1 //! See the Book for more information.
3 pub use self::freshen::TypeFreshener;
4 pub use self::LateBoundRegionConversionTime::*;
5 pub use self::RegionVariableOrigin::*;
6 pub use self::SubregionOrigin::*;
7 pub use self::ValuePairs::*;
9 use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
11 use rustc::infer::canonical::{Canonical, CanonicalVarValues};
12 use rustc::infer::unify_key::{ConstVarValue, ConstVariableValue};
13 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind, ToType};
14 use rustc::middle::free_region::RegionRelations;
15 use rustc::middle::region;
17 use rustc::mir::interpret::ConstEvalResult;
18 use rustc::traits::select;
19 use rustc::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
20 use rustc::ty::fold::{TypeFoldable, TypeFolder};
21 use rustc::ty::relate::RelateResult;
22 use rustc::ty::subst::{GenericArg, GenericArgKind, InternalSubsts, SubstsRef};
23 pub use rustc::ty::IntVarValue;
24 use rustc::ty::{self, GenericParamDefKind, InferConst, Ty, TyCtxt};
25 use rustc::ty::{ConstVid, FloatVid, IntVid, TyVid};
27 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
28 use rustc_data_structures::sync::Lrc;
29 use rustc_data_structures::unify as ut;
30 use rustc_errors::DiagnosticBuilder;
32 use rustc_hir::def_id::{DefId, LocalDefId};
33 use rustc_session::config::BorrowckMode;
34 use rustc_span::symbol::Symbol;
37 use std::cell::{Cell, Ref, RefCell};
38 use std::collections::BTreeMap;
41 use self::combine::CombineFields;
42 use self::lexical_region_resolve::LexicalRegionResolutions;
43 use self::outlives::env::OutlivesEnvironment;
44 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
45 use self::region_constraints::{RegionConstraintCollector, RegionSnapshot};
46 use self::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
52 pub mod error_reporting;
58 mod lexical_region_resolve;
62 pub mod region_constraints;
65 pub mod type_variable;
67 use crate::infer::canonical::OriginalQueryValues;
68 pub use rustc::infer::unify_key;
72 pub struct InferOk<'tcx, T> {
74 pub obligations: PredicateObligations<'tcx>,
76 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
78 pub type Bound<T> = Option<T>;
79 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
80 pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
82 /// How we should handle region solving.
84 /// This is used so that the region values inferred by HIR region solving are
85 /// not exposed, and so that we can avoid doing work in HIR typeck that MIR
86 /// typeck will also do.
87 #[derive(Copy, Clone, Debug)]
88 pub enum RegionckMode {
89 /// The default mode: report region errors, don't erase regions.
91 /// Erase the results of region after solving.
93 /// A flag that is used to suppress region errors, when we are doing
94 /// region checks that the NLL borrow checker will also do -- it might
96 suppress_errors: bool,
100 impl Default for RegionckMode {
101 fn default() -> Self {
107 pub fn suppressed(self) -> bool {
109 Self::Solve => false,
110 Self::Erase { suppress_errors } => suppress_errors,
114 /// Indicates that the MIR borrowck will repeat these region
115 /// checks, so we should ignore errors if NLL is (unconditionally)
117 pub fn for_item_body(tcx: TyCtxt<'_>) -> Self {
118 // FIXME(Centril): Once we actually remove `::Migrate` also make
119 // this always `true` and then proceed to eliminate the dead code.
120 match tcx.borrowck_mode() {
121 // If we're on Migrate mode, report AST region errors
122 BorrowckMode::Migrate => RegionckMode::Erase { suppress_errors: false },
124 // If we're on MIR, don't report AST region errors as they should be reported by NLL
125 BorrowckMode::Mir => RegionckMode::Erase { suppress_errors: true },
130 /// This type contains all the things within `InferCtxt` that sit within a
131 /// `RefCell` and are involved with taking/rolling back snapshots. Snapshot
132 /// operations are hot enough that we want only one call to `borrow_mut` per
133 /// call to `start_snapshot` and `rollback_to`.
134 pub struct InferCtxtInner<'tcx> {
135 /// Cache for projections. This cache is snapshotted along with the infcx.
137 /// Public so that `traits::project` can use it.
138 pub projection_cache: traits::ProjectionCache<'tcx>,
140 /// We instantiate `UnificationTable` with `bounds<Ty>` because the types
141 /// that might instantiate a general type variable have an order,
142 /// represented by its upper and lower bounds.
143 type_variables: type_variable::TypeVariableTable<'tcx>,
145 /// Map from const parameter variable to the kind of const it represents.
146 const_unification_table: ut::UnificationTable<ut::InPlace<ty::ConstVid<'tcx>>>,
148 /// Map from integral variable to the kind of integer it represents.
149 int_unification_table: ut::UnificationTable<ut::InPlace<ty::IntVid>>,
151 /// Map from floating variable to the kind of float it represents.
152 float_unification_table: ut::UnificationTable<ut::InPlace<ty::FloatVid>>,
154 /// Tracks the set of region variables and the constraints between them.
155 /// This is initially `Some(_)` but when
156 /// `resolve_regions_and_report_errors` is invoked, this gets set to `None`
157 /// -- further attempts to perform unification, etc., may fail if new
158 /// region constraints would've been added.
159 region_constraints: Option<RegionConstraintCollector<'tcx>>,
161 /// A set of constraints that regionck must validate. Each
162 /// constraint has the form `T:'a`, meaning "some type `T` must
163 /// outlive the lifetime 'a". These constraints derive from
164 /// instantiated type parameters. So if you had a struct defined
167 /// struct Foo<T:'static> { ... }
169 /// then in some expression `let x = Foo { ... }` it will
170 /// instantiate the type parameter `T` with a fresh type `$0`. At
171 /// the same time, it will record a region obligation of
172 /// `$0:'static`. This will get checked later by regionck. (We
173 /// can't generally check these things right away because we have
174 /// to wait until types are resolved.)
176 /// These are stored in a map keyed to the id of the innermost
177 /// enclosing fn body / static initializer expression. This is
178 /// because the location where the obligation was incurred can be
179 /// relevant with respect to which sublifetime assumptions are in
180 /// place. The reason that we store under the fn-id, and not
181 /// something more fine-grained, is so that it is easier for
182 /// regionck to be sure that it has found *all* the region
183 /// obligations (otherwise, it's easy to fail to walk to a
184 /// particular node-id).
186 /// Before running `resolve_regions_and_report_errors`, the creator
187 /// of the inference context is expected to invoke
188 /// `process_region_obligations` (defined in `self::region_obligations`)
189 /// for each body-id in this map, which will process the
190 /// obligations within. This is expected to be done 'late enough'
191 /// that all type inference variables have been bound and so forth.
192 pub region_obligations: Vec<(hir::HirId, RegionObligation<'tcx>)>,
195 impl<'tcx> InferCtxtInner<'tcx> {
196 fn new() -> InferCtxtInner<'tcx> {
198 projection_cache: Default::default(),
199 type_variables: type_variable::TypeVariableTable::new(),
200 const_unification_table: ut::UnificationTable::new(),
201 int_unification_table: ut::UnificationTable::new(),
202 float_unification_table: ut::UnificationTable::new(),
203 region_constraints: Some(RegionConstraintCollector::new()),
204 region_obligations: vec![],
208 pub fn unwrap_region_constraints(&mut self) -> &mut RegionConstraintCollector<'tcx> {
209 self.region_constraints.as_mut().expect("region constraints already solved")
213 pub struct InferCtxt<'a, 'tcx> {
214 pub tcx: TyCtxt<'tcx>,
216 /// During type-checking/inference of a body, `in_progress_tables`
217 /// contains a reference to the tables being built up, which are
218 /// used for reading closure kinds/signatures as they are inferred,
219 /// and for error reporting logic to read arbitrary node types.
