//! Methods for lowering the HIR to types. There are two main cases here: //! //! - Lowering a type reference like `&usize` or `Option` to a //! type: The entry point for this is `Ty::from_hir`. //! - Building the type for an item: This happens through the `type_for_def` query. //! //! This usually involves resolving names, collecting generic arguments etc. use std::cell::{Cell, RefCell}; use std::{iter, sync::Arc}; use base_db::CrateId; use chalk_ir::{cast::Cast, fold::Shift, interner::HasInterner, Mutability, Safety}; use hir_def::intern::Interned; use hir_def::{ adt::StructKind, body::{Expander, LowerCtx}, builtin_type::BuiltinType, generics::{TypeParamProvenance, WherePredicate, WherePredicateTypeTarget}, path::{GenericArg, Path, PathSegment, PathSegments}, resolver::{HasResolver, Resolver, TypeNs}, type_ref::{TraitRef as HirTraitRef, TypeBound, TypeRef}, AdtId, AssocContainerId, AssocItemId, ConstId, ConstParamId, EnumId, EnumVariantId, FunctionId, GenericDefId, HasModule, ImplId, LocalFieldId, Lookup, StaticId, StructId, TraitId, TypeAliasId, TypeParamId, UnionId, VariantId, }; use hir_expand::{name::Name, ExpandResult}; use la_arena::ArenaMap; use smallvec::SmallVec; use stdx::impl_from; use syntax::ast; use crate::{ consteval, db::HirDatabase, mapping::ToChalk, static_lifetime, to_assoc_type_id, to_chalk_trait_id, to_placeholder_idx, utils::{ all_super_trait_refs, associated_type_by_name_including_super_traits, generics, Generics, }, AliasEq, AliasTy, Binders, BoundVar, CallableSig, DebruijnIndex, DynTy, FnPointer, FnSig, FnSubst, ImplTraitId, Interner, OpaqueTy, PolyFnSig, ProjectionTy, QuantifiedWhereClause, QuantifiedWhereClauses, ReturnTypeImplTrait, ReturnTypeImplTraits, Substitution, TraitEnvironment, TraitRef, TraitRefExt, Ty, TyBuilder, TyKind, WhereClause, }; #[derive(Debug)] pub struct TyLoweringContext<'a> { pub db: &'a dyn HirDatabase, pub resolver: &'a Resolver, in_binders: DebruijnIndex, /// Note: Conceptually, it's thinkable that we could be in a location where /// some type params should be represented as placeholders, and others /// should be converted to variables. I think in practice, this isn't /// possible currently, so this should be fine for now. pub type_param_mode: TypeParamLoweringMode, pub impl_trait_mode: ImplTraitLoweringMode, impl_trait_counter: Cell, /// When turning `impl Trait` into opaque types, we have to collect the /// bounds at the same time to get the IDs correct (without becoming too /// complicated). I don't like using interior mutability (as for the /// counter), but I've tried and failed to make the lifetimes work for /// passing around a `&mut TyLoweringContext`. The core problem is that /// we're grouping the mutable data (the counter and this field) together /// with the immutable context (the references to the DB and resolver). /// Splitting this up would be a possible fix. opaque_type_data: RefCell>, expander: RefCell>, } impl<'a> TyLoweringContext<'a> { pub fn new(db: &'a dyn HirDatabase, resolver: &'a Resolver) -> Self { let impl_trait_counter = Cell::new(0); let impl_trait_mode = ImplTraitLoweringMode::Disallowed; let type_param_mode = TypeParamLoweringMode::Placeholder; let in_binders = DebruijnIndex::INNERMOST; let opaque_type_data = RefCell::new(Vec::new()); Self { db, resolver, in_binders, impl_trait_mode, impl_trait_counter, type_param_mode, opaque_type_data, expander: RefCell::new(None), } } pub fn with_debruijn( &self, debruijn: DebruijnIndex, f: impl FnOnce(&TyLoweringContext) -> T, ) -> T { let opaque_ty_data_vec = self.opaque_type_data.replace(Vec::new()); let expander = self.expander.replace(None); let new_ctx = Self { in_binders: debruijn, impl_trait_counter: Cell::new(self.impl_trait_counter.get()), opaque_type_data: RefCell::new(opaque_ty_data_vec), expander: RefCell::new(expander), ..*self }; let result = f(&new_ctx); self.impl_trait_counter.set(new_ctx.impl_trait_counter.get()); self.opaque_type_data.replace(new_ctx.opaque_type_data.into_inner()); self.expander.replace(new_ctx.expander.into_inner()); result } pub fn with_shifted_in( &self, debruijn: DebruijnIndex, f: impl FnOnce(&TyLoweringContext) -> T, ) -> T { self.with_debruijn(self.in_binders.shifted_in_from(debruijn), f) } pub fn with_impl_trait_mode(self, impl_trait_mode: ImplTraitLoweringMode) -> Self { Self { impl_trait_mode, ..self } } pub fn with_type_param_mode(self, type_param_mode: TypeParamLoweringMode) -> Self { Self { type_param_mode, ..self } } } #[derive(Copy, Clone, Debug, PartialEq, Eq)] pub enum ImplTraitLoweringMode { /// `impl Trait` gets lowered into an opaque type that doesn't unify with /// anything except itself. This is used in places where values flow 'out', /// i.e. for arguments of the function we're currently checking, and return /// types of functions we're calling. Opaque, /// `impl Trait` gets lowered into a type variable. Used for argument /// position impl Trait when inside the respective function, since it allows /// us to support that without Chalk. Param, /// `impl Trait` gets lowered into a variable that can unify with some /// type. This is used in places where values flow 'in', i.e. for arguments /// of functions we're calling, and the return type of the function we're /// currently checking. Variable, /// `impl Trait` is disallowed and will be an error. Disallowed, } #[derive(Copy, Clone, Debug, PartialEq, Eq)] pub enum TypeParamLoweringMode { Placeholder, Variable, } impl<'a> TyLoweringContext<'a> { pub