1 // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
11 use super::MethodError
;
12 use super::NoMatchData
;
13 use super::{CandidateSource, ImplSource, TraitSource}
;
17 use check
::{FnCtxt, UnresolvedTypeAction}
;
18 use middle
::def_id
::DefId
;
20 use middle
::subst
::Subst
;
22 use middle
::ty
::{self, NoPreference, Ty, ToPolyTraitRef, TraitRef, TypeFoldable}
;
24 use middle
::infer
::{InferCtxt, TypeOrigin}
;
26 use syntax
::codemap
::{Span, DUMMY_SP}
;
28 use std
::collections
::HashSet
;
32 use self::CandidateKind
::*;
33 pub use self::PickKind
::*;
35 struct ProbeContext
<'a
, 'tcx
:'a
> {
36 fcx
: &'a FnCtxt
<'a
, 'tcx
>,
40 steps
: Rc
<Vec
<CandidateStep
<'tcx
>>>,
41 opt_simplified_steps
: Option
<Vec
<ty
::fast_reject
::SimplifiedType
>>,
42 inherent_candidates
: Vec
<Candidate
<'tcx
>>,
43 extension_candidates
: Vec
<Candidate
<'tcx
>>,
44 impl_dups
: HashSet
<DefId
>,
46 /// Collects near misses when the candidate functions are missing a `self` keyword and is only
47 /// used for error reporting
48 static_candidates
: Vec
<CandidateSource
>,
50 /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
51 /// for error reporting
52 unsatisfied_predicates
: Vec
<TraitRef
<'tcx
>>
56 struct CandidateStep
<'tcx
> {
63 struct Candidate
<'tcx
> {
64 xform_self_ty
: Ty
<'tcx
>,
65 item
: ty
::ImplOrTraitItem
<'tcx
>,
66 kind
: CandidateKind
<'tcx
>,
70 enum CandidateKind
<'tcx
> {
71 InherentImplCandidate(subst
::Substs
<'tcx
>,
72 /* Normalize obligations */ Vec
<traits
::PredicateObligation
<'tcx
>>),
73 ExtensionImplCandidate(/* Impl */ DefId
, subst
::Substs
<'tcx
>,
74 /* Normalize obligations */ Vec
<traits
::PredicateObligation
<'tcx
>>),
77 WhereClauseCandidate(/* Trait */ ty
::PolyTraitRef
<'tcx
>),
81 pub struct Pick
<'tcx
> {
82 pub item
: ty
::ImplOrTraitItem
<'tcx
>,
83 pub kind
: PickKind
<'tcx
>,
85 // Indicates that the source expression should be autoderef'd N times
87 // A = expr | *expr | **expr | ...
88 pub autoderefs
: usize,
90 // Indicates that an autoref is applied after the optional autoderefs
92 // B = A | &A | &mut A
93 pub autoref
: Option
<hir
::Mutability
>,
95 // Indicates that the source expression should be "unsized" to a
96 // target type. This should probably eventually go away in favor
97 // of just coercing method receivers.
100 pub unsize
: Option
<Ty
<'tcx
>>,
103 #[derive(Clone,Debug)]
104 pub enum PickKind
<'tcx
> {
106 ExtensionImplPick(/* Impl */ DefId
),
109 WhereClausePick(/* Trait */ ty
::PolyTraitRef
<'tcx
>),
112 pub type PickResult
<'tcx
> = Result
<Pick
<'tcx
>, MethodError
<'tcx
>>;
114 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
116 // An expression of the form `receiver.method_name(...)`.
117 // Autoderefs are performed on `receiver`, lookup is done based on the
118 // `self` argument of the method, and static methods aren't considered.
120 // An expression of the form `Type::item` or `<T>::item`.
121 // No autoderefs are performed, lookup is done based on the type each
122 // implementation is for, and static methods are included.
126 pub fn probe
<'a
, 'tcx
>(fcx
: &FnCtxt
<'a
, 'tcx
>,
129 item_name
: ast
::Name
,
131 scope_expr_id
: ast
::NodeId
)
134 debug
!("probe(self_ty={:?}, item_name={}, scope_expr_id={})",
139 // FIXME(#18741) -- right now, creating the steps involves evaluating the
140 // `*` operator, which registers obligations that then escape into
141 // the global fulfillment context and thus has global
142 // side-effects. This is a bit of a pain to refactor. So just let
143 // it ride, although it's really not great, and in fact could I
144 // think cause spurious errors. Really though this part should
145 // take place in the `fcx.infcx().probe` below.
146 let steps
= if mode
== Mode
::MethodCall
{
147 match create_steps(fcx
, span
, self_ty
) {
148 Some(steps
) => steps
,
149 None
=>return Err(MethodError
::NoMatch(NoMatchData
::new(Vec
::new(), Vec
::new(),
160 // Create a list of simplified self types, if we can.
