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::*;
8 pub use crate::ty::IntVarValue;
11 use crate::hir::def_id::DefId;
12 use crate::infer::canonical::{Canonical, CanonicalVarValues};
13 use crate::infer::unify_key::{ConstVarValue, ConstVariableValue};
14 use crate::middle::free_region::RegionRelations;
15 use crate::middle::lang_items;
16 use crate::middle::region;
17 use crate::mir::interpret::ConstValue;
18 use crate::session::config::BorrowckMode;
19 use crate::traits::{self, ObligationCause, PredicateObligations, TraitEngine};
20 use crate::ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
21 use crate::ty::fold::{TypeFolder, TypeFoldable};
22 use crate::ty::relate::RelateResult;
23 use crate::ty::subst::{Kind, InternalSubsts, SubstsRef};
24 use crate::ty::{self, GenericParamDefKind, Ty, TyCtxt, CtxtInterners, InferConst};
25 use crate::ty::{FloatVid, IntVid, TyVid, ConstVid};
26 use crate::util::nodemap::FxHashMap;
28 use arena::SyncDroplessArena;
29 use errors::DiagnosticBuilder;
30 use rustc_data_structures::unify as ut;
31 use std::cell::{Cell, Ref, RefCell, RefMut};
32 use std::collections::BTreeMap;
35 use syntax_pos::symbol::InternedString;
38 use self::combine::CombineFields;
39 use self::lexical_region_resolve::LexicalRegionResolutions;
40 use self::outlives::env::OutlivesEnvironment;
41 use self::region_constraints::{GenericKind, RegionConstraintData, VarInfos, VerifyBound};
42 use self::region_constraints::{RegionConstraintCollector, RegionSnapshot};
43 use self::type_variable::TypeVariableOrigin;
44 use self::unify_key::{ToType, ConstVariableOrigin};
50 pub mod error_reporting;
56 mod lexical_region_resolve;
61 pub mod region_constraints;
64 pub mod type_variable;
69 pub struct InferOk<'tcx, T> {
71 pub obligations: PredicateObligations<'tcx>,
73 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
75 pub type Bound<T> = Option<T>;
76 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
77 pub type FixupResult<'tcx, T> = Result<T, FixupError<'tcx>>; // "fixup result"
79 /// A flag that is used to suppress region errors. This is normally
80 /// false, but sometimes -- when we are doing region checks that the
81 /// NLL borrow checker will also do -- it might be set to true.
82 #[derive(Copy, Clone, Default, Debug)]
83 pub struct SuppressRegionErrors {
87 impl SuppressRegionErrors {
88 pub fn suppressed(self) -> bool {
92 /// Indicates that the MIR borrowck will repeat these region
93 /// checks, so we should ignore errors if NLL is (unconditionally)
95 pub fn when_nll_is_enabled(tcx: TyCtxt<'_, '_, '_>) -> Self {
96 match tcx.borrowck_mode() {
97 // If we're on Migrate mode, report AST region errors
98 BorrowckMode::Migrate => SuppressRegionErrors { suppressed: false },
100 // If we're on MIR, don't report AST region errors as they should be reported by NLL
101 BorrowckMode::Mir => SuppressRegionErrors { suppressed: true },
106 pub struct InferCtxt<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
107 pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
109 /// During type-checking/inference of a body, `in_progress_tables`
110 /// contains a reference to the tables being built up, which are
111 /// used for reading closure kinds/signatures as they are inferred,
112 /// and for error reporting logic to read arbitrary node types.
113 pub in_progress_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
115 /// Cache for projections. This cache is snapshotted along with the
118 /// Public so that `traits::project` can use it.
119 pub projection_cache: RefCell<traits::ProjectionCache<'tcx>>,
121 /// We instantiate `UnificationTable` with `bounds<Ty>` because the
122 /// types that might instantiate a general type variable have an
123 /// order, represented by its upper and lower bounds.
124 pub type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
126 /// Map from const parameter variable to the kind of const it represents.
127 const_unification_table: RefCell<ut::UnificationTable<ut::InPlace<ty::ConstVid<'tcx>>>>,
129 /// Map from integral variable to the kind of integer it represents.
130 int_unification_table: RefCell<ut::UnificationTable<ut::InPlace<ty::IntVid>>>,
132 /// Map from floating variable to the kind of float it represents
133 float_unification_table: RefCell<ut::UnificationTable<ut::InPlace<ty::FloatVid>>>,
135 /// Tracks the set of region variables and the constraints between
136 /// them. This is initially `Some(_)` but when
137 /// `resolve_regions_and_report_errors` is invoked, this gets set
138 /// to `None` -- further attempts to perform unification etc may
139 /// fail if new region constraints would've been added.
140 region_constraints: RefCell<Option<RegionConstraintCollector<'tcx>>>,
142 /// Once region inference is done, the values for each variable.
143 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
145 /// Caches the results of trait selection. This cache is used
146 /// for things that have to do with the parameters in scope.
147 pub selection_cache: traits::SelectionCache<'tcx>,
149 /// Caches the results of trait evaluation.
150 pub evaluation_cache: traits::EvaluationCache<'tcx>,
152 /// the set of predicates on which errors have been reported, to
153 /// avoid reporting the same error twice.
154 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
156 /// When an error occurs, we want to avoid reporting "derived"
157 /// errors that are due to this original failure. Normally, we
158 /// handle this with the `err_count_on_creation` count, which
159 /// basically just tracks how many errors were reported when we
160 /// started type-checking a fn and checks to see if any new errors
161 /// have been reported since then. Not great, but it works.
163 /// However, when errors originated in other passes -- notably
164 /// resolve -- this heuristic breaks down. Therefore, we have this
165 /// auxiliary flag that one can set whenever one creates a
166 /// type-error that is due to an error in a prior pass.
168 /// Don't read this flag directly, call `is_tainted_by_errors()`
169 /// and `set_tainted_by_errors()`.
170 tainted_by_errors_flag: Cell<bool>,
172 /// Track how many errors were reported when this infcx is created.
173 /// If the number of errors increases, that's also a sign (line
174 /// `tained_by_errors`) to avoid reporting certain kinds of errors.
175 err_count_on_creation: usize,
177 /// This flag is true while there is an active snapshot.
178 in_snapshot: Cell<bool>,
180 /// A set of constraints that regionck must validate. Each
181 /// constraint has the form `T:'a`, meaning "some type `T` must
182 /// outlive the lifetime 'a". These constraints derive from
183 /// instantiated type parameters. So if you had a struct defined
186 /// struct Foo<T:'static> { ... }
188 /// then in some expression `let x = Foo { ... }` it will
189 /// instantiate the type parameter `T` with a fresh type `$0`. At
190 /// the same time, it will record a region obligation of
191 /// `$0:'static`. This will get checked later by regionck. (We
192 /// can't generally check these things right away because we have
193 /// to wait until types are resolved.)
