1 //! Methods for lowering the HIR to types. There are two main cases here:
3 //! - Lowering a type reference like `&usize` or `Option<foo::bar::Baz>` to a
4 //! type: The entry point for this is `Ty::from_hir`.
5 //! - Building the type for an item: This happens through the `type_for_def` query.
7 //! This usually involves resolving names, collecting generic arguments etc.
8 use std::{iter, sync::Arc};
11 use chalk_ir::{cast::Cast, fold::Shift, interner::HasInterner, Mutability, Safety};
14 builtin_type::BuiltinType,
15 generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget},
16 path::{GenericArg, Path, PathSegment, PathSegments},
17 resolver::{HasResolver, Resolver, TypeNs},
18 type_ref::{TraitRef as HirTraitRef, TypeBound, TypeRef},
19 AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId,
20 GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId,
21 TypeAliasId, TypeParamId, UnionId, VariantId,
23 use hir_expand::name::Name;
24 use la_arena::ArenaMap;
25 use smallvec::SmallVec;
32 static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx,
34 all_super_trait_refs, associated_type_by_name_including_super_traits, generics, Generics,
36 AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig,
37 FnSubst, ImplTraitId, Interner, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause,
38 QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution,
39 TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause,
43 pub struct TyLoweringContext<'a> {
44 pub db: &'a dyn HirDatabase,
45 pub resolver: &'a Resolver,
46 in_binders: DebruijnIndex,
47 /// Note: Conceptually, it's thinkable that we could be in a location where
48 /// some type params should be represented as placeholders, and others
49 /// should be converted to variables. I think in practice, this isn't
50 /// possible currently, so this should be fine for now.
51 pub type_param_mode: TypeParamLoweringMode,
52 pub impl_trait_mode: ImplTraitLoweringMode,
53 impl_trait_counter: std::cell::Cell<u16>,
54 /// When turning `impl Trait` into opaque types, we have to collect the
55 /// bounds at the same time to get the IDs correct (without becoming too
56 /// complicated). I don't like using interior mutability (as for the
57 /// counter), but I've tried and failed to make the lifetimes work for
58 /// passing around a `&mut TyLoweringContext`. The core problem is that
59 /// we're grouping the mutable data (the counter and this field) together
60 /// with the immutable context (the references to the DB and resolver).
61 /// Splitting this up would be a possible fix.
62 opaque_type_data: std::cell::RefCell<Vec<ReturnTypeImplTrait>>,
65 impl<'a> TyLoweringContext<'a> {
66 pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self {
67 let impl_trait_counter = std::cell::Cell::new(0);
68 let impl_trait_mode = ImplTraitLoweringMode::Disallowed;
69 let type_param_mode = TypeParamLoweringMode::Placeholder;
70 let in_binders = DebruijnIndex::INNERMOST;
71 let opaque_type_data = std::cell::RefCell::new(Vec::new());
83 pub fn with_debruijn<T>(
85 debruijn: DebruijnIndex,
86 f: impl FnOnce(&TyLoweringContext) -> T,
88 let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new());
91 impl_trait_counter: std::cell::Cell::new(self.impl_trait_counter.get()),
92 opaque_type_data: std::cell::RefCell::new(opaque_ty_data_vec),
95 let result = f(&new_ctx);
96 self.impl_trait_counter.set(new_ctx.impl_trait_counter.get());
97 self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner());
101 pub fn with_shifted_in<T>(
103 debruijn: DebruijnIndex,
104 f: impl FnOnce(&TyLoweringContext) -> T,
106 self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f)
109 pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self {
110 Self { impl_trait_mode, ..self }
113 pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self {
114 Self { type_param_mode, ..self }
118 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
119 pub enum ImplTraitLoweringMode {
120 /// `impl Trait` gets lowered into an opaque type that doesn't unify with
121 /// anything except itself. This is used in places where values flow 'out',
122 /// i.e. for arguments of the function we're currently checking, and return
123 /// types of functions we're calling.
125 /// `impl Trait` gets lowered into a type variable. Used for argument
126 /// position impl Trait when inside the respective function, since it allows
127 /// us to support that without Chalk.
129 /// `impl Trait` gets lowered into a variable that can unify with some
130 /// type. This is used in places where values flow 'in', i.e. for arguments
131 /// of functions we're calling, and the return type of the function we're
132 /// currently checking.
134 /// `impl Trait` is disallowed and will be an error.
