1 // Copyright 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 //! Trait Resolution. See [rustc guide] for more info on how this works.
13 //! [rustc guide]: https://rust-lang-nursery.github.io/rustc-guide/traits/resolution.html
15 pub use self::SelectionError::*;
16 pub use self::FulfillmentErrorCode::*;
17 pub use self::Vtable::*;
18 pub use self::ObligationCauseCode::*;
22 use hir::def_id::DefId;
23 use infer::outlives::env::OutlivesEnvironment;
25 use middle::const_val::ConstEvalErr;
26 use ty::subst::Substs;
27 use ty::{self, AdtKind, Slice, Ty, TyCtxt, GenericParamDefKind, ToPredicate};
28 use ty::error::{ExpectedFound, TypeError};
29 use ty::fold::{TypeFolder, TypeFoldable, TypeVisitor};
30 use infer::canonical::{Canonical, Canonicalize};
31 use infer::{InferCtxt};
33 use rustc_data_structures::sync::Lrc;
37 use syntax_pos::{Span, DUMMY_SP};
39 pub use self::coherence::{orphan_check, overlapping_impls, OrphanCheckErr, OverlapResult};
40 pub use self::fulfill::{FulfillmentContext, PendingPredicateObligation};
41 pub use self::project::MismatchedProjectionTypes;
42 pub use self::project::{normalize, normalize_projection_type, poly_project_and_unify_type};
43 pub use self::project::{ProjectionCache, ProjectionCacheSnapshot, Reveal, Normalized};
44 pub use self::object_safety::ObjectSafetyViolation;
45 pub use self::object_safety::MethodViolationCode;
46 pub use self::on_unimplemented::{OnUnimplementedDirective, OnUnimplementedNote};
47 pub use self::select::{EvaluationCache, SelectionContext, SelectionCache};
48 pub use self::select::{EvaluationResult, IntercrateAmbiguityCause, OverflowError};
49 pub use self::specialize::{OverlapError, specialization_graph, translate_substs};
50 pub use self::specialize::{SpecializesCache, find_associated_item};
51 pub use self::engine::TraitEngine;
52 pub use self::util::elaborate_predicates;
53 pub use self::util::supertraits;
54 pub use self::util::Supertraits;
55 pub use self::util::supertrait_def_ids;
56 pub use self::util::SupertraitDefIds;
57 pub use self::util::transitive_bounds;
62 pub mod error_reporting;
76 // Whether to enable bug compatibility with issue #43355
77 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
78 pub enum IntercrateMode {
83 // The mode that trait queries run in
84 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
85 pub enum TraitQueryMode {
86 // Standard/un-canonicalized queries get accurate
87 // spans etc. passed in and hence can do reasonable
88 // error reporting on their own.
90 // Canonicalized queries get dummy spans and hence
91 // must generally propagate errors to
92 // pre-canonicalization callsites.
96 /// An `Obligation` represents some trait reference (e.g. `int:Eq`) for
97 /// which the vtable must be found. The process of finding a vtable is
98 /// called "resolving" the `Obligation`. This process consists of
99 /// either identifying an `impl` (e.g., `impl Eq for int`) that
100 /// provides the required vtable, or else finding a bound that is in
101 /// scope. The eventual result is usually a `Selection` (defined below).
102 #[derive(Clone, PartialEq, Eq, Hash)]
103 pub struct Obligation<'tcx, T> {
104 /// Why do we have to prove this thing?
105 pub cause: ObligationCause<'tcx>,
107 /// In which environment should we prove this thing?
108 pub param_env: ty::ParamEnv<'tcx>,
110 /// What are we trying to prove?
113 /// If we started proving this as a result of trying to prove
114 /// something else, track the total depth to ensure termination.
115 /// If this goes over a certain threshold, we abort compilation --
116 /// in such cases, we can not say whether or not the predicate
117 /// holds for certain. Stupid halting problem. Such a drag.
118 pub recursion_depth: usize,
121 pub type PredicateObligation<'tcx> = Obligation<'tcx, ty::Predicate<'tcx>>;
122 pub type TraitObligation<'tcx> = Obligation<'tcx, ty::PolyTraitPredicate<'tcx>>;
124 /// Why did we incur this obligation? Used for error reporting.
