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) => {
176 let inner_ty = self.lower_ty(inner);
177 TyKind::Array(inner_ty, dummy_usize_const()).intern(&Interner)
179 TypeRef::Slice(inner) => {
180 let inner_ty = self.lower_ty(inner);
181 TyKind::Slice(inner_ty).intern(&Interner)
183 TypeRef::Reference(inner, _, mutability) => {
184 let inner_ty = self.lower_ty(inner);
185 let lifetime = static_lifetime();
186 TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
189 TypeRef::Placeholder => TyKind::Error.intern(&Interner),
190 TypeRef::Fn(params, is_varargs) => {
191 let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
192 Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr)))
194 TyKind::Function(FnPointer {
195 num_binders: 0, // FIXME lower `for<'a> fn()` correctly
196 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
197 substitution: FnSubst(substs),
201 TypeRef::DynTrait(bounds) => {
203 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
204 let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
205 QuantifiedWhereClauses::from_iter(
207 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
210 let bounds = crate::make_only_type_binders(1, bounds);
211 TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner)
213 TypeRef::ImplTrait(bounds) => {
214 match self.impl_trait_mode {
215 ImplTraitLoweringMode::Opaque => {
216 let idx = self.impl_trait_counter.get();
217 self.impl_trait_counter.set(idx + 1);
219 assert!(idx as usize == self.opaque_type_data.borrow().len());
220 // this dance is to make sure the data is in the right
221 // place even if we encounter more opaque types while
222 // lowering the bounds
223 self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait {
224 bounds: crate::make_only_type_binders(1, Vec::new()),
226 // We don't want to lower the bounds inside the binders
227 // we're currently in, because they don't end up inside
228 // those binders. E.g. when we have `impl Trait<impl
229 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
230 // to the self parameter from `impl Trait`, and the
231 // bounds aren't actually stored nested within each
232 // other, but separately. So if the `T` refers to a type
233 // parameter of the outer function, it's just one binder
234 // away instead of two.
235 let actual_opaque_type_data = self
236 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
237 ctx.lower_impl_trait(&bounds)
239 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
241 let func = match self.resolver.generic_def() {
242 Some(GenericDefId::FunctionId(f)) => f,
243 _ => panic!("opaque impl trait lowering in non-function"),
245 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
246 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
247 let generics = generics(self.db.upcast(), func.into());
248 let parameters = generics.bound_vars_subst(self.in_binders);
249 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
251 substitution: parameters,
255 ImplTraitLoweringMode::Param => {
256 let idx = self.impl_trait_counter.get();
257 // FIXME we're probably doing something wrong here
258 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
259 if let Some(def) = self.resolver.generic_def() {
260 let generics = generics(self.db.upcast(), def);
263 .filter(|(_, data)| {
264 data.provenance == TypeParamProvenance::ArgumentImplTrait
267 .map_or(TyKind::Error, |(id, _)| {
268 TyKind::Placeholder(to_placeholder_idx(self.db, id))
270 param.intern(&Interner)
272 TyKind::Error.intern(&Interner)
275 ImplTraitLoweringMode::Variable => {
276 let idx = self.impl_trait_counter.get();
277 // FIXME we're probably doing something wrong here
278 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
279 let (parent_params, self_params, list_params, _impl_trait_params) =
280 if let Some(def) = self.resolver.generic_def() {
281 let generics = generics(self.db.upcast(), def);
282 generics.provenance_split()
286 TyKind::BoundVar(BoundVar::new(
288 idx as usize + parent_params + self_params + list_params,
292 ImplTraitLoweringMode::Disallowed => {
293 // FIXME: report error
294 TyKind::Error.intern(&Interner)
298 TypeRef::Macro(macro_call) => {
299 let (expander, recursion_start) = {
300 let mut expander = self.expander.borrow_mut();
301 if expander.is_some() {
302 (Some(expander), false)
304 if let Some(module_id) = self.resolver.module() {
305 *expander = Some(Expander::new(
310 (Some(expander), true)
316 let ty = if let Some(mut expander) = expander {
317 let expander_mut = expander.as_mut().unwrap();
318 let macro_call = macro_call.to_node(self.db.upcast());
319 match expander_mut.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
320 Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
322 LowerCtx::new(self.db.upcast(), expander_mut.current_file_id());
323 let type_ref = TypeRef::from_ast(&ctx, expanded);
326 let ty = self.lower_ty(&type_ref);
332 .exit(self.db.upcast(), mark);
341 *self.expander.borrow_mut() = None;
343 ty.unwrap_or_else(|| TyKind::Error.intern(&Interner))
345 TypeRef::Error => TyKind::Error.intern(&Interner),
350 /// This is only for `generic_predicates_for_param`, where we can't just
351 /// lower the self types of the predicates since that could lead to cycles.
