1 //! Methods for lowering the HIR to types. There are two main cases here:
3 //! - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
4 //! type: The entry point for this is `Ty::from_hir`.
5 //! - Building the type for an item: This happens through the `type_for_def` query.
7 //! This usually involves resolving names, collecting generic arguments etc.
8 use std::{iter, sync::Arc};
10 use arena::map::ArenaMap;
14 builtin_type::BuiltinType,
15 generics::{TypeParamProvenance, WherePredicate, WherePredicateTarget},
16 path::{GenericArg, Path, PathSegment, PathSegments},
17 resolver::{HasResolver, Resolver, TypeNs},
18 type_ref::{TypeBound, TypeRef},
19 AdtId, AssocContainerId, AssocItemId, ConstId, EnumId, EnumVariantId, FunctionId, GenericDefId,
20 HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId, TypeAliasId, TypeParamId,
23 use hir_expand::name::Name;
24 use smallvec::SmallVec;
30 primitive::{FloatTy, IntTy},
32 all_super_trait_refs, associated_type_by_name_including_super_traits, generics,
33 make_mut_slice, variant_data,
35 Binders, BoundVar, DebruijnIndex, FnSig, GenericPredicate, OpaqueTy, OpaqueTyId, PolyFnSig,
36 ProjectionPredicate, ProjectionTy, ReturnTypeImplTrait, ReturnTypeImplTraits, Substs,
37 TraitEnvironment, TraitRef, Ty, TypeCtor, TypeWalk,
41 pub struct TyLoweringContext<'a> {
42 pub db: &'a dyn HirDatabase,
43 pub resolver: &'a Resolver,
44 in_binders: DebruijnIndex,
45 /// Note: Conceptually, it's thinkable that we could be in a location where
46 /// some type params should be represented as placeholders, and others
47 /// should be converted to variables. I think in practice, this isn't
48 /// possible currently, so this should be fine for now.
49 pub type_param_mode: TypeParamLoweringMode,
50 pub impl_trait_mode: ImplTraitLoweringMode,
51 impl_trait_counter: std::cell::Cell<u16>,
52 /// When turning `impl Trait` into opaque types, we have to collect the
53 /// bounds at the same time to get the IDs correct (without becoming too
54 /// complicated). I don't like using interior mutability (as for the
55 /// counter), but I've tried and failed to make the lifetimes work for
56 /// passing around a `&mut TyLoweringContext`. The core problem is that
57 /// we're grouping the mutable data (the counter and this field) together
58 /// with the immutable context (the references to the DB and resolver).
59 /// Splitting this up would be a possible fix.
60 opaque_type_data: std::cell::RefCell<Vec<ReturnTypeImplTrait>>,
63 impl<'a> TyLoweringContext<'a> {
64 pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
65 let impl_trait_counter = std::cell::Cell::new(0);
66 let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
67 let type_param_mode = TypeParamLoweringMode::Placeholder;
68 let in_binders = DebruijnIndex::INNERMOST;
69 let opaque_type_data = std::cell::RefCell::new(Vec::new());
81 pub fn with_debruijn<T>(
83 debruijn: DebruijnIndex,
84 f: impl FnOnce(&TyLoweringContext) -> T,
86 let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
89 impl_trait_counter: std::cell::Cell::new(self.impl_trait_counter.get()),
90 opaque_type_data: std::cell::RefCell::new(opaque_ty_data_vec),
93 let result = f(&new_ctx);
94 self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
95 self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
99 pub fn with_shifted_in<T>(
101 debruijn: DebruijnIndex,
102 f: impl FnOnce(&TyLoweringContext) -> T,
104 self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
107 pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
108 Self { impl_trait_mode, ..self }
111 pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
112 Self { type_param_mode, ..self }
116 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
117 pub enum ImplTraitLoweringMode {
118 /// `impl Trait` gets lowered into an opaque type that doesn't unify with
119 /// anything except itself. This is used in places where values flow 'out',
120 /// i.e. for arguments of the function we're currently checking, and return
121 /// types of functions we're calling.
123 /// `impl Trait` gets lowered into a type variable. Used for argument
124 /// position impl Trait when inside the respective function, since it allows
125 /// us to support that without Chalk.
127 /// `impl Trait` gets lowered into a variable that can unify with some
128 /// type. This is used in places where values flow 'in', i.e. for arguments
129 /// of functions we're calling, and the return type of the function we're
130 /// currently checking.
132 /// `impl Trait` is disallowed and will be an error.
