1 // Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 //! See the Book for more information.
13 pub use self::LateBoundRegionConversionTime::*;
14 pub use self::RegionVariableOrigin::*;
15 pub use self::SubregionOrigin::*;
16 pub use self::ValuePairs::*;
17 pub use ty::IntVarValue;
18 pub use self::freshen::TypeFreshener;
20 use hir::def_id::DefId;
21 use middle::free_region::RegionRelations;
23 use middle::lang_items;
24 use mir::tcx::PlaceTy;
25 use ty::subst::Substs;
26 use ty::{TyVid, IntVid, FloatVid};
27 use ty::{self, Ty, TyCtxt};
28 use ty::error::{ExpectedFound, TypeError, UnconstrainedNumeric};
29 use ty::fold::{TypeFoldable, TypeFolder, TypeVisitor};
30 use ty::relate::RelateResult;
31 use traits::{self, ObligationCause, PredicateObligations, Reveal};
32 use rustc_data_structures::unify as ut;
33 use std::cell::{Cell, RefCell, Ref, RefMut};
34 use std::collections::BTreeMap;
37 use errors::DiagnosticBuilder;
38 use syntax_pos::{self, Span, DUMMY_SP};
39 use util::nodemap::FxHashMap;
40 use arena::DroplessArena;
42 use self::combine::CombineFields;
43 use self::higher_ranked::HrMatchResult;
44 use self::region_constraints::{RegionConstraintCollector, RegionSnapshot};
45 use self::region_constraints::{GenericKind, VerifyBound, RegionConstraintData, VarOrigins};
46 use self::lexical_region_resolve::LexicalRegionResolutions;
47 use self::outlives::env::OutlivesEnvironment;
48 use self::type_variable::TypeVariableOrigin;
49 use self::unify_key::ToType;
55 pub mod error_reporting;
61 pub mod region_constraints;
62 mod lexical_region_resolve;
67 pub mod type_variable;
71 pub struct InferOk<'tcx, T> {
73 pub obligations: PredicateObligations<'tcx>,
75 pub type InferResult<'tcx, T> = Result<InferOk<'tcx, T>, TypeError<'tcx>>;
77 pub type Bound<T> = Option<T>;
78 pub type UnitResult<'tcx> = RelateResult<'tcx, ()>; // "unify result"
79 pub type FixupResult<T> = Result<T, FixupError>; // "fixup result"
81 pub struct InferCtxt<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
82 pub tcx: TyCtxt<'a, 'gcx, 'tcx>,
84 /// During type-checking/inference of a body, `in_progress_tables`
85 /// contains a reference to the tables being built up, which are
86 /// used for reading closure kinds/signatures as they are inferred,
87 /// and for error reporting logic to read arbitrary node types.
88 pub in_progress_tables: Option<&'a RefCell<ty::TypeckTables<'tcx>>>,
90 // Cache for projections. This cache is snapshotted along with the
93 // Public so that `traits::project` can use it.
94 pub projection_cache: RefCell<traits::ProjectionCache<'tcx>>,
96 // We instantiate UnificationTable with bounds<Ty> because the
97 // types that might instantiate a general type variable have an
98 // order, represented by its upper and lower bounds.
99 pub type_variables: RefCell<type_variable::TypeVariableTable<'tcx>>,
101 // Map from integral variable to the kind of integer it represents
102 int_unification_table: RefCell<ut::UnificationTable<ut::InPlace<ty::IntVid>>>,
104 // Map from floating variable to the kind of float it represents
105 float_unification_table: RefCell<ut::UnificationTable<ut::InPlace<ty::FloatVid>>>,
107 // Tracks the set of region variables and the constraints between
108 // them. This is initially `Some(_)` but when
109 // `resolve_regions_and_report_errors` is invoked, this gets set
110 // to `None` -- further attempts to perform unification etc may
111 // fail if new region constraints would've been added.
112 region_constraints: RefCell<Option<RegionConstraintCollector<'tcx>>>,
114 // Once region inference is done, the values for each variable.
115 lexical_region_resolutions: RefCell<Option<LexicalRegionResolutions<'tcx>>>,
117 /// Caches the results of trait selection. This cache is used
118 /// for things that have to do with the parameters in scope.
119 pub selection_cache: traits::SelectionCache<'tcx>,
121 /// Caches the results of trait evaluation.
122 pub evaluation_cache: traits::EvaluationCache<'tcx>,
124 // the set of predicates on which errors have been reported, to
125 // avoid reporting the same error twice.
126 pub reported_trait_errors: RefCell<FxHashMap<Span, Vec<ty::Predicate<'tcx>>>>,
128 // When an error occurs, we want to avoid reporting "derived"
129 // errors that are due to this original failure. Normally, we
130 // handle this with the `err_count_on_creation` count, which
131 // basically just tracks how many errors were reported when we
132 // started type-checking a fn and checks to see if any new errors
133 // have been reported since then. Not great, but it works.
135 // However, when errors originated in other passes -- notably
136 // resolve -- this heuristic breaks down. Therefore, we have this
137 // auxiliary flag that one can set whenever one creates a
138 // type-error that is due to an error in a prior pass.
140 // Don't read this flag directly, call `is_tainted_by_errors()`
141 // and `set_tainted_by_errors()`.
142 tainted_by_errors_flag: Cell<bool>,
144 // Track how many errors were reported when this infcx is created.
145 // If the number of errors increases, that's also a sign (line
146 // `tained_by_errors`) to avoid reporting certain kinds of errors.
147 err_count_on_creation: usize,
149 // This flag is true while there is an active snapshot.
150 in_snapshot: Cell<bool>,
152 // A set of constraints that regionck must validate. Each
153 // constraint has the form `T:'a`, meaning "some type `T` must
154 // outlive the lifetime 'a". These constraints derive from
155 // instantiated type parameters. So if you had a struct defined
158 // struct Foo<T:'static> { ... }
160 // then in some expression `let x = Foo { ... }` it will
161 // instantiate the type parameter `T` with a fresh type `$0`. At
162 // the same time, it will record a region obligation of
163 // `$0:'static`. This will get checked later by regionck. (We
164 // can't generally check these things right away because we have
165 // to wait until types are resolved.)
