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;
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 Regions(ExpectedFound<ty::Region<'tcx>>),
195 TraitRefs(ExpectedFound<ty::TraitRef<'tcx>>),
196 PolyTraitRefs(ExpectedFound<ty::PolyTraitRef<'tcx>>),
199 /// The trace designates the path through inference that we took to
200 /// encounter an error or subtyping constraint.
202 /// See `error_reporting` module for more details.
204 pub struct TypeTrace<'tcx> {
205 cause: ObligationCause<'tcx>,
206 values: ValuePairs<'tcx>,
209 /// The origin of a `r1 <= r2` constraint.
211 /// See `error_reporting` module for more details
212 #[derive(Clone, Debug)]
213 pub enum SubregionOrigin<'tcx> {
214 // Arose from a subtyping relation
215 Subtype(TypeTrace<'tcx>),
217 // Stack-allocated closures cannot outlive innermost loop
218 // or function so as to ensure we only require finite stack
219 InfStackClosure(Span),
221 // Invocation of closure must be within its lifetime
224 // Dereference of reference must be within its lifetime
227 // Closure bound must not outlive captured free variables
228 FreeVariable(Span, ast::NodeId),
230 // Index into slice must be within its lifetime
233 // When casting `&'a T` to an `&'b Trait` object,
234 // relating `'a` to `'b`
235 RelateObjectBound(Span),
237 // Some type parameter was instantiated with the given type,
238 // and that type must outlive some region.
239 RelateParamBound(Span, Ty<'tcx>),
241 // The given region parameter was instantiated with a region
242 // that must outlive some other region.
243 RelateRegionParamBound(Span),
245 // A bound placed on type parameters that states that must outlive
246 // the moment of their instantiation.
247 RelateDefaultParamBound(Span, Ty<'tcx>),
249 // Creating a pointer `b` to contents of another reference
252 // Creating a pointer `b` to contents of an upvar
253 ReborrowUpvar(Span, ty::UpvarId),
255 // Data with type `Ty<'tcx>` was borrowed
256 DataBorrowed(Ty<'tcx>, Span),
258 // (&'a &'b T) where a >= b
259 ReferenceOutlivesReferent(Ty<'tcx>, Span),
261 // Type or region parameters must be in scope.
262 ParameterInScope(ParameterOrigin, Span),
264 // The type T of an expression E must outlive the lifetime for E.
265 ExprTypeIsNotInScope(Ty<'tcx>, Span),
267 // A `ref b` whose region does not enclose the decl site
268 BindingTypeIsNotValidAtDecl(Span),
270 // Regions appearing in a method receiver must outlive method call
273 // Regions appearing in a function argument must outlive func call
276 // Region in return type of invoked fn must enclose call
279 // Operands must be in scope
282 // Region resulting from a `&` expr must enclose the `&` expr
285 // An auto-borrow that does not enclose the expr where it occurs
288 // Region constraint arriving from destructor safety
289 SafeDestructor(Span),
291 // Comparing the signature and requirements of an impl method against
292 // the containing trait.
293 CompareImplMethodObligation {
295 item_name: ast::Name,
296 impl_item_def_id: DefId,
297 trait_item_def_id: DefId,
301 /// Places that type/region parameters can appear.
302 #[derive(Clone, Copy, Debug)]
303 pub enum ParameterOrigin {
305 MethodCall, // foo.bar() <-- parameters on impl providing bar()
306 OverloadedOperator, // a + b when overloaded
307 OverloadedDeref, // *a when overloaded
310 /// Times when we replace late-bound regions with variables:
311 #[derive(Clone, Copy, Debug)]
312 pub enum LateBoundRegionConversionTime {
313 /// when a fn is called
316 /// when two higher-ranked types are compared
319 /// when projecting an associated type
320 AssocTypeProjection(DefId),
323 /// Reasons to create a region inference variable
325 /// See `error_reporting` module for more details
326 #[derive(Copy, Clone, Debug)]
327 pub enum RegionVariableOrigin {
328 // Region variables created for ill-categorized reasons,
329 // mostly indicates places in need of refactoring
332 // Regions created by a `&P` or `[...]` pattern
335 // Regions created by `&` operator
338 // Regions created as part of an autoref of a method receiver
341 // Regions created as part of an automatic coercion
344 // Region variables created as the values for early-bound regions
345 EarlyBoundRegion(Span, ast::Name),
347 // Region variables created for bound regions
348 // in a function or method that is called
349 LateBoundRegion(Span, ty::BoundRegion, LateBoundRegionConversionTime),
351 UpvarRegion(ty::UpvarId, Span),
353 BoundRegionInCoherence(ast::Name),
355 // This origin is used for the inference variables that we create
356 // during NLL region processing.
357 NLL(NLLRegionVariableOrigin),
360 #[derive(Copy, Clone, Debug, PartialEq, Eq, Hash)]
361 pub enum NLLRegionVariableOrigin {
362 // During NLL region processing, we create variables for free
363 // regions that we encounter in the function signature and
364 // elsewhere. This origin indices we've got one of those.
367 Inferred(::mir::visit::TyContext),
370 #[derive(Copy, Clone, Debug)]
371 pub enum FixupError {
372 UnresolvedIntTy(IntVid),
373 UnresolvedFloatTy(FloatVid),
377 /// See the `region_obligations` field for more information.
379 pub struct RegionObligation<'tcx> {
380 pub sub_region: ty::Region<'tcx>,
381 pub sup_type: Ty<'tcx>,
382 pub cause: ObligationCause<'tcx>,
385 impl fmt::Display for FixupError {
386 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
387 use self::FixupError::*;
390 UnresolvedIntTy(_) => {
391 write!(f, "cannot determine the type of this integer; \
392 add a suffix to specify the type explicitly")
394 UnresolvedFloatTy(_) => {
395 write!(f, "cannot determine the type of this number; \
396 add a suffix to specify the type explicitly")
398 UnresolvedTy(_) => write!(f, "unconstrained type")
403 /// Helper type of a temporary returned by tcx.infer_ctxt().
