Move RPITIT stuff to a new module

Author: ChayimFriedman2

crates/hir-ty/src/chalk_db.rs

@@ -5,45 +5,40 @@ use std::{iter, ops::ControlFlow, sync::Arc};
 
 use hir_expand::name::Name;
 use intern::sym;
-use rustc_hash::FxHashMap;
 use span::Edition;
 use tracing::debug;
 
 use chalk_ir::{
     Binders, CanonicalVarKinds,
     cast::{Cast, Caster},
-    fold::{TypeFoldable, TypeFolder, TypeSuperFoldable, shift::Shift},
+    fold::shift::Shift,
 };
 use chalk_solve::rust_ir::{self, AssociatedTyDatumBound, OpaqueTyDatumBound, WellKnownTrait};
 
 use base_db::Crate;
 use hir_def::{
-    AssocItemId, BlockId, CallableDefId, FunctionId, GenericDefId, HasModule, ItemContainerId,
-    Lookup, TypeAliasId, VariantId,
+    AssocItemId, BlockId, CallableDefId, GenericDefId, HasModule, ItemContainerId, Lookup,
+    TypeAliasId, VariantId,
     data::{TraitFlags, adt::StructFlags},
-    generics::{GenericParams, TypeOrConstParamData},
     hir::Movability,
     lang_item::{LangItem, LangItemTarget},
 };
 
 use crate::{
-    AliasEq, AliasTy, BoundVar, Const, ConstData, ConstValue, DebruijnIndex, DomainGoal, FnDefId,
-    Goal, GoalData, InferenceTable, Interner, Lifetime, LifetimeData, PlaceholderIndex,
-    ProjectionTy, ProjectionTyExt, QuantifiedWhereClause, Substitution, TraitRef, TraitRefExt, Ty,
-    TyBuilder, TyExt, TyKind, VariableKinds, WhereClause,
-    db::{
-        HirDatabase, InternedCoroutine, RpititImplAssocTy, RpititImplAssocTyId,
-        RpititTraitAssocTyId,
-    },
-    from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id, from_placeholder_idx,
+    AliasEq, AliasTy, BoundVar, DebruijnIndex, FnDefId, Interner, ProjectionTy, ProjectionTyExt,
+    QuantifiedWhereClause, Substitution, TraitRef, TraitRefExt, Ty, TyBuilder, TyExt, TyKind,
+    VariableKinds, WhereClause,
+    db::{HirDatabase, InternedCoroutine},
+    from_assoc_type_id, from_chalk_trait_id, from_foreign_def_id,
     generics::generics,
     lower::trait_fn_signature,
-    lt_from_placeholder_idx, make_binders, make_single_type_binders,
+    make_binders, make_single_type_binders,
     mapping::{
         AnyImplAssocType, AnyTraitAssocType, ToChalk, from_assoc_type_value_id, from_chalk,
         to_assoc_type_id_rpitit, to_assoc_type_value_id, to_assoc_type_value_id_rpitit,
     },
     method_resolution::{ALL_FLOAT_FPS, ALL_INT_FPS, TraitImpls, TyFingerprint},
+    rpitit::{RpititImplAssocTy, RpititImplAssocTyId, impl_method_rpitit_values},
     to_assoc_type_id, to_chalk_trait_id,
     traits::ChalkContext,
     utils::ClosureSubst,
@@ -952,265 +947,6 @@ fn impl_def_datum(db: &dyn HirDatabase, krate: Crate, impl_id: hir_def::ImplId)
     Arc::new(impl_datum)
 }
 
