static Class boxedToPrimitiveType(Class type) {
  if (type == Bool.class) return bool.class;
  if (type == Int.class) return int.class;
  if (type == Long.class) return long.class;
  if (type == Float.class) return float.class;
  if (type == Short.class) return short.class;
  if (type == Char.class) return char.class;
  if (type == Byte.class) return byte.class;
  if (type == Double.class) return double.class;
  null;
}

Began life as a copy of #1017021