[majewsky]

This only works because you're working with number literals here, which have the very liberal type "Num a => a". If I replace your main function by

  check :: Int -> Bool
  check x = x == (Just x)

  main = print (check 5)

I get a compile error:

  Main.hs:7:17: error:
      • Couldn't match expected type ‘Int’ with actual type ‘Maybe Int’
      • In the second argument of ‘(==)’, namely ‘(Just x)’
        In the expression: x == (Just x)
        In an equation for ‘check’: check x = x == (Just x)

[GregBuchholz]

Right, it was just a fun little "Well Actually" moment.

http://tirania.org/blog/archive/2011/Feb-17.html

[wyager]

That is possibly the most condescending thing I've ever read. Whatever the author tried to make themselves less abrasive, it didn't work very well.