Make impls UpcastFrom, implement Upcast for UpcastFrom

compiler/rustc_trait_selection/src/solve/assembly/mod.rs

@@ -286,7 +286,7 @@ impl<'tcx> EvalCtxt<'_, 'tcx> {
             return self.forced_ambiguity(MaybeCause::Ambiguity).into_iter().collect();
         }
 
-        let goal =
+        let goal: Goal<'tcx, G> =
             goal.with(self.tcx(), goal.predicate.with_self_ty(self.tcx(), normalized_self_ty));
         // Vars that show up in the rest of the goal substs may have been constrained by
         // normalizing the self type as well, since type variables are not uniquified.