使用Akka Java API时Kotlin类型推断编译错误

问题描述：

我想在Kotlin程序中使用Akka Java API。当我想为akka Future 设置akka onComplete 回调时，我遇到Kotlin编译器错误，而Java等效工作不错：

I want to use Akka java API in a Kotlin program. When i want to set onComplete callback for a akka Future, i encounter the Kotlin compiler error, while the java equivalent work nice:

val future: Future<Any> = ask(sender, MyActor.Greeting("Saeed"), 5000)

future.onComplete(object : OnComplete<Object>() {
    override fun onComplete(failure: Throwable?, success: Object?) {
        throw UnsupportedOperationException()
    }
}, context.dispatcher())

java代码：

Future<Object> future = ask(sender(), new MyActor.Greeting("Saeed"), 5000);

future.onComplete(new OnComplete<Object>() {
    public void onComplete(Throwable failure, Object result) {
        if (failure != null) {
            System.out.println("We got a failure, handle it here");
        } else {
            System.out.println("result = "+(String) result);
        }
    }
},context().dispatcher());

Kotlin编译器错误：

The Kotlin compiler error:

Error:(47, 24) Kotlin: Type inference failed: 
fun <U : kotlin.Any!> onComplete(p0: scala.Function1<scala.util.Try<kotlin.Any!>!, U!>!, p1: scala.concurrent.ExecutionContext!): 
kotlin.Unit cannot be applied to (<no name provided>,scala.concurrent.ExecutionContextExecutor!)
Error:(47, 35) Kotlin: Type mismatch: inferred type is <no name provided> but scala.Function1<scala.util.Try<kotlin.Any!>!, scala.runtime.BoxedUnit!>! was expected

我将项目推送到 github 。

答

嗯，错误消息可能由于很多Scala内容和<未提供名称> 而不清楚，但是它清楚地定义了错误点：您的函数应接受任何，而不是对象。下列代码可以毫无问题地编译：

Well, the error message may be a bit unclear because of a lot of Scala stuff and <no name provided>, but it clearly defines the point of the error: your function should accept an Any, not an Object. The following codes compiles without any problems:

val future: Future<Any> = ask(sender, MyActor.Greeting("Saeed"), 5000)

future.onComplete(object : OnComplete<Any?>() {
    override fun onComplete(failure: Throwable?, success: Any?) {
        throw UnsupportedOperationException()
    }
}, context.dispatcher())

使用Akka Java API时Kotlin类型推断编译错误

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