pub use self::freshen::TypeFreshener; pub use self::lexical_region_resolve::RegionResolutionError; pub use self::LateBoundRegionConversionTime::*; pub use self::RegionVariableOrigin::*; pub use self::SubregionOrigin::*; pub use self::ValuePairs::*; use self::opaque_types::OpaqueTypeStorage; pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog}; use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine, TraitEngineExt}; use rustc_data_structures::fx::{FxHashMap, FxHashSet}; use rustc_data_structures::sync::Lrc; use rustc_data_structures::undo_log::Rollback; use rustc_data_structures::unify as ut; use rustc_errors::{DiagnosticBuilder, ErrorGuaranteed}; use rustc_hir::def_id::{DefId, LocalDefId}; use rustc_middle::infer::canonical::{Canonical, CanonicalVarValues}; use rustc_middle::infer::unify_key::{ConstVarValue, ConstVariableValue}; use rustc_middle::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType}; use rustc_middle::mir::interpret::{ErrorHandled, EvalToValTreeResult}; use rustc_middle::mir::ConstraintCategory; use rustc_middle::traits::select; use rustc_middle::ty::abstract_const::{AbstractConst, FailureKind}; use rustc_middle::ty::error::{ExpectedFound, TypeError}; use rustc_middle::ty::fold::BoundVarReplacerDelegate; use rustc_middle::ty::fold::{TypeFoldable, TypeFolder, TypeSuperFoldable}; use rustc_middle::ty::relate::RelateResult; use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef}; use rustc_middle::ty::visit::TypeVisitable; pub use rustc_middle::ty::IntVarValue; use rustc_middle::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt}; use rustc_middle::ty::{ConstVid, FloatVid, IntVid, TyVid}; use rustc_span::symbol::Symbol; use rustc_span::{Span, DUMMY_SP}; use std::cell::{Cell, RefCell}; use std::fmt; use self::combine::CombineFields; use self::error_reporting::TypeErrCtxt; use self::free_regions::RegionRelations; use self::lexical_region_resolve::LexicalRegionResolutions; use self::outlives::env::OutlivesEnvironment; use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound}; use self::region_constraints::{ RegionConstraintCollector, RegionConstraintStorage, RegionSnapshot, }; use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind}; pub mod at; pub mod canonical; mod combine; mod equate; pub mod error_reporting; pub mod free_regions; mod freshen; mod fudge; mod glb; mod higher_ranked; pub mod lattice; mod lexical_region_resolve; mod lub; pub mod nll_relate; pub mod opaque_types; pub mod outlives; mod projection; pub mod region_constraints; pub mod resolve; mod sub; pub mod type_variable; mod undo_log; #[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 type Bound = Option; pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result" pub type FixupResult<'tcx, T> = 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> { /// Cache for projections. This cache is snapshotted along with the infcx. /// /// Public so that `traits::project` can use it. pub 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 /// ```ignore (illustrative) /// struct Foo { ... } /// ``` /// then 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>, undo_log: InferCtxtUndoLogs<'tcx>, /// Caches for opaque type inference. pub opaque_type_storage: OpaqueTypeStorage<'tcx>, } impl<'tcx> InferCtxtInner<'tcx> { fn new() -> InferCtxtInner<'tcx> { InferCtxtInner { projection_cache: Default::default(), type_variable_storage: type_variable::TypeVariableStorage::new(), undo_log: InferCtxtUndoLogs::default(), const_unification_storage: ut::UnificationTableStorage::new(), int_unification_storage: ut::UnificationTableStorage::new(), float_unification_storage: ut::UnificationTableStorage::new(), region_constraint_storage: Some(RegionConstraintStorage::new()), region_obligations: vec![], opaque_type_storage: Default::default(), } } #[inline] pub fn region_obligations(&self) -> &[RegionObligation<'tcx>] { &self.region_obligations } #[inline] pub fn projection_cache(&mut self) -> traits::ProjectionCache<'_, 'tcx> { self.projection_cache.with_log(&mut self.undo_log) } #[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, ) -> ut::UnificationTable< ut::InPlace< ty::IntVid, &mut ut::UnificationStorage, &mut InferCtxtUndoLogs<'tcx>, >, > { self.int_unification_storage.with_log(&mut self.undo_log) } #[inline] fn float_unification_table( &mut self, ) -> ut::UnificationTable< ut::InPlace< ty::FloatVid, &mut ut::UnificationStorage, &mut InferCtxtUndoLogs<'tcx>, >, > { self.float_unification_storage.with_log(&mut self.undo_log) } #[inline] fn const_unification_table( &mut self, ) -> ut::UnificationTable< ut::InPlace< ty::ConstVid<'tcx>, &mut ut::UnificationStorage>, &mut InferCtxtUndoLogs<'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) } } #[derive(Clone, Copy, Debug, PartialEq, Eq)] pub enum DefiningAnchor { /// `DefId` of the item. Bind(LocalDefId), /// When opaque types are not resolved, we `Bubble` up, meaning /// return the opaque/hidden type pair from query, for caller of query to handle it. Bubble, /// Used to catch type mismatch errors when handling opaque types. Error, } pub struct InferCtxt<'tcx> { pub tcx: TyCtxt<'tcx>, /// The `DefId` of the item in whose context we are performing inference or typeck. /// It is used to check whether an opaque type use is a defining use. /// /// If it is `DefiningAnchor::Bubble`, we can't resolve opaque types here and need to bubble up /// the obligation. This frequently happens for /// short lived InferCtxt within queries. The opaque