1 use super::MethodError;
2 use super::NoMatchData;
3 use super::{CandidateSource, ImplSource, TraitSource};
6 use crate::check::autoderef::{self, Autoderef};
7 use crate::check::FnCtxt;
8 use crate::hir::def_id::DefId;
9 use crate::hir::def::DefKind;
10 use crate::namespace::Namespace;
12 use rustc_data_structures::sync::Lrc;
15 use rustc::session::config::nightly_options;
16 use rustc::ty::subst::{Subst, InternalSubsts, SubstsRef};
17 use rustc::traits::{self, ObligationCause};
18 use rustc::traits::query::{CanonicalTyGoal};
19 use rustc::traits::query::method_autoderef::{CandidateStep, MethodAutoderefStepsResult};
20 use rustc::traits::query::method_autoderef::{MethodAutoderefBadTy};
21 use rustc::ty::{self, ParamEnvAnd, Ty, TyCtxt, ToPolyTraitRef, ToPredicate, TraitRef, TypeFoldable};
22 use rustc::ty::GenericParamDefKind;
23 use rustc::infer::type_variable::TypeVariableOrigin;
24 use rustc::infer::unify_key::ConstVariableOrigin;
25 use rustc::util::nodemap::FxHashSet;
26 use rustc::infer::{self, InferOk};
27 use rustc::infer::canonical::{Canonical, QueryResponse};
28 use rustc::infer::canonical::{OriginalQueryValues};
29 use rustc::middle::stability;
31 use syntax::util::lev_distance::{lev_distance, find_best_match_for_name};
32 use syntax_pos::{DUMMY_SP, Span, symbol::Symbol};
38 use smallvec::{smallvec, SmallVec};
40 use self::CandidateKind::*;
41 pub use self::PickKind::*;
43 /// Boolean flag used to indicate if this search is for a suggestion
44 /// or not. If true, we can allow ambiguity and so forth.
45 #[derive(Clone, Copy)]
46 pub struct IsSuggestion(pub bool);
48 struct ProbeContext<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
49 fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
52 method_name: Option<ast::Ident>,
53 return_type: Option<Ty<'tcx>>,
55 /// This is the OriginalQueryValues for the steps queries
56 /// that are answered in steps.
57 orig_steps_var_values: OriginalQueryValues<'tcx>,
58 steps: Lrc<Vec<CandidateStep<'gcx>>>,
60 inherent_candidates: Vec<Candidate<'tcx>>,
61 extension_candidates: Vec<Candidate<'tcx>>,
62 impl_dups: FxHashSet<DefId>,
64 /// Collects near misses when the candidate functions are missing a `self` keyword and is only
65 /// used for error reporting
66 static_candidates: Vec<CandidateSource>,
68 /// When probing for names, include names that are close to the
69 /// requested name (by Levensthein distance)
70 allow_similar_names: bool,
72 /// Some(candidate) if there is a private candidate
73 private_candidate: Option<(DefKind, DefId)>,
75 /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
76 /// for error reporting
77 unsatisfied_predicates: Vec<TraitRef<'tcx>>,
79 is_suggestion: IsSuggestion,
82 impl<'a, 'gcx, 'tcx> Deref for ProbeContext<'a, 'gcx, 'tcx> {
83 type Target = FnCtxt<'a, 'gcx, 'tcx>;
84 fn deref(&self) -> &Self::Target {
90 struct Candidate<'tcx> {
91 // Candidates are (I'm not quite sure, but they are mostly) basically
92 // some metadata on top of a `ty::AssocItem` (without substs).
94 // However, method probing wants to be able to evaluate the predicates
95 // for a function with the substs applied - for example, if a function
96 // has `where Self: Sized`, we don't want to consider it unless `Self`
97 // is actually `Sized`, and similarly, return-type suggestions want
98 // to consider the "actual" return type.
100 // The way this is handled is through `xform_self_ty`. It contains
101 // the receiver type of this candidate, but `xform_self_ty`,
102 // `xform_ret_ty` and `kind` (which contains the predicates) have the
103 // generic parameters of this candidate substituted with the *same set*
104 // of inference variables, which acts as some weird sort of "query".
106 // When we check out a candidate, we require `xform_self_ty` to be
107 // a subtype of the passed-in self-type, and this equates the type
108 // variables in the rest of the fields.
110 // For example, if we have this candidate:
113 // fn foo(&self) where Self: Sized;
117 // Then `xform_self_ty` will be `&'erased ?X` and `kind` will contain
118 // the predicate `?X: Sized`, so if we are evaluating `Foo` for a
119 // the receiver `&T`, we'll do the subtyping which will make `?X`
120 // get the right value, then when we evaluate the predicate we'll check
122 xform_self_ty: Ty<'tcx>,
123 xform_ret_ty: Option<Ty<'tcx>>,
125 kind: CandidateKind<'tcx>,
126 import_ids: SmallVec<[hir::HirId; 1]>,
130 enum CandidateKind<'tcx> {
131 InherentImplCandidate(SubstsRef<'tcx>,
132 // Normalize obligations
133 Vec<traits::PredicateObligation<'tcx>>),
135 TraitCandidate(ty::TraitRef<'tcx>),
136 WhereClauseCandidate(// Trait
137 ty::PolyTraitRef<'tcx>),
140 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
147 #[derive(Debug, PartialEq, Clone)]
148 pub struct Pick<'tcx> {
149 pub item: ty::AssocItem,
150 pub kind: PickKind<'tcx>,
151 pub import_ids: SmallVec<[hir::HirId; 1]>,
153 // Indicates that the source expression should be autoderef'd N times
155 // A = expr | *expr | **expr | ...
156 pub autoderefs: usize,
158 // Indicates that an autoref is applied after the optional autoderefs
160 // B = A | &A | &mut A
161 pub autoref: Option<hir::Mutability>,
163 // Indicates that the source expression should be "unsized" to a
164 // target type. This should probably eventually go away in favor
165 // of just coercing method receivers.
168 pub unsize: Option<Ty<'tcx>>,
171 #[derive(Clone, Debug, PartialEq, Eq)]
172 pub enum PickKind<'tcx> {
176 WhereClausePick(// Trait
177 ty::PolyTraitRef<'tcx>),
180 pub type PickResult<'tcx> = Result<Pick<'tcx>, MethodError<'tcx>>;
182 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
184 // An expression of the form `receiver.method_name(...)`.
185 // Autoderefs are performed on `receiver`, lookup is done based on the
186 // `self` argument of the method, and static methods aren't considered.
188 // An expression of the form `Type::item` or `<T>::item`.
