2 use super::MethodError;
3 use super::NoMatchData;
4 use super::{CandidateSource, ImplSource, TraitSource};
6 use crate::check::autoderef::{self, Autoderef};
7 use crate::check::FnCtxt;
8 use crate::hir::def::DefKind;
9 use crate::hir::def_id::DefId;
11 use rustc::middle::stability;
12 use rustc::ty::subst::{InternalSubsts, Subst, SubstsRef};
13 use rustc::ty::GenericParamDefKind;
15 self, ParamEnvAnd, ToPolyTraitRef, ToPredicate, Ty, TyCtxt, TypeFoldable, WithConstness,
18 use rustc_ast::util::lev_distance::{find_best_match_for_name, lev_distance};
19 use rustc_data_structures::fx::FxHashSet;
20 use rustc_data_structures::sync::Lrc;
21 use rustc_errors::struct_span_err;
23 use rustc_hir::def::Namespace;
24 use rustc_infer::infer::canonical::OriginalQueryValues;
25 use rustc_infer::infer::canonical::{Canonical, QueryResponse};
26 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
27 use rustc_infer::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
28 use rustc_infer::infer::{self, InferOk, TyCtxtInferExt};
29 use rustc_session::config::nightly_options;
30 use rustc_session::lint;
31 use rustc_span::{symbol::Symbol, Span, DUMMY_SP};
32 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt;
33 use rustc_trait_selection::traits::query::method_autoderef::MethodAutoderefBadTy;
34 use rustc_trait_selection::traits::query::method_autoderef::{
35 CandidateStep, MethodAutoderefStepsResult,
37 use rustc_trait_selection::traits::query::CanonicalTyGoal;
38 use rustc_trait_selection::traits::{self, ObligationCause};
44 use smallvec::{smallvec, SmallVec};
46 use self::CandidateKind::*;
47 pub use self::PickKind::*;
49 /// Boolean flag used to indicate if this search is for a suggestion
50 /// or not. If true, we can allow ambiguity and so forth.
51 #[derive(Clone, Copy)]
52 pub struct IsSuggestion(pub bool);
54 struct ProbeContext<'a, 'tcx> {
55 fcx: &'a FnCtxt<'a, 'tcx>,
58 method_name: Option<ast::Ident>,
59 return_type: Option<Ty<'tcx>>,
61 /// This is the OriginalQueryValues for the steps queries
62 /// that are answered in steps.
63 orig_steps_var_values: OriginalQueryValues<'tcx>,
64 steps: Lrc<Vec<CandidateStep<'tcx>>>,
66 inherent_candidates: Vec<Candidate<'tcx>>,
67 extension_candidates: Vec<Candidate<'tcx>>,
68 impl_dups: FxHashSet<DefId>,
70 /// Collects near misses when the candidate functions are missing a `self` keyword and is only
71 /// used for error reporting
72 static_candidates: Vec<CandidateSource>,
74 /// When probing for names, include names that are close to the
75 /// requested name (by Levensthein distance)
76 allow_similar_names: bool,
78 /// Some(candidate) if there is a private candidate
79 private_candidate: Option<(DefKind, DefId)>,
81 /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
82 /// for error reporting
83 unsatisfied_predicates: Vec<(ty::Predicate<'tcx>, Option<ty::Predicate<'tcx>>)>,
85 is_suggestion: IsSuggestion,
88 impl<'a, 'tcx> Deref for ProbeContext<'a, 'tcx> {
89 type Target = FnCtxt<'a, 'tcx>;
90 fn deref(&self) -> &Self::Target {
96 struct Candidate<'tcx> {
97 // Candidates are (I'm not quite sure, but they are mostly) basically
98 // some metadata on top of a `ty::AssocItem` (without substs).
100 // However, method probing wants to be able to evaluate the predicates
101 // for a function with the substs applied - for example, if a function
102 // has `where Self: Sized`, we don't want to consider it unless `Self`
103 // is actually `Sized`, and similarly, return-type suggestions want
104 // to consider the "actual" return type.
106 // The way this is handled is through `xform_self_ty`. It contains
107 // the receiver type of this candidate, but `xform_self_ty`,
108 // `xform_ret_ty` and `kind` (which contains the predicates) have the
109 // generic parameters of this candidate substituted with the *same set*
110 // of inference variables, which acts as some weird sort of "query".
112 // When we check out a candidate, we require `xform_self_ty` to be
113 // a subtype of the passed-in self-type, and this equates the type
114 // variables in the rest of the fields.
116 // For example, if we have this candidate:
119 // fn foo(&self) where Self: Sized;
123 // Then `xform_self_ty` will be `&'erased ?X` and `kind` will contain
124 // the predicate `?X: Sized`, so if we are evaluating `Foo` for a
125 // the receiver `&T`, we'll do the subtyping which will make `?X`
126 // get the right value, then when we evaluate the predicate we'll check
128 xform_self_ty: Ty<'tcx>,
129 xform_ret_ty: Option<Ty<'tcx>>,
131 kind: CandidateKind<'tcx>,
132 import_ids: SmallVec<[hir::HirId; 1]>,
136 enum CandidateKind<'tcx> {
137 InherentImplCandidate(
139 // Normalize obligations
140 Vec<traits::PredicateObligation<'tcx>>,
143 TraitCandidate(ty::TraitRef<'tcx>),
144 WhereClauseCandidate(
146 ty::PolyTraitRef<'tcx>,
150 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
157 #[derive(Debug, PartialEq, Clone)]
158 pub struct Pick<'tcx> {
159 pub item: ty::AssocItem,
160 pub kind: PickKind<'tcx>,
161 pub import_ids: SmallVec<[hir::HirId; 1]>,
163 // Indicates that the source expression should be autoderef'd N times
165 // A = expr | *expr | **expr | ...
166 pub autoderefs: usize,
168 // Indicates that an autoref is applied after the optional autoderefs
170 // B = A | &A | &mut A
171 pub autoref: Option<hir::Mutability>,
173 // Indicates that the source expression should be "unsized" to a
174 // target type. This should probably eventually go away in favor
175 // of just coercing method receivers.
178 pub unsize: Option<Ty<'tcx>>,
181 #[derive(Clone, Debug, PartialEq, Eq)]
182 pub enum PickKind<'tcx> {
188 ty::PolyTraitRef<'tcx>,
192 pub type PickResult<'tcx> = Result<Pick<'tcx>, MethodError<'tcx>>;
194 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
196 // An expression of the form `receiver.method_name(...)`.
