%
+% (c) The University of Glasgow 2006
% (c) The AQUA Project, Glasgow University, 1996-1998
%
-\section[TcTyClsDecls]{Typecheck type and class declarations}
+
+TcTyClsDecls: Typecheck type and class declarations
\begin{code}
module TcTyClsDecls (
- tcTyAndClassDecls, tcIdxTyInstDecl
+ tcTyAndClassDecls, tcFamInstDecl
) where
#include "HsVersions.h"
-import HsSyn ( TyClDecl(..), HsConDetails(..), HsTyVarBndr(..),
- ConDecl(..), Sig(..), NewOrData(..), ResType(..),
- tyClDeclTyVars, isSynDecl, isClassDecl, isIdxTyDecl,
- isKindSigDecl, hsConArgs, LTyClDecl, tcdName,
- hsTyVarName, LHsTyVarBndr, LHsType, HsType(..),
- mkHsAppTy
- )
-import HsTypes ( HsBang(..), getBangStrictness, hsLTyVarNames )
-import BasicTypes ( RecFlag(..), StrictnessMark(..) )
-import HscTypes ( implicitTyThings, ModDetails )
-import BuildTyCl ( buildClass, buildAlgTyCon, buildSynTyCon, buildDataCon,
- mkDataTyConRhs, mkNewTyConRhs )
+import HsSyn
+import HsTypes
+import BasicTypes
+import HscTypes
+import BuildTyCl
import TcRnMonad
-import TcEnv ( TyThing(..),
- tcLookupLocated, tcLookupLocatedGlobal,
- tcExtendGlobalEnv, tcExtendKindEnv,
- tcExtendKindEnvTvs, newFamInstTyConName,
- tcExtendRecEnv, tcLookupTyVar, InstInfo,
- tcLookupLocatedTyCon )
-import TcTyDecls ( calcRecFlags, calcClassCycles, calcSynCycles )
-import TcClassDcl ( tcClassSigs, tcAddDeclCtxt )
-import TcHsType ( kcHsTyVars, kcHsLiftedSigType, kcHsType,
- kcHsContext, tcTyVarBndrs, tcHsKindedType, tcHsKindedContext,
- kcHsSigType, tcHsBangType, tcLHsConResTy,
- tcDataKindSig, kcCheckHsType )
-import TcMType ( newKindVar, checkValidTheta, checkValidType,
- -- checkFreeness,
- UserTypeCtxt(..), SourceTyCtxt(..) )
-import TcType ( TcKind, TcType, Type, tyVarsOfType, mkPhiTy,
- mkArrowKind, liftedTypeKind, mkTyVarTys,
- tcSplitSigmaTy, tcEqTypes, tcGetTyVar_maybe )
-import Type ( PredType(..), splitTyConApp_maybe, mkTyVarTy,
- newTyConInstRhs, isLiftedTypeKind, Kind
- -- pprParendType, pprThetaArrow
- )
-import Generics ( validGenericMethodType, canDoGenerics )
-import Class ( Class, className, classTyCon, DefMeth(..), classBigSig, classTyVars )
-import TyCon ( TyCon, AlgTyConRhs( AbstractTyCon, OpenDataTyCon,
- OpenNewTyCon ),
- SynTyConRhs( OpenSynTyCon, SynonymTyCon ),
- tyConDataCons, mkForeignTyCon, isProductTyCon,
- isRecursiveTyCon, isOpenTyCon,
- tyConStupidTheta, synTyConRhs, isSynTyCon, tyConName,
- isNewTyCon, isDataTyCon, tyConKind,
- setTyConArgPoss )
-import DataCon ( DataCon, dataConUserType, dataConName,
- dataConFieldLabels, dataConTyCon, dataConAllTyVars,
- dataConFieldType, dataConResTys )
-import Var ( TyVar, idType, idName )
-import VarSet ( elemVarSet, mkVarSet )
-import Name ( Name, getSrcLoc )
+import TcEnv
+import TcTyDecls
+import TcClassDcl
+import TcHsType
+import TcMType
+import TcType
+import FunDeps
+import Type
+import Generics
+import Class
+import TyCon
+import DataCon
+import Var
+import VarSet
+import Name
+import OccName
import Outputable
-import Maybe ( isJust, fromJust, isNothing, catMaybes )
-import Maybes ( expectJust )
-import Monad ( unless )
-import Unify ( tcMatchTys, tcMatchTyX )
-import Util ( zipLazy, isSingleton, notNull, sortLe )
-import List ( partition, elemIndex )
-import SrcLoc ( Located(..), unLoc, getLoc, srcLocSpan,
- srcSpanStart )
-import ListSetOps ( equivClasses, minusList )
-import Digraph ( SCC(..) )
-import DynFlags ( DynFlag( Opt_GlasgowExts, Opt_Generics,
- Opt_UnboxStrictFields, Opt_IndexedTypes ) )
+import Maybes
+import Monad
+import Unify
+import Util
+import SrcLoc
+import ListSetOps
+import Digraph
+import DynFlags
+
+import Data.List ( partition, elemIndex )
+import Control.Monad ( mplus )
\end{code}
tcTyAndClassDecls boot_details allDecls
= do { -- Omit instances of indexed types; they are handled together
-- with the *heads* of class instances
- ; let decls = filter (not . isIdxTyDecl . unLoc) allDecls
