> Specialisation is something that should happen before the optimiser. That's true, but your example shows a very important point: These cases are limited and

> Specialisation is something that should happen before the optimiser. That's true, but your example shows a very important point: These cases are limited and (in current languages) known by the compiler developers. I don't know a language that would allow a user-defined datatype to come with such specific optimizations. So for today's languages one could probably enumerate the special optimizations before specialization and then later only dispatch to the optimized code. But even if we say that optimization must happen after specialization, I still think that these optimizations are general enough to be put into a dynamic linker. That's what all JIT engines do, after all.