352 /// So we just check here if the `type_ref` resolves to a generic param, and which.
353 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
354 let path = match type_ref {
355 TypeRef::Path(path) => path,
358 if path.type_anchor().is_some() {
361 if path.segments().len() > 1 {
365 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
366 Some((it, None)) => it,
369 if let TypeNs::GenericParam(param_id) = resolution {
376 pub(crate) fn lower_ty_relative_path(
379 // We need the original resolution to lower `Self::AssocTy` correctly
381 remaining_segments: PathSegments<'_>,
382 ) -> (Ty, Option<TypeNs>) {
383 if remaining_segments.len() == 1 {
384 // resolve unselected assoc types
385 let segment = remaining_segments.first().unwrap();
386 (self.select_associated_type(res, segment), None)
387 } else if remaining_segments.len() > 1 {
388 // FIXME report error (ambiguous associated type)
389 (TyKind::Error.intern(&Interner), None)
395 pub(crate) fn lower_partly_resolved_path(
398 resolved_segment: PathSegment<'_>,
399 remaining_segments: PathSegments<'_>,
401 ) -> (Ty, Option<TypeNs>) {
402 let ty = match resolution {
403 TypeNs::TraitId(trait_) => {
404 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
405 let self_ty = if remaining_segments.len() == 0 {
407 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
414 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
415 let ty = if remaining_segments.len() == 1 {
416 let segment = remaining_segments.first().unwrap();
417 let found = associated_type_by_name_including_super_traits(
423 Some((super_trait_ref, associated_ty)) => {
424 // FIXME handle type parameters on the segment
425 TyKind::Alias(AliasTy::Projection(ProjectionTy {
426 associated_ty_id: to_assoc_type_id(associated_ty),
427 substitution: super_trait_ref.substitution,
432 // FIXME: report error (associated type not found)
433 TyKind::Error.intern(&Interner)
436 } else if remaining_segments.len() > 1 {
437 // FIXME report error (ambiguous associated type)
438 TyKind::Error.intern(&Interner)
441 bounds: crate::make_only_type_binders(
443 QuantifiedWhereClauses::from_iter(
445 Some(crate::wrap_empty_binders(WhereClause::Implemented(
450 lifetime: static_lifetime(),
452 TyKind::Dyn(dyn_ty).intern(&Interner)
456 TypeNs::GenericParam(param_id) => {
457 let generics = generics(
459 self.resolver.generic_def().expect("generics in scope"),
461 match self.type_param_mode {
462 TypeParamLoweringMode::Placeholder => {
463 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
465 TypeParamLoweringMode::Variable => {
466 let idx = generics.param_idx(param_id).expect("matching generics");
467 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
472 TypeNs::SelfType(impl_id) => {
473 let generics = generics(self.db.upcast(), impl_id.into());
474 let substs = match self.type_param_mode {
475 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
476 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
478 self.db.impl_self_ty(impl_id).substitute(&Interner, &substs)
480 TypeNs::AdtSelfType(adt) => {
481 let generics = generics(self.db.upcast(), adt.into());
482 let substs = match self.type_param_mode {
483 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
484 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
486 self.db.ty(adt.into()).substitute(&Interner, &substs)
489 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
490 TypeNs::BuiltinType(it) => {
491 self.lower_path_inner(resolved_segment, it.into(), infer_args)
493 TypeNs::TypeAliasId(it) => {
494 self.lower_path_inner(resolved_segment, it.into(), infer_args)
496 // FIXME: report error
497 TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None),
499 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
502 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
503 // Resolve the path (in type namespace)
504 if let Some(type_ref) = path.type_anchor() {
505 let (ty, res) = self.lower_ty_ext(&type_ref);
506 return self.lower_ty_relative_path(ty, res, path.segments());
508 let (resolution, remaining_index) =
509 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
511 None => return (TyKind::Error.intern(&Interner), None),
513 let (resolved_segment, remaining_segments) = match remaining_index {
515 path.segments().last().expect("resolved path has at least one element"),
