How do you return a subclass instance from a base class method?

[Daniel]

On Thursday, 17 November 2022 at 05:21:05 UTC, MorteFeuille123 
wrote:
> On Thursday, 17 November 2022 at 04:25:13 UTC, Daniel Donnelly, 
> Jr. wrote:
>> [...]
>
> You can use TypeInfoClass:
>
> [...]

I don't get it - you never made use of b1 or b2...