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, BlockId, 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 impls.collect_def_map(db, &crate_def_map);
144 return Arc::new(impls);
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 return 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::Raw(Mutability::Not, _) => lang_item_crate!("const_ptr"),
352 TyKind::Raw(Mutability::Mut, _) => lang_item_crate!("mut_ptr"),
354 return ty.dyn_trait().and_then(|trait_| {
355 mod_to_crate_ids(GenericDefId::TraitId(trait_).module(db.upcast()))
360 let res = lang_item_targets
362 .filter_map(|it| match it {
363 LangItemTarget::ImplDefId(it) => Some(it),
366 .map(|it| it.lookup(db.upcast()).container.krate())
371 /// Look up the method with the given name, returning the actual autoderefed
372 /// receiver type (but without autoref applied yet).
373 pub(crate) fn lookup_method(
375 db: &dyn HirDatabase,
376 env: Arc<TraitEnvironment>,
378 traits_in_scope: &FxHashSet<TraitId>,
379 visible_from_module: Option<ModuleId>,
381 ) -> Option<(Ty, FunctionId)> {
382 iterate_method_candidates(
390 LookupMode::MethodCall,
392 AssocItemId::FunctionId(f) => Some((ty.clone(), f)),
398 /// Whether we're looking up a dotted method call (like `v.len()`) or a path
399 /// (like `Vec::new`).
400 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
401 pub enum LookupMode {
402 /// Looking up a method call like `v.len()`: We only consider candidates
403 /// that have a `self` parameter, and do autoderef.
405 /// Looking up a path like `Vec::new` or `Vec::default`: We consider all
406 /// candidates including associated constants, but don't do autoderef.
410 // This would be nicer if it just returned an iterator, but that runs into
411 // lifetime problems, because we need to borrow temp `CrateImplDefs`.
412 // FIXME add a context type here?
413 pub fn iterate_method_candidates<T>(
415 db: &dyn HirDatabase,
416 env: Arc<TraitEnvironment>,
418 traits_in_scope: &FxHashSet<TraitId>,
419 visible_from_module: Option<ModuleId>,
422 mut callback: impl FnMut(&Ty, AssocItemId) -> Option<T>,
425 iterate_method_candidates_impl(
435 assert!(slot.is_none());
436 slot = callback(ty, item);
443 fn iterate_method_candidates_impl(
445 db: &dyn HirDatabase,
446 env: Arc<TraitEnvironment>,
448 traits_in_scope: &FxHashSet<TraitId>,
449 visible_from_module: Option<ModuleId>,
452 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
455 LookupMode::MethodCall => {
456 // For method calls, rust first does any number of autoderef, and then one
457 // autoref (i.e. when the method takes &self or &mut self). We just ignore
458 // the autoref currently -- when we find a method matching the given name,
459 // we assume it fits.
461 // Also note that when we've got a receiver like &S, even if the method we
462 // find in the end takes &self, we still do the autoderef step (just as
463 // rustc does an autoderef and then autoref again).
464 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
466 // We have to be careful about the order we're looking at candidates
467 // in here. Consider the case where we're resolving `x.clone()`
468 // where `x: &Vec<_>`. This resolves to the clone method with self
469 // type `Vec<_>`, *not* `&_`. I.e. we need to consider methods where
470 // the receiver type exactly matches before cases where we have to
471 // do autoref. But in the autoderef steps, the `&_` self type comes
472 // up *before* the `Vec<_>` self type.
