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;
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(|trait_| TyFingerprint::Dyn(trait_))?,
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(|trait_| TyFingerprint::Dyn(trait_))?,
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 map: FxHashMap<_, Vec<_>> = FxHashMap::default();
251 let crate_def_map = db.crate_def_map(krate);
252 for (_module_id, module_data) in crate_def_map.modules() {
253 for impl_id in module_data.scope.impls() {
254 let data = db.impl_data(impl_id);
255 if data.target_trait.is_some() {
259 let self_ty = db.impl_self_ty(impl_id);
260 let fp = TyFingerprint::for_inherent_impl(self_ty.skip_binders());
261 if let Some(fp) = fp {
262 map.entry(fp).or_default().push(impl_id);
264 // `fp` should only be `None` in error cases (either erroneous code or incomplete name resolution)
268 // NOTE: We're not collecting inherent impls from unnamed consts here, we intentionally only
269 // support trait impls there.
271 Arc::new(Self { map })
274 pub fn for_self_ty(&self, self_ty: &Ty) -> &[ImplId] {
275 match TyFingerprint::for_inherent_impl(self_ty) {
276 Some(fp) => self.map.get(&fp).map(|vec| vec.as_ref()).unwrap_or(&[]),
281 pub fn all_impls(&self) -> impl Iterator<Item = ImplId> + '_ {
282 self.map.values().flat_map(|v| v.iter().copied())
287 db: &dyn HirDatabase,
290 ) -> Option<ArrayVec<CrateId, 2>> {
291 // Types like slice can have inherent impls in several crates, (core and alloc).
292 // The corresponding impls are marked with lang items, so we can use them to find the required crates.
293 macro_rules! lang_item_crate {
294 ($($name:expr),+ $(,)?) => {{
295 let mut v = ArrayVec::<LangItemTarget, 2>::new();
297 v.extend(db.lang_item(cur_crate, $name.into()));
303 let mod_to_crate_ids = |module: ModuleId| Some(std::iter::once(module.krate()).collect());
305 let lang_item_targets = match ty.kind(&Interner) {
306 TyKind::Adt(AdtId(def_id), _) => {
307 return mod_to_crate_ids(def_id.module(db.upcast()));
309 TyKind::Foreign(id) => {
310 return mod_to_crate_ids(
311 from_foreign_def_id(*id).lookup(db.upcast()).module(db.upcast()),
314 TyKind::Scalar(Scalar::Bool) => lang_item_crate!("bool"),
315 TyKind::Scalar(Scalar::Char) => lang_item_crate!("char"),
316 TyKind::Scalar(Scalar::Float(f)) => match f {
317 // There are two lang items: one in libcore (fXX) and one in libstd (fXX_runtime)
318 FloatTy::F32 => lang_item_crate!("f32", "f32_runtime"),
319 FloatTy::F64 => lang_item_crate!("f64", "f64_runtime"),
321 &TyKind::Scalar(Scalar::Int(t)) => {
322 lang_item_crate!(primitive::int_ty_to_string(t))
324 &TyKind::Scalar(Scalar::Uint(t)) => {
325 lang_item_crate!(primitive::uint_ty_to_string(t))
327 TyKind::Str => lang_item_crate!("str_alloc", "str"),
328 TyKind::Slice(_) => lang_item_crate!("slice_alloc", "slice"),
329 TyKind::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
330 TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
332 return ty.dyn_trait().and_then(|trait_| {
333 mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
338 let res = lang_item_targets
340 .filter_map(|it| match it {
341 LangItemTarget::ImplDefId(it) => Some(it),
344 .map(|it| it.lookup(db.upcast()).container.krate())
349 /// Look up the method with the given name, returning the actual autoderefed
350 /// receiver type (but without autoref applied yet).
351 pub(crate) fn lookup_method(
353 db: &dyn HirDatabase,
354 env: Arc<TraitEnvironment>,
356 traits_in_scope: &FxHashSet<TraitId>,
357 visible_from_module: Option<ModuleId>,
359 ) -> Option<(Ty, FunctionId)> {
360 iterate_method_candidates(
368 LookupMode::MethodCall,
370 AssocItemId::FunctionId(f) => Some((ty.clone(), f)),
376 /// Whether we're looking up a dotted method call (like `v.len()`) or a path
377 /// (like `Vec::new`).
