zapTvSubstEnv :: TvSubst -> TvSubst
zapTvSubstEnv (TvSubst in_scope _) = TvSubst in_scope emptyVarEnv
zapTvSubstEnv :: TvSubst -> TvSubst
zapTvSubstEnv (TvSubst in_scope _) = TvSubst in_scope emptyVarEnv
zapTvSubstEnv (TvSubst in_scope _) = TvSubst in_scope emptyVarEnv