197 // Autoderefs are performed on `receiver`, lookup is done based on the
198 // `self` argument of the method, and static methods aren't considered.
200 // An expression of the form `Type::item` or `<T>::item`.
201 // No autoderefs are performed, lookup is done based on the type each
202 // implementation is for, and static methods are included.
206 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
207 pub enum ProbeScope {
208 // Assemble candidates coming only from traits in scope.
211 // Assemble candidates coming from all traits.
215 impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
216 /// This is used to offer suggestions to users. It returns methods
217 /// that could have been called which have the desired return
218 /// type. Some effort is made to rule out methods that, if called,
219 /// would result in an error (basically, the same criteria we
220 /// would use to decide if a method is a plausible fit for
221 /// ambiguity purposes).
222 pub fn probe_for_return_type(
226 return_type: Ty<'tcx>,
228 scope_expr_id: hir::HirId,
229 ) -> Vec<ty::AssocItem> {
231 "probe(self_ty={:?}, return_type={}, scope_expr_id={})",
232 self_ty, return_type, scope_expr_id
234 let method_names = self
243 ProbeScope::AllTraits,
244 |probe_cx| Ok(probe_cx.candidate_method_names()),
249 .flat_map(|&method_name| {
258 ProbeScope::AllTraits,
259 |probe_cx| probe_cx.pick(),
262 .map(|pick| pick.item)
267 pub fn probe_for_name(
271 item_name: ast::Ident,
272 is_suggestion: IsSuggestion,
274 scope_expr_id: hir::HirId,
276 ) -> PickResult<'tcx> {
278 "probe(self_ty={:?}, item_name={}, scope_expr_id={})",
279 self_ty, item_name, scope_expr_id
290 |probe_cx| probe_cx.pick(),
298 method_name: Option<ast::Ident>,
299 return_type: Option<Ty<'tcx>>,
300 is_suggestion: IsSuggestion,
302 scope_expr_id: hir::HirId,
305 ) -> Result<R, MethodError<'tcx>>
307 OP: FnOnce(ProbeContext<'a, 'tcx>) -> Result<R, MethodError<'tcx>>,
309 let mut orig_values = OriginalQueryValues::default();
310 let param_env_and_self_ty = self.infcx.canonicalize_query(
311 &ParamEnvAnd { param_env: self.param_env, value: self_ty },
315 let steps = if mode == Mode::MethodCall {
316 self.tcx.method_autoderef_steps(param_env_and_self_ty)
318 self.infcx.probe(|_| {
319 // Mode::Path - the deref steps is "trivial". This turns
320 // our CanonicalQuery into a "trivial" QueryResponse. This
321 // is a bit inefficient, but I don't think that writing
322 // special handling for this "trivial case" is a good idea.
324 let infcx = &self.infcx;
325 let (ParamEnvAnd { param_env: _, value: self_ty }, canonical_inference_vars) =
326 infcx.instantiate_canonical_with_fresh_inference_vars(
328 ¶m_env_and_self_ty,
331 "probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}",
332 param_env_and_self_ty, self_ty
334 MethodAutoderefStepsResult {
335 steps: Lrc::new(vec![CandidateStep {
336 self_ty: self.make_query_response_ignoring_pending_obligations(
337 canonical_inference_vars,
341 from_unsafe_deref: false,
345 reached_recursion_limit: false,
350 // If our autoderef loop had reached the recursion limit,
351 // report an overflow error, but continue going on with
352 // the truncated autoderef list.
353 if steps.reached_recursion_limit {
358 .unwrap_or_else(|| span_bug!(span, "reached the recursion limit in 0 steps?"))
361 .probe_instantiate_query_response(span, &orig_values, ty)
362 .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
363 autoderef::report_autoderef_recursion_limit_error(self.tcx, span, ty.value);
367 // If we encountered an `_` type or an error type during autoderef, this is
369 if let Some(bad_ty) = &steps.opt_bad_ty {
371 // Ambiguity was encountered during a suggestion. Just keep going.
372 debug!("ProbeContext: encountered ambiguity in suggestion");
373 } else if bad_ty.reached_raw_pointer && !self.tcx.features().arbitrary_self_types {
374 // this case used to be allowed by the compiler,
375 // so we do a future-compat lint here for the 2015 edition
376 // (see https://github.com/rust-lang/rust/issues/46906)
377 if self.tcx.sess.rust_2018() {
382 "the type of this value must be known \
383 to call a method on a raw pointer on it"
387 self.tcx.struct_span_lint_hir(
388 lint::builtin::TYVAR_BEHIND_RAW_POINTER,
391 |lint| lint.build("type annotations needed").emit(),
395 // Encountered a real ambiguity, so abort the lookup. If `ty` is not
396 // an `Err`, report the right "type annotations needed" error pointing
400 .probe_instantiate_query_response(span, &orig_values, ty)
401 .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
402 let ty = self.structurally_resolved_type(span, ty.value);
403 assert_eq!(ty, self.tcx.types.err);
404 return Err(MethodError::NoMatch(NoMatchData::new(
414 debug!("ProbeContext: steps for self_ty={:?} are {:?}", self_ty, steps);
416 // this creates one big transaction so that all type variables etc
417 // that we create during the probe process are removed later
419 let mut probe_cx = ProbeContext::new(
430 probe_cx.assemble_inherent_candidates();
432 ProbeScope::TraitsInScope => {
433 probe_cx.assemble_extension_candidates_for_traits_in_scope(scope_expr_id)?
