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.
5 use std::{iter, ops::ControlFlow, sync::Arc};
7 use arrayvec::ArrayVec;
8 use base_db::{CrateId, Edition};
9 use chalk_ir::{cast::Cast, Mutability, UniverseIndex};
11 lang_item::LangItemTarget, nameres::DefMap, AssocContainerId, AssocItemId, BlockId, FunctionId,
12 GenericDefId, HasModule, ImplId, Lookup, ModuleId, TraitId,
14 use hir_expand::name::Name;
15 use rustc_hash::{FxHashMap, FxHashSet};
19 consteval::{self, ConstExt},
22 primitive::{self, FloatTy, IntTy, UintTy},
24 utils::all_super_traits,
25 AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, ForeignDefId, InEnvironment, Interner,
26 Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
29 /// This is used as a key for indexing impls.
30 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
31 pub enum TyFingerprint {
32 // These are lang item impls:
39 // These can have user-defined impls:
42 ForeignType(ForeignDefId),
43 // These only exist for trait impls
50 /// Creates a TyFingerprint for looking up an inherent impl. Only certain
51 /// types can have inherent impls: if we have some `struct S`, we can have
52 /// an `impl S`, but not `impl &S`. Hence, this will return `None` for
53 /// reference types and such.
54 pub fn for_inherent_impl(ty: &Ty) -> Option<TyFingerprint> {
55 let fp = match ty.kind(&Interner) {
56 TyKind::Str => TyFingerprint::Str,
57 TyKind::Never => TyFingerprint::Never,
58 TyKind::Slice(..) => TyFingerprint::Slice,
59 TyKind::Array(..) => TyFingerprint::Array,
60 TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
61 TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
62 TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
63 TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
64 TyKind::Dyn(_) => ty.dyn_trait().map(TyFingerprint::Dyn)?,
70 /// Creates a TyFingerprint for looking up a trait impl.
71 pub fn for_trait_impl(ty: &Ty) -> Option<TyFingerprint> {
72 let fp = match ty.kind(&Interner) {
73 TyKind::Str => TyFingerprint::Str,
74 TyKind::Never => TyFingerprint::Never,
75 TyKind::Slice(..) => TyFingerprint::Slice,
76 TyKind::Array(..) => TyFingerprint::Array,
77 TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
78 TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
79 TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
80 TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
81 TyKind::Dyn(_) => ty.dyn_trait().map(TyFingerprint::Dyn)?,
82 TyKind::Ref(_, _, ty) => return TyFingerprint::for_trait_impl(ty),
83 TyKind::Tuple(_, subst) => {
84 let first_ty = subst.interned().get(0).map(|arg| arg.assert_ty_ref(&Interner));
86 Some(ty) => return TyFingerprint::for_trait_impl(ty),
87 None => TyFingerprint::Unit,
90 TyKind::AssociatedType(_, _)
91 | TyKind::OpaqueType(_, _)
93 | TyKind::Closure(_, _)
94 | TyKind::Generator(..)
95 | TyKind::GeneratorWitness(..) => TyFingerprint::Unnameable,
96 TyKind::Function(fn_ptr) => {
97 TyFingerprint::Function(fn_ptr.substitution.0.len(&Interner) as u32)
100 | TyKind::Placeholder(_)
101 | TyKind::BoundVar(_)
102 | TyKind::InferenceVar(_, _)
103 | TyKind::Error => return None,
109 pub(crate) const ALL_INT_FPS: [TyFingerprint; 12] = [
110 TyFingerprint::Scalar(Scalar::Int(IntTy::I8)),
111 TyFingerprint::Scalar(Scalar::Int(IntTy::I16)),
112 TyFingerprint::Scalar(Scalar::Int(IntTy::I32)),
113 TyFingerprint::Scalar(Scalar::Int(IntTy::I64)),
114 TyFingerprint::Scalar(Scalar::Int(IntTy::I128)),
115 TyFingerprint::Scalar(Scalar::Int(IntTy::Isize)),
116 TyFingerprint::Scalar(Scalar::Uint(UintTy::U8)),
117 TyFingerprint::Scalar(Scalar::Uint(UintTy::U16)),
118 TyFingerprint::Scalar(Scalar::Uint(UintTy::U32)),
119 TyFingerprint::Scalar(Scalar::Uint(UintTy::U64)),
120 TyFingerprint::Scalar(Scalar::Uint(UintTy::U128)),
121 TyFingerprint::Scalar(Scalar::Uint(UintTy::Usize)),
124 pub(crate) const ALL_FLOAT_FPS: [TyFingerprint; 2] = [
125 TyFingerprint::Scalar(Scalar::Float(FloatTy::F32)),
126 TyFingerprint::Scalar(Scalar::Float(FloatTy::F64)),
129 /// Trait impls defined or available in some crate.
