compute all rpitit of a trait

compiler/rustc_hir_analysis/src/check/wfcheck.rs

@@ -326,7 +326,9 @@ pub(crate) fn check_trait_item<'tcx>(
     let mut res = Ok(());
 
     if matches!(tcx.def_kind(def_id), DefKind::AssocFn) {
-        for &assoc_ty_def_id in tcx.associated_types_for_impl_traits_in_associated_fn(def_id) {
+        for &assoc_ty_def_id in
+            tcx.associated_types_for_impl_traits_in_associated_fn(def_id.to_def_id())
+        {
             res = res.and(check_associated_item(tcx, assoc_ty_def_id.expect_local()));
         }
     }

compiler/rustc_hir_analysis/src/hir_ty_lowering/mod.rs

@@ -2602,7 +2602,7 @@ impl<'tcx> dyn HirTyLowerer<'tcx> + '_ {
         // do a linear search to map this to the synthetic associated type that
         // it will be lowered to.
         let def_id = if let Some(parent_def_id) = in_trait {
-            *tcx.associated_types_for_impl_traits_in_associated_fn(parent_def_id)
+            *tcx.associated_types_for_impl_traits_in_associated_fn(parent_def_id.to_def_id())
                 .iter()
                 .find(|rpitit| match tcx.opt_rpitit_info(**rpitit) {
                     Some(ty::ImplTraitInTraitData::Trait { opaque_def_id, .. }) => {

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -326,7 +326,7 @@ provide! { tcx, def_id, other, cdata,
             .process_decoded(tcx, || panic!("{def_id:?} does not have trait_impl_trait_tys")))
     }
 
-    associated_types_for_impl_traits_in_associated_fn => { table_defaulted_array }
+    associated_types_for_impl_traits_in_trait_or_impl => { table }
 
     visibility => { cdata.get_visibility(def_id.index) }
     adt_def => { cdata.get_adt_def(def_id.index, tcx) }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1382,17 +1382,6 @@ fn should_encode_const(def_kind: DefKind) -> bool {
     }
 }
 
-fn should_encode_fn_impl_trait_in_trait<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> bool {
-    if let Some(assoc_item) = tcx.opt_associated_item(def_id)
-        && assoc_item.container == ty::AssocItemContainer::Trait
-        && assoc_item.is_fn()
-    {
-        true
-    } else {
-        false
-    }
-}
-
 impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
     fn encode_attrs(&mut self, def_id: LocalDefId) {
         let tcx = self.tcx;
@@ -1617,9 +1606,9 @@ impl<'a, 'tcx> EncodeContext<'a, 'tcx> {
             {
                 record!(self.tables.trait_impl_trait_tys[def_id] <- table);
             }
-            if should_encode_fn_impl_trait_in_trait(tcx, def_id) {
-                let table = tcx.associated_types_for_impl_traits_in_associated_fn(def_id);
-                record_defaulted_array!(self.tables.associated_types_for_impl_traits_in_associated_fn[def_id] <- table);
+            if let DefKind::Impl { .. } | DefKind::Trait = def_kind {
+                let table = tcx.associated_types_for_impl_traits_in_trait_or_impl(def_id);
+                record!(self.tables.associated_types_for_impl_traits_in_trait_or_impl[def_id] <- table);
             }
         }
 

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -403,7 +403,6 @@ define_tables! {
     explicit_implied_predicates_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     explicit_implied_const_bounds: Table<DefIndex, LazyArray<(ty::PolyTraitRef<'static>, Span)>>,
     inherent_impls: Table<DefIndex, LazyArray<DefIndex>>,
-    associated_types_for_impl_traits_in_associated_fn: Table<DefIndex, LazyArray<DefId>>,
     opt_rpitit_info: Table<DefIndex, Option<LazyValue<ty::ImplTraitInTraitData>>>,
     // Reexported names are not associated with individual `DefId`s,
     // e.g. a glob import can introduce a lot of names, all with the same `DefId`.
@@ -482,6 +481,7 @@ define_tables! {
     assumed_wf_types_for_rpitit: Table<DefIndex, LazyArray<(Ty<'static>, Span)>>,
     opaque_ty_origin: Table<DefIndex, LazyValue<hir::OpaqueTyOrigin<DefId>>>,
     anon_const_kind: Table<DefIndex, LazyValue<ty::AnonConstKind>>,
+    associated_types_for_impl_traits_in_trait_or_impl: Table<DefIndex, LazyValue<DefIdMap<Vec<DefId>>>>,
 }
 
