| pub use self::freshen::TypeFreshener; |
| pub use self::LateBoundRegionConversionTime::*; |
| pub use self::RegionVariableOrigin::*; |
| pub use self::SubregionOrigin::*; |
| pub use self::ValuePairs::*; |
| |
| pub(crate) use self::undo_log::{InferCtxtUndoLogs, Snapshot, UndoLog}; |
| |
| use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine}; |
| |
| 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; |
| use rustc_hir as hir; |
| 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::EvalToConstValueResult; |
| use rustc_middle::traits::select; |
| use rustc_middle::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric}; |
| use rustc_middle::ty::fold::{TypeFoldable, TypeFolder}; |
| use rustc_middle::ty::relate::RelateResult; |
| use rustc_middle::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef}; |
| 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_session::config::BorrowckMode; |
| use rustc_span::symbol::Symbol; |
| use rustc_span::Span; |
| |
| use std::cell::{Cell, Ref, RefCell}; |
| use std::collections::BTreeMap; |
| use std::fmt; |
| |
| use self::combine::CombineFields; |
| 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 outlives; |
| pub mod region_constraints; |
| pub mod resolve; |
| mod sub; |
| pub mod type_variable; |
| mod undo_log; |
| |
| use crate::infer::canonical::OriginalQueryValues; |
| pub use rustc_middle::infer::unify_key; |
| |
| #[must_use] |
| #[derive(Debug)] |
| pub struct InferOk<'tcx, T> { |
| pub value: T, |
| pub obligations: PredicateObligations<'tcx>, |
| } |
| pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>; |
| |
| pub type Bound<T> = Option<T>; |
| pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result" |
| pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result" |
| |
| pub(crate) type UnificationTable<'a, 'tcx, T> = ut::UnificationTable< |
| ut::InPlace<T, &'a mut ut::UnificationStorage<T>, &'a mut InferCtxtUndoLogs<'tcx>>, |
| >; |
| |
| /// How we should handle region solving. |
| /// |
| /// This is used so that the region values inferred by HIR region solving are |
| /// not exposed, and so that we can avoid doing work in HIR typeck that MIR |
| /// typeck will also do. |
| #[derive(Copy, Clone, Debug)] |
| pub enum RegionckMode { |
| /// The default mode: report region errors, don't erase regions. |
| Solve, |
| /// Erase the results of region after solving. |
| Erase { |
| /// A flag that is used to suppress region errors, when we are doing |
| /// region checks that the NLL borrow checker will also do -- it might |
| /// be set to true. |
| suppress_errors: bool, |
| }, |
| } |
| |
| impl Default for RegionckMode { |
| fn default() -> Self { |
| RegionckMode::Solve |
| } |
| } |
| |
| impl RegionckMode { |
| /// Indicates that the MIR borrowck will repeat these region |
| /// checks, so we should ignore errors if NLL is (unconditionally) |
| /// enabled. |
| pub fn for_item_body(tcx: TyCtxt<'_>) -> Self { |
| // FIXME(Centril): Once we actually remove `::Migrate` also make |
| // this always `true` and then proceed to eliminate the dead code. |
| match tcx.borrowck_mode() { |
| // If we're on Migrate mode, report AST region errors |
| BorrowckMode::Migrate => RegionckMode::Erase { suppress_errors: false }, |
| |
| // If we're on MIR, don't report AST region errors as they should be reported by NLL |
| BorrowckMode::Mir => RegionckMode::Erase { suppress_errors: true }, |
| } |
| } |
| } |
| |
| /// 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`. |
| 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<Ty>` 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<ty::ConstVid<'tcx>>, |
| |
| /// Map from integral variable to the kind of integer it represents. |
| int_unification_storage: ut::UnificationTableStorage<ty::IntVid>, |
| |
| /// Map from floating variable to the kind of float it represents. |
| float_unification_storage: ut::UnificationTableStorage<ty::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. |
| region_constraint_storage: Option<RegionConstraintStorage<'tcx>>, |
| |
| /// 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 |
| /// |
| /// struct Foo<T:'static> { ... } |
| /// |
| /// 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 |
| /// `process_region_obligations` (defined in `self::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<(hir::HirId, RegionObligation<'tcx>)>, |