125 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
126 pub struct ObligationCause<'tcx> {
129 // The id of the fn body that triggered this obligation. This is
130 // used for region obligations to determine the precise
131 // environment in which the region obligation should be evaluated
132 // (in particular, closures can add new assumptions). See the
133 // field `region_obligations` of the `FulfillmentContext` for more
135 pub body_id: ast::NodeId,
137 pub code: ObligationCauseCode<'tcx>
140 impl<'tcx> ObligationCause<'tcx> {
141 pub fn span<'a, 'gcx>(&self, tcx: &TyCtxt<'a, 'gcx, 'tcx>) -> Span {
143 ObligationCauseCode::CompareImplMethodObligation { .. } |
144 ObligationCauseCode::MainFunctionType |
145 ObligationCauseCode::StartFunctionType => {
146 tcx.sess.codemap().def_span(self.span)
153 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
154 pub enum ObligationCauseCode<'tcx> {
155 /// Not well classified or should be obvious from span.
158 /// A slice or array is WF only if `T: Sized`
161 /// A tuple is WF only if its middle elements are Sized
164 /// This is the trait reference from the given projection
165 ProjectionWf(ty::ProjectionTy<'tcx>),
167 /// In an impl of trait X for type Y, type Y must
168 /// also implement all supertraits of X.
169 ItemObligation(DefId),
171 /// A type like `&'a T` is WF only if `T: 'a`.
172 ReferenceOutlivesReferent(Ty<'tcx>),
174 /// A type like `Box<Foo<'a> + 'b>` is WF only if `'b: 'a`.
175 ObjectTypeBound(Ty<'tcx>, ty::Region<'tcx>),
177 /// Obligation incurred due to an object cast.
178 ObjectCastObligation(/* Object type */ Ty<'tcx>),
180 // Various cases where expressions must be sized/copy/etc:
181 /// L = X implies that L is Sized
183 /// (x1, .., xn) must be Sized
184 TupleInitializerSized,
185 /// S { ... } must be Sized
186 StructInitializerSized,
187 /// Type of each variable must be Sized
188 VariableType(ast::NodeId),
189 /// Return type must be Sized
191 /// Yield type must be Sized
193 /// [T,..n] --> T must be Copy
196 /// Types of fields (other than the last) in a struct must be sized.
199 /// Constant expressions must be sized.
202 /// static items must have `Sync` type
205 BuiltinDerivedObligation(DerivedObligationCause<'tcx>),
207 ImplDerivedObligation(DerivedObligationCause<'tcx>),
209 /// error derived when matching traits/impls; see ObligationCause for more details
210 CompareImplMethodObligation {
211 item_name: ast::Name,
212 impl_item_def_id: DefId,
213 trait_item_def_id: DefId,
216 /// Checking that this expression can be assigned where it needs to be
217 // FIXME(eddyb) #11161 is the original Expr required?
220 /// Computing common supertype in the arms of a match expression
221 MatchExpressionArm { arm_span: Span,
222 source: hir::MatchSource },
224 /// Computing common supertype in an if expression
227 /// Computing common supertype of an if expression with no else counter-part
228 IfExpressionWithNoElse,
230 /// `main` has wrong type
233 /// `start` has wrong type
236 /// intrinsic has wrong type
242 /// `return` with no expression
245 /// `return` with an expression
246 ReturnType(ast::NodeId),
248 /// Block implicit return
249 BlockTailExpression(ast::NodeId),
251 /// #[feature(trivial_bounds)] is not enabled
255 #[derive(Clone, Debug, PartialEq, Eq, Hash)]
256 pub struct DerivedObligationCause<'tcx> {
257 /// The trait reference of the parent obligation that led to the
258 /// current obligation. Note that only trait obligations lead to
259 /// derived obligations, so we just store the trait reference here
261 parent_trait_ref: ty::PolyTraitRef<'tcx>,
263 /// The parent trait had this cause
264 parent_code: Rc<ObligationCauseCode<'tcx>>
267 pub type Obligations<'tcx, O> = Vec<Obligation<'tcx, O>>;
268 pub type PredicateObligations<'tcx> = Vec<PredicateObligation<'tcx>>;
269 pub type TraitObligations<'tcx> = Vec<TraitObligation<'tcx>>;
271 /// The following types:
278 /// are used for representing the trait system in the form of
279 /// logic programming clauses. They are part of the interface
280 /// for the chalk SLG solver.
