If you want to make it as a standard library so it can compile once and others link to it, then you have this issue. You need to compile on use in order to only

If you want to make it as a standard library so it can compile once and others link to it, then you have this issue. You need to compile on use in order to only add the function signatures based on use, so if you're doing this from types the user is giving you (say, a generic differential equation solver where the state can be any type with the right overloads) then you're out of luck. If you know of a big set of types the user might want to give you, then you can compile those ahead of time, but for the diffeq example you can have different types for the dependent and independent variable, so you'd want each combination. The solution here of course is just to make people statically compile against it if you want to use all of these features, but you need to compile as a shared library if you want to build an easy interface to a high level scripting language (Julia, Python, R, MATLAB, etc.). So what tends to happen is that libraries which do make some extra features possible are constrained when used from a scripting language and they compile a bunch of choices to mitigate that a bit (see SUNDIALS and its built-in NVector compilations). The true solution here of course is to compile on demand based on the new types you see from the user codes, and this is what Julia does automatically. As for boxing, boxing works but it's slow. The developer of LightGraphs.jl tried using Swift for awhile but went back to Julia when he realized that actually using generics in Swift is really really slow because they do this boxing (your code is generic! But...). To finish the story, he tried Go a bit but generics in Go... he went to C++ but templates but they were difficult to use and the compile times were too long to be anything close to interactive, and has done extremely well over the last few years in Julia (though it is admittedly missing some tools for (partial) AOT compilation and building binaries, but these tools are in development).