scala - Scala —互斥的特征

Question

有没有一种方法可以定义一组常见类型的替代项:

trait Mutability
trait Mutable extends Mutability
trait Immutable extends Mutability

并让编译器排除类似以下内容的情况:

object Hat extends Mutable with Immutable

我相信我可以通过拥有一个通用的，冲突的成员来强制执行一些编译器错误，但是错误消息有点儿斜:

trait Mutability
trait Mutable extends Mutability { protected val conflict = true }
trait Immutable extends Mutability { protected val conflict = true }

object Hat extends Mutable with Immutable

<console>:10: error: object Hat inherits conflicting members:
value conflict in class Immutable$class of type Boolean  and
value conflict in class Mutable$class of type Boolean
(Note: this can be resolved by declaring an override in object Hat.)
   object Hat extends Immutable with Mutable

有没有更直接的方法来表达此约束，而不允许某人通过采用编译器提供的提示来解决该约束(在Hat中覆盖“冲突”)？

感谢您的任何见解

Answer 1

我认为这可能有效

sealed trait Mutability
case object Immutable extends Mutability
case object Mutable extends Mutability

trait MutabilityLevel[A <: Mutability]

class Foo extends MutabilityLevel[Immutable.type]

(ab？)使用以下事实:您无法使用不同的参数化来扩展相同的特征两次

scala> class Foo extends MutabilityLevel[Immutable.type] with MutabilityLevel[Mutable.type]
<console>:11: error: illegal inheritance;
 self-type Foo does not conform to MutabilityLevel[Immutable.type]'s selftype MutabilityLevel[Immutable.type]
       class Foo extends MutabilityLevel[Immutable.type] with MutabilityLevel[Mutable.type]
                         ^
<console>:11: error: illegal inheritance;
 self-type Foo does not conform to MutabilityLevel[Mutable.type]'s selftype MutabilityLevel[Mutable.type]
       class Foo extends MutabilityLevel[Immutable.type] with MutabilityLevel[Mutable.type]

然而..

scala> class Foo extends MutabilityLevel[Mutability]
defined class Foo