adding metadata to a lazy sequence - lisp

Question

When I try to add metadata to an infinite lazy sequence in Clojure, I get a stack overflow, and if I take off the metadata, then it works just fine. Why does adding the with-meta macro break the lazy seq?
First create an infinite seq of a very nice number:
(defn good []
(lazy-seq
(cons 42
(good))))
user> (take 5 (good))
(42 42 42 42 42)
Then, add some metadata to each of the lazy-seq instances:
(defn bad []
(lazy-seq
(cons 42
(with-meta
(bad)
{:padding 4}))))
user> (take 5 (bad))
java.lang.StackOverflowError (NO_SOURCE_FILE:0)
[Thrown class clojure.lang.Compiler$CompilerException]
Try moving the meta data up one level:
(defn also-bad []
(with-meta
(lazy-seq
(cons 42
(also-bad)))
{:padding 4}))
user> (take 5 (foo))
java.lang.StackOverflowError (NO_SOURCE_FILE:0)
[Thrown class clojure.lang.Compiler$CompilerException]
Here is an example of meta data on a finite sequence:
(defn also-works []
(lazy-seq
(cons 4
(with-meta
()
{:a 5}))))
user> (also-works)
(4)
user> (meta (rest (also-works)))
{:a 5}
user>

Answer 1

Because a LazySeq evaluates its body as soon as you call withMeta on the LazySeq. You lose your laziness.
public final class LazySeq extends Obj implements ISeq, List{
...
public Obj withMeta(IPersistentMap meta){
return new LazySeq(meta, seq());
}
...
}
seq() evaluates the lazy seq's body if it hasn't already been evaluated. Your code above keeps calling with-meta on successive lazy seqs, which evaluates them all until the stack explodes. I don't think there's currently any way to add metadata to a lazy seq without causing it to evaluate its body.