Update names/comments for new return-position impl trait in trait lowering strategy

compiler/rustc_hir_analysis/src/astconv/mod.rs

@@ -3068,7 +3068,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                         // generate the def_id of an associated type for the trait and return as
                         // type a projection.
                         let def_id = if in_trait && tcx.lower_impl_trait_in_trait_to_assoc_ty() {
-                            tcx.associated_item_for_impl_trait_in_trait(local_def_id).to_def_id()
+                            tcx.associated_type_for_impl_trait_in_trait(local_def_id).to_def_id()
                         } else {
                             local_def_id.to_def_id()
                         };

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

@@ -254,7 +254,7 @@ provide! { tcx, def_id, other, cdata,
             .process_decoded(tcx, || panic!("{def_id:?} does not have trait_impl_trait_tys")))
      }
 
-    associated_items_for_impl_trait_in_trait => { table_defaulted_array }
+    associated_types_for_impl_traits_in_associated_fn => { table_defaulted_array }
 
     visibility => { cdata.get_visibility(def_id.index) }
     adt_def => { cdata.get_adt_def(def_id.index, tcx) }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1198,8 +1198,8 @@ 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_items_for_impl_trait_in_trait(def_id);
-                record_defaulted_array!(self.tables.associated_items_for_impl_trait_in_trait[def_id] <- table);
+                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);
             }
         }
 

compiler/rustc_metadata/src/rmeta/mod.rs

@@ -354,7 +354,7 @@ define_tables! {
     explicit_item_bounds: Table<DefIndex, LazyArray<(ty::Predicate<'static>, Span)>>,
     inferred_outlives_of: Table<DefIndex, LazyArray<(ty::Clause<'static>, Span)>>,
     inherent_impls: Table<DefIndex, LazyArray<DefIndex>>,
-    associated_items_for_impl_trait_in_trait: Table<DefIndex, LazyArray<DefId>>,
+    associated_types_for_impl_traits_in_associated_fn: Table<DefIndex, LazyArray<DefId>>,
     opt_rpitit_info: Table<DefIndex, Option<LazyValue<ty::ImplTraitInTraitData>>>,
     unused_generic_params: Table<DefIndex, UnusedGenericParams>,
 

compiler/rustc_middle/src/query/mod.rs

@@ -785,15 +785,15 @@ rustc_queries! {
     /// 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_items_for_impl_trait_in_trait(fn_def_id: DefId) -> &'tcx [DefId] {
+    query associated_types_for_impl_traits_in_associated_fn(fn_def_id: DefId) -> &'tcx [DefId] {
         desc { |tcx| "creating associated items for impl trait in trait returned by `{}`", tcx.def_path_str(fn_def_id) }
         cache_on_disk_if { fn_def_id.is_local() }
         separate_provide_extern
     }
 
     /// Given an impl trait in trait `opaque_ty_def_id`, create and return the corresponding
     /// associated item.
-    query associated_item_for_impl_trait_in_trait(opaque_ty_def_id: LocalDefId) -> LocalDefId {
+    query associated_type_for_impl_trait_in_trait(opaque_ty_def_id: LocalDefId) -> LocalDefId {
         desc { |tcx| "creates the associated item corresponding to the opaque type `{}`", tcx.def_path_str(opaque_ty_def_id.to_def_id()) }
         cache_on_disk_if { true }
         separate_provide_extern

compiler/rustc_middle/src/ty/mod.rs

@@ -2579,7 +2579,9 @@ impl<'tcx> TyCtxt<'tcx> {
         let Some(trait_item_def_id) = item.trait_item_def_id else { return false; };
 
         if self.lower_impl_trait_in_trait_to_assoc_ty() {
-            return !self.associated_items_for_impl_trait_in_trait(trait_item_def_id).is_empty();
+            return !self
+                .associated_types_for_impl_traits_in_associated_fn(trait_item_def_id)
+                .is_empty();
         }
 
