Method return types clash? Does Apex support covariant return types?

Question

I have a class inheritance as follows.

public virtual class A{
   public virtual A myMethod(){
      return new A();
   }
}

public class B extends A{
   public override B myMethod(){
      return new B();
   }
}

But it throws an compile error:

Method return types clash: myMethod()

And my question is How to return child type instead of father type when overriding a method?

Answer 1

You can't alter the return type for overridden methods. Either return the parent type, which you can then cast to the child type, if it is a child, or simply return it as an Object (which is how various methods like JSON.deserialize works). In either case, you'll need to do casting at least some of the time.

Example:

public class B extends A {
    public override A construct() {
        return new B();
     }
}

Answer 2

What interesting it works with interfaces.

✅ Interface

public interface Factory {
   SObject getRecord();
}

public class AccountFactory implements Factory {
    public Account getRecord() {
       return new Account(Name = 'Test');
    }
}

❌ Abstract/Virtual

Method return types clash: Account vs SObject from the type AccountFactory

public abstract class Factory {
   abstract SObject getRecord();
}

public class AccountFactory extends Factory {
    public override Account getRecord() {
       return new Account(Name = 'Test');
    }
}

There is idea for it since 2014 :(

https://ideas.salesforce.com/s/idea/a0B8W00000GdXOCUA3/support-covariant-return-types-in-apex