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1//! This module is concerned with finding methods that a given type provides.
2//! For details about how this works in rustc, see the method lookup page in the
3//! [rustc guide](https://rust-lang.github.io/rustc-guide/method-lookup.html)
4//! and the corresponding code mostly in librustc_typeck/check/method/probe.rs.
5use std::{iter, sync::Arc};
6
7use arrayvec::ArrayVec;
8use base_db::CrateId;
9use hir_def::{
10 builtin_type::{IntBitness, Signedness},
11 lang_item::LangItemTarget,
12 type_ref::Mutability,
13 AssocContainerId, AssocItemId, FunctionId, HasModule, ImplId, Lookup, TraitId,
14};
15use hir_expand::name::Name;
16use rustc_hash::{FxHashMap, FxHashSet};
17
18use super::Substs;
19use crate::{
20 autoderef,
21 db::HirDatabase,
22 primitive::{FloatBitness, FloatTy, IntTy},
23 utils::all_super_traits,
24 ApplicationTy, Canonical, DebruijnIndex, InEnvironment, TraitEnvironment, TraitRef, Ty, TyKind,
25 TypeCtor, TypeWalk,
26};
27
28/// This is used as a key for indexing impls.
29#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
30pub enum TyFingerprint {
31 Apply(TypeCtor),
32}
33
34impl TyFingerprint {
35 /// Creates a TyFingerprint for looking up an impl. Only certain types can
36 /// have impls: if we have some `struct S`, we can have an `impl S`, but not
37 /// `impl &S`. Hence, this will return `None` for reference types and such.
38 pub(crate) fn for_impl(ty: &Ty) -> Option<TyFingerprint> {
39 match ty {
40 Ty::Apply(a_ty) => Some(TyFingerprint::Apply(a_ty.ctor)),
41 _ => None,
42 }
43 }
44}
45
46pub(crate) const ALL_INT_FPS: [TyFingerprint; 12] = [
47 TyFingerprint::Apply(TypeCtor::Int(IntTy {
48 signedness: Signedness::Unsigned,
49 bitness: IntBitness::X8,
50 })),
51 TyFingerprint::Apply(TypeCtor::Int(IntTy {
52 signedness: Signedness::Unsigned,
53 bitness: IntBitness::X16,
54 })),
55 TyFingerprint::Apply(TypeCtor::Int(IntTy {
56 signedness: Signedness::Unsigned,
57 bitness: IntBitness::X32,
58 })),
59 TyFingerprint::Apply(TypeCtor::Int(IntTy {
60 signedness: Signedness::Unsigned,
61 bitness: IntBitness::X64,
62 })),
63 TyFingerprint::Apply(TypeCtor::Int(IntTy {
64 signedness: Signedness::Unsigned,
65 bitness: IntBitness::X128,
66 })),
67 TyFingerprint::Apply(TypeCtor::Int(IntTy {
68 signedness: Signedness::Unsigned,
69 bitness: IntBitness::Xsize,
70 })),
71 TyFingerprint::Apply(TypeCtor::Int(IntTy {
72 signedness: Signedness::Signed,
73 bitness: IntBitness::X8,
74 })),
75 TyFingerprint::Apply(TypeCtor::Int(IntTy {
76 signedness: Signedness::Signed,
77 bitness: IntBitness::X16,
78 })),
79 TyFingerprint::Apply(TypeCtor::Int(IntTy {
80 signedness: Signedness::Signed,
81 bitness: IntBitness::X32,
82 })),
83 TyFingerprint::Apply(TypeCtor::Int(IntTy {
84 signedness: Signedness::Signed,
85 bitness: IntBitness::X64,
86 })),
87 TyFingerprint::Apply(TypeCtor::Int(IntTy {
88 signedness: Signedness::Signed,
89 bitness: IntBitness::X128,
90 })),
91 TyFingerprint::Apply(TypeCtor::Int(IntTy {
92 signedness: Signedness::Signed,
93 bitness: IntBitness::Xsize,
94 })),
95];
96
97pub(crate) const ALL_FLOAT_FPS: [TyFingerprint; 2] = [
98 TyFingerprint::Apply(TypeCtor::Float(FloatTy { bitness: FloatBitness::X32 })),
99 TyFingerprint::Apply(TypeCtor::Float(FloatTy { bitness: FloatBitness::X64 })),
100];
101
102/// Trait impls defined or available in some crate.
