module FirstIncludeModule
  def same_name_method
    :first_include_module
  end
end

module SecondIncludeModule
  def same_name_method
    :second_include_module
  end
end

class Klass
  include FirstIncludeModule
  include SecondIncludeModule
end

object = Klass.new
object.same_name_method

class Klass
  define_method :same_name_method, FirstIncludeModule.instance_method(:same_name_method)
end

object = Klass.new
object.same_name_method

module UnIncludeModule
  def un_include_module_method
    :un_include_module_method
  end
end

class Klass2
  # TypeErrr にならない
  define_method :un_include_module_method, UnIncludeModule.instance_method(:un_include_module_method)
end

object = Klass2.new
object.un_include_module_method

class OriginalClass
end

obj = OriginalClass.new

def obj.new_singleton_method
  :new_singleton_method
end

obj.class.method_defined? :new_singleton_method

obj.singleton_class.method_defined? :new_singleton_method

class Klass3; end

p klass = Klass3.new
klass.singleton_class

KLASS_OBJECT = klass

class << klass; self; end == KLASS_OBJECT.singleton_class

obj = Object.new

def obj.define_singleton_method
  :singleton_method
end

class << obj
end

obj.singleton_class

class OriginalClass2
end

obj = OriginalClass2.new
obj.singleton_class.superclass

p obj.instance_of? obj.singleton_class
obj.instance_of? OriginalClass2

1.singleton_class

:symbol.singleton_class

p true.singleton_class
p false.singleton_class
nil.singleton_class

class Klass3; end

p klass = Klass.new

p EigenClass = klass.singleton_class

EigenClass.new

class NewClass < EigenClass
end

module ExtendedModule
  def extend_method
    :extend_method
  end
end

obj = Object.new
obj.extend ExtendedModule

obj.extend_method

obj = Object.new
p obj.singleton_class.ancestors

obj.extend ExtendedModule
obj.singleton_class.ancestors

SINGLETON_OBJECT = Object.new

class << SINGLETON_OBJECT
  def only_method
    :only_method
  end
end

SingletonClass = SINGLETON_OBJECT.singleton_class

def SingletonClass.instance_get
  SINGLETON_OBJECT
end

SingletonClass.instance_get.only_method