use std::cell::{Cell, RefCell}; use std::fmt; pub use at::DefineOpaqueTypes; use free_regions::RegionRelations; pub use freshen::TypeFreshener; use lexical_region_resolve::LexicalRegionResolutions; pub use lexical_region_resolve::RegionResolutionError; pub use opaque_types::{OpaqueTypeStorage, OpaqueTypeStorageEntries, OpaqueTypeTable}; use region_constraints::{ GenericKind, RegionConstraintCollector, RegionConstraintStorage, VarInfos, VerifyBound, }; pub use relate::StructurallyRelateAliases; pub use relate::combine::PredicateEmittingRelation; use rustc_data_structures::fx::{FxHashSet, FxIndexMap}; use rustc_data_structures::undo_log::{Rollback, UndoLogs}; use rustc_data_structures::unify as ut; use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed}; use rustc_hir as hir; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_macros::extension; pub use rustc_macros::{TypeFoldable, TypeVisitable}; use rustc_middle::bug; use rustc_middle::infer::canonical::{CanonicalQueryInput, CanonicalVarValues}; use rustc_middle::mir::ConstraintCategory; use rustc_middle::traits::select; use rustc_middle::traits::solve::Goal; use rustc_middle::ty::error::{ExpectedFound, TypeError}; use rustc_middle::ty::{ self, BoundVarReplacerDelegate, ConstVid, FloatVid, GenericArg, GenericArgKind, GenericArgs, GenericArgsRef, GenericParamDefKind, InferConst, IntVid, OpaqueHiddenType, OpaqueTypeKey, PseudoCanonicalInput, Term, TermKind, Ty, TyCtxt, TyVid, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitable, TypeVisitableExt, TypingEnv, TypingMode, fold_regions, }; use rustc_span::{DUMMY_SP, Span, Symbol}; use snapshot::undo_log::InferCtxtUndoLogs; use tracing::{debug, instrument}; use type_variable::TypeVariableOrigin; use crate::infer::snapshot::undo_log::UndoLog; use crate::infer::unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey}; use crate::traits::{ self, ObligationCause, ObligationInspector, PredicateObligation, PredicateObligations, TraitEngine, }; pub mod at; pub mod canonical; mod context; mod free_regions; mod freshen; mod lexical_region_resolve; mod opaque_types; pub mod outlives; mod projection; pub mod region_constraints; pub mod relate; pub mod resolve; pub(crate) mod snapshot; mod type_variable; mod unify_key; /// `InferOk<'tcx, ()>` is used a lot. It may seem like a useless wrapper /// around `PredicateObligations<'tcx>`, but it has one important property: /// because `InferOk` is marked with `#[must_use]`, if you have a method /// `InferCtxt::f` that returns `InferResult<'tcx, ()>` and you call it with /// `infcx.f()?;` you'll get a warning about the obligations being discarded /// without use, which is probably unintentional and has been a source of bugs /// in the past. #[must_use] #[derive(Debug)] pub struct InferOk<'tcx, T> { pub value: T, pub obligations: PredicateObligations<'tcx>, } pub type InferResult<'tcx, T> = Result, TypeError<'tcx>>; pub(crate) type FixupResult = Result; // "fixup result" pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable< ut::InPlace, &'a mut InferCtxtUndoLogs<'tcx>>, >; /// This type contains all the things within `InferCtxt` that sit within a /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot /// operations are hot enough that we want only one call to `borrow_mut` per /// call to `start_snapshot` and `rollback_to`. #[derive(Clone)] pub struct InferCtxtInner<'tcx> { undo_log: InferCtxtUndoLogs<'tcx>, /// Cache for projections. /// /// This cache is snapshotted along with the infcx. projection_cache: traits::ProjectionCacheStorage<'tcx>, /// We instantiate `UnificationTable` with `bounds` because the types /// that might instantiate a general type variable have an order, /// represented by its upper and lower bounds. type_variable_storage: type_variable::TypeVariableStorage<'tcx>, /// Map from const parameter variable to the kind of const it represents. const_unification_storage: ut::UnificationTableStorage>, /// Map from integral variable to the kind of integer it represents. int_unification_storage: ut::UnificationTableStorage, /// Map from floating variable to the kind of float it represents. float_unification_storage: ut::UnificationTableStorage, /// Tracks the set of region variables and the constraints between them. /// /// This is initially `Some(_)` but when /// `resolve_regions_and_report_errors` is invoked, this gets set to `None` /// -- further attempts to perform unification, etc., may fail if new /// region constraints would've been added. region_constraint_storage: Option>, /// A set of constraints that regionck must validate. /// /// Each constraint has the form `T:'a`, meaning "some type `T` must /// outlive the lifetime 'a". These constraints derive from /// instantiated type parameters. So if you had a struct defined /// like the following: /// ```ignore (illustrative) /// struct Foo { ... } /// ``` /// In some expression `let x = Foo { ... }`, it will /// instantiate the type parameter `T` with a fresh type `$0`. At /// the same time, it will record a region obligation of /// `$0: 'static`. This will get checked later by regionck. (We /// can't generally check these things right away because we have /// to wait until types are resolved.) /// /// These are stored in a map keyed to the id of the innermost /// enclosing fn body / static initializer expression. This is /// because the location where the obligation was incurred can be /// relevant with respect to which sublifetime assumptions are in /// place. The reason that we store under the fn-id, and not /// something more fine-grained, is so that it is easier for /// regionck to be sure that it has found *all* the region /// obligations (otherwise, it's easy to fail to walk to a /// particular node-id). /// /// Before running `resolve_regions_and_report_errors`, the creator /// of the inference context is expected to invoke /// [`InferCtxt::process_registered_region_obligations`] /// for each body-id in this map, which will process the /// obligations within. This is expected to be done 'late enough' /// that all type inference variables have been bound and so forth. region_obligations: Vec>, /// The outlives bounds that we assume must hold about placeholders that /// come from instantiating the binder of coroutine-witnesses. These bounds /// are deduced from the well-formedness of the witness's types, and are /// necessary because of the way we anonymize the regions in a coroutine, /// which may cause types to no longer be considered well-formed. region_assumptions: Vec>, /// `-Znext-solver`: Successfully proven goals during HIR typeck which /// reference inference variables and get reproven in case MIR type check /// fails to prove something. /// /// See the documentation of `InferCtxt::in_hir_typeck` for more details. hir_typeck_potentially_region_dependent_goals: Vec>, /// Caches for opaque type inference. opaque_type_storage: OpaqueTypeStorage<'tcx>, } impl<'tcx> InferCtxtInner<'tcx> { fn