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, RegionEscape, Ty, ToPolyTraitRef, TraitRef}
;
23 use middle
::ty
::HasTypeFlags
;
24 use middle
::ty
::fold
::TypeFoldable
;
26 use middle
::infer
::{InferCtxt, TypeOrigin}
;
28 use syntax
::codemap
::{Span, DUMMY_SP}
;
30 use std
::collections
::HashSet
;
34 use self::CandidateKind
::*;
35 pub use self::PickKind
::*;
37 struct ProbeContext
<'a
, 'tcx
:'a
> {
38 fcx
: &'a FnCtxt
<'a
, 'tcx
>,
42 steps
: Rc
<Vec
<CandidateStep
<'tcx
>>>,
43 opt_simplified_steps
: Option
<Vec
<ty
::fast_reject
::SimplifiedType
>>,
44 inherent_candidates
: Vec
<Candidate
<'tcx
>>,
45 extension_candidates
: Vec
<Candidate
<'tcx
>>,
46 impl_dups
: HashSet
<DefId
>,
48 /// Collects near misses when the candidate functions are missing a `self` keyword and is only
49 /// used for error reporting
50 static_candidates
: Vec
<CandidateSource
>,
52 /// Collects near misses when trait bounds for type parameters are unsatisfied and is only used
53 /// for error reporting
54 unsatisfied_predicates
: Vec
<TraitRef
<'tcx
>>
58 struct CandidateStep
<'tcx
> {
65 struct Candidate
<'tcx
> {
66 xform_self_ty
: Ty
<'tcx
>,
67 item
: ty
::ImplOrTraitItem
<'tcx
>,
68 kind
: CandidateKind
<'tcx
>,
72 enum CandidateKind
<'tcx
> {
73 InherentImplCandidate(subst
::Substs
<'tcx
>,
74 /* Normalize obligations */ Vec
<traits
::PredicateObligation
<'tcx
>>),
75 ExtensionImplCandidate(/* Impl */ DefId
, subst
::Substs
<'tcx
>,
76 /* Normalize obligations */ Vec
<traits
::PredicateObligation
<'tcx
>>),
79 WhereClauseCandidate(/* Trait */ ty
::PolyTraitRef
<'tcx
>),
83 pub struct Pick
<'tcx
> {
84 pub item
: ty
::ImplOrTraitItem
<'tcx
>,
85 pub kind
: PickKind
<'tcx
>,
87 // Indicates that the source expression should be autoderef'd N times
89 // A = expr | *expr | **expr | ...
90 pub autoderefs
: usize,
92 // Indicates that an autoref is applied after the optional autoderefs
94 // B = A | &A | &mut A
95 pub autoref
: Option
<hir
::Mutability
>,
97 // Indicates that the source expression should be "unsized" to a
98 // target type. This should probably eventually go away in favor
99 // of just coercing method receivers.
102 pub unsize
: Option
<Ty
<'tcx
>>,
105 #[derive(Clone,Debug)]
106 pub enum PickKind
<'tcx
> {
108 ExtensionImplPick(/* Impl */ DefId
),
111 WhereClausePick(/* Trait */ ty
::PolyTraitRef
<'tcx
>),
114 pub type PickResult
<'tcx
> = Result
<Pick
<'tcx
>, MethodError
<'tcx
>>;
116 #[derive(PartialEq, Eq, Copy, Clone, Debug)]
118 // An expression of the form `receiver.method_name(...)`.
119 // Autoderefs are performed on `receiver`, lookup is done based on the
120 // `self` argument of the method, and static methods aren't considered.
122 // An expression of the form `Type::item` or `<T>::item`.
123 // No autoderefs are performed, lookup is done based on the type each
124 // implementation is for, and static methods are included.
128 pub fn probe
<'a
, 'tcx
>(fcx
: &FnCtxt
<'a
, 'tcx
>,
131 item_name
: ast
::Name
,
133 scope_expr_id
: ast
::NodeId
)
136 debug
!("probe(self_ty={:?}, item_name={}, scope_expr_id={})",
141 // FIXME(#18741) -- right now, creating the steps involves evaluating the
142 // `*` operator, which registers obligations that then escape into
143 // the global fulfillment context and thus has global
144 // side-effects. This is a bit of a pain to refactor. So just let
145 // it ride, although it's really not great, and in fact could I
146 // think cause spurious errors. Really though this part should
147 // take place in the `fcx.infcx().probe` below.
148 let steps
= if mode
== Mode
::MethodCall
{
149 match create_steps(fcx
, span
, self_ty
) {
150 Some(steps
) => steps
,
151 None
=>return Err(MethodError
::NoMatch(NoMatchData
::new(Vec
::new(), Vec
::new(),
162 // Create a list of simplified self types, if we can.