518 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
520 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
523 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
524 if let Some(res) = res {
525 let ty = associated_type_shorthand_candidates(
528 move |name, t, associated_ty| {
529 if name == segment.name {
530 let substs = match self.type_param_mode {
531 TypeParamLoweringMode::Placeholder => {
532 // if we're lowering to placeholders, we have to put
534 let generics = generics(
536 self.resolver.generic_def().expect(
537 "there should be generics if there's a generic param",
540 let s = generics.type_params_subst(self.db);
541 s.apply(t.substitution.clone(), &Interner)
543 TypeParamLoweringMode::Variable => t.substitution.clone(),
545 // We need to shift in the bound vars, since
546 // associated_type_shorthand_candidates does not do that
547 let substs = substs.shifted_in_from(&Interner, self.in_binders);
548 // FIXME handle type parameters on the segment
550 TyKind::Alias(AliasTy::Projection(ProjectionTy {
551 associated_ty_id: to_assoc_type_id(associated_ty),
552 substitution: substs,
562 ty.unwrap_or(TyKind::Error.intern(&Interner))
564 TyKind::Error.intern(&Interner)
570 segment: PathSegment<'_>,
574 let generic_def = match typeable {
575 TyDefId::BuiltinType(_) => None,
576 TyDefId::AdtId(it) => Some(it.into()),
577 TyDefId::TypeAliasId(it) => Some(it.into()),
579 let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
580 self.db.ty(typeable).substitute(&Interner, &substs)
583 /// Collect generic arguments from a path into a `Substs`. See also
584 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
585 pub(super) fn substs_from_path(
588 // Note that we don't call `db.value_type(resolved)` here,
589 // `ValueTyDefId` is just a convenient way to pass generics and
590 // special-case enum variants
591 resolved: ValueTyDefId,
594 let last = path.segments().last().expect("path should have at least one segment");
595 let (segment, generic_def) = match resolved {
596 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
597 ValueTyDefId::StructId(it) => (last, Some(it.into())),
598 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
599 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
600 ValueTyDefId::StaticId(_) => (last, None),
601 ValueTyDefId::EnumVariantId(var) => {
602 // the generic args for an enum variant may be either specified
603 // on the segment referring to the enum, or on the segment
604 // referring to the variant. So `Option::<T>::None` and
605 // `Option::None::<T>` are both allowed (though the former is
606 // preferred). See also `def_ids_for_path_segments` in rustc.
607 let len = path.segments().len();
608 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
609 let segment = match penultimate {
610 Some(segment) if segment.args_and_bindings.is_some() => segment,
613 (segment, Some(var.parent.into()))
616 self.substs_from_path_segment(segment, generic_def, infer_args, None)
619 fn substs_from_path_segment(
621 segment: PathSegment<'_>,
622 def_generic: Option<GenericDefId>,
624 explicit_self_ty: Option<Ty>,
626 let mut substs = Vec::new();
627 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
629 let (parent_params, self_params, type_params, impl_trait_params) =
630 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
631 let total_len = parent_params + self_params + type_params + impl_trait_params;
633 substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params));
635 let fill_self_params = || {
639 .chain(iter::repeat(TyKind::Error.intern(&Interner)))
643 let mut had_explicit_type_args = false;
645 if let Some(generic_args) = &segment.args_and_bindings {
646 if !generic_args.has_self_type {
650 if generic_args.has_self_type { self_params + type_params } else { type_params };
651 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
652 // if args are provided, it should be all of them, but we can't rely on that
653 for arg in generic_args
656 .filter(|arg| matches!(arg, GenericArg::Type(_)))
661 GenericArg::Type(type_ref) => {
662 had_explicit_type_args = true;
663 let ty = self.lower_ty(type_ref);
666 GenericArg::Lifetime(_) => {}
673 // handle defaults. In expression or pattern path segments without
674 // explicitly specified type arguments, missing type arguments are inferred
675 // (i.e. defaults aren't used).
