Created
August 30, 2020 17:41
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CanBuild scala
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| // An example of building a Concrete class with implicitly available CanBuild | |
| sealed trait Top { | |
| type ActualType | |
| } | |
| trait CanBuild[A <: Top] { | |
| def apply(v: String): A#ActualType | |
| } | |
| object Top { | |
| final case class A(v: String) extends Top { | |
| def a: A = this | |
| override type ActualType = A | |
| } | |
| final case class B(v: String) extends Top { | |
| def b: B = this | |
| override type ActualType = this.type | |
| } | |
| implicit val aCanBuild: CanBuild[A] = (v: String) => A(v) | |
| implicit val bCanBuild: CanBuild[B] = (v: String) => B(v) | |
| def apply[V <: Top](value: String)(implicit builder: CanBuild[V]): V#ActualType = | |
| builder(value) | |
| apply[A]("aaa").a | |
| apply[B]("aaa").b | |
| apply[B]("aaa").a // doesn't compile | |
| } |
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