fn lower_ty(&self, type_ref: &TypeRef) -> Ty { self.lower_ty_ext(type_ref).0 } pub fn lower_ty_ext(&self, type_ref: &TypeRef) -> (Ty, Option) { let mut res = None; let ty = match type_ref { TypeRef::Never => TyKind::Never.intern(&Interner), TypeRef::Tuple(inner) => { let inner_tys = inner.iter().map(|tr| self.lower_ty(tr)); TyKind::Tuple(inner_tys.len(), Substitution::from_iter(&Interner, inner_tys)) .intern(&Interner) } TypeRef::Path(path) => { let (ty, res_) = self.lower_path(path); res = res_; ty } TypeRef::RawPtr(inner, mutability) => { let inner_ty = self.lower_ty(inner); TyKind::Raw(lower_to_chalk_mutability(*mutability), inner_ty).intern(&Interner) } TypeRef::Array(inner, len) => { let inner_ty = self.lower_ty(inner); let const_len = consteval::usize_const(len.as_usize()); TyKind::Array(inner_ty, const_len).intern(&Interner) } TypeRef::Slice(inner) => { let inner_ty = self.lower_ty(inner); TyKind::Slice(inner_ty).intern(&Interner) } TypeRef::Reference(inner, _, mutability) => { let inner_ty = self.lower_ty(inner); let lifetime = static_lifetime(); TyKind::Ref(lower_to_chalk_mutability(*mutability), lifetime, inner_ty) .intern(&Interner) } TypeRef::Placeholder => TyKind::Error.intern(&Interner), TypeRef::Fn(params, is_varargs) => { let substs = self.with_shifted_in(DebruijnIndex::ONE, |ctx| { Substitution::from_iter(&Interner, params.iter().map(|tr| ctx.lower_ty(tr))) }); TyKind::Function(FnPointer { num_binders: 0, // FIXME lower `for<'a> fn()` correctly sig: FnSig { abi: (), safety: Safety::Safe, variadic: *is_varargs }, substitution: FnSubst(substs), }) .intern(&Interner) } TypeRef::DynTrait(bounds) => { let self_ty = TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner); let bounds = self.with_shifted_in(DebruijnIndex::ONE, |ctx| { QuantifiedWhereClauses::from_iter( &Interner, bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)), ) }); let bounds = crate::make_only_type_binders(1, bounds); TyKind::Dyn(DynTy { bounds, lifetime: static_lifetime() }).intern(&Interner) } TypeRef::ImplTrait(bounds) => { match self.impl_trait_mode { ImplTraitLoweringMode::Opaque => { let idx = self.impl_trait_counter.get(); self.impl_trait_counter.set(idx + 1); assert!(idx as usize == self.opaque_type_data.borrow().len()); // this dance is to make sure the data is in the right // place even if we encounter more opaque types while // lowering the bounds self.opaque_type_data.borrow_mut().push(ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, Vec::new()), }); // We don't want to lower the bounds inside the binders // we're currently in, because they don't end up inside // those binders. E.g. when we have `impl Trait>`, the `impl OtherTrait` can't refer // to the self parameter from `impl Trait`, and the // bounds aren't actually stored nested within each // other, but separately. So if the `T` refers to a type // parameter of the outer function, it's just one binder // away instead of two. let actual_opaque_type_data = self .with_debruijn(DebruijnIndex::INNERMOST, |ctx| { ctx.lower_impl_trait(bounds) }); self.opaque_type_data.borrow_mut()[idx as usize] = actual_opaque_type_data; let func = match self.resolver.generic_def() { Some(GenericDefId::FunctionId(f)) => f, _ => panic!("opaque impl trait lowering in non-function"), }; let impl_trait_id = ImplTraitId::ReturnTypeImplTrait(func, idx); let opaque_ty_id = self.db.intern_impl_trait_id(impl_trait_id).into(); let generics = generics(self.db.upcast(), func.into()); let parameters = generics.bound_vars_subst(self.in_binders); TyKind::Alias(AliasTy::Opaque(OpaqueTy { opaque_ty_id, substitution: parameters, })) .intern(&Interner) } ImplTraitLoweringMode::Param => { let idx = self.impl_trait_counter.get(); // FIXME we're probably doing something wrong here self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16); if let Some(def) = self.resolver.generic_def() { let generics = generics(self.db.upcast(), def); let param = generics .iter() .filter(|(_, data)| { data.provenance == TypeParamProvenance::ArgumentImplTrait }) .nth(idx as usize) .map_or(TyKind::Error, |(id, _)| { TyKind::Placeholder(to_placeholder_idx(self.db, id)) }); param.intern(&Interner) } else { TyKind::Error.intern(&Interner) } } ImplTraitLoweringMode::Variable => { let idx = self.impl_trait_counter.get(); // FIXME we're probably doing something wrong here self.impl_trait_counter.set(idx + count_impl_traits(type_ref) as u16); let (parent_params, self_params, list_params, _impl_trait_params) = if let Some(def) = self.resolver.generic_def() { let generics = generics(self.db.upcast(), def); generics.provenance_split() } else { (0, 0, 0, 0) }; TyKind::BoundVar(BoundVar::new( self.in_binders, idx as usize + parent_params + self_params + list_params, )) .intern(&Interner) } ImplTraitLoweringMode::Disallowed => { // FIXME: report error TyKind::Error.intern(&Interner) } } } TypeRef::Macro(macro_call) => { let (expander, recursion_start) = { let mut expander = self.expander.borrow_mut(); if expander.is_some() { (Some(expander), false) } else { if let Some(module_id) = self.resolver.module() { *expander = Some(Expander::new( self.db.upcast(), macro_call.file_id, module_id, )); (Some(expander), true) } else { (None, false) } } }; let ty = if let Some(mut expander) = expander { let expander_mut = expander.as_mut().unwrap(); let macro_call = macro_call.to_node(self.db.upcast()); match expander_mut.enter_expand::(self.db.upcast(), macro_call) { Ok(ExpandResult { value: Some((mark, expanded)), .. }) => { let ctx = LowerCtx::new(self.db.upcast(), expander_mut.current_file_id()); let type_ref = TypeRef::from_ast(&ctx, expanded); drop(expander); let ty = self.lower_ty(&type_ref); self.expander .borrow_mut() .as_mut() .unwrap() .exit(self.db.upcast(), mark); Some(ty) } _ => None, } } else { None }; if recursion_start { *self.expander.borrow_mut() = None; } ty.unwrap_or_else(|| TyKind::Error.intern(&Interner)) } TypeRef::Error => TyKind::Error.intern(&Interner), }; (ty, res) } /// This is only for `generic_predicates_for_param`, where we can't just /// lower the self types of the predicates since that could lead to cycles. /// So we just check here if the `type_ref` resolves to a generic param, and which. fn lower_ty_only_param(&self, type_ref: &TypeRef) -> Option { let path = match type_ref { TypeRef::Path(path) => path, _ => return None, }; if path.type_anchor().is_some() { return None; } if path.segments().len() > 1 { return None; } let resolution = match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) { Some((it, None)) => it, _ => return None, }; if let TypeNs::GenericParam(param_id) = resolution { Some(param_id) } else { None } } pub(crate) fn lower_ty_relative_path( &self, ty: Ty, // We need the original resolution to lower `Self::AssocTy` correctly res: Option, remaining_segments: PathSegments<'_>, ) -> (Ty, Option) { if remaining_segments.len() == 1 { // resolve unselected assoc types let segment = remaining_segments.first().unwrap(); (self.select_associated_type(res, segment), None) } else if remaining_segments.len() > 1 { // FIXME report error (ambiguous associated type) (TyKind::Error.intern(&Interner), None) } else { (ty, res) } } pub(crate) fn lower_partly_resolved_path( &self, resolution: TypeNs, resolved_segment: PathSegment<'_>, remaining_segments: PathSegments<'_>, infer_args: bool, ) -> (Ty, Option) { let ty = match resolution { TypeNs::TraitId(trait_) => { // if this is a bare dyn Trait, we'll directly put the required ^0 for the self type in there let self_ty = if remaining_segments.len() == 0 { Some( TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)) .intern(&Interner), ) } else { None }; let trait_ref = self.lower_trait_ref_from_resolved_path(trait_, resolved_segment, self_ty); let ty = if remaining_segments.len() == 1 { let segment = remaining_segments.first().unwrap(); let found = self .db .trait_data(trait_ref.hir_trait_id()) .associated_type_by_name(segment.name); match found { Some(associated_ty) => { // FIXME handle type parameters on the segment TyKind::Alias(AliasTy::Projection(ProjectionTy { associated_ty_id: to_assoc_type_id(associated_ty), substitution: trait_ref.substitution, })) .intern(&Interner) } None => { // FIXME: report error (associated type not found) TyKind::Error.intern(&Interner) } } } else if remaining_segments.len() > 1 { // FIXME report error (ambiguous associated type) TyKind::Error.intern(&Interner) } else { let dyn_ty = DynTy { bounds: crate::make_only_type_binders( 1, QuantifiedWhereClauses::from_iter( &Interner, Some(crate::wrap_empty_binders(WhereClause::Implemented( trait_ref, ))), ), ), lifetime: static_lifetime(), }; TyKind::Dyn(dyn_ty).intern(&Interner) }; return (ty, None); } TypeNs::GenericParam(param_id) => { let generics = generics( self.db.upcast(), self.resolver.generic_def().expect("generics in scope"), ); match self.type_param_mode { TypeParamLoweringMode::Placeholder => { TyKind::Placeholder(to_placeholder_idx(self.db, param_id)) } TypeParamLoweringMode::Variable => { let idx = generics.param_idx(param_id).expect("matching generics"); TyKind::BoundVar(BoundVar::new(self.in_binders, idx)) } } .intern(&Interner) } TypeNs::SelfType(impl_id) => { let generics = generics(self.db.upcast(), impl_id.into()); let substs = match self.type_param_mode { TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db), TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders), }; self.db.impl_self_ty(impl_id).substitute(&Interner, &substs) } TypeNs::AdtSelfType(adt) => { let generics = generics(self.db.upcast(), adt.into()); let substs = match self.type_param_mode { TypeParamLoweringMode::Placeholder => generics.type_params_subst(self.db), TypeParamLoweringMode::Variable => generics.bound_vars_subst(self.in_binders), }; self.db.ty(adt.into()).substitute(&Interner, &substs) } TypeNs::AdtId(it) => self.lower_path_inner(resolved_segment, it.into(), infer_args), TypeNs::BuiltinType(it) => { self.lower_path_inner(resolved_segment, it.into(), infer_args) } TypeNs::TypeAliasId(it) => { self.lower_path_inner(resolved_segment, it.into(), infer_args) } // FIXME: report error TypeNs::EnumVariantId(_) => return (TyKind::Error.intern(&Interner), None), }; self.lower_ty_relative_path(ty, Some(resolution), remaining_segments) } pub(crate) fn lower_path(&self, path: &Path) -> (Ty, Option) { // Resolve the path (in type namespace) if let Some(type_ref) = path.type_anchor() { let (ty, res) = self.lower_ty_ext(type_ref); return self.lower_ty_relative_path(ty, res, path.segments()); } let (resolution, remaining_index) = match self.resolver.resolve_path_in_type_ns(self.db.upcast(), path.mod_path()) { Some(it) => it, None => return (TyKind::Error.intern(&Interner), None), }; let (resolved_segment, remaining_segments) = match remaining_index { None => ( path.segments().last().expect("resolved path has at least one element"), PathSegments::EMPTY, ), Some(i) => (path.segments().get(i - 