138 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
139 pub enum TypeParamLoweringMode {
144 impl<'a> TyLoweringContext<'a> {
145 pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty {
146 self.lower_ty_ext(type_ref).0
149 pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option<TypeNs>) {
151 let ty = match type_ref {
152 TypeRef::Never => TyKind::Never.intern(&Interner),
153 TypeRef::Tuple(inner) => {
154 let inner_tys = inner.iter().map(|tr| self.lower_ty(tr));
155 TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys))
158 TypeRef::Path(path) => {
159 let (ty, res_) = self.lower_path(path);
163 TypeRef::RawPtr(inner, mutability) => {
164 let inner_ty = self.lower_ty(inner);
165 TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner)
167 TypeRef::Array(inner) => {
168 let inner_ty = self.lower_ty(inner);
169 TyKind::Array(inner_ty, dummy_usize_const()).intern(&Interner)
171 TypeRef::Slice(inner) => {
172 let inner_ty = self.lower_ty(inner);
173 TyKind::Slice(inner_ty).intern(&Interner)
175 TypeRef::Reference(inner, _, mutability) => {
176 let inner_ty = self.lower_ty(inner);
177 let lifetime = static_lifetime();
178 TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty)
181 TypeRef::Placeholder => TyKind::Error.intern(&Interner),
182 TypeRef::Fn(params, is_varargs) => {
183 let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
184 Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr)))
186 TyKind::Function(FnPointer {
187 num_binders: 0, // FIXME lower `for<'a> fn()` correctly
188 sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs },
189 substitution: FnSubst(substs),
193 TypeRef::DynTrait(bounds) => {
195 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
196 let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
197 QuantifiedWhereClauses::from_iter(
199 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)),
202 let bounds = crate::make_only_type_binders(1, bounds);
203 TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner)
205 TypeRef::ImplTrait(bounds) => {
206 match self.impl_trait_mode {
207 ImplTraitLoweringMode::Opaque => {
208 let idx = self.impl_trait_counter.get();
209 self.impl_trait_counter.set(idx + 1);
211 assert!(idx as usize == self.opaque_type_data.borrow().len());
212 // this dance is to make sure the data is in the right
213 // place even if we encounter more opaque types while
214 // lowering the bounds
215 self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait {
216 bounds: crate::make_only_type_binders(1, Vec::new()),
218 // We don't want to lower the bounds inside the binders
219 // we're currently in, because they don't end up inside
220 // those binders. E.g. when we have `impl Trait<impl
221 // OtherTrait<T>>`, the `impl OtherTrait<T>` can't refer
222 // to the self parameter from `impl Trait`, and the
223 // bounds aren't actually stored nested within each
224 // other, but separately. So if the `T` refers to a type
225 // parameter of the outer function, it's just one binder
226 // away instead of two.
227 let actual_opaque_type_data = self
228 .with_debruijn(DebruijnIndex::INNERMOST, |ctx| {
229 ctx.lower_impl_trait(&bounds)
231 self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data;
233 let func = match self.resolver.generic_def() {
234 Some(GenericDefId::FunctionId(f)) => f,
235 _ => panic!("opaque impl trait lowering in non-function"),
237 let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx);
238 let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into();
239 let generics = generics(self.db.upcast(), func.into());
240 let parameters = generics.bound_vars_subst(self.in_binders);
241 TyKind::Alias(AliasTy::Opaque(OpaqueTy {
243 substitution: parameters,
247 ImplTraitLoweringMode::Param => {
248 let idx = self.impl_trait_counter.get();
249 // FIXME we're probably doing something wrong here
250 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
251 if let Some(def) = self.resolver.generic_def() {
252 let generics = generics(self.db.upcast(), def);
255 .filter(|(_, data)| {
256 data.provenance == TypeParamProvenance::ArgumentImplTrait
259 .map_or(TyKind::Error, |(id, _)| {
260 TyKind::Placeholder(to_placeholder_idx(self.db, id))
262 param.intern(&Interner)
264 TyKind::Error.intern(&Interner)
267 ImplTraitLoweringMode::Variable => {
268 let idx = self.impl_trait_counter.get();
269 // FIXME we're probably doing something wrong here
270 self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16);
271 let (parent_params, self_params, list_params, _impl_trait_params) =
272 if let Some(def) = self.resolver.generic_def() {
273 let generics = generics(self.db.upcast(), def);
274 generics.provenance_split()
278 TyKind::BoundVar(BoundVar::new(
280 idx as usize + parent_params + self_params + list_params,
284 ImplTraitLoweringMode::Disallowed => {
285 // FIXME: report error
286 TyKind::Error.intern(&Interner)
290 TypeRef::Error => TyKind::Error.intern(&Interner),
295 /// This is only for `generic_predicates_for_param`, where we can't just
296 /// lower the self types of the predicates since that could lead to cycles.
297 /// So we just check here if the `type_ref` resolves to a generic param, and which.
