yeet upcast_trait_def_id from ImplSourceObjectData

compiler/rustc_middle/src/traits/mod.rs

@@ -703,7 +703,6 @@ impl<'tcx, N> ImplSource<'tcx, N> {
             ImplSource::Param(n, ct) => ImplSource::Param(n.into_iter().map(f).collect(), ct),
             ImplSource::Builtin(n) => ImplSource::Builtin(n.into_iter().map(f).collect()),
             ImplSource::Object(o) => ImplSource::Object(ImplSourceObjectData {
-                upcast_trait_def_id: o.upcast_trait_def_id,
                 vtable_base: o.vtable_base,
                 nested: o.nested.into_iter().map(f).collect(),
             }),
@@ -750,9 +749,6 @@ pub struct ImplSourceTraitUpcastingData<N> {
 #[derive(PartialEq, Eq, Clone, TyEncodable, TyDecodable, HashStable, Lift)]
 #[derive(TypeFoldable, TypeVisitable)]
 pub struct ImplSourceObjectData<N> {
-    /// `Foo` upcast to the obligation trait. This will be some supertrait of `Foo`.
-    pub upcast_trait_def_id: DefId,
-
     /// The vtable is formed by concatenating together the method lists of
     /// the base object trait and all supertraits, pointers to supertrait vtable will
     /// be provided when necessary; this is the start of `upcast_trait_ref`'s methods

compiler/rustc_middle/src/traits/structural_impls.rs

@@ -46,8 +46,8 @@ impl<N: fmt::Debug> fmt::Debug for traits::ImplSourceObjectData<N> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(
             f,
-            "ImplSourceObjectData(upcast={:?}, vtable_base={}, nested={:?})",
-            self.upcast_trait_def_id, self.vtable_base, self.nested
+            "ImplSourceObjectData(vtable_base={}, nested={:?})",
+            self.vtable_base, self.nested
         )
     }
 }

compiler/rustc_trait_selection/src/traits/select/confirmation.rs

@@ -651,11 +651,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
             (unnormalized_upcast_trait_ref, ty::Binder::dummy(object_trait_ref)),
         );
 
-        Ok(ImplSourceObjectData {
-            upcast_trait_def_id: upcast_trait_ref.def_id(),
-            vtable_base,
-            nested,
-        })
+        Ok(ImplSourceObjectData { vtable_base, nested })
     }
 
     fn confirm_fn_pointer_candidate(

compiler/rustc_trait_selection/src/traits/util.rs

@@ -248,7 +248,7 @@ pub fn get_vtable_index_of_object_method<'tcx, N>(
 ) -> Option<usize> {
     // Count number of methods preceding the one we are selecting and
     // add them to the total offset.
-    tcx.own_existential_vtable_entries(object.upcast_trait_def_id)
+    tcx.own_existential_vtable_entries(tcx.parent(method_def_id))
         .iter()
         .copied()
         .position(|def_id| def_id == method_def_id)