167 // These are stored in a map keyed to the id of the innermost
168 // enclosing fn body / static initializer expression. This is
169 // because the location where the obligation was incurred can be
170 // relevant with respect to which sublifetime assumptions are in
171 // place. The reason that we store under the fn-id, and not
172 // something more fine-grained, is so that it is easier for
173 // regionck to be sure that it has found *all* the region
174 // obligations (otherwise, it's easy to fail to walk to a
175 // particular node-id).
177 // Before running `resolve_regions_and_report_errors`, the creator
178 // of the inference context is expected to invoke
179 // `process_region_obligations` (defined in `self::region_obligations`)
180 // for each body-id in this map, which will process the
181 // obligations within. This is expected to be done 'late enough'
182 // that all type inference variables have been bound and so forth.
183 pub region_obligations: RefCell<Vec<(ast::NodeId, RegionObligation<'tcx>)>>,
186 /// A map returned by `skolemize_late_bound_regions()` indicating the skolemized
187 /// region that each late-bound region was replaced with.
188 pub type SkolemizationMap<'tcx> = BTreeMap<ty::BoundRegion, ty::Region<'tcx>>;
190 /// See `error_reporting` module for more details
191 #[derive(Clone, Debug)]
192 pub enum ValuePairs<'tcx> {
193 Types(ExpectedFound<Ty<'tcx>>),
194 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
195 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
198 /// The trace designates the path through inference that we took to
199 /// encounter an error or subtyping constraint.
201 /// See `error_reporting` module for more details.
203 pub struct TypeTrace<'tcx> {
204 cause: ObligationCause<'tcx>,
205 values: ValuePairs<'tcx>,
208 /// The origin of a `r1 <= r2` constraint.
210 /// See `error_reporting` module for more details
211 #[derive(Clone, Debug)]
212 pub enum SubregionOrigin<'tcx> {
213 // Arose from a subtyping relation
214 Subtype(TypeTrace<'tcx>),
216 // Stack-allocated closures cannot outlive innermost loop
217 // or function so as to ensure we only require finite stack
218 InfStackClosure(Span),
220 // Invocation of closure must be within its lifetime
223 // Dereference of reference must be within its lifetime
226 // Closure bound must not outlive captured free variables
227 FreeVariable(Span, ast::NodeId),
229 // Index into slice must be within its lifetime
232 // When casting `&'a T` to an `&'b Trait` object,
233 // relating `'a` to `'b`
234 RelateObjectBound(Span),
236 // Some type parameter was instantiated with the given type,
237 // and that type must outlive some region.
238 RelateParamBound(Span, Ty<'tcx>),
240 // The given region parameter was instantiated with a region
241 // that must outlive some other region.
242 RelateRegionParamBound(Span),
244 // A bound placed on type parameters that states that must outlive
245 // the moment of their instantiation.
246 RelateDefaultParamBound(Span, Ty<'tcx>),
248 // Creating a pointer `b` to contents of another reference
251 // Creating a pointer `b` to contents of an upvar
252 ReborrowUpvar(Span, ty::UpvarId),
254 // Data with type `Ty<'tcx>` was borrowed
255 DataBorrowed(Ty<'tcx>, Span),
257 // (&'a &'b T) where a >= b
258 ReferenceOutlivesReferent(Ty<'tcx>, Span),
260 // Type or region parameters must be in scope.
261 ParameterInScope(ParameterOrigin, Span),
263 // The type T of an expression E must outlive the lifetime for E.
264 ExprTypeIsNotInScope(Ty<'tcx>, Span),
266 // A `ref b` whose region does not enclose the decl site
267 BindingTypeIsNotValidAtDecl(Span),
269 // Regions appearing in a method receiver must outlive method call
272 // Regions appearing in a function argument must outlive func call
275 // Region in return type of invoked fn must enclose call
278 // Operands must be in scope
281 // Region resulting from a `&` expr must enclose the `&` expr
284 // An auto-borrow that does not enclose the expr where it occurs
287 // Region constraint arriving from destructor safety
288 SafeDestructor(Span),
290 // Comparing the signature and requirements of an impl method against
291 // the containing trait.
292 CompareImplMethodObligation {
294 item_name: ast::Name,
295 impl_item_def_id: DefId,
296 trait_item_def_id: DefId,
300 /// Places that type/region parameters can appear.
301 #[derive(Clone, Copy, Debug)]
302 pub enum ParameterOrigin {
304 MethodCall, // foo.bar() <-- parameters on impl providing bar()
305 OverloadedOperator, // a + b when overloaded
306 OverloadedDeref, // *a when overloaded
309 /// Times when we replace late-bound regions with variables:
310 #[derive(Clone, Copy, Debug)]
311 pub enum LateBoundRegionConversionTime {
312 /// when a fn is called
315 /// when two higher-ranked types are compared
318 /// when projecting an associated type
319 AssocTypeProjection(DefId),
322 /// Reasons to create a region inference variable
324 /// See `error_reporting` module for more details
325 #[derive(Copy, Clone, Debug)]
326 pub enum RegionVariableOrigin {
327 // Region variables created for ill-categorized reasons,
328 // mostly indicates places in need of refactoring
331 // Regions created by a `&P` or `[...]` pattern
334 // Regions created by `&` operator
337 // Regions created as part of an autoref of a method receiver
340 // Regions created as part of an automatic coercion
343 // Region variables created as the values for early-bound regions
344 EarlyBoundRegion(Span, ast::Name),
346 // Region variables created for bound regions
347 // in a function or method that is called
348 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
350 UpvarRegion(ty::UpvarId, Span),
352 BoundRegionInCoherence(ast::Name),
354 // This origin is used for the inference variables that we create
355 // during NLL region processing.
356 NLL(NLLRegionVariableOrigin),
359 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
360 pub enum NLLRegionVariableOrigin {
361 // During NLL region processing, we create variables for free
362 // regions that we encounter in the function signature and
363 // elsewhere. This origin indices we've got one of those.
366 Inferred(::mir::visit::TyContext),
369 #[derive(Copy, Clone, Debug)]
370 pub enum FixupError {
371 UnresolvedIntTy(IntVid),
372 UnresolvedFloatTy(FloatVid),
376 /// See the `region_obligations` field for more information.
