= recoverM (return ([], emptyValBindsOut)) $
do { -- Fish the "deriving"-related information out of the TcEnv
-- And make the necessary "equations".
- ; early_specs <- makeDerivSpecs tycl_decls inst_decls deriv_decls
+ is_boot <- tcIsHsBoot
+ ; traceTc (text "tcDeriving" <+> ppr is_boot)
+ ; early_specs <- makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls
; overlap_flag <- getOverlapFlag
; let (infer_specs, given_specs) = splitEithers early_specs
; insts2 <- mapM (genInst overlap_flag) final_specs
- ; is_boot <- tcIsHsBoot
-- Generate the generic to/from functions from each type declaration
; gen_binds <- mkGenericBinds is_boot
; (inst_info, rn_binds) <- renameDeriv is_boot gen_binds (insts1 ++ insts2)
| otherwise
= discardWarnings $ -- Discard warnings about unused bindings etc
- do { (rn_gen, dus_gen) <- setOptM Opt_PatternSignatures $ -- Type signatures in patterns
- -- are used in the generic binds
+ do { (rn_gen, dus_gen) <- setOptM Opt_ScopedTypeVariables $ -- Type signatures in patterns
+ -- are used in the generic binds
rnTopBinds (ValBindsIn gen_binds [])
; keepAliveSetTc (duDefs dus_gen) -- Mark these guys to be kept alive
all those.
\begin{code}
-makeDerivSpecs :: [LTyClDecl Name]
+makeDerivSpecs :: Bool
+ -> [LTyClDecl Name]
-> [LInstDecl Name]
-> [LDerivDecl Name]
-> TcM [EarlyDerivSpec]
-makeDerivSpecs tycl_decls inst_decls deriv_decls
- = do { eqns1 <- mapAndRecoverM deriveTyData $
- extractTyDataPreds tycl_decls ++
- [ pd -- traverse assoc data families
- | L _ (InstDecl _ _ _ ats) <- inst_decls
- , pd <- extractTyDataPreds ats ]
+makeDerivSpecs is_boot tycl_decls inst_decls deriv_decls
+ | is_boot -- No 'deriving' at all in hs-boot files
+ = do { mapM_ add_deriv_err deriv_locs
+ ; return [] }
+ | otherwise
+ = do { eqns1 <- mapAndRecoverM deriveTyData all_tydata
; eqns2 <- mapAndRecoverM deriveStandalone deriv_decls
; return (catMaybes (eqns1 ++ eqns2)) }
where
- extractTyDataPreds decls =
- [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds]
+ extractTyDataPreds decls
+ = [(p, d) | d@(L _ (TyData {tcdDerivs = Just preds})) <- decls, p <- preds]
+
+ all_tydata :: [(LHsType Name, LTyClDecl Name)]
+ -- Derived predicate paired with its data type declaration
+ all_tydata = extractTyDataPreds tycl_decls ++
+ [ pd -- Traverse assoc data families
+ | L _ (InstDecl _ _ _ ats) <- inst_decls
+ , pd <- extractTyDataPreds ats ]
+
+ deriv_locs = map (getLoc . snd) all_tydata
+ ++ map getLoc deriv_decls
+ add_deriv_err loc = setSrcSpan loc $
+ addErr (hang (ptext (sLit "Deriving not permitted in hs-boot file"))
+ 2 (ptext (sLit "Use an instance declaration instead")))
------------------------------------------------------------------
deriveStandalone :: LDerivDecl Name -> TcM (Maybe EarlyDerivSpec)
-- Standalone deriving declarations
--- e.g. deriving instance show a => Show (T a)
+-- e.g. deriving instance Show a => Show (T a)
-- Rather like tcLocalInstDecl
deriveStandalone (L loc (DerivDecl deriv_ty))
= setSrcSpan loc $
famInstNotFound :: TyCon -> [Type] -> TcM a
famInstNotFound tycon tys
= failWithTc (ptext (sLit "No family instance for")
- <+> quotes (pprTypeApp tycon (ppr tycon) tys))
+ <+> quotes (pprTypeApp tycon tys))
\end{code}
mkDataTypeEqn orig mayDeriveDataTypeable tvs cls cls_tys
tycon tc_args rep_tc rep_tc_args mtheta
- | Just err <- checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc
+ = case checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc of
-- NB: pass the *representation* tycon to checkSideConditions
- = baleOut (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) err)
-
- | otherwise
- = ASSERT( null cls_tys )
- mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta
+ CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tc rep_tc_args mtheta
+ NonDerivableClass -> bale_out (nonStdErr cls)
+ DerivableClassError msg -> bale_out msg
+ where
+ bale_out msg = baleOut (derivingThingErr cls cls_tys (mkTyConApp tycon tc_args) msg)
mk_data_eqn, mk_typeable_eqn
:: InstOrigin -> [TyVar] -> Class
-- the data constructors - but we need to be careful to fall back to the
-- family tycon (with indexes) in error messages.
-checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> Maybe SDoc
+data DerivStatus = CanDerive
+ | NonDerivableClass
+ | DerivableClassError SDoc
+
+checkSideConditions :: Bool -> Class -> [TcType] -> TyCon -> DerivStatus
checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tc
| notNull cls_tys
- = Just ty_args_why -- e.g. deriving( Foo s )
+ = DerivableClassError ty_args_why -- e.g. deriving( Foo s )
| otherwise
= case sideConditions cls of
- Just cond -> cond (mayDeriveDataTypeable, rep_tc)
- Nothing -> Just non_std_why
+ Nothing -> NonDerivableClass
+ Just cond -> case (cond (mayDeriveDataTypeable, rep_tc)) of
+ Nothing -> CanDerive
+ Just err -> DerivableClassError err
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")
+
+nonStdErr :: Class -> SDoc
+nonStdErr cls = quotes (ppr cls) <+> ptext (sLit "is not a derivable class")
sideConditions :: Class -> Maybe Condition
sideConditions cls
; return (if isJust mtheta then Just (Right spec)
else Just (Left spec)) }
- | isNothing mb_std_err -- Use the standard H98 method
- = mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta
-
- -- Otherwise we can't derive
- | newtype_deriving = baleOut cant_derive_err -- Too hard
- | otherwise = baleOut std_err -- Just complain about being a non-std instance
+ | otherwise
+ = case check_conditions of
+ CanDerive -> mk_data_eqn orig tvs cls tycon tc_args rep_tycon rep_tc_args mtheta
+ -- Use the standard H98 method
+ DerivableClassError msg -> bale_out msg -- Error with standard class
+ NonDerivableClass -- Must use newtype deriving
+ | newtype_deriving -> bale_out cant_derive_err -- Too hard, even with newtype deriving
+ | otherwise -> bale_out non_std_err -- Try newtype deriving!
where
- 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")]
+ check_conditions = checkSideConditions mayDeriveDataTypeable cls cls_tys rep_tycon
+ bale_out msg = baleOut (derivingThingErr cls cls_tys tc_app msg)
+
+ non_std_err = nonStdErr cls $$
+ 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, ...)
-- (d) in case of newtype family instances, the eta-dropped
-- 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:"),
- if isRecursiveTyCon tycon then
- 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")
- else empty,
- if not (n_tyargs_to_keep >= 0) then
- 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")
- else if not eta_ok then
- ptext (sLit "the eta-reduction property does not hold")
- else empty
- ])
+ cant_derive_err = vcat [ptext (sLit "even with cunning newtype deriving:"),
+ if isRecursiveTyCon tycon then
+ 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")
+ else empty,
+ if not (n_tyargs_to_keep >= 0) then
+ 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")
+ else if not eta_ok then
+ ptext (sLit "the eta-reduction property does not hold")
+ else empty
+ ]
\end{code}
projects / ghc-hetmet.git / blobdiff