2 use super::MethodError
;
3 use super::NoMatchData
;
4 use super::{CandidateSource, ImplSource, TraitSource}
;
6 use crate::check
::FnCtxt
;
7 use crate::errors
::MethodCallOnUnknownType
;
8 use crate::hir
::def
::DefKind
;
9 use crate::hir
::def_id
::DefId
;
11 use rustc_data_structures
::fx
::FxHashSet
;
12 use rustc_errors
::Applicability
;
14 use rustc_hir
::def
::Namespace
;
15 use rustc_infer
::infer
::canonical
::OriginalQueryValues
;
16 use rustc_infer
::infer
::canonical
::{Canonical, QueryResponse}
;
17 use rustc_infer
::infer
::type_variable
::{TypeVariableOrigin, TypeVariableOriginKind}
;
18 use rustc_infer
::infer
::unify_key
::{ConstVariableOrigin, ConstVariableOriginKind}
;
19 use rustc_infer
::infer
::{self, InferOk, TyCtxtInferExt}
;
20 use rustc_middle
::middle
::stability
;
21 use rustc_middle
::ty
::subst
::{InternalSubsts, Subst, SubstsRef}
;
22 use rustc_middle
::ty
::GenericParamDefKind
;
23 use rustc_middle
::ty
::{self, ParamEnvAnd, ToPredicate, Ty, TyCtxt, TypeFoldable}
;
24 use rustc_session
::lint
;
25 use rustc_span
::def_id
::LocalDefId
;
26 use rustc_span
::lev_distance
::{find_best_match_for_name, lev_distance}
;
27 use rustc_span
::{symbol::Ident, Span, Symbol, DUMMY_SP}
;
28 use rustc_trait_selection
::autoderef
::{self, Autoderef}
;
29 use rustc_trait_selection
::traits
::query
::evaluate_obligation
::InferCtxtExt
;
30 use rustc_trait_selection
::traits
::query
::method_autoderef
::MethodAutoderefBadTy
;
31 use rustc_trait_selection
::traits
::query
::method_autoderef
::{
32 CandidateStep
, MethodAutoderefStepsResult
,
34 use rustc_trait_selection
::traits
::query
::CanonicalTyGoal
;
35 use rustc_trait_selection
::traits
::{self, ObligationCause}
;
41 use smallvec
::{smallvec, SmallVec}
;
43 use self::CandidateKind
::*;
44 pub use self::PickKind
::*;
46 /// Boolean flag used to indicate if this search is for a suggestion
47 /// or not. If true, we can allow ambiguity and so forth.
48 #[derive(Clone, Copy, Debug)]
49 pub struct IsSuggestion(pub bool
);
51 struct ProbeContext
<'a
, 'tcx
> {
52 fcx
: &'a FnCtxt
<'a
, 'tcx
>,
55 method_name
: Option
<Ident
>,
56 return_type
: Option
<Ty
<'tcx
>>,
58 /// This is the OriginalQueryValues for the steps queries
59 /// that are answered in steps.
60 orig_steps_var_values
: OriginalQueryValues
<'tcx
>,
61 steps
: &'tcx
[CandidateStep
<'tcx
>],
63 inherent_candidates
: Vec
<Candidate
<'tcx
>>,
64 extension_candidates
: Vec
<Candidate
<'tcx
>>,
65 impl_dups
: FxHashSet
<DefId
>,
67 /// Collects near misses when the candidate functions are missing a `self` keyword and is only
68 /// used for error reporting
69 static_candidates
: Vec
<CandidateSource
>,
71 /// When probing for names, include names that are close to the
72 /// requested name (by Levensthein distance)
73 allow_similar_names
: bool
,
75 /// Some(candidate) if there is a private candidate
76 private_candidate
: Option
<(DefKind
, DefId
)>,
78 /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
79 /// for error reporting
80 unsatisfied_predicates
:
81 Vec
<(ty
::Predicate
<'tcx
>, Option
<ty
::Predicate
<'tcx
>>, Option
<ObligationCause
<'tcx
>>)>,
83 is_suggestion
: IsSuggestion
,
85 scope_expr_id
: hir
::HirId
,
88 impl<'a
, 'tcx
> Deref
for ProbeContext
<'a
, 'tcx
> {
89 type Target
= FnCtxt
<'a
, 'tcx
>;
90 fn deref(&self) -> &Self::Target
{
95 #[derive(Debug, Clone)]
96 struct Candidate
<'tcx
> {
97 // Candidates are (I'm not quite sure, but they are mostly) basically
98 // some metadata on top of a `ty::AssocItem` (without substs).
100 // However, method probing wants to be able to evaluate the predicates
101 // for a function with the substs applied - for example, if a function
102 // has `where Self: Sized`, we don't want to consider it unless `Self`
103 // is actually `Sized`, and similarly, return-type suggestions want
104 // to consider the "actual" return type.
106 // The way this is handled is through `xform_self_ty`. It contains
107 // the receiver type of this candidate, but `xform_self_ty`,
108 // `xform_ret_ty` and `kind` (which contains the predicates) have the
109 // generic parameters of this candidate substituted with the *same set*
110 // of inference variables, which acts as some weird sort of "query".
112 // When we check out a candidate, we require `xform_self_ty` to be
113 // a subtype of the passed-in self-type, and this equates the type
114 // variables in the rest of the fields.
116 // For example, if we have this candidate:
119 // fn foo(&self) where Self: Sized;
123 // Then `xform_self_ty` will be `&'erased ?X` and `kind` will contain
124 // the predicate `?X: Sized`, so if we are evaluating `Foo` for a
125 // the receiver `&T`, we'll do the subtyping which will make `?X`
126 // get the right value, then when we evaluate the predicate we'll check
128 xform_self_ty
: Ty
<'tcx
>,
129 xform_ret_ty
: Option
<Ty
<'tcx
>>,
131 kind
: CandidateKind
<'tcx
>,
132 import_ids
: SmallVec
<[LocalDefId
; 1]>,
135 #[derive(Debug, Clone)]
136 enum CandidateKind
<'tcx
> {
137 InherentImplCandidate(
139 // Normalize obligations
140 Vec
<traits
::PredicateObligation
<'tcx
>>,
143 TraitCandidate(ty
::TraitRef
<'tcx
>),
144 WhereClauseCandidate(
146 ty
::PolyTraitRef
<'tcx
>,
150 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
157 /// When adjusting a receiver we often want to do one of
159 /// - Add a `&` (or `&mut`), converting the receiver from `T` to `&T` (or `&mut T`)
160 /// - If the receiver has type `*mut T`, convert it to `*const T`
162 /// This type tells us which one to do.
164 /// Note that in principle we could do both at the same time. For example, when the receiver has
165 /// type `T`, we could autoref it to `&T`, then convert to `*const T`. Or, when it has type `*mut
166 /// T`, we could convert it to `*const T`, then autoref to `&*const T`. However, currently we do
167 /// (at most) one of these. Either the receiver has type `T` and we convert it to `&T` (or with
168 /// `mut`), or it has type `*mut T` and we convert it to `*const T`.
169 #[derive(Debug, PartialEq, Copy, Clone)]
170 pub enum AutorefOrPtrAdjustment
{
171 /// Receiver has type `T`, add `&` or `&mut` (it `T` is `mut`), and maybe also "unsize" it.
172 /// Unsizing is used to convert a `[T; N]` to `[T]`, which only makes sense when autorefing.
174 mutbl
: hir
::Mutability
,
176 /// Indicates that the source expression should be "unsized" to a target type.
177 /// This is special-cased for just arrays unsizing to slices.
180 /// Receiver has type `*mut T`, convert to `*const T`
184 impl AutorefOrPtrAdjustment
{
185 fn get_unsize(&self) -> bool
{
187 AutorefOrPtrAdjustment
::Autoref { mutbl: _, unsize }
=> *unsize
,
188 AutorefOrPtrAdjustment
::ToConstPtr
=> false,
193 #[derive(Debug, PartialEq, Clone)]
194 pub struct Pick
<'tcx
> {
195 pub item
: ty
::AssocItem
,
196 pub kind
: PickKind
<'tcx
>,
197 pub import_ids
: SmallVec
<[LocalDefId
; 1]>,
199 /// Indicates that the source expression should be autoderef'd N times
201 /// A = expr | *expr | **expr | ...
202 pub autoderefs
: usize,
204 /// Indicates that we want to add an autoref (and maybe also unsize it), or if the receiver is
205 /// `*mut T`, convert it to `*const T`.