161 let mut simplified_steps
= Vec
::new();
163 match ty
::fast_reject
::simplify_type(fcx
.tcx(), step
.self_ty
, true) {
165 Some(simplified_type
) => { simplified_steps.push(simplified_type); }
168 let opt_simplified_steps
=
169 if simplified_steps
.len() < steps
.len() {
170 None
// failed to convert at least one of the steps
172 Some(simplified_steps
)
175 debug
!("ProbeContext: steps for self_ty={:?} are {:?}",
179 // this creates one big transaction so that all type variables etc
180 // that we create during the probe process are removed later
181 fcx
.infcx().probe(|_
| {
182 let mut probe_cx
= ProbeContext
::new(fcx
,
187 opt_simplified_steps
);
188 probe_cx
.assemble_inherent_candidates();
189 try
!(probe_cx
.assemble_extension_candidates_for_traits_in_scope(scope_expr_id
));
194 fn create_steps
<'a
, 'tcx
>(fcx
: &FnCtxt
<'a
, 'tcx
>,
197 -> Option
<Vec
<CandidateStep
<'tcx
>>> {
198 let mut steps
= Vec
::new();
200 let (final_ty
, dereferences
, _
) = check
::autoderef(fcx
,
204 UnresolvedTypeAction
::Error
,
207 steps
.push(CandidateStep
{
212 None
::<()> // keep iterating until we can't anymore
216 ty
::TyArray(elem_ty
, _
) => {
217 steps
.push(CandidateStep
{
218 self_ty
: fcx
.tcx().mk_slice(elem_ty
),
219 autoderefs
: dereferences
,
223 ty
::TyError
=> return None
,
230 impl<'a
,'tcx
> ProbeContext
<'a
,'tcx
> {
231 fn new(fcx
: &'a FnCtxt
<'a
,'tcx
>,
234 item_name
: ast
::Name
,
235 steps
: Vec
<CandidateStep
<'tcx
>>,
236 opt_simplified_steps
: Option
<Vec
<ty
::fast_reject
::SimplifiedType
>>)
237 -> ProbeContext
<'a
,'tcx
>
243 item_name
: item_name
,
244 inherent_candidates
: Vec
::new(),
245 extension_candidates
: Vec
::new(),
246 impl_dups
: HashSet
::new(),
247 steps
: Rc
::new(steps
),
248 opt_simplified_steps
: opt_simplified_steps
,
249 static_candidates
: Vec
::new(),
250 unsatisfied_predicates
: Vec
::new(),
254 fn reset(&mut self) {
255 self.inherent_candidates
.clear();
256 self.extension_candidates
.clear();
257 self.impl_dups
.clear();
258 self.static_candidates
.clear();
261 fn tcx(&self) -> &'a ty
::ctxt
<'tcx
> {
265 fn infcx(&self) -> &'a InferCtxt
<'a
, 'tcx
> {
269 ///////////////////////////////////////////////////////////////////////////
270 // CANDIDATE ASSEMBLY
272 fn assemble_inherent_candidates(&mut self) {
273 let steps
= self.steps
.clone();
274 for step
in steps
.iter() {
275 self.assemble_probe(step
.self_ty
);
279 fn assemble_probe(&mut self, self_ty
: Ty
<'tcx
>) {
280 debug
!("assemble_probe: self_ty={:?}",
284 ty
::TyTrait(box ref data
) => {
285 self.assemble_inherent_candidates_from_object(self_ty
, data
);
286 self.assemble_inherent_impl_candidates_for_type(data
.principal_def_id());
289 ty
::TyStruct(def
, _
) => {
290 self.assemble_inherent_impl_candidates_for_type(def
.did
);
293 if let Some(box_did
) = self.tcx().lang_items
.owned_box() {
294 self.assemble_inherent_impl_candidates_for_type(box_did
);
298 self.assemble_inherent_candidates_from_param(self_ty
, p
);
301 let lang_def_id
= self.tcx().lang_items
.char_impl();
302 self.assemble_inherent_impl_for_primitive(lang_def_id
);
305 let lang_def_id
= self.tcx().lang_items
.str_impl();
306 self.assemble_inherent_impl_for_primitive(lang_def_id
);
309 let lang_def_id
= self.tcx().lang_items
.slice_impl();
310 self.assemble_inherent_impl_for_primitive(lang_def_id
);
312 ty
::TyRawPtr(ty
::TypeAndMut { ty: _, mutbl: hir::MutImmutable }
) => {
313 let lang_def_id
= self.tcx().lang_items
.const_ptr_impl();
314 self.assemble_inherent_impl_for_primitive(lang_def_id
);
316 ty
::TyRawPtr(ty
::TypeAndMut { ty: _, mutbl: hir::MutMutable }
) => {
317 let lang_def_id
= self.tcx().lang_items
.mut_ptr_impl();
318 self.assemble_inherent_impl_for_primitive(lang_def_id
);
320 ty
::TyInt(ast
::TyI8
) => {
321 let lang_def_id
= self.tcx().lang_items
.i8_impl();
322 self.assemble_inherent_impl_for_primitive(lang_def_id
);
324 ty
::TyInt(ast
::TyI16
) => {
325 let lang_def_id
= self.tcx().lang_items
.i16_impl();
326 self.assemble_inherent_impl_for_primitive(lang_def_id
);
328 ty
::TyInt(ast
::TyI32
) => {
329 let lang_def_id
= self.tcx().lang_items
.i32_impl();
330 self.assemble_inherent_impl_for_primitive(lang_def_id
);
332 ty
::TyInt(ast
::TyI64
) => {
333 let lang_def_id
= self.tcx().lang_items
.i64_impl();
334 self.assemble_inherent_impl_for_primitive(lang_def_id
);
336 ty
::TyInt(ast
::TyIs
) => {
337 let lang_def_id
= self.tcx().lang_items
.isize_impl();
338 self.assemble_inherent_impl_for_primitive(lang_def_id
);
340 ty
::TyUint(ast
::TyU8
) => {
341 let lang_def_id
= self.tcx().lang_items
.u8_impl();
342 self.assemble_inherent_impl_for_primitive(lang_def_id
);
344 ty
::TyUint(ast
::TyU16
) => {
345 let lang_def_id
= self.tcx().lang_items
.u16_impl();
346 self.assemble_inherent_impl_for_primitive(lang_def_id
);
348 ty
::TyUint(ast
::TyU32
) => {
349 let lang_def_id
= self.tcx().lang_items
.u32_impl();
350 self.assemble_inherent_impl_for_primitive(lang_def_id
);
352 ty
::TyUint(ast
::TyU64
) => {
353 let lang_def_id
= self.tcx().lang_items
.u64_impl();
354 self.assemble_inherent_impl_for_primitive(lang_def_id
);
356 ty
::TyUint(ast
::TyUs
) => {
357 let lang_def_id
= self.tcx().lang_items
.usize_impl();
358 self.assemble_inherent_impl_for_primitive(lang_def_id
);
360 ty
::TyFloat(ast
::TyF32
) => {
361 let lang_def_id
= self.tcx().lang_items
.f32_impl();
362 self.assemble_inherent_impl_for_primitive(lang_def_id
);
364 ty
::TyFloat(ast
::TyF64
) => {
365 let lang_def_id
= self.tcx().lang_items
.f64_impl();
366 self.assemble_inherent_impl_for_primitive(lang_def_id
);
373 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id
: Option
<DefId
>) {
374 if let Some(impl_def_id
) = lang_def_id
{
375 self.tcx().populate_implementations_for_primitive_if_necessary(impl_def_id
);
377 self.assemble_inherent_impl_probe(impl_def_id
);
381 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id
: DefId
) {
382 // Read the inherent implementation candidates for this type from the
383 // metadata if necessary.