281 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
282 pub enum WhereClause<'tcx> {
283 Implemented(ty::TraitPredicate<'tcx>),
284 ProjectionEq(ty::ProjectionPredicate<'tcx>),
285 RegionOutlives(ty::RegionOutlivesPredicate<'tcx>),
286 TypeOutlives(ty::TypeOutlivesPredicate<'tcx>),
289 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
290 pub enum WellFormed<'tcx> {
291 Trait(ty::TraitPredicate<'tcx>),
295 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
296 pub enum FromEnv<'tcx> {
297 Trait(ty::TraitPredicate<'tcx>),
301 #[derive(Clone, Copy, PartialEq, Eq, Hash, Debug)]
302 pub enum DomainGoal<'tcx> {
303 Holds(WhereClause<'tcx>),
304 WellFormed(WellFormed<'tcx>),
305 FromEnv(FromEnv<'tcx>),
306 Normalize(ty::ProjectionPredicate<'tcx>),
309 pub type PolyDomainGoal<'tcx> = ty::Binder<DomainGoal<'tcx>>;
311 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
312 pub enum QuantifierKind {
317 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
318 pub enum Goal<'tcx> {
319 Implies(Clauses<'tcx>, &'tcx Goal<'tcx>),
320 And(&'tcx Goal<'tcx>, &'tcx Goal<'tcx>),
321 Not(&'tcx Goal<'tcx>),
322 DomainGoal(DomainGoal<'tcx>),
323 Quantified(QuantifierKind, ty::Binder<&'tcx Goal<'tcx>>),
327 pub type Goals<'tcx> = &'tcx Slice<Goal<'tcx>>;
329 impl<'tcx> DomainGoal<'tcx> {
330 pub fn into_goal(self) -> Goal<'tcx> {
331 Goal::DomainGoal(self)
335 impl<'tcx> Goal<'tcx> {
336 pub fn from_poly_domain_goal<'a>(
337 domain_goal: PolyDomainGoal<'tcx>,
338 tcx: TyCtxt<'a, 'tcx, 'tcx>,
340 match domain_goal.no_late_bound_regions() {
341 Some(p) => p.into_goal(),
342 None => Goal::Quantified(
343 QuantifierKind::Universal,
344 domain_goal.map_bound(|p| tcx.mk_goal(p.into_goal()))
350 /// This matches the definition from Page 7 of "A Proof Procedure for the Logic of Hereditary
351 /// Harrop Formulas".
352 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
353 pub enum Clause<'tcx> {
354 Implies(ProgramClause<'tcx>),
355 ForAll(ty::Binder<ProgramClause<'tcx>>),
358 /// Multiple clauses.
359 pub type Clauses<'tcx> = &'tcx Slice<Clause<'tcx>>;
361 /// A "program clause" has the form `D :- G1, ..., Gn`. It is saying
362 /// that the domain goal `D` is true if `G1...Gn` are provable. This
363 /// is equivalent to the implication `G1..Gn => D`; we usually write
364 /// it with the reverse implication operator `:-` to emphasize the way
365 /// that programs are actually solved (via backchaining, which starts
366 /// with the goal to solve and proceeds from there).
367 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
368 pub struct ProgramClause<'tcx> {
369 /// This goal will be considered true...
370 pub goal: DomainGoal<'tcx>,
372 /// ...if we can prove these hypotheses (there may be no hypotheses at all):
373 pub hypotheses: Goals<'tcx>,
376 pub type Selection<'tcx> = Vtable<'tcx, PredicateObligation<'tcx>>;
378 #[derive(Clone,Debug)]
379 pub enum SelectionError<'tcx> {
381 OutputTypeParameterMismatch(ty::PolyTraitRef<'tcx>,
382 ty::PolyTraitRef<'tcx>,
383 ty::error::TypeError<'tcx>),
384 TraitNotObjectSafe(DefId),
385 ConstEvalFailure(ConstEvalErr<'tcx>),
389 pub struct FulfillmentError<'tcx> {
390 pub obligation: PredicateObligation<'tcx>,
391 pub code: FulfillmentErrorCode<'tcx>
395 pub enum FulfillmentErrorCode<'tcx> {
396 CodeSelectionError(SelectionError<'tcx>),
397 CodeProjectionError(MismatchedProjectionTypes<'tcx>),
398 CodeSubtypeError(ExpectedFound<Ty<'tcx>>,
399 TypeError<'tcx>), // always comes from a SubtypePredicate
403 /// When performing resolution, it is typically the case that there
404 /// can be one of three outcomes:
406 /// - `Ok(Some(r))`: success occurred with result `r`
407 /// - `Ok(None)`: could not definitely determine anything, usually due
408 /// to inconclusive type inference.
409 /// - `Err(e)`: error `e` occurred
410 pub type SelectionResult<'tcx, T> = Result<Option<T>, SelectionError<'tcx>>;
412 /// Given the successful resolution of an obligation, the `Vtable`
413 /// indicates where the vtable comes from. Note that while we call this
414 /// a "vtable", it does not necessarily indicate dynamic dispatch at
415 /// runtime. `Vtable` instances just tell the compiler where to find
416 /// methods, but in generic code those methods are typically statically
417 /// dispatched -- only when an object is constructed is a `Vtable`
418 /// instance reified into an actual vtable.
420 /// For example, the vtable may be tied to a specific impl (case A),
421 /// or it may be relative to some bound that is in scope (case B).