130 #[derive(Debug, Eq, PartialEq)]
131 pub struct TraitImpls {
132 // If the `Option<TyFingerprint>` is `None`, the impl may apply to any self type.
133 map: FxHashMap<TraitId, FxHashMap<Option<TyFingerprint>, Vec<ImplId>>>,
137 pub(crate) fn trait_impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
138 let _p = profile::span("trait_impls_in_crate_query");
139 let mut impls = Self { map: FxHashMap::default() };
141 let crate_def_map = db.crate_def_map(krate);
142 impls.collect_def_map(db, &crate_def_map);
147 pub(crate) fn trait_impls_in_block_query(
148 db: &dyn HirDatabase,
150 ) -> Option<Arc<Self>> {
151 let _p = profile::span("trait_impls_in_block_query");
152 let mut impls = Self { map: FxHashMap::default() };
154 let block_def_map = db.block_def_map(block)?;
155 impls.collect_def_map(db, &block_def_map);
157 Some(Arc::new(impls))
160 fn collect_def_map(&mut self, db: &dyn HirDatabase, def_map: &DefMap) {
161 for (_module_id, module_data) in def_map.modules() {
162 for impl_id in module_data.scope.impls() {
163 let target_trait = match db.impl_trait(impl_id) {
164 Some(tr) => tr.skip_binders().hir_trait_id(),
167 let self_ty = db.impl_self_ty(impl_id);
168 let self_ty_fp = TyFingerprint::for_trait_impl(self_ty.skip_binders());
177 // To better support custom derives, collect impls in all unnamed const items.
178 // const _: () = { ... };
179 for konst in module_data.scope.unnamed_consts() {
180 let body = db.body(konst.into());
181 for (_, block_def_map) in body.blocks(db.upcast()) {
182 self.collect_def_map(db, &block_def_map);
188 pub(crate) fn trait_impls_in_deps_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
189 let _p = profile::span("trait_impls_in_deps_query");
190 let crate_graph = db.crate_graph();
191 let mut res = Self { map: FxHashMap::default() };
193 for krate in crate_graph.transitive_deps(krate) {
194 res.merge(&db.trait_impls_in_crate(krate));
200 fn merge(&mut self, other: &Self) {
201 for (trait_, other_map) in &other.map {
202 let map = self.map.entry(*trait_).or_default();
203 for (fp, impls) in other_map {
204 let vec = map.entry(*fp).or_default();
210 /// Queries all trait impls for the given type.
211 pub fn for_self_ty_without_blanket_impls(
214 ) -> impl Iterator<Item = ImplId> + '_ {
217 .flat_map(move |impls| impls.get(&Some(fp)).into_iter())
218 .flat_map(|it| it.iter().copied())
221 /// Queries all impls of the given trait.
222 pub fn for_trait(&self, trait_: TraitId) -> impl Iterator<Item = ImplId> + '_ {
226 .flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
229 /// Queries all impls of `trait_` that may apply to `self_ty`.
230 pub fn for_trait_and_self_ty(
233 self_ty: TyFingerprint,
234 ) -> impl Iterator<Item = ImplId> + '_ {
238 .flat_map(move |map| map.get(&None).into_iter().chain(map.get(&Some(self_ty))))
239 .flat_map(|v| v.iter().copied())
242 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
243 self.map.values().flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
247 /// Inherent impls defined in some crate.