+ ; let decls = filter (not . isFamInstDecl . unLoc) allDecls
-- First check for cyclic type synonysm or classes
-- See notes with checkCycleErrs
; let { -- Calculate rec-flag
; calc_rec = calcRecFlags boot_details rec_alg_tyclss
; tc_decl = addLocM (tcTyClDecl calc_rec) }
+
-- Type-check the type synonyms, and extend the envt
; syn_tycons <- tcSynDecls kc_syn_decls
; tcExtendGlobalEnv syn_tycons $ do
%************************************************************************
%* *
-\subsection{Type checking instances of indexed types}
+\subsection{Type checking family instances}
%* *
%************************************************************************
-Instances of indexed types are somewhat of a hybrid. They are processed
-together with class instance heads, but can contain data constructors and hence
-they share a lot of kinding and type checking code with ordinary algebraic
-data types (and GADTs).
+Family instances are somewhat of a hybrid. They are processed together with
+class instance heads, but can contain data constructors and hence they share a
+lot of kinding and type checking code with ordinary algebraic data types (and
+GADTs).
\begin{code}
-tcIdxTyInstDecl :: LTyClDecl Name
- -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
-tcIdxTyInstDecl (L loc decl)
+tcFamInstDecl :: LTyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
+tcFamInstDecl (L loc decl)
= -- Prime error recovery, set source location
- recoverM (returnM (Nothing, Nothing)) $
+ recoverM (returnM Nothing) $
setSrcSpan loc $
tcAddDeclCtxt decl $
- do { -- indexed data types require -findexed-types and can't be in an
+ do { -- type families require -findexed-types and can't be in an
-- hs-boot file
; gla_exts <- doptM Opt_IndexedTypes
; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
- ; checkTc gla_exts $ badIdxTyDecl (tcdLName decl)
- ; checkTc (not is_boot) $ badBootTyIdxDeclErr
+ ; checkTc gla_exts $ badFamInstDecl (tcdLName decl)
+ ; checkTc (not is_boot) $ badBootFamInstDeclErr
-- perform kind and type checking
- ; tcIdxTyInstDecl1 decl
+ ; tcFamInstDecl1 decl
}
-tcIdxTyInstDecl1 :: TyClDecl Name
- -> TcM (Maybe InstInfo, Maybe TyThing) -- Nothing if error
+tcFamInstDecl1 :: TyClDecl Name -> TcM (Maybe TyThing) -- Nothing if error
-tcIdxTyInstDecl1 (decl@TySynonym {})
+tcFamInstDecl1 (decl@TySynonym {})
= kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
do { -- check that the family declaration is for a synonym
unless (isSynTyCon family) $
; t_typats <- mappM tcHsKindedType k_typats
; t_rhs <- tcHsKindedType k_rhs
- -- construct type rewrite rule
-- !!!of the form: forall t_tvs. (tcdLName decl) t_typats = t_rhs
- ; return (Nothing, Nothing) -- !!!TODO: need InstInfo for eq axioms
+ ; return Nothing -- !!!TODO: need TyThing for indexed synonym
}}
-tcIdxTyInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
- tcdCons = cons})
+tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
+ tcdCons = cons})
= kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
do { -- check that the family declaration is for the right kind
unless (new_or_data == NewType && isNewTyCon family ||
; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
; tycon <- fixM (\ tycon -> do
- { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
- tycon t_tvs))
+ { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
k_cons
; tc_rhs <-
case new_or_data of
})
-- construct result
- ; return (Nothing, Just (ATyCon tycon))
+ ; return $ Just (ATyCon tycon)
}}
where
h98_syntax = case cons of -- All constructors have same shape
-- type functions can have a higher-kinded result
; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
- ; typats <- zipWithM kcCheckHsType hs_typats kinds
+ ; typats <- TcRnMonad.zipWithM kcCheckHsType hs_typats kinds
; thing_inside tvs typats resultKind family
}
where
This treatment of type synonyms only applies to Haskell 98-style synonyms.