new() -> InferCtxtInner<'tcx> { InferCtxtInner { undo_log: InferCtxtUndoLogs::default(), projection_cache: Default::default(), type_variable_storage: Default::default(), const_unification_storage: Default::default(), int_unification_storage: Default::default(), float_unification_storage: Default::default(), region_constraint_storage: Some(Default::default()), region_obligations: Default::default(), region_assumptions: Default::default(), hir_typeck_potentially_region_dependent_goals: Default::default(), opaque_type_storage: Default::default(), } } #[inline] pub fn region_obligations(&self) -> &[TypeOutlivesConstraint<'tcx>] { &self.region_obligations } #[inline] pub fn region_assumptions(&self) -> &[ty::ArgOutlivesPredicate<'tcx>] { &self.region_assumptions } #[inline] pub fn projection_cache(&mut self) -> traits::ProjectionCache<'_, 'tcx> { self.projection_cache.with_log(&mut self.undo_log) } #[inline] fn try_type_variables_probe_ref( &self, vid: ty::TyVid, ) -> Option<&type_variable::TypeVariableValue<'tcx>> { // Uses a read-only view of the unification table, this way we don't // need an undo log. self.type_variable_storage.eq_relations_ref().try_probe_value(vid) } #[inline] fn type_variables(&mut self) -> type_variable::TypeVariableTable<'_, 'tcx> { self.type_variable_storage.with_log(&mut self.undo_log) } #[inline] pub fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'tcx> { self.opaque_type_storage.with_log(&mut self.undo_log) } #[inline] fn int_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::IntVid> { self.int_unification_storage.with_log(&mut self.undo_log) } #[inline] fn float_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ty::FloatVid> { self.float_unification_storage.with_log(&mut self.undo_log) } #[inline] fn const_unification_table(&mut self) -> UnificationTable<'_, 'tcx, ConstVidKey<'tcx>> { self.const_unification_storage.with_log(&mut self.undo_log) } #[inline] pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'_, 'tcx> { self.region_constraint_storage .as_mut() .expect("region constraints already solved") .with_log(&mut self.undo_log) } } pub struct InferCtxt<'tcx> { pub tcx: TyCtxt<'tcx>, /// The mode of this inference context, see the struct documentation /// for more details. typing_mode: TypingMode<'tcx>, /// Whether this inference context should care about region obligations in /// the root universe. Most notably, this is used during HIR typeck as region /// solving is left to borrowck instead. pub considering_regions: bool, /// `-Znext-solver`: Whether this inference context is used by HIR typeck. If so, we /// need to make sure we don't rely on region identity in the trait solver or when /// relating types. This is necessary as borrowck starts by replacing each occurrence of a /// free region with a unique inference variable. If HIR typeck ends up depending on two /// regions being equal we'd get unexpected mismatches between HIR typeck and MIR typeck, /// resulting in an ICE. /// /// The trait solver sometimes depends on regions being identical. As a concrete example /// the trait solver ignores other candidates if one candidate exists without any constraints. /// The goal `&'a u32: Equals<&'a u32>` has no constraints right now. If we replace each /// occurrence of `'a` with a unique region the goal now equates these regions. See /// the tests in trait-system-refactor-initiative#27 for concrete examples. /// /// We handle this by *uniquifying* region when canonicalizing root goals during HIR typeck. /// This is still insufficient as inference variables may *hide* region variables, so e.g. /// `dyn TwoSuper: Super` may hold but MIR typeck could end up having to prove /// `dyn TwoSuper<&'0 (), &'1 ()>: Super<&'2 ()>` which is now ambiguous. Because of this we /// stash all successfully proven goals which reference inference variables and then reprove /// them after writeback. pub in_hir_typeck: bool, /// If set, this flag causes us to skip the 'leak check' during /// higher-ranked subtyping operations. This flag is a temporary one used /// to manage the removal of the leak-check: for the time being, we still run the /// leak-check, but we issue warnings. skip_leak_check: bool, pub inner: RefCell>, /// Once region inference is done, the values for each variable. lexical_region_resolutions: RefCell>>, /// Caches the results of trait selection. This cache is used /// for things that depends on inference variables or placeholders. pub selection_cache: select::SelectionCache<'tcx, ty::ParamEnv<'tcx>>, /// Caches the results of trait evaluation. This cache is used /// for things that depends on inference variables or placeholders. pub evaluation_cache: select::EvaluationCache<'tcx, ty::ParamEnv<'tcx>>, /// The set of predicates on which errors have been reported, to /// avoid reporting the same error twice. pub reported_trait_errors: RefCell>>, ErrorGuaranteed)>>, pub reported_signature_mismatch: RefCell)>>, /// When an error occurs, we want to avoid reporting "derived" /// errors that are due to this original failure. We have this /// flag that one can set whenever one creates a type-error that /// is due to an error in a prior pass. /// /// Don't read this flag directly, call `is_tainted_by_errors()` /// and `set_tainted_by_errors()`. tainted_by_errors: Cell>, /// What is the innermost universe we have created? Starts out as /// `UniverseIndex::root()` but grows from there as we enter /// universal quantifiers. /// /// N.B., at present, we exclude the universal quantifiers on the /// item we are type-checking, and just consider those names as /// part of the root universe. So this would only get incremented /// when we enter into a higher-ranked (`for<..>`) type or trait /// bound. universe: Cell, next_trait_solver: bool, pub obligation_inspector: Cell>>, } /// See the `error_reporting` module for more details. #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)] pub enum ValuePairs<'tcx> { Regions(ExpectedFound>), Terms(ExpectedFound>), Aliases(ExpectedFound>), TraitRefs(ExpectedFound>), PolySigs(ExpectedFound>), ExistentialTraitRef(ExpectedFound>), ExistentialProjection(ExpectedFound>), } impl<'tcx> ValuePairs<'tcx> { pub fn ty(&self) -> Option<(Ty<'tcx>, Ty<'tcx>)> { if let ValuePairs::Terms(ExpectedFound { expected, found }) = self && let Some(expected) = expected.as_type() && let Some(found) = found.as_type() { Some((expected, found)) } else { None } } } /// The trace designates the path through inference that we took to /// encounter an error or subtyping constraint. /// /// See the `error_reporting` module for more details. #[derive(Clone, Debug)] pub struct TypeTrace<'tcx> { pub cause: ObligationCause<'tcx>, pub values: ValuePairs<'tcx>, } /// The origin of a `r1 <= r2` constraint. /// /// See `error_reporting` module for more details #[derive(Clone, Debug)] pub enum SubregionOrigin<'tcx> { /// Arose from a subtyping relation Subtype(Box>), /// When casting `&'a T` to an `&'b