136 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
137 pub enum TypeParamLoweringMode {
143 pub fn from_hir(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Self {
144 Ty::from_hir_ext(ctx, type_ref).0
146 pub fn from_hir_ext(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> (Self, Option<TypeNs>) {
148 let ty = match type_ref {
149 TypeRef::Never => Ty::simple(TypeCtor::Never),
150 TypeRef::Tuple(inner) => {
151 let inner_tys: Arc<[Ty]> = inner.iter().map(|tr| Ty::from_hir(ctx, tr)).collect();
153 TypeCtor::Tuple { cardinality: inner_tys.len() as u16 },
157 TypeRef::Path(path) => {
158 let (ty, res_) = Ty::from_hir_path(ctx, path);
162 TypeRef::RawPtr(inner, mutability) => {
163 let inner_ty = Ty::from_hir(ctx, inner);
164 Ty::apply_one(TypeCtor::RawPtr(*mutability), inner_ty)
166 TypeRef::Array(inner) => {
167 let inner_ty = Ty::from_hir(ctx, inner);
168 Ty::apply_one(TypeCtor::Array, inner_ty)
170 TypeRef::Slice(inner) => {
171 let inner_ty = Ty::from_hir(ctx, inner);
172 Ty::apply_one(TypeCtor::Slice, inner_ty)
174 TypeRef::Reference(inner, mutability) => {
175 let inner_ty = Ty::from_hir(ctx, inner);
176 Ty::apply_one(TypeCtor::Ref(*mutability), inner_ty)
178 TypeRef::Placeholder => Ty::Unknown,
179 TypeRef::Fn(params, is_varargs) => {
180 let sig = Substs(params.iter().map(|tr| Ty::from_hir(ctx, tr)).collect());
182 TypeCtor::FnPtr { num_args: sig.len() as u16 - 1, is_varargs: *is_varargs },
186 TypeRef::DynTrait(bounds) => {
187 let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
188 let predicates = ctx.with_shifted_in(DebruijnIndex::ONE, |ctx| {
191 .flat_map(|b| GenericPredicate::from_type_bound(ctx, b, self_ty.clone()))
196 TypeRef::ImplTrait(bounds) => {
197 match ctx.impl_trait_mode {
198 ImplTraitLoweringMode::Opaque => {
199 let idx = ctx.impl_trait_counter.get();
200 ctx.impl_trait_counter.set(idx + 1);
202 assert!(idx as usize == ctx.opaque_type_data.borrow().len());
203 // this dance is to make sure the data is in the right
204 // place even if we encounter more opaque types while
205 // lowering the bounds
208 .push(ReturnTypeImplTrait { bounds: Binders::new(1, Vec::new()) });
209 // We don't want to lower the bounds inside the binders
210 // we're currently in, because they don't end up inside
211 // those binders. E.g. when we have `impl Trait<impl
212 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
213 // to the self parameter from `impl Trait`, and the
214 // bounds aren't actually stored nested within each
215 // other, but separately. So if the `T` refers to a type
216 // parameter of the outer function, it's just one binder
217 // away instead of two.
218 let actual_opaque_type_data = ctx
219 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
220 ReturnTypeImplTrait::from_hir(ctx, &bounds)
222 ctx.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
224 let func = match ctx.resolver.generic_def() {
225 Some(GenericDefId::FunctionId(f)) => f,
226 _ => panic!("opaque impl trait lowering in non-function"),
228 let impl_trait_id = OpaqueTyId::ReturnTypeImplTrait(func, idx);
229 let generics = generics(ctx.db.upcast(), func.into());
230 let parameters = Substs::bound_vars(&generics, ctx.in_binders);
231 Ty::Opaque(OpaqueTy { opaque_ty_id: impl_trait_id, parameters })
233 ImplTraitLoweringMode::Param => {
234 let idx = ctx.impl_trait_counter.get();
235 // FIXME we're probably doing something wrong here
236 ctx.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
237 if let Some(def) = ctx.resolver.generic_def() {
238 let generics = generics(ctx.db.upcast(), def);
241 .filter(|(_, data)| {
242 data.provenance == TypeParamProvenance::ArgumentImplTrait
245 .map_or(Ty::Unknown, |(id, _)| Ty::Placeholder(id));
251 ImplTraitLoweringMode::Variable => {
252 let idx = ctx.impl_trait_counter.get();
253 // FIXME we're probably doing something wrong here
254 ctx.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
255 let (parent_params, self_params, list_params, _impl_trait_params) =
256 if let Some(def) = ctx.resolver.generic_def() {
257 let generics = generics(ctx.db.upcast(), def);
258 generics.provenance_split()
262 Ty::Bound(BoundVar::new(
264 idx as usize + parent_params + self_params + list_params,
267 ImplTraitLoweringMode::Disallowed => {
268 // FIXME: report error
273 TypeRef::Error => Ty::Unknown,
278 /// This is only for `generic_predicates_for_param`, where we can't just
279 /// lower the self types of the predicates since that could lead to cycles.
280 /// So we just check here if the `type_ref` resolves to a generic param, and which.
