//! Infer context the next-trait-solver. use std::cell::{Cell, RefCell}; use std::fmt; use std::ops::Range; use std::sync::Arc; pub use BoundRegionConversionTime::*; use ena::unify as ut; use hir_def::GenericParamId; use opaque_types::{OpaqueHiddenType, OpaqueTypeStorage}; use region_constraints::{RegionConstraintCollector, RegionConstraintStorage}; use rustc_next_trait_solver::solve::{GoalEvaluation, SolverDelegateEvalExt}; use rustc_pattern_analysis::Captures; use rustc_type_ir::solve::{NoSolution, inspect}; use rustc_type_ir::{ ClosureKind, ConstVid, FloatVarValue, FloatVid, GenericArgKind, InferConst, InferTy, IntVarValue, IntVid, OutlivesPredicate, RegionVid, TermKind, TyVid, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt, UniverseIndex, error::{ExpectedFound, TypeError}, inherent::{ Const as _, GenericArg as _, GenericArgs as _, IntoKind, SliceLike, Term as _, Ty as _, }, }; use snapshot::undo_log::InferCtxtUndoLogs; use tracing::{debug, instrument}; use traits::{ObligationCause, PredicateObligations}; use type_variable::TypeVariableOrigin; use unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey}; pub use crate::next_solver::infer::traits::ObligationInspector; use crate::next_solver::{ ArgOutlivesPredicate, BoundConst, BoundRegion, BoundTy, BoundVarKind, Goal, Predicate, SolverContext, fold::BoundVarReplacerDelegate, infer::{at::ToTrace, select::EvaluationResult, traits::PredicateObligation}, obligation_ctxt::ObligationCtxt, }; use super::{ AliasTerm, Binder, CanonicalQueryInput, CanonicalVarValues, Const, ConstKind, DbInterner, ErrorGuaranteed, GenericArg, GenericArgs, OpaqueTypeKey, ParamEnv, PolyCoercePredicate, PolyExistentialProjection, PolyExistentialTraitRef, PolyFnSig, PolyRegionOutlivesPredicate, PolySubtypePredicate, Region, SolverDefId, SubtypePredicate, Term, TraitRef, Ty, TyKind, TypingMode, }; pub mod at; pub mod canonical; mod context; pub mod opaque_types; mod outlives; pub mod region_constraints; pub mod relate; pub mod resolve; pub(crate) mod select; pub(crate) mod snapshot; pub(crate) mod traits; mod type_variable; mod unify_key; /// `InferOk<'db, ()>` is used a lot. It may seem like a useless wrapper /// around `PredicateObligations`, but it has one important property: /// because `InferOk` is marked with `#[must_use]`, if you have a method /// `InferCtxt::f` that returns `InferResult<()>` 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<'db, T> { pub value: T, pub obligations: PredicateObligations<'db>, } pub type InferResult<'db, T> = Result, TypeError>>; pub(crate) type UnificationTable<'a, 'db, T> = ut::UnificationTable< ut::InPlace, &'a mut InferCtxtUndoLogs<'db>>, >; fn iter_idx_range + Into>(range: Range) -> impl Iterator { (range.start.into()..range.end.into()).map(Into::into) } /// 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<'db> { pub(crate) undo_log: InferCtxtUndoLogs<'db>, /// 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. pub(crate) type_variable_storage: type_variable::TypeVariableStorage<'db>, /// Map from const parameter variable to the kind of const it represents. pub(crate) const_unification_storage: ut::UnificationTableStorage>, /// Map from integral variable to the kind of integer it represents. pub(crate) int_unification_storage: ut::UnificationTableStorage, /// Map from floating variable to the kind of float it represents. pub(crate) 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. pub(crate) 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. pub(crate) 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>, /// Caches for opaque type inference. pub(crate) opaque_type_storage: OpaqueTypeStorage<'db>, } impl<'db> InferCtxtInner<'db> { fn new() -> InferCtxtInner<'db> { InferCtxtInner { undo_log: InferCtxtUndoLogs::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: vec![], region_assumptions: Default::default(), opaque_type_storage: Default::default(), } } #[inline] pub fn region_obligations(&self) -> &[TypeOutlivesConstraint<'db>] { &self.region_obligations } #[inline] fn try_type_variables_probe_ref( &self, vid: TyVid, ) -> Option<&type_variable::TypeVariableValue<'db>> { // 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<'_, 'db> { self.type_variable_storage.with_log(&mut self.undo_log) } #[inline] pub(crate) fn opaque_types(&mut self) -> opaque_types::OpaqueTypeTable<'_, 'db> { self.opaque_type_storage.with_log(&mut self.undo_log) } #[inline] pub(crate) fn int_unification_table(&mut self) -> UnificationTable<'_, 'db, IntVid> { tracing::debug!