378 pub struct RegionObligation<'tcx> {
379 pub sub_region: ty::Region<'tcx>,
380 pub sup_type: Ty<'tcx>,
381 pub cause: ObligationCause<'tcx>,
384 impl fmt::Display for FixupError {
385 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
386 use self::FixupError::*;
389 UnresolvedIntTy(_) => {
390 write!(f, "cannot determine the type of this integer; \
391 add a suffix to specify the type explicitly")
393 UnresolvedFloatTy(_) => {
394 write!(f, "cannot determine the type of this number; \
395 add a suffix to specify the type explicitly")
397 UnresolvedTy(_) => write!(f, "unconstrained type")
402 /// Helper type of a temporary returned by tcx.infer_ctxt().
403 /// Necessary because we can't write the following bound:
404 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(InferCtxt<'b, 'gcx, 'tcx>).
405 pub struct InferCtxtBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
406 global_tcx: TyCtxt<'a, 'gcx, 'gcx>,
407 arena: DroplessArena,
408 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
411 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
412 pub fn infer_ctxt(self) -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
415 arena: DroplessArena::new(),
422 impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
423 /// Used only by `rustc_typeck` during body type-checking/inference,
424 /// will initialize `in_progress_tables` with fresh `TypeckTables`.
425 pub fn with_fresh_in_progress_tables(mut self, table_owner: DefId) -> Self {
426 self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
430 pub fn enter<F, R>(&'tcx mut self, f: F) -> R
431 where F: for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>) -> R
433 let InferCtxtBuilder {
438 let in_progress_tables = fresh_tables.as_ref();
439 global_tcx.enter_local(arena, |tcx| f(InferCtxt {
442 projection_cache: RefCell::new(traits::ProjectionCache::new()),
443 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
444 int_unification_table: RefCell::new(ut::UnificationTable::new()),
445 float_unification_table: RefCell::new(ut::UnificationTable::new()),
446 region_constraints: RefCell::new(Some(RegionConstraintCollector::new())),
447 lexical_region_resolutions: RefCell::new(None),
448 selection_cache: traits::SelectionCache::new(),
449 evaluation_cache: traits::EvaluationCache::new(),
450 reported_trait_errors: RefCell::new(FxHashMap()),
451 tainted_by_errors_flag: Cell::new(false),
452 err_count_on_creation: tcx.sess.err_count(),
453 in_snapshot: Cell::new(false),
454 region_obligations: RefCell::new(vec![]),
459 impl<T> ExpectedFound<T> {
460 pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
462 ExpectedFound {expected: a, found: b}
464 ExpectedFound {expected: b, found: a}
469 impl<'tcx, T> InferOk<'tcx, T> {
470 pub fn unit(self) -> InferOk<'tcx, ()> {
471 InferOk { value: (), obligations: self.obligations }
475 #[must_use = "once you start a snapshot, you should always consume it"]
476 pub struct CombinedSnapshot<'a, 'tcx:'a> {
477 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
478 type_snapshot: type_variable::Snapshot<'tcx>,
479 int_snapshot: ut::Snapshot<ut::InPlace<ty::IntVid>>,
480 float_snapshot: ut::Snapshot<ut::InPlace<ty::FloatVid>>,
481 region_constraints_snapshot: RegionSnapshot,
482 region_obligations_snapshot: usize,
483 was_in_snapshot: bool,
484 _in_progress_tables: Option<Ref<'a, ty::TypeckTables<'tcx>>>,
487 /// Helper trait for shortening the lifetimes inside a
488 /// value for post-type-checking normalization.
489 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
490 fn trans_normalize<'a, 'tcx>(&self,
491 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
492 param_env: ty::ParamEnv<'tcx>)
496 macro_rules! items { ($($item:item)+) => ($($item)+) }
497 macro_rules! impl_trans_normalize {
498 ($lt_gcx:tt, $($ty:ty),+) => {
499 items!($(impl<$lt_gcx> TransNormalize<$lt_gcx> for $ty {
500 fn trans_normalize<'a, 'tcx>(&self,
501 infcx: &InferCtxt<'a, $lt_gcx, 'tcx>,
502 param_env: ty::ParamEnv<'tcx>)
504 infcx.normalize_projections_in(param_env, self)
510 impl_trans_normalize!('gcx,
512 &'gcx ty::Const<'gcx>,
516 ty::ClosureSubsts<'gcx>,
517 ty::PolyTraitRef<'gcx>,
518 ty::ExistentialTraitRef<'gcx>
521 impl<'gcx> TransNormalize<'gcx> for PlaceTy<'gcx> {
522 fn trans_normalize<'a, 'tcx>(&self,
523 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
524 param_env: ty::ParamEnv<'tcx>)
527 PlaceTy::Ty { ty } => PlaceTy::Ty { ty: ty.trans_normalize(infcx, param_env) },
528 PlaceTy::Downcast { adt_def, substs, variant_index } => {
531 substs: substs.trans_normalize(infcx, param_env),
539 // NOTE: Callable from trans only!
540 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
541 /// Currently, higher-ranked type bounds inhibit normalization. Therefore,
542 /// each time we erase them in translation, we need to normalize
544 pub fn erase_late_bound_regions_and_normalize<T>(self, value: &ty::Binder<T>)
546 where T: TransNormalize<'tcx>
548 assert!(!value.needs_subst());
549 let value = self.erase_late_bound_regions(value);
550 self.fully_normalize_associated_types_in(&value)
553 /// Fully normalizes any associated types in `value`, using an
554 /// empty environment and `Reveal::All` mode (therefore, suitable
555 /// only for monomorphized code during trans, basically).
556 pub fn fully_normalize_associated_types_in<T>(self, value: &T) -> T
557 where T: TransNormalize<'tcx>
559 debug!("fully_normalize_associated_types_in(t={:?})", value);
561 let param_env = ty::ParamEnv::empty(Reveal::All);
562 let value = self.erase_regions(value);
564 if !value.has_projections() {
568 self.infer_ctxt().enter(|infcx| {
569 value.trans_normalize(&infcx, param_env)
573 /// Does a best-effort to normalize any associated types in
574 /// `value`; this includes revealing specializable types, so this
575 /// should be not be used during type-checking, but only during
576 /// optimization and code generation.
