TcTyClsDecls: Typecheck type and class declarations
\begin{code}
+{-# OPTIONS_GHC -w #-}
+-- The above warning supression flag is a temporary kludge.
+-- While working on this module you are encouraged to remove it and fix
+-- any warnings in the module. See
+-- http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
+-- for details
+
module TcTyClsDecls (
tcTyAndClassDecls, tcFamInstDecl
) where
import BasicTypes
import HscTypes
import BuildTyCl
+import TcUnify
import TcRnMonad
import TcEnv
import TcTyDecls
import Digraph
import DynFlags
-import Data.List ( partition, elemIndex )
+import Data.List
import Control.Monad ( mplus )
\end{code}
-> TcM TcGblEnv -- Input env extended by types and classes
-- and their implicit Ids,DataCons
tcTyAndClassDecls boot_details allDecls
- = do { -- Omit instances of indexed types; they are handled together
+ = do { -- Omit instances of type families; they are handled together
-- with the *heads* of class instances
; let decls = filter (not . isFamInstDecl . unLoc) allDecls
recoverM (returnM Nothing) $
setSrcSpan loc $
tcAddDeclCtxt decl $
- do { -- type families require -findexed-types and can't be in an
+ do { -- type families require -ftype-families and can't be in an
-- hs-boot file
- ; gla_exts <- doptM Opt_IndexedTypes
+ ; type_families <- doptM Opt_TypeFamilies
; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
- ; checkTc gla_exts $ badFamInstDecl (tcdLName decl)
+ ; checkTc type_families $ badFamInstDecl (tcdLName decl)
; checkTc (not is_boot) $ badBootFamInstDeclErr
-- perform kind and type checking
unless (isSynTyCon family) $
addErr (wrongKindOfFamily family)
- ; -- (1) kind check the right hand side of the type equation
+ ; -- (1) kind check the right-hand side of the type equation
; k_rhs <- kcCheckHsType (tcdSynRhs decl) resKind
+ -- we need the exact same number of type parameters as the family
+ -- declaration
+ ; let famArity = tyConArity family
+ ; checkTc (length k_typats == famArity) $
+ wrongNumberOfParmsErr famArity
+
-- (2) type check type equation
; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
; t_typats <- mappM tcHsKindedType k_typats
; t_rhs <- tcHsKindedType k_rhs
- -- (3) construct representation tycon
- ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
+ -- (3) check that
+ -- - check the well-formedness of the instance
+ ; checkValidTypeInst t_typats t_rhs
+
+ -- (4) construct representation tycon
+ ; rep_tc_name <- newFamInstTyConName tc_name loc
; tycon <- buildSynTyCon rep_tc_name t_tvs (SynonymTyCon t_rhs)
(Just (family, t_typats))
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 ||
- new_or_data == DataType && isDataTyCon family) $
+ unless (isAlgTyCon family) $
addErr (wrongKindOfFamily family)
; -- (1) kind check the data declaration as usual
k_cons = tcdCons k_decl
-- result kind must be '*' (otherwise, we have too few patterns)
- ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr tc_name
+ ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
-- (2) type check indexed data type declaration
; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
; unbox_strict <- doptM Opt_UnboxStrictFields
- -- Check that we don't use GADT syntax for indexed types
+ -- kind check the type indexes and the context
+ ; t_typats <- mappM tcHsKindedType k_typats
+ ; stupid_theta <- tcHsKindedContext k_ctxt
+
+ -- (3) Check that
+ -- - left-hand side contains no type family applications
+ -- (vanilla synonyms are fine, though, and we checked for
+ -- foralls earlier)
+ ; mappM_ checkTyFamFreeness t_typats
+
+ -- - we don't use GADT syntax for indexed types
; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
- -- Check that a newtype has exactly one constructor
+ -- - a newtype has exactly one constructor
; checkTc (new_or_data == DataType || isSingleton k_cons) $
newtypeConError tc_name (length k_cons)
- ; t_typats <- mappM tcHsKindedType k_typats
- ; stupid_theta <- tcHsKindedContext k_ctxt
-
- -- (3) construct representation tycon
- ; rep_tc_name <- newFamInstTyConName tc_name (srcSpanStart loc)
+ -- (4) construct representation tycon
+ ; rep_tc_name <- newFamInstTyConName tc_name loc
; tycon <- fixM (\ tycon -> do
{ data_cons <- mappM (addLocM (tcConDecl unbox_strict tycon t_tvs))
k_cons
; tc_rhs <-
case new_or_data of
DataType -> return (mkDataTyConRhs data_cons)
- NewType -> ASSERT( isSingleton data_cons )
- mkNewTyConRhs tc_name tycon (head data_cons)
+ NewType -> ASSERT( not (null data_cons) )
+ mkNewTyConRhs rep_tc_name tycon (head data_cons)
; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
False h98_syntax (Just (family, t_typats))
-- We always assume that indexed types are recursive. Why?
