> {
1872 impl<'tcx> TypeFolder<'tcx> for InferenceLiteralEraser<'tcx> {
1873 fn tcx(&self) -> TyCtxt<'tcx> {
1877 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1879 ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32,
1880 ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64,
1881 _ => ty.super_fold_with(self),
1886 struct ShallowResolver<'a, 'tcx> {
1887 infcx: &'a InferCtxt<'a, 'tcx>,
1890 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
1891 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1895 /// If `ty` is a type variable of some kind, resolve it one level
1896 /// (but do not resolve types found in the result). If `typ` is
1897 /// not a type variable, just return it unmodified.
1898 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1900 ty::Infer(ty::TyVar(v)) => {
1901 // Not entirely obvious: if `typ` is a type variable,
1902 // it can be resolved to an int/float variable, which
1903 // can then be recursively resolved, hence the
1904 // recursion. Note though that we prevent type
1905 // variables from unifying to other type variables
1906 // directly (though they may be embedded
1907 // structurally), and we prevent cycles in any case,
1908 // so this recursion should always be of very limited
1911 // Note: if these two lines are combined into one we get
1912 // dynamic borrow errors on `self.inner`.
1913 let known = self.infcx.inner.borrow_mut().type_variables().probe(v).known();
1914 known.map_or(ty, |t| self.fold_ty(t))
1917 ty::Infer(ty::IntVar(v)) => self
1921 .int_unification_table()
1923 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1925 ty::Infer(ty::FloatVar(v)) => self
1929 .float_unification_table()
1931 .map_or(ty, |v| v.to_type(self.infcx.tcx)),
1937 fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> {
1938 if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() {
1942 .const_unification_table()
1953 impl<'tcx> TypeTrace<'tcx> {
1954 pub fn span(&self) -> Span {
1959 cause: &ObligationCause<'tcx>,
1960 a_is_expected: bool,
1963 ) -> TypeTrace<'tcx> {
1965 cause: cause.clone(),
1966 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1970 pub fn poly_trait_refs(
1971 cause: &ObligationCause<'tcx>,
1972 a_is_expected: bool,
1973 a: ty::PolyTraitRef<'tcx>,
1974 b: ty::PolyTraitRef<'tcx>,
1975 ) -> TypeTrace<'tcx> {
1977 cause: cause.clone(),
1978 values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1983 cause: &ObligationCause<'tcx>,
1984 a_is_expected: bool,
1987 ) -> TypeTrace<'tcx> {
1989 cause: cause.clone(),
1990 values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())),
1995 impl<'tcx> SubregionOrigin<'tcx> {
1996 pub fn span(&self) -> Span {
1998 Subtype(ref a) => a.span(),
1999 RelateObjectBound(a) => a,
2000 RelateParamBound(a, ..) => a,
2001 RelateRegionParamBound(a) => a,
2003 ReborrowUpvar(a, _) => a,
2004 DataBorrowed(_, a) => a,
2005 ReferenceOutlivesReferent(_, a) => a,
2006 CompareImplItemObligation { span, .. } => span,
2007 AscribeUserTypeProvePredicate(span) => span,
2008 CheckAssociatedTypeBounds { ref parent, .. } => parent.span(),
2012 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
2014 F: FnOnce() -> Self,
2016 match *cause.code() {
2017 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
2018 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
2021 traits::ObligationCauseCode::CompareImplItemObligation {
2025 } => SubregionOrigin::CompareImplItemObligation {
2031 traits::ObligationCauseCode::CheckAssociatedTypeBounds {
2034 } => SubregionOrigin::CheckAssociatedTypeBounds {
2037 parent: Box::new(default()),
2040 traits::ObligationCauseCode::AscribeUserTypeProvePredicate(span) => {
2041 SubregionOrigin::AscribeUserTypeProvePredicate(span)
2049 impl RegionVariableOrigin {
2050 pub fn span(&self) -> Span {
2057 | EarlyBoundRegion(a, ..)
2058 | LateBoundRegion(a, ..)
2059 | UpvarRegion(_, a) => a,
2060 Nll(..) => bug!("NLL variable used with `span`"),
2065 /// Replaces substs that reference param or infer variables with suitable
2066 /// placeholders. This function is meant to remove these param and infer
2067 /// substs when they're not actually needed to evaluate a constant.
2068 fn replace_param_and_infer_substs_with_placeholder<'tcx>(
2070 substs: SubstsRef<'tcx>,
2071 ) -> SubstsRef<'tcx> {
2072 tcx.mk_substs(substs.iter().enumerate().map(|(idx, arg)| {
2073 match arg.unpack() {
2074 GenericArgKind::Type(_)
2075 if arg.has_param_types_or_consts() || arg.has_infer_types_or_consts() =>
2077 tcx.mk_ty(ty::Placeholder(ty::PlaceholderType {
2078 universe: ty::UniverseIndex::ROOT,
2079 name: ty::BoundVar::from_usize(idx),
2083 GenericArgKind::Const(ct)
2084 if ct.has_infer_types_or_consts() || ct.has_param_types_or_consts() =>
2087 // If the type references param or infer, replace that too...
2088 if ty.has_param_types_or_consts() || ty.has_infer_types_or_consts() {
2089 bug!("const `{ct}`'s type should not reference params or types");
2091 tcx.mk_const(ty::ConstS {
2093 kind: ty::ConstKind::Placeholder(ty::PlaceholderConst {
2094 universe: ty::UniverseIndex::ROOT,
2095 name: ty::BoundVar::from_usize(idx),