577 pub fn normalize_associated_type_in_env<T>(
578 self, value: &T, env: ty::ParamEnv<'tcx>
580 where T: TransNormalize<'tcx>
582 debug!("normalize_associated_type_in_env(t={:?})", value);
584 let value = self.erase_regions(value);
586 if !value.has_projections() {
590 self.infer_ctxt().enter(|infcx| {
591 value.trans_normalize(&infcx, env.reveal_all())
596 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
597 fn normalize_projections_in<T>(&self, param_env: ty::ParamEnv<'tcx>, value: &T) -> T::Lifted
598 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
600 let mut selcx = traits::SelectionContext::new(self);
601 let cause = traits::ObligationCause::dummy();
602 let traits::Normalized { value: result, obligations } =
603 traits::normalize(&mut selcx, param_env, cause, value);
605 debug!("normalize_projections_in: result={:?} obligations={:?}",
606 result, obligations);
608 let mut fulfill_cx = traits::FulfillmentContext::new();
610 for obligation in obligations {
611 fulfill_cx.register_predicate_obligation(self, obligation);
614 self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
617 /// Finishes processes any obligations that remain in the
618 /// fulfillment context, and then returns the result with all type
619 /// variables removed and regions erased. Because this is intended
620 /// for use after type-check has completed, if any errors occur,
621 /// it will panic. It is used during normalization and other cases
622 /// where processing the obligations in `fulfill_cx` may cause
623 /// type inference variables that appear in `result` to be
624 /// unified, and hence we need to process those obligations to get
625 /// the complete picture of the type.
626 pub fn drain_fulfillment_cx_or_panic<T>(&self,
628 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
631 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
633 debug!("drain_fulfillment_cx_or_panic()");
635 // In principle, we only need to do this so long as `result`
636 // contains unbound type parameters. It could be a slight
637 // optimization to stop iterating early.
638 match fulfill_cx.select_all_or_error(self) {
641 span_bug!(span, "Encountered errors `{:?}` resolving bounds after type-checking",
646 let result = self.resolve_type_vars_if_possible(result);
647 let result = self.tcx.erase_regions(&result);
649 match self.tcx.lift_to_global(&result) {
650 Some(result) => result,
652 span_bug!(span, "Uninferred types/regions in `{:?}`", result);
657 pub fn is_in_snapshot(&self) -> bool {
658 self.in_snapshot.get()
661 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
662 t.fold_with(&mut self.freshener())
665 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
667 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
672 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'gcx, 'tcx> {
673 freshen::TypeFreshener::new(self)
676 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
677 use ty::error::UnconstrainedNumeric::Neither;
678 use ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
680 ty::TyInfer(ty::IntVar(vid)) => {
681 if self.int_unification_table.borrow_mut().probe_value(vid).is_some() {
687 ty::TyInfer(ty::FloatVar(vid)) => {
688 if self.float_unification_table.borrow_mut().probe_value(vid).is_some() {
698 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
699 let mut variables = Vec::new();
702 let mut type_variables = self.type_variables.borrow_mut();
705 .unsolved_variables()
707 .map(|t| self.tcx.mk_var(t)));
711 let mut int_unification_table = self.int_unification_table.borrow_mut();
713 (0..int_unification_table.len())
714 .map(|i| ty::IntVid { index: i as u32 })
715 .filter(|&vid| int_unification_table.probe_value(vid).is_none())
716 .map(|v| self.tcx.mk_int_var(v)));
720 let mut float_unification_table = self.float_unification_table.borrow_mut();
722 (0..float_unification_table.len())
723 .map(|i| ty::FloatVid { index: i as u32 })
724 .filter(|&vid| float_unification_table.probe_value(vid).is_none())
725 .map(|v| self.tcx.mk_float_var(v)));
731 fn combine_fields(&'a self, trace: TypeTrace<'tcx>, param_env: ty::ParamEnv<'tcx>)
732 -> CombineFields<'a, 'gcx, 'tcx> {
738 obligations: PredicateObligations::new(),
742 // Clear the "currently in a snapshot" flag, invoke the closure,
743 // then restore the flag to its original value. This flag is a
744 // debugging measure designed to detect cases where we start a
745 // snapshot, create type variables, and register obligations
746 // which may involve those type variables in the fulfillment cx,
747 // potentially leaving "dangling type variables" behind.
748 // In such cases, an assertion will fail when attempting to
749 // register obligations, within a snapshot. Very useful, much
750 // better than grovelling through megabytes of RUST_LOG output.
752 // HOWEVER, in some cases the flag is unhelpful. In particular, we
753 // sometimes create a "mini-fulfilment-cx" in which we enroll
754 // obligations. As long as this fulfillment cx is fully drained
755 // before we return, this is not a problem, as there won't be any
756 // escaping obligations in the main cx. In those cases, you can
757 // use this function.
758 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
759 where F: FnOnce(&Self) -> R
761 let flag = self.in_snapshot.get();
762 self.in_snapshot.set(false);
763 let result = func(self);
764 self.in_snapshot.set(flag);
768 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
769 debug!("start_snapshot()");
771 let in_snapshot = self.in_snapshot.get();
772 self.in_snapshot.set(true);
775 projection_cache_snapshot: self.projection_cache.borrow_mut().snapshot(),
776 type_snapshot: self.type_variables.borrow_mut().snapshot(),
777 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
778 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
779 region_constraints_snapshot: self.borrow_region_constraints().start_snapshot(),
780 region_obligations_snapshot: self.region_obligations.borrow().len(),
781 was_in_snapshot: in_snapshot,
782 // Borrow tables "in progress" (i.e. during typeck)
783 // to ban writes from within a snapshot to them.