404 /// Necessary because we can't write the following bound:
405 /// F: for<'b, 'tcx> where 'gcx: 'tcx FnOnce(InferCtxt<'b, 'gcx, 'tcx>).
406 pub struct InferCtxtBuilder<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
407 global_tcx: TyCtxt<'a, 'gcx, 'gcx>,
408 arena: DroplessArena,
409 fresh_tables: Option<RefCell<ty::TypeckTables<'tcx>>>,
412 impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'gcx> {
413 pub fn infer_ctxt(self) -> InferCtxtBuilder<'a, 'gcx, 'tcx> {
416 arena: DroplessArena::new(),
423 impl<'a, 'gcx, 'tcx> InferCtxtBuilder<'a, 'gcx, 'tcx> {
424 /// Used only by `rustc_typeck` during body type-checking/inference,
425 /// will initialize `in_progress_tables` with fresh `TypeckTables`.
426 pub fn with_fresh_in_progress_tables(mut self, table_owner: DefId) -> Self {
427 self.fresh_tables = Some(RefCell::new(ty::TypeckTables::empty(Some(table_owner))));
431 pub fn enter<F, R>(&'tcx mut self, f: F) -> R
432 where F: for<'b> FnOnce(InferCtxt<'b, 'gcx, 'tcx>) -> R
434 let InferCtxtBuilder {
439 let in_progress_tables = fresh_tables.as_ref();
440 global_tcx.enter_local(arena, |tcx| f(InferCtxt {
443 projection_cache: RefCell::new(traits::ProjectionCache::new()),
444 type_variables: RefCell::new(type_variable::TypeVariableTable::new()),
445 int_unification_table: RefCell::new(ut::UnificationTable::new()),
446 float_unification_table: RefCell::new(ut::UnificationTable::new()),
447 region_constraints: RefCell::new(Some(RegionConstraintCollector::new())),
448 lexical_region_resolutions: RefCell::new(None),
449 selection_cache: traits::SelectionCache::new(),
450 evaluation_cache: traits::EvaluationCache::new(),
451 reported_trait_errors: RefCell::new(FxHashMap()),
452 tainted_by_errors_flag: Cell::new(false),
453 err_count_on_creation: tcx.sess.err_count(),
454 in_snapshot: Cell::new(false),
455 region_obligations: RefCell::new(vec![]),
460 impl<T> ExpectedFound<T> {
461 pub fn new(a_is_expected: bool, a: T, b: T) -> Self {
463 ExpectedFound {expected: a, found: b}
465 ExpectedFound {expected: b, found: a}
470 impl<'tcx, T> InferOk<'tcx, T> {
471 pub fn unit(self) -> InferOk<'tcx, ()> {
472 InferOk { value: (), obligations: self.obligations }
476 #[must_use = "once you start a snapshot, you should always consume it"]
477 pub struct CombinedSnapshot<'a, 'tcx:'a> {
478 projection_cache_snapshot: traits::ProjectionCacheSnapshot,
479 type_snapshot: type_variable::Snapshot<'tcx>,
480 int_snapshot: ut::Snapshot<ut::InPlace<ty::IntVid>>,
481 float_snapshot: ut::Snapshot<ut::InPlace<ty::FloatVid>>,
482 region_constraints_snapshot: RegionSnapshot,
483 region_obligations_snapshot: usize,
484 was_in_snapshot: bool,
485 _in_progress_tables: Option<Ref<'a, ty::TypeckTables<'tcx>>>,
488 /// Helper trait for shortening the lifetimes inside a
489 /// value for post-type-checking normalization.
490 pub trait TransNormalize<'gcx>: TypeFoldable<'gcx> {
491 fn trans_normalize<'a, 'tcx>(&self,
492 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
493 param_env: ty::ParamEnv<'tcx>)
497 macro_rules! items { ($($item:item)+) => ($($item)+) }
498 macro_rules! impl_trans_normalize {
499 ($lt_gcx:tt, $($ty:ty),+) => {
500 items!($(impl<$lt_gcx> TransNormalize<$lt_gcx> for $ty {
501 fn trans_normalize<'a, 'tcx>(&self,
502 infcx: &InferCtxt<'a, $lt_gcx, 'tcx>,
503 param_env: ty::ParamEnv<'tcx>)
505 infcx.normalize_projections_in(param_env, self)
511 impl_trans_normalize!('gcx,
513 &'gcx ty::Const<'gcx>,
517 ty::ClosureSubsts<'gcx>,
518 ty::PolyTraitRef<'gcx>,
519 ty::ExistentialTraitRef<'gcx>
522 impl<'gcx> TransNormalize<'gcx> for PlaceTy<'gcx> {
523 fn trans_normalize<'a, 'tcx>(&self,
524 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
525 param_env: ty::ParamEnv<'tcx>)
528 PlaceTy::Ty { ty } => PlaceTy::Ty { ty: ty.trans_normalize(infcx, param_env) },
529 PlaceTy::Downcast { adt_def, substs, variant_index } => {
532 substs: substs.trans_normalize(infcx, param_env),
540 // NOTE: Callable from trans only!
541 impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
542 /// Currently, higher-ranked type bounds inhibit normalization. Therefore,
543 /// each time we erase them in translation, we need to normalize
545 pub fn erase_late_bound_regions_and_normalize<T>(self, value: &ty::Binder<T>)
547 where T: TransNormalize<'tcx>
549 assert!(!value.needs_subst());
550 let value = self.erase_late_bound_regions(value);
551 self.fully_normalize_associated_types_in(&value)
554 /// Fully normalizes any associated types in `value`, using an
555 /// empty environment and `Reveal::All` mode (therefore, suitable
556 /// only for monomorphized code during trans, basically).
