fixes #11350

tests/destructor/tdangingref_simple.nim

@@ -0,0 +1,32 @@
+discard """
+  output: '''a
+[FATAL] dangling references exist
+'''
+  exitCode: 1
+  cmd: "nim c --newruntime $file"
+"""
+
+# bug #11350
+
+type
+  Node = ref object
+    data: int
+
+proc use(x: Node) = discard
+
+proc main =
+  var x = Node(data: 3) # inferred to be an ``owned ref``
+  var dangling = unown x
+  assert dangling.data == 3
+  #use x
+  #dangling = nil
+  # reassignment causes the memory of what ``x`` points to to be freed:
+  echo "a"
+  x = Node(data: 4)
+  echo "b"
+  # accessing 'dangling' here is invalid as it is nil.
+  # at scope exit the memory of what ``x`` points to is freed
+  if dangling != nil:
+    echo dangling.data
+
+main()