206 pub autoref_or_ptr_adjustment
: Option
<AutorefOrPtrAdjustment
>,
207 pub self_ty
: Ty
<'tcx
>,
210 #[derive(Clone, Debug, PartialEq, Eq)]
211 pub enum PickKind
<'tcx
> {
217 ty
::PolyTraitRef
<'tcx
>,
221 pub type PickResult
<'tcx
> = Result
<Pick
<'tcx
>, MethodError
<'tcx
>>;
223 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
225 // An expression of the form `receiver.method_name(...)`.
226 // Autoderefs are performed on `receiver`, lookup is done based on the
227 // `self` argument of the method, and static methods aren't considered.
229 // An expression of the form `Type::item` or `<T>::item`.
230 // No autoderefs are performed, lookup is done based on the type each
231 // implementation is for, and static methods are included.
235 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
236 pub enum ProbeScope
{
237 // Assemble candidates coming only from traits in scope.
240 // Assemble candidates coming from all traits.
244 impl<'a
, 'tcx
> FnCtxt
<'a
, 'tcx
> {
245 /// This is used to offer suggestions to users. It returns methods
246 /// that could have been called which have the desired return
247 /// type. Some effort is made to rule out methods that, if called,
248 /// would result in an error (basically, the same criteria we
249 /// would use to decide if a method is a plausible fit for
250 /// ambiguity purposes).
251 #[instrument(level = "debug", skip(self, scope_expr_id))]
252 pub fn probe_for_return_type(
256 return_type
: Ty
<'tcx
>,
258 scope_expr_id
: hir
::HirId
,
259 ) -> Vec
<ty
::AssocItem
> {
261 "probe(self_ty={:?}, return_type={}, scope_expr_id={})",
262 self_ty
, return_type
, scope_expr_id
264 let method_names
= self
273 ProbeScope
::AllTraits
,
274 |probe_cx
| Ok(probe_cx
.candidate_method_names()),
276 .unwrap_or_default();
279 .flat_map(|&method_name
| {
288 ProbeScope
::AllTraits
,
289 |probe_cx
| probe_cx
.pick(),
292 .map(|pick
| pick
.item
)
297 #[instrument(level = "debug", skip(self, scope_expr_id))]
298 pub fn probe_for_name(
303 is_suggestion
: IsSuggestion
,
305 scope_expr_id
: hir
::HirId
,
307 ) -> PickResult
<'tcx
> {
309 "probe(self_ty={:?}, item_name={}, scope_expr_id={})",
310 self_ty
, item_name
, scope_expr_id
321 |probe_cx
| probe_cx
.pick(),
329 method_name
: Option
<Ident
>,
330 return_type
: Option
<Ty
<'tcx
>>,
331 is_suggestion
: IsSuggestion
,
333 scope_expr_id
: hir
::HirId
,
336 ) -> Result
<R
, MethodError
<'tcx
>>
338 OP
: FnOnce(ProbeContext
<'a
, 'tcx
>) -> Result
<R
, MethodError
<'tcx
>>,
340 let mut orig_values
= OriginalQueryValues
::default();
341 let param_env_and_self_ty
= self.infcx
.canonicalize_query(
342 ParamEnvAnd { param_env: self.param_env, value: self_ty }
,
346 let steps
= if mode
== Mode
::MethodCall
{
347 self.tcx
.method_autoderef_steps(param_env_and_self_ty
)
349 self.infcx
.probe(|_
| {
350 // Mode::Path - the deref steps is "trivial". This turns
351 // our CanonicalQuery into a "trivial" QueryResponse. This
352 // is a bit inefficient, but I don't think that writing
353 // special handling for this "trivial case" is a good idea.
355 let infcx
= &self.infcx
;
356 let (ParamEnvAnd { param_env: _, value: self_ty }
, canonical_inference_vars
) =
357 infcx
.instantiate_canonical_with_fresh_inference_vars(
359 ¶m_env_and_self_ty
,
362 "probe_op: Mode::Path, param_env_and_self_ty={:?} self_ty={:?}",
363 param_env_and_self_ty
, self_ty
365 MethodAutoderefStepsResult
{
366 steps
: infcx
.tcx
.arena
.alloc_from_iter([CandidateStep
{
367 self_ty
: self.make_query_response_ignoring_pending_obligations(
368 canonical_inference_vars
,
372 from_unsafe_deref
: false,
376 reached_recursion_limit
: false,
381 // If our autoderef loop had reached the recursion limit,
382 // report an overflow error, but continue going on with
383 // the truncated autoderef list.
384 if steps
.reached_recursion_limit
{
389 .unwrap_or_else(|| span_bug
!(span
, "reached the recursion limit in 0 steps?"))
392 .probe_instantiate_query_response(span
, &orig_values
, ty
)
393 .unwrap_or_else(|_
| span_bug
!(span
, "instantiating {:?} failed?", ty
));
394 autoderef
::report_autoderef_recursion_limit_error(self.tcx
, span
, ty
.value
);
398 // If we encountered an `_` type or an error type during autoderef, this is
400 if let Some(bad_ty
) = &steps
.opt_bad_ty
{
402 // Ambiguity was encountered during a suggestion. Just keep going.
403 debug
!("ProbeContext: encountered ambiguity in suggestion");
404 } else if bad_ty
.reached_raw_pointer
&& !self.tcx
.features().arbitrary_self_types
{
405 // this case used to be allowed by the compiler,
406 // so we do a future-compat lint here for the 2015 edition
407 // (see https://github.com/rust-lang/rust/issues/46906)
408 if self.tcx
.sess
.rust_2018() {
409 self.tcx
.sess
.emit_err(MethodCallOnUnknownType { span }
);
411 self.tcx
.struct_span_lint_hir(
412 lint
::builtin
::TYVAR_BEHIND_RAW_POINTER
,
415 |lint
| lint
.build("type annotations needed").emit(),
419 // Encountered a real ambiguity, so abort the lookup. If `ty` is not
420 // an `Err`, report the right "type annotations needed" error pointing
424 .probe_instantiate_query_response(span
, &orig_values
, ty
)
425 .unwrap_or_else(|_
| span_bug
!(span
, "instantiating {:?} failed?", ty
));
426 let ty
= self.structurally_resolved_type(span
, ty
.value
);
427 assert
!(matches
!(ty
.kind(), ty
::Error(_
)));
428 return Err(MethodError
::NoMatch(NoMatchData
::new(
438 debug
!("ProbeContext: steps for self_ty={:?} are {:?}", self_ty
, steps
);
440 // this creates one big transaction so that all type variables etc
441 // that we create during the probe process are removed later
443 let mut probe_cx
= ProbeContext
::new(
455 probe_cx
.assemble_inherent_candidates();
457 ProbeScope
::TraitsInScope
=> {
458 probe_cx
.assemble_extension_candidates_for_traits_in_scope(scope_expr_id
)
460 ProbeScope
::AllTraits
=> probe_cx
.assemble_extension_candidates_for_all_traits(),
467 pub fn provide(providers
: &mut ty
::query
::Providers
) {
468 providers
.method_autoderef_steps
= method_autoderef_steps
;
471 fn method_autoderef_steps
<'tcx
>(
473 goal
: CanonicalTyGoal
<'tcx
>,
474 ) -> MethodAutoderefStepsResult
<'tcx
> {
475 debug
!("method_autoderef_steps({:?})", goal
);
477 tcx
.infer_ctxt().enter_with_canonical(DUMMY_SP
, &goal
, |ref infcx
, goal
, inference_vars
| {
478 let ParamEnvAnd { param_env, value: self_ty }
= goal
;
481 Autoderef
::new(infcx
, param_env
, hir
::CRATE_HIR_ID
, DUMMY_SP
, self_ty
, DUMMY_SP
)
482 .include_raw_pointers()
484 let mut reached_raw_pointer
= false;
485 let mut steps
: Vec
<_
> = autoderef
488 let step
= CandidateStep
{
489 self_ty
: infcx
.make_query_response_ignoring_pending_obligations(
490 inference_vars
.clone(),
494 from_unsafe_deref
: reached_raw_pointer
,
497 if let ty
::RawPtr(_
) = ty
.kind() {
498 // all the subsequent steps will be from_unsafe_deref
499 reached_raw_pointer
= true;
505 let final_ty
= autoderef
.final_ty(true);
506 let opt_bad_ty
= match final_ty
.kind() {
507 ty
::Infer(ty
::TyVar(_
)) | ty
::Error(_
) => Some(MethodAutoderefBadTy
{
510 .make_query_response_ignoring_pending_obligations(inference_vars
, final_ty
),
512 ty
::Array(elem_ty
, _
) => {
513 let dereferences
= steps
.len() - 1;
515 steps
.push(CandidateStep