103#[derive(Debug, Eq, PartialEq)]
104pub struct TraitImpls {
105 // If the `Option<TyFingerprint>` is `None`, the impl may apply to any self type.
106 map: FxHashMap<TraitId, FxHashMap<Option<TyFingerprint>, Vec<ImplId>>>,
107}
108
109impl TraitImpls {
110 pub(crate) fn trait_impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
111 let _p = profile::span("trait_impls_in_crate_query");
112 let mut impls = Self { map: FxHashMap::default() };
113
114 let crate_def_map = db.crate_def_map(krate);
115 for (_module_id, module_data) in crate_def_map.modules.iter() {
116 for impl_id in module_data.scope.impls() {
117 let target_trait = match db.impl_trait(impl_id) {
118 Some(tr) => tr.value.trait_,
119 None => continue,
120 };
121 let self_ty = db.impl_self_ty(impl_id);
122 let self_ty_fp = TyFingerprint::for_impl(&self_ty.value);
123 impls
124 .map
125 .entry(target_trait)
126 .or_default()
127 .entry(self_ty_fp)
128 .or_default()
129 .push(impl_id);
130 }
131 }
132
133 Arc::new(impls)
134 }
135
136 pub(crate) fn trait_impls_in_deps_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
137 let _p = profile::span("trait_impls_in_deps_query");
138 let crate_graph = db.crate_graph();
139 let mut res = Self { map: FxHashMap::default() };
140
141 for krate in crate_graph.transitive_deps(krate) {
142 res.merge(&db.trait_impls_in_crate(krate));
143 }
144
145 Arc::new(res)
146 }
147
148 fn merge(&mut self, other: &Self) {
149 for (trait_, other_map) in &other.map {
150 let map = self.map.entry(*trait_).or_default();
151 for (fp, impls) in other_map {
152 let vec = map.entry(*fp).or_default();
153 vec.extend(impls);
154 }
155 }
156 }
157
158 /// Queries all impls of the given trait.
159 pub fn for_trait(&self, trait_: TraitId) -> impl Iterator<Item = ImplId> + '_ {
160 self.map
161 .get(&trait_)
162 .into_iter()
163 .flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
164 }
165
166 /// Queries all impls of `trait_` that may apply to `self_ty`.
167 pub fn for_trait_and_self_ty(
168 &self,
169 trait_: TraitId,
170 self_ty: TyFingerprint,
171 ) -> impl Iterator<Item = ImplId> + '_ {
172 self.map
173 .get(&trait_)
174 .into_iter()
175 .flat_map(move |map| map.get(&None).into_iter().chain(map.get(&Some(self_ty))))
176 .flat_map(|v| v.iter().copied())
177 }
178
179 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
180 self.map.values().flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
181 }
182}
183
184/// Inherent impls defined in some crate.
185///
186/// Inherent impls can only be defined in the crate that also defines the self type of the impl
187/// (note that some primitives are considered to be defined by both libcore and liballoc).
188///
189/// This makes inherent impl lookup easier than trait impl lookup since we only have to consider a
190/// single crate.
