What do people think space safety requires for structures? For example, structure S = struct val l = List.tabulate (1000000, fn i => i) val x = 13 end val f = fn _ => .... S.x ... Is it OK for f to keep S.l alive? Of course, MLton won't do this right now, since we will evaluate away the structure S at compile time. But I could imagine other implementations keeping S.l alive.