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, ImplTraitId,
37 OpaqueTy, PolyFnSig, ProjectionTy, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
38 TraitEnvironment, TraitRef, Ty, TyKind, TypeWalk, WhereClause,
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| {
194 .flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false))
197 TyKind::Dyn(predicates).intern(&Interner)
199 TypeRef::ImplTrait(bounds) => {
200 match self.impl_trait_mode {
201 ImplTraitLoweringMode::Opaque => {
202 let idx = self.impl_trait_counter.get();
203 self.impl_trait_counter.set(idx + 1);
205 assert!(idx as usize == self.opaque_type_data.borrow().len());
206 // this dance is to make sure the data is in the right
207 // place even if we encounter more opaque types while
208 // lowering the bounds
209 self.opaque_type_data
211 .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
212 // We don't want to lower the bounds inside the binders
213 // we're currently in, because they don't end up inside
214 // those binders. E.g. when we have `impl Trait<impl
215 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
216 // to the self parameter from `impl Trait`, and the
217 // bounds aren't actually stored nested within each
218 // other, but separately. So if the `T` refers to a type
219 // parameter of the outer function, it's just one binder
220 // away instead of two.
221 let actual_opaque_type_data = self
222 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
223 ctx.lower_impl_trait(&bounds)
225 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
227 let func = match self.resolver.generic_def() {
228 Some(GenericDefId::FunctionId(f)) => f,
229 _ => panic!("opaque impl trait lowering in non-function"),
231 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
232 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
233 let generics = generics(self.db.upcast(), func.into());
234 let parameters = Substitution::bound_vars(&generics, self.in_binders);
235 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
237 substitution: parameters,
241 ImplTraitLoweringMode::Param => {
242 let idx = self.impl_trait_counter.get();
243 // FIXME we're probably doing something wrong here
244 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
245 if let Some(def) = self.resolver.generic_def() {
246 let generics = generics(self.db.upcast(), def);
249 .filter(|(_, data)| {
250 data.provenance == TypeParamProvenance::ArgumentImplTrait
253 .map_or(TyKind::Unknown, |(id, _)| {
254 TyKind::Placeholder(to_placeholder_idx(self.db, id))
256 param.intern(&Interner)
258 TyKind::Unknown.intern(&Interner)
261 ImplTraitLoweringMode::Variable => {
262 let idx = self.impl_trait_counter.get();
263 // FIXME we're probably doing something wrong here
264 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
265 let (parent_params, self_params, list_params, _impl_trait_params) =
266 if let Some(def) = self.resolver.generic_def() {
267 let generics = generics(self.db.upcast(), def);
268 generics.provenance_split()
272 TyKind::BoundVar(BoundVar::new(
274 idx as usize + parent_params + self_params + list_params,
278 ImplTraitLoweringMode::Disallowed => {
279 // FIXME: report error
280 TyKind::Unknown.intern(&Interner)
284 TypeRef::Error => TyKind::Unknown.intern(&Interner),
289 /// This is only for `generic_predicates_for_param`, where we can't just
290 /// lower the self types of the predicates since that could lead to cycles.
291 /// So we just check here if the `type_ref` resolves to a generic param, and which.
