该规范将重载解析视为对类成员选择的消歧。但是隐式解析使用静态重载解析在不是成员的引用之间进行选择。
可以说,以下是对规范的误解,因为zzz
它是在派生自X
much as yyy
is 的类中定义的:
$ scala
Welcome to Scala 2.12.0 (Java HotSpot(TM) 64-Bit Server VM, Java 1.8.0_101).
Type in expressions for evaluation. Or try :help.
scala> import concurrent._, ExecutionContext.global
import concurrent._
import ExecutionContext.global
scala> trait X { implicit val xxx: ExecutionContext = global }
defined trait X
scala> class Y extends X { implicit val yyy: ExecutionContext = global ; def f = implicitly[ExecutionContext] }
defined class Y
scala> class Z extends X { def f(implicit zzz: ExecutionContext) = implicitly[ExecutionContext] }
<console>:16: error: ambiguous implicit values:
both value xxx in trait X of type => scala.concurrent.ExecutionContext
and value zzz of type scala.concurrent.ExecutionContext
match expected type scala.concurrent.ExecutionContext
class Z extends X { def f(implicit zzz: ExecutionContext) = implicitly[ExecutionContext] }
^
目前,您必须依靠命名来隐藏封闭范围的隐含:
scala> class Z extends X { def f(implicit xxx: ExecutionContext) = implicitly[ExecutionContext] }
defined class Z
或者,
scala> :pa
// Entering paste mode (ctrl-D to finish)
package object p { import concurrent._ ; implicit val xxx: ExecutionContext = ExecutionContext.global }
package p { import concurrent._ ;
class P { def f(implicit xxx: ExecutionContext) = implicitly[ExecutionContext]
def g = implicitly[ExecutionContext] }
}
// Exiting paste mode, now interpreting.
scala>