Comment by titzer

Tree-shaking is such a bad misnomer. Virgil's compiler calls this "reachability analysis" and it's built into the compilation model. The compiler will parse and typecheck a program's (and libraries' code), and run initializers, but after that the compilation proceeds by exploring from the main entrypoint(s) and only reachable code is analyzed and ends in the final binary. It will happily generate a program (without runtime system) that just consists of a single main function. The runtime system is only necessary for stacktraces and GC, and can be omitted if desired.