1).unwrap(), path.segments().skip(i)), }; self.lower_partly_resolved_path(resolution, resolved_segment, remaining_segments, false) } fn select_associated_type(&self, res: Option, segment: PathSegment<'_>) -> Ty { if let Some(res) = res { let ty = associated_type_shorthand_candidates( self.db, res, move |name, t, associated_ty| { if name == segment.name { let substs = match self.type_param_mode { TypeParamLoweringMode::Placeholder => { // if we're lowering to placeholders, we have to put // them in now let generics = generics( self.db.upcast(), self.resolver.generic_def().expect( "there should be generics if there's a generic param", ), ); let s = generics.type_params_subst(self.db); s.apply(t.substitution.clone(), &Interner) } TypeParamLoweringMode::Variable => t.substitution.clone(), }; // We need to shift in the bound vars, since // associated_type_shorthand_candidates does not do that let substs = substs.shifted_in_from(&Interner, self.in_binders); // FIXME handle type parameters on the segment return Some( TyKind::Alias(AliasTy::Projection(ProjectionTy { associated_ty_id: to_assoc_type_id(associated_ty), substitution: substs, })) .intern(&Interner), ); } None }, ); ty.unwrap_or_else(|| TyKind::Error.intern(&Interner)) } else { TyKind::Error.intern(&Interner) } } fn lower_path_inner( &self, segment: PathSegment<'_>, typeable: TyDefId, infer_args: bool, ) -> Ty { let generic_def = match typeable { TyDefId::BuiltinType(_) => None, TyDefId::AdtId(it) => Some(it.into()), TyDefId::TypeAliasId(it) => Some(it.into()), }; let substs = self.substs_from_path_segment(segment, generic_def, infer_args, None); self.db.ty(typeable).substitute(&Interner, &substs) } /// Collect generic arguments from a path into a `Substs`. See also /// `create_substs_for_ast_path` and `def_to_ty` in rustc. pub(super) fn substs_from_path( &self, path: &Path, // Note that we don't call `db.value_type(resolved)` here, // `ValueTyDefId` is just a convenient way to pass generics and // special-case enum variants resolved: ValueTyDefId, infer_args: bool, ) -> Substitution { let last = path.segments().last().expect("path should have at least one segment"); let (segment, generic_def) = match resolved { ValueTyDefId::FunctionId(it) => (last, Some(it.into())), ValueTyDefId::StructId(it) => (last, Some(it.into())), ValueTyDefId::UnionId(it) => (last, Some(it.into())), ValueTyDefId::ConstId(it) => (last, Some(it.into())), ValueTyDefId::StaticId(_) => (last, None), ValueTyDefId::EnumVariantId(var) => { // the generic args for an enum variant may be either specified // on the segment referring to the enum, or on the segment // referring to the variant. So `Option::::None` and // `Option::None::` are both allowed (though the former is // preferred). See also `def_ids_for_path_segments` in rustc. let len = path.segments().len(); let penultimate = if len >= 2 { path.segments().get(len - 2) } else { None }; let segment = match penultimate { Some(segment) if segment.args_and_bindings.is_some() => segment, _ => last, }; (segment, Some(var.parent.into())) } }; self.substs_from_path_segment(segment, generic_def, infer_args, None) } fn substs_from_path_segment( &self, segment: PathSegment<'_>, def_generic: Option, infer_args: bool, explicit_self_ty: Option, ) -> Substitution { let mut substs = Vec::new(); let def_generics = def_generic.map(|def| generics(self.db.upcast(), def)); let (parent_params, self_params, type_params, impl_trait_params) = def_generics.map_or((0, 0, 0, 0), |g| g.provenance_split()); let total_len = parent_params + self_params + type_params + impl_trait_params; substs.extend(iter::repeat(TyKind::Error.intern(&Interner)).take(parent_params)); let fill_self_params = || { substs.extend( explicit_self_ty .into_iter() .chain(iter::repeat(TyKind::Error.intern(&Interner))) .take(self_params), ) }; let mut had_explicit_type_args = false; if let Some(generic_args) = &segment.args_and_bindings { if !generic_args.has_self_type { fill_self_params(); } let expected_num = if generic_args.has_self_type { self_params + type_params } else { type_params }; let skip = if generic_args.has_self_type && self_params == 0 { 1 } else { 0 }; // if args are provided, it should be all of them, but we can't rely on that for arg in generic_args .args .iter() .filter(|arg| matches!(arg, GenericArg::Type(_))) .skip(skip) .take(expected_num) { match arg { GenericArg::Type(type_ref) => { had_explicit_type_args = true; let ty = self.lower_ty(type_ref); substs.push(ty); } GenericArg::Lifetime(_) => {} } } } else { fill_self_params(); } // handle defaults. In expression or pattern path segments without // explicitly specified type arguments, missing type arguments are inferred // (i.e. defaults aren't used). if !infer_args || had_explicit_type_args { if let Some(def_generic) = def_generic { let defaults = self.db.generic_defaults(def_generic); assert_eq!(total_len, defaults.len()); for default_ty in defaults.iter().skip(substs.len()) { // each default can depend on the previous parameters let substs_so_far = Substitution::from_iter(&Interner, substs.clone()); substs.push(default_ty.clone().substitute(&Interner, &substs_so_far)); } } } // add placeholders for args that were not provided // FIXME: emit diagnostics in contexts where this is not allowed for _ in substs.len()..total_len { substs.push(TyKind::Error.intern(&Interner)); } assert_eq!