type obligations are forwarded /// to the outside until the end up in an `InferCtxt` for typeck or borrowck. /// /// It is default value is `DefiningAnchor::Error`, this way it is easier to catch errors that /// might come up during inference or typeck. pub defining_use_anchor: DefiningAnchor, /// 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, pub inner: RefCell>, /// 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. This flag can only be set to true /// when entering a snapshot. skip_leak_check: Cell, /// 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 have to do with the parameters in scope. pub selection_cache: select::SelectionCache<'tcx>, /// Caches the results of trait evaluation. pub evaluation_cache: select::EvaluationCache<'tcx>, /// the set of predicates on which errors have been reported, to /// avoid reporting the same error twice. pub reported_trait_errors: RefCell>>>, pub reported_closure_mismatch: RefCell)>>, /// When an error occurs, we want to avoid reporting "derived" /// errors that are due to this original failure. Normally, we /// handle this with the `err_count_on_creation` count, which /// basically just tracks how many errors were reported when we /// started type-checking a fn and checks to see if any new errors /// have been reported since then. Not great, but it works. /// /// However, when errors originated in other passes -- notably /// resolve -- this heuristic breaks down. Therefore, we have this /// auxiliary 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>, /// Track how many errors were reported when this infcx is created. /// If the number of errors increases, that's also a sign (line /// `tainted_by_errors`) to avoid reporting certain kinds of errors. // FIXME(matthewjasper) Merge into `tainted_by_errors` err_count_on_creation: usize, /// This flag is true while there is an active snapshot. in_snapshot: 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, normalize_fn_sig_for_diagnostic: Option, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>>, } /// See the `error_reporting` module for more details. #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable, TypeVisitable)] pub enum ValuePairs<'tcx> { Regions(ExpectedFound>), Terms(ExpectedFound>), TraitRefs(ExpectedFound>), PolyTraitRefs(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.ty() && let Some(found) = found.ty() { 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), /// Creating a pointer `b` to contents of another reference Reborrow(Span), /// Creating a pointer `b` to contents of an upvar ReborrowUpvar(Span, ty::UpvarId), /// Data with type `Ty<'tcx>` was borrowed DataBorrowed(Ty<'tcx>, 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(all(target_arch = "x86_64", target_pointer_width = "64"))] 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 late-bound regions with variables: #[derive(Clone, Copy, Debug)] pub enum LateBoundRegionConversionTime { /// 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, /// mostly indicates places in need of refactoring MiscVariable(Span), /// Regions created by a `&P` or `[...]` pattern PatternRegion(Span), /// Regions created by `&` operator AddrOfRegion(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 EarlyBoundRegion(Span, Symbol), /// Region variables created for bound regions /// in a function or method that is called LateBoundRegion(Span, ty::BoundRegionKind, LateBoundRegionConversionTime), 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 { /// If this is true, then this variable was created to represent a lifetime /// bound in a `for` binder. For example, it might have been created to /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`. /// Such variables are created when we are trying to figure out if there /// is any valid instantiation of `'a` that could fit into some scenario. /// /// This is used to inform error reporting: in the case that we are trying to /// determine whether there is any valid instantiation of a `'a` variable that meets /// some constraint C, we want to blame the "source" of that `for` type, /// rather than blaming the source of the constraint C. from_forall: bool, }, } // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`. #[derive(Copy, Clone, Debug)] pub enum FixupError<'tcx> { UnresolvedIntTy(IntVid), UnresolvedFloatTy(FloatVid), UnresolvedTy(TyVid), UnresolvedConst(ConstVid<'tcx>), } /// See the `region_obligations` field for more information. #[derive(Clone, Debug)] pub struct RegionObligation<'tcx> { pub sub_region: ty::Region<'tcx>, pub sup_type: Ty<'tcx>, pub origin: SubregionOrigin<'tcx>, } impl<'tcx> fmt::Display for FixupError<'tcx> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { use self::FixupError::*; match *self { UnresolvedIntTy(_) => write!( f, "cannot determine the type of this integer; \ add a suffix to specify the type explicitly" ), UnresolvedFloatTy(_) => write!( f, "cannot determine the type of this number; \ add a suffix to specify the type explicitly" ), UnresolvedTy(_) => write!(f, "unconstrained type"), UnresolvedConst(_) => write!