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::cell::{Cell, RefCell};
9 use std::{iter, sync::Arc};
12 use chalk_ir::{cast::Cast, fold::Shift, interner::HasInterner, Mutability, Safety};
15 body::{Expander, LowerCtx},
16 builtin_type::BuiltinType,
17 generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
18 path::{GenericArg, Path, PathSegment, PathSegments},
19 resolver::{HasResolver, Resolver, TypeNs},
20 type_ref::{TraitRef as HirTraitRef, TypeBound, TypeRef},
21 AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
22 GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
23 TypeAliasId, TypeParamId, UnionId, VariantId,
25 use hir_expand::{name::Name, ExpandResult};
26 use la_arena::ArenaMap;
27 use smallvec::SmallVec;
35 static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
37 all_super_trait_refs, associated_type_by_name_including_super_traits, generics, Generics,
39 AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
40 FnSubst, ImplTraitId, Interner, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
41 QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
42 TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause,
46 pub struct TyLoweringContext<'a> {
47 pub db: &'a dyn HirDatabase,
48 pub resolver: &'a Resolver,
49 in_binders: DebruijnIndex,
50 /// Note: Conceptually, it's thinkable that we could be in a location where
51 /// some type params should be represented as placeholders, and others
52 /// should be converted to variables. I think in practice, this isn't
53 /// possible currently, so this should be fine for now.
54 pub type_param_mode: TypeParamLoweringMode,
55 pub impl_trait_mode: ImplTraitLoweringMode,
56 impl_trait_counter: Cell<u16>,
57 /// When turning `impl Trait` into opaque types, we have to collect the
58 /// bounds at the same time to get the IDs correct (without becoming too
59 /// complicated). I don't like using interior mutability (as for the
60 /// counter), but I've tried and failed to make the lifetimes work for
61 /// passing around a `&mut TyLoweringContext`. The core problem is that
62 /// we're grouping the mutable data (the counter and this field) together
63 /// with the immutable context (the references to the DB and resolver).
64 /// Splitting this up would be a possible fix.
65 opaque_type_data: RefCell<Vec<ReturnTypeImplTrait>>,
66 expander: RefCell<Option<Expander>>,
69 impl<'a> TyLoweringContext<'a> {
70 pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
71 let impl_trait_counter = Cell::new(0);
72 let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
73 let type_param_mode = TypeParamLoweringMode::Placeholder;
74 let in_binders = DebruijnIndex::INNERMOST;
75 let opaque_type_data = RefCell::new(Vec::new());
84 expander: RefCell::new(None),
88 pub fn with_debruijn<T>(
90 debruijn: DebruijnIndex,
91 f: impl FnOnce(&TyLoweringContext) -> T,
93 let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
94 let expander = self.expander.replace(None);
97 impl_trait_counter: Cell::new(self.impl_trait_counter.get()),
98 opaque_type_data: RefCell::new(opaque_ty_data_vec),
99 expander: RefCell::new(expander),
102 let result = f(&new_ctx);
103 self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
104 self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
105 self.expander.replace(new_ctx.expander.into_inner());
109 pub fn with_shifted_in<T>(
111 debruijn: DebruijnIndex,
112 f: impl FnOnce(&TyLoweringContext) -> T,
114 self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
117 pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
118 Self { impl_trait_mode, ..self }
121 pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
122 Self { type_param_mode, ..self }
126 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
127 pub enum ImplTraitLoweringMode {
128 /// `impl Trait` gets lowered into an opaque type that doesn't unify with
129 /// anything except itself. This is used in places where values flow 'out',
130 /// i.e. for arguments of the function we're currently checking, and return
131 /// types of functions we're calling.
133 /// `impl Trait` gets lowered into a type variable. Used for argument
134 /// position impl Trait when inside the respective function, since it allows
135 /// us to support that without Chalk.
137 /// `impl Trait` gets lowered into a variable that can unify with some
138 /// type. This is used in places where values flow 'in', i.e. for arguments
139 /// of functions we're calling, and the return type of the function we're
140 /// currently checking.
142 /// `impl Trait` is disallowed and will be an error.