| |
| undo_log: InferCtxtUndoLogs<'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![], |
| } |
| } |
| |
| #[inline] |
| pub fn region_obligations(&self) -> &[(hir::HirId, 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] |
| fn int_unification_table( |
| &mut self, |
| ) -> ut::UnificationTable< |
| ut::InPlace< |
| ty::IntVid, |
| &mut ut::UnificationStorage<ty::IntVid>, |
| &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<ty::FloatVid>, |
| &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<ty::ConstVid<'tcx>>, |
| &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) |
| } |
| } |
| |
| pub struct InferCtxt<'a, 'tcx> { |
| pub tcx: TyCtxt<'tcx>, |
| |
| /// During type-checking/inference of a body, `in_progress_typeck_results` |
| /// contains a reference to the typeck results being built up, which are |
| /// used for reading closure kinds/signatures as they are inferred, |
| /// and for error reporting logic to read arbitrary node types. |
| pub in_progress_typeck_results: Option<&'a RefCell<ty::TypeckResults<'tcx>>>, |
| |
| pub inner: RefCell<InferCtxtInner<'tcx>>, |
| |
| /// 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<bool>, |
| |
| /// Once region inference is done, the values for each variable. |
| lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>, |
| |
| /// 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<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>, |
| |
| pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>, |
| |
| /// 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_flag: Cell<bool>, |
| |
| /// Track how many errors were reported when this infcx is created. |
| /// If the number of errors increases, that's also a sign (line |
| /// `tained_by_errors`) to avoid reporting certain kinds of errors. |
| // FIXME(matthewjasper) Merge into `tainted_by_errors_flag` |
| err_count_on_creation: usize, |
| |
| /// This flag is true while there is an active snapshot. |
| in_snapshot: Cell<bool>, |
| |
| /// 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<ty::UniverseIndex>, |
| } |
| |
| /// See the `error_reporting` module for more details. |
| #[derive(Clone, Copy, Debug, PartialEq, Eq, TypeFoldable)] |
| pub enum ValuePairs<'tcx> { |
| Types(ExpectedFound<Ty<'tcx>>), |
| Regions(ExpectedFound<ty::Region<'tcx>>), |
| Consts(ExpectedFound<&'tcx ty::Const<'tcx>>), |
| TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>), |
| PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>), |
| } |
| |
| /// 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> { |
| cause: ObligationCause<'tcx>, |
| 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<TypeTrace<'tcx>>), |
| |
| /// 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>), |
| |
| /// 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), |
| |
| /// Region in return type of invoked fn must enclose call |
| CallReturn(Span), |
| |
| /// Comparing the signature and requirements of an impl method against |
| /// the containing trait. |
| CompareImplMethodObligation { |
| span: Span, |
| item_name: Symbol, |
| impl_item_def_id: DefId, |
| trait_item_def_id: DefId, |
| }, |
| } |
| |
| // `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); |
| |
| /// 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, ty::AssocItem), |
| |
| /// 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), |
| |
| BoundRegionInCoherence(Symbol), |
| |
| /// 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), |
| |
| /// The variable we create to represent `'empty(U0)`. |
| RootEmptyRegion, |
| |
| 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)] |
| 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"), |
| } |
| } |
| } |
| |
| /// Helper type of a temporary returned by `tcx.infer_ctxt()`. |
| /// Necessary because we can't write the following bound: |
| /// `F: for<'b, 'tcx> where 'tcx FnOnce(InferCtxt<'b, 'tcx>)`. |
| pub struct InferCtxtBuilder<'tcx> { |
| tcx: TyCtxt<'tcx>, |
| fresh_typeck_results: Option<RefCell<ty::TypeckResults<'tcx>>>, |
| } |
| |
| pub trait TyCtxtInferExt<'tcx> { |
| fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>; |
| } |
| |
| impl TyCtxtInferExt<'tcx> for TyCtxt<'tcx> { |
| fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> { |
| InferCtxtBuilder { tcx: self, fresh_typeck_results: None } |