(?self.int_unification_storage); self.int_unification_storage.with_log(&mut self.undo_log) } #[inline] pub(crate) fn float_unification_table(&mut self) -> UnificationTable<'_, 'db, FloatVid> { self.float_unification_storage.with_log(&mut self.undo_log) } #[inline] fn const_unification_table(&mut self) -> UnificationTable<'_, 'db, ConstVidKey<'db>> { self.const_unification_storage.with_log(&mut self.undo_log) } #[inline] pub fn unwrap_region_constraints(&mut self) -> RegionConstraintCollector<'db, '_> { self.region_constraint_storage .as_mut() .expect("region constraints already solved") .with_log(&mut self.undo_log) } } #[derive(Clone)] pub struct InferCtxt<'db> { pub interner: DbInterner<'db>, /// The mode of this inference context, see the struct documentation /// for more details. typing_mode: TypingMode<'db>, pub inner: 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, obligation_inspector: Cell>>, } /// See the `error_reporting` module for more details. #[derive(Clone, Debug, PartialEq, Eq)] pub enum ValuePairs<'db> { Regions(ExpectedFound>), Terms(ExpectedFound>), Aliases(ExpectedFound>), TraitRefs(ExpectedFound>), PolySigs(ExpectedFound>), ExistentialTraitRef(ExpectedFound>), ExistentialProjection(ExpectedFound>), } impl<'db> ValuePairs<'db> { pub fn ty(&self) -> Option<(Ty<'db>, Ty<'db>)> { if let ValuePairs::Terms(ExpectedFound { expected, found }) = self && let Some(expected) = expected.as_type() && let Some(found) = found.as_type() { return Some((expected, found)); } 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<'db> { pub cause: ObligationCause, pub values: ValuePairs<'db>, } /// 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(SolverDefId), } #[derive(Copy, Clone, Debug)] pub struct FixupError { unresolved: TyOrConstInferVar, } impl fmt::Display for FixupError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { use TyOrConstInferVar::*; match self.unresolved { TyInt(_) => write!( f, "cannot determine the type of this integer; \ add a suffix to specify the type explicitly" ), TyFloat(_) => write!( f, "cannot determine the type of this number; \ add a suffix to specify the type explicitly" ), Ty(_) => write!(f, "unconstrained type"), Const(_) => write!(f, "unconstrained const value"), } } } /// See the `region_obligations` field for more information. #[derive(Clone, Debug)] pub struct TypeOutlivesConstraint<'db> { pub sub_region: Region<'db>, pub sup_type: Ty<'db>, } /// Used to configure inference contexts before their creation. pub struct InferCtxtBuilder<'db> { interner: DbInterner<'db>, } pub trait DbInternerInferExt<'db> { fn infer_ctxt(self) -> InferCtxtBuilder<'db>; } impl<'db> DbInternerInferExt<'db> for DbInterner<'db> { fn infer_ctxt(self) -> InferCtxtBuilder<'db> { InferCtxtBuilder { interner: self } } } impl<'db> InferCtxtBuilder<'db> { /// 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, input: &CanonicalQueryInput<'db, T>, ) -> (InferCtxt<'db>, T, CanonicalVarValues<'db>) where T: TypeFoldable>, { let infcx = self.build(input.typing_mode); let (value, args) = infcx.instantiate_canonical(&input.canonical); (infcx, value, args) } pub fn build(&mut self, typing_mode: TypingMode<'db>) -> InferCtxt<'db> { let InferCtxtBuilder { interner } = *self; InferCtxt { interner, typing_mode, inner: RefCell::new(InferCtxtInner::new()), tainted_by_errors: Cell::new(None), universe: Cell::new(UniverseIndex::ROOT), obligation_inspector: Cell::new(None), } } } impl<'db> InferOk<'db, ()> { pub fn into_obligations(self) -> PredicateObligations<'db> { self.obligations } } impl<'db> InferCtxt<'db> { #[inline(always)] pub fn typing_mode(&self) -> TypingMode<'db> { self.typing_mode } #[inline(always)] pub fn