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, TypeVariableOriginKind};
24 use rustc::infer::unify_key::{ConstVariableOrigin, ConstVariableOriginKind};
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<'gcx, 'tcx>(
399 tcx: TyCtxt<'gcx, 'gcx>,
400 goal: CanonicalTyGoal<'tcx>,
401 ) -> 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;
514 self.tcx.adjust_ident_and_get_scope(name, item.container.id(), self.body_id).1;
515 item.vis.is_accessible_from(def_scope, self.tcx)
521 self.inherent_candidates.push(candidate);
523 self.extension_candidates.push(candidate);
525 } else if self.private_candidate.is_none() {
526 self.private_candidate =
527 Some((candidate.item.def_kind(), candidate.item.def_id));
531 fn assemble_inherent_candidates(&mut self) {
532 let steps = self.steps.clone();
533 for step in steps.iter() {
534 self.assemble_probe(&step.self_ty);
538 fn assemble_probe(&mut self, self_ty: &Canonical<'gcx, QueryResponse<'gcx, Ty<'gcx>>>) {
539 debug!("assemble_probe: self_ty={:?}", self_ty);
540 let lang_items = self.tcx.lang_items();
542 match self_ty.value.value.sty {
543 ty::Dynamic(ref data, ..) => {
544 if let Some(p) = data.principal() {
545 // Subtle: we can't use `instantiate_query_response` here: using it will
546 // commit to all of the type equalities assumed by inference going through
547 // autoderef (see the `method-probe-no-guessing` test).
549 // However, in this code, it is OK if we end up with an object type that is
550 // "more general" than the object type that we are evaluating. For *every*
551 // object type `MY_OBJECT`, a function call that goes through a trait-ref
552 // of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid
553 // `ObjectCandidate`, and it should be discoverable "exactly" through one
554 // of the iterations in the autoderef loop, so there is no problem with it
555 // being discoverable in another one of these iterations.
557 // Using `instantiate_canonical_with_fresh_inference_vars` on our
558 // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
559 // `CanonicalVarValues` will exactly give us such a generalization - it
560 // will still match the original object type, but it won't pollute our
561 // type variables in any form, so just do that!
562 let (QueryResponse { value: generalized_self_ty, .. }, _ignored_var_values) =
563 self.fcx.instantiate_canonical_with_fresh_inference_vars(
564 self.span, &self_ty);
566 self.assemble_inherent_candidates_from_object(generalized_self_ty);
567 self.assemble_inherent_impl_candidates_for_type(p.def_id());
571 self.assemble_inherent_impl_candidates_for_type(def.did);
573 ty::Foreign(did) => {
574 self.assemble_inherent_impl_candidates_for_type(did);
577 self.assemble_inherent_candidates_from_param(p);
580 let lang_def_id = lang_items.char_impl();
581 self.assemble_inherent_impl_for_primitive(lang_def_id);
584 let lang_def_id = lang_items.str_impl();
585 self.assemble_inherent_impl_for_primitive(lang_def_id);
587 let lang_def_id = lang_items.str_alloc_impl();
588 self.assemble_inherent_impl_for_primitive(lang_def_id);
591 let lang_def_id = lang_items.slice_impl();
592 self.assemble_inherent_impl_for_primitive(lang_def_id);
594 let lang_def_id = lang_items.slice_u8_impl();
595 self.assemble_inherent_impl_for_primitive(lang_def_id);
597 let lang_def_id = lang_items.slice_alloc_impl();
598 self.assemble_inherent_impl_for_primitive(lang_def_id);
600 let lang_def_id = lang_items.slice_u8_alloc_impl();
601 self.assemble_inherent_impl_for_primitive(lang_def_id);
603 ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutImmutable }) => {
604 let lang_def_id = lang_items.const_ptr_impl();
605 self.assemble_inherent_impl_for_primitive(lang_def_id);
607 ty::RawPtr(ty::TypeAndMut { ty: _, mutbl: hir::MutMutable }) => {
608 let lang_def_id = lang_items.mut_ptr_impl();
609 self.assemble_inherent_impl_for_primitive(lang_def_id);
611 ty::Int(ast::IntTy::I8) => {
612 let lang_def_id = lang_items.i8_impl();
613 self.assemble_inherent_impl_for_primitive(lang_def_id);
615 ty::Int(ast::IntTy::I16) => {
616 let lang_def_id = lang_items.i16_impl();
617 self.assemble_inherent_impl_for_primitive(lang_def_id);
619 ty::Int(ast::IntTy::I32) => {
620 let lang_def_id = lang_items.i32_impl();
621 self.assemble_inherent_impl_for_primitive(lang_def_id);
