Hi Ian and all,
My change is mostly confined to TcSplice.lhs, where I have a function that
gets the instance information given the name of a type class. When I call
it with names of type classes defined in source code I'm currently
compiling, it works fine. When I call it with names of type classes defined
with linked code, I get the type variable not in scope problem. (As I said
in my original e-mail I think this might be coming from some renaming phase
somewhere?)
I've included the function I added (which is n
compiler/typecheck/TcSplice.lhs) below.
Thanks,
Jean
instances :: TH.Name -> TcM [[(String, TH.Info)]]
instances th_name = do
-- First get class information.
name <- lookupThName th_name
classThing <- tcLookupTh name
let (classTvars, classMethodNames, classMethodSigs) = getMethodInfo
classThing
-- Now get instance information.
elts <- lookupInsts $ getTyThing classThing
{-
instEnv <- getInstEnv $ getTyThing classThing
let elts = instEnvElts instEnv -}
-- instTys :: [[Type]]
let instTys = map is_tys $ filter matches elts
instantiatedClassMethods <-
mapM (instantiate classTvars classMethodSigs classMethodNames)
instTys
return instantiatedClassMethods
where
getTyThing :: TcTyThing -> TyThing
getTyThing thing = case thing of
AGlobal tything -> tything
ATcId _id _co _type _level -> panic "Type ID is not a class."
ATyVar _name _type -> panic "Type var is not a class."
AThing _kind -> panic "Thing is not a class"
getMethodInfo :: TcTyThing -> ([TyVar], [Name], [Type])
getMethodInfo thing = case (getTyThing thing) of
AnId _id -> panic "Not a class."
ADataCon _con -> panic "Not a class."
ATyCon _tycon -> panic "Not a class."
AClass c -> processClass c
where
processClass c =
let tyvars = classTyVars c
methodIds = classSelIds c
in (tyvars, map getName methodIds, map processMethodId methodIds)
processMethodId id =
if isId id
then varType id
else panic "Expected id"
getInstanceName :: Instance -> String
getInstanceName = occNameString . nameOccName . is_cls
matches inst = getInstanceName inst == (TH.occString (get_name th_name))
get_name (TH.Name occ _) = occ
instantiate :: [TyVar] -- ^ Type variables
-> [Type] -- ^ Class signatures
-> [Name]
-> [Type] -- ^ Instance args
-> TcM [(String, TH.Info)]
instantiate tyvars classSigs methodNames instArgs = do
mapM instMethods (zip classSigs methodNames)
where
tymap = zip tyvars instArgs
getTy tvar = case lookup tvar tymap of
Just ty -> case ty of
TyVarTy _ -> panic "cannot insert another var"
_ -> ty
Nothing -> panic "cannot find tyvar"
instMethods :: (Type, Name) -> TcM (String, TH.Info)
instMethods (ty, name) = do
let nameStr = (occNameString . nameOccName) name
let name' = reifyName name
ty' <- reifyType $ inst' ty
return $ (nameStr, TH.VarI name' ty' Nothing TH.defaultFixity)
inst' :: Type -> Type
inst' ty = case ty of
TyVarTy tvar -> getTy tvar
AppTy t1 t2 -> AppTy (inst' t1) (inst' t2)
TyConApp tcon tys -> TyConApp tcon $ map inst' tys
FunTy t1 t2 ->
if isPredTy t1
then inst' t2
else FunTy (inst' t1) (inst' t2)
ForAllTy tyvar ty ->
if elem tyvar tyvars
then inst' ty
else ForAllTy tyvar (inst' ty)
PredTy pr -> PredTy (case pr of
ClassP cl tys -> ClassP cl (map inst' tys)
IParam ipn ty -> IParam ipn ty
EqPred t1 t2 -> EqPred (inst' t1) (inst' t2))
On Fri, Mar 6, 2009 at 11:37 AM, Ian Lynagh <[email protected]> wrote:
>
> Hi Jean,
>
> On Thu, Feb 19, 2009 at 09:41:37AM -0500, Jean Yang wrote:
> >
> > I've been trying to extend the Template Haskell parts of GHC (mostly
> > compiler/typechek/TcSplice.lhs) so that I can get back the signatures of
> > methods for all instances of a given type class. I get unbound type
> > variable errors (ex. Main.hs:21:9: Not in scope: type variable `l[i19B]')
> at
> > compile time when I am accessing type classes not defined in my source
> code
> > (ex. Show).
> >
> > Could this be caused by some renaming stage? If so, could someone
> point
> > me to where this occurs?
> >
> > Also, is this the right place for such questions?
>
> This is the right place, but I'm afraid I don't know what the problem
> is. If you show us your patch then perhaps we will be able to work out
> what's going on.
>
>
> Thanks
> Ian
>
>
--
Jean Yang
http://web.mit.edu/jeanyang/www/
Save us! Think before you print.
*^^`
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