189 // No autoderefs are performed, lookup is done based on the type each
190 // implementation is for, and static methods are included.
194 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
195 pub enum ProbeScope {
196 // Assemble candidates coming only from traits in scope.
199 // Assemble candidates coming from all traits.
203 impl<'a, 'gcx, 'tcx> FnCtxt<'a, 'gcx, 'tcx> {
204 /// This is used to offer suggestions to users. It returns methods
205 /// that could have been called which have the desired return
206 /// type. Some effort is made to rule out methods that, if called,
207 /// would result in an error (basically, the same criteria we
208 /// would use to decide if a method is a plausible fit for
209 /// ambiguity purposes).
210 pub fn probe_for_return_type(&self,
213 return_type: Ty<'tcx>,
215 scope_expr_id: hir::HirId)
216 -> Vec<ty::AssocItem> {
217 debug!("probe(self_ty={:?}, return_type={}, scope_expr_id={})",
222 self.probe_op(span, mode, None, Some(return_type), IsSuggestion(true),
223 self_ty, scope_expr_id, ProbeScope::AllTraits,
224 |probe_cx| Ok(probe_cx.candidate_method_names()))
228 .flat_map(|&method_name| {
230 span, mode, Some(method_name), Some(return_type),
231 IsSuggestion(true), self_ty, scope_expr_id,
232 ProbeScope::AllTraits, |probe_cx| probe_cx.pick()
233 ).ok().map(|pick| pick.item)
238 pub fn probe_for_name(&self,
241 item_name: ast::Ident,
242 is_suggestion: IsSuggestion,
244 scope_expr_id: hir::HirId,
246 -> PickResult<'tcx> {
247 debug!("probe(self_ty={:?}, item_name={}, scope_expr_id={})",
259 |probe_cx| probe_cx.pick())
262 fn probe_op<OP,R>(&'a self,
265 method_name: Option<ast::Ident>,
266 return_type: Option<Ty<'tcx>>,
267 is_suggestion: IsSuggestion,
269 scope_expr_id: hir::HirId,
272 -> Result<R, MethodError<'tcx>>
273 where OP: FnOnce(ProbeContext<'a, 'gcx, 'tcx>) -> Result<R, MethodError<'tcx>>
275 let mut orig_values = OriginalQueryValues::default();
276 let param_env_and_self_ty =
277 self.infcx.canonicalize_query(
279 param_env: self.param_env,
281 }, &mut orig_values);
283 let steps = if mode == Mode::MethodCall {
284 self.tcx.method_autoderef_steps(param_env_and_self_ty)
286 self.infcx.probe(|_| {
287 // Mode::Path - the deref steps is "trivial". This turns
288 // our CanonicalQuery into a "trivial" QueryResponse. This
289 // is a bit inefficient, but I don't think that writing
290 // special handling for this "trivial case" is a good idea.
292 let infcx = &self.infcx;
296 }, canonical_inference_vars) =
297 infcx.instantiate_canonical_with_fresh_inference_vars(
298 span, ¶m_env_and_self_ty);
299 debug!("probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}",
300 param_env_and_self_ty, self_ty);
301 MethodAutoderefStepsResult {
302 steps: Lrc::new(vec![CandidateStep {
303 self_ty: self.make_query_response_ignoring_pending_obligations(
304 canonical_inference_vars, self_ty),
306 from_unsafe_deref: false,
310 reached_recursion_limit: false
315 // If our autoderef loop had reached the recursion limit,
316 // report an overflow error, but continue going on with
317 // the truncated autoderef list.
318 if steps.reached_recursion_limit {
320 let ty = &steps.steps.last().unwrap_or_else(|| {
321 span_bug!(span, "reached the recursion limit in 0 steps?")
323 let ty = self.probe_instantiate_query_response(span, &orig_values, ty)
324 .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
325 autoderef::report_autoderef_recursion_limit_error(self.tcx, span,
331 // If we encountered an `_` type or an error type during autoderef, this is
333 if let Some(bad_ty) = &steps.opt_bad_ty {
335 // Ambiguity was encountered during a suggestion. Just keep going.
336 debug!("ProbeContext: encountered ambiguity in suggestion");
337 } else if bad_ty.reached_raw_pointer && !self.tcx.features().arbitrary_self_types {
338 // this case used to be allowed by the compiler,
339 // so we do a future-compat lint here for the 2015 edition
340 // (see https://github.com/rust-lang/rust/issues/46906)
341 if self.tcx.sess.rust_2018() {
342 span_err!(self.tcx.sess, span, E0699,
343 "the type of this value must be known \
344 to call a method on a raw pointer on it");
347 lint::builtin::TYVAR_BEHIND_RAW_POINTER,
350 "type annotations needed");
353 // Encountered a real ambiguity, so abort the lookup. If `ty` is not
354 // an `Err`, report the right "type annotations needed" error pointing
357 let ty = self.probe_instantiate_query_response(span, &orig_values, ty)
358 .unwrap_or_else(|_| span_bug!(span, "instantiating {:?} failed?", ty));
359 let ty = self.structurally_resolved_type(span, ty.value);
360 assert_eq!(ty, self.tcx.types.err);
361 return Err(MethodError::NoMatch(NoMatchData::new(Vec::new(),
369 debug!("ProbeContext: steps for self_ty={:?} are {:?}",
374 // this creates one big transaction so that all type variables etc
375 // that we create during the probe process are removed later
377 let mut probe_cx = ProbeContext::new(
378 self, span, mode, method_name, return_type, orig_values,
379 steps.steps, is_suggestion,
382 probe_cx.assemble_inherent_candidates();
