add test case

tests/gc/t22173.nim

@@ -0,0 +1,20 @@
+discard """
+  cmd: '''nim c --gc:refc -r $file'''
+"""
+const Memo = 100 * 1024
+
+proc fff(v: sink string): iterator(): char =
+  return iterator(): char =
+    for c in v:
+      yield c
+
+var tmp = newString(Memo)
+
+let iter = fff(move(tmp))
+
+while true:
+  let v = iter()
+  if finished(iter):
+    break
+
+doAssert getOccupiedMem() < Memo * 3