378 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
379 pub enum LookupMode {
380 /// Looking up a method call like `v.len()`: We only consider candidates
381 /// that have a `self` parameter, and do autoderef.
383 /// Looking up a path like `Vec::new` or `Vec::default`: We consider all
384 /// candidates including associated constants, but don't do autoderef.
388 // This would be nicer if it just returned an iterator, but that runs into
389 // lifetime problems, because we need to borrow temp `CrateImplDefs`.
390 // FIXME add a context type here?
391 pub fn iterate_method_candidates<T>(
393 db: &dyn HirDatabase,
394 env: Arc<TraitEnvironment>,
396 traits_in_scope: &FxHashSet<TraitId>,
397 visible_from_module: Option<ModuleId>,
400 mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>,
403 iterate_method_candidates_impl(
413 assert!(slot.is_none());
414 slot = callback(ty, item);
421 fn iterate_method_candidates_impl(
423 db: &dyn HirDatabase,
424 env: Arc<TraitEnvironment>,
426 traits_in_scope: &FxHashSet<TraitId>,
427 visible_from_module: Option<ModuleId>,
430 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
433 LookupMode::MethodCall => {
434 // For method calls, rust first does any number of autoderef, and then one
435 // autoref (i.e. when the method takes &self or &mut self). We just ignore
436 // the autoref currently -- when we find a method matching the given name,
437 // we assume it fits.
439 // Also note that when we've got a receiver like &S, even if the method we
440 // find in the end takes &self, we still do the autoderef step (just as
441 // rustc does an autoderef and then autoref again).
442 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
444 // We have to be careful about the order we're looking at candidates
445 // in here. Consider the case where we're resolving `x.clone()`
446 // where `x: &Vec<_>`. This resolves to the clone method with self
447 // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where
448 // the receiver type exactly matches before cases where we have to
449 // do autoref. But in the autoderef steps, the `&_` self type comes
450 // up *before* the `Vec<_>` self type.
452 // On the other hand, we don't want to just pick any by-value method
453 // before any by-autoref method; it's just that we need to consider
454 // the methods by autoderef order of *receiver types*, not *self
457 let deref_chain = autoderef_method_receiver(db, krate, ty);
458 for i in 0..deref_chain.len() {
459 if iterate_method_candidates_with_autoref(
474 LookupMode::Path => {
475 // No autoderef for path lookups
476 iterate_method_candidates_for_self_ty(
490 fn iterate_method_candidates_with_autoref(
491 deref_chain: &[Canonical<Ty>],
492 db: &dyn HirDatabase,
493 env: Arc<TraitEnvironment>,
495 traits_in_scope: &FxHashSet<TraitId>,
496 visible_from_module: Option<ModuleId>,
498 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
500 if iterate_method_candidates_by_receiver(
513 let refed = Canonical {
514 binders: deref_chain[0].binders.clone(),
515 value: TyKind::Ref(Mutability::Not, static_lifetime(), deref_chain[0].value.clone())
518 if iterate_method_candidates_by_receiver(
531 let ref_muted = Canonical {
532 binders: deref_chain[0].binders.clone(),
533 value: TyKind::Ref(Mutability::Mut, static_lifetime(), deref_chain[0].value.clone())
536 if iterate_method_candidates_by_receiver(
552 fn iterate_method_candidates_by_receiver(
553 receiver_ty: &Canonical<Ty>,
554 rest_of_deref_chain: &[Canonical<Ty>],
555 db: &dyn HirDatabase,
556 env: Arc<TraitEnvironment>,
558 traits_in_scope: &FxHashSet<TraitId>,
559 visible_from_module: Option<ModuleId>,
561 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
563 // We're looking for methods with *receiver* type receiver_ty. These could
564 // be found in any of the derefs of receiver_ty, so we have to go through
566 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
567 if iterate_inherent_methods(
579 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
580 if iterate_trait_method_candidates(
596 fn iterate_method_candidates_for_self_ty(
597 self_ty: &Canonical<Ty>,
598 db: &dyn HirDatabase,
599 env: Arc<TraitEnvironment>,
601 traits_in_scope: &FxHashSet<TraitId>,
602 visible_from_module: Option<ModuleId>,
604 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
606 if iterate_inherent_methods(self_ty, db, name, None, krate, visible_from_module, &mut callback)
610 iterate_trait_method_candidates(self_ty, db, env, krate, traits_in_scope, name, None, callback)
613 fn iterate_trait_method_candidates(
614 self_ty: &Canonical<Ty>,
615 db: &dyn HirDatabase,
616 env: Arc<TraitEnvironment>,