384 self.tcx().populate_inherent_implementations_for_type_if_necessary(def_id
);
386 if let Some(impl_infos
) = self.tcx().inherent_impls
.borrow().get(&def_id
) {
387 for &impl_def_id
in impl_infos
.iter() {
388 self.assemble_inherent_impl_probe(impl_def_id
);
393 fn assemble_inherent_impl_probe(&mut self, impl_def_id
: DefId
) {
394 if !self.impl_dups
.insert(impl_def_id
) {
395 return; // already visited
398 debug
!("assemble_inherent_impl_probe {:?}", impl_def_id
);
400 let item
= match impl_item(self.tcx(), impl_def_id
, self.item_name
) {
402 None
=> { return; }
// No method with correct name on this impl
405 if !self.has_applicable_self(&item
) {
406 // No receiver declared. Not a candidate.
407 return self.record_static_candidate(ImplSource(impl_def_id
));
410 let (impl_ty
, impl_substs
) = self.impl_ty_and_substs(impl_def_id
);
411 let impl_ty
= impl_ty
.subst(self.tcx(), &impl_substs
);
413 // Determine the receiver type that the method itself expects.
414 let xform_self_ty
= self.xform_self_ty(&item
, impl_ty
, &impl_substs
);
416 // We can't use normalize_associated_types_in as it will pollute the
417 // fcx's fulfillment context after this probe is over.
418 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
419 let mut selcx
= &mut traits
::SelectionContext
::new(self.fcx
.infcx());
420 let traits
::Normalized { value: xform_self_ty, obligations }
=
421 traits
::normalize(selcx
, cause
, &xform_self_ty
);
422 debug
!("assemble_inherent_impl_probe: xform_self_ty = {:?}",
425 self.inherent_candidates
.push(Candidate
{
426 xform_self_ty
: xform_self_ty
,
428 kind
: InherentImplCandidate(impl_substs
, obligations
)
432 fn assemble_inherent_candidates_from_object(&mut self,
434 data
: &ty
::TraitTy
<'tcx
>) {
435 debug
!("assemble_inherent_candidates_from_object(self_ty={:?})",
438 // It is illegal to invoke a method on a trait instance that
439 // refers to the `Self` type. An error will be reported by
440 // `enforce_object_limitations()` if the method refers to the
441 // `Self` type anywhere other than the receiver. Here, we use
442 // a substitution that replaces `Self` with the object type
443 // itself. Hence, a `&self` method will wind up with an
444 // argument type like `&Trait`.
445 let trait_ref
= data
.principal_trait_ref_with_self_ty(self.tcx(), self_ty
);
446 self.elaborate_bounds(&[trait_ref
], |this
, new_trait_ref
, item
| {
447 let new_trait_ref
= this
.erase_late_bound_regions(&new_trait_ref
);
449 let xform_self_ty
= this
.xform_self_ty(&item
,
450 new_trait_ref
.self_ty(),
451 new_trait_ref
.substs
);
453 this
.inherent_candidates
.push(Candidate
{
454 xform_self_ty
: xform_self_ty
,
456 kind
: ObjectCandidate
461 fn assemble_inherent_candidates_from_param(&mut self,
463 param_ty
: ty
::ParamTy
) {
464 // FIXME -- Do we want to commit to this behavior for param bounds?