281 fn from_hir_only_param(ctx: &TyLoweringContext<'_>, type_ref: &TypeRef) -> Option<TypeParamId> {
282 let path = match type_ref {
283 TypeRef::Path(path) => path,
286 if path.type_anchor().is_some() {
289 if path.segments().len() > 1 {
293 match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
294 Some((it, None)) => it,
297 if let TypeNs::GenericParam(param_id) = resolution {
304 pub(crate) fn from_type_relative_path(
305 ctx: &TyLoweringContext<'_>,
307 // We need the original resolution to lower `Self::AssocTy` correctly
309 remaining_segments: PathSegments<'_>,
310 ) -> (Ty, Option<TypeNs>) {
311 if remaining_segments.len() == 1 {
312 // resolve unselected assoc types
313 let segment = remaining_segments.first().unwrap();
314 (Ty::select_associated_type(ctx, res, segment), None)
315 } else if remaining_segments.len() > 1 {
316 // FIXME report error (ambiguous associated type)
323 pub(crate) fn from_partly_resolved_hir_path(
324 ctx: &TyLoweringContext<'_>,
326 resolved_segment: PathSegment<'_>,
327 remaining_segments: PathSegments<'_>,
329 ) -> (Ty, Option<TypeNs>) {
330 let ty = match resolution {
331 TypeNs::TraitId(trait_) => {
332 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
333 let self_ty = if remaining_segments.len() == 0 {
334 Some(Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0)))
339 TraitRef::from_resolved_path(ctx, trait_, resolved_segment, self_ty);
340 let ty = if remaining_segments.len() == 1 {
341 let segment = remaining_segments.first().unwrap();
342 let found = associated_type_by_name_including_super_traits(
348 Some((super_trait_ref, associated_ty)) => {
349 // FIXME handle type parameters on the segment
350 Ty::Projection(ProjectionTy {
352 parameters: super_trait_ref.substs,
356 // FIXME: report error (associated type not found)
360 } else if remaining_segments.len() > 1 {
361 // FIXME report error (ambiguous associated type)
364 Ty::Dyn(Arc::new([GenericPredicate::Implemented(trait_ref)]))
368 TypeNs::GenericParam(param_id) => {
369 let generics = generics(
371 ctx.resolver.generic_def().expect("generics in scope"),
373 match ctx.type_param_mode {
374 TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
375 TypeParamLoweringMode::Variable => {
376 let idx = generics.param_idx(param_id).expect("matching generics");
377 Ty::Bound(BoundVar::new(ctx.in_binders, idx))
381 TypeNs::SelfType(impl_id) => {
382 let generics = generics(ctx.db.upcast(), impl_id.into());
383 let substs = match ctx.type_param_mode {
384 TypeParamLoweringMode::Placeholder => {
385 Substs::type_params_for_generics(&generics)
387 TypeParamLoweringMode::Variable => {
388 Substs::bound_vars(&generics, ctx.in_binders)
391 ctx.db.impl_self_ty(impl_id).subst(&substs)
393 TypeNs::AdtSelfType(adt) => {
394 let generics = generics(ctx.db.upcast(), adt.into());
395 let substs = match ctx.type_param_mode {
396 TypeParamLoweringMode::Placeholder => {
397 Substs::type_params_for_generics(&generics)
399 TypeParamLoweringMode::Variable => {
400 Substs::bound_vars(&generics, ctx.in_binders)
403 ctx.db.ty(adt.into()).subst(&substs)
406 TypeNs::AdtId(it) => {
407 Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
409 TypeNs::BuiltinType(it) => {
410 Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
412 TypeNs::TypeAliasId(it) => {
413 Ty::from_hir_path_inner(ctx, resolved_segment, it.into(), infer_args)
415 // FIXME: report error
416 TypeNs::EnumVariantId(_) => return (Ty::Unknown, None),
419 Ty::from_type_relative_path(ctx, ty, Some(resolution), remaining_segments)
422 pub(crate) fn from_hir_path(ctx: &TyLoweringContext<'_>, path: &Path) -> (Ty, Option<TypeNs>) {
423 // Resolve the path (in type namespace)
424 if let Some(type_ref) = path.type_anchor() {
425 let (ty, res) = Ty::from_hir_ext(ctx, &type_ref);
426 return Ty::from_type_relative_path(ctx, ty, res, path.segments());
428 let (resolution, remaining_index) =
429 match ctx.resolver.resolve_path_in_type_ns(ctx.db.upcast(), path.mod_path()) {
431 None => return (Ty::Unknown, None),
433 let (resolved_segment, remaining_segments) = match remaining_index {
435 path.segments().last().expect("resolved path has at least one element"),