(f, "unconstrained const value"), } } } /// Used to configure inference contexts before their creation pub struct InferCtxtBuilder<'tcx> { tcx: TyCtxt<'tcx>, defining_use_anchor: DefiningAnchor, considering_regions: bool, normalize_fn_sig_for_diagnostic: Option, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>>, } pub trait TyCtxtInferExt<'tcx> { fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>; } impl<'tcx> TyCtxtInferExt<'tcx> for TyCtxt<'tcx> { fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> { InferCtxtBuilder { tcx: self, defining_use_anchor: DefiningAnchor::Error, considering_regions: true, normalize_fn_sig_for_diagnostic: None, } } } impl<'tcx> InferCtxtBuilder<'tcx> { /// Whenever the `InferCtxt` should be able to handle defining uses of opaque types, /// you need to call this function. Otherwise the opaque type will be treated opaquely. /// /// It is only meant to be called in two places, for typeck /// (via `Inherited::build`) and for the inference context used /// in mir borrowck. pub fn with_opaque_type_inference(mut self, defining_use_anchor: DefiningAnchor) -> Self { self.defining_use_anchor = defining_use_anchor; self } pub fn ignoring_regions(mut self) -> Self { self.considering_regions = false; self } pub fn with_normalize_fn_sig_for_diagnostic( mut self, fun: Lrc, ty::PolyFnSig<'tcx>) -> ty::PolyFnSig<'tcx>>, ) -> Self { self.normalize_fn_sig_for_diagnostic = Some(fun); 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 substitution `S`. This substitution `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, canonical: &Canonical<'tcx, T>, ) -> (InferCtxt<'tcx>, T, CanonicalVarValues<'tcx>) where T: TypeFoldable<'tcx>, { let infcx = self.build(); let (value, subst) = infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical); (infcx, value, subst) } pub fn build(&mut self) -> InferCtxt<'tcx> { let InferCtxtBuilder { tcx, defining_use_anchor, considering_regions, ref normalize_fn_sig_for_diagnostic, } = *self; InferCtxt { tcx, defining_use_anchor, considering_regions, 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_closure_mismatch: Default::default(), tainted_by_errors: Cell::new(None), err_count_on_creation: tcx.sess.err_count(), in_snapshot: Cell::new(false), skip_leak_check: Cell::new(false), universe: Cell::new(ty::UniverseIndex::ROOT), normalize_fn_sig_for_diagnostic: normalize_fn_sig_for_diagnostic .as_ref() .map(|f| f.clone()), } } } impl<'tcx, T> InferOk<'tcx, T> { pub fn unit(self) -> InferOk<'tcx, ()> { InferOk { value: (), obligations: self.obligations } } /// Extracts `value`, registering any obligations into `fulfill_cx`. pub fn into_value_registering_obligations( self, infcx: &InferCtxt<'tcx>, fulfill_cx: &mut dyn TraitEngine<'tcx>, ) -> 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 } } #[must_use = "once you start a snapshot, you should always consume it"] pub struct CombinedSnapshot<'tcx> { undo_snapshot: Snapshot<'tcx>, region_constraints_snapshot: RegionSnapshot, universe: ty::UniverseIndex, was_in_snapshot: bool, } impl<'tcx> InferCtxt<'tcx> { /// Creates a `TypeErrCtxt` for emitting various inference errors. /// During typeck, use `FnCtxt::infer_err` instead. pub fn err_ctxt(&self) -> TypeErrCtxt<'_, 'tcx> { TypeErrCtxt { infcx: self, typeck_results: None } } /// calls `tcx.try_unify_abstract_consts` after /// canonicalizing the consts. #[instrument(skip(self), level = "debug")] pub fn try_unify_abstract_consts( &self, a: ty::UnevaluatedConst<'tcx>, b: ty::UnevaluatedConst<'tcx>, param_env: ty::ParamEnv<'tcx>, ) -> bool { // Reject any attempt to unify two unevaluated constants that contain inference // variables, since inference variables in queries lead to ICEs. if a.substs.has_non_region_infer() || b.substs.has_non_region_infer() || param_env.has_non_region_infer() { debug!("a or b or param_env contain infer vars in its substs -> cannot unify"); return false; } let param_env_and = param_env.and((a, b)); let erased = self.tcx.erase_regions(param_env_and); debug!("after erase_regions: {:?}", erased); self.tcx.try_unify_abstract_consts(erased) } pub fn is_in_snapshot(&self) -> bool { self.in_snapshot.get() } pub fn freshen>(&self, t: T) -> T { t.fold_with(&mut self.freshener()) } /// Returns the origin of the type variable identified by `vid`, or `None` /// if this is not a type variable. /// /// No attempt is made to resolve `ty`. pub fn type_var_origin(&self, ty: Ty<'tcx>) -> Option { match *ty.kind() { ty::Infer(ty::TyVar(vid)) => { Some(*self.inner.borrow_mut().type_variables().var_origin(vid)) } _ => None, } } pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> { freshen::TypeFreshener::new(self, false) } /// Like `freshener`, but does not replace `'static` regions. pub fn freshener_keep_static<'b>(&'b self) -> TypeFreshener<'b, 'tcx> { freshen::TypeFreshener::new(self, true) } pub fn unsolved_variables(&self) -> Vec> { let mut inner = self.inner.borrow_mut(); let mut vars: Vec> = inner .type_variables() .unsolved_variables() .into_iter() .map(|t| self.tcx.mk_ty_var(t)) .collect(); vars.extend( (0..inner.int_unification_table().len()) .map(|i| ty::IntVid { index: i as u32 }) .filter(|&vid| inner.int_unification_table().probe_value(vid).is_none()) .map(|v| self.tcx.mk_int_var(v)), ); vars.extend( (0..inner.float_unification_table().len()) .map(|i| ty::FloatVid { index: i as u32 }) .filter(|&vid| inner.float_unification_table().probe_value(vid).is_none()) .map(|v| self.tcx.mk_float_var(v)), ); vars } fn combine_fields<'a>( &'a self, trace: TypeTrace<'tcx>, param_env: ty::ParamEnv<'tcx>, define_opaque_types: bool, ) -> CombineFields<'a, 'tcx> { CombineFields { infcx: self, trace, cause: None, param_env, obligations: PredicateObligations::new(), define_opaque_types, } } /// Clear the "currently in a snapshot" flag, invoke the closure, /// then restore the flag to its original value. This flag is