extendTvInScope :: TvSubst -> Var -> TvSubst
extendTvInScope (TvSubst in_scope tenv) var = TvSubst (extendInScopeSet in_scope var) tenv
extendTvInScope :: TvSubst -> Var -> TvSubst
extendTvInScope (TvSubst in_scope tenv) var = TvSubst (extendInScopeSet in_scope var) tenv
extendTvInScope (TvSubst in_scope tenv) var = TvSubst (extendInScopeSet in_scope var) tenv