General type functions can be recursive, and hence, appear in `alg_decls'.
-The kind of an indexed type is solely determinded by its kind signature;
+The kind of a type family is solely determinded by its kind signature;
hence, only kind signatures participate in the construction of the initial
kind environment (as constructed by `getInitialKind'). In fact, we ignore
-instances of indexed types altogether in the following. However, we need to
-include the kind signatures of associated types into the construction of the
+instances of families altogether in the following. However, we need to
+include the kinds of associated families into the construction of the
initial kind environment. (This is handled by `allDecls').
\begin{code}
-- instances of indexed types yet, but leave this to
-- `tcInstDecls1'
{ kc_alg_decls <- mappM (wrapLocM kcTyClDecl)
- (filter (not . isIdxTyDecl . unLoc) alg_decls)
+ (filter (not . isFamInstDecl . unLoc) alg_decls)
; return (kc_syn_decls, kc_alg_decls) }}}
where
-- environment
allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at
| L _ at <- ats
- , isKindSigDecl at]
- allDecls decl | isIdxTyDecl decl = []
- | otherwise = [decl]
+ , isFamilyDecl at]
+ allDecls decl | isFamInstDecl decl = []
+ | otherwise = [decl]
------------------------------------------------------------------------
getInitialKind :: TyClDecl Name -> TcM (Name, TcKind)
mk_arg_kind (UserTyVar _) = newKindVar
mk_arg_kind (KindedTyVar _ kind) = return kind
- mk_res_kind (TyFunction { tcdKind = kind }) = return kind
- mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
- -- On GADT-style and data signature declarations we allow a kind
- -- signature
+ mk_res_kind (TyFamily { tcdKind = Just kind }) = return kind
+ mk_res_kind (TyData { tcdKindSig = Just kind }) = return kind
+ -- On GADT-style declarations we allow a kind signature
-- data T :: *->* where { ... }
mk_res_kind other = return liftedTypeKind
-- Not used for type synonyms (see kcSynDecl)
kcTyClDecl decl@(TyData {})
- = ASSERT( not . isJust $ tcdTyPats decl ) -- must not be instance of idx ty
+ = ASSERT( not . isFamInstDecl $ decl ) -- must not be a family instance
kcTyClDeclBody decl $
kcDataDecl decl
-kcTyClDecl decl@(TyFunction {})
+kcTyClDecl decl@(TyFamily {tcdKind = kind})
= kcTyClDeclBody decl $ \ tvs' ->
- return (decl {tcdTyVars = tvs'})
+ return (decl {tcdTyVars = tvs',
+ tcdKind = kind `mplus` Just liftedTypeKind})
+ -- default result kind is '*'
kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
= kcTyClDeclBody decl $ \ tvs' ->
; cons' <- mappM (wrapLocM kc_con_decl) cons
; return (decl {tcdTyVars = tvs, tcdCtxt = ctxt', tcdCons = cons'}) }
where
- kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res) = do
+ -- doc comments are typechecked to Nothing here
+ kc_con_decl (ConDecl name expl ex_tvs ex_ctxt details res _) = do
kcHsTyVars ex_tvs $ \ex_tvs' -> do
ex_ctxt' <- kcHsContext ex_ctxt
details' <- kc_con_details details
res' <- case res of
ResTyH98 -> return ResTyH98
ResTyGADT ty -> do { ty' <- kcHsSigType ty; return (ResTyGADT ty') }
- return (ConDecl name expl ex_tvs' ex_ctxt' details' res')
+ return (ConDecl name expl ex_tvs' ex_ctxt' details' res' Nothing)
kc_con_details (PrefixCon btys)
= do { btys' <- mappM kc_larg_ty btys ; return (PrefixCon btys') }
kc_con_details (RecCon fields)
= do { fields' <- mappM kc_field fields; return (RecCon fields') }
- kc_field (fld, bty) = do { bty' <- kc_larg_ty bty ; return (fld, bty') }
+ kc_field (HsRecField fld bty d) = do { bty' <- kc_larg_ty bty ; return (HsRecField fld bty' d) }
kc_larg_ty bty = case new_or_data of
DataType -> kcHsSigType bty
tcTyClDecl calc_isrec decl
= tcAddDeclCtxt decl (tcTyClDecl1 calc_isrec decl)
- -- kind signature for a type function
+ -- "type family" declarations
tcTyClDecl1 _calc_isrec
- (TyFunction {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = kind})
+ (TyFamily {tcdFlavour = TypeFamily,
+ tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = Just kind})
+ -- NB: kind at latest
+ -- added during
+ -- kind checking
= tcTyVarBndrs tvs $ \ tvs' -> do
{ traceTc (text "type family: " <+> ppr tc_name)
