Merge pull request scala/scala#10937 from lrytz/t13062

Reduce memory footprint of evaluated values in LazyList

Author: lrytz

library/src/scala/collection/IterableOnce.scala

@@ -1372,7 +1372,7 @@ trait IterableOnceOps[+A, +CC[_], +C] extends Any { this: IterableOnce[A] =>
     if (it.hasNext) {
       jsb.append(it.next())
       while (it.hasNext) {
-        jsb.append(sep)
+        if (sep.length != 0) jsb.append(sep)
         jsb.append(it.next())
       }
     }