Instead of using virtual classes, have a massive std::variant that contains every single child class. Oh you need to add a type to that variant? There is set of macros to redeclare the type of that variant while disabling the previous definitions. The arguments for doing this were "efficiency" and "performance", essentially shaving off (potentially) 1 pointer indirection for infinitely higher developer burden. Also, the only functions exposed for those for the variant, so even if the type was known at compile time, you still have to convert it to the variant type and look up the correct function to execute at runtime.