a /// debugging measure designed to detect cases where we start a /// snapshot, create type variables, and register obligations /// which may involve those type variables in the fulfillment cx, /// potentially leaving "dangling type variables" behind. /// In such cases, an assertion will fail when attempting to /// register obligations, within a snapshot. Very useful, much /// better than grovelling through megabytes of `RUSTC_LOG` output. /// /// HOWEVER, in some cases the flag is unhelpful. In particular, we /// sometimes create a "mini-fulfilment-cx" in which we enroll /// obligations. As long as this fulfillment cx is fully drained /// before we return, this is not a problem, as there won't be any /// escaping obligations in the main cx. In those cases, you can /// use this function. pub fn save_and_restore_in_snapshot_flag(&self, func: F) -> R where F: FnOnce(&Self) -> R, { let flag = self.in_snapshot.replace(false); let result = func(self); self.in_snapshot.set(flag); result } fn start_snapshot(&self) -> CombinedSnapshot<'tcx> { debug!("start_snapshot()"); let in_snapshot = self.in_snapshot.replace(true); let mut inner = self.inner.borrow_mut(); CombinedSnapshot { undo_snapshot: inner.undo_log.start_snapshot(), region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(), universe: self.universe(), was_in_snapshot: in_snapshot, } } #[instrument(skip(self, snapshot), level = "debug")] fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'tcx>) { let CombinedSnapshot { undo_snapshot, region_constraints_snapshot, universe, was_in_snapshot, } = snapshot; self.in_snapshot.set(was_in_snapshot); self.universe.set(universe); let mut inner = self.inner.borrow_mut(); inner.rollback_to(undo_snapshot); inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot); } #[instrument(skip(self, snapshot), level = "debug")] fn commit_from(&self, snapshot: CombinedSnapshot<'tcx>) { let CombinedSnapshot { undo_snapshot, region_constraints_snapshot: _, universe: _, was_in_snapshot, } = snapshot; self.in_snapshot.set(was_in_snapshot); self.inner.borrow_mut().commit(undo_snapshot); } /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`. #[instrument(skip(self, f), level = "debug")] pub fn commit_if_ok(&self, f: F) -> Result where F: FnOnce(&CombinedSnapshot<'tcx>) -> Result, { let snapshot = self.start_snapshot(); let r = f(&snapshot); debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok()); match r { Ok(_) => { self.commit_from(snapshot); } Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); } } r } /// Execute `f` then unroll any bindings it creates. #[instrument(skip(self, f), level = "debug")] pub fn probe(&self, f: F) -> R where F: FnOnce(&CombinedSnapshot<'tcx>) -> R, { let snapshot = self.start_snapshot(); let r = f(&snapshot); self.rollback_to("probe", snapshot); r } /// If `should_skip` is true, then execute `f` then unroll any bindings it creates. #[instrument(skip(self, f), level = "debug")] pub fn probe_maybe_skip_leak_check(&self, should_skip: bool, f: F) -> R where F: FnOnce(&CombinedSnapshot<'tcx>) -> R, { let snapshot = self.start_snapshot(); let was_skip_leak_check = self.skip_leak_check.get(); if should_skip { self.skip_leak_check.set(true); } let r = f(&snapshot); self.rollback_to("probe", snapshot); self.skip_leak_check.set(was_skip_leak_check); r } /// Scan the constraints produced since `snapshot` began and returns: /// /// - `None` -- if none of them involve "region outlives" constraints /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders pub fn region_constraints_added_in_snapshot( &self, snapshot: &CombinedSnapshot<'tcx>, ) -> Option { self.inner .borrow_mut() .unwrap_region_constraints() .region_constraints_added_in_snapshot(&snapshot.undo_snapshot) } pub fn opaque_types_added_in_snapshot(&self, snapshot: &CombinedSnapshot<'tcx>) -> bool { self.inner.borrow().undo_log.opaque_types_in_snapshot(&snapshot.undo_snapshot) } pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) { self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup); } pub fn can_sub(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx> where T: at::ToTrace<'tcx>, { let origin = &ObligationCause::dummy(); self.probe(|_| { self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| { // Ignore obligations, since we are unrolling // everything anyway. }) }) } pub fn can_eq(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx> where T: at::ToTrace<'tcx>, { let origin = &ObligationCause::dummy(); self.probe(|_| { self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| { // Ignore obligations, since we are unrolling // everything anyway. }) }) } #[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); } /// Require that the region `r` be equal to one of the regions in /// the set `regions`. #[instrument(skip(self), level = "debug")] pub fn member_constraint( &self, key: ty::OpaqueTypeKey<'tcx>, definition_span: Span, hidden_ty: Ty<'tcx>, region: ty::Region<'tcx>, in_regions: &Lrc>>, ) { self.inner.borrow_mut().unwrap_region_constraints().member_constraint( key, definition_span, hidden_ty, region, in_regions, ); } /// 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.inner.borrow_mut().type_variables().sub(a_vid, b_vid); return Err((a_vid, b_vid)); } _ => {} } Ok(self.commit_if_ok(|_snapshot| { let ty::SubtypePredicate { a_is_expected, a, b } = self.replace_bound_vars_with_placeholders(predicate); let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?; Ok(ok.unit()) })) } pub fn