isTyVarTy, getTyVar_maybe, funTyCon
)
import TcHsSyn ( mkSimpleHsAlt )
-import TcType ( tcSplitTyConApp_maybe, tcSplitSigmaTy, tcSplitSigmaTy, isTauTy )
-import DataCon ( DataCon, dataConOrigArgTys, isExistentialDataCon,
+import TcType ( tcSplitTyConApp_maybe, tcSplitSigmaTy, tcSplitPhiTy, applyTy,
+ isTauTy, mkTyVarTy )
+import DataCon ( DataCon, dataConOrigArgTys, isVanillaDataCon,
dataConSourceArity )
import TyCon ( TyCon, tyConName, tyConDataCons,
import Var ( TyVar )
import VarSet ( varSetElems )
import Id ( Id, idType )
+import TysWiredIn ( listTyCon )
import PrelNames
import SrcLoc ( srcLocSpan, noLoc, Located(..) )
-import Util ( takeList )
+import Util ( takeList, isSingleton )
import Bag
import Outputable
import FastString
-- * type variables
-- * function arrow
-- * boxed tuples
+ -- * lists
-- * an arbitrary type not involving the class type variables
-- e.g. this is ok: forall b. Ord b => [b] -> a
-- where a is the class variable
where
no_tyvars_in_ty = all (`elem` local_tvs) (varSetElems (tyVarsOfType ty))
- valid_tycon tc = tc == funTyCon || isBoxedTupleTyCon tc
+ valid_tycon tc = tc == funTyCon || tc == listTyCon || isBoxedTupleTyCon tc
-- Compare bimapApp, below
\end{code}
= not (any bad_con data_cons) -- See comment below
&& not (null data_cons) -- No values of the type
where
- bad_con dc = any bad_arg_type (dataConOrigArgTys dc) || isExistentialDataCon dc
+ bad_con dc = any bad_arg_type (dataConOrigArgTys dc) || not (isVanillaDataCon dc)
-- If any of the constructor has an unboxed type as argument,
-- then we can't build the embedding-projection pair, because
-- it relies on instantiating *polymorphic* sum and product types
mkTyConGenericBinds :: TyCon -> LHsBinds RdrName
mkTyConGenericBinds tycon
= unitBag (L loc (FunBind (L loc from_RDR) False {- Not infix -}
- [mkSimpleHsAlt pat rhs | (pat,rhs) <- from_alts]))
+ (mkMatchGroup [mkSimpleHsAlt pat rhs | (pat,rhs) <- from_alts])))
`unionBags`
unitBag (L loc (FunBind (L loc to_RDR) False
- [mkSimpleHsAlt to_pat to_body]))
+ (mkMatchGroup [mkSimpleHsAlt to_pat to_body])))
where
loc = srcLocSpan (getSrcLoc tycon)
datacons = tyConDataCons tycon
= (wrap inlDataCon_RDR l_from_alts ++ wrap inrDataCon_RDR r_from_alts,
nlVarPat to_arg,
noLoc (HsCase (nlHsVar to_arg)
- [mkSimpleHsAlt (nlConPat inlDataCon_RDR [l_to_pat]) l_to_body,
- mkSimpleHsAlt (nlConPat inrDataCon_RDR [r_to_pat]) r_to_body]))
+ (mkMatchGroup [mkSimpleHsAlt (nlConPat inlDataCon_RDR [l_to_pat]) l_to_body,
+ mkSimpleHsAlt (nlConPat inrDataCon_RDR [r_to_pat]) r_to_body])))
where
(l_datacons, r_datacons) = splitInHalf datacons
(l_from_alts, l_to_pat, l_to_body) = mk_sum_stuff us' l_datacons
= (us'',
nlHsApps crossDataCon_RDR [l_alt_rhs, r_alt_rhs],
nlVarPat to_arg,
- \x -> noLoc (HsCase (nlHsVar to_arg)
- [mkSimpleHsAlt pat (l_to_body_fn (r_to_body_fn x))]))
+-- gaw 2004 FIX?
+ \x -> noLoc (HsCase (nlHsVar to_arg)
+ (mkMatchGroup [mkSimpleHsAlt pat (l_to_body_fn (r_to_body_fn x))])))
where
to_arg = mkGenericLocal us
(l_arg_vars, r_arg_vars) = splitInHalf arg_vars
at the representation type for T, Trep.
-A note about polymorphism. Suppose the class op is polymorphic:
+Note [Polymorphic methods]
+~~~~~~~~~~~~~~~~~~~~~~~~~~
+Suppose the class op is polymorphic:
class Baz a where
op :: forall b. Ord b => a -> b -> b
\begin{code}
mkGenericRhs :: Id -> TyVar -> TyCon -> LHsExpr RdrName
mkGenericRhs sel_id tyvar tycon
- = mkHsApp (toEP bimap) (nlHsVar (getRdrName sel_id))
+ = ASSERT( isSingleton ctxt ) -- Checks shape of selector-id context
+ pprTrace "mkGenericRhs" (vcat [ppr sel_id, ppr (idType sel_id), ppr tyvar, ppr tycon, ppr local_tvs, ppr final_ty]) $
+ mkHsApp (toEP bimap) (nlHsVar (getRdrName sel_id))
where
-- Initialising the "Environment" with the from/to functions
-- on the datatype (actually tycon) in question
(from_RDR, to_RDR) = mkGenericNames tycon
- -- Takes out the ForAll and the Class restrictions
- -- in front of the type of the method.
- (_,_,op_ty) = tcSplitSigmaTy (idType sel_id)
+ -- Instantiate the selector type, and strip off its class context
+ (ctxt, op_ty) = tcSplitPhiTy (applyTy (idType sel_id) (mkTyVarTy tyvar))
-- Do it again! This deals with the case where the method type
- -- is polymorphic -- see notes above
+ -- is polymorphic -- see Note [Polymorphic methods] above
(local_tvs,_,final_ty) = tcSplitSigmaTy op_ty
-- Now we probably have a tycon in front
bimapApp env Nothing = panic "TcClassDecl: Type Application!"
bimapApp env (Just (tycon, ty_args))
| tycon == funTyCon = bimapArrow arg_eps
+ | tycon == listTyCon = bimapList arg_eps
| isBoxedTupleTyCon tycon = bimapTuple arg_eps
| otherwise = -- Otherwise validGenericMethodType will
-- have checked that the type is a constant type
to_body = toEP ep2 `mkHsApp` (mkHsPar $ nlHsVar a_RDR `mkHsApp` (mkHsPar $ fromEP ep1 `mkHsApp` nlHsVar b_RDR))
-------------------
+-- bimapTuple :: [EP a1 b1, ... EP an bn] -> EP (a1,...an) (b1,..bn)
bimapTuple eps
= EP { fromEP = mkHsLam [noLoc tuple_pat] (noLoc from_body),
toEP = mkHsLam [noLoc tuple_pat] (noLoc to_body) }
from_body = ExplicitTuple [fromEP ep `mkHsApp` nlHsVar g | (ep,g) <- eps_w_names] Boxed
-------------------
+-- bimapList :: EP a b -> EP [a] [b]
+bimapList [ep]
+ = EP { fromEP = nlHsApp (nlHsVar map_RDR) (fromEP ep),
+ toEP = nlHsApp (nlHsVar map_RDR) (toEP ep) }
+
+-------------------
a_RDR = mkVarUnqual FSLIT("a")
b_RDR = mkVarUnqual FSLIT("b")
gs_RDR = [ mkVarUnqual (mkFastString ("g"++show i)) | i <- [(1::Int) .. ] ]
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