425 /// impl<T:Clone> Clone<T> for Option<T> { ... } // Impl_1
426 /// impl<T:Clone> Clone<T> for Box<T> { ... } // Impl_2
427 /// impl Clone for int { ... } // Impl_3
429 /// fn foo<T:Clone>(concrete: Option<Box<int>>,
431 /// mixed: Option<T>) {
433 /// // Case A: Vtable points at a specific impl. Only possible when
434 /// // type is concretely known. If the impl itself has bounded
435 /// // type parameters, Vtable will carry resolutions for those as well:
436 /// concrete.clone(); // Vtable(Impl_1, [Vtable(Impl_2, [Vtable(Impl_3)])])
438 /// // Case B: Vtable must be provided by caller. This applies when
439 /// // type is a type parameter.
440 /// param.clone(); // VtableParam
442 /// // Case C: A mix of cases A and B.
443 /// mixed.clone(); // Vtable(Impl_1, [VtableParam])
447 /// ### The type parameter `N`
449 /// See explanation on `VtableImplData`.
450 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
451 pub enum Vtable<'tcx, N> {
452 /// Vtable identifying a particular impl.
453 VtableImpl(VtableImplData<'tcx, N>),
455 /// Vtable for auto trait implementations
456 /// This carries the information and nested obligations with regards
457 /// to an auto implementation for a trait `Trait`. The nested obligations
458 /// ensure the trait implementation holds for all the constituent types.
459 VtableAutoImpl(VtableAutoImplData<N>),
461 /// Successful resolution to an obligation provided by the caller
462 /// for some type parameter. The `Vec<N>` represents the
463 /// obligations incurred from normalizing the where-clause (if
467 /// Virtual calls through an object
468 VtableObject(VtableObjectData<'tcx, N>),
470 /// Successful resolution for a builtin trait.
471 VtableBuiltin(VtableBuiltinData<N>),
473 /// Vtable automatically generated for a closure. The def ID is the ID
474 /// of the closure expression. This is a `VtableImpl` in spirit, but the
475 /// impl is generated by the compiler and does not appear in the source.
476 VtableClosure(VtableClosureData<'tcx, N>),
478 /// Same as above, but for a fn pointer type with the given signature.
479 VtableFnPointer(VtableFnPointerData<'tcx, N>),
481 /// Vtable automatically generated for a generator
482 VtableGenerator(VtableGeneratorData<'tcx, N>),
485 /// Identifies a particular impl in the source, along with a set of
486 /// substitutions from the impl's type/lifetime parameters. The
487 /// `nested` vector corresponds to the nested obligations attached to
488 /// the impl's type parameters.
490 /// The type parameter `N` indicates the type used for "nested
491 /// obligations" that are required by the impl. During type check, this
492 /// is `Obligation`, as one might expect. During codegen, however, this
493 /// is `()`, because codegen only requires a shallow resolution of an
494 /// impl, and nested obligations are satisfied later.
495 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
496 pub struct VtableImplData<'tcx, N> {
497 pub impl_def_id: DefId,
498 pub substs: &'tcx Substs<'tcx>,
502 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
503 pub struct VtableGeneratorData<'tcx, N> {
504 pub generator_def_id: DefId,
505 pub substs: ty::GeneratorSubsts<'tcx>,
506 /// Nested obligations. This can be non-empty if the generator
507 /// signature contains associated types.
511 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
512 pub struct VtableClosureData<'tcx, N> {
513 pub closure_def_id: DefId,
514 pub substs: ty::ClosureSubsts<'tcx>,
515 /// Nested obligations. This can be non-empty if the closure
516 /// signature contains associated types.
520 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
521 pub struct VtableAutoImplData<N> {
522 pub trait_def_id: DefId,
526 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
527 pub struct VtableBuiltinData<N> {
531 /// A vtable for some object-safe trait `Foo` automatically derived
532 /// for the object type `Foo`.
533 #[derive(PartialEq, Eq, Clone, RustcEncodable, RustcDecodable)]
534 pub struct VtableObjectData<'tcx, N> {
535 /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
536 pub upcast_trait_ref: ty::PolyTraitRef<'tcx>,
538 /// The vtable is formed by concatenating together the method lists of
539 /// the base object trait and all supertraits; this is the start of
540 /// `upcast_trait_ref`'s methods in that vtable.
541 pub vtable_base: usize,
546 #[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable)]
547 pub struct VtableFnPointerData<'tcx, N> {
552 /// Creates predicate obligations from the generic bounds.
