1 //! Methods for lowering the HIR to types. There are two main cases here:
3 //! - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
4 //! type: The entry point for this is `Ty::from_hir`.
5 //! - Building the type for an item: This happens through the `type_for_def` query.
7 //! This usually involves resolving names, collecting generic arguments etc.
8 use std::{iter, sync::Arc};
11 use chalk_ir::{cast::Cast, Mutability, Safety};
14 builtin_type::BuiltinType,
15 generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
16 path::{GenericArg, Path, PathSegment, PathSegments},
17 resolver::{HasResolver, Resolver, TypeNs},
18 type_ref::{TypeBound, TypeRef},
19 AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
20 GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
21 TypeAliasId, TypeParamId, UnionId, VariantId,
23 use hir_expand::name::Name;
24 use la_arena::ArenaMap;
25 use smallvec::SmallVec;
30 to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
31 traits::chalk::{Interner, ToChalk},
33 all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
36 AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, FnPointer, FnSig,
37 GenericPredicate, ImplTraitId, OpaqueTy, PolyFnSig, ProjectionTy, ReturnTypeImplTrait,
38 ReturnTypeImplTraits, Substitution, TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk,
42 pub struct TyLoweringContext<'a> {
43 pub db: &'a dyn HirDatabase,
44 pub resolver: &'a Resolver,
45 in_binders: DebruijnIndex,
46 /// Note: Conceptually, it's thinkable that we could be in a location where
47 /// some type params should be represented as placeholders, and others
48 /// should be converted to variables. I think in practice, this isn't
49 /// possible currently, so this should be fine for now.
50 pub type_param_mode: TypeParamLoweringMode,
51 pub impl_trait_mode: ImplTraitLoweringMode,
52 impl_trait_counter: std::cell::Cell<u16>,
53 /// When turning `impl Trait` into opaque types, we have to collect the
54 /// bounds at the same time to get the IDs correct (without becoming too
55 /// complicated). I don't like using interior mutability (as for the
56 /// counter), but I've tried and failed to make the lifetimes work for
57 /// passing around a `&mut TyLoweringContext`. The core problem is that
58 /// we're grouping the mutable data (the counter and this field) together
59 /// with the immutable context (the references to the DB and resolver).
60 /// Splitting this up would be a possible fix.
61 opaque_type_data: std::cell::RefCell<Vec<ReturnTypeImplTrait>>,
64 impl<'a> TyLoweringContext<'a> {
65 pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
66 let impl_trait_counter = std::cell::Cell::new(0);
67 let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
68 let type_param_mode = TypeParamLoweringMode::Placeholder;
69 let in_binders = DebruijnIndex::INNERMOST;
70 let opaque_type_data = std::cell::RefCell::new(Vec::new());
82 pub fn with_debruijn<T>(
84 debruijn: DebruijnIndex,
85 f: impl FnOnce(&TyLoweringContext) -> T,
87 let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
90 impl_trait_counter: std::cell::Cell::new(self.impl_trait_counter.get()),
91 opaque_type_data: std::cell::RefCell::new(opaque_ty_data_vec),
94 let result = f(&new_ctx);
95 self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
96 self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
100 pub fn with_shifted_in<T>(
102 debruijn: DebruijnIndex,
103 f: impl FnOnce(&TyLoweringContext) -> T,
105 self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
108 pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
109 Self { impl_trait_mode, ..self }
112 pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
113 Self { type_param_mode, ..self }
117 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
118 pub enum ImplTraitLoweringMode {
119 /// `impl Trait` gets lowered into an opaque type that doesn't unify with
120 /// anything except itself. This is used in places where values flow 'out',
121 /// i.e. for arguments of the function we're currently checking, and return
122 /// types of functions we're calling.
124 /// `impl Trait` gets lowered into a type variable. Used for argument
125 /// position impl Trait when inside the respective function, since it allows
126 /// us to support that without Chalk.
128 /// `impl Trait` gets lowered into a variable that can unify with some
129 /// type. This is used in places where values flow 'in', i.e. for arguments
130 /// of functions we're calling, and the return type of the function we're
131 /// currently checking.
133 /// `impl Trait` is disallowed and will be an error.