195 /// These are stored in a map keyed to the id of the innermost
196 /// enclosing fn body / static initializer expression. This is
197 /// because the location where the obligation was incurred can be
198 /// relevant with respect to which sublifetime assumptions are in
199 /// place. The reason that we store under the fn-id, and not
200 /// something more fine-grained, is so that it is easier for
201 /// regionck to be sure that it has found *all* the region
202 /// obligations (otherwise, it's easy to fail to walk to a
203 /// particular node-id).
205 /// Before running `resolve_regions_and_report_errors`, the creator
206 /// of the inference context is expected to invoke
207 /// `process_region_obligations` (defined in `self::region_obligations`)
208 /// for each body-id in this map, which will process the
209 /// obligations within. This is expected to be done 'late enough'
210 /// that all type inference variables have been bound and so forth.
211 pub region_obligations: RefCell<Vec<(hir::HirId, RegionObligation<'tcx>)>>,
213 /// What is the innermost universe we have created? Starts out as
214 /// `UniverseIndex::root()` but grows from there as we enter
215 /// universal quantifiers.
217 /// N.B., at present, we exclude the universal quantifiers on the
218 /// item we are type-checking, and just consider those names as
219 /// part of the root universe. So this would only get incremented
220 /// when we enter into a higher-ranked (`for<..>`) type or trait
222 universe: Cell<ty::UniverseIndex>,
225 /// A map returned by `replace_bound_vars_with_placeholders()`
226 /// indicating the placeholder region that each late-bound region was
228 pub type PlaceholderMap<'tcx> = BTreeMap<ty::BoundRegion, ty::Region<'tcx>>;
230 /// See the `error_reporting` module for more details.
231 #[derive(Clone, Debug, PartialEq, Eq)]
232 pub enum ValuePairs<'tcx> {
233 Types(ExpectedFound<Ty<'tcx>>),
234 Regions(ExpectedFound<ty::Region<'tcx>>),
235 Consts(ExpectedFound<&'tcx ty::Const<'tcx>>),
236 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
237 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
240 /// The trace designates the path through inference that we took to
241 /// encounter an error or subtyping constraint.
243 /// See the `error_reporting` module for more details.
245 pub struct TypeTrace<'tcx> {
246 cause: ObligationCause<'tcx>,
247 values: ValuePairs<'tcx>,
250 /// The origin of a `r1 <= r2` constraint.
252 /// See `error_reporting` module for more details
253 #[derive(Clone, Debug)]
254 pub enum SubregionOrigin<'tcx> {
255 /// Arose from a subtyping relation
256 Subtype(TypeTrace<'tcx>),
258 /// Stack-allocated closures cannot outlive innermost loop
259 /// or function so as to ensure we only require finite stack
260 InfStackClosure(Span),
262 /// Invocation of closure must be within its lifetime
265 /// Dereference of reference must be within its lifetime
268 /// Closure bound must not outlive captured variables
269 ClosureCapture(Span, ast::NodeId),
271 /// Index into slice must be within its lifetime
274 /// When casting `&'a T` to an `&'b Trait` object,
275 /// relating `'a` to `'b`
276 RelateObjectBound(Span),
278 /// Some type parameter was instantiated with the given type,
279 /// and that type must outlive some region.
280 RelateParamBound(Span, Ty<'tcx>),
282 /// The given region parameter was instantiated with a region
283 /// that must outlive some other region.
284 RelateRegionParamBound(Span),
286 /// A bound placed on type parameters that states that must outlive
287 /// the moment of their instantiation.
288 RelateDefaultParamBound(Span, Ty<'tcx>),
290 /// Creating a pointer `b` to contents of another reference
293 /// Creating a pointer `b` to contents of an upvar
294 ReborrowUpvar(Span, ty::UpvarId),
296 /// Data with type `Ty<'tcx>` was borrowed
297 DataBorrowed(Ty<'tcx>, Span),
299 /// (&'a &'b T) where a >= b
300 ReferenceOutlivesReferent(Ty<'tcx>, Span),
302 /// Type or region parameters must be in scope.
303 ParameterInScope(ParameterOrigin, Span),
305 /// The type T of an expression E must outlive the lifetime for E.
306 ExprTypeIsNotInScope(Ty<'tcx>, Span),
308 /// A `ref b` whose region does not enclose the decl site
309 BindingTypeIsNotValidAtDecl(Span),
311 /// Regions appearing in a method receiver must outlive method call
314 /// Regions appearing in a function argument must outlive func call
317 /// Region in return type of invoked fn must enclose call
320 /// Operands must be in scope
323 /// Region resulting from a `&` expr must enclose the `&` expr
326 /// An auto-borrow that does not enclose the expr where it occurs
329 /// Region constraint arriving from destructor safety
330 SafeDestructor(Span),
332 /// Comparing the signature and requirements of an impl method against
333 /// the containing trait.
334 CompareImplMethodObligation {
336 item_name: ast::Name,
337 impl_item_def_id: DefId,
338 trait_item_def_id: DefId,
342 /// Places that type/region parameters can appear.
343 #[derive(Clone, Copy, Debug)]
344 pub enum ParameterOrigin {
346 MethodCall, // foo.bar() <-- parameters on impl providing bar()
347 OverloadedOperator, // a + b when overloaded
348 OverloadedDeref, // *a when overloaded
351 /// Times when we replace late-bound regions with variables:
352 #[derive(Clone, Copy, Debug)]
353 pub enum LateBoundRegionConversionTime {
354 /// when a fn is called
357 /// when two higher-ranked types are compared
360 /// when projecting an associated type
361 AssocTypeProjection(DefId),
364 /// Reasons to create a region inference variable
366 /// See `error_reporting` module for more details
367 #[derive(Copy, Clone, Debug)]
368 pub enum RegionVariableOrigin {
369 /// Region variables created for ill-categorized reasons,
370 /// mostly indicates places in need of refactoring
373 /// Regions created by a `&P` or `[...]` pattern
376 /// Regions created by `&` operator
379 /// Regions created as part of an autoref of a method receiver
382 /// Regions created as part of an automatic coercion
385 /// Region variables created as the values for early-bound regions
386 EarlyBoundRegion(Span, InternedString),
388 /// Region variables created for bound regions
389 /// in a function or method that is called
390 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
392 UpvarRegion(ty::UpvarId, Span),
394 BoundRegionInCoherence(ast::Name),
396 /// This origin is used for the inference variables that we create
397 /// during NLL region processing.
398 NLL(NLLRegionVariableOrigin),
401 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
402 pub enum NLLRegionVariableOrigin {
403 /// During NLL region processing, we create variables for free
404 /// regions that we encounter in the function signature and
405 /// elsewhere. This origin indices we've got one of those.