298 fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option<TypeParamId> {
299 let path = match type_ref {
300 TypeRef::Path(path) => path,
303 if path.type_anchor().is_some() {
306 if path.segments().len() > 1 {
310 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
311 Some((it, None)) => it,
314 if let TypeNs::GenericParam(param_id) = resolution {
321 pub(crate) fn lower_ty_relative_path(
324 // We need the original resolution to lower `Self::AssocTy` correctly
326 remaining_segments: PathSegments<'_>,
327 ) -> (Ty, Option<TypeNs>) {
328 if remaining_segments.len() == 1 {
329 // resolve unselected assoc types
330 let segment = remaining_segments.first().unwrap();
331 (self.select_associated_type(res, segment), None)
332 } else if remaining_segments.len() > 1 {
333 // FIXME report error (ambiguous associated type)
334 (TyKind::Error.intern(&Interner), None)
340 pub(crate) fn lower_partly_resolved_path(
343 resolved_segment: PathSegment<'_>,
344 remaining_segments: PathSegments<'_>,
346 ) -> (Ty, Option<TypeNs>) {
347 let ty = match resolution {
348 TypeNs::TraitId(trait_) => {
349 // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there
350 let self_ty = if remaining_segments.len() == 0 {
352 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0))
359 self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty);
360 let ty = if remaining_segments.len() == 1 {
361 let segment = remaining_segments.first().unwrap();
362 let found = associated_type_by_name_including_super_traits(
368 Some((super_trait_ref, associated_ty)) => {
369 // FIXME handle type parameters on the segment
370 TyKind::Alias(AliasTy::Projection(ProjectionTy {
371 associated_ty_id: to_assoc_type_id(associated_ty),
372 substitution: super_trait_ref.substitution,
377 // FIXME: report error (associated type not found)
378 TyKind::Error.intern(&Interner)
381 } else if remaining_segments.len() > 1 {
382 // FIXME report error (ambiguous associated type)
383 TyKind::Error.intern(&Interner)
386 bounds: crate::make_only_type_binders(
388 QuantifiedWhereClauses::from_iter(
390 Some(crate::wrap_empty_binders(WhereClause::Implemented(
395 lifetime: static_lifetime(),
397 TyKind::Dyn(dyn_ty).intern(&Interner)
401 TypeNs::GenericParam(param_id) => {
402 let generics = generics(
404 self.resolver.generic_def().expect("generics in scope"),
406 match self.type_param_mode {
407 TypeParamLoweringMode::Placeholder => {
408 TyKind::Placeholder(to_placeholder_idx(self.db, param_id))
410 TypeParamLoweringMode::Variable => {
411 let idx = generics.param_idx(param_id).expect("matching generics");
412 TyKind::BoundVar(BoundVar::new(self.in_binders, idx))
417 TypeNs::SelfType(impl_id) => {
418 let generics = generics(self.db.upcast(), impl_id.into());
419 let substs = match self.type_param_mode {
420 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
421 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
423 self.db.impl_self_ty(impl_id).substitute(&Interner, &substs)
425 TypeNs::AdtSelfType(adt) => {
426 let generics = generics(self.db.upcast(), adt.into());
427 let substs = match self.type_param_mode {
428 TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db),
429 TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders),
431 self.db.ty(adt.into()).substitute(&Interner, &substs)
434 TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args),
435 TypeNs::BuiltinType(it) => {
436 self.lower_path_inner(resolved_segment, it.into(), infer_args)
438 TypeNs::TypeAliasId(it) => {
439 self.lower_path_inner(resolved_segment, it.into(), infer_args)
441 // FIXME: report error
442 TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None),
444 self.lower_ty_relative_path(ty, Some(resolution), remaining_segments)
447 pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option<TypeNs>) {
448 // Resolve the path (in type namespace)
449 if let Some(type_ref) = path.type_anchor() {
450 let (ty, res) = self.lower_ty_ext(&type_ref);
451 return self.lower_ty_relative_path(ty, res, path.segments());
453 let (resolution, remaining_index) =
454 match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) {
456 None => return (TyKind::Error.intern(&Interner), None),
458 let (resolved_segment, remaining_segments) = match remaining_index {
460 path.segments().last().expect("resolved path has at least one element"),
463 Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)),
465 self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false)
468 fn select_associated_type(&self, res: Option<TypeNs>, segment: PathSegment<'_>) -> Ty {
469 if let Some(res) = res {
470 let ty = associated_type_shorthand_candidates(
473 move |name, t, associated_ty| {
474 if name == segment.name {
475 let substs = match self.type_param_mode {
476 TypeParamLoweringMode::Placeholder => {
477 // if we're lowering to placeholders, we have to put
479 let generics = generics(
481 self.resolver.generic_def().expect(
482 "there should be generics if there's a generic param",
485 let s = generics.type_params_subst(self.db);
486 s.apply(t.substitution.clone(), &Interner)
488 TypeParamLoweringMode::Variable => t.substitution.clone(),
490 // We need to shift in the bound vars, since
491 // associated_type_shorthand_candidates does not do that
492 let substs = substs.shifted_in_from(&Interner, self.in_binders);
493 // FIXME handle type parameters on the segment
495 TyKind::Alias(AliasTy::Projection(ProjectionTy {
496 associated_ty_id: to_assoc_type_id(associated_ty),
497 substitution: substs,
507 ty.unwrap_or(TyKind::Error.intern(&Interner))
509 TyKind::Error.intern(&Interner)
515 segment: PathSegment<'_>,
519 let generic_def = match typeable {
520 TyDefId::BuiltinType(_) => None,
521 TyDefId::AdtId(it) => Some(it.into()),
522 TyDefId::TypeAliasId(it) => Some(it.into()),
524 let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None);
525 self.db.ty(typeable).substitute(&Interner, &substs)
528 /// Collect generic arguments from a path into a `Substs`. See also
529 /// `create_substs_for_ast_path` and `def_to_ty` in rustc.