467 self.fcx
.inh
.infcx
.parameter_environment
.caller_bounds
469 .filter_map(|predicate
| {
471 ty
::Predicate
::Trait(ref trait_predicate
) => {
472 match trait_predicate
.0.trait_ref
.self_ty().sty
{
473 ty
::TyParam(ref p
) if *p
== param_ty
=> {
474 Some(trait_predicate
.to_poly_trait_ref())
479 ty
::Predicate
::Equate(..) |
480 ty
::Predicate
::Projection(..) |
481 ty
::Predicate
::RegionOutlives(..) |
482 ty
::Predicate
::WellFormed(..) |
483 ty
::Predicate
::ObjectSafe(..) |
484 ty
::Predicate
::TypeOutlives(..) => {
491 self.elaborate_bounds(&bounds
, |this
, poly_trait_ref
, item
| {
493 this
.erase_late_bound_regions(&poly_trait_ref
);
496 this
.xform_self_ty(&item
,
500 if let Some(ref m
) = item
.as_opt_method() {
501 debug
!("found match: trait_ref={:?} substs={:?} m={:?}",
505 assert_eq
!(m
.generics
.types
.get_slice(subst
::TypeSpace
).len(),
506 trait_ref
.substs
.types
.get_slice(subst
::TypeSpace
).len());
507 assert_eq
!(m
.generics
.regions
.get_slice(subst
::TypeSpace
).len(),
508 trait_ref
.substs
.regions().get_slice(subst
::TypeSpace
).len());
509 assert_eq
!(m
.generics
.types
.get_slice(subst
::SelfSpace
).len(),
510 trait_ref
.substs
.types
.get_slice(subst
::SelfSpace
).len());
511 assert_eq
!(m
.generics
.regions
.get_slice(subst
::SelfSpace
).len(),
512 trait_ref
.substs
.regions().get_slice(subst
::SelfSpace
).len());
515 // Because this trait derives from a where-clause, it
516 // should not contain any inference variables or other
517 // artifacts. This means it is safe to put into the
518 // `WhereClauseCandidate` and (eventually) into the
519 // `WhereClausePick`.
520 assert
!(!trait_ref
.substs
.types
.needs_infer());
522 this
.inherent_candidates
.push(Candidate
{
523 xform_self_ty
: xform_self_ty
,
525 kind
: WhereClauseCandidate(poly_trait_ref
)
530 // Do a search through a list of bounds, using a callback to actually
531 // create the candidates.
532 fn elaborate_bounds
<F
>(
534 bounds
: &[ty
::PolyTraitRef
<'tcx
>],
538 &mut ProbeContext
<'b
, 'tcx
>,
539 ty
::PolyTraitRef
<'tcx
>,
540 ty
::ImplOrTraitItem
<'tcx
>,
543 debug
!("elaborate_bounds(bounds={:?})", bounds
);
545 let tcx
= self.tcx();
546 for bound_trait_ref
in traits
::transitive_bounds(tcx
, bounds
) {
547 let item
= match trait_item(tcx
,
548 bound_trait_ref
.def_id(),
551 None
=> { continue; }
554 if !self.has_applicable_self(&item
) {
555 self.record_static_candidate(TraitSource(bound_trait_ref
.def_id()));
557 mk_cand(self, bound_trait_ref
, item
);
562 fn assemble_extension_candidates_for_traits_in_scope(&mut self,
563 expr_id
: ast
::NodeId
)
564 -> Result
<(), MethodError
<'tcx
>>
566 let mut duplicates
= HashSet
::new();
567 let opt_applicable_traits
= self.fcx
.ccx
.trait_map
.get(&expr_id
);
568 if let Some(applicable_traits
) = opt_applicable_traits
{
569 for &trait_did
in applicable_traits
{
570 if duplicates
.insert(trait_did
) {
571 try
!(self.assemble_extension_candidates_for_trait(trait_did
));
578 fn assemble_extension_candidates_for_all_traits(&mut self) -> Result
<(), MethodError
<'tcx
>> {
579 let mut duplicates
= HashSet
::new();
580 for trait_info
in suggest
::all_traits(self.fcx
.ccx
) {
581 if duplicates
.insert(trait_info
.def_id
) {
582 try
!(self.assemble_extension_candidates_for_trait(trait_info
.def_id
));
588 fn assemble_extension_candidates_for_trait(&mut self,
590 -> Result
<(), MethodError
<'tcx
>>
592 debug
!("assemble_extension_candidates_for_trait(trait_def_id={:?})",
595 // Check whether `trait_def_id` defines a method with suitable name:
597 self.tcx().trait_items(trait_def_id
);
600 .find(|item
| item
.name() == self.item_name
);
601 let item
= match maybe_item
{
603 None
=> { return Ok(()); }
606 // Check whether `trait_def_id` defines a method with suitable name:
607 if !self.has_applicable_self(item
) {
608 debug
!("method has inapplicable self");
609 self.record_static_candidate(TraitSource(trait_def_id
));
613 self.assemble_extension_candidates_for_trait_impls(trait_def_id
, item
.clone());
615 try
!(self.assemble_closure_candidates(trait_def_id
, item
.clone()));
617 self.assemble_projection_candidates(trait_def_id
, item
.clone());
619 self.assemble_where_clause_candidates(trait_def_id
, item
.clone());
624 fn assemble_extension_candidates_for_trait_impls(&mut self,
626 item
: ty
::ImplOrTraitItem
<'tcx
>)
628 let trait_def
= self.tcx().lookup_trait_def(trait_def_id
);
630 // FIXME(arielb1): can we use for_each_relevant_impl here?
631 trait_def
.for_each_impl(self.tcx(), |impl_def_id
| {
632 debug
!("assemble_extension_candidates_for_trait_impl: trait_def_id={:?} \
637 if !self.impl_can_possibly_match(impl_def_id
) {
641 let (_
, impl_substs
) = self.impl_ty_and_substs(impl_def_id
);
643 debug
!("impl_substs={:?}", impl_substs
);
646 self.tcx().impl_trait_ref(impl_def_id
)
647 .unwrap() // we know this is a trait impl
648 .subst(self.tcx(), &impl_substs
);
650 debug
!("impl_trait_ref={:?}", impl_trait_ref
);
652 // Determine the receiver type that the method itself expects.