220 pub in_progress_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
222 pub inner: RefCell<InferCtxtInner<'tcx>>,
224 /// If set, this flag causes us to skip the 'leak check' during
225 /// higher-ranked subtyping operations. This flag is a temporary one used
226 /// to manage the removal of the leak-check: for the time being, we still run the
227 /// leak-check, but we issue warnings. This flag can only be set to true
228 /// when entering a snapshot.
229 skip_leak_check: Cell<bool>,
231 /// Once region inference is done, the values for each variable.
232 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
234 /// Caches the results of trait selection. This cache is used
235 /// for things that have to do with the parameters in scope.
236 pub selection_cache: select::SelectionCache<'tcx>,
238 /// Caches the results of trait evaluation.
239 pub evaluation_cache: select::EvaluationCache<'tcx>,
241 /// the set of predicates on which errors have been reported, to
242 /// avoid reporting the same error twice.
243 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
245 pub reported_closure_mismatch: RefCell<FxHashSet<(Span, Option<Span>)>>,
247 /// When an error occurs, we want to avoid reporting "derived"
248 /// errors that are due to this original failure. Normally, we
249 /// handle this with the `err_count_on_creation` count, which
250 /// basically just tracks how many errors were reported when we
251 /// started type-checking a fn and checks to see if any new errors
252 /// have been reported since then. Not great, but it works.
254 /// However, when errors originated in other passes -- notably
255 /// resolve -- this heuristic breaks down. Therefore, we have this
256 /// auxiliary flag that one can set whenever one creates a
257 /// type-error that is due to an error in a prior pass.
259 /// Don't read this flag directly, call `is_tainted_by_errors()`
260 /// and `set_tainted_by_errors()`.
261 tainted_by_errors_flag: Cell<bool>,
263 /// Track how many errors were reported when this infcx is created.
264 /// If the number of errors increases, that's also a sign (line
265 /// `tained_by_errors`) to avoid reporting certain kinds of errors.
266 // FIXME(matthewjasper) Merge into `tainted_by_errors_flag`
267 err_count_on_creation: usize,
269 /// This flag is true while there is an active snapshot.
270 in_snapshot: Cell<bool>,
272 /// What is the innermost universe we have created? Starts out as
273 /// `UniverseIndex::root()` but grows from there as we enter
274 /// universal quantifiers.
276 /// N.B., at present, we exclude the universal quantifiers on the
277 /// item we are type-checking, and just consider those names as
278 /// part of the root universe. So this would only get incremented
279 /// when we enter into a higher-ranked (`for<..>`) type or trait
281 universe: Cell<ty::UniverseIndex>,
284 /// A map returned by `replace_bound_vars_with_placeholders()`
285 /// indicating the placeholder region that each late-bound region was
287 pub type PlaceholderMap<'tcx> = BTreeMap<ty::BoundRegion, ty::Region<'tcx>>;
289 /// See the `error_reporting` module for more details.
290 #[derive(Clone, Debug, PartialEq, Eq, TypeFoldable)]
291 pub enum ValuePairs<'tcx> {
292 Types(ExpectedFound<Ty<'tcx>>),
293 Regions(ExpectedFound<ty::Region<'tcx>>),
294 Consts(ExpectedFound<&'tcx ty::Const<'tcx>>),
295 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
296 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
299 /// The trace designates the path through inference that we took to
300 /// encounter an error or subtyping constraint.
302 /// See the `error_reporting` module for more details.
303 #[derive(Clone, Debug)]
304 pub struct TypeTrace<'tcx> {
305 cause: ObligationCause<'tcx>,
306 values: ValuePairs<'tcx>,
309 /// The origin of a `r1 <= r2` constraint.
311 /// See `error_reporting` module for more details
312 #[derive(Clone, Debug)]
313 pub enum SubregionOrigin<'tcx> {
314 /// Arose from a subtyping relation
315 Subtype(Box<TypeTrace<'tcx>>),
317 /// Stack-allocated closures cannot outlive innermost loop
318 /// or function so as to ensure we only require finite stack
319 InfStackClosure(Span),
321 /// Invocation of closure must be within its lifetime
324 /// Dereference of reference must be within its lifetime
327 /// Closure bound must not outlive captured variables
328 ClosureCapture(Span, hir::HirId),
330 /// Index into slice must be within its lifetime
333 /// When casting `&'a T` to an `&'b Trait` object,
334 /// relating `'a` to `'b`
335 RelateObjectBound(Span),
337 /// Some type parameter was instantiated with the given type,
338 /// and that type must outlive some region.
339 RelateParamBound(Span, Ty<'tcx>),
341 /// The given region parameter was instantiated with a region
342 /// that must outlive some other region.
343 RelateRegionParamBound(Span),
345 /// A bound placed on type parameters that states that must outlive
346 /// the moment of their instantiation.
347 RelateDefaultParamBound(Span, Ty<'tcx>),
349 /// Creating a pointer `b` to contents of another reference
352 /// Creating a pointer `b` to contents of an upvar
353 ReborrowUpvar(Span, ty::UpvarId),
355 /// Data with type `Ty<'tcx>` was borrowed
356 DataBorrowed(Ty<'tcx>, Span),
358 /// (&'a &'b T) where a >= b
359 ReferenceOutlivesReferent(Ty<'tcx>, Span),
361 /// Type or region parameters must be in scope.
362 ParameterInScope(ParameterOrigin, Span),
364 /// The type T of an expression E must outlive the lifetime for E.
365 ExprTypeIsNotInScope(Ty<'tcx>, Span),
367 /// A `ref b` whose region does not enclose the decl site
368 BindingTypeIsNotValidAtDecl(Span),
370 /// Regions appearing in a method receiver must outlive method call
373 /// Regions appearing in a function argument must outlive func call
376 /// Region in return type of invoked fn must enclose call
379 /// Operands must be in scope
382 /// Region resulting from a `&` expr must enclose the `&` expr
385 /// An auto-borrow that does not enclose the expr where it occurs
388 /// Region constraint arriving from destructor safety
389 SafeDestructor(Span),
391 /// Comparing the signature and requirements of an impl method against
392 /// the containing trait.
393 CompareImplMethodObligation {
395 item_name: ast::Name,
396 impl_item_def_id: DefId,
397 trait_item_def_id: DefId,
401 // `SubregionOrigin` is used a lot. Make sure it doesn't unintentionally get bigger.
402 #[cfg(target_arch = "x86_64")]
403 static_assert_size!(SubregionOrigin<'_>, 32);
405 /// Places that type/region parameters can appear.