474 // On the other hand, we don't want to just pick any by-value method
475 // before any by-autoref method; it's just that we need to consider
476 // the methods by autoderef order of *receiver types*, not *self
479 let deref_chain = autoderef_method_receiver(db, krate, ty);
480 for i in 0..deref_chain.len() {
481 if iterate_method_candidates_with_autoref(
496 LookupMode::Path => {
497 // No autoderef for path lookups
498 iterate_method_candidates_for_self_ty(
512 fn iterate_method_candidates_with_autoref(
513 deref_chain: &[Canonical<Ty>],
514 db: &dyn HirDatabase,
515 env: Arc<TraitEnvironment>,
517 traits_in_scope: &FxHashSet<TraitId>,
518 visible_from_module: Option<ModuleId>,
520 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
522 if iterate_method_candidates_by_receiver(
535 let refed = Canonical {
536 binders: deref_chain[0].binders.clone(),
537 value: TyKind::Ref(Mutability::Not, static_lifetime(), deref_chain[0].value.clone())
540 if iterate_method_candidates_by_receiver(
553 let ref_muted = Canonical {
554 binders: deref_chain[0].binders.clone(),
555 value: TyKind::Ref(Mutability::Mut, static_lifetime(), deref_chain[0].value.clone())
558 if iterate_method_candidates_by_receiver(
574 fn iterate_method_candidates_by_receiver(
575 receiver_ty: &Canonical<Ty>,
576 rest_of_deref_chain: &[Canonical<Ty>],
577 db: &dyn HirDatabase,
578 env: Arc<TraitEnvironment>,
580 traits_in_scope: &FxHashSet<TraitId>,
581 visible_from_module: Option<ModuleId>,
583 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
585 // We're looking for methods with *receiver* type receiver_ty. These could
586 // be found in any of the derefs of receiver_ty, so we have to go through
588 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
589 if iterate_inherent_methods(
602 for self_ty in std::iter::once(receiver_ty).chain(rest_of_deref_chain) {
603 if iterate_trait_method_candidates(
619 fn iterate_method_candidates_for_self_ty(
620 self_ty: &Canonical<Ty>,
621 db: &dyn HirDatabase,
622 env: Arc<TraitEnvironment>,
624 traits_in_scope: &FxHashSet<TraitId>,
625 visible_from_module: Option<ModuleId>,
627 mut callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
629 if iterate_inherent_methods(
641 iterate_trait_method_candidates(self_ty, db, env, krate, traits_in_scope, name, None, callback)
644 fn iterate_trait_method_candidates(
645 self_ty: &Canonical<Ty>,
646 db: &dyn HirDatabase,
647 env: Arc<TraitEnvironment>,
649 traits_in_scope: &FxHashSet<TraitId>,
651 receiver_ty: Option<&Canonical<Ty>>,
652 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
654 let receiver_is_array = matches!(self_ty.value.kind(&Interner), chalk_ir::TyKind::Array(..));
655 // if ty is `dyn Trait`, the trait doesn't need to be in scope
657 self_ty.value.dyn_trait().into_iter().flat_map(|t| all_super_traits(db.upcast(), t));
658 let env_traits = if let TyKind::Placeholder(_) = self_ty.value.kind(&Interner) {
659 // if we have `T: Trait` in the param env, the trait doesn't need to be in scope
660 env.traits_in_scope_from_clauses(&self_ty.value)
661 .flat_map(|t| all_super_traits(db.upcast(), t))
667 inherent_trait.chain(env_traits.into_iter()).chain(traits_in_scope.iter().copied());
668 'traits: for t in traits {
669 let data = db.trait_data(t);
671 // Traits annotated with `#[rustc_skip_array_during_method_dispatch]` are skipped during
672 // method resolution, if the receiver is an array, and we're compiling for editions before
674 // This is to make `[a].into_iter()` not break code with the new `IntoIterator` impl for
676 if data.skip_array_during_method_dispatch && receiver_is_array {
677 // FIXME: this should really be using the edition of the method name's span, in case it
678 // comes from a macro
679 if db.crate_graph()[krate].edition < Edition::Edition2021 {
684 // we'll be lazy about checking whether the type implements the
685 // trait, but if we find out it doesn't, we'll skip the rest of the
687 let mut known_implemented = false;
688 for (_name, item) in data.items.iter() {
689 // Don't pass a `visible_from_module` down to `is_valid_candidate`,
690 // since only inherent methods should be included into visibility checking.