553 pub fn predicates_for_generics<'tcx>(cause: ObligationCause<'tcx>,
554 param_env: ty::ParamEnv<'tcx>,
555 generic_bounds: &ty::InstantiatedPredicates<'tcx>)
556 -> PredicateObligations<'tcx>
558 util::predicates_for_generics(cause, 0, param_env, generic_bounds)
561 /// Determines whether the type `ty` is known to meet `bound` and
562 /// returns true if so. Returns false if `ty` either does not meet
563 /// `bound` or is not known to meet bound (note that this is
564 /// conservative towards *no impl*, which is the opposite of the
565 /// `evaluate` methods).
566 pub fn type_known_to_meet_bound<'a, 'gcx, 'tcx>(infcx: &InferCtxt<'a, 'gcx, 'tcx>,
567 param_env: ty::ParamEnv<'tcx>,
573 debug!("type_known_to_meet_bound(ty={:?}, bound={:?})",
575 infcx.tcx.item_path_str(def_id));
577 let trait_ref = ty::TraitRef {
579 substs: infcx.tcx.mk_substs_trait(ty, &[]),
581 let obligation = Obligation {
583 cause: ObligationCause::misc(span, ast::DUMMY_NODE_ID),
585 predicate: trait_ref.to_predicate(),
588 let result = infcx.predicate_must_hold(&obligation);
589 debug!("type_known_to_meet_ty={:?} bound={} => {:?}",
590 ty, infcx.tcx.item_path_str(def_id), result);
592 if result && (ty.has_infer_types() || ty.has_closure_types()) {
593 // Because of inference "guessing", selection can sometimes claim
594 // to succeed while the success requires a guess. To ensure
595 // this function's result remains infallible, we must confirm
596 // that guess. While imperfect, I believe this is sound.
598 // The handling of regions in this area of the code is terrible,
599 // see issue #29149. We should be able to improve on this with
601 let mut fulfill_cx = FulfillmentContext::new_ignoring_regions();
603 // We can use a dummy node-id here because we won't pay any mind
604 // to region obligations that arise (there shouldn't really be any
606 let cause = ObligationCause::misc(span, ast::DUMMY_NODE_ID);
608 fulfill_cx.register_bound(infcx, param_env, ty, def_id, cause);
610 // Note: we only assume something is `Copy` if we can
611 // *definitively* show that it implements `Copy`. Otherwise,
612 // assume it is move; linear is always ok.
613 match fulfill_cx.select_all_or_error(infcx) {
615 debug!("type_known_to_meet_bound: ty={:?} bound={} success",
617 infcx.tcx.item_path_str(def_id));
621 debug!("type_known_to_meet_bound: ty={:?} bound={} errors={:?}",
623 infcx.tcx.item_path_str(def_id),
633 // FIXME: this is gonna need to be removed ...
634 /// Normalizes the parameter environment, reporting errors if they occur.
635 pub fn normalize_param_env_or_error<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
636 region_context: DefId,
637 unnormalized_env: ty::ParamEnv<'tcx>,
638 cause: ObligationCause<'tcx>)
639 -> ty::ParamEnv<'tcx>
641 // I'm not wild about reporting errors here; I'd prefer to
642 // have the errors get reported at a defined place (e.g.,
643 // during typeck). Instead I have all parameter
644 // environments, in effect, going through this function
645 // and hence potentially reporting errors. This ensurse of
646 // course that we never forget to normalize (the
647 // alternative seemed like it would involve a lot of
648 // manual invocations of this fn -- and then we'd have to
649 // deal with the errors at each of those sites).
651 // In any case, in practice, typeck constructs all the
652 // parameter environments once for every fn as it goes,
653 // and errors will get reported then; so after typeck we
654 // can be sure that no errors should occur.
656 let span = cause.span;
658 debug!("normalize_param_env_or_error(unnormalized_env={:?})",
661 let predicates: Vec<_> =
662 util::elaborate_predicates(tcx, unnormalized_env.caller_bounds.to_vec())
665 debug!("normalize_param_env_or_error: elaborated-predicates={:?}",
668 let elaborated_env = ty::ParamEnv::new(tcx.intern_predicates(&predicates),
669 unnormalized_env.reveal);
671 tcx.infer_ctxt().enter(|infcx| {
672 // FIXME. We should really... do something with these region
673 // obligations. But this call just continues the older
674 // behavior (i.e., doesn't cause any new bugs), and it would
675 // take some further refactoring to actually solve them. In
676 // particular, we would have to handle implied bounds
677 // properly, and that code is currently largely confined to
678 // regionck (though I made some efforts to extract it
681 // @arielby: In any case, these obligations are checked
682 // by wfcheck anyway, so I'm not sure we have to check
683 // them here too, and we will remove this function when
684 // we move over to lazy normalization *anyway*.
