fixes #668

tests/ccgbugs/tobjconstr_bad_aliasing.nim

@@ -0,0 +1,26 @@
+discard """
+  output: '''(10, (20, ))'''
+"""
+
+import strutils, sequtils
+
+# bug #668
+
+type
+  TThing = ref object
+    data: int
+    children: seq[TThing]
+
+proc `$`(t: TThing): string =
+  result = "($1, $2)" % @[$t.data, join(map(t.children, proc(th: TThing): string = $th), ", ")]
+
+proc somethingelse(): seq[TThing] =
+  result = @[TThing(data: 20, children: @[])]
+
+proc dosomething(): seq[TThing] =
+  result = somethingelse()
+
+  result = @[TThing(data: 10, children: result)]
+
+when isMainModule:
+  echo($dosomething()[0])