{
516 self_ty
: infcx
.make_query_response_ignoring_pending_obligations(
518 infcx
.tcx
.mk_slice(*elem_ty
),
520 autoderefs
: dereferences
,
521 // this could be from an unsafe deref if we had
522 // a *mut/const [T; N]
523 from_unsafe_deref
: reached_raw_pointer
,
532 debug
!("method_autoderef_steps: steps={:?} opt_bad_ty={:?}", steps
, opt_bad_ty
);
534 MethodAutoderefStepsResult
{
535 steps
: tcx
.arena
.alloc_from_iter(steps
),
536 opt_bad_ty
: opt_bad_ty
.map(|ty
| &*tcx
.arena
.alloc(ty
)),
537 reached_recursion_limit
: autoderef
.reached_recursion_limit(),
542 impl<'a
, 'tcx
> ProbeContext
<'a
, 'tcx
> {
544 fcx
: &'a FnCtxt
<'a
, 'tcx
>,
547 method_name
: Option
<Ident
>,
548 return_type
: Option
<Ty
<'tcx
>>,
549 orig_steps_var_values
: OriginalQueryValues
<'tcx
>,
550 steps
: &'tcx
[CandidateStep
<'tcx
>],
551 is_suggestion
: IsSuggestion
,
552 scope_expr_id
: hir
::HirId
,
553 ) -> ProbeContext
<'a
, 'tcx
> {
560 inherent_candidates
: Vec
::new(),
561 extension_candidates
: Vec
::new(),
562 impl_dups
: FxHashSet
::default(),
563 orig_steps_var_values
,
565 static_candidates
: Vec
::new(),
566 allow_similar_names
: false,
567 private_candidate
: None
,
568 unsatisfied_predicates
: Vec
::new(),
574 fn reset(&mut self) {
575 self.inherent_candidates
.clear();
576 self.extension_candidates
.clear();
577 self.impl_dups
.clear();
578 self.static_candidates
.clear();
579 self.private_candidate
= None
;
582 ///////////////////////////////////////////////////////////////////////////
583 // CANDIDATE ASSEMBLY
585 fn push_candidate(&mut self, candidate
: Candidate
<'tcx
>, is_inherent
: bool
) {
586 let is_accessible
= if let Some(name
) = self.method_name
{
587 let item
= candidate
.item
;
589 self.tcx
.adjust_ident_and_get_scope(name
, item
.container
.id(), self.body_id
).1;
590 item
.vis
.is_accessible_from(def_scope
, self.tcx
)
596 self.inherent_candidates
.push(candidate
);
598 self.extension_candidates
.push(candidate
);
600 } else if self.private_candidate
.is_none() {
601 self.private_candidate
=
602 Some((candidate
.item
.kind
.as_def_kind(), candidate
.item
.def_id
));
606 fn assemble_inherent_candidates(&mut self) {
607 for step
in self.steps
.iter() {
608 self.assemble_probe(&step
.self_ty
);
612 fn assemble_probe(&mut self, self_ty
: &Canonical
<'tcx
, QueryResponse
<'tcx
, Ty
<'tcx
>>>) {
613 debug
!("assemble_probe: self_ty={:?}", self_ty
);
614 let lang_items
= self.tcx
.lang_items();
616 match *self_ty
.value
.value
.kind() {
617 ty
::Dynamic(data
, ..) if let Some(p
) = data
.principal() => {
618 // Subtle: we can't use `instantiate_query_response` here: using it will
619 // commit to all of the type equalities assumed by inference going through
620 // autoderef (see the `method-probe-no-guessing` test).
622 // However, in this code, it is OK if we end up with an object type that is
623 // "more general" than the object type that we are evaluating. For *every*
624 // object type `MY_OBJECT`, a function call that goes through a trait-ref
625 // of the form `<MY_OBJECT as SuperTraitOf(MY_OBJECT)>::func` is a valid
626 // `ObjectCandidate`, and it should be discoverable "exactly" through one
627 // of the iterations in the autoderef loop, so there is no problem with it
628 // being discoverable in another one of these iterations.
630 // Using `instantiate_canonical_with_fresh_inference_vars` on our
631 // `Canonical<QueryResponse<Ty<'tcx>>>` and then *throwing away* the
632 // `CanonicalVarValues` will exactly give us such a generalization - it
633 // will still match the original object type, but it won't pollute our
634 // type variables in any form, so just do that!
635 let (QueryResponse { value: generalized_self_ty, .. }
, _ignored_var_values
) =
637 .instantiate_canonical_with_fresh_inference_vars(self.span
, self_ty
);
639 self.assemble_inherent_candidates_from_object(generalized_self_ty
);
640 self.assemble_inherent_impl_candidates_for_type(p
.def_id());
643 self.assemble_inherent_impl_candidates_for_type(def
.did
);
645 ty
::Foreign(did
) => {
646 self.assemble_inherent_impl_candidates_for_type(did
);
649 self.assemble_inherent_candidates_from_param(p
);
652 let lang_def_id
= lang_items
.bool_impl();
653 self.assemble_inherent_impl_for_primitive(lang_def_id
);
656 let lang_def_id
= lang_items
.char_impl();
657 self.assemble_inherent_impl_for_primitive(lang_def_id
);
660 let lang_def_id
= lang_items
.str_impl();
661 self.assemble_inherent_impl_for_primitive(lang_def_id
);
663 let lang_def_id
= lang_items
.str_alloc_impl();
664 self.assemble_inherent_impl_for_primitive(lang_def_id
);
668 lang_items
.slice_impl(),
669 lang_items
.slice_u8_impl(),
670 lang_items
.slice_alloc_impl(),
671 lang_items
.slice_u8_alloc_impl(),
673 self.assemble_inherent_impl_for_primitive(lang_def_id
);
677 let lang_def_id
= lang_items
.array_impl();
678 self.assemble_inherent_impl_for_primitive(lang_def_id
);
680 ty
::RawPtr(ty
::TypeAndMut { ty: _, mutbl }
) => {
681 let (lang_def_id1
, lang_def_id2
) = match mutbl
{
682 hir
::Mutability
::Not
=> {
683 (lang_items
.const_ptr_impl(), lang_items
.const_slice_ptr_impl())
685 hir
::Mutability
::Mut
=> {
686 (lang_items
.mut_ptr_impl(), lang_items
.mut_slice_ptr_impl())
689 self.assemble_inherent_impl_for_primitive(lang_def_id1
);
690 self.assemble_inherent_impl_for_primitive(lang_def_id2
);
693 let lang_def_id
= match i
{
694 ty
::IntTy
::I8
=> lang_items
.i8_impl(),
695 ty
::IntTy
::I16
=> lang_items
.i16_impl(),
696 ty
::IntTy
::I32
=> lang_items
.i32_impl(),
697 ty
::IntTy
::I64
=> lang_items
.i64_impl(),
698 ty
::IntTy
::I128
=> lang_items
.i128_impl(),
699 ty
::IntTy
::Isize
=> lang_items
.isize_impl(),
701 self.assemble_inherent_impl_for_primitive(lang_def_id
);
704 let lang_def_id
= match i
{
705 ty
::UintTy
::U8
=> lang_items
.u8_impl(),
706 ty
::UintTy
::U16
=> lang_items
.u16_impl(),
707 ty
::UintTy
::U32
=> lang_items
.u32_impl(),
708 ty
::UintTy
::U64
=> lang_items
.u64_impl(),
709 ty
::UintTy
::U128
=> lang_items
.u128_impl(),
710 ty
::UintTy
::Usize
=> lang_items
.usize_impl(),
712 self.assemble_inherent_impl_for_primitive(lang_def_id
);
715 let (lang_def_id1
, lang_def_id2
) = match f
{
716 ty
::FloatTy
::F32
=> (lang_items
.f32_impl(), lang_items
.f32_runtime_impl()),
717 ty
::FloatTy
::F64
=> (lang_items
.f64_impl(), lang_items
.f64_runtime_impl()),
719 self.assemble_inherent_impl_for_primitive(lang_def_id1
);
720 self.assemble_inherent_impl_for_primitive(lang_def_id2
);
726 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id
: Option
<DefId
>) {
727 if let Some(impl_def_id
) = lang_def_id
{
728 self.assemble_inherent_impl_probe(impl_def_id
);
732 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id
: DefId
) {
733 let impl_def_ids
= self.tcx
.at(self.span
).inherent_impls(def_id
);
734 for &impl_def_id
in impl_def_ids
.iter() {
735 self.assemble_inherent_impl_probe(impl_def_id
);
739 fn assemble_inherent_impl_probe(&mut self, impl_def_id
: DefId
) {
740 if !self.impl_dups
.insert(impl_def_id
) {
741 return; // already visited
744 debug
!("assemble_inherent_impl_probe {:?}", impl_def_id
);
746 for item
in self.impl_or_trait_item(impl_def_id
) {
747 if !self.has_applicable_self(&item
) {
748 // No receiver declared. Not a candidate.
