[eigenspace]

> why not just compile a static but generic version of the method with branches based on the tags of values? ("Can't figure out the types, wait until runtime and then just branch to the specialized method instances which I do know the types for")

This is exactly what the new AOT compiler (juliac) does. The original article is just a bit inaccurate.

The problem though, is that if you have a truly dynamic call-site where you have no idea which method body will be called, then the AOT compiler can't know if the right method specializations will survive the trimming process, so you'll get errors or warnings when compiling with the --trim feature active (--trim is what is used to make the AOT compiled binaries small).

However, there are still lots of cases where you can have a dynamic dispatch but can convince the compiler that there will be an already compiled method signature for every possible specialization. In that case --trimm will work fine and do exactly what you described above.