249 /// Inherent impls can only be defined in the crate that also defines the self type of the impl
250 /// (note that some primitives are considered to be defined by both libcore and liballoc).
252 /// This makes inherent impl lookup easier than trait impl lookup since we only have to consider a
254 #[derive(Debug, Eq, PartialEq)]
255 pub struct InherentImpls {
256 map: FxHashMap<TyFingerprint, Vec<ImplId>>,
260 pub(crate) fn inherent_impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
261 let mut impls = Self { map: FxHashMap::default() };
263 let crate_def_map = db.crate_def_map(krate);
264 collect_def_map(db, &crate_def_map, &mut impls);
266 return Arc::new(impls);
268 fn collect_def_map(db: &dyn HirDatabase, def_map: &DefMap, impls: &mut InherentImpls) {
269 for (_module_id, module_data) in def_map.modules() {
270 for impl_id in module_data.scope.impls() {
271 let data = db.impl_data(impl_id);
272 if data.target_trait.is_some() {
276 let self_ty = db.impl_self_ty(impl_id);
277 let fp = TyFingerprint::for_inherent_impl(self_ty.skip_binders());
278 if let Some(fp) = fp {
279 impls.map.entry(fp).or_default().push(impl_id);
281 // `fp` should only be `None` in error cases (either erroneous code or incomplete name resolution)
284 // To better support custom derives, collect impls in all unnamed const items.
285 // const _: () = { ... };
286 for konst in module_data.scope.unnamed_consts() {
287 let body = db.body(konst.into());
288 for (_, block_def_map) in body.blocks(db.upcast()) {
289 collect_def_map(db, &block_def_map, impls);
296 pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
297 match TyFingerprint::for_inherent_impl(self_ty) {
298 Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
303 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
304 self.map.values().flat_map(|v| v.iter().copied())
309 db: &dyn HirDatabase,
312 ) -> Option<ArrayVec<CrateId, 2>> {
313 // Types like slice can have inherent impls in several crates, (core and alloc).
314 // The corresponding impls are marked with lang items, so we can use them to find the required crates.
315 macro_rules! lang_item_crate {
316 ($($name:expr),+ $(,)?) => {{
317 let mut v = ArrayVec::<LangItemTarget, 2>::new();
319 v.extend(db.lang_item(cur_crate, $name.into()));
325 let mod_to_crate_ids = |module: ModuleId| Some(std::iter::once(module.krate()).collect());
327 let lang_item_targets = match ty.kind(&Interner) {
328 TyKind::Adt(AdtId(def_id), _) => {
329 return mod_to_crate_ids(def_id.module(db.upcast()));
331 TyKind::Foreign(id) => {
332 return mod_to_crate_ids(
333 from_foreign_def_id(*id).lookup(db.upcast()).module(db.upcast()),
336 TyKind::Scalar(Scalar::Bool) => lang_item_crate!("bool"),
337 TyKind::Scalar(Scalar::Char) => lang_item_crate!("char"),
338 TyKind::Scalar(Scalar::Float(f)) => match f {
339 // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
340 FloatTy::F32 => lang_item_crate!("f32", "f32_runtime"),
341 FloatTy::F64 => lang_item_crate!("f64", "f64_runtime"),
343 &TyKind::Scalar(Scalar::Int(t)) => {
344 lang_item_crate!(primitive::int_ty_to_string(t))
346 &TyKind::Scalar(Scalar::Uint(t)) => {
347 lang_item_crate!(primitive::uint_ty_to_string(t))
349 TyKind::Str => lang_item_crate!("str_alloc", "str"),
350 TyKind::Slice(_) => lang_item_crate!("slice_alloc", "slice"),
351 TyKind::Array(..) => lang_item_crate!("array"),
352 TyKind::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
353 TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
355 return ty.dyn_trait().and_then(|trait_| {
356 mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
361 let res = lang_item_targets
363 .filter_map(|it| match it {
364 LangItemTarget::ImplDefId(it) => Some(it),
367 .map(|it| it.lookup(db.upcast()).container.krate())
372 /// Look up the method with the given name, returning the actual autoderefed
373 /// receiver type (but without autoref applied yet).