691 if !is_valid_candidate(db, env.clone(), name, receiver_ty, *item, self_ty, None) {
694 if !known_implemented {
695 let goal = generic_implements_goal(db, env.clone(), t, self_ty.clone());
696 if db.trait_solve(krate, goal.cast(&Interner)).is_none() {
700 known_implemented = true;
701 // FIXME: we shouldn't be ignoring the binders here
702 if callback(&self_ty.value, *item) {
710 fn iterate_inherent_methods(
711 self_ty: &Canonical<Ty>,
712 db: &dyn HirDatabase,
713 env: Arc<TraitEnvironment>,
715 receiver_ty: Option<&Canonical<Ty>>,
717 visible_from_module: Option<ModuleId>,
718 callback: &mut dyn FnMut(&Ty, AssocItemId) -> bool,
720 let def_crates = match def_crates(db, &self_ty.value, krate) {
722 None => return false,
724 for krate in def_crates {
725 let impls = db.inherent_impls_in_crate(krate);
727 for &impl_def in impls.for_self_ty(&self_ty.value) {
728 for &item in db.impl_data(impl_def).items.iter() {
729 if !is_valid_candidate(
740 // we have to check whether the self type unifies with the type
741 // that the impl is for. If we have a receiver type, this
742 // already happens in `is_valid_candidate` above; if not, we
744 if receiver_ty.is_none()
745 && inherent_impl_substs(db, env.clone(), impl_def, self_ty).is_none()
747 cov_mark::hit!(impl_self_type_match_without_receiver);
750 let receiver_ty = receiver_ty.map(|x| &x.value).unwrap_or(&self_ty.value);
751 if callback(receiver_ty, item) {
760 /// Returns the self type for the index trait call.
761 pub fn resolve_indexing_op(
762 db: &dyn HirDatabase,
764 env: Arc<TraitEnvironment>,
766 index_trait: TraitId,
767 ) -> Option<Canonical<Ty>> {
768 let ty = InEnvironment { goal: ty.clone(), environment: env.env.clone() };
769 let deref_chain = autoderef_method_receiver(db, krate, ty);
770 for ty in deref_chain {
771 let goal = generic_implements_goal(db, env.clone(), index_trait, ty.clone());
772 if db.trait_solve(krate, goal.cast(&Interner)).is_some() {
779 fn is_valid_candidate(
780 db: &dyn HirDatabase,
781 env: Arc<TraitEnvironment>,
783 receiver_ty: Option<&Canonical<Ty>>,
785 self_ty: &Canonical<Ty>,
786 visible_from_module: Option<ModuleId>,
789 AssocItemId::FunctionId(m) => {
790 let data = db.function_data(m);
791 if let Some(name) = name {
792 if &data.name != name {
796 if let Some(receiver_ty) = receiver_ty {
797 if !data.has_self_param() {
800 let transformed_receiver_ty = match transform_receiver_ty(db, env, m, self_ty) {
802 None => return false,
804 if transformed_receiver_ty != receiver_ty.value {
808 if let Some(from_module) = visible_from_module {
809 if !db.function_visibility(m).is_visible_from(db.upcast(), from_module) {
810 cov_mark::hit!(autoderef_candidate_not_visible);
817 AssocItemId::ConstId(c) => {
818 let data = db.const_data(c);
819 name.map_or(true, |name| data.name.as_ref() == Some(name)) && receiver_ty.is_none()
825 pub(crate) fn inherent_impl_substs(
826 db: &dyn HirDatabase,
827 env: Arc<TraitEnvironment>,
829 self_ty: &Canonical<Ty>,
830 ) -> Option<Substitution> {
831 // we create a var for each type parameter of the impl; we need to keep in
832 // mind here that `self_ty` might have vars of its own
833 let self_ty_vars = self_ty.binders.len(&Interner);
834 let vars = TyBuilder::subst_for_def(db, impl_id)
835 .fill_with_bound_vars(DebruijnIndex::INNERMOST, self_ty_vars)
837 let self_ty_with_vars = db.impl_self_ty(impl_id).substitute(&Interner, &vars);
838 let mut kinds = self_ty.binders.interned().to_vec();
840 iter::repeat(chalk_ir::WithKind::new(
841 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
844 .take(vars.len(&Interner)),
846 let tys = Canonical {
847 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
848 value: (self_ty_with_vars, self_ty.value.clone()),
850 let substs = super::infer::unify(db, env, &tys)?;
851 // We only want the substs for the vars we added, not the ones from self_ty.
