From dee5e63f6253d3a8134e0926ff7b32fbf740822e Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Thu, 23 Nov 2017 02:37:23 +0100
Subject: [PATCH] fixes #4686

---
 compiler/semtypes.nim | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index 52d992a667..35abbc21de 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -1360,7 +1360,7 @@ proc semTypeNode(c: PContext, n: PNode, prev: PType): PType =
         case n.len
         of 3:
           result = semTypeNode(c, n.sons[1], prev)
-          if result.skipTypes({tyGenericInst, tyAlias}).kind in NilableTypes+GenericTypes and
+          if result.skipTypes({tyGenericInst, tyAlias}).kind in NilableTypes+GenericTypes+{tyForward} and
               n.sons[2].kind == nkNilLit:
             result = freshType(result, prev)
             result.flags.incl(tfNotNil)