region_outlives_predicate( &self, cause: &traits::ObligationCause<'tcx>, predicate: ty::PolyRegionOutlivesPredicate<'tcx>, ) { let ty::OutlivesPredicate(r_a, r_b) = self.replace_bound_vars_with_placeholders(predicate); let origin = SubregionOrigin::from_obligation_cause(cause, || RelateRegionParamBound(cause.span)); self.sub_regions(origin, 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_id(&self, origin: TypeVariableOrigin) -> TyVid { self.inner.borrow_mut().type_variables().new_var(self.universe(), origin) } pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> { self.tcx.mk_ty_var(self.next_ty_var_id(origin)) } pub fn next_ty_var_id_in_universe( &self, origin: TypeVariableOrigin, universe: ty::UniverseIndex, ) -> TyVid { self.inner.borrow_mut().type_variables().new_var(universe, origin) } pub fn next_ty_var_in_universe( &self, origin: TypeVariableOrigin, universe: ty::UniverseIndex, ) -> Ty<'tcx> { let vid = self.next_ty_var_id_in_universe(origin, universe); self.tcx.mk_ty_var(vid) } pub fn next_const_var(&self, ty: Ty<'tcx>, origin: ConstVariableOrigin) -> ty::Const<'tcx> { self.tcx.mk_const_var(self.next_const_var_id(origin), ty) } pub fn next_const_var_in_universe( &self, ty: Ty<'tcx>, origin: ConstVariableOrigin, universe: ty::UniverseIndex, ) -> ty::Const<'tcx> { let vid = self .inner .borrow_mut() .const_unification_table() .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } }); self.tcx.mk_const_var(vid, ty) } pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> { self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe: self.universe() }, }) } fn next_int_var_id(&self) -> IntVid { self.inner.borrow_mut().int_unification_table().new_key(None) } pub fn next_int_var(&self) -> Ty<'tcx> { self.tcx.mk_int_var(self.next_int_var_id()) } fn next_float_var_id(&self) -> FloatVid { self.inner.borrow_mut().float_unification_table().new_key(None) } pub fn next_float_var(&self) -> Ty<'tcx> { self.tcx.mk_float_var(self.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); self.tcx.mk_region(ty::ReVar(region_var)) } /// 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. 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. 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(EarlyBoundRegion(span, param.name)).into() } GenericParamDefKind::Type { .. } => { // Create a type inference variable for the given // type parameter definition. The substitutions 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 substitutions for the default, `(T, U)`. let ty_var_id = self.inner.borrow_mut().type_variables().new_var( self.universe(), TypeVariableOrigin { kind: TypeVariableOriginKind::TypeParameterDefinition( param.name, Some(param.def_id), ), span, }, ); self.tcx.mk_ty_var(ty_var_id).into() } GenericParamDefKind::Const { .. } => { let origin = ConstVariableOrigin { kind: ConstVariableOriginKind::ConstParameterDefinition( param.name, param.def_id, ), span, }; let const_var_id = self.inner.borrow_mut().const_unification_table().new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe: self.universe() }, }); self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into() } } } /// Given a set of generics defined on a type or impl, returns a substitution mapping each /// type/region parameter to a fresh inference variable. pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> { InternalSubsts::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). pub fn is_tainted_by_errors(&self) -> bool { debug!( "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \ tainted_by_errors={})", self.tcx.sess.err_count(), self.err_count_on_creation, self.tainted_by_errors.get().is_some() ); if self.tcx.sess.err_count() > self.err_count_on_creation { return true; // errors reported since this infcx was made } self.tainted_by_errors.get().is_some() } /// 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) { debug!("set_tainted_by_errors()"); self.tainted_by_errors.set(Some( self.tcx.sess.delay_span_bug(DUMMY_SP, "`InferCtxt` incorrectly tainted by errors"), )); } pub fn skip_region_resolution(&self) { let (var_infos, _) = { let mut inner = self.inner.borrow_mut(); let inner = &mut *inner; // Note: `inner.region_obligations` may not be empty, because we // didn't necessarily call `process_registered_region_obligations`. // This is okay, because that doesn't introduce new vars. inner .region_constraint_storage .take() .expect("regions already resolved") .with_log(&mut inner.undo_log) .into_infos_and_data() }; let lexical_region_resolutions = LexicalRegionResolutions { values: rustc_index::vec::IndexVec::from_elem_n( crate::infer::lexical_region_resolve::VarValue::Value(self.tcx.lifetimes.re_erased), var_infos.len(), ), }; let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions)); assert!(old_value.is_none()); } /// Process the region constraints and return any errors that /// result. After this, no more unification operations should be /// done -- or the compiler will panic -- but it is legal to use /// `resolve_vars_if_possible` as well as `fully_resolve`. pub fn resolve_regions( &self, outlives_env: &OutlivesEnvironment<'tcx>, ) -> Vec> { let (var_infos, data) = { let mut inner = self.inner.borrow_mut(); let inner = &mut *inner; assert!( self.is_tainted_by_errors() || inner.region_obligations.is_empty(), "region_obligations not empty: {:#?