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 // FIXME: we don't have length info here because we don't store an expression for
179 TyKind::Array(inner_ty, dummy_usize_const()).intern(&Interner)
181 TypeRef::Slice(inner) => {
182 let inner_ty = self.lower_ty(inner);
183 TyKind::Slice(inner_ty).intern(&Interner)
185 TypeRef::Reference(inner, _, mutability) => {
186 let inner_ty = self.lower_ty(inner);
187 let lifetime = static_lifetime();
188 TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
191 TypeRef::Placeholder => TyKind::Error.intern(&Interner),
192 TypeRef::Fn(params, is_varargs) => {
193 let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
194 Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr)))
196 TyKind::Function(FnPointer {
197 num_binders: 0, // FIXME lower `for<'a> fn()` correctly
198 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
199 substitution: FnSubst(substs),
203 TypeRef::DynTrait(bounds) => {
205 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
206 let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
207 QuantifiedWhereClauses::from_iter(
209 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
212 let bounds = crate::make_only_type_binders(1, bounds);
213 TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner)
215 TypeRef::ImplTrait(bounds) => {
216 match self.impl_trait_mode {
217 ImplTraitLoweringMode::Opaque => {
218 let idx = self.impl_trait_counter.get();
219 self.impl_trait_counter.set(idx + 1);
221 assert!(idx as usize == self.opaque_type_data.borrow().len());
222 // this dance is to make sure the data is in the right
223 // place even if we encounter more opaque types while
224 // lowering the bounds
225 self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait {
226 bounds: crate::make_only_type_binders(1, Vec::new()),
228 // We don't want to lower the bounds inside the binders
229 // we're currently in, because they don't end up inside
230 // those binders. E.g. when we have `impl Trait<impl
231 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
232 // to the self parameter from `impl Trait`, and the
233 // bounds aren't actually stored nested within each
234 // other, but separately. So if the `T` refers to a type
235 // parameter of the outer function, it's just one binder
236 // away instead of two.
237 let actual_opaque_type_data = self
238 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
239 ctx.lower_impl_trait(&bounds)
241 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
243 let func = match self.resolver.generic_def() {
244 Some(GenericDefId::FunctionId(f)) => f,
245 _ => panic!("opaque impl trait lowering in non-function"),
247 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
248 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
249 let generics = generics(self.db.upcast(), func.into());
250 let parameters = generics.bound_vars_subst(self.in_binders);
251 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
253 substitution: parameters,
257 ImplTraitLoweringMode::Param => {
258 let idx = self.impl_trait_counter.get();
259 // FIXME we're probably doing something wrong here
260 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
261 if let Some(def) = self.resolver.generic_def() {
262 let generics = generics(self.db.upcast(), def);
265 .filter(|(_, data)| {
266 data.provenance == TypeParamProvenance::ArgumentImplTrait
269 .map_or(TyKind::Error, |(id, _)| {
270 TyKind::Placeholder(to_placeholder_idx(self.db, id))
272 param.intern(&Interner)
274 TyKind::Error.intern(&Interner)
277 ImplTraitLoweringMode::Variable => {
278 let idx = self.impl_trait_counter.get();
279 // FIXME we're probably doing something wrong here
280 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
281 let (parent_params, self_params, list_params, _impl_trait_params) =
282 if let Some(def) = self.resolver.generic_def() {
283 let generics = generics(self.db.upcast(), def);
284 generics.provenance_split()
288 TyKind::BoundVar(BoundVar::new(
290 idx as usize + parent_params + self_params + list_params,
294 ImplTraitLoweringMode::Disallowed => {
295 // FIXME: report error
296 TyKind::Error.intern(&Interner)
300 TypeRef::Macro(macro_call) => {
301 let (expander, recursion_start) = {
302 let mut expander = self.expander.borrow_mut();
303 if expander.is_some() {
304 (Some(expander), false)
306 if let Some(module_id) = self.resolver.module() {
307 *expander = Some(Expander::new(
312 (Some(expander), true)
318 let ty = if let Some(mut expander) = expander {
319 let expander_mut = expander.as_mut().unwrap();
320 let macro_call = macro_call.to_node(self.db.upcast());
321 match expander_mut.enter_expand::<ast::Type>(self.db.upcast(), macro_call) {
322 Ok(ExpandResult { value: Some((mark, expanded)), .. }) => {
324 LowerCtx::new(self.db.upcast(), expander_mut.current_file_id());
325 let type_ref = TypeRef::from_ast(&ctx, expanded);
328 let ty = self.lower_ty(&type_ref);
334 .exit(self.db.upcast(), mark);
343 *self.expander.borrow_mut() = None;
345 ty.unwrap_or_else(|| TyKind::Error.intern(&Interner))
347 TypeRef::Error => TyKind::Error.intern(&Interner),
352 /// This is only for `generic_predicates_for_param`, where we can't just
353 /// lower the self types of the predicates since that could lead to cycles.