typing_mode_unchecked(&self) -> TypingMode<'db> { self.typing_mode } /// Evaluates whether the predicate can be satisfied (by any means) /// in the given `ParamEnv`. pub fn predicate_may_hold(&self, obligation: &PredicateObligation<'db>) -> bool { self.evaluate_obligation(obligation).may_apply() } /// See the comment on `GeneralAutoderef::overloaded_deref_ty` /// for more details. pub fn predicate_may_hold_opaque_types_jank( &self, obligation: &PredicateObligation<'db>, ) -> bool { <&SolverContext<'db>>::from(self).root_goal_may_hold_opaque_types_jank(Goal::new( self.interner, obligation.param_env, obligation.predicate, )) } pub(crate) fn insert_type_vars(&self, ty: T) -> T where T: TypeFoldable>, { struct Folder<'a, 'db> { infcx: &'a InferCtxt<'db>, } impl<'db> TypeFolder> for Folder<'_, 'db> { fn cx(&self) -> DbInterner<'db> { self.infcx.interner } fn fold_ty(&mut self, ty: Ty<'db>) -> Ty<'db> { if !ty.references_error() { return ty; } if ty.is_ty_error() { self.infcx.next_ty_var() } else { ty.super_fold_with(self) } } fn fold_const(&mut self, ct: Const<'db>) -> Const<'db> { if !ct.references_error() { return ct; } if ct.is_ct_error() { self.infcx.next_const_var() } else { ct.super_fold_with(self) } } fn fold_region(&mut self, r: Region<'db>) -> Region<'db> { if r.is_error() { self.infcx.next_region_var() } else { r } } } ty.fold_with(&mut Folder { infcx: self }) } /// Evaluates whether the predicate can be satisfied in the given /// `ParamEnv`, and returns `false` if not certain. However, this is /// not entirely accurate if inference variables are involved. /// /// This version may conservatively fail when outlives obligations /// are required. Therefore, this version should only be used for /// optimizations or diagnostics and be treated as if it can always /// return `false`. /// /// # Example /// /// ``` /// # #![allow(dead_code)] /// trait Trait {} /// /// fn check() {} /// /// fn foo() /// where /// &'static T: Trait, /// { /// // Evaluating `&'?0 T: Trait` adds a `'?0: 'static` outlives obligation, /// // which means that `predicate_must_hold_considering_regions` will return /// // `false`. /// check::<&'_ T>(); /// } /// ``` #[expect(dead_code, reason = "this is used in rustc")] fn predicate_must_hold_considering_regions( &self, obligation: &PredicateObligation<'db>, ) -> bool { self.evaluate_obligation(obligation).must_apply_considering_regions() } /// Evaluates whether the predicate can be satisfied in the given /// `ParamEnv`, and returns `false` if not certain. However, this is /// not entirely accurate if inference variables are involved. /// /// This version ignores all outlives constraints. #[expect(dead_code, reason = "this is used in rustc")] fn predicate_must_hold_modulo_regions(&self, obligation: &PredicateObligation<'db>) -> bool { self.evaluate_obligation(obligation).must_apply_modulo_regions() } /// Evaluate a given predicate, capturing overflow and propagating it back. fn evaluate_obligation(&self, obligation: &PredicateObligation<'db>) -> EvaluationResult { self.probe(|snapshot| { let mut ocx = ObligationCtxt::new(self); ocx.register_obligation(obligation.clone()); let mut result = EvaluationResult::EvaluatedToOk; for error in ocx.evaluate_obligations_error_on_ambiguity() { if error.is_true_error() { return EvaluationResult::EvaluatedToErr; } else { result = result.max(EvaluationResult::EvaluatedToAmbig); } } if self.opaque_types_added_in_snapshot(snapshot) { result = result.max(EvaluationResult::EvaluatedToOkModuloOpaqueTypes); } else if self.region_constraints_added_in_snapshot(snapshot) { result = result.max(EvaluationResult::EvaluatedToOkModuloRegions); } result }) } pub fn can_eq>(&self, param_env: ParamEnv<'db>, a: T, b: T) -> bool { self.probe(|_| { let mut ocx = ObligationCtxt::new(self); let Ok(()) = ocx.eq(&ObligationCause::dummy(), param_env, a, b) else { return false; }; ocx.try_evaluate_obligations().is_empty() }) } /// See the comment on `GeneralAutoderef::overloaded_deref_ty` /// for more details. pub fn goal_may_hold_opaque_types_jank(&self, goal: Goal<'db, Predicate<'db>>) -> bool { <&SolverContext<'db>>::from(self).root_goal_may_hold_opaque_types_jank(goal) } pub