163 let mut simplified_steps
= Vec
::new();
165 match ty
::fast_reject
::simplify_type(fcx
.tcx(), step
.self_ty
, true) {
167 Some(simplified_type
) => { simplified_steps.push(simplified_type); }
170 let opt_simplified_steps
=
171 if simplified_steps
.len() < steps
.len() {
172 None
// failed to convert at least one of the steps
174 Some(simplified_steps
)
177 debug
!("ProbeContext: steps for self_ty={:?} are {:?}",
181 // this creates one big transaction so that all type variables etc
182 // that we create during the probe process are removed later
183 fcx
.infcx().probe(|_
| {
184 let mut probe_cx
= ProbeContext
::new(fcx
,
189 opt_simplified_steps
);
190 probe_cx
.assemble_inherent_candidates();
191 try
!(probe_cx
.assemble_extension_candidates_for_traits_in_scope(scope_expr_id
));
196 fn create_steps
<'a
, 'tcx
>(fcx
: &FnCtxt
<'a
, 'tcx
>,
199 -> Option
<Vec
<CandidateStep
<'tcx
>>> {
200 let mut steps
= Vec
::new();
202 let (final_ty
, dereferences
, _
) = check
::autoderef(fcx
,
206 UnresolvedTypeAction
::Error
,
209 steps
.push(CandidateStep
{
214 None
::<()> // keep iterating until we can't anymore
218 ty
::TyArray(elem_ty
, _
) => {
219 steps
.push(CandidateStep
{
220 self_ty
: fcx
.tcx().mk_slice(elem_ty
),
221 autoderefs
: dereferences
,
225 ty
::TyError
=> return None
,
232 impl<'a
,'tcx
> ProbeContext
<'a
,'tcx
> {
233 fn new(fcx
: &'a FnCtxt
<'a
,'tcx
>,
236 item_name
: ast
::Name
,
237 steps
: Vec
<CandidateStep
<'tcx
>>,
238 opt_simplified_steps
: Option
<Vec
<ty
::fast_reject
::SimplifiedType
>>)
239 -> ProbeContext
<'a
,'tcx
>
245 item_name
: item_name
,
246 inherent_candidates
: Vec
::new(),
247 extension_candidates
: Vec
::new(),
248 impl_dups
: HashSet
::new(),
249 steps
: Rc
::new(steps
),
250 opt_simplified_steps
: opt_simplified_steps
,
251 static_candidates
: Vec
::new(),
252 unsatisfied_predicates
: Vec
::new(),
256 fn reset(&mut self) {
257 self.inherent_candidates
.clear();
258 self.extension_candidates
.clear();
259 self.impl_dups
.clear();
260 self.static_candidates
.clear();
263 fn tcx(&self) -> &'a ty
::ctxt
<'tcx
> {
267 fn infcx(&self) -> &'a InferCtxt
<'a
, 'tcx
> {
271 ///////////////////////////////////////////////////////////////////////////
272 // CANDIDATE ASSEMBLY
274 fn assemble_inherent_candidates(&mut self) {
275 let steps
= self.steps
.clone();
276 for step
in steps
.iter() {
277 self.assemble_probe(step
.self_ty
);
281 fn assemble_probe(&mut self, self_ty
: Ty
<'tcx
>) {
282 debug
!("assemble_probe: self_ty={:?}",
286 ty
::TyTrait(box ref data
) => {
287 self.assemble_inherent_candidates_from_object(self_ty
, data
);
288 self.assemble_inherent_impl_candidates_for_type(data
.principal_def_id());
291 ty
::TyStruct(def
, _
) => {
292 self.assemble_inherent_impl_candidates_for_type(def
.did
);
295 if let Some(box_did
) = self.tcx().lang_items
.owned_box() {
296 self.assemble_inherent_impl_candidates_for_type(box_did
);
300 self.assemble_inherent_candidates_from_param(self_ty
, p
);
303 let lang_def_id
= self.tcx().lang_items
.char_impl();
304 self.assemble_inherent_impl_for_primitive(lang_def_id
);
307 let lang_def_id
= self.tcx().lang_items
.str_impl();
308 self.assemble_inherent_impl_for_primitive(lang_def_id
);
311 let lang_def_id
= self.tcx().lang_items
.slice_impl();
312 self.assemble_inherent_impl_for_primitive(lang_def_id
);
314 ty
::TyRawPtr(ty
::TypeAndMut { ty: _, mutbl: hir::MutImmutable }
) => {
315 let lang_def_id
= self.tcx().lang_items
.const_ptr_impl();
316 self.assemble_inherent_impl_for_primitive(lang_def_id
);
318 ty
::TyRawPtr(ty
::TypeAndMut { ty: _, mutbl: hir::MutMutable }
) => {
319 let lang_def_id
= self.tcx().lang_items
.mut_ptr_impl();
320 self.assemble_inherent_impl_for_primitive(lang_def_id
);
322 ty
::TyInt(ast
::TyI8
) => {
323 let lang_def_id
= self.tcx().lang_items
.i8_impl();
324 self.assemble_inherent_impl_for_primitive(lang_def_id
);
326 ty
::TyInt(ast
::TyI16
) => {
327 let lang_def_id
= self.tcx().lang_items
.i16_impl();
328 self.assemble_inherent_impl_for_primitive(lang_def_id
);
330 ty
::TyInt(ast
::TyI32
) => {
331 let lang_def_id
= self.tcx().lang_items
.i32_impl();
332 self.assemble_inherent_impl_for_primitive(lang_def_id
);
334 ty
::TyInt(ast
::TyI64
) => {
335 let lang_def_id
= self.tcx().lang_items
.i64_impl();
336 self.assemble_inherent_impl_for_primitive(lang_def_id
);
338 ty
::TyInt(ast
::TyIs
) => {
339 let lang_def_id
= self.tcx().lang_items
.isize_impl();
340 self.assemble_inherent_impl_for_primitive(lang_def_id
);
342 ty
::TyUint(ast
::TyU8
) => {
343 let lang_def_id
= self.tcx().lang_items
.u8_impl();
344 self.assemble_inherent_impl_for_primitive(lang_def_id
);
346 ty
::TyUint(ast
::TyU16
) => {
347 let lang_def_id
= self.tcx().lang_items
.u16_impl();
348 self.assemble_inherent_impl_for_primitive(lang_def_id
);
350 ty
::TyUint(ast
::TyU32
) => {
351 let lang_def_id
= self.tcx().lang_items
.u32_impl();
352 self.assemble_inherent_impl_for_primitive(lang_def_id
);
354 ty
::TyUint(ast
::TyU64
) => {
355 let lang_def_id
= self.tcx().lang_items
.u64_impl();
356 self.assemble_inherent_impl_for_primitive(lang_def_id
);
358 ty
::TyUint(ast
::TyUs
) => {
359 let lang_def_id
= self.tcx().lang_items
.usize_impl();
360 self.assemble_inherent_impl_for_primitive(lang_def_id
);
362 ty
::TyFloat(ast
::TyF32
) => {
363 let lang_def_id
= self.tcx().lang_items
.f32_impl();
364 self.assemble_inherent_impl_for_primitive(lang_def_id
);
366 ty
::TyFloat(ast
::TyF64
) => {
367 let lang_def_id
= self.tcx().lang_items
.f64_impl();
368 self.assemble_inherent_impl_for_primitive(lang_def_id
);
375 fn assemble_inherent_impl_for_primitive(&mut self, lang_def_id
: Option
<DefId
>) {
376 if let Some(impl_def_id
) = lang_def_id
{
377 self.tcx().populate_implementations_for_primitive_if_necessary(impl_def_id
);
379 self.assemble_inherent_impl_probe(impl_def_id
);
383 fn assemble_inherent_impl_candidates_for_type(&mut self, def_id
: DefId
) {
384 // Read the inherent implementation candidates for this type from the
385 // metadata if necessary.