(substs.len(), total_len); Substitution::from_iter(&Interner, substs) } fn lower_trait_ref_from_path( &self, path: &Path, explicit_self_ty: Option, ) -> Option { let resolved = match self.resolver.resolve_path_in_type_ns_fully(self.db.upcast(), path.mod_path())? { TypeNs::TraitId(tr) => tr, _ => return None, }; let segment = path.segments().last().expect("path should have at least one segment"); Some(self.lower_trait_ref_from_resolved_path(resolved, segment, explicit_self_ty)) } pub(crate) fn lower_trait_ref_from_resolved_path( &self, resolved: TraitId, segment: PathSegment<'_>, explicit_self_ty: Option, ) -> TraitRef { let substs = self.trait_ref_substs_from_path(segment, resolved, explicit_self_ty); TraitRef { trait_id: to_chalk_trait_id(resolved), substitution: substs } } fn lower_trait_ref( &self, trait_ref: &HirTraitRef, explicit_self_ty: Option, ) -> Option { self.lower_trait_ref_from_path(&trait_ref.path, explicit_self_ty) } fn trait_ref_substs_from_path( &self, segment: PathSegment<'_>, resolved: TraitId, explicit_self_ty: Option, ) -> Substitution { self.substs_from_path_segment(segment, Some(resolved.into()), false, explicit_self_ty) } pub(crate) fn lower_where_predicate( &'a self, where_predicate: &'a WherePredicate, ignore_bindings: bool, ) -> impl Iterator + 'a { match where_predicate { WherePredicate::ForLifetime { target, bound, .. } | WherePredicate::TypeBound { target, bound } => { let self_ty = match target { WherePredicateTypeTarget::TypeRef(type_ref) => self.lower_ty(type_ref), WherePredicateTypeTarget::TypeParam(param_id) => { let generic_def = self.resolver.generic_def().expect("generics in scope"); let generics = generics(self.db.upcast(), generic_def); let param_id = hir_def::TypeParamId { parent: generic_def, local_id: *param_id }; let placeholder = to_placeholder_idx(self.db, param_id); match self.type_param_mode { TypeParamLoweringMode::Placeholder => TyKind::Placeholder(placeholder), TypeParamLoweringMode::Variable => { let idx = generics.param_idx(param_id).expect("matching generics"); TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, idx)) } } .intern(&Interner) } }; self.lower_type_bound(bound, self_ty, ignore_bindings) .collect::>() .into_iter() } WherePredicate::Lifetime { .. } => vec![].into_iter(), } } pub(crate) fn lower_type_bound( &'a self, bound: &'a TypeBound, self_ty: Ty, ignore_bindings: bool, ) -> impl Iterator + 'a { let mut bindings = None; let trait_ref = match bound { TypeBound::Path(path) => { bindings = self.lower_trait_ref_from_path(path, Some(self_ty)); bindings.clone().map(WhereClause::Implemented).map(crate::wrap_empty_binders) } TypeBound::Lifetime(_) => None, TypeBound::Error => None, }; trait_ref.into_iter().chain( bindings .into_iter() .filter(move |_| !ignore_bindings) .flat_map(move |tr| self.assoc_type_bindings_from_type_bound(bound, tr)), ) } fn assoc_type_bindings_from_type_bound( &'a self, bound: &'a TypeBound, trait_ref: TraitRef, ) -> impl Iterator + 'a { let last_segment = match bound { TypeBound::Path(path) => path.segments().last(), TypeBound::Error | TypeBound::Lifetime(_) => None, }; last_segment .into_iter() .flat_map(|segment| segment.args_and_bindings.into_iter()) .flat_map(|args_and_bindings| args_and_bindings.bindings.iter()) .flat_map(move |binding| { let found = associated_type_by_name_including_super_traits( self.db, trait_ref.clone(), &binding.name, ); let (super_trait_ref, associated_ty) = match found { None => return SmallVec::<[QuantifiedWhereClause; 1]>::new(), Some(t) => t, }; let projection_ty = ProjectionTy { associated_ty_id: to_assoc_type_id(associated_ty), substitution: super_trait_ref.substitution, }; let mut preds = SmallVec::with_capacity( binding.type_ref.as_ref().map_or(0, |_| 1) + binding.bounds.len(), ); if let Some(type_ref) = &binding.type_ref { let ty = self.lower_ty(type_ref); let alias_eq = AliasEq { alias: AliasTy::Projection(projection_ty.clone()), ty }; preds.push(crate::wrap_empty_binders(WhereClause::AliasEq(alias_eq))); } for bound in &binding.bounds { preds.extend(self.lower_type_bound( bound, TyKind::Alias(AliasTy::Projection(projection_ty.clone())).intern(&Interner), false, )); } preds }) } fn lower_impl_trait(&self, bounds: &[Interned]) -> ReturnTypeImplTrait { cov_mark::hit!(lower_rpit); let self_ty = TyKind::BoundVar(BoundVar::new(DebruijnIndex::INNERMOST, 0)).intern(&Interner); let predicates = self.with_shifted_in(DebruijnIndex::ONE, |ctx| { bounds.iter().flat_map(|b| ctx.lower_type_bound(b, self_ty.clone(), false)).collect() }); ReturnTypeImplTrait { bounds: crate::make_only_type_binders(1, predicates) } } } fn count_impl_traits(type_ref: &TypeRef) -> usize { let mut count = 0; type_ref.walk(&mut |type_ref| { if matches!(type_ref, TypeRef::ImplTrait(_)) { count += 1; } }); count } /// Build the signature of a callable item (function, struct or enum variant). pub fn callable_item_sig(db: &dyn HirDatabase, def: CallableDefId) -> PolyFnSig { match def { CallableDefId::FunctionId(f) => fn_sig_for_fn(db, f), CallableDefId::StructId(s) => fn_sig_for_struct_constructor(db, s), CallableDefId::EnumVariantId(e) => fn_sig_for_enum_variant_constructor(db, e), } } pub fn associated_type_shorthand_candidates( db: &dyn HirDatabase, res: TypeNs, mut cb: impl FnMut(&Name, &TraitRef, TypeAliasId) -> Option, ) -> Option { let mut search = |t| { for t in all_super_trait_refs(db, t) { let data = db.trait_data(t.hir_trait_id()); for (name, assoc_id) in &data.items { if let AssocItemId::TypeAliasId(alias) = assoc_id { if let Some(result) = cb(name, &t, *alias) { return