Trait` object, /// relating `'a` to `'b`. RelateObjectBound(Span), /// Some type parameter was instantiated with the given type, /// and that type must outlive some region. RelateParamBound(Span, Ty<'tcx>, Option), /// The given region parameter was instantiated with a region /// that must outlive some other region. RelateRegionParamBound(Span, Option>), /// Creating a pointer `b` to contents of another reference. Reborrow(Span), /// (&'a &'b T) where a >= b ReferenceOutlivesReferent(Ty<'tcx>, Span), /// Comparing the signature and requirements of an impl method against /// the containing trait. CompareImplItemObligation { span: Span, impl_item_def_id: LocalDefId, trait_item_def_id: DefId, }, /// Checking that the bounds of a trait's associated type hold for a given impl. CheckAssociatedTypeBounds { parent: Box>, impl_item_def_id: LocalDefId, trait_item_def_id: DefId, }, AscribeUserTypeProvePredicate(Span), } // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger. #[cfg(target_pointer_width = "64")] rustc_data_structures::static_assert_size!(SubregionOrigin<'_>, 32); impl<'tcx> SubregionOrigin<'tcx> { pub fn to_constraint_category(&self) -> ConstraintCategory<'tcx> { match self { Self::Subtype(type_trace) => type_trace.cause.to_constraint_category(), Self::AscribeUserTypeProvePredicate(span) => ConstraintCategory::Predicate(*span), _ => ConstraintCategory::BoringNoLocation, } } } /// Times when we replace bound regions with existentials: #[derive(Clone, Copy, Debug)] pub enum BoundRegionConversionTime { /// when a fn is called FnCall, /// when two higher-ranked types are compared HigherRankedType, /// when projecting an associated type AssocTypeProjection(DefId), } /// Reasons to create a region inference variable. /// /// See `error_reporting` module for more details. #[derive(Copy, Clone, Debug)] pub enum RegionVariableOrigin { /// Region variables created for ill-categorized reasons. /// /// They mostly indicate places in need of refactoring. Misc(Span), /// Regions created by a `&P` or `[...]` pattern. PatternRegion(Span), /// Regions created by `&` operator. BorrowRegion(Span), /// Regions created as part of an autoref of a method receiver. Autoref(Span), /// Regions created as part of an automatic coercion. Coercion(Span), /// Region variables created as the values for early-bound regions. /// /// FIXME(@lcnr): This should also store a `DefId`, similar to /// `TypeVariableOrigin`. RegionParameterDefinition(Span, Symbol), /// Region variables created when instantiating a binder with /// existential variables, e.g. when calling a function or method. BoundRegion(Span, ty::BoundRegionKind, BoundRegionConversionTime), UpvarRegion(ty::UpvarId, Span), /// This origin is used for the inference variables that we create /// during NLL region processing. Nll(NllRegionVariableOrigin), } #[derive(Copy, Clone, Debug)] pub enum NllRegionVariableOrigin { /// During NLL region processing, we create variables for free /// regions that we encounter in the function signature and /// elsewhere. This origin indices we've got one of those. FreeRegion, /// "Universal" instantiation of a higher-ranked region (e.g., /// from a `for<'a> T` binder). Meant to represent "any region". Placeholder(ty::PlaceholderRegion), Existential { name: Option, }, } #[derive(Copy, Clone, Debug)] pub struct FixupError { unresolved: TyOrConstInferVar, } impl fmt::Display for FixupError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match self.unresolved { TyOrConstInferVar::TyInt(_) => write!( f, "cannot determine the type of this integer; \ add a suffix to specify the type explicitly" ), TyOrConstInferVar::TyFloat(_) => write!( f, "cannot determine the type of this number; \ add a suffix to specify the type explicitly" ), TyOrConstInferVar::Ty(_) => write!(f, "unconstrained type"), TyOrConstInferVar::Const(_) => write!(f, "unconstrained const value"), } } } /// See the `region_obligations` field for more information. #[derive(Clone, Debug)] pub struct TypeOutlivesConstraint<'tcx> { pub sub_region: ty::Region<'tcx>, pub sup_type: Ty<'tcx>, pub origin: SubregionOrigin<'tcx>, } /// Used to configure inference contexts before their creation. pub struct InferCtxtBuilder<'tcx> { tcx: TyCtxt<'tcx>, considering_regions: bool, in_hir_typeck: bool, skip_leak_check: bool, /// Whether we should use the new trait solver in the local inference context, /// which affects things like which solver is used in `predicate_may_hold`. next_trait_solver: bool, } #[extension(pub trait TyCtxtInferExt<'tcx>)] impl<'tcx> TyCtxt<'tcx> { fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> { InferCtxtBuilder { tcx: self, considering_regions: true, in_hir_typeck: false, skip_leak_check: false, next_trait_solver: self.next_trait_solver_globally(), } } } impl<'tcx> InferCtxtBuilder<'tcx> { pub fn with_next_trait_solver(mut self, next_trait_solver: bool) -> Self { self.next_trait_solver = next_trait_solver; self } pub fn ignoring_regions(mut self) -> Self { self.considering_regions = false; self } pub fn in_hir_typeck(mut self) -> Self { self.in_hir_typeck = true; self } pub fn skip_leak_check(mut self, skip_leak_check: bool) -> Self { self.skip_leak_check = skip_leak_check; self } /// Given a canonical value `C` as a starting point, create an /// inference context that contains each of the bound values /// within instantiated as a fresh variable. The `f` closure is /// invoked with the new infcx, along with the instantiated value /// `V` and a instantiation `S`. This instantiation `S` maps from /// the bound values in `C` to their instantiated values in `V` /// (in other words, `S(C) = V`). pub fn build_with_canonical( mut self, span: Span, input: &CanonicalQueryInput<'tcx, T>, ) -> (InferCtxt<'tcx>, T, CanonicalVarValues<'tcx>) where T: TypeFoldable>, { let infcx = self.build(input.typing_mode); let (value, args) = infcx.instantiate_canonical(span, &input.canonical); (infcx, value, args) } pub fn build_with_typing_env( mut self, TypingEnv { typing_mode, param_env }: TypingEnv<'tcx>, ) -> (InferCtxt<'tcx>, ty::ParamEnv<'tcx>) { (self.build(typing_mode), param_env) } pub fn build(&mut self, typing_mode: TypingMode<'tcx>) -> InferCtxt<'tcx> { let InferCtxtBuilder { tcx, considering_regions, in_hir_typeck, skip_leak_check, next_trait_solver, } = *self; InferCtxt { tcx, typing_mode, considering_regions, in_hir_typeck, skip_leak_check, inner: RefCell::new(InferCtxtInner::new()), lexical_region_resolutions: RefCell::new(None), selection_cache: Default::default(), evaluation_cache: Default::default(), reported_trait_errors: Default::default(), reported_signature_mismatch: Default::default(), tainted_by_errors: Cell::new(None), universe: Cell::new(ty::UniverseIndex::ROOT), next_trait_solver, obligation_inspector: Cell::new(None), } } } impl<'tcx, T> InferOk<'tcx, T> { /// Extracts `value`, registering any obligations into `fulfill_cx`. pub fn into_value_registering_obligations( self, infcx: &InferCtxt<'tcx>, fulfill_cx: &mut dyn TraitEngine<'tcx, E>, ) -> T { let InferOk { value, obligations } = self; fulfill_cx.register_predicate_obligations(infcx, obligations); value } } impl<'tcx> InferOk<'tcx, ()> { pub fn into_obligations(self) -> PredicateObligations<'tcx> { self.obligations } } impl<'tcx> InferCtxt<'tcx> { pub fn dcx(&self) -> DiagCtxtHandle<'_> { self.tcx.dcx().taintable_handle(&self.tainted_by_errors) } pub fn next_trait_solver(&self) -> bool { self.next_trait_solver } #[inline(always)] pub fn typing_mode(&self) -> TypingMode<'tcx> { self.typing_mode } pub fn freshen>>(&self, t: T) -> T { t.fold_with(&mut self.freshener()) } /// Returns the origin of the type variable identified by `vid`. /// /// No attempt is made to resolve `vid` to its root variable. pub fn type_var_origin(&self, vid: TyVid) -> TypeVariableOrigin { self.inner.borrow_mut().type_variables().var_origin(vid) } /// Returns the origin of the const variable identified by `vid` // FIXME: We should store origins separately from the unification table // so this doesn't need to be optional. pub fn const_var_origin(&self, vid: ConstVid) -> Option { match self.inner.borrow_mut().const_unification_table().probe_value(vid) { ConstVariableValue::Known { .. } => None, ConstVariableValue::Unknown { origin, .. } => Some(origin), } } pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> { freshen::TypeFreshener::new(self) } pub fn unresolved_variables(&self) -> Vec> { let mut inner = self.inner.borrow_mut(); let mut vars: Vec> = inner .type_variables() .unresolved_variables() .into_iter() .map(|t| Ty::new_var(self.tcx, t)) .collect(); vars.extend( (0..inner.int_unification_table().len()) .map(|i| ty::IntVid::from_usize(i)) .filter(|&vid| inner.int_unification_table().probe_value(vid).is_unknown()) .map(|v| Ty::new_int_var(self.tcx, v)), ); vars.extend( (0..inner.float_unification_table().len()) .map(|i| ty::FloatVid::from_usize(i)) .filter(|&vid| inner.float_unification_table().probe_value(vid).is_unknown()) .map(|v| Ty::new_float_var(self.tcx, v)), ); vars } #[instrument(skip(self), level = "debug")] pub fn sub_regions( &self, origin: SubregionOrigin<'tcx>, a: ty::Region<'tcx>, b: ty::Region<'tcx>, ) { self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b); } /// Processes a `Coerce` predicate from the fulfillment context. /// This is NOT the preferred way to handle coercion, which is to /// invoke `FnCtxt::coerce` or a similar method (see `coercion.rs`). /// /// This method here is actually a fallback that winds up being /// invoked when `FnCtxt::coerce` encounters unresolved type variables /// and records a coercion predicate. Presently, this method is equivalent /// to `subtype_predicate` -- that is, "coercing" `a` to `b` winds up /// actually requiring `a <: b`. This is of course a valid coercion, /// but it's not as flexible as `FnCtxt::coerce` would be. /// /// (We may refactor this in the future, but there are a number of /// practical obstacles. Among other things, `FnCtxt::coerce` presently /// records adjustments that are required on the HIR in order to perform /// the coercion, and we don't currently have a way to manage that.) pub fn coerce_predicate( &self, cause: &ObligationCause<'tcx>, param_env: ty::ParamEnv<'tcx>, predicate: ty::PolyCoercePredicate<'tcx>, ) -> Result, (TyVid, TyVid)> { let subtype_predicate = predicate.map_bound(|p| ty::SubtypePredicate { a_is_expected: false, // when coercing from `a` to `b`, `b` is expected a: p.a, b: p.b, }); self.subtype_predicate(cause, param_env, subtype_predicate) } pub fn subtype_predicate( &self, cause: &ObligationCause<'tcx>, param_env: ty::ParamEnv<'tcx>, predicate: ty::PolySubtypePredicate<'tcx>, ) -> Result, (TyVid, TyVid)> { // Check for two unresolved inference variables, in which case we can // make no progress. This is partly a micro-optimization, but it's // also an opportunity to "sub-unify" the variables. This isn't // *necessary* to prevent cycles, because they would eventually be sub-unified // anyhow during generalization, but it helps with diagnostics (we can detect // earlier that they are sub-unified). // // Note that we can just skip the binders here because // type variables can't (at present, at // least) capture any of the things bound by this binder. // // Note that this sub here is not just for diagnostics - it has semantic // effects as well. let r_a = self.shallow_resolve(predicate.skip_binder().a); let r_b = self.shallow_resolve(predicate.skip_binder().b); match (r_a.kind(), r_b.kind()) { (&ty::Infer(ty::TyVar(a_vid)), &ty::Infer(ty::TyVar(b_vid))) => { self.sub_unify_ty_vids_raw(a_vid, b_vid); return Err((a_vid, b_vid)); } _ => {} } self.enter_forall(predicate, |ty::SubtypePredicate { a_is_expected, a, b }| { if a_is_expected { Ok(self.at(cause, param_env).sub(DefineOpaqueTypes::Yes, a, b)) } else { Ok(self.at(cause, param_env).sup(DefineOpaqueTypes::Yes, b, a)) } }) } /// Number of type variables created so far. pub fn num_ty_vars(&self) -> usize { self.inner.borrow_mut().type_variables().num_vars() } pub fn next_ty_vid(&self, span: Span) -> TyVid { self.next_ty_vid_with_origin(TypeVariableOrigin { span, param_def_id: None }) } pub fn next_ty_vid_with_origin(&self, origin: TypeVariableOrigin) -> TyVid { self.inner.borrow_mut().type_variables().new_var(self.universe(), origin) } pub fn next_ty_vid_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> TyVid { let origin = TypeVariableOrigin { span, param_def_id: None }; self.inner.borrow_mut().type_variables().new_var(universe, origin) } pub fn next_ty_var(&self, span: Span) -> Ty<'tcx> { self.next_ty_var_with_origin(TypeVariableOrigin { span, param_def_id: None }) } pub fn next_ty_var_with_origin(&self, origin: TypeVariableOrigin) -> Ty<'tcx> { let vid = self.next_ty_vid_with_origin(origin); Ty::new_var(self.tcx, vid) } pub fn next_ty_var_in_universe(&self, span: Span, universe: ty::UniverseIndex) -> Ty<'tcx> { let vid = self.next_ty_vid_in_universe(span, universe); Ty::new_var(self.tcx, vid) } pub fn next_const_var(&self, span: Span) -> ty::Const<'tcx> { self.next_const_var_with_origin(ConstVariableOrigin { span, param_def_id: None }) } pub fn next_const_var_with_origin(&self, origin: ConstVariableOrigin) -> ty::Const<'tcx> { let vid = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe: self.universe() }) .vid; ty::Const::new_var(self.tcx, vid) } pub fn next_const_var_in_universe( &self, span: Span, universe: ty::UniverseIndex, ) -> ty::Const<'tcx> { let origin = ConstVariableOrigin { span, param_def_id: None }; let vid = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe }) .vid; ty::Const::new_var(self.tcx, vid) } pub fn next_int_var(&self) -> Ty<'tcx> { let next_int_var_id = self.inner.borrow_mut().int_unification_table().new_key(ty::IntVarValue::Unknown); Ty::new_int_var(self.tcx, next_int_var_id) } pub fn next_float_var(&self) -> Ty<'tcx> { let next_float_var_id = self.inner.borrow_mut().float_unification_table().new_key(ty::FloatVarValue::Unknown); Ty::new_float_var(self.tcx, next_float_var_id) } /// Creates a fresh region variable with the next available index. /// The variable will be created in the maximum universe created /// thus far, allowing it to name any region created thus far. pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> { self.next_region_var_in_universe(origin, self.universe()) } /// Creates a fresh region variable with the next available index /// in the given universe; typically, you can use /// `next_region_var` and just use the maximal universe. pub fn next_region_var_in_universe( &self, origin: RegionVariableOrigin, universe: ty::UniverseIndex, ) -> ty::Region<'tcx> { let region_var = self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin); ty::Region::new_var(self.tcx, region_var) } pub fn next_term_var_of_kind(&self, term: ty::Term<'tcx>, span: Span) -> ty::Term<'tcx> { match term.kind() { ty::TermKind::Ty(_) => self.next_ty_var(span).into(), ty::TermKind::Const(_) => self.next_const_var(span).into(), } } /// Return the universe that the region `r` was created in. For /// most regions (e.g., `'static`, named regions from the user, /// etc) this is the root universe U0. For inference variables or /// placeholders, however, it will return the universe which they /// are associated. pub fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex { self.inner.borrow_mut().unwrap_region_constraints().universe(r) } /// Number of region variables created so far. pub fn num_region_vars(&self) -> usize { self.inner.borrow_mut().unwrap_region_constraints().num_region_vars() } /// Just a convenient wrapper of `next_region_var` for using during NLL. #[instrument(skip(self), level = "debug")] pub fn next_nll_region_var(&self, origin: NllRegionVariableOrigin) -> ty::Region<'tcx> { self.next_region_var(RegionVariableOrigin::Nll(origin)) } /// Just a convenient wrapper of `next_region_var` for using during NLL. #[instrument(skip(self), level = "debug")] pub fn next_nll_region_var_in_universe( &self, origin: NllRegionVariableOrigin, universe: ty::UniverseIndex, ) -> ty::Region<'tcx> { self.next_region_var_in_universe(RegionVariableOrigin::Nll(origin), universe) } pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> { match param.kind { GenericParamDefKind::Lifetime => { // Create a region inference variable for the given // region parameter definition. self.next_region_var(RegionVariableOrigin::RegionParameterDefinition( span, param.name, )) .into() } GenericParamDefKind::Type { .. } => { // Create a type inference variable for the given // type parameter definition. The generic parameters are // for actual parameters that may be referred to by // the default of this type parameter, if it exists. // e.g., `struct Foo(...);` when // used in a path such as `Foo::::new()` will // use an inference variable for `C` with `[T, U]` // as the generic parameters for the default, `(T, U)`. let ty_var_id = self.inner.borrow_mut().type_variables().new_var( self.universe(), TypeVariableOrigin { param_def_id: Some(param.def_id), span }, ); Ty::new_var(self.tcx, ty_var_id).into() } GenericParamDefKind::Const { .. } => { let origin = ConstVariableOrigin { param_def_id: Some(param.def_id), span }; let const_var_id = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe: self.universe() }) .vid; ty::Const::new_var(self.tcx, const_var_id).into() } } } /// Given a set of generics defined on a type or impl, returns the generic parameters mapping /// each type/region parameter to a fresh inference variable. pub fn fresh_args_for_item(&self, span: Span, def_id: DefId) -> GenericArgsRef<'tcx> { GenericArgs::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param)) } /// Returns `true` if errors have been reported since this infcx was /// created. This is sometimes used as a heuristic to skip /// reporting errors that often occur as a result of earlier /// errors, but where it's hard to be 100% sure (e.g., unresolved /// inference variables, regionck errors). #[must_use = "this method does not have any side effects"] pub fn tainted_by_errors(&self) -> Option { self.tainted_by_errors.get() } /// Set the "tainted by errors" flag to true. We call this when we /// observe an error from a prior pass. pub fn set_tainted_by_errors(&self, e: ErrorGuaranteed) { debug!("set_tainted_by_errors(ErrorGuaranteed)"); self.tainted_by_errors.set(Some(e)); } pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin { let mut inner = self.inner.borrow_mut(); let inner = &mut *inner; inner.unwrap_region_constraints().var_origin(vid) } /// Clone the list of variable regions. This is used only during NLL processing /// to put the set of region variables into the NLL region context. pub fn get_region_var_infos(&self) -> VarInfos { let inner = self.inner.borrow(); assert!(!UndoLogs::>::in_snapshot(&inner.undo_log)); let storage = inner.region_constraint_storage.as_ref().expect("regions already resolved"); assert!(storage.data.is_empty(), "{:#?}", storage.data); // We clone instead of taking because borrowck still wants to use the // inference context after calling this for diagnostics and the new // trait solver. storage.var_infos.clone() } pub fn has_opaque_types_in_storage(&self) -> bool { !self.inner.borrow().opaque_type_storage.is_empty() } #[instrument(level = "debug", skip(self), ret)] pub fn take_opaque_types(&self) -> Vec<(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)> { self.inner.borrow_mut().opaque_type_storage.take_opaque_types().collect() } #[instrument(level = "debug", skip(self), ret)] pub fn clone_opaque_types(&self) -> Vec<(OpaqueTypeKey<'tcx>, OpaqueHiddenType<'tcx>)> { self.inner.borrow_mut().opaque_type_storage.iter_opaque_types().collect() } pub fn has_opaques_with_sub_unified_hidden_type(&self, ty_vid: TyVid) -> bool { if !self.next_trait_solver() { return false; } let ty_sub_vid = self.sub_unification_table_root_var(ty_vid); let inner = &mut *self.inner.borrow_mut(); let mut type_variables = inner.type_variable_storage.with_log(&mut inner.undo_log); inner.opaque_type_storage.iter_opaque_types().any(|(_, hidden_ty)| { if let ty::Infer(ty::TyVar(hidden_vid)) = *hidden_ty.ty.kind() { let opaque_sub_vid = type_variables.sub_unification_table_root_var(hidden_vid); if opaque_sub_vid == ty_sub_vid { return true; } } false }) } /// Searches for an opaque type key whose hidden type is related to `ty_vid`. /// /// This only checks for a subtype relation, it does not require equality. pub fn opaques_with_sub_unified_hidden_type(&self, ty_vid: TyVid) -> Vec> { // Avoid accidentally allowing more code to compile with the old solver. if !self.next_trait_solver() { return vec![]; } let ty_sub_vid = self.sub_unification_table_root_var(ty_vid); let inner = &mut *self.inner.borrow_mut(); // This is iffy, can't call `type_variables()` as we're already // borrowing the `opaque_type_storage` here. let mut type_variables = inner.type_variable_storage.with_log(&mut inner.undo_log); inner .opaque_type_storage .iter_opaque_types() .filter_map(|(key, hidden_ty)| { if let ty::Infer(ty::TyVar(hidden_vid)) = *hidden_ty.ty.kind() { let opaque_sub_vid = type_variables.sub_unification_table_root_var(hidden_vid); if opaque_sub_vid == ty_sub_vid { return Some(ty::AliasTy::new_from_args( self.tcx, key.def_id.into(), key.args, )); } } None }) .collect() } #[inline(always)] pub fn can_define_opaque_ty(&self, id: impl Into) -> bool { debug_assert!