386 self.tcx().populate_inherent_implementations_for_type_if_necessary(def_id
);
388 if let Some(impl_infos
) = self.tcx().inherent_impls
.borrow().get(&def_id
) {
389 for &impl_def_id
in impl_infos
.iter() {
390 self.assemble_inherent_impl_probe(impl_def_id
);
395 fn assemble_inherent_impl_probe(&mut self, impl_def_id
: DefId
) {
396 if !self.impl_dups
.insert(impl_def_id
) {
397 return; // already visited
400 debug
!("assemble_inherent_impl_probe {:?}", impl_def_id
);
402 let item
= match impl_item(self.tcx(), impl_def_id
, self.item_name
) {
404 None
=> { return; }
// No method with correct name on this impl
407 if !self.has_applicable_self(&item
) {
408 // No receiver declared. Not a candidate.
409 return self.record_static_candidate(ImplSource(impl_def_id
));
412 let (impl_ty
, impl_substs
) = self.impl_ty_and_substs(impl_def_id
);
413 let impl_ty
= impl_ty
.subst(self.tcx(), &impl_substs
);
415 // Determine the receiver type that the method itself expects.
416 let xform_self_ty
= self.xform_self_ty(&item
, impl_ty
, &impl_substs
);
418 // We can't use normalize_associated_types_in as it will pollute the
419 // fcx's fulfillment context after this probe is over.
420 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
421 let mut selcx
= &mut traits
::SelectionContext
::new(self.fcx
.infcx());
422 let traits
::Normalized { value: xform_self_ty, obligations }
=
423 traits
::normalize(selcx
, cause
, &xform_self_ty
);
424 debug
!("assemble_inherent_impl_probe: xform_self_ty = {:?}",
427 self.inherent_candidates
.push(Candidate
{
428 xform_self_ty
: xform_self_ty
,
430 kind
: InherentImplCandidate(impl_substs
, obligations
)
434 fn assemble_inherent_candidates_from_object(&mut self,
436 data
: &ty
::TraitTy
<'tcx
>) {
437 debug
!("assemble_inherent_candidates_from_object(self_ty={:?})",
440 // It is illegal to invoke a method on a trait instance that
441 // refers to the `Self` type. An error will be reported by
442 // `enforce_object_limitations()` if the method refers to the
443 // `Self` type anywhere other than the receiver. Here, we use
444 // a substitution that replaces `Self` with the object type
445 // itself. Hence, a `&self` method will wind up with an
446 // argument type like `&Trait`.
447 let trait_ref
= data
.principal_trait_ref_with_self_ty(self.tcx(), self_ty
);
448 self.elaborate_bounds(&[trait_ref
], |this
, new_trait_ref
, item
| {
449 let new_trait_ref
= this
.erase_late_bound_regions(&new_trait_ref
);
451 let xform_self_ty
= this
.xform_self_ty(&item
,
452 new_trait_ref
.self_ty(),
453 new_trait_ref
.substs
);
455 this
.inherent_candidates
.push(Candidate
{
456 xform_self_ty
: xform_self_ty
,
458 kind
: ObjectCandidate
463 fn assemble_inherent_candidates_from_param(&mut self,
465 param_ty
: ty
::ParamTy
) {
466 // FIXME -- Do we want to commit to this behavior for param bounds?
469 self.fcx
.inh
.infcx
.parameter_environment
.caller_bounds
471 .filter_map(|predicate
| {
473 ty
::Predicate
::Trait(ref trait_predicate
) => {
474 match trait_predicate
.0.trait_ref
.self_ty().sty
{
475 ty
::TyParam(ref p
) if *p
== param_ty
=> {
476 Some(trait_predicate
.to_poly_trait_ref())
481 ty
::Predicate
::Equate(..) |
482 ty
::Predicate
::Projection(..) |
483 ty
::Predicate
::RegionOutlives(..) |
484 ty
::Predicate
::WellFormed(..) |
485 ty
::Predicate
::ObjectSafe(..) |
486 ty
::Predicate
::TypeOutlives(..) => {
493 self.elaborate_bounds(&bounds
, |this
, poly_trait_ref
, item
| {
495 this
.erase_late_bound_regions(&poly_trait_ref
);
498 this
.xform_self_ty(&item
,
502 if let Some(ref m
) = item
.as_opt_method() {
503 debug
!("found match: trait_ref={:?} substs={:?} m={:?}",
507 assert_eq
!(m
.generics
.types
.get_slice(subst
::TypeSpace
).len(),
508 trait_ref
.substs
.types
.get_slice(subst
::TypeSpace
).len());
509 assert_eq
!(m
.generics
.regions
.get_slice(subst
::TypeSpace
).len(),
510 trait_ref
.substs
.regions().get_slice(subst
::TypeSpace
).len());
511 assert_eq
!(m
.generics
.types
.get_slice(subst
::SelfSpace
).len(),
512 trait_ref
.substs
.types
.get_slice(subst
::SelfSpace
).len());
513 assert_eq
!(m
.generics
.regions
.get_slice(subst
::SelfSpace
).len(),
514 trait_ref
.substs
.regions().get_slice(subst
::SelfSpace
).len());
517 // Because this trait derives from a where-clause, it
518 // should not contain any inference variables or other
519 // artifacts. This means it is safe to put into the
520 // `WhereClauseCandidate` and (eventually) into the
521 // `WhereClausePick`.