384 ProbeScope::TraitsInScope =>
385 probe_cx.assemble_extension_candidates_for_traits_in_scope(scope_expr_id)?,
386 ProbeScope::AllTraits =>
387 probe_cx.assemble_extension_candidates_for_all_traits()?,
394 pub fn provide(providers: &mut ty::query::Providers<'_>) {
395 providers.method_autoderef_steps = method_autoderef_steps;
398 fn method_autoderef_steps<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'gcx>,
399 goal: CanonicalTyGoal<'tcx>)
400 -> MethodAutoderefStepsResult<'gcx>
402 debug!("method_autoderef_steps({:?})", goal);
404 tcx.infer_ctxt().enter_with_canonical(DUMMY_SP, &goal, |ref infcx, goal, inference_vars| {
405 let ParamEnvAnd { param_env, value: self_ty } = goal;
407 let mut autoderef = Autoderef::new(infcx, param_env, hir::DUMMY_HIR_ID, DUMMY_SP, self_ty)
408 .include_raw_pointers()
410 let mut reached_raw_pointer = false;
411 let mut steps: Vec<_> = autoderef.by_ref()
413 let step = CandidateStep {
414 self_ty: infcx.make_query_response_ignoring_pending_obligations(
415 inference_vars.clone(), ty),
417 from_unsafe_deref: reached_raw_pointer,
420 if let ty::RawPtr(_) = ty.sty {
421 // all the subsequent steps will be from_unsafe_deref
422 reached_raw_pointer = true;
428 let final_ty = autoderef.maybe_ambiguous_final_ty();
429 let opt_bad_ty = match final_ty.sty {
430 ty::Infer(ty::TyVar(_)) |
432 Some(MethodAutoderefBadTy {
434 ty: infcx.make_query_response_ignoring_pending_obligations(
435 inference_vars, final_ty)
438 ty::Array(elem_ty, _) => {
439 let dereferences = steps.len() - 1;
441 steps.push(CandidateStep {
442 self_ty: infcx.make_query_response_ignoring_pending_obligations(
443 inference_vars, infcx.tcx.mk_slice(elem_ty)),
444 autoderefs: dereferences,
445 // this could be from an unsafe deref if we had
446 // a *mut/const [T; N]
447 from_unsafe_deref: reached_raw_pointer,
456 debug!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps, opt_bad_ty);
458 MethodAutoderefStepsResult {
459 steps: Lrc::new(steps),
460 opt_bad_ty: opt_bad_ty.map(Lrc::new),
461 reached_recursion_limit: autoderef.reached_recursion_limit()
467 impl<'a, 'gcx, 'tcx> ProbeContext<'a, 'gcx, 'tcx> {
468 fn new(fcx: &'a FnCtxt<'a, 'gcx, 'tcx>,
471 method_name: Option<ast::Ident>,
472 return_type: Option<Ty<'tcx>>,
473 orig_steps_var_values: OriginalQueryValues<'tcx>,
474 steps: Lrc<Vec<CandidateStep<'gcx>>>,
475 is_suggestion: IsSuggestion)
476 -> ProbeContext<'a, 'gcx, 'tcx> {
483 inherent_candidates: Vec::new(),
484 extension_candidates: Vec::new(),
485 impl_dups: FxHashSet::default(),
486 orig_steps_var_values,
488 static_candidates: Vec::new(),
489 allow_similar_names: false,
490 private_candidate: None,
491 unsatisfied_predicates: Vec::new(),
496 fn reset(&mut self) {
497 self.inherent_candidates.clear();
498 self.extension_candidates.clear();
499 self.impl_dups.clear();
500 self.static_candidates.clear();
501 self.private_candidate = None;
504 ///////////////////////////////////////////////////////////////////////////
505 // CANDIDATE ASSEMBLY
507 fn push_candidate(&mut self,
508 candidate: Candidate<'tcx>,
511 let is_accessible = if let Some(name) = self.method_name {
512 let item = candidate.item;
513 let def_scope = self.tcx.adjust_ident(name, item.container.id(), self.body_id).1;
514 item.vis.is_accessible_from(def_scope, self.tcx)
520 self.inherent_candidates.push(candidate);
522 self.extension_candidates.push(candidate);
524 } else if self.private_candidate.is_none() {
525 self.private_candidate =
526 Some((candidate.item.def_kind(), candidate.item.def_id));
530 fn assemble_inherent_candidates(&mut self) {
531 let steps = self.steps.clone();
532 for step in steps.iter() {
533 self.assemble_probe(&step.self_ty);
537 fn assemble_probe(&mut self, self_ty: &Canonical<'gcx, QueryResponse<'gcx, Ty<'gcx>>>) {
538 debug!("assemble_probe: self_ty={:?}", self_ty);
539 let lang_items = self.tcx.lang_items();
541 match self_ty.value.value.sty {
542 ty::Dynamic(ref data, ..) => {
543 if let Some(p) = data.principal() {
544 // Subtle: we can't use `instantiate_query_response` here: using it will
545 // commit to all of the type equalities assumed by inference going through
546 // autoderef (see the `method-probe-no-guessing` test).
548 // However, in this code, it is OK if we end up with an object type that is
549 // "more general" than the object type that we are evaluating. For *every*
550 // object type `MY_OBJECT`, a function call that goes through a trait-ref
551 // of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid
552 // `ObjectCandidate`, and it should be discoverable "exactly" through one
553 // of the iterations in the autoderef loop, so there is no problem with it
554 // being discoverable in another one of these iterations.
556 // Using `instantiate_canonical_with_fresh_inference_vars` on our
557 // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
558 // `CanonicalVarValues` will exactly give us such a generalization - it
559 // will still match the original object type, but it won't pollute our
560 // type variables in any form, so just do that!