374 pub(crate) fn lookup_method(
376 db: &dyn HirDatabase,
377 env: Arc<TraitEnvironment>,
379 traits_in_scope: &FxHashSet<TraitId>,
380 visible_from_module: Option<ModuleId>,
382 ) -> Option<(Canonical<Ty>, FunctionId)> {
383 iterate_method_candidates(
391 LookupMode::MethodCall,
393 AssocItemId::FunctionId(f) => Some((ty.clone(), f)),
399 /// Whether we're looking up a dotted method call (like `v.len()`) or a path
400 /// (like `Vec::new`).
401 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
402 pub enum LookupMode {
403 /// Looking up a method call like `v.len()`: We only consider candidates
404 /// that have a `self` parameter, and do autoderef.
406 /// Looking up a path like `Vec::new` or `Vec::default`: We consider all
407 /// candidates including associated constants, but don't do autoderef.
411 // This would be nicer if it just returned an iterator, but that runs into
412 // lifetime problems, because we need to borrow temp `CrateImplDefs`.
413 // FIXME add a context type here?
414 pub fn iterate_method_candidates<T>(
416 db: &dyn HirDatabase,
417 env: Arc<TraitEnvironment>,
419 traits_in_scope: &FxHashSet<TraitId>,
420 visible_from_module: Option<ModuleId>,
423 mut callback: impl FnMut(&Canonical<Ty>, AssocItemId) -> Option<T>,
426 iterate_method_candidates_dyn(
436 assert!(slot.is_none());
437 if let Some(it) = callback(ty, item) {
439 return ControlFlow::Break(());
441 ControlFlow::Continue(())
447 pub fn iterate_method_candidates_dyn(
449 db: &dyn HirDatabase,
450 env: Arc<TraitEnvironment>,
452 traits_in_scope: &FxHashSet<TraitId>,
453 visible_from_module: Option<ModuleId>,
456 callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
457 ) -> ControlFlow<()> {
459 LookupMode::MethodCall => {
460 // For method calls, rust first does any number of autoderef, and then one
461 // autoref (i.e. when the method takes &self or &mut self). We just ignore
462 // the autoref currently -- when we find a method matching the given name,
463 // we assume it fits.
465 // Also note that when we've got a receiver like &S, even if the method we
466 // find in the end takes &self, we still do the autoderef step (just as
467 // rustc does an autoderef and then autoref again).
468 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
470 // We have to be careful about the order we're looking at candidates
471 // in here. Consider the case where we're resolving `x.clone()`
472 // where `x: &Vec<_>`. This resolves to the clone method with self
473 // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where
474 // the receiver type exactly matches before cases where we have to
475 // do autoref. But in the autoderef steps, the `&_` self type comes
476 // up *before* the `Vec<_>` self type.
478 // On the other hand, we don't want to just pick any by-value method
479 // before any by-autoref method; it's just that we need to consider
480 // the methods by autoderef order of *receiver types*, not *self
483 let deref_chain = autoderef_method_receiver(db, krate, ty);
484 for i in 0..deref_chain.len() {
485 iterate_method_candidates_with_autoref(
496 ControlFlow::Continue(())
498 LookupMode::Path => {
499 // No autoderef for path lookups
500 iterate_method_candidates_for_self_ty(
514 fn iterate_method_candidates_with_autoref(
515 deref_chain: &[Canonical<Ty>],
516 db: &dyn HirDatabase,
517 env: Arc<TraitEnvironment>,
519 traits_in_scope: &FxHashSet<TraitId>,
520 visible_from_module: Option<ModuleId>,
522 mut callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
523 ) -> ControlFlow<()> {
524 iterate_method_candidates_by_receiver(
536 let refed = Canonical {
537 binders: deref_chain[0].binders.clone(),
