继承中的默认类型参数

Question

Say I have the following classes:

class A[T] { ... }

abstract class B[T1,T2](t: T1)(implicit ev: A[T2]) {
... 
}

On some instances, when I inherit from B, the type for T2 is the same as that for T1. Is there I way I can define my class to avoid having to specify this explicitly?

So rather than having to do:

class C extends B[String, String]("Some string") {
...
}

Can I have the compiler some how infer this so I only need to write:

class C extends B("Some string") {
...
}

Answer 1

I think a type alias should work:

type B1[T] = B[T, T]

class C extends B1("Some string") {
   ...
}