Scala – 相互排斥的特征

发布时间：2020-12-16 19:14:05 所属栏目：安全来源：网络整理

导读：有没有办法定义一个常见类型的替代品集合： trait Mutabilitytrait Mutable extends Mutabilitytrait Immutable extends Mutability 并让编译器排除类似的东西： object Hat extends Mutable with Immutable 我相信我可以通过拥有一个共同的,冲突的成员来强

有没有办法定义一个常见类型的替代品集合：

trait Mutability
trait Mutable extends Mutability
trait Immutable extends Mutability

并让编译器排除类似的东西：

object Hat extends Mutable with Immutable

我相信我可以通过拥有一个共同的,冲突的成员来强制一些编译器错误,但错误消息有点倾斜：

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

是否有更直接的方式来表达这种约束,并且不允许某人通过获取编译器提供的提示来解决它(在Hat中覆盖“冲突”)？

感谢您的任何见解

解决方法

我认为这可能有用

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

trait MutabilityLevel[A <: Mutability]

class Foo extends MutabilityLevel[Immutable.type]

这个(ab？)使用的事实是你不能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

（编辑：李大同）

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