| } |
| } |
| |
| impl<'tcx> InferCtxtBuilder<'tcx> { |
| /// Used only by `rustc_typeck` during body type-checking/inference, |
| /// will initialize `in_progress_typeck_results` with fresh `TypeckResults`. |
| pub fn with_fresh_in_progress_typeck_results(mut self, table_owner: LocalDefId) -> Self { |
| self.fresh_typeck_results = Some(RefCell::new(ty::TypeckResults::new(table_owner))); |
| 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 enter_with_canonical<T, R>( |
| &mut self, |
| span: Span, |
| canonical: &Canonical<'tcx, T>, |
| f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R, |
| ) -> R |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| self.enter(|infcx| { |
| let (value, subst) = |
| infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical); |
| f(infcx, value, subst) |
| }) |
| } |
| |
| pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R { |
| let InferCtxtBuilder { tcx, ref fresh_typeck_results } = *self; |
| let in_progress_typeck_results = fresh_typeck_results.as_ref(); |
| f(InferCtxt { |
| tcx, |
| in_progress_typeck_results, |
| 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_flag: Cell::new(false), |
| 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), |
| }) |
| } |
| } |
| |
| 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; |
| for obligation in obligations { |
| fulfill_cx.register_predicate_obligation(infcx, obligation); |
| } |
| 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<'a, 'tcx> { |
| undo_snapshot: Snapshot<'tcx>, |
| region_constraints_snapshot: RegionSnapshot, |
| universe: ty::UniverseIndex, |
| was_in_snapshot: bool, |
| _in_progress_typeck_results: Option<Ref<'a, ty::TypeckResults<'tcx>>>, |
| } |
| |
| impl<'a, 'tcx> InferCtxt<'a, 'tcx> { |
| pub fn is_in_snapshot(&self) -> bool { |
| self.in_snapshot.get() |
| } |
| |
| pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T { |
| t.fold_with(&mut self.freshener()) |
| } |
| |
| pub fn type_var_diverges(&'a self, ty: Ty<'_>) -> bool { |
| match *ty.kind() { |
| ty::Infer(ty::TyVar(vid)) => self.inner.borrow_mut().type_variables().var_diverges(vid), |
| _ => false, |
| } |
| } |
| |
| pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> { |
| freshen::TypeFreshener::new(self) |
| } |
| |
| pub fn type_is_unconstrained_numeric(&'a self, ty: Ty<'_>) -> UnconstrainedNumeric { |
| use rustc_middle::ty::error::UnconstrainedNumeric::Neither; |
| use rustc_middle::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt}; |
| match *ty.kind() { |
| ty::Infer(ty::IntVar(vid)) => { |
| if self.inner.borrow_mut().int_unification_table().probe_value(vid).is_some() { |
| Neither |
| } else { |
| UnconstrainedInt |
| } |
| } |
| ty::Infer(ty::FloatVar(vid)) => { |
| if self.inner.borrow_mut().float_unification_table().probe_value(vid).is_some() { |
| Neither |
| } else { |
| UnconstrainedFloat |
| } |
| } |
| _ => Neither, |
| } |
| } |
| |
| pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> { |
| let mut inner = self.inner.borrow_mut(); |
| let mut vars: Vec<Ty<'_>> = 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 self, |
| trace: TypeTrace<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> CombineFields<'a, 'tcx> { |
| CombineFields { |
| infcx: self, |
| trace, |
| cause: None, |
| param_env, |
| obligations: PredicateObligations::new(), |
| } |
| } |
| |
| /// 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<F, R>(&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<'a, '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, |
| // Borrow typeck results "in progress" (i.e., during typeck) |
| // to ban writes from within a snapshot to them. |
| _in_progress_typeck_results: self |
| .in_progress_typeck_results |
| .map(|typeck_results| typeck_results.borrow()), |
| } |
| } |
| |
| fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) { |
| debug!("rollback_to(cause={})", cause); |
| let CombinedSnapshot { |
| undo_snapshot, |
| region_constraints_snapshot, |
| universe, |
| was_in_snapshot, |
| _in_progress_typeck_results, |
| } = 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); |
| } |
| |
| fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) { |
| debug!("commit_from()"); |
| let CombinedSnapshot { |
| undo_snapshot, |
| region_constraints_snapshot: _, |
| universe: _, |
| was_in_snapshot, |