292 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
293 let path = match type_ref {
294 TypeRef::Path(path) => path,
297 if path.type_anchor().is_some() {
300 if path.segments().len() > 1 {
304 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
305 Some((it, None)) => it,
308 if let TypeNs::GenericParam(param_id) = resolution {
315 pub(crate) fn lower_ty_relative_path(
318 // We need the original resolution to lower `Self::AssocTy` correctly
320 remaining_segments: PathSegments<'_>,
321 ) -> (Ty, Option<TypeNs>) {
322 if remaining_segments.len() == 1 {
323 // resolve unselected assoc types
324 let segment = remaining_segments.first().unwrap();
325 (self.select_associated_type(res, segment), None)
326 } else if remaining_segments.len() > 1 {
327 // FIXME report error (ambiguous associated type)
328 (TyKind::Unknown.intern(&Interner), None)
334 pub(crate) fn lower_partly_resolved_path(
337 resolved_segment: PathSegment<'_>,
338 remaining_segments: PathSegments<'_>,
340 ) -> (Ty, Option<TypeNs>) {
341 let ty = match resolution {
342 TypeNs::TraitId(trait_) => {
343 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
344 let self_ty = if remaining_segments.len() == 0 {
346 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
353 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
354 let ty = if remaining_segments.len() == 1 {
355 let segment = remaining_segments.first().unwrap();
356 let found = associated_type_by_name_including_super_traits(
362 Some((super_trait_ref, associated_ty)) => {
363 // FIXME handle type parameters on the segment
364 TyKind::Alias(AliasTy::Projection(ProjectionTy {
365 associated_ty_id: to_assoc_type_id(associated_ty),
366 substitution: super_trait_ref.substitution,
371 // FIXME: report error (associated type not found)
372 TyKind::Unknown.intern(&Interner)
375 } else if remaining_segments.len() > 1 {
376 // FIXME report error (ambiguous associated type)
377 TyKind::Unknown.intern(&Interner)
379 TyKind::Dyn(Arc::new([WhereClause::Implemented(trait_ref)])).intern(&Interner)
383 TypeNs::GenericParam(param_id) => {
384 let generics = generics(
386 self.resolver.generic_def().expect("generics in scope"),
388 match self.type_param_mode {
389 TypeParamLoweringMode::Placeholder => {
390 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
392 TypeParamLoweringMode::Variable => {
393 let idx = generics.param_idx(param_id).expect("matching generics");
394 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
399 TypeNs::SelfType(impl_id) => {
400 let generics = generics(self.db.upcast(), impl_id.into());
401 let substs = match self.type_param_mode {
402 TypeParamLoweringMode::Placeholder => {
403 Substitution::type_params_for_generics(self.db, &generics)
405 TypeParamLoweringMode::Variable => {
406 Substitution::bound_vars(&generics, self.in_binders)
409 self.db.impl_self_ty(impl_id).subst(&substs)
411 TypeNs::AdtSelfType(adt) => {
412 let generics = generics(self.db.upcast(), adt.into());
413 let substs = match self.type_param_mode {
414 TypeParamLoweringMode::Placeholder => {
415 Substitution::type_params_for_generics(self.db, &generics)
417 TypeParamLoweringMode::Variable => {
418 Substitution::bound_vars(&generics, self.in_binders)
421 self.db.ty(adt.into()).subst(&substs)
424 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
425 TypeNs::BuiltinType(it) => {
426 self.lower_path_inner(resolved_segment, it.into(), infer_args)
428 TypeNs::TypeAliasId(it) => {
429 self.lower_path_inner(resolved_segment, it.into(), infer_args)
431 // FIXME: report error
432 TypeNs::EnumVariantId(_) => return (TyKind::Unknown.intern(&Interner), None),
434 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
437 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
438 // Resolve the path (in type namespace)
439 if let Some(type_ref) = path.type_anchor() {
440 let (ty, res) = self.lower_ty_ext(&type_ref);
441 return self.lower_ty_relative_path(ty, res, path.segments());
443 let (resolution, remaining_index) =
444 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
446 None => return (TyKind::Unknown.intern(&Interner), None),
448 let (resolved_segment, remaining_segments) = match remaining_index {
450 path.segments().last().expect("resolved path has at least one element"),
453 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
455 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
458 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
459 if let Some(res) = res {
460 let ty = associated_type_shorthand_candidates(
463 move |name, t, associated_ty| {
464 if name == segment.name {
465 let substs = match self.type_param_mode {
466 TypeParamLoweringMode::Placeholder => {
467 // if we're lowering to placeholders, we have to put
469 let s = Substitution::type_params(
471 self.resolver.generic_def().expect(
472 "there should be generics if there's a generic param",
475 t.substitution.clone().subst_bound_vars(&s)
477 TypeParamLoweringMode::Variable => t.substitution.clone(),
479 // We need to shift in the bound vars, since