676 if !infer_args || had_explicit_type_args {
677 if let Some(def_generic) = def_generic {
678 let defaults = self.db.generic_defaults(def_generic);
679 assert_eq!(total_len, defaults.len());
681 for default_ty in defaults.iter().skip(substs.len()) {
682 // each default can depend on the previous parameters
683 let substs_so_far = Substitution::from_iter(&Interner, substs.clone());
684 substs.push(default_ty.clone().substitute(&Interner, &substs_so_far));
689 // add placeholders for args that were not provided
690 // FIXME: emit diagnostics in contexts where this is not allowed
691 for _ in substs.len()..total_len {
692 substs.push(TyKind::Error.intern(&Interner));
694 assert_eq!(substs.len(), total_len);
696 Substitution::from_iter(&Interner, substs)
699 fn lower_trait_ref_from_path(
702 explicit_self_ty: Option<Ty>,
703 ) -> Option<TraitRef> {
705 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
706 TypeNs::TraitId(tr) => tr,
709 let segment = path.segments().last().expect("path should have at least one segment");
710 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
713 pub(crate) fn lower_trait_ref_from_resolved_path(
716 segment: PathSegment<'_>,
717 explicit_self_ty: Option<Ty>,
719 let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
720 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
725 trait_ref: &HirTraitRef,
726 explicit_self_ty: Option<Ty>,
727 ) -> Option<TraitRef> {
728 self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
731 fn trait_ref_substs_from_path(
733 segment: PathSegment<'_>,
735 explicit_self_ty: Option<Ty>,
737 self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
740 pub(crate) fn lower_where_predicate(
742 where_predicate: &'a WherePredicate,
743 ignore_bindings: bool,
744 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
745 match where_predicate {
746 WherePredicate::ForLifetime { target, bound, .. }
747 | WherePredicate::TypeBound { target, bound } => {
748 let self_ty = match target {
749 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
750 WherePredicateTypeTarget::TypeParam(param_id) => {
751 let generic_def = self.resolver.generic_def().expect("generics in scope");
752 let generics = generics(self.db.upcast(), generic_def);
754 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
755 let placeholder = to_placeholder_idx(self.db, param_id);
756 match self.type_param_mode {
757 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
758 TypeParamLoweringMode::Variable => {
759 let idx = generics.param_idx(param_id).expect("matching generics");
760 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
766 self.lower_type_bound(bound, self_ty, ignore_bindings)
770 WherePredicate::Lifetime { .. } => vec![].into_iter(),
774 pub(crate) fn lower_type_bound(
776 bound: &'a TypeBound,
778 ignore_bindings: bool,
779 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
780 let mut bindings = None;
781 let trait_ref = match bound {
782 TypeBound::Path(path) => {
783 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
784 bindings.clone().map(WhereClause::Implemented).map(|b| crate::wrap_empty_binders(b))
786 TypeBound::Lifetime(_) => None,
787 TypeBound::Error => None,
789 trait_ref.into_iter().chain(
792 .filter(move |_| !ignore_bindings)
793 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
797 fn assoc_type_bindings_from_type_bound(
799 bound: &'a TypeBound,
801 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
802 let last_segment = match bound {
803 TypeBound::Path(path) => path.segments().last(),
804 TypeBound::Error | TypeBound::Lifetime(_) => None,
808 .flat_map(|segment| segment.args_and_bindings.into_iter())
809 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
810 .flat_map(move |binding| {
811 let found = associated_type_by_name_including_super_traits(
816 let (super_trait_ref, associated_ty) = match found {
817 None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(),
820 let projection_ty = ProjectionTy {
821 associated_ty_id: to_assoc_type_id(associated_ty),
822 substitution: super_trait_ref.substitution,
824 let mut preds = SmallVec::with_capacity(
825 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
827 if let Some(type_ref) = &binding.type_ref {
828 let ty = self.lower_ty(type_ref);
830 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
831 preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
833 for bound in &binding.bounds {
834 preds.extend(self.lower_type_bound(
836 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
844 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
845 cov_mark::hit!(lower_rpit);
847 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
848 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
849 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
851 ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) }
855 fn count_impl_traits(type_ref: &TypeRef) -> usize {
857 type_ref.walk(&mut |type_ref| {
858 if matches!(type_ref, TypeRef::ImplTrait(_)) {
865 /// Build the signature of a callable item (function, struct or enum variant).