146 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
147 pub enum TypeParamLoweringMode {
152 impl<'a> TyLoweringContext<'a> {
153 pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
154 self.lower_ty_ext(type_ref).0
157 pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
159 let ty = match type_ref {
160 TypeRef::Never => TyKind::Never.intern(&Interner),
161 TypeRef::Tuple(inner) => {
162 let inner_tys = inner.iter().map(|tr| self.lower_ty(tr));
163 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
166 TypeRef::Path(path) => {
167 let (ty, res_) = self.lower_path(path);
171 TypeRef::RawPtr(inner, mutability) => {
172 let inner_ty = self.lower_ty(inner);
173 TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
175 TypeRef::Array(inner, len) => {
176 let inner_ty = self.lower_ty(inner);
178 let const_len = consteval::usize_const(len.as_usize());
180 TyKind::Array(inner_ty, const_len).intern(&Interner)
182 TypeRef::Slice(inner) => {
183 let inner_ty = self.lower_ty(inner);
184 TyKind::Slice(inner_ty).intern(&Interner)
186 TypeRef::Reference(inner, _, mutability) => {
187 let inner_ty = self.lower_ty(inner);
188 let lifetime = static_lifetime();
189 TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
192 TypeRef::Placeholder => TyKind::Error.intern(&Interner),
193 TypeRef::Fn(params, is_varargs) => {
194 let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
195 Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr)))
197 TyKind::Function(FnPointer {
198 num_binders: 0, // FIXME lower `for<'a> fn()` correctly
199 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
200 substitution: FnSubst(substs),
204 TypeRef::DynTrait(bounds) => {
206 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
207 let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
208 QuantifiedWhereClauses::from_iter(
210 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
213 let bounds = crate::make_only_type_binders(1, bounds);
214 TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner)
216 TypeRef::ImplTrait(bounds) => {
217 match self.impl_trait_mode {
218 ImplTraitLoweringMode::Opaque => {
219 let idx = self.impl_trait_counter.get();
220 self.impl_trait_counter.set(idx + 1);
222 assert!(idx as usize == self.opaque_type_data.borrow().len());
223 // this dance is to make sure the data is in the right
224 // place even if we encounter more opaque types while
225 // lowering the bounds
226 self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait {
227 bounds: crate::make_only_type_binders(1, Vec::new()),
229 // We don't want to lower the bounds inside the binders
230 // we're currently in, because they don't end up inside
231 // those binders. E.g. when we have `impl Trait<impl
232 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
233 // to the self parameter from `impl Trait`, and the
234 // bounds aren't actually stored nested within each
235 // other, but separately. So if the `T` refers to a type
236 // parameter of the outer function, it's just one binder
237 // away instead of two.
238 let actual_opaque_type_data = self
239 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
240 ctx.lower_impl_trait(&bounds)
242 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
244 let func = match self.resolver.generic_def() {
245 Some(GenericDefId::FunctionId(f)) => f,
246 _ => panic!("opaque impl trait lowering in non-function"),
248 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
249 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
250 let generics = generics(self.db.upcast(), func.into());
251 let parameters = generics.bound_vars_subst(self.in_binders);
252 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
254 substitution: parameters,
258 ImplTraitLoweringMode::Param => {
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 if let Some(def) = self.resolver.generic_def() {
263 let generics = generics(self.db.upcast(), def);
266 .filter(|(_, data)| {
267 data.provenance == TypeParamProvenance::ArgumentImplTrait
270 .map_or(TyKind::Error, |(id, _)| {
271 TyKind::Placeholder(to_placeholder_idx(self.db, id))
273 param.intern(&Interner)
275 TyKind::Error.intern(&Interner)
278 ImplTraitLoweringMode::Variable => {
279 let idx = self.impl_trait_counter.get();
280 // FIXME we're probably doing something wrong here
281 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
282 let (parent_params, self_params, list_params, _impl_trait_params) =
283 if let Some(def) = self.resolver.generic_def() {
284 let generics = generics(self.db.upcast(), def);
285 generics.provenance_split()
289 TyKind::BoundVar(BoundVar::new(
291 idx as usize + parent_params + self_params + list_params,
295 ImplTraitLoweringMode::Disallowed => {
296 // FIXME: report error
297 TyKind::Error.intern(&Interner)
301 TypeRef::Macro(macro_call) => {
302 let (expander, recursion_start) = {
303 let mut expander = self.expander.borrow_mut();
304 if expander.is_some() {
305 (Some(expander), false)
307 if let Some(module_id) = self.resolver.module() {
308 *expander = Some(Expander::new(
313 (Some(expander), true)
319 let ty = if let Some(mut expander) = expander {
320 let expander_mut = expander.as_mut().unwrap();
321 let macro_call = macro_call.to_node(self.db.upcast());
322 match expander_mut.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
323 Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
325 LowerCtx::new(self.db.upcast(), expander_mut.current_file_id());
326 let type_ref = TypeRef::from_ast(&ctx, expanded);
329 let ty = self.lower_ty(&type_ref);
335 .exit(self.db.upcast(), mark);
344 *self.expander.borrow_mut() = None;
346 ty.unwrap_or_else(|| TyKind::Error.intern(&Interner))
348 TypeRef::Error => TyKind::Error.intern(&Interner),
353 /// This is only for `generic_predicates_for_param`, where we can't just
354 /// lower the self types of the predicates since that could lead to cycles.