623 ty::Int(ast::IntTy::I64) => {
624 let lang_def_id = lang_items.i64_impl();
625 self.assemble_inherent_impl_for_primitive(lang_def_id);
627 ty::Int(ast::IntTy::I128) => {
628 let lang_def_id = lang_items.i128_impl();
629 self.assemble_inherent_impl_for_primitive(lang_def_id);
631 ty::Int(ast::IntTy::Isize) => {
632 let lang_def_id = lang_items.isize_impl();
633 self.assemble_inherent_impl_for_primitive(lang_def_id);
635 ty::Uint(ast::UintTy::U8) => {
636 let lang_def_id = lang_items.u8_impl();
637 self.assemble_inherent_impl_for_primitive(lang_def_id);
639 ty::Uint(ast::UintTy::U16) => {
640 let lang_def_id = lang_items.u16_impl();
641 self.assemble_inherent_impl_for_primitive(lang_def_id);
643 ty::Uint(ast::UintTy::U32) => {
644 let lang_def_id = lang_items.u32_impl();
645 self.assemble_inherent_impl_for_primitive(lang_def_id);
647 ty::Uint(ast::UintTy::U64) => {
648 let lang_def_id = lang_items.u64_impl();
649 self.assemble_inherent_impl_for_primitive(lang_def_id);
651 ty::Uint(ast::UintTy::U128) => {
652 let lang_def_id = lang_items.u128_impl();
653 self.assemble_inherent_impl_for_primitive(lang_def_id);
655 ty::Uint(ast::UintTy::Usize) => {
656 let lang_def_id = lang_items.usize_impl();
657 self.assemble_inherent_impl_for_primitive(lang_def_id);
659 ty::Float(ast::FloatTy::F32) => {
660 let lang_def_id = lang_items.f32_impl();
661 self.assemble_inherent_impl_for_primitive(lang_def_id);
663 let lang_def_id = lang_items.f32_runtime_impl();
664 self.assemble_inherent_impl_for_primitive(lang_def_id);
666 ty::Float(ast::FloatTy::F64) => {
667 let lang_def_id = lang_items.f64_impl();
668 self.assemble_inherent_impl_for_primitive(lang_def_id);
670 let lang_def_id = lang_items.f64_runtime_impl();
671 self.assemble_inherent_impl_for_primitive(lang_def_id);
677 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id: Option<DefId>) {
678 if let Some(impl_def_id) = lang_def_id {
679 self.assemble_inherent_impl_probe(impl_def_id);
683 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id: DefId) {
684 let impl_def_ids = self.tcx.at(self.span).inherent_impls(def_id);
685 for &impl_def_id in impl_def_ids.iter() {
686 self.assemble_inherent_impl_probe(impl_def_id);
690 fn assemble_inherent_impl_probe(&mut self, impl_def_id: DefId) {
691 if !self.impl_dups.insert(impl_def_id) {
692 return; // already visited
695 debug!("assemble_inherent_impl_probe {:?}", impl_def_id);
697 for item in self.impl_or_trait_item(impl_def_id) {
698 if !self.has_applicable_self(&item) {
699 // No receiver declared. Not a candidate.
700 self.record_static_candidate(ImplSource(impl_def_id));
704 let (impl_ty, impl_substs) = self.impl_ty_and_substs(impl_def_id);
705 let impl_ty = impl_ty.subst(self.tcx, impl_substs);
707 // Determine the receiver type that the method itself expects.
708 let xform_tys = self.xform_self_ty(&item, impl_ty, impl_substs);
710 // We can't use normalize_associated_types_in as it will pollute the
711 // fcx's fulfillment context after this probe is over.
712 let cause = traits::ObligationCause::misc(self.span, self.body_id);
713 let selcx = &mut traits::SelectionContext::new(self.fcx);
714 let traits::Normalized { value: (xform_self_ty, xform_ret_ty), obligations } =
715 traits::normalize(selcx, self.param_env, cause, &xform_tys);
716 debug!("assemble_inherent_impl_probe: xform_self_ty = {:?}/{:?}",
717 xform_self_ty, xform_ret_ty);
719 self.push_candidate(Candidate {
720 xform_self_ty, xform_ret_ty, item,
721 kind: InherentImplCandidate(impl_substs, obligations),
722 import_ids: smallvec![]
727 fn assemble_inherent_candidates_from_object(&mut self,
729 debug!("assemble_inherent_candidates_from_object(self_ty={:?})",
732 let principal = match self_ty.sty {
733 ty::Dynamic(ref data, ..) => Some(data),
735 }.and_then(|data| data.principal()).unwrap_or_else(|| {
736 span_bug!(self.span, "non-object {:?} in assemble_inherent_candidates_from_object",
740 // It is illegal to invoke a method on a trait instance that
741 // refers to the `Self` type. An error will be reported by
742 // `enforce_object_limitations()` if the method refers to the
743 // `Self` type anywhere other than the receiver. Here, we use
744 // a substitution that replaces `Self` with the object type
745 // itself. Hence, a `&self` method will wind up with an
746 // argument type like `&Trait`.
