%
\begin{code}
+{-# OPTIONS -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/CodingStyle#Warnings
+-- for details
+
module BuildTyCl (
buildSynTyCon, buildAlgTyCon, buildDataCon,
buildClass,
- mkAbstractTyConRhs, mkOpenDataTyConRhs, mkOpenNewTyConRhs,
+ mkAbstractTyConRhs, mkOpenDataTyConRhs,
mkNewTyConRhs, mkDataTyConRhs
) where
import Type
import Coercion
+import TcRnMonad
+import Outputable
+
import Data.List
\end{code}
mkAbstractTyConRhs = AbstractTyCon
mkOpenDataTyConRhs :: AlgTyConRhs
-mkOpenDataTyConRhs = OpenTyCon Nothing False
-
-mkOpenNewTyConRhs :: AlgTyConRhs
-mkOpenNewTyConRhs = OpenTyCon Nothing True
+mkOpenDataTyConRhs = OpenTyCon Nothing
mkDataTyConRhs :: [DataCon] -> AlgTyConRhs
mkDataTyConRhs cons
= Just co_tycon
| otherwise
= Nothing
+ ; traceIf (text "mkNewTyConRhs" <+> ppr cocon_maybe)
; return (NewTyCon { data_con = con,
nt_rhs = rhs_ty,
nt_etad_rhs = (etad_tvs, etad_rhs),
-- non-recursive newtypes
all_coercions = True
tvs = tyConTyVars tycon
- rhs_ty = head (dataConInstOrigArgTys con (mkTyVarTys tvs))
+ rhs_ty = ASSERT(not (null (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs))))
+ -- head (dataConInstOrigArgTys con (mkTyVarTys tvs))
+ head (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs))
-- Instantiate the data con with the
-- type variables from the tycon
+ -- NB: a newtype DataCon has no existentials; hence the
+ -- call to dataConInstOrigArgTys has the right type args
etad_tvs :: [TyVar] -- Matched lazily, so that mkNewTypeCoercion can
etad_rhs :: Type -- return a TyCon without pulling on rhs_ty
-> TcRnIf m n Class
buildClass class_name tvs sc_theta fds ats sig_stuff tc_isrec
- = do { tycon_name <- newImplicitBinder class_name mkClassTyConOcc
+ = do { traceIf (text "buildClass")
+ ; tycon_name <- newImplicitBinder class_name mkClassTyConOcc
; datacon_name <- newImplicitBinder class_name mkClassDataConOcc
-- The class name is the 'parent' for this datacon, not its tycon,
-- because one should import the class to get the binding for
-- the datacon
- ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc)
- [1..length sc_theta]
- -- We number off the superclass selectors, 1, 2, 3 etc so that we
- -- can construct names for the selectors. Thus
- -- class (C a, C b) => D a b where ...
- -- gives superclass selectors
- -- D_sc1, D_sc2
- -- (We used to call them D_C, but now we can have two different
- -- superclasses both called C!)
; fixM (\ rec_clas -> do { -- Only name generation inside loop
- let { rec_tycon = classTyCon rec_clas
- ; op_tys = [ty | (_,_,ty) <- sig_stuff]
- ; sc_tys = mkPredTys sc_theta
- ; dict_component_tys = sc_tys ++ op_tys
- ; sc_sel_ids = [mkDictSelId sc_name rec_clas | sc_name <- sc_sel_names]
- ; op_items = [ (mkDictSelId op_name rec_clas, dm_info)
- | (op_name, dm_info, _) <- sig_stuff ] }
+ let { rec_tycon = classTyCon rec_clas
+ ; op_tys = [ty | (_,_,ty) <- sig_stuff]
+ ; op_items = [ (mkDictSelId op_name rec_clas, dm_info)
+ | (op_name, dm_info, _) <- sig_stuff ] }
-- Build the selector id and default method id
; dict_con <- buildDataCon datacon_name
False -- Not declared infix
- (map (const NotMarkedStrict) dict_component_tys)
+ (map (const NotMarkedStrict) op_tys)
[{- No labelled fields -}]
tvs [{- no existentials -}]
- [{- No equalities -}] [{-No context-}]
- dict_component_tys
+ [{- No GADT equalities -}] sc_theta
+ op_tys
rec_tycon
- ; rhs <- case dict_component_tys of
- [rep_ty] -> mkNewTyConRhs tycon_name rec_tycon dict_con
- other -> return (mkDataTyConRhs [dict_con])
+ ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc)
+ [1..length (dataConDictTheta dict_con)]
+ -- We number off the Dict superclass selectors, 1, 2, 3 etc so that we
+ -- can construct names for the selectors. Thus
+ -- class (C a, C b) => D a b where ...
+ -- gives superclass selectors
+ -- D_sc1, D_sc2
+ -- (We used to call them D_C, but now we can have two different
+ -- superclasses both called C!)
+ ; let sc_sel_ids = [mkDictSelId sc_name rec_clas | sc_name <- sc_sel_names]
+
+ -- Use a newtype if the class constructor has exactly one field:
+ -- i.e. exactly one operation or superclass taken together
+ -- Watch out: the sc_theta includes equality predicates,
+ -- which don't count for this purpose; hence dataConDictTheta
+ ; rhs <- if ((length $ dataConDictTheta dict_con) + length sig_stuff) == 1
+ then mkNewTyConRhs tycon_name rec_tycon dict_con
+ else return (mkDataTyConRhs [dict_con])
; let { clas_kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
-- newtype like a synonym, but that will lead to an infinite
-- type]
; atTyCons = [tycon | ATyCon tycon <- ats]
+
+ ; result = mkClass class_name tvs fds
+ sc_theta sc_sel_ids atTyCons
+ op_items tycon
}
- ; return (mkClass class_name tvs fds
- sc_theta sc_sel_ids atTyCons op_items
- tycon)
+ ; traceIf (text "buildClass" <+> ppr tycon)
+ ; return result
})}
\end{code}
projects / ghc-hetmet.git / blobdiff