fn type_is_copy_modulo_regions(&self, param_env: ParamEnv<'db>, ty: Ty<'db>) -> bool { let ty = self.resolve_vars_if_possible(ty); let Some(copy_def_id) = self.interner.lang_items().Copy else { return false; }; // This can get called from typeck (by euv), and `moves_by_default` // rightly refuses to work with inference variables, but // moves_by_default has a cache, which we want to use in other // cases. traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id) } 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.interner, t)) .collect(); vars.extend( (0..inner.int_unification_table().len()) .map(IntVid::from_usize) .filter(|&vid| inner.int_unification_table().probe_value(vid).is_unknown()) .map(|v| Ty::new_int_var(self.interner, v)), ); vars.extend( (0..inner.float_unification_table().len()) .map(FloatVid::from_usize) .filter(|&vid| inner.float_unification_table().probe_value(vid).is_unknown()) .map(|v| Ty::new_float_var(self.interner, v)), ); vars } #[instrument(skip(self), level = "debug")] pub fn sub_regions(&self, a: Region<'db>, b: Region<'db>) { self.inner.borrow_mut().unwrap_region_constraints().make_subregion(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, param_env: ParamEnv<'db>, predicate: PolyCoercePredicate<'db>, ) -> Result, (TyVid, TyVid)> { let subtype_predicate = predicate.map_bound(|p| 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, param_env: ParamEnv<'db>, predicate: PolySubtypePredicate<'db>, ) -> 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()) { (TyKind::Infer(InferTy::TyVar(a_vid)), TyKind::Infer(InferTy::TyVar(b_vid))) => { return Err((a_vid, b_vid)); } _ => {} } self.enter_forall(predicate, |SubtypePredicate { a_is_expected, a, b }| { if a_is_expected { Ok(self.at(cause, param_env).sub(a, b)) } else { Ok(self.at(cause, param_env).sup(b, a)) } }) } pub fn region_outlives_predicate( &self, _cause: &traits::ObligationCause, predicate: PolyRegionOutlivesPredicate<'db>, ) { self.enter_forall(predicate, |OutlivesPredicate(r_a, r_b)| { self.sub_regions(r_b, r_a); // `b : a` ==> `a <= b` }) } /// 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_var_for_param(&self, id: GenericParamId) -> GenericArg<'db> { match id { GenericParamId::TypeParamId(_) => self.next_ty_var().into(), GenericParamId::ConstParamId(_) => self.next_const_var().into(), GenericParamId::LifetimeParamId(_) => self.next_region_var().into(), } } pub fn next_ty_var(&self) -> Ty<'db> { self.next_ty_var_with_origin(TypeVariableOrigin { param_def_id: None }) } pub fn next_ty_vid(&self) -> TyVid { self.inner .borrow_mut() .type_variables() .new_var(self.universe(), TypeVariableOrigin { param_def_id: None }) } pub fn next_ty_var_with_origin(&self, origin: TypeVariableOrigin) -> Ty<'db> { let vid = self.inner.borrow_mut().type_variables().new_var(self.universe(), origin); Ty::new_var(self.interner, vid) } pub fn next_ty_var_id_in_universe(&self, universe: UniverseIndex) -> TyVid { let origin = TypeVariableOrigin { param_def_id: None }; self.inner.borrow_mut().type_variables().new_var(universe, origin) } pub fn next_ty_var_in_universe(&self, universe: UniverseIndex) -> Ty<'db> { let vid = self.next_ty_var_id_in_universe(universe); Ty::new_var(self.interner, vid) } pub fn next_const_var(&self) -> Const<'db> { self.next_const_var_with_origin(ConstVariableOrigin {}) } pub fn next_const_vid(&self) -> ConstVid { self.inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin: ConstVariableOrigin {}, universe: self.universe(), }) .vid } pub fn next_const_var_with_origin(&self, origin: ConstVariableOrigin) -> Const<'db> { let vid = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe: self.universe() }) .vid; Const::new_var(self.interner, vid) } pub fn next_const_var_in_universe(&self, universe: UniverseIndex) -> Const<'db> { let origin = ConstVariableOrigin {}; let vid = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe }) .vid; Const::new_var(self.interner, vid) } pub fn next_int_var(&self) -> Ty<'db> { let next_int_var_id = self.inner.borrow_mut().int_unification_table().new_key(IntVarValue::Unknown); Ty::new_int_var(self.interner, next_int_var_id) } pub