What is the correct syntax for specifying generic boundaries while inheriting from superclass in Kot-CodePudding

I've encountered a problem.

The classes I have in reality are more complex, but here's the general outline. There's a class A:

open class A(
    val id: Any
)

And class B that bounds that Any to a more specific class:

class B<T>(
    val clazz: Class<T>,
    nonnull: T
) : A(nonnull)

But it won't compile as T is by default bounds to Any?, and class A has a non-nullable Any. And usually I'd write where T : Any, or even where T : OneInterface, SecondInterface. But it does not compile. I am sure I'm just writing something wrong way, but what?..

I've tried both googling and looking into the documentation, but I am not the master of Google-Fu, and documentation is silent on this matter. Both Inheritance and Generics are easy to understand, but they lack this exact intersection of language syntax. :/

CodePudding user response：

Put the constraint in a different place:

class B<T: Any>(
    val clazz: Class<T>,
    nonnull: T
) : A(nonnull)

class B<T>(
    val clazz: Class<T>,
    nonnull: T
) : A(nonnull) where T: Any

I'd prefer the first one and only use where when you can't use it, e.g. for multiple constraints.

CodePudding user response：

Restrict T to not accept a nullable Any:

class B<T: Any>(
  ...