module RuboCop::Cop::NegativeConditional

def check_negative_conditional(node)
  condition, _body, _rest = *node
  # Look at last expression of contents if there's a parenthesis
  # around condition.
  condition = condition.children.last while condition.type == :begin
  return unless condition.type == :send
  _object, method = *condition
  return unless method == :! && !(node.loc.respond_to?(:else) &&
                                  node.loc.else)
  add_offense(node, :expression)
end