530 pub(super) fn substs_from_path(
533 // Note that we don't call `db.value_type(resolved)` here,
534 // `ValueTyDefId` is just a convenient way to pass generics and
535 // special-case enum variants
536 resolved: ValueTyDefId,
539 let last = path.segments().last().expect("path should have at least one segment");
540 let (segment, generic_def) = match resolved {
541 ValueTyDefId::FunctionId(it) => (last, Some(it.into())),
542 ValueTyDefId::StructId(it) => (last, Some(it.into())),
543 ValueTyDefId::UnionId(it) => (last, Some(it.into())),
544 ValueTyDefId::ConstId(it) => (last, Some(it.into())),
545 ValueTyDefId::StaticId(_) => (last, None),
546 ValueTyDefId::EnumVariantId(var) => {
547 // the generic args for an enum variant may be either specified
548 // on the segment referring to the enum, or on the segment
549 // referring to the variant. So `Option::<T>::None` and
550 // `Option::None::<T>` are both allowed (though the former is
551 // preferred). See also `def_ids_for_path_segments` in rustc.
552 let len = path.segments().len();
553 let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None };
554 let segment = match penultimate {
555 Some(segment) if segment.args_and_bindings.is_some() => segment,
558 (segment, Some(var.parent.into()))
561 self.substs_from_path_segment(segment, generic_def, infer_args, None)
564 fn substs_from_path_segment(
566 segment: PathSegment<'_>,
567 def_generic: Option<GenericDefId>,
569 explicit_self_ty: Option<Ty>,
571 let mut substs = Vec::new();
572 let def_generics = def_generic.map(|def| generics(self.db.upcast(), def));
574 let (parent_params, self_params, type_params, impl_trait_params) =
575 def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split());
576 let total_len = parent_params + self_params + type_params + impl_trait_params;
578 substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params));
580 let fill_self_params = || {
584 .chain(iter::repeat(TyKind::Error.intern(&Interner)))
588 let mut had_explicit_type_args = false;
590 if let Some(generic_args) = &segment.args_and_bindings {
591 if !generic_args.has_self_type {
595 if generic_args.has_self_type { self_params + type_params } else { type_params };
596 let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 };
597 // if args are provided, it should be all of them, but we can't rely on that
598 for arg in generic_args
601 .filter(|arg| matches!(arg, GenericArg::Type(_)))
606 GenericArg::Type(type_ref) => {
607 had_explicit_type_args = true;
608 let ty = self.lower_ty(type_ref);
611 GenericArg::Lifetime(_) => {}
618 // handle defaults. In expression or pattern path segments without
619 // explicitly specified type arguments, missing type arguments are inferred
620 // (i.e. defaults aren't used).