354 /// So we just check here if the `type_ref` resolves to a generic param, and which.
355 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
356 let path = match type_ref {
357 TypeRef::Path(path) => path,
360 if path.type_anchor().is_some() {
363 if path.segments().len() > 1 {
367 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
368 Some((it, None)) => it,
371 if let TypeNs::GenericParam(param_id) = resolution {
378 pub(crate) fn lower_ty_relative_path(
381 // We need the original resolution to lower `Self::AssocTy` correctly
383 remaining_segments: PathSegments<'_>,
384 ) -> (Ty, Option<TypeNs>) {
385 if remaining_segments.len() == 1 {
386 // resolve unselected assoc types
387 let segment = remaining_segments.first().unwrap();
388 (self.select_associated_type(res, segment), None)
389 } else if remaining_segments.len() > 1 {
390 // FIXME report error (ambiguous associated type)
391 (TyKind::Error.intern(&Interner), None)
397 pub(crate) fn lower_partly_resolved_path(
400 resolved_segment: PathSegment<'_>,
401 remaining_segments: PathSegments<'_>,
403 ) -> (Ty, Option<TypeNs>) {
404 let ty = match resolution {
405 TypeNs::TraitId(trait_) => {
406 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
407 let self_ty = if remaining_segments.len() == 0 {
409 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
416 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
417 let ty = if remaining_segments.len() == 1 {
418 let segment = remaining_segments.first().unwrap();
421 .trait_data(trait_ref.hir_trait_id())
422 .associated_type_by_name(&segment.name);
424 Some(associated_ty) => {
425 // FIXME handle type parameters on the segment
426 TyKind::Alias(AliasTy::Projection(ProjectionTy {
427 associated_ty_id: to_assoc_type_id(associated_ty),
428 substitution: trait_ref.substitution,
433 // FIXME: report error (associated type not found)
434 TyKind::Error.intern(&Interner)
437 } else if remaining_segments.len() > 1 {
438 // FIXME report error (ambiguous associated type)
439 TyKind::Error.intern(&Interner)
442 bounds: crate::make_only_type_binders(
444 QuantifiedWhereClauses::from_iter(
446 Some(crate::wrap_empty_binders(WhereClause::Implemented(
451 lifetime: static_lifetime(),
453 TyKind::Dyn(dyn_ty).intern(&Interner)
457 TypeNs::GenericParam(param_id) => {
458 let generics = generics(
460 self.resolver.generic_def().expect("generics in scope"),
462 match self.type_param_mode {
463 TypeParamLoweringMode::Placeholder => {
464 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
466 TypeParamLoweringMode::Variable => {
467 let idx = generics.param_idx(param_id).expect("matching generics");
468 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
473 TypeNs::SelfType(impl_id) => {
474 let generics = generics(self.db.upcast(), impl_id.into());
475 let substs = match self.type_param_mode {
476 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
477 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
479 self.db.impl_self_ty(impl_id).substitute(&Interner, &substs)
481 TypeNs::AdtSelfType(adt) => {
482 let generics = generics(self.db.upcast(), adt.into());
483 let substs = match self.type_param_mode {
484 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
485 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
487 self.db.ty(adt.into()).substitute(&Interner, &substs)
490 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
491 TypeNs::BuiltinType(it) => {
492 self.lower_path_inner(resolved_segment, it.into(), infer_args)
494 TypeNs::TypeAliasId(it) => {
495 self.lower_path_inner(resolved_segment, it.into(), infer_args)
497 // FIXME: report error
498 TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None),
500 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
503 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
504 // Resolve the path (in type namespace)
505 if let Some(type_ref) = path.type_anchor() {
506 let (ty, res) = self.lower_ty_ext(&type_ref);
507 return self.lower_ty_relative_path(ty, res, path.segments());
509 let (resolution, remaining_index) =
510 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
512 None => return (TyKind::Error.intern(&Interner), None),
514 let (resolved_segment, remaining_segments) = match remaining_index {
516 path.segments().last().expect("resolved path has at least one element"),