784 _in_progress_tables: self.in_progress_tables.map(|tables| {
790 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
791 debug!("rollback_to(cause={})", cause);
792 let CombinedSnapshot { projection_cache_snapshot,
796 region_constraints_snapshot,
797 region_obligations_snapshot,
799 _in_progress_tables } = snapshot;
801 self.in_snapshot.set(was_in_snapshot);
803 self.projection_cache
805 .rollback_to(projection_cache_snapshot);
808 .rollback_to(type_snapshot);
809 self.int_unification_table
811 .rollback_to(int_snapshot);
812 self.float_unification_table
814 .rollback_to(float_snapshot);
815 self.region_obligations
817 .truncate(region_obligations_snapshot);
818 self.borrow_region_constraints()
819 .rollback_to(region_constraints_snapshot);
822 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
823 debug!("commit_from()");
824 let CombinedSnapshot { projection_cache_snapshot,
828 region_constraints_snapshot,
829 region_obligations_snapshot: _,
831 _in_progress_tables } = snapshot;
833 self.in_snapshot.set(was_in_snapshot);
835 self.projection_cache
837 .commit(projection_cache_snapshot);
840 .commit(type_snapshot);
841 self.int_unification_table
843 .commit(int_snapshot);
844 self.float_unification_table
846 .commit(float_snapshot);
847 self.borrow_region_constraints()
848 .commit(region_constraints_snapshot);
851 /// Execute `f` and commit the bindings
852 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
856 let snapshot = self.start_snapshot();
858 self.commit_from(snapshot);
862 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
863 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
864 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>
866 debug!("commit_if_ok()");
867 let snapshot = self.start_snapshot();
868 let r = f(&snapshot);
869 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
871 Ok(_) => { self.commit_from(snapshot); }
872 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
877 // Execute `f` in a snapshot, and commit the bindings it creates
878 pub fn in_snapshot<T, F>(&self, f: F) -> T where
879 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> T
881 debug!("in_snapshot()");
882 let snapshot = self.start_snapshot();
883 let r = f(&snapshot);
884 self.commit_from(snapshot);
888 /// Execute `f` then unroll any bindings it creates
889 pub fn probe<R, F>(&self, f: F) -> R where
890 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
893 let snapshot = self.start_snapshot();
894 let r = f(&snapshot);
895 self.rollback_to("probe", snapshot);
899 pub fn add_given(&self,
900 sub: ty::Region<'tcx>,
903 self.borrow_region_constraints().add_given(sub, sup);
906 pub fn can_sub<T>(&self,
907 param_env: ty::ParamEnv<'tcx>,
911 where T: at::ToTrace<'tcx>
913 let origin = &ObligationCause::dummy();
915 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
916 // Ignore obligations, since we are unrolling
917 // everything anyway.
922 pub fn can_eq<T>(&self,
923 param_env: ty::ParamEnv<'tcx>,
927 where T: at::ToTrace<'tcx>
929 let origin = &ObligationCause::dummy();
931 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
932 // Ignore obligations, since we are unrolling
933 // everything anyway.
938 pub fn sub_regions(&self,
939 origin: SubregionOrigin<'tcx>,
941 b: ty::Region<'tcx>) {
942 debug!("sub_regions({:?} <: {:?})", a, b);
943 self.borrow_region_constraints().make_subregion(origin, a, b);
946 pub fn subtype_predicate(&self,
947 cause: &ObligationCause<'tcx>,
948 param_env: ty::ParamEnv<'tcx>,
949 predicate: &ty::PolySubtypePredicate<'tcx>)
950 -> Option<InferResult<'tcx, ()>>
952 // Subtle: it's ok to skip the binder here and resolve because
953 // `shallow_resolve` just ignores anything that is not a type
954 // variable, and because type variable's can't (at present, at
955 // least) capture any of the things bound by this binder.
957 // Really, there is no *particular* reason to do this
958 // `shallow_resolve` here except as a
959 // micro-optimization. Naturally I could not
960 // resist. -nmatsakis
961 let two_unbound_type_vars = {
962 let a = self.shallow_resolve(predicate.skip_binder().a);
963 let b = self.shallow_resolve(predicate.skip_binder().b);
964 a.is_ty_var() && b.is_ty_var()
967 if two_unbound_type_vars {
968 // Two unbound type variables? Can't make progress.
972 Some(self.commit_if_ok(|snapshot| {
973 let (ty::SubtypePredicate { a_is_expected, a, b}, skol_map) =
974 self.skolemize_late_bound_regions(predicate, snapshot);
976 let cause_span = cause.span;
977 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
978 self.leak_check(false, cause_span, &skol_map, snapshot)?;
979 self.pop_skolemized(skol_map, snapshot);
984 pub fn region_outlives_predicate(&self,
985 cause: &traits::ObligationCause<'tcx>,
986 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>)
989 self.commit_if_ok(|snapshot| {
990 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
991 self.skolemize_late_bound_regions(predicate, snapshot);
993 SubregionOrigin::from_obligation_cause(cause,
994 || RelateRegionParamBound(cause.span));
995 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
996 self.leak_check(false, cause.span, &skol_map, snapshot)?;
997 Ok(self.pop_skolemized(skol_map, snapshot))
1001 pub fn next_ty_var_id(&self,
1002 universe: ty::UniverseIndex,
1004 origin: TypeVariableOrigin)
1008 .new_var(universe, diverging, origin)
1011 pub fn next_ty_var(&self, universe: ty::UniverseIndex, origin: TypeVariableOrigin) -> Ty<'tcx> {
1012 self.tcx.mk_var(self.next_ty_var_id(universe, false, origin))
1015 pub fn next_diverging_ty_var(&self,
1016 universe: ty::UniverseIndex,
1017 origin: TypeVariableOrigin)
1019 self.tcx.mk_var(self.next_ty_var_id(universe, true, origin))
1022 pub fn next_int_var_id(&self) -> IntVid {
1023 self.int_unification_table
1028 pub fn next_float_var_id(&self) -> FloatVid {
1029 self.float_unification_table
1034 /// Create a fresh region variable with the next available index.
1038 /// - `origin`: information about why we created this variable, for use
1039 /// during diagnostics / error-reporting.
1040 pub fn next_region_var(&self, origin: RegionVariableOrigin)
1041 -> ty::Region<'tcx> {
1042 self.tcx.mk_region(ty::ReVar(self.borrow_region_constraints().new_region_var(origin)))
1045 /// Number of region variables created so far.
1046 pub fn num_region_vars(&self) -> usize {
1047 self.borrow_region_constraints().var_origins().len()
1050 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1051 pub fn next_nll_region_var(&self, origin: NLLRegionVariableOrigin)
1052 -> ty::Region<'tcx> {
1053 self.next_region_var(RegionVariableOrigin::NLL(origin))
1056 /// Create a region inference variable for the given
1057 /// region parameter definition.