-// We return a list and not a hasmap because the number of RPITITs in a function should be small.
-#[salsa::tracked(return_ref)]
-fn impl_method_rpitit_values(
-    db: &dyn HirDatabase,
-    impl_id: hir_def::ImplId,
-    trait_method_id: FunctionId,
-) -> Box<[Arc<AssociatedTyValue>]> {
-    let impl_items = db.impl_items(impl_id);
-    let trait_method_generics = generics(db.upcast(), trait_method_id.into());
-    let impl_datum =
-        db.impl_datum(impl_id.loc(db).container.krate(), hir_def::ImplId::to_chalk(impl_id, db));
-    let trait_method = db.function_data(trait_method_id);
-    let Some(impl_method) = impl_items.items.iter().find_map(|(name, id)| {
-        if *name == trait_method.name {
-            match *id {
-                AssocItemId::FunctionId(it) => Some(it),
-                _ => None,
-            }
-        } else {
-            None
-        }
-    }) else {
-        // FIXME: Handle defaulted methods.
-        return Box::default();
-    };
-
-    let impl_method_generics = generics(db.upcast(), impl_method.into());
-
-    // First, just so we won't ICE, check that the impl method generics match the trait method generics.
-    if !check_method_generics_are_structurally_compatible(
-        trait_method_generics.self_params(),
-        impl_method_generics.self_params(),
-    ) {
-        return Box::default();
-    }
-
-    // The inference algorithm works as follows: in the trait method, we replace each RPITIT with an infer var,
-    // then we equate the return type of the trait method with the return type of the impl method. The values
-    // of the inference vars now represent the value of the RPITIT assoc types.
-    let mut table = InferenceTable::new(db, db.trait_environment(impl_method.into()));
-    let impl_method_placeholder_subst = impl_method_generics.placeholder_subst(db);
-
-    let impl_method_ret = db
-        .callable_item_signature(impl_method.into())
-        .substitute(Interner, &impl_method_placeholder_subst)
-        .ret()
-        .clone();
-    let impl_method_ret = table.normalize_associated_types_in(impl_method_ret);
-
-    // Create mapping from trait to impl (i.e. impl trait header + impl method identity args).
-    let trait_ref_placeholder_subst =
-        &impl_method_placeholder_subst.as_slice(Interner)[impl_method_generics.len_self()..];
-    // We want to substitute the TraitRef with placeholders, but placeholders from the method, not the impl.
-    let impl_trait_ref = impl_datum
-        .binders
-        .as_ref()
-        .map(|it| it.trait_ref.clone())
-        .substitute(Interner, trait_ref_placeholder_subst);
-    let trait_to_impl_args = Substitution::from_iter(
-        Interner,
-        impl_method_placeholder_subst.as_slice(Interner)[..impl_method_generics.len_self()]
-            .iter()
-            .chain(impl_trait_ref.substitution.as_slice(Interner)),
-    );
-    let trait_method_ret = db
-        .callable_item_signature(trait_method_id.into())
-        .substitute(Interner, &trait_to_impl_args)
-        .ret()
-        .clone();
-    let mut rpitit_to_infer_var_folder = RpititToInferVarFolder {
-        db,
-        table: &mut table,
-        trait_method_id,
-        trait_rpitit_to_infer_var: FxHashMap::default(),
-    };
-    let trait_method_ret =
-        trait_method_ret.fold_with(&mut rpitit_to_infer_var_folder, DebruijnIndex::INNERMOST);
-    let trait_rpitit_to_infer_var = rpitit_to_infer_var_folder.trait_rpitit_to_infer_var;
-    let trait_method_ret = table.normalize_associated_types_in(trait_method_ret);
-
-    table.resolve_obligations_as_possible();
-    // Even if unification fails, we want to continue. We will fill the RPITITs with error types.
-    table.unify(&trait_method_ret, &impl_method_ret);
-    table.resolve_obligations_as_possible();
-
-    return trait_rpitit_to_infer_var
-        .into_iter()
-        .map(|(trait_assoc_id, infer_var)| {
-            let impl_rpitit = table.resolve_completely(infer_var);
-            let impl_rpitit = impl_rpitit.fold_with(
-                &mut PlaceholderToBoundVarFolder {
-                    db,
-                    method: impl_method.into(),
-                    method_generics: impl_method_generics.self_params(),
-                },
-                DebruijnIndex::INNERMOST,
-            );
-            let trait_assoc = trait_assoc_id.loc(db);
-            // Completely unlike the docs, Chalk requires both the impl generics and the associated type
-            // generics in the binder.
-            let impl_rpitit_binders = VariableKinds::from_iter(
-                Interner,
-                trait_assoc.bounds.binders.as_slice(Interner)[..trait_method_generics.len()]
-                    .iter()
-                    .cloned()
-                    .chain(variable_kinds_from_generics(db, impl_method_generics.iter_parent_id())),
-            );
-            let impl_rpitit = Binders::new(
-                impl_rpitit_binders,
-                rust_ir::AssociatedTyValueBound { ty: impl_rpitit },
-            );
-            Arc::new(AssociatedTyValue {
-                associated_ty_id: to_assoc_type_id_rpitit(trait_assoc_id),
-                impl_id: hir_def::ImplId::to_chalk(impl_id, db),
-                value: impl_rpitit,
-            })
-        })
-        .collect();
-
-    #[derive(chalk_derive::FallibleTypeFolder)]
-    #[has_interner(Interner)]
-    struct RpititToInferVarFolder<'a, 'b> {
-        db: &'a dyn HirDatabase,
-        table: &'a mut InferenceTable<'b>,
-        trait_rpitit_to_infer_var: FxHashMap<RpititTraitAssocTyId, Ty>,
-        trait_method_id: FunctionId,
-    }