355 /// So we just check here if the `type_ref` resolves to a generic param, and which.
356 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
357 let path = match type_ref {
358 TypeRef::Path(path) => path,
361 if path.type_anchor().is_some() {
364 if path.segments().len() > 1 {
368 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
369 Some((it, None)) => it,
372 if let TypeNs::GenericParam(param_id) = resolution {
379 pub(crate) fn lower_ty_relative_path(
382 // We need the original resolution to lower `Self::AssocTy` correctly
384 remaining_segments: PathSegments<'_>,
385 ) -> (Ty, Option<TypeNs>) {
386 if remaining_segments.len() == 1 {
387 // resolve unselected assoc types
388 let segment = remaining_segments.first().unwrap();
389 (self.select_associated_type(res, segment), None)
390 } else if remaining_segments.len() > 1 {
391 // FIXME report error (ambiguous associated type)
392 (TyKind::Error.intern(&Interner), None)
398 pub(crate) fn lower_partly_resolved_path(
401 resolved_segment: PathSegment<'_>,
402 remaining_segments: PathSegments<'_>,
404 ) -> (Ty, Option<TypeNs>) {
405 let ty = match resolution {
406 TypeNs::TraitId(trait_) => {
407 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
408 let self_ty = if remaining_segments.len() == 0 {
410 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
417 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
418 let ty = if remaining_segments.len() == 1 {
419 let segment = remaining_segments.first().unwrap();
422 .trait_data(trait_ref.hir_trait_id())
423 .associated_type_by_name(&segment.name);
425 Some(associated_ty) => {
426 // FIXME handle type parameters on the segment
427 TyKind::Alias(AliasTy::Projection(ProjectionTy {
428 associated_ty_id: to_assoc_type_id(associated_ty),
429 substitution: trait_ref.substitution,
434 // FIXME: report error (associated type not found)
435 TyKind::Error.intern(&Interner)
438 } else if remaining_segments.len() > 1 {
439 // FIXME report error (ambiguous associated type)
440 TyKind::Error.intern(&Interner)
443 bounds: crate::make_only_type_binders(
445 QuantifiedWhereClauses::from_iter(
447 Some(crate::wrap_empty_binders(WhereClause::Implemented(
452 lifetime: static_lifetime(),
454 TyKind::Dyn(dyn_ty).intern(&Interner)
458 TypeNs::GenericParam(param_id) => {
459 let generics = generics(
461 self.resolver.generic_def().expect("generics in scope"),
463 match self.type_param_mode {
464 TypeParamLoweringMode::Placeholder => {
465 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
467 TypeParamLoweringMode::Variable => {
468 let idx = generics.param_idx(param_id).expect("matching generics");
469 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
474 TypeNs::SelfType(impl_id) => {
475 let generics = generics(self.db.upcast(), impl_id.into());
476 let substs = match self.type_param_mode {
477 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
478 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
480 self.db.impl_self_ty(impl_id).substitute(&Interner, &substs)
482 TypeNs::AdtSelfType(adt) => {
483 let generics = generics(self.db.upcast(), adt.into());
484 let substs = match self.type_param_mode {
485 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
486 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
488 self.db.ty(adt.into()).substitute(&Interner, &substs)
491 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
492 TypeNs::BuiltinType(it) => {
493 self.lower_path_inner(resolved_segment, it.into(), infer_args)
495 TypeNs::TypeAliasId(it) => {
496 self.lower_path_inner(resolved_segment, it.into(), infer_args)
498 // FIXME: report error
499 TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None),
501 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
504 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
505 // Resolve the path (in type namespace)
506 if let Some(type_ref) = path.type_anchor() {
507 let (ty, res) = self.lower_ty_ext(&type_ref);
508 return self.lower_ty_relative_path(ty, res, path.segments());
510 let (resolution, remaining_index) =
511 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
513 None => return (TyKind::Error.intern(&Interner), None),
515 let (resolved_segment, remaining_segments) = match remaining_index {
517 path.segments().last().expect("resolved path has at least one element"),