654 self.xform_self_ty(&item
,
655 impl_trait_ref
.self_ty(),
656 impl_trait_ref
.substs
);
658 // Normalize the receiver. We can't use normalize_associated_types_in
659 // as it will pollute the fcx's fulfillment context after this probe
661 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
662 let mut selcx
= &mut traits
::SelectionContext
::new(self.fcx
.infcx());
663 let traits
::Normalized { value: xform_self_ty, obligations }
=
664 traits
::normalize(selcx
, cause
, &xform_self_ty
);
666 debug
!("xform_self_ty={:?}", xform_self_ty
);
668 self.extension_candidates
.push(Candidate
{
669 xform_self_ty
: xform_self_ty
,
671 kind
: ExtensionImplCandidate(impl_def_id
, impl_substs
, obligations
)
676 fn impl_can_possibly_match(&self, impl_def_id
: DefId
) -> bool
{
677 let simplified_steps
= match self.opt_simplified_steps
{
678 Some(ref simplified_steps
) => simplified_steps
,
679 None
=> { return true; }
682 let impl_type
= self.tcx().lookup_item_type(impl_def_id
);
683 let impl_simplified_type
=
684 match ty
::fast_reject
::simplify_type(self.tcx(), impl_type
.ty
, false) {
685 Some(simplified_type
) => simplified_type
,
686 None
=> { return true; }
689 simplified_steps
.contains(&impl_simplified_type
)
692 fn assemble_closure_candidates(&mut self,
694 item
: ty
::ImplOrTraitItem
<'tcx
>)
695 -> Result
<(), MethodError
<'tcx
>>
697 // Check if this is one of the Fn,FnMut,FnOnce traits.
698 let tcx
= self.tcx();
699 let kind
= if Some(trait_def_id
) == tcx
.lang_items
.fn_trait() {
701 } else if Some(trait_def_id
) == tcx
.lang_items
.fn_mut_trait() {
703 } else if Some(trait_def_id
) == tcx
.lang_items
.fn_once_trait() {
704 ty
::FnOnceClosureKind
709 // Check if there is an unboxed-closure self-type in the list of receivers.
710 // If so, add "synthetic impls".
711 let steps
= self.steps
.clone();
712 for step
in steps
.iter() {
713 let closure_def_id
= match step
.self_ty
.sty
{
714 ty
::TyClosure(a
, _
) => a
,
718 let closure_kinds
= &self.fcx
.inh
.tables
.borrow().closure_kinds
;
719 let closure_kind
= match closure_kinds
.get(&closure_def_id
) {
722 return Err(MethodError
::ClosureAmbiguity(trait_def_id
));
726 // this closure doesn't implement the right kind of `Fn` trait
727 if !closure_kind
.extends(kind
) {
731 // create some substitutions for the argument/return type;
732 // for the purposes of our method lookup, we only take
733 // receiver type into account, so we can just substitute
734 // fresh types here to use during substitution and subtyping.
735 let trait_def
= self.tcx().lookup_trait_def(trait_def_id
);
736 let substs
= self.infcx().fresh_substs_for_trait(self.span
,
740 let xform_self_ty
= self.xform_self_ty(&item
,
743 self.inherent_candidates
.push(Candidate
{
744 xform_self_ty
: xform_self_ty
,
753 fn assemble_projection_candidates(&mut self,
755 item
: ty
::ImplOrTraitItem
<'tcx
>)
757 debug
!("assemble_projection_candidates(\
763 for step
in self.steps
.iter() {
764 debug
!("assemble_projection_candidates: step={:?}",
767 let projection_trait_ref
= match step
.self_ty
.sty
{
768 ty
::TyProjection(ref data
) => &data
.trait_ref
,
772 debug
!("assemble_projection_candidates: projection_trait_ref={:?}",
773 projection_trait_ref
);
775 let trait_predicates
= self.tcx().lookup_predicates(projection_trait_ref
.def_id
);
776 let bounds
= trait_predicates
.instantiate(self.tcx(), projection_trait_ref
.substs
);
777 let predicates
= bounds
.predicates
.into_vec();
778 debug
!("assemble_projection_candidates: predicates={:?}",
781 traits
::elaborate_predicates(self.tcx(), predicates
)
782 .filter_map(|p
| p
.to_opt_poly_trait_ref())
783 .filter(|b
| b
.def_id() == trait_def_id
)
785 let bound
= self.erase_late_bound_regions(&poly_bound
);
787 debug
!("assemble_projection_candidates: projection_trait_ref={:?} bound={:?}",
788 projection_trait_ref
,
791 if self.infcx().can_equate(&step
.self_ty
, &bound
.self_ty()).is_ok() {
792 let xform_self_ty
= self.xform_self_ty(&item
,
796 debug
!("assemble_projection_candidates: bound={:?} xform_self_ty={:?}",
800 self.extension_candidates
.push(Candidate
{
801 xform_self_ty
: xform_self_ty
,
810 fn assemble_where_clause_candidates(&mut self,
812 item
: ty
::ImplOrTraitItem
<'tcx
>)
814 debug
!("assemble_where_clause_candidates(trait_def_id={:?})",
817 let caller_predicates
= self.fcx
.inh
.infcx
.parameter_environment
.caller_bounds
.clone();
818 for poly_bound
in traits
::elaborate_predicates(self.tcx(), caller_predicates
)
819 .filter_map(|p
| p
.to_opt_poly_trait_ref())
820 .filter(|b
| b
.def_id() == trait_def_id
)
822 let bound
= self.erase_late_bound_regions(&poly_bound
);
823 let xform_self_ty
= self.xform_self_ty(&item
,
827 debug
!("assemble_where_clause_candidates: bound={:?} xform_self_ty={:?}",
831 self.extension_candidates
.push(Candidate
{
832 xform_self_ty
: xform_self_ty
,
834 kind
: WhereClauseCandidate(poly_bound
)
839 ///////////////////////////////////////////////////////////////////////////
842 fn pick(mut self) -> PickResult
