Fix replace missing value

[fvlad]

Fix to the issue #244 to avoid throwing AssertionError when value is missing by key on replace

[coveralls]

Pull Request Test Coverage Report for Build 533

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 47.595%

---

Totals
Change from base Build 529:	0.0%
Covered Lines:	1672
Relevant Lines:	3513

---

💛 - Coveralls

[nitsanw]

Javadoc for replace:
"replace(K key, V value): Replaces the entry for the specified key only if it is currently mapped to some value."
So, we expect a null reply, and the assert in putIfMatch seems to contradict the contract.

The code in putIfMatch has an assert that is stronger than the guarantees in the static putIfMatch, but that assert is valid for all case where the oldVal param is not MATCH_ANY. I think the right move here is to add this observation to the assert:

assert res != null || oldVal == MATCH_ANY;

[nitsanw]

See other comment

[nitsanw]

Further digging after #246 (comment) leads me to think that putIfMatch should have returned TOMBSTONE instead of null here.

[nitsanw]

Please see changes in 1475be5 which resolve the issue. I'm very grateful for the PR and would happily merge it if you revert the change to NBHM. Thanks!

[fvlad]

Great, thanks for your fix!