}", inner.region_obligations ); inner .region_constraint_storage .take() .expect("regions already resolved") .with_log(&mut inner.undo_log) .into_infos_and_data() }; let region_rels = &RegionRelations::new(self.tcx, outlives_env.free_region_map()); let (lexical_region_resolutions, errors) = lexical_region_resolve::resolve(outlives_env.param_env, region_rels, var_infos, data); let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions)); assert!(old_value.is_none()); errors } /// Obtains (and clears) the current set of region /// constraints. The inference context is still usable: further /// unifications will simply add new constraints. /// /// This method is not meant to be used with normal lexical region /// resolution. Rather, it is used in the NLL mode as a kind of /// interim hack: basically we run normal type-check and generate /// region constraints as normal, but then we take them and /// translate them into the form that the NLL solver /// understands. See the NLL module for mode details. pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> { assert!( self.inner.borrow().region_obligations.is_empty(), "region_obligations not empty: {:#?}", self.inner.borrow().region_obligations ); self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data() } /// Gives temporary access to the region constraint data. pub fn with_region_constraints( &self, op: impl FnOnce(&RegionConstraintData<'tcx>) -> R, ) -> R { let mut inner = self.inner.borrow_mut(); op(inner.unwrap_region_constraints().data()) } pub fn region_var_origin(&self, vid: ty::RegionVid) -> RegionVariableOrigin { let mut inner = self.inner.borrow_mut(); let inner = &mut *inner; inner .region_constraint_storage .as_mut() .expect("regions already resolved") .with_log(&mut inner.undo_log) .var_origin(vid) } /// Takes ownership of the list of variable regions. This implies /// that all the region constraints have already been taken, and /// hence that `resolve_regions_and_report_errors` can never be /// called. This is used only during NLL processing to "hand off" ownership /// of the set of region variables into the NLL region context. pub fn take_region_var_origins(&self) -> VarInfos { let mut inner = self.inner.borrow_mut(); let (var_infos, data) = inner .region_constraint_storage .take() .expect("regions already resolved") .with_log(&mut inner.undo_log) .into_infos_and_data(); assert!(data.is_empty()); var_infos } 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), } } /// Resolve any type variables found in `value` -- but only one /// level. So, if the variable `?X` is bound to some type /// `Foo`, then this would return `Foo` (but `?Y` may /// itself be bound to a type). /// /// Useful when you only need to inspect the outermost level of /// the type and don't care about nested types (or perhaps you /// will be resolving them as well, e.g. in a loop). pub fn shallow_resolve(&self, value: T) -> T where T: TypeFoldable<'tcx>, { value.fold_with(&mut ShallowResolver { infcx: self }) } pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid { self.inner.borrow_mut().type_variables().root_var(var) } /// 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<'tcx>, { if !value.needs_infer() { return value; // Avoid duplicated subst-folding. } 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<'tcx>, { if !value.needs_infer() { return value; // Avoid duplicated subst-folding. } let mut r = InferenceLiteralEraser { tcx: self.tcx }; value.fold_with(&mut r) } /// Returns the first unresolved variable contained in `T`. In the /// process of visiting `T`, this will resolve (where possible) /// type variables in `T`, but it never constructs the final, /// resolved type, so it's more efficient than /// `resolve_vars_if_possible()`. pub fn unresolved_type_vars(&self, value: &T) -> Option<(Ty<'tcx>, Option)> where T: TypeVisitable<'tcx>, { value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value() } pub fn probe_const_var( &self, vid: ty::ConstVid<'tcx>, ) -> Result, ty::UniverseIndex> { match self.inner.borrow_mut().const_unification_table().probe_value(vid).val { ConstVariableValue::Known { value } => Ok(value), ConstVariableValue::Unknown { universe } => Err(universe), } } pub fn fully_resolve>(&self, value: T) -> FixupResult<'tcx, T> { /*! * 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. */ let value = resolve::fully_resolve(self, value); assert!( value.as_ref().map_or(true, |value| !value.needs_infer()), "`{value:?}` is not fully resolved" ); value } pub fn replace_bound_vars_with_fresh_vars( &self, span: Span, lbrct: LateBoundRegionConversionTime, value: ty::Binder<'tcx, T>, ) -> T where T: TypeFoldable<'tcx> + Copy, { if let Some(inner) = value.no_bound_vars() { return inner; } struct ToFreshVars<'a, 'tcx> { infcx: &'a InferCtxt<'tcx>, span: Span, lbrct: LateBoundRegionConversionTime, map: FxHashMap>, } impl<'tcx> BoundVarReplacerDelegate<'tcx> for ToFreshVars<'_, 'tcx> { fn replace_region(&mut self, br: ty::BoundRegion) -> ty::Region<'tcx> { self.map .entry(br.var) .or_insert_with(|| { self.infcx .next_region_var(LateBoundRegion(self.span, br.kind, self.lbrct)) .into() }) .expect_region() } fn replace_ty(&mut self, bt: ty::BoundTy) -> Ty<'tcx> { self.map .entry(bt.var) .or_insert_with(|| { self.infcx .next_ty_var(TypeVariableOrigin { kind: TypeVariableOriginKind::MiscVariable, span: self.span, }) .into() }) .expect_ty() } fn replace_const(&mut self, bv: ty::BoundVar, ty: Ty<'tcx>) -> ty::Const<'tcx> { self.map .entry(bv) .or_insert_with(|| { self.infcx .next_const_var( ty, ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span: self.span, }, ) .into() }) .expect_const() } } let