adds a test case (#24534)

closes #16845

(cherry picked from commit 80af252025)

tests/ccgbugs/tccgissues.nim

@@ -12,3 +12,46 @@ proc varargsToSeq(vals: varargs[int32]): seq[int32] =
     result.add v
 
 echo varargsToSeq(1, 2, 3, 4)
+
+type # bug #16845
+  MyObjectKind = enum
+    SomeKind
+
+block:
+  type
+    MyObject = ref object
+      case kind: MyObjectKind:
+        of SomeKind:
+          c: string
+
+  var obj = MyObject(kind:SomeKind)
+  obj.c = "some string"
+
+block:
+  type
+    MyObject = ref object
+      kind: MyObjectKind
+      c: string
+
+  var obj = MyObject(kind:SomeKind)
+  obj.c = "some string"
+
+block:
+  type
+    MyBaseObj[T] = object of RootObj
+      test: seq[T]
+    MyObj = object
+      attr: MyBaseObj[string]
+
+  var myObj: MyObj
+
+block:
+  type
+    MyBaseAttrObj[T] = object of RootObj
+      test: seq[T]
+    MyBaseObj[T] = object of RootObj
+      myBaseObj: MyBaseAttrObj[T]
+    MyObj = object
+      attr: MyBaseObj[string]
+
+  var myObj: MyObj