480 // associated_type_shorthand_candidates does not do that
481 let substs = substs.shift_bound_vars(self.in_binders);
482 // FIXME handle type parameters on the segment
484 TyKind::Alias(AliasTy::Projection(ProjectionTy {
485 associated_ty_id: to_assoc_type_id(associated_ty),
486 substitution: substs,
496 ty.unwrap_or(TyKind::Unknown.intern(&Interner))
498 TyKind::Unknown.intern(&Interner)
504 segment: PathSegment<'_>,
508 let generic_def = match typeable {
509 TyDefId::BuiltinType(_) => None,
510 TyDefId::AdtId(it) => Some(it.into()),
511 TyDefId::TypeAliasId(it) => Some(it.into()),
513 let substs = self.substs_from_path_segment(segment, generic_def, infer_args);
514 self.db.ty(typeable).subst(&substs)
517 /// Collect generic arguments from a path into a `Substs`. See also
518 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
519 pub(super) fn substs_from_path(
522 // Note that we don't call `db.value_type(resolved)` here,
523 // `ValueTyDefId` is just a convenient way to pass generics and
524 // special-case enum variants
525 resolved: ValueTyDefId,
528 let last = path.segments().last().expect("path should have at least one segment");
529 let (segment, generic_def) = match resolved {
530 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
531 ValueTyDefId::StructId(it) => (last, Some(it.into())),
532 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
533 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
534 ValueTyDefId::StaticId(_) => (last, None),
535 ValueTyDefId::EnumVariantId(var) => {
536 // the generic args for an enum variant may be either specified
537 // on the segment referring to the enum, or on the segment
538 // referring to the variant. So `Option::<T>::None` and
539 // `Option::None::<T>` are both allowed (though the former is
540 // preferred). See also `def_ids_for_path_segments` in rustc.
541 let len = path.segments().len();
542 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
543 let segment = match penultimate {
544 Some(segment) if segment.args_and_bindings.is_some() => segment,
547 (segment, Some(var.parent.into()))
550 self.substs_from_path_segment(segment, generic_def, infer_args)
553 fn substs_from_path_segment(
555 segment: PathSegment<'_>,
556 def_generic: Option<GenericDefId>,
559 let mut substs = Vec::new();
560 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
562 let (parent_params, self_params, type_params, impl_trait_params) =
563 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
564 let total_len = parent_params + self_params + type_params + impl_trait_params;
566 substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(parent_params));
568 let mut had_explicit_type_args = false;
570 if let Some(generic_args) = &segment.args_and_bindings {
571 if !generic_args.has_self_type {
572 substs.extend(iter::repeat(TyKind::Unknown.intern(&Interner)).take(self_params));
575 if generic_args.has_self_type { self_params + type_params } else { type_params };
576 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
577 // if args are provided, it should be all of them, but we can't rely on that
578 for arg in generic_args
581 .filter(|arg| matches!(arg, GenericArg::Type(_)))
586 GenericArg::Type(type_ref) => {
587 had_explicit_type_args = true;
588 let ty = self.lower_ty(type_ref);
591 GenericArg::Lifetime(_) => {}
596 // handle defaults. In expression or pattern path segments without
597 // explicitly specified type arguments, missing type arguments are inferred
598 // (i.e. defaults aren't used).
599 if !infer_args || had_explicit_type_args {
600 if let Some(def_generic) = def_generic {
601 let defaults = self.db.generic_defaults(def_generic);
602 assert_eq!(total_len, defaults.len());
604 for default_ty in defaults.iter().skip(substs.len()) {
605 // each default can depend on the previous parameters
606 let substs_so_far = Substitution(substs.clone().into());
607 substs.push(default_ty.clone().subst(&substs_so_far));
612 // add placeholders for args that were not provided
613 // FIXME: emit diagnostics in contexts where this is not allowed
614 for _ in substs.len()..total_len {
615 substs.push(TyKind::Unknown.intern(&Interner));
617 assert_eq!(substs.len(), total_len);
619 Substitution(substs.into())
622 fn lower_trait_ref_from_path(
625 explicit_self_ty: Option<Ty>,
626 ) -> Option<TraitRef> {
628 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
629 TypeNs::TraitId(tr) => tr,
632 let segment = path.segments().last().expect("path should have at least one segment");
633 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
636 pub(crate) fn lower_trait_ref_from_resolved_path(
639 segment: PathSegment<'_>,
640 explicit_self_ty: Option<Ty>,
642 let mut substs = self.trait_ref_substs_from_path(segment, resolved);
643 if let Some(self_ty) = explicit_self_ty {
644 substs.0[0] = self_ty;
646 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
652 explicit_self_ty: Option<Ty>,
653 ) -> Option<TraitRef> {
654 let path = match type_ref {
655 TypeRef::Path(path) => path,
658 self.lower_trait_ref_from_path(path, explicit_self_ty)
661 fn trait_ref_substs_from_path(