408 /// "Universal" instantiation of a higher-ranked region (e.g.,
409 /// from a `for<'a> T` binder). Meant to represent "any region".
410 Placeholder(ty::PlaceholderRegion),
415 impl NLLRegionVariableOrigin {
416 pub fn is_universal(self) -> bool {
418 NLLRegionVariableOrigin::FreeRegion => true,
419 NLLRegionVariableOrigin::Placeholder(..) => true,
420 NLLRegionVariableOrigin::Existential => false,
424 pub fn is_existential(self) -> bool {
429 #[derive(Copy, Clone, Debug)]
430 pub enum FixupError<'tcx> {
431 UnresolvedIntTy(IntVid),
432 UnresolvedFloatTy(FloatVid),
434 UnresolvedConst(ConstVid<'tcx>),
437 /// See the `region_obligations` field for more information.
439 pub struct RegionObligation<'tcx> {
440 pub sub_region: ty::Region<'tcx>,
441 pub sup_type: Ty<'tcx>,
442 pub origin: SubregionOrigin<'tcx>,
445 impl<'tcx> fmt::Display for FixupError<'tcx> {
446 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
447 use self::FixupError::*;
450 UnresolvedIntTy(_) => write!(
452 "cannot determine the type of this integer; \
453 add a suffix to specify the type explicitly"
455 UnresolvedFloatTy(_) => write!(
457 "cannot determine the type of this number; \
458 add a suffix to specify the type explicitly"
460 UnresolvedTy(_) => write!(f, "unconstrained type"),
461 UnresolvedConst(_) => write!(f, "unconstrained const value"),
466 /// Helper type of a temporary returned by `tcx.infer_ctxt()`.
467 /// Necessary because we can't write the following bound:
468 /// `F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(InferCtxt<'b, 'gcx, 'tcx>)`.
469 pub struct InferCtxtBuilder<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
470 global_tcx: TyCtxt<'a, 'gcx, 'gcx>,
471 arena: SyncDroplessArena,
472 interners: Option<CtxtInterners<'tcx>>,
473 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
476 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
477 pub fn infer_ctxt(self) -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
480 arena: SyncDroplessArena::default(),
487 impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
488 /// Used only by `rustc_typeck` during body type-checking/inference,
489 /// will initialize `in_progress_tables` with fresh `TypeckTables`.
490 pub fn with_fresh_in_progress_tables(mut self, table_owner: DefId) -> Self {
491 self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
495 /// Given a canonical value `C` as a starting point, create an
496 /// inference context that contains each of the bound values
497 /// within instantiated as a fresh variable. The `f` closure is
498 /// invoked with the new infcx, along with the instantiated value
499 /// `V` and a substitution `S`. This substitution `S` maps from
500 /// the bound values in `C` to their instantiated values in `V`
501 /// (in other words, `S(C) = V`).
502 pub fn enter_with_canonical<T, R>(
505 canonical: &Canonical<'tcx, T>,
506 f: impl for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>, T, CanonicalVarValues<'tcx>) -> R,
509 T: TypeFoldable<'tcx>,
513 infcx.instantiate_canonical_with_fresh_inference_vars(span, canonical);
514 f(infcx, value, subst)
518 pub fn enter<R>(&'tcx mut self, f: impl for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>) -> R) -> R {
519 let InferCtxtBuilder {
525 let in_progress_tables = fresh_tables.as_ref();
526 // Check that we haven't entered before
527 assert!(interners.is_none());
528 global_tcx.enter_local(arena, interners, |tcx| {
532 projection_cache: Default::default(),
533 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
534 const_unification_table: RefCell::new(ut::UnificationTable::new()),
535 int_unification_table: RefCell::new(ut::UnificationTable::new()),
536 float_unification_table: RefCell::new(ut::UnificationTable::new()),
537 region_constraints: RefCell::new(Some(RegionConstraintCollector::new())),
538 lexical_region_resolutions: RefCell::new(None),
539 selection_cache: Default::default(),
540 evaluation_cache: Default::default(),
541 reported_trait_errors: Default::default(),
542 tainted_by_errors_flag: Cell::new(false),
543 err_count_on_creation: tcx.sess.err_count(),
544 in_snapshot: Cell::new(false),
545 region_obligations: RefCell::new(vec![]),
546 universe: Cell::new(ty::UniverseIndex::ROOT),
552 impl<T> ExpectedFound<T> {
553 pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
568 impl<'tcx, T> InferOk<'tcx, T> {
569 pub fn unit(self) -> InferOk<'tcx, ()> {
572 obligations: self.obligations,
576 /// Extracts `value`, registering any obligations into `fulfill_cx`.
577 pub fn into_value_registering_obligations(
579 infcx: &InferCtxt<'_, '_, 'tcx>,
580 fulfill_cx: &mut dyn TraitEngine<'tcx>,
582 let InferOk { value, obligations } = self;
583 for obligation in obligations {
584 fulfill_cx.register_predicate_obligation(infcx, obligation);
590 impl<'tcx> InferOk<'tcx, ()> {
591 pub fn into_obligations(self) -> PredicateObligations<'tcx> {
596 #[must_use = "once you start a snapshot, you should always consume it"]
597 pub struct CombinedSnapshot<'a, 'tcx: 'a> {
598 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
599 type_snapshot: type_variable::Snapshot<'tcx>,
600 const_snapshot: ut::Snapshot<ut::InPlace<ty::ConstVid<'tcx>>>,
601 int_snapshot: ut::Snapshot<ut::InPlace<ty::IntVid>>,
602 float_snapshot: ut::Snapshot<ut::InPlace<ty::FloatVid>>,
603 region_constraints_snapshot: RegionSnapshot,
604 region_obligations_snapshot: usize,
605 universe: ty::UniverseIndex,
606 was_in_snapshot: bool,
607 _in_progress_tables: Option<Ref<'a, ty::TypeckTables<'tcx>>>,
610 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
611 pub fn is_in_snapshot(&self) -> bool {
612 self.in_snapshot.get()
615 pub fn freshen<T: TypeFoldable<'tcx>>(&self, t: T) -> T {
616 t.fold_with(&mut self.freshener())
619 pub fn type_var_diverges(&'a self, ty: Ty<'_>) -> bool {
621 ty::Infer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
626 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'gcx, 'tcx> {
627 freshen::TypeFreshener::new(self)
630 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty<'_>) -> UnconstrainedNumeric {
631 use crate::ty::error::UnconstrainedNumeric::Neither;
632 use crate::ty::error::UnconstrainedNumeric::{UnconstrainedFloat, UnconstrainedInt};
634 ty::Infer(ty::IntVar(vid)) => {
635 if self.int_unification_table
645 ty::Infer(ty::FloatVar(vid)) => {
646 if self.float_unification_table
660 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
661 let mut type_variables = self.type_variables.borrow_mut();
662 let mut int_unification_table = self.int_unification_table.borrow_mut();
663 let mut float_unification_table = self.float_unification_table.borrow_mut();
664 // FIXME(const_generics): should there be an equivalent function for const variables?