519 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
521 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
524 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
525 if let Some(res) = res {
526 let ty = associated_type_shorthand_candidates(
529 move |name, t, associated_ty| {
530 if name == segment.name {
531 let substs = match self.type_param_mode {
532 TypeParamLoweringMode::Placeholder => {
533 // if we're lowering to placeholders, we have to put
535 let generics = generics(
537 self.resolver.generic_def().expect(
538 "there should be generics if there's a generic param",
541 let s = generics.type_params_subst(self.db);
542 s.apply(t.substitution.clone(), &Interner)
544 TypeParamLoweringMode::Variable => t.substitution.clone(),
546 // We need to shift in the bound vars, since
547 // associated_type_shorthand_candidates does not do that
548 let substs = substs.shifted_in_from(&Interner, self.in_binders);
549 // FIXME handle type parameters on the segment
551 TyKind::Alias(AliasTy::Projection(ProjectionTy {
552 associated_ty_id: to_assoc_type_id(associated_ty),
553 substitution: substs,
563 ty.unwrap_or(TyKind::Error.intern(&Interner))
565 TyKind::Error.intern(&Interner)
571 segment: PathSegment<'_>,
575 let generic_def = match typeable {
576 TyDefId::BuiltinType(_) => None,
577 TyDefId::AdtId(it) => Some(it.into()),
578 TyDefId::TypeAliasId(it) => Some(it.into()),
580 let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
581 self.db.ty(typeable).substitute(&Interner, &substs)
584 /// Collect generic arguments from a path into a `Substs`. See also
585 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
586 pub(super) fn substs_from_path(
589 // Note that we don't call `db.value_type(resolved)` here,
590 // `ValueTyDefId` is just a convenient way to pass generics and
591 // special-case enum variants
592 resolved: ValueTyDefId,
595 let last = path.segments().last().expect("path should have at least one segment");
596 let (segment, generic_def) = match resolved {
597 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
598 ValueTyDefId::StructId(it) => (last, Some(it.into())),
599 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
600 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
601 ValueTyDefId::StaticId(_) => (last, None),
602 ValueTyDefId::EnumVariantId(var) => {
603 // the generic args for an enum variant may be either specified
604 // on the segment referring to the enum, or on the segment
605 // referring to the variant. So `Option::<T>::None` and
606 // `Option::None::<T>` are both allowed (though the former is
607 // preferred). See also `def_ids_for_path_segments` in rustc.
608 let len = path.segments().len();
609 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
610 let segment = match penultimate {
611 Some(segment) if segment.args_and_bindings.is_some() => segment,
614 (segment, Some(var.parent.into()))
617 self.substs_from_path_segment(segment, generic_def, infer_args, None)
620 fn substs_from_path_segment(
622 segment: PathSegment<'_>,
623 def_generic: Option<GenericDefId>,
625 explicit_self_ty: Option<Ty>,
627 let mut substs = Vec::new();
628 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
630 let (parent_params, self_params, type_params, impl_trait_params) =
631 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
632 let total_len = parent_params + self_params + type_params + impl_trait_params;
634 substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params));
636 let fill_self_params = || {
640 .chain(iter::repeat(TyKind::Error.intern(&Interner)))
644 let mut had_explicit_type_args = false;
646 if let Some(generic_args) = &segment.args_and_bindings {
647 if !generic_args.has_self_type {
651 if generic_args.has_self_type { self_params + type_params } else { type_params };
652 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
653 // if args are provided, it should be all of them, but we can't rely on that
654 for arg in generic_args
657 .filter(|arg| matches!(arg, GenericArg::Type(_)))
662 GenericArg::Type(type_ref) => {
663 had_explicit_type_args = true;
664 let ty = self.lower_ty(type_ref);
667 GenericArg::Lifetime(_) => {}
674 // handle defaults. In expression or pattern path segments without
675 // explicitly specified type arguments, missing type arguments are inferred
676 // (i.e. defaults aren't used).