435 ProbeScope::AllTraits => probe_cx.assemble_extension_candidates_for_all_traits()?,
442 pub fn provide(providers: &mut ty::query::Providers<'_>) {
443 providers.method_autoderef_steps = method_autoderef_steps;
446 fn method_autoderef_steps<'tcx>(
448 goal: CanonicalTyGoal<'tcx>,
449 ) -> MethodAutoderefStepsResult<'tcx> {
450 debug!("method_autoderef_steps({:?})", goal);
452 tcx.infer_ctxt().enter_with_canonical(DUMMY_SP, &goal, |ref infcx, goal, inference_vars| {
453 let ParamEnvAnd { param_env, value: self_ty } = goal;
455 let mut autoderef = Autoderef::new(infcx, param_env, hir::DUMMY_HIR_ID, DUMMY_SP, self_ty)
456 .include_raw_pointers()
458 let mut reached_raw_pointer = false;
459 let mut steps: Vec<_> = autoderef
462 let step = CandidateStep {
463 self_ty: infcx.make_query_response_ignoring_pending_obligations(
464 inference_vars.clone(),
468 from_unsafe_deref: reached_raw_pointer,
471 if let ty::RawPtr(_) = ty.kind {
472 // all the subsequent steps will be from_unsafe_deref
473 reached_raw_pointer = true;
479 let final_ty = autoderef.maybe_ambiguous_final_ty();
480 let opt_bad_ty = match final_ty.kind {
481 ty::Infer(ty::TyVar(_)) | ty::Error => Some(MethodAutoderefBadTy {
484 .make_query_response_ignoring_pending_obligations(inference_vars, final_ty),
486 ty::Array(elem_ty, _) => {
487 let dereferences = steps.len() - 1;
489 steps.push(CandidateStep {
490 self_ty: infcx.make_query_response_ignoring_pending_obligations(
492 infcx.tcx.mk_slice(elem_ty),
494 autoderefs: dereferences,
495 // this could be from an unsafe deref if we had
496 // a *mut/const [T; N]
497 from_unsafe_deref: reached_raw_pointer,
506 debug!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps, opt_bad_ty);
508 MethodAutoderefStepsResult {
509 steps: Lrc::new(steps),
510 opt_bad_ty: opt_bad_ty.map(Lrc::new),
511 reached_recursion_limit: autoderef.reached_recursion_limit(),
516 impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
518 fcx: &'a FnCtxt<'a, 'tcx>,
521 method_name: Option<ast::Ident>,
522 return_type: Option<Ty<'tcx>>,
523 orig_steps_var_values: OriginalQueryValues<'tcx>,
524 steps: Lrc<Vec<CandidateStep<'tcx>>>,
525 is_suggestion: IsSuggestion,
526 ) -> ProbeContext<'a, 'tcx> {
533 inherent_candidates: Vec::new(),
534 extension_candidates: Vec::new(),
535 impl_dups: FxHashSet::default(),
536 orig_steps_var_values,
538 static_candidates: Vec::new(),
539 allow_similar_names: false,
540 private_candidate: None,
541 unsatisfied_predicates: Vec::new(),
546 fn reset(&mut self) {
547 self.inherent_candidates.clear();
548 self.extension_candidates.clear();
549 self.impl_dups.clear();
550 self.static_candidates.clear();
551 self.private_candidate = None;
554 ///////////////////////////////////////////////////////////////////////////
555 // CANDIDATE ASSEMBLY
557 fn push_candidate(&mut self, candidate: Candidate<'tcx>, is_inherent: bool) {
558 let is_accessible = if let Some(name) = self.method_name {
559 let item = candidate.item;
561 self.tcx.adjust_ident_and_get_scope(name, item.container.id(), self.body_id).1;
562 item.vis.is_accessible_from(def_scope, self.tcx)
568 self.inherent_candidates.push(candidate);
570 self.extension_candidates.push(candidate);
572 } else if self.private_candidate.is_none() {
573 self.private_candidate = Some((candidate.item.def_kind(), candidate.item.def_id));
577 fn assemble_inherent_candidates(&mut self) {
578 let steps = Lrc::clone(&self.steps);
579 for step in steps.iter() {
580 self.assemble_probe(&step.self_ty);
584 fn assemble_probe(&mut self, self_ty: &Canonical<'tcx, QueryResponse<'tcx, Ty<'tcx>>>) {
585 debug!("assemble_probe: self_ty={:?}", self_ty);
586 let lang_items = self.tcx.lang_items();
588 match self_ty.value.value.kind {
589 ty::Dynamic(ref data, ..) => {
590 if let Some(p) = data.principal() {
591 // Subtle: we can't use `instantiate_query_response` here: using it will
592 // commit to all of the type equalities assumed by inference going through
593 // autoderef (see the `method-probe-no-guessing` test).
595 // However, in this code, it is OK if we end up with an object type that is
596 // "more general" than the object type that we are evaluating. For *every*
597 // object type `MY_OBJECT`, a function call that goes through a trait-ref
598 // of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid
599 // `ObjectCandidate`, and it should be discoverable "exactly" through one
600 // of the iterations in the autoderef loop, so there is no problem with it
601 // being discoverable in another one of these iterations.
603 // Using `instantiate_canonical_with_fresh_inference_vars` on our
604 // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
605 // `CanonicalVarValues` will exactly give us such a generalization - it
606 // will still match the original object type, but it won't pollute our
607 // type variables in any form, so just do that!
