A DESCRIPTION OF THE PROBLEM :
The `Map.merge` method of the map created by `Collections.checkedMap` (and related factory methods) does not check the key and value type when no entry exists yet.

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
Run the code provided below

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
The `merge` call should fail with a ClassCastException because both the key and value type are incorrect.
ACTUAL -
No exception is thrown and the invalid key and value are added to the map.

---------- BEGIN SOURCE ----------
Map m = Collections.checkedMap(new HashMap<>(), Integer.class, Integer.class);
m.merge("key", "value", (v1, v2) -> null);

---------- END SOURCE ----------

FREQUENCY : always