520 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
522 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
525 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
526 if let Some(res) = res {
527 let ty = associated_type_shorthand_candidates(
530 move |name, t, associated_ty| {
531 if name == segment.name {
532 let substs = match self.type_param_mode {
533 TypeParamLoweringMode::Placeholder => {
534 // if we're lowering to placeholders, we have to put
536 let generics = generics(
538 self.resolver.generic_def().expect(
539 "there should be generics if there's a generic param",
542 let s = generics.type_params_subst(self.db);
543 s.apply(t.substitution.clone(), &Interner)
545 TypeParamLoweringMode::Variable => t.substitution.clone(),
547 // We need to shift in the bound vars, since
548 // associated_type_shorthand_candidates does not do that
549 let substs = substs.shifted_in_from(&Interner, self.in_binders);
550 // FIXME handle type parameters on the segment
552 TyKind::Alias(AliasTy::Projection(ProjectionTy {
553 associated_ty_id: to_assoc_type_id(associated_ty),
554 substitution: substs,
564 ty.unwrap_or(TyKind::Error.intern(&Interner))
566 TyKind::Error.intern(&Interner)
572 segment: PathSegment<'_>,
576 let generic_def = match typeable {
577 TyDefId::BuiltinType(_) => None,
578 TyDefId::AdtId(it) => Some(it.into()),
579 TyDefId::TypeAliasId(it) => Some(it.into()),
581 let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
582 self.db.ty(typeable).substitute(&Interner, &substs)
585 /// Collect generic arguments from a path into a `Substs`. See also
586 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
587 pub(super) fn substs_from_path(
590 // Note that we don't call `db.value_type(resolved)` here,
591 // `ValueTyDefId` is just a convenient way to pass generics and
592 // special-case enum variants
593 resolved: ValueTyDefId,
596 let last = path.segments().last().expect("path should have at least one segment");
597 let (segment, generic_def) = match resolved {
598 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
599 ValueTyDefId::StructId(it) => (last, Some(it.into())),
600 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
601 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
602 ValueTyDefId::StaticId(_) => (last, None),
603 ValueTyDefId::EnumVariantId(var) => {
604 // the generic args for an enum variant may be either specified
605 // on the segment referring to the enum, or on the segment
606 // referring to the variant. So `Option::<T>::None` and
607 // `Option::None::<T>` are both allowed (though the former is
608 // preferred). See also `def_ids_for_path_segments` in rustc.
609 let len = path.segments().len();
610 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
611 let segment = match penultimate {
612 Some(segment) if segment.args_and_bindings.is_some() => segment,
615 (segment, Some(var.parent.into()))
618 self.substs_from_path_segment(segment, generic_def, infer_args, None)
621 fn substs_from_path_segment(
623 segment: PathSegment<'_>,
624 def_generic: Option<GenericDefId>,
626 explicit_self_ty: Option<Ty>,
628 let mut substs = Vec::new();
629 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
631 let (parent_params, self_params, type_params, impl_trait_params) =
632 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
633 let total_len = parent_params + self_params + type_params + impl_trait_params;
635 substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params));
637 let fill_self_params = || {
641 .chain(iter::repeat(TyKind::Error.intern(&Interner)))
645 let mut had_explicit_type_args = false;
647 if let Some(generic_args) = &segment.args_and_bindings {
648 if !generic_args.has_self_type {
652 if generic_args.has_self_type { self_params + type_params } else { type_params };
653 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
654 // if args are provided, it should be all of them, but we can't rely on that
655 for arg in generic_args
658 .filter(|arg| matches!(arg, GenericArg::Type(_)))
663 GenericArg::Type(type_ref) => {
664 had_explicit_type_args = true;
665 let ty = self.lower_ty(type_ref);
668 GenericArg::Lifetime(_) => {}
675 // handle defaults. In expression or pattern path segments without
676 // explicitly specified type arguments, missing type arguments are inferred
677 // (i.e. defaults aren't used).