621 if !infer_args || had_explicit_type_args {
622 if let Some(def_generic) = def_generic {
623 let defaults = self.db.generic_defaults(def_generic);
624 assert_eq!(total_len, defaults.len());
626 for default_ty in defaults.iter().skip(substs.len()) {
627 // each default can depend on the previous parameters
628 let substs_so_far = Substitution::from_iter(&Interner, substs.clone());
629 substs.push(default_ty.clone().substitute(&Interner, &substs_so_far));
634 // add placeholders for args that were not provided
635 // FIXME: emit diagnostics in contexts where this is not allowed
636 for _ in substs.len()..total_len {
637 substs.push(TyKind::Error.intern(&Interner));
639 assert_eq!(substs.len(), total_len);
641 Substitution::from_iter(&Interner, substs)
644 fn lower_trait_ref_from_path(
647 explicit_self_ty: Option<Ty>,
648 ) -> Option<TraitRef> {
650 match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? {
651 TypeNs::TraitId(tr) => tr,
654 let segment = path.segments().last().expect("path should have at least one segment");
655 Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty))
658 pub(crate) fn lower_trait_ref_from_resolved_path(
661 segment: PathSegment<'_>,
662 explicit_self_ty: Option<Ty>,
664 let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty);
665 TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs }
670 trait_ref: &HirTraitRef,
671 explicit_self_ty: Option<Ty>,
672 ) -> Option<TraitRef> {
673 self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty)
676 fn trait_ref_substs_from_path(
678 segment: PathSegment<'_>,
680 explicit_self_ty: Option<Ty>,
682 self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty)
685 pub(crate) fn lower_where_predicate(
687 where_predicate: &'a WherePredicate,
688 ignore_bindings: bool,
689 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
690 match where_predicate {
691 WherePredicate::ForLifetime { target, bound, .. }
692 | WherePredicate::TypeBound { target, bound } => {
693 let self_ty = match target {
694 WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref),
695 WherePredicateTypeTarget::TypeParam(param_id) => {
696 let generic_def = self.resolver.generic_def().expect("generics in scope");
697 let generics = generics(self.db.upcast(), generic_def);
699 hir_def::TypeParamId { parent: generic_def, local_id: *param_id };
700 let placeholder = to_placeholder_idx(self.db, param_id);
701 match self.type_param_mode {
702 TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder),
703 TypeParamLoweringMode::Variable => {
704 let idx = generics.param_idx(param_id).expect("matching generics");
705 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx))
711 self.lower_type_bound(bound, self_ty, ignore_bindings)
715 WherePredicate::Lifetime { .. } => vec![].into_iter(),
719 pub(crate) fn lower_type_bound(
721 bound: &'a TypeBound,
723 ignore_bindings: bool,
724 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
725 let mut bindings = None;
726 let trait_ref = match bound {
727 TypeBound::Path(path) => {
728 bindings = self.lower_trait_ref_from_path(path, Some(self_ty));
729 bindings.clone().map(WhereClause::Implemented).map(|b| crate::wrap_empty_binders(b))
731 TypeBound::Lifetime(_) => None,
732 TypeBound::Error => None,
734 trait_ref.into_iter().chain(
737 .filter(move |_| !ignore_bindings)
738 .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)),
742 fn assoc_type_bindings_from_type_bound(
744 bound: &'a TypeBound,
746 ) -> impl Iterator<Item = QuantifiedWhereClause> + 'a {
747 let last_segment = match bound {
748 TypeBound::Path(path) => path.segments().last(),
749 TypeBound::Error | TypeBound::Lifetime(_) => None,
753 .flat_map(|segment| segment.args_and_bindings.into_iter())
754 .flat_map(|args_and_bindings| args_and_bindings.bindings.iter())
755 .flat_map(move |binding| {
756 let found = associated_type_by_name_including_super_traits(
761 let (super_trait_ref, associated_ty) = match found {
762 None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(),
765 let projection_ty = ProjectionTy {
766 associated_ty_id: to_assoc_type_id(associated_ty),
767 substitution: super_trait_ref.substitution,
769 let mut preds = SmallVec::with_capacity(
770 binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(),
772 if let Some(type_ref) = &binding.type_ref {
773 let ty = self.lower_ty(type_ref);
775 AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty };
776 preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq)));
778 for bound in &binding.bounds {
779 preds.extend(self.lower_type_bound(
781 TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner),
789 fn lower_impl_trait(&self, bounds: &[TypeBound]) -> ReturnTypeImplTrait {
790 cov_mark::hit!(lower_rpit);
792 TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner);
793 let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| {
794 bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect()
796 ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) }
800 fn count_impl_traits(type_ref: &TypeRef) -> usize {
802 type_ref.walk(&mut |type_ref| {
803 if matches!(type_ref, TypeRef::ImplTrait(_)) {
810 /// Build the signature of a callable item (function, struct or enum variant).
811 pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig {
813 CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f),
814 CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s),
815 CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e),
819 pub fn associated_type_shorthand_candidates<R>(
820 db: &dyn HirDatabase,
822 mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option<R>,
824 let mut search = |t| {
825 for t in all_super_trait_refs(db, t) {
826 let data = db.trait_data(t.hir_trait_id());
828 for (name, assoc_id) in &data.items {
829 if let AssocItemId::TypeAliasId(alias) = assoc_id {
830 if let Some(result) = cb(name, &t, *alias) {
840 TypeNs::SelfType(impl_id) => search(
841 // we're _in_ the impl -- the binders get added back later. Correct,
842 // but it would be nice to make this more explicit
843 db.impl_trait(impl_id)?.into_value_and_skipped_binders().0,
845 TypeNs::GenericParam(param_id) => {
846 let predicates = db.generic_predicates_for_param(param_id);
847 let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() {
848 // FIXME: how to correctly handle higher-ranked bounds here?