561 let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
562 self.fcx.instantiate_canonical_with_fresh_inference_vars(
563 self.span, &self_ty);
565 self.assemble_inherent_candidates_from_object(generalized_self_ty);
566 self.assemble_inherent_impl_candidates_for_type(p.def_id());
570 self.assemble_inherent_impl_candidates_for_type(def.did);
572 ty::Foreign(did) => {
573 self.assemble_inherent_impl_candidates_for_type(did);
576 self.assemble_inherent_candidates_from_param(p);
579 let lang_def_id = lang_items.char_impl();
580 self.assemble_inherent_impl_for_primitive(lang_def_id);
583 let lang_def_id = lang_items.str_impl();
584 self.assemble_inherent_impl_for_primitive(lang_def_id);
586 let lang_def_id = lang_items.str_alloc_impl();
587 self.assemble_inherent_impl_for_primitive(lang_def_id);
590 let lang_def_id = lang_items.slice_impl();
591 self.assemble_inherent_impl_for_primitive(lang_def_id);
593 let lang_def_id = lang_items.slice_u8_impl();
594 self.assemble_inherent_impl_for_primitive(lang_def_id);
596 let lang_def_id = lang_items.slice_alloc_impl();
597 self.assemble_inherent_impl_for_primitive(lang_def_id);
599 let lang_def_id = lang_items.slice_u8_alloc_impl();
600 self.assemble_inherent_impl_for_primitive(lang_def_id);
602 ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutImmutable }) => {
603 let lang_def_id = lang_items.const_ptr_impl();
604 self.assemble_inherent_impl_for_primitive(lang_def_id);
606 ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutMutable }) => {
607 let lang_def_id = lang_items.mut_ptr_impl();
608 self.assemble_inherent_impl_for_primitive(lang_def_id);
610 ty::Int(ast::IntTy::I8) => {
611 let lang_def_id = lang_items.i8_impl();
612 self.assemble_inherent_impl_for_primitive(lang_def_id);
614 ty::Int(ast::IntTy::I16) => {
615 let lang_def_id = lang_items.i16_impl();
616 self.assemble_inherent_impl_for_primitive(lang_def_id);
618 ty::Int(ast::IntTy::I32) => {
619 let lang_def_id = lang_items.i32_impl();
620 self.assemble_inherent_impl_for_primitive(lang_def_id);
622 ty::Int(ast::IntTy::I64) => {
623 let lang_def_id = lang_items.i64_impl();
624 self.assemble_inherent_impl_for_primitive(lang_def_id);
626 ty::Int(ast::IntTy::I128) => {
627 let lang_def_id = lang_items.i128_impl();
628 self.assemble_inherent_impl_for_primitive(lang_def_id);
630 ty::Int(ast::IntTy::Isize) => {
631 let lang_def_id = lang_items.isize_impl();
632 self.assemble_inherent_impl_for_primitive(lang_def_id);
634 ty::Uint(ast::UintTy::U8) => {
635 let lang_def_id = lang_items.u8_impl();
636 self.assemble_inherent_impl_for_primitive(lang_def_id);
638 ty::Uint(ast::UintTy::U16) => {
639 let lang_def_id = lang_items.u16_impl();
640 self.assemble_inherent_impl_for_primitive(lang_def_id);
642 ty::Uint(ast::UintTy::U32) => {
643 let lang_def_id = lang_items.u32_impl();
644 self.assemble_inherent_impl_for_primitive(lang_def_id);
646 ty::Uint(ast::UintTy::U64) => {
647 let lang_def_id = lang_items.u64_impl();
648 self.assemble_inherent_impl_for_primitive(lang_def_id);
650 ty::Uint(ast::UintTy::U128) => {
651 let lang_def_id = lang_items.u128_impl();
652 self.assemble_inherent_impl_for_primitive(lang_def_id);
654 ty::Uint(ast::UintTy::Usize) => {
655 let lang_def_id = lang_items.usize_impl();
656 self.assemble_inherent_impl_for_primitive(lang_def_id);
658 ty::Float(ast::FloatTy::F32) => {
659 let lang_def_id = lang_items.f32_impl();
660 self.assemble_inherent_impl_for_primitive(lang_def_id);
662 let lang_def_id = lang_items.f32_runtime_impl();
663 self.assemble_inherent_impl_for_primitive(lang_def_id);
665 ty::Float(ast::FloatTy::F64) => {
666 let lang_def_id = lang_items.f64_impl();
667 self.assemble_inherent_impl_for_primitive(lang_def_id);
669 let lang_def_id = lang_items.f64_runtime_impl();
670 self.assemble_inherent_impl_for_primitive(lang_def_id);
676 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id: Option<DefId>) {
677 if let Some(impl_def_id) = lang_def_id {
678 self.assemble_inherent_impl_probe(impl_def_id);
682 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
683 let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id);
684 for &impl_def_id in impl_def_ids.iter() {
685 self.assemble_inherent_impl_probe(impl_def_id);
689 fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) {
690 if !self.impl_dups.insert(impl_def_id) {
691 return; // already visited
694 debug!("assemble_inherent_impl_probe {:?}", impl_def_id);
696 for item in self.impl_or_trait_item(impl_def_id) {
697 if !self.has_applicable_self(&item) {
698 // No receiver declared. Not a candidate.
699 self.record_static_candidate(ImplSource(impl_def_id));
703 let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
704 let impl_ty = impl_ty.subst(self.tcx, impl_substs);
706 // Determine the receiver type that the method itself expects.
707 let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs);
709 // We can't use normalize_associated_types_in as it will pollute the
710 // fcx's fulfillment context after this probe is over.
711 let cause = traits::ObligationCause::misc(self.span, self.body_id);
712 let selcx = &mut traits::SelectionContext::new(self.fcx);
713 let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } =
714 traits::normalize(selcx, self.param_env, cause, &xform_tys);
715 debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}",
716 xform_self_ty, xform_ret_ty);
718 self.push_candidate(Candidate {
719 xform_self_ty, xform_ret_ty, item,
720 kind: InherentImplCandidate(impl_substs, obligations),
721 import_ids: smallvec![]
726 fn assemble_inherent_candidates_from_object(&mut self,
728 debug!("assemble_inherent_candidates_from_object(self_ty={:?})",
731 let principal = match self_ty.sty {
732 ty::Dynamic(ref data, ..) => Some(data),
734 }.and_then(|data| data.principal()).unwrap_or_else(|| {
735 span_bug!(self.span, "non-object {:?} in assemble_inherent_candidates_from_object",
739 // It is illegal to invoke a method on a trait instance that
740 // refers to the `Self` type. An error will be reported by
741 // `enforce_object_limitations()` if the method refers to the
742 // `Self` type anywhere other than the receiver. Here, we use
743 // a substitution that replaces `Self` with the object type
744 // itself. Hence, a `&self` method will wind up with an
745 // argument type like `&Trait`.
746 let trait_ref = principal.with_self_ty(self.tcx, self_ty);
747 self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| {
748 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
750 let (xform_self_ty, xform_ret_ty) =
751 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
752 this.push_candidate(Candidate {
753 xform_self_ty, xform_ret_ty, item,
754 kind: ObjectCandidate,
755 import_ids: smallvec![]
760 fn assemble_inherent_candidates_from_param(&mut self, param_ty: ty::ParamTy) {
761 // FIXME: do we want to commit to this behavior for param bounds?
763 let bounds = self.param_env
766 .filter_map(|predicate| {
768 ty::Predicate::Trait(ref trait_predicate) => {
769 match trait_predicate.skip_binder().trait_ref.self_ty().sty {
770 ty::Param(ref p) if *p == param_ty => {
771 Some(trait_predicate.to_poly_trait_ref())
776 ty::Predicate::Subtype(..) |
777 ty::Predicate::Projection(..) |
778 ty::Predicate::RegionOutlives(..) |
779 ty::Predicate::WellFormed(..) |
780 ty::Predicate::ObjectSafe(..) |
781 ty::Predicate::ClosureKind(..) |
782 ty::Predicate::TypeOutlives(..) |
783 ty::Predicate::ConstEvaluatable(..) => None,
787 self.elaborate_bounds(bounds, |this, poly_trait_ref, item| {
788 let trait_ref = this.erase_late_bound_regions(&poly_trait_ref);
790 let (xform_self_ty, xform_ret_ty) =
791 this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs);
793 // Because this trait derives from a where-clause, it
794 // should not contain any inference variables or other
795 // artifacts. This means it is safe to put into the
796 // `WhereClauseCandidate` and (eventually) into the
797 // `WhereClausePick`.