191#[derive(Debug, Eq, PartialEq)]
192pub struct InherentImpls {
193 map: FxHashMap<TyFingerprint, Vec<ImplId>>,
194}
195
196impl InherentImpls {
197 pub(crate) fn inherent_impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
198 let mut map: FxHashMap<_, Vec<_>> = FxHashMap::default();
199
200 let crate_def_map = db.crate_def_map(krate);
201 for (_module_id, module_data) in crate_def_map.modules.iter() {
202 for impl_id in module_data.scope.impls() {
203 let data = db.impl_data(impl_id);
204 if data.target_trait.is_some() {
205 continue;
206 }
207
208 let self_ty = db.impl_self_ty(impl_id);
209 if let Some(fp) = TyFingerprint::for_impl(&self_ty.value) {
210 map.entry(fp).or_default().push(impl_id);
211 }
212 }
213 }
214
215 Arc::new(Self { map })
216 }
217
218 pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
219 match TyFingerprint::for_impl(self_ty) {
220 Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
221 None => &[],
222 }
223 }
224
225 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
226 self.map.values().flat_map(|v| v.iter().copied())
227 }
228}
229
230impl Ty {
231 pub fn def_crates(
232 &self,
233 db: &dyn HirDatabase,
234 cur_crate: CrateId,
235 ) -> Option<ArrayVec<[CrateId; 2]>> {
236 // Types like slice can have inherent impls in several crates, (core and alloc).
237 // The corresponding impls are marked with lang items, so we can use them to find the required crates.
238 macro_rules! lang_item_crate {
239 ($($name:expr),+ $(,)?) => {{
240 let mut v = ArrayVec::<[LangItemTarget; 2]>::new();
241 $(
242 v.extend(db.lang_item(cur_crate, $name.into()));
243 )+
244 v
245 }};
246 }
247
248 let lang_item_targets = match self {
249 Ty::Apply(a_ty) => match a_ty.ctor {
250 TypeCtor::Adt(def_id) => {
251 return Some(std::iter::once(def_id.module(db.upcast()).krate).collect())
252 }
253 TypeCtor::Bool => lang_item_crate!("bool"),
254 TypeCtor::Char => lang_item_crate!("char"),
255 TypeCtor::Float(f) => match f.bitness {
256 // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
257 FloatBitness::X32 => lang_item_crate!("f32", "f32_runtime"),
258 FloatBitness::X64 => lang_item_crate!("f64", "f64_runtime"),
259 },
260 TypeCtor::Int(i) => lang_item_crate!(i.ty_to_string()),
261 TypeCtor::Str => lang_item_crate!("str_alloc", "str"),
262 TypeCtor::Slice => lang_item_crate!("slice_alloc", "slice"),
263 TypeCtor::RawPtr(Mutability::Shared) => lang_item_crate!("const_ptr"),
264 TypeCtor::RawPtr(Mutability::Mut) => lang_item_crate!("mut_ptr"),
265 _ => return None,
266 },
267 _ => return None,
268 };
269 let res = lang_item_targets
270 .into_iter()
271 .filter_map(|it| match it {
272 LangItemTarget::ImplDefId(it) => Some(it),
273 _ => None,
274 })
275 .map(|it| it.lookup(db.upcast()).container.module(db.upcast()).krate)
276 .collect();
277 Some(res)
278 }
279}
280/// Look up the method with the given name, returning the actual autoderefed
281/// receiver type (but without autoref applied yet).
282pub(crate) fn lookup_method(
283 ty: &Canonical<Ty>,
284 db: &dyn HirDatabase,
285 env: Arc<TraitEnvironment>,
286 krate: CrateId,
287 traits_in_scope: &FxHashSet<TraitId>,
288 name: &Name,
289) -> Option<(Ty, FunctionId)> {
290 iterate_method_candidates(
291 ty,
292 db,
293 env,
294 krate,
295 &traits_in_scope,
296 Some(name),
297 LookupMode::MethodCall,
298 |ty, f| match f {
299 AssocItemId::FunctionId(f) => Some((ty.clone(), f)),
300 _ => None,
301 },
302 )
303}
304
305/// Whether we're looking up a dotted method call (like `v.len()`) or a path
306/// (like `Vec::new`).