749 self.record_static_candidate(ImplSource(impl_def_id
));
753 let (impl_ty
, impl_substs
) = self.impl_ty_and_substs(impl_def_id
);
754 let impl_ty
= impl_ty
.subst(self.tcx
, impl_substs
);
756 debug
!("impl_ty: {:?}", impl_ty
);
758 // Determine the receiver type that the method itself expects.
759 let (xform_self_ty
, xform_ret_ty
) = self.xform_self_ty(&item
, impl_ty
, impl_substs
);
760 debug
!("xform_self_ty: {:?}, xform_ret_ty: {:?}", xform_self_ty
, xform_ret_ty
);
762 // We can't use normalize_associated_types_in as it will pollute the
763 // fcx's fulfillment context after this probe is over.
764 // Note: we only normalize `xform_self_ty` here since the normalization
765 // of the return type can lead to inference results that prohibit
766 // valid canidates from being found, see issue #85671
767 // FIXME Postponing the normalization of the return type likely only hides a deeper bug,
768 // which might be caused by the `param_env` itself. The clauses of the `param_env`
769 // maybe shouldn't include `Param`s, but rather fresh variables or be canonicalized,
771 let cause
= traits
::ObligationCause
::misc(self.span
, self.body_id
);
772 let selcx
= &mut traits
::SelectionContext
::new(self.fcx
);
773 let traits
::Normalized { value: xform_self_ty, obligations }
=
774 traits
::normalize(selcx
, self.param_env
, cause
, xform_self_ty
);
776 "assemble_inherent_impl_probe after normalization: xform_self_ty = {:?}/{:?}",
777 xform_self_ty
, xform_ret_ty
785 kind
: InherentImplCandidate(impl_substs
, obligations
),
786 import_ids
: smallvec
![],
793 fn assemble_inherent_candidates_from_object(&mut self, self_ty
: Ty
<'tcx
>) {
794 debug
!("assemble_inherent_candidates_from_object(self_ty={:?})", self_ty
);
796 let principal
= match self_ty
.kind() {
797 ty
::Dynamic(ref data
, ..) => Some(data
),
800 .and_then(|data
| data
.principal())
804 "non-object {:?} in assemble_inherent_candidates_from_object",
809 // It is illegal to invoke a method on a trait instance that refers to
810 // the `Self` type. An [`ObjectSafetyViolation::SupertraitSelf`] error
811 // will be reported by `object_safety.rs` if the method refers to the
812 // `Self` type anywhere other than the receiver. Here, we use a
813 // substitution that replaces `Self` with the object type itself. Hence,
814 // a `&self` method will wind up with an argument type like `&dyn Trait`.
815 let trait_ref
= principal
.with_self_ty(self.tcx
, self_ty
);
816 self.elaborate_bounds(iter
::once(trait_ref
), |this
, new_trait_ref
, item
| {
817 let new_trait_ref
= this
.erase_late_bound_regions(new_trait_ref
);
819 let (xform_self_ty
, xform_ret_ty
) =
820 this
.xform_self_ty(&item
, new_trait_ref
.self_ty(), new_trait_ref
.substs
);
826 kind
: ObjectCandidate
,
827 import_ids
: smallvec
![],
834 fn assemble_inherent_candidates_from_param(&mut self, param_ty
: ty
::ParamTy
) {
835 // FIXME: do we want to commit to this behavior for param bounds?
836 debug
!("assemble_inherent_candidates_from_param(param_ty={:?})", param_ty
);
838 let bounds
= self.param_env
.caller_bounds().iter().filter_map(|predicate
| {
839 let bound_predicate
= predicate
.kind();
840 match bound_predicate
.skip_binder() {
841 ty
::PredicateKind
::Trait(trait_predicate
) => {
842 match *trait_predicate
.trait_ref
.self_ty().kind() {
843 ty
::Param(p
) if p
== param_ty
=> {
844 Some(bound_predicate
.rebind(trait_predicate
.trait_ref
))
849 ty
::PredicateKind
::Subtype(..)
850 | ty
::PredicateKind
::Coerce(..)
851 | ty
::PredicateKind
::Projection(..)
852 | ty
::PredicateKind
::RegionOutlives(..)
853 | ty
::PredicateKind
::WellFormed(..)
854 | ty
::PredicateKind
::ObjectSafe(..)
855 | ty
::PredicateKind
::ClosureKind(..)
856 | ty
::PredicateKind
::TypeOutlives(..)
857 | ty
::PredicateKind
::ConstEvaluatable(..)
858 | ty
::PredicateKind
::ConstEquate(..)
859 | ty
::PredicateKind
::TypeWellFormedFromEnv(..) => None
,
863 self.elaborate_bounds(bounds
, |this
, poly_trait_ref
, item
| {
864 let trait_ref
= this
.erase_late_bound_regions(poly_trait_ref
);
866 let (xform_self_ty
, xform_ret_ty
) =
867 this
.xform_self_ty(&item
, trait_ref
.self_ty(), trait_ref
.substs
);
869 // Because this trait derives from a where-clause, it
870 // should not contain any inference variables or other
871 // artifacts. This means it is safe to put into the
872 // `WhereClauseCandidate` and (eventually) into the
873 // `WhereClausePick`.
874 assert
!(!trait_ref
.substs
.needs_infer());
881 kind
: WhereClauseCandidate(poly_trait_ref
),
882 import_ids
: smallvec
![],
889 // Do a search through a list of bounds, using a callback to actually
890 // create the candidates.
891 fn elaborate_bounds
<F
>(
893 bounds
: impl Iterator
<Item
= ty
::PolyTraitRef
<'tcx
>>,
896 F
: for<'b
> FnMut(&mut ProbeContext
<'b
, 'tcx
>, ty
::PolyTraitRef
<'tcx
>, ty
::AssocItem
),
899 for bound_trait_ref
in traits
::transitive_bounds(tcx
, bounds
) {
900 debug
!("elaborate_bounds(bound_trait_ref={:?})", bound_trait_ref
);
901 for item
in self.impl_or_trait_item(bound_trait_ref
.def_id()) {
902 if !self.has_applicable_self(&item
) {
903 self.record_static_candidate(TraitSource(bound_trait_ref
.def_id()));
905 mk_cand(self, bound_trait_ref
, item
);
911 fn assemble_extension_candidates_for_traits_in_scope(&mut self, expr_hir_id
: hir
::HirId
) {
912 let mut duplicates
= FxHashSet
::default();
913 let opt_applicable_traits
= self.tcx
.in_scope_traits(expr_hir_id
);
914 if let Some(applicable_traits
) = opt_applicable_traits
{
915 for trait_candidate
in applicable_traits
.iter() {
916 let trait_did
= trait_candidate
.def_id
;
917 if duplicates
.insert(trait_did
) {
918 self.assemble_extension_candidates_for_trait(
919 &trait_candidate
.import_ids
,
927 fn assemble_extension_candidates_for_all_traits(&mut self) {
928 let mut duplicates
= FxHashSet
::default();
929 for trait_info
in suggest
::all_traits(self.tcx
) {
930 if duplicates
.insert(trait_info
.def_id
) {
931 self.assemble_extension_candidates_for_trait(&smallvec
![], trait_info
.def_id
);
936 pub fn matches_return_type(
938 method
: &ty
::AssocItem
,
939 self_ty
: Option
<Ty
<'tcx
>>,
943 ty
::AssocKind
::Fn
=> {
944 let fty
= self.tcx
.fn_sig(method
.def_id
);
946 let substs
= self.fresh_substs_for_item(self.span
, method
.def_id
);
947 let fty
= fty
.subst(self.tcx
, substs
);
949 self.replace_bound_vars_with_fresh_vars(self.span
, infer
::FnCall
, fty
);
951 if let Some(self_ty
) = self_ty
{
953 .at(&ObligationCause
::dummy(), self.param_env
)
954 .sup(fty
.inputs()[0], self_ty
)
960 self.can_sub(self.param_env
, fty
.output(), expected
).is_ok()
967 fn assemble_extension_candidates_for_trait(
969 import_ids
: &SmallVec
<[LocalDefId
; 1]>,
972 debug
!("assemble_extension_candidates_for_trait(trait_def_id={:?})", trait_def_id
);
973 let trait_substs
= self.fresh_item_substs(trait_def_id
);
974 let trait_ref
= ty
::TraitRef
::new(trait_def_id
, trait_substs
);
976 if self.tcx
.is_trait_alias(trait_def_id
) {
977 // For trait aliases, assume all supertraits are relevant.