<'tcx
> {
843 match self.pick_core() {
848 let static_candidates
= mem
::replace(&mut self.static_candidates
, vec
![]);
849 let unsatisfied_predicates
= mem
::replace(&mut self.unsatisfied_predicates
, vec
![]);
851 // things failed, so lets look at all traits, for diagnostic purposes now:
854 let span
= self.span
;
855 let tcx
= self.tcx();
857 try
!(self.assemble_extension_candidates_for_all_traits());
859 let out_of_scope_traits
= match self.pick_core() {
860 Some(Ok(p
)) => vec
![p
.item
.container().id()],
861 Some(Err(MethodError
::Ambiguity(v
))) => v
.into_iter().map(|source
| {
863 TraitSource(id
) => id
,
864 ImplSource(impl_id
) => {
865 match tcx
.trait_id_of_impl(impl_id
) {
868 tcx
.sess
.span_bug(span
,
869 "found inherent method when looking at traits")
874 Some(Err(MethodError
::NoMatch(NoMatchData { out_of_scope_traits: others, .. }
))) => {
875 assert
!(others
.is_empty());
878 Some(Err(MethodError
::ClosureAmbiguity(..))) => {
879 // this error only occurs when assembling candidates
880 tcx
.sess
.span_bug(span
, "encountered ClosureAmbiguity from pick_core");
885 Err(MethodError
::NoMatch(NoMatchData
::new(static_candidates
, unsatisfied_predicates
,
886 out_of_scope_traits
, self.mode
)))
889 fn pick_core(&mut self) -> Option
<PickResult
<'tcx
>> {
890 let steps
= self.steps
.clone();
892 // find the first step that works
893 steps
.iter().filter_map(|step
| self.pick_step(step
)).next()
896 fn pick_step(&mut self, step
: &CandidateStep
<'tcx
>) -> Option
<PickResult
<'tcx
>> {
897 debug
!("pick_step: step={:?}", step
);
899 if step
.self_ty
.references_error() {
903 match self.pick_by_value_method(step
) {
904 Some(result
) => return Some(result
),
908 self.pick_autorefd_method(step
)
911 fn pick_by_value_method(&mut self,
912 step
: &CandidateStep
<'tcx
>)
913 -> Option
<PickResult
<'tcx
>>
916 * For each type `T` in the step list, this attempts to find a
917 * method where the (transformed) self type is exactly `T`. We
918 * do however do one transformation on the adjustment: if we
919 * are passing a region pointer in, we will potentially
920 * *reborrow* it to a shorter lifetime. This allows us to
921 * transparently pass `&mut` pointers, in particular, without
922 * consuming them for their entire lifetime.
929 self.pick_method(step
.self_ty
).map(|r
| r
.map(|mut pick
| {
930 pick
.autoderefs
= step
.autoderefs
;
932 // Insert a `&*` or `&mut *` if this is a reference type:
933 if let ty
::TyRef(_
, mt
) = step
.self_ty
.sty
{
934 pick
.autoderefs
+= 1;
935 pick
.autoref
= Some(mt
.mutbl
);
942 fn pick_autorefd_method(&mut self,
943 step
: &CandidateStep
<'tcx
>)
944 -> Option
<PickResult
<'tcx
>>
946 let tcx
= self.tcx();
948 // In general, during probing we erase regions. See
949 // `impl_self_ty()` for an explanation.
950 let region
= tcx
.mk_region(ty
::ReStatic
);
952 // Search through mutabilities in order to find one where pick works:
953 [hir
::MutImmutable
, hir
::MutMutable
].iter().filter_map(|&m
| {
954 let autoref_ty
= tcx
.mk_ref(region
, ty
::TypeAndMut
{
958 self.pick_method(autoref_ty
).map(|r
| r
.map(|mut pick
| {
959 pick
.autoderefs
= step
.autoderefs
;
960 pick
.autoref
= Some(m
);
961 pick
.unsize
= if step
.unsize
{
971 fn pick_method(&mut self, self_ty
: Ty
<'tcx
>) -> Option
<PickResult
<'tcx
>> {
972 debug
!("pick_method(self_ty={})", self.infcx().ty_to_string(self_ty
));
974 let mut possibly_unsatisfied_predicates
= Vec
::new();
976 debug
!("searching inherent candidates");
977 match self.consider_candidates(self_ty
, &self.inherent_candidates
,
978 &mut possibly_unsatisfied_predicates
) {
985 debug
!("searching extension candidates");
986 let res
= self.consider_candidates(self_ty
, &self.extension_candidates
,
987 &mut possibly_unsatisfied_predicates
);
989 self.unsatisfied_predicates
.extend(possibly_unsatisfied_predicates
);
994 fn consider_candidates(&self,
996 probes
: &[Candidate
<'tcx
>],
997 possibly_unsatisfied_predicates
: &mut Vec
<TraitRef
<'tcx
>>)
998 -> Option
<PickResult
<'tcx
>> {
999 let mut applicable_candidates
: Vec
<_
> =
1001 .filter(|&probe
| self.consider_probe(self_ty
,
1002 probe
,possibly_unsatisfied_predicates
))
1005 debug
!("applicable_candidates: {:?}", applicable_candidates
);
1007 if applicable_candidates
.len() > 1 {
1008 match self.collapse_candidates_to_trait_pick(&applicable_candidates
[..]) {
1009 Some(pick
) => { return Some(Ok(pick)); }
1014 if applicable_candidates
.len() > 1 {
1015 let sources
= probes
.iter().map(|p
| p
.to_source()).collect();
1016 return Some(Err(MethodError
::Ambiguity(sources
)));
1019 applicable_candidates
.pop().map(|probe
| {
1020 Ok(probe
.to_unadjusted_pick())
1024 fn consider_probe(&self, self_ty
: Ty
<'tcx
>, probe
: &Candidate
<'tcx
>,
1025 possibly_unsatisfied_predicates
: &mut Vec
<TraitRef
<'tcx
>>) -> bool
{
1026 debug
!("consider_probe: self_ty={:?} probe={:?}",
1030 self.infcx().probe(|_
| {
1031 // First check that the self type can be related.