Some(result); } } } } None }; match res { TypeNs::SelfType(impl_id) => search( // we're _in_ the impl -- the binders get added back later. Correct, // but it would be nice to make this more explicit db.impl_trait(impl_id)?.into_value_and_skipped_binders().0, ), TypeNs::GenericParam(param_id) => { let predicates = db.generic_predicates_for_param(param_id); let res = predicates.iter().find_map(|pred| match pred.skip_binders().skip_binders() { // FIXME: how to correctly handle higher-ranked bounds here? WhereClause::Implemented(tr) => search( tr.clone() .shifted_out_to(&Interner, DebruijnIndex::ONE) .expect("FIXME unexpected higher-ranked trait bound"), ), _ => None, }); if let res @ Some(_) = res { return res; } // Handle `Self::Type` referring to own associated type in trait definitions if let GenericDefId::TraitId(trait_id) = param_id.parent { let generics = generics(db.upcast(), trait_id.into()); if generics.params.types[param_id.local_id].provenance == TypeParamProvenance::TraitSelf { let trait_ref = TyBuilder::trait_ref(db, trait_id) .fill_with_bound_vars(DebruijnIndex::INNERMOST, 0) .build(); return search(trait_ref); } } None } _ => None, } } /// Build the type of all specific fields of a struct or enum variant. pub(crate) fn field_types_query( db: &dyn HirDatabase, variant_id: VariantId, ) -> Arc>> { let var_data = variant_id.variant_data(db.upcast()); let (resolver, def): (_, GenericDefId) = match variant_id { VariantId::StructId(it) => (it.resolver(db.upcast()), it.into()), VariantId::UnionId(it) => (it.resolver(db.upcast()), it.into()), VariantId::EnumVariantId(it) => (it.parent.resolver(db.upcast()), it.parent.into()), }; let generics = generics(db.upcast(), def); let mut res = ArenaMap::default(); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); for (field_id, field_data) in var_data.fields().iter() { res.insert(field_id, make_binders(&generics, ctx.lower_ty(&field_data.type_ref))) } Arc::new(res) } /// This query exists only to be used when resolving short-hand associated types /// like `T::Item`. /// /// See the analogous query in rustc and its comment: /// /// This is a query mostly to handle cycles somewhat gracefully; e.g. the /// following bounds are disallowed: `T: Foo, U: Foo`, but /// these are fine: `T: Foo, U: Foo<()>`. pub(crate) fn generic_predicates_for_param_query( db: &dyn HirDatabase, param_id: TypeParamId, ) -> Arc<[Binders]> { let resolver = param_id.parent.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let generics = generics(db.upcast(), param_id.parent); resolver .where_predicates_in_scope() // we have to filter out all other predicates *first*, before attempting to lower them .filter(|pred| match pred { WherePredicate::ForLifetime { target, .. } | WherePredicate::TypeBound { target, .. } => match target { WherePredicateTypeTarget::TypeRef(type_ref) => { ctx.lower_ty_only_param(type_ref) == Some(param_id) } WherePredicateTypeTarget::TypeParam(local_id) => *local_id == param_id.local_id, }, WherePredicate::Lifetime { .. } => false, }) .flat_map(|pred| ctx.lower_where_predicate(pred, true).map(|p| make_binders(&generics, p))) .collect() } pub(crate) fn generic_predicates_for_param_recover( _db: &dyn HirDatabase, _cycle: &[String], _param_id: &TypeParamId, ) -> Arc<[Binders]> { Arc::new([]) } pub(crate) fn trait_environment_query( db: &dyn HirDatabase, def: GenericDefId, ) -> Arc { let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver) .with_type_param_mode(TypeParamLoweringMode::Placeholder); let mut traits_in_scope = Vec::new(); let mut clauses = Vec::new(); for pred in resolver.where_predicates_in_scope() { for pred in ctx.lower_where_predicate(pred, false) { if let WhereClause::Implemented(tr) = &pred.skip_binders() { traits_in_scope .push((tr.self_type_parameter(&Interner).clone(), tr.hir_trait_id())); } let program_clause: chalk_ir::ProgramClause = pred.clone().cast(&Interner); clauses.push(program_clause.into_from_env_clause(&Interner)); } } let container: Option = match def { // FIXME: is there a function for this? GenericDefId::FunctionId(f) => Some(f.lookup(db.upcast()).container), GenericDefId::AdtId(_) => None, GenericDefId::TraitId(_) => None, GenericDefId::TypeAliasId(t) => Some(t.lookup(db.upcast()).container), GenericDefId::ImplId(_) => None, GenericDefId::EnumVariantId(_) => None, GenericDefId::ConstId(c) => Some(c.lookup(db.upcast()).container), }; if let Some(AssocContainerId::TraitId(trait_id)) = container { // add `Self: Trait` to the environment in trait // function default implementations (and speculative code // inside consts or type aliases) cov_mark::hit!(trait_self_implements_self); let substs = TyBuilder::type_params_subst(db, trait_id); let trait_ref = TraitRef { trait_id: to_chalk_trait_id(trait_id), substitution: substs }; let pred = WhereClause::Implemented(trait_ref); let program_clause: chalk_ir::ProgramClause = pred.cast(&Interner); clauses.push(program_clause.into_from_env_clause(&Interner)); } let krate = def.module(db.upcast()).krate(); let env = chalk_ir::Environment::new(&Interner).add_clauses(&Interner, clauses); Arc::new(TraitEnvironment { krate, traits_from_clauses: traits_in_scope, env }) } /// Resolve the where clause(s) of an item with generics. pub(crate) fn generic_predicates_query( db: &dyn HirDatabase, def: GenericDefId, ) -> Arc<[Binders]> { let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let generics = generics(db.upcast(), def); resolver .where_predicates_in_scope() .flat_map(|pred| ctx.lower_where_predicate(pred, false).map(|p| make_binders(&generics, p))) .collect() } /// Resolve the default type params from generics pub(crate) fn generic_defaults_query( db: &dyn HirDatabase, def: GenericDefId, ) -> Arc<[Binders]> { let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let generic_params = generics(db.upcast(), def); let defaults = generic_params .iter() .enumerate() .map(|(idx, (_, p))| { let mut ty = p.default.as_ref().map_or(TyKind::Error.intern(&Interner), |t| ctx.lower_ty(t)); // Each default can only refer to previous parameters. ty = crate::fold_free_vars(ty, |bound, binders| { if bound.index >= idx && bound.debruijn == DebruijnIndex::INNERMOST { // type variable default referring to parameter coming // after it. This is forbidden (FIXME: report // diagnostic) TyKind::Error.intern(&Interner) } else { bound.shifted_in_from(binders).to_ty(&Interner) } }); crate::make_only_type_binders(idx, ty) }) .collect(); defaults } pub(crate) fn generic_defaults_recover( db: &dyn HirDatabase, _cycle: &[String], def: &GenericDefId, ) -> Arc<[Binders]> { let generic_params = generics(db.upcast(), *def); // we still need one default per parameter let defaults = generic_params .iter() .enumerate() .map(|(idx, _)| { let ty = TyKind::Error.intern(&Interner); crate::make_only_type_binders(idx, ty) }) .collect(); defaults } fn fn_sig_for_fn(db: &dyn HirDatabase, def: FunctionId) -> PolyFnSig { let data = db.function_data(def); let resolver = def.resolver(db.upcast()); let ctx_params = TyLoweringContext::new(db, &resolver) .with_impl_trait_mode(ImplTraitLoweringMode::Variable) .with_type_param_mode(TypeParamLoweringMode::Variable); let params = data.params.iter().map(|tr| ctx_params.lower_ty(tr)).collect::>(); let ctx_ret = TyLoweringContext::new(db, &resolver) .with_impl_trait_mode(ImplTraitLoweringMode::Opaque) .with_type_param_mode(TypeParamLoweringMode::Variable); let ret = ctx_ret.lower_ty(&data.ret_type); let generics = generics(db.upcast(), def.into()); make_binders(&generics, CallableSig::from_params_and_return(params, ret, data.is_varargs())) } /// Build the declared type of a function. This should not need to look at the /// function body. fn type_for_fn(db: &dyn HirDatabase, def: FunctionId) -> Binders { let generics = generics(db.upcast(), def.into()); let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST); make_binders( &generics, TyKind::FnDef(CallableDefId::FunctionId(def).to_chalk(db), substs).intern(&Interner), ) } /// Build the declared type of a const. fn type_for_const(db: &dyn HirDatabase, def: ConstId) -> Binders { let data = db.const_data(def); let generics = generics(db.upcast(), def.into()); let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); make_binders(&generics, ctx.lower_ty(&data.type_ref)) } /// Build the declared type of a static. fn type_for_static(db: &dyn HirDatabase, def: StaticId) -> Binders { let data = db.static_data(def); let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver); Binders::empty(&Interner, ctx.lower_ty(&data.type_ref)) } fn fn_sig_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> PolyFnSig { let struct_data = db.struct_data(def); let fields = struct_data.variant_data.fields(); let resolver = def.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::>(); let (ret, binders) = type_for_adt(db, def.into()).into_value_and_skipped_binders(); Binders::new(binders, CallableSig::from_params_and_return(params, ret, false)) } /// Build the type of a tuple struct constructor. fn type_for_struct_constructor(db: &dyn HirDatabase, def: StructId) -> Binders { let struct_data = db.struct_data(def); if let StructKind::Unit = struct_data.variant_data.kind() { return type_for_adt(db, def.into()); } let generics = generics(db.upcast(), def.into()); let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST); make_binders( &generics, TyKind::FnDef(CallableDefId::StructId(def).to_chalk(db), substs).intern(&Interner), ) } fn fn_sig_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> PolyFnSig { let enum_data = db.enum_data(def.parent); let var_data = &enum_data.variants[def.local_id]; let fields = var_data.variant_data.fields(); let resolver = def.parent.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let params = fields.iter().map(|(_, field)| ctx.lower_ty(&field.type_ref)).collect::>(); let (ret, binders) = type_for_adt(db, def.parent.into()).into_value_and_skipped_binders(); Binders::new(binders, CallableSig::from_params_and_return(params, ret, false)) } /// Build the type of a tuple enum variant constructor. fn type_for_enum_variant_constructor(db: &dyn HirDatabase, def: EnumVariantId) -> Binders { let enum_data = db.enum_data(def.parent); let var_data = &enum_data.variants[def.local_id].variant_data; if let StructKind::Unit = var_data.kind() { return type_for_adt(db, def.parent.into()); } let generics = generics(db.upcast(), def.parent.into()); let substs = generics.bound_vars_subst(DebruijnIndex::INNERMOST); make_binders( &generics, TyKind::FnDef(CallableDefId::EnumVariantId(def).to_chalk(db), substs).intern(&Interner), ) } fn type_for_adt(db: &dyn HirDatabase, adt: AdtId) -> Binders { let generics = generics(db.upcast(), adt.into()); let b = TyBuilder::adt(db, adt); let ty = b.fill_with_bound_vars(DebruijnIndex::INNERMOST, 0).build(); make_binders(&generics, ty) } fn type_for_type_alias(db: &dyn HirDatabase, t: TypeAliasId) -> Binders { let generics = generics(db.upcast(), t.into()); let resolver = t.