866 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
868 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
869 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
870 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
874 pub fn associated_type_shorthand_candidates<R>(
875 db: &dyn HirDatabase,
877 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
879 let mut search = |t| {
880 for t in all_super_trait_refs(db, t) {
881 let data = db.trait_data(t.hir_trait_id());
883 for (name, assoc_id) in &data.items {
884 if let AssocItemId::TypeAliasId(alias) = assoc_id {
885 if let Some(result) = cb(name, &t, *alias) {
895 TypeNs::SelfType(impl_id) => search(
896 // we're _in_ the impl -- the binders get added back later. Correct,
897 // but it would be nice to make this more explicit
898 db.impl_trait(impl_id)?.into_value_and_skipped_binders().0,
900 TypeNs::GenericParam(param_id) => {
901 let predicates = db.generic_predicates_for_param(param_id);
902 let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
903 // FIXME: how to correctly handle higher-ranked bounds here?
904 WhereClause::Implemented(tr) => search(
906 .shifted_out_to(&Interner, DebruijnIndex::ONE)
907 .expect("FIXME unexpected higher-ranked trait bound"),
911 if let res @ Some(_) = res {
914 // Handle `Self::Type` referring to own associated type in trait definitions
915 if let GenericDefId::TraitId(trait_id) = param_id.parent {
916 let generics = generics(db.upcast(), trait_id.into());
917 if generics.params.types[param_id.local_id].provenance
918 == TypeParamProvenance::TraitSelf
920 let trait_ref = TyBuilder::trait_ref(db, trait_id)
921 .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
923 return search(trait_ref);
932 /// Build the type of all specific fields of a struct or enum variant.
933 pub(crate) fn field_types_query(
934 db: &dyn HirDatabase,
935 variant_id: VariantId,
936 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
937 let var_data = variant_id.variant_data(db.upcast());
938 let (resolver, def): (_, GenericDefId) = match variant_id {
939 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
940 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
941 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
943 let generics = generics(db.upcast(), def);
944 let mut res = ArenaMap::default();
946 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
947 for (field_id, field_data) in var_data.fields().iter() {
948 res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref)))
953 /// This query exists only to be used when resolving short-hand associated types
956 /// See the analogous query in rustc and its comment:
957 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
958 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
959 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
960 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
961 pub(crate) fn generic_predicates_for_param_query(
962 db: &dyn HirDatabase,
963 param_id: TypeParamId,
964 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
965 let resolver = param_id.parent.resolver(db.upcast());
967 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
968 let generics = generics(db.upcast(), param_id.parent);
970 .where_predicates_in_scope()
971 // we have to filter out all other predicates *first*, before attempting to lower them
972 .filter(|pred| match pred {
973 WherePredicate::ForLifetime { target, .. }
974 | WherePredicate::TypeBound { target, .. } => match target {
975 WherePredicateTypeTarget::TypeRef(type_ref) => {
976 ctx.lower_ty_only_param(type_ref) == Some(param_id)
978 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
980 WherePredicate::Lifetime { .. } => false,
982 .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
986 pub(crate) fn generic_predicates_for_param_recover(
987 _db: &dyn HirDatabase,
989 _param_id: &TypeParamId,
990 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
994 pub(crate) fn trait_environment_query(
995 db: &dyn HirDatabase,
997 ) -> Arc<TraitEnvironment> {
998 let resolver = def.resolver(db.upcast());
999 let ctx = TyLoweringContext::new(db, &resolver)
1000 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
1001 let mut traits_in_scope = Vec::new();
1002 let mut clauses = Vec::new();
1003 for pred in resolver.where_predicates_in_scope() {
1004 for pred in ctx.lower_where_predicate(pred, false) {
1005 if let WhereClause::Implemented(tr) = &pred.skip_binders() {
1007 .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id()));
1009 let program_clause: chalk_ir::ProgramClause<Interner> = pred.clone().cast(&Interner);
1010 clauses.push(program_clause.into_from_env_clause(&Interner));
1014 let container: Option<AssocContainerId> = match def {
1015 // FIXME: is there a function for this?
