I have the same problem with a compiler plugin that I am writing. In GHC Core I need to get from a dict-fun identifier (e.g. $fMyClassDouble to the type class instance bindr (starting with $c). lookupInstEnv from the InstEnv module seemed to do it, but it seems to look up the matching key from a set of instEnv keys and not anything that contains the instance bindr. Not sure. Where is the dictionary lookup that gives me the bindr? What I did so far: evalExpr :: DynFlags -> ModGuts -> CoreExpr -> Var -> CoreM NodeType evalExpr dflags guts (Var iD) v = do hsc_env <- getHscEnv eps <- liftIO (hscEPS hsc_env) let instEnvs = InstEnvs (eps_inst_env eps) (mg_inst_env guts) (mkModuleSet (dep_orphs (mg_deps guts))) let ty = tyConAppTyCon_maybe (idType iD) let cl = fromJust (tyConClass_maybe (fromJust ty)) let tys = snd (splitTyConApp (idType iD)) let (matches,_,_) | isDictId iD = lookupInstEnv False instEnvs cl tys | otherwise = ([],[],[]) let inst = map (nameStableString . varName . is_dfun . fst) matches liftIO $ B.appendFile ("debug.txt") (B.pack (show inst))