663 segment: PathSegment<'_>,
666 self.substs_from_path_segment(segment, Some(resolved.into()), false)
669 pub(crate) fn lower_where_predicate(
671 where_predicate: &'a WherePredicate,
672 ignore_bindings: bool,
673 ) -> impl Iterator<Item = WhereClause> + 'a {
674 match where_predicate {
675 WherePredicate::ForLifetime { target, bound, .. }
676 | WherePredicate::TypeBound { target, bound } => {
677 let self_ty = match target {
678 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
679 WherePredicateTypeTarget::TypeParam(param_id) => {
680 let generic_def = self.resolver.generic_def().expect("generics in scope");
681 let generics = generics(self.db.upcast(), generic_def);
683 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
684 let placeholder = to_placeholder_idx(self.db, param_id);
685 match self.type_param_mode {
686 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
687 TypeParamLoweringMode::Variable => {
688 let idx = generics.param_idx(param_id).expect("matching generics");
689 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
695 self.lower_type_bound(bound, self_ty, ignore_bindings)
699 WherePredicate::Lifetime { .. } => vec![].into_iter(),
703 pub(crate) fn lower_type_bound(
705 bound: &'a TypeBound,
707 ignore_bindings: bool,
708 ) -> impl Iterator<Item = WhereClause> + 'a {
709 let mut bindings = None;
710 let trait_ref = match bound {
711 TypeBound::Path(path) => {
712 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
713 bindings.clone().map(WhereClause::Implemented)
715 TypeBound::Lifetime(_) => None,
716 TypeBound::Error => None,
718 trait_ref.into_iter().chain(
721 .filter(move |_| !ignore_bindings)
722 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
726 fn assoc_type_bindings_from_type_bound(
728 bound: &'a TypeBound,
730 ) -> impl Iterator<Item = WhereClause> + 'a {
731 let last_segment = match bound {
732 TypeBound::Path(path) => path.segments().last(),
733 TypeBound::Error | TypeBound::Lifetime(_) => None,
737 .flat_map(|segment| segment.args_and_bindings.into_iter())
738 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
739 .flat_map(move |binding| {
740 let found = associated_type_by_name_including_super_traits(
745 let (super_trait_ref, associated_ty) = match found {
746 None => return SmallVec::<[WhereClause; 1]>::new(),
749 let projection_ty = ProjectionTy {
750 associated_ty_id: to_assoc_type_id(associated_ty),
751 substitution: super_trait_ref.substitution,
753 let mut preds = SmallVec::with_capacity(
754 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
756 if let Some(type_ref) = &binding.type_ref {
757 let ty = self.lower_ty(type_ref);
759 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
760 preds.push(WhereClause::AliasEq(alias_eq));
762 for bound in &binding.bounds {
763 preds.extend(self.lower_type_bound(
765 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
773 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
774 cov_mark::hit!(lower_rpit);
776 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
777 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
778 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
780 ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
784 fn count_impl_traits(type_ref: &TypeRef) -> usize {
786 type_ref.walk(&mut |type_ref| {
787 if matches!(type_ref, TypeRef::ImplTrait(_)) {
794 /// Build the signature of a callable item (function, struct or enum variant).
795 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
797 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
798 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
799 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
803 pub fn associated_type_shorthand_candidates<R>(
804 db: &dyn HirDatabase,
806 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
808 let traits_from_env: Vec<_> = match res {
809 TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
811 Some(trait_ref) => vec![trait_ref.value],
813 TypeNs::GenericParam(param_id) => {
814 let predicates = db.generic_predicates_for_param(param_id);
815 let mut traits_: Vec<_> = predicates
817 .filter_map(|pred| match &pred.value {
818 WhereClause::Implemented(tr) => Some(tr.clone()),
822 // Handle `Self::Type` referring to own associated type in trait definitions
823 if let GenericDefId::TraitId(trait_id) = param_id.parent {
824 let generics = generics(db.upcast(), trait_id.into());
825 if generics.params.types[param_id.local_id].provenance
826 == TypeParamProvenance::TraitSelf
828 let trait_ref = TraitRef {
829 trait_id: to_chalk_trait_id(trait_id),
830 substitution: Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST),
832 traits_.push(trait_ref);
840 for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
841 let data = db.trait_data(t.hir_trait_id());
843 for (name, assoc_id) in &data.items {
845 AssocItemId::TypeAliasId(alias) => {
846 if let Some(result) = cb(name, &t, *alias) {
850 AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
858 /// Build the type of all specific fields of a struct or enum variant.