618 traits_in_scope: &FxHashSet<TraitId>,
620 receiver_ty: Option<&Canonical<Ty>>,
621 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
623 // if ty is `dyn Trait`, the trait doesn't need to be in scope
625 self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
626 let env_traits = if let TyKind::Placeholder(_) = self_ty.value.kind(&Interner) {
627 // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
628 env.traits_in_scope_from_clauses(&self_ty.value)
629 .flat_map(|t| all_super_traits(db.upcast(), t))
635 inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied());
636 'traits: for t in traits {
637 let data = db.trait_data(t);
639 // we'll be lazy about checking whether the type implements the
640 // trait, but if we find out it doesn't, we'll skip the rest of the
642 let mut known_implemented = false;
643 for (_name, item) in data.items.iter() {
644 // Don't pass a `visible_from_module` down to `is_valid_candidate`,
645 // since only inherent methods should be included into visibility checking.
646 if !is_valid_candidate(db, name, receiver_ty, *item, self_ty, None) {
649 if !known_implemented {
650 let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone());
651 if db.trait_solve(krate, goal).is_none() {
655 known_implemented = true;
656 // FIXME: we shouldn't be ignoring the binders here
657 if callback(&self_ty.value, *item) {
665 fn iterate_inherent_methods(
666 self_ty: &Canonical<Ty>,
667 db: &dyn HirDatabase,
669 receiver_ty: Option<&Canonical<Ty>>,
671 visible_from_module: Option<ModuleId>,
672 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
674 let def_crates = match def_crates(db, &self_ty.value, krate) {
676 None => return false,
678 for krate in def_crates {
679 let impls = db.inherent_impls_in_crate(krate);
681 for &impl_def in impls.for_self_ty(&self_ty.value) {
682 for &item in db.impl_data(impl_def).items.iter() {
683 if !is_valid_candidate(db, name, receiver_ty, item, self_ty, visible_from_module) {
686 // we have to check whether the self type unifies with the type
687 // that the impl is for. If we have a receiver type, this
688 // already happens in `is_valid_candidate` above; if not, we
690 if receiver_ty.is_none() && inherent_impl_substs(db, impl_def, self_ty).is_none() {
691 cov_mark::hit!(impl_self_type_match_without_receiver);
694 if callback(&self_ty.value, item) {
703 /// Returns the self type for the index trait call.
704 pub fn resolve_indexing_op(
705 db: &dyn HirDatabase,
707 env: Arc<TraitEnvironment>,
709 index_trait: TraitId,
710 ) -> Option<Canonical<Ty>> {
711 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
712 let deref_chain = autoderef_method_receiver(db, krate, ty);
713 for ty in deref_chain {
714 let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
715 if db.trait_solve(krate, goal).is_some() {
722 fn is_valid_candidate(
723 db: &dyn HirDatabase,
725 receiver_ty: Option<&Canonical<Ty>>,
727 self_ty: &Canonical<Ty>,
728 visible_from_module: Option<ModuleId>,
731 AssocItemId::FunctionId(m) => {
732 let data = db.function_data(m);
733 if let Some(name) = name {
734 if &data.name != name {
738 if let Some(receiver_ty) = receiver_ty {
739 if !data.has_self_param() {
742 let transformed_receiver_ty = match transform_receiver_ty(db, m, self_ty) {
744 None => return false,
746 if transformed_receiver_ty != receiver_ty.value {
750 if let Some(from_module) = visible_from_module {
751 if !db.function_visibility(m).is_visible_from(db.upcast(), from_module) {
752 cov_mark::hit!(autoderef_candidate_not_visible);
759 AssocItemId::ConstId(c) => {
760 let data = db.const_data(c);
761 name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none()
767 pub(crate) fn inherent_impl_substs(
768 db: &dyn HirDatabase,
770 self_ty: &Canonical<Ty>,
771 ) -> Option<Substitution> {
772 // we create a var for each type parameter of the impl; we need to keep in
773 // mind here that `self_ty` might have vars of its own
774 let self_ty_vars = self_ty.binders.len(&Interner);
775 let vars = TyBuilder::subst_for_def(db, impl_id)
776 .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty_vars)
778 let self_ty_with_vars = db.impl_self_ty(impl_id).substitute(&Interner, &vars);
779 let mut kinds = self_ty.binders.interned().to_vec();
781 iter::repeat(chalk_ir::WithKind::new(
782 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
785 .take(vars.len(&Interner)),
787 let tys = Canonical {
788 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
789 value: (self_ty_with_vars, self_ty.value.clone()),
791 let substs = super::infer::unify(&tys)?;
792 // We only want the substs for the vars we added, not the ones from self_ty.
