Literals should be allowed in case statements

[sferik]

IMHO, literals should be allowed in case statements. They were disallowed in 56fa5fc.

Consider a case statement that is conditional on two variables. For example, here is a method that geocodes an address, latitude/longitude pair, or US zip code, depending on the number of arguments specified and their type.

def extract_location(args)
  case [args.size, args.first.class]
  when [1, Integer]
    {zip: to_zip_code(args[0])}
  when [1, String]
    place = Geocoder.search(args[0]).first
    {latitude: place.latitude, longitude: place.longitude}
  when [2, Numeric]
    {latitude: args[1], longitude: args[1]}
  else
    fail(ArgumentError, 'Must pass a latitude/longitude, zip or address')
  end
end

Obviously, this code could be rewritten as as nested conditional statements but that would require duplicating the else clause. I think this a valid use case for a literal in a case statement.

[bbatsov]

Yeah, this totally slipped my mind. Obviously not all literals make sense as a condition (therefore the change I made), though. I'll update this.