--
-- * Here we check that a type instance matches its kind signature, but we do
-- not check whether there is a pattern for each type index; the latter
--- check is only required for type functions.
+-- check is only required for type synonym instances.
--
kcIdxTyPats :: TyClDecl Name
-> ([LHsTyVarBndr Name] -> [LHsType Name] -> Kind -> TyCon -> TcM a)
use them, whereas for the mutually recursive data types D we bring into
scope kind bindings D -> k, where k is a kind variable, and do inference.
-Indexed Types
+Type families
~~~~~~~~~~~~~
This treatment of type synonyms only applies to Haskell 98-style synonyms.
General type functions can be recursive, and hence, appear in `alg_decls'.
kcTyClDeclBody decl $
kcDataDecl decl
-kcTyClDecl decl@(TyFamily {tcdKind = kind})
- = kcTyClDeclBody decl $ \ tvs' ->
- return (decl {tcdTyVars = tvs',
- tcdKind = kind `mplus` Just liftedTypeKind})
- -- default result kind is '*'
+kcTyClDecl decl@(TyFamily {})
+ = kcFamilyDecl [] decl -- the empty list signals a toplevel decl
kcTyClDecl decl@(ClassDecl {tcdCtxt = ctxt, tcdSigs = sigs, tcdATs = ats})
= kcTyClDeclBody decl $ \ tvs' ->
do { is_boot <- tcIsHsBoot
; ctxt' <- kcHsContext ctxt
- ; ats' <- mappM (wrapLocM kcTyClDecl) ats
- ; sigs' <- mappM (wrapLocM kc_sig ) sigs
+ ; ats' <- mappM (wrapLocM (kcFamilyDecl tvs')) ats
+ ; sigs' <- mappM (wrapLocM kc_sig) sigs
; return (decl {tcdTyVars = tvs', tcdCtxt = ctxt', tcdSigs = sigs',
tcdATs = ats'}) }
where
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') }
+ = do { btys' <- mappM kc_larg_ty btys
+ ; return (PrefixCon btys') }
kc_con_details (InfixCon bty1 bty2)
- = do { bty1' <- kc_larg_ty bty1; bty2' <- kc_larg_ty bty2; return (InfixCon bty1' bty2') }
+ = do { bty1' <- kc_larg_ty bty1
+ ; bty2' <- kc_larg_ty bty2
+ ; return (InfixCon bty1' bty2') }
kc_con_details (RecCon fields)
- = do { fields' <- mappM kc_field fields; return (RecCon fields') }
+ = do { fields' <- mappM kc_field fields
+ ; return (RecCon fields') }
- kc_field (HsRecField fld bty d) = do { bty' <- kc_larg_ty bty ; return (HsRecField fld bty' d) }
+ kc_field (ConDeclField fld bty d) = do { bty' <- kc_larg_ty bty
+ ; return (ConDeclField fld bty' d) }
kc_larg_ty bty = case new_or_data of
DataType -> kcHsSigType bty
-- Can't allow an unlifted type for newtypes, because we're effectively
-- going to remove the constructor while coercing it to a lifted type.
-- And newtypes can't be bang'd
+
+-- Kind check a family declaration or type family default declaration.