747 let trait_ref = principal.with_self_ty(self.tcx, self_ty);
748 self.elaborate_bounds(iter::once(trait_ref), |this, new_trait_ref, item| {
749 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
751 let (xform_self_ty, xform_ret_ty) =
752 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
753 this.push_candidate(Candidate {
754 xform_self_ty, xform_ret_ty, item,
755 kind: ObjectCandidate,
756 import_ids: smallvec![]
761 fn assemble_inherent_candidates_from_param(&mut self, param_ty: ty::ParamTy) {
762 // FIXME: do we want to commit to this behavior for param bounds?
764 let bounds = self.param_env
767 .filter_map(|predicate| {
769 ty::Predicate::Trait(ref trait_predicate) => {
770 match trait_predicate.skip_binder().trait_ref.self_ty().sty {
771 ty::Param(ref p) if *p == param_ty => {
772 Some(trait_predicate.to_poly_trait_ref())
777 ty::Predicate::Subtype(..) |
778 ty::Predicate::Projection(..) |
779 ty::Predicate::RegionOutlives(..) |
780 ty::Predicate::WellFormed(..) |
781 ty::Predicate::ObjectSafe(..) |
782 ty::Predicate::ClosureKind(..) |
783 ty::Predicate::TypeOutlives(..) |
784 ty::Predicate::ConstEvaluatable(..) => None,
788 self.elaborate_bounds(bounds, |this, poly_trait_ref, item| {
789 let trait_ref = this.erase_late_bound_regions(&poly_trait_ref);
791 let (xform_self_ty, xform_ret_ty) =
792 this.xform_self_ty(&item, trait_ref.self_ty(), trait_ref.substs);
794 // Because this trait derives from a where-clause, it
795 // should not contain any inference variables or other
796 // artifacts. This means it is safe to put into the
797 // `WhereClauseCandidate` and (eventually) into the
798 // `WhereClausePick`.
799 assert!(!trait_ref.substs.needs_infer());
801 this.push_candidate(Candidate {
802 xform_self_ty, xform_ret_ty, item,
803 kind: WhereClauseCandidate(poly_trait_ref),
804 import_ids: smallvec![]
809 // Do a search through a list of bounds, using a callback to actually
810 // create the candidates.
811 fn elaborate_bounds<F>(&mut self,
812 bounds: impl Iterator<Item = ty::PolyTraitRef<'tcx>>,
814 where F: for<'b> FnMut(&mut ProbeContext<'b, 'gcx, 'tcx>,
815 ty::PolyTraitRef<'tcx>,
819 for bound_trait_ref in traits::transitive_bounds(tcx, bounds) {
820 debug!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref);
821 for item in self.impl_or_trait_item(bound_trait_ref.def_id()) {
822 if !self.has_applicable_self(&item) {
823 self.record_static_candidate(TraitSource(bound_trait_ref.def_id()));
825 mk_cand(self, bound_trait_ref, item);
831 fn assemble_extension_candidates_for_traits_in_scope(&mut self,
832 expr_hir_id: hir::HirId)
833 -> Result<(), MethodError<'tcx>> {
834 if expr_hir_id == hir::DUMMY_HIR_ID {
837 let mut duplicates = FxHashSet::default();
838 let opt_applicable_traits = self.tcx.in_scope_traits(expr_hir_id);
839 if let Some(applicable_traits) = opt_applicable_traits {
840 for trait_candidate in applicable_traits.iter() {
841 let trait_did = trait_candidate.def_id;
842 if duplicates.insert(trait_did) {
843 let import_ids = trait_candidate.import_ids.iter().map(|node_id|
844 self.fcx.tcx.hir().node_to_hir_id(*node_id)).collect();
845 let result = self.assemble_extension_candidates_for_trait(import_ids,
854 fn assemble_extension_candidates_for_all_traits(&mut self) -> Result<(), MethodError<'tcx>> {
855 let mut duplicates = FxHashSet::default();
856 for trait_info in suggest::all_traits(self.tcx) {
857 if duplicates.insert(trait_info.def_id) {
858 self.assemble_extension_candidates_for_trait(smallvec![], trait_info.def_id)?;
864 pub fn matches_return_type(&self,
865 method: &ty::AssocItem,
866 self_ty: Option<Ty<'tcx>>,
867 expected: Ty<'tcx>) -> bool {
869 ty::AssocKind::Method => {
870 let fty = self.tcx.fn_sig(method.def_id);
872 let substs = self.fresh_substs_for_item(self.span, method.def_id);
873 let fty = fty.subst(self.tcx, substs);
874 let (fty, _) = self.replace_bound_vars_with_fresh_vars(
880 if let Some(self_ty) = self_ty {
881 if self.at(&ObligationCause::dummy(), self.param_env)
882 .sup(fty.inputs()[0], self_ty)
888 self.can_sub(self.param_env, fty.output(), expected).is_ok()
895 fn assemble_extension_candidates_for_trait(&mut self,
896 import_ids: SmallVec<[hir::HirId; 1]>,
898 -> Result<(), MethodError<'tcx>> {
899 debug!("assemble_extension_candidates_for_trait(trait_def_id={:?})",
901 let trait_substs = self.fresh_item_substs(trait_def_id);
902 let trait_ref = ty::TraitRef::new(trait_def_id, trait_substs);
904 if self.tcx.is_trait_alias(trait_def_id) {
905 // For trait aliases, assume all super-traits are relevant.
906 let bounds = iter::once(trait_ref.to_poly_trait_ref());
907 self.elaborate_bounds(bounds, |this, new_trait_ref, item| {
908 let new_trait_ref = this.erase_late_bound_regions(&new_trait_ref);
910 let (xform_self_ty, xform_ret_ty) =
911 this.xform_self_ty(&item, new_trait_ref.self_ty(), new_trait_ref.substs);
912 this.push_candidate(Candidate {
913 xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(),
914 kind: TraitCandidate(new_trait_ref),
918 debug_assert!(self.tcx.is_trait(trait_def_id));
919 for item in self.impl_or_trait_item(trait_def_id) {
920 // Check whether `trait_def_id` defines a method with suitable name.
921 if !self.has_applicable_self(&item) {
922 debug!("method has inapplicable self");
923 self.record_static_candidate(TraitSource(trait_def_id));
927 let (xform_self_ty, xform_ret_ty) =
928 self.xform_self_ty(&item, trait_ref.self_ty(), trait_substs);
929 self.push_candidate(Candidate {
930 xform_self_ty, xform_ret_ty, item, import_ids: import_ids.clone(),
931 kind: TraitCandidate(trait_ref),
938 fn candidate_method_names(&self) -> Vec<ast::Ident> {
939 let mut set = FxHashSet::default();
940 let mut names: Vec<_> = self.inherent_candidates
942 .chain(&self.extension_candidates)
943 .filter(|candidate| {
944 if let Some(return_ty) = self.return_type {
945 self.matches_return_type(&candidate.item, None, return_ty)
950 .map(|candidate| candidate.item.ident)
951 .filter(|&name| set.insert(name))
954 // Sort them by the name so we have a stable result.
955 names.sort_by_cached_key(|n| n.as_str());
959 ///////////////////////////////////////////////////////////////////////////
962 fn pick(mut self) -> PickResult<'tcx> {
963 assert!(self.method_name.is_some());
965 if let Some(r) = self.pick_core() {
969 debug!("pick: actual search failed, assemble diagnotics");
971 let static_candidates = mem::replace(&mut self.static_candidates, vec![]);
972 let private_candidate = self.private_candidate.take();
973 let unsatisfied_predicates = mem::replace(&mut self.unsatisfied_predicates, vec![]);
975 // things failed, so lets look at all traits, for diagnostic purposes now:
978 let span = self.span;
981 self.assemble_extension_candidates_for_all_traits()?;
983 let out_of_scope_traits = match self.pick_core() {
984 Some(Ok(p)) => vec![p.item.container.id()],
985 //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(),
986 Some(Err(MethodError::Ambiguity(v))) => {
990 TraitSource(id) => id,
991 ImplSource(impl_id) => {
992 match tcx.trait_id_of_impl(impl_id) {
996 "found inherent method when looking at traits")
1004 Some(Err(MethodError::NoMatch(NoMatchData { out_of_scope_traits: others, .. }))) => {
1005 assert!(others.is_empty());
1011 if let Some((kind, def_id)) = private_candidate {
1012 return Err(MethodError::PrivateMatch(kind, def_id, out_of_scope_traits));
1014 let lev_candidate = self.probe_for_lev_candidate()?;
1016 Err(MethodError::NoMatch(NoMatchData::new(static_candidates,
1017 unsatisfied_predicates,
1018 out_of_scope_traits,
1023 fn pick_core(&mut self) -> Option<PickResult<'tcx>> {
1024 let steps = self.steps.clone();
1026 // find the first step that works
1030 debug!("pick_core: step={:?}", step);
1031 // skip types that are from a type error or that would require dereferencing
1033 !step.self_ty.references_error() && !step.from_unsafe_deref
1034 }).flat_map(|step| {
1035 let InferOk { value: self_ty, obligations: _ } =
1036 self.fcx.probe_instantiate_query_response(
1037 self.span, &self.orig_steps_var_values, &step.self_ty
1038 ).unwrap_or_else(|_| {
1039 span_bug!(self.span, "{:?} was applicable but now isn't?", step.self_ty)
1041 self.pick_by_value_method(step, self_ty).or_else(|| {
1042 self.pick_autorefd_method(step, self_ty, hir::MutImmutable).or_else(|| {
1043 self.pick_autorefd_method(step, self_ty, hir::MutMutable)
1048 fn pick_by_value_method(&mut self, step: &CandidateStep<'gcx>, self_ty: Ty<'tcx>)
1049 -> Option<PickResult<'tcx>>
1051 //! For each type `T` in the step list, this attempts to find a
1052 //! method where the (transformed) self type is exactly `T`. We
1053 //! do however do one transformation on the adjustment: if we
1054 //! are passing a region pointer in, we will potentially
1055 //! *reborrow* it to a shorter lifetime. This allows us to
1056 //! transparently pass `&mut` pointers, in particular, without
1057 //! consuming them for their entire lifetime.