522 assert
!(!trait_ref
.substs
.types
.needs_infer());
524 this
.inherent_candidates
.push(Candidate
{
525 xform_self_ty
: xform_self_ty
,
527 kind
: WhereClauseCandidate(poly_trait_ref
)
532 // Do a search through a list of bounds, using a callback to actually
533 // create the candidates.
534 fn elaborate_bounds
<F
>(
536 bounds
: &[ty
::PolyTraitRef
<'tcx
>],
540 &mut ProbeContext
<'b
, 'tcx
>,
541 ty
::PolyTraitRef
<'tcx
>,
542 ty
::ImplOrTraitItem
<'tcx
>,
545 debug
!("elaborate_bounds(bounds={:?})", bounds
);
547 let tcx
= self.tcx();
548 for bound_trait_ref
in traits
::transitive_bounds(tcx
, bounds
) {
549 let item
= match trait_item(tcx
,
550 bound_trait_ref
.def_id(),
553 None
=> { continue; }
556 if !self.has_applicable_self(&item
) {
557 self.record_static_candidate(TraitSource(bound_trait_ref
.def_id()));
559 mk_cand(self, bound_trait_ref
, item
);
564 fn assemble_extension_candidates_for_traits_in_scope(&mut self,
565 expr_id
: ast
::NodeId
)
566 -> Result
<(), MethodError
<'tcx
>>
568 let mut duplicates
= HashSet
::new();
569 let opt_applicable_traits
= self.fcx
.ccx
.trait_map
.get(&expr_id
);
570 if let Some(applicable_traits
) = opt_applicable_traits
{
571 for &trait_did
in applicable_traits
{
572 if duplicates
.insert(trait_did
) {
573 try
!(self.assemble_extension_candidates_for_trait(trait_did
));
580 fn assemble_extension_candidates_for_all_traits(&mut self) -> Result
<(), MethodError
<'tcx
>> {
581 let mut duplicates
= HashSet
::new();
582 for trait_info
in suggest
::all_traits(self.fcx
.ccx
) {
583 if duplicates
.insert(trait_info
.def_id
) {
584 try
!(self.assemble_extension_candidates_for_trait(trait_info
.def_id
));
590 fn assemble_extension_candidates_for_trait(&mut self,
592 -> Result
<(), MethodError
<'tcx
>>
594 debug
!("assemble_extension_candidates_for_trait(trait_def_id={:?})",
597 // Check whether `trait_def_id` defines a method with suitable name:
599 self.tcx().trait_items(trait_def_id
);
602 .find(|item
| item
.name() == self.item_name
);
603 let item
= match maybe_item
{
605 None
=> { return Ok(()); }
608 // Check whether `trait_def_id` defines a method with suitable name:
609 if !self.has_applicable_self(item
) {
610 debug
!("method has inapplicable self");
611 self.record_static_candidate(TraitSource(trait_def_id
));
615 self.assemble_extension_candidates_for_trait_impls(trait_def_id
, item
.clone());
617 try
!(self.assemble_closure_candidates(trait_def_id
, item
.clone()));
619 self.assemble_projection_candidates(trait_def_id
, item
.clone());
621 self.assemble_where_clause_candidates(trait_def_id
, item
.clone());
626 fn assemble_extension_candidates_for_trait_impls(&mut self,
628 item
: ty
::ImplOrTraitItem
<'tcx
>)
630 let trait_def
= self.tcx().lookup_trait_def(trait_def_id
);
632 // FIXME(arielb1): can we use for_each_relevant_impl here?
633 trait_def
.for_each_impl(self.tcx(), |impl_def_id
| {
634 debug
!("assemble_extension_candidates_for_trait_impl: trait_def_id={:?} \
639 if !self.impl_can_possibly_match(impl_def_id
) {
643 let (_
, impl_substs
) = self.impl_ty_and_substs(impl_def_id
);
645 debug
!("impl_substs={:?}", impl_substs
);
648 self.tcx().impl_trait_ref(impl_def_id
)
649 .unwrap() // we know this is a trait impl
650 .subst(self.tcx(), &impl_substs
);
652 debug
!("impl_trait_ref={:?}", impl_trait_ref
);
654 // Determine the receiver type that the method itself expects.