307#[derive(Copy, Clone, Debug, PartialEq, Eq)]
308pub enum LookupMode {
309 /// Looking up a method call like `v.len()`: We only consider candidates
310 /// that have a `self` parameter, and do autoderef.
311 MethodCall,
312 /// Looking up a path like `Vec::new` or `Vec::default`: We consider all
313 /// candidates including associated constants, but don't do autoderef.
314 Path,
315}
316
317// This would be nicer if it just returned an iterator, but that runs into
318// lifetime problems, because we need to borrow temp `CrateImplDefs`.
319// FIXME add a context type here?
320pub fn iterate_method_candidates<T>(
321 ty: &Canonical<Ty>,
322 db: &dyn HirDatabase,
323 env: Arc<TraitEnvironment>,
324 krate: CrateId,
325 traits_in_scope: &FxHashSet<TraitId>,
326 name: Option<&Name>,
327 mode: LookupMode,
328 mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>,
329) -> Option<T> {
330 let mut slot = None;
331 iterate_method_candidates_impl(
332 ty,
333 db,
334 env,
335 krate,
336 traits_in_scope,
337 name,
338 mode,
339 &mut |ty, item| {
340 assert!(slot.is_none());
341 slot = callback(ty, item);
342 slot.is_some()
343 },
344 );
345 slot
346}
347
348fn iterate_method_candidates_impl(
349 ty: &Canonical<Ty>,
350 db: &dyn HirDatabase,
351 env: Arc<TraitEnvironment>,
352 krate: CrateId,
353 traits_in_scope: &FxHashSet<TraitId>,
354 name: Option<&Name>,
355 mode: LookupMode,
356 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
357) -> bool {
358 match mode {
359 LookupMode::MethodCall => {
360 // For method calls, rust first does any number of autoderef, and then one
361 // autoref (i.e. when the method takes &self or &mut self). We just ignore
362 // the autoref currently -- when we find a method matching the given name,
363 // we assume it fits.
364
365 // Also note that when we've got a receiver like &S, even if the method we
366 // find in the end takes &self, we still do the autoderef step (just as
367 // rustc does an autoderef and then autoref again).
368 let ty = InEnvironment { value: ty.clone(), environment: env.clone() };
369
370 // We have to be careful about the order we're looking at candidates
371 // in here. Consider the case where we're resolving `x.clone()`
372 // where `x: &Vec<_>`. This resolves to the clone method with self
373 // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where
374 // the receiver type exactly matches before cases where we have to
375 // do autoref. But in the autoderef steps, the `&_` self type comes
376 // up *before* the `Vec<_>` self type.
377 //
378 // On the other hand, we don't want to just pick any by-value method
379 // before any by-autoref method; it's just that we need to consider
380 // the methods by autoderef order of *receiver types*, not *self
381 // types*.
