fix #966

test for ``map`` defined as inline iterator

tests/iter/titerable.nim

@@ -0,0 +1,26 @@
+discard """
+  output: '''2
+4
+6
+4
+8
+12
+'''
+"""
+
+iterator map[T, U](s: iterator:T{.inline.}, f: proc(x: T): U): U =
+  for e in s: yield f(e)
+
+template toSeq(s: expr): expr =
+  var res = newSeq[type(s)](0)
+  for e in s: res.add(e)
+  res
+
+var s1 = @[1, 2, 3]
+for x in map(s1.items, proc (a:int): int = a*2):
+  echo x
+
+var s2 = toSeq(map(s1.items, proc (a:int): int = a*4))
+for x in s2:
+  echo x
+