async works again

tests/iter/tclosureiters.nim

@@ -0,0 +1,73 @@
+discard """
+  output: '''0
+1
+2
+3
+4
+5
+6
+7
+8
+9
+10
+5 5
+7 7
+9 9
+0
+0
+0
+0
+1
+2'''
+"""
+
+when true:
+  proc main() =
+    let
+      lo=0
+      hi=10
+
+    iterator itA(): int =
+      for x in lo..hi:
+        yield x
+
+    for x in itA():
+      echo x
+
+    var y: int
+
+    iterator itB(): int =
+      while y <= hi:
+        yield y
+        inc y
+
+    y = 5
+    for x in itB():
+      echo x, " ", y
+      inc y
+
+  main()
+
+
+iterator infinite(): int {.closure.} =
+  var i = 0
+  while true:
+    yield i
+    inc i
+
+iterator take[T](it: iterator (): T, numToTake: int): T {.closure.} =
+  var i = 0
+  for x in it():
+    if i >= numToTake:
+      break
+    yield x
+    inc i
+
+# gives wrong reasult (3 times 0)
+for x in infinite.take(3):
+  echo x
+
+# does what we want
+let inf = infinite
+for x in inf.take(3):
+  echo x