438 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
440 Ty::from_partly_resolved_hir_path(
449 fn select_associated_type(
450 ctx: &TyLoweringContext<'_>,
452 segment: PathSegment<'_>,
454 if let Some(res) = res {
456 associated_type_shorthand_candidates(ctx.db, res, move |name, t, associated_ty| {
457 if name == segment.name {
458 let substs = match ctx.type_param_mode {
459 TypeParamLoweringMode::Placeholder => {
460 // if we're lowering to placeholders, we have to put
462 let s = Substs::type_params(
464 ctx.resolver.generic_def().expect(
465 "there should be generics if there's a generic param",
468 t.substs.clone().subst_bound_vars(&s)
470 TypeParamLoweringMode::Variable => t.substs.clone(),
472 // We need to shift in the bound vars, since
473 // associated_type_shorthand_candidates does not do that
474 let substs = substs.shift_bound_vars(ctx.in_binders);
475 // FIXME handle type parameters on the segment
476 return Some(Ty::Projection(ProjectionTy {
485 ty.unwrap_or(Ty::Unknown)
491 fn from_hir_path_inner(
492 ctx: &TyLoweringContext<'_>,
493 segment: PathSegment<'_>,
497 let generic_def = match typable {
498 TyDefId::BuiltinType(_) => None,
499 TyDefId::AdtId(it) => Some(it.into()),
500 TyDefId::TypeAliasId(it) => Some(it.into()),
502 let substs = substs_from_path_segment(ctx, segment, generic_def, infer_args);
503 ctx.db.ty(typable).subst(&substs)
506 /// Collect generic arguments from a path into a `Substs`. See also
507 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
508 pub(super) fn substs_from_path(
509 ctx: &TyLoweringContext<'_>,
511 // Note that we don't call `db.value_type(resolved)` here,
512 // `ValueTyDefId` is just a convenient way to pass generics and
513 // special-case enum variants
514 resolved: ValueTyDefId,
517 let last = path.segments().last().expect("path should have at least one segment");
518 let (segment, generic_def) = match resolved {
519 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
520 ValueTyDefId::StructId(it) => (last, Some(it.into())),
521 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
522 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
523 ValueTyDefId::StaticId(_) => (last, None),
524 ValueTyDefId::EnumVariantId(var) => {
525 // the generic args for an enum variant may be either specified
526 // on the segment referring to the enum, or on the segment
527 // referring to the variant. So `Option::<T>::None` and
528 // `Option::None::<T>` are both allowed (though the former is
529 // preferred). See also `def_ids_for_path_segments` in rustc.
530 let len = path.segments().len();
531 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
532 let segment = match penultimate {
533 Some(segment) if segment.args_and_bindings.is_some() => segment,
536 (segment, Some(var.parent.into()))
539 substs_from_path_segment(ctx, segment, generic_def, infer_args)
543 fn substs_from_path_segment(
544 ctx: &TyLoweringContext<'_>,
545 segment: PathSegment<'_>,
546 def_generic: Option<GenericDefId>,
549 let mut substs = Vec::new();
550 let def_generics = def_generic.map(|def| generics(ctx.db.upcast(), def));
552 let (parent_params, self_params, type_params, impl_trait_params) =
553 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
554 let total_len = parent_params + self_params + type_params + impl_trait_params;
556 substs.extend(iter::repeat(Ty::Unknown).take(parent_params));
558 let mut had_explicit_args = false;
560 if let Some(generic_args) = &segment.args_and_bindings {
561 if !generic_args.has_self_type {
562 substs.extend(iter::repeat(Ty::Unknown).take(self_params));
565 if generic_args.has_self_type { self_params + type_params } else { type_params };
566 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
567 // if args are provided, it should be all of them, but we can't rely on that
568 for arg in generic_args.args.iter().skip(skip).take(expected_num) {
570 GenericArg::Type(type_ref) => {
571 had_explicit_args = true;
572 let ty = Ty::from_hir(ctx, type_ref);
579 // handle defaults. In expression or pattern path segments without
580 // explicitly specified type arguments, missing type arguments are inferred
581 // (i.e. defaults aren't used).