677 if !infer_args || had_explicit_type_args {
678 if let Some(def_generic) = def_generic {
679 let defaults = self.db.generic_defaults(def_generic);
680 assert_eq!(total_len, defaults.len());
682 for default_ty in defaults.iter().skip(substs.len()) {
683 // each default can depend on the previous parameters
684 let substs_so_far = Substitution::from_iter(&Interner, substs.clone());
685 substs.push(default_ty.clone().substitute(&Interner, &substs_so_far));
690 // add placeholders for args that were not provided
691 // FIXME: emit diagnostics in contexts where this is not allowed
692 for _ in substs.len()..total_len {
693 substs.push(TyKind::Error.intern(&Interner));
695 assert_eq!(substs.len(), total_len);
697 Substitution::from_iter(&Interner, substs)
700 fn lower_trait_ref_from_path(
703 explicit_self_ty: Option<Ty>,
704 ) -> Option<TraitRef> {
706 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
707 TypeNs::TraitId(tr) => tr,
710 let segment = path.segments().last().expect("path should have at least one segment");
711 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
714 pub(crate) fn lower_trait_ref_from_resolved_path(
717 segment: PathSegment<'_>,
718 explicit_self_ty: Option<Ty>,
720 let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
721 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
726 trait_ref: &HirTraitRef,
727 explicit_self_ty: Option<Ty>,
728 ) -> Option<TraitRef> {
729 self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
732 fn trait_ref_substs_from_path(
734 segment: PathSegment<'_>,
736 explicit_self_ty: Option<Ty>,
738 self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
741 pub(crate) fn lower_where_predicate(
743 where_predicate: &'a WherePredicate,
744 ignore_bindings: bool,
745 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
746 match where_predicate {
747 WherePredicate::ForLifetime { target, bound, .. }
748 | WherePredicate::TypeBound { target, bound } => {
749 let self_ty = match target {
750 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
751 WherePredicateTypeTarget::TypeParam(param_id) => {
752 let generic_def = self.resolver.generic_def().expect("generics in scope");
753 let generics = generics(self.db.upcast(), generic_def);
755 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
756 let placeholder = to_placeholder_idx(self.db, param_id);
757 match self.type_param_mode {
758 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
759 TypeParamLoweringMode::Variable => {
760 let idx = generics.param_idx(param_id).expect("matching generics");
761 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
767 self.lower_type_bound(bound, self_ty, ignore_bindings)
771 WherePredicate::Lifetime { .. } => vec![].into_iter(),
775 pub(crate) fn lower_type_bound(
777 bound: &'a TypeBound,
779 ignore_bindings: bool,
780 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
781 let mut bindings = None;
782 let trait_ref = match bound {
783 TypeBound::Path(path) => {
784 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
785 bindings.clone().map(WhereClause::Implemented).map(|b| crate::wrap_empty_binders(b))
787 TypeBound::Lifetime(_) => None,
788 TypeBound::Error => None,
790 trait_ref.into_iter().chain(
793 .filter(move |_| !ignore_bindings)
794 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
798 fn assoc_type_bindings_from_type_bound(
800 bound: &'a TypeBound,
802 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
803 let last_segment = match bound {
804 TypeBound::Path(path) => path.segments().last(),
805 TypeBound::Error | TypeBound::Lifetime(_) => None,
809 .flat_map(|segment| segment.args_and_bindings.into_iter())
810 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
811 .flat_map(move |binding| {
812 let found = associated_type_by_name_including_super_traits(
817 let (super_trait_ref, associated_ty) = match found {
818 None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(),
821 let projection_ty = ProjectionTy {
822 associated_ty_id: to_assoc_type_id(associated_ty),
823 substitution: super_trait_ref.substitution,
825 let mut preds = SmallVec::with_capacity(
826 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
828 if let Some(type_ref) = &binding.type_ref {
829 let ty = self.lower_ty(type_ref);
831 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
832 preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
834 for bound in &binding.bounds {
835 preds.extend(self.lower_type_bound(
837 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
845 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
846 cov_mark::hit!(lower_rpit);
848 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
849 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
850 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
852 ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) }
856 fn count_impl_traits(type_ref: &TypeRef) -> usize {
858 type_ref.walk(&mut |type_ref| {
859 if matches!(type_ref, TypeRef::ImplTrait(_)) {
866 /// Build the signature of a callable item (function, struct or enum variant).