137 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
138 pub enum TypeParamLoweringMode {
143 impl<'a> TyLoweringContext<'a> {
144 pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
145 self.lower_ty_ext(type_ref).0
148 fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
150 let ty = match type_ref {
151 TypeRef::Never => TyKind::Never.intern(&Interner),
152 TypeRef::Tuple(inner) => {
153 let inner_tys = inner.iter().map(|tr| self.lower_ty(tr));
154 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
157 TypeRef::Path(path) => {
158 let (ty, res_) = self.lower_path(path);
162 TypeRef::RawPtr(inner, mutability) => {
163 let inner_ty = self.lower_ty(inner);
164 TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
166 TypeRef::Array(inner) => {
167 let inner_ty = self.lower_ty(inner);
168 TyKind::Array(inner_ty).intern(&Interner)
170 TypeRef::Slice(inner) => {
171 let inner_ty = self.lower_ty(inner);
172 TyKind::Slice(inner_ty).intern(&Interner)
174 TypeRef::Reference(inner, _, mutability) => {
175 let inner_ty = self.lower_ty(inner);
176 TyKind::Ref(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
178 TypeRef::Placeholder => TyKind::Unknown.intern(&Interner),
179 TypeRef::Fn(params, is_varargs) => {
180 let substs = Substitution(params.iter().map(|tr| self.lower_ty(tr)).collect());
181 TyKind::Function(FnPointer {
182 num_args: substs.len() - 1,
183 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
188 TypeRef::DynTrait(bounds) => {
190 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
191 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
192 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
194 TyKind::Dyn(predicates).intern(&Interner)
196 TypeRef::ImplTrait(bounds) => {
197 match self.impl_trait_mode {
198 ImplTraitLoweringMode::Opaque => {
199 let idx = self.impl_trait_counter.get();
200 self.impl_trait_counter.set(idx + 1);
202 assert!(idx as usize == self.opaque_type_data.borrow().len());
203 // this dance is to make sure the data is in the right
204 // place even if we encounter more opaque types while
205 // lowering the bounds
206 self.opaque_type_data
208 .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
209 // We don't want to lower the bounds inside the binders
210 // we're currently in, because they don't end up inside
211 // those binders. E.g. when we have `impl Trait<impl
212 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
213 // to the self parameter from `impl Trait`, and the
214 // bounds aren't actually stored nested within each
215 // other, but separately. So if the `T` refers to a type
216 // parameter of the outer function, it's just one binder
217 // away instead of two.
218 let actual_opaque_type_data = self
219 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
220 ctx.lower_impl_trait(&bounds)
222 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
224 let func = match self.resolver.generic_def() {
225 Some(GenericDefId::FunctionId(f)) => f,
226 _ => panic!("opaque impl trait lowering in non-function"),
228 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
229 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
230 let generics = generics(self.db.upcast(), func.into());
231 let parameters = Substitution::bound_vars(&generics, self.in_binders);
232 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
234 substitution: parameters,
238 ImplTraitLoweringMode::Param => {
239 let idx = self.impl_trait_counter.get();
240 // FIXME we're probably doing something wrong here
241 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
242 if let Some(def) = self.resolver.generic_def() {
243 let generics = generics(self.db.upcast(), def);
246 .filter(|(_, data)| {
247 data.provenance == TypeParamProvenance::ArgumentImplTrait
250 .map_or(TyKind::Unknown, |(id, _)| {
251 TyKind::Placeholder(to_placeholder_idx(self.db, id))
253 param.intern(&Interner)
255 TyKind::Unknown.intern(&Interner)
258 ImplTraitLoweringMode::Variable => {
259 let idx = self.impl_trait_counter.get();
260 // FIXME we're probably doing something wrong here
261 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
262 let (parent_params, self_params, list_params, _impl_trait_params) =
263 if let Some(def) = self.resolver.generic_def() {
264 let generics = generics(self.db.upcast(), def);
265 generics.provenance_split()
269 TyKind::BoundVar(BoundVar::new(
271 idx as usize + parent_params + self_params + list_params,
275 ImplTraitLoweringMode::Disallowed => {
276 // FIXME: report error
277 TyKind::Unknown.intern(&Interner)
281 TypeRef::Error => TyKind::Unknown.intern(&Interner),
286 /// This is only for `generic_predicates_for_param`, where we can't just
287 /// lower the self types of the predicates since that could lead to cycles.