557 pub fn fully_normalize_associated_types_in<T>(self, value: &T) -> T
558 where T: TransNormalize<'tcx>
560 debug!("fully_normalize_associated_types_in(t={:?})", value);
562 let param_env = ty::ParamEnv::empty(Reveal::All);
563 let value = self.erase_regions(value);
565 if !value.has_projections() {
569 self.infer_ctxt().enter(|infcx| {
570 value.trans_normalize(&infcx, param_env)
574 /// Does a best-effort to normalize any associated types in
575 /// `value`; this includes revealing specializable types, so this
576 /// should be not be used during type-checking, but only during
577 /// optimization and code generation.
578 pub fn normalize_associated_type_in_env<T>(
579 self, value: &T, env: ty::ParamEnv<'tcx>
581 where T: TransNormalize<'tcx>
583 debug!("normalize_associated_type_in_env(t={:?})", value);
585 let value = self.erase_regions(value);
587 if !value.has_projections() {
591 self.infer_ctxt().enter(|infcx| {
592 value.trans_normalize(&infcx, env.reveal_all())
597 impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
598 fn normalize_projections_in<T>(&self, param_env: ty::ParamEnv<'tcx>, value: &T) -> T::Lifted
599 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
601 let mut selcx = traits::SelectionContext::new(self);
602 let cause = traits::ObligationCause::dummy();
603 let traits::Normalized { value: result, obligations } =
604 traits::normalize(&mut selcx, param_env, cause, value);
606 debug!("normalize_projections_in: result={:?} obligations={:?}",
607 result, obligations);
609 let mut fulfill_cx = traits::FulfillmentContext::new();
611 for obligation in obligations {
612 fulfill_cx.register_predicate_obligation(self, obligation);
615 self.drain_fulfillment_cx_or_panic(DUMMY_SP, &mut fulfill_cx, &result)
618 /// Finishes processes any obligations that remain in the
619 /// fulfillment context, and then returns the result with all type
620 /// variables removed and regions erased. Because this is intended
621 /// for use after type-check has completed, if any errors occur,
622 /// it will panic. It is used during normalization and other cases
623 /// where processing the obligations in `fulfill_cx` may cause
624 /// type inference variables that appear in `result` to be
625 /// unified, and hence we need to process those obligations to get
626 /// the complete picture of the type.
627 pub fn drain_fulfillment_cx_or_panic<T>(&self,
629 fulfill_cx: &mut traits::FulfillmentContext<'tcx>,
632 where T: TypeFoldable<'tcx> + ty::Lift<'gcx>
634 debug!("drain_fulfillment_cx_or_panic()");
636 // In principle, we only need to do this so long as `result`
637 // contains unbound type parameters. It could be a slight
638 // optimization to stop iterating early.
639 match fulfill_cx.select_all_or_error(self) {
642 span_bug!(span, "Encountered errors `{:?}` resolving bounds after type-checking",
647 let result = self.resolve_type_vars_if_possible(result);
648 let result = self.tcx.erase_regions(&result);
650 match self.tcx.lift_to_global(&result) {
651 Some(result) => result,
653 span_bug!(span, "Uninferred types/regions in `{:?}`", result);
658 pub fn is_in_snapshot(&self) -> bool {
659 self.in_snapshot.get()
662 pub fn freshen<T:TypeFoldable<'tcx>>(&self, t: T) -> T {
663 t.fold_with(&mut self.freshener())
666 pub fn type_var_diverges(&'a self, ty: Ty) -> bool {
668 ty::TyInfer(ty::TyVar(vid)) => self.type_variables.borrow().var_diverges(vid),
673 pub fn freshener<'b>(&'b self) -> TypeFreshener<'b, 'gcx, 'tcx> {
674 freshen::TypeFreshener::new(self)
677 pub fn type_is_unconstrained_numeric(&'a self, ty: Ty) -> UnconstrainedNumeric {
678 use ty::error::UnconstrainedNumeric::Neither;
679 use ty::error::UnconstrainedNumeric::{UnconstrainedInt, UnconstrainedFloat};
681 ty::TyInfer(ty::IntVar(vid)) => {
682 if self.int_unification_table.borrow_mut().probe_value(vid).is_some() {
688 ty::TyInfer(ty::FloatVar(vid)) => {
689 if self.float_unification_table.borrow_mut().probe_value(vid).is_some() {
699 pub fn unsolved_variables(&self) -> Vec<Ty<'tcx>> {
700 let mut variables = Vec::new();
703 let mut type_variables = self.type_variables.borrow_mut();
706 .unsolved_variables()
708 .map(|t| self.tcx.mk_var(t)));
712 let mut int_unification_table = self.int_unification_table.borrow_mut();
714 (0..int_unification_table.len())
715 .map(|i| ty::IntVid { index: i as u32 })
716 .filter(|&vid| int_unification_table.probe_value(vid).is_none())
717 .map(|v| self.tcx.mk_int_var(v)));
721 let mut float_unification_table = self.float_unification_table.borrow_mut();
723 (0..float_unification_table.len())
724 .map(|i| ty::FloatVid { index: i as u32 })
725 .filter(|&vid| float_unification_table.probe_value(vid).is_none())
726 .map(|v| self.tcx.mk_float_var(v)));
732 fn combine_fields(&'a self, trace: TypeTrace<'tcx>, param_env: ty::ParamEnv<'tcx>)
733 -> CombineFields<'a, 'gcx, 'tcx> {
739 obligations: PredicateObligations::new(),
743 // Clear the "currently in a snapshot" flag, invoke the closure,
744 // then restore the flag to its original value. This flag is a
745 // debugging measure designed to detect cases where we start a
746 // snapshot, create type variables, and register obligations
747 // which may involve those type variables in the fulfillment cx,
748 // potentially leaving "dangling type variables" behind.
749 // In such cases, an assertion will fail when attempting to
750 // register obligations, within a snapshot. Very useful, much
751 // better than grovelling through megabytes of RUST_LOG output.
753 // HOWEVER, in some cases the flag is unhelpful. In particular, we
754 // sometimes create a "mini-fulfilment-cx" in which we enroll
755 // obligations. As long as this fulfillment cx is fully drained
756 // before we return, this is not a problem, as there won't be any
757 // escaping obligations in the main cx. In those cases, you can
758 // use this function.