667 .unsolved_variables()
669 .map(|t| self.tcx.mk_ty_var(t))
671 (0..int_unification_table.len())
672 .map(|i| ty::IntVid { index: i as u32 })
673 .filter(|&vid| int_unification_table.probe_value(vid).is_none())
674 .map(|v| self.tcx.mk_int_var(v)),
677 (0..float_unification_table.len())
678 .map(|i| ty::FloatVid { index: i as u32 })
679 .filter(|&vid| float_unification_table.probe_value(vid).is_none())
680 .map(|v| self.tcx.mk_float_var(v)),
687 trace: TypeTrace<'tcx>,
688 param_env: ty::ParamEnv<'tcx>,
689 ) -> CombineFields<'a, 'gcx, 'tcx> {
695 obligations: PredicateObligations::new(),
699 /// Clear the "currently in a snapshot" flag, invoke the closure,
700 /// then restore the flag to its original value. This flag is a
701 /// debugging measure designed to detect cases where we start a
702 /// snapshot, create type variables, and register obligations
703 /// which may involve those type variables in the fulfillment cx,
704 /// potentially leaving "dangling type variables" behind.
705 /// In such cases, an assertion will fail when attempting to
706 /// register obligations, within a snapshot. Very useful, much
707 /// better than grovelling through megabytes of `RUSTC_LOG` output.
709 /// HOWEVER, in some cases the flag is unhelpful. In particular, we
710 /// sometimes create a "mini-fulfilment-cx" in which we enroll
711 /// obligations. As long as this fulfillment cx is fully drained
712 /// before we return, this is not a problem, as there won't be any
713 /// escaping obligations in the main cx. In those cases, you can
714 /// use this function.
715 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
717 F: FnOnce(&Self) -> R,
719 let flag = self.in_snapshot.get();
720 self.in_snapshot.set(false);
721 let result = func(self);
722 self.in_snapshot.set(flag);
726 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
727 debug!("start_snapshot()");
729 let in_snapshot = self.in_snapshot.get();
730 self.in_snapshot.set(true);
733 projection_cache_snapshot: self.projection_cache.borrow_mut().snapshot(),
734 type_snapshot: self.type_variables.borrow_mut().snapshot(),
735 const_snapshot: self.const_unification_table.borrow_mut().snapshot(),
736 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
737 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
738 region_constraints_snapshot: self.borrow_region_constraints().start_snapshot(),
739 region_obligations_snapshot: self.region_obligations.borrow().len(),
740 universe: self.universe(),
741 was_in_snapshot: in_snapshot,
742 // Borrow tables "in progress" (i.e., during typeck)
743 // to ban writes from within a snapshot to them.
744 _in_progress_tables: self.in_progress_tables.map(|tables| tables.borrow()),
748 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
749 debug!("rollback_to(cause={})", cause);
750 let CombinedSnapshot {
751 projection_cache_snapshot,
756 region_constraints_snapshot,
757 region_obligations_snapshot,
763 self.in_snapshot.set(was_in_snapshot);
764 self.universe.set(universe);
766 self.projection_cache.borrow_mut().rollback_to(projection_cache_snapshot);
767 self.type_variables.borrow_mut().rollback_to(type_snapshot);
768 self.const_unification_table.borrow_mut().rollback_to(const_snapshot);
769 self.int_unification_table.borrow_mut().rollback_to(int_snapshot);
770 self.float_unification_table.borrow_mut().rollback_to(float_snapshot);
771 self.region_obligations.borrow_mut().truncate(region_obligations_snapshot);
772 self.borrow_region_constraints().rollback_to(region_constraints_snapshot);
775 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
776 debug!("commit_from()");
777 let CombinedSnapshot {
778 projection_cache_snapshot,
783 region_constraints_snapshot,
784 region_obligations_snapshot: _,
790 self.in_snapshot.set(was_in_snapshot);
792 self.projection_cache.borrow_mut().commit(projection_cache_snapshot);
793 self.type_variables.borrow_mut().commit(type_snapshot);
794 self.const_unification_table.borrow_mut().commit(const_snapshot);
795 self.int_unification_table.borrow_mut().commit(int_snapshot);
796 self.float_unification_table.borrow_mut().commit(float_snapshot);
797 self.borrow_region_constraints().commit(region_constraints_snapshot);
800 /// Executes `f` and commit the bindings.
801 pub fn commit_unconditionally<R, F>(&self, f: F) -> R
806 let snapshot = self.start_snapshot();
808 self.commit_from(snapshot);
812 /// Executes `f` and commit the bindings if closure `f` returns `Ok(_)`.
813 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E>
815 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>,
817 debug!("commit_if_ok()");
818 let snapshot = self.start_snapshot();
819 let r = f(&snapshot);
820 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
823 self.commit_from(snapshot);
826 self.rollback_to("commit_if_ok -- error", snapshot);
832 /// Execute `f` in a snapshot, and commit the bindings it creates.
833 pub fn in_snapshot<T, F>(&self, f: F) -> T
835 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> T,
837 debug!("in_snapshot()");
838 let snapshot = self.start_snapshot();
839 let r = f(&snapshot);
840 self.commit_from(snapshot);
844 /// Executes `f` then unroll any bindings it creates.
845 pub fn probe<R, F>(&self, f: F) -> R
847 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
850 let snapshot = self.start_snapshot();
851 let r = f(&snapshot);
852 self.rollback_to("probe", snapshot);
856 /// Scan the constraints produced since `snapshot` began and returns:
858 /// - `None` -- if none of them involve "region outlives" constraints
859 /// - `Some(true)` -- if there are `'a: 'b` constraints where `'a` or `'b` is a placeholder
860 /// - `Some(false)` -- if there are `'a: 'b` constraints but none involve placeholders
861 pub fn region_constraints_added_in_snapshot(
863 snapshot: &CombinedSnapshot<'a, 'tcx>,
865 self.borrow_region_constraints().region_constraints_added_in_snapshot(
866 &snapshot.region_constraints_snapshot,
870 pub fn add_given(&self, sub: ty::Region<'tcx>, sup: ty::RegionVid) {
871 self.borrow_region_constraints().add_given(sub, sup);
874 pub fn can_sub<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
876 T: at::ToTrace<'tcx>,
878 let origin = &ObligationCause::dummy();
880 self.at(origin, param_env)
882 .map(|InferOk { obligations: _, .. }| {
883 // Ignore obligations, since we are unrolling
884 // everything anyway.