582 if !infer_args || had_explicit_args {
583 if let Some(def_generic) = def_generic {
584 let defaults = ctx.db.generic_defaults(def_generic);
585 assert_eq!(total_len, defaults.len());
587 for default_ty in defaults.iter().skip(substs.len()) {
588 // each default can depend on the previous parameters
589 let substs_so_far = Substs(substs.clone().into());
590 substs.push(default_ty.clone().subst(&substs_so_far));
595 // add placeholders for args that were not provided
596 // FIXME: emit diagnostics in contexts where this is not allowed
597 for _ in substs.len()..total_len {
598 substs.push(Ty::Unknown);
600 assert_eq!(substs.len(), total_len);
602 Substs(substs.into())
607 ctx: &TyLoweringContext<'_>,
609 explicit_self_ty: Option<Ty>,
612 match ctx.resolver.resolve_path_in_type_ns_fully(ctx.db.upcast(), path.mod_path())? {
613 TypeNs::TraitId(tr) => tr,
616 let segment = path.segments().last().expect("path should have at least one segment");
617 Some(TraitRef::from_resolved_path(ctx, resolved, segment, explicit_self_ty))
620 pub(crate) fn from_resolved_path(
621 ctx: &TyLoweringContext<'_>,
623 segment: PathSegment<'_>,
624 explicit_self_ty: Option<Ty>,
626 let mut substs = TraitRef::substs_from_path(ctx, segment, resolved);
627 if let Some(self_ty) = explicit_self_ty {
628 make_mut_slice(&mut substs.0)[0] = self_ty;
630 TraitRef { trait_: resolved, substs }
634 ctx: &TyLoweringContext<'_>,
636 explicit_self_ty: Option<Ty>,
638 let path = match type_ref {
639 TypeRef::Path(path) => path,
642 TraitRef::from_path(ctx, path, explicit_self_ty)
646 ctx: &TyLoweringContext<'_>,
647 segment: PathSegment<'_>,
650 substs_from_path_segment(ctx, segment, Some(resolved.into()), false)
653 pub(crate) fn from_type_bound(
654 ctx: &TyLoweringContext<'_>,
657 ) -> Option<TraitRef> {
659 TypeBound::Path(path) => TraitRef::from_path(ctx, path, Some(self_ty)),
660 TypeBound::Error => None,
665 impl GenericPredicate {
666 pub(crate) fn from_where_predicate<'a>(
667 ctx: &'a TyLoweringContext<'a>,
668 where_predicate: &'a WherePredicate,
669 ) -> impl Iterator<Item = GenericPredicate> + 'a {
670 let self_ty = match &where_predicate.target {
671 WherePredicateTarget::TypeRef(type_ref) => Ty::from_hir(ctx, type_ref),
672 WherePredicateTarget::TypeParam(param_id) => {
673 let generic_def = ctx.resolver.generic_def().expect("generics in scope");
674 let generics = generics(ctx.db.upcast(), generic_def);
675 let param_id = hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
676 match ctx.type_param_mode {
677 TypeParamLoweringMode::Placeholder => Ty::Placeholder(param_id),
678 TypeParamLoweringMode::Variable => {
679 let idx = generics.param_idx(param_id).expect("matching generics");
680 Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, idx))
685 GenericPredicate::from_type_bound(ctx, &where_predicate.bound, self_ty)
688 pub(crate) fn from_type_bound<'a>(
689 ctx: &'a TyLoweringContext<'a>,
690 bound: &'a TypeBound,
692 ) -> impl Iterator<Item = GenericPredicate> + 'a {
693 let trait_ref = TraitRef::from_type_bound(ctx, bound, self_ty);
694 iter::once(trait_ref.clone().map_or(GenericPredicate::Error, GenericPredicate::Implemented))
698 .flat_map(move |tr| assoc_type_bindings_from_type_bound(ctx, bound, tr)),
703 fn assoc_type_bindings_from_type_bound<'a>(
704 ctx: &'a TyLoweringContext<'a>,
705 bound: &'a TypeBound,
707 ) -> impl Iterator<Item = GenericPredicate> + 'a {
708 let last_segment = match bound {
709 TypeBound::Path(path) => path.segments().last(),
710 TypeBound::Error => None,
714 .flat_map(|segment| segment.args_and_bindings.into_iter())
715 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
716 .flat_map(move |binding| {
717 let found = associated_type_by_name_including_super_traits(
722 let (super_trait_ref, associated_ty) = match found {
723 None => return SmallVec::<[GenericPredicate; 1]>::new(),
726 let projection_ty = ProjectionTy { associated_ty, parameters: super_trait_ref.substs };
727 let mut preds = SmallVec::with_capacity(
728 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
730 if let Some(type_ref) = &binding.type_ref {
731 let ty = Ty::from_hir(ctx, type_ref);
732 let projection_predicate =
733 ProjectionPredicate { projection_ty: projection_ty.clone(), ty };
734 preds.push(GenericPredicate::Projection(projection_predicate));
736 for bound in &binding.bounds {
737 preds.extend(GenericPredicate::from_type_bound(
740 Ty::Projection(projection_ty.clone()),
747 impl ReturnTypeImplTrait {
748 fn from_hir(ctx: &TyLoweringContext, bounds: &[TypeBound]) -> Self {
749 mark::hit!(lower_rpit);
750 let self_ty = Ty::Bound(BoundVar::new(DebruijnIndex::INNERMOST, 0));
751 let predicates = ctx.with_shifted_in(DebruijnIndex::ONE, |ctx| {
754 .flat_map(|b| GenericPredicate::from_type_bound(ctx, b, self_ty.clone()))
757 ReturnTypeImplTrait { bounds: Binders::new(1, predicates) }
761 fn count_impl_traits(type_ref: &TypeRef) -> usize {
763 type_ref.walk(&mut |type_ref| {
764 if matches!(type_ref, TypeRef::ImplTrait(_)) {
771 /// Build the signature of a callable item (function, struct or enum variant).