759 pub fn save_and_restore_in_snapshot_flag<F, R>(&self, func: F) -> R
760 where F: FnOnce(&Self) -> R
762 let flag = self.in_snapshot.get();
763 self.in_snapshot.set(false);
764 let result = func(self);
765 self.in_snapshot.set(flag);
769 fn start_snapshot(&self) -> CombinedSnapshot<'a, 'tcx> {
770 debug!("start_snapshot()");
772 let in_snapshot = self.in_snapshot.get();
773 self.in_snapshot.set(true);
776 projection_cache_snapshot: self.projection_cache.borrow_mut().snapshot(),
777 type_snapshot: self.type_variables.borrow_mut().snapshot(),
778 int_snapshot: self.int_unification_table.borrow_mut().snapshot(),
779 float_snapshot: self.float_unification_table.borrow_mut().snapshot(),
780 region_constraints_snapshot: self.borrow_region_constraints().start_snapshot(),
781 region_obligations_snapshot: self.region_obligations.borrow().len(),
782 was_in_snapshot: in_snapshot,
783 // Borrow tables "in progress" (i.e. during typeck)
784 // to ban writes from within a snapshot to them.
785 _in_progress_tables: self.in_progress_tables.map(|tables| {
791 fn rollback_to(&self, cause: &str, snapshot: CombinedSnapshot<'a, 'tcx>) {
792 debug!("rollback_to(cause={})", cause);
793 let CombinedSnapshot { projection_cache_snapshot,
797 region_constraints_snapshot,
798 region_obligations_snapshot,
800 _in_progress_tables } = snapshot;
802 self.in_snapshot.set(was_in_snapshot);
804 self.projection_cache
806 .rollback_to(projection_cache_snapshot);
809 .rollback_to(type_snapshot);
810 self.int_unification_table
812 .rollback_to(int_snapshot);
813 self.float_unification_table
815 .rollback_to(float_snapshot);
816 self.region_obligations
818 .truncate(region_obligations_snapshot);
819 self.borrow_region_constraints()
820 .rollback_to(region_constraints_snapshot);
823 fn commit_from(&self, snapshot: CombinedSnapshot<'a, 'tcx>) {
824 debug!("commit_from()");
825 let CombinedSnapshot { projection_cache_snapshot,
829 region_constraints_snapshot,
830 region_obligations_snapshot: _,
832 _in_progress_tables } = snapshot;
834 self.in_snapshot.set(was_in_snapshot);
836 self.projection_cache
838 .commit(projection_cache_snapshot);
841 .commit(type_snapshot);
842 self.int_unification_table
844 .commit(int_snapshot);
845 self.float_unification_table
847 .commit(float_snapshot);
848 self.borrow_region_constraints()
849 .commit(region_constraints_snapshot);
852 /// Execute `f` and commit the bindings
853 pub fn commit_unconditionally<R, F>(&self, f: F) -> R where
857 let snapshot = self.start_snapshot();
859 self.commit_from(snapshot);
863 /// Execute `f` and commit the bindings if closure `f` returns `Ok(_)`
864 pub fn commit_if_ok<T, E, F>(&self, f: F) -> Result<T, E> where
865 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> Result<T, E>
867 debug!("commit_if_ok()");
868 let snapshot = self.start_snapshot();
869 let r = f(&snapshot);
870 debug!("commit_if_ok() -- r.is_ok() = {}", r.is_ok());
872 Ok(_) => { self.commit_from(snapshot); }
873 Err(_) => { self.rollback_to("commit_if_ok -- error", snapshot); }
878 // Execute `f` in a snapshot, and commit the bindings it creates
879 pub fn in_snapshot<T, F>(&self, f: F) -> T where
880 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> T
882 debug!("in_snapshot()");
883 let snapshot = self.start_snapshot();
884 let r = f(&snapshot);
885 self.commit_from(snapshot);
889 /// Execute `f` then unroll any bindings it creates
890 pub fn probe<R, F>(&self, f: F) -> R where
891 F: FnOnce(&CombinedSnapshot<'a, 'tcx>) -> R,
894 let snapshot = self.start_snapshot();
895 let r = f(&snapshot);
896 self.rollback_to("probe", snapshot);
900 pub fn add_given(&self,
901 sub: ty::Region<'tcx>,
904 self.borrow_region_constraints().add_given(sub, sup);
907 pub fn can_sub<T>(&self,
908 param_env: ty::ParamEnv<'tcx>,
912 where T: at::ToTrace<'tcx>
914 let origin = &ObligationCause::dummy();
916 self.at(origin, param_env).sub(a, b).map(|InferOk { obligations: _, .. }| {
917 // Ignore obligations, since we are unrolling
918 // everything anyway.
923 pub fn can_eq<T>(&self,
924 param_env: ty::ParamEnv<'tcx>,
928 where T: at::ToTrace<'tcx>
930 let origin = &ObligationCause::dummy();
932 self.at(origin, param_env).eq(a, b).map(|InferOk { obligations: _, .. }| {
933 // Ignore obligations, since we are unrolling
934 // everything anyway.
939 pub fn sub_regions(&self,
940 origin: SubregionOrigin<'tcx>,
942 b: ty::Region<'tcx>) {
943 debug!("sub_regions({:?} <: {:?})", a, b);
944 self.borrow_region_constraints().make_subregion(origin, a, b);
947 pub fn subtype_predicate(&self,
948 cause: &ObligationCause<'tcx>,
949 param_env: ty::ParamEnv<'tcx>,
950 predicate: &ty::PolySubtypePredicate<'tcx>)
951 -> Option<InferResult<'tcx, ()>>
953 // Subtle: it's ok to skip the binder here and resolve because
954 // `shallow_resolve` just ignores anything that is not a type
955 // variable, and because type variable's can't (at present, at
956 // least) capture any of the things bound by this binder.