delegate = ToFreshVars { infcx: self, span, lbrct, map: Default::default() }; self.tcx.replace_bound_vars_uncached(value, delegate) } /// See the [`region_constraints::RegionConstraintCollector::verify_generic_bound`] method. pub 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_substs: SubstsRef<'tcx>) -> Option { let closure_kind_ty = closure_substs.as_closure().kind_ty(); let closure_kind_ty = self.shallow_resolve(closure_kind_ty); closure_kind_ty.to_opt_closure_kind() } /// Clears the selection, evaluation, and projection caches. This is useful when /// repeatedly attempting to select an `Obligation` while changing only /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing. pub fn clear_caches(&self) { self.selection_cache.clear(); self.evaluation_cache.clear(); self.inner.borrow_mut().projection_cache().clear(); } 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(); self.universe.set(u); u } pub fn try_const_eval_resolve( &self, param_env: ty::ParamEnv<'tcx>, unevaluated: ty::UnevaluatedConst<'tcx>, ty: Ty<'tcx>, span: Option, ) -> Result, ErrorHandled> { match self.const_eval_resolve(param_env, unevaluated, span) { Ok(Some(val)) => Ok(ty::Const::from_value(self.tcx, val, ty)), Ok(None) => { let tcx = self.tcx; let def_id = unevaluated.def.did; span_bug!( tcx.def_span(def_id), "unable to construct a constant value for the unevaluated constant {:?}", unevaluated ); } Err(err) => Err(err), } } /// Resolves and evaluates a constant. /// /// The constant can be located on a trait like `::C`, in which case the given /// substitutions and environment are used to resolve the constant. Alternatively if the /// constant has generic parameters in scope the substitutions are used to evaluate the value of /// the constant. For example in `fn foo() { let _ = [0; bar::()]; }` the repeat count /// constant `bar::()` requires a substitution for `T`, if the substitution for `T` is still /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is /// returned. /// /// This handles inferences variables within both `param_env` and `substs` by /// performing the operation on their respective canonical forms. #[instrument(skip(self), level = "debug")] pub fn const_eval_resolve( &self, mut param_env: ty::ParamEnv<'tcx>, unevaluated: ty::UnevaluatedConst<'tcx>, span: Option, ) -> EvalToValTreeResult<'tcx> { let mut substs = self.resolve_vars_if_possible(unevaluated.substs); debug!(?substs); // Postpone the evaluation of constants whose substs depend on inference // variables if substs.has_non_region_infer() { let ac = AbstractConst::new(self.tcx, unevaluated); match ac { Ok(None) => { substs = InternalSubsts::identity_for_item(self.tcx, unevaluated.def.did); param_env = self.tcx.param_env(unevaluated.def.did); } Ok(Some(ct)) => { if ct.unify_failure_kind(self.tcx) == FailureKind::Concrete { substs = replace_param_and_infer_substs_with_placeholder(self.tcx, substs); } else { return Err(ErrorHandled::TooGeneric); } } Err(guar) => return Err(ErrorHandled::Reported(guar)), } } let param_env_erased = self.tcx.erase_regions(param_env); let substs_erased = self.tcx.erase_regions(substs); debug!(?param_env_erased); debug!(?substs_erased); let unevaluated = ty::UnevaluatedConst { def: unevaluated.def, substs: substs_erased }; // The return value is the evaluated value which doesn't contain any reference to inference // variables, thus we don't need to substitute back the original values. self.tcx.const_eval_resolve_for_typeck(param_env_erased, unevaluated, span) } /// `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<'tcx>) -> 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_some() } 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_some() } 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).val { ConstVariableValue::Unknown { .. } => false, ConstVariableValue::Known { .. } => true, } } } } } impl<'tcx> TypeErrCtxt<'_, 'tcx> { /// Process the region constraints and report any errors that /// result. After this, no more unification operations should be /// done -- or the compiler will panic -- but it is legal to use /// `resolve_vars_if_possible` as well as `fully_resolve`. /// /// Make sure to call [`InferCtxt::process_registered_region_obligations`] /// first, or preferably use [`InferCtxt::check_region_obligations_and_report_errors`] /// to do both of these operations together. pub fn resolve_regions_and_report_errors( &self, generic_param_scope: LocalDefId, outlives_env: &OutlivesEnvironment<'tcx>, ) { let errors = self.resolve_regions(outlives_env); if !self.is_tainted_by_errors() { // As a heuristic, just skip reporting region errors // altogether if other errors have been reported while // this infcx was in use. This is totally hokey but // otherwise we have a hard time separating legit region // errors from silly ones. self.report_region_errors(generic_param_scope, &errors); } } // [Note-Type-error-reporting] // An invariant is that anytime the expected or actual type is Error (the special // error type, meaning that an error occurred when typechecking this expression), // this is a derived error. The error cascaded from another error (that was already // reported), so it's not useful to display it to the user. // The following methods implement this logic. // They check if either the actual or expected type is Error, and don't print the error // in this case. The typechecker should only ever report type errors involving mismatched // types using one of