678 if !infer_args || had_explicit_type_args {
679 if let Some(def_generic) = def_generic {
680 let defaults = self.db.generic_defaults(def_generic);
681 assert_eq!(total_len, defaults.len());
683 for default_ty in defaults.iter().skip(substs.len()) {
684 // each default can depend on the previous parameters
685 let substs_so_far = Substitution::from_iter(&Interner, substs.clone());
686 substs.push(default_ty.clone().substitute(&Interner, &substs_so_far));
691 // add placeholders for args that were not provided
692 // FIXME: emit diagnostics in contexts where this is not allowed
693 for _ in substs.len()..total_len {
694 substs.push(TyKind::Error.intern(&Interner));
696 assert_eq!(substs.len(), total_len);
698 Substitution::from_iter(&Interner, substs)
701 fn lower_trait_ref_from_path(
704 explicit_self_ty: Option<Ty>,
705 ) -> Option<TraitRef> {
707 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
708 TypeNs::TraitId(tr) => tr,
711 let segment = path.segments().last().expect("path should have at least one segment");
712 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
715 pub(crate) fn lower_trait_ref_from_resolved_path(
718 segment: PathSegment<'_>,
719 explicit_self_ty: Option<Ty>,
721 let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
722 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
727 trait_ref: &HirTraitRef,
728 explicit_self_ty: Option<Ty>,
729 ) -> Option<TraitRef> {
730 self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
733 fn trait_ref_substs_from_path(
735 segment: PathSegment<'_>,
737 explicit_self_ty: Option<Ty>,
739 self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
742 pub(crate) fn lower_where_predicate(
744 where_predicate: &'a WherePredicate,
745 ignore_bindings: bool,
746 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
747 match where_predicate {
748 WherePredicate::ForLifetime { target, bound, .. }
749 | WherePredicate::TypeBound { target, bound } => {
750 let self_ty = match target {
751 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
752 WherePredicateTypeTarget::TypeParam(param_id) => {
753 let generic_def = self.resolver.generic_def().expect("generics in scope");
754 let generics = generics(self.db.upcast(), generic_def);
756 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
757 let placeholder = to_placeholder_idx(self.db, param_id);
758 match self.type_param_mode {
759 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
760 TypeParamLoweringMode::Variable => {
761 let idx = generics.param_idx(param_id).expect("matching generics");
762 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
768 self.lower_type_bound(bound, self_ty, ignore_bindings)
772 WherePredicate::Lifetime { .. } => vec![].into_iter(),
776 pub(crate) fn lower_type_bound(
778 bound: &'a TypeBound,
780 ignore_bindings: bool,
781 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
782 let mut bindings = None;
783 let trait_ref = match bound {
784 TypeBound::Path(path) => {
785 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
786 bindings.clone().map(WhereClause::Implemented).map(|b| crate::wrap_empty_binders(b))
788 TypeBound::Lifetime(_) => None,
789 TypeBound::Error => None,
791 trait_ref.into_iter().chain(
794 .filter(move |_| !ignore_bindings)
795 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
799 fn assoc_type_bindings_from_type_bound(
801 bound: &'a TypeBound,
803 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
804 let last_segment = match bound {
805 TypeBound::Path(path) => path.segments().last(),
806 TypeBound::Error | TypeBound::Lifetime(_) => None,
810 .flat_map(|segment| segment.args_and_bindings.into_iter())
811 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
812 .flat_map(move |binding| {
813 let found = associated_type_by_name_including_super_traits(
818 let (super_trait_ref, associated_ty) = match found {
819 None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(),
822 let projection_ty = ProjectionTy {
823 associated_ty_id: to_assoc_type_id(associated_ty),
824 substitution: super_trait_ref.substitution,
826 let mut preds = SmallVec::with_capacity(
827 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
829 if let Some(type_ref) = &binding.type_ref {
830 let ty = self.lower_ty(type_ref);
832 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
833 preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
835 for bound in &binding.bounds {
836 preds.extend(self.lower_type_bound(
838 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
846 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
847 cov_mark::hit!(lower_rpit);
849 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
850 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
851 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
853 ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) }
857 fn count_impl_traits(type_ref: &TypeRef) -> usize {
859 type_ref.walk(&mut |type_ref| {
860 if matches!(type_ref, TypeRef::ImplTrait(_)) {
867 /// Build the signature of a callable item (function, struct or enum variant).