793 // Also, if any of the vars we added are still in there, we replace them by
794 // Unknown. I think this can only really happen if self_ty contained
795 // Unknown, and in that case we want the result to contain Unknown in those
798 Substitution::from_iter(&Interner, substs.iter(&Interner).cloned().skip(self_ty_vars));
799 Some(fallback_bound_vars(suffix, self_ty_vars))
802 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
803 /// num_vars_to_keep) by `TyKind::Unknown`.
804 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
805 crate::fold_free_vars(s, |bound, binders| {
806 if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
807 TyKind::Error.intern(&Interner)
809 bound.shifted_in_from(binders).to_ty(&Interner)
814 fn transform_receiver_ty(
815 db: &dyn HirDatabase,
816 function_id: FunctionId,
817 self_ty: &Canonical<Ty>,
819 let substs = match function_id.lookup(db.upcast()).container {
820 AssocContainerId::TraitId(_) => TyBuilder::subst_for_def(db, function_id)
821 .push(self_ty.value.clone())
824 AssocContainerId::ImplId(impl_id) => {
825 let impl_substs = inherent_impl_substs(db, impl_id, &self_ty)?;
826 TyBuilder::subst_for_def(db, function_id)
827 .use_parent_substs(&impl_substs)
831 AssocContainerId::ModuleId(_) => unreachable!(),
833 let sig = db.callable_item_signature(function_id.into());
834 Some(sig.map(|s| s.params()[0].clone()).substitute(&Interner, &substs))
837 pub fn implements_trait(
839 db: &dyn HirDatabase,
840 env: Arc<TraitEnvironment>,
844 let goal = generic_implements_goal(db, env, trait_, ty.clone());
845 let solution = db.trait_solve(krate, goal);
850 pub fn implements_trait_unique(
852 db: &dyn HirDatabase,
853 env: Arc<TraitEnvironment>,
857 let goal = generic_implements_goal(db, env, trait_, ty.clone());
858 let solution = db.trait_solve(krate, goal);
860 matches!(solution, Some(crate::Solution::Unique(_)))
863 /// This creates Substs for a trait with the given Self type and type variables
864 /// for all other parameters, to query Chalk with it.
865 fn generic_implements_goal(
866 db: &dyn HirDatabase,
867 env: Arc<TraitEnvironment>,
869 self_ty: Canonical<Ty>,
870 ) -> Canonical<InEnvironment<super::DomainGoal>> {
871 let mut kinds = self_ty.binders.interned().to_vec();
872 let trait_ref = TyBuilder::trait_ref(db, trait_)
874 .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
877 iter::repeat(chalk_ir::WithKind::new(
878 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
881 .take(trait_ref.substitution.len(&Interner) - 1),
883 let obligation = trait_ref.cast(&Interner);
885 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
886 value: InEnvironment::new(&env.env, obligation),
890 fn autoderef_method_receiver(
891 db: &dyn HirDatabase,
893 ty: InEnvironment<Canonical<Ty>>,
894 ) -> Vec<Canonical<Ty>> {
895 let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
896 // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
897 if let Some(TyKind::Array(parameters, _)) =
898 deref_chain.last().map(|ty| ty.value.kind(&Interner))
900 let kinds = deref_chain.last().unwrap().binders.clone();
901 let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
902 deref_chain.push(Canonical { value: unsized_ty, binders: kinds })