958 // Really, there is no *particular* reason to do this
959 // `shallow_resolve` here except as a
960 // micro-optimization. Naturally I could not
961 // resist. -nmatsakis
962 let two_unbound_type_vars = {
963 let a = self.shallow_resolve(predicate.skip_binder().a);
964 let b = self.shallow_resolve(predicate.skip_binder().b);
965 a.is_ty_var() && b.is_ty_var()
968 if two_unbound_type_vars {
969 // Two unbound type variables? Can't make progress.
973 Some(self.commit_if_ok(|snapshot| {
974 let (ty::SubtypePredicate { a_is_expected, a, b}, skol_map) =
975 self.skolemize_late_bound_regions(predicate, snapshot);
977 let cause_span = cause.span;
978 let ok = self.at(cause, param_env).sub_exp(a_is_expected, a, b)?;
979 self.leak_check(false, cause_span, &skol_map, snapshot)?;
980 self.pop_skolemized(skol_map, snapshot);
985 pub fn region_outlives_predicate(&self,
986 cause: &traits::ObligationCause<'tcx>,
987 predicate: &ty::PolyRegionOutlivesPredicate<'tcx>)
990 self.commit_if_ok(|snapshot| {
991 let (ty::OutlivesPredicate(r_a, r_b), skol_map) =
992 self.skolemize_late_bound_regions(predicate, snapshot);
994 SubregionOrigin::from_obligation_cause(cause,
995 || RelateRegionParamBound(cause.span));
996 self.sub_regions(origin, r_b, r_a); // `b : a` ==> `a <= b`
997 self.leak_check(false, cause.span, &skol_map, snapshot)?;
998 Ok(self.pop_skolemized(skol_map, snapshot))
1002 pub fn next_ty_var_id(&self,
1003 universe: ty::UniverseIndex,
1005 origin: TypeVariableOrigin)
1009 .new_var(universe, diverging, origin)
1012 pub fn next_ty_var(&self, universe: ty::UniverseIndex, origin: TypeVariableOrigin) -> Ty<'tcx> {
1013 self.tcx.mk_var(self.next_ty_var_id(universe, false, origin))
1016 pub fn next_diverging_ty_var(&self,
1017 universe: ty::UniverseIndex,
1018 origin: TypeVariableOrigin)
1020 self.tcx.mk_var(self.next_ty_var_id(universe, true, origin))
1023 pub fn next_int_var_id(&self) -> IntVid {
1024 self.int_unification_table
1029 pub fn next_float_var_id(&self) -> FloatVid {
1030 self.float_unification_table
1035 /// Create a fresh region variable with the next available index.
1039 /// - `origin`: information about why we created this variable, for use
1040 /// during diagnostics / error-reporting.
1041 pub fn next_region_var(&self, origin: RegionVariableOrigin)
1042 -> ty::Region<'tcx> {
1043 self.tcx.mk_region(ty::ReVar(self.borrow_region_constraints().new_region_var(origin)))
1046 /// Number of region variables created so far.
1047 pub fn num_region_vars(&self) -> usize {
1048 self.borrow_region_constraints().var_origins().len()
1051 /// Just a convenient wrapper of `next_region_var` for using during NLL.
1052 pub fn next_nll_region_var(&self, origin: NLLRegionVariableOrigin)
1053 -> ty::Region<'tcx> {
1054 self.next_region_var(RegionVariableOrigin::NLL(origin))
1057 /// Create a region inference variable for the given
1058 /// region parameter definition.
1059 pub fn region_var_for_def(&self,
1061 def: &ty::RegionParameterDef)
1062 -> ty::Region<'tcx> {
1063 self.next_region_var(EarlyBoundRegion(span, def.name))
1066 /// Create a type inference variable for the given
1067 /// type parameter definition. The substitutions are
1068 /// for actual parameters that may be referred to by
1069 /// the default of this type parameter, if it exists.
1070 /// E.g. `struct Foo<A, B, C = (A, B)>(...);` when
1071 /// used in a path such as `Foo::<T, U>::new()` will
1072 /// use an inference variable for `C` with `[T, U]`
1073 /// as the substitutions for the default, `(T, U)`.
1074 pub fn type_var_for_def(&self,
1075 universe: ty::UniverseIndex,
1077 def: &ty::TypeParameterDef)
1079 let ty_var_id = self.type_variables
1083 TypeVariableOrigin::TypeParameterDefinition(span, def.name));
1085 self.tcx.mk_var(ty_var_id)
1088 /// Given a set of generics defined on a type or impl, returns a substitution mapping each
1089 /// type/region parameter to a fresh inference variable.
1090 pub fn fresh_substs_for_item(&self,
1091 universe: ty::UniverseIndex,
1094 -> &'tcx Substs<'tcx> {
1095 Substs::for_item(self.tcx, def_id, |def, _| {
1096 self.region_var_for_def(span, def)
1098 self.type_var_for_def(universe, span, def)
1102 /// True if errors have been reported since this infcx was
1103 /// created. This is sometimes used as a heuristic to skip
1104 /// reporting errors that often occur as a result of earlier
1105 /// errors, but where it's hard to be 100% sure (e.g., unresolved
1106 /// inference variables, regionck errors).
1107 pub fn is_tainted_by_errors(&self) -> bool {
1108 debug!("is_tainted_by_errors(err_count={}, err_count_on_creation={}, \
1109 tainted_by_errors_flag={})",
1110 self.tcx.sess.err_count(),
1111 self.err_count_on_creation,
1112 self.tainted_by_errors_flag.get());
1114 if self.tcx.sess.err_count() > self.err_count_on_creation {
1115 return true; // errors reported since this infcx was made
1117 self.tainted_by_errors_flag.get()
1120 /// Set the "tainted by errors" flag to true. We call this when we
1121 /// observe an error from a prior pass.