(!self.next_trait_solver()); match self.typing_mode() { TypingMode::Analysis { defining_opaque_types_and_generators: defining_opaque_types, } | TypingMode::Borrowck { defining_opaque_types } => { id.into().as_local().is_some_and(|def_id| defining_opaque_types.contains(&def_id)) } // FIXME(#132279): This function is quite weird in post-analysis // and post-borrowck analysis mode. We may need to modify its uses // to support PostBorrowckAnalysis in the old solver as well. TypingMode::Coherence | TypingMode::PostBorrowckAnalysis { .. } | TypingMode::PostAnalysis => false, } } pub fn push_hir_typeck_potentially_region_dependent_goal( &self, goal: PredicateObligation<'tcx>, ) { let mut inner = self.inner.borrow_mut(); inner.undo_log.push(UndoLog::PushHirTypeckPotentiallyRegionDependentGoal); inner.hir_typeck_potentially_region_dependent_goals.push(goal); } pub fn take_hir_typeck_potentially_region_dependent_goals( &self, ) -> Vec> { assert!(!self.in_snapshot(), "cannot take goals in a snapshot"); std::mem::take(&mut self.inner.borrow_mut().hir_typeck_potentially_region_dependent_goals) } pub fn ty_to_string(&self, t: Ty<'tcx>) -> String { self.resolve_vars_if_possible(t).to_string() } /// If `TyVar(vid)` resolves to a type, return that type. Else, return the /// universe index of `TyVar(vid)`. pub fn probe_ty_var(&self, vid: TyVid) -> Result, ty::UniverseIndex> { use self::type_variable::TypeVariableValue; match self.inner.borrow_mut().type_variables().probe(vid) { TypeVariableValue::Known { value } => Ok(value), TypeVariableValue::Unknown { universe } => Err(universe), } } pub fn shallow_resolve(&self, ty: Ty<'tcx>) -> Ty<'tcx> { if let ty::Infer(v) = *ty.kind() { match v { ty::TyVar(v) => { // Not entirely obvious: if `typ` is a type variable, // it can be resolved to an int/float variable, which // can then be recursively resolved, hence the // recursion. Note though that we prevent type // variables from unifying to other type variables // directly (though they may be embedded // structurally), and we prevent cycles in any case, // so this recursion should always be of very limited // depth. // // Note: if these two lines are combined into one we get // dynamic borrow errors on `self.inner`. let known = self.inner.borrow_mut().type_variables().probe(v).known(); known.map_or(ty, |t| self.shallow_resolve(t)) } ty::IntVar(v) => { match self.inner.borrow_mut().int_unification_table().probe_value(v) { ty::IntVarValue::IntType(ty) => Ty::new_int(self.tcx, ty), ty::IntVarValue::UintType(ty) => Ty::new_uint(self.tcx, ty), ty::IntVarValue::Unknown => ty, } } ty::FloatVar(v) => { match self.inner.borrow_mut().float_unification_table().probe_value(v) { ty::FloatVarValue::Known(ty) => Ty::new_float(self.tcx, ty), ty::FloatVarValue::Unknown => ty, } } ty::FreshTy(_) | ty::FreshIntTy(_) | ty::FreshFloatTy(_) => ty, } } else { ty } } pub fn shallow_resolve_const(&self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { match ct.kind() { ty::ConstKind::Infer(infer_ct) => match infer_ct { InferConst::Var(vid) => self .inner .borrow_mut() .const_unification_table() .probe_value(vid) .known() .unwrap_or(ct), InferConst::Fresh(_) => ct, }, ty::ConstKind::Param(_) | ty::ConstKind::Bound(_, _) | ty::ConstKind::Placeholder(_) | ty::ConstKind::Unevaluated(_) | ty::ConstKind::Value(_) | ty::ConstKind::Error(_) | ty::ConstKind::Expr(_) => ct, } } pub fn shallow_resolve_term(&self, term: ty::Term<'tcx>) -> ty::Term<'tcx> { match term.kind() { ty::TermKind::Ty(ty) => self.shallow_resolve(ty).into(), ty::TermKind::Const(ct) => self.shallow_resolve_const(ct).into(), } } pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid { self.inner.borrow_mut().type_variables().root_var(var) } pub fn sub_unify_ty_vids_raw(&self, a: ty::TyVid, b: ty::TyVid) { self.inner.borrow_mut().type_variables().sub_unify(a, b); } pub fn sub_unification_table_root_var(&self, var: ty::TyVid) -> ty::TyVid { self.inner.borrow_mut().type_variables().sub_unification_table_root_var(var) } pub fn root_const_var(&self, var: ty::ConstVid) -> ty::ConstVid { self.inner.borrow_mut().const_unification_table().find(var).vid } /// Resolves an int var to a rigid int type, if it was constrained to one, /// or else the root int var in the unification table. pub fn opportunistic_resolve_int_var(&self, vid: ty::IntVid) -> Ty<'tcx> { let mut inner = self.inner.borrow_mut(); let value = inner.int_unification_table().probe_value(vid); match value { ty::IntVarValue::IntType(ty) => Ty::new_int(self.tcx, ty), ty::IntVarValue::UintType(ty) => Ty::new_uint(self.tcx, ty), ty::IntVarValue::Unknown => { Ty::new_int_var(self.tcx, inner.int_unification_table().find(vid)) } } } /// Resolves a float var to a rigid int type, if it was constrained to one, /// or else the root float var in the unification table. pub fn opportunistic_resolve_float_var(&self, vid: ty::FloatVid) -> Ty<'tcx> { let mut inner = self.inner.borrow_mut(); let value = inner.float_unification_table().probe_value(vid); match value { ty::FloatVarValue::Known(ty) => Ty::new_float(self.tcx, ty), ty::FloatVarValue::Unknown => { Ty::new_float_var(self.tcx, inner.float_unification_table().find(vid)) } } } /// Where possible, replaces type/const variables in /// `value` with their final value. Note that region variables /// are unaffected. If a type/const variable has not been unified, it /// is left as is. This is an idempotent operation that does /// not affect inference state in any way and so you can do it /// at will. pub fn resolve_vars_if_possible(&self, value: T) -> T where T: TypeFoldable>, { if let Err(guar) = value.error_reported() { self.set_tainted_by_errors(guar); } if !value.has_non_region_infer() { return value; } let mut r = resolve::OpportunisticVarResolver::new(self); value.fold_with(&mut r) } pub fn resolve_numeric_literals_with_default(&self, value: T) -> T where T: TypeFoldable>, { if !value.has_infer() { return value; // Avoid duplicated type-folding. } let mut r = InferenceLiteralEraser { tcx: self.tcx }; value.fold_with(&mut r) } pub fn probe_const_var(&self, vid: ty::ConstVid) -> Result, ty::UniverseIndex> { match self.inner.borrow_mut().const_unification_table().probe_value(vid) { ConstVariableValue::Known { value } => Ok(value), ConstVariableValue::Unknown { origin: _, universe } => Err(universe), } } /// Attempts to resolve all type/region/const variables in /// `value`. Region inference must have been run already (e.g., /// by calling `resolve_regions_and_report_errors`). If some /// variable was never unified, an `Err` results. /// /// This method is idempotent, but it not typically not invoked /// except during the writeback phase. pub fn fully_resolve>>(&self, value: T) -> FixupResult { match resolve::fully_resolve(self, value) { Ok(value) => { if value.has_non_region_infer() { bug!