| _in_progress_typeck_results, |
| } = snapshot; |
| |
| self.in_snapshot.set(was_in_snapshot); |
| |
| self.inner.borrow_mut().commit(undo_snapshot); |
| } |
| |
| /// Executes `f` and commit the bindings. |
| pub fn commit_unconditionally<R, F>(&self, f: F) -> R |
| where |
| F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R, |
| { |
| debug!("commit_unconditionally()"); |
| let snapshot = self.start_snapshot(); |
| let r = f(&snapshot); |
| self.commit_from(snapshot); |
| r |
| } |
| |
| /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`. |
| pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> |
| where |
| F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>, |
| { |
| debug!("commit_if_ok()"); |
| 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. |
| pub fn probe<R, F>(&self, f: F) -> R |
| where |
| F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R, |
| { |
| debug!("probe()"); |
| 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. |
| pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R |
| where |
| F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R, |
| { |
| debug!("probe()"); |
| 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<'a, 'tcx>, |
| ) -> Option<bool> { |
| self.inner |
| .borrow_mut() |
| .unwrap_region_constraints() |
| .region_constraints_added_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<T>(&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<T>(&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. |
| }) |
| }) |
| } |
| |
| pub fn sub_regions( |
| &self, |
| origin: SubregionOrigin<'tcx>, |
| a: ty::Region<'tcx>, |
| b: ty::Region<'tcx>, |
| ) { |
| debug!("sub_regions({:?} <: {:?})", a, b); |
| 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`. |
| pub fn member_constraint( |
| &self, |
| opaque_type_def_id: DefId, |
| definition_span: Span, |
| hidden_ty: Ty<'tcx>, |
| region: ty::Region<'tcx>, |
| in_regions: &Lrc<Vec<ty::Region<'tcx>>>, |
| ) { |
| debug!("member_constraint({:?} <: {:?})", region, in_regions); |
| self.inner.borrow_mut().unwrap_region_constraints().member_constraint( |
| opaque_type_def_id, |
| definition_span, |
| hidden_ty, |
| region, |
| in_regions, |
| ); |
| } |
| |
| pub fn subtype_predicate( |
| &self, |
| cause: &ObligationCause<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| predicate: ty::PolySubtypePredicate<'tcx>, |
| ) -> Option<InferResult<'tcx, ()>> { |
| // Subtle: it's ok to skip the binder here and resolve because |
| // `shallow_resolve` just ignores anything that is not a type |
| // variable, and because type variable's can't (at present, at |
| // least) capture any of the things bound by this binder. |
| // |
| // NOTE(nmatsakis): really, there is no *particular* reason to do this |
| // `shallow_resolve` here except as a micro-optimization. |
| // Naturally I could not resist. |
| let two_unbound_type_vars = { |
| let a = self.shallow_resolve(predicate.skip_binder().a); |
| let b = self.shallow_resolve(predicate.skip_binder().b); |
| a.is_ty_var() && b.is_ty_var() |
| }; |
| |
| if two_unbound_type_vars { |
| // Two unbound type variables? Can't make progress. |
| return None; |
| } |
| |
| Some(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>, |
| ) -> UnitResult<'tcx> { |
| self.commit_if_ok(|_snapshot| { |
| 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` |
| Ok(()) |
| }) |
| } |
| |
| pub fn next_ty_var_id(&self, diverging: bool, origin: TypeVariableOrigin) -> TyVid { |
| self.inner.borrow_mut().type_variables().new_var(self.universe(), diverging, origin) |
| } |
| |
| pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> { |
| self.tcx.mk_ty_var(self.next_ty_var_id(false, origin)) |
| } |
| |
| pub fn next_ty_var_in_universe( |
| &self, |
| origin: TypeVariableOrigin, |
| universe: ty::UniverseIndex, |
| ) -> Ty<'tcx> { |
| let vid = self.inner.borrow_mut().type_variables().new_var(universe, false, origin); |
| self.tcx.mk_ty_var(vid) |
| } |
| |
| pub fn next_diverging_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> { |
| self.tcx.mk_ty_var(self.next_ty_var_id(true, origin)) |
| } |
| |
| pub fn next_const_var( |
| &self, |
| ty: Ty<'tcx>, |
| origin: ConstVariableOrigin, |
| ) -> &'tcx 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, |
| ) -> &'tcx 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 which |