406 #[derive(Clone, Copy, Debug)]
407 pub enum ParameterOrigin {
409 MethodCall, // foo.bar() <-- parameters on impl providing bar()
410 OverloadedOperator, // a + b when overloaded
411 OverloadedDeref, // *a when overloaded
414 /// Times when we replace late-bound regions with variables:
415 #[derive(Clone, Copy, Debug)]
416 pub enum LateBoundRegionConversionTime {
417 /// when a fn is called
420 /// when two higher-ranked types are compared
423 /// when projecting an associated type
424 AssocTypeProjection(DefId),
427 /// Reasons to create a region inference variable
429 /// See `error_reporting` module for more details
430 #[derive(Copy, Clone, Debug)]
431 pub enum RegionVariableOrigin {
432 /// Region variables created for ill-categorized reasons,
433 /// mostly indicates places in need of refactoring
436 /// Regions created by a `&P` or `[...]` pattern
439 /// Regions created by `&` operator
442 /// Regions created as part of an autoref of a method receiver
445 /// Regions created as part of an automatic coercion
448 /// Region variables created as the values for early-bound regions
449 EarlyBoundRegion(Span, Symbol),
451 /// Region variables created for bound regions
452 /// in a function or method that is called
453 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
455 UpvarRegion(ty::UpvarId, Span),
457 BoundRegionInCoherence(ast::Name),
459 /// This origin is used for the inference variables that we create
460 /// during NLL region processing.
461 NLL(NLLRegionVariableOrigin),
464 #[derive(Copy, Clone, Debug)]
465 pub enum NLLRegionVariableOrigin {
466 /// During NLL region processing, we create variables for free
467 /// regions that we encounter in the function signature and
468 /// elsewhere. This origin indices we've got one of those.
471 /// "Universal" instantiation of a higher-ranked region (e.g.,
472 /// from a `for<'a> T` binder). Meant to represent "any region".
473 Placeholder(ty::PlaceholderRegion),
476 /// If this is true, then this variable was created to represent a lifetime
477 /// bound in a `for` binder. For example, it might have been created to
478 /// represent the lifetime `'a` in a type like `for<'a> fn(&'a u32)`.
479 /// Such variables are created when we are trying to figure out if there
480 /// is any valid instantiation of `'a` that could fit into some scenario.
482 /// This is used to inform error reporting: in the case that we are trying to
483 /// determine whether there is any valid instantiation of a `'a` variable that meets
484 /// some constraint C, we want to blame the "source" of that `for` type,
485 /// rather than blaming the source of the constraint C.
490 impl NLLRegionVariableOrigin {
491 pub fn is_universal(self) -> bool {
493 NLLRegionVariableOrigin::FreeRegion => true,
494 NLLRegionVariableOrigin::Placeholder(..) => true,
495 NLLRegionVariableOrigin::Existential { .. } => false,
499 pub fn is_existential(self) -> bool {
504 // FIXME(eddyb) investigate overlap between this and `TyOrConstInferVar`.
505 #[derive(Copy, Clone, Debug)]
506 pub enum FixupError<'tcx> {
507 UnresolvedIntTy(IntVid),
508 UnresolvedFloatTy(FloatVid),
510 UnresolvedConst(ConstVid<'tcx>),
513 /// See the `region_obligations` field for more information.
515 pub struct RegionObligation<'tcx> {
516 pub sub_region: ty::Region<'tcx>,
517 pub sup_type: Ty<'tcx>,
518 pub origin: SubregionOrigin<'tcx>,
521 impl<'tcx> fmt::Display for FixupError<'tcx> {
522 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
523 use self::FixupError::*;
526 UnresolvedIntTy(_) => write!(
528 "cannot determine the type of this integer; \
529 add a suffix to specify the type explicitly"
531 UnresolvedFloatTy(_) => write!(
533 "cannot determine the type of this number; \
534 add a suffix to specify the type explicitly"
536 UnresolvedTy(_) => write!(f, "unconstrained type"),
537 UnresolvedConst(_) => write!(f, "unconstrained const value"),
542 /// Helper type of a temporary returned by `tcx.infer_ctxt()`.
543 /// Necessary because we can't write the following bound:
544 /// `F: for<'b, 'tcx> where 'tcx FnOnce(InferCtxt<'b, 'tcx>)`.
545 pub struct InferCtxtBuilder<'tcx> {
546 global_tcx: TyCtxt<'tcx>,
547 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
550 pub trait TyCtxtInferExt<'tcx> {
551 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx>;
554 impl TyCtxtInferExt<'tcx> for TyCtxt<'tcx> {
555 fn infer_ctxt(self) -> InferCtxtBuilder<'tcx> {
556 InferCtxtBuilder { global_tcx: self, fresh_tables: None }
560 impl<'tcx> InferCtxtBuilder<'tcx> {
561 /// Used only by `rustc_typeck` during body type-checking/inference,
562 /// will initialize `in_progress_tables` with fresh `TypeckTables`.
563 pub fn with_fresh_in_progress_tables(mut self, table_owner: LocalDefId) -> Self {
564 self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
568 /// Given a canonical value `C` as a starting point, create an
569 /// inference context that contains each of the bound values
570 /// within instantiated as a fresh variable. The `f` closure is
571 /// invoked with the new infcx, along with the instantiated value
572 /// `V` and a substitution `S`. This substitution `S` maps from
573 /// the bound values in `C` to their instantiated values in `V`
574 /// (in other words, `S(C) = V`).
575 pub fn enter_with_canonical<T, R>(
578 canonical: &Canonical<'tcx, T>,
579 f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
582 T: TypeFoldable<'tcx>,
586 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
587 f(infcx, value, subst)
591 pub fn enter<R>(&mut self, f: impl for<'a> FnOnce(InferCtxt<'a, 'tcx>) -> R) -> R {
592 let InferCtxtBuilder { global_tcx, ref fresh_tables } = *self;
593 let in_progress_tables = fresh_tables.as_ref();
594 global_tcx.enter_local(|tcx| {
598 inner: RefCell::new(InferCtxtInner::new()),
599 lexical_region_resolutions: RefCell::new(None),
600 selection_cache: Default::default(),
601 evaluation_cache: Default::default(),
602 reported_trait_errors: Default::default(),
603 reported_closure_mismatch: Default::default(),
604 tainted_by_errors_flag: Cell::new(false),
605 err_count_on_creation: tcx.sess.err_count(),
606 in_snapshot: Cell::new(false),
607 skip_leak_check: Cell::new(false),
608 universe: Cell::new(ty::UniverseIndex::ROOT),
614 impl<'tcx, T> InferOk<'tcx, T> {
615 pub fn unit(self) -> InferOk<'tcx, ()> {
616 InferOk { value: (), obligations: self.obligations }
619 /// Extracts `value`, registering any obligations into `fulfill_cx`.