1063 self.pick_method(self_ty).map(|r| {
1065 pick.autoderefs = step.autoderefs;
1067 // Insert a `&*` or `&mut *` if this is a reference type:
1068 if let ty::Ref(_, _, mutbl) = step.self_ty.value.value.sty {
1069 pick.autoderefs += 1;
1070 pick.autoref = Some(mutbl);
1078 fn pick_autorefd_method(&mut self,
1079 step: &CandidateStep<'gcx>,
1081 mutbl: hir::Mutability)
1082 -> Option<PickResult<'tcx>> {
1085 // In general, during probing we erase regions. See
1086 // `impl_self_ty()` for an explanation.
1087 let region = tcx.lifetimes.re_erased;
1089 let autoref_ty = tcx.mk_ref(region,
1093 self.pick_method(autoref_ty).map(|r| {
1095 pick.autoderefs = step.autoderefs;
1096 pick.autoref = Some(mutbl);
1097 pick.unsize = if step.unsize {
1107 fn pick_method(&mut self, self_ty: Ty<'tcx>) -> Option<PickResult<'tcx>> {
1108 debug!("pick_method(self_ty={})", self.ty_to_string(self_ty));
1110 let mut possibly_unsatisfied_predicates = Vec::new();
1111 let mut unstable_candidates = Vec::new();
1113 for (kind, candidates) in &[
1114 ("inherent", &self.inherent_candidates),
1115 ("extension", &self.extension_candidates),
1117 debug!("searching {} candidates", kind);
1118 let res = self.consider_candidates(
1121 &mut possibly_unsatisfied_predicates,
1122 Some(&mut unstable_candidates),
1124 if let Some(pick) = res {
1125 if !self.is_suggestion.0 && !unstable_candidates.is_empty() {
1126 if let Ok(p) = &pick {
1127 // Emit a lint if there are unstable candidates alongside the stable ones.
1129 // We suppress warning if we're picking the method only because it is a
1131 self.emit_unstable_name_collision_hint(p, &unstable_candidates);
1138 debug!("searching unstable candidates");
1139 let res = self.consider_candidates(
1141 unstable_candidates.into_iter().map(|(c, _)| c),
1142 &mut possibly_unsatisfied_predicates,
1146 self.unsatisfied_predicates.extend(possibly_unsatisfied_predicates);
1151 fn consider_candidates<'b, ProbesIter>(
1155 possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>,
1156 unstable_candidates: Option<&mut Vec<(&'b Candidate<'tcx>, Symbol)>>,
1157 ) -> Option<PickResult<'tcx>>
1159 ProbesIter: Iterator<Item = &'b Candidate<'tcx>> + Clone,
1161 let mut applicable_candidates: Vec<_> = probes.clone()
1163 (probe, self.consider_probe(self_ty, probe, possibly_unsatisfied_predicates))
1165 .filter(|&(_, status)| status != ProbeResult::NoMatch)
1168 debug!("applicable_candidates: {:?}", applicable_candidates);
1170 if applicable_candidates.len() > 1 {
1171 if let Some(pick) = self.collapse_candidates_to_trait_pick(&applicable_candidates[..]) {
1172 return Some(Ok(pick));
1176 if let Some(uc) = unstable_candidates {
1177 applicable_candidates.retain(|&(p, _)| {
1178 if let stability::EvalResult::Deny { feature, .. } =
1179 self.tcx.eval_stability(p.item.def_id, None, self.span)
1181 uc.push((p, feature));
1188 if applicable_candidates.len() > 1 {
1189 let sources = probes
1190 .map(|p| self.candidate_source(p, self_ty))
1192 return Some(Err(MethodError::Ambiguity(sources)));
1195 applicable_candidates.pop().map(|(probe, status)| {
1196 if status == ProbeResult::Match {
1197 Ok(probe.to_unadjusted_pick())
1199 Err(MethodError::BadReturnType)
1204 fn emit_unstable_name_collision_hint(
1206 stable_pick: &Pick<'_>,
1207 unstable_candidates: &[(&Candidate<'tcx>, Symbol)],
1209 let mut diag = self.tcx.struct_span_lint_hir(
1210 lint::builtin::UNSTABLE_NAME_COLLISIONS,
1213 "a method with this name may be added to the standard library in the future",
1216 // FIXME: This should be a `span_suggestion` instead of `help`
1217 // However `self.span` only
1218 // highlights the method name, so we can't use it. Also consider reusing the code from
1219 // `report_method_error()`.
