Michał Pałka向我展示了这个工作黑客：

object OpaqueScope:
  opaque type BigNumber = BigInt

  object BigNumber:
    def apply(s: String): BigNumber = BigInt(s)

    extension (cv: BigNumber)
      def value: BigInt = cv
      export value.{unary_- as myUnary}

import OpaqueScope.BigNumber
val c = BigNumber("7")

c.myUnary // returns -7 as BigInt

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官方文件里也有。

DRAWBACK：类型不保留：（

为了保留返回类型BigNumber，你不能像2023一样使用export：

object OpaqueScope:
  opaque type BigNumber = BigInt

  object BigNumber:
    def apply(s: String): BigNumber = BigInt(s)

    extension (cv: BigNumber)
      def myUnary: BigNumber = cv.unary_-

import OpaqueScope.BigNumber
val c = BigNumber("7")

c.myUnary // returns -7 as BigNumber

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