- ; gla_exts <- doptM Opt_IndexedTypes
+ ; idx_tys <- doptM Opt_IndexedTypes
- -- Check that we don't use kind signatures without Glasgow extensions
- ; checkTc gla_exts $ badSigTyDecl tc_name
+ -- Check that we don't use families without -findexed-types
+ ; checkTc idx_tys $ badFamInstDecl tc_name
- ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind)]
+ ; return [ATyCon $ buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing)]
}
- -- kind signature for an indexed data type
+ -- "newtype family" or "data family" declaration
tcTyClDecl1 _calc_isrec
- (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
- tcdLName = L _ tc_name, tcdKindSig = Just ksig, tcdCons = []})
+ (TyFamily {tcdFlavour = DataFamily new_or_data,
+ tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
= tcTyVarBndrs tvs $ \ tvs' -> do
{ traceTc (text "data/newtype family: " <+> ppr tc_name)
- ; extra_tvs <- tcDataKindSig (Just ksig)
+ ; extra_tvs <- tcDataKindSig mb_kind
; let final_tvs = tvs' ++ extra_tvs -- we may not need these
- ; checkTc (null . unLoc $ ctxt) $ badKindSigCtxt tc_name
- ; gla_exts <- doptM Opt_IndexedTypes
+ ; idx_tys <- doptM Opt_IndexedTypes
- -- Check that we don't use kind signatures without Glasgow extensions
- ; checkTc gla_exts $ badSigTyDecl tc_name
+ -- Check that we don't use families without -findexed-types
+ ; checkTc idx_tys $ badFamInstDecl tc_name
; tycon <- buildAlgTyCon tc_name final_tvs []
(case new_or_data of
- DataType -> OpenDataTyCon
- NewType -> OpenNewTyCon)
+ DataType -> mkOpenDataTyConRhs
+ NewType -> mkOpenNewTyConRhs)
Recursive False True Nothing
; return [ATyCon tycon]
}
+ -- "newtype", "data", "newtype instance", "data instance"
tcTyClDecl1 calc_isrec
(TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs,
tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons})
(newtypeConError tc_name (length cons))
; tycon <- fixM (\ tycon -> do
- { data_cons <- mappM (addLocM (tcConDecl unbox_strict new_or_data
- tycon final_tvs))
+ { data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon final_tvs))
cons
; tc_rhs <-
if null cons && is_boot -- In a hs-boot file, empty cons means
-----------------------------------
tcConDecl :: Bool -- True <=> -funbox-strict_fields
- -> NewOrData
-> TyCon -> [TyVar]
-> ConDecl Name
-> TcM DataCon
-tcConDecl unbox_strict NewType tycon tc_tvs -- Newtypes
- (ConDecl name _ ex_tvs ex_ctxt details ResTyH98)
- = do { let tc_datacon field_lbls arg_ty
- = do { arg_ty' <- tcHsKindedType arg_ty -- No bang on newtype
- ; buildDataCon (unLoc name) False {- Prefix -}
- [NotMarkedStrict]
- (map unLoc field_lbls)
- tc_tvs [] -- No existentials
- [] [] -- No equalities, predicates
- [arg_ty']
- tycon }
-
- -- Check that a newtype has no existential stuff
- ; checkTc (null ex_tvs && null (unLoc ex_ctxt)) (newtypeExError name)
-
- ; case details of
- PrefixCon [arg_ty] -> tc_datacon [] arg_ty
- RecCon [(field_lbl, arg_ty)] -> tc_datacon [field_lbl] arg_ty
- other ->
- failWithTc (newtypeFieldErr name (length (hsConArgs details)))
- -- Check that the constructor has exactly one field
- }
-
-tcConDecl unbox_strict DataType tycon tc_tvs -- Data types
- (ConDecl name _ tvs ctxt details res_ty)
+tcConDecl unbox_strict tycon tc_tvs -- Data types
+ (ConDecl name _ tvs ctxt details res_ty _)
= tcTyVarBndrs tvs $ \ tvs' -> do
{ ctxt' <- tcHsKindedContext ctxt
; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
; let
+ -- Tiresome: tidy the tyvar binders, since tc_tvs and tvs' may have the same OccNames
tc_datacon is_infix field_lbls btys
= do { let bangs = map getBangStrictness btys
; arg_tys <- mappM tcHsBangType btys
; buildDataCon (unLoc name) is_infix
- (argStrictness unbox_strict tycon bangs arg_tys)
+ (argStrictness unbox_strict bangs arg_tys)
(map unLoc field_lbls)
univ_tvs ex_tvs eq_preds ctxt' arg_tys
data_tc }
InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
RecCon fields -> tc_datacon False field_names btys
where
- (field_names, btys) = unzip fields
+ (field_names, btys) = unzip [ (n, t) | HsRecField n t _ <- fields ]
}
-> [TyVar] -- where MkT :: forall a b c. ...