685 let fulfill_cx = FulfillmentContext::new_ignoring_regions();
687 let predicates = match fully_normalize(
692 // You would really want to pass infcx.param_env.caller_bounds here,
693 // but that is an interned slice, and fully_normalize takes &T and returns T, so
694 // without further refactoring, a slice can't be used. Luckily, we still have the
695 // predicate vector from which we created the ParamEnv in infcx, so we
696 // can pass that instead. It's roundabout and a bit brittle, but this code path
697 // ought to be refactored anyway, and until then it saves us from having to copy.
700 Ok(predicates) => predicates,
702 infcx.report_fulfillment_errors(&errors, None, false);
703 // An unnormalized env is better than nothing.
704 return elaborated_env;
708 debug!("normalize_param_env_or_error: normalized predicates={:?}",
711 let region_scope_tree = region::ScopeTree::default();
713 // We can use the `elaborated_env` here; the region code only
714 // cares about declarations like `'a: 'b`.
715 let outlives_env = OutlivesEnvironment::new(elaborated_env);
717 infcx.resolve_regions_and_report_errors(region_context, ®ion_scope_tree, &outlives_env);
719 let predicates = match infcx.fully_resolve(&predicates) {
720 Ok(predicates) => predicates,
722 // If we encounter a fixup error, it means that some type
723 // variable wound up unconstrained. I actually don't know
724 // if this can happen, and I certainly don't expect it to
725 // happen often, but if it did happen it probably
726 // represents a legitimate failure due to some kind of
727 // unconstrained variable, and it seems better not to ICE,
728 // all things considered.
729 tcx.sess.span_err(span, &fixup_err.to_string());
730 // An unnormalized env is better than nothing.
731 return elaborated_env;
735 let predicates = match tcx.lift_to_global(&predicates) {
736 Some(predicates) => predicates,
737 None => return elaborated_env,
740 debug!("normalize_param_env_or_error: resolved predicates={:?}",
743 ty::ParamEnv::new(tcx.intern_predicates(&predicates), unnormalized_env.reveal)
747 pub fn fully_normalize<'a, 'gcx, 'tcx, T>(
748 infcx: &InferCtxt<'a, 'gcx, 'tcx>,
749 mut fulfill_cx: FulfillmentContext<'tcx>,
750 cause: ObligationCause<'tcx>,
751 param_env: ty::ParamEnv<'tcx>,
753 -> Result<T, Vec<FulfillmentError<'tcx>>>
754 where T : TypeFoldable<'tcx>
756 debug!("fully_normalize_with_fulfillcx(value={:?})", value);
757 let selcx = &mut SelectionContext::new(infcx);
758 let Normalized { value: normalized_value, obligations } =
759 project::normalize(selcx, param_env, cause, value);
760 debug!("fully_normalize: normalized_value={:?} obligations={:?}",
763 for obligation in obligations {
764 fulfill_cx.register_predicate_obligation(selcx.infcx(), obligation);
767 debug!("fully_normalize: select_all_or_error start");
768 fulfill_cx.select_all_or_error(infcx)?;
769 debug!("fully_normalize: select_all_or_error complete");
770 let resolved_value = infcx.resolve_type_vars_if_possible(&normalized_value);
771 debug!("fully_normalize: resolved_value={:?}", resolved_value);
775 /// Normalizes the predicates and checks whether they hold in an empty
776 /// environment. If this returns false, then either normalize
777 /// encountered an error or one of the predicates did not hold. Used
778 /// when creating vtables to check for unsatisfiable methods.
779 fn normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
780 predicates: Vec<ty::Predicate<'tcx>>)
783 debug!("normalize_and_test_predicates(predicates={:?})",
786 let result = tcx.infer_ctxt().enter(|infcx| {
787 let param_env = ty::ParamEnv::reveal_all();
788 let mut selcx = SelectionContext::new(&infcx);
789 let mut fulfill_cx = FulfillmentContext::new();
790 let cause = ObligationCause::dummy();
791 let Normalized { value: predicates, obligations } =
792 normalize(&mut selcx, param_env, cause.clone(), &predicates);
793 for obligation in obligations {
794 fulfill_cx.register_predicate_obligation(&infcx, obligation);
796 for predicate in predicates {
797 let obligation = Obligation::new(cause.clone(), param_env, predicate);
798 fulfill_cx.register_predicate_obligation(&infcx, obligation);
801 fulfill_cx.select_all_or_error(&infcx).is_ok()
803 debug!("normalize_and_test_predicates(predicates={:?}) = {:?}",
808 fn substitute_normalize_and_test_predicates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
809 key: (DefId, &'tcx Substs<'tcx>))
812 use ty::subst::Subst;
813 debug!("substitute_normalize_and_test_predicates(key={:?})",
816 let predicates = tcx.predicates_of(key.0).predicates.subst(tcx, key.1);
817 let result = normalize_and_test_predicates(tcx, predicates);
819 debug!("substitute_normalize_and_test_predicates(key={:?}) = {:?}",
824 /// Given a trait `trait_ref`, iterates the vtable entries
825 /// that come from `trait_ref`, including its supertraits.
