From bfb085da9fa218a45a7bae9f68d731aa48b2ae77 Mon Sep 17 00:00:00 2001
From: Oli Scherer <rust@oli-obk.de>
Date: Fri, 24 Apr 2026 12:50:21 +0200
Subject: [PATCH] All generated associated types for opaque types in
 traits/impls have the same parent

---
 compiler/rustc_ty_utils/src/assoc.rs | 24 +++++++++++-------------
 1 file changed, 11 insertions(+), 13 deletions(-)

diff --git a/compiler/rustc_ty_utils/src/assoc.rs b/compiler/rustc_ty_utils/src/assoc.rs
index 1d24a207103c..443f33aaa0b0 100644
--- a/compiler/rustc_ty_utils/src/assoc.rs
+++ b/compiler/rustc_ty_utils/src/assoc.rs
@@ -1,8 +1,6 @@
 use rustc_hir::def::DefKind;
-use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId, LocalDefIdMap};
-use rustc_hir::definitions::{
-    DefPathData, PerParentDisambiguatorState, PerParentDisambiguatorsMap,
-};
+use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
+use rustc_hir::definitions::{DefPathData, PerParentDisambiguatorState};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_hir::{self as hir, ConstItemRhs, ImplItemImplKind, ItemKind};
 use rustc_middle::query::Providers;
@@ -131,7 +129,7 @@ struct RPITVisitor<'a, 'tcx> {
     tcx: TyCtxt<'tcx>,
     synthetics: Vec<LocalDefId>,
     data: DefPathData,
-    disambiguators: &'a mut LocalDefIdMap<PerParentDisambiguatorState>,
+    disambiguator: &'a mut PerParentDisambiguatorState,
 }
 
 impl<'tcx> Visitor<'tcx> for RPITVisitor<'_, 'tcx> {
@@ -140,7 +138,7 @@ fn visit_opaque_ty(&mut self, opaque: &'tcx hir::OpaqueTy<'tcx>) -> Self::Result
             self.tcx,
             opaque.def_id,
             self.data,
-            &mut self.disambiguators,
+            &mut self.disambiguator,
         ));
         intravisit::walk_opaque_ty(self, opaque)
     }
@@ -151,7 +149,7 @@ fn associated_types_for_impl_traits_in_trait_or_impl<'tcx>(
     def_id: LocalDefId,
 ) -> DefIdMap<Vec<DefId>> {
     let item = tcx.hir_expect_item(def_id);
-    let disambiguators = &mut Default::default();
+    let disambiguator = &mut PerParentDisambiguatorState::new(def_id);
     match item.kind {
         ItemKind::Trait(.., trait_item_refs) => trait_item_refs
             .iter()
@@ -165,7 +163,7 @@ fn associated_types_for_impl_traits_in_trait_or_impl<'tcx>(
                 };
                 let def_name = tcx.item_name(fn_def_id.to_def_id());
                 let data = DefPathData::AnonAssocTy(def_name);
-                let mut visitor = RPITVisitor { tcx, synthetics: vec![], data, disambiguators };
+                let mut visitor = RPITVisitor { tcx, synthetics: vec![], data, disambiguator };
                 visitor.visit_fn_ret_ty(output);
                 let defs = visitor
                     .synthetics
@@ -199,7 +197,7 @@ fn associated_types_for_impl_traits_in_trait_or_impl<'tcx>(
                         return Some((did, vec![]));
                     };
                     let iter = in_trait_def[&trait_item_def_id].iter().map(|&id| {
-                        associated_type_for_impl_trait_in_impl(tcx, id, item, disambiguators)
+                        associated_type_for_impl_trait_in_impl(tcx, id, item, disambiguator)
                             .to_def_id()
                     });
                     Some((did, iter.collect()))
@@ -223,7 +221,7 @@ fn associated_type_for_impl_trait_in_trait(
     tcx: TyCtxt<'_>,
     opaque_ty_def_id: LocalDefId,
     data: DefPathData,
-    disambiguators: &mut LocalDefIdMap<PerParentDisambiguatorState>,
+    disambiguator: &mut PerParentDisambiguatorState,
 ) -> LocalDefId {
     let (hir::OpaqueTyOrigin::FnReturn { parent: fn_def_id, .. }
     | hir::OpaqueTyOrigin::AsyncFn { parent: fn_def_id, .. }) =
@@ -242,7 +240,7 @@ fn associated_type_for_impl_trait_in_trait(
         None,
         DefKind::AssocTy,
         Some(data),
-        disambiguators.get_or_create(trait_def_id),
+        disambiguator,
     );
 
     let local_def_id = trait_assoc_ty.def_id();
@@ -285,7 +283,7 @@ fn associated_type_for_impl_trait_in_impl(
     tcx: TyCtxt<'_>,
     trait_assoc_def_id: DefId,
     impl_fn: &hir::ImplItem<'_>,
-    disambiguators: &mut LocalDefIdMap<PerParentDisambiguatorState>,
+    disambiguator: &mut PerParentDisambiguatorState,
 ) -> LocalDefId {
     let impl_local_def_id = tcx.local_parent(impl_fn.owner_id.def_id);
 
@@ -308,7 +306,7 @@ fn associated_type_for_impl_trait_in_impl(
         None,
         DefKind::AssocTy,
         Some(data),
-        disambiguators.get_or_create(impl_local_def_id),
+        disambiguator,
     );
 
     let local_def_id = impl_assoc_ty.def_id();