Use compileAndLint in UnusedPrivateClassSpec

[BraisGabin]

This is the commit where I found #2206. Here I'm using a workaround (all those ugly objects).

[codecov-io]

Codecov Report

Merging #2208 into master will not change coverage.
The diff coverage is n/a.

@@            Coverage Diff            @@
##             master    #2208   +/-   ##
=========================================
  Coverage     81.19%   81.19%           
  Complexity     2064     2064           
=========================================
  Files           340      340           
  Lines          5907     5907           
  Branches       1076     1076           
=========================================
  Hits           4796     4796           
  Misses          535      535           
  Partials        576      576

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