538 value: TyKind::Ref(Mutability::Not, static_lifetime(), deref_chain[0].value.clone())
542 iterate_method_candidates_by_receiver(
554 let ref_muted = Canonical {
555 binders: deref_chain[0].binders.clone(),
556 value: TyKind::Ref(Mutability::Mut, static_lifetime(), deref_chain[0].value.clone())
560 iterate_method_candidates_by_receiver(
573 fn iterate_method_candidates_by_receiver(
574 receiver_ty: &Canonical<Ty>,
575 rest_of_deref_chain: &[Canonical<Ty>],
576 db: &dyn HirDatabase,
577 env: Arc<TraitEnvironment>,
579 traits_in_scope: &FxHashSet<TraitId>,
580 visible_from_module: Option<ModuleId>,
582 mut callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
583 ) -> ControlFlow<()> {
584 // We're looking for methods with *receiver* type receiver_ty. These could
585 // be found in any of the derefs of receiver_ty, so we have to go through
587 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
588 iterate_inherent_methods(
600 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
601 iterate_trait_method_candidates(
613 ControlFlow::Continue(())
616 fn iterate_method_candidates_for_self_ty(
617 self_ty: &Canonical<Ty>,
618 db: &dyn HirDatabase,
619 env: Arc<TraitEnvironment>,
621 traits_in_scope: &FxHashSet<TraitId>,
622 visible_from_module: Option<ModuleId>,
624 mut callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
625 ) -> ControlFlow<()> {
626 iterate_inherent_methods(
636 iterate_trait_method_candidates(self_ty, db, env, krate, traits_in_scope, name, None, callback)
639 fn iterate_trait_method_candidates(
640 self_ty: &Canonical<Ty>,
641 db: &dyn HirDatabase,
642 env: Arc<TraitEnvironment>,
644 traits_in_scope: &FxHashSet<TraitId>,
646 receiver_ty: Option<&Canonical<Ty>>,
647 callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
648 ) -> ControlFlow<()> {
649 let receiver_is_array = matches!(self_ty.value.kind(&Interner), chalk_ir::TyKind::Array(..));
650 // if ty is `dyn Trait`, the trait doesn't need to be in scope
652 self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
653 let env_traits = match self_ty.value.kind(&Interner) {
654 TyKind::Placeholder(_) => {
655 // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
656 env.traits_in_scope_from_clauses(&self_ty.value)
657 .flat_map(|t| all_super_traits(db.upcast(), t))
663 inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied());
665 'traits: for t in traits {
666 let data = db.trait_data(t);
668 // Traits annotated with `#[rustc_skip_array_during_method_dispatch]` are skipped during
669 // method resolution, if the receiver is an array, and we're compiling for editions before
671 // This is to make `[a].into_iter()` not break code with the new `IntoIterator` impl for
673 if data.skip_array_during_method_dispatch && receiver_is_array {
674 // FIXME: this should really be using the edition of the method name's span, in case it
675 // comes from a macro
676 if db.crate_graph()[krate].edition < Edition::Edition2021 {
681 // we'll be lazy about checking whether the type implements the
682 // trait, but if we find out it doesn't, we'll skip the rest of the
684 let mut known_implemented = false;
685 for (_name, item) in data.items.iter() {
686 // Don't pass a `visible_from_module` down to `is_valid_candidate`,
687 // since only inherent methods should be included into visibility checking.
688 if !is_valid_candidate(db, env.clone(), name, receiver_ty, *item, self_ty, None) {
691 if !known_implemented {
692 let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone());
693 if db.trait_solve(krate, goal.cast(&Interner)).is_none() {
697 known_implemented = true;
698 // FIXME: we shouldn't be ignoring the binders here
699 callback(self_ty, *item)?
