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, 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, FunctionId,
12 GenericDefId, HasModule, ImplId, Lookup, ModuleId, TraitId,
14 use hir_expand::name::Name;
15 use rustc_hash::{FxHashMap, FxHashSet};
21 primitive::{self, FloatTy, IntTy, UintTy},
23 utils::all_super_traits,
24 AdtId, Canonical, CanonicalVarKinds, DebruijnIndex, ForeignDefId, InEnvironment, Interner,
25 Scalar, Substitution, TraitEnvironment, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
28 /// This is used as a key for indexing impls.
29 #[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
30 pub enum TyFingerprint {
31 // These are lang item impls:
38 // These can have user-defined impls:
41 ForeignType(ForeignDefId),
42 // These only exist for trait impls
49 /// Creates a TyFingerprint for looking up an inherent impl. Only certain
50 /// types can have inherent impls: if we have some `struct S`, we can have
51 /// an `impl S`, but not `impl &S`. Hence, this will return `None` for
52 /// reference types and such.
53 pub fn for_inherent_impl(ty: &Ty) -> Option<TyFingerprint> {
54 let fp = match ty.kind(&Interner) {
55 TyKind::Str => TyFingerprint::Str,
56 TyKind::Never => TyFingerprint::Never,
57 TyKind::Slice(..) => TyFingerprint::Slice,
58 TyKind::Array(..) => TyFingerprint::Array,
59 TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
60 TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
61 TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
62 TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
63 TyKind::Dyn(_) => ty.dyn_trait().map(TyFingerprint::Dyn)?,
69 /// Creates a TyFingerprint for looking up a trait impl.
70 pub fn for_trait_impl(ty: &Ty) -> Option<TyFingerprint> {
71 let fp = match ty.kind(&Interner) {
72 TyKind::Str => TyFingerprint::Str,
73 TyKind::Never => TyFingerprint::Never,
74 TyKind::Slice(..) => TyFingerprint::Slice,
75 TyKind::Array(..) => TyFingerprint::Array,
76 TyKind::Scalar(scalar) => TyFingerprint::Scalar(*scalar),
77 TyKind::Adt(AdtId(adt), _) => TyFingerprint::Adt(*adt),
78 TyKind::Raw(mutability, ..) => TyFingerprint::RawPtr(*mutability),
79 TyKind::Foreign(alias_id, ..) => TyFingerprint::ForeignType(*alias_id),
80 TyKind::Dyn(_) => ty.dyn_trait().map(TyFingerprint::Dyn)?,
81 TyKind::Ref(_, _, ty) => return TyFingerprint::for_trait_impl(ty),
82 TyKind::Tuple(_, subst) => {
83 let first_ty = subst.interned().get(0).map(|arg| arg.assert_ty_ref(&Interner));
84 if let Some(ty) = first_ty {
85 return TyFingerprint::for_trait_impl(ty);
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 collect_def_map(db, &crate_def_map, &mut impls);
144 return Arc::new(impls);
146 fn collect_def_map(db: &dyn HirDatabase, def_map: &DefMap, impls: &mut TraitImpls) {
147 for (_module_id, module_data) in def_map.modules() {
148 for impl_id in module_data.scope.impls() {
149 let target_trait = match db.impl_trait(impl_id) {
150 Some(tr) => tr.skip_binders().hir_trait_id(),
153 let self_ty = db.impl_self_ty(impl_id);
154 let self_ty_fp = TyFingerprint::for_trait_impl(self_ty.skip_binders());
164 // To better support custom derives, collect impls in all unnamed const items.