-> ResType Name
-> TcM ([TyVar], -- Universal
- [TyVar], -- Existential
+ [TyVar], -- Existential (distinct OccNames from univs)
[(TyVar,Type)], -- Equality predicates
TyCon) -- TyCon given in the ResTy
-- We don't check that the TyCon given in the ResTy is
-- ([a,z,c], [x,y], [a:=:(x,y), c:=:z], T)
= do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
- -- NB: tc_tvs and dc_tvs are distinct
- ; let univ_tvs = choose_univs [] tc_tvs res_tys
+
+ ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
-- Each univ_tv is either a dc_tv or a tc_tv
ex_tvs = dc_tvs `minusList` univ_tvs
eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
| otherwise
= tc_tv : choose_univs used tc_tvs res_tys
--------------------
+ -- NB: tc_tvs and dc_tvs are distinct, but
+ -- we want them to be *visibly* distinct, both for
+ -- interface files and general confusion. So rename
+ -- the tc_tvs, since they are not used yet (no
+ -- consequential renaming needed)
+ init_occ_env = initTidyOccEnv (map getOccName dc_tvs)
+ (_, tidy_tc_tvs) = mapAccumL tidy_one init_occ_env tc_tvs
+ tidy_one env tv = (env', setTyVarName tv (tidyNameOcc name occ'))
+ where
+ name = tyVarName tv
+ (env', occ') = tidyOccName env (getOccName name)
+
+ -------------------
argStrictness :: Bool -- True <=> -funbox-strict_fields
- -> TyCon -> [HsBang]
+ -> [HsBang]
-> [TcType] -> [StrictnessMark]
-argStrictness unbox_strict tycon bangs arg_tys
+argStrictness unbox_strict bangs arg_tys
= ASSERT( length bangs == length arg_tys )
- zipWith (chooseBoxingStrategy unbox_strict tycon) arg_tys bangs
+ zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
-- We attempt to unbox/unpack a strict field when either:
-- (i) The field is marked '!!', or
--
-- We have turned off unboxing of newtypes because coercions make unboxing
-- and reboxing more complicated
-chooseBoxingStrategy :: Bool -> TyCon -> TcType -> HsBang -> StrictnessMark
-chooseBoxingStrategy unbox_strict_fields tycon arg_ty bang
+chooseBoxingStrategy :: Bool -> TcType -> HsBang -> StrictnessMark
+chooseBoxingStrategy unbox_strict_fields arg_ty bang
= case bang of
HsNoBang -> NotMarkedStrict
HsStrict | unbox_strict_fields
can_unbox arg_ty = case splitTyConApp_maybe arg_ty of
Nothing -> False
Just (arg_tycon, tycon_args) ->
- not (isRecursiveTyCon tycon) &&
+ not (isRecursiveTyCon arg_tycon) && -- Note [Recusive unboxing]
isProductTyCon arg_tycon &&
(if isNewTyCon arg_tycon then
can_unbox (newTyConInstRhs arg_tycon tycon_args)
else True)
\end{code}
+Note [Recursive unboxing]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+Be careful not to try to unbox this!
+ data T = MkT !T Int
+But it's the *argument* type that matters. This is fine:
+ data S = MkS S !Int
+because Int is non-recursive.
