Augment Test for Confusing ExpressibleByNilLiteral Case
Augment Test for Confusing ExpressibleByNilLiteral Case

Add a test for an extremely confusing behavior of switches for
ExpressibleByNilLiteral-conforming types. From the looks of the expression
tree, one would hope that `case nil` would match such types. Instead, the
subject value is up-converted to an optional and compared to `nil` directly
with ~=.

ahoppen/swift,roambotics/swift,atrick/swift,glessard/swift,glessard/swift,benlangmuir/swift,gregomni/swift,JGiola/swift,apple/swift,gregomni/swift,glessard/swift,atrick/swift,atrick/swift,apple/swift,gregomni/swift,roambotics/swift,rudkx/swift,apple/swift,glessard/swift,rudkx/swift,benlangmuir/swift,gregomni/swift,gregomni/swift,glessard/swift,atrick/swift,ahoppen/swift,roambotics/swift,ahoppen/swift,atrick/swift,JGiola/swift,gregomni/swift,roambotics/swift,roambotics/swift,apple/swift,atrick/swift,benlangmuir/swift,roambotics/swift,glessard/swift,rudkx/swift,benlangmuir/swift,rudkx/swift,ahoppen/swift,JGiola/swift,rudkx/swift,ahoppen/swift,ahoppen/swift,JGiola/swift,benlangmuir/swift,rudkx/swift,benlangmuir/swift,JGiola/swift,apple/swift,apple/swift,JGiola/swift