165 // const _: () = { ... };
166 for konst in module_data.scope.unnamed_consts() {
167 let body = db.body(konst.into());
168 for (_, block_def_map) in body.blocks(db.upcast()) {
169 collect_def_map(db, &block_def_map, impls);
176 pub(crate) fn trait_impls_in_deps_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
177 let _p = profile::span("trait_impls_in_deps_query");
178 let crate_graph = db.crate_graph();
179 let mut res = Self { map: FxHashMap::default() };
181 for krate in crate_graph.transitive_deps(krate) {
182 res.merge(&db.trait_impls_in_crate(krate));
188 fn merge(&mut self, other: &Self) {
189 for (trait_, other_map) in &other.map {
190 let map = self.map.entry(*trait_).or_default();
191 for (fp, impls) in other_map {
192 let vec = map.entry(*fp).or_default();
198 /// Queries all trait impls for the given type.
199 pub fn for_self_ty_without_blanket_impls(
202 ) -> impl Iterator<Item = ImplId> + '_ {
205 .flat_map(move |impls| impls.get(&Some(fp)).into_iter())
206 .flat_map(|it| it.iter().copied())
209 /// Queries all impls of the given trait.
210 pub fn for_trait(&self, trait_: TraitId) -> impl Iterator<Item = ImplId> + '_ {
214 .flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
217 /// Queries all impls of `trait_` that may apply to `self_ty`.
218 pub fn for_trait_and_self_ty(
221 self_ty: TyFingerprint,
222 ) -> impl Iterator<Item = ImplId> + '_ {
226 .flat_map(move |map| map.get(&None).into_iter().chain(map.get(&Some(self_ty))))
227 .flat_map(|v| v.iter().copied())
230 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
231 self.map.values().flat_map(|map| map.values().flat_map(|v| v.iter().copied()))
235 /// Inherent impls defined in some crate.
237 /// Inherent impls can only be defined in the crate that also defines the self type of the impl
238 /// (note that some primitives are considered to be defined by both libcore and liballoc).
240 /// This makes inherent impl lookup easier than trait impl lookup since we only have to consider a
242 #[derive(Debug, Eq, PartialEq)]
243 pub struct InherentImpls {
244 map: FxHashMap<TyFingerprint, Vec<ImplId>>,
248 pub(crate) fn inherent_impls_in_crate_query(db: &dyn HirDatabase, krate: CrateId) -> Arc<Self> {
249 let mut impls = Self { map: FxHashMap::default() };
251 let crate_def_map = db.crate_def_map(krate);
252 collect_def_map(db, &crate_def_map, &mut impls);
254 return Arc::new(impls);
256 fn collect_def_map(db: &dyn HirDatabase, def_map: &DefMap, impls: &mut InherentImpls) {
257 for (_module_id, module_data) in def_map.modules() {
258 for impl_id in module_data.scope.impls() {
259 let data = db.impl_data(impl_id);
260 if data.target_trait.is_some() {
264 let self_ty = db.impl_self_ty(impl_id);
265 let fp = TyFingerprint::for_inherent_impl(self_ty.skip_binders());
266 if let Some(fp) = fp {
267 impls.map.entry(fp).or_default().push(impl_id);
269 // `fp` should only be `None` in error cases (either erroneous code or incomplete name resolution)
272 // To better support custom derives, collect impls in all unnamed const items.
273 // const _: () = { ... };
274 for konst in module_data.scope.unnamed_consts() {
275 let body = db.body(konst.into());
276 for (_, block_def_map) in body.blocks(db.upcast()) {
277 collect_def_map(db, &block_def_map, impls);
284 pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
285 match TyFingerprint::for_inherent_impl(self_ty) {
286 Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
291 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
292 self.map.values().flat_map(|v| v.iter().copied())
297 db: &dyn HirDatabase,
300 ) -> Option<ArrayVec<CrateId, 2>> {
301 // Types like slice can have inherent impls in several crates, (core and alloc).
302 // The corresponding impls are marked with lang items, so we can use them to find the required crates.
