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))
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