656 self.xform_self_ty(&item
,
657 impl_trait_ref
.self_ty(),
658 impl_trait_ref
.substs
);
660 // Normalize the receiver. We can't use normalize_associated_types_in
661 // as it will pollute the fcx's fulfillment context after this probe
663 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
664 let mut selcx
= &mut traits
::SelectionContext
::new(self.fcx
.infcx());
665 let traits
::Normalized { value: xform_self_ty, obligations }
=
666 traits
::normalize(selcx
, cause
, &xform_self_ty
);
668 debug
!("xform_self_ty={:?}", xform_self_ty
);
670 self.extension_candidates
.push(Candidate
{
671 xform_self_ty
: xform_self_ty
,
673 kind
: ExtensionImplCandidate(impl_def_id
, impl_substs
, obligations
)
678 fn impl_can_possibly_match(&self, impl_def_id
: DefId
) -> bool
{
679 let simplified_steps
= match self.opt_simplified_steps
{
680 Some(ref simplified_steps
) => simplified_steps
,
681 None
=> { return true; }
684 let impl_type
= self.tcx().lookup_item_type(impl_def_id
);
685 let impl_simplified_type
=
686 match ty
::fast_reject
::simplify_type(self.tcx(), impl_type
.ty
, false) {
687 Some(simplified_type
) => simplified_type
,
688 None
=> { return true; }
691 simplified_steps
.contains(&impl_simplified_type
)
694 fn assemble_closure_candidates(&mut self,
696 item
: ty
::ImplOrTraitItem
<'tcx
>)
697 -> Result
<(), MethodError
<'tcx
>>
699 // Check if this is one of the Fn,FnMut,FnOnce traits.
700 let tcx
= self.tcx();
701 let kind
= if Some(trait_def_id
) == tcx
.lang_items
.fn_trait() {
703 } else if Some(trait_def_id
) == tcx
.lang_items
.fn_mut_trait() {
705 } else if Some(trait_def_id
) == tcx
.lang_items
.fn_once_trait() {
706 ty
::FnOnceClosureKind
711 // Check if there is an unboxed-closure self-type in the list of receivers.
712 // If so, add "synthetic impls".
713 let steps
= self.steps
.clone();
714 for step
in steps
.iter() {
715 let closure_def_id
= match step
.self_ty
.sty
{
716 ty
::TyClosure(a
, _
) => a
,
720 let closure_kinds
= &self.fcx
.inh
.tables
.borrow().closure_kinds
;
721 let closure_kind
= match closure_kinds
.get(&closure_def_id
) {
724 return Err(MethodError
::ClosureAmbiguity(trait_def_id
));
728 // this closure doesn't implement the right kind of `Fn` trait
729 if !closure_kind
.extends(kind
) {
733 // create some substitutions for the argument/return type;
734 // for the purposes of our method lookup, we only take
735 // receiver type into account, so we can just substitute
736 // fresh types here to use during substitution and subtyping.
737 let trait_def
= self.tcx().lookup_trait_def(trait_def_id
);
738 let substs
= self.infcx().fresh_substs_for_trait(self.span
,
742 let xform_self_ty
= self.xform_self_ty(&item
,
745 self.inherent_candidates
.push(Candidate
{
746 xform_self_ty
: xform_self_ty
,
755 fn assemble_projection_candidates(&mut self,
757 item
: ty
::ImplOrTraitItem
<'tcx
>)
759 debug
!("assemble_projection_candidates(\
765 for step
in self.steps
.iter() {
766 debug
!("assemble_projection_candidates: step={:?}",
769 let projection_trait_ref
= match step
.self_ty
.sty
{
770 ty
::TyProjection(ref data
) => &data
.trait_ref
,
774 debug
!("assemble_projection_candidates: projection_trait_ref={:?}",
775 projection_trait_ref
);
777 let trait_predicates
= self.tcx().lookup_predicates(projection_trait_ref
.def_id
);
778 let bounds
= trait_predicates
.instantiate(self.tcx(), projection_trait_ref
.substs
);
779 let predicates
= bounds
.predicates
.into_vec();
780 debug
!("assemble_projection_candidates: predicates={:?}",
783 traits
::elaborate_predicates(self.tcx(), predicates
)
784 .filter_map(|p
| p
.to_opt_poly_trait_ref())
785 .filter(|b
| b
.def_id() == trait_def_id
)
787 let bound
= self.erase_late_bound_regions(&poly_bound
);
789 debug
!("assemble_projection_candidates: projection_trait_ref={:?} bound={:?}",
790 projection_trait_ref
,
793 if self.infcx().can_equate(&step
.self_ty
, &bound
.self_ty()).is_ok() {
794 let xform_self_ty
= self.xform_self_ty(&item
,
798 debug
!("assemble_projection_candidates: bound={:?} xform_self_ty={:?}",
802 self.extension_candidates
.push(Candidate
{
803 xform_self_ty
: xform_self_ty
,
812 fn assemble_where_clause_candidates(&mut self,
814 item
: ty
::ImplOrTraitItem
<'tcx
>)
816 debug
!("assemble_where_clause_candidates(trait_def_id={:?})",
819 let caller_predicates
= self.fcx
.inh
.infcx
.parameter_environment
.caller_bounds
.clone();
820 for poly_bound
in traits
::elaborate_predicates(self.tcx(), caller_predicates
)
821 .filter_map(|p
| p
.to_opt_poly_trait_ref())
822 .filter(|b
| b
.def_id() == trait_def_id
)
824 let bound
= self.erase_late_bound_regions(&poly_bound
);
825 let xform_self_ty
= self.xform_self_ty(&item
,
829 debug
!("assemble_where_clause_candidates: bound={:?} xform_self_ty={:?}",
833 self.extension_candidates
.push(Candidate
{
834 xform_self_ty
: xform_self_ty
,
836 kind
: WhereClauseCandidate(poly_bound
)
841 ///////////////////////////////////////////////////////////////////////////
844 fn pick(mut self) -> PickResult
