class Seasoning
  getter :name, :calories

  def initialize(@name, @calories=0)
  end

  SPICY_SEASONINGS = [
    "Cayenne", 
    "Wasabi"
  ]

  def spicy?
    SPICY_SEASONINGS.include?(name)
  end 
end

$ crystal build my_program.cr
      color.red = "FF"
           ^~~

undefined method 'red=' for Color
===================================

$ crystal build my_program.cr 
$ ./my_program
"Hello, World!"

It's fast

class Seasoning
  getter :name, :calories

  def initialize(@name, @calories=0)
  end

  SPICY_SEASONINGS = [
    "Cayenne", 
    "Wasabi"
  ]

  def spicy?
    SPICY_SEASONINGS.include?(name)
  end 
end

Seasoning.new("Bacon Grease", 50)
Seasoning.new(100) # oops

$ crystal tool hierarchy -e Seasoning seasoning.cr

- class Object (4 bytes)
  |
  +- class Reference (4 bytes)
     |
     +- class Seasoning (32 bytes)
            @name     : (String | Int32) (16 bytes)
            @calories : Int32            ( 4 bytes)

Error in ./seasonings.cr:22: 
    undefined method 'upcase' for Nil 
    (compile-time type is (Nil | String | Int32))

grease = Seasoning.new("Bacon Grease", 50)
Seasoning.new(nil)

puts grease.name.upcase

alias Player = {String, Int32}
alias Team = Array(Players)
# ... 
def play_match(home : Team, away : Team); end 

def play_match(home : Player, away : Player); end 

macro define_method(name, &block)
  def {{name.id}} 
    {{block.body}}
  end
end

macro method_missing(name, args, block)
  puts "> Called {{name.id}} with {{args.size}} arguments"
end