         // FIXME(RPITIT): This does a somewhat manual walk through the signature

compiler/rustc_ty_utils/src/assoc.rs

@@ -11,8 +11,8 @@ pub fn provide(providers: &mut ty::query::Providers) {
         associated_item,
         associated_item_def_ids,
         associated_items,
-        associated_items_for_impl_trait_in_trait,
-        associated_item_for_impl_trait_in_trait,
+        associated_types_for_impl_traits_in_associated_fn,
+        associated_type_for_impl_trait_in_trait,
         impl_item_implementor_ids,
         ..*providers
     };
@@ -24,7 +24,7 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
         hir::ItemKind::Trait(.., ref trait_item_refs) => {
             if tcx.lower_impl_trait_in_trait_to_assoc_ty() {
                 // We collect RPITITs for each trait method's return type and create a
-                // corresponding associated item using associated_items_for_impl_trait_in_trait
+                // corresponding associated item using associated_types_for_impl_traits_in_associated_fn
                 // query.
                 tcx.arena.alloc_from_iter(
                     trait_item_refs
@@ -39,7 +39,9 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
                                 .flat_map(|trait_item_ref| {
                                     let trait_fn_def_id =
                                         trait_item_ref.id.owner_id.def_id.to_def_id();
-                                    tcx.associated_items_for_impl_trait_in_trait(trait_fn_def_id)
+                                    tcx.associated_types_for_impl_traits_in_associated_fn(
+                                        trait_fn_def_id,
+                                    )
                                 })
                                 .map(|def_id| *def_id),
                         ),
@@ -56,7 +58,7 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
             if tcx.lower_impl_trait_in_trait_to_assoc_ty() {
                 // We collect RPITITs for each trait method's return type, on the impl side too and
                 // create a corresponding associated item using
-                // associated_items_for_impl_trait_in_trait query.
+                // associated_types_for_impl_traits_in_associated_fn query.
                 tcx.arena.alloc_from_iter(
                     impl_
                         .items
@@ -72,7 +74,9 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
                                 .flat_map(|impl_item_ref| {
                                     let impl_fn_def_id =
                                         impl_item_ref.id.owner_id.def_id.to_def_id();
-                                    tcx.associated_items_for_impl_trait_in_trait(impl_fn_def_id)
+                                    tcx.associated_types_for_impl_traits_in_associated_fn(
+                                        impl_fn_def_id,
+                                    )
                                 })
                                 .map(|def_id| *def_id)
                         })),
@@ -176,13 +180,19 @@ fn associated_item_from_impl_item_ref(impl_item_ref: &hir::ImplItemRef) -> ty::A
     }
 }
 
-/// Given an `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.
-fn associated_items_for_impl_trait_in_trait(tcx: TyCtxt<'_>, fn_def_id: DefId) -> &'_ [DefId] {
+/// 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.
+fn associated_types_for_impl_traits_in_associated_fn(
+    tcx: TyCtxt<'_>,
+    fn_def_id: DefId,
+) -> &'_ [DefId] {
     let parent_def_id = tcx.parent(fn_def_id);
 
     match tcx.def_kind(parent_def_id) {
@@ -206,7 +216,7 @@ fn associated_items_for_impl_trait_in_trait(tcx: TyCtxt<'_>, fn_def_id: DefId) -
                 visitor.visit_fn_ret_ty(output);
 
                 tcx.arena.alloc_from_iter(visitor.rpits.iter().map(|opaque_ty_def_id| {
-                    tcx.associated_item_for_impl_trait_in_trait(opaque_ty_def_id).to_def_id()
+                    tcx.associated_type_for_impl_trait_in_trait(opaque_ty_def_id).to_def_id()
                 }))
             } else {
                 &[]
@@ -217,9 +227,9 @@ fn associated_items_for_impl_trait_in_trait(tcx: TyCtxt<'_>, fn_def_id: DefId) -
             let Some(trait_fn_def_id) = tcx.associated_item(fn_def_id).trait_item_def_id else { return &[] };
 
             tcx.arena.alloc_from_iter(
-                tcx.associated_items_for_impl_trait_in_trait(trait_fn_def_id).iter().map(
+                tcx.associated_types_for_impl_traits_in_associated_fn(trait_fn_def_id).iter().map(
                     move |trait_assoc_def_id| {
-                        impl_associated_item_for_impl_trait_in_trait(
+                        associated_type_for_impl_trait_in_impl(
                             tcx,
                             trait_assoc_def_id.expect_local(),
                             fn_def_id.expect_local(),
@@ -231,16 +241,17 @@ fn associated_items_for_impl_trait_in_trait(tcx: TyCtxt<'_>, fn_def_id: DefId) -
         }
 
         def_kind => bug!(
-            "associated_items_for_impl_trait_in_trait: {:?} should be Trait or Impl but is {:?}",
+            "associated_types_for_impl_traits_in_associated_fn: {:?} should be Trait or Impl but is {:?}",
             parent_def_id,
             def_kind
         ),
     }
 }
 
-/// Given an `opaque_ty_def_id` corresponding to an impl trait in trait, create and return the
-/// corresponding associated item.
-fn associated_item_for_impl_trait_in_trait(
+/// Given an `opaque_ty_def_id` corresponding to an `impl Trait` in an associated
+/// function from a trait, synthesize an associated type for that `impl Trait`
+/// that inherits properties that we infer from the method and the opaque type.
+fn associated_type_for_impl_trait_in_trait(
     tcx: TyCtxt<'_>,
     opaque_ty_def_id: LocalDefId,
 ) -> LocalDefId {
@@ -335,10 +346,12 @@ fn associated_item_for_impl_trait_in_trait(
     local_def_id
 }
 
-/// Given an `trait_assoc_def_id` that corresponds to a previously synthesized impl trait in trait
-/// into an associated type and an `impl_def_id` corresponding to an impl block, create and return
-/// the corresponding associated item inside the impl block.
-fn impl_associated_item_for_impl_trait_in_trait(
+/// Given an `trait_assoc_def_id` corresponding to an associated item synthesized
+/// from an `impl Trait` in an associated function from a trait, and an
+/// `impl_fn_def_id` that represents an implementation of the associated function
+/// that the `impl Trait` comes from, synthesize an associated type for that `impl Trait`
+/// that inherits properties that we infer from the method and the associated type.
+fn associated_type_for_impl_trait_in_impl(
     tcx: TyCtxt<'_>,
     trait_assoc_def_id: LocalDefId,
     impl_fn_def_id: LocalDefId,