868 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
870 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
871 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
872 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
876 pub fn associated_type_shorthand_candidates<R>(
877 db: &dyn HirDatabase,
879 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
881 let mut search = |t| {
882 for t in all_super_trait_refs(db, t) {
883 let data = db.trait_data(t.hir_trait_id());
885 for (name, assoc_id) in &data.items {
886 if let AssocItemId::TypeAliasId(alias) = assoc_id {
887 if let Some(result) = cb(name, &t, *alias) {
897 TypeNs::SelfType(impl_id) => search(
898 // we're _in_ the impl -- the binders get added back later. Correct,
899 // but it would be nice to make this more explicit
900 db.impl_trait(impl_id)?.into_value_and_skipped_binders().0,
902 TypeNs::GenericParam(param_id) => {
903 let predicates = db.generic_predicates_for_param(param_id);
904 let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
905 // FIXME: how to correctly handle higher-ranked bounds here?
906 WhereClause::Implemented(tr) => search(
908 .shifted_out_to(&Interner, DebruijnIndex::ONE)
909 .expect("FIXME unexpected higher-ranked trait bound"),
913 if let res @ Some(_) = res {
916 // Handle `Self::Type` referring to own associated type in trait definitions
917 if let GenericDefId::TraitId(trait_id) = param_id.parent {
918 let generics = generics(db.upcast(), trait_id.into());
919 if generics.params.types[param_id.local_id].provenance
920 == TypeParamProvenance::TraitSelf
922 let trait_ref = TyBuilder::trait_ref(db, trait_id)
923 .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
925 return search(trait_ref);
934 /// Build the type of all specific fields of a struct or enum variant.
935 pub(crate) fn field_types_query(
936 db: &dyn HirDatabase,
937 variant_id: VariantId,
938 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
939 let var_data = variant_id.variant_data(db.upcast());
940 let (resolver, def): (_, GenericDefId) = match variant_id {
941 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
942 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
943 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
945 let generics = generics(db.upcast(), def);
946 let mut res = ArenaMap::default();
948 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
949 for (field_id, field_data) in var_data.fields().iter() {
950 res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref)))
955 /// This query exists only to be used when resolving short-hand associated types
958 /// See the analogous query in rustc and its comment:
959 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
960 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
961 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
962 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
963 pub(crate) fn generic_predicates_for_param_query(
964 db: &dyn HirDatabase,
965 param_id: TypeParamId,
966 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
967 let resolver = param_id.parent.resolver(db.upcast());
969 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
970 let generics = generics(db.upcast(), param_id.parent);
972 .where_predicates_in_scope()
973 // we have to filter out all other predicates *first*, before attempting to lower them
974 .filter(|pred| match pred {
975 WherePredicate::ForLifetime { target, .. }
976 | WherePredicate::TypeBound { target, .. } => match target {
977 WherePredicateTypeTarget::TypeRef(type_ref) => {
978 ctx.lower_ty_only_param(type_ref) == Some(param_id)
980 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
982 WherePredicate::Lifetime { .. } => false,
984 .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
988 pub(crate) fn generic_predicates_for_param_recover(
989 _db: &dyn HirDatabase,
991 _param_id: &TypeParamId,
992 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
996 pub(crate) fn trait_environment_query(
997 db: &dyn HirDatabase,
999 ) -> Arc<TraitEnvironment> {
1000 let resolver = def.resolver(db.upcast());
1001 let ctx = TyLoweringContext::new(db, &resolver)
1002 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
1003 let mut traits_in_scope = Vec::new();
1004 let mut clauses = Vec::new();
1005 for pred in resolver.where_predicates_in_scope() {
1006 for pred in ctx.lower_where_predicate(pred, false) {
1007 if let WhereClause::Implemented(tr) = &pred.skip_binders() {
1009 .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id()));
1011 let program_clause: chalk_ir::ProgramClause<Interner> = pred.clone().cast(&Interner);
1012 clauses.push(program_clause.into_from_env_clause(&Interner));
1016 let container: Option<AssocContainerId> = match def {
1017 // FIXME: is there a function for this?
