X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcDeriv.lhs;h=6930b681fe5de702163626e4847dd715dd9e1b61;hb=0f5e104c36b1dc3d8deeec5fef3d65e7b3a1b5ad;hp=2edd8361058480088578edd57eba6f22d0a69acf;hpb=30c122df62ec75f9ed7f392f24c2925675bf1d06;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs index 2edd836..6930b68 100644 --- a/compiler/typecheck/TcDeriv.lhs +++ b/compiler/typecheck/TcDeriv.lhs @@ -459,15 +459,35 @@ mkEqnHelp orig tvs cls cls_tys tc_app mtheta tycon tc_args rep_tc rep_tc_args mtheta } | otherwise = baleOut (derivingThingErr cls cls_tys tc_app - (ptext SLIT("Last argument of the instance must be a type application"))) + (ptext (sLit "Last argument of the instance must be a type application"))) baleOut :: Message -> TcM (Maybe a) baleOut err = do { addErrTc err; return Nothing } \end{code} -Auxiliary lookup wrapper which requires that looked up family instances are -not type instances. If called with a vanilla tycon, the old type application -is simply returned. +Note [Looking up family instances for deriving] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +tcLookupFamInstExact is an auxiliary lookup wrapper which requires +that looked-up family instances exist. If called with a vanilla +tycon, the old type application is simply returned. + +If we have + data instance F () = ... deriving Eq + data instance F () = ... deriving Eq +then tcLookupFamInstExact will be confused by the two matches; +but that can't happen because tcInstDecls1 doesn't call tcDeriving +if there are any overlaps. + +There are two other things that might go wrong with the lookup. +First, we might see a standalone deriving clause + deriving Eq (F ()) +when there is no data instance F () in scope. + +Note that it's OK to have + data instance F [a] = ... + deriving Eq (F [(a,b)]) +where the match is not exact; the same holds for ordinary data types +with standalone deriving declrations. \begin{code} tcLookupFamInstExact :: TyCon -> [Type] -> TcM (TyCon, [Type]) @@ -477,18 +497,14 @@ tcLookupFamInstExact tycon tys | otherwise = do { maybeFamInst <- tcLookupFamInst tycon tys ; case maybeFamInst of - Nothing -> famInstNotFound tycon tys False - Just famInst@(_, rep_tys) - | not variable_only_subst -> famInstNotFound tycon tys True - | otherwise -> return famInst - where - tvs = map (Type.getTyVar - "TcDeriv.tcLookupFamInstExact") - rep_tys - variable_only_subst = all Type.isTyVarTy rep_tys && - sizeVarSet (mkVarSet tvs) == length tvs - -- renaming may have no repetitions + Nothing -> famInstNotFound tycon tys + Just famInst -> return famInst } + +famInstNotFound :: TyCon -> [Type] -> TcM a +famInstNotFound tycon tys + = failWithTc (ptext (sLit "No family instance for") + <+> quotes (pprTypeApp tycon (ppr tycon) tys)) \end{code} @@ -561,13 +577,13 @@ mk_typeable_eqn orig tvs cls tycon tc_args rep_tc _rep_tc_args mtheta -- Typeable; it depends on the arity of the type | isNothing mtheta -- deriving on a data type decl = do { checkTc (cls `hasKey` typeableClassKey) - (ptext SLIT("Use deriving( Typeable ) on a data type declaration")) + (ptext (sLit "Use deriving( Typeable ) on a data type declaration")) ; real_cls <- tcLookupClass (typeableClassNames !! tyConArity tycon) ; mk_typeable_eqn orig tvs real_cls tycon [] rep_tc [] (Just []) } | otherwise -- standaone deriving = do { checkTc (null tc_args) - (ptext SLIT("Derived typeable instance must be of form (Typeable") + (ptext (sLit "Derived typeable instance must be of form (Typeable") <> int (tyConArity tycon) <+> ppr tycon <> rparen) ; dfun_name <- new_dfun_name cls tycon ; loc <- getSrcSpanM @@ -593,8 +609,8 @@ checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc Just cond -> cond (mayDeriveDataTypeable, rep_tc) Nothing -> Just non_std_why where - ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("is not a class") - non_std_why = quotes (ppr cls) <+> ptext SLIT("is not a derivable class") + ty_args_why = quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "is not a class") + non_std_why = quotes (ppr cls) <+> ptext (sLit "is not a derivable class") sideConditions :: Class -> Maybe Condition sideConditions cls @@ -623,7 +639,7 @@ orCond c1 c2 tc Nothing -> Nothing -- c1 succeeds Just x -> case c2 tc of -- c1 fails Nothing -> Nothing - Just y -> Just (x $$ ptext SLIT(" and") $$ y) + Just y -> Just (x $$ ptext (sLit " and") $$ y) -- Both fail andCond :: Condition -> Condition -> Condition @@ -639,9 +655,9 @@ cond_std (_, rep_tc) where data_cons = tyConDataCons rep_tc no_cons_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has no data constructors") + ptext (sLit "has no data constructors") existential_why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-Haskell-98 constructor(s)") + ptext (sLit "has non-Haskell-98 constructor(s)") cond_isEnumeration :: Condition cond_isEnumeration (_, rep_tc) @@ -649,7 +665,7 @@ cond_isEnumeration (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has non-nullary constructors") + ptext (sLit "has non-nullary constructors") cond_isProduct :: Condition cond_isProduct (_, rep_tc) @@ -657,7 +673,7 @@ cond_isProduct (_, rep_tc) | otherwise = Just why where why = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has