bugfixes for closures

tests/run/tfilter.nim

@@ -0,0 +1,28 @@
+discard """
+  output: "02468101214161820"
+"""
+
+proc filter[T](list: seq[T], f: proc (item: T): bool {.closure.}): seq[T] =
+  result = @[]
+  for i in items(list):
+    if f(i):
+      result.add(i)
+
+let nums = @[0, 1, 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20]
+
+when true:
+  let nums2 = filter(nums,
+               (proc (item: int): bool =
+                 result = (item mod 2) == 0)
+               )
+
+proc outer =
+  # lets use a proper closure this time:
+  var modulo = 2
+  let nums2 = filter(nums,
+               (proc (item: int): bool = result = (item mod modulo) == 0)
+               )
+
+  for n in nums2: stdout.write(n)
+
+outer()