Optimize impl_trait_ref usage in sanitizer

Author: camsteffen

compiler/rustc_sanitizers/src/cfi/typeid/itanium_cxx_abi/transform.rs

@@ -10,8 +10,9 @@ use rustc_hir as hir;
 use rustc_hir::LangItem;
 use rustc_middle::bug;
 use rustc_middle::ty::{
-    self, ExistentialPredicateStableCmpExt as _, Instance, InstanceKind, IntTy, List, TraitRef, Ty,
-    TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt, UintTy,
+    self, AssocContainer, ExistentialPredicateStableCmpExt as _, Instance, InstanceKind, IntTy,
+    List, TraitRef, Ty, TyCtxt, TypeFoldable, TypeFolder, TypeSuperFoldable, TypeVisitableExt,
+    UintTy,
 };
 use rustc_span::def_id::DefId;
 use rustc_span::{DUMMY_SP, sym};
@@ -466,20 +467,20 @@ fn implemented_method<'tcx>(
     let method_id;
     let trait_id;
     let trait_method;
-    let ancestor = if let Some(impl_id) = tcx.impl_of_assoc(instance.def_id()) {
-        // Implementation in an `impl` block
-        trait_ref = tcx.impl_trait_ref(impl_id)?;
-        method_id = tcx.trait_item_of(instance.def_id())?;
+    let assoc = tcx.opt_associated_item(instance.def_id())?;
+    let ancestor = if let AssocContainer::TraitImpl(Ok(trait_method_id)) = assoc.container {
+        let impl_id = tcx.parent(instance.def_id());
+        trait_ref = tcx.impl_trait_ref(impl_id).unwrap();
+        method_id = trait_method_id;
         trait_method = tcx.associated_item(method_id);
         trait_id = trait_ref.skip_binder().def_id;
         impl_id
-    } else if let InstanceKind::Item(def_id) = instance.def
-        && let Some(trait_method_bound) = tcx.opt_associated_item(def_id)
+    } else if let AssocContainer::Trait = assoc.container
+        && let InstanceKind::Item(def_id) = instance.def
     {
-        // Provided method in a `trait` block
-        trait_method = trait_method_bound;
-        method_id = instance.def_id();
-        trait_id = tcx.trait_of_assoc(method_id)?;
+        trait_method = assoc;
+        method_id = def_id;
+        trait_id = tcx.parent(method_id);
         trait_ref = ty::EarlyBinder::bind(TraitRef::from_assoc(tcx, trait_id, instance.args));
         trait_id
     } else {