fixes #1053, fixes #924

tests/objects/tinherentedvalues.nim

@@ -0,0 +1,55 @@
+discard """
+  output: '''tbObj of TC false
+false
+true
+5
+false'''
+"""
+
+# bug #1053
+type
+  TA = object of TObject
+    a: int
+
+  TB = object of TA
+    b: int
+
+  TC = object of TB
+    c: int
+
+proc test(p: TA) =
+  #echo "p of TB ", p of TB
+  if p of TB:
+    var tbObj = TB(p)
+
+    # tbObj is actually no longer compatible with TC:
+    echo "tbObj of TC ", tbObj of TC
+
+var v = TC()
+v.a = 1
+v.b = 2
+v.c = 3
+test(v)
+
+
+# bug #924
+type
+  MyObject = object of TObject
+    x: int
+
+var
+  asd: MyObject
+
+proc isMyObject(obj: TObject) =
+    echo obj of MyObject
+    if obj of MyObject:
+        let a = MyObject(obj)
+        echo a.x
+
+asd.x = 5
+
+var asdCopy = TObject(asd)
+echo asdCopy of MyObject
+
+isMyObject(asd)
+isMyObject(asdCopy)