978 let bounds
= iter
::once(ty
::Binder
::dummy(trait_ref
));
979 self.elaborate_bounds(bounds
, |this
, new_trait_ref
, item
| {
980 let new_trait_ref
= this
.erase_late_bound_regions(new_trait_ref
);
982 let (xform_self_ty
, xform_ret_ty
) =
983 this
.xform_self_ty(&item
, new_trait_ref
.self_ty(), new_trait_ref
.substs
);
989 import_ids
: import_ids
.clone(),
990 kind
: TraitCandidate(new_trait_ref
),
996 debug_assert
!(self.tcx
.is_trait(trait_def_id
));
997 for item
in self.impl_or_trait_item(trait_def_id
) {
998 // Check whether `trait_def_id` defines a method with suitable name.
999 if !self.has_applicable_self(&item
) {
1000 debug
!("method has inapplicable self");
1001 self.record_static_candidate(TraitSource(trait_def_id
));
1005 let (xform_self_ty
, xform_ret_ty
) =
1006 self.xform_self_ty(&item
, trait_ref
.self_ty(), trait_substs
);
1007 self.push_candidate(
1012 import_ids
: import_ids
.clone(),
1013 kind
: TraitCandidate(trait_ref
),
1021 fn candidate_method_names(&self) -> Vec
<Ident
> {
1022 let mut set
= FxHashSet
::default();
1023 let mut names
: Vec
<_
> = self
1024 .inherent_candidates
1026 .chain(&self.extension_candidates
)
1027 .filter(|candidate
| {
1028 if let Some(return_ty
) = self.return_type
{
1029 self.matches_return_type(&candidate
.item
, None
, return_ty
)
1034 .map(|candidate
| candidate
.item
.ident(self.tcx
))
1035 .filter(|&name
| set
.insert(name
))
1038 // Sort them by the name so we have a stable result.
1039 names
.sort_by(|a
, b
| a
.as_str().partial_cmp(b
.as_str()).unwrap());
1043 ///////////////////////////////////////////////////////////////////////////
1044 // THE ACTUAL SEARCH
1046 fn pick(mut self) -> PickResult
<'tcx
> {
1047 assert
!(self.method_name
.is_some());
1049 if let Some(r
) = self.pick_core() {
1053 debug
!("pick: actual search failed, assemble diagnostics");
1055 let static_candidates
= mem
::take(&mut self.static_candidates
);
1056 let private_candidate
= self.private_candidate
.take();
1057 let unsatisfied_predicates
= mem
::take(&mut self.unsatisfied_predicates
);
1059 // things failed, so lets look at all traits, for diagnostic purposes now:
1062 let span
= self.span
;
1065 self.assemble_extension_candidates_for_all_traits();
1067 let out_of_scope_traits
= match self.pick_core() {
1068 Some(Ok(p
)) => vec
![p
.item
.container
.id()],
1069 //Some(Ok(p)) => p.iter().map(|p| p.item.container().id()).collect(),
1070 Some(Err(MethodError
::Ambiguity(v
))) => v
1072 .map(|source
| match source
{
1073 TraitSource(id
) => id
,
1074 ImplSource(impl_id
) => match tcx
.trait_id_of_impl(impl_id
) {
1076 None
=> span_bug
!(span
, "found inherent method when looking at traits"),
1080 Some(Err(MethodError
::NoMatch(NoMatchData
{
1081 out_of_scope_traits
: others
, ..
1083 assert
!(others
.is_empty());
1089 if let Some((kind
, def_id
)) = private_candidate
{
1090 return Err(MethodError
::PrivateMatch(kind
, def_id
, out_of_scope_traits
));
1092 let lev_candidate
= self.probe_for_lev_candidate()?
;
1094 Err(MethodError
::NoMatch(NoMatchData
::new(
1096 unsatisfied_predicates
,
1097 out_of_scope_traits
,
1103 fn pick_core(&mut self) -> Option
<PickResult
<'tcx
>> {
1104 let mut unstable_candidates
= Vec
::new();
1105 let pick
= self.pick_all_method(Some(&mut unstable_candidates
));
1107 // In this case unstable picking is done by `pick_method`.
1108 if !self.tcx
.sess
.opts
.debugging_opts
.pick_stable_methods_before_any_unstable
{
1113 // Emit a lint if there are unstable candidates alongside the stable ones.
1115 // We suppress warning if we're picking the method only because it is a
1117 Some(Ok(ref p
)) if !self.is_suggestion
.0 && !unstable_candidates
.is_empty() => {
1118 self.emit_unstable_name_collision_hint(p
, &unstable_candidates
);
1122 None
=> self.pick_all_method(None
),
1128 mut unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1129 ) -> Option
<PickResult
<'tcx
>> {
1130 let steps
= self.steps
.clone();
1134 debug
!("pick_all_method: step={:?}", step
);
1135 // skip types that are from a type error or that would require dereferencing
1137 !step
.self_ty
.references_error() && !step
.from_unsafe_deref
1140 let InferOk { value: self_ty, obligations: _ }
= self
1142 .probe_instantiate_query_response(
1144 &self.orig_steps_var_values
,
1147 .unwrap_or_else(|_
| {
1148 span_bug
!(self.span
, "{:?} was applicable but now isn't?", step
.self_ty
)
1150 self.pick_by_value_method(step
, self_ty
, unstable_candidates
.as_deref_mut())
1152 self.pick_autorefd_method(
1155 hir
::Mutability
::Not
,
1156 unstable_candidates
.as_deref_mut(),
1159 self.pick_autorefd_method(
1162 hir
::Mutability
::Mut
,
1163 unstable_candidates
.as_deref_mut(),
1167 self.pick_const_ptr_method(
1170 unstable_candidates
.as_deref_mut(),
1178 /// For each type `T` in the step list, this attempts to find a method where
1179 /// the (transformed) self type is exactly `T`. We do however do one
1180 /// transformation on the adjustment: if we are passing a region pointer in,
1181 /// we will potentially *reborrow* it to a shorter lifetime. This allows us
1182 /// to transparently pass `&mut` pointers, in particular, without consuming
1183 /// them for their entire lifetime.
1184 fn pick_by_value_method(
1186 step
: &CandidateStep
<'tcx
>,
1188 unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1189 ) -> Option
<PickResult
<'tcx
>> {
1194 self.pick_method(self_ty
, unstable_candidates
).map(|r
| {
1196 pick
.autoderefs
= step
.autoderefs
;
1198 // Insert a `&*` or `&mut *` if this is a reference type:
1199 if let ty
::Ref(_
, _
, mutbl
) = *step
.self_ty
.value
.value
.kind() {
1200 pick
.autoderefs
+= 1;
1201 pick
.autoref_or_ptr_adjustment
= Some(AutorefOrPtrAdjustment
::Autoref
{
1203 unsize
: pick
.autoref_or_ptr_adjustment
.map_or(false, |a
| a
.get_unsize()),
1212 fn pick_autorefd_method(
1214 step
: &CandidateStep
<'tcx
>,
1216 mutbl
: hir
::Mutability
,
1217 unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1218 ) -> Option
<PickResult
<'tcx
>> {
1221 // In general, during probing we erase regions.
1222 let region
= tcx
.lifetimes
.re_erased
;
1224 let autoref_ty
= tcx
.mk_ref(region
, ty
::TypeAndMut { ty: self_ty, mutbl }
);
1225 self.pick_method(autoref_ty
, unstable_candidates
).map(|r
| {
1227 pick
.autoderefs
= step
.autoderefs
;
1228 pick
.autoref_or_ptr_adjustment
=
1229 Some(AutorefOrPtrAdjustment
::Autoref { mutbl, unsize: step.unsize }
);
1235 /// If `self_ty` is `*mut T` then this picks `*const T` methods. The reason why we have a
1236 /// special case for this is because going from `*mut T` to `*const T` with autoderefs and
1237 /// autorefs would require dereferencing the pointer, which is not safe.