608 let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
610 .instantiate_canonical_with_fresh_inference_vars(self.span, &self_ty);
612 self.assemble_inherent_candidates_from_object(generalized_self_ty);
613 self.assemble_inherent_impl_candidates_for_type(p.def_id());
617 self.assemble_inherent_impl_candidates_for_type(def.did);
619 ty::Foreign(did) => {
620 self.assemble_inherent_impl_candidates_for_type(did);
623 self.assemble_inherent_candidates_from_param(p);
626 let lang_def_id = lang_items.bool_impl();
627 self.assemble_inherent_impl_for_primitive(lang_def_id);
630 let lang_def_id = lang_items.char_impl();
631 self.assemble_inherent_impl_for_primitive(lang_def_id);
634 let lang_def_id = lang_items.str_impl();
635 self.assemble_inherent_impl_for_primitive(lang_def_id);
637 let lang_def_id = lang_items.str_alloc_impl();
638 self.assemble_inherent_impl_for_primitive(lang_def_id);
641 for &lang_def_id in &[
642 lang_items.slice_impl(),
643 lang_items.slice_u8_impl(),
644 lang_items.slice_alloc_impl(),
645 lang_items.slice_u8_alloc_impl(),
647 self.assemble_inherent_impl_for_primitive(lang_def_id);
650 ty::RawPtr(ty::TypeAndMut { ty: _, mutbl }) => {
651 let lang_def_id = match mutbl {
652 hir::Mutability::Not => lang_items.const_ptr_impl(),
653 hir::Mutability::Mut => lang_items.mut_ptr_impl(),
655 self.assemble_inherent_impl_for_primitive(lang_def_id);
658 let lang_def_id = match i {
659 ast::IntTy::I8 => lang_items.i8_impl(),
660 ast::IntTy::I16 => lang_items.i16_impl(),
661 ast::IntTy::I32 => lang_items.i32_impl(),
662 ast::IntTy::I64 => lang_items.i64_impl(),
663 ast::IntTy::I128 => lang_items.i128_impl(),
664 ast::IntTy::Isize => lang_items.isize_impl(),
666 self.assemble_inherent_impl_for_primitive(lang_def_id);
669 let lang_def_id = match i {
670 ast::UintTy::U8 => lang_items.u8_impl(),
671 ast::UintTy::U16 => lang_items.u16_impl(),
672 ast::UintTy::U32 => lang_items.u32_impl(),
673 ast::UintTy::U64 => lang_items.u64_impl(),
674 ast::UintTy::U128 => lang_items.u128_impl(),
675 ast::UintTy::Usize => lang_items.usize_impl(),
677 self.assemble_inherent_impl_for_primitive(lang_def_id);
680 let (lang_def_id1, lang_def_id2) = match f {
681 ast::FloatTy::F32 => (lang_items.f32_impl(), lang_items.f32_runtime_impl()),
682 ast::FloatTy::F64 => (lang_items.f64_impl(), lang_items.f64_runtime_impl()),
684 self.assemble_inherent_impl_for_primitive(lang_def_id1);
685 self.assemble_inherent_impl_for_primitive(lang_def_id2);
691 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id: Option<DefId>) {
692 if let Some(impl_def_id) = lang_def_id {
693 self.assemble_inherent_impl_probe(impl_def_id);
697 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
698 let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id);
699 for &impl_def_id in impl_def_ids.iter() {
700 self.assemble_inherent_impl_probe(impl_def_id);
704 fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) {
705 if !self.impl_dups.insert(impl_def_id) {
706 return; // already visited
709 debug!("assemble_inherent_impl_probe {:?}", impl_def_id);
711 for item in self.impl_or_trait_item(impl_def_id) {
712 if !self.has_applicable_self(&item) {
713 // No receiver declared. Not a candidate.
714 self.record_static_candidate(ImplSource(impl_def_id));
718 let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
719 let impl_ty = impl_ty.subst(self.tcx, impl_substs);
721 // Determine the receiver type that the method itself expects.
722 let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs);
724 // We can't use normalize_associated_types_in as it will pollute the
725 // fcx's fulfillment context after this probe is over.
726 let cause = traits::ObligationCause::misc(self.span, self.body_id);
727 let selcx = &mut traits::SelectionContext::new(self.fcx);
728 let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } =
729 traits::normalize(selcx, self.param_env, cause, &xform_tys);
731 "assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}",
732 xform_self_ty, xform_ret_ty
740 kind: InherentImplCandidate(impl_substs, obligations),
741 import_ids: smallvec![],
748 fn assemble_inherent_candidates_from_object(&mut self, self_ty: Ty<'tcx>) {
749 debug!("assemble_inherent_candidates_from_object(self_ty={:?})", self_ty);
751 let principal = match self_ty.kind {
752 ty::Dynamic(ref data, ..) => Some(data),
755 .and_then(|data| data.principal())
759 "non-object {:?} in assemble_inherent_candidates_from_object",
764 // It is illegal to invoke a method on a trait instance that
765 // refers to the `Self` type. An error will be reported by
766 // `enforce_object_limitations()` if the method refers to the
767 // `Self` type anywhere other than the receiver. Here, we use
768 // a substitution that replaces `Self` with the object type
769 // itself. Hence, a `&self` method will wind up with an
770 // argument type like `&Trait`.
771 let trait_ref = principal.with_self_ty(self.tcx, self_ty);
772 self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| {
773 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
775 let (xform_self_ty, xform_ret_ty) =
776 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
782 kind: ObjectCandidate,
783 import_ids: smallvec![],
790 fn assemble_inherent_candidates_from_param(&mut self, param_ty: ty::ParamTy) {
791 // FIXME: do we want to commit to this behavior for param bounds?
793 let bounds = self.param_env.caller_bounds.iter().filter_map(|predicate| match *predicate {
794 ty::Predicate::Trait(ref trait_predicate, _) => {
795 match trait_predicate.skip_binder().trait_ref.self_ty().kind {
796 ty::Param(ref p) if *p == param_ty => Some(trait_predicate.to_poly_trait_ref()),
800 ty::Predicate::Subtype(..)
801 | ty::Predicate::Projection(..)
802 | ty::Predicate::RegionOutlives(..)
803 | ty::Predicate::WellFormed(..)
804 | ty::Predicate::ObjectSafe(..)
805 | ty::Predicate::ClosureKind(..)
806 | ty::Predicate::TypeOutlives(..)
807 | ty::Predicate::ConstEvaluatable(..) => None,
810 self.elaborate_bounds(bounds, |this, poly_trait_ref, item| {
811 let trait_ref = this.erase_late_bound_regions(&poly_trait_ref);
813 let (xform_self_ty, xform_ret_ty) =
814 this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs);
816 // Because this trait derives from a where-clause, it
817 // should not contain any inference variables or other
818 // artifacts. This means it is safe to put into the
819 // `WhereClauseCandidate` and (eventually) into the
820 // `WhereClausePick`.
821 assert!(!trait_ref.substs.needs_infer());
828 kind: WhereClauseCandidate(poly_trait_ref),
829 import_ids: smallvec![],
836 // Do a search through a list of bounds, using a callback to actually
837 // create the candidates.
