| data LiteralDesugaring m = | LiteralDesugaring | { desugarInt :: MonadThings m => Integer -> m CoreExpr | , desugarWord :: MonadThings m => Integer -> m CoreExpr ... I am not sure why you want to control the desugaring of literals. Why literals? And why is literals enough? | But I don't still understand what can I do with foreign | imports/exports. DsForeign module seems to be too complicated. As I | can see, I shouldn't make whole dsForeigns function replaceable, but I | can't understand what part of it should be replaceble. I still think that the stub generation for foreign declarations should be easily separable. The desugarer generates a certainly amount of unwrapping, but you'll want that for JavaScript too. The actual calling convention is embedded inside the Id: see the FCallId constructor of IdDetails in IdInfo.lhs, and the ForeignCall type in ForiegnCall.lhs. Simon