fixes more regressions

tests/iter/tkeep_state_between_yield.nim

@@ -0,0 +1,36 @@
+discard """
+  output: '''@[1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 18, 20, 21, 24, 27, 30, 36, 40, 42]
+1002'''
+"""
+
+import strutils
+
+proc slice[T](iter: iterator(): T {.closure.}, sl: auto): seq[T] =
+  var res: seq[int64] = @[]
+  var i = 0
+  for n in iter():
+    if i > sl.b:
+      break
+    if i >= sl.a:
+      res.add(n)
+    inc i
+  res
+
+iterator harshad(): int64 {.closure.} =
+  for n in 1 .. < int64.high:
+    var sum = 0
+    for ch in string($n):
+      sum += parseInt("" & ch)
+    if n mod sum == 0:
+      yield n
+
+echo harshad.slice 0 .. <20
+
+for n in harshad():
+  if n > 1000:
+    echo n
+    break
+
+
+# bug #3499 last snippet fixed
+# bug 705  last snippet fixed