-    impl TypeFolder<Interner> for RpititToInferVarFolder<'_, '_> {
-        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner> {
-            self
-        }
-
-        fn interner(&self) -> Interner {
-            Interner
-        }
-
-        fn fold_ty(&mut self, ty: Ty, outer_binder: DebruijnIndex) -> Ty {
-            let result = match ty.kind(Interner) {
-                TyKind::Alias(AliasTy::Projection(ProjectionTy {
-                    associated_ty_id,
-                    substitution,
-                }))
-                | TyKind::AssociatedType(associated_ty_id, substitution) => {
-                    if let AnyTraitAssocType::Rpitit(assoc_id) =
-                        from_assoc_type_id(self.db, *associated_ty_id)
-                    {
-                        let assoc = assoc_id.loc(self.db);
-                        if assoc.synthesized_from_method == self.trait_method_id {
-                            if let Some(ty) = self.trait_rpitit_to_infer_var.get(&assoc_id) {
-                                return ty.clone();
-                            }
-
-                            // Replace with new infer var.
-                            // This needs to come before we fold the bounds, because they also contain this associated type.
-                            let var = self.table.new_type_var();
-                            self.trait_rpitit_to_infer_var.insert(assoc_id, var.clone());
-
-                            // Recurse into bounds, so that nested RPITITs will be handled correctly.
-                            for bound in assoc.bounds.clone().substitute(Interner, substitution) {
-                                let bound = inline_bound_to_generic_predicate(&bound, var.clone());
-                                let bound = bound.fold_with(self, outer_binder);
-                                let bound = self.table.normalize_associated_types_in(bound);
-                                self.table.register_obligation(Goal::new(
-                                    Interner,
-                                    GoalData::Quantified(
-                                        chalk_ir::QuantifierKind::ForAll,
-                                        bound.map(|bound| {
-                                            Goal::new(
-                                                Interner,
-                                                GoalData::DomainGoal(DomainGoal::Holds(bound)),
-                                            )
-                                        }),
-                                    ),
-                                ));
-                            }
-
-                            return var;
-                        }
-                    }
-                    ty.clone()
-                }
-                _ => ty.clone(),
-            };
-            result.super_fold_with(self, outer_binder)
-        }
-    }
-
-    #[derive(chalk_derive::FallibleTypeFolder)]
-    #[has_interner(Interner)]
-    struct PlaceholderToBoundVarFolder<'a> {
-        db: &'a dyn HirDatabase,
-        method: GenericDefId,
-        method_generics: &'a GenericParams,
-    }
-    impl TypeFolder<Interner> for PlaceholderToBoundVarFolder<'_> {
-        fn as_dyn(&mut self) -> &mut dyn TypeFolder<Interner> {
-            self
-        }
-
-        fn interner(&self) -> Interner {
-            Interner
-        }
-
-        fn fold_free_placeholder_ty(
-            &mut self,
-            universe: PlaceholderIndex,
-            _outer_binder: DebruijnIndex,
-        ) -> Ty {
-            let placeholder = from_placeholder_idx(self.db, universe);
-            if placeholder.parent == self.method {
-                BoundVar::new(
-                    DebruijnIndex::INNERMOST,
-                    placeholder.local_id.into_raw().into_u32() as usize
-                        + self.method_generics.len_lifetimes(),
-                )
-                .to_ty(Interner)
-            } else {
-                TyKind::Placeholder(universe).intern(Interner)
-            }
-        }
-
-        fn fold_free_placeholder_const(
-            &mut self,
-            ty: Ty,
-            universe: PlaceholderIndex,
-            _outer_binder: DebruijnIndex,
-        ) -> Const {
-            let placeholder = from_placeholder_idx(self.db, universe);
-            if placeholder.parent == self.method {
-                BoundVar::new(
-                    DebruijnIndex::INNERMOST,
-                    placeholder.local_id.into_raw().into_u32() as usize
-                        + self.method_generics.len_lifetimes(),
-                )
-                .to_const(Interner, ty)
-            } else {
-                Const::new(Interner, ConstData { ty, value: ConstValue::Placeholder(universe) })
-            }
-        }
-
-        fn fold_free_placeholder_lifetime(
-            &mut self,
-            universe: PlaceholderIndex,
-            _outer_binder: DebruijnIndex,
-        ) -> Lifetime {
-            let placeholder = lt_from_placeholder_idx(self.db, universe);
-            if placeholder.parent == self.method {
-                BoundVar::new(
-                    DebruijnIndex::INNERMOST,
-                    placeholder.local_id.into_raw().into_u32() as usize,
-                )
-                .to_lifetime(Interner)
-            } else {
-                Lifetime::new(Interner, LifetimeData::Placeholder(universe))
-            }
-        }
-    }
-}
-
 pub(crate) fn inline_bound_to_generic_predicate(
     bound: &Binders<rust_ir::InlineBound<Interner>>,
     self_ty: Ty,
@@ -1250,29 +986,6 @@ pub(crate) fn inline_bound_to_generic_predicate(
     }
 }
 