838 fn elaborate_bounds<F>(
840 bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
843 F: for<'b> FnMut(&mut ProbeContext<'b, 'tcx>, ty::PolyTraitRef<'tcx>, ty::AssocItem),
846 for bound_trait_ref in traits::transitive_bounds(tcx, bounds) {
847 debug!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref);
848 for item in self.impl_or_trait_item(bound_trait_ref.def_id()) {
849 if !self.has_applicable_self(&item) {
850 self.record_static_candidate(TraitSource(bound_trait_ref.def_id()));
852 mk_cand(self, bound_trait_ref, item);
858 fn assemble_extension_candidates_for_traits_in_scope(
860 expr_hir_id: hir::HirId,
861 ) -> Result<(), MethodError<'tcx>> {
862 if expr_hir_id == hir::DUMMY_HIR_ID {
865 let mut duplicates = FxHashSet::default();
866 let opt_applicable_traits = self.tcx.in_scope_traits(expr_hir_id);
867 if let Some(applicable_traits) = opt_applicable_traits {
868 for trait_candidate in applicable_traits.iter() {
869 let trait_did = trait_candidate.def_id;
870 if duplicates.insert(trait_did) {
871 let result = self.assemble_extension_candidates_for_trait(
872 &trait_candidate.import_ids,
882 fn assemble_extension_candidates_for_all_traits(&mut self) -> Result<(), MethodError<'tcx>> {
883 let mut duplicates = FxHashSet::default();
884 for trait_info in suggest::all_traits(self.tcx) {
885 if duplicates.insert(trait_info.def_id) {
886 self.assemble_extension_candidates_for_trait(&smallvec![], trait_info.def_id)?;
892 pub fn matches_return_type(
894 method: &ty::AssocItem,
895 self_ty: Option<Ty<'tcx>>,
899 ty::AssocKind::Method => {
900 let fty = self.tcx.fn_sig(method.def_id);
902 let substs = self.fresh_substs_for_item(self.span, method.def_id);
903 let fty = fty.subst(self.tcx, substs);
905 self.replace_bound_vars_with_fresh_vars(self.span, infer::FnCall, &fty);
907 if let Some(self_ty) = self_ty {
909 .at(&ObligationCause::dummy(), self.param_env)
910 .sup(fty.inputs()[0], self_ty)
916 self.can_sub(self.param_env, fty.output(), expected).is_ok()
923 fn assemble_extension_candidates_for_trait(
925 import_ids: &SmallVec<[hir::HirId; 1]>,
927 ) -> Result<(), MethodError<'tcx>> {
928 debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})", trait_def_id);
929 let trait_substs = self.fresh_item_substs(trait_def_id);
930 let trait_ref = ty::TraitRef::new(trait_def_id, trait_substs);
932 if self.tcx.is_trait_alias(trait_def_id) {
933 // For trait aliases, assume all super-traits are relevant.
934 let bounds = iter::once(trait_ref.to_poly_trait_ref());
935 self.elaborate_bounds(bounds, |this, new_trait_ref, item| {
936 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
938 let (xform_self_ty, xform_ret_ty) =
939 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
945 import_ids: import_ids.clone(),
946 kind: TraitCandidate(new_trait_ref),
952 debug_assert!(self.tcx.is_trait(trait_def_id));
953 for item in self.impl_or_trait_item(trait_def_id) {
954 // Check whether `trait_def_id` defines a method with suitable name.
955 if !self.has_applicable_self(&item) {
956 debug!("method has inapplicable self");
957 self.record_static_candidate(TraitSource(trait_def_id));
961 let (xform_self_ty, xform_ret_ty) =
962 self.xform_self_ty(&item, trait_ref.self_ty(), trait_substs);
968 import_ids: import_ids.clone(),
969 kind: TraitCandidate(trait_ref),
978 fn candidate_method_names(&self) -> Vec<ast::Ident> {
979 let mut set = FxHashSet::default();
980 let mut names: Vec<_> = self
983 .chain(&self.extension_candidates)
984 .filter(|candidate| {
985 if let Some(return_ty) = self.return_type {
986 self.matches_return_type(&candidate.item, None, return_ty)
991 .map(|candidate| candidate.item.ident)
992 .filter(|&name| set.insert(name))
995 // Sort them by the name so we have a stable result.
996 names.sort_by_cached_key(|n| n.as_str());
1000 ///////////////////////////////////////////////////////////////////////////
1001 // THE ACTUAL SEARCH
1003 fn pick(mut self) -> PickResult<'tcx> {
1004 assert!(self.method_name.is_some());
1006 if let Some(r) = self.pick_core() {
1010 debug!("pick: actual search failed, assemble diagnostics");
1012 let static_candidates = mem::take(&mut self.static_candidates);
1013 let private_candidate = self.private_candidate.take();
1014 let unsatisfied_predicates = mem::take(&mut self.unsatisfied_predicates);
1016 // things failed, so lets look at all traits, for diagnostic purposes now:
1019 let span = self.span;
1022 self.assemble_extension_candidates_for_all_traits()?;
1024 let out_of_scope_traits = match self.pick_core() {
1025 Some(Ok(p)) => vec![p.item.container.id()],
1026 //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(),
1027 Some(Err(MethodError::Ambiguity(v))) => v
1029 .map(|source| match source {
1030 TraitSource(id) => id,
1031 ImplSource(impl_id) => match tcx.trait_id_of_impl(impl_id) {
1033 None => span_bug!(span, "found inherent method when looking at traits"),
1037 Some(Err(MethodError::NoMatch(NoMatchData {
1038 out_of_scope_traits: others, ..
1040 assert!(others.is_empty());
1046 if let Some((kind, def_id)) = private_candidate {
1047 return Err(MethodError::PrivateMatch(kind, def_id, out_of_scope_traits));
1049 let lev_candidate = self.probe_for_lev_candidate()?;
1051 Err(MethodError::NoMatch(NoMatchData::new(
1053 unsatisfied_predicates,
1054 out_of_scope_traits,
1060 fn pick_core(&mut self) -> Option<PickResult<'tcx>> {
1061 let steps = self.steps.clone();
1063 // find the first step that works
1067 debug!("pick_core: step={:?}", step);
1068 // skip types that are from a type error or that would require dereferencing
1070 !step.self_ty.references_error() && !step.from_unsafe_deref
1073 let InferOk { value: self_ty, obligations: _ } = self
1075 .probe_instantiate_query_response(
1077 &self.orig_steps_var_values,
1080 .unwrap_or_else(|_| {
1081 span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty)
1083 self.pick_by_value_method(step, self_ty).or_else(|| {
1084 self.pick_autorefd_method(step, self_ty, hir::Mutability::Not)
1085 .or_else(|| self.pick_autorefd_method(step, self_ty, hir::Mutability::Mut))
1091 fn pick_by_value_method(
1093 step: &CandidateStep<'tcx>,
1095 ) -> Option<PickResult<'tcx>> {
1096 //! For each type `T` in the step list, this attempts to find a
1097 //! method where the (transformed) self type is exactly `T`. We
1098 //! do however do one transformation on the adjustment: if we
1099 //! are passing a region pointer in, we will potentially
1100 //! *reborrow* it to a shorter lifetime. This allows us to
1101 //! transparently pass `&mut` pointers, in particular, without
1102 //! consuming them for their entire lifetime.