620 pub fn into_value_registering_obligations(
622 infcx: &InferCtxt<'_, 'tcx>,
623 fulfill_cx: &mut dyn TraitEngine<'tcx>,
625 let InferOk { value, obligations } = self;
626 for obligation in obligations {
627 fulfill_cx.register_predicate_obligation(infcx, obligation);
633 impl<'tcx> InferOk<'tcx, ()> {
634 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
639 #[must_use = "once you start a snapshot, you should always consume it"]
640 pub struct CombinedSnapshot<'a, 'tcx> {
641 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
642 type_snapshot: type_variable::Snapshot<'tcx>,
643 const_snapshot: ut::Snapshot<ut::InPlace<ty::ConstVid<'tcx>>>,
644 int_snapshot: ut::Snapshot<ut::InPlace<ty::IntVid>>,
645 float_snapshot: ut::Snapshot<ut::InPlace<ty::FloatVid>>,
646 region_constraints_snapshot: RegionSnapshot,
647 region_obligations_snapshot: usize,
648 universe: ty::UniverseIndex,
649 was_in_snapshot: bool,
650 was_skip_leak_check: bool,
651 _in_progress_tables: Option<Ref<'a, ty::TypeckTables<'tcx>>>,
654 impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
655 pub fn is_in_snapshot(&self) -> bool {
656 self.in_snapshot.get()
659 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
660 t.fold_with(&mut self.freshener())
663 pub fn type_var_diverges(&'a self, ty: Ty<'_>) -> bool {
665 ty::Infer(ty::TyVar(vid)) => self.inner.borrow().type_variables.var_diverges(vid),
670 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'tcx> {
671 freshen::TypeFreshener::new(self)
674 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty<'_>) -> UnconstrainedNumeric {
675 use rustc::ty::error::UnconstrainedNumeric::Neither;
676 use rustc::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
678 ty::Infer(ty::IntVar(vid)) => {
679 if self.inner.borrow_mut().int_unification_table.probe_value(vid).is_some() {
685 ty::Infer(ty::FloatVar(vid)) => {
686 if self.inner.borrow_mut().float_unification_table.probe_value(vid).is_some() {
696 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
697 let mut inner = self.inner.borrow_mut();
698 // FIXME(const_generics): should there be an equivalent function for const variables?
700 let mut vars: Vec<Ty<'_>> = inner
702 .unsolved_variables()
704 .map(|t| self.tcx.mk_ty_var(t))
707 (0..inner.int_unification_table.len())
708 .map(|i| ty::IntVid { index: i as u32 })
709 .filter(|&vid| inner.int_unification_table.probe_value(vid).is_none())
710 .map(|v| self.tcx.mk_int_var(v)),
713 (0..inner.float_unification_table.len())
714 .map(|i| ty::FloatVid { index: i as u32 })
715 .filter(|&vid| inner.float_unification_table.probe_value(vid).is_none())
716 .map(|v| self.tcx.mk_float_var(v)),
723 trace: TypeTrace<'tcx>,
724 param_env: ty::ParamEnv<'tcx>,
725 ) -> CombineFields<'a, 'tcx> {
731 obligations: PredicateObligations::new(),
735 /// Clear the "currently in a snapshot" flag, invoke the closure,
736 /// then restore the flag to its original value. This flag is a
737 /// debugging measure designed to detect cases where we start a
738 /// snapshot, create type variables, and register obligations
739 /// which may involve those type variables in the fulfillment cx,
740 /// potentially leaving "dangling type variables" behind.
741 /// In such cases, an assertion will fail when attempting to
742 /// register obligations, within a snapshot. Very useful, much
743 /// better than grovelling through megabytes of `RUSTC_LOG` output.
745 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
746 /// sometimes create a "mini-fulfilment-cx" in which we enroll
747 /// obligations. As long as this fulfillment cx is fully drained
748 /// before we return, this is not a problem, as there won't be any
749 /// escaping obligations in the main cx. In those cases, you can
750 /// use this function.
751 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
753 F: FnOnce(&Self) -> R,
755 let flag = self.in_snapshot.replace(false);
756 let result = func(self);
757 self.in_snapshot.set(flag);
761 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
762 debug!("start_snapshot()");
764 let in_snapshot = self.in_snapshot.replace(true);
766 let mut inner = self.inner.borrow_mut();
768 projection_cache_snapshot: inner.projection_cache.snapshot(),
769 type_snapshot: inner.type_variables.snapshot(),
770 const_snapshot: inner.const_unification_table.snapshot(),
771 int_snapshot: inner.int_unification_table.snapshot(),
772 float_snapshot: inner.float_unification_table.snapshot(),
773 region_constraints_snapshot: inner.unwrap_region_constraints().start_snapshot(),
774 region_obligations_snapshot: inner.region_obligations.len(),
775 universe: self.universe(),
776 was_in_snapshot: in_snapshot,
777 was_skip_leak_check: self.skip_leak_check.get(),
778 // Borrow tables "in progress" (i.e., during typeck)
779 // to ban writes from within a snapshot to them.
780 _in_progress_tables: self.in_progress_tables.map(|tables| tables.borrow()),
784 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
785 debug!("rollback_to(cause={})", cause);
786 let CombinedSnapshot {
787 projection_cache_snapshot,
792 region_constraints_snapshot,
793 region_obligations_snapshot,
800 self.in_snapshot.set(was_in_snapshot);
801 self.universe.set(universe);
802 self.skip_leak_check.set(was_skip_leak_check);
804 let mut inner = self.inner.borrow_mut();
805 inner.projection_cache.rollback_to(projection_cache_snapshot);
806 inner.type_variables.rollback_to(type_snapshot);
807 inner.const_unification_table.rollback_to(const_snapshot);
808 inner.int_unification_table.rollback_to(int_snapshot);
809 inner.float_unification_table.rollback_to(float_snapshot);
810 inner.unwrap_region_constraints().rollback_to(region_constraints_snapshot);
811 inner.region_obligations.truncate(region_obligations_snapshot);
814 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
815 debug!("commit_from()");
816 let CombinedSnapshot {
817 projection_cache_snapshot,
822 region_constraints_snapshot,
823 region_obligations_snapshot: _,
830 self.in_snapshot.set(was_in_snapshot);
831 self.skip_leak_check.set(was_skip_leak_check);
833 let mut inner = self.inner.borrow_mut();
834 inner.projection_cache.commit(projection_cache_snapshot);
835 inner.type_variables.commit(type_snapshot);
836 inner.const_unification_table.commit(const_snapshot);
837 inner.int_unification_table.commit(int_snapshot);
838 inner.float_unification_table.commit(float_snapshot);
839 inner.unwrap_region_constraints().commit(region_constraints_snapshot);
842 /// Executes `f` and commit the bindings.
843 pub fn commit_unconditionally<R, F>(&self, f: F) -> R
845 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
847 debug!("commit_unconditionally()");
848 let snapshot = self.start_snapshot();
849 let r = f(&snapshot);
850 self.commit_from(snapshot);
854 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`.
855 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
857 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
859 debug!("commit_if_ok()");
860 let snapshot = self.start_snapshot();
861 let r = f(&snapshot);
862 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
865 self.commit_from(snapshot);
868 self.rollback_to("commit_if_ok -- error", snapshot);
874 /// Execute `f` then unroll any bindings it creates.
875 pub fn probe<R, F>(&self, f: F) -> R
877 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
880 let snapshot = self.start_snapshot();
881 let r = f(&snapshot);
882 self.rollback_to("probe", snapshot);
886 /// If `should_skip` is true, then execute `f` then unroll any bindings it creates.