288 /// So we just check here if the `type_ref` resolves to a generic param, and which.
289 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
290 let path = match type_ref {
291 TypeRef::Path(path) => path,
294 if path.type_anchor().is_some() {
297 if path.segments().len() > 1 {
301 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
302 Some((it, None)) => it,
305 if let TypeNs::GenericParam(param_id) = resolution {
312 pub(crate) fn lower_ty_relative_path(
315 // We need the original resolution to lower `Self::AssocTy` correctly
317 remaining_segments: PathSegments<'_>,
318 ) -> (Ty, Option<TypeNs>) {
319 if remaining_segments.len() == 1 {
320 // resolve unselected assoc types
321 let segment = remaining_segments.first().unwrap();
322 (self.select_associated_type(res, segment), None)
323 } else if remaining_segments.len() > 1 {
324 // FIXME report error (ambiguous associated type)
325 (TyKind::Unknown.intern(&Interner), None)
331 pub(crate) fn lower_partly_resolved_path(
334 resolved_segment: PathSegment<'_>,
335 remaining_segments: PathSegments<'_>,
337 ) -> (Ty, Option<TypeNs>) {
338 let ty = match resolution {
339 TypeNs::TraitId(trait_) => {
340 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
341 let self_ty = if remaining_segments.len() == 0 {
343 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
350 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
351 let ty = if remaining_segments.len() == 1 {
352 let segment = remaining_segments.first().unwrap();
353 let found = associated_type_by_name_including_super_traits(
359 Some((super_trait_ref, associated_ty)) => {
360 // FIXME handle type parameters on the segment
361 TyKind::Alias(AliasTy::Projection(ProjectionTy {
362 associated_ty_id: to_assoc_type_id(associated_ty),
363 substitution: super_trait_ref.substitution,
368 // FIXME: report error (associated type not found)
369 TyKind::Unknown.intern(&Interner)
372 } else if remaining_segments.len() > 1 {
373 // FIXME report error (ambiguous associated type)
374 TyKind::Unknown.intern(&Interner)
376 TyKind::Dyn(Arc::new([GenericPredicate::Implemented(trait_ref)]))
381 TypeNs::GenericParam(param_id) => {
382 let generics = generics(
384 self.resolver.generic_def().expect("generics in scope"),
386 match self.type_param_mode {
387 TypeParamLoweringMode::Placeholder => {
388 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
390 TypeParamLoweringMode::Variable => {
391 let idx = generics.param_idx(param_id).expect("matching generics");
392 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
397 TypeNs::SelfType(impl_id) => {
398 let generics = generics(self.db.upcast(), impl_id.into());
399 let substs = match self.type_param_mode {
400 TypeParamLoweringMode::Placeholder => {
401 Substitution::type_params_for_generics(self.db, &generics)
403 TypeParamLoweringMode::Variable => {
404 Substitution::bound_vars(&generics, self.in_binders)
407 self.db.impl_self_ty(impl_id).subst(&substs)
409 TypeNs::AdtSelfType(adt) => {
410 let generics = generics(self.db.upcast(), adt.into());
411 let substs = match self.type_param_mode {
412 TypeParamLoweringMode::Placeholder => {
413 Substitution::type_params_for_generics(self.db, &generics)
415 TypeParamLoweringMode::Variable => {
416 Substitution::bound_vars(&generics, self.in_binders)
419 self.db.ty(adt.into()).subst(&substs)
422 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
423 TypeNs::BuiltinType(it) => {
424 self.lower_path_inner(resolved_segment, it.into(), infer_args)
426 TypeNs::TypeAliasId(it) => {
427 self.lower_path_inner(resolved_segment, it.into(), infer_args)
429 // FIXME: report error
430 TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
432 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
435 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
436 // Resolve the path (in type namespace)
437 if let Some(type_ref) = path.type_anchor() {
438 let (ty, res) = self.lower_ty_ext(&type_ref);
439 return self.lower_ty_relative_path(ty, res, path.segments());
441 let (resolution, remaining_index) =
442 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
444 None => return (TyKind::Unknown.intern(&Interner), None),
446 let (resolved_segment, remaining_segments) = match remaining_index {
448 path.segments().last().expect("resolved path has at least one element"),
