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It actually works really well in practice for the example I'm thinking of (and this is deep in the bones of a code base, not just something I thought of for fun

It actually works really well in practice for the example I'm thinking of (and this is deep in the bones of a code base, not just something I thought of for fun). Each functionality is a true subset of the other. It's not different families of functionalities. Also, I don't see how your suggestion would help with void foo(const AInterface& someObject); What type should foo take instead if it can handle all levels of guarantee but might engage better code paths the more guarantees are available? Would you use a sum type (which in C++ boils down to type erasure, i.e. polymorphy but hidden and costlier)? Would you overload it (and then have code duplication)? I'm not convinced you could make it simpler.

CoolGuySteve 7y ago
"template<typename ABCType> foo(const ABCType& someObject)" will call the most optimized code path at compile time if the type is properly cast before the call. In this case, the inheritance is unnecessary as long as all the types implement the same function names. So the runtime type detection, whatever it is, only needs to be run once at the start of the callstack and then an entire chain of operations will be more optimized than if you had used interfaces and virtual functions throughout.
- MauranKilom 7y ago
  ...and every single piece of code in your entire code base that touches these classes (and that's like 80% of the higher level code in this particular case) would have to be templated. So either everything has to be in headers, or you need 3 (well, 5 in reality, I abbreviated the example) explicit template instantiation declarations per function in the header and as many explicit template instantiation definitions in the source file. Either way lies madness.