1122 pub fn set_tainted_by_errors(&self) {
1123 debug!("set_tainted_by_errors()");
1124 self.tainted_by_errors_flag.set(true)
1127 /// Process the region constraints and report any errors that
1128 /// result. After this, no more unification operations should be
1129 /// done -- or the compiler will panic -- but it is legal to use
1130 /// `resolve_type_vars_if_possible` as well as `fully_resolve`.
1131 pub fn resolve_regions_and_report_errors(
1133 region_context: DefId,
1134 region_map: ®ion::ScopeTree,
1135 outlives_env: &OutlivesEnvironment<'tcx>,
1137 self.resolve_regions_and_report_errors_inner(
1145 /// Like `resolve_regions_and_report_errors`, but skips error
1146 /// reporting if NLL is enabled. This is used for fn bodies where
1147 /// the same error may later be reported by the NLL-based
1149 pub fn resolve_regions_and_report_errors_unless_nll(
1151 region_context: DefId,
1152 region_map: ®ion::ScopeTree,
1153 outlives_env: &OutlivesEnvironment<'tcx>,
1155 self.resolve_regions_and_report_errors_inner(
1163 fn resolve_regions_and_report_errors_inner(
1165 region_context: DefId,
1166 region_map: ®ion::ScopeTree,
1167 outlives_env: &OutlivesEnvironment<'tcx>,
1168 will_later_be_reported_by_nll: bool,
1170 assert!(self.is_tainted_by_errors() || self.region_obligations.borrow().is_empty(),
1171 "region_obligations not empty: {:#?}",
1172 self.region_obligations.borrow());
1174 let region_rels = &RegionRelations::new(self.tcx,
1177 outlives_env.free_region_map());
1178 let (var_origins, data) = self.region_constraints.borrow_mut()
1180 .expect("regions already resolved")
1181 .into_origins_and_data();
1182 let (lexical_region_resolutions, errors) =
1183 lexical_region_resolve::resolve(region_rels, var_origins, data);
1185 let old_value = self.lexical_region_resolutions.replace(Some(lexical_region_resolutions));
1186 assert!(old_value.is_none());
1188 if !self.is_tainted_by_errors() {
1189 // As a heuristic, just skip reporting region errors
1190 // altogether if other errors have been reported while
1191 // this infcx was in use. This is totally hokey but
1192 // otherwise we have a hard time separating legit region
1193 // errors from silly ones.
1194 self.report_region_errors(region_map, &errors, will_later_be_reported_by_nll);
1198 /// Obtains (and clears) the current set of region
1199 /// constraints. The inference context is still usable: further
1200 /// unifications will simply add new constraints.
1202 /// This method is not meant to be used with normal lexical region
1203 /// resolution. Rather, it is used in the NLL mode as a kind of
1204 /// interim hack: basically we run normal type-check and generate
1205 /// region constraints as normal, but then we take them and
1206 /// translate them into the form that the NLL solver
1207 /// understands. See the NLL module for mode details.
1208 pub fn take_and_reset_region_constraints(&self) -> RegionConstraintData<'tcx> {
1209 assert!(self.region_obligations.borrow().is_empty(),
1210 "region_obligations not empty: {:#?}",
1211 self.region_obligations.borrow());
1213 self.borrow_region_constraints().take_and_reset_data()
1216 /// Takes ownership of the list of variable regions. This implies
1217 /// that all the region constriants have already been taken, and
1218 /// hence that `resolve_regions_and_report_errors` can never be
1219 /// called. This is used only during NLL processing to "hand off" ownership
1220 /// of the set of region vairables into the NLL region context.
1221 pub fn take_region_var_origins(&self) -> VarOrigins {
1222 let (var_origins, data) = self.region_constraints.borrow_mut()
1224 .expect("regions already resolved")
1225 .into_origins_and_data();
1226 assert!(data.is_empty());
1230 pub fn ty_to_string(&self, t: Ty<'tcx>) -> String {
1231 self.resolve_type_vars_if_possible(&t).to_string()
1234 pub fn tys_to_string(&self, ts: &[Ty<'tcx>]) -> String {
1235 let tstrs: Vec<String> = ts.iter().map(|t| self.ty_to_string(*t)).collect();
1236 format!("({})", tstrs.join(", "))
1239 pub fn trait_ref_to_string(&self, t: &ty::TraitRef<'tcx>) -> String {
1240 self.resolve_type_vars_if_possible(t).to_string()
1243 pub fn shallow_resolve(&self, typ: Ty<'tcx>) -> Ty<'tcx> {
1245 ty::TyInfer(ty::TyVar(v)) => {
1246 // Not entirely obvious: if `typ` is a type variable,
1247 // it can be resolved to an int/float variable, which
1248 // can then be recursively resolved, hence the
1249 // recursion. Note though that we prevent type
1250 // variables from unifyxing to other type variables
1251 // directly (though they may be embedded
1252 // structurally), and we prevent cycles in any case,
1253 // so this recursion should always be of very limited
1255 self.type_variables.borrow_mut()
1258 .map(|t| self.shallow_resolve(t))
1262 ty::TyInfer(ty::IntVar(v)) => {
1263 self.int_unification_table
1266 .map(|v| v.to_type(self.tcx))
1270 ty::TyInfer(ty::FloatVar(v)) => {
1271 self.float_unification_table
1274 .map(|v| v.to_type(self.tcx))
1284 pub fn resolve_type_vars_if_possible<T>(&self, value: &T) -> T
1285 where T: TypeFoldable<'tcx>
1288 * Where possible, replaces type/int/float variables in
1289 * `value` with their final value. Note that region variables
1290 * are unaffected. If a type variable has not been unified, it
1291 * is left as is. This is an idempotent operation that does
1292 * not affect inference state in any way and so you can do it
1296 if !value.needs_infer() {
1297 return value.clone(); // avoid duplicated subst-folding
1299 let mut r = resolve::OpportunisticTypeResolver::new(self);
1300 value.fold_with(&mut r)
1303 /// Returns true if `T` contains unresolved type variables. In the
1304 /// process of visiting `T`, this will resolve (where possible)
1305 /// type variables in `T`, but it never constructs the final,
1306 /// resolved type, so it's more efficient than
1307 /// `resolve_type_vars_if_possible()`.
