How to specify that a property type must extend another type?

Question

I'm trying to declare a type which it should only accept objects where they extend another type.

For example:

export interface A extends B {
  aProp: string;
}

export interface B {
  bProp: string;
  // Feels wrong but how to tell something like ReadonlyArray<subClass extends B>?
  // I need children to contain A (or anything that extends B) & B properties
  children: ReadonlyArray<any & B>;
  childrenThatDoesntWork: ReadonlyArray<any extends B>; // <-- error here
}

class SomeClass {
  fun(obj: any extends B) { // <-- error '?' expected

  }
}

How to do this?

Thanks!

Answer 1

Here is my solution:

export interface A extends B {
    aProp: string;
}

export interface B {
    bProp: string;
    // Feels wrong but how to tell something like ReadonlyArray<subClass extends B>?
    // I need children to contain A (or anything that extends B) & B properties
    children: ReadonlyArray<A | B>;
    childrenThatDoesntWork: ReadonlyArray<B>; 
}

class SomeClass {
    fun<T extends B>(obj: T) { 

    }
}

Please check if it works for your case. If not, please provide the code for tests