702 ControlFlow::Continue(())
705 fn filter_inherent_impls_for_self_ty<'i>(
706 impls: &'i InherentImpls,
708 ) -> impl Iterator<Item = &'i ImplId> {
709 // inherent methods on arrays are fingerprinted as [T; {unknown}], so we must also consider them when
710 // resolving a method call on an array with a known len
712 if let TyKind::Array(parameters, array_len) = self_ty.kind(&Interner) {
713 if !array_len.is_unknown() {
714 let unknown_array_len_ty =
715 TyKind::Array(parameters.clone(), consteval::usize_const(None))
718 Some(impls.for_self_ty(&unknown_array_len_ty))
729 impls.for_self_ty(self_ty).iter().chain(array_impls)
732 fn iterate_inherent_methods(
733 self_ty: &Canonical<Ty>,
734 db: &dyn HirDatabase,
735 env: Arc<TraitEnvironment>,
737 receiver_ty: Option<&Canonical<Ty>>,
739 visible_from_module: Option<ModuleId>,
740 callback: &mut dyn FnMut(&Canonical<Ty>, AssocItemId) -> ControlFlow<()>,
741 ) -> ControlFlow<()> {
742 let def_crates = match def_crates(db, &self_ty.value, krate) {
744 None => return ControlFlow::Continue(()),
747 for krate in def_crates {
748 let impls = db.inherent_impls_in_crate(krate);
750 let impls_for_self_ty = filter_inherent_impls_for_self_ty(&impls, &self_ty.value);
752 for &impl_def in impls_for_self_ty {
753 for &item in db.impl_data(impl_def).items.iter() {
754 if !is_valid_candidate(
765 // we have to check whether the self type unifies with the type
766 // that the impl is for. If we have a receiver type, this
767 // already happens in `is_valid_candidate` above; if not, we
769 if receiver_ty.is_none()
770 && inherent_impl_substs(db, env.clone(), impl_def, self_ty).is_none()
772 cov_mark::hit!(impl_self_type_match_without_receiver);
775 let receiver_ty = receiver_ty.unwrap_or(self_ty);
776 callback(receiver_ty, item)?;
780 ControlFlow::Continue(())
783 /// Returns the self type for the index trait call.
784 pub fn resolve_indexing_op(
785 db: &dyn HirDatabase,
787 env: Arc<TraitEnvironment>,
789 index_trait: TraitId,
790 ) -> Option<Canonical<Ty>> {
791 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
792 let deref_chain = autoderef_method_receiver(db, krate, ty);
793 for ty in deref_chain {
794 let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
795 if db.trait_solve(krate, goal.cast(&Interner)).is_some() {
802 fn is_transformed_receiver_ty_equal(transformed_receiver_ty: &Ty, receiver_ty: &Ty) -> bool {
803 if transformed_receiver_ty == receiver_ty {
807 // a transformed receiver may be considered equal (and a valid method call candidate) if it is an array
808 // with an unknown (i.e. generic) length, and the receiver is an array with the same item type but a known len,
809 // this allows inherent methods on arrays to be considered valid resolution candidates
810 match (transformed_receiver_ty.kind(&Interner), receiver_ty.kind(&Interner)) {
812 TyKind::Array(transformed_array_ty, transformed_array_len),
813 TyKind::Array(receiver_array_ty, receiver_array_len),
814 ) if transformed_array_ty == receiver_array_ty
815 && transformed_array_len.is_unknown()
816 && !receiver_array_len.is_unknown() =>
824 fn is_valid_candidate(
825 db: &dyn HirDatabase,
826 env: Arc<TraitEnvironment>,
828 receiver_ty: Option<&Canonical<Ty>>,
830 self_ty: &Canonical<Ty>,
831 visible_from_module: Option<ModuleId>,
834 AssocItemId::FunctionId(m) => {
835 let data = db.function_data(m);
836 if let Some(name) = name {
837 if &data.name != name {
841 if let Some(receiver_ty) = receiver_ty {
842 if !data.has_self_param() {
845 let transformed_receiver_ty = match transform_receiver_ty(db, env, m, self_ty) {
847 None => return false,
850 if !is_transformed_receiver_ty_equal(&transformed_receiver_ty, &receiver_ty.value) {
854 if let Some(from_module) = visible_from_module {
855 if !db.function_visibility(m).is_visible_from(db.upcast(), from_module) {
856 cov_mark::hit!(autoderef_candidate_not_visible);
863 AssocItemId::ConstId(c) => {
864 let data = db.const_data(c);
865 name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none()
871 pub(crate) fn inherent_impl_substs(
872 db: &dyn HirDatabase,
873 env: Arc<TraitEnvironment>,
875 self_ty: &Canonical<Ty>,
876 ) -> Option<Substitution> {
877 // we create a var for each type parameter of the impl; we need to keep in
878 // mind here that `self_ty` might have vars of its own
879 let self_ty_vars = self_ty.binders.len(&Interner);
880 let vars = TyBuilder::subst_for_def(db, impl_id)
881 .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty_vars)
883 let self_ty_with_vars = db.impl_self_ty(impl_id).substitute(&Interner, &vars);
884 let mut kinds = self_ty.binders.interned().to_vec();
886 iter::repeat(chalk_ir::WithKind::new(
887 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
890 .take(vars.len(&Interner)),
892 let tys = Canonical {
893 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
894 value: (self_ty_with_vars, self_ty.value.clone()),
896 let substs = super::infer::unify(db, env, &tys)?;
897 // We only want the substs for the vars we added, not the ones from self_ty.