798 assert!(!trait_ref.substs.needs_infer());
800 this.push_candidate(Candidate {
801 xform_self_ty, xform_ret_ty, item,
802 kind: WhereClauseCandidate(poly_trait_ref),
803 import_ids: smallvec![]
808 // Do a search through a list of bounds, using a callback to actually
809 // create the candidates.
810 fn elaborate_bounds<F>(&mut self,
811 bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
813 where F: for<'b> FnMut(&mut ProbeContext<'b, 'gcx, 'tcx>,
814 ty::PolyTraitRef<'tcx>,
818 for bound_trait_ref in traits::transitive_bounds(tcx, bounds) {
819 debug!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref);
820 for item in self.impl_or_trait_item(bound_trait_ref.def_id()) {
821 if !self.has_applicable_self(&item) {
822 self.record_static_candidate(TraitSource(bound_trait_ref.def_id()));
824 mk_cand(self, bound_trait_ref, item);
830 fn assemble_extension_candidates_for_traits_in_scope(&mut self,
831 expr_hir_id: hir::HirId)
832 -> Result<(), MethodError<'tcx>> {
833 if expr_hir_id == hir::DUMMY_HIR_ID {
836 let mut duplicates = FxHashSet::default();
837 let opt_applicable_traits = self.tcx.in_scope_traits(expr_hir_id);
838 if let Some(applicable_traits) = opt_applicable_traits {
839 for trait_candidate in applicable_traits.iter() {
840 let trait_did = trait_candidate.def_id;
841 if duplicates.insert(trait_did) {
842 let import_ids = trait_candidate.import_ids.iter().map(|node_id|
843 self.fcx.tcx.hir().node_to_hir_id(*node_id)).collect();
844 let result = self.assemble_extension_candidates_for_trait(import_ids,
853 fn assemble_extension_candidates_for_all_traits(&mut self) -> Result<(), MethodError<'tcx>> {
854 let mut duplicates = FxHashSet::default();
855 for trait_info in suggest::all_traits(self.tcx) {
856 if duplicates.insert(trait_info.def_id) {
857 self.assemble_extension_candidates_for_trait(smallvec![], trait_info.def_id)?;
863 pub fn matches_return_type(&self,
864 method: &ty::AssocItem,
865 self_ty: Option<Ty<'tcx>>,
866 expected: Ty<'tcx>) -> bool {
868 ty::AssocKind::Method => {
869 let fty = self.tcx.fn_sig(method.def_id);
871 let substs = self.fresh_substs_for_item(self.span, method.def_id);
872 let fty = fty.subst(self.tcx, substs);
873 let (fty, _) = self.replace_bound_vars_with_fresh_vars(
879 if let Some(self_ty) = self_ty {
880 if self.at(&ObligationCause::dummy(), self.param_env)
881 .sup(fty.inputs()[0], self_ty)
887 self.can_sub(self.param_env, fty.output(), expected).is_ok()
894 fn assemble_extension_candidates_for_trait(&mut self,
895 import_ids: SmallVec<[hir::HirId; 1]>,
897 -> Result<(), MethodError<'tcx>> {
898 debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})",
900 let trait_substs = self.fresh_item_substs(trait_def_id);
901 let trait_ref = ty::TraitRef::new(trait_def_id, trait_substs);
903 if self.tcx.is_trait_alias(trait_def_id) {
904 // For trait aliases, assume all super-traits are relevant.
905 let bounds = iter::once(trait_ref.to_poly_trait_ref());
906 self.elaborate_bounds(bounds, |this, new_trait_ref, item| {
907 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
909 let (xform_self_ty, xform_ret_ty) =
910 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
911 this.push_candidate(Candidate {
912 xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(),
913 kind: TraitCandidate(new_trait_ref),
917 debug_assert!(self.tcx.is_trait(trait_def_id));
918 for item in self.impl_or_trait_item(trait_def_id) {
919 // Check whether `trait_def_id` defines a method with suitable name.
920 if !self.has_applicable_self(&item) {
921 debug!("method has inapplicable self");
922 self.record_static_candidate(TraitSource(trait_def_id));
926 let (xform_self_ty, xform_ret_ty) =
927 self.xform_self_ty(&item, trait_ref.self_ty(), trait_substs);
928 self.push_candidate(Candidate {
929 xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(),
930 kind: TraitCandidate(trait_ref),
937 fn candidate_method_names(&self) -> Vec<ast::Ident> {
938 let mut set = FxHashSet::default();
939 let mut names: Vec<_> = self.inherent_candidates
941 .chain(&self.extension_candidates)
942 .filter(|candidate| {
943 if let Some(return_ty) = self.return_type {
944 self.matches_return_type(&candidate.item, None, return_ty)
949 .map(|candidate| candidate.item.ident)
950 .filter(|&name| set.insert(name))
953 // Sort them by the name so we have a stable result.
954 names.sort_by_cached_key(|n| n.as_str());
958 ///////////////////////////////////////////////////////////////////////////
961 fn pick(mut self) -> PickResult<'tcx> {
962 assert!(self.method_name.is_some());
964 if let Some(r) = self.pick_core() {
968 debug!("pick: actual search failed, assemble diagnotics");
970 let static_candidates = mem::replace(&mut self.static_candidates, vec![]);
971 let private_candidate = self.private_candidate.take();
972 let unsatisfied_predicates = mem::replace(&mut self.unsatisfied_predicates, vec![]);
974 // things failed, so lets look at all traits, for diagnostic purposes now:
977 let span = self.span;
980 self.assemble_extension_candidates_for_all_traits()?;
982 let out_of_scope_traits = match self.pick_core() {
983 Some(Ok(p)) => vec![p.item.container.id()],
984 //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(),
985 Some(Err(MethodError::Ambiguity(v))) => {
989 TraitSource(id) => id,
990 ImplSource(impl_id) => {
991 match tcx.trait_id_of_impl(impl_id) {
995 "found inherent method when looking at traits")
1003 Some(Err(MethodError::NoMatch(NoMatchData { out_of_scope_traits: others, .. }))) => {
1004 assert!(others.is_empty());
1010 if let Some((kind, def_id)) = private_candidate {
1011 return Err(MethodError::PrivateMatch(kind, def_id, out_of_scope_traits));
1013 let lev_candidate = self.probe_for_lev_candidate()?;
1015 Err(MethodError::NoMatch(NoMatchData::new(static_candidates,
1016 unsatisfied_predicates,
1017 out_of_scope_traits,
1022 fn pick_core(&mut self) -> Option<PickResult<'tcx>> {
1023 let steps = self.steps.clone();
1025 // find the first step that works
1029 debug!("pick_core: step={:?}", step);
1030 // skip types that are from a type error or that would require dereferencing
1032 !step.self_ty.references_error() && !step.from_unsafe_deref
1033 }).flat_map(|step| {
1034 let InferOk { value: self_ty, obligations: _ } =
1035 self.fcx.probe_instantiate_query_response(
1036 self.span, &self.orig_steps_var_values, &step.self_ty
1037 ).unwrap_or_else(|_| {
1038 span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty)
1040 self.pick_by_value_method(step, self_ty).or_else(|| {
1041 self.pick_autorefd_method(step, self_ty, hir::MutImmutable).or_else(|| {
1042 self.pick_autorefd_method(step, self_ty, hir::MutMutable)
1047 fn pick_by_value_method(&mut self, step: &CandidateStep<'gcx>, self_ty: Ty<'tcx>)
1048 -> Option<PickResult<'tcx>>
1050 //! For each type `T` in the step list, this attempts to find a
1051 //! method where the (transformed) self type is exactly `T`. We
1052 //! do however do one transformation on the adjustment: if we
1053 //! are passing a region pointer in, we will potentially
1054 //! *reborrow* it to a shorter lifetime. This allows us to
1055 //! transparently pass `&mut` pointers, in particular, without
1056 //! consuming them for their entire lifetime.