859 pub(crate) fn field_types_query(
860 db: &dyn HirDatabase,
861 variant_id: VariantId,
862 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
863 let var_data = variant_data(db.upcast(), variant_id);
864 let (resolver, def): (_, GenericDefId) = match variant_id {
865 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
866 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
867 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
869 let generics = generics(db.upcast(), def);
870 let mut res = ArenaMap::default();
872 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
873 for (field_id, field_data) in var_data.fields().iter() {
874 res.insert(field_id, Binders::new(generics.len(), ctx.lower_ty(&field_data.type_ref)))
879 /// This query exists only to be used when resolving short-hand associated types
882 /// See the analogous query in rustc and its comment:
883 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
884 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
885 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
886 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
887 pub(crate) fn generic_predicates_for_param_query(
888 db: &dyn HirDatabase,
889 param_id: TypeParamId,
890 ) -> Arc<[Binders<WhereClause>]> {
891 let resolver = param_id.parent.resolver(db.upcast());
893 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
894 let generics = generics(db.upcast(), param_id.parent);
896 .where_predicates_in_scope()
897 // we have to filter out all other predicates *first*, before attempting to lower them
898 .filter(|pred| match pred {
899 WherePredicate::ForLifetime { target, .. }
900 | WherePredicate::TypeBound { target, .. } => match target {
901 WherePredicateTypeTarget::TypeRef(type_ref) => {
902 ctx.lower_ty_only_param(type_ref) == Some(param_id)
904 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
906 WherePredicate::Lifetime { .. } => false,
909 ctx.lower_where_predicate(pred, true).map(|p| Binders::new(generics.len(), p))
914 pub(crate) fn generic_predicates_for_param_recover(
915 _db: &dyn HirDatabase,
917 _param_id: &TypeParamId,
918 ) -> Arc<[Binders<WhereClause>]> {
922 pub(crate) fn trait_environment_query(
923 db: &dyn HirDatabase,
925 ) -> Arc<TraitEnvironment> {
926 let resolver = def.resolver(db.upcast());
927 let ctx = TyLoweringContext::new(db, &resolver)
928 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
929 let mut traits_in_scope = Vec::new();
930 let mut clauses = Vec::new();
931 for pred in resolver.where_predicates_in_scope() {
932 for pred in ctx.lower_where_predicate(pred, false) {
933 if let WhereClause::Implemented(tr) = &pred {
934 traits_in_scope.push((tr.self_type_parameter().clone(), tr.hir_trait_id()));
936 let program_clause: chalk_ir::ProgramClause<Interner> =
937 pred.clone().to_chalk(db).cast(&Interner);
938 clauses.push(program_clause.into_from_env_clause(&Interner));
942 let container: Option<AssocContainerId> = match def {
943 // FIXME: is there a function for this?
944 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
945 GenericDefId::AdtId(_) => None,
946 GenericDefId::TraitId(_) => None,
947 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
948 GenericDefId::ImplId(_) => None,
949 GenericDefId::EnumVariantId(_) => None,
950 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
952 if let Some(AssocContainerId::TraitId(trait_id)) = container {
953 // add `Self: Trait<T1, T2, ...>` to the environment in trait
954 // function default implementations (and hypothetical code
955 // inside consts or type aliases)
956 cov_mark::hit!(trait_self_implements_self);
957 let substs = Substitution::type_params(db, trait_id);
958 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
959 let pred = WhereClause::Implemented(trait_ref);
960 let program_clause: chalk_ir::ProgramClause<Interner> = pred.to_chalk(db).cast(&Interner);
961 clauses.push(program_clause.into_from_env_clause(&Interner));
964 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
966 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
969 /// Resolve the where clause(s) of an item with generics.