fn next_int_vid(&self) -> IntVid { self.inner.borrow_mut().int_unification_table().new_key(IntVarValue::Unknown) } pub fn next_float_var(&self) -> Ty<'db> { Ty::new_float_var(self.interner, self.next_float_vid()) } pub fn next_float_vid(&self) -> FloatVid { self.inner.borrow_mut().float_unification_table().new_key(FloatVarValue::Unknown) } /// 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) -> Region<'db> { self.next_region_var_in_universe(self.universe()) } pub fn next_region_vid(&self) -> RegionVid { self.inner.borrow_mut().unwrap_region_constraints().new_region_var(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, universe: UniverseIndex) -> Region<'db> { let region_var = self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe); Region::new_var(self.interner, region_var) } pub fn next_term_var_of_kind(&self, term: Term<'db>) -> Term<'db> { match term.kind() { TermKind::Ty(_) => self.next_ty_var().into(), TermKind::Const(_) => self.next_const_var().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: Region<'db>) -> 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) -> Region<'db> { self.next_region_var() } /// 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, universe: UniverseIndex) -> Region<'db> { self.next_region_var_in_universe(universe) } fn var_for_def(&self, id: GenericParamId) -> GenericArg<'db> { match id { GenericParamId::LifetimeParamId(_) => { // Create a region inference variable for the given // region parameter definition. self.next_region_var().into() } GenericParamId::TypeParamId(_) => { // 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: None }); Ty::new_var(self.interner, ty_var_id).into() } GenericParamId::ConstParamId(_) => { let origin = ConstVariableOrigin {}; let const_var_id = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVariableValue::Unknown { origin, universe: self.universe() }) .vid; Const::new_var(self.interner, 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, def_id: SolverDefId) -> GenericArgs<'db> { GenericArgs::for_item(self.interner, def_id, |_index, kind, _| self.var_for_def(kind)) } /// Like `fresh_args_for_item()`, but first uses the args from `first`. pub fn fill_rest_fresh_args( &self, def_id: SolverDefId, first: impl IntoIterator>, ) -> GenericArgs<'db> { GenericArgs::fill_rest(self.interner, def_id, first, |_index, kind, _| { self.var_for_def(kind) }) } /// 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)); } #[instrument(level = "debug", skip(self))] pub fn take_opaque_types( &self, ) -> impl IntoIterator, OpaqueHiddenType<'db>)> + use<'db> { self.inner.borrow_mut().opaque_type_storage.take_opaque_types() } #[instrument(level = "debug", skip(self), ret)] pub fn clone_opaque_types(&self) -> Vec<(OpaqueTypeKey<'db>, OpaqueHiddenType<'db>)> { 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 { 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 TyKind::Infer(InferTy::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 }) } #[inline(always)] pub fn can_define_opaque_ty(&self, id: impl Into) -> bool { match self.typing_mode_unchecked() { TypingMode::Analysis { defining_opaque_types_and_generators } => { defining_opaque_types_and_generators.contains(&id.into()) } TypingMode::Coherence | TypingMode::PostAnalysis => false, TypingMode::Borrowck { defining_opaque_types: _ } => unimplemented!(), TypingMode::PostBorrowckAnalysis { defined_opaque_types: _ } => unimplemented!(), } } /// 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, 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<'db>) -> Ty<'db> { if let TyKind::Infer(v) = ty.kind() { match v { InferTy::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)) } InferTy::IntVar(v) => { match self.inner.borrow_mut().int_unification_table().probe_value(v) { IntVarValue::IntType(ty) => Ty::new_int(self.interner, ty), IntVarValue::UintType(ty) => Ty::new_uint(self.interner, ty), IntVarValue::Unknown => ty, } } InferTy::FloatVar(v) => { match self.inner.borrow_mut().float_unification_table().probe_value(v) { FloatVarValue::Known(ty) => Ty::new_float(self.interner, ty), FloatVarValue::Unknown => ty, } } InferTy::FreshTy(_) | InferTy::FreshIntTy(_) | InferTy::FreshFloatTy(_) => ty, } } else { ty } } pub fn shallow_resolve_const(&self, ct: Const<'db>) -> Const<'db> { match ct.kind() { 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, }, ConstKind::Param(_) | ConstKind::Bound(_, _) | ConstKind::Placeholder(_) | ConstKind::Unevaluated(_) | ConstKind::Value(_) | ConstKind::Error(_) | ConstKind::Expr(_) => ct, } } pub fn root_var(&self, var: TyVid) -> TyVid { self.inner.borrow_mut().type_variables().root_var(var) } pub fn root_const_var(&self, var: ConstVid) -> 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: IntVid) -> Ty<'db> { let mut inner = self.inner.borrow_mut(); let value = inner.int_unification_table().probe_value(vid); match value { IntVarValue::IntType(ty) => Ty::new_int(self.interner, ty), IntVarValue::UintType(ty) => Ty::new_uint(self.interner, ty), IntVarValue::Unknown => { Ty::new_int_var(self.interner, inner.int_unification_table().find(vid)) } } } pub fn resolve_int_var(&self, vid: IntVid) -> Option> { let mut inner = self.inner.borrow_mut(); let value = inner.int_unification_table().probe_value(vid); match value { IntVarValue::IntType(ty) => Some(Ty::new_int(self.interner, ty)), IntVarValue::UintType(ty) => Some(Ty::new_uint(self.interner, ty)), IntVarValue::Unknown => None, } } /// 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: FloatVid) -> Ty<'db> { let mut inner = self.inner.borrow_mut(); let value = inner.float_unification_table().probe_value(vid); match value { FloatVarValue::Known(ty) => Ty::new_float(self.interner, ty), FloatVarValue::Unknown => { Ty::new_float_var(self.interner, inner.float_unification_table().find(vid)) } } } pub fn resolve_float_var(&self, vid: FloatVid) -> Option> { let mut inner = self.inner.borrow_mut(); let value = inner.float_unification_table().probe_value(vid); match value { FloatVarValue::Known(ty) => Some(Ty::new_float(self.interner, ty)), FloatVarValue::Unknown => None, } } /// 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 probe_const_var(&self, vid: ConstVid) -> Result, UniverseIndex> { match self.inner.borrow_mut().const_unification_table().probe_value(vid) { ConstVariableValue::Known { value } => Ok(value), ConstVariableValue::Unknown { origin: _, universe } => Err(universe), } } // 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, _lbrct: BoundRegionConversionTime, value: Binder<'db, T>, ) -> T where T: TypeFoldable> + Clone, { if let Some(inner) = value.clone().no_bound_vars() { return inner; } let bound_vars = value.clone().bound_vars(); let mut args = Vec::with_capacity(bound_vars.len()); for bound_var_kind in bound_vars { let arg: GenericArg<'db> = match bound_var_kind { BoundVarKind::Ty(_) => self.next_ty_var().into(), BoundVarKind::Region(_) => self.next_region_var().into(), BoundVarKind::Const => self.next_const_var().into(), }; args.push(arg); } struct ToFreshVars<'db> { args: Vec>, } impl<'db> BoundVarReplacerDelegate<'db> for ToFreshVars<'db> { fn replace_region(&mut self, br: BoundRegion) -> Region<'db> { self.args[br.var.index()].expect_region() } fn replace_ty(&mut self, bt: BoundTy) -> Ty<'db> { self.args[bt.var.index()].expect_ty() } fn replace_const(&mut self, bv: BoundConst) -> Const<'db> { self.args[bv.var.index()].expect_const() } } let delegate = ToFreshVars { args }; self.interner.replace_bound_vars_uncached(value, delegate) } /// 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<'db>) -> Option { let unresolved_kind_ty = match closure_ty.kind() { TyKind::Closure(_, args) => args.as_closure().kind_ty(), TyKind::CoroutineClosure(_, args) => args.as_coroutine_closure().kind_ty(), _ => panic!("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) -> 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) -> UniverseIndex { let u = self.universe.get().next_universe(); debug!("create_next_universe {u:?