more than one constructor") + ptext (sLit "has more than one constructor") cond_typeableOK :: Condition -- OK for Typeable class @@ -671,18 +687,18 @@ cond_typeableOK (_, rep_tc) | otherwise = Nothing where too_many = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has too many arguments") + ptext (sLit "has too many arguments") bad_kind = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("has arguments of kind other than `*'") + ptext (sLit "has arguments of kind other than `*'") fam_inst = quotes (pprSourceTyCon rep_tc) <+> - ptext SLIT("is a type family") + ptext (sLit "is a type family") cond_mayDeriveDataTypeable :: Condition cond_mayDeriveDataTypeable (mayDeriveDataTypeable, _) | mayDeriveDataTypeable = Nothing | otherwise = Just why where - why = ptext SLIT("You need -XDeriveDataTypeable to derive an instance for this class") + why = ptext (sLit "You need -XDeriveDataTypeable to derive an instance for this class") std_class_via_iso :: Class -> Bool std_class_via_iso clas -- These standard classes can be derived for a newtype @@ -759,7 +775,7 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs mb_std_err = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon std_err = derivingThingErr cls cls_tys tc_app $ vcat [fromJust mb_std_err, - ptext SLIT("Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] + ptext (sLit "Try -XGeneralizedNewtypeDeriving for GHC's newtype-deriving extension")] -- Here is the plan for newtype derivings. We see -- newtype T a1...an = MkT (t ak+1...an) deriving (.., C s1 .. sm, ...) @@ -893,19 +909,19 @@ mkNewTypeEqn orig mayDeriveDataTypeable newtype_deriving tvs -- arguments must be type variables (not more complex indexes) cant_derive_err = derivingThingErr cls cls_tys tc_app - (vcat [ptext SLIT("even with cunning newtype deriving:"), + (vcat [ptext (sLit "even with cunning newtype deriving:"), if isRecursiveTyCon tycon then - ptext SLIT("the newtype may be recursive") + ptext (sLit "the newtype may be recursive") else empty, if not right_arity then - quotes (ppr (mkClassPred cls cls_tys)) <+> ptext SLIT("does not have arity 1") + quotes (ppr (mkClassPred cls cls_tys)) <+> ptext (sLit "does not have arity 1") else empty, if not (n_tyargs_to_keep >= 0) then - ptext SLIT("the type constructor has wrong kind") + ptext (sLit "the type constructor has wrong kind") else if not (n_args_to_keep >= 0) then - ptext SLIT("the representation type has wrong kind") + ptext (sLit "the representation type has wrong kind") else if not eta_ok then - ptext SLIT("the eta-reduction property does not hold") + ptext (sLit "the eta-reduction property does not hold") else empty ]) \end{code} @@ -955,7 +971,7 @@ inferInstanceContexts oflag infer_specs iterate_deriv :: Int -> [ThetaType] -> TcM [DerivSpec] iterate_deriv n current_solns | n > 20 -- Looks as if we are in an infinite loop - -- This can happen if we have -fallow-undecidable-instances + -- This can happen if we have -XUndecidableInstances -- (See TcSimplify.tcSimplifyDeriv.) = pprPanic "solveDerivEqns: probable loop" (vcat (map pprDerivSpec infer_specs) $$ ppr current_solns) @@ -1158,7 +1174,7 @@ genDerivBinds clas fix_env tycon \begin{code} derivingThingErr :: Class -> [Type] -> Type -> Message -> Message derivingThingErr clas tys ty why - = sep [hsep [ptext SLIT("Can't make a derived instance of"), + = sep [hsep [ptext (sLit "Can't make a derived instance of"), quotes (ppr pred)], nest 2 (parens why)] where @@ -1166,28 +1182,20 @@ derivingThingErr clas tys ty why derivingHiddenErr :: TyCon -> SDoc derivingHiddenErr tc - = hang (ptext SLIT("The data constructors of") <+> quotes (ppr tc) <+> ptext SLIT("are not all in scope")) - 2 (ptext SLIT("so you cannot derive an instance for it")) + = hang (ptext (sLit "The data constructors of") <+> quotes (ppr tc) <+> ptext (sLit "are not all in scope")) + 2 (ptext (sLit "so you cannot derive an instance for it")) standaloneCtxt :: LHsType Name -> SDoc -standaloneCtxt ty = hang (ptext SLIT("In the stand-alone deriving instance for")) +standaloneCtxt ty = hang (ptext (sLit "In the stand-alone deriving instance for")) 2 (quotes (ppr ty)) derivInstCtxt :: Class -> [Type] -> Message derivInstCtxt clas inst_tys - = ptext SLIT("When deriving the instance for") <+> parens (pprClassPred clas inst_tys) + = ptext (sLit "When deriving the instance for") <+> parens (pprClassPred clas inst_tys) badDerivedPred :: PredType -> Message badDerivedPred pred - = vcat [ptext SLIT("Can't derive instances where the instance context mentions"), - ptext SLIT("type variables that are not data type parameters"), - nest 2 (ptext SLIT("Offending constraint:") <+> ppr pred)] - -famInstNotFound :: TyCon -> [Type] -> Bool -> TcM a -famInstNotFound tycon tys notExact - = failWithTc (msg <+> quotes (pprTypeApp tycon (ppr tycon) tys)) - where - msg = ptext $ if notExact - then SLIT("No family instance exactly matching") - else SLIT("More than one family instance for") + = vcat [ptext (sLit "Can't derive instances where the instance context mentions"), + ptext (sLit "type variables that are not data type parameters"), + nest 2 (ptext (sLit "Offending constraint:") <+> ppr pred)] \end{code}