I wouldn't despair too much. People don't write evil conjunctions (er, or adverbs). In practice whether a conjunction reduces to a noun or a verb can be statically deduced. A parser (to produce an AST and thence a Haskell program or whatever desyntaxified result you want) could just be told about the rules for the built-in conjuctions. Essentially its just decorating all conjunction with their type. User defined conjunctions would need to be introduced to the parser in the same way. Or... you could probably programmatically derive a type for most user-defined conjunctions that actually got written (just not my Evil Conjunction).