849 WhereClause::Implemented(tr) => search(
851 .shifted_out_to(&Interner, DebruijnIndex::ONE)
852 .expect("FIXME unexpected higher-ranked trait bound"),
856 if let res @ Some(_) = res {
859 // Handle `Self::Type` referring to own associated type in trait definitions
860 if let GenericDefId::TraitId(trait_id) = param_id.parent {
861 let generics = generics(db.upcast(), trait_id.into());
862 if generics.params.types[param_id.local_id].provenance
863 == TypeParamProvenance::TraitSelf
865 let trait_ref = TyBuilder::trait_ref(db, trait_id)
866 .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0)
868 return search(trait_ref);
877 /// Build the type of all specific fields of a struct or enum variant.
878 pub(crate) fn field_types_query(
879 db: &dyn HirDatabase,
880 variant_id: VariantId,
881 ) -> Arc<ArenaMap<LocalFieldId, Binders<Ty>>> {
882 let var_data = variant_id.variant_data(db.upcast());
883 let (resolver, def): (_, GenericDefId) = match variant_id {
884 VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()),
885 VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()),
886 VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()),
888 let generics = generics(db.upcast(), def);
889 let mut res = ArenaMap::default();
891 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
892 for (field_id, field_data) in var_data.fields().iter() {
893 res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref)))
898 /// This query exists only to be used when resolving short-hand associated types
901 /// See the analogous query in rustc and its comment:
902 /// https://github.com/rust-lang/rust/blob/9150f844e2624eb013ec78ca08c1d416e6644026/src/librustc_typeck/astconv.rs#L46
903 /// This is a query mostly to handle cycles somewhat gracefully; e.g. the
904 /// following bounds are disallowed: `T: Foo<U::Item>, U: Foo<T::Item>`, but
905 /// these are fine: `T: Foo<U::Item>, U: Foo<()>`.
906 pub(crate) fn generic_predicates_for_param_query(
907 db: &dyn HirDatabase,
908 param_id: TypeParamId,
909 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
910 let resolver = param_id.parent.resolver(db.upcast());
912 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
913 let generics = generics(db.upcast(), param_id.parent);
915 .where_predicates_in_scope()
916 // we have to filter out all other predicates *first*, before attempting to lower them
917 .filter(|pred| match pred {
918 WherePredicate::ForLifetime { target, .. }
919 | WherePredicate::TypeBound { target, .. } => match target {
920 WherePredicateTypeTarget::TypeRef(type_ref) => {
921 ctx.lower_ty_only_param(type_ref) == Some(param_id)
923 WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id,
925 WherePredicate::Lifetime { .. } => false,
927 .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p)))
931 pub(crate) fn generic_predicates_for_param_recover(
932 _db: &dyn HirDatabase,
934 _param_id: &TypeParamId,
935 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
939 pub(crate) fn trait_environment_query(
940 db: &dyn HirDatabase,
942 ) -> Arc<TraitEnvironment> {
943 let resolver = def.resolver(db.upcast());
944 let ctx = TyLoweringContext::new(db, &resolver)
945 .with_type_param_mode(TypeParamLoweringMode::Placeholder);
946 let mut traits_in_scope = Vec::new();
947 let mut clauses = Vec::new();
948 for pred in resolver.where_predicates_in_scope() {
949 for pred in ctx.lower_where_predicate(pred, false) {
950 if let WhereClause::Implemented(tr) = &pred.skip_binders() {
952 .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id()));
954 let program_clause: chalk_ir::ProgramClause<Interner> = pred.clone().cast(&Interner);
955 clauses.push(program_clause.into_from_env_clause(&Interner));
959 let container: Option<AssocContainerId> = match def {
960 // FIXME: is there a function for this?
961 GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container),
962 GenericDefId::AdtId(_) => None,
963 GenericDefId::TraitId(_) => None,
964 GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container),
965 GenericDefId::ImplId(_) => None,
966 GenericDefId::EnumVariantId(_) => None,
967 GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container),
969 if let Some(AssocContainerId::TraitId(trait_id)) = container {
970 // add `Self: Trait<T1, T2, ...>` to the environment in trait
971 // function default implementations (and hypothetical code
972 // inside consts or type aliases)
973 cov_mark::hit!(trait_self_implements_self);
974 let substs = TyBuilder::type_params_subst(db, trait_id);
975 let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs };
976 let pred = WhereClause::Implemented(trait_ref);
977 let program_clause: chalk_ir::ProgramClause<Interner> = pred.cast(&Interner);
978 clauses.push(program_clause.into_from_env_clause(&Interner));
981 let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses);
983 Arc::new(TraitEnvironment { traits_from_clauses: traits_in_scope, env })
986 /// Resolve the where clause(s) of an item with generics.