1062 self.pick_method(self_ty).map(|r| {
1064 pick.autoderefs = step.autoderefs;
1066 // Insert a `&*` or `&mut *` if this is a reference type:
1067 if let ty::Ref(_, _, mutbl) = step.self_ty.value.value.sty {
1068 pick.autoderefs += 1;
1069 pick.autoref = Some(mutbl);
1077 fn pick_autorefd_method(&mut self,
1078 step: &CandidateStep<'gcx>,
1080 mutbl: hir::Mutability)
1081 -> Option<PickResult<'tcx>> {
1084 // In general, during probing we erase regions. See
1085 // `impl_self_ty()` for an explanation.
1086 let region = tcx.lifetimes.re_erased;
1088 let autoref_ty = tcx.mk_ref(region,
1092 self.pick_method(autoref_ty).map(|r| {
1094 pick.autoderefs = step.autoderefs;
1095 pick.autoref = Some(mutbl);
1096 pick.unsize = if step.unsize {
1106 fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> {
1107 debug!("pick_method(self_ty={})", self.ty_to_string(self_ty));
1109 let mut possibly_unsatisfied_predicates = Vec::new();
1110 let mut unstable_candidates = Vec::new();
1112 for (kind, candidates) in &[
1113 ("inherent", &self.inherent_candidates),
1114 ("extension", &self.extension_candidates),
1116 debug!("searching {} candidates", kind);
1117 let res = self.consider_candidates(
1120 &mut possibly_unsatisfied_predicates,
1121 Some(&mut unstable_candidates),
1123 if let Some(pick) = res {
1124 if !self.is_suggestion.0 && !unstable_candidates.is_empty() {
1125 if let Ok(p) = &pick {
1126 // Emit a lint if there are unstable candidates alongside the stable ones.
1128 // We suppress warning if we're picking the method only because it is a
1130 self.emit_unstable_name_collision_hint(p, &unstable_candidates);
1137 debug!("searching unstable candidates");
1138 let res = self.consider_candidates(
1140 unstable_candidates.into_iter().map(|(c, _)| c),
1141 &mut possibly_unsatisfied_predicates,
1145 self.unsatisfied_predicates.extend(possibly_unsatisfied_predicates);
1150 fn consider_candidates<'b, ProbesIter>(
1154 possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>,
1155 unstable_candidates: Option<&mut Vec<(&'b Candidate<'tcx>, Symbol)>>,
1156 ) -> Option<PickResult<'tcx>>
1158 ProbesIter: Iterator<Item = &'b Candidate<'tcx>> + Clone,
1160 let mut applicable_candidates: Vec<_> = probes.clone()
1162 (probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
1164 .filter(|&(_, status)| status != ProbeResult::NoMatch)
1167 debug!("applicable_candidates: {:?}", applicable_candidates);
1169 if applicable_candidates.len() > 1 {
1170 if let Some(pick) = self.collapse_candidates_to_trait_pick(&applicable_candidates[..]) {
1171 return Some(Ok(pick));
1175 if let Some(uc) = unstable_candidates {
1176 applicable_candidates.retain(|&(p, _)| {
1177 if let stability::EvalResult::Deny { feature, .. } =
1178 self.tcx.eval_stability(p.item.def_id, None, self.span)
1180 uc.push((p, feature));
1187 if applicable_candidates.len() > 1 {
1188 let sources = probes
1189 .map(|p| self.candidate_source(p, self_ty))
1191 return Some(Err(MethodError::Ambiguity(sources)));
1194 applicable_candidates.pop().map(|(probe, status)| {
1195 if status == ProbeResult::Match {
1196 Ok(probe.to_unadjusted_pick())
1198 Err(MethodError::BadReturnType)
1203 fn emit_unstable_name_collision_hint(
1205 stable_pick: &Pick<'_>,
1206 unstable_candidates: &[(&Candidate<'tcx>, Symbol)],
1208 let mut diag = self.tcx.struct_span_lint_hir(
1209 lint::builtin::UNSTABLE_NAME_COLLISIONS,
1212 "a method with this name may be added to the standard library in the future",
1215 // FIXME: This should be a `span_suggestion` instead of `help`
1216 // However `self.span` only
1217 // highlights the method name, so we can't use it. Also consider reusing the code from
1218 // `report_method_error()`.
1220 "call with fully qualified syntax `{}(...)` to keep using the current method",
1221 self.tcx.def_path_str(stable_pick.item.def_id),
1224 if nightly_options::is_nightly_build() {
1225 for (candidate, feature) in unstable_candidates {
1227 "add #![feature({})] to the crate attributes to enable `{}`",
1229 self.tcx.def_path_str(candidate.item.def_id),
1237 fn select_trait_candidate(&self, trait_ref: ty::TraitRef<'tcx>)
1238 -> traits::SelectionResult<'tcx, traits::Selection<'tcx>>
1240 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1242 trait_ref.to_poly_trait_ref().to_poly_trait_predicate();
1243 let obligation = traits::Obligation::new(cause, self.param_env, predicate);
1244 traits::SelectionContext::new(self).select(&obligation)
1247 fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>)
1250 match candidate.kind {
1251 InherentImplCandidate(..) => ImplSource(candidate.item.container.id()),
1253 WhereClauseCandidate(_) => TraitSource(candidate.item.container.id()),
1254 TraitCandidate(trait_ref) => self.probe(|_| {
1255 let _ = self.at(&ObligationCause::dummy(), self.param_env)
1256 .sup(candidate.xform_self_ty, self_ty);
1257 match self.select_trait_candidate(trait_ref) {
1258 Ok(Some(traits::Vtable::VtableImpl(ref impl_data))) => {
1259 // If only a single impl matches, make the error message point
1261 ImplSource(impl_data.impl_def_id)
1264 TraitSource(candidate.item.container.id())
1271 fn consider_probe(&self,
1273 probe: &Candidate<'tcx>,
1274 possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>)
1276 debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
1279 // First check that the self type can be related.