}"); self.universe.set(u); u } /// 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<'a>( &'a self, ) -> impl Fn(TyOrConstInferVar) -> bool + Captures<'db> + 'a { // 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 = Infer(_)`) /// * `shallow_resolve(ct) != ct` (where `ct.kind = 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 `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 // `Infer(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 // `Int(_)` or `UInt(_)`, which never matches a // `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 // `Float(_)`, which never matches a `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 // `ConstKind::Infer(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, } } } } fn sub_unification_table_root_var(&self, var: rustc_type_ir::TyVid) -> rustc_type_ir::TyVid { self.inner.borrow_mut().type_variables().sub_unification_table_root_var(var) } fn sub_unify_ty_vids_raw(&self, a: rustc_type_ir::TyVid, b: rustc_type_ir::TyVid) { self.inner.borrow_mut().type_variables().sub_unify(a, b); } /// Attach a callback to be invoked on each root obligation evaluated in the new trait solver. pub fn attach_obligation_inspector(&self, inspector: ObligationInspector<'db>) { debug_assert!( self.obligation_inspector.get().is_none(), "shouldn't override a set obligation inspector" ); self.obligation_inspector.set(Some(inspector)); } pub fn inspect_evaluated_obligation( &self, obligation: &PredicateObligation<'db>, result: &Result>, NoSolution>, get_proof_tree: impl FnOnce() -> Option>>, ) { if let Some(inspector) = self.obligation_inspector.get() { let result = match result { Ok(GoalEvaluation { certainty, .. }) => Ok(*certainty), Err(_) => Err(NoSolution), }; (inspector)(self, obligation, result, get_proof_tree()); } } } /// 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 `Infer(TyVar(_))`. Ty(TyVid), /// Equivalent to `Infer(IntVar(_))`. TyInt(IntVid), /// Equivalent to `Infer(FloatVar(_))`. TyFloat(FloatVid), /// Equivalent to `ConstKind::Infer(InferConst::Var(_))`. Const(ConstVid), } impl TyOrConstInferVar { /// Tries to extract an inference variable from a type or a constant, returns `None` /// for types other than `Infer(_)` (or `InferTy::Fresh*`) and /// for constants other than `ConstKind::Infer(_)` (or `InferConst::Fresh`). pub fn maybe_from_generic_arg<'db>(arg: GenericArg<'db>) -> 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, returns `None` /// for types other than `Infer(_)` (or `InferTy::Fresh*`). fn maybe_from_ty<'db>(ty: Ty<'db>) -> Option { match ty.kind() { TyKind::Infer(InferTy::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)), TyKind::Infer(InferTy::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)), TyKind::Infer(InferTy::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)), _ => None, } } /// Tries to extract an inference variable from a constant, returns `None` /// for constants other than `ConstKind::Infer(_)` (or `InferConst::Fresh`). fn maybe_from_const<'db>(ct: Const<'db>) -> Option { match ct.kind() { ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)), _ => None, } } } impl<'db> TypeTrace<'db> { pub fn types(cause: &ObligationCause, a: Ty<'db>, b: Ty<'db>) -> TypeTrace<'db> { TypeTrace { cause: cause.clone(), values: ValuePairs::Terms(ExpectedFound::new(a.into(), b.into())), } } pub fn trait_refs( cause: &ObligationCause, a: TraitRef<'db>, b: TraitRef<'db>, ) -> TypeTrace<'db> { TypeTrace { cause: cause.clone(), values: ValuePairs::TraitRefs(ExpectedFound::new(a, b)) } } pub fn consts(cause: &ObligationCause, a: Const<'db>, b: Const<'db>) -> TypeTrace<'db> { TypeTrace { cause: cause.clone(), values: ValuePairs::Terms(ExpectedFound::new(a.into(), b.into())), } } } /// Requires that `region` must be equal to one of the regions in `choice_regions`. /// We often denote this using the syntax: /// /// ```text /// R0 member of [O1..On] /// ``` #[derive(Debug, Clone, PartialEq, Eq, Hash)] pub struct MemberConstraint<'db> { /// The `DefId` and args of the opaque type causing this constraint. /// Used for error reporting. pub key: OpaqueTypeKey<'db>, /// The hidden type in which `member_region` appears: used for error reporting. pub hidden_ty: Ty<'db>, /// The region `R0`. pub member_region: Region<'db>, /// The options `O1..On`. pub choice_regions: Arc>>, }