772 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
774 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
775 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
776 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
780 pub fn associated_type_shorthand_candidates<R>(
781 db: &dyn HirDatabase,
783 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
785 let traits_from_env: Vec<_> = match res {
786 TypeNs::SelfType(impl_id) => match db.impl_trait(impl_id) {
788 Some(trait_ref) => vec![trait_ref.value],
790 TypeNs::GenericParam(param_id) => {
791 let predicates = db.generic_predicates_for_param(param_id);
792 let mut traits_: Vec<_> = predicates
794 .filter_map(|pred| match &pred.value {
795 GenericPredicate::Implemented(tr) => Some(tr.clone()),
799 // Handle `Self::Type` referring to own associated type in trait definitions
800 if let GenericDefId::TraitId(trait_id) = param_id.parent {
801 let generics = generics(db.upcast(), trait_id.into());
802 if generics.params.types[param_id.local_id].provenance
803 == TypeParamProvenance::TraitSelf
805 let trait_ref = TraitRef {
807 substs: Substs::bound_vars(&generics, DebruijnIndex::INNERMOST),
809 traits_.push(trait_ref);
817 for t in traits_from_env.into_iter().flat_map(move |t| all_super_trait_refs(db, t)) {
818 let data = db.trait_data(t.trait_);
820 for (name, assoc_id) in &data.items {
822 AssocItemId::TypeAliasId(alias) => {
823 if let Some(result) = cb(name, &t, *alias) {
827 AssocItemId::FunctionId(_) | AssocItemId::ConstId(_) => {}
835 /// Build the type of all specific fields of a struct or enum variant.
836 pub(crate) fn field_types_query(
837 db: &dyn HirDatabase,
838 variant_id: VariantId,
839 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
840 let var_data = variant_data(db.upcast(), variant_id);
841 let (resolver, def): (_, GenericDefId) = match variant_id {
842 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
843 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
844 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
846 let generics = generics(db.upcast(), def);
847 let mut res = ArenaMap::default();
849 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
850 for (field_id, field_data) in var_data.fields().iter() {
851 res.insert(field_id, Binders::new(generics.len(), Ty::from_hir(&ctx, &field_data.type_ref)))
856 /// This query exists only to be used when resolving short-hand associated types
859 /// See the analogous query in rustc and its comment:
860 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
861 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
862 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
863 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
864 pub(crate) fn generic_predicates_for_param_query(
865 db: &dyn HirDatabase,
866 param_id: TypeParamId,
867 ) -> Arc<[Binders<GenericPredicate>]> {
868 let resolver = param_id.parent.resolver(db.upcast());
870 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
871 let generics = generics(db.upcast(), param_id.parent);
873 .where_predicates_in_scope()
874 // we have to filter out all other predicates *first*, before attempting to lower them
875 .filter(|pred| match &pred.target {
876 WherePredicateTarget::TypeRef(type_ref) => {
877 Ty::from_hir_only_param(&ctx, type_ref) == Some(param_id)
879 WherePredicateTarget::TypeParam(local_id) => *local_id == param_id.local_id,
882 GenericPredicate::from_where_predicate(&ctx, pred)
883 .map(|p| Binders::new(generics.len(), p))
888 pub(crate) fn generic_predicates_for_param_recover(
889 _db: &dyn HirDatabase,
891 _param_id: &TypeParamId,
892 ) -> Arc<[Binders<GenericPredicate>]> {
896 impl TraitEnvironment {
897 pub fn lower(db: &dyn HirDatabase, resolver: &Resolver) -> Arc<TraitEnvironment> {
898 let ctx = TyLoweringContext::new(db, &resolver)
899 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
900 let mut predicates = resolver
901 .where_predicates_in_scope()
902 .flat_map(|pred| GenericPredicate::from_where_predicate(&ctx, pred))
903 .collect::<Vec<_>>();
905 if let Some(def) = resolver.generic_def() {
906 let container: Option<AssocContainerId> = match def {
907 // FIXME: is there a function for this?