1032 match self.make_sub_ty(self_ty
, probe
.xform_self_ty
) {
1035 debug
!("--> cannot relate self-types");
1040 // If so, impls may carry other conditions (e.g., where
1041 // clauses) that must be considered. Make sure that those
1042 // match as well (or at least may match, sometimes we
1043 // don't have enough information to fully evaluate).
1044 let (impl_def_id
, substs
, ref_obligations
) = match probe
.kind
{
1045 InherentImplCandidate(ref substs
, ref ref_obligations
) => {
1046 (probe
.item
.container().id(), substs
, ref_obligations
)
1049 ExtensionImplCandidate(impl_def_id
, ref substs
, ref ref_obligations
) => {
1050 (impl_def_id
, substs
, ref_obligations
)
1055 WhereClauseCandidate(..) => {
1056 // These have no additional conditions to check.
1061 let selcx
= &mut traits
::SelectionContext
::new(self.infcx());
1062 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
1064 // Check whether the impl imposes obligations we have to worry about.
1065 let impl_bounds
= self.tcx().lookup_predicates(impl_def_id
);
1066 let impl_bounds
= impl_bounds
.instantiate(self.tcx(), substs
);
1067 let traits
::Normalized
{ value
: impl_bounds
,
1068 obligations
: norm_obligations
} =
1069 traits
::normalize(selcx
, cause
.clone(), &impl_bounds
);
1071 // Convert the bounds into obligations.
1073 traits
::predicates_for_generics(cause
.clone(),
1075 debug
!("impl_obligations={:?}", obligations
);
1077 // Evaluate those obligations to see if they might possibly hold.
1078 let mut all_true
= true;
1079 for o
in obligations
.iter()
1080 .chain(norm_obligations
.iter())
1081 .chain(ref_obligations
.iter()) {
1082 if !selcx
.evaluate_obligation(o
) {
1084 if let &ty
::Predicate
::Trait(ref pred
) = &o
.predicate
{
1085 possibly_unsatisfied_predicates
.push(pred
.0.trait_ref
);
1093 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1094 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1095 /// external interface of the method can be determined from the trait, it's ok not to decide.
1096 /// We can basically just collapse all of the probes for various impls into one where-clause
1097 /// probe. This will result in a pending obligation so when more type-info is available we can
1098 /// make the final decision.
1100 /// Example (`src/test/run-pass/method-two-trait-defer-resolution-1.rs`):
1103 /// trait Foo { ... }
1104 /// impl Foo for Vec<int> { ... }
1105 /// impl Foo for Vec<usize> { ... }
1108 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1109 /// use, so it's ok to just commit to "using the method from the trait Foo".
1110 fn collapse_candidates_to_trait_pick(&self,
1111 probes
: &[&Candidate
<'tcx
>])
1112 -> Option
<Pick
<'tcx
>> {
1113 // Do all probes correspond to the same trait?
1114 let container
= probes
[0].item
.container();
1116 ty
::TraitContainer(_
) => {}
1117 ty
::ImplContainer(_
) => return None
1119 if probes
[1..].iter().any(|p
| p
.item
.container() != container
) {
1123 // If so, just use this trait and call it a day.
1125 item
: probes
[0].item
.clone(),
1133 ///////////////////////////////////////////////////////////////////////////
1136 fn make_sub_ty(&self, sub
: Ty
<'tcx
>, sup
: Ty
<'tcx
>) -> infer
::UnitResult
<'tcx
> {
1137 self.infcx().sub_types(false, TypeOrigin
::Misc(DUMMY_SP
), sub
, sup
)
1140 fn has_applicable_self(&self, item
: &ty
::ImplOrTraitItem
) -> bool
{
1141 // "fast track" -- check for usage of sugar
1143 ty
::ImplOrTraitItem
::MethodTraitItem(ref method
) =>
1144 match method
.explicit_self
{
1145 ty
::ExplicitSelfCategory
::Static
=> self.mode
== Mode
::Path
,
1146 ty
::ExplicitSelfCategory
::ByValue
|
1147 ty
::ExplicitSelfCategory
::ByReference(..) |
1148 ty
::ExplicitSelfCategory
::ByBox
=> true,
1150 ty
::ImplOrTraitItem
::ConstTraitItem(..) => self.mode
== Mode
::Path
,
1153 // FIXME -- check for types that deref to `Self`,
1154 // like `Rc<Self>` and so on.
1156 // Note also that the current code will break if this type
1157 // includes any of the type parameters defined on the method
1158 // -- but this could be overcome.
1161 fn record_static_candidate(&mut self, source
: CandidateSource
) {
1162 self.static_candidates
.push(source
);
1165 fn xform_self_ty(&self,
1166 item
: &ty
::ImplOrTraitItem
<'tcx
>,
1168 substs
: &subst
::Substs
<'tcx
>)
1171 match item
.as_opt_method() {
1172 Some(ref method
) => self.xform_method_self_ty(method
, impl_ty
,
1178 fn xform_method_self_ty(&self,
1179 method
: &Rc
<ty
::Method
<'tcx
>>,
1181 substs
: &subst
::Substs
<'tcx
>)
1184 debug
!("xform_self_ty(impl_ty={:?}, self_ty={:?}, substs={:?})",
1186 method
.fty
.sig
.0.inputs
.get(0),
1189 assert
!(!substs
.has_escaping_regions());
1191 // It is possible for type parameters or early-bound lifetimes
1192 // to appear in the signature of `self`. The substitutions we
1193 // are given do not include type/lifetime parameters for the
1194 // method yet. So create fresh variables here for those too,
1195 // if there are any.