1238 fn pick_const_ptr_method(
1240 step
: &CandidateStep
<'tcx
>,
1242 unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1243 ) -> Option
<PickResult
<'tcx
>> {
1244 // Don't convert an unsized reference to ptr
1249 let ty
= match self_ty
.kind() {
1250 &ty
::RawPtr(ty
::TypeAndMut { ty, mutbl: hir::Mutability::Mut }
) => ty
,
1254 let const_self_ty
= ty
::TypeAndMut { ty, mutbl: hir::Mutability::Not }
;
1255 let const_ptr_ty
= self.tcx
.mk_ptr(const_self_ty
);
1256 self.pick_method(const_ptr_ty
, unstable_candidates
).map(|r
| {
1258 pick
.autoderefs
= step
.autoderefs
;
1259 pick
.autoref_or_ptr_adjustment
= Some(AutorefOrPtrAdjustment
::ToConstPtr
);
1265 fn pick_method_with_unstable(&mut self, self_ty
: Ty
<'tcx
>) -> Option
<PickResult
<'tcx
>> {
1266 debug
!("pick_method_with_unstable(self_ty={})", self.ty_to_string(self_ty
));
1268 let mut possibly_unsatisfied_predicates
= Vec
::new();
1269 let mut unstable_candidates
= Vec
::new();
1271 for (kind
, candidates
) in
1272 &[("inherent", &self.inherent_candidates
), ("extension", &self.extension_candidates
)]
1274 debug
!("searching {} candidates", kind
);
1275 let res
= self.consider_candidates(
1278 &mut possibly_unsatisfied_predicates
,
1279 Some(&mut unstable_candidates
),
1281 if let Some(pick
) = res
{
1282 if !self.is_suggestion
.0 && !unstable_candidates
.is_empty() {
1283 if let Ok(p
) = &pick
{
1284 // Emit a lint if there are unstable candidates alongside the stable ones.
1286 // We suppress warning if we're picking the method only because it is a
1288 self.emit_unstable_name_collision_hint(p
, &unstable_candidates
);
1295 debug
!("searching unstable candidates");
1296 let res
= self.consider_candidates(
1298 unstable_candidates
.iter().map(|(c
, _
)| c
),
1299 &mut possibly_unsatisfied_predicates
,
1303 self.unsatisfied_predicates
.extend(possibly_unsatisfied_predicates
);
1311 mut unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1312 ) -> Option
<PickResult
<'tcx
>> {
1313 if !self.tcx
.sess
.opts
.debugging_opts
.pick_stable_methods_before_any_unstable
{
1314 return self.pick_method_with_unstable(self_ty
);
1317 debug
!("pick_method(self_ty={})", self.ty_to_string(self_ty
));
1319 let mut possibly_unsatisfied_predicates
= Vec
::new();
1321 for (kind
, candidates
) in
1322 &[("inherent", &self.inherent_candidates
), ("extension", &self.extension_candidates
)]
1324 debug
!("searching {} candidates", kind
);
1325 let res
= self.consider_candidates(
1328 &mut possibly_unsatisfied_predicates
,
1329 unstable_candidates
.as_deref_mut(),
1331 if let Some(pick
) = res
{
1336 // `pick_method` may be called twice for the same self_ty if no stable methods
1337 // match. Only extend once.
1338 if unstable_candidates
.is_some() {
1339 self.unsatisfied_predicates
.extend(possibly_unsatisfied_predicates
);
1344 fn consider_candidates
<'b
, ProbesIter
>(
1348 possibly_unsatisfied_predicates
: &mut Vec
<(
1349 ty
::Predicate
<'tcx
>,
1350 Option
<ty
::Predicate
<'tcx
>>,
1351 Option
<ObligationCause
<'tcx
>>,
1353 unstable_candidates
: Option
<&mut Vec
<(Candidate
<'tcx
>, Symbol
)>>,
1354 ) -> Option
<PickResult
<'tcx
>>
1356 ProbesIter
: Iterator
<Item
= &'b Candidate
<'tcx
>> + Clone
,
1359 let mut applicable_candidates
: Vec
<_
> = probes
1362 (probe
, self.consider_probe(self_ty
, probe
, possibly_unsatisfied_predicates
))
1364 .filter(|&(_
, status
)| status
!= ProbeResult
::NoMatch
)
1367 debug
!("applicable_candidates: {:?}", applicable_candidates
);
1369 if applicable_candidates
.len() > 1 {
1371 self.collapse_candidates_to_trait_pick(self_ty
, &applicable_candidates
)
1373 return Some(Ok(pick
));
1377 if let Some(uc
) = unstable_candidates
{
1378 applicable_candidates
.retain(|&(p
, _
)| {
1379 if let stability
::EvalResult
::Deny { feature, .. }
=
1380 self.tcx
.eval_stability(p
.item
.def_id
, None
, self.span
, None
)
1382 uc
.push((p
.clone(), feature
));
1389 if applicable_candidates
.len() > 1 {
1390 let sources
= probes
.map(|p
| self.candidate_source(p
, self_ty
)).collect();
1391 return Some(Err(MethodError
::Ambiguity(sources
)));
1394 applicable_candidates
.pop().map(|(probe
, status
)| {
1395 if status
== ProbeResult
::Match
{
1396 Ok(probe
.to_unadjusted_pick(self_ty
))
1398 Err(MethodError
::BadReturnType
)
1403 fn emit_unstable_name_collision_hint(
1405 stable_pick
: &Pick
<'_
>,
1406 unstable_candidates
: &[(Candidate
<'tcx
>, Symbol
)],
1408 self.tcx
.struct_span_lint_hir(
1409 lint
::builtin
::UNSTABLE_NAME_COLLISIONS
,
1413 let def_kind
= stable_pick
.item
.kind
.as_def_kind();
1414 let mut diag
= lint
.build(&format
!(
1415 "{} {} with this name may be added to the standard library in the future",
1417 def_kind
.descr(stable_pick
.item
.def_id
),
1419 match (stable_pick
.item
.kind
, stable_pick
.item
.container
) {
1420 (ty
::AssocKind
::Fn
, _
) => {
1421 // FIXME: This should be a `span_suggestion` instead of `help`
1422 // However `self.span` only
1423 // highlights the method name, so we can't use it. Also consider reusing
1424 // the code from `report_method_error()`.
1426 "call with fully qualified syntax `{}(...)` to keep using the current \
1428 self.tcx
.def_path_str(stable_pick
.item
.def_id
),
1431 (ty
::AssocKind
::Const
, ty
::AssocItemContainer
::TraitContainer(def_id
)) => {
1432 diag
.span_suggestion(
1434 "use the fully qualified path to the associated const",
1437 stable_pick
.self_ty
,
1438 self.tcx
.def_path_str(def_id
),
1439 stable_pick
.item
.name
1441 Applicability
::MachineApplicable
,
1446 if self.tcx
.sess
.is_nightly_build() {
1447 for (candidate
, feature
) in unstable_candidates
{
1449 "add `#![feature({})]` to the crate attributes to enable `{}`",
1451 self.tcx
.def_path_str(candidate
.item
.def_id
),
1461 fn select_trait_candidate(
1463 trait_ref
: ty
::TraitRef
<'tcx
>,
1464 ) -> traits
::SelectionResult
<'tcx
, traits
::Selection
<'tcx
>> {
1465 let cause
= traits
::ObligationCause
::misc(self.span
, self.body_id
);
1466 let predicate
= ty
::Binder
::dummy(trait_ref
).to_poly_trait_predicate();
1467 let obligation
= traits
::Obligation
::new(cause
, self.param_env
, predicate
);
1468 traits
::SelectionContext
::new(self).select(&obligation
)
1471 fn candidate_source(&self, candidate
: &Candidate
<'tcx
>, self_ty
: Ty
<'tcx
>) -> CandidateSource
{
1472 match candidate
.kind
{
1473 InherentImplCandidate(..) => ImplSource(candidate
.item
.container
.id()),
1474 ObjectCandidate
| WhereClauseCandidate(_
) => TraitSource(candidate
.item
.container
.id()),
1475 TraitCandidate(trait_ref
) => self.probe(|_
| {
1477 .at(&ObligationCause
::dummy(), self.param_env
)
1478 .sup(candidate
.xform_self_ty
, self_ty
);
1479 match self.select_trait_candidate(trait_ref
) {
1480 Ok(Some(traits
::ImplSource
::UserDefined(ref impl_data
))) => {
1481 // If only a single impl matches, make the error message point
1483 ImplSource(impl_data
.impl_def_id
)
1485 _
=> TraitSource(candidate
.item
.container
.id()),
1494 probe
: &Candidate
<'tcx
>,
1495 possibly_unsatisfied_predicates
: &mut Vec
<(
1496 ty
::Predicate
<'tcx
>,
1497 Option
<ty
::Predicate
<'tcx
>>,
1498 Option
<ObligationCause
<'tcx
>>,
1501 debug
!("consider_probe: self_ty={:?} probe={:?}", self_ty
, probe
);
1504 // First check that the self type can be related.