826 #[inline] // FIXME(#35870) Avoid closures being unexported due to impl Trait.
827 fn vtable_methods<'a, 'tcx>(
828 tcx: TyCtxt<'a, 'tcx, 'tcx>,
829 trait_ref: ty::PolyTraitRef<'tcx>)
830 -> Lrc<Vec<Option<(DefId, &'tcx Substs<'tcx>)>>>
832 debug!("vtable_methods({:?})", trait_ref);
835 supertraits(tcx, trait_ref).flat_map(move |trait_ref| {
836 let trait_methods = tcx.associated_items(trait_ref.def_id())
837 .filter(|item| item.kind == ty::AssociatedKind::Method);
839 // Now list each method's DefId and Substs (for within its trait).
840 // If the method can never be called from this object, produce None.
841 trait_methods.map(move |trait_method| {
842 debug!("vtable_methods: trait_method={:?}", trait_method);
843 let def_id = trait_method.def_id;
845 // Some methods cannot be called on an object; skip those.
846 if !tcx.is_vtable_safe_method(trait_ref.def_id(), &trait_method) {
847 debug!("vtable_methods: not vtable safe");
851 // the method may have some early-bound lifetimes, add
853 let substs = trait_ref.map_bound(|trait_ref| {
854 Substs::for_item(tcx, def_id, |param, _| {
856 GenericParamDefKind::Lifetime => tcx.types.re_erased.into(),
857 GenericParamDefKind::Type {..} => {
858 trait_ref.substs[param.index as usize]
864 // the trait type may have higher-ranked lifetimes in it;
865 // so erase them if they appear, so that we get the type
866 // at some particular call site
867 let substs = tcx.normalize_erasing_late_bound_regions(
868 ty::ParamEnv::reveal_all(),
872 // It's possible that the method relies on where clauses that
873 // do not hold for this particular set of type parameters.
874 // Note that this method could then never be called, so we
875 // do not want to try and codegen it, in that case (see #23435).
876 let predicates = tcx.predicates_of(def_id).instantiate_own(tcx, substs);
877 if !normalize_and_test_predicates(tcx, predicates.predicates) {
878 debug!("vtable_methods: predicates do not hold");
882 Some((def_id, substs))
888 impl<'tcx,O> Obligation<'tcx,O> {
889 pub fn new(cause: ObligationCause<'tcx>,
890 param_env: ty::ParamEnv<'tcx>,
892 -> Obligation<'tcx, O>
894 Obligation { cause, param_env, recursion_depth: 0, predicate }
897 fn with_depth(cause: ObligationCause<'tcx>,
898 recursion_depth: usize,
899 param_env: ty::ParamEnv<'tcx>,
901 -> Obligation<'tcx, O>
903 Obligation { cause, param_env, recursion_depth, predicate }
906 pub fn misc(span: Span,
907 body_id: ast::NodeId,
908 param_env: ty::ParamEnv<'tcx>,
910 -> Obligation<'tcx, O> {
911 Obligation::new(ObligationCause::misc(span, body_id), param_env, trait_ref)
914 pub fn with<P>(&self, value: P) -> Obligation<'tcx,P> {
915 Obligation { cause: self.cause.clone(),
916 param_env: self.param_env,
917 recursion_depth: self.recursion_depth,
922 impl<'tcx> ObligationCause<'tcx> {
923 pub fn new(span: Span,
924 body_id: ast::NodeId,
925 code: ObligationCauseCode<'tcx>)
926 -> ObligationCause<'tcx> {
927 ObligationCause { span: span, body_id: body_id, code: code }
930 pub fn misc(span: Span, body_id: ast::NodeId) -> ObligationCause<'tcx> {
931 ObligationCause { span: span, body_id: body_id, code: MiscObligation }
934 pub fn dummy() -> ObligationCause<'tcx> {
935 ObligationCause { span: DUMMY_SP, body_id: ast::CRATE_NODE_ID, code: MiscObligation }
939 impl<'tcx, N> Vtable<'tcx, N> {
940 pub fn nested_obligations(self) -> Vec<N> {
942 VtableImpl(i) => i.nested,
944 VtableBuiltin(i) => i.nested,
