Transformation systems such as Stratego/XT provide powerful analysis and transformation frameworks and concise languages for language processing, but instantiating them for every subject language is an arduous task, most often resulting in half-completed frontends. Open compilers, like the Eclipse Compiler for Java, provide mature frontends with robust parsers and type checkers, but solving language processing problems in general purpose languages without transformation libraries is tedious. Reusing these frontends with existing transformation systems is therefore attractive. However, for this reuse to be optimal, the functional logic found in the frontend should be exposed to the transformation system