avoid the unnecessary reassign with the equivalent comparison result

[kuitos]

Now the computed value will be reassign although the assignment was equivalent by the comparer.

@mweststrate
Here is the jsfiddle demo which describes the unexpected behavior, or u can check the added unit test for details🙂

• Added unit tests
• Updated changelog
• Updated docs (either in the description of this PR as markdown, or as separate PR on the gh-pages branch. Please refer to this PR). For new functionality, at least API.md should be updated
• Added typescript typings
• Verified that there is no significant performance drop (npm run perf)

[coveralls]

Coverage increased (+0.05%) to 92.983% when pulling cff477c on kuitos:fork-master into 7179b96 on mobxjs:master.

[mweststrate]

Thanks! This makes a lot of sense :-). Thanks for catching and fixing

[mweststrate]

Released as 4.2.0