Unnamed repository; edit this file 'description' to name the repository.
Diffstat (limited to 'crates/hir-ty/src/next_solver/infer/mod.rs')
| -rw-r--r-- | crates/hir-ty/src/next_solver/infer/mod.rs | 1130 |
1 files changed, 1130 insertions, 0 deletions
diff --git a/crates/hir-ty/src/next_solver/infer/mod.rs b/crates/hir-ty/src/next_solver/infer/mod.rs new file mode 100644 index 0000000000..8e922abacb --- /dev/null +++ b/crates/hir-ty/src/next_solver/infer/mod.rs @@ -0,0 +1,1130 @@ +//! 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::*; +pub use at::DefineOpaqueTypes; +use ena::undo_log::UndoLogs; +use ena::unify as ut; +use hir_def::GenericParamId; +use intern::Symbol; +use opaque_types::{OpaqueHiddenType, OpaqueTypeStorage}; +use region_constraints::{ + GenericKind, RegionConstraintCollector, RegionConstraintStorage, UndoLog, VarInfos, VerifyBound, +}; +pub use relate::StructurallyRelateAliases; +pub use relate::combine::PredicateEmittingRelation; +use rustc_hash::{FxHashMap, FxHashSet}; +use rustc_pattern_analysis::Captures; +use rustc_type_ir::error::{ExpectedFound, TypeError}; +use rustc_type_ir::inherent::{ + Const as _, GenericArg as _, GenericArgs as _, IntoKind, ParamEnv as _, SliceLike, Term as _, + Ty as _, +}; +use rustc_type_ir::{ + BoundVar, ClosureKind, ConstVid, FloatTy, FloatVarValue, FloatVid, GenericArgKind, InferConst, + InferTy, IntTy, IntVarValue, IntVid, OutlivesPredicate, RegionVid, TyVid, UniverseIndex, +}; +use rustc_type_ir::{TermKind, TypeVisitableExt}; +use rustc_type_ir::{TypeFoldable, TypeFolder, TypeSuperFoldable}; +use snapshot::undo_log::InferCtxtUndoLogs; +use tracing::{debug, instrument}; +use traits::{ObligationCause, PredicateObligations}; +use type_variable::TypeVariableOrigin; +use unify_key::{ConstVariableOrigin, ConstVariableValue, ConstVidKey}; + +use crate::next_solver::fold::BoundVarReplacerDelegate; +use crate::next_solver::infer::opaque_types::table::OpaqueTypeStorageEntries; +use crate::next_solver::{BoundConst, BoundRegion, BoundTy, BoundVarKind}; + +use super::generics::GenericParamDef; +use super::{ + AliasTerm, Binder, BoundRegionKind, CanonicalQueryInput, CanonicalVarValues, Const, ConstKind, + DbInterner, ErrorGuaranteed, FxIndexMap, GenericArg, GenericArgs, OpaqueTypeKey, ParamEnv, + PlaceholderRegion, PolyCoercePredicate, PolyExistentialProjection, PolyExistentialTraitRef, + PolyFnSig, PolyRegionOutlivesPredicate, PolySubtypePredicate, Predicate, Region, SolverDefId, + SubtypePredicate, Term, TraitPredicate, TraitRef, Ty, TyKind, TypingMode, +}; + +pub mod at; +pub mod canonical; +mod context; +mod opaque_types; +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<'tcx, ()>` 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<InferOk<'db, T>, TypeError<DbInterner<'db>>>; + +pub(crate) type FixupResult<T> = Result<T, FixupError>; // "fixup result" + +pub(crate) type UnificationTable<'a, 'db, T> = ut::UnificationTable< + ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'db>>, +>; + +fn iter_idx_range<T: From<u32> + Into<u32>>(range: Range<T>) -> impl Iterator<Item = T> { + (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<Ty>` 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<ConstVidKey<'db>>, + + /// Map from integral variable to the kind of integer it represents. + pub(crate) int_unification_storage: ut::UnificationTableStorage<IntVid>, + + /// Map from floating variable to the kind of float it represents. + pub(crate) float_unification_storage: ut::UnificationTableStorage<FloatVid>, + + /// 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<RegionConstraintStorage<'db>>, + + /// 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<T: 'static> { ... } + /// ``` + /// 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<RegionObligation<'db>>, + + /// 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![], + opaque_type_storage: Default::default(), + } + } + + #[inline] + pub fn region_obligations(&self) -> &[RegionObligation<'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<InferCtxtInner<'db>>, + + /// 