451 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
453 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
456 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
457 if let Some(res) = res {
458 let ty = associated_type_shorthand_candidates(
461 move |name, t, associated_ty| {
462 if name == segment.name {
463 let substs = match self.type_param_mode {
464 TypeParamLoweringMode::Placeholder => {
465 // if we're lowering to placeholders, we have to put
467 let s = Substitution::type_params(
469 self.resolver.generic_def().expect(
470 "there should be generics if there's a generic param",
473 t.substitution.clone().subst_bound_vars(&s)
475 TypeParamLoweringMode::Variable => t.substitution.clone(),
477 // We need to shift in the bound vars, since
478 // associated_type_shorthand_candidates does not do that
479 let substs = substs.shift_bound_vars(self.in_binders);
480 // FIXME handle type parameters on the segment
482 TyKind::Alias(AliasTy::Projection(ProjectionTy {
483 associated_ty_id: to_assoc_type_id(associated_ty),
484 substitution: substs,
494 ty.unwrap_or(TyKind::Unknown.intern(&Interner))
496 TyKind::Unknown.intern(&Interner)
502 segment: PathSegment<'_>,
506 let generic_def = match typeable {
507 TyDefId::BuiltinType(_) => None,
508 TyDefId::AdtId(it) => Some(it.into()),
509 TyDefId::TypeAliasId(it) => Some(it.into()),
511 let substs = self.substs_from_path_segment(segment, generic_def, infer_args);
512 self.db.ty(typeable).subst(&substs)
515 /// Collect generic arguments from a path into a `Substs`. See also
516 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
517 pub(super) fn substs_from_path(
520 // Note that we don't call `db.value_type(resolved)` here,
521 // `ValueTyDefId` is just a convenient way to pass generics and
522 // special-case enum variants
523 resolved: ValueTyDefId,
526 let last = path.segments().last().expect("path should have at least one segment");
527 let (segment, generic_def) = match resolved {
528 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
529 ValueTyDefId::StructId(it) => (last, Some(it.into())),
530 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
531 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
532 ValueTyDefId::StaticId(_) => (last, None),
533 ValueTyDefId::EnumVariantId(var) => {
534 // the generic args for an enum variant may be either specified
535 // on the segment referring to the enum, or on the segment
536 // referring to the variant. So `Option::<T>::None` and
537 // `Option::None::<T>` are both allowed (though the former is
538 // preferred). See also `def_ids_for_path_segments` in rustc.
539 let len = path.segments().len();
540 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
541 let segment = match penultimate {
542 Some(segment) if segment.args_and_bindings.is_some() => segment,
545 (segment, Some(var.parent.into()))
548 self.substs_from_path_segment(segment, generic_def, infer_args)
551 fn substs_from_path_segment(
553 segment: PathSegment<'_>,
554 def_generic: Option<GenericDefId>,
557 let mut substs = Vec::new();
558 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
560 let (parent_params, self_params, type_params, impl_trait_params) =
561 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
562 let total_len = parent_params + self_params + type_params + impl_trait_params;
564 substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
566 let mut had_explicit_type_args = false;
568 if let Some(generic_args) = &segment.args_and_bindings {
569 if !generic_args.has_self_type {
570 substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(self_params));
573 if generic_args.has_self_type { self_params + type_params } else { type_params };
574 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
575 // if args are provided, it should be all of them, but we can't rely on that
576 for arg in generic_args
579 .filter(|arg| matches!(arg, GenericArg::Type(_)))
584 GenericArg::Type(type_ref) => {
585 had_explicit_type_args = true;
586 let ty = self.lower_ty(type_ref);
589 GenericArg::Lifetime(_) => {}
594 // handle defaults. In expression or pattern path segments without
595 // explicitly specified type arguments, missing type arguments are inferred
596 // (i.e. defaults aren't used).