382
383 let deref_chain = autoderef_method_receiver(db, krate, ty);
384 for i in 0..deref_chain.len() {
385 if iterate_method_candidates_with_autoref(
386 &deref_chain[i..],
387 db,
388 env.clone(),
389 krate,
390 traits_in_scope,
391 name,
392 callback,
393 ) {
394 return true;
395 }
396 }
397 false
398 }
399 LookupMode::Path => {
400 // No autoderef for path lookups
401 iterate_method_candidates_for_self_ty(
402 &ty,
403 db,
404 env,
405 krate,
406 traits_in_scope,
407 name,
408 callback,
409 )
410 }
411 }
412}
413
414fn iterate_method_candidates_with_autoref(
415 deref_chain: &[Canonical<Ty>],
416 db: &dyn HirDatabase,
417 env: Arc<TraitEnvironment>,
418 krate: CrateId,
419 traits_in_scope: &FxHashSet<TraitId>,
420 name: Option<&Name>,
421 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
422) -> bool {
423 if iterate_method_candidates_by_receiver(
424 &deref_chain[0],
425 &deref_chain[1..],
426 db,
427 env.clone(),
428 krate,
429 &traits_in_scope,
430 name,
431 &mut callback,
432 ) {
433 return true;
434 }
435 let refed = Canonical {
436 kinds: deref_chain[0].kinds.clone(),
437 value: Ty::apply_one(TypeCtor::Ref(Mutability::Shared), deref_chain[0].value.clone()),
438 };
439 if iterate_method_candidates_by_receiver(
440 &refed,
441 deref_chain,
442 db,
443 env.clone(),
444 krate,
445 &traits_in_scope,
446 name,
447 &mut callback,
448 ) {
449 return true;
450 }
451 let ref_muted = Canonical {
452 kinds: deref_chain[0].kinds.clone(),
453 value: Ty::apply_one(TypeCtor::Ref(Mutability::Mut), deref_chain[0].value.clone()),
454 };
455 if iterate_method_candidates_by_receiver(
456 &ref_muted,
457 deref_chain,
458 db,
459 env,
460 krate,
461 &traits_in_scope,
462 name,
463 &mut callback,
464 ) {
465 return true;
466 }
467 false
468}
469
470fn iterate_method_candidates_by_receiver(
471 receiver_ty: &Canonical<Ty>,
472 rest_of_deref_chain: &[Canonical<Ty>],
473 db: &dyn HirDatabase,
474 env: Arc<TraitEnvironment>,
475 krate: CrateId,
476 traits_in_scope: &FxHashSet<TraitId>,
477 name: Option<&Name>,
478 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
479) -> bool {
480 // We're looking for methods with *receiver* type receiver_ty. These could
481 // be found in any of the derefs of receiver_ty, so we have to go through
482 // that.
483 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
484 if iterate_inherent_methods(self_ty, db, name, Some(receiver_ty), krate, &mut callback) {
485 return true;
486 }
487 }
488 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
489 if iterate_trait_method_candidates(
490 self_ty,
491 db,
492 env.clone(),
493 krate,
494 &traits_in_scope,
495 name,
496 Some(receiver_ty),
497 &mut callback,
498 ) {
499 return true;
500 }
501 }
502 false
503}
504
505fn iterate_method_candidates_for_self_ty(
506 self_ty: &Canonical<Ty>,
507 db: &dyn HirDatabase,
508 env: Arc<TraitEnvironment>,
509 krate: CrateId,
510 traits_in_scope: &FxHashSet<TraitId>,
511 name: Option<&Name>,
512 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
513) -> bool {
514 if iterate_inherent_methods(self_ty, db, name, None, krate, &mut callback) {
515 return true;
516 }
517 iterate_trait_method_candidates(self_ty, db, env, krate, traits_in_scope, name, None, callback)
518}
519
520fn iterate_trait_method_candidates(
521 self_ty: &Canonical<Ty>,
522 db: &dyn HirDatabase,
523 env: Arc<TraitEnvironment>,
524 krate: CrateId,
525 traits_in_scope: &FxHashSet<TraitId>,
526 name: Option<&Name>,
527 receiver_ty: Option<&Canonical<Ty>>,
528 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
529) -> bool {
530 // if ty is `dyn Trait`, the trait doesn't need to be in scope
531 let inherent_trait =
532 self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
533 let env_traits = if let Ty::Placeholder(_) = self_ty.value {
534 // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
535 env.trait_predicates_for_self_ty(&self_ty.value)
536 .map(|tr| tr.trait_)
537 .flat_map(|t| all_super_traits(db.upcast(), t))
538 .collect()
539 } else {
540 Vec::new()
541 };
542 let traits =
543 inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied());