1016 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
1017 GenericDefId::AdtId(_) => None,
1018 GenericDefId::TraitId(_) => None,
1019 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
1020 GenericDefId::ImplId(_) => None,
1021 GenericDefId::EnumVariantId(_) => None,
1022 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
1024 if let Some(AssocContainerId::TraitId(trait_id)) = container {
1025 // add `Self: Trait<T1, T2, ...>` to the environment in trait
1026 // function default implementations (and hypothetical code
1027 // inside consts or type aliases)
1028 cov_mark::hit!(trait_self_implements_self);
1029 let substs = TyBuilder::type_params_subst(db, trait_id);
1030 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
1031 let pred = WhereClause::Implemented(trait_ref);
1032 let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(&Interner);
1033 clauses.push(program_clause.into_from_env_clause(&Interner));
1036 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
1038 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
1041 /// Resolve the where clause(s) of an item with generics.
1042 pub(crate) fn generic_predicates_query(
1043 db: &dyn HirDatabase,
1045 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
1046 let resolver = def.resolver(db.upcast());
1048 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1049 let generics = generics(db.upcast(), def);
1051 .where_predicates_in_scope()
1052 .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p)))
1056 /// Resolve the default type params from generics
1057 pub(crate) fn generic_defaults_query(
1058 db: &dyn HirDatabase,
1060 ) -> Arc<[Binders<Ty>]> {
1061 let resolver = def.resolver(db.upcast());
1063 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1064 let generic_params = generics(db.upcast(), def);
1066 let defaults = generic_params
1069 .map(|(idx, (_, p))| {
1071 p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t));
1073 // Each default can only refer to previous parameters.
1074 ty = crate::fold_free_vars(ty, |bound, binders| {
1075 if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST {
1076 // type variable default referring to parameter coming
1077 // after it. This is forbidden (FIXME: report
1079 TyKind::Error.intern(&Interner)
1081 bound.shifted_in_from(binders).to_ty(&Interner)
1085 crate::make_only_type_binders(idx, ty)
1092 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1093 let data = db.function_data(def);
1094 let resolver = def.resolver(db.upcast());
1095 let ctx_params = TyLoweringContext::new(db, &resolver)
1096 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1097 .with_type_param_mode(TypeParamLoweringMode::Variable);
1098 let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
1099 let ctx_ret = TyLoweringContext::new(db, &resolver)
1100 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1101 .with_type_param_mode(TypeParamLoweringMode::Variable);
1102 let ret = ctx_ret.lower_ty(&data.ret_type);
1103 let generics = generics(db.upcast(), def.into());
1104 make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs()))
1107 /// Build the declared type of a function. This should not need to look at the
1109 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1110 let generics = generics(db.upcast(), def.into());
1111 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1114 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1118 /// Build the declared type of a const.
1119 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1120 let data = db.const_data(def);
1121 let generics = generics(db.upcast(), def.into());
1122 let resolver = def.resolver(db.upcast());
1124 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1126 make_binders(&generics, ctx.lower_ty(&data.type_ref))
1129 /// Build the declared type of a static.
1130 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1131 let data = db.static_data(def);
1132 let resolver = def.resolver(db.upcast());
1133 let ctx = TyLoweringContext::new(db, &resolver);
1135 Binders::empty(&Interner, ctx.lower_ty(&data.type_ref))
1138 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1139 let struct_data = db.struct_data(def);
1140 let fields = struct_data.variant_data.fields();
1141 let resolver = def.resolver(db.upcast());
1143 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1144 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1145 let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
1146 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1149 /// Build the type of a tuple struct constructor.
1150 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1151 let struct_data = db.struct_data(def);
1152 if let StructKind::Unit = struct_data.variant_data.kind() {
1153 return type_for_adt(db, def.into());
1155 let generics = generics(db.upcast(), def.into());
1156 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1159 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1163 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1164 let enum_data = db.enum_data(def.parent);
1165 let var_data = &enum_data.variants[def.local_id];
1166 let fields = var_data.variant_data.fields();
1167 let resolver = def.parent.resolver(db.upcast());
1169 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1170 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1171 let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
1172 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1175 /// Build the type of a tuple enum variant constructor.
