diff options
| -rw-r--r-- | ghc/compiler/typecheck/TcTyClsDecls.lhs | 2 | ||||
| -rw-r--r-- | ghc/compiler/types/Generics.lhs | 32 |
2 files changed, 24 insertions, 10 deletions
diff --git a/ghc/compiler/typecheck/TcTyClsDecls.lhs b/ghc/compiler/typecheck/TcTyClsDecls.lhs index 1c9447d2cf..95166861ec 100644 --- a/ghc/compiler/typecheck/TcTyClsDecls.lhs +++ b/ghc/compiler/typecheck/TcTyClsDecls.lhs @@ -702,7 +702,7 @@ genericMultiParamErr clas badGenericMethodType op op_ty = hang (ptext SLIT("Generic method type is too complex")) 4 (vcat [ppr op <+> dcolon <+> ppr op_ty, - ptext SLIT("You can only use type variables, arrows, and tuples")]) + ptext SLIT("You can only use type variables, arrows, lists, and tuples")]) recSynErr syn_decls = setSrcSpan (getLoc (head sorted_decls)) $ diff --git a/ghc/compiler/types/Generics.lhs b/ghc/compiler/types/Generics.lhs index 0063140322..61b1a0f470 100644 --- a/ghc/compiler/types/Generics.lhs +++ b/ghc/compiler/types/Generics.lhs @@ -10,7 +10,8 @@ import Type ( Type, isUnLiftedType, tyVarsOfType, tyVarsOfTypes, isTyVarTy, getTyVar_maybe, funTyCon ) import TcHsSyn ( mkSimpleHsAlt ) -import TcType ( tcSplitTyConApp_maybe, tcSplitSigmaTy, tcSplitSigmaTy, isTauTy ) +import TcType ( tcSplitTyConApp_maybe, tcSplitSigmaTy, tcSplitPhiTy, applyTy, + isTauTy, mkTyVarTy ) import DataCon ( DataCon, dataConOrigArgTys, isVanillaDataCon, dataConSourceArity ) @@ -24,10 +25,11 @@ import BasicTypes ( EP(..), Boxity(..) ) 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 @@ -190,6 +192,7 @@ validGenericMethodType :: Type -> Bool -- * 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 @@ -207,7 +210,7 @@ validGenericMethodType ty 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} @@ -429,7 +432,9 @@ will be fed to the type checker. So the 'op' on the RHS will be 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 @@ -451,18 +456,19 @@ By the time the type checker has done its stuff we'll get \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 @@ -492,6 +498,7 @@ bimapApp :: EPEnv -> Maybe (TyCon, [Type]) -> EP (LHsExpr RdrName) 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 @@ -511,6 +518,7 @@ bimapArrow [ep1, ep2] 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) } @@ -522,6 +530,12 @@ bimapTuple eps 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) .. ] ] |