1196 assert_eq
!(substs
.types
.len(subst
::FnSpace
), 0);
1197 assert_eq
!(substs
.regions().len(subst
::FnSpace
), 0);
1199 if self.mode
== Mode
::Path
{
1203 let mut placeholder
;
1204 let mut substs
= substs
;
1206 !method
.generics
.types
.is_empty_in(subst
::FnSpace
) ||
1207 !method
.generics
.regions
.is_empty_in(subst
::FnSpace
)
1209 // In general, during probe we erase regions. See
1210 // `impl_self_ty()` for an explanation.
1211 let method_regions
=
1212 method
.generics
.regions
.get_slice(subst
::FnSpace
)
1214 .map(|_
| ty
::ReStatic
)
1217 placeholder
= (*substs
).clone().with_method(Vec
::new(), method_regions
);
1219 self.infcx().type_vars_for_defs(
1223 method
.generics
.types
.get_slice(subst
::FnSpace
));
1225 substs
= &placeholder
;
1228 // Erase any late-bound regions from the method and substitute
1229 // in the values from the substitution.
1230 let xform_self_ty
= method
.fty
.sig
.input(0);
1231 let xform_self_ty
= self.erase_late_bound_regions(&xform_self_ty
);
1232 let xform_self_ty
= xform_self_ty
.subst(self.tcx(), substs
);
1237 /// Get the type of an impl and generate substitutions with placeholders.
1238 fn impl_ty_and_substs(&self,
1240 -> (Ty
<'tcx
>, subst
::Substs
<'tcx
>)
1242 let impl_pty
= self.tcx().lookup_item_type(impl_def_id
);
1245 impl_pty
.generics
.types
.map(
1246 |_
| self.infcx().next_ty_var());
1248 let region_placeholders
=
1249 impl_pty
.generics
.regions
.map(
1250 |_
| ty
::ReStatic
); // see erase_late_bound_regions() for an expl of why 'static
1252 let substs
= subst
::Substs
::new(type_vars
, region_placeholders
);
1253 (impl_pty
.ty
, substs
)
1256 /// Replace late-bound-regions bound by `value` with `'static` using
1257 /// `ty::erase_late_bound_regions`.
1259 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1260 /// method matching. It is reasonable during the probe phase because we don't consider region
1261 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1262 /// rather than creating fresh region variables. This is nice for two reasons:
1264 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1265 /// particular method call, it winds up creating fewer types overall, which helps for memory
1266 /// usage. (Admittedly, this is a rather small effect, though measureable.)
1268 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1269 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1270 /// regions with actual region variables as is proper, we'd have to ensure that the same
1271 /// region got replaced with the same variable, which requires a bit more coordination
1272 /// and/or tracking the substitution and
1274 fn erase_late_bound_regions
<T
>(&self, value
: &ty
::Binder
<T
>) -> T
1275 where T
: TypeFoldable
<'tcx
>
1277 self.tcx().erase_late_bound_regions(value
)
1281 fn impl_item
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
1283 item_name
: ast
::Name
)
1284 -> Option
<ty
::ImplOrTraitItem
<'tcx
>>
1286 let impl_items
= tcx
.impl_items
.borrow();
1287 let impl_items
= impl_items
.get(&impl_def_id
).unwrap();
1290 .map(|&did
| tcx
.impl_or_trait_item(did
.def_id()))
1291 .find(|item
| item
.name() == item_name
)
1294 /// Find item with name `item_name` defined in `trait_def_id`
1295 /// and return it, or `None`, if no such item.
1296 fn trait_item
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
1297 trait_def_id
: DefId
,
1298 item_name
: ast
::Name
)
1299 -> Option
<ty
::ImplOrTraitItem
<'tcx
>>
1301 let trait_items
= tcx
.trait_items(trait_def_id
);
1302 debug
!("trait_method; items: {:?}", trait_items
);
1304 .find(|item
| item
.name() == item_name
)
1308 impl<'tcx
> Candidate
<'tcx
> {
1309 fn to_unadjusted_pick(&self) -> Pick
<'tcx
> {
1311 item
: self.item
.clone(),
1312 kind
: match self.kind
{
1313 InherentImplCandidate(_
, _
) => InherentImplPick
,
1314 ExtensionImplCandidate(def_id
, _
, _
) => {
1315 ExtensionImplPick(def_id
)
1317 ObjectCandidate
=> ObjectPick
,
1318 TraitCandidate
=> TraitPick
,
1319 WhereClauseCandidate(ref trait_ref
) => {
1320 // Only trait derived from where-clauses should
1321 // appear here, so they should not contain any
1322 // inference variables or other artifacts. This
1323 // means they are safe to put into the
1324 // `WhereClausePick`.
1325 assert
!(!trait_ref
.substs().types
.needs_infer());
1327 WhereClausePick(trait_ref
.clone())
1336 fn to_source(&self) -> CandidateSource
{
1338 InherentImplCandidate(_
, _
) => {
1339 ImplSource(self.item
.container().id())
1341 ExtensionImplCandidate(def_id
, _
, _
) => ImplSource(def_id
),
1344 WhereClauseCandidate(_
) => TraitSource(self.item
.container().id()),