597 if !infer_args || had_explicit_type_args {
598 if let Some(def_generic) = def_generic {
599 let defaults = self.db.generic_defaults(def_generic);
600 assert_eq!(total_len, defaults.len());
602 for default_ty in defaults.iter().skip(substs.len()) {
603 // each default can depend on the previous parameters
604 let substs_so_far = Substitution(substs.clone().into());
605 substs.push(default_ty.clone().subst(&substs_so_far));
610 // add placeholders for args that were not provided
611 // FIXME: emit diagnostics in contexts where this is not allowed
612 for _ in substs.len()..total_len {
613 substs.push(TyKind::Unknown.intern(&Interner));
615 assert_eq!(substs.len(), total_len);
617 Substitution(substs.into())
620 fn lower_trait_ref_from_path(
623 explicit_self_ty: Option<Ty>,
624 ) -> Option<TraitRef> {
626 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
627 TypeNs::TraitId(tr) => tr,
630 let segment = path.segments().last().expect("path should have at least one segment");
631 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
634 pub(crate) fn lower_trait_ref_from_resolved_path(
637 segment: PathSegment<'_>,
638 explicit_self_ty: Option<Ty>,
640 let mut substs = self.trait_ref_substs_from_path(segment, resolved);
641 if let Some(self_ty) = explicit_self_ty {
642 substs.0[0] = self_ty;
644 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
650 explicit_self_ty: Option<Ty>,
651 ) -> Option<TraitRef> {
652 let path = match type_ref {
653 TypeRef::Path(path) => path,
656 self.lower_trait_ref_from_path(path, explicit_self_ty)
659 fn trait_ref_substs_from_path(
661 segment: PathSegment<'_>,
664 self.substs_from_path_segment(segment, Some(resolved.into()), false)
667 pub(crate) fn lower_where_predicate(
669 where_predicate: &'a WherePredicate,
670 ) -> impl Iterator<Item = GenericPredicate> + 'a {
671 match where_predicate {
672 WherePredicate::ForLifetime { target, bound, .. }
673 | WherePredicate::TypeBound { target, bound } => {
674 let self_ty = match target {
675 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
676 WherePredicateTypeTarget::TypeParam(param_id) => {
677 let generic_def = self.resolver.generic_def().expect("generics in scope");
678 let generics = generics(self.db.upcast(), generic_def);
680 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
681 let placeholder = to_placeholder_idx(self.db, param_id);
682 match self.type_param_mode {
683 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
684 TypeParamLoweringMode::Variable => {
685 let idx = generics.param_idx(param_id).expect("matching generics");
686 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
692 self.lower_type_bound(bound, self_ty).collect::<Vec<_>>().into_iter()
694 WherePredicate::Lifetime { .. } => vec![].into_iter(),
698 pub(crate) fn lower_type_bound(
700 bound: &'a TypeBound,
702 ) -> impl Iterator<Item = GenericPredicate> + 'a {
703 let mut bindings = None;
704 let trait_ref = match bound {
705 TypeBound::Path(path) => {
706 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
708 bindings.clone().map_or(GenericPredicate::Error, GenericPredicate::Implemented),
711 TypeBound::Lifetime(_) => None,
712 TypeBound::Error => Some(GenericPredicate::Error),
714 trait_ref.into_iter().chain(
717 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
721 fn assoc_type_bindings_from_type_bound(
723 bound: &'a TypeBound,
725 ) -> impl Iterator<Item = GenericPredicate> + 'a {
726 let last_segment = match bound {
727 TypeBound::Path(path) => path.segments().last(),
728 TypeBound::Error | TypeBound::Lifetime(_) => None,
732 .flat_map(|segment| segment.args_and_bindings.into_iter())
733 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
734 .flat_map(move |binding| {
735 let found = associated_type_by_name_including_super_traits(
740 let (super_trait_ref, associated_ty) = match found {
741 None => return SmallVec::<[GenericPredicate; 1]>::new(),
744 let projection_ty = ProjectionTy {
745 associated_ty_id: to_assoc_type_id(associated_ty),
746 substitution: super_trait_ref.substitution,
748 let mut preds = SmallVec::with_capacity(
749 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
751 if let Some(type_ref) = &binding.type_ref {
752 let ty = self.lower_ty(type_ref);
754 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
755 preds.push(GenericPredicate::AliasEq(alias_eq));
757 for bound in &binding.bounds {
758 preds.extend(self.lower_type_bound(
760 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
767 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
768 cov_mark::hit!(lower_rpit);
770 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
771 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
772 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone())).collect()
774 ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
778 fn count_impl_traits(type_ref: &TypeRef) -> usize {
780 type_ref.walk(&mut |type_ref| {
781 if matches!(type_ref, TypeRef::ImplTrait(_)) {
788 /// Build the signature of a callable item (function, struct or enum variant).