| /// they are associated. |
| 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<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 substitutions for the default, `(T, U)`. |
| let ty_var_id = self.inner.borrow_mut().type_variables().new_var( |
| self.universe(), |
| false, |
| 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_flag={})", |
| self.tcx.sess.err_count(), |
| self.err_count_on_creation, |
| self.tainted_by_errors_flag.get() |
| ); |
| |
| if self.tcx.sess.err_count() > self.err_count_on_creation { |
| return true; // errors reported since this infcx was made |
| } |
| self.tainted_by_errors_flag.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) { |
| debug!("set_tainted_by_errors()"); |
| self.tainted_by_errors_flag.set(true) |
| } |
| |
| /// 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`. |
| pub fn resolve_regions_and_report_errors( |
| &self, |
| region_context: DefId, |
| outlives_env: &OutlivesEnvironment<'tcx>, |
| mode: RegionckMode, |
| ) { |
| 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, region_context, outlives_env.free_region_map()); |
| |
| let (lexical_region_resolutions, errors) = |
| lexical_region_resolve::resolve(region_rels, var_infos, data, mode); |
| |
| let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions)); |
| assert!(old_value.is_none()); |
| |
| 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(&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<R>( |
| &self, |
| op: impl FnOnce(&RegionConstraintData<'tcx>) -> R, |
| ) -> R { |
| let mut inner = self.inner.borrow_mut(); |
| op(inner.unwrap_region_constraints().data()) |
| } |
| |
| /// 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<'tcx>, 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<?Y>`, then this would return `Foo<?Y>` (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<T>(&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<T>(&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) |
| } |
| |
| /// 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<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)> |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| value.visit_with(&mut resolve::UnresolvedTypeFinder::new(self)).break_value() |
| } |
| |
| pub fn probe_const_var( |
| &self, |
| vid: ty::ConstVid<'tcx>, |
| ) -> Result<&'tcx ty::Const<'tcx>, 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<T: TypeFoldable<'tcx>>(&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. |
| */ |
| |
| resolve::fully_resolve(self, value) |
| } |
| |
| // [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<M>( |
| &self, |
| sp: Span, |
| mk_diag: M, |
| actual_ty: Ty<'tcx>, |
| ) -> DiagnosticBuilder<'tcx> |
| where |
| M: FnOnce(String) -> DiagnosticBuilder<'tcx>, |
| { |
| let actual_ty = self.resolve_vars_if_possible(actual_ty); |
| debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty); |
| |
| // Don't report an error if actual type is `Error`. |
| if actual_ty.references_error() { |
| return self.tcx.sess.diagnostic().struct_dummy(); |
| } |
| |
| mk_diag(self.ty_to_string(actual_ty)) |
| } |
| |
| pub fn report_mismatched_types( |
| &self, |
| cause: &ObligationCause<'tcx>, |
| expected: Ty<'tcx>, |
| actual: Ty<'tcx>, |
| err: TypeError<'tcx>, |
| ) -> DiagnosticBuilder<'tcx> { |
| let trace = TypeTrace::types(cause, true, expected, actual); |
| self.report_and_explain_type_error(trace, &err) |
| } |
| |
| pub fn report_mismatched_consts( |
| &self, |
| cause: &ObligationCause<'tcx>, |
| expected: &'tcx ty::Const<'tcx>, |
| actual: &'tcx ty::Const<'tcx>, |
| err: TypeError<'tcx>, |
| ) -> DiagnosticBuilder<'tcx> { |
| let trace = TypeTrace::consts(cause, true, expected, actual); |
| self.report_and_explain_type_error(trace, &err) |
| } |
| |
| pub fn replace_bound_vars_with_fresh_vars<T>( |
| &self, |
| span: Span, |
| lbrct: LateBoundRegionConversionTime, |
| value: ty::Binder<'tcx, T>, |
| ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>) |
| where |
| T: TypeFoldable<'tcx>, |
| { |
| let fld_r = |
| |br: ty::BoundRegion| self.next_region_var(LateBoundRegion(span, br.kind, lbrct)); |
| let fld_t = |_| { |
| self.next_ty_var(TypeVariableOrigin { |
| kind: TypeVariableOriginKind::MiscVariable, |
| span, |
| }) |
| }; |
| let fld_c = |_, ty| { |
| self.next_const_var( |
| ty, |
| ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span }, |
| ) |
| }; |
| self.tcx.replace_bound_vars(value, fld_r, fld_t, fld_c) |
| } |
| |
| /// 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<ty::ClosureKind> { |
| 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(); |
| } |
| |
| 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 |
| } |
| |
| /// Resolves and evaluates a constant. |
| /// |
| /// The constant can be located on a trait like `<A as B>::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<T>() { let _ = [0; bar::<T>()]; }` the repeat count |
| /// constant `bar::<T>()` 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. |
| pub fn const_eval_resolve( |
| &self, |
| param_env: ty::ParamEnv<'tcx>, |
| ty::Unevaluated { def, substs, promoted }: ty::Unevaluated<'tcx>, |
| span: Option<Span>, |
| ) -> EvalToConstValueResult<'tcx> { |
| let mut original_values = OriginalQueryValues::default(); |
| let canonical = self.canonicalize_query((param_env, substs), &mut original_values); |
| |
| let (param_env, substs) = canonical.value; |
| // 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(param_env, ty::Unevaluated { def, substs, promoted }, span) |
| } |
| |
| /// If `typ` 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. |
| // FIXME(eddyb) inline into `ShallowResolver::visit_ty`. |
| fn shallow_resolve_ty(&self, typ: Ty<'tcx>) -> Ty<'tcx> { |
| match *typ.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.inner.borrow_mut().type_variables().probe(v).known(); |
| known.map_or(typ, |t| self.shallow_resolve_ty(t)) |
| } |
| |
| ty::Infer(ty::IntVar(v)) => self |
| .inner |
| .borrow_mut() |
| .int_unification_table() |
| .probe_value(v) |
| .map(|v| v.to_type(self.tcx)) |
| .unwrap_or(typ), |
| |
| ty::Infer(ty::FloatVar(v)) => self |
| .inner |
| .borrow_mut() |
| .float_unification_table() |
| .probe_value(v) |
| .map(|v| v.to_type(self.tcx)) |
| .unwrap_or(typ), |
| |
| _ => typ, |
| } |
| } |
| |
| /// `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, |
| } |
| } |
| } |
| } |
| } |
| |
| /// 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 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<Self> { |
| 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*`). |
| pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> { |
| 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`). |
| pub fn maybe_from_const(ct: &'tcx ty::Const<'tcx>) -> Option<Self> { |
| match ct.val { |
| ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)), |
| _ => None, |
| } |
| } |
| } |
| |
| struct ShallowResolver<'a, 'tcx> { |
| infcx: &'a InferCtxt<'a, 'tcx>, |
| } |
| |
| impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> { |
| fn tcx<'b>(&'b self) -> TyCtxt<'tcx> { |
| self.infcx.tcx |
| } |
| |
| fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> { |
| self.infcx.shallow_resolve_ty(ty) |
| } |
| |
| fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> { |
| if let ty::Const { val: ty::ConstKind::Infer(InferConst::Var(vid)), .. } = ct { |
| 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: Types(ExpectedFound::new(a_is_expected, a, b)) } |
| } |
| |
| pub fn consts( |
| cause: &ObligationCause<'tcx>, |
| a_is_expected: bool, |
| a: &'tcx ty::Const<'tcx>, |
| b: &'tcx ty::Const<'tcx>, |
| ) -> TypeTrace<'tcx> { |
| TypeTrace { cause: cause.clone(), values: Consts(ExpectedFound::new(a_is_expected, a, b)) } |
| } |
| } |
| |
| 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, |
| CallReturn(a) => a, |
| CompareImplMethodObligation { span, .. } => span, |
| } |
| } |
| |
| pub fn from_obligation_cause<F>(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::CompareImplMethodObligation { |
| item_name, |
| impl_item_def_id, |
| trait_item_def_id, |
| } => SubregionOrigin::CompareImplMethodObligation { |
| span: cause.span, |
| item_name, |
| impl_item_def_id, |
| trait_item_def_id, |
| }, |
| |
| _ => 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, |
| BoundRegionInCoherence(_) => rustc_span::DUMMY_SP, |
| Nll(..) => bug!("NLL variable used with `span`"), |
| } |
| } |
| } |
| |
| impl<'tcx> fmt::Debug for RegionObligation<'tcx> { |
| fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { |
| write!( |
| f, |
| "RegionObligation(sub_region={:?}, sup_type={:?})", |
| self.sub_region, self.sup_type |
| ) |
| } |
| } |