1058 pub fn region_var_for_def(&self,
1060 def: &ty::RegionParameterDef)
1061 -> ty::Region<'tcx> {
1062 self.next_region_var(EarlyBoundRegion(span, def.name))
1065 /// Create a type inference variable for the given
1066 /// type parameter definition. The substitutions are
1067 /// for actual parameters that may be referred to by
1068 /// the default of this type parameter, if it exists.
1069 /// E.g. `struct Foo<A, B, C = (A, B)>(...);` when
1070 /// used in a path such as `Foo::<T, U>::new()` will
1071 /// use an inference variable for `C` with `[T, U]`
1072 /// as the substitutions for the default, `(T, U)`.
1073 pub fn type_var_for_def(&self,
1074 universe: ty::UniverseIndex,
1076 def: &ty::TypeParameterDef)
1078 let ty_var_id = self.type_variables
1082 TypeVariableOrigin::TypeParameterDefinition(span, def.name));
1084 self.tcx.mk_var(ty_var_id)
1087 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1088 /// type/region parameter to a fresh inference variable.
1089 pub fn fresh_substs_for_item(&self,
1090 universe: ty::UniverseIndex,
1093 -> &'tcx Substs<'tcx> {
1094 Substs::for_item(self.tcx, def_id, |def, _| {
1095 self.region_var_for_def(span, def)
1097 self.type_var_for_def(universe, span, def)
1101 /// True if errors have been reported since this infcx was
1102 /// created. This is sometimes used as a heuristic to skip
1103 /// reporting errors that often occur as a result of earlier
1104 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1105 /// inference variables, regionck errors).
1106 pub fn is_tainted_by_errors(&self) -> bool {
1107 debug!("is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1108 tainted_by_errors_flag={})",
1109 self.tcx.sess.err_count(),
1110 self.err_count_on_creation,
1111 self.tainted_by_errors_flag.get());
1113 if self.tcx.sess.err_count() > self.err_count_on_creation {
1114 return true; // errors reported since this infcx was made
1116 self.tainted_by_errors_flag.get()
1119 /// Set the "tainted by errors" flag to true. We call this when we
1120 /// observe an error from a prior pass.
1121 pub fn set_tainted_by_errors(&self) {
1122 debug!("set_tainted_by_errors()");
1123 self.tainted_by_errors_flag.set(true)
1126 /// Process the region constraints and report any errors that
1127 /// result. After this, no more unification operations should be
1128 /// done -- or the compiler will panic -- but it is legal to use
1129 /// `resolve_type_vars_if_possible` as well as `fully_resolve`.
1130 pub fn resolve_regions_and_report_errors(
1132 region_context: DefId,
1133 region_map: ®ion::ScopeTree,
1134 outlives_env: &OutlivesEnvironment<'tcx>,
1136 self.resolve_regions_and_report_errors_inner(
1144 /// Like `resolve_regions_and_report_errors`, but skips error
1145 /// reporting if NLL is enabled. This is used for fn bodies where
1146 /// the same error may later be reported by the NLL-based
1148 pub fn resolve_regions_and_report_errors_unless_nll(
1150 region_context: DefId,
1151 region_map: ®ion::ScopeTree,
1152 outlives_env: &OutlivesEnvironment<'tcx>,
1154 self.resolve_regions_and_report_errors_inner(
1162 fn resolve_regions_and_report_errors_inner(
1164 region_context: DefId,
1165 region_map: ®ion::ScopeTree,
1166 outlives_env: &OutlivesEnvironment<'tcx>,
1167 will_later_be_reported_by_nll: bool,
1169 assert!(self.is_tainted_by_errors() || self.region_obligations.borrow().is_empty(),
1170 "region_obligations not empty: {:#?}",
1171 self.region_obligations.borrow());
1173 let region_rels = &RegionRelations::new(self.tcx,
1176 outlives_env.free_region_map());
1177 let (var_origins, data) = self.region_constraints.borrow_mut()
1179 .expect("regions already resolved")
1180 .into_origins_and_data();
1181 let (lexical_region_resolutions, errors) =
1182 lexical_region_resolve::resolve(region_rels, var_origins, data);
1184 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1185 assert!(old_value.is_none());
1187 if !self.is_tainted_by_errors() {
1188 // As a heuristic, just skip reporting region errors
1189 // altogether if other errors have been reported while
1190 // this infcx was in use. This is totally hokey but
1191 // otherwise we have a hard time separating legit region
1192 // errors from silly ones.
1193 self.report_region_errors(region_map, &errors, will_later_be_reported_by_nll);
1197 /// Obtains (and clears) the current set of region
1198 /// constraints. The inference context is still usable: further
1199 /// unifications will simply add new constraints.
1201 /// This method is not meant to be used with normal lexical region
1202 /// resolution. Rather, it is used in the NLL mode as a kind of
1203 /// interim hack: basically we run normal type-check and generate
1204 /// region constraints as normal, but then we take them and
1205 /// translate them into the form that the NLL solver
1206 /// understands. See the NLL module for mode details.
1207 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1208 assert!(self.region_obligations.borrow().is_empty(),
1209 "region_obligations not empty: {:#?}",
1210 self.region_obligations.borrow());
1212 self.borrow_region_constraints().take_and_reset_data()
1215 /// Takes ownership of the list of variable regions. This implies
1216 /// that all the region constriants have already been taken, and
1217 /// hence that `resolve_regions_and_report_errors` can never be
1218 /// called. This is used only during NLL processing to "hand off" ownership
1219 /// of the set of region vairables into the NLL region context.