1221 "call with fully qualified syntax `{}(...)` to keep using the current method",
1222 self.tcx.def_path_str(stable_pick.item.def_id),
1225 if nightly_options::is_nightly_build() {
1226 for (candidate, feature) in unstable_candidates {
1228 "add #![feature({})] to the crate attributes to enable `{}`",
1230 self.tcx.def_path_str(candidate.item.def_id),
1238 fn select_trait_candidate(&self, trait_ref: ty::TraitRef<'tcx>)
1239 -> traits::SelectionResult<'tcx, traits::Selection<'tcx>>
1241 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1243 trait_ref.to_poly_trait_ref().to_poly_trait_predicate();
1244 let obligation = traits::Obligation::new(cause, self.param_env, predicate);
1245 traits::SelectionContext::new(self).select(&obligation)
1248 fn candidate_source(&self, candidate: &Candidate<'tcx>, self_ty: Ty<'tcx>)
1251 match candidate.kind {
1252 InherentImplCandidate(..) => ImplSource(candidate.item.container.id()),
1254 WhereClauseCandidate(_) => TraitSource(candidate.item.container.id()),
1255 TraitCandidate(trait_ref) => self.probe(|_| {
1256 let _ = self.at(&ObligationCause::dummy(), self.param_env)
1257 .sup(candidate.xform_self_ty, self_ty);
1258 match self.select_trait_candidate(trait_ref) {
1259 Ok(Some(traits::Vtable::VtableImpl(ref impl_data))) => {
1260 // If only a single impl matches, make the error message point
1262 ImplSource(impl_data.impl_def_id)
1265 TraitSource(candidate.item.container.id())
1272 fn consider_probe(&self,
1274 probe: &Candidate<'tcx>,
1275 possibly_unsatisfied_predicates: &mut Vec<TraitRef<'tcx>>)
1277 debug!("consider_probe: self_ty={:?} probe={:?}", self_ty, probe);
1280 // First check that the self type can be related.
1281 let sub_obligations = match self.at(&ObligationCause::dummy(), self.param_env)
1282 .sup(probe.xform_self_ty, self_ty) {
1283 Ok(InferOk { obligations, value: () }) => obligations,
1285 debug!("--> cannot relate self-types");
1286 return ProbeResult::NoMatch;
1290 let mut result = ProbeResult::Match;
1291 let selcx = &mut traits::SelectionContext::new(self);
1292 let cause = traits::ObligationCause::misc(self.span, self.body_id);
1294 // If so, impls may carry other conditions (e.g., where
1295 // clauses) that must be considered. Make sure that those
1296 // match as well (or at least may match, sometimes we
1297 // don't have enough information to fully evaluate).
1298 let candidate_obligations : Vec<_> = match probe.kind {
1299 InherentImplCandidate(ref substs, ref ref_obligations) => {
1300 // Check whether the impl imposes obligations we have to worry about.
1301 let impl_def_id = probe.item.container.id();
1302 let impl_bounds = self.tcx.predicates_of(impl_def_id);
1303 let impl_bounds = impl_bounds.instantiate(self.tcx, substs);
1304 let traits::Normalized { value: impl_bounds, obligations: norm_obligations } =
1305 traits::normalize(selcx, self.param_env, cause.clone(), &impl_bounds);
1307 // Convert the bounds into obligations.
1308 let impl_obligations = traits::predicates_for_generics(
1309 cause, self.param_env, &impl_bounds);
1311 debug!("impl_obligations={:?}", impl_obligations);
1312 impl_obligations.into_iter()
1313 .chain(norm_obligations.into_iter())
1314 .chain(ref_obligations.iter().cloned())
1319 WhereClauseCandidate(..) => {
1320 // These have no additional conditions to check.
1324 TraitCandidate(trait_ref) => {
1325 let predicate = trait_ref.to_predicate();
1327 traits::Obligation::new(cause, self.param_env, predicate);
1328 if !self.predicate_may_hold(&obligation) {
1329 if self.probe(|_| self.select_trait_candidate(trait_ref).is_err()) {
1330 // This candidate's primary obligation doesn't even
1331 // select - don't bother registering anything in
1332 // `potentially_unsatisfied_predicates`.
1333 return ProbeResult::NoMatch;
1335 // Some nested subobligation of this predicate
1338 // FIXME: try to find the exact nested subobligation
1339 // and point at it rather than reporting the entire
1341 result = ProbeResult::NoMatch;
1342 let trait_ref = self.resolve_vars_if_possible(&trait_ref);
1343 possibly_unsatisfied_predicates.push(trait_ref);
1350 debug!("consider_probe - candidate_obligations={:?} sub_obligations={:?}",
1351 candidate_obligations, sub_obligations);
1353 // Evaluate those obligations to see if they might possibly hold.