+
%************************************************************************
%* *
\subsection{Dependency analysis}
checkValidTyCon tc
| isSynTyCon tc
= case synTyConRhs tc of
- OpenSynTyCon _ -> return ()
- SynonymTyCon ty -> checkValidType syn_ctxt ty
+ OpenSynTyCon _ _ -> return ()
+ SynonymTyCon ty -> checkValidType syn_ctxt ty
| otherwise
= -- Check the context on the data decl
checkValidTheta (DataTyCtxt name) (tyConStupidTheta tc) `thenM_`
= setSrcSpan (srcLocSpan (getSrcLoc con)) $
addErrCtxt (dataConCtxt con) $
do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
- ; checkValidType ctxt (dataConUserType con) }
+ ; checkValidType ctxt (dataConUserType con)
+ ; ifM (isNewTyCon tc) (checkNewDataCon con)
+ }
where
ctxt = ConArgCtxt (dataConName con)
-------------------------------
+checkNewDataCon :: DataCon -> TcM ()
+-- Checks for the data constructor of a newtype
+checkNewDataCon con
+ = do { checkTc (isSingleton arg_tys) (newtypeFieldErr con (length arg_tys))
+ -- One argument
+ ; checkTc (null eq_spec) (newtypePredError con)
+ -- Return type is (T a b c)
+ ; checkTc (null ex_tvs && null theta) (newtypeExError con)
+ -- No existentials
+ }
+ where
+ (univ_tvs, ex_tvs, eq_spec, theta, arg_tys) = dataConFullSig con
+
+-------------------------------
checkValidClass :: Class -> TcM ()
checkValidClass cls
= do { -- CHECK ARITY 1 FOR HASKELL 1.4
; checkValidType (FunSigCtxt op_name) tau
-- Check that the type mentions at least one of
- -- the class type variables
- ; checkTc (any (`elemVarSet` tyVarsOfType tau) tyvars)
+ -- the class type variables...or at least one reachable
+ -- from one of the class variables. Example: tc223
+ -- class Error e => Game b mv e | b -> mv e where
+ -- newBoard :: MonadState b m => m ()
+ -- Here, MonadState has a fundep m->b, so newBoard is fine
+ ; let grown_tyvars = grow theta (mkVarSet tyvars)
+ ; checkTc (tyVarsOfType tau `intersectsVarSet` grown_tyvars)
(noClassTyVarErr cls sel_id)
-- Check that for a generic method, the type of
= sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
+newtypePredError con
+ = sep [ptext SLIT("A newtype constructor must have a return type of form T a b c"),
+ nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
+
newtypeFieldErr con_name n_flds
= sep [ptext SLIT("The constructor of a newtype must have exactly one field"),
nest 2 $ ptext SLIT("but") <+> quotes (ppr con_name) <+> ptext SLIT("has") <+> speakN n_flds]
badSigTyDecl tc_name
= vcat [ ptext SLIT("Illegal kind signature") <+>
quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
-
-badKindSigCtxt tc_name
- = vcat [ ptext SLIT("Illegal context in kind signature") <+>
- quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Currently, kind signatures cannot have a context")) ]
+ , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow kind signatures")) ]
-badIdxTyDecl tc_name
- = vcat [ ptext SLIT("Illegal indexed type instance for") <+>
+badFamInstDecl tc_name
+ = vcat [ ptext SLIT("Illegal family instance for") <+>
quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow indexed types")) ]
+ , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed type families")) ]
badGadtIdxTyDecl tc_name
= vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Indexed types cannot use GADT declarations")) ]
+ , nest 2 (parens $ ptext SLIT("Family instances can not yet use GADT declarations")) ]
tooManyParmsErr tc_name
- = ptext SLIT("Indexed type instance has too many parameters:") <+>
+ = ptext SLIT("Family instance has too many parameters:") <+>
quotes (ppr tc_name)
tooFewParmsErr tc_name
- = ptext SLIT("Indexed type instance has too few parameters:") <+>
+ = ptext SLIT("Family instance has too few parameters:") <+>
quotes (ppr tc_name)
-badBootTyIdxDeclErr =
- ptext SLIT("Illegal indexed type instance in hs-boot file")
+badBootFamInstDeclErr =
+ ptext SLIT("Illegal family instance in hs-boot file")
wrongKindOfFamily family =
- ptext SLIT("Wrong category of type instance; declaration was for a") <+>
+ ptext SLIT("Wrong category of family instance; declaration was for a") <+>
kindOfFamily
where
kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")