789 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
791 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
792 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
793 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
797 pub fn associated_type_shorthand_candidates<R>(
798 db: &dyn HirDatabase,
800 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
802 let traits_from_env: Vec<_> = match res {
803 TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
805 Some(trait_ref) => vec![trait_ref.value],
807 TypeNs::GenericParam(param_id) => {
808 let predicates = db.generic_predicates_for_param(param_id);
809 let mut traits_: Vec<_> = predicates
811 .filter_map(|pred| match &pred.value {
812 GenericPredicate::Implemented(tr) => Some(tr.clone()),
816 // Handle `Self::Type` referring to own associated type in trait definitions
817 if let GenericDefId::TraitId(trait_id) = param_id.parent {
818 let generics = generics(db.upcast(), trait_id.into());
819 if generics.params.types[param_id.local_id].provenance
820 == TypeParamProvenance::TraitSelf
822 let trait_ref = TraitRef {
823 trait_id: to_chalk_trait_id(trait_id),
824 substitution: Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST),
826 traits_.push(trait_ref);
834 for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
835 let data = db.trait_data(t.hir_trait_id());
837 for (name, assoc_id) in &data.items {
839 AssocItemId::TypeAliasId(alias) => {
840 if let Some(result) = cb(name, &t, *alias) {
844 AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
852 /// Build the type of all specific fields of a struct or enum variant.
853 pub(crate) fn field_types_query(
854 db: &dyn HirDatabase,
855 variant_id: VariantId,
856 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
857 let var_data = variant_data(db.upcast(), variant_id);
858 let (resolver, def): (_, GenericDefId) = match variant_id {
859 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
860 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
861 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
863 let generics = generics(db.upcast(), def);
864 let mut res = ArenaMap::default();
866 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
867 for (field_id, field_data) in var_data.fields().iter() {
868 res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
873 /// This query exists only to be used when resolving short-hand associated types
876 /// See the analogous query in rustc and its comment:
877 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
878 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
879 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
880 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
881 pub(crate) fn generic_predicates_for_param_query(
882 db: &dyn HirDatabase,
883 param_id: TypeParamId,
884 ) -> Arc<[Binders<GenericPredicate>]> {
885 let resolver = param_id.parent.resolver(db.upcast());
887 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
888 let generics = generics(db.upcast(), param_id.parent);
890 .where_predicates_in_scope()
891 // we have to filter out all other predicates *first*, before attempting to lower them
892 .filter(|pred| match pred {
893 WherePredicate::ForLifetime { target, .. }
894 | WherePredicate::TypeBound { target, .. } => match target {
895 WherePredicateTypeTarget::TypeRef(type_ref) => {
896 ctx.lower_ty_only_param(type_ref) == Some(param_id)
898 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
900 WherePredicate::Lifetime { .. } => false,
902 .flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
906 pub(crate) fn generic_predicates_for_param_recover(
907 _db: &dyn HirDatabase,
909 _param_id: &TypeParamId,
910 ) -> Arc<[Binders<GenericPredicate>]> {
914 pub(crate) fn trait_environment_query(
915 db: &dyn HirDatabase,
917 ) -> Arc<TraitEnvironment> {
918 let resolver = def.resolver(db.upcast());
919 let ctx = TyLoweringContext::new(db, &resolver)
920 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
921 let mut traits_in_scope = Vec::new();
922 let mut clauses = Vec::new();
923 for pred in resolver.where_predicates_in_scope() {
924 for pred in ctx.lower_where_predicate(pred) {
928 if let GenericPredicate::Implemented(tr) = &pred {
929 traits_in_scope.push((tr.self_type_parameter().clone(), tr.hir_trait_id()));
931 let program_clause: chalk_ir::ProgramClause<Interner> =
932 pred.clone().to_chalk(db).cast(&Interner);
933 clauses.push(program_clause.into_from_env_clause(&Interner));
937 let container: Option<AssocContainerId> = match def {
938 // FIXME: is there a function for this?