1280 let sub_obligations = match self.at(&ObligationCause::dummy(), self.param_env)
1281 .sup(probe.xform_self_ty, self_ty) {
1282 Ok(InferOk { obligations, value: () }) => obligations,
1284 debug!("--> cannot relate self-types");
1285 return ProbeResult::NoMatch;
1289 let mut result = ProbeResult::Match;
1290 let selcx = &mut traits::SelectionContext::new(self);
1291 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1293 // If so, impls may carry other conditions (e.g., where
1294 // clauses) that must be considered. Make sure that those
1295 // match as well (or at least may match, sometimes we
1296 // don't have enough information to fully evaluate).
1297 let candidate_obligations : Vec<_> = match probe.kind {
1298 InherentImplCandidate(ref substs, ref ref_obligations) => {
1299 // Check whether the impl imposes obligations we have to worry about.
1300 let impl_def_id = probe.item.container.id();
1301 let impl_bounds = self.tcx.predicates_of(impl_def_id);
1302 let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
1303 let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
1304 traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
1306 // Convert the bounds into obligations.
1307 let impl_obligations = traits::predicates_for_generics(
1308 cause, self.param_env, &impl_bounds);
1310 debug!("impl_obligations={:?}", impl_obligations);
1311 impl_obligations.into_iter()
1312 .chain(norm_obligations.into_iter())
1313 .chain(ref_obligations.iter().cloned())
1318 WhereClauseCandidate(..) => {
1319 // These have no additional conditions to check.
1323 TraitCandidate(trait_ref) => {
1324 let predicate = trait_ref.to_predicate();
1326 traits::Obligation::new(cause, self.param_env, predicate);
1327 if !self.predicate_may_hold(&obligation) {
1328 if self.probe(|_| self.select_trait_candidate(trait_ref).is_err()) {
1329 // This candidate's primary obligation doesn't even
1330 // select - don't bother registering anything in
1331 // `potentially_unsatisfied_predicates`.
1332 return ProbeResult::NoMatch;
1334 // Some nested subobligation of this predicate
1337 // FIXME: try to find the exact nested subobligation
1338 // and point at it rather than reporting the entire
1340 result = ProbeResult::NoMatch;
1341 let trait_ref = self.resolve_vars_if_possible(&trait_ref);
1342 possibly_unsatisfied_predicates.push(trait_ref);
1349 debug!("consider_probe - candidate_obligations={:?} sub_obligations={:?}",
1350 candidate_obligations, sub_obligations);
1352 // Evaluate those obligations to see if they might possibly hold.
1353 for o in candidate_obligations.into_iter().chain(sub_obligations) {
1354 let o = self.resolve_vars_if_possible(&o);
1355 if !self.predicate_may_hold(&o) {
1356 result = ProbeResult::NoMatch;
1357 if let &ty::Predicate::Trait(ref pred) = &o.predicate {
1358 possibly_unsatisfied_predicates.push(pred.skip_binder().trait_ref);
1363 if let ProbeResult::Match = result {
1364 if let (Some(return_ty), Some(xform_ret_ty)) =
1365 (self.return_type, probe.xform_ret_ty)
1367 let xform_ret_ty = self.resolve_vars_if_possible(&xform_ret_ty);
1368 debug!("comparing return_ty {:?} with xform ret ty {:?}",
1370 probe.xform_ret_ty);
1371 if self.at(&ObligationCause::dummy(), self.param_env)
1372 .sup(return_ty, xform_ret_ty)
1375 return ProbeResult::BadReturnType;
1384 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1385 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1386 /// external interface of the method can be determined from the trait, it's ok not to decide.
1387 /// We can basically just collapse all of the probes for various impls into one where-clause
1388 /// probe. This will result in a pending obligation so when more type-info is available we can
1389 /// make the final decision.
1391 /// Example (`src/test/run-pass/method-two-trait-defer-resolution-1.rs`):
1394 /// trait Foo { ... }
1395 /// impl Foo for Vec<int> { ... }
1396 /// impl Foo for Vec<usize> { ... }
1399 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1400 /// use, so it's ok to just commit to "using the method from the trait Foo".
1401 fn collapse_candidates_to_trait_pick(&self, probes: &[(&Candidate<'tcx>, ProbeResult)])
1402 -> Option<Pick<'tcx>>
1404 // Do all probes correspond to the same trait?
1405 let container = probes[0].0.item.container;
1406 if let ty::ImplContainer(_) = container {
1409 if probes[1..].iter().any(|&(p, _)| p.item.container != container) {
1413 // FIXME: check the return type here somehow.
1414 // If so, just use this trait and call it a day.
1416 item: probes[0].0.item.clone(),
1418 import_ids: probes[0].0.import_ids.clone(),
1425 /// Similarly to `probe_for_return_type`, this method attempts to find the best matching
1426 /// candidate method where the method name may have been misspelt. Similarly to other
1427 /// Levenshtein based suggestions, we provide at most one such suggestion.
1428 fn probe_for_lev_candidate(&mut self) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> {
1429 debug!("Probing for method names similar to {:?}",
1432 let steps = self.steps.clone();
1434 let mut pcx = ProbeContext::new(self.fcx, self.span, self.mode, self.method_name,
1436 self.orig_steps_var_values.clone(),
1437 steps, IsSuggestion(true));
1438 pcx.allow_similar_names = true;
1439 pcx.assemble_inherent_candidates();
1440 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)?;
1442 let method_names = pcx.candidate_method_names();
1443 pcx.allow_similar_names = false;
1444 let applicable_close_candidates: Vec<ty::AssocItem> = method_names
1446 .filter_map(|&method_name| {
1448 pcx.method_name = Some(method_name);
1449 pcx.assemble_inherent_candidates();
1450 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)
1451 .ok().map_or(None, |_| {
1453 .and_then(|pick| pick.ok())
1454 .and_then(|pick| Some(pick.item))
1459 if applicable_close_candidates.is_empty() {
1463 let names = applicable_close_candidates.iter().map(|cand| &cand.ident.name);
1464 find_best_match_for_name(names,
1465 &self.method_name.unwrap().as_str(),
1468 Ok(applicable_close_candidates
1470 .find(|method| method.ident.name == best_name))
1475 ///////////////////////////////////////////////////////////////////////////
1477 fn has_applicable_self(&self, item: &ty::AssocItem) -> bool {
1478 // "Fast track" -- check for usage of sugar when in method call
1481 // In Path mode (i.e., resolving a value like `T::next`), consider any
1482 // associated value (i.e., methods, constants) but not types.