1176 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1177 let enum_data = db.enum_data(def.parent);
1178 let var_data = &enum_data.variants[def.local_id].variant_data;
1179 if let StructKind::Unit = var_data.kind() {
1180 return type_for_adt(db, def.parent.into());
1182 let generics = generics(db.upcast(), def.parent.into());
1183 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1186 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1190 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1191 let generics = generics(db.upcast(), adt.into());
1192 let b = TyBuilder::adt(db, adt);
1193 let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
1194 make_binders(&generics, ty)
1197 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1198 let generics = generics(db.upcast(), t.into());
1199 let resolver = t.resolver(db.upcast());
1201 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1202 if db.type_alias_data(t).is_extern {
1203 Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner))
1205 let type_ref = &db.type_alias_data(t).type_ref;
1206 let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
1207 make_binders(&generics, inner)
1211 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1212 pub enum CallableDefId {
1213 FunctionId(FunctionId),
1215 EnumVariantId(EnumVariantId),
1217 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1219 impl CallableDefId {
1220 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1221 let db = db.upcast();
1223 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1224 CallableDefId::StructId(s) => s.lookup(db).container,
1225 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1231 impl From<CallableDefId> for GenericDefId {
1232 fn from(def: CallableDefId) -> GenericDefId {
1234 CallableDefId::FunctionId(f) => f.into(),
1235 CallableDefId::StructId(s) => s.into(),
1236 CallableDefId::EnumVariantId(e) => e.into(),
1241 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1243 BuiltinType(BuiltinType),
1245 TypeAliasId(TypeAliasId),
1247 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1249 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1250 pub enum ValueTyDefId {
1251 FunctionId(FunctionId),
1254 EnumVariantId(EnumVariantId),
1258 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1260 /// Build the declared type of an item. This depends on the namespace; e.g. for
1261 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1262 /// the constructor function `(usize) -> Foo` which lives in the values
1264 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1266 TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)),
1267 TyDefId::AdtId(it) => type_for_adt(db, it),
1268 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1272 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1273 let generics = match *def {
1274 TyDefId::BuiltinType(_) => {
1275 return Binders::empty(&Interner, TyKind::Error.intern(&Interner))
1277 TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
1278 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
1280 make_binders(&generics, TyKind::Error.intern(&Interner))
1283 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1285 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1286 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1287 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1288 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1289 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1290 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1294 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1295 let impl_data = db.impl_data(impl_id);
1296 let resolver = impl_id.resolver(db.upcast());
1297 let generics = generics(db.upcast(), impl_id.into());
1299 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1300 make_binders(&generics, ctx.lower_ty(&impl_data.self_ty))
1303 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1304 let parent_data = db.generic_params(def.parent);
1305 let data = &parent_data.consts[def.local_id];
1306 let resolver = def.parent.resolver(db.upcast());
1307 let ctx = TyLoweringContext::new(db, &resolver);
1309 ctx.lower_ty(&data.ty)
1312 pub(crate) fn impl_self_ty_recover(
1313 db: &dyn HirDatabase,
1317 let generics = generics(db.upcast(), (*impl_id).into());
1318 make_binders(&generics, TyKind::Error.intern(&Interner))
1321 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1322 let impl_data = db.impl_data(impl_id);
1323 let resolver = impl_id.resolver(db.upcast());
1325 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1326 let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
1327 let target_trait = impl_data.target_trait.as_ref()?;
1328 Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
1331 pub(crate) fn return_type_impl_traits(
1332 db: &dyn HirDatabase,
1333 def: hir_def::FunctionId,
1334 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1335 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1336 let data = db.function_data(def);
1337 let resolver = def.resolver(db.upcast());
1338 let ctx_ret = TyLoweringContext::new(db, &resolver)
1339 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1340 .with_type_param_mode(TypeParamLoweringMode::Variable);
1341 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1342 let generics = generics(db.upcast(), def.into());
1343 let return_type_impl_traits =
1344 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1345 if return_type_impl_traits.impl_traits.is_empty() {
1348 Some(Arc::new(make_binders(&generics, return_type_impl_traits)))
1352 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1354 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1355 hir_def::type_ref::Mutability::Mut => Mutability::Mut,
1359 fn make_binders<T: HasInterner<Interner = Interner>>(generics: &Generics, value: T) -> Binders<T> {
1360 crate::make_only_type_binders(generics.len(), value)