<'tcx
> {
845 match self.pick_core() {
850 let static_candidates
= mem
::replace(&mut self.static_candidates
, vec
![]);
851 let unsatisfied_predicates
= mem
::replace(&mut self.unsatisfied_predicates
, vec
![]);
853 // things failed, so lets look at all traits, for diagnostic purposes now:
856 let span
= self.span
;
857 let tcx
= self.tcx();
859 try
!(self.assemble_extension_candidates_for_all_traits());
861 let out_of_scope_traits
= match self.pick_core() {
862 Some(Ok(p
)) => vec
![p
.item
.container().id()],
863 Some(Err(MethodError
::Ambiguity(v
))) => v
.into_iter().map(|source
| {
865 TraitSource(id
) => id
,
866 ImplSource(impl_id
) => {
867 match tcx
.trait_id_of_impl(impl_id
) {
870 tcx
.sess
.span_bug(span
,
871 "found inherent method when looking at traits")
876 Some(Err(MethodError
::NoMatch(NoMatchData { out_of_scope_traits: others, .. }
))) => {
877 assert
!(others
.is_empty());
880 Some(Err(MethodError
::ClosureAmbiguity(..))) => {
881 // this error only occurs when assembling candidates
882 tcx
.sess
.span_bug(span
, "encountered ClosureAmbiguity from pick_core");
887 Err(MethodError
::NoMatch(NoMatchData
::new(static_candidates
, unsatisfied_predicates
,
888 out_of_scope_traits
, self.mode
)))
891 fn pick_core(&mut self) -> Option
<PickResult
<'tcx
>> {
892 let steps
= self.steps
.clone();
894 // find the first step that works
895 steps
.iter().filter_map(|step
| self.pick_step(step
)).next()
898 fn pick_step(&mut self, step
: &CandidateStep
<'tcx
>) -> Option
<PickResult
<'tcx
>> {
899 debug
!("pick_step: step={:?}", step
);
901 if step
.self_ty
.references_error() {
905 match self.pick_by_value_method(step
) {
906 Some(result
) => return Some(result
),
910 self.pick_autorefd_method(step
)
913 fn pick_by_value_method(&mut self,
914 step
: &CandidateStep
<'tcx
>)
915 -> Option
<PickResult
<'tcx
>>
918 * For each type `T` in the step list, this attempts to find a
919 * method where the (transformed) self type is exactly `T`. We
920 * do however do one transformation on the adjustment: if we
921 * are passing a region pointer in, we will potentially
922 * *reborrow* it to a shorter lifetime. This allows us to
923 * transparently pass `&mut` pointers, in particular, without
924 * consuming them for their entire lifetime.
931 self.pick_method(step
.self_ty
).map(|r
| r
.map(|mut pick
| {
932 pick
.autoderefs
= step
.autoderefs
;
934 // Insert a `&*` or `&mut *` if this is a reference type:
935 if let ty
::TyRef(_
, mt
) = step
.self_ty
.sty
{
936 pick
.autoderefs
+= 1;
937 pick
.autoref
= Some(mt
.mutbl
);
944 fn pick_autorefd_method(&mut self,
945 step
: &CandidateStep
<'tcx
>)
946 -> Option
<PickResult
<'tcx
>>
948 let tcx
= self.tcx();
950 // In general, during probing we erase regions. See
951 // `impl_self_ty()` for an explanation.
952 let region
= tcx
.mk_region(ty
::ReStatic
);
954 // Search through mutabilities in order to find one where pick works:
955 [hir
::MutImmutable
, hir
::MutMutable
].iter().filter_map(|&m
| {
956 let autoref_ty
= tcx
.mk_ref(region
, ty
::TypeAndMut
{
960 self.pick_method(autoref_ty
).map(|r
| r
.map(|mut pick
| {
961 pick
.autoderefs
= step
.autoderefs
;
962 pick
.autoref
= Some(m
);
963 pick
.unsize
= if step
.unsize
{
973 fn pick_method(&mut self, self_ty
: Ty
<'tcx
>) -> Option
<PickResult
<'tcx
>> {
974 debug
!("pick_method(self_ty={})", self.infcx().ty_to_string(self_ty
));
976 let mut possibly_unsatisfied_predicates
= Vec
::new();
978 debug
!("searching inherent candidates");
979 match self.consider_candidates(self_ty
, &self.inherent_candidates
,
980 &mut possibly_unsatisfied_predicates
) {
987 debug
!("searching extension candidates");
988 let res
= self.consider_candidates(self_ty
, &self.extension_candidates
,
989 &mut possibly_unsatisfied_predicates
);
991 self.unsatisfied_predicates
.extend(possibly_unsatisfied_predicates
);
996 fn consider_candidates(&self,
998 probes
: &[Candidate
<'tcx
>],
999 possibly_unsatisfied_predicates
: &mut Vec
<TraitRef
<'tcx
>>)
1000 -> Option
<PickResult
<'tcx
>> {
1001 let mut applicable_candidates
: Vec
<_
> =
1003 .filter(|&probe
| self.consider_probe(self_ty
,
1004 probe
,possibly_unsatisfied_predicates
))
1007 debug
!("applicable_candidates: {:?}", applicable_candidates
);
1009 if applicable_candidates
.len() > 1 {
1010 match self.collapse_candidates_to_trait_pick(&applicable_candidates
[..]) {
1011 Some(pick
) => { return Some(Ok(pick)); }
1016 if applicable_candidates
.len() > 1 {
1017 let sources
= probes
.iter().map(|p
| p
.to_source()).collect();
1018 return Some(Err(MethodError
::Ambiguity(sources
)));
1021 applicable_candidates
.pop().map(|probe
| {
1022 Ok(probe
.to_unadjusted_pick())
1026 fn consider_probe(&self, self_ty
: Ty
<'tcx
>, probe
: &Candidate
<'tcx
>,
1027 possibly_unsatisfied_predicates
: &mut Vec
<TraitRef
<'tcx
>>) -> bool
{
1028 debug
!("consider_probe: self_ty={:?} probe={:?}",
1032 self.infcx().probe(|_
| {
1033 // First check that the self type can be related.
