Jon Pretty

If you go the source dependencies way, you cannot add a public method to any of your types, ever. Because that breaks backward source compatibility. Yes, binary compatibility is hard. But source compatibility is *impossible*.

But source compatibility is *safe* (the compiler checks it), whereas binary compatibility is *risky*. Composing a classpath at the same time as compilation guarantees there's no mismatch between the two... at the not-insignificant cost of having to compile the world.

I don't understand how you can "fix it right there and then" for source compat any more than for binary compat. In both cases, you'll have to fiddle with your dependency's source code, which means forking it in either case.

I think the point is that Fury makes that easy. It will be a single command to move a source dependency out of Fury's private control and into your workspace to edit. Then you can fork and create a PR quite easily.

making that easy is orthogonal though. also let's not forget not all jvm classpath users will be re-compiling with scalac from source: this path might lead to the scala ecosystem becoming hostile to the java ecosystem..