1018 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
1019 GenericDefId::AdtId(_) => None,
1020 GenericDefId::TraitId(_) => None,
1021 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
1022 GenericDefId::ImplId(_) => None,
1023 GenericDefId::EnumVariantId(_) => None,
1024 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
1026 if let Some(AssocContainerId::TraitId(trait_id)) = container {
1027 // add `Self: Trait<T1, T2, ...>` to the environment in trait
1028 // function default implementations (and hypothetical code
1029 // inside consts or type aliases)
1030 cov_mark::hit!(trait_self_implements_self);
1031 let substs = TyBuilder::type_params_subst(db, trait_id);
1032 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
1033 let pred = WhereClause::Implemented(trait_ref);
1034 let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(&Interner);
1035 clauses.push(program_clause.into_from_env_clause(&Interner));
1038 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
1040 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
1043 /// Resolve the where clause(s) of an item with generics.
1044 pub(crate) fn generic_predicates_query(
1045 db: &dyn HirDatabase,
1047 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
1048 let resolver = def.resolver(db.upcast());
1050 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1051 let generics = generics(db.upcast(), def);
1053 .where_predicates_in_scope()
1054 .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p)))
1058 /// Resolve the default type params from generics
1059 pub(crate) fn generic_defaults_query(
1060 db: &dyn HirDatabase,
1062 ) -> Arc<[Binders<Ty>]> {
1063 let resolver = def.resolver(db.upcast());
1065 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1066 let generic_params = generics(db.upcast(), def);
1068 let defaults = generic_params
1071 .map(|(idx, (_, p))| {
1073 p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t));
1075 // Each default can only refer to previous parameters.
1076 ty = crate::fold_free_vars(ty, |bound, binders| {
1077 if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST {
1078 // type variable default referring to parameter coming
1079 // after it. This is forbidden (FIXME: report
1081 TyKind::Error.intern(&Interner)
1083 bound.shifted_in_from(binders).to_ty(&Interner)
1087 crate::make_only_type_binders(idx, ty)
1094 pub(crate) fn generic_defaults_recover(
1095 db: &dyn HirDatabase,
1098 ) -> Arc<[Binders<Ty>]> {
1099 let generic_params = generics(db.upcast(), *def);
1101 // we still need one default per parameter
1102 let defaults = generic_params
1106 let ty = TyKind::Error.intern(&Interner);
1108 crate::make_only_type_binders(idx, ty)
1115 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1116 let data = db.function_data(def);
1117 let resolver = def.resolver(db.upcast());
1118 let ctx_params = TyLoweringContext::new(db, &resolver)
1119 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1120 .with_type_param_mode(TypeParamLoweringMode::Variable);
1121 let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
1122 let ctx_ret = TyLoweringContext::new(db, &resolver)
1123 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1124 .with_type_param_mode(TypeParamLoweringMode::Variable);
1125 let ret = ctx_ret.lower_ty(&data.ret_type);
1126 let generics = generics(db.upcast(), def.into());
1127 make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs()))
1130 /// Build the declared type of a function. This should not need to look at the
1132 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1133 let generics = generics(db.upcast(), def.into());
1134 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1137 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1141 /// Build the declared type of a const.
1142 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1143 let data = db.const_data(def);
1144 let generics = generics(db.upcast(), def.into());
1145 let resolver = def.resolver(db.upcast());
1147 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1149 make_binders(&generics, ctx.lower_ty(&data.type_ref))
1152 /// Build the declared type of a static.
1153 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1154 let data = db.static_data(def);
1155 let resolver = def.resolver(db.upcast());
1156 let ctx = TyLoweringContext::new(db, &resolver);
1158 Binders::empty(&Interner, ctx.lower_ty(&data.type_ref))
1161 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1162 let struct_data = db.struct_data(def);
1163 let fields = struct_data.variant_data.fields();
1164 let resolver = def.resolver(db.upcast());
1166 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1167 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1168 let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
1169 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1172 /// Build the type of a tuple struct constructor.
1173 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1174 let struct_data = db.struct_data(def);
1175 if let StructKind::Unit = struct_data.variant_data.kind() {
1176 return type_for_adt(db, def.into());
1178 let generics = generics(db.upcast(), def.into());
1179 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1182 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1186 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1187 let enum_data = db.enum_data(def.parent);
1188 let var_data = &enum_data.variants[def.local_id];
1189 let fields = var_data.variant_data.fields();
1190 let resolver = def.parent.resolver(db.upcast());
1192 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1193 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1194 let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
1195 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1198 /// Build the type of a tuple enum variant constructor.
