Is it possible to remove an inherited field/method in a child class/interface?

Question

Something along these lines:

interface A {
  a: number;
  x: any;
}

interface B extends A {
  b: number;
}

interface C {
  a: number;
  b: number;
}

So the B would be equal to C (omitting field x but still extending A). Is it possible? If so, how?

Answer 1

It is impossible to remove an inherited field/method of an interface in TypeScript.

But you can overcome this via interfaces reengineering:

1. Extract base interface

   interface BaseA {
     a: number;
   }
   
   interface A extends Base A {
     x: any;
   }
   
   interface B extends A {
     b: number;
   }
   
   interface C extends BaseA {
     b: number;
   }
   

Both C and B will be castable to BaseA.

2. Use optional field

   interface A {
     a: number;
     x?: any;
   }
   
   interface B extends A {
     b: number;
   }
   
   interface C extends A {
     b: number;
   }
   

I'm sure there are other ways depending on the certain task context.