867 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
869 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
870 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
871 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
875 pub fn associated_type_shorthand_candidates<R>(
876 db: &dyn HirDatabase,
878 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
880 let mut search = |t| {
881 for t in all_super_trait_refs(db, t) {
882 let data = db.trait_data(t.hir_trait_id());
884 for (name, assoc_id) in &data.items {
885 if let AssocItemId::TypeAliasId(alias) = assoc_id {
886 if let Some(result) = cb(name, &t, *alias) {
896 TypeNs::SelfType(impl_id) => search(
897 // we're _in_ the impl -- the binders get added back later. Correct,
898 // but it would be nice to make this more explicit
899 db.impl_trait(impl_id)?.into_value_and_skipped_binders().0,
901 TypeNs::GenericParam(param_id) => {
902 let predicates = db.generic_predicates_for_param(param_id);
903 let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
904 // FIXME: how to correctly handle higher-ranked bounds here?
905 WhereClause::Implemented(tr) => search(
907 .shifted_out_to(&Interner, DebruijnIndex::ONE)
908 .expect("FIXME unexpected higher-ranked trait bound"),
912 if let res @ Some(_) = res {
915 // Handle `Self::Type` referring to own associated type in trait definitions
916 if let GenericDefId::TraitId(trait_id) = param_id.parent {
917 let generics = generics(db.upcast(), trait_id.into());
918 if generics.params.types[param_id.local_id].provenance
919 == TypeParamProvenance::TraitSelf
921 let trait_ref = TyBuilder::trait_ref(db, trait_id)
922 .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
924 return search(trait_ref);
933 /// Build the type of all specific fields of a struct or enum variant.
934 pub(crate) fn field_types_query(
935 db: &dyn HirDatabase,
936 variant_id: VariantId,
937 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
938 let var_data = variant_id.variant_data(db.upcast());
939 let (resolver, def): (_, GenericDefId) = match variant_id {
940 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
941 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
942 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
944 let generics = generics(db.upcast(), def);
945 let mut res = ArenaMap::default();
947 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
948 for (field_id, field_data) in var_data.fields().iter() {
949 res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref)))
954 /// This query exists only to be used when resolving short-hand associated types
957 /// See the analogous query in rustc and its comment:
958 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
959 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
960 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
961 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
962 pub(crate) fn generic_predicates_for_param_query(
963 db: &dyn HirDatabase,
964 param_id: TypeParamId,
965 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
966 let resolver = param_id.parent.resolver(db.upcast());
968 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
969 let generics = generics(db.upcast(), param_id.parent);
971 .where_predicates_in_scope()
972 // we have to filter out all other predicates *first*, before attempting to lower them
973 .filter(|pred| match pred {
974 WherePredicate::ForLifetime { target, .. }
975 | WherePredicate::TypeBound { target, .. } => match target {
976 WherePredicateTypeTarget::TypeRef(type_ref) => {
977 ctx.lower_ty_only_param(type_ref) == Some(param_id)
979 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
981 WherePredicate::Lifetime { .. } => false,
983 .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
987 pub(crate) fn generic_predicates_for_param_recover(
988 _db: &dyn HirDatabase,
990 _param_id: &TypeParamId,
991 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
995 pub(crate) fn trait_environment_query(
996 db: &dyn HirDatabase,
998 ) -> Arc<TraitEnvironment> {
999 let resolver = def.resolver(db.upcast());
1000 let ctx = TyLoweringContext::new(db, &resolver)
1001 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
1002 let mut traits_in_scope = Vec::new();
1003 let mut clauses = Vec::new();
1004 for pred in resolver.where_predicates_in_scope() {
1005 for pred in ctx.lower_where_predicate(pred, false) {
1006 if let WhereClause::Implemented(tr) = &pred.skip_binders() {
1008 .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id()));
1010 let program_clause: chalk_ir::ProgramClause<Interner> = pred.clone().cast(&Interner);
1011 clauses.push(program_clause.into_from_env_clause(&Interner));
1015 let container: Option<AssocContainerId> = match def {
1016 // FIXME: is there a function for this?