889 pub fn can_eq<T>(&self, param_env: ty::ParamEnv<'tcx>, a: T, b: T) -> UnitResult<'tcx>
891 T: at::ToTrace<'tcx>,
893 let origin = &ObligationCause::dummy();
895 self.at(origin, param_env)
897 .map(|InferOk { obligations: _, .. }| {
898 // Ignore obligations, since we are unrolling
899 // everything anyway.
906 origin: SubregionOrigin<'tcx>,
910 debug!("sub_regions({:?} <: {:?})", a, b);
911 self.borrow_region_constraints()
912 .make_subregion(origin, a, b);
915 pub fn subtype_predicate(
917 cause: &ObligationCause<'tcx>,
918 param_env: ty::ParamEnv<'tcx>,
919 predicate: &ty::PolySubtypePredicate<'tcx>,
920 ) -> Option<InferResult<'tcx, ()>> {
921 // Subtle: it's ok to skip the binder here and resolve because
922 // `shallow_resolve` just ignores anything that is not a type
923 // variable, and because type variable's can't (at present, at
924 // least) capture any of the things bound by this binder.
926 // Really, there is no *particular* reason to do this
927 // `shallow_resolve` here except as a
928 // micro-optimization. Naturally I could not
929 // resist. -nmatsakis
930 let two_unbound_type_vars = {
931 let a = self.shallow_resolve(predicate.skip_binder().a);
932 let b = self.shallow_resolve(predicate.skip_binder().b);
933 a.is_ty_var() && b.is_ty_var()
936 if two_unbound_type_vars {
937 // Two unbound type variables? Can't make progress.
941 Some(self.commit_if_ok(|snapshot| {
943 ty::SubtypePredicate {
949 ) = self.replace_bound_vars_with_placeholders(predicate);
951 let ok = self.at(cause, param_env)
952 .sub_exp(a_is_expected, a, b)?;
954 self.leak_check(false, &placeholder_map, snapshot)?;
960 pub fn region_outlives_predicate(
962 cause: &traits::ObligationCause<'tcx>,
963 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>,
964 ) -> UnitResult<'tcx> {
965 self.commit_if_ok(|snapshot| {
966 let (ty::OutlivesPredicate(r_a, r_b), placeholder_map) =
967 self.replace_bound_vars_with_placeholders(predicate);
968 let origin = SubregionOrigin::from_obligation_cause(
970 || RelateRegionParamBound(cause.span),
972 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
973 self.leak_check(false, &placeholder_map, snapshot)?;
978 pub fn next_ty_var_id(&self, diverging: bool, origin: TypeVariableOrigin) -> TyVid {
981 .new_var(self.universe(), diverging, origin)
984 pub fn next_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
985 self.tcx.mk_ty_var(self.next_ty_var_id(false, origin))
988 pub fn next_ty_var_in_universe(
990 origin: TypeVariableOrigin,
991 universe: ty::UniverseIndex
993 let vid = self.type_variables
995 .new_var(universe, false, origin);
996 self.tcx.mk_ty_var(vid)
999 pub fn next_diverging_ty_var(&self, origin: TypeVariableOrigin) -> Ty<'tcx> {
1000 self.tcx.mk_ty_var(self.next_ty_var_id(true, origin))
1003 pub fn next_const_var(
1006 origin: ConstVariableOrigin
1007 ) -> &'tcx ty::Const<'tcx> {
1008 self.tcx.mk_const_var(self.next_const_var_id(origin), ty)
1011 pub fn next_const_var_in_universe(
1014 origin: ConstVariableOrigin,
1015 universe: ty::UniverseIndex,
1016 ) -> &'tcx ty::Const<'tcx> {
1017 let vid = self.const_unification_table
1019 .new_key(ConstVarValue {
1021 val: ConstVariableValue::Unknown { universe },
1023 self.tcx.mk_const_var(vid, ty)
1026 pub fn next_const_var_id(&self, origin: ConstVariableOrigin) -> ConstVid<'tcx> {
1027 self.const_unification_table
1029 .new_key(ConstVarValue {
1031 val: ConstVariableValue::Unknown { universe: self.universe() },
1035 fn next_int_var_id(&self) -> IntVid {
1036 self.int_unification_table.borrow_mut().new_key(None)
1039 pub fn next_int_var(&self) -> Ty<'tcx> {
1040 self.tcx.mk_int_var(self.next_int_var_id())
1043 fn next_float_var_id(&self) -> FloatVid {
1044 self.float_unification_table.borrow_mut().new_key(None)
1047 pub fn next_float_var(&self) -> Ty<'tcx> {
1048 self.tcx.mk_float_var(self.next_float_var_id())
1051 /// Creates a fresh region variable with the next available index.
1052 /// The variable will be created in the maximum universe created
1053 /// thus far, allowing it to name any region created thus far.
1054 pub fn next_region_var(&self, origin: RegionVariableOrigin) -> ty::Region<'tcx> {
1055 self.next_region_var_in_universe(origin, self.universe())
1058 /// Creates a fresh region variable with the next available index
1059 /// in the given universe; typically, you can use
1060 /// `next_region_var` and just use the maximal universe.
1061 pub fn next_region_var_in_universe(
1063 origin: RegionVariableOrigin,
1064 universe: ty::UniverseIndex,
1065 ) -> ty::Region<'tcx> {
1066 let region_var = self.borrow_region_constraints()
1067 .new_region_var(universe, origin);
1068 self.tcx.mk_region(ty::ReVar(region_var))
1071 /// Return the universe that the region `r` was created in. For
1072 /// most regions (e.g., `'static`, named regions from the user,
1073 /// etc) this is the root universe U0. For inference variables or
1074 /// placeholders, however, it will return the universe which which
1075 /// they are associated.
1076 fn universe_of_region(
1078 r: ty::Region<'tcx>,
1079 ) -> ty::UniverseIndex {
1080 self.borrow_region_constraints().universe(r)
1083 /// Number of region variables created so far.
1084 pub fn num_region_vars(&self) -> usize {
1085 self.borrow_region_constraints().num_region_vars()
1088 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1089 pub fn next_nll_region_var(&self, origin: NLLRegionVariableOrigin) -> ty::Region<'tcx> {
1090 self.next_region_var(RegionVariableOrigin::NLL(origin))
1093 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1094 pub fn next_nll_region_var_in_universe(
1096 origin: NLLRegionVariableOrigin,
1097 universe: ty::UniverseIndex,
1098 ) -> ty::Region<'tcx> {
1099 self.next_region_var_in_universe(RegionVariableOrigin::NLL(origin), universe)
1102 pub fn var_for_def(&self, span: Span, param: &ty::GenericParamDef) -> Kind<'tcx> {
1104 GenericParamDefKind::Lifetime => {
1105 // Create a region inference variable for the given
1106 // region parameter definition.