1108 self.pick_method(self_ty).map(|r| {
1110 pick.autoderefs = step.autoderefs;
1112 // Insert a `&*` or `&mut *` if this is a reference type:
1113 if let ty::Ref(_, _, mutbl) = step.self_ty.value.value.kind {
1114 pick.autoderefs += 1;
1115 pick.autoref = Some(mutbl);
1123 fn pick_autorefd_method(
1125 step: &CandidateStep<'tcx>,
1127 mutbl: hir::Mutability,
1128 ) -> Option<PickResult<'tcx>> {
1131 // In general, during probing we erase regions. See
1132 // `impl_self_ty()` for an explanation.
1133 let region = tcx.lifetimes.re_erased;
1135 let autoref_ty = tcx.mk_ref(region, ty::TypeAndMut { ty: self_ty, mutbl });
1136 self.pick_method(autoref_ty).map(|r| {
1138 pick.autoderefs = step.autoderefs;
1139 pick.autoref = Some(mutbl);
1140 pick.unsize = step.unsize.then_some(self_ty);
1146 fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> {
1147 debug!("pick_method(self_ty={})", self.ty_to_string(self_ty));
1149 let mut possibly_unsatisfied_predicates = Vec::new();
1150 let mut unstable_candidates = Vec::new();
1152 for (kind, candidates) in
1153 &[("inherent", &self.inherent_candidates), ("extension", &self.extension_candidates)]
1155 debug!("searching {} candidates", kind);
1156 let res = self.consider_candidates(
1159 &mut possibly_unsatisfied_predicates,
1160 Some(&mut unstable_candidates),
1162 if let Some(pick) = res {
1163 if !self.is_suggestion.0 && !unstable_candidates.is_empty() {
1164 if let Ok(p) = &pick {
1165 // Emit a lint if there are unstable candidates alongside the stable ones.
1167 // We suppress warning if we're picking the method only because it is a
1169 self.emit_unstable_name_collision_hint(p, &unstable_candidates);
1176 debug!("searching unstable candidates");
1177 let res = self.consider_candidates(
1179 unstable_candidates.into_iter().map(|(c, _)| c),
1180 &mut possibly_unsatisfied_predicates,
1184 self.unsatisfied_predicates.extend(possibly_unsatisfied_predicates);
1189 fn consider_candidates<'b, ProbesIter>(
1193 possibly_unsatisfied_predicates: &mut Vec<(
1194 ty::Predicate<'tcx>,
1195 Option<ty::Predicate<'tcx>>,
1197 unstable_candidates: Option<&mut Vec<(&'b Candidate<'tcx>, Symbol)>>,
1198 ) -> Option<PickResult<'tcx>>
1200 ProbesIter: Iterator<Item = &'b Candidate<'tcx>> + Clone,
1202 let mut applicable_candidates: Vec<_> = probes
1205 (probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
1207 .filter(|&(_, status)| status != ProbeResult::NoMatch)
1210 debug!("applicable_candidates: {:?}", applicable_candidates);
1212 if applicable_candidates.len() > 1 {
1213 if let Some(pick) = self.collapse_candidates_to_trait_pick(&applicable_candidates[..]) {
1214 return Some(Ok(pick));
1218 if let Some(uc) = unstable_candidates {
1219 applicable_candidates.retain(|&(p, _)| {
1220 if let stability::EvalResult::Deny { feature, .. } =
1221 self.tcx.eval_stability(p.item.def_id, None, self.span)
1223 uc.push((p, feature));
1230 if applicable_candidates.len() > 1 {
1231 let sources = probes.map(|p| self.candidate_source(p, self_ty)).collect();
1232 return Some(Err(MethodError::Ambiguity(sources)));
1235 applicable_candidates.pop().map(|(probe, status)| {
1236 if status == ProbeResult::Match {
1237 Ok(probe.to_unadjusted_pick())
1239 Err(MethodError::BadReturnType)
1244 fn emit_unstable_name_collision_hint(
1246 stable_pick: &Pick<'_>,
1247 unstable_candidates: &[(&Candidate<'tcx>, Symbol)],
1249 self.tcx.struct_span_lint_hir(
1250 lint::builtin::UNSTABLE_NAME_COLLISIONS,
1254 let mut diag = lint.build(
1255 "a method with this name may be added to the standard library in the future",
1257 // FIXME: This should be a `span_suggestion` instead of `help`
1258 // However `self.span` only
1259 // highlights the method name, so we can't use it. Also consider reusing the code from
1260 // `report_method_error()`.
1262 "call with fully qualified syntax `{}(...)` to keep using the current method",
1263 self.tcx.def_path_str(stable_pick.item.def_id),
1266 if nightly_options::is_nightly_build() {
1267 for (candidate, feature) in unstable_candidates {
1269 "add `#![feature({})]` to the crate attributes to enable `{}`",
1271 self.tcx.def_path_str(candidate.item.def_id),
1281 fn select_trait_candidate(
1283 trait_ref: ty::TraitRef<'tcx>,
1284 ) -> traits::SelectionResult<'tcx, traits::Selection<'tcx>> {
1285 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1286 let predicate = trait_ref.to_poly_trait_ref().to_poly_trait_predicate();
1287 let obligation = traits::Obligation::new(cause, self.param_env, predicate);
1288 traits::SelectionContext::new(self).select(&obligation)
1291 fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>) -> CandidateSource {
1292 match candidate.kind {
1293 InherentImplCandidate(..) => ImplSource(candidate.item.container.id()),
1294 ObjectCandidate | WhereClauseCandidate(_) => TraitSource(candidate.item.container.id()),
1295 TraitCandidate(trait_ref) => self.probe(|_| {
1297 .at(&ObligationCause::dummy(), self.param_env)
1298 .sup(candidate.xform_self_ty, self_ty);
1299 match self.select_trait_candidate(trait_ref) {
1300 Ok(Some(traits::Vtable::VtableImpl(ref impl_data))) => {
1301 // If only a single impl matches, make the error message point
1303 ImplSource(impl_data.impl_def_id)
1305 _ => TraitSource(candidate.item.container.id()),
1314 probe: &Candidate<'tcx>,
1315 possibly_unsatisfied_predicates: &mut Vec<(
1316 ty::Predicate<'tcx>,
1317 Option<ty::Predicate<'tcx>>,
1320 debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
1323 // First check that the self type can be related.