1017 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
1018 GenericDefId::AdtId(_) => None,
1019 GenericDefId::TraitId(_) => None,
1020 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
1021 GenericDefId::ImplId(_) => None,
1022 GenericDefId::EnumVariantId(_) => None,
1023 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
1025 if let Some(AssocContainerId::TraitId(trait_id)) = container {
1026 // add `Self: Trait<T1, T2, ...>` to the environment in trait
1027 // function default implementations (and hypothetical code
1028 // inside consts or type aliases)
1029 cov_mark::hit!(trait_self_implements_self);
1030 let substs = TyBuilder::type_params_subst(db, trait_id);
1031 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
1032 let pred = WhereClause::Implemented(trait_ref);
1033 let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(&Interner);
1034 clauses.push(program_clause.into_from_env_clause(&Interner));
1037 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
1039 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
1042 /// Resolve the where clause(s) of an item with generics.
1043 pub(crate) fn generic_predicates_query(
1044 db: &dyn HirDatabase,
1046 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
1047 let resolver = def.resolver(db.upcast());
1049 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1050 let generics = generics(db.upcast(), def);
1052 .where_predicates_in_scope()
1053 .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p)))
1057 /// Resolve the default type params from generics
1058 pub(crate) fn generic_defaults_query(
1059 db: &dyn HirDatabase,
1061 ) -> Arc<[Binders<Ty>]> {
1062 let resolver = def.resolver(db.upcast());
1064 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1065 let generic_params = generics(db.upcast(), def);
1067 let defaults = generic_params
1070 .map(|(idx, (_, p))| {
1072 p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t));
1074 // Each default can only refer to previous parameters.
1075 ty = crate::fold_free_vars(ty, |bound, binders| {
1076 if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST {
1077 // type variable default referring to parameter coming
1078 // after it. This is forbidden (FIXME: report
1080 TyKind::Error.intern(&Interner)
1082 bound.shifted_in_from(binders).to_ty(&Interner)
1086 crate::make_only_type_binders(idx, ty)
1093 pub(crate) fn generic_defaults_recover(
1094 db: &dyn HirDatabase,
1097 ) -> Arc<[Binders<Ty>]> {
1098 let generic_params = generics(db.upcast(), *def);
1100 // we still need one default per parameter
1101 let defaults = generic_params
1105 let ty = TyKind::Error.intern(&Interner);
1107 crate::make_only_type_binders(idx, ty)
1114 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1115 let data = db.function_data(def);
1116 let resolver = def.resolver(db.upcast());
1117 let ctx_params = TyLoweringContext::new(db, &resolver)
1118 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1119 .with_type_param_mode(TypeParamLoweringMode::Variable);
1120 let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
1121 let ctx_ret = TyLoweringContext::new(db, &resolver)
1122 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1123 .with_type_param_mode(TypeParamLoweringMode::Variable);
1124 let ret = ctx_ret.lower_ty(&data.ret_type);
1125 let generics = generics(db.upcast(), def.into());
1126 make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs()))
1129 /// Build the declared type of a function. This should not need to look at the
1131 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1132 let generics = generics(db.upcast(), def.into());
1133 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1136 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1140 /// Build the declared type of a const.
1141 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1142 let data = db.const_data(def);
1143 let generics = generics(db.upcast(), def.into());
1144 let resolver = def.resolver(db.upcast());
1146 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1148 make_binders(&generics, ctx.lower_ty(&data.type_ref))
1151 /// Build the declared type of a static.
1152 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1153 let data = db.static_data(def);
1154 let resolver = def.resolver(db.upcast());
1155 let ctx = TyLoweringContext::new(db, &resolver);
1157 Binders::empty(&Interner, ctx.lower_ty(&data.type_ref))
1160 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1161 let struct_data = db.struct_data(def);
1162 let fields = struct_data.variant_data.fields();
1163 let resolver = def.resolver(db.upcast());
1165 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1166 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1167 let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
1168 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1171 /// Build the type of a tuple struct constructor.
1172 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1173 let struct_data = db.struct_data(def);
1174 if let StructKind::Unit = struct_data.variant_data.kind() {
1175 return type_for_adt(db, def.into());
1177 let generics = generics(db.upcast(), def.into());
1178 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1181 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1185 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1186 let enum_data = db.enum_data(def.parent);
1187 let var_data = &enum_data.variants[def.local_id];
1188 let fields = var_data.variant_data.fields();
1189 let resolver = def.parent.resolver(db.upcast());
1191 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1192 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1193 let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
1194 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1197 /// Build the type of a tuple enum variant constructor.