303 macro_rules! lang_item_crate {
304 ($($name:expr),+ $(,)?) => {{
305 let mut v = ArrayVec::<LangItemTarget, 2>::new();
307 v.extend(db.lang_item(cur_crate, $name.into()));
313 let mod_to_crate_ids = |module: ModuleId| Some(std::iter::once(module.krate()).collect());
315 let lang_item_targets = match ty.kind(&Interner) {
316 TyKind::Adt(AdtId(def_id), _) => {
317 return mod_to_crate_ids(def_id.module(db.upcast()));
319 TyKind::Foreign(id) => {
320 return mod_to_crate_ids(
321 from_foreign_def_id(*id).lookup(db.upcast()).module(db.upcast()),
324 TyKind::Scalar(Scalar::Bool) => lang_item_crate!("bool"),
325 TyKind::Scalar(Scalar::Char) => lang_item_crate!("char"),
326 TyKind::Scalar(Scalar::Float(f)) => match f {
327 // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
328 FloatTy::F32 => lang_item_crate!("f32", "f32_runtime"),
329 FloatTy::F64 => lang_item_crate!("f64", "f64_runtime"),
331 &TyKind::Scalar(Scalar::Int(t)) => {
332 lang_item_crate!(primitive::int_ty_to_string(t))
334 &TyKind::Scalar(Scalar::Uint(t)) => {
335 lang_item_crate!(primitive::uint_ty_to_string(t))
337 TyKind::Str => lang_item_crate!("str_alloc", "str"),
338 TyKind::Slice(_) => lang_item_crate!("slice_alloc", "slice"),
339 TyKind::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
340 TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
342 return ty.dyn_trait().and_then(|trait_| {
343 mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
348 let res = lang_item_targets
350 .filter_map(|it| match it {
351 LangItemTarget::ImplDefId(it) => Some(it),
354 .map(|it| it.lookup(db.upcast()).container.krate())
359 /// Look up the method with the given name, returning the actual autoderefed
360 /// receiver type (but without autoref applied yet).
361 pub(crate) fn lookup_method(
363 db: &dyn HirDatabase,
364 env: Arc<TraitEnvironment>,
366 traits_in_scope: &FxHashSet<TraitId>,
367 visible_from_module: Option<ModuleId>,
369 ) -> Option<(Ty, FunctionId)> {
370 iterate_method_candidates(
378 LookupMode::MethodCall,
380 AssocItemId::FunctionId(f) => Some((ty.clone(), f)),
386 /// Whether we're looking up a dotted method call (like `v.len()`) or a path
387 /// (like `Vec::new`).
388 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
389 pub enum LookupMode {
390 /// Looking up a method call like `v.len()`: We only consider candidates
391 /// that have a `self` parameter, and do autoderef.
393 /// Looking up a path like `Vec::new` or `Vec::default`: We consider all
394 /// candidates including associated constants, but don't do autoderef.
398 // This would be nicer if it just returned an iterator, but that runs into
399 // lifetime problems, because we need to borrow temp `CrateImplDefs`.
400 // FIXME add a context type here?
401 pub fn iterate_method_candidates<T>(
403 db: &dyn HirDatabase,
404 env: Arc<TraitEnvironment>,
406 traits_in_scope: &FxHashSet<TraitId>,
407 visible_from_module: Option<ModuleId>,
410 mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>,
413 iterate_method_candidates_impl(
423 assert!(slot.is_none());
424 slot = callback(ty, item);
431 fn iterate_method_candidates_impl(
433 db: &dyn HirDatabase,
434 env: Arc<TraitEnvironment>,
436 traits_in_scope: &FxHashSet<TraitId>,
437 visible_from_module: Option<ModuleId>,
440 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
443 LookupMode::MethodCall => {
444 // For method calls, rust first does any number of autoderef, and then one
445 // autoref (i.e. when the method takes &self or &mut self). We just ignore
446 // the autoref currently -- when we find a method matching the given name,
447 // we assume it fits.
449 // Also note that when we've got a receiver like &S, even if the method we
450 // find in the end takes &self, we still do the autoderef step (just as
451 // rustc does an autoderef and then autoref again).
