crystal.txt

# cr getter.cr
nil

# crystal tool expand -c getter.cr:2:3 getter.cr
1 expansion found
expansion 1:
   class_getter?(bar : String | ::Nil) do
     "str"
   end

# expand macro 'class_getter?' (/usr/lib/crystal/core/object.cr:230:3)
~> @@bar : String | ::Nil
   def self.bar? : String | ::Nil
     @@bar
   end

program.cr

class Foo
  class_getter? bar : String? do
    "str"
  end
end

p Foo.bar?