1107 self.next_region_var(EarlyBoundRegion(span, param.name))
1110 GenericParamDefKind::Type { .. } => {
1111 // Create a type inference variable for the given
1112 // type parameter definition. The substitutions are
1113 // for actual parameters that may be referred to by
1114 // the default of this type parameter, if it exists.
1115 // e.g., `struct Foo<A, B, C = (A, B)>(...);` when
1116 // used in a path such as `Foo::<T, U>::new()` will
1117 // use an inference variable for `C` with `[T, U]`
1118 // as the substitutions for the default, `(T, U)`.
1119 let ty_var_id = self.type_variables.borrow_mut().new_var(
1122 TypeVariableOrigin::TypeParameterDefinition(span, param.name),
1125 self.tcx.mk_ty_var(ty_var_id).into()
1127 GenericParamDefKind::Const { .. } => {
1128 let origin = ConstVariableOrigin::ConstParameterDefinition(span, param.name);
1130 self.const_unification_table
1132 .new_key(ConstVarValue {
1134 val: ConstVariableValue::Unknown { universe: self.universe() },
1136 self.tcx.mk_const_var(const_var_id, self.tcx.type_of(param.def_id)).into()
1141 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1142 /// type/region parameter to a fresh inference variable.
1143 pub fn fresh_substs_for_item(&self, span: Span, def_id: DefId) -> SubstsRef<'tcx> {
1144 InternalSubsts::for_item(self.tcx, def_id, |param, _| self.var_for_def(span, param))
1147 /// Returns `true` if errors have been reported since this infcx was
1148 /// created. This is sometimes used as a heuristic to skip
1149 /// reporting errors that often occur as a result of earlier
1150 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1151 /// inference variables, regionck errors).
1152 pub fn is_tainted_by_errors(&self) -> bool {
1154 "is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1155 tainted_by_errors_flag={})",
1156 self.tcx.sess.err_count(),
1157 self.err_count_on_creation,
1158 self.tainted_by_errors_flag.get()
1161 if self.tcx.sess.err_count() > self.err_count_on_creation {
1162 return true; // errors reported since this infcx was made
1164 self.tainted_by_errors_flag.get()
1167 /// Set the "tainted by errors" flag to true. We call this when we
1168 /// observe an error from a prior pass.
1169 pub fn set_tainted_by_errors(&self) {
1170 debug!("set_tainted_by_errors()");
1171 self.tainted_by_errors_flag.set(true)
1174 /// Process the region constraints and report any errors that
1175 /// result. After this, no more unification operations should be
1176 /// done -- or the compiler will panic -- but it is legal to use
1177 /// `resolve_vars_if_possible` as well as `fully_resolve`.
1178 pub fn resolve_regions_and_report_errors(
1180 region_context: DefId,
1181 region_map: ®ion::ScopeTree,
1182 outlives_env: &OutlivesEnvironment<'tcx>,
1183 suppress: SuppressRegionErrors,
1186 self.is_tainted_by_errors() || self.region_obligations.borrow().is_empty(),
1187 "region_obligations not empty: {:#?}",
1188 self.region_obligations.borrow()
1191 let region_rels = &RegionRelations::new(
1195 outlives_env.free_region_map(),
1197 let (var_infos, data) = self.region_constraints
1200 .expect("regions already resolved")
1201 .into_infos_and_data();
1202 let (lexical_region_resolutions, errors) =
1203 lexical_region_resolve::resolve(region_rels, var_infos, data);
1205 let old_value = self.lexical_region_resolutions
1206 .replace(Some(lexical_region_resolutions));
1207 assert!(old_value.is_none());
1209 if !self.is_tainted_by_errors() {
1210 // As a heuristic, just skip reporting region errors
1211 // altogether if other errors have been reported while
1212 // this infcx was in use. This is totally hokey but
1213 // otherwise we have a hard time separating legit region
1214 // errors from silly ones.
1215 self.report_region_errors(region_map, &errors, suppress);
1219 /// Obtains (and clears) the current set of region
1220 /// constraints. The inference context is still usable: further
1221 /// unifications will simply add new constraints.
1223 /// This method is not meant to be used with normal lexical region
1224 /// resolution. Rather, it is used in the NLL mode as a kind of
1225 /// interim hack: basically we run normal type-check and generate
1226 /// region constraints as normal, but then we take them and
1227 /// translate them into the form that the NLL solver
1228 /// understands. See the NLL module for mode details.
1229 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1231 self.region_obligations.borrow().is_empty(),
1232 "region_obligations not empty: {:#?}",
1233 self.region_obligations.borrow()
1236 self.borrow_region_constraints().take_and_reset_data()
1239 /// Gives temporary access to the region constraint data.
1240 #[allow(non_camel_case_types)] // bug with impl trait
1241 pub fn with_region_constraints<R>(
1243 op: impl FnOnce(&RegionConstraintData<'tcx>) -> R,
1245 let region_constraints = self.borrow_region_constraints();
1246 op(region_constraints.data())
1249 /// Takes ownership of the list of variable regions. This implies
1250 /// that all the region constraints have already been taken, and
1251 /// hence that `resolve_regions_and_report_errors` can never be
1252 /// called. This is used only during NLL processing to "hand off" ownership
1253 /// of the set of region variables into the NLL region context.
1254 pub fn take_region_var_origins(&self) -> VarInfos {
1255 let (var_infos, data) = self.region_constraints
1258 .expect("regions already resolved")
1259 .into_infos_and_data();
1260 assert!(data.is_empty());
1264 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1265 self.resolve_vars_if_possible(&t).to_string()
1268 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1269 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1270 format!("({})", tstrs.join(", "))
1273 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1274 self.resolve_vars_if_possible(t).to_string()
1277 /// If `TyVar(vid)` resolves to a type, return that type. Else, return the
1278 /// universe index of `TyVar(vid)`.
1279 pub fn probe_ty_var(&self, vid: TyVid) -> Result<Ty<'tcx>, ty::UniverseIndex> {
1280 use self::type_variable::TypeVariableValue;
1282 match self.type_variables.borrow_mut().probe(vid) {
1283 TypeVariableValue::Known { value } => Ok(value),
1284 TypeVariableValue::Unknown { universe } => Err(universe),
1288 pub fn shallow_resolve<T>(&self, value: T) -> T
1290 T: TypeFoldable<'tcx>,
1292 let mut r = ShallowResolver::new(self);
1293 value.fold_with(&mut r)
1296 pub fn root_var(&self, var: ty::TyVid) -> ty::TyVid {
1297 self.type_variables.borrow_mut().root_var(var)
1300 /// Where possible, replaces type/const variables in
1301 /// `value` with their final value. Note that region variables
1302 /// are unaffected. If a type/const variable has not been unified, it
1303 /// is left as is. This is an idempotent operation that does
1304 /// not affect inference state in any way and so you can do it
1306 pub fn resolve_vars_if_possible<T>(&self, value: &T) -> T
1308 T: TypeFoldable<'tcx>,
1310 if !value.needs_infer() {
1311 return value.clone(); // avoid duplicated subst-folding
1313 let mut r = resolve::OpportunisticVarResolver::new(self);
1314 value.fold_with(&mut r)
1317 /// Returns first unresolved variable contained in `T`. In the
1318 /// process of visiting `T`, this will resolve (where possible)
1319 /// type variables in `T`, but it never constructs the final,
1320 /// resolved type, so it's more efficient than
1321 /// `resolve_vars_if_possible()`.