987 pub(crate) fn generic_predicates_query(
988 db: &dyn HirDatabase,
990 ) -> Arc<[Binders<QuantifiedWhereClause>]> {
991 let resolver = def.resolver(db.upcast());
993 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
994 let generics = generics(db.upcast(), def);
996 .where_predicates_in_scope()
997 .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p)))
1001 /// Resolve the default type params from generics
1002 pub(crate) fn generic_defaults_query(
1003 db: &dyn HirDatabase,
1005 ) -> Arc<[Binders<Ty>]> {
1006 let resolver = def.resolver(db.upcast());
1008 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1009 let generic_params = generics(db.upcast(), def);
1011 let defaults = generic_params
1014 .map(|(idx, (_, p))| {
1016 p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t));
1018 // Each default can only refer to previous parameters.
1019 ty = crate::fold_free_vars(ty, |bound, binders| {
1020 if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST {
1021 // type variable default referring to parameter coming
1022 // after it. This is forbidden (FIXME: report
1024 TyKind::Error.intern(&Interner)
1026 bound.shifted_in_from(binders).to_ty(&Interner)
1030 crate::make_only_type_binders(idx, ty)
1037 fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig {
1038 let data = db.function_data(def);
1039 let resolver = def.resolver(db.upcast());
1040 let ctx_params = TyLoweringContext::new(db, &resolver)
1041 .with_impl_trait_mode(ImplTraitLoweringMode::Variable)
1042 .with_type_param_mode(TypeParamLoweringMode::Variable);
1043 let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::<Vec<_>>();
1044 let ctx_ret = TyLoweringContext::new(db, &resolver)
1045 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1046 .with_type_param_mode(TypeParamLoweringMode::Variable);
1047 let ret = ctx_ret.lower_ty(&data.ret_type);
1048 let generics = generics(db.upcast(), def.into());
1049 make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs()))
1052 /// Build the declared type of a function. This should not need to look at the
1054 fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders<Ty> {
1055 let generics = generics(db.upcast(), def.into());
1056 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1059 TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner),
1063 /// Build the declared type of a const.
1064 fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders<Ty> {
1065 let data = db.const_data(def);
1066 let generics = generics(db.upcast(), def.into());
1067 let resolver = def.resolver(db.upcast());
1069 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1071 make_binders(&generics, ctx.lower_ty(&data.type_ref))
1074 /// Build the declared type of a static.
1075 fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders<Ty> {
1076 let data = db.static_data(def);
1077 let resolver = def.resolver(db.upcast());
1078 let ctx = TyLoweringContext::new(db, &resolver);
1080 Binders::empty(&Interner, ctx.lower_ty(&data.type_ref))
1083 fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig {
1084 let struct_data = db.struct_data(def);
1085 let fields = struct_data.variant_data.fields();
1086 let resolver = def.resolver(db.upcast());
1088 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1089 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1090 let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders();
1091 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1094 /// Build the type of a tuple struct constructor.
1095 fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders<Ty> {
1096 let struct_data = db.struct_data(def);
1097 if let StructKind::Unit = struct_data.variant_data.kind() {
1098 return type_for_adt(db, def.into());
1100 let generics = generics(db.upcast(), def.into());
1101 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1104 TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner),
1108 fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig {
1109 let enum_data = db.enum_data(def.parent);
1110 let var_data = &enum_data.variants[def.local_id];
1111 let fields = var_data.variant_data.fields();
1112 let resolver = def.parent.resolver(db.upcast());
1114 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1115 let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::<Vec<_>>();
1116 let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders();
1117 Binders::new(binders, CallableSig::from_params_and_return(params, ret, false))
1120 /// Build the type of a tuple enum variant constructor.