544 'traits: for t in traits {
545 let data = db.trait_data(t);
546
547 // we'll be lazy about checking whether the type implements the
548 // trait, but if we find out it doesn't, we'll skip the rest of the
549 // iteration
550 let mut known_implemented = false;
551 for (_name, item) in data.items.iter() {
552 if !is_valid_candidate(db, name, receiver_ty, *item, self_ty) {
553 continue;
554 }
555 if !known_implemented {
556 let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone());
557 if db.trait_solve(krate, goal).is_none() {
558 continue 'traits;
559 }
560 }
561 known_implemented = true;
562 if callback(&self_ty.value, *item) {
563 return true;
564 }
565 }
566 }
567 false
568}
569
570fn iterate_inherent_methods(
571 self_ty: &Canonical<Ty>,
572 db: &dyn HirDatabase,
573 name: Option<&Name>,
574 receiver_ty: Option<&Canonical<Ty>>,
575 krate: CrateId,
576 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
577) -> bool {
578 let def_crates = match self_ty.value.def_crates(db, krate) {
579 Some(k) => k,
580 None => return false,
581 };
582 for krate in def_crates {
583 let impls = db.inherent_impls_in_crate(krate);
584
585 for &impl_def in impls.for_self_ty(&self_ty.value) {
586 for &item in db.impl_data(impl_def).items.iter() {
587 if !is_valid_candidate(db, name, receiver_ty, item, self_ty) {
588 continue;
589 }
590 // we have to check whether the self type unifies with the type
591 // that the impl is for. If we have a receiver type, this
592 // already happens in `is_valid_candidate` above; if not, we
593 // check it here
594 if receiver_ty.is_none() && inherent_impl_substs(db, impl_def, self_ty).is_none() {
595 test_utils::mark::hit!(impl_self_type_match_without_receiver);
596 continue;
597 }
598 if callback(&self_ty.value, item) {
599 return true;
600 }
601 }
602 }
603 }
604 false
605}
606
607/// Returns the self type for the index trait call.
608pub fn resolve_indexing_op(
609 db: &dyn HirDatabase,
610 ty: &Canonical<Ty>,
611 env: Arc<TraitEnvironment>,
612 krate: CrateId,
613 index_trait: TraitId,
614) -> Option<Canonical<Ty>> {
615 let ty = InEnvironment { value: ty.clone(), environment: env.clone() };
616 let deref_chain = autoderef_method_receiver(db, krate, ty);
617 for ty in deref_chain {
618 let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
619 if db.trait_solve(krate, goal).is_some() {
620 return Some(ty);
621 }
622 }
623 None
624}
625
626fn is_valid_candidate(
627 db: &dyn HirDatabase,
628 name: Option<&Name>,
629 receiver_ty: Option<&Canonical<Ty>>,
630 item: AssocItemId,
631 self_ty: &Canonical<Ty>,
632) -> bool {
633 match item {
634 AssocItemId::FunctionId(m) => {
635 let data = db.function_data(m);
636 if let Some(name) = name {
637 if &data.name != name {
638 return false;
639 }
640 }
641 if let Some(receiver_ty) = receiver_ty {
642 if !data.has_self_param {
643 return false;
644 }
645 let transformed_receiver_ty = match transform_receiver_ty(db, m, self_ty) {
646 Some(ty) => ty,
647 None => return false,
648 };
649 if transformed_receiver_ty != receiver_ty.value {
650 return false;
651 }
652 }
653 true
654 }
655 AssocItemId::ConstId(c) => {
656 let data = db.const_data(c);
657 name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none()
658 }
659 _ => false,
660 }
661}
662
663pub(crate) fn inherent_impl_substs(
664 db: &dyn HirDatabase,
665 impl_id: ImplId,
666 self_ty: &Canonical<Ty>,
667) -> Option<Substs> {
668 // we create a var for each type parameter of the impl; we need to keep in
669 // mind here that `self_ty` might have vars of its own
670 let vars = Substs::build_for_def(db, impl_id)
671 .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty.kinds.len())
672 .build();
673 let self_ty_with_vars = db.impl_self_ty(impl_id).subst(&vars);
674 let mut kinds = self_ty.kinds.to_vec();
675 kinds.extend(iter::repeat(TyKind::General).take(vars.len()));
676 let tys = Canonical { kinds: kinds.into(), value: (self_ty_with_vars, self_ty.value.clone()) };
677 let substs = super::infer::unify(&tys);
678 // We only want the substs for the vars we added, not the ones from self_ty.