("`{value:?}` is not fully resolved"); } if value.has_infer_regions() { let guar = self.dcx().delayed_bug(format!("`{value:?}` is not fully resolved")); Ok(fold_regions(self.tcx, value, |re, _| { if re.is_var() { ty::Region::new_error(self.tcx, guar) } else { re } })) } else { Ok(value) } } Err(e) => Err(e), } } // Instantiates the bound variables in a given binder with fresh inference // variables in the current universe. // // Use this method if you'd like to find some generic parameters of the binder's // variables (e.g. during a method call). If there isn't a [`BoundRegionConversionTime`] // that corresponds to your use case, consider whether or not you should // use [`InferCtxt::enter_forall`] instead. pub fn instantiate_binder_with_fresh_vars( &self, span: Span, lbrct: BoundRegionConversionTime, value: ty::Binder<'tcx, T>, ) -> T where T: TypeFoldable> + Copy, { if let Some(inner) = value.no_bound_vars() { return inner; } let bound_vars = value.bound_vars(); let mut args = Vec::with_capacity(bound_vars.len()); for bound_var_kind in bound_vars { let arg: ty::GenericArg<'_> = match bound_var_kind { ty::BoundVariableKind::Ty(_) => self.next_ty_var(span).into(), ty::BoundVariableKind::Region(br) => { self.next_region_var(RegionVariableOrigin::BoundRegion(span, br, lbrct)).into() } ty::BoundVariableKind::Const => self.next_const_var(span).into(), }; args.push(arg); } struct ToFreshVars<'tcx> { args: Vec>, } impl<'tcx> BoundVarReplacerDelegate<'tcx> for ToFreshVars<'tcx> { fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> { self.args[br.var.index()].expect_region() } fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> { self.args[bt.var.index()].expect_ty() } fn replace_const(&mut self, bc: ty::BoundConst) -> ty::Const<'tcx> { self.args[bc.var.index()].expect_const() } } let delegate = ToFreshVars { args }; self.tcx.replace_bound_vars_uncached(value, delegate) } /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method. pub(crate) fn verify_generic_bound( &self, origin: SubregionOrigin<'tcx>, kind: GenericKind<'tcx>, a: ty::Region<'tcx>, bound: VerifyBound<'tcx>, ) { debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound); self.inner .borrow_mut() .unwrap_region_constraints() .verify_generic_bound(origin, kind, a, bound); } /// Obtains the latest type of the given closure; this may be a /// closure in the current function, in which case its /// `ClosureKind` may not yet be known. pub fn closure_kind(&self, closure_ty: Ty<'tcx>) -> Option { let unresolved_kind_ty = match *closure_ty.kind() { ty::Closure(_, args) => args.as_closure().kind_ty(), ty::CoroutineClosure(_, args) => args.as_coroutine_closure().kind_ty(), _ => bug!("unexpected type {closure_ty}"), }; let closure_kind_ty = self.shallow_resolve(unresolved_kind_ty); closure_kind_ty.to_opt_closure_kind() } pub fn universe(&self) -> ty::UniverseIndex { self.universe.get() } /// Creates and return a fresh universe that extends all previous /// universes. Updates `self.universe` to that new universe. pub fn create_next_universe(&self) -> ty::UniverseIndex { let u = self.universe.get().next_universe(); debug!("create_next_universe {u:?}"); self.universe.set(u); u } /// Extract [`ty::TypingMode`] of this inference context to get a `TypingEnv` /// which contains the necessary information to use the trait system without /// using canonicalization or carrying this inference context around. pub fn typing_env(&self, param_env: ty::ParamEnv<'tcx>) -> ty::TypingEnv<'tcx> { let typing_mode = match self.typing_mode() { // FIXME(#132279): This erases the `defining_opaque_types` as it isn't possible // to handle them without proper canonicalization. This means we may cause cycle // errors and fail to reveal opaques while inside of bodies. We should rename this // function and require explicit comments on all use-sites in the future. ty::TypingMode::Analysis { defining_opaque_types_and_generators: _ } | ty::TypingMode::Borrowck { defining_opaque_types: _ } => { TypingMode::non_body_analysis() } mode @ (ty::TypingMode::Coherence | ty::TypingMode::PostBorrowckAnalysis { .. } | ty::TypingMode::PostAnalysis) => mode, }; ty::TypingEnv { typing_mode, param_env } } /// Similar to [`Self::canonicalize_query`], except that it returns /// a [`PseudoCanonicalInput`] and requires both the `value` and the /// `param_env` to not contain any inference variables or placeholders. pub fn pseudo_canonicalize_query( &self, param_env: ty::ParamEnv<'tcx>, value: V, ) -> PseudoCanonicalInput<'tcx, V> where V: TypeVisitable>, { debug_assert!(!value.has_infer()); debug_assert!(!value.has_placeholders()); debug_assert!(!param_env.has_infer()); debug_assert!(!param_env.has_placeholders()); self.typing_env(param_env).as_query_input(value) } /// The returned function is used in a fast path. If it returns `true` the variable is /// unchanged, `false` indicates that the status is unknown. #[inline] pub fn is_ty_infer_var_definitely_unchanged(&self) -> impl Fn(TyOrConstInferVar) -> bool { // This hoists the borrow/release out of the loop body. let inner = self.inner.try_borrow(); move |infer_var: TyOrConstInferVar| match (infer_var, &inner) { (TyOrConstInferVar::Ty(ty_var), Ok(inner)) => { use self::type_variable::TypeVariableValue; matches!( inner.try_type_variables_probe_ref(ty_var), Some(TypeVariableValue::Unknown { .. }) ) } _ => false, } } /// `ty_or_const_infer_var_changed` is equivalent to one of these two: /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`) /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`) /// /// However, `ty_or_const_infer_var_changed` is more efficient. It's always /// inlined, despite being large, because it has only two call sites that /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on` /// inference variables), and it handles both `Ty` and `ty::Const` without /// having to resort to storing full `GenericArg`s in `stalled_on`. #[inline(always)] pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar) -> bool { match infer_var { TyOrConstInferVar::Ty(v) => { use self::type_variable::TypeVariableValue; // If `inlined_probe` returns a `Known` value, it never equals // `ty::Infer(ty::TyVar(v))`. match self.inner.borrow_mut().type_variables().inlined_probe(v) { TypeVariableValue::Unknown { .. } => false, TypeVariableValue::Known { .. } => true, } } TyOrConstInferVar::TyInt(v) => { // If `inlined_probe_value` returns a value it's always a // `ty::Int(_)` or `ty::UInt(_)`, which never matches a // `ty::Infer(_)`. self.inner.borrow_mut().int_unification_table().inlined_probe_value(v).is_known() } TyOrConstInferVar::TyFloat(v) => { // If `probe_value` returns a value it's always a // `ty::Float(_)`, which never matches a `ty::Infer(_)`. // // Not `inlined_probe_value(v)` because this call site is colder. self.inner.borrow_mut().float_unification_table().probe_value(v).is_known() } TyOrConstInferVar::Const(v) => { // If `probe_value` returns a `Known` value, it never equals // `ty::ConstKind::Infer(ty::InferConst::Var(v))`. // // Not `inlined_probe_value(v)` because this call site is colder. match self.inner.borrow_mut().const_unification_table().probe_value(v) { ConstVariableValue::Unknown { .. } => false, ConstVariableValue::Known { .. } => true, } } } } /// Attach a callback to be invoked on each root obligation evaluated in the new trait solver. pub fn attach_obligation_inspector(&self, inspector: ObligationInspector<'tcx>) { debug_assert!