these methods, and should not call span_err directly for such // errors. pub fn type_error_struct_with_diag( &self, sp: Span, mk_diag: M, actual_ty: Ty<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> where M: FnOnce(String) -> DiagnosticBuilder<'tcx, ErrorGuaranteed>, { let actual_ty = self.resolve_vars_if_possible(actual_ty); debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty); let mut err = mk_diag(self.ty_to_string(actual_ty)); // Don't report an error if actual type is `Error`. if actual_ty.references_error() { err.downgrade_to_delayed_bug(); } err } pub fn report_mismatched_types( &self, cause: &ObligationCause<'tcx>, expected: Ty<'tcx>, actual: Ty<'tcx>, err: TypeError<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { self.report_and_explain_type_error(TypeTrace::types(cause, true, expected, actual), err) } pub fn report_mismatched_consts( &self, cause: &ObligationCause<'tcx>, expected: ty::Const<'tcx>, actual: ty::Const<'tcx>, err: TypeError<'tcx>, ) -> DiagnosticBuilder<'tcx, ErrorGuaranteed> { self.report_and_explain_type_error(TypeTrace::consts(cause, true, expected, actual), err) } } /// Helper for `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<'tcx> { /// 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<'tcx>), } impl<'tcx> TyOrConstInferVar<'tcx> { /// 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.unpack() { 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 `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<'tcx> for InferenceLiteralEraser<'tcx> { fn tcx(&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), } } } struct ShallowResolver<'a, 'tcx> { infcx: &'a InferCtxt<'tcx>, } impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> { fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { self.infcx.tcx } /// If `ty` is a type variable of some kind, resolve it one level /// (but do not resolve types found in the result). If `typ` is /// not a type variable, just return it unmodified. fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { match *ty.kind() { ty::Infer(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.infcx.inner.borrow_mut().type_variables().probe(v).known(); known.map_or(ty, |t| self.fold_ty(t)) } ty::Infer(ty::IntVar(v)) => self .infcx .inner .borrow_mut() .int_unification_table() .probe_value(v) .map_or(ty, |v| v.to_type(self.infcx.tcx)), ty::Infer(ty::FloatVar(v)) => self .infcx .inner .borrow_mut() .float_unification_table() .probe_value(v) .map_or(ty, |v| v.to_type(self.infcx.tcx)), _ => ty, } } fn fold_const(&mut self, ct: ty::Const<'tcx>) -> ty::Const<'tcx> { if let ty::ConstKind::Infer(InferConst::Var(vid)) = ct.kind() { self.infcx .inner .borrow_mut() .const_unification_table() .probe_value(vid) .val .known() .unwrap_or(ct) } else { ct } } } impl<'tcx> TypeTrace<'tcx> { pub fn span(&self) -> Span { self.cause.span } pub fn types( cause: &ObligationCause<'tcx>, a_is_expected: bool, a: Ty<'tcx>, b: Ty<'tcx>, ) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())), } } pub fn poly_trait_refs( cause: &ObligationCause<'tcx>, a_is_expected: bool, a: ty::PolyTraitRef<'tcx>, b: ty::PolyTraitRef<'tcx>, ) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: PolyTraitRefs(ExpectedFound::new(a_is_expected, a.into(), b.into())), } } pub fn consts( cause: &ObligationCause<'tcx>, a_is_expected: bool, a: ty::Const<'tcx>, b: ty::Const<'tcx>, ) -> TypeTrace<'tcx> { TypeTrace { cause: cause.clone(), values: Terms(ExpectedFound::new(a_is_expected, a.into(), b.into())), } } } impl<'tcx> SubregionOrigin<'tcx> { pub fn span(&self) -> Span { match *self { Subtype(ref a) => a.span(), RelateObjectBound(a) => a, RelateParamBound(a, ..) => a, RelateRegionParamBound(a) => a, Reborrow(a) => a, ReborrowUpvar(a, _) => a, DataBorrowed(_, a) => a, ReferenceOutlivesReferent(_, a) => a, CompareImplItemObligation { span, .. } => span, AscribeUserTypeProvePredicate(span) => span, 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::CompareImplItemObligation { 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) } _ => default(), } } } impl RegionVariableOrigin { pub fn span(&self) -> Span { match *self { MiscVariable(a) | PatternRegion(a) | AddrOfRegion(a) | Autoref(a) | Coercion(a) | EarlyBoundRegion(a, ..) | LateBoundRegion(a, ..) | UpvarRegion(_, a) => a, Nll(..) => bug!("NLL variable used with `span`"), } } } /// Replaces substs that reference param or infer variables with suitable /// placeholders. This function is meant to remove these param and infer /// substs when they're not actually needed to evaluate a constant. fn replace_param_and_infer_substs_with_placeholder<'tcx>( tcx: TyCtxt<'tcx>, substs: SubstsRef<'tcx>, ) -> SubstsRef<'tcx> { tcx.mk_substs(substs.iter().enumerate().map(|(idx, arg)| { match arg.unpack() { GenericArgKind::Type(_) if arg.has_non_region_param() || arg.has_non_region_infer() => { tcx.mk_ty(ty::Placeholder(ty::PlaceholderType { universe: ty::UniverseIndex::ROOT, name: ty::BoundVar::from_usize(idx), })) .into() } GenericArgKind::Const(ct) if ct.has_non_region_infer() || ct.has_non_region_param() => { let ty = ct.ty(); // If the type references param or infer, replace that too... if ty.has_non_region_param() || ty.has_non_region_infer() { bug!("const `{ct}`'s type should not reference params or types"); } tcx.mk_const(ty::ConstS { ty, kind: ty::ConstKind::Placeholder(ty::PlaceholderConst { universe: ty::UniverseIndex::ROOT, name: ty::BoundVar::from_usize(idx), }), }) .into() } _ => arg, } })) }