452 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
454 // We have to be careful about the order we're looking at candidates
455 // in here. Consider the case where we're resolving `x.clone()`
456 // where `x: &Vec<_>`. This resolves to the clone method with self
457 // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where
458 // the receiver type exactly matches before cases where we have to
459 // do autoref. But in the autoderef steps, the `&_` self type comes
460 // up *before* the `Vec<_>` self type.
462 // On the other hand, we don't want to just pick any by-value method
463 // before any by-autoref method; it's just that we need to consider
464 // the methods by autoderef order of *receiver types*, not *self
467 let deref_chain = autoderef_method_receiver(db, krate, ty);
468 for i in 0..deref_chain.len() {
469 if iterate_method_candidates_with_autoref(
484 LookupMode::Path => {
485 // No autoderef for path lookups
486 iterate_method_candidates_for_self_ty(
500 fn iterate_method_candidates_with_autoref(
501 deref_chain: &[Canonical<Ty>],
502 db: &dyn HirDatabase,
503 env: Arc<TraitEnvironment>,
505 traits_in_scope: &FxHashSet<TraitId>,
506 visible_from_module: Option<ModuleId>,
508 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
510 if iterate_method_candidates_by_receiver(
523 let refed = Canonical {
524 binders: deref_chain[0].binders.clone(),
525 value: TyKind::Ref(Mutability::Not, static_lifetime(), deref_chain[0].value.clone())
528 if iterate_method_candidates_by_receiver(
541 let ref_muted = Canonical {
542 binders: deref_chain[0].binders.clone(),
543 value: TyKind::Ref(Mutability::Mut, static_lifetime(), deref_chain[0].value.clone())
546 if iterate_method_candidates_by_receiver(
562 fn iterate_method_candidates_by_receiver(
563 receiver_ty: &Canonical<Ty>,
564 rest_of_deref_chain: &[Canonical<Ty>],
565 db: &dyn HirDatabase,
566 env: Arc<TraitEnvironment>,
568 traits_in_scope: &FxHashSet<TraitId>,
569 visible_from_module: Option<ModuleId>,
571 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
573 // We're looking for methods with *receiver* type receiver_ty. These could
574 // be found in any of the derefs of receiver_ty, so we have to go through
576 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
577 if iterate_inherent_methods(
590 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
591 if iterate_trait_method_candidates(
607 fn iterate_method_candidates_for_self_ty(
608 self_ty: &Canonical<Ty>,
609 db: &dyn HirDatabase,
610 env: Arc<TraitEnvironment>,
612 traits_in_scope: &FxHashSet<TraitId>,
613 visible_from_module: Option<ModuleId>,
615 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
617 if iterate_inherent_methods(
629 iterate_trait_method_candidates(self_ty, db, env, krate, traits_in_scope, name, None, callback)
632 fn iterate_trait_method_candidates(
633 self_ty: &Canonical<Ty>,
634 db: &dyn HirDatabase,
635 env: Arc<TraitEnvironment>,
637 traits_in_scope: &FxHashSet<TraitId>,
639 receiver_ty: Option<&Canonical<Ty>>,
640 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
642 let receiver_is_array = matches!(self_ty.value.kind(&Interner), chalk_ir::TyKind::Array(..));
643 // if ty is `dyn Trait`, the trait doesn't need to be in scope
645 self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
646 let env_traits = if let TyKind::Placeholder(_) = self_ty.value.kind(&Interner) {
647 // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
648 env.traits_in_scope_from_clauses(&self_ty.value)
649 .flat_map(|t| all_super_traits(db.upcast(), t))
655 inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied());
656 'traits: for t in traits {
657 let data = db.trait_data(t);
659 // Traits annotated with `#[rustc_skip_array_during_method_dispatch]` are skipped during
660 // method resolution, if the receiver is an array, and we're compiling for editions before
662 // This is to make `[a].into_iter()` not break code with the new `IntoIterator` impl for
664 if data.skip_array_during_method_dispatch && receiver_is_array {
665 // FIXME: this should really be using the edition of the method name's span, in case it
666 // comes from a macro
667 if db.crate_graph()[krate].edition < Edition::Edition2021 {
672 // we'll be lazy about checking whether the type implements the
673 // trait, but if we find out it doesn't, we'll skip the rest of the
675 let mut known_implemented = false;
676 for (_name, item) in data.items.iter() {
677 // Don't pass a `visible_from_module` down to `is_valid_candidate`,
678 // since only inherent methods should be included into visibility checking.
