Lint selections from unit value

[som-snytt]

Reproduction steps

Scala version: 2.13.10

scala> ().
!=(          (universal)   ==(          (universal)   formatted(  (deprecated)   toString()   (universal)
##           (universal)   asInstanceOf (universal)   getClass()                 →(          (deprecated)
+(          (deprecated)   ensuring(    (universal)   hashCode()   (universal)
->(          (universal)   equals(      (universal)   isInstanceOf (universal)

Problem

None of these is a good idea.

https://github.com/scala/scala/pull/6535#issuecomment-383485026 https://github.com/scala/scala/pull/10293#issuecomment-1434095201

Though the parser now supports () == ()!

[lrytz]

someInt.isNaN and similar could be included (see https://github.com/scala/scala/pull/10313)

[som-snytt]

Another lint request for function values https://github.com/scala/bug/issues/11547#issuecomment-1434149738