[英]Cannot specialize a Scala method with specializable trait as return type
trait Eq[@specialized -X] {
def eq(x: X, y: X): Boolean
}
trait Keyed[@specialized(Int) X] {
def eqOnKey: Eq[X]
}
The method eqOnKey
is not specialized in the generated class Keyed$mcI$sp
. 方法eqOnKey
不是专门生成的类Keyed$mcI$sp
。
How can I specialize this method, ie making the return type of method eqOnKey$mcI$sp
in class Keyed$mcI$sp
to be Eq$mcI$sp
? 我怎样才能专注这个方法,即制作方法的返回类型eqOnKey$mcI$sp
类Keyed$mcI$sp
是Eq$mcI$sp
?
If you extend Keyed with Eq, you end up with a specialized eq method. 如果你使用Eq扩展Keyed,你最终会得到一个专门的eq方法。 This might not work for you, depending on your use case. 根据您的使用情况,这可能对您不起作用。
trait Eq[@specialized -X] {
def eq(x: X, y: X): Boolean
}
trait Keyed[@specialized(Int) X] extends Eq[X]
class Foo extends Keyed[Int] {
def eq(x: Int, y: Int) : Boolean = x == y
}
Will generate the following bytecode for Foo 将为Foo生成以下字节码
public boolean eq$mcI$sp(int, int);
Code:
0: iload_1
1: iload_2
2: if_icmpne 9
5: iconst_1
6: goto 10
9: iconst_0
10: ireturn
public boolean eq(java.lang.Object, java.lang.Object);
Code:
0: aload_0
1: aload_1
2: invokestatic #146 // Method scala/runtime/BoxesRunTime.unboxToInt:(Ljava/lang/Object;)I
5: aload_2
6: invokestatic #146 // Method scala/runtime/BoxesRunTime.unboxToInt:(Ljava/lang/Object;)I
9: invokevirtual #148 // Method eq:(II)Z
12: ireturn
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