skip normalizing param env if it is already normalized

compiler/rustc_trait_selection/src/traits/mod.rs

@@ -409,6 +409,9 @@ pub fn normalize_param_env_or_error<'tcx>(
  debug!("normalize_param_env_or_error: elaborated-predicates={:?}", predicates);
 
  let elaborated_env = ty::ParamEnv::new(tcx.mk_clauses(&predicates), unnormalized_env.reveal());
+ if !normalize::needs_normalization(&elaborated_env, unnormalized_env.reveal()) {
+ return elaborated_env;
+ }
 
  // HACK: we are trying to normalize the param-env inside *itself*. The problem is that
  // normalization expects its param-env to be already normalized, which means we have