1505 let sub_obligations
= match self
1506 .at(&ObligationCause
::dummy(), self.param_env
)
1507 .sup(probe
.xform_self_ty
, self_ty
)
1509 Ok(InferOk { obligations, value: () }
) => obligations
,
1511 debug
!("--> cannot relate self-types {:?}", err
);
1512 return ProbeResult
::NoMatch
;
1516 let mut result
= ProbeResult
::Match
;
1517 let mut xform_ret_ty
= probe
.xform_ret_ty
;
1518 debug
!(?xform_ret_ty
);
1520 let selcx
= &mut traits
::SelectionContext
::new(self);
1521 let cause
= traits
::ObligationCause
::misc(self.span
, self.body_id
);
1523 // If so, impls may carry other conditions (e.g., where
1524 // clauses) that must be considered. Make sure that those
1525 // match as well (or at least may match, sometimes we
1526 // don't have enough information to fully evaluate).
1528 InherentImplCandidate(ref substs
, ref ref_obligations
) => {
1529 // `xform_ret_ty` hasn't been normalized yet, only `xform_self_ty`,
1530 // see the reasons mentioned in the comments in `assemble_inherent_impl_probe`
1531 // for why this is necessary
1532 let traits
::Normalized
{
1533 value
: normalized_xform_ret_ty
,
1534 obligations
: normalization_obligations
,
1535 } = traits
::normalize(selcx
, self.param_env
, cause
.clone(), probe
.xform_ret_ty
);
1536 xform_ret_ty
= normalized_xform_ret_ty
;
1537 debug
!("xform_ret_ty after normalization: {:?}", xform_ret_ty
);
1539 // Check whether the impl imposes obligations we have to worry about.
1540 let impl_def_id
= probe
.item
.container
.id();
1541 let impl_bounds
= self.tcx
.predicates_of(impl_def_id
);
1542 let impl_bounds
= impl_bounds
.instantiate(self.tcx
, substs
);
1543 let traits
::Normalized { value: impl_bounds, obligations: norm_obligations }
=
1544 traits
::normalize(selcx
, self.param_env
, cause
.clone(), impl_bounds
);
1546 // Convert the bounds into obligations.
1547 let impl_obligations
=
1548 traits
::predicates_for_generics(cause
, self.param_env
, impl_bounds
);
1550 let candidate_obligations
= impl_obligations
1551 .chain(norm_obligations
.into_iter())
1552 .chain(ref_obligations
.iter().cloned())
1553 .chain(normalization_obligations
.into_iter());
1555 // Evaluate those obligations to see if they might possibly hold.
1556 for o
in candidate_obligations
{
1557 let o
= self.resolve_vars_if_possible(o
);
1558 if !self.predicate_may_hold(&o
) {
1559 result
= ProbeResult
::NoMatch
;
1560 possibly_unsatisfied_predicates
.push((
1569 ObjectCandidate
| WhereClauseCandidate(..) => {
1570 // These have no additional conditions to check.
1573 TraitCandidate(trait_ref
) => {
1574 if let Some(method_name
) = self.method_name
{
1575 // Some trait methods are excluded for arrays before 2021.
1576 // (`array.into_iter()` wants a slice iterator for compatibility.)
1577 if self_ty
.is_array() && !method_name
.span
.rust_2021() {
1578 let trait_def
= self.tcx
.trait_def(trait_ref
.def_id
);
1579 if trait_def
.skip_array_during_method_dispatch
{
1580 return ProbeResult
::NoMatch
;
1585 ty
::Binder
::dummy(trait_ref
).without_const().to_predicate(self.tcx
);
1586 let obligation
= traits
::Obligation
::new(cause
, self.param_env
, predicate
);
1587 if !self.predicate_may_hold(&obligation
) {
1588 result
= ProbeResult
::NoMatch
;
1590 match self.select_trait_candidate(trait_ref
) {
1591 Err(_
) => return true,
1592 Ok(Some(impl_source
))
1593 if !impl_source
.borrow_nested_obligations().is_empty() =>
1595 for obligation
in impl_source
.borrow_nested_obligations() {
1596 // Determine exactly which obligation wasn't met, so
1597 // that we can give more context in the error.
1598 if !self.predicate_may_hold(obligation
) {
1599 let nested_predicate
=
1600 self.resolve_vars_if_possible(obligation
.predicate
);
1602 self.resolve_vars_if_possible(predicate
);
1603 let p
= if predicate
== nested_predicate
{
1604 // Avoid "`MyStruct: Foo` which is required by
1605 // `MyStruct: Foo`" in E0599.
1610 possibly_unsatisfied_predicates
.push((
1613 Some(obligation
.cause
.clone()),
1619 // Some nested subobligation of this predicate
1621 let predicate
= self.resolve_vars_if_possible(predicate
);
1622 possibly_unsatisfied_predicates
.push((predicate
, None
, None
));
1627 // This candidate's primary obligation doesn't even
1628 // select - don't bother registering anything in
1629 // `potentially_unsatisfied_predicates`.
1630 return ProbeResult
::NoMatch
;
1636 // Evaluate those obligations to see if they might possibly hold.
1637 for o
in sub_obligations
{
1638 let o
= self.resolve_vars_if_possible(o
);
1639 if !self.predicate_may_hold(&o
) {
1640 result
= ProbeResult
::NoMatch
;
1641 possibly_unsatisfied_predicates
.push((o
.predicate
, None
, Some(o
.cause
)));
1645 if let ProbeResult
::Match
= result
{
1646 if let (Some(return_ty
), Some(xform_ret_ty
)) = (self.return_type
, xform_ret_ty
) {
1647 let xform_ret_ty
= self.resolve_vars_if_possible(xform_ret_ty
);
1649 "comparing return_ty {:?} with xform ret ty {:?}",
1650 return_ty
, probe
.xform_ret_ty
1653 .at(&ObligationCause
::dummy(), self.param_env
)
1654 .sup(return_ty
, xform_ret_ty
)
1657 return ProbeResult
::BadReturnType
;
1666 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1667 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1668 /// external interface of the method can be determined from the trait, it's ok not to decide.
1669 /// We can basically just collapse all of the probes for various impls into one where-clause
1670 /// probe. This will result in a pending obligation so when more type-info is available we can
1671 /// make the final decision.
1673 /// Example (`src/test/ui/method-two-trait-defer-resolution-1.rs`):
1676 /// trait Foo { ... }
1677 /// impl Foo for Vec<i32> { ... }
1678 /// impl Foo for Vec<usize> { ... }
1681 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1682 /// use, so it's ok to just commit to "using the method from the trait Foo".
1683 fn collapse_candidates_to_trait_pick(
1686 probes
: &[(&Candidate
<'tcx
>, ProbeResult
)],
1687 ) -> Option
<Pick
<'tcx
>> {
1688 // Do all probes correspond to the same trait?
1689 let container
= probes
[0].0.item
.container
;
1690 if let ty
::ImplContainer(_
) = container
{
1693 if probes
[1..].iter().any(|&(p
, _
)| p
.item
.container
!= container
) {
1697 // FIXME: check the return type here somehow.
1698 // If so, just use this trait and call it a day.
1700 item
: probes
[0].0.item
,
1702 import_ids
: probes
[0].0.import_ids
.clone(),
1704 autoref_or_ptr_adjustment
: None
,
1709 /// Similarly to `probe_for_return_type`, this method attempts to find the best matching
1710 /// candidate method where the method name may have been misspelt. Similarly to other
1711 /// Levenshtein based suggestions, we provide at most one such suggestion.