-fn check_method_generics_are_structurally_compatible(
-    trait_method_generics: &GenericParams,
-    impl_method_generics: &GenericParams,
-) -> bool {
-    if trait_method_generics.len_type_or_consts() != impl_method_generics.len_type_or_consts() {
-        return false;
-    }
-
-    for ((_, trait_arg), (_, impl_arg)) in iter::zip(
-        trait_method_generics.iter_type_or_consts(),
-        impl_method_generics.iter_type_or_consts(),
-    ) {
-        match (trait_arg, impl_arg) {
-            (TypeOrConstParamData::TypeParamData(_), TypeOrConstParamData::TypeParamData(_))
-            | (TypeOrConstParamData::ConstParamData(_), TypeOrConstParamData::ConstParamData(_)) => {
-            }
-            _ => return false,
-        }
-    }
-
-    true
-}
-
 pub(crate) fn associated_ty_value_query(
     db: &dyn HirDatabase,
     krate: Crate,

crates/hir-ty/src/db.rs

@@ -3,7 +3,7 @@
 
 use std::sync;
 
-use base_db::{Crate, Upcast, impl_intern_key, impl_intern_key_ref};
+use base_db::{Crate, Upcast, impl_intern_key};
 use hir_def::{
     AdtId, BlockId, CallableDefId, ConstParamId, DefWithBodyId, EnumVariantId, FunctionId,
     GeneralConstId, GenericDefId, ImplId, LifetimeParamId, LocalFieldId, StaticId, TraitId,
@@ -337,30 +337,3 @@ impl_intern_key!(InternedCoroutineId, InternedCoroutine);
 // This exists just for Chalk, because Chalk just has a single `FnDefId` where
 // we have different IDs for struct and enum variant constructors.
 impl_intern_key!(InternedCallableDefId, CallableDefId);
-
-/// An associated type synthesized from a Return Position Impl Trait In Trait
-/// of the trait (not the impls).
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct RpititTraitAssocTy {
-    pub trait_id: TraitId,
-    /// The method that contains this RPITIT.
-    pub synthesized_from_method: FunctionId,
-    /// The bounds of this associated type (coming from the `impl Bounds`).
-    ///
-    /// The generics are the generics of the method (with some modifications that we
-    /// don't currently implement, see https://rustc-dev-guide.rust-lang.org/return-position-impl-trait-in-trait.html).
-    pub bounds: Binders<Vec<chalk_solve::rust_ir::QuantifiedInlineBound<Interner>>>,
-}
-
-impl_intern_key_ref!(RpititTraitAssocTyId, RpititTraitAssocTy);
-
-/// An associated type synthesized from a Return Position Impl Trait In Trait
-/// of the impl (not the trait).
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct RpititImplAssocTy {
-    pub impl_id: ImplId,
-    /// The definition of this associated type in the trait.
-    pub trait_assoc: RpititTraitAssocTyId,
-}
-
-impl_intern_key_ref!(RpititImplAssocTyId, RpititImplAssocTy);

crates/hir-ty/src/lib.rs

@@ -30,6 +30,7 @@ mod inhabitedness;
 mod interner;
 mod lower;
 mod mapping;
+mod rpitit;
 mod target_feature;
 mod tls;
 mod utils;