1322 pub fn unresolved_type_vars<T>(&self, value: &T) -> Option<(Ty<'tcx>, Option<Span>)>
1324 T: TypeFoldable<'tcx>,
1326 let mut r = resolve::UnresolvedTypeFinder::new(self);
1327 value.visit_with(&mut r);
1331 pub fn probe_const_var(
1333 vid: ty::ConstVid<'tcx>
1334 ) -> Result<&'tcx ty::Const<'tcx>, ty::UniverseIndex> {
1335 match self.const_unification_table.borrow_mut().probe_value(vid).val {
1336 ConstVariableValue::Known { value } => Ok(value),
1337 ConstVariableValue::Unknown { universe } => Err(universe),
1341 pub fn resolve_const_var(
1343 ct: &'tcx ty::Const<'tcx>
1344 ) -> &'tcx ty::Const<'tcx> {
1345 if let ty::Const { val: ConstValue::Infer(InferConst::Var(v)), .. } = ct {
1346 self.const_unification_table
1351 .map(|c| self.resolve_const_var(c))
1358 pub fn fully_resolve<T: TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<'tcx, T> {
1360 * Attempts to resolve all type/region/const variables in
1361 * `value`. Region inference must have been run already (e.g.,
1362 * by calling `resolve_regions_and_report_errors`). If some
1363 * variable was never unified, an `Err` results.
1365 * This method is idempotent, but it not typically not invoked
1366 * except during the writeback phase.
1369 resolve::fully_resolve(self, value)
1372 // [Note-Type-error-reporting]
1373 // An invariant is that anytime the expected or actual type is Error (the special
1374 // error type, meaning that an error occurred when typechecking this expression),
1375 // this is a derived error. The error cascaded from another error (that was already
1376 // reported), so it's not useful to display it to the user.
1377 // The following methods implement this logic.
1378 // They check if either the actual or expected type is Error, and don't print the error
1379 // in this case. The typechecker should only ever report type errors involving mismatched
1380 // types using one of these methods, and should not call span_err directly for such
1383 pub fn type_error_struct_with_diag<M>(
1387 actual_ty: Ty<'tcx>,
1388 ) -> DiagnosticBuilder<'tcx>
1390 M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1392 let actual_ty = self.resolve_vars_if_possible(&actual_ty);
1393 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1395 // Don't report an error if actual type is `Error`.
1396 if actual_ty.references_error() {
1397 return self.tcx.sess.diagnostic().struct_dummy();
1400 mk_diag(self.ty_to_string(actual_ty))
1403 pub fn report_mismatched_types(
1405 cause: &ObligationCause<'tcx>,
1408 err: TypeError<'tcx>,
1409 ) -> DiagnosticBuilder<'tcx> {
1410 let trace = TypeTrace::types(cause, true, expected, actual);
1411 self.report_and_explain_type_error(trace, &err)
1414 pub fn replace_bound_vars_with_fresh_vars<T>(
1417 lbrct: LateBoundRegionConversionTime,
1418 value: &ty::Binder<T>
1419 ) -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
1421 T: TypeFoldable<'tcx>
1423 let fld_r = |br| self.next_region_var(LateBoundRegion(span, br, lbrct));
1424 let fld_t = |_| self.next_ty_var(TypeVariableOrigin::MiscVariable(span));
1425 let fld_c = |_, ty| self.next_const_var(ty, ConstVariableOrigin::MiscVariable(span));
1426 self.tcx.replace_bound_vars(value, fld_r, fld_t, fld_c)
1429 /// See the [`region_constraints::verify_generic_bound`] method.
1430 pub fn verify_generic_bound(
1432 origin: SubregionOrigin<'tcx>,
1433 kind: GenericKind<'tcx>,
1434 a: ty::Region<'tcx>,
1435 bound: VerifyBound<'tcx>,
1437 debug!("verify_generic_bound({:?}, {:?} <: {:?})", kind, a, bound);
1439 self.borrow_region_constraints()
1440 .verify_generic_bound(origin, kind, a, bound);
1443 pub fn type_is_copy_modulo_regions(
1445 param_env: ty::ParamEnv<'tcx>,
1449 let ty = self.resolve_vars_if_possible(&ty);
1451 // Even if the type may have no inference variables, during
1452 // type-checking closure types are in local tables only.
1453 if !self.in_progress_tables.is_some() || !ty.has_closure_types() {
1454 if let Some((param_env, ty)) = self.tcx.lift_to_global(&(param_env, ty)) {
1455 return ty.is_copy_modulo_regions(self.tcx.global_tcx(), param_env, span);
1459 let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
1461 // this can get called from typeck (by euv), and moves_by_default
1462 // rightly refuses to work with inference variables, but
1463 // moves_by_default has a cache, which we want to use in other
1465 traits::type_known_to_meet_bound_modulo_regions(self, param_env, ty, copy_def_id, span)
1468 /// Obtains the latest type of the given closure; this may be a
1469 /// closure in the current function, in which case its
1470 /// `ClosureKind` may not yet be known.
1471 pub fn closure_kind(
1473 closure_def_id: DefId,
1474 closure_substs: ty::ClosureSubsts<'tcx>,
1475 ) -> Option<ty::ClosureKind> {
1476 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self.tcx);
1477 let closure_kind_ty = self.shallow_resolve(closure_kind_ty);
1478 closure_kind_ty.to_opt_closure_kind()
1481 /// Obtain the signature of a closure. For closures, unlike
1482 /// `tcx.fn_sig(def_id)`, this method will work during the
1483 /// type-checking of the enclosing function and return the closure
1484 /// signature in its partially inferred state.
1488 substs: ty::ClosureSubsts<'tcx>,
1489 ) -> ty::PolyFnSig<'tcx> {
1490 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
1491 let closure_sig_ty = self.shallow_resolve(closure_sig_ty);
1492 closure_sig_ty.fn_sig(self.tcx)
1495 /// Normalizes associated types in `value`, potentially returning
1496 /// new obligations that must further be processed.
