class Opal::Rewriters::BinaryOperatorAssignment::ConditionalSendHandler

def self.call(node, lhs, operation, rhs)
  recvr, meth, *args = *lhs
  recvr_tmp = new_temp
  cache_recvr = s(:lvasgn, recvr_tmp, recvr) # $tmp = recvr
  recvr = s(:js_tmp, recvr_tmp)
  recvr_is_nil = s(:send, recvr, :nil?)                   # recvr.nil?
  plain_send = lhs.updated(:send, [recvr, meth, *args])   # recvr.meth
  plain_op_asgn = node.updated(:op_asgn, [plain_send, operation, rhs]) # recvr.meth += rhs
  s(:begin,
    cache_recvr,
    s(:if, recvr_is_nil,                          # if recvr.nil?
      s(:nil),                                    #   nil
                                                  # else
      plain_op_asgn                               #   recvr.meth ||= rhs
    ),
  )                                               # end
end