module ActiveRecord::AttributeMethods::ClassMethods

def dangerous_class_method?(method_name)

not by any ancestors. (So 'puts' is not dangerous but 'new' is.)
A class method is 'dangerous' if it is already (re)defined by Active Record, but

def dangerous_class_method?(method_name)
  return true if RESTRICTED_CLASS_METHODS.include?(method_name.to_s)
  if Base.respond_to?(method_name, true)
    if Object.respond_to?(method_name, true)
      Base.method(method_name).owner != Object.method(method_name).owner
    else
      true
    end
  else
    false
  end
end

Instance Methods