From b0684ec425dca5e76eb6b27eb09a84fb523af49c Mon Sep 17 00:00:00 2001
From: Araq <rumpf_a@web.de>
Date: Tue, 10 Mar 2020 09:42:23 +0100
Subject: [PATCH] fixes #12757

---
 compiler/semtypes.nim | 19 +++++++++++++------
 1 file changed, 13 insertions(+), 6 deletions(-)

diff --git a/compiler/semtypes.nim b/compiler/semtypes.nim
index abc5de7e8b..f05affc6b5 100644
--- a/compiler/semtypes.nim
+++ b/compiler/semtypes.nim
@@ -893,7 +893,7 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
       localError(c.config, n.info, "type '$1 void' is not allowed" % kindToStr[kind])
     result = newOrPrevType(kind, prev, c)
     var isNilable = false
-    var isOwned = false
+    var wrapperKind = tyNone
     # check every except the last is an object:
     for i in isCall..<n.len-1:
       let ni = n[i]
@@ -901,8 +901,8 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
         isNilable = true
       else:
         let region = semTypeNode(c, ni, nil)
-        if region.kind == tyOwned:
-          isOwned = true
+        if region.kind in {tyOwned, tySink}:
+          wrapperKind = region.kind
         elif region.skipTypes({tyGenericInst, tyAlias, tySink}).kind notin {
               tyError, tyObject}:
           message c.config, n[i].info, errGenerated, "region needs to be an object type"
@@ -914,11 +914,18 @@ proc semAnyRef(c: PContext; n: PNode; kind: TTypeKind; prev: PType): PType =
     if tfPartial in result.flags:
       if result.lastSon.kind == tyObject: incl(result.lastSon.flags, tfPartial)
     #if not isNilable: result.flags.incl tfNotNil
-    if isOwned and optOwnedRefs in c.config.globalOptions:
-      let t = newTypeS(tyOwned, c)
-      t.flags.incl tfHasOwned
+    case wrapperKind
+    of tyOwned:
+      if optOwnedRefs in c.config.globalOptions:
+        let t = newTypeS(tyOwned, c)
+        t.flags.incl tfHasOwned
+        t.rawAddSonNoPropagationOfTypeFlags result
+        result = t
+    of tySink:
+      let t = newTypeS(tySink, c)
       t.rawAddSonNoPropagationOfTypeFlags result
       result = t
+    else: discard
     #if result.kind == tyRef and c.config.selectedGC == gcDestructors:
     #  result.flags.incl tfHasAsgn
     # XXX Something like this is a good idea but it should be done