Hi, you can blame me for this. It's a Java compiler plugin[1], which is similar to an annotation processor, but can hook into the compiler at a much earlier stage, which allows it to contribute to all phases of the compiler, including the Parser phase. The Manifold plugin takes full advantage of this, hence its ability to analyze comments, contribute to bytecode generation, etc.
Amazing! Reading the posted link this looks much bigger than embedding, which is crazy impressive btw. Do you anticipate building support for more resources? I notice you have GraphQL support... what about SQL?
At compile-time manifold-js[1] parses JS and generates Java types (stubs), which forward execution to rhino at runtime. Basically, JS seamlessly mapped onto Java's type system.
[1] https://docs.oracle.com/javase/8/docs/jdk/api/javac/tree/com...