679 if !is_valid_candidate(db, env.clone(), name, receiver_ty, *item, self_ty, None) {
682 if !known_implemented {
683 let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone());
684 if db.trait_solve(krate, goal.cast(&Interner)).is_none() {
688 known_implemented = true;
689 // FIXME: we shouldn't be ignoring the binders here
690 if callback(&self_ty.value, *item) {
698 fn iterate_inherent_methods(
699 self_ty: &Canonical<Ty>,
700 db: &dyn HirDatabase,
701 env: Arc<TraitEnvironment>,
703 receiver_ty: Option<&Canonical<Ty>>,
705 visible_from_module: Option<ModuleId>,
706 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
708 let def_crates = match def_crates(db, &self_ty.value, krate) {
710 None => return false,
712 for krate in def_crates {
713 let impls = db.inherent_impls_in_crate(krate);
715 for &impl_def in impls.for_self_ty(&self_ty.value) {
716 for &item in db.impl_data(impl_def).items.iter() {
717 if !is_valid_candidate(
728 // we have to check whether the self type unifies with the type
729 // that the impl is for. If we have a receiver type, this
730 // already happens in `is_valid_candidate` above; if not, we
732 if receiver_ty.is_none()
733 && inherent_impl_substs(db, env.clone(), impl_def, self_ty).is_none()
735 cov_mark::hit!(impl_self_type_match_without_receiver);
738 let receiver_ty = receiver_ty.map(|x| &x.value).unwrap_or(&self_ty.value);
739 if callback(receiver_ty, item) {
748 /// Returns the self type for the index trait call.
749 pub fn resolve_indexing_op(
750 db: &dyn HirDatabase,
752 env: Arc<TraitEnvironment>,
754 index_trait: TraitId,
755 ) -> Option<Canonical<Ty>> {
756 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
757 let deref_chain = autoderef_method_receiver(db, krate, ty);
758 for ty in deref_chain {
759 let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
760 if db.trait_solve(krate, goal.cast(&Interner)).is_some() {
767 fn is_valid_candidate(
768 db: &dyn HirDatabase,
769 env: Arc<TraitEnvironment>,
771 receiver_ty: Option<&Canonical<Ty>>,
773 self_ty: &Canonical<Ty>,
774 visible_from_module: Option<ModuleId>,
777 AssocItemId::FunctionId(m) => {
778 let data = db.function_data(m);
779 if let Some(name) = name {
780 if &data.name != name {
784 if let Some(receiver_ty) = receiver_ty {
785 if !data.has_self_param() {
788 let transformed_receiver_ty = match transform_receiver_ty(db, env, m, self_ty) {
790 None => return false,
792 if transformed_receiver_ty != receiver_ty.value {
796 if let Some(from_module) = visible_from_module {
797 if !db.function_visibility(m).is_visible_from(db.upcast(), from_module) {
798 cov_mark::hit!(autoderef_candidate_not_visible);
805 AssocItemId::ConstId(c) => {
806 let data = db.const_data(c);
807 name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none()
813 pub(crate) fn inherent_impl_substs(
814 db: &dyn HirDatabase,
815 env: Arc<TraitEnvironment>,
817 self_ty: &Canonical<Ty>,
818 ) -> Option<Substitution> {
819 // we create a var for each type parameter of the impl; we need to keep in
820 // mind here that `self_ty` might have vars of its own
821 let self_ty_vars = self_ty.binders.len(&Interner);
822 let vars = TyBuilder::subst_for_def(db, impl_id)
823 .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty_vars)
825 let self_ty_with_vars = db.impl_self_ty(impl_id).substitute(&Interner, &vars);
826 let mut kinds = self_ty.binders.interned().to_vec();
828 iter::repeat(chalk_ir::WithKind::new(
829 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
832 .take(vars.len(&Interner)),
834 let tys = Canonical {
835 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
836 value: (self_ty_with_vars, self_ty.value.clone()),
838 let substs = super::infer::unify(db, env, &tys)?;
839 // We only want the substs for the vars we added, not the ones from self_ty.