+--
+kcFamilyDecl :: [LHsTyVarBndr Name] -- tyvars of enclosing class decl if any
+ -> TyClDecl Name -> TcM (TyClDecl Name)
+kcFamilyDecl classTvs decl@(TyFamily {tcdKind = kind})
+ = kcTyClDeclBody decl $ \tvs' ->
+ do { mapM_ unifyClassParmKinds tvs'
+ ; return (decl {tcdTyVars = tvs',
+ tcdKind = kind `mplus` Just liftedTypeKind})
+ -- default result kind is '*'
+ }
+ where
+ unifyClassParmKinds (L _ (KindedTyVar n k))
+ | Just classParmKind <- lookup n classTyKinds = unifyKind k classParmKind
+ | otherwise = return ()
+ classTyKinds = [(n, k) | L _ (KindedTyVar n k) <- classTvs]
+kcFamilyDecl _ decl@(TySynonym {}) -- type family defaults
+ = panic "TcTyClsDecls.kcFamilyDecl: not implemented yet"
\end{code}
-- kind checking
= tcTyVarBndrs tvs $ \ tvs' -> do
{ traceTc (text "type family: " <+> ppr tc_name)
- ; idx_tys <- doptM Opt_IndexedTypes
+ ; idx_tys <- doptM Opt_TypeFamilies
- -- Check that we don't use families without -findexed-types
+ -- Check that we don't use families without -ftype-families
; checkTc idx_tys $ badFamInstDecl tc_name
; tycon <- buildSynTyCon tc_name tvs' (OpenSynTyCon kind Nothing) Nothing
-- "newtype family" or "data family" declaration
tcTyClDecl1 _calc_isrec
- (TyFamily {tcdFlavour = DataFamily new_or_data,
+ (TyFamily {tcdFlavour = DataFamily,
tcdLName = L _ tc_name, tcdTyVars = tvs, tcdKind = mb_kind})
= tcTyVarBndrs tvs $ \ tvs' -> do
- { traceTc (text "data/newtype family: " <+> ppr tc_name)
+ { traceTc (text "data family: " <+> ppr tc_name)
; extra_tvs <- tcDataKindSig mb_kind
; let final_tvs = tvs' ++ extra_tvs -- we may not need these
- ; idx_tys <- doptM Opt_IndexedTypes
+ ; idx_tys <- doptM Opt_TypeFamilies
- -- Check that we don't use families without -findexed-types
+ -- Check that we don't use families without -ftype-families
; checkTc idx_tys $ badFamInstDecl tc_name
; tycon <- buildAlgTyCon tc_name final_tvs []
- (case new_or_data of
- DataType -> mkOpenDataTyConRhs
- NewType -> mkOpenNewTyConRhs)
- Recursive False True Nothing
+ mkOpenDataTyConRhs Recursive False True Nothing
; return [ATyCon tycon]
}
; stupid_theta <- tcHsKindedContext ctxt
; want_generic <- doptM Opt_Generics
; unbox_strict <- doptM Opt_UnboxStrictFields
- ; gla_exts <- doptM Opt_GlasgowExts
+ ; empty_data_decls <- doptM Opt_EmptyDataDecls
+ ; kind_signatures <- doptM Opt_KindSignatures
+ ; gadt_ok <- doptM Opt_GADTs
; is_boot <- tcIsHsBoot -- Are we compiling an hs-boot file?
-- Check that we don't use GADT syntax in H98 world
- ; checkTc (gla_exts || h98_syntax) (badGadtDecl tc_name)
+ ; checkTc (gadt_ok || h98_syntax) (badGadtDecl tc_name)
-- Check that we don't use kind signatures without Glasgow extensions
- ; checkTc (gla_exts || isNothing mb_ksig) (badSigTyDecl tc_name)
+ ; checkTc (kind_signatures || isNothing mb_ksig) (badSigTyDecl tc_name)
-- Check that the stupid theta is empty for a GADT-style declaration
; checkTc (null stupid_theta || h98_syntax) (badStupidTheta tc_name)
-- Check that there's at least one condecl,
- -- or else we're reading an hs-boot file, or -fglasgow-exts
- ; checkTc (not (null cons) || gla_exts || is_boot)
+ -- or else we're reading an hs-boot file, or -XEmptyDataDecls
+ ; checkTc (not (null cons) || empty_data_decls || is_boot)
(emptyConDeclsErr tc_name)
-- Check that a newtype has exactly one constructor
else case new_or_data of
DataType -> return (mkDataTyConRhs data_cons)
NewType ->
- ASSERT( isSingleton data_cons )
+ ASSERT( not (null data_cons) )
mkNewTyConRhs tc_name tycon (head data_cons)
; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec
(want_generic && canDoGenerics data_cons) h98_syntax Nothing
InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
RecCon fields -> tc_datacon False field_names btys
where
- (field_names, btys) = unzip [ (n, t) | HsRecField n t _ <- fields ]
-
+ field_names = map cd_fld_name fields
+ btys = map cd_fld_type fields
}
tcResultType :: TyCon
-- One argument
; checkTc (null eq_spec) (newtypePredError con)
-- Return type is (T a b c)
- ; checkTc (null ex_tvs && null theta) (newtypeExError con)
+ ; checkTc (null ex_tvs && null eq_theta && null dict_theta) (newtypeExError con)
-- No existentials
+ ; checkTc (not (any isMarkedStrict (dataConStrictMarks con)))
+ (newtypeStrictError con)
+ -- No strictness
}
where
- (_univ_tvs, ex_tvs, eq_spec, theta, arg_tys, _res_ty) = dataConFullSig con
+ (_univ_tvs, ex_tvs, eq_spec, eq_theta, dict_theta, arg_tys, _res_ty) = dataConFullSig con
-------------------------------
checkValidClass :: Class -> TcM ()
checkValidClass cls
- = do { -- CHECK ARITY 1 FOR HASKELL 1.4
- gla_exts <- doptM Opt_GlasgowExts
+ = do { constrained_class_methods <- doptM Opt_ConstrainedClassMethods
+ ; multi_param_type_classes <- doptM Opt_MultiParamTypeClasses
+ ; fundep_classes <- doptM Opt_FunctionalDependencies
-- Check that the class is unary, unless GlaExs
; checkTc (notNull tyvars) (nullaryClassErr cls)
- ; checkTc (gla_exts || unary) (classArityErr cls)
+ ; checkTc (multi_param_type_classes || unary) (classArityErr cls)
+ ; checkTc (fundep_classes || null fundeps) (classFunDepsErr cls)
-- Check the super-classes
; checkValidTheta (ClassSCCtxt (className cls)) theta
-- Check the class operations
- ; mappM_ (check_op gla_exts) op_stuff
+ ; mappM_ (check_op constrained_class_methods) op_stuff
-- Check that if the class has generic methods, then the
-- class has only one parameter. We can't do generic
; checkTc (unary || no_generics) (genericMultiParamErr cls)
}
where
- (tyvars, theta, _, op_stuff) = classBigSig cls
+ (tyvars, fundeps, theta, _, _, op_stuff) = classExtraBigSig cls
unary = isSingleton tyvars
no_generics = null [() | (_, GenDefMeth) <- op_stuff]
- check_op gla_exts (sel_id, dm)
+ check_op constrained_class_methods (sel_id, dm)
= addErrCtxt (classOpCtxt sel_id tau) $ do
{ checkValidTheta SigmaCtxt (tail theta)
-- The 'tail' removes the initial (C a) from the
-- class itself, leaving just the method type
+ ; traceTc (text "class op type" <+> ppr op_ty <+> ppr tau)
; checkValidType (FunSigCtxt op_name) tau
-- Check that the type mentions at least one of
op_ty = idType sel_id
(_,theta1,tau1) = tcSplitSigmaTy op_ty
(_,theta2,tau2) = tcSplitSigmaTy tau1
- (theta,tau) | gla_exts = (theta1 ++ theta2, tau2)
- | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
+ (theta,tau) | constrained_class_methods = (theta1 ++ theta2, tau2)
+ | otherwise = (theta1, mkPhiTy (tail theta1) tau1)
-- Ugh! The function might have a type like
-- op :: forall a. C a => forall b. (Eq b, Eq a) => tau2
- -- With -fglasgow-exts, we want to allow this, even though the inner
+ -- With -XConstrainedClassMethods, we want to allow this, even though the inner
-- forall has an (Eq a) constraint. Whereas in general, each constraint
-- in the context of a for-all must mention at least one quantified
-- type variable. What a mess!
classArityErr cls
= vcat [ptext SLIT("Too many parameters for class") <+> quotes (ppr cls),
- parens (ptext SLIT("Use -fglasgow-exts to allow multi-parameter classes"))]
+ parens (ptext SLIT("Use -XMultiParamTypeClasses to allow multi-parameter classes"))]
+
+classFunDepsErr cls
+ = vcat [ptext SