https://dlang.org/spec/abi.html states: The leftmost side of the inheritance graph of the interfaces all share their vptrs, this is the single inheritance model. Every time the inheritance graph forks (for multiple inheritance) a new vptr is created and stored in the class' instance.

Then: Every time a virtual method is overridden, a new vtbl[] must be created with the updated method pointers in it.

Since the first entry of the vtbl is a pointer to instance of TypeInfo, it seems to me that each class has its own vtbl[], distinct from all others, even if it does not add any virtual function.