lu4nm3

abstract case class EmailAddress(emailAddress: String)

lu4nm3

scala> EmailAddress("[email protected]").map(_.copy(emailAddress = "@example.com"))
<console>:13: error: value copy is not a member of EmailAddress
       EmailAddress("[email protected]").map(_.copy(emailAddress = "@example.com"))
       ^

lu4nm3

new EmailAddress(emailAddress) {}

lu4nm3

class EvilEmailAddress(address: String) extends EmailAddress(address)

EmailClient.sendEmail(from = new EvilEmailAddress("[email protected]"), to = new EvilEmailAddress("@example.com")) {
  ...
}

lu4nm3

sealed abstract case class EmailAddress(emailAddress: String)

lu4nm3

scala> class EvilEmailAddress(address: String) extends EmailAddress(address)
<console>:14: error: illegal inheritance from sealed class EmailAddress
       class EvilEmailAddress(address: String) extends EmailAddress(address)

lu4nm3

scala> new EmailAddress("@example.com") {}
<console>:15: error: illegal inheritance from sealed class EmailAddress
       new EmailAddress(""){}