1034 match self.make_sub_ty(self_ty
, probe
.xform_self_ty
) {
1037 debug
!("--> cannot relate self-types");
1042 // If so, impls may carry other conditions (e.g., where
1043 // clauses) that must be considered. Make sure that those
1044 // match as well (or at least may match, sometimes we
1045 // don't have enough information to fully evaluate).
1046 let (impl_def_id
, substs
, ref_obligations
) = match probe
.kind
{
1047 InherentImplCandidate(ref substs
, ref ref_obligations
) => {
1048 (probe
.item
.container().id(), substs
, ref_obligations
)
1051 ExtensionImplCandidate(impl_def_id
, ref substs
, ref ref_obligations
) => {
1052 (impl_def_id
, substs
, ref_obligations
)
1057 WhereClauseCandidate(..) => {
1058 // These have no additional conditions to check.
1063 let selcx
= &mut traits
::SelectionContext
::new(self.infcx());
1064 let cause
= traits
::ObligationCause
::misc(self.span
, self.fcx
.body_id
);
1066 // Check whether the impl imposes obligations we have to worry about.
1067 let impl_bounds
= self.tcx().lookup_predicates(impl_def_id
);
1068 let impl_bounds
= impl_bounds
.instantiate(self.tcx(), substs
);
1069 let traits
::Normalized
{ value
: impl_bounds
,
1070 obligations
: norm_obligations
} =
1071 traits
::normalize(selcx
, cause
.clone(), &impl_bounds
);
1073 // Convert the bounds into obligations.
1075 traits
::predicates_for_generics(cause
.clone(),
1077 debug
!("impl_obligations={:?}", obligations
);
1079 // Evaluate those obligations to see if they might possibly hold.
1080 let mut all_true
= true;
1081 for o
in obligations
.iter()
1082 .chain(norm_obligations
.iter())
1083 .chain(ref_obligations
.iter()) {
1084 if !selcx
.evaluate_obligation(o
) {
1086 if let &ty
::Predicate
::Trait(ref pred
) = &o
.predicate
{
1087 possibly_unsatisfied_predicates
.push(pred
.0.trait_ref
);
1095 /// Sometimes we get in a situation where we have multiple probes that are all impls of the
1096 /// same trait, but we don't know which impl to use. In this case, since in all cases the
1097 /// external interface of the method can be determined from the trait, it's ok not to decide.
1098 /// We can basically just collapse all of the probes for various impls into one where-clause
1099 /// probe. This will result in a pending obligation so when more type-info is available we can
1100 /// make the final decision.
1102 /// Example (`src/test/run-pass/method-two-trait-defer-resolution-1.rs`):
1105 /// trait Foo { ... }
1106 /// impl Foo for Vec<int> { ... }
1107 /// impl Foo for Vec<usize> { ... }
1110 /// Now imagine the receiver is `Vec<_>`. It doesn't really matter at this time which impl we
1111 /// use, so it's ok to just commit to "using the method from the trait Foo".
1112 fn collapse_candidates_to_trait_pick(&self,
1113 probes
: &[&Candidate
<'tcx
>])
1114 -> Option
<Pick
<'tcx
>> {
1115 // Do all probes correspond to the same trait?
1116 let container
= probes
[0].item
.container();
1118 ty
::TraitContainer(_
) => {}
1119 ty
::ImplContainer(_
) => return None
1121 if probes
[1..].iter().any(|p
| p
.item
.container() != container
) {
1125 // If so, just use this trait and call it a day.
1127 item
: probes
[0].item
.clone(),
1135 ///////////////////////////////////////////////////////////////////////////
1138 fn make_sub_ty(&self, sub
: Ty
<'tcx
>, sup
: Ty
<'tcx
>) -> infer
::UnitResult
<'tcx
> {
1139 self.infcx().sub_types(false, TypeOrigin
::Misc(DUMMY_SP
), sub
, sup
)
1142 fn has_applicable_self(&self, item
: &ty
::ImplOrTraitItem
) -> bool
{
1143 // "fast track" -- check for usage of sugar
1145 ty
::ImplOrTraitItem
::MethodTraitItem(ref method
) =>
1146 match method
.explicit_self
{
1147 ty
::StaticExplicitSelfCategory
=> self.mode
== Mode
::Path
,
1148 ty
::ByValueExplicitSelfCategory
|
1149 ty
::ByReferenceExplicitSelfCategory(..) |
1150 ty
::ByBoxExplicitSelfCategory
=> true,
1152 ty
::ImplOrTraitItem
::ConstTraitItem(..) => self.mode
== Mode
::Path
,
1155 // FIXME -- check for types that deref to `Self`,
1156 // like `Rc<Self>` and so on.
1158 // Note also that the current code will break if this type
1159 // includes any of the type parameters defined on the method
1160 // -- but this could be overcome.
1163 fn record_static_candidate(&mut self, source
: CandidateSource
) {
1164 self.static_candidates
.push(source
);
1167 fn xform_self_ty(&self,
1168 item
: &ty
::ImplOrTraitItem
<'tcx
>,
1170 substs
: &subst
::Substs
<'tcx
>)
1173 match item
.as_opt_method() {
1174 Some(ref method
) => self.xform_method_self_ty(method
, impl_ty
,
1180 fn xform_method_self_ty(&self,
1181 method
: &Rc
<ty
::Method
<'tcx
>>,
1183 substs
: &subst
::Substs
<'tcx
>)
1186 debug
!("xform_self_ty(impl_ty={:?}, self_ty={:?}, substs={:?})",
1188 method
.fty
.sig
.0.inputs
.get(0),
1191 assert
!(!substs
.has_escaping_regions());
1193 // It is possible for type parameters or early-bound lifetimes
1194 // to appear in the signature of `self`. The substitutions we
1195 // are given do not include type/lifetime parameters for the
1196 // method yet. So create fresh variables here for those too,
1197 // if there are any.