887 pub fn probe_maybe_skip_leak_check<R, F>(&self, should_skip: bool, f: F) -> R
889 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
892 let snapshot = self.start_snapshot();
893 let skip_leak_check = should_skip || self.skip_leak_check.get();
894 self.skip_leak_check.set(skip_leak_check);
895 let r = f(&snapshot);
896 self.rollback_to("probe", snapshot);
900 /// Scan the constraints produced since `snapshot` began and returns:
902 /// - `None` -- if none of them involve "region outlives" constraints
903 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
904 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
905 pub fn region_constraints_added_in_snapshot(
907 snapshot: &CombinedSnapshot<'a, 'tcx>,
911 .unwrap_region_constraints()
912 .region_constraints_added_in_snapshot(&snapshot.region_constraints_snapshot)
915 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
916 self.inner.borrow_mut().unwrap_region_constraints().add_given(sub, sup);
919 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
921 T: at::ToTrace<'tcx>,
923 let origin = &ObligationCause::dummy();
925 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
926 // Ignore obligations, since we are unrolling
927 // everything anyway.
932 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
934 T: at::ToTrace<'tcx>,
936 let origin = &ObligationCause::dummy();
938 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
939 // Ignore obligations, since we are unrolling
940 // everything anyway.
947 origin: SubregionOrigin<'tcx>,
951 debug!("sub_regions({:?} <: {:?})", a, b);
952 self.inner.borrow_mut().unwrap_region_constraints().make_subregion(origin, a, b);
955 /// Require that the region `r` be equal to one of the regions in
956 /// the set `regions`.
957 pub fn member_constraint(
959 opaque_type_def_id: DefId,
960 definition_span: Span,
962 region: ty::Region<'tcx>,
963 in_regions: &Lrc<Vec<ty::Region<'tcx>>>,
965 debug!("member_constraint({:?} <: {:?})", region, in_regions);
966 self.inner.borrow_mut().unwrap_region_constraints().member_constraint(
975 pub fn subtype_predicate(
977 cause: &ObligationCause<'tcx>,
978 param_env: ty::ParamEnv<'tcx>,
979 predicate: &ty::PolySubtypePredicate<'tcx>,
980 ) -> Option<InferResult<'tcx, ()>> {
981 // Subtle: it's ok to skip the binder here and resolve because
982 // `shallow_resolve` just ignores anything that is not a type
983 // variable, and because type variable's can't (at present, at
984 // least) capture any of the things bound by this binder.
986 // NOTE(nmatsakis): really, there is no *particular* reason to do this
987 // `shallow_resolve` here except as a micro-optimization.
988 // Naturally I could not resist.
989 let two_unbound_type_vars = {
990 let a = self.shallow_resolve(predicate.skip_binder().a);
991 let b = self.shallow_resolve(predicate.skip_binder().b);
992 a.is_ty_var() && b.is_ty_var()
995 if two_unbound_type_vars {
996 // Two unbound type variables? Can't make progress.
1000 Some(self.commit_if_ok(|snapshot| {
1001 let (ty::SubtypePredicate { a_is_expected, a, b }, placeholder_map) =
1002 self.replace_bound_vars_with_placeholders(predicate);
1004 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
1006 self.leak_check(false, &placeholder_map, snapshot)?;
1012 pub fn region_outlives_predicate(
1014 cause: &traits::ObligationCause<'tcx>,
1015 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>,
1016 ) -> UnitResult<'tcx> {
1017 self.commit_if_ok(|snapshot| {
1018 let (ty::OutlivesPredicate(r_a, r_b), placeholder_map) =
1019 self.replace_bound_vars_with_placeholders(predicate);
1020 let origin = SubregionOrigin::from_obligation_cause(cause, || {
1021 RelateRegionParamBound(cause.span)
1023 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
1024 self.leak_check(false, &placeholder_map, snapshot)?;
1029 pub fn next_ty_var_id(&self, diverging: bool, origin: TypeVariableOrigin) -> TyVid {
1030 self.inner.borrow_mut().type_variables.new_var(self.universe(), diverging, origin)
1033 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1034 self.tcx.mk_ty_var(self.next_ty_var_id(false, origin))
1037 pub fn next_ty_var_in_universe(
1039 origin: TypeVariableOrigin,
1040 universe: ty::UniverseIndex,
1042 let vid = self.inner.borrow_mut().type_variables.new_var(universe, false, origin);
1043 self.tcx.mk_ty_var(vid)
1046 pub fn next_diverging_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1047 self.tcx.mk_ty_var(self.next_ty_var_id(true, origin))
1050 pub fn next_const_var(
1053 origin: ConstVariableOrigin,
1054 ) -> &'tcx ty::Const<'tcx> {
1055 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1058 pub fn next_const_var_in_universe(
1061 origin: ConstVariableOrigin,
1062 universe: ty::UniverseIndex,
1063 ) -> &'tcx ty::Const<'tcx> {
1067 .const_unification_table
1068 .new_key(ConstVarValue { origin, val: ConstVariableValue::Unknown { universe } });
1069 self.tcx.mk_const_var(vid, ty)
1072 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1073 self.inner.borrow_mut().const_unification_table.new_key(ConstVarValue {
1075 val: ConstVariableValue::Unknown { universe: self.universe() },
1079 fn next_int_var_id(&self) -> IntVid {
1080 self.inner.borrow_mut().int_unification_table.new_key(None)
1083 pub fn next_int_var(&self) -> Ty<'tcx> {
1084 self.tcx.mk_int_var(self.next_int_var_id())
1087 fn next_float_var_id(&self) -> FloatVid {
1088 self.inner.borrow_mut().float_unification_table.new_key(None)
1091 pub fn next_float_var(&self) -> Ty<'tcx> {
1092 self.tcx.mk_float_var(self.next_float_var_id())
1095 /// Creates a fresh region variable with the next available index.
1096 /// The variable will be created in the maximum universe created
1097 /// thus far, allowing it to name any region created thus far.
1098 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1099 self.next_region_var_in_universe(origin, self.universe())
1102 /// Creates a fresh region variable with the next available index
1103 /// in the given universe; typically, you can use
1104 /// `next_region_var` and just use the maximal universe.
1105 pub fn next_region_var_in_universe(
1107 origin: RegionVariableOrigin,
1108 universe: ty::UniverseIndex,
1109 ) -> ty::Region<'tcx> {
1111 self.inner.borrow_mut().unwrap_region_constraints().new_region_var(universe, origin);
1112 self.tcx.mk_region(ty::ReVar(region_var))
1115 /// Return the universe that the region `r` was created in. For
1116 /// most regions (e.g., `'static`, named regions from the user,
1117 /// etc) this is the root universe U0. For inference variables or
1118 /// placeholders, however, it will return the universe which which
1119 /// they are associated.
1120 fn universe_of_region(&self, r: ty::Region<'tcx>) -> ty::UniverseIndex {
1121 self.inner.borrow_mut().unwrap_region_constraints().universe(r)
1124 /// Number of region variables created so far.
1125 pub fn num_region_vars(&self) -> usize {
1126 self.inner.borrow_mut().unwrap_region_constraints().num_region_vars()
1129 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1130 pub fn next_nll_region_var(&self, origin: NLLRegionVariableOrigin) -> ty::Region<'tcx> {
1131 self.next_region_var(RegionVariableOrigin::NLL(origin))
1134 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1135 pub fn next_nll_region_var_in_universe(
1137 origin: NLLRegionVariableOrigin,
1138 universe: ty::UniverseIndex,
1139 ) -> ty::Region<'tcx> {
1140 self.next_region_var_in_universe(RegionVariableOrigin::NLL(origin), universe)
1143 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> GenericArg<'tcx> {
1145 GenericParamDefKind::Lifetime => {
1146 // Create a region inference variable for the given
1147 // region parameter definition.