1308 pub fn any_unresolved_type_vars<T>(&self, value: &T) -> bool
1309 where T: TypeFoldable<'tcx>
1311 let mut r = resolve::UnresolvedTypeFinder::new(self);
1312 value.visit_with(&mut r)
1315 pub fn resolve_type_and_region_vars_if_possible<T>(&self, value: &T) -> T
1316 where T: TypeFoldable<'tcx>
1318 let mut r = resolve::OpportunisticTypeAndRegionResolver::new(self);
1319 value.fold_with(&mut r)
1322 pub fn fully_resolve<T:TypeFoldable<'tcx>>(&self, value: &T) -> FixupResult<T> {
1324 * Attempts to resolve all type/region variables in
1325 * `value`. Region inference must have been run already (e.g.,
1326 * by calling `resolve_regions_and_report_errors`). If some
1327 * variable was never unified, an `Err` results.
1329 * This method is idempotent, but it not typically not invoked
1330 * except during the writeback phase.
1333 resolve::fully_resolve(self, value)
1336 // [Note-Type-error-reporting]
1337 // An invariant is that anytime the expected or actual type is TyError (the special
1338 // error type, meaning that an error occurred when typechecking this expression),
1339 // this is a derived error. The error cascaded from another error (that was already
1340 // reported), so it's not useful to display it to the user.
1341 // The following methods implement this logic.
1342 // They check if either the actual or expected type is TyError, and don't print the error
1343 // in this case. The typechecker should only ever report type errors involving mismatched
1344 // types using one of these methods, and should not call span_err directly for such
1347 pub fn type_error_struct_with_diag<M>(&self,
1350 actual_ty: Ty<'tcx>)
1351 -> DiagnosticBuilder<'tcx>
1352 where M: FnOnce(String) -> DiagnosticBuilder<'tcx>,
1354 let actual_ty = self.resolve_type_vars_if_possible(&actual_ty);
1355 debug!("type_error_struct_with_diag({:?}, {:?})", sp, actual_ty);
1357 // Don't report an error if actual type is TyError.
1358 if actual_ty.references_error() {
1359 return self.tcx.sess.diagnostic().struct_dummy();
1362 mk_diag(self.ty_to_string(actual_ty))
1365 pub fn report_mismatched_types(&self,
1366 cause: &ObligationCause<'tcx>,
1369 err: TypeError<'tcx>)
1370 -> DiagnosticBuilder<'tcx> {
1371 let trace = TypeTrace::types(cause, true, expected, actual);
1372 self.report_and_explain_type_error(trace, &err)
1375 pub fn replace_late_bound_regions_with_fresh_var<T>(
1378 lbrct: LateBoundRegionConversionTime,
1379 value: &ty::Binder<T>)
1380 -> (T, BTreeMap<ty::BoundRegion, ty::Region<'tcx>>)
1381 where T : TypeFoldable<'tcx>
1383 self.tcx.replace_late_bound_regions(
1385 |br| self.next_region_var(LateBoundRegion(span, br, lbrct)))
1388 /// Given a higher-ranked projection predicate like:
1390 /// for<'a> <T as Fn<&'a u32>>::Output = &'a u32
1392 /// and a target trait-ref like:
1394 /// <T as Fn<&'x u32>>
1396 /// find a substitution `S` for the higher-ranked regions (here,
1397 /// `['a => 'x]`) such that the predicate matches the trait-ref,
1398 /// and then return the value (here, `&'a u32`) but with the
1399 /// substitution applied (hence, `&'x u32`).
1401 /// See `higher_ranked_match` in `higher_ranked/mod.rs` for more
1403 pub fn match_poly_projection_predicate(&self,
1404 cause: ObligationCause<'tcx>,
1405 param_env: ty::ParamEnv<'tcx>,
1406 match_a: ty::PolyProjectionPredicate<'tcx>,
1407 match_b: ty::TraitRef<'tcx>)
1408 -> InferResult<'tcx, HrMatchResult<Ty<'tcx>>>
1410 let match_pair = match_a.map_bound(|p| (p.projection_ty.trait_ref(self.tcx), p.ty));
1411 let trace = TypeTrace {
1413 values: TraitRefs(ExpectedFound::new(true, match_pair.skip_binder().0, match_b))
1416 let mut combine = self.combine_fields(trace, param_env);
1417 let result = combine.higher_ranked_match(&match_pair, &match_b, true)?;
1418 Ok(InferOk { value: result, obligations: combine.obligations })
1421 /// See `verify_generic_bound` method in `region_constraints`
1422 pub fn verify_generic_bound(&self,
1423 origin: SubregionOrigin<'tcx>,
1424 kind: GenericKind<'tcx>,
1425 a: ty::Region<'tcx>,
1426 bound: VerifyBound<'tcx>) {
1427 debug!("verify_generic_bound({:?}, {:?} <: {:?})",
1432 self.borrow_region_constraints().verify_generic_bound(origin, kind, a, bound);
1435 pub fn type_moves_by_default(&self,
1436 param_env: ty::ParamEnv<'tcx>,
1440 let ty = self.resolve_type_vars_if_possible(&ty);
1441 // Even if the type may have no inference variables, during
1442 // type-checking closure types are in local tables only.
1443 if !self.in_progress_tables.is_some() || !ty.has_closure_types() {
1444 if let Some((param_env, ty)) = self.tcx.lift_to_global(&(param_env, ty)) {
1445 return ty.moves_by_default(self.tcx.global_tcx(), param_env, span);
1449 let copy_def_id = self.tcx.require_lang_item(lang_items::CopyTraitLangItem);
1451 // this can get called from typeck (by euv), and moves_by_default
1452 // rightly refuses to work with inference variables, but
1453 // moves_by_default has a cache, which we want to use in other
1455 !traits::type_known_to_meet_bound(self, param_env, ty, copy_def_id, span)
1458 /// Obtains the latest type of the given closure; this may be a
1459 /// closure in the current function, in which case its
1460 /// `ClosureKind` may not yet be known.