1712 fn probe_for_lev_candidate(&mut self) -> Result
<Option
<ty
::AssocItem
>, MethodError
<'tcx
>> {
1713 debug
!("probing for method names similar to {:?}", self.method_name
);
1715 let steps
= self.steps
.clone();
1717 let mut pcx
= ProbeContext
::new(
1723 self.orig_steps_var_values
.clone(),
1728 pcx
.allow_similar_names
= true;
1729 pcx
.assemble_inherent_candidates();
1731 let method_names
= pcx
.candidate_method_names();
1732 pcx
.allow_similar_names
= false;
1733 let applicable_close_candidates
: Vec
<ty
::AssocItem
> = method_names
1735 .filter_map(|&method_name
| {
1737 pcx
.method_name
= Some(method_name
);
1738 pcx
.assemble_inherent_candidates();
1739 pcx
.pick_core().and_then(|pick
| pick
.ok()).map(|pick
| pick
.item
)
1743 if applicable_close_candidates
.is_empty() {
1747 let names
= applicable_close_candidates
1749 .map(|cand
| cand
.name
)
1750 .collect
::<Vec
<Symbol
>>();
1751 find_best_match_for_name(&names
, self.method_name
.unwrap().name
, None
)
1754 Ok(applicable_close_candidates
.into_iter().find(|method
| method
.name
== best_name
))
1759 ///////////////////////////////////////////////////////////////////////////
1761 fn has_applicable_self(&self, item
: &ty
::AssocItem
) -> bool
{
1762 // "Fast track" -- check for usage of sugar when in method call
1765 // In Path mode (i.e., resolving a value like `T::next`), consider any
1766 // associated value (i.e., methods, constants) but not types.
1768 Mode
::MethodCall
=> item
.fn_has_self_parameter
,
1769 Mode
::Path
=> match item
.kind
{
1770 ty
::AssocKind
::Type
=> false,
1771 ty
::AssocKind
::Fn
| ty
::AssocKind
::Const
=> true,
1774 // FIXME -- check for types that deref to `Self`,
1775 // like `Rc<Self>` and so on.
1777 // Note also that the current code will break if this type
1778 // includes any of the type parameters defined on the method
1779 // -- but this could be overcome.
1782 fn record_static_candidate(&mut self, source
: CandidateSource
) {
1783 self.static_candidates
.push(source
);
1786 #[instrument(level = "debug", skip(self))]
1789 item
: &ty
::AssocItem
,
1791 substs
: SubstsRef
<'tcx
>,
1792 ) -> (Ty
<'tcx
>, Option
<Ty
<'tcx
>>) {
1793 if item
.kind
== ty
::AssocKind
::Fn
&& self.mode
== Mode
::MethodCall
{
1794 let sig
= self.xform_method_sig(item
.def_id
, substs
);
1795 (sig
.inputs()[0], Some(sig
.output()))
1801 #[instrument(level = "debug", skip(self))]
1802 fn xform_method_sig(&self, method
: DefId
, substs
: SubstsRef
<'tcx
>) -> ty
::FnSig
<'tcx
> {
1803 let fn_sig
= self.tcx
.fn_sig(method
);
1806 assert
!(!substs
.has_escaping_bound_vars());
1808 // It is possible for type parameters or early-bound lifetimes
1809 // to appear in the signature of `self`. The substitutions we
1810 // are given do not include type/lifetime parameters for the
1811 // method yet. So create fresh variables here for those too,
1812 // if there are any.
1813 let generics
= self.tcx
.generics_of(method
);
1814 assert_eq
!(substs
.len(), generics
.parent_count
as usize);
1816 // Erase any late-bound regions from the method and substitute
1817 // in the values from the substitution.
1818 let xform_fn_sig
= self.erase_late_bound_regions(fn_sig
);
1820 if generics
.params
.is_empty() {
1821 xform_fn_sig
.subst(self.tcx
, substs
)
1823 let substs
= InternalSubsts
::for_item(self.tcx
, method
, |param
, _
| {
1824 let i
= param
.index
as usize;
1825 if i
< substs
.len() {
1829 GenericParamDefKind
::Lifetime
=> {
1830 // In general, during probe we erase regions.
1831 self.tcx
.lifetimes
.re_erased
.into()
1833 GenericParamDefKind
::Type { .. }
| GenericParamDefKind
::Const { .. }
=> {
1834 self.var_for_def(self.span
, param
)
1839 xform_fn_sig
.subst(self.tcx
, substs
)
1843 /// Gets the type of an impl and generate substitutions with placeholders.
1844 fn impl_ty_and_substs(&self, impl_def_id
: DefId
) -> (Ty
<'tcx
>, SubstsRef
<'tcx
>) {
1845 (self.tcx
.type_of(impl_def_id
), self.fresh_item_substs(impl_def_id
))
1848 fn fresh_item_substs(&self, def_id
: DefId
) -> SubstsRef
<'tcx
> {
1849 InternalSubsts
::for_item(self.tcx
, def_id
, |param
, _
| match param
.kind
{
1850 GenericParamDefKind
::Lifetime
=> self.tcx
.lifetimes
.re_erased
.into(),
1851 GenericParamDefKind
::Type { .. }
=> self
1852 .next_ty_var(TypeVariableOrigin
{
1853 kind
: TypeVariableOriginKind
::SubstitutionPlaceholder
,
1854 span
: self.tcx
.def_span(def_id
),
1857 GenericParamDefKind
::Const { .. }
=> {
1858 let span
= self.tcx
.def_span(def_id
);
1859 let origin
= ConstVariableOrigin
{
1860 kind
: ConstVariableOriginKind
::SubstitutionPlaceholder
,
1863 self.next_const_var(self.tcx
.type_of(param
.def_id
), origin
).into()
1868 /// Replaces late-bound-regions bound by `value` with `'static` using
1869 /// `ty::erase_late_bound_regions`.
1871 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1872 /// method matching. It is reasonable during the probe phase because we don't consider region
1873 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1874 /// rather than creating fresh region variables. This is nice for two reasons:
1876 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1877 /// particular method call, it winds up creating fewer types overall, which helps for memory
1878 /// usage. (Admittedly, this is a rather small effect, though measurable.)
1880 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1881 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1882 /// regions with actual region variables as is proper, we'd have to ensure that the same
1883 /// region got replaced with the same variable, which requires a bit more coordination
1884 /// and/or tracking the substitution and
1886 fn erase_late_bound_regions
<T
>(&self, value
: ty
::Binder
<'tcx
, T
>) -> T
1888 T
: TypeFoldable
<'tcx
>,
1890 self.tcx
.erase_late_bound_regions(value
)
1893 /// Finds the method with the appropriate name (or return type, as the case may be). If
1894 /// `allow_similar_names` is set, find methods with close-matching names.
1895 // The length of the returned iterator is nearly always 0 or 1 and this
1896 // method is fairly hot.
1897 fn impl_or_trait_item(&self, def_id
: DefId
) -> SmallVec
<[ty
::AssocItem
; 1]> {
1898 if let Some(name
) = self.method_name
{
1899 if self.allow_similar_names
{
1900 let max_dist
= max(name
.as_str().len(), 3) / 3;
1902 .associated_items(def_id
)
1903 .in_definition_order()
1905 if x
.kind
.namespace() != Namespace
::ValueNS
{
1908 match lev_distance(name
.as_str(), x
.name
.as_str(), max_dist
) {
1917 .associated_value(def_id
, name
)
1918 .map_or_else(SmallVec
::new
, |x
| SmallVec
::from_buf([x
]))
1921 self.tcx
.associated_items(def_id
).in_definition_order().copied().collect()
1926 impl<'tcx
> Candidate
<'tcx
> {
1927 fn to_unadjusted_pick(&self, self_ty
: Ty
<'tcx
>) -> Pick
<'tcx
> {
1930 kind
: match self.kind
{
1931 InherentImplCandidate(..) => InherentImplPick
,
1932 ObjectCandidate
=> ObjectPick
,
1933 TraitCandidate(_
) => TraitPick
,
1934 WhereClauseCandidate(ref trait_ref
) => {
1935 // Only trait derived from where-clauses should
1936 // appear here, so they should not contain any
1937 // inference variables or other artifacts. This
1938 // means they are safe to put into the
1939 // `WhereClausePick`.
1941 !trait_ref
.skip_binder().substs
.needs_infer()
1942 && !trait_ref
.skip_binder().substs
.has_placeholders()
1945 WhereClausePick(*trait_ref
)
1948 import_ids
: self.import_ids
.clone(),
1950 autoref_or_ptr_adjustment
: None
,