Assert that various types have the right amount of generic args and fix the sites that used the wrong amount

compiler/rustc_infer/src/traits/engine.rs

@@ -27,7 +27,7 @@ pub trait TraitEngine<'tcx>: 'tcx {
         def_id: DefId,
         cause: ObligationCause<'tcx>,
     ) {
-        let trait_ref = ty::TraitRef { def_id, substs: infcx.tcx.mk_substs_trait(ty, &[]) };
+        let trait_ref = infcx.tcx.mk_trait_ref(def_id, ty, &[]);
         self.register_predicate_obligation(
             infcx,
             Obligation {