1220 pub fn take_region_var_origins(&self) -> VarOrigins {
1221 let (var_origins, data) = self.region_constraints.borrow_mut()
1223 .expect("regions already resolved")
1224 .into_origins_and_data();
1225 assert!(data.is_empty());
1229 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1230 self.resolve_type_vars_if_possible(&t).to_string()
1233 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1234 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1235 format!("({})", tstrs.join(", "))
1238 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1239 self.resolve_type_vars_if_possible(t).to_string()
1242 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1244 ty::TyInfer(ty::TyVar(v)) => {
1245 // Not entirely obvious: if `typ` is a type variable,
1246 // it can be resolved to an int/float variable, which
1247 // can then be recursively resolved, hence the
1248 // recursion. Note though that we prevent type
1249 // variables from unifying to other type variables
1250 // directly (though they may be embedded
1251 // structurally), and we prevent cycles in any case,
1252 // so this recursion should always be of very limited
1254 self.type_variables.borrow_mut()
1257 .map(|t| self.shallow_resolve(t))
1261 ty::TyInfer(ty::IntVar(v)) => {
1262 self.int_unification_table
1265 .map(|v| v.to_type(self.tcx))
1269 ty::TyInfer(ty::FloatVar(v)) => {
1270 self.float_unification_table
1273 .map(|v| v.to_type(self.tcx))
1283 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1284 where T: TypeFoldable<'tcx>
1287 * Where possible, replaces type/int/float variables in
1288 * `value` with their final value. Note that region variables
1289 * are unaffected. If a type variable has not been unified, it
1290 * is left as is. This is an idempotent operation that does
1291 * not affect inference state in any way and so you can do it
1295 if !value.needs_infer() {
1296 return value.clone(); // avoid duplicated subst-folding
1298 let mut r = resolve::OpportunisticTypeResolver::new(self);
1299 value.fold_with(&mut r)
1302 /// Returns true if `T` contains unresolved type variables. In the
1303 /// process of visiting `T`, this will resolve (where possible)
1304 /// type variables in `T`, but it never constructs the final,
1305 /// resolved type, so it's more efficient than
1306 /// `resolve_type_vars_if_possible()`.
1307 pub fn any_unresolved_type_vars<T>(&self, value: &T) -> bool
1308 where T: TypeFoldable<'tcx>
1310 let mut r = resolve::UnresolvedTypeFinder::new(self);
1311 value.visit_with(&mut r)
1314 pub fn resolve_type_and_region_vars_if_possible<T>(&self, value: &T) -> T
1315 where T: TypeFoldable<'tcx>
1317 let mut r = resolve::OpportunisticTypeAndRegionResolver::new(self);
1318 value.fold_with(&mut r)
1321 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1323 * Attempts to resolve all type/region variables in
1324 * `value`. Region inference must have been run already (e.g.,
1325 * by calling `resolve_regions_and_report_errors`). If some
1326 * variable was never unified, an `Err` results.
1328 * This method is idempotent, but it not typically not invoked
1329 * except during the writeback phase.
1332 resolve::fully_resolve(self, value)
1335 // [Note-Type-error-reporting]
1336 // An invariant is that anytime the expected or actual type is TyError (the special
1337 // error type, meaning that an error occurred when typechecking this expression),
1338 // this is a derived error. The error cascaded from another error (that was already
1339 // reported), so it's not useful to display it to the user.
1340 // The following methods implement this logic.
1341 // They check if either the actual or expected type is TyError, and don't print the error
1342 // in this case. The typechecker should only ever report type errors involving mismatched
1343 // types using one of these methods, and should not call span_err directly for such
1346 pub fn type_error_struct_with_diag<M>(&self,
1349 actual_ty: Ty<'tcx>)
1350 -> DiagnosticBuilder<'tcx>
1351 where M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1353 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1354 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1356 // Don't report an error if actual type is TyError.
1357 if actual_ty.references_error() {
1358 return self.tcx.sess.diagnostic().struct_dummy();
1361 mk_diag(self.ty_to_string(actual_ty))
1364 pub fn report_mismatched_types(&self,
1365 cause: &ObligationCause<'tcx>,
1368 err: TypeError<'tcx>)
1369 -> DiagnosticBuilder<'tcx> {
1370 let trace = TypeTrace::types(cause, true, expected, actual);
1371 self.report_and_explain_type_error(trace, &err)
1374 pub fn replace_late_bound_regions_with_fresh_var<T>(
1377 lbrct: LateBoundRegionConversionTime,
1378 value: &ty::Binder<T>)
1379 -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
1380 where T : TypeFoldable<'tcx>
1382 self.tcx.replace_late_bound_regions(
1384 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1387 /// Given a higher-ranked projection predicate like:
1389 /// for<'a> <T as Fn<&'a u32>>::Output = &'a u32
1391 /// and a target trait-ref like:
1393 /// <T as Fn<&'x u32>>
1395 /// find a substitution `S` for the higher-ranked regions (here,
1396 /// `['a => 'x]`) such that the predicate matches the trait-ref,
1397 /// and then return the value (here, `&'a u32`) but with the
1398 /// substitution applied (hence, `&'x u32`).
1400 /// See `higher_ranked_match` in `higher_ranked/mod.rs` for more
1402 pub fn match_poly_projection_predicate(&self,
1403 cause: ObligationCause<'tcx>,
1404 param_env: ty::ParamEnv<'tcx>,
1405 match_a: ty::PolyProjectionPredicate<'tcx>,
1406 match_b: ty::TraitRef<'tcx>)
1407 -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
1409 let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref(self.tcx), p.ty));
1410 let trace = TypeTrace {
1412 values: TraitRefs(ExpectedFound::new(true, match_pair.skip_binder().0, match_b))
1415 let mut combine = self.combine_fields(trace, param_env);
1416 let result = combine.higher_ranked_match(&match_pair, &match_b, true)?;
1417 Ok(InferOk { value: result, obligations: combine.obligations })
1420 /// See `verify_generic_bound` method in `region_constraints`
1421 pub fn verify_generic_bound(&self,
1422 origin: SubregionOrigin<'tcx>,
1423 kind: GenericKind<'tcx>,
1424 a: ty::Region<'tcx>,
1425 bound: VerifyBound<'tcx>) {
1426 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1431 self.borrow_region_constraints().verify_generic_bound(origin, kind, a, bound);
1434 pub fn type_moves_by_default(&self,
1435 param_env: ty::ParamEnv<'tcx>,
1439 let ty = self.resolve_type_vars_if_possible(&ty);
1440 // Even if the type may have no inference variables, during
1441 // type-checking closure types are in local tables only.
1442 if !self.in_progress_tables.is_some() || !ty.has_closure_types() {
1443 if let Some((param_env, ty)) = self.tcx.lift_to_global(&(param_env, ty)) {
1444 return ty.moves_by_default(self.tcx.global_tcx(), param_env, span);
1448 let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
1450 // this can get called from typeck (by euv), and moves_by_default
1451 // rightly refuses to work with inference variables, but
1452 // moves_by_default has a cache, which we want to use in other
1454 !traits::type_known_to_meet_bound(self, param_env, ty, copy_def_id, span)
1457 /// Obtains the latest type of the given closure; this may be a
1458 /// closure in the current function, in which case its
1459 /// `ClosureKind` may not yet be known.