1461 pub fn closure_kind(&self,
1462 closure_def_id: DefId,
1463 closure_substs: ty::ClosureSubsts<'tcx>)
1464 -> Option<ty::ClosureKind>
1466 let closure_kind_ty = closure_substs.closure_kind_ty(closure_def_id, self.tcx);
1467 let closure_kind_ty = self.shallow_resolve(&closure_kind_ty);
1468 closure_kind_ty.to_opt_closure_kind()
1471 /// Obtain the signature of a closure. For closures, unlike
1472 /// `tcx.fn_sig(def_id)`, this method will work during the
1473 /// type-checking of the enclosing function and return the closure
1474 /// signature in its partially inferred state.
1478 substs: ty::ClosureSubsts<'tcx>
1479 ) -> ty::PolyFnSig<'tcx> {
1480 let closure_sig_ty = substs.closure_sig_ty(def_id, self.tcx);
1481 let closure_sig_ty = self.shallow_resolve(&closure_sig_ty);
1482 closure_sig_ty.fn_sig(self.tcx)
1485 /// Normalizes associated types in `value`, potentially returning
1486 /// new obligations that must further be processed.
1487 pub fn partially_normalize_associated_types_in<T>(&self,
1489 body_id: ast::NodeId,
1490 param_env: ty::ParamEnv<'tcx>,
1493 where T : TypeFoldable<'tcx>
1495 debug!("partially_normalize_associated_types_in(value={:?})", value);
1496 let mut selcx = traits::SelectionContext::new(self);
1497 let cause = ObligationCause::misc(span, body_id);
1498 let traits::Normalized { value, obligations } =
1499 traits::normalize(&mut selcx, param_env, cause, value);
1500 debug!("partially_normalize_associated_types_in: result={:?} predicates={:?}",
1503 InferOk { value, obligations }
1506 pub fn borrow_region_constraints(&self) -> RefMut<'_, RegionConstraintCollector<'tcx>> {
1508 self.region_constraints.borrow_mut(),
1509 |c| c.as_mut().expect("region constraints already solved"))
1512 /// Clears the selection, evaluation, and projection cachesThis is useful when
1513 /// repeatedly attemping to select an Obligation while changing only
1514 /// its ParamEnv, since FulfillmentContext doesn't use 'probe'
1515 pub fn clear_caches(&self) {
1516 self.selection_cache.clear();
1517 self.evaluation_cache.clear();
1518 self.projection_cache.borrow_mut().clear();
1522 impl<'a, 'gcx, 'tcx> TypeTrace<'tcx> {
1523 pub fn span(&self) -> Span {
1527 pub fn types(cause: &ObligationCause<'tcx>,
1528 a_is_expected: bool,
1531 -> TypeTrace<'tcx> {
1533 cause: cause.clone(),
1534 values: Types(ExpectedFound::new(a_is_expected, a, b))
1538 pub fn dummy(tcx: TyCtxt<'a, 'gcx, 'tcx>) -> TypeTrace<'tcx> {
1540 cause: ObligationCause::dummy(),
1541 values: Types(ExpectedFound {
1542 expected: tcx.types.err,
1543 found: tcx.types.err,
1549 impl<'tcx> fmt::Debug for TypeTrace<'tcx> {
1550 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1551 write!(f, "TypeTrace({:?})", self.cause)
1555 impl<'tcx> SubregionOrigin<'tcx> {
1556 pub fn span(&self) -> Span {
1558 Subtype(ref a) => a.span(),
1559 InfStackClosure(a) => a,
1560 InvokeClosure(a) => a,
1561 DerefPointer(a) => a,
1562 FreeVariable(a, _) => a,
1564 RelateObjectBound(a) => a,
1565 RelateParamBound(a, _) => a,
1566 RelateRegionParamBound(a) => a,
1567 RelateDefaultParamBound(a, _) => a,
1569 ReborrowUpvar(a, _) => a,
1570 DataBorrowed(_, a) => a,
1571 ReferenceOutlivesReferent(_, a) => a,
1572 ParameterInScope(_, a) => a,
1573 ExprTypeIsNotInScope(_, a) => a,
1574 BindingTypeIsNotValidAtDecl(a) => a,
1581 SafeDestructor(a) => a,
1582 CompareImplMethodObligation { span, .. } => span,
1586 pub fn from_obligation_cause<F>(cause: &traits::ObligationCause<'tcx>,
1589 where F: FnOnce() -> Self
1592 traits::ObligationCauseCode::ReferenceOutlivesReferent(ref_type) =>
1593 SubregionOrigin::ReferenceOutlivesReferent(ref_type, cause.span),
1595 traits::ObligationCauseCode::CompareImplMethodObligation { item_name,
1597 trait_item_def_id, } =>
1598 SubregionOrigin::CompareImplMethodObligation {
1610 impl RegionVariableOrigin {
1611 pub fn span(&self) -> Span {
1613 MiscVariable(a) => a,
1614 PatternRegion(a) => a,
1615 AddrOfRegion(a) => a,
1618 EarlyBoundRegion(a, ..) => a,
1619 LateBoundRegion(a, ..) => a,
1620 BoundRegionInCoherence(_) => syntax_pos::DUMMY_SP,
1621 UpvarRegion(_, a) => a,
1622 NLL(..) => bug!("NLL variable used with `span`"),
1627 EnumTypeFoldableImpl! {
1628 impl<'tcx> TypeFoldable<'tcx> for ValuePairs<'tcx> {
1629 (ValuePairs::Types)(a),
1630 (ValuePairs::Regions)(a),
1631 (ValuePairs::TraitRefs)(a),
1632 (ValuePairs::PolyTraitRefs)(a),
1636 impl<'tcx> fmt::Debug for RegionObligation<'tcx> {
1637 fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
1638 write!(f, "RegionObligation(sub_region={:?}, sup_type={:?})",