1198 assert_eq
!(substs
.types
.len(subst
::FnSpace
), 0);
1199 assert_eq
!(substs
.regions().len(subst
::FnSpace
), 0);
1201 if self.mode
== Mode
::Path
{
1205 let mut placeholder
;
1206 let mut substs
= substs
;
1208 !method
.generics
.types
.is_empty_in(subst
::FnSpace
) ||
1209 !method
.generics
.regions
.is_empty_in(subst
::FnSpace
)
1211 // In general, during probe we erase regions. See
1212 // `impl_self_ty()` for an explanation.
1213 let method_regions
=
1214 method
.generics
.regions
.get_slice(subst
::FnSpace
)
1216 .map(|_
| ty
::ReStatic
)
1219 placeholder
= (*substs
).clone().with_method(Vec
::new(), method_regions
);
1221 self.infcx().type_vars_for_defs(
1225 method
.generics
.types
.get_slice(subst
::FnSpace
));
1227 substs
= &placeholder
;
1230 // Erase any late-bound regions from the method and substitute
1231 // in the values from the substitution.
1232 let xform_self_ty
= method
.fty
.sig
.input(0);
1233 let xform_self_ty
= self.erase_late_bound_regions(&xform_self_ty
);
1234 let xform_self_ty
= xform_self_ty
.subst(self.tcx(), substs
);
1239 /// Get the type of an impl and generate substitutions with placeholders.
1240 fn impl_ty_and_substs(&self,
1242 -> (Ty
<'tcx
>, subst
::Substs
<'tcx
>)
1244 let impl_pty
= self.tcx().lookup_item_type(impl_def_id
);
1247 impl_pty
.generics
.types
.map(
1248 |_
| self.infcx().next_ty_var());
1250 let region_placeholders
=
1251 impl_pty
.generics
.regions
.map(
1252 |_
| ty
::ReStatic
); // see erase_late_bound_regions() for an expl of why 'static
1254 let substs
= subst
::Substs
::new(type_vars
, region_placeholders
);
1255 (impl_pty
.ty
, substs
)
1258 /// Replace late-bound-regions bound by `value` with `'static` using
1259 /// `ty::erase_late_bound_regions`.
1261 /// This is only a reasonable thing to do during the *probe* phase, not the *confirm* phase, of
1262 /// method matching. It is reasonable during the probe phase because we don't consider region
1263 /// relationships at all. Therefore, we can just replace all the region variables with 'static
1264 /// rather than creating fresh region variables. This is nice for two reasons:
1266 /// 1. Because the numbers of the region variables would otherwise be fairly unique to this
1267 /// particular method call, it winds up creating fewer types overall, which helps for memory
1268 /// usage. (Admittedly, this is a rather small effect, though measureable.)
1270 /// 2. It makes it easier to deal with higher-ranked trait bounds, because we can replace any
1271 /// late-bound regions with 'static. Otherwise, if we were going to replace late-bound
1272 /// regions with actual region variables as is proper, we'd have to ensure that the same
1273 /// region got replaced with the same variable, which requires a bit more coordination
1274 /// and/or tracking the substitution and
1276 fn erase_late_bound_regions
<T
>(&self, value
: &ty
::Binder
<T
>) -> T
1277 where T
: TypeFoldable
<'tcx
>
1279 self.tcx().erase_late_bound_regions(value
)
1283 fn impl_item
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
1285 item_name
: ast
::Name
)
1286 -> Option
<ty
::ImplOrTraitItem
<'tcx
>>
1288 let impl_items
= tcx
.impl_items
.borrow();
1289 let impl_items
= impl_items
.get(&impl_def_id
).unwrap();
1292 .map(|&did
| tcx
.impl_or_trait_item(did
.def_id()))
1293 .find(|item
| item
.name() == item_name
)
1296 /// Find item with name `item_name` defined in `trait_def_id`
1297 /// and return it, or `None`, if no such item.
1298 fn trait_item
<'tcx
>(tcx
: &ty
::ctxt
<'tcx
>,
1299 trait_def_id
: DefId
,
1300 item_name
: ast
::Name
)
1301 -> Option
<ty
::ImplOrTraitItem
<'tcx
>>
1303 let trait_items
= tcx
.trait_items(trait_def_id
);
1304 debug
!("trait_method; items: {:?}", trait_items
);
1306 .find(|item
| item
.name() == item_name
)
1310 impl<'tcx
> Candidate
<'tcx
> {
1311 fn to_unadjusted_pick(&self) -> Pick
<'tcx
> {
1313 item
: self.item
.clone(),
1314 kind
: match self.kind
{
1315 InherentImplCandidate(_
, _
) => InherentImplPick
,
1316 ExtensionImplCandidate(def_id
, _
, _
) => {
1317 ExtensionImplPick(def_id
)
1319 ObjectCandidate
=> ObjectPick
,
1320 TraitCandidate
=> TraitPick
,
1321 WhereClauseCandidate(ref trait_ref
) => {
1322 // Only trait derived from where-clauses should
1323 // appear here, so they should not contain any
1324 // inference variables or other artifacts. This
1325 // means they are safe to put into the
1326 // `WhereClausePick`.
1327 assert
!(!trait_ref
.substs().types
.needs_infer());
1329 WhereClausePick(trait_ref
.clone())
1338 fn to_source(&self) -> CandidateSource
{
1340 InherentImplCandidate(_
, _
) => {
1341 ImplSource(self.item
.container().id())
1343 ExtensionImplCandidate(def_id
, _
, _
) => ImplSource(def_id
),
1346 WhereClauseCandidate(_
) => TraitSource(self.item
.container().id()),