class RuboCop::Cop::Style::MutableConstant

def on_casgn(node)
  _scope, _const_name, value = *node
  if value.nil? # This is only the case for `CONST += ...` or similarg66
    parent = node.parent
    return unless parent.or_asgn_type? # We only care about `CONST ||= ...`
    value = parent.children.last
  end
  on_assignment(value)
end