939 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
940 GenericDefId::AdtId(_) => None,
941 GenericDefId::TraitId(_) => None,
942 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
943 GenericDefId::ImplId(_) => None,
944 GenericDefId::EnumVariantId(_) => None,
945 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
947 if let Some(AssocContainerId::TraitId(trait_id)) = container {
948 // add `Self: Trait<T1, T2, ...>` to the environment in trait
949 // function default implementations (and hypothetical code
950 // inside consts or type aliases)
951 cov_mark::hit!(trait_self_implements_self);
952 let substs = Substitution::type_params(db, trait_id);
953 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
954 let pred = GenericPredicate::Implemented(trait_ref);
955 let program_clause: chalk_ir::ProgramClause<Interner> =
956 pred.clone().to_chalk(db).cast(&Interner);
957 clauses.push(program_clause.into_from_env_clause(&Interner));
960 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
962 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
965 /// Resolve the where clause(s) of an item with generics.
966 pub(crate) fn generic_predicates_query(
967 db: &dyn HirDatabase,
969 ) -> Arc<[Binders<GenericPredicate>]> {
970 let resolver = def.resolver(db.upcast());
972 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
973 let generics = generics(db.upcast(), def);
975 .where_predicates_in_scope()
976 .flat_map(|pred| ctx.lower_where_predicate(pred).map(|p| Binders::new(generics.len(), p)))
980 /// Resolve the default type params from generics
981 pub(crate) fn generic_defaults_query(
982 db: &dyn HirDatabase,
984 ) -> Arc<[Binders<Ty>]> {
985 let resolver = def.resolver(db.upcast());
987 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
988 let generic_params = generics(db.upcast(), def);
990 let defaults = generic_params
993 .map(|(idx, (_, p))| {
995 p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
997 // Each default can only refer to previous parameters.
999 &mut |ty, binders| match ty.interned_mut() {
1000 TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
1002 // type variable default referring to parameter coming
1003 // after it. This is forbidden (FIXME: report
1005 *ty = TyKind::Unknown.intern(&Interner);
1010 DebruijnIndex::INNERMOST,
1013 Binders::new(idx, ty)
1020 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1021 let data = db.function_data(def);
1022 let resolver = def.resolver(db.upcast());
1023 let ctx_params = TyLoweringContext::new(db, &resolver)
1024 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1025 .with_type_param_mode(TypeParamLoweringMode::Variable);
1026 let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
1027 let ctx_ret = TyLoweringContext::new(db, &resolver)
1028 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1029 .with_type_param_mode(TypeParamLoweringMode::Variable);
1030 let ret = (&ctx_ret).lower_ty(&data.ret_type);
1031 let generics = generics(db.upcast(), def.into());
1032 let num_binders = generics.len();
1033 Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
1036 /// Build the declared type of a function. This should not need to look at the
1038 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1039 let generics = generics(db.upcast(), def.into());
1040 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1043 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1047 /// Build the declared type of a const.
1048 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1049 let data = db.const_data(def);
1050 let generics = generics(db.upcast(), def.into());
1051 let resolver = def.resolver(db.upcast());
1053 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1055 Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
1058 /// Build the declared type of a static.
1059 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1060 let data = db.static_data(def);
1061 let resolver = def.resolver(db.upcast());
1062 let ctx = TyLoweringContext::new(db, &resolver);
1064 Binders::new(0, ctx.lower_ty(&data.type_ref))
1067 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1068 let struct_data = db.struct_data(def);
1069 let fields = struct_data.variant_data.fields();
1070 let resolver = def.resolver(db.upcast());
1072 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1073 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1074 let ret = type_for_adt(db, def.into());
1075 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1078 /// Build the type of a tuple struct constructor.
1079 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1080 let struct_data = db.struct_data(def);
1081 if let StructKind::Unit = struct_data.variant_data.kind() {
1082 return type_for_adt(db, def.into());
1084 let generics = generics(db.upcast(), def.into());
1085 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1088 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1092 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1093 let enum_data = db.enum_data(def.parent);
1094 let var_data = &enum_data.variants[def.local_id];
1095 let fields = var_data.variant_data.fields();
1096 let resolver = def.parent.resolver(db.upcast());
1098 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1099 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1100 let ret = type_for_adt(db, def.parent.into());
1101 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1104 /// Build the type of a tuple enum variant constructor.