1148 self.next_region_var(EarlyBoundRegion(span, param.name)).into()
1150 GenericParamDefKind::Type { .. } => {
1151 // Create a type inference variable for the given
1152 // type parameter definition. The substitutions are
1153 // for actual parameters that may be referred to by
1154 // the default of this type parameter, if it exists.
1155 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1156 // used in a path such as `Foo::<T, U>::new()` will
1157 // use an inference variable for `C` with `[T, U]`
1158 // as the substitutions for the default, `(T, U)`.
1159 let ty_var_id = self.inner.borrow_mut().type_variables.new_var(
1162 TypeVariableOrigin {
1163 kind: TypeVariableOriginKind::TypeParameterDefinition(
1171 self.tcx.mk_ty_var(ty_var_id).into()
1173 GenericParamDefKind::Const { .. } => {
1174 let origin = ConstVariableOrigin {
1175 kind: ConstVariableOriginKind::ConstParameterDefinition(param.name),
1179 self.inner.borrow_mut().const_unification_table.new_key(ConstVarValue {
1181 val: ConstVariableValue::Unknown { universe: self.universe() },
1183 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1188 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1189 /// type/region parameter to a fresh inference variable.
1190 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1191 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1194 /// Returns `true` if errors have been reported since this infcx was
1195 /// created. This is sometimes used as a heuristic to skip
1196 /// reporting errors that often occur as a result of earlier
1197 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1198 /// inference variables, regionck errors).
1199 pub fn is_tainted_by_errors(&self) -> bool {
1201 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1202 tainted_by_errors_flag={})",
1203 self.tcx.sess.err_count(),
1204 self.err_count_on_creation,
1205 self.tainted_by_errors_flag.get()
1208 if self.tcx.sess.err_count() > self.err_count_on_creation {
1209 return true; // errors reported since this infcx was made
1211 self.tainted_by_errors_flag.get()
1214 /// Set the "tainted by errors" flag to true. We call this when we
1215 /// observe an error from a prior pass.
1216 pub fn set_tainted_by_errors(&self) {
1217 debug!("set_tainted_by_errors()");
1218 self.tainted_by_errors_flag.set(true)
1221 /// Process the region constraints and report any errors that
1222 /// result. After this, no more unification operations should be
1223 /// done -- or the compiler will panic -- but it is legal to use
1224 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1225 pub fn resolve_regions_and_report_errors(
1227 region_context: DefId,
1228 region_map: ®ion::ScopeTree,
1229 outlives_env: &OutlivesEnvironment<'tcx>,
1233 self.is_tainted_by_errors() || self.inner.borrow().region_obligations.is_empty(),
1234 "region_obligations not empty: {:#?}",
1235 self.inner.borrow().region_obligations
1237 let (var_infos, data) = self
1242 .expect("regions already resolved")
1243 .into_infos_and_data();
1245 let region_rels = &RegionRelations::new(
1249 outlives_env.free_region_map(),
1252 let (lexical_region_resolutions, errors) =
1253 lexical_region_resolve::resolve(region_rels, var_infos, data, mode);
1255 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1256 assert!(old_value.is_none());
1258 if !self.is_tainted_by_errors() {
1259 // As a heuristic, just skip reporting region errors
1260 // altogether if other errors have been reported while
1261 // this infcx was in use. This is totally hokey but
1262 // otherwise we have a hard time separating legit region
1263 // errors from silly ones.
1264 self.report_region_errors(region_map, &errors);
1268 /// Obtains (and clears) the current set of region
1269 /// constraints. The inference context is still usable: further
1270 /// unifications will simply add new constraints.
1272 /// This method is not meant to be used with normal lexical region
1273 /// resolution. Rather, it is used in the NLL mode as a kind of
1274 /// interim hack: basically we run normal type-check and generate
1275 /// region constraints as normal, but then we take them and
1276 /// translate them into the form that the NLL solver
1277 /// understands. See the NLL module for mode details.
1278 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1280 self.inner.borrow().region_obligations.is_empty(),
1281 "region_obligations not empty: {:#?}",
1282 self.inner.borrow().region_obligations
1285 self.inner.borrow_mut().unwrap_region_constraints().take_and_reset_data()
1288 /// Gives temporary access to the region constraint data.
1289 #[allow(non_camel_case_types)] // bug with impl trait
1290 pub fn with_region_constraints<R>(
1292 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1294 let mut inner = self.inner.borrow_mut();
1295 op(inner.unwrap_region_constraints().data())
1298 /// Takes ownership of the list of variable regions. This implies
1299 /// that all the region constraints have already been taken, and
1300 /// hence that `resolve_regions_and_report_errors` can never be
1301 /// called. This is used only during NLL processing to "hand off" ownership
1302 /// of the set of region variables into the NLL region context.
1303 pub fn take_region_var_origins(&self) -> VarInfos {
1304 let (var_infos, data) = self
1309 .expect("regions already resolved")
1310 .into_infos_and_data();
1311 assert!(data.is_empty());
1315 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1316 self.resolve_vars_if_possible(&t).to_string()
1319 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1320 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1321 format!("({})", tstrs.join(", "))
1324 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1325 self.resolve_vars_if_possible(t).print_only_trait_path().to_string()
1328 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1329 /// universe index of `TyVar(vid)`.
1330 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1331 use self::type_variable::TypeVariableValue;
1333 match self.inner.borrow_mut().type_variables.probe(vid) {
1334 TypeVariableValue::Known { value } => Ok(value),
1335 TypeVariableValue::Unknown { universe } => Err(universe),
1339 /// Resolve any type variables found in `value` -- but only one
1340 /// level. So, if the variable `?X` is bound to some type
1341 /// `Foo<?Y>`, then this would return `Foo<?Y>` (but `?Y` may
1342 /// itself be bound to a type).
1344 /// Useful when you only need to inspect the outermost level of
1345 /// the type and don't care about nested types (or perhaps you
1346 /// will be resolving them as well, e.g. in a loop).
1347 pub fn shallow_resolve<T>(&self, value: T) -> T
1349 T: TypeFoldable<'tcx>,
1351 value.fold_with(&mut ShallowResolver { infcx: self })
1354 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1355 self.inner.borrow_mut().type_variables.root_var(var)
1358 /// Where possible, replaces type/const variables in
1359 /// `value` with their final value. Note that region variables
1360 /// are unaffected. If a type/const variable has not been unified, it
1361 /// is left as is. This is an idempotent operation that does
1362 /// not affect inference state in any way and so you can do it
1364 pub fn resolve_vars_if_possible<T>(&self, value: &T) -> T
1366 T: TypeFoldable<'tcx>,
1368 if !value.needs_infer() {
1369 return value.clone(); // Avoid duplicated subst-folding.
1371 let mut r = resolve::OpportunisticVarResolver::new(self);
1372 value.fold_with(&mut r)
1375 /// Returns the first unresolved variable contained in `T`. In the
1376 /// process of visiting `T`, this will resolve (where possible)
1377 /// type variables in `T`, but it never constructs the final,
1378 /// resolved type, so it's more efficient than
1379 /// `resolve_vars_if_possible()`.