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); if db.type_alias_data(t).is_extern { Binders::empty(&Interner, TyKind::Foreign(crate::to_foreign_def_id(t)).intern(&Interner)) } else { let type_ref = &db.type_alias_data(t).type_ref; let inner = ctx.lower_ty(type_ref.as_deref().unwrap_or(&TypeRef::Error)); make_binders(&generics, inner) } } #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)] pub enum CallableDefId { FunctionId(FunctionId), StructId(StructId), EnumVariantId(EnumVariantId), } impl_from!(FunctionId, StructId, EnumVariantId for CallableDefId); impl CallableDefId { pub fn krate(self, db: &dyn HirDatabase) -> CrateId { let db = db.upcast(); match self { CallableDefId::FunctionId(f) => f.lookup(db).module(db), CallableDefId::StructId(s) => s.lookup(db).container, CallableDefId::EnumVariantId(e) => e.parent.lookup(db).container, } .krate() } } impl From for GenericDefId { fn from(def: CallableDefId) -> GenericDefId { match def { CallableDefId::FunctionId(f) => f.into(), CallableDefId::StructId(s) => s.into(), CallableDefId::EnumVariantId(e) => e.into(), } } } #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)] pub enum TyDefId { BuiltinType(BuiltinType), AdtId(AdtId), TypeAliasId(TypeAliasId), } impl_from!(BuiltinType, AdtId(StructId, EnumId, UnionId), TypeAliasId for TyDefId); #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)] pub enum ValueTyDefId { FunctionId(FunctionId), StructId(StructId), UnionId(UnionId), EnumVariantId(EnumVariantId), ConstId(ConstId), StaticId(StaticId), } impl_from!(FunctionId, StructId, UnionId, EnumVariantId, ConstId, StaticId for ValueTyDefId); /// Build the declared type of an item. This depends on the namespace; e.g. for /// `struct Foo(usize)`, we have two types: The type of the struct itself, and /// the constructor function `(usize) -> Foo` which lives in the values /// namespace. pub(crate) fn ty_query(db: &dyn HirDatabase, def: TyDefId) -> Binders { match def { TyDefId::BuiltinType(it) => Binders::empty(&Interner, TyBuilder::builtin(it)), TyDefId::AdtId(it) => type_for_adt(db, it), TyDefId::TypeAliasId(it) => type_for_type_alias(db, it), } } pub(crate) fn ty_recover(db: &dyn HirDatabase, _cycle: &[String], def: &TyDefId) -> Binders { let generics = match *def { TyDefId::BuiltinType(_) => { return Binders::empty(&Interner, TyKind::Error.intern(&Interner)) } TyDefId::AdtId(it) => generics(db.upcast(), it.into()), TyDefId::TypeAliasId(it) => generics(db.upcast(), it.into()), }; make_binders(&generics, TyKind::Error.intern(&Interner)) } pub(crate) fn value_ty_query(db: &dyn HirDatabase, def: ValueTyDefId) -> Binders { match def { ValueTyDefId::FunctionId(it) => type_for_fn(db, it), ValueTyDefId::StructId(it) => type_for_struct_constructor(db, it), ValueTyDefId::UnionId(it) => type_for_adt(db, it.into()), ValueTyDefId::EnumVariantId(it) => type_for_enum_variant_constructor(db, it), ValueTyDefId::ConstId(it) => type_for_const(db, it), ValueTyDefId::StaticId(it) => type_for_static(db, it), } } pub(crate) fn impl_self_ty_query(db: &dyn HirDatabase, impl_id: ImplId) -> Binders { let impl_data = db.impl_data(impl_id); let resolver = impl_id.resolver(db.upcast()); let generics = generics(db.upcast(), impl_id.into()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); make_binders(&generics, ctx.lower_ty(&impl_data.self_ty)) } pub(crate) fn const_param_ty_query(db: &dyn HirDatabase, def: ConstParamId) -> Ty { let parent_data = db.generic_params(def.parent); let data = &parent_data.consts[def.local_id]; let resolver = def.parent.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver); ctx.lower_ty(&data.ty) } pub(crate) fn impl_self_ty_recover( db: &dyn HirDatabase, _cycle: &[String], impl_id: &ImplId, ) -> Binders { let generics = generics(db.upcast(), (*impl_id).into()); make_binders(&generics, TyKind::Error.intern(&Interner)) } pub(crate) fn impl_trait_query(db: &dyn HirDatabase, impl_id: ImplId) -> Option> { let impl_data = db.impl_data(impl_id); let resolver = impl_id.resolver(db.upcast()); let ctx = TyLoweringContext::new(db, &resolver).with_type_param_mode(TypeParamLoweringMode::Variable); let (self_ty, binders) = db.impl_self_ty(impl_id).into_value_and_skipped_binders(); let target_trait = impl_data.target_trait.as_ref()?; Some(Binders::new(binders, ctx.lower_trait_ref(target_trait, Some(self_ty))?)) } pub(crate) fn return_type_impl_traits( db: &dyn HirDatabase, def: hir_def::FunctionId, ) -> Option>> { // FIXME unify with fn_sig_for_fn instead of doing lowering twice, maybe let data = db.function_data(def); let resolver = def.resolver(db.upcast()); let ctx_ret = TyLoweringContext::new(db, &resolver) .with_impl_trait_mode(ImplTraitLoweringMode::Opaque) .with_type_param_mode(TypeParamLoweringMode::Variable); let _ret = (&ctx_ret).lower_ty(&data.ret_type); let generics = generics(db.upcast(), def.into()); let return_type_impl_traits = ReturnTypeImplTraits { impl_traits: ctx_ret.opaque_type_data.into_inner() }; if return_type_impl_traits.impl_traits.is_empty() { None } else { Some(Arc::new(make_binders(&generics, return_type_impl_traits))) } } pub(crate) fn lower_to_chalk_mutability(m: hir_def::type_ref::Mutability) -> Mutability { match m { hir_def::type_ref::Mutability::Shared => Mutability::Not, hir_def::type_ref::Mutability::Mut => Mutability::Mut, } } fn make_binders>(generics: &Generics, value: T) -> Binders { crate::make_only_type_binders(generics.len(), value) }