898 // Also, if any of the vars we added are still in there, we replace them by
899 // Unknown. I think this can only really happen if self_ty contained
900 // Unknown, and in that case we want the result to contain Unknown in those
903 Substitution::from_iter(&Interner, substs.iter(&Interner).cloned().skip(self_ty_vars));
904 Some(fallback_bound_vars(suffix, self_ty_vars))
907 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
908 /// num_vars_to_keep) by `TyKind::Unknown`.
909 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
910 crate::fold_free_vars(s, |bound, binders| {
911 if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
912 TyKind::Error.intern(&Interner)
914 bound.shifted_in_from(binders).to_ty(&Interner)
919 fn transform_receiver_ty(
920 db: &dyn HirDatabase,
921 env: Arc<TraitEnvironment>,
922 function_id: FunctionId,
923 self_ty: &Canonical<Ty>,
925 let substs = match function_id.lookup(db.upcast()).container {
926 AssocContainerId::TraitId(_) => TyBuilder::subst_for_def(db, function_id)
927 .push(self_ty.value.clone())
930 AssocContainerId::ImplId(impl_id) => {
931 let impl_substs = inherent_impl_substs(db, env, impl_id, self_ty)?;
932 TyBuilder::subst_for_def(db, function_id)
933 .use_parent_substs(&impl_substs)
937 AssocContainerId::ModuleId(_) => unreachable!(),
939 let sig = db.callable_item_signature(function_id.into());
940 Some(sig.map(|s| s.params()[0].clone()).substitute(&Interner, &substs))
943 pub fn implements_trait(
945 db: &dyn HirDatabase,
946 env: Arc<TraitEnvironment>,
950 let goal = generic_implements_goal(db, env, trait_, ty.clone());
951 let solution = db.trait_solve(krate, goal.cast(&Interner));
956 pub fn implements_trait_unique(
958 db: &dyn HirDatabase,
959 env: Arc<TraitEnvironment>,
963 let goal = generic_implements_goal(db, env, trait_, ty.clone());
964 let solution = db.trait_solve(krate, goal.cast(&Interner));
966 matches!(solution, Some(crate::Solution::Unique(_)))
969 /// This creates Substs for a trait with the given Self type and type variables
970 /// for all other parameters, to query Chalk with it.
971 fn generic_implements_goal(
972 db: &dyn HirDatabase,
973 env: Arc<TraitEnvironment>,
975 self_ty: Canonical<Ty>,
976 ) -> Canonical<InEnvironment<super::DomainGoal>> {
977 let mut kinds = self_ty.binders.interned().to_vec();
978 let trait_ref = TyBuilder::trait_ref(db, trait_)
980 .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
983 iter::repeat(chalk_ir::WithKind::new(
984 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
987 .take(trait_ref.substitution.len(&Interner) - 1),
989 let obligation = trait_ref.cast(&Interner);
991 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
992 value: InEnvironment::new(&env.env, obligation),
996 fn autoderef_method_receiver(
997 db: &dyn HirDatabase,
999 ty: InEnvironment<Canonical<Ty>>,
1000 ) -> Vec<Canonical<Ty>> {
1001 let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
1002 // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
1003 if let Some(TyKind::Array(parameters, _)) =
1004 deref_chain.last().map(|ty| ty.value.kind(&Interner))
1006 let kinds = deref_chain.last().unwrap().binders.clone();
1007 let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
1008 deref_chain.push(Canonical { value: unsized_ty, binders: kinds })