Replace two uses of old_defining_use_anchor with error

They were already `Error` at all use sites

Author: oli-obk

compiler/rustc_hir_analysis/src/check/compare_impl_item.rs

@@ -238,8 +238,6 @@ fn compare_method_predicate_entailment<'tcx>(
     // type.
 
     // Compute placeholder form of impl and trait method tys.
-    let tcx = infcx.tcx;
-
     let mut wf_tys = FxIndexSet::default();
 
     let unnormalized_impl_sig = infcx.instantiate_binder_with_fresh_vars(

compiler/rustc_trait_selection/src/traits/coherence.rs

@@ -376,7 +376,7 @@ fn resolve_negative_obligation<'tcx>(
     };
 
     let param_env = o.param_env;
-    if !super::fully_solve_obligation(&infcx, o, infcx.old_defining_use_anchor).is_empty() {
+    if !super::fully_solve_obligation(&infcx, o, DefiningAnchor::Error).is_empty() {
         return false;
     }
 

compiler/rustc_trait_selection/src/traits/outlives_bounds.rs

@@ -83,7 +83,7 @@ impl<'a, 'tcx: 'a> InferCtxtExt<'a, 'tcx> for InferCtxt<'tcx> {
                         param_env,
                     )
                 }),
-                self.old_defining_use_anchor,
+                rustc_infer::infer::DefiningAnchor::Error,
             );
             if !constraints.member_constraints.is_empty() {
                 span_bug!(span, "{:#?}", constraints.member_constraints);