908 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
909 GenericDefId::AdtId(_) => None,
910 GenericDefId::TraitId(_) => None,
911 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
912 GenericDefId::ImplId(_) => None,
913 GenericDefId::EnumVariantId(_) => None,
914 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
916 if let Some(AssocContainerId::TraitId(trait_id)) = container {
917 // add `Self: Trait<T1, T2, ...>` to the environment in trait
918 // function default implementations (and hypothetical code
919 // inside consts or type aliases)
920 test_utils::mark::hit!(trait_self_implements_self);
921 let substs = Substs::type_params(db, trait_id);
922 let trait_ref = TraitRef { trait_: trait_id, substs };
923 let pred = GenericPredicate::Implemented(trait_ref);
925 predicates.push(pred);
929 Arc::new(TraitEnvironment { predicates })
933 /// Resolve the where clause(s) of an item with generics.
934 pub(crate) fn generic_predicates_query(
935 db: &dyn HirDatabase,
937 ) -> Arc<[Binders<GenericPredicate>]> {
938 let resolver = def.resolver(db.upcast());
940 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
941 let generics = generics(db.upcast(), def);
943 .where_predicates_in_scope()
945 GenericPredicate::from_where_predicate(&ctx, pred)
946 .map(|p| Binders::new(generics.len(), p))
951 /// Resolve the default type params from generics
952 pub(crate) fn generic_defaults_query(
953 db: &dyn HirDatabase,
955 ) -> Arc<[Binders<Ty>]> {
956 let resolver = def.resolver(db.upcast());
958 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
959 let generic_params = generics(db.upcast(), def);
961 let defaults = generic_params
964 .map(|(idx, (_, p))| {
965 let mut ty = p.default.as_ref().map_or(Ty::Unknown, |t| Ty::from_hir(&ctx, t));
967 // Each default can only refer to previous parameters.
969 &mut |ty, binders| match ty {
970 Ty::Bound(BoundVar { debruijn, index }) if *debruijn == binders => {
972 // type variable default referring to parameter coming
973 // after it. This is forbidden (FIXME: report
980 DebruijnIndex::INNERMOST,
983 Binders::new(idx, ty)
990 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
991 let data = db.function_data(def);
992 let resolver = def.resolver(db.upcast());
993 let ctx_params = TyLoweringContext::new(db, &resolver)
994 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
995 .with_type_param_mode(TypeParamLoweringMode::Variable);
996 let params = data.params.iter().map(|tr| Ty::from_hir(&ctx_params, tr)).collect::<Vec<_>>();
997 let ctx_ret = TyLoweringContext::new(db, &resolver)
998 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
999 .with_type_param_mode(TypeParamLoweringMode::Variable);
1000 let ret = Ty::from_hir(&ctx_ret, &data.ret_type);
1001 let generics = generics(db.upcast(), def.into());
1002 let num_binders = generics.len();
1003 Binders::new(num_binders, FnSig::from_params_and_return(params, ret, data.is_varargs))
1006 /// Build the declared type of a function. This should not need to look at the
1008 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1009 let generics = generics(db.upcast(), def.into());
1010 let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
1011 Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
1014 /// Build the declared type of a const.
1015 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1016 let data = db.const_data(def);
1017 let generics = generics(db.upcast(), def.into());
1018 let resolver = def.resolver(db.upcast());
1020 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1022 Binders::new(generics.len(), Ty::from_hir(&ctx, &data.type_ref))
1025 /// Build the declared type of a static.
1026 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1027 let data = db.static_data(def);
1028 let resolver = def.resolver(db.upcast());
1029 let ctx = TyLoweringContext::new(db, &resolver);
1031 Binders::new(0, Ty::from_hir(&ctx, &data.type_ref))
1034 /// Build the declared type of a static.
1035 fn type_for_builtin(def: BuiltinType) -> Ty {
1036 Ty::simple(match def {
1037 BuiltinType::Char => TypeCtor::Char,
1038 BuiltinType::Bool => TypeCtor::Bool,
1039 BuiltinType::Str => TypeCtor::Str,
1040 BuiltinType::Int(t) => TypeCtor::Int(IntTy::from(t).into()),
1041 BuiltinType::Float(t) => TypeCtor::Float(FloatTy::from(t).into()),
1045 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1046 let struct_data = db.struct_data(def);
1047 let fields = struct_data.variant_data.fields();
1048 let resolver = def.resolver(db.upcast());
1050 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1052 fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
1053 let ret = type_for_adt(db, def.into());
1054 Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value, false))
1057 /// Build the type of a tuple struct constructor.
1058 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1059 let struct_data = db.struct_data(def);
1060 if let StructKind::Unit = struct_data.variant_data.kind() {
1061 return type_for_adt(db, def.into());
1063 let generics = generics(db.upcast(), def.into());
1064 let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
1065 Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
1068 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1069 let enum_data = db.enum_data(def.parent);
1070 let var_data = &enum_data.variants[def.local_id];
1071 let fields = var_data.variant_data.fields();
1072 let resolver = def.parent.resolver(db.upcast());
1074 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1076 fields.iter().map(|(_, field)| Ty::from_hir(&ctx, &field.type_ref)).collect::<Vec<_>>();
1077 let ret = type_for_adt(db, def.parent.into());
1078 Binders::new(ret.num_binders, FnSig::from_params_and_return(params, ret.value, false))
1081 /// Build the type of a tuple enum variant constructor.