852 // Also, if any of the vars we added are still in there, we replace them by
853 // Unknown. I think this can only really happen if self_ty contained
854 // Unknown, and in that case we want the result to contain Unknown in those
857 Substitution::from_iter(&Interner, substs.iter(&Interner).cloned().skip(self_ty_vars));
858 Some(fallback_bound_vars(suffix, self_ty_vars))
861 /// This replaces any 'free' Bound vars in `s` (i.e. those with indices past
862 /// num_vars_to_keep) by `TyKind::Unknown`.
863 fn fallback_bound_vars(s: Substitution, num_vars_to_keep: usize) -> Substitution {
864 crate::fold_free_vars(s, |bound, binders| {
865 if bound.index >= num_vars_to_keep && bound.debruijn == DebruijnIndex::INNERMOST {
866 TyKind::Error.intern(&Interner)
868 bound.shifted_in_from(binders).to_ty(&Interner)
873 fn transform_receiver_ty(
874 db: &dyn HirDatabase,
875 env: Arc<TraitEnvironment>,
876 function_id: FunctionId,
877 self_ty: &Canonical<Ty>,
879 let substs = match function_id.lookup(db.upcast()).container {
880 AssocContainerId::TraitId(_) => TyBuilder::subst_for_def(db, function_id)
881 .push(self_ty.value.clone())
884 AssocContainerId::ImplId(impl_id) => {
885 let impl_substs = inherent_impl_substs(db, env, impl_id, self_ty)?;
886 TyBuilder::subst_for_def(db, function_id)
887 .use_parent_substs(&impl_substs)
891 AssocContainerId::ModuleId(_) => unreachable!(),
893 let sig = db.callable_item_signature(function_id.into());
894 Some(sig.map(|s| s.params()[0].clone()).substitute(&Interner, &substs))
897 pub fn implements_trait(
899 db: &dyn HirDatabase,
900 env: Arc<TraitEnvironment>,
904 let goal = generic_implements_goal(db, env, trait_, ty.clone());
905 let solution = db.trait_solve(krate, goal.cast(&Interner));
910 pub fn implements_trait_unique(
912 db: &dyn HirDatabase,
913 env: Arc<TraitEnvironment>,
917 let goal = generic_implements_goal(db, env, trait_, ty.clone());
918 let solution = db.trait_solve(krate, goal.cast(&Interner));
920 matches!(solution, Some(crate::Solution::Unique(_)))
923 /// This creates Substs for a trait with the given Self type and type variables
924 /// for all other parameters, to query Chalk with it.
925 fn generic_implements_goal(
926 db: &dyn HirDatabase,
927 env: Arc<TraitEnvironment>,
929 self_ty: Canonical<Ty>,
930 ) -> Canonical<InEnvironment<super::DomainGoal>> {
931 let mut kinds = self_ty.binders.interned().to_vec();
932 let trait_ref = TyBuilder::trait_ref(db, trait_)
934 .fill_with_bound_vars(DebruijnIndex::INNERMOST, kinds.len())
937 iter::repeat(chalk_ir::WithKind::new(
938 chalk_ir::VariableKind::Ty(chalk_ir::TyVariableKind::General),
941 .take(trait_ref.substitution.len(&Interner) - 1),
943 let obligation = trait_ref.cast(&Interner);
945 binders: CanonicalVarKinds::from_iter(&Interner, kinds),
946 value: InEnvironment::new(&env.env, obligation),
950 fn autoderef_method_receiver(
951 db: &dyn HirDatabase,
953 ty: InEnvironment<Canonical<Ty>>,
954 ) -> Vec<Canonical<Ty>> {
955 let mut deref_chain: Vec<_> = autoderef::autoderef(db, Some(krate), ty).collect();
956 // As a last step, we can do array unsizing (that's the only unsizing that rustc does for method receivers!)
957 if let Some(TyKind::Array(parameters, _)) =
958 deref_chain.last().map(|ty| ty.value.kind(&Interner))
960 let kinds = deref_chain.last().unwrap().binders.clone();
961 let unsized_ty = TyKind::Slice(parameters.clone()).intern(&Interner);
962 deref_chain.push(Canonical { value: unsized_ty, binders: kinds })