scala - 隐式类也可以是动态的吗？

Question

我尝试通过执行以下操作为类隐式添加动态功能:

case class C(map: Map[String, String])

implicit class Enhancer(c: C) extends Dynamic {
    def selectDynamic(str: String) = c.map.getOrElse(str, "")
}

val c = C(Map("a" -> "A"))

这不会编译

val up = c.a

但是显式调用将:

val up = Enhancer(c).a

为什么是这样？

Answer 1

the specification中的规则是

Selection on Dynamic

If none of the previous conversions applies, and eis a prefix of a selection e.x, and e's type conforms to class scala.Dynamic, then the selection is rewritten according to the rules for dynamic member selection.

Conformance不包括“可以隐式转换”；所以不，你不能添加 Dynamic含蓄地。你可以为 Scala 的 future 版本提出它，但如果它被接受，我会感到惊讶。