1082 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1083 let enum_data = db.enum_data(def.parent);
1084 let var_data = &enum_data.variants[def.local_id].variant_data;
1085 if let StructKind::Unit = var_data.kind() {
1086 return type_for_adt(db, def.parent.into());
1088 let generics = generics(db.upcast(), def.parent.into());
1089 let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
1090 Binders::new(substs.len(), Ty::apply(TypeCtor::FnDef(def.into()), substs))
1093 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1094 let generics = generics(db.upcast(), adt.into());
1095 let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
1096 Binders::new(substs.len(), Ty::apply(TypeCtor::Adt(adt), substs))
1099 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1100 let generics = generics(db.upcast(), t.into());
1101 let resolver = t.resolver(db.upcast());
1103 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1104 let substs = Substs::bound_vars(&generics, DebruijnIndex::INNERMOST);
1105 if db.type_alias_data(t).is_extern {
1106 Binders::new(substs.len(), Ty::apply(TypeCtor::ForeignType(t), substs))
1108 let type_ref = &db.type_alias_data(t).type_ref;
1109 let inner = Ty::from_hir(&ctx, type_ref.as_ref().unwrap_or(&TypeRef::Error));
1110 Binders::new(substs.len(), inner)
1114 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1115 pub enum CallableDefId {
1116 FunctionId(FunctionId),
1118 EnumVariantId(EnumVariantId),
1120 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1122 impl CallableDefId {
1123 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1124 let db = db.upcast();
1126 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1127 CallableDefId::StructId(s) => s.lookup(db).container.module(db),
1128 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container.module(db),
1134 impl From<CallableDefId> for GenericDefId {
1135 fn from(def: CallableDefId) -> GenericDefId {
1137 CallableDefId::FunctionId(f) => f.into(),
1138 CallableDefId::StructId(s) => s.into(),
1139 CallableDefId::EnumVariantId(e) => e.into(),
1144 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1146 BuiltinType(BuiltinType),
1148 TypeAliasId(TypeAliasId),
1150 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1152 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1153 pub enum ValueTyDefId {
1154 FunctionId(FunctionId),
1157 EnumVariantId(EnumVariantId),
1161 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1163 /// Build the declared type of an item. This depends on the namespace; e.g. for
1164 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1165 /// the constructor function `(usize) -> Foo` which lives in the values
1167 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1169 TyDefId::BuiltinType(it) => Binders::new(0, type_for_builtin(it)),
1170 TyDefId::AdtId(it) => type_for_adt(db, it),
1171 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1175 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1176 let num_binders = match *def {
1177 TyDefId::BuiltinType(_) => 0,
1178 TyDefId::AdtId(it) => generics(db.upcast(), it.into()).len(),
1179 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()).len(),
1181 Binders::new(num_binders, Ty::Unknown)
1184 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1186 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1187 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1188 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1189 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1190 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1191 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1195 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1196 let impl_data = db.impl_data(impl_id);
1197 let resolver = impl_id.resolver(db.upcast());
1198 let generics = generics(db.upcast(), impl_id.into());
1200 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1201 Binders::new(generics.len(), Ty::from_hir(&ctx, &impl_data.target_type))
1204 pub(crate) fn impl_self_ty_recover(
1205 db: &dyn HirDatabase,
1209 let generics = generics(db.upcast(), (*impl_id).into());
1210 Binders::new(generics.len(), Ty::Unknown)
1213 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1214 let impl_data = db.impl_data(impl_id);
1215 let resolver = impl_id.resolver(db.upcast());
1217 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1218 let self_ty = db.impl_self_ty(impl_id);
1219 let target_trait = impl_data.target_trait.as_ref()?;
1221 self_ty.num_binders,
1222 TraitRef::from_hir(&ctx, target_trait, Some(self_ty.value))?,
1226 pub(crate) fn return_type_impl_traits(
1227 db: &dyn HirDatabase,
1228 def: hir_def::FunctionId,
1229 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1230 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1231 let data = db.function_data(def);
1232 let resolver = def.resolver(db.upcast());
1233 let ctx_ret = TyLoweringContext::new(db, &resolver)
1234 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1235 .with_type_param_mode(TypeParamLoweringMode::Variable);
1236 let _ret = Ty::from_hir(&ctx_ret, &data.ret_type);
1237 let generics = generics(db.upcast(), def.into());
1238 let num_binders = generics.len();
1239 let return_type_impl_traits =
1240 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1241 if return_type_impl_traits.impl_traits.is_empty() {
1244 Some(Arc::new(Binders::new(num_binders, return_type_impl_traits)))