 #[derive(TyEncodable, TyDecodable)]

compiler/rustc_middle/src/query/mod.rs

@@ -1079,15 +1079,11 @@ rustc_queries! {
         desc { |tcx| "comparing impl items against trait for `{}`", tcx.def_path_str(impl_id) }
     }
 
-    /// Given `fn_def_id` of a trait or of an impl that implements a given trait:
-    /// if `fn_def_id` is the def id of a function defined inside a trait, then it creates and returns
-    /// the associated items that correspond to each impl trait in return position for that trait.
-    /// if `fn_def_id` is the def id of a function defined inside an impl that implements a trait, then it
-    /// creates and returns the associated items that correspond to each impl trait in return position
-    /// of the implemented trait.
-    query associated_types_for_impl_traits_in_associated_fn(fn_def_id: DefId) -> &'tcx [DefId] {
-        desc { |tcx| "creating associated items for opaque types returned by `{}`", tcx.def_path_str(fn_def_id) }
-        cache_on_disk_if { fn_def_id.is_local() }
+    /// Given the `item_def_id` of a trait or impl, return a mapping from associated fn def id
+    /// to its associated type items that correspond to the RPITITs in its signature.
+    query associated_types_for_impl_traits_in_trait_or_impl(item_def_id: DefId) -> &'tcx DefIdMap<Vec<DefId>> {
+        arena_cache
+        desc { |tcx| "synthesizing RPITIT items for the opaque types for methods in `{}`", tcx.def_path_str(item_def_id) }
         separate_provide_extern
     }
 

compiler/rustc_middle/src/ty/assoc.rs

@@ -285,3 +285,22 @@ impl AssocItems {
             .find(|item| tcx.hygienic_eq(ident, item.ident(tcx), parent_def_id))
     }
 }
+
+impl<'tcx> TyCtxt<'tcx> {
+    /// Given an `fn_def_id` of a trait or a trait implementation:
+    ///
+    /// if `fn_def_id` is a function defined inside a trait, then it synthesizes
+    /// a new def id corresponding to a new associated type for each return-
+    /// position `impl Trait` in the signature.
+    ///
+    /// if `fn_def_id` is a function inside of an impl, then for each synthetic
+    /// associated type generated for the corresponding trait function described
+    /// above, synthesize a corresponding associated type in the impl.
+    pub fn associated_types_for_impl_traits_in_associated_fn(
+        self,
+        fn_def_id: DefId,
+    ) -> &'tcx [DefId] {
+        let parent_def_id = self.parent(fn_def_id);
+        &self.associated_types_for_impl_traits_in_trait_or_impl(parent_def_id)[&fn_def_id]
+    }
+}

compiler/rustc_middle/src/ty/parameterized.rs

@@ -23,6 +23,10 @@ impl<A: ParameterizedOverTcx, B: ParameterizedOverTcx> ParameterizedOverTcx for
     type Value<'tcx> = (A::Value<'tcx>, B::Value<'tcx>);
 }
 
+impl<T: ParameterizedOverTcx> ParameterizedOverTcx for Vec<T> {
+    type Value<'tcx> = Vec<T::Value<'tcx>>;
+}
+
 impl<I: Idx + 'static, T: ParameterizedOverTcx> ParameterizedOverTcx for IndexVec<I, T> {
     type Value<'tcx> = IndexVec<I, T::Value<'tcx>>;
 }