1380 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1382 T: TypeFoldable<'tcx>,
1384 let mut r = resolve::UnresolvedTypeFinder::new(self);
1385 value.visit_with(&mut r);
1389 pub fn probe_const_var(
1391 vid: ty::ConstVid<'tcx>,
1392 ) -> Result<&'tcx ty::Const<'tcx>, ty::UniverseIndex> {
1393 match self.inner.borrow_mut().const_unification_table.probe_value(vid).val {
1394 ConstVariableValue::Known { value } => Ok(value),
1395 ConstVariableValue::Unknown { universe } => Err(universe),
1399 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<'tcx, T> {
1401 * Attempts to resolve all type/region/const variables in
1402 * `value`. Region inference must have been run already (e.g.,
1403 * by calling `resolve_regions_and_report_errors`). If some
1404 * variable was never unified, an `Err` results.
1406 * This method is idempotent, but it not typically not invoked
1407 * except during the writeback phase.
1410 resolve::fully_resolve(self, value)
1413 // [Note-Type-error-reporting]
1414 // An invariant is that anytime the expected or actual type is Error (the special
1415 // error type, meaning that an error occurred when typechecking this expression),
1416 // this is a derived error. The error cascaded from another error (that was already
1417 // reported), so it's not useful to display it to the user.
1418 // The following methods implement this logic.
1419 // They check if either the actual or expected type is Error, and don't print the error
1420 // in this case. The typechecker should only ever report type errors involving mismatched
1421 // types using one of these methods, and should not call span_err directly for such
1424 pub fn type_error_struct_with_diag<M>(
1428 actual_ty: Ty<'tcx>,
1429 ) -> DiagnosticBuilder<'tcx>
1431 M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1433 let actual_ty = self.resolve_vars_if_possible(&actual_ty);
1434 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1436 // Don't report an error if actual type is `Error`.
1437 if actual_ty.references_error() {
1438 return self.tcx.sess.diagnostic().struct_dummy();
1441 mk_diag(self.ty_to_string(actual_ty))
1444 pub fn report_mismatched_types(
1446 cause: &ObligationCause<'tcx>,
1449 err: TypeError<'tcx>,
1450 ) -> DiagnosticBuilder<'tcx> {
1451 let trace = TypeTrace::types(cause, true, expected, actual);
1452 self.report_and_explain_type_error(trace, &err)
1455 pub fn replace_bound_vars_with_fresh_vars<T>(
1458 lbrct: LateBoundRegionConversionTime,
1459 value: &ty::Binder<T>,
1460 ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
1462 T: TypeFoldable<'tcx>,
1464 let fld_r = |br| self.next_region_var(LateBoundRegion(span, br, lbrct));
1466 self.next_ty_var(TypeVariableOrigin {
1467 kind: TypeVariableOriginKind::MiscVariable,
1471 let fld_c = |_, ty| {
1472 self.next_const_var(
1474 ConstVariableOrigin { kind: ConstVariableOriginKind::MiscVariable, span },
1477 self.tcx.replace_bound_vars(value, fld_r, fld_t, fld_c)
1480 /// See the [`region_constraints::verify_generic_bound`] method.
1481 pub fn verify_generic_bound(
1483 origin: SubregionOrigin<'tcx>,
1484 kind: GenericKind<'tcx>,
1485 a: ty::Region<'tcx>,
1486 bound: VerifyBound<'tcx>,
1488 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1492 .unwrap_region_constraints()
1493 .verify_generic_bound(origin, kind, a, bound);
1496 /// Obtains the latest type of the given closure; this may be a
1497 /// closure in the current function, in which case its
1498 /// `ClosureKind` may not yet be known.
1499 pub fn closure_kind(&self, closure_substs: SubstsRef<'tcx>) -> Option<ty::ClosureKind> {
1500 let closure_kind_ty = closure_substs.as_closure().kind_ty();
1501 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1502 closure_kind_ty.to_opt_closure_kind()
1505 /// Clears the selection, evaluation, and projection caches. This is useful when
1506 /// repeatedly attempting to select an `Obligation` while changing only
1507 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1508 pub fn clear_caches(&self) {
1509 self.selection_cache.clear();
1510 self.evaluation_cache.clear();
1511 self.inner.borrow_mut().projection_cache.clear();
1514 fn universe(&self) -> ty::UniverseIndex {
1518 /// Creates and return a fresh universe that extends all previous
1519 /// universes. Updates `self.universe` to that new universe.
1520 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1521 let u = self.universe.get().next_universe();
1522 self.universe.set(u);
1526 /// Resolves and evaluates a constant.
1528 /// The constant can be located on a trait like `<A as B>::C`, in which case the given
1529 /// substitutions and environment are used to resolve the constant. Alternatively if the
1530 /// constant has generic parameters in scope the substitutions are used to evaluate the value of
1531 /// the constant. For example in `fn foo<T>() { let _ = [0; bar::<T>()]; }` the repeat count
1532 /// constant `bar::<T>()` requires a substitution for `T`, if the substitution for `T` is still
1533 /// too generic for the constant to be evaluated then `Err(ErrorHandled::TooGeneric)` is
1536 /// This handles inferences variables within both `param_env` and `substs` by
1537 /// performing the operation on their respective canonical forms.
1538 pub fn const_eval_resolve(
1540 param_env: ty::ParamEnv<'tcx>,
1542 substs: SubstsRef<'tcx>,
1543 promoted: Option<mir::Promoted>,
1545 ) -> ConstEvalResult<'tcx> {
1546 let mut original_values = OriginalQueryValues::default();
1547 let canonical = self.canonicalize_query(&(param_env, substs), &mut original_values);
1549 let (param_env, substs) = canonical.value;
1550 // The return value is the evaluated value which doesn't contain any reference to inference
1551 // variables, thus we don't need to substitute back the original values.
1552 self.tcx.const_eval_resolve(param_env, def_id, substs, promoted, span)
1555 /// If `typ` is a type variable of some kind, resolve it one level
1556 /// (but do not resolve types found in the result). If `typ` is
1557 /// not a type variable, just return it unmodified.
1558 // FIXME(eddyb) inline into `ShallowResolver::visit_ty`.
1559 fn shallow_resolve_ty(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1561 ty::Infer(ty::TyVar(v)) => {
1562 // Not entirely obvious: if `typ` is a type variable,
1563 // it can be resolved to an int/float variable, which
1564 // can then be recursively resolved, hence the
1565 // recursion. Note though that we prevent type
1566 // variables from unifying to other type variables
1567 // directly (though they may be embedded
1568 // structurally), and we prevent cycles in any case,
1569 // so this recursion should always be of very limited
1572 // Note: if these two lines are combined into one we get
1573 // dynamic borrow errors on `self.inner`.
1574 let known = self.inner.borrow_mut().type_variables.probe(v).known();
1575 known.map(|t| self.shallow_resolve_ty(t)).unwrap_or(typ)
1578 ty::Infer(ty::IntVar(v)) => self
1581 .int_unification_table
1583 .map(|v| v.to_type(self.tcx))
1586 ty::Infer(ty::FloatVar(v)) => self
1589 .float_unification_table
1591 .map(|v| v.to_type(self.tcx))
1598 /// `ty_or_const_infer_var_changed` is equivalent to one of these two:
1599 /// * `shallow_resolve(ty) != ty` (where `ty.kind = ty::Infer(_)`)
1600 /// * `shallow_resolve(ct) != ct` (where `ct.kind = ty::ConstKind::Infer(_)`)
1602 /// However, `ty_or_const_infer_var_changed` is more efficient. It's always
1603 /// inlined, despite being large, because it has only two call sites that
1604 /// are extremely hot (both in `traits::fulfill`'s checking of `stalled_on`
1605 /// inference variables), and it handles both `Ty` and `ty::Const` without
1606 /// having to resort to storing full `GenericArg`s in `stalled_on`.