970 pub(crate) fn generic_predicates_query(
971 db: &dyn HirDatabase,
973 ) -> Arc<[Binders<WhereClause>]> {
974 let resolver = def.resolver(db.upcast());
976 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
977 let generics = generics(db.upcast(), def);
979 .where_predicates_in_scope()
981 ctx.lower_where_predicate(pred, false).map(|p| Binders::new(generics.len(), p))
986 /// Resolve the default type params from generics
987 pub(crate) fn generic_defaults_query(
988 db: &dyn HirDatabase,
990 ) -> Arc<[Binders<Ty>]> {
991 let resolver = def.resolver(db.upcast());
993 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
994 let generic_params = generics(db.upcast(), def);
996 let defaults = generic_params
999 .map(|(idx, (_, p))| {
1001 p.default.as_ref().map_or(TyKind::Unknown.intern(&Interner), |t| ctx.lower_ty(t));
1003 // Each default can only refer to previous parameters.
1004 ty.walk_mut_binders(
1005 &mut |ty, binders| match ty.interned_mut() {
1006 TyKind::BoundVar(BoundVar { debruijn, index }) if *debruijn == binders => {
1008 // type variable default referring to parameter coming
1009 // after it. This is forbidden (FIXME: report
1011 *ty = TyKind::Unknown.intern(&Interner);
1016 DebruijnIndex::INNERMOST,
1019 Binders::new(idx, ty)
1026 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1027 let data = db.function_data(def);
1028 let resolver = def.resolver(db.upcast());
1029 let ctx_params = TyLoweringContext::new(db, &resolver)
1030 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1031 .with_type_param_mode(TypeParamLoweringMode::Variable);
1032 let params = data.params.iter().map(|tr| (&ctx_params).lower_ty(tr)).collect::<Vec<_>>();
1033 let ctx_ret = TyLoweringContext::new(db, &resolver)
1034 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1035 .with_type_param_mode(TypeParamLoweringMode::Variable);
1036 let ret = (&ctx_ret).lower_ty(&data.ret_type);
1037 let generics = generics(db.upcast(), def.into());
1038 let num_binders = generics.len();
1039 Binders::new(num_binders, CallableSig::from_params_and_return(params, ret, data.is_varargs))
1042 /// Build the declared type of a function. This should not need to look at the
1044 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1045 let generics = generics(db.upcast(), def.into());
1046 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1049 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1053 /// Build the declared type of a const.
1054 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1055 let data = db.const_data(def);
1056 let generics = generics(db.upcast(), def.into());
1057 let resolver = def.resolver(db.upcast());
1059 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1061 Binders::new(generics.len(), ctx.lower_ty(&data.type_ref))
1064 /// Build the declared type of a static.
1065 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1066 let data = db.static_data(def);
1067 let resolver = def.resolver(db.upcast());
1068 let ctx = TyLoweringContext::new(db, &resolver);
1070 Binders::new(0, ctx.lower_ty(&data.type_ref))
1073 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1074 let struct_data = db.struct_data(def);
1075 let fields = struct_data.variant_data.fields();
1076 let resolver = def.resolver(db.upcast());
1078 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1079 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1080 let ret = type_for_adt(db, def.into());
1081 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1084 /// Build the type of a tuple struct constructor.
1085 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1086 let struct_data = db.struct_data(def);
1087 if let StructKind::Unit = struct_data.variant_data.kind() {
1088 return type_for_adt(db, def.into());
1090 let generics = generics(db.upcast(), def.into());
1091 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1094 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1098 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1099 let enum_data = db.enum_data(def.parent);
1100 let var_data = &enum_data.variants[def.local_id];
1101 let fields = var_data.variant_data.fields();
1102 let resolver = def.parent.resolver(db.upcast());
1104 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1105 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1106 let ret = type_for_adt(db, def.parent.into());
1107 Binders::new(ret.num_binders, CallableSig::from_params_and_return(params, ret.value, false))
1110 /// Build the type of a tuple enum variant constructor.