679 // Also, if any of the vars we added are still in there, we replace them by
680 // Unknown. I think this can only really happen if self_ty contained
681 // Unknown, and in that case we want the result to contain Unknown in those
682 // places again.
683 substs.map(|s| fallback_bound_vars(s.suffix(vars.len()), self_ty.kinds.len()))
684}
685
686/// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
687/// num_vars_to_keep) by `Ty::Unknown`.
688fn fallback_bound_vars(s: Substs, num_vars_to_keep: usize) -> Substs {
689 s.fold_binders(
690 &mut |ty, binders| {
691 if let Ty::Bound(bound) = &ty {
692 if bound.index >= num_vars_to_keep && bound.debruijn >= binders {
693 Ty::Unknown
694 } else {
695 ty
696 }
697 } else {
698 ty
699 }
700 },
701 DebruijnIndex::INNERMOST,
702 )
703}
704
705fn transform_receiver_ty(
706 db: &dyn HirDatabase,
707 function_id: FunctionId,
708 self_ty: &Canonical<Ty>,
709) -> Option<Ty> {
710 let substs = match function_id.lookup(db.upcast()).container {
711 AssocContainerId::TraitId(_) => Substs::build_for_def(db, function_id)
712 .push(self_ty.value.clone())
713 .fill_with_unknown()
714 .build(),
715 AssocContainerId::ImplId(impl_id) => inherent_impl_substs(db, impl_id, &self_ty)?,
716 AssocContainerId::ContainerId(_) => unreachable!(),
717 };
718 let sig = db.callable_item_signature(function_id.into());
719 Some(sig.value.params()[0].clone().subst_bound_vars(&substs))
720}
721
722pub fn implements_trait(
723 ty: &Canonical<Ty>,
724 db: &dyn HirDatabase,
725 env: Arc<TraitEnvironment>,
726 krate: CrateId,
727 trait_: TraitId,
728) -> bool {
729 let goal = generic_implements_goal(db, env, trait_, ty.clone());
730 let solution = db.trait_solve(krate, goal);
731
732 solution.is_some()
733}
734
735/// This creates Substs for a trait with the given Self type and type variables
736/// for all other parameters, to query Chalk with it.
737fn generic_implements_goal(
738 db: &dyn HirDatabase,
739 env: Arc<TraitEnvironment>,
740 trait_: TraitId,
741 self_ty: Canonical<Ty>,
742) -> Canonical<InEnvironment<super::Obligation>> {
743 let mut kinds = self_ty.kinds.to_vec();
744 let substs = super::Substs::build_for_def(db, trait_)
745 .push(self_ty.value)
746 .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
747 .build();
748 kinds.extend(iter::repeat(TyKind::General).take(substs.len() - 1));
749 let trait_ref = TraitRef { trait_, substs };
750 let obligation = super::Obligation::Trait(trait_ref);
751 Canonical { kinds: kinds.into(), value: InEnvironment::new(env, obligation) }
752}
753
754fn autoderef_method_receiver(
755 db: &dyn HirDatabase,
756 krate: CrateId,
757 ty: InEnvironment<Canonical<Ty>>,
758) -> Vec<Canonical<Ty>> {
759 let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
760 // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
761 if let Some(Ty::Apply(ApplicationTy { ctor: TypeCtor::Array, parameters })) =
762 deref_chain.last().map(|ty| &ty.value)
763 {
764 let kinds = deref_chain.last().unwrap().kinds.clone();
765 let unsized_ty = Ty::apply(TypeCtor::Slice, parameters.clone());
766 deref_chain.push(Canonical { value: unsized_ty, kinds })
767 }
768 deref_chain
769}