Troubles running crystal tool expand

[opensas opensas]

I was trying to learn a little bit about macros, so I copied the source example from http://devdocs.io/crystal/api/0.23.0/json#mapping(properties,strict=false)-macro and then tried with:

crystal tool expand mapping_test.cr

But all I get is the help text, I tried with several options but always get the same result. am I missing anything?

[Vitalii Elenhaupt]

$ cat mapping_test.cr
require "json"

class Location
  JSON.mapping(  # <---- line: 4, column: 3
    lat: Float64,
    lng: Float64,
  )
end

class House
  JSON.mapping(
    address: String,
    location: {type: Location, nilable: true},
  )
end

house = House.from_json(%({"address": "Crystal Road 1234", "location": {"lat": 12.3, "lng": 34.5}}))
house.address  # => "Crystal Road 1234"
house.location # => #<Location:0x10cd93d80 @lat=12.3, @lng=34.5>
house.to_json  # => %({"address":"Crystal Road 1234","location":{"lat":12.3,"lng":34.5}})

$ crystal tool expand -c mapping_test.cr:4:3 mapping_test.cr  
                                                                                                   
1 expansion found
expansion 1:
   JSON.mapping(lat: Float64, lng: Float64)


~> ::JSON.mapping({lat: {type: Float64}, lng: {type: Float64}})


~> @lat : Float64
   def lat=(_lat : Float64)
     @lat = _lat
   end
   def lat
     @lat
   end
   @lng : Float64
   def lng=(_lng : Float64)
     @lng = _lng
   end
   def lng
     @lng
   end
   def initialize(__temp_25 : ::JSON::PullParser)
     __temp_26 = nil
     __temp_27 = false
     __temp_28 = nil
     __temp_29 = false
     __temp_25.read_object do |key|
       case key
       when "lat"
         __temp_27 = true
         __temp_26 = Float64.new(__temp_25)
       when "lng"
         __temp_29 = true
         __temp_28 = Float64.new(__temp_25)
       else
         __temp_25.skip
       end
     end
     if ((__temp_26.nil?) && (!__temp_27)) && (!::Union(Float64).nilable?)
       raise(::JSON::ParseException.new("Missing json attribute: lat", 0, 0))
     end
     if ((__temp_28.nil?) && (!__temp_29)) && (!::Union(Float64).nilable?)
       raise(::JSON::ParseException.new("Missing json attribute: lng", 0, 0))
     end
     @lat = __temp_26.as(Float64)
     @lng = __temp_28.as(Float64)
   end
   def to_json(json : ::JSON::Builder)
     json.object do
       _lat = @lat
       if _lat.nil?
       else
         json.field("lat") do
           _lat.to_json(json)
         end
       end
       _lng = @lng
       if _lng.nil?
       else
         json.field("lng") do
           _lng.to_json(json)
         end
       end
     end
   end