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<Option<ErrorGuaranteed>>, + + /// 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<UniverseIndex>, +} + +/// See the `error_reporting` module for more details. +#[derive(Clone, Debug, PartialEq, Eq)] +pub enum ValuePairs<'db> { + Regions(ExpectedFound<Region<'db>>), + Terms(ExpectedFound<Term<'db>>), + Aliases(ExpectedFound<AliasTerm<'db>>), + TraitRefs(ExpectedFound<TraitRef<'db>>), + PolySigs(ExpectedFound<PolyFnSig<'db>>), + ExistentialTraitRef(ExpectedFound<PolyExistentialTraitRef<'db>>), + ExistentialProjection(ExpectedFound<PolyExistentialProjection<'db>>), +} + +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 RegionObligation<'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<T>( + mut self, + input: &CanonicalQueryInput<'db, T>, + ) -> (InferCtxt<'db>, T, CanonicalVarValues<'db>) + where + T: TypeFoldable<DbInterner<'db>>, + { + 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), + } + } +} + +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 + } + + pub fn unresolved_variables(&self) -> Vec<Ty<'db>> { + let mut inner = self.inner.borrow_mut(); + let mut vars: Vec<Ty<'db>> = 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<InferResult<'db, ()>, (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<InferResult<'db, ()>, (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(DefineOpaqueTypes::Yes, a, b)) + } else { + Ok(self.at(cause, param_env).sup(DefineOpaqueTypes::Yes, 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_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 { param_def_id: None }) + } + + pub fn next_const_vid(&self) -> ConstVid { + self.inner + .borrow_mut() + .const_unification_table() + .new_key(ConstVariableValue::Unknown { + origin: ConstVariableOrigin { param_def_id: None }, + 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 { param_def_id: None }; + 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, name: &Symbol) -> 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<A, B, C = (A, B)>(...);` when + // used in a path such as `Foo::<T, U>::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 { param_def_id: None }; + 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, |name, index, kind, _| { + self.var_for_def(kind, name) + }) + } + + /// 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<ErrorGuaranteed> { + 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), ret)] + pub fn take_opaque_types(&self) -> Vec<(OpaqueTypeKey<'db>, OpaqueHiddenType<'db>)> { + 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<'db>, OpaqueHiddenType<'db>)> { + self.inner.borrow_mut().opaque_type_storage.iter_opaque_types().collect() + } + + #[inline(always)] + pub fn can_define_opaque_ty(&self, id: impl Into<SolverDefId>) -> 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<Ty<'db>, 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<Ty<'db>> { + 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<Ty<'db>> { + 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<T>(&self, value: T) -> T + where + T: TypeFoldable<DbInterner<'db>>, + { + 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<Const<'db>, 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<T>( + &self, + lbrct: BoundRegionConversionTime, + value: Binder<'db, T>, + ) -> T + where + T: TypeFoldable<DbInterner<'db>> + 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(br) => self.next_region_var().into(), + BoundVarKind::Const => self.next_const_var().into(), + }; + args.push(arg); + } + + struct ToFreshVars<'db> { + args: Vec<GenericArg<'db>>, + } + + 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<ClosureKind> { + 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); + } +} + +/// 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<Self> { + 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<Self> { + 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<Self> { + 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<Vec<Region<'db>>>, +} |