1608 pub fn ty_or_const_infer_var_changed(&self, infer_var: TyOrConstInferVar<'tcx>) -> bool {
1610 TyOrConstInferVar::Ty(v) => {
1611 use self::type_variable::TypeVariableValue;
1613 // If `inlined_probe` returns a `Known` value, it never equals
1614 // `ty::Infer(ty::TyVar(v))`.
1615 match self.inner.borrow_mut().type_variables.inlined_probe(v) {
1616 TypeVariableValue::Unknown { .. } => false,
1617 TypeVariableValue::Known { .. } => true,
1621 TyOrConstInferVar::TyInt(v) => {
1622 // If `inlined_probe_value` returns a value it's always a
1623 // `ty::Int(_)` or `ty::UInt(_)`, which never matches a
1625 self.inner.borrow_mut().int_unification_table.inlined_probe_value(v).is_some()
1628 TyOrConstInferVar::TyFloat(v) => {
1629 // If `probe_value` returns a value it's always a
1630 // `ty::Float(_)`, which never matches a `ty::Infer(_)`.
1632 // Not `inlined_probe_value(v)` because this call site is colder.
1633 self.inner.borrow_mut().float_unification_table.probe_value(v).is_some()
1636 TyOrConstInferVar::Const(v) => {
1637 // If `probe_value` returns a `Known` value, it never equals
1638 // `ty::ConstKind::Infer(ty::InferConst::Var(v))`.
1640 // Not `inlined_probe_value(v)` because this call site is colder.
1641 match self.inner.borrow_mut().const_unification_table.probe_value(v).val {
1642 ConstVariableValue::Unknown { .. } => false,
1643 ConstVariableValue::Known { .. } => true,
1650 /// Helper for `ty_or_const_infer_var_changed` (see comment on that), currently
1651 /// used only for `traits::fulfill`'s list of `stalled_on` inference variables.
1652 #[derive(Copy, Clone, Debug)]
1653 pub enum TyOrConstInferVar<'tcx> {
1654 /// Equivalent to `ty::Infer(ty::TyVar(_))`.
1656 /// Equivalent to `ty::Infer(ty::IntVar(_))`.
1658 /// Equivalent to `ty::Infer(ty::FloatVar(_))`.
1661 /// Equivalent to `ty::ConstKind::Infer(ty::InferConst::Var(_))`.
1662 Const(ConstVid<'tcx>),
1665 impl TyOrConstInferVar<'tcx> {
1666 /// Tries to extract an inference variable from a type or a constant, returns `None`
1667 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`) and
1668 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1669 pub fn maybe_from_generic_arg(arg: GenericArg<'tcx>) -> Option<Self> {
1670 match arg.unpack() {
1671 GenericArgKind::Type(ty) => Self::maybe_from_ty(ty),
1672 GenericArgKind::Const(ct) => Self::maybe_from_const(ct),
1673 GenericArgKind::Lifetime(_) => None,
1677 /// Tries to extract an inference variable from a type, returns `None`
1678 /// for types other than `ty::Infer(_)` (or `InferTy::Fresh*`).
1679 pub fn maybe_from_ty(ty: Ty<'tcx>) -> Option<Self> {
1681 ty::Infer(ty::TyVar(v)) => Some(TyOrConstInferVar::Ty(v)),
1682 ty::Infer(ty::IntVar(v)) => Some(TyOrConstInferVar::TyInt(v)),
1683 ty::Infer(ty::FloatVar(v)) => Some(TyOrConstInferVar::TyFloat(v)),
1688 /// Tries to extract an inference variable from a constant, returns `None`
1689 /// for constants other than `ty::ConstKind::Infer(_)` (or `InferConst::Fresh`).
1690 pub fn maybe_from_const(ct: &'tcx ty::Const<'tcx>) -> Option<Self> {
1692 ty::ConstKind::Infer(InferConst::Var(v)) => Some(TyOrConstInferVar::Const(v)),
1698 struct ShallowResolver<'a, 'tcx> {
1699 infcx: &'a InferCtxt<'a, 'tcx>,
1702 impl<'a, 'tcx> TypeFolder<'tcx> for ShallowResolver<'a, 'tcx> {
1703 fn tcx<'b>(&'b self) -> TyCtxt<'tcx> {
1707 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1708 self.infcx.shallow_resolve_ty(ty)
1711 fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
1712 if let ty::Const { val: ty::ConstKind::Infer(InferConst::Var(vid)), .. } = ct {
1716 .const_unification_table
1727 impl<'tcx> TypeTrace<'tcx> {
1728 pub fn span(&self) -> Span {
1733 cause: &ObligationCause<'tcx>,
1734 a_is_expected: bool,
1737 ) -> TypeTrace<'tcx> {
1738 TypeTrace { cause: cause.clone(), values: Types(ExpectedFound::new(a_is_expected, a, b)) }
1741 pub fn dummy(tcx: TyCtxt<'tcx>) -> TypeTrace<'tcx> {
1743 cause: ObligationCause::dummy(),
1744 values: Types(ExpectedFound { expected: tcx.types.err, found: tcx.types.err }),
1749 impl<'tcx> SubregionOrigin<'tcx> {
1750 pub fn span(&self) -> Span {
1752 Subtype(ref a) => a.span(),
1753 InfStackClosure(a) => a,
1754 InvokeClosure(a) => a,
1755 DerefPointer(a) => a,
1756 ClosureCapture(a, _) => a,
1758 RelateObjectBound(a) => a,
1759 RelateParamBound(a, _) => a,
1760 RelateRegionParamBound(a) => a,
1761 RelateDefaultParamBound(a, _) => a,
1763 ReborrowUpvar(a, _) => a,
1764 DataBorrowed(_, a) => a,
1765 ReferenceOutlivesReferent(_, a) => a,
1766 ParameterInScope(_, a) => a,
1767 ExprTypeIsNotInScope(_, a) => a,
1768 BindingTypeIsNotValidAtDecl(a) => a,
1775 SafeDestructor(a) => a,
1776 CompareImplMethodObligation { span, .. } => span,
1780 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
1782 F: FnOnce() -> Self,
1785 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
1786 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
1789 traits::ObligationCauseCode::CompareImplMethodObligation {
1793 } => SubregionOrigin::CompareImplMethodObligation {
1805 impl RegionVariableOrigin {
1806 pub fn span(&self) -> Span {
1808 MiscVariable(a) => a,
1809 PatternRegion(a) => a,
1810 AddrOfRegion(a) => a,
1813 EarlyBoundRegion(a, ..) => a,
1814 LateBoundRegion(a, ..) => a,
1815 BoundRegionInCoherence(_) => rustc_span::DUMMY_SP,
1816 UpvarRegion(_, a) => a,
1817 NLL(..) => bug!("NLL variable used with `span`"),
1822 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
1823 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1826 "RegionObligation(sub_region={:?}, sup_type={:?})",
1827 self.sub_region, self.sup_type