1111 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1112 let enum_data = db.enum_data(def.parent);
1113 let var_data = &enum_data.variants[def.local_id].variant_data;
1114 if let StructKind::Unit = var_data.kind() {
1115 return type_for_adt(db, def.parent.into());
1117 let generics = generics(db.upcast(), def.parent.into());
1118 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1121 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1125 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1126 let generics = generics(db.upcast(), adt.into());
1127 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1128 Binders::new(substs.len(), Ty::adt_ty(adt, substs))
1131 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1132 let generics = generics(db.upcast(), t.into());
1133 let resolver = t.resolver(db.upcast());
1135 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1136 if db.type_alias_data(t).is_extern {
1137 Binders::new(0, TyKind::ForeignType(crate::to_foreign_def_id(t)).intern(&Interner))
1139 let substs = Substitution::bound_vars(&generics, DebruijnIndex::INNERMOST);
1140 let type_ref = &db.type_alias_data(t).type_ref;
1141 let inner = ctx.lower_ty(type_ref.as_ref().unwrap_or(&TypeRef::Error));
1142 Binders::new(substs.len(), inner)
1146 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1147 pub enum CallableDefId {
1148 FunctionId(FunctionId),
1150 EnumVariantId(EnumVariantId),
1152 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1154 impl CallableDefId {
1155 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1156 let db = db.upcast();
1158 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1159 CallableDefId::StructId(s) => s.lookup(db).container,
1160 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1166 impl From<CallableDefId> for GenericDefId {
1167 fn from(def: CallableDefId) -> GenericDefId {
1169 CallableDefId::FunctionId(f) => f.into(),
1170 CallableDefId::StructId(s) => s.into(),
1171 CallableDefId::EnumVariantId(e) => e.into(),
1176 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1178 BuiltinType(BuiltinType),
1180 TypeAliasId(TypeAliasId),
1182 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1184 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1185 pub enum ValueTyDefId {
1186 FunctionId(FunctionId),
1189 EnumVariantId(EnumVariantId),
1193 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1195 /// Build the declared type of an item. This depends on the namespace; e.g. for
1196 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1197 /// the constructor function `(usize) -> Foo` which lives in the values
1199 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1201 TyDefId::BuiltinType(it) => Binders::new(0, Ty::builtin(it)),
1202 TyDefId::AdtId(it) => type_for_adt(db, it),
1203 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1207 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1208 let num_binders = match *def {
1209 TyDefId::BuiltinType(_) => 0,
1210 TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
1211 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
1213 Binders::new(num_binders, TyKind::Unknown.intern(&Interner))
1216 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1218 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1219 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1220 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1221 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1222 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1223 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1227 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1228 let impl_data = db.impl_data(impl_id);
1229 let resolver = impl_id.resolver(db.upcast());
1230 let generics = generics(db.upcast(), impl_id.into());
1232 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1233 Binders::new(generics.len(), ctx.lower_ty(&impl_data.target_type))
1236 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1237 let parent_data = db.generic_params(def.parent);
1238 let data = &parent_data.consts[def.local_id];
1239 let resolver = def.parent.resolver(db.upcast());
1240 let ctx = TyLoweringContext::new(db, &resolver);
1242 ctx.lower_ty(&data.ty)
1245 pub(crate) fn impl_self_ty_recover(
1246 db: &dyn HirDatabase,
1250 let generics = generics(db.upcast(), (*impl_id).into());
1251 Binders::new(generics.len(), TyKind::Unknown.intern(&Interner))
1254 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1255 let impl_data = db.impl_data(impl_id);
1256 let resolver = impl_id.resolver(db.upcast());
1258 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1259 let self_ty = db.impl_self_ty(impl_id);
1260 let target_trait = impl_data.target_trait.as_ref()?;
1261 Some(Binders::new(self_ty.num_binders, ctx.lower_trait_ref(target_trait, Some(self_ty.value))?))
1264 pub(crate) fn return_type_impl_traits(
1265 db: &dyn HirDatabase,
1266 def: hir_def::FunctionId,
1267 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1268 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1269 let data = db.function_data(def);
1270 let resolver = def.resolver(db.upcast());
1271 let ctx_ret = TyLoweringContext::new(db, &resolver)
1272 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1273 .with_type_param_mode(TypeParamLoweringMode::Variable);
1274 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1275 let generics = generics(db.upcast(), def.into());
1276 let num_binders = generics.len();
1277 let return_type_impl_traits =
1278 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1279 if return_type_impl_traits.impl_traits.is_empty() {
1282 Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))
1286 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1288 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1289 hir_def::type_ref::Mutability::Mut => Mutability::Mut,