Warns if Map key or Set element was overwritten in the sequence of add/put calls or using a Java 9 factory method like Set.of (which will result in runtime exception). This usually occurs due to copy-paste error. Example:
  map.put("A", 1);
  map.put("B", 2);
  map.put("C", 3);
  map.put("D", 4);
  map.put("A", 5); // duplicating key "A", overwrites previously written entry

New in 2017.3