Comment by hinkley

At the time that article was published in SIGPLAN, the dominant language was Java, which is officially statically, strongly typed.

Although really it isn’t because the JVM is strongly typed but evaluates some things at load or first invocation so it allows some languages that run in the JVM to be a bit tricky. They first generics implementation on the JVM, called Pizza, leveraged this load time concretization to do its thing.

But if you have a language that can resolve the type system at link time then you can do this trick. Alternatively you could switch to cuckoo hashing and if you next module load starts causing collisions, then so be it.