840 // Also, if any of the vars we added are still in there, we replace them by
841 // Unknown. I think this can only really happen if self_ty contained
842 // Unknown, and in that case we want the result to contain Unknown in those
845 Substitution::from_iter(&Interner, substs.iter(&Interner).cloned().skip(self_ty_vars));
846 Some(fallback_bound_vars(suffix, self_ty_vars))
849 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
850 /// num_vars_to_keep) by `TyKind::Unknown`.
851 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
852 crate::fold_free_vars(s, |bound, binders| {
853 if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
854 TyKind::Error.intern(&Interner)
856 bound.shifted_in_from(binders).to_ty(&Interner)
861 fn transform_receiver_ty(
862 db: &dyn HirDatabase,
863 env: Arc<TraitEnvironment>,
864 function_id: FunctionId,
865 self_ty: &Canonical<Ty>,
867 let substs = match function_id.lookup(db.upcast()).container {
868 AssocContainerId::TraitId(_) => TyBuilder::subst_for_def(db, function_id)
869 .push(self_ty.value.clone())
872 AssocContainerId::ImplId(impl_id) => {
873 let impl_substs = inherent_impl_substs(db, env, impl_id, self_ty)?;
874 TyBuilder::subst_for_def(db, function_id)
875 .use_parent_substs(&impl_substs)
879 AssocContainerId::ModuleId(_) => unreachable!(),
881 let sig = db.callable_item_signature(function_id.into());
882 Some(sig.map(|s| s.params()[0].clone()).substitute(&Interner, &substs))
885 pub fn implements_trait(
887 db: &dyn HirDatabase,
888 env: Arc<TraitEnvironment>,
892 let goal = generic_implements_goal(db, env, trait_, ty.clone());
893 let solution = db.trait_solve(krate, goal.cast(&Interner));
898 pub fn implements_trait_unique(
900 db: &dyn HirDatabase,
901 env: Arc<TraitEnvironment>,
905 let goal = generic_implements_goal(db, env, trait_, ty.clone());
906 let solution = db.trait_solve(krate, goal.cast(&Interner));
908 matches!(solution, Some(crate::Solution::Unique(_)))
911 /// This creates Substs for a trait with the given Self type and type variables
912 /// for all other parameters, to query Chalk with it.
913 fn generic_implements_goal(
914 db: &dyn HirDatabase,
915 env: Arc<TraitEnvironment>,
917 self_ty: Canonical<Ty>,
918 ) -> Canonical<InEnvironment<super::DomainGoal>> {
919 let mut kinds = self_ty.binders.interned().to_vec();
920 let trait_ref = TyBuilder::trait_ref(db, trait_)
922 .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
925 iter::repeat(chalk_ir::WithKind::new(
926 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
929 .take(trait_ref.substitution.len(&Interner) - 1),
931 let obligation = trait_ref.cast(&Interner);
933 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
934 value: InEnvironment::new(&env.env, obligation),
938 fn autoderef_method_receiver(
939 db: &dyn HirDatabase,
941 ty: InEnvironment<Canonical<Ty>>,
942 ) -> Vec<Canonical<Ty>> {
943 let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
944 // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
945 if let Some(TyKind::Array(parameters, _)) =
946 deref_chain.last().map(|ty| ty.value.kind(&Interner))
948 let kinds = deref_chain.last().unwrap().binders.clone();
949 let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
950 deref_chain.push(Canonical { value: unsized_ty, binders: kinds })