1484 Mode::MethodCall => item.method_has_self_argument,
1485 Mode::Path => match item.kind {
1486 ty::AssocKind::Existential |
1487 ty::AssocKind::Type => false,
1488 ty::AssocKind::Method | ty::AssocKind::Const => true
1491 // FIXME -- check for types that deref to `Self`,
1492 // like `Rc<Self>` and so on.
1494 // Note also that the current code will break if this type
1495 // includes any of the type parameters defined on the method
1496 // -- but this could be overcome.
1499 fn record_static_candidate(&mut self, source: CandidateSource) {
1500 self.static_candidates.push(source);
1503 fn xform_self_ty(&self,
1504 item: &ty::AssocItem,
1506 substs: SubstsRef<'tcx>)
1507 -> (Ty<'tcx>, Option<Ty<'tcx>>) {
1508 if item.kind == ty::AssocKind::Method && self.mode == Mode::MethodCall {
1509 let sig = self.xform_method_sig(item.def_id, substs);
1510 (sig.inputs()[0], Some(sig.output()))
1516 fn xform_method_sig(&self,
1518 substs: SubstsRef<'tcx>)
1521 let fn_sig = self.tcx.fn_sig(method);
1522 debug!("xform_self_ty(fn_sig={:?}, substs={:?})",
1526 assert!(!substs.has_escaping_bound_vars());
1528 // It is possible for type parameters or early-bound lifetimes
1529 // to appear in the signature of `self`. The substitutions we
1530 // are given do not include type/lifetime parameters for the
1531 // method yet. So create fresh variables here for those too,
1532 // if there are any.
1533 let generics = self.tcx.generics_of(method);
1534 assert_eq!(substs.len(), generics.parent_count as usize);
1536 // Erase any late-bound regions from the method and substitute
1537 // in the values from the substitution.
1538 let xform_fn_sig = self.erase_late_bound_regions(&fn_sig);
1540 if generics.params.is_empty() {
1541 xform_fn_sig.subst(self.tcx, substs)
1543 let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
1544 let i = param.index as usize;
1545 if i < substs.len() {
1549 GenericParamDefKind::Lifetime => {
1550 // In general, during probe we erase regions. See
1551 // `impl_self_ty()` for an explanation.
1552 self.tcx.lifetimes.re_erased.into()
1554 GenericParamDefKind::Type { .. }
1555 | GenericParamDefKind::Const => {
1556 self.var_for_def(self.span, param)
1561 xform_fn_sig.subst(self.tcx, substs)
1565 /// Gets the type of an impl and generate substitutions with placeholders.
1566 fn impl_ty_and_substs(&self, impl_def_id: DefId) -> (Ty<'tcx>, SubstsRef<'tcx>) {
1567 (self.tcx.type_of(impl_def_id), self.fresh_item_substs(impl_def_id))
1570 fn fresh_item_substs(&self, def_id: DefId) -> SubstsRef<'tcx> {
1571 InternalSubsts::for_item(self.tcx, def_id, |param, _| {
1573 GenericParamDefKind::Lifetime => self.tcx.lifetimes.re_erased.into(),
1574 GenericParamDefKind::Type { .. } => {
1575 self.next_ty_var(TypeVariableOrigin::SubstitutionPlaceholder(
1576 self.tcx.def_span(def_id))).into()
1578 GenericParamDefKind::Const { .. } => {
1579 let span = self.tcx.def_span(def_id);
1580 let origin = ConstVariableOrigin::SubstitutionPlaceholder(span);
1581 self.next_const_var(self.tcx.type_of(param.def_id), origin).into()
1587 /// Replaces late-bound-regions bound by `value` with `'static` using
1588 /// `ty::erase_late_bound_regions`.
1590 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1591 /// method matching. It is reasonable during the probe phase because we don't consider region
1592 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1593 /// rather than creating fresh region variables. This is nice for two reasons:
1595 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1596 /// particular method call, it winds up creating fewer types overall, which helps for memory
1597 /// usage. (Admittedly, this is a rather small effect, though measurable.)
1599 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1600 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1601 /// regions with actual region variables as is proper, we'd have to ensure that the same
1602 /// region got replaced with the same variable, which requires a bit more coordination
1603 /// and/or tracking the substitution and
1605 fn erase_late_bound_regions<T>(&self, value: &ty::Binder<T>) -> T
1606 where T: TypeFoldable<'tcx>
1608 self.tcx.erase_late_bound_regions(value)
1611 /// Finds the method with the appropriate name (or return type, as the case may be). If
1612 /// `allow_similar_names` is set, find methods with close-matching names.
1613 fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssocItem> {
1614 if let Some(name) = self.method_name {
1615 if self.allow_similar_names {
1616 let max_dist = max(name.as_str().len(), 3) / 3;
1617 self.tcx.associated_items(def_id)
1619 let dist = lev_distance(&*name.as_str(), &x.ident.as_str());
1620 Namespace::from(x.kind) == Namespace::Value && dist > 0
1626 .associated_item(def_id, name, Namespace::Value)
1627 .map_or(Vec::new(), |x| vec![x])
1630 self.tcx.associated_items(def_id).collect()
1635 impl<'tcx> Candidate<'tcx> {
1636 fn to_unadjusted_pick(&self) -> Pick<'tcx> {
1638 item: self.item.clone(),
1639 kind: match self.kind {
1640 InherentImplCandidate(..) => InherentImplPick,
1641 ObjectCandidate => ObjectPick,
1642 TraitCandidate(_) => TraitPick,
1643 WhereClauseCandidate(ref trait_ref) => {
1644 // Only trait derived from where-clauses should
1645 // appear here, so they should not contain any
1646 // inference variables or other artifacts. This
1647 // means they are safe to put into the
1648 // `WhereClausePick`.
1650 !trait_ref.skip_binder().substs.needs_infer()
1651 && !trait_ref.skip_binder().substs.has_placeholders()
1654 WhereClausePick(trait_ref.clone())
1657 import_ids: self.import_ids.clone(),