1460 pub fn closure_kind(&self,
1461 closure_def_id: DefId,
1462 closure_substs: ty::ClosureSubsts<'tcx>)
1463 -> Option<ty::ClosureKind>
1465 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self.tcx);
1466 let closure_kind_ty = self.shallow_resolve(&closure_kind_ty);
1467 closure_kind_ty.to_opt_closure_kind()
1470 /// Obtain the signature of a closure. For closures, unlike
1471 /// `tcx.fn_sig(def_id)`, this method will work during the
1472 /// type-checking of the enclosing function and return the closure
1473 /// signature in its partially inferred state.
1477 substs: ty::ClosureSubsts<'tcx>
1478 ) -> ty::PolyFnSig<'tcx> {
1479 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
1480 let closure_sig_ty = self.shallow_resolve(&closure_sig_ty);
1481 closure_sig_ty.fn_sig(self.tcx)
1484 /// Normalizes associated types in `value`, potentially returning
1485 /// new obligations that must further be processed.
1486 pub fn partially_normalize_associated_types_in<T>(&self,
1488 body_id: ast::NodeId,
1489 param_env: ty::ParamEnv<'tcx>,
1492 where T : TypeFoldable<'tcx>
1494 debug!("partially_normalize_associated_types_in(value={:?})", value);
1495 let mut selcx = traits::SelectionContext::new(self);
1496 let cause = ObligationCause::misc(span, body_id);
1497 let traits::Normalized { value, obligations } =
1498 traits::normalize(&mut selcx, param_env, cause, value);
1499 debug!("partially_normalize_associated_types_in: result={:?} predicates={:?}",
1502 InferOk { value, obligations }
1505 pub fn borrow_region_constraints(&self) -> RefMut<'_, RegionConstraintCollector<'tcx>> {
1507 self.region_constraints.borrow_mut(),
1508 |c| c.as_mut().expect("region constraints already solved"))
1511 /// Clears the selection, evaluation, and projection cachesThis is useful when
1512 /// repeatedly attemping to select an Obligation while changing only
1513 /// its ParamEnv, since FulfillmentContext doesn't use 'probe'
1514 pub fn clear_caches(&self) {
1515 self.selection_cache.clear();
1516 self.evaluation_cache.clear();
1517 self.projection_cache.borrow_mut().clear();
1521 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
1522 pub fn span(&self) -> Span {
1526 pub fn types(cause: &ObligationCause<'tcx>,
1527 a_is_expected: bool,
1530 -> TypeTrace<'tcx> {
1532 cause: cause.clone(),
1533 values: Types(ExpectedFound::new(a_is_expected, a, b))
1537 pub fn dummy(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> TypeTrace<'tcx> {
1539 cause: ObligationCause::dummy(),
1540 values: Types(ExpectedFound {
1541 expected: tcx.types.err,
1542 found: tcx.types.err,
1548 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1549 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1550 write!(f, "TypeTrace({:?})", self.cause)
1554 impl<'tcx> SubregionOrigin<'tcx> {
1555 pub fn span(&self) -> Span {
1557 Subtype(ref a) => a.span(),
1558 InfStackClosure(a) => a,
1559 InvokeClosure(a) => a,
1560 DerefPointer(a) => a,
1561 FreeVariable(a, _) => a,
1563 RelateObjectBound(a) => a,
1564 RelateParamBound(a, _) => a,
1565 RelateRegionParamBound(a) => a,
1566 RelateDefaultParamBound(a, _) => a,
1568 ReborrowUpvar(a, _) => a,
1569 DataBorrowed(_, a) => a,
1570 ReferenceOutlivesReferent(_, a) => a,
1571 ParameterInScope(_, a) => a,
1572 ExprTypeIsNotInScope(_, a) => a,
1573 BindingTypeIsNotValidAtDecl(a) => a,
1580 SafeDestructor(a) => a,
1581 CompareImplMethodObligation { span, .. } => span,
1585 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>,
1588 where F: FnOnce() -> Self
1591 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) =>
1592 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span),
1594 traits::ObligationCauseCode::CompareImplMethodObligation { item_name,
1596 trait_item_def_id, } =>
1597 SubregionOrigin::CompareImplMethodObligation {
1609 impl RegionVariableOrigin {
1610 pub fn span(&self) -> Span {
1612 MiscVariable(a) => a,
1613 PatternRegion(a) => a,
1614 AddrOfRegion(a) => a,
1617 EarlyBoundRegion(a, ..) => a,
1618 LateBoundRegion(a, ..) => a,
1619 BoundRegionInCoherence(_) => syntax_pos::DUMMY_SP,
1620 UpvarRegion(_, a) => a,
1621 NLL(..) => bug!("NLL variable used with `span`"),
1626 impl<'tcx> TypeFoldable<'tcx> for ValuePairs<'tcx> {
1627 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1629 ValuePairs::Types(ref ef) => {
1630 ValuePairs::Types(ef.fold_with(folder))
1632 ValuePairs::TraitRefs(ref ef) => {
1633 ValuePairs::TraitRefs(ef.fold_with(folder))
1635 ValuePairs::PolyTraitRefs(ref ef) => {
1636 ValuePairs::PolyTraitRefs(ef.fold_with(folder))
1641 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1643 ValuePairs::Types(ref ef) => ef.visit_with(visitor),
1644 ValuePairs::TraitRefs(ref ef) => ef.visit_with(visitor),
1645 ValuePairs::PolyTraitRefs(ref ef) => ef.visit_with(visitor),
1650 impl<'tcx> TypeFoldable<'tcx> for TypeTrace<'tcx> {
1651 fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
1653 cause: self.cause.fold_with(folder),
1654 values: self.values.fold_with(folder)
1658 fn super_visit_with<V: TypeVisitor<'tcx>>(&self, visitor: &mut V) -> bool {
1659 self.cause.visit_with(visitor) || self.values.visit_with(visitor)
1663 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
1664 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1665 write!(f, "RegionObligation(sub_region={:?}, sup_type={:?})",