1354 for o in candidate_obligations.into_iter().chain(sub_obligations) {
1355 let o = self.resolve_vars_if_possible(&o);
1356 if !self.predicate_may_hold(&o) {
1357 result = ProbeResult::NoMatch;
1358 if let &ty::Predicate::Trait(ref pred) = &o.predicate {
1359 possibly_unsatisfied_predicates.push(pred.skip_binder().trait_ref);
1364 if let ProbeResult::Match = result {
1365 if let (Some(return_ty), Some(xform_ret_ty)) =
1366 (self.return_type, probe.xform_ret_ty)
1368 let xform_ret_ty = self.resolve_vars_if_possible(&xform_ret_ty);
1369 debug!("comparing return_ty {:?} with xform ret ty {:?}",
1371 probe.xform_ret_ty);
1372 if self.at(&ObligationCause::dummy(), self.param_env)
1373 .sup(return_ty, xform_ret_ty)
1376 return ProbeResult::BadReturnType;
1385 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1386 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1387 /// external interface of the method can be determined from the trait, it's ok not to decide.
1388 /// We can basically just collapse all of the probes for various impls into one where-clause
1389 /// probe. This will result in a pending obligation so when more type-info is available we can
1390 /// make the final decision.
1392 /// Example (`src/test/run-pass/method-two-trait-defer-resolution-1.rs`):
1395 /// trait Foo { ... }
1396 /// impl Foo for Vec<int> { ... }
1397 /// impl Foo for Vec<usize> { ... }
1400 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1401 /// use, so it's ok to just commit to "using the method from the trait Foo".
1402 fn collapse_candidates_to_trait_pick(&self, probes: &[(&Candidate<'tcx>, ProbeResult)])
1403 -> Option<Pick<'tcx>>
1405 // Do all probes correspond to the same trait?
1406 let container = probes[0].0.item.container;
1407 if let ty::ImplContainer(_) = container {
1410 if probes[1..].iter().any(|&(p, _)| p.item.container != container) {
1414 // FIXME: check the return type here somehow.
1415 // If so, just use this trait and call it a day.
1417 item: probes[0].0.item.clone(),
1419 import_ids: probes[0].0.import_ids.clone(),
1426 /// Similarly to `probe_for_return_type`, this method attempts to find the best matching
1427 /// candidate method where the method name may have been misspelt. Similarly to other
1428 /// Levenshtein based suggestions, we provide at most one such suggestion.
1429 fn probe_for_lev_candidate(&mut self) -> Result<Option<ty::AssocItem>, MethodError<'tcx>> {
1430 debug!("Probing for method names similar to {:?}",
1433 let steps = self.steps.clone();
1435 let mut pcx = ProbeContext::new(self.fcx, self.span, self.mode, self.method_name,
1437 self.orig_steps_var_values.clone(),
1438 steps, IsSuggestion(true));
1439 pcx.allow_similar_names = true;
1440 pcx.assemble_inherent_candidates();
1441 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)?;
1443 let method_names = pcx.candidate_method_names();
1444 pcx.allow_similar_names = false;
1445 let applicable_close_candidates: Vec<ty::AssocItem> = method_names
1447 .filter_map(|&method_name| {
1449 pcx.method_name = Some(method_name);
1450 pcx.assemble_inherent_candidates();
1451 pcx.assemble_extension_candidates_for_traits_in_scope(hir::DUMMY_HIR_ID)
1452 .ok().map_or(None, |_| {
1454 .and_then(|pick| pick.ok())
1455 .and_then(|pick| Some(pick.item))
1460 if applicable_close_candidates.is_empty() {
1464 let names = applicable_close_candidates.iter().map(|cand| &cand.ident.name);
1465 find_best_match_for_name(names,
1466 &self.method_name.unwrap().as_str(),
1469 Ok(applicable_close_candidates
1471 .find(|method| method.ident.name == best_name))
1476 ///////////////////////////////////////////////////////////////////////////
1478 fn has_applicable_self(&self, item: &ty::AssocItem) -> bool {
1479 // "Fast track" -- check for usage of sugar when in method call
1482 // In Path mode (i.e., resolving a value like `T::next`), consider any
1483 // associated value (i.e., methods, constants) but not types.
1485 Mode::MethodCall => item.method_has_self_argument,
1486 Mode::Path => match item.kind {
1487 ty::AssocKind::Existential |
1488 ty::AssocKind::Type => false,
1489 ty::AssocKind::Method | ty::AssocKind::Const => true
1492 // FIXME -- check for types that deref to `Self`,
1493 // like `Rc<Self>` and so on.
1495 // Note also that the current code will break if this type
1496 // includes any of the type parameters defined on the method
1497 // -- but this could be overcome.
1500 fn record_static_candidate(&mut self, source: CandidateSource) {
1501 self.static_candidates.push(source);
1504 fn xform_self_ty(&self,
1505 item: &ty::AssocItem,
1507 substs: SubstsRef<'tcx>)
1508 -> (Ty<'tcx>, Option<Ty<'tcx>>) {
1509 if item.kind == ty::AssocKind::Method && self.mode == Mode::MethodCall {
1510 let sig = self.xform_method_sig(item.def_id, substs);
1511 (sig.inputs()[0], Some(sig.output()))
1517 fn xform_method_sig(&self,
1519 substs: SubstsRef<'tcx>)
1522 let fn_sig = self.tcx.fn_sig(method);
1523 debug!("xform_self_ty(fn_sig={:?}, substs={:?})",
1527 assert!(!substs.has_escaping_bound_vars());
1529 // It is possible for type parameters or early-bound lifetimes
1530 // to appear in the signature of `self`. The substitutions we
1531 // are given do not include type/lifetime parameters for the
1532 // method yet. So create fresh variables here for those too,
1533 // if there are any.
