scala – 隐式转换和null

import scala.language.implicitConversions

object myObj {
  implicit def nullToInt(x: Null) = 0

  def main(args: Array[String]): Unit = {
    val x = 1 + null
    val y = 1 + nullToInt(null)

    println(x + " " + y)
  }
}

给出以下结果

1null 1

我期待两个val都是Int并且等于1.

显然,第一个val是String,等于“1null”.

Xprint：typer显示源代码被翻译成

package <empty> {
  import scala.language.implicitConversions;
  object myObj extends scala.AnyRef {
    def <init>(): myObj.type = {
      myObj.super.<init>();
      ()
    };
    implicit def nullToInt(x: Null): Int = 0;
    def main(args: Array[String]): Unit = {
      val x: String = 1.+(null);
      val y: Int = 1.+(myObj.this.nullToInt(null));
      scala.Predef.println(x.+(" ").+(y))
    }
  }
}

int没有符号方法接受null

scala> 10+null
res0: String = 10null

scala> 10*null
<console>:12: error: overloaded method value * with alternatives:
  (x: Double)Double <and>
  (x: Float)Float <and>
  (x: Long)Long <and>
  (x: Int)Int <and>
  (x: Char)Int <and>
  (x: Short)Int <and>
  (x: Byte)Int
 cannot be applied to (Null)
       10*null
         ^

scala> 10-null
<console>:12: error: overloaded method value - with alternatives:
  (x: Double)Double <and>
  (x: Float)Float <and>
  (x: Long)Long <and>
  (x: Int)Int <and>
  (x: Char)Int <and>
  (x: Short)Int <and>
  (x: Byte)Int
 cannot be applied to (Null)
       10-null
         ^

我假设“1”和“null”都转换为String而不是应用隐式nullToInt.有人可以解释编译器如何提出这个问题吗？使用了什么逻辑/工作流程？

另一个问题是是否有办法启用implcit nullToInt？

PS.我不是在谈论这里的最佳做法.随意考虑一个问题作为学术兴趣.