( self.obligation_inspector.get().is_none(), "shouldn't override a set obligation inspector" ); self.obligation_inspector.set(Some(inspector)); } } /// Helper for [InferCtxt::ty_or_const_infer_var_changed] (see comment on that), currently /// used only for `traits::fulfill`'s list of `stalled_on` inference variables. #[derive(Copy, Clone, Debug)] pub enum TyOrConstInferVar { /// Equivalent to `ty::Infer(ty::TyVar(_))`. Ty(TyVid), /// Equivalent to `ty::Infer(ty::IntVar(_))`. TyInt(IntVid), /// Equivalent to `ty::Infer(ty::FloatVar(_))`. TyFloat(FloatVid), /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`. Const(ConstVid), } impl<'tcx> TyOrConstInferVar { /// Tries to extract an inference variable from a type or a constant, returns `None` /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`). pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option { match arg.kind() { GenericArgKind::Type(ty) => Self::maybe_from_ty(ty), GenericArgKind::Const(ct) => Self::maybe_from_const(ct), GenericArgKind::Lifetime(_) => None, } } /// Tries to extract an inference variable from a type or a constant, returns `None` /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`). pub fn maybe_from_term(term: Term<'tcx>) -> Option { match term.kind() { TermKind::Ty(ty) => Self::maybe_from_ty(ty), TermKind::Const(ct) => Self::maybe_from_const(ct), } } /// Tries to extract an inference variable from a type, returns `None` /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`). fn maybe_from_ty(ty: Ty<'tcx>) -> Option { match *ty.kind() { ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)), ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)), ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)), _ => None, } } /// Tries to extract an inference variable from a constant, returns `None` /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`). fn maybe_from_const(ct: ty::Const<'tcx>) -> Option { match ct.kind() { ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)), _ => None, } } } /// Replace `{integer}` with `i32` and `{float}` with `f64`. /// Used only for diagnostics. struct InferenceLiteralEraser<'tcx> { tcx: TyCtxt<'tcx>, } impl<'tcx> TypeFolder> for InferenceLiteralEraser<'tcx> { fn cx(&self) -> TyCtxt<'tcx> { self.tcx } fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { match ty.kind() { ty::Infer(ty::IntVar(_) | ty::FreshIntTy(_)) => self.tcx.types.i32, ty::Infer(ty::FloatVar(_) | ty::FreshFloatTy(_)) => self.tcx.types.f64, _ => ty.super_fold_with(self), } } } impl<'tcx> TypeTrace<'tcx> { pub fn span(&self) -> Span { self.cause.span } pub fn types(cause: &ObligationCause<'tcx>, a: Ty<'tcx>, b: Ty<'tcx>) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: ValuePairs::Terms(ExpectedFound::new(a.into(), b.into())), } } pub fn trait_refs( cause: &ObligationCause<'tcx>, a: ty::TraitRef<'tcx>, b: ty::TraitRef<'tcx>, ) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: ValuePairs::TraitRefs(ExpectedFound::new(a, b)) } } pub fn consts( cause: &ObligationCause<'tcx>, a: ty::Const<'tcx>, b: ty::Const<'tcx>, ) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: ValuePairs::Terms(ExpectedFound::new(a.into(), b.into())), } } } impl<'tcx> SubregionOrigin<'tcx> { pub fn span(&self) -> Span { match *self { SubregionOrigin::Subtype(ref a) => a.span(), SubregionOrigin::RelateObjectBound(a) => a, SubregionOrigin::RelateParamBound(a, ..) => a, SubregionOrigin::RelateRegionParamBound(a, _) => a, SubregionOrigin::Reborrow(a) => a, SubregionOrigin::ReferenceOutlivesReferent(_, a) => a, SubregionOrigin::CompareImplItemObligation { span, .. } => span, SubregionOrigin::AscribeUserTypeProvePredicate(span) => span, SubregionOrigin::CheckAssociatedTypeBounds { ref parent, .. } => parent.span(), } } pub fn from_obligation_cause(cause: &traits::ObligationCause<'tcx>, default: F) -> Self where F: FnOnce() -> Self, { match *cause.code() { traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => { SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span) } traits::ObligationCauseCode::CompareImplItem { impl_item_def_id, trait_item_def_id, kind: _, } => SubregionOrigin::CompareImplItemObligation { span: cause.span, impl_item_def_id, trait_item_def_id, }, traits::ObligationCauseCode::CheckAssociatedTypeBounds { impl_item_def_id, trait_item_def_id, } => SubregionOrigin::CheckAssociatedTypeBounds { impl_item_def_id, trait_item_def_id, parent: Box::new(default()), }, traits::ObligationCauseCode::AscribeUserTypeProvePredicate(span) => { SubregionOrigin::AscribeUserTypeProvePredicate(span) } traits::ObligationCauseCode::ObjectTypeBound(ty, _reg) => { SubregionOrigin::RelateRegionParamBound(cause.span, Some(ty)) } _ => default(), } } } impl RegionVariableOrigin { pub fn span(&self) -> Span { match *self { RegionVariableOrigin::Misc(a) | RegionVariableOrigin::PatternRegion(a) | RegionVariableOrigin::BorrowRegion(a) | RegionVariableOrigin::Autoref(a) | RegionVariableOrigin::Coercion(a) | RegionVariableOrigin::RegionParameterDefinition(a, ..) | RegionVariableOrigin::BoundRegion(a, ..) | RegionVariableOrigin::UpvarRegion(_, a) => a, RegionVariableOrigin::Nll(..) => bug!("NLL variable used with `span`"), } } } impl<'tcx> InferCtxt<'tcx> { /// Given a [`hir::Block`], get the span of its last expression or /// statement, peeling off any inner blocks. pub fn find_block_span(&self, block: &'tcx hir::Block<'tcx>) -> Span { let block = block.innermost_block(); if let Some(expr) = &block.expr { expr.span } else if let Some(stmt) = block.stmts.last() { // possibly incorrect trailing `;` in the else arm stmt.span } else { // empty block; point at its entirety block.span } } /// Given a [`hir::HirId`] for a block (or an expr of a block), get the span /// of its last expression or statement, peeling off any inner blocks. pub fn find_block_span_from_hir_id(&self, hir_id: hir::HirId) -> Span { match self.tcx.hir_node(hir_id) { hir::Node::Block(blk) | hir::Node::Expr(&hir::Expr { kind: hir::ExprKind::Block(blk, _), .. }) => { self.find_block_span(blk) } hir::Node::Expr(e) => e.span, _ => DUMMY_SP, } } }