1534 let generics = self.tcx.generics_of(method);
1535 assert_eq!(substs.len(), generics.parent_count as usize);
1537 // Erase any late-bound regions from the method and substitute
1538 // in the values from the substitution.
1539 let xform_fn_sig = self.erase_late_bound_regions(&fn_sig);
1541 if generics.params.is_empty() {
1542 xform_fn_sig.subst(self.tcx, substs)
1544 let substs = InternalSubsts::for_item(self.tcx, method, |param, _| {
1545 let i = param.index as usize;
1546 if i < substs.len() {
1550 GenericParamDefKind::Lifetime => {
1551 // In general, during probe we erase regions. See
1552 // `impl_self_ty()` for an explanation.
1553 self.tcx.lifetimes.re_erased.into()
1555 GenericParamDefKind::Type { .. }
1556 | GenericParamDefKind::Const => {
1557 self.var_for_def(self.span, param)
1562 xform_fn_sig.subst(self.tcx, substs)
1566 /// Gets the type of an impl and generate substitutions with placeholders.
1567 fn impl_ty_and_substs(&self, impl_def_id: DefId) -> (Ty<'tcx>, SubstsRef<'tcx>) {
1568 (self.tcx.type_of(impl_def_id), self.fresh_item_substs(impl_def_id))
1571 fn fresh_item_substs(&self, def_id: DefId) -> SubstsRef<'tcx> {
1572 InternalSubsts::for_item(self.tcx, def_id, |param, _| {
1574 GenericParamDefKind::Lifetime => self.tcx.lifetimes.re_erased.into(),
1575 GenericParamDefKind::Type { .. } => {
1576 self.next_ty_var(TypeVariableOrigin {
1577 kind: TypeVariableOriginKind::SubstitutionPlaceholder,
1578 span: self.tcx.def_span(def_id),
1581 GenericParamDefKind::Const { .. } => {
1582 let span = self.tcx.def_span(def_id);
1583 let origin = ConstVariableOrigin {
1584 kind: ConstVariableOriginKind::SubstitutionPlaceholder,
1587 self.next_const_var(self.tcx.type_of(param.def_id), origin).into()
1593 /// Replaces late-bound-regions bound by `value` with `'static` using
1594 /// `ty::erase_late_bound_regions`.
1596 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1597 /// method matching. It is reasonable during the probe phase because we don't consider region
1598 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1599 /// rather than creating fresh region variables. This is nice for two reasons:
1601 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1602 /// particular method call, it winds up creating fewer types overall, which helps for memory
1603 /// usage. (Admittedly, this is a rather small effect, though measurable.)
1605 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1606 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1607 /// regions with actual region variables as is proper, we'd have to ensure that the same
1608 /// region got replaced with the same variable, which requires a bit more coordination
1609 /// and/or tracking the substitution and
1611 fn erase_late_bound_regions<T>(&self, value: &ty::Binder<T>) -> T
1612 where T: TypeFoldable<'tcx>
1614 self.tcx.erase_late_bound_regions(value)
1617 /// Finds the method with the appropriate name (or return type, as the case may be). If
1618 /// `allow_similar_names` is set, find methods with close-matching names.
1619 fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssocItem> {
1620 if let Some(name) = self.method_name {
1621 if self.allow_similar_names {
1622 let max_dist = max(name.as_str().len(), 3) / 3;
1623 self.tcx.associated_items(def_id)
1625 let dist = lev_distance(&*name.as_str(), &x.ident.as_str());
1626 Namespace::from(x.kind) == Namespace::Value && dist > 0
1632 .associated_item(def_id, name, Namespace::Value)
1633 .map_or(Vec::new(), |x| vec![x])
1636 self.tcx.associated_items(def_id).collect()
1641 impl<'tcx> Candidate<'tcx> {
1642 fn to_unadjusted_pick(&self) -> Pick<'tcx> {
1644 item: self.item.clone(),
1645 kind: match self.kind {
1646 InherentImplCandidate(..) => InherentImplPick,
1647 ObjectCandidate => ObjectPick,
1648 TraitCandidate(_) => TraitPick,
1649 WhereClauseCandidate(ref trait_ref) => {
1650 // Only trait derived from where-clauses should
1651 // appear here, so they should not contain any
1652 // inference variables or other artifacts. This
1653 // means they are safe to put into the
1654 // `WhereClausePick`.
1656 !trait_ref.skip_binder().substs.needs_infer()
1657 && !trait_ref.skip_binder().substs.has_placeholders()
1660 WhereClausePick(trait_ref.clone())
1663 import_ids: self.import_ids.clone(),