1324 let sub_obligations = match self
1325 .at(&ObligationCause::dummy(), self.param_env)
1326 .sup(probe.xform_self_ty, self_ty)
1328 Ok(InferOk { obligations, value: () }) => obligations,
1330 debug!("--> cannot relate self-types");
1331 return ProbeResult::NoMatch;
1335 let mut result = ProbeResult::Match;
1336 let selcx = &mut traits::SelectionContext::new(self);
1337 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1339 // If so, impls may carry other conditions (e.g., where
1340 // clauses) that must be considered. Make sure that those
1341 // match as well (or at least may match, sometimes we
1342 // don't have enough information to fully evaluate).
1343 let candidate_obligations: Vec<_> = match probe.kind {
1344 InherentImplCandidate(ref substs, ref ref_obligations) => {
1345 // Check whether the impl imposes obligations we have to worry about.
1346 let impl_def_id = probe.item.container.id();
1347 let impl_bounds = self.tcx.predicates_of(impl_def_id);
1348 let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
1349 let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
1350 traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
1352 // Convert the bounds into obligations.
1353 let impl_obligations =
1354 traits::predicates_for_generics(cause, self.param_env, &impl_bounds);
1356 debug!("impl_obligations={:?}", impl_obligations);
1359 .chain(norm_obligations.into_iter())
1360 .chain(ref_obligations.iter().cloned())
1364 ObjectCandidate | WhereClauseCandidate(..) => {
1365 // These have no additional conditions to check.
1369 TraitCandidate(trait_ref) => {
1370 let predicate = trait_ref.without_const().to_predicate();
1371 let obligation = traits::Obligation::new(cause, self.param_env, predicate);
1372 if !self.predicate_may_hold(&obligation) {
1373 result = ProbeResult::NoMatch;
1375 match self.select_trait_candidate(trait_ref) {
1376 Err(_) => return true,
1378 if !vtable.borrow_nested_obligations().is_empty() =>
1380 for obligation in vtable.borrow_nested_obligations() {
1381 // Determine exactly which obligation wasn't met, so
1382 // that we can give more context in the error.
1383 if !self.predicate_may_hold(&obligation) {
1384 let o = self.resolve_vars_if_possible(obligation);
1386 self.resolve_vars_if_possible(&predicate);
1387 let p = if predicate == o.predicate {
1388 // Avoid "`MyStruct: Foo` which is required by
1389 // `MyStruct: Foo`" in E0599.
1394 possibly_unsatisfied_predicates.push((o.predicate, p));
1399 // Some nested subobligation of this predicate
1401 let predicate = self.resolve_vars_if_possible(&predicate);
1402 possibly_unsatisfied_predicates.push((predicate, None));
1407 // This candidate's primary obligation doesn't even
1408 // select - don't bother registering anything in
1409 // `potentially_unsatisfied_predicates`.
1410 return ProbeResult::NoMatch;
1418 "consider_probe - candidate_obligations={:?} sub_obligations={:?}",
1419 candidate_obligations, sub_obligations
1422 // Evaluate those obligations to see if they might possibly hold.
1423 for o in candidate_obligations.into_iter().chain(sub_obligations) {
1424 let o = self.resolve_vars_if_possible(&o);
1425 if !self.predicate_may_hold(&o) {
1426 result = ProbeResult::NoMatch;
1427 possibly_unsatisfied_predicates.push((o.predicate, None));
1431 if let ProbeResult::Match = result {
1432 if let (Some(return_ty), Some(xform_ret_ty)) =
1433 (self.return_type, probe.xform_ret_ty)
1435 let xform_ret_ty = self.resolve_vars_if_possible(&xform_ret_ty);
1437 "comparing return_ty {:?} with xform ret ty {:?}",
1438 return_ty, probe.xform_ret_ty
1441 .at(&ObligationCause::dummy(), self.param_env)
1442 .sup(return_ty, xform_ret_ty)
1445 return ProbeResult::BadReturnType;
1454 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1455 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1456 /// external interface of the method can be determined from the trait, it's ok not to decide.
1457 /// We can basically just collapse all of the probes for various impls into one where-clause
1458 /// probe. This will result in a pending obligation so when more type-info is available we can
1459 /// make the final decision.
1461 /// Example (`src/test/ui/method-two-trait-defer-resolution-1.rs`):
1464 /// trait Foo { ... }
1465 /// impl Foo for Vec<int> { ... }
1466 /// impl Foo for Vec<usize> { ... }
1469 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1470 /// use, so it's ok to just commit to "using the method from the trait Foo".
1471 fn collapse_candidates_to_trait_pick(
1473 probes: &[(&Candidate<'tcx>, ProbeResult)],
1474 ) -> Option<Pick<'tcx>> {
1475 // Do all probes correspond to the same trait?
1476 let container = probes[0].0.item.container;
1477 if let ty::ImplContainer(_) = container {
1480 if probes[1..].iter().any(|&(p, _)| p.item.container != container) {
1484 // FIXME: check the return type here somehow.
1485 // If so, just use this trait and call it a day.
1487 item: probes[0].0.item,
1489 import_ids: probes[0].0.import_ids.clone(),
1496 /// Similarly to `probe_for_return_type`, this method attempts to find the best matching
1497 /// candidate method where the method name may have been misspelt. Similarly to other
1498 /// Levenshtein based suggestions, we provide at most one such suggestion.
1499 fn probe_for_lev_candidate(&mut self) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> {
1500 debug!("probing for method names similar to {:?}", self.method_name);
1502 let steps = self.steps.clone();
1504 let mut pcx = ProbeContext::new(
1510 self.orig_steps_var_values.clone(),
1514 pcx.allow_similar_names = true;
1515 pcx.assemble_inherent_candidates();
1516 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)?;
1518 let method_names = pcx.candidate_method_names();
1519 pcx.allow_similar_names = false;
1520 let applicable_close_candidates: Vec<ty::AssocItem> = method_names
1522 .filter_map(|&method_name| {
1524 pcx.method_name = Some(method_name);
1525 pcx.assemble_inherent_candidates();
1526 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)
1528 pcx.pick_core().and_then(|pick| pick.ok()).map(|pick| pick.item)
1533 if applicable_close_candidates.is_empty() {
1537 let names = applicable_close_candidates.iter().map(|cand| &cand.ident.name);
1538 find_best_match_for_name(names, &self.method_name.unwrap().as_str(), None)
1541 Ok(applicable_close_candidates
1543 .find(|method| method.ident.name == best_name))
1548 ///////////////////////////////////////////////////////////////////////////
1550 fn has_applicable_self(&self, item: &ty::AssocItem) -> bool {
1551 // "Fast track" -- check for usage of sugar when in method call
1554 // In Path mode (i.e., resolving a value like `T::next`), consider any
1555 // associated value (i.e., methods, constants) but not types.