1497 pub fn partially_normalize_associated_types_in<T>(
1500 body_id: hir::HirId,
1501 param_env: ty::ParamEnv<'tcx>,
1503 ) -> InferOk<'tcx, T>
1505 T: TypeFoldable<'tcx>,
1507 debug!("partially_normalize_associated_types_in(value={:?})", value);
1508 let mut selcx = traits::SelectionContext::new(self);
1509 let cause = ObligationCause::misc(span, body_id);
1510 let traits::Normalized { value, obligations } =
1511 traits::normalize(&mut selcx, param_env, cause, value);
1513 "partially_normalize_associated_types_in: result={:?} predicates={:?}",
1516 InferOk { value, obligations }
1519 pub fn borrow_region_constraints(&self) -> RefMut<'_, RegionConstraintCollector<'tcx>> {
1520 RefMut::map(self.region_constraints.borrow_mut(), |c| {
1521 c.as_mut().expect("region constraints already solved")
1525 /// Clears the selection, evaluation, and projection caches. This is useful when
1526 /// repeatedly attempting to select an `Obligation` while changing only
1527 /// its `ParamEnv`, since `FulfillmentContext` doesn't use probing.
1528 pub fn clear_caches(&self) {
1529 self.selection_cache.clear();
1530 self.evaluation_cache.clear();
1531 self.projection_cache.borrow_mut().clear();
1534 fn universe(&self) -> ty::UniverseIndex {
1538 /// Creates and return a fresh universe that extends all previous
1539 /// universes. Updates `self.universe` to that new universe.
1540 pub fn create_next_universe(&self) -> ty::UniverseIndex {
1541 let u = self.universe.get().next_universe();
1542 self.universe.set(u);
1547 pub struct ShallowResolver<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
1548 infcx: &'a InferCtxt<'a, 'gcx, 'tcx>,
1551 impl<'a, 'gcx, 'tcx> ShallowResolver<'a, 'gcx, 'tcx> {
1553 pub fn new(infcx: &'a InferCtxt<'a, 'gcx, 'tcx>) -> Self {
1554 ShallowResolver { infcx }
1557 // We have this force-inlined variant of `shallow_resolve` for the one
1558 // callsite that is extremely hot. All other callsites use the normal
1561 pub fn inlined_shallow_resolve(&mut self, typ: Ty<'tcx>) -> Ty<'tcx> {
1563 ty::Infer(ty::TyVar(v)) => {
1564 // Not entirely obvious: if `typ` is a type variable,
1565 // it can be resolved to an int/float variable, which
1566 // can then be recursively resolved, hence the
1567 // recursion. Note though that we prevent type
1568 // variables from unifyxing to other type variables
1569 // directly (though they may be embedded
1570 // structurally), and we prevent cycles in any case,
1571 // so this recursion should always be of very limited
1573 self.infcx.type_variables
1577 .map(|t| self.fold_ty(t))
1581 ty::Infer(ty::IntVar(v)) => self.infcx.int_unification_table
1584 .map(|v| v.to_type(self.infcx.tcx))
1587 ty::Infer(ty::FloatVar(v)) => self.infcx.float_unification_table
1590 .map(|v| v.to_type(self.infcx.tcx))
1598 impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for ShallowResolver<'a, 'gcx, 'tcx> {
1599 fn tcx<'b>(&'b self) -> TyCtxt<'b, 'gcx, 'tcx> {
1603 fn fold_ty(&mut self, ty: Ty<'tcx>) -> Ty<'tcx> {
1604 self.inlined_shallow_resolve(ty)
1607 fn fold_const(&mut self, ct: &'tcx ty::Const<'tcx>) -> &'tcx ty::Const<'tcx> {
1609 ty::Const { val: ConstValue::Infer(InferConst::Var(vid)), .. } => {
1610 self.infcx.const_unification_table
1615 .map(|c| self.fold_const(c))
1623 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
1624 pub fn span(&self) -> Span {
1629 cause: &ObligationCause<'tcx>,
1630 a_is_expected: bool,
1633 ) -> TypeTrace<'tcx> {
1635 cause: cause.clone(),
1636 values: Types(ExpectedFound::new(a_is_expected, a, b)),
1640 pub fn dummy(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> TypeTrace<'tcx> {
1642 cause: ObligationCause::dummy(),
1643 values: Types(ExpectedFound {
1644 expected: tcx.types.err,
1645 found: tcx.types.err,
1651 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1652 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1653 write!(f, "TypeTrace({:?})", self.cause)
1657 impl<'tcx> SubregionOrigin<'tcx> {
1658 pub fn span(&self) -> Span {
1660 Subtype(ref a) => a.span(),
1661 InfStackClosure(a) => a,
1662 InvokeClosure(a) => a,
1663 DerefPointer(a) => a,
1664 ClosureCapture(a, _) => a,
1666 RelateObjectBound(a) => a,
1667 RelateParamBound(a, _) => a,
1668 RelateRegionParamBound(a) => a,
1669 RelateDefaultParamBound(a, _) => a,
1671 ReborrowUpvar(a, _) => a,
1672 DataBorrowed(_, a) => a,
1673 ReferenceOutlivesReferent(_, a) => a,
1674 ParameterInScope(_, a) => a,
1675 ExprTypeIsNotInScope(_, a) => a,
1676 BindingTypeIsNotValidAtDecl(a) => a,
1683 SafeDestructor(a) => a,
1684 CompareImplMethodObligation { span, .. } => span,
1688 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>, default: F) -> Self
1690 F: FnOnce() -> Self,
1693 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) => {
1694 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span)
1697 traits::ObligationCauseCode::CompareImplMethodObligation {
1701 } => SubregionOrigin::CompareImplMethodObligation {
1713 impl RegionVariableOrigin {
1714 pub fn span(&self) -> Span {
1716 MiscVariable(a) => a,
1717 PatternRegion(a) => a,
1718 AddrOfRegion(a) => a,
1721 EarlyBoundRegion(a, ..) => a,
1722 LateBoundRegion(a, ..) => a,
1723 BoundRegionInCoherence(_) => syntax_pos::DUMMY_SP,
1724 UpvarRegion(_, a) => a,
1725 NLL(..) => bug!("NLL variable used with `span`"),
1730 EnumTypeFoldableImpl! {
1731 impl<'tcx> TypeFoldable<'tcx> for ValuePairs<'tcx> {
1732 (ValuePairs::Types)(a),
1733 (ValuePairs::Regions)(a),
1734 (ValuePairs::Consts)(a),
1735 (ValuePairs::TraitRefs)(a),
1736 (ValuePairs::PolyTraitRefs)(a),
1740 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
1741 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
1744 "RegionObligation(sub_region={:?}, sup_type={:?})",
1745 self.sub_region, self.sup_type