1198 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1199 let enum_data = db.enum_data(def.parent);
1200 let var_data = &enum_data.variants[def.local_id].variant_data;
1201 if let StructKind::Unit = var_data.kind() {
1202 return type_for_adt(db, def.parent.into());
1204 let generics = generics(db.upcast(), def.parent.into());
1205 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1208 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1212 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1213 let generics = generics(db.upcast(), adt.into());
1214 let b = TyBuilder::adt(db, adt);
1215 let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
1216 make_binders(&generics, ty)
1219 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1220 let generics = generics(db.upcast(), t.into());
1221 let resolver = t.resolver(db.upcast());
1223 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1224 if db.type_alias_data(t).is_extern {
1225 Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner))
1227 let type_ref = &db.type_alias_data(t).type_ref;
1228 let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
1229 make_binders(&generics, inner)
1233 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1234 pub enum CallableDefId {
1235 FunctionId(FunctionId),
1237 EnumVariantId(EnumVariantId),
1239 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1241 impl CallableDefId {
1242 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1243 let db = db.upcast();
1245 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1246 CallableDefId::StructId(s) => s.lookup(db).container,
1247 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1253 impl From<CallableDefId> for GenericDefId {
1254 fn from(def: CallableDefId) -> GenericDefId {
1256 CallableDefId::FunctionId(f) => f.into(),
1257 CallableDefId::StructId(s) => s.into(),
1258 CallableDefId::EnumVariantId(e) => e.into(),
1263 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1265 BuiltinType(BuiltinType),
1267 TypeAliasId(TypeAliasId),
1269 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1271 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1272 pub enum ValueTyDefId {
1273 FunctionId(FunctionId),
1276 EnumVariantId(EnumVariantId),
1280 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1282 /// Build the declared type of an item. This depends on the namespace; e.g. for
1283 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1284 /// the constructor function `(usize) -> Foo` which lives in the values
1286 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1288 TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)),
1289 TyDefId::AdtId(it) => type_for_adt(db, it),
1290 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1294 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1295 let generics = match *def {
1296 TyDefId::BuiltinType(_) => {
1297 return Binders::empty(&Interner, TyKind::Error.intern(&Interner))
1299 TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
1300 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
1302 make_binders(&generics, TyKind::Error.intern(&Interner))
1305 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1307 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1308 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1309 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1310 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1311 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1312 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1316 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1317 let impl_data = db.impl_data(impl_id);
1318 let resolver = impl_id.resolver(db.upcast());
1319 let generics = generics(db.upcast(), impl_id.into());
1321 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1322 make_binders(&generics, ctx.lower_ty(&impl_data.self_ty))
1325 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1326 let parent_data = db.generic_params(def.parent);
1327 let data = &parent_data.consts[def.local_id];
1328 let resolver = def.parent.resolver(db.upcast());
1329 let ctx = TyLoweringContext::new(db, &resolver);
1331 ctx.lower_ty(&data.ty)
1334 pub(crate) fn impl_self_ty_recover(
1335 db: &dyn HirDatabase,
1339 let generics = generics(db.upcast(), (*impl_id).into());
1340 make_binders(&generics, TyKind::Error.intern(&Interner))
1343 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1344 let impl_data = db.impl_data(impl_id);
1345 let resolver = impl_id.resolver(db.upcast());
1347 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1348 let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
1349 let target_trait = impl_data.target_trait.as_ref()?;
1350 Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
1353 pub(crate) fn return_type_impl_traits(
1354 db: &dyn HirDatabase,
1355 def: hir_def::FunctionId,
1356 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1357 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1358 let data = db.function_data(def);
1359 let resolver = def.resolver(db.upcast());
1360 let ctx_ret = TyLoweringContext::new(db, &resolver)
1361 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1362 .with_type_param_mode(TypeParamLoweringMode::Variable);
1363 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1364 let generics = generics(db.upcast(), def.into());
1365 let return_type_impl_traits =
1366 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1367 if return_type_impl_traits.impl_traits.is_empty() {
1370 Some(Arc::new(make_binders(&generics, return_type_impl_traits)))
1374 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1376 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1377 hir_def::type_ref::Mutability::Mut => Mutability::Mut,
1381 fn make_binders<T: HasInterner<Interner = Interner>>(generics: &Generics, value: T) -> Binders<T> {
1382 crate::make_only_type_binders(generics.len(), value)