1199 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1200 let enum_data = db.enum_data(def.parent);
1201 let var_data = &enum_data.variants[def.local_id].variant_data;
1202 if let StructKind::Unit = var_data.kind() {
1203 return type_for_adt(db, def.parent.into());
1205 let generics = generics(db.upcast(), def.parent.into());
1206 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1209 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1213 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1214 let generics = generics(db.upcast(), adt.into());
1215 let b = TyBuilder::adt(db, adt);
1216 let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
1217 make_binders(&generics, ty)
1220 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1221 let generics = generics(db.upcast(), t.into());
1222 let resolver = t.resolver(db.upcast());
1224 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1225 if db.type_alias_data(t).is_extern {
1226 Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner))
1228 let type_ref = &db.type_alias_data(t).type_ref;
1229 let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
1230 make_binders(&generics, inner)
1234 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1235 pub enum CallableDefId {
1236 FunctionId(FunctionId),
1238 EnumVariantId(EnumVariantId),
1240 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1242 impl CallableDefId {
1243 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1244 let db = db.upcast();
1246 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1247 CallableDefId::StructId(s) => s.lookup(db).container,
1248 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1254 impl From<CallableDefId> for GenericDefId {
1255 fn from(def: CallableDefId) -> GenericDefId {
1257 CallableDefId::FunctionId(f) => f.into(),
1258 CallableDefId::StructId(s) => s.into(),
1259 CallableDefId::EnumVariantId(e) => e.into(),
1264 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1266 BuiltinType(BuiltinType),
1268 TypeAliasId(TypeAliasId),
1270 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1272 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1273 pub enum ValueTyDefId {
1274 FunctionId(FunctionId),
1277 EnumVariantId(EnumVariantId),
1281 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1283 /// Build the declared type of an item. This depends on the namespace; e.g. for
1284 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1285 /// the constructor function `(usize) -> Foo` which lives in the values
1287 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1289 TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)),
1290 TyDefId::AdtId(it) => type_for_adt(db, it),
1291 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1295 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1296 let generics = match *def {
1297 TyDefId::BuiltinType(_) => {
1298 return Binders::empty(&Interner, TyKind::Error.intern(&Interner))
1300 TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
1301 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
1303 make_binders(&generics, TyKind::Error.intern(&Interner))
1306 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1308 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1309 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1310 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1311 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1312 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1313 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1317 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1318 let impl_data = db.impl_data(impl_id);
1319 let resolver = impl_id.resolver(db.upcast());
1320 let generics = generics(db.upcast(), impl_id.into());
1322 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1323 make_binders(&generics, ctx.lower_ty(&impl_data.self_ty))
1326 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1327 let parent_data = db.generic_params(def.parent);
1328 let data = &parent_data.consts[def.local_id];
1329 let resolver = def.parent.resolver(db.upcast());
1330 let ctx = TyLoweringContext::new(db, &resolver);
1332 ctx.lower_ty(&data.ty)
1335 pub(crate) fn impl_self_ty_recover(
1336 db: &dyn HirDatabase,
1340 let generics = generics(db.upcast(), (*impl_id).into());
1341 make_binders(&generics, TyKind::Error.intern(&Interner))
1344 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1345 let impl_data = db.impl_data(impl_id);
1346 let resolver = impl_id.resolver(db.upcast());
1348 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1349 let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
1350 let target_trait = impl_data.target_trait.as_ref()?;
1351 Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
1354 pub(crate) fn return_type_impl_traits(
1355 db: &dyn HirDatabase,
1356 def: hir_def::FunctionId,
1357 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1358 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1359 let data = db.function_data(def);
1360 let resolver = def.resolver(db.upcast());
1361 let ctx_ret = TyLoweringContext::new(db, &resolver)
1362 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1363 .with_type_param_mode(TypeParamLoweringMode::Variable);
1364 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1365 let generics = generics(db.upcast(), def.into());
1366 let return_type_impl_traits =
1367 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1368 if return_type_impl_traits.impl_traits.is_empty() {
1371 Some(Arc::new(make_binders(&generics, return_type_impl_traits)))
1375 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1377 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1378 hir_def::type_ref::Mutability::Mut => Mutability::Mut,
1382 fn make_binders<T: HasInterner<Interner = Interner>>(generics: &Generics, value: T) -> Binders<T> {
1383 crate::make_only_type_binders(generics.len(), value)