1105 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1106 let enum_data = db.enum_data(def.parent);
1107 let var_data = &enum_data.variants[def.local_id].variant_data;
1108 if let StructKind::Unit = var_data.kind() {
1109 return type_for_adt(db, def.parent.into());
1111 let generics = generics(db.upcast(), def.parent.into());
1112 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1115 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1119 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1120 let generics = generics(db.upcast(), adt.into());
1121 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1122 Binders::new(substs.len(), Ty::adt_ty(adt, substs))
1125 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1126 let generics = generics(db.upcast(), t.into());
1127 let resolver = t.resolver(db.upcast());
1129 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1130 if db.type_alias_data(t).is_extern {
1131 Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
1133 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1134 let type_ref = &db.type_alias_data(t).type_ref;
1135 let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
1136 Binders::new(substs.len(), inner)
1140 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1141 pub enum CallableDefId {
1142 FunctionId(FunctionId),
1144 EnumVariantId(EnumVariantId),
1146 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1148 impl CallableDefId {
1149 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1150 let db = db.upcast();
1152 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1153 CallableDefId::StructId(s) => s.lookup(db).container,
1154 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1160 impl From<CallableDefId> for GenericDefId {
1161 fn from(def: CallableDefId) -> GenericDefId {
1163 CallableDefId::FunctionId(f) => f.into(),
1164 CallableDefId::StructId(s) => s.into(),
1165 CallableDefId::EnumVariantId(e) => e.into(),
1170 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1172 BuiltinType(BuiltinType),
1174 TypeAliasId(TypeAliasId),
1176 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1178 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1179 pub enum ValueTyDefId {
1180 FunctionId(FunctionId),
1183 EnumVariantId(EnumVariantId),
1187 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1189 /// Build the declared type of an item. This depends on the namespace; e.g. for
1190 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1191 /// the constructor function `(usize) -> Foo` which lives in the values
1193 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1195 TyDefId::BuiltinType(it) => Binders::new(0, Ty::builtin(it)),
1196 TyDefId::AdtId(it) => type_for_adt(db, it),
1197 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1201 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1202 let num_binders = match *def {
1203 TyDefId::BuiltinType(_) => 0,
1204 TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
1205 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
1207 Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
1210 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1212 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1213 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1214 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1215 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1216 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1217 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1221 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1222 let impl_data = db.impl_data(impl_id);
1223 let resolver = impl_id.resolver(db.upcast());
1224 let generics = generics(db.upcast(), impl_id.into());
1226 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1227 Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
1230 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1231 let parent_data = db.generic_params(def.parent);
1232 let data = &parent_data.consts[def.local_id];
1233 let resolver = def.parent.resolver(db.upcast());
1234 let ctx = TyLoweringContext::new(db, &resolver);
1236 ctx.lower_ty(&data.ty)
1239 pub(crate) fn impl_self_ty_recover(
1240 db: &dyn HirDatabase,
1244 let generics = generics(db.upcast(), (*impl_id).into());
1245 Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
1248 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1249 let impl_data = db.impl_data(impl_id);
1250 let resolver = impl_id.resolver(db.upcast());
1252 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1253 let self_ty = db.impl_self_ty(impl_id);
1254 let target_trait = impl_data.target_trait.as_ref()?;
1255 Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
1258 pub(crate) fn return_type_impl_traits(
1259 db: &dyn HirDatabase,
1260 def: hir_def::FunctionId,
1261 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1262 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1263 let data = db.function_data(def);
1264 let resolver = def.resolver(db.upcast());
1265 let ctx_ret = TyLoweringContext::new(db, &resolver)
1266 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1267 .with_type_param_mode(TypeParamLoweringMode::Variable);
1268 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1269 let generics = generics(db.upcast(), def.into());
1270 let num_binders = generics.len();
1271 let return_type_impl_traits =
1272 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1273 if return_type_impl_traits.impl_traits.is_empty() {
1276 Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))
1280 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1282 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1283 hir_def::type_ref::Mutability::Mut => Mutability::Mut,