1121 fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders<Ty> {
1122 let enum_data = db.enum_data(def.parent);
1123 let var_data = &enum_data.variants[def.local_id].variant_data;
1124 if let StructKind::Unit = var_data.kind() {
1125 return type_for_adt(db, def.parent.into());
1127 let generics = generics(db.upcast(), def.parent.into());
1128 let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST);
1131 TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner),
1135 fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders<Ty> {
1136 let generics = generics(db.upcast(), adt.into());
1137 let b = TyBuilder::adt(db, adt);
1138 let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build();
1139 make_binders(&generics, ty)
1142 fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders<Ty> {
1143 let generics = generics(db.upcast(), t.into());
1144 let resolver = t.resolver(db.upcast());
1146 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1147 if db.type_alias_data(t).is_extern {
1148 Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner))
1150 let type_ref = &db.type_alias_data(t).type_ref;
1151 let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error));
1152 make_binders(&generics, inner)
1156 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
1157 pub enum CallableDefId {
1158 FunctionId(FunctionId),
1160 EnumVariantId(EnumVariantId),
1162 impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId);
1164 impl CallableDefId {
1165 pub fn krate(self, db: &dyn HirDatabase) -> CrateId {
1166 let db = db.upcast();
1168 CallableDefId::FunctionId(f) => f.lookup(db).module(db),
1169 CallableDefId::StructId(s) => s.lookup(db).container,
1170 CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container,
1176 impl From<CallableDefId> for GenericDefId {
1177 fn from(def: CallableDefId) -> GenericDefId {
1179 CallableDefId::FunctionId(f) => f.into(),
1180 CallableDefId::StructId(s) => s.into(),
1181 CallableDefId::EnumVariantId(e) => e.into(),
1186 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1188 BuiltinType(BuiltinType),
1190 TypeAliasId(TypeAliasId),
1192 impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId);
1194 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1195 pub enum ValueTyDefId {
1196 FunctionId(FunctionId),
1199 EnumVariantId(EnumVariantId),
1203 impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId);
1205 /// Build the declared type of an item. This depends on the namespace; e.g. for
1206 /// `struct Foo(usize)`, we have two types: The type of the struct itself, and
1207 /// the constructor function `(usize) -> Foo` which lives in the values
1209 pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders<Ty> {
1211 TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)),
1212 TyDefId::AdtId(it) => type_for_adt(db, it),
1213 TyDefId::TypeAliasId(it) => type_for_type_alias(db, it),
1217 pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders<Ty> {
1218 let generics = match *def {
1219 TyDefId::BuiltinType(_) => {
1220 return Binders::empty(&Interner, TyKind::Error.intern(&Interner))
1222 TyDefId::AdtId(it) => generics(db.upcast(), it.into()),
1223 TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()),
1225 make_binders(&generics, TyKind::Error.intern(&Interner))
1228 pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders<Ty> {
1230 ValueTyDefId::FunctionId(it) => type_for_fn(db, it),
1231 ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it),
1232 ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()),
1233 ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it),
1234 ValueTyDefId::ConstId(it) => type_for_const(db, it),
1235 ValueTyDefId::StaticId(it) => type_for_static(db, it),
1239 pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders<Ty> {
1240 let impl_data = db.impl_data(impl_id);
1241 let resolver = impl_id.resolver(db.upcast());
1242 let generics = generics(db.upcast(), impl_id.into());
1244 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1245 make_binders(&generics, ctx.lower_ty(&impl_data.self_ty))
1248 pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty {
1249 let parent_data = db.generic_params(def.parent);
1250 let data = &parent_data.consts[def.local_id];
1251 let resolver = def.parent.resolver(db.upcast());
1252 let ctx = TyLoweringContext::new(db, &resolver);
1254 ctx.lower_ty(&data.ty)
1257 pub(crate) fn impl_self_ty_recover(
1258 db: &dyn HirDatabase,
1262 let generics = generics(db.upcast(), (*impl_id).into());
1263 make_binders(&generics, TyKind::Error.intern(&Interner))
1266 pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option<Binders<TraitRef>> {
1267 let impl_data = db.impl_data(impl_id);
1268 let resolver = impl_id.resolver(db.upcast());
1270 TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable);
1271 let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders();
1272 let target_trait = impl_data.target_trait.as_ref()?;
1273 Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?))
1276 pub(crate) fn return_type_impl_traits(
1277 db: &dyn HirDatabase,
1278 def: hir_def::FunctionId,
1279 ) -> Option<Arc<Binders<ReturnTypeImplTraits>>> {
1280 // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe
1281 let data = db.function_data(def);
1282 let resolver = def.resolver(db.upcast());
1283 let ctx_ret = TyLoweringContext::new(db, &resolver)
1284 .with_impl_trait_mode(ImplTraitLoweringMode::Opaque)
1285 .with_type_param_mode(TypeParamLoweringMode::Variable);
1286 let _ret = (&ctx_ret).lower_ty(&data.ret_type);
1287 let generics = generics(db.upcast(), def.into());
1288 let return_type_impl_traits =
1289 ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() };
1290 if return_type_impl_traits.impl_traits.is_empty() {
1293 Some(Arc::new(make_binders(&generics, return_type_impl_traits)))
1297 pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability {
1299 hir_def::type_ref::Mutability::Shared => Mutability::Not,
1300 hir_def::type_ref::Mutability::Mut => Mutability::Mut,
1304 fn make_binders<T: HasInterner<Interner = Interner>>(generics: &Generics, value: T) -> Binders<T> {
1305 crate::make_only_type_binders(generics.len(), value)