Changes:
* Do not return anything in a method that is not expected to return
something.
* Inline some previously hard to read code.
* More specific type hints, if possible.
Change-Id: I0e460899eea07d8733f638a11133adc3000f0542
And also, avoid deprecated use of wfMemcKey() global function. So,
create a BagOStuff cache object and use. ::getMainStashInstance() was
deprecated in 1.28 and the MainObjectStash service was marked available.
Currently, extension requires MediaWiki 1.31 at the minimum so the
replacement is safe.
Change-Id: I01494a2dcbcbf30fe9960fdfb55b4912a648c7b6