1557 Mode::MethodCall => item.method_has_self_argument,
1558 Mode::Path => match item.kind {
1559 ty::AssocKind::OpaqueTy | ty::AssocKind::Type => false,
1560 ty::AssocKind::Method | ty::AssocKind::Const => true,
1563 // FIXME -- check for types that deref to `Self`,
1564 // like `Rc<Self>` and so on.
1566 // Note also that the current code will break if this type
1567 // includes any of the type parameters defined on the method
1568 // -- but this could be overcome.
1571 fn record_static_candidate(&mut self, source: CandidateSource) {
1572 self.static_candidates.push(source);
1577 item: &ty::AssocItem,
1579 substs: SubstsRef<'tcx>,
1580 ) -> (Ty<'tcx>, Option<Ty<'tcx>>) {
1581 if item.kind == ty::AssocKind::Method && self.mode == Mode::MethodCall {
1582 let sig = self.xform_method_sig(item.def_id, substs);
1583 (sig.inputs()[0], Some(sig.output()))
1589 fn xform_method_sig(&self, method: DefId, substs: SubstsRef<'tcx>) -> ty::FnSig<'tcx> {
1590 let fn_sig = self.tcx.fn_sig(method);
1591 debug!("xform_self_ty(fn_sig={:?}, substs={:?})", fn_sig, substs);
1593 assert!(!substs.has_escaping_bound_vars());
1595 // It is possible for type parameters or early-bound lifetimes
1596 // to appear in the signature of `self`. The substitutions we
1597 // are given do not include type/lifetime parameters for the
1598 // method yet. So create fresh variables here for those too,
1599 // if there are any.
1600 let generics = self.tcx.generics_of(method);
1601 assert_eq!(substs.len(), generics.parent_count as usize);
1603 // Erase any late-bound regions from the method and substitute
1604 // in the values from the substitution.
1605 let xform_fn_sig = self.erase_late_bound_regions(&fn_sig);
1607 if generics.params.is_empty() {
1608 xform_fn_sig.subst(self.tcx, substs)
1610 let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
1611 let i = param.index as usize;
1612 if i < substs.len() {
1616 GenericParamDefKind::Lifetime => {
1617 // In general, during probe we erase regions. See
1618 // `impl_self_ty()` for an explanation.
1619 self.tcx.lifetimes.re_erased.into()
1621 GenericParamDefKind::Type { .. } | GenericParamDefKind::Const => {
1622 self.var_for_def(self.span, param)
1627 xform_fn_sig.subst(self.tcx, substs)
1631 /// Gets the type of an impl and generate substitutions with placeholders.
1632 fn impl_ty_and_substs(&self, impl_def_id: DefId) -> (Ty<'tcx>, SubstsRef<'tcx>) {
1633 (self.tcx.type_of(impl_def_id), self.fresh_item_substs(impl_def_id))
1636 fn fresh_item_substs(&self, def_id: DefId) -> SubstsRef<'tcx> {
1637 InternalSubsts::for_item(self.tcx, def_id, |param, _| match param.kind {
1638 GenericParamDefKind::Lifetime => self.tcx.lifetimes.re_erased.into(),
1639 GenericParamDefKind::Type { .. } => self
1640 .next_ty_var(TypeVariableOrigin {
1641 kind: TypeVariableOriginKind::SubstitutionPlaceholder,
1642 span: self.tcx.def_span(def_id),
1645 GenericParamDefKind::Const { .. } => {
1646 let span = self.tcx.def_span(def_id);
1647 let origin = ConstVariableOrigin {
1648 kind: ConstVariableOriginKind::SubstitutionPlaceholder,
1651 self.next_const_var(self.tcx.type_of(param.def_id), origin).into()
1656 /// Replaces late-bound-regions bound by `value` with `'static` using
1657 /// `ty::erase_late_bound_regions`.
1659 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1660 /// method matching. It is reasonable during the probe phase because we don't consider region
1661 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1662 /// rather than creating fresh region variables. This is nice for two reasons:
1664 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1665 /// particular method call, it winds up creating fewer types overall, which helps for memory
1666 /// usage. (Admittedly, this is a rather small effect, though measurable.)
1668 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1669 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1670 /// regions with actual region variables as is proper, we'd have to ensure that the same
1671 /// region got replaced with the same variable, which requires a bit more coordination
1672 /// and/or tracking the substitution and
1674 fn erase_late_bound_regions<T>(&self, value: &ty::Binder<T>) -> T
1676 T: TypeFoldable<'tcx>,
1678 self.tcx.erase_late_bound_regions(value)
1681 /// Finds the method with the appropriate name (or return type, as the case may be). If
1682 /// `allow_similar_names` is set, find methods with close-matching names.
1683 fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssocItem> {
1684 if let Some(name) = self.method_name {
1685 if self.allow_similar_names {
1686 let max_dist = max(name.as_str().len(), 3) / 3;
1688 .associated_items(def_id)
1689 .in_definition_order()
1691 let dist = lev_distance(&*name.as_str(), &x.ident.as_str());
1692 x.kind.namespace() == Namespace::ValueNS && dist > 0 && dist <= max_dist
1698 .associated_item(def_id, name, Namespace::ValueNS)
1699 .map_or(Vec::new(), |x| vec![x])
1702 self.tcx.associated_items(def_id).in_definition_order().copied().collect()
1707 impl<'tcx> Candidate<'tcx> {
1708 fn to_unadjusted_pick(&self) -> Pick<'tcx> {
1711 kind: match self.kind {
1712 InherentImplCandidate(..) => InherentImplPick,
1713 ObjectCandidate => ObjectPick,
1714 TraitCandidate(_) => TraitPick,
1715 WhereClauseCandidate(ref trait_ref) => {
1716 // Only trait derived from where-clauses should
1717 // appear here, so they should not contain any
1718 // inference variables or other artifacts. This
1719 // means they are safe to put into the
1720 // `WhereClausePick`.
1722 !trait_ref.skip_binder().substs.needs_infer()
1723 && !trait_ref.skip_binder().substs.has_placeholders()
1726 WhereClausePick(*trait_ref)
1729 import_ids: self.import_ids.clone(),