945 VtableAutoImpl(d) => d.nested,
946 VtableClosure(c) => c.nested,
947 VtableGenerator(c) => c.nested,
948 VtableObject(d) => d.nested,
949 VtableFnPointer(d) => d.nested,
953 pub fn map<M, F>(self, f: F) -> Vtable<'tcx, M> where F: FnMut(N) -> M {
955 VtableImpl(i) => VtableImpl(VtableImplData {
956 impl_def_id: i.impl_def_id,
958 nested: i.nested.into_iter().map(f).collect(),
960 VtableParam(n) => VtableParam(n.into_iter().map(f).collect()),
961 VtableBuiltin(i) => VtableBuiltin(VtableBuiltinData {
962 nested: i.nested.into_iter().map(f).collect(),
964 VtableObject(o) => VtableObject(VtableObjectData {
965 upcast_trait_ref: o.upcast_trait_ref,
966 vtable_base: o.vtable_base,
967 nested: o.nested.into_iter().map(f).collect(),
969 VtableAutoImpl(d) => VtableAutoImpl(VtableAutoImplData {
970 trait_def_id: d.trait_def_id,
971 nested: d.nested.into_iter().map(f).collect(),
973 VtableFnPointer(p) => VtableFnPointer(VtableFnPointerData {
975 nested: p.nested.into_iter().map(f).collect(),
977 VtableGenerator(c) => VtableGenerator(VtableGeneratorData {
978 generator_def_id: c.generator_def_id,
980 nested: c.nested.into_iter().map(f).collect(),
982 VtableClosure(c) => VtableClosure(VtableClosureData {
983 closure_def_id: c.closure_def_id,
985 nested: c.nested.into_iter().map(f).collect(),
991 impl<'tcx> FulfillmentError<'tcx> {
992 fn new(obligation: PredicateObligation<'tcx>,
993 code: FulfillmentErrorCode<'tcx>)
994 -> FulfillmentError<'tcx>
996 FulfillmentError { obligation: obligation, code: code }
1000 impl<'tcx> TraitObligation<'tcx> {
1001 fn self_ty(&self) -> ty::Binder<Ty<'tcx>> {
1002 self.predicate.map_bound(|p| p.self_ty())
1006 pub fn provide(providers: &mut ty::query::Providers) {
1007 *providers = ty::query::Providers {
1008 is_object_safe: object_safety::is_object_safe_provider,
1009 specialization_graph_of: specialize::specialization_graph_provider,
1010 specializes: specialize::specializes,
1011 codegen_fulfill_obligation: codegen::codegen_fulfill_obligation,
1013 substitute_normalize_and_test_predicates,
1018 impl<'gcx: 'tcx, 'tcx> Canonicalize<'gcx, 'tcx> for ty::ParamEnvAnd<'tcx, Goal<'tcx>> {
1019 // we ought to intern this, but I'm too lazy just now
1020 type Canonicalized = Canonical<'gcx, ty::ParamEnvAnd<'gcx, Goal<'gcx>>>;
1023 _gcx: TyCtxt<'_, 'gcx, 'gcx>,
1024 value: Canonical<'gcx, Self::Lifted>,
1025 ) -> Self::Canonicalized {
1030 pub trait ExClauseFold<'tcx>
1032 Self: chalk_engine::context::Context + Clone,
1034 fn fold_ex_clause_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(
1035 ex_clause: &chalk_engine::ExClause<Self>,
1037 ) -> chalk_engine::ExClause<Self>;
1039 fn visit_ex_clause_with<'gcx: 'tcx, V: TypeVisitor<'tcx>>(
1040 ex_clause: &chalk_engine::ExClause<Self>,
1045 pub trait ExClauseLift<'tcx>
1047 Self: chalk_engine::context::Context + Clone,
1049 type LiftedExClause: Debug + 'tcx;
1051 fn lift_ex_clause_to_tcx<'a, 'gcx>(
1052 ex_clause: &chalk_engine::ExClause<Self>,
1053 tcx: TyCtxt<'a, 'gcx, 'tcx>,
1054 ) -> Option<Self::LiftedExClause>;
1057 impl<'gcx: 'tcx, 'tcx, C> Canonicalize<'gcx, 'tcx> for chalk_engine::ExClause<C>
1059 C: chalk_engine::context::Context + Clone,
1060 C: ExClauseLift<'gcx> + ExClauseFold<'tcx>,
1061 C::Substitution: Clone,
1062 C::RegionConstraint: Clone,
1064 type Canonicalized = Canonical<'gcx, C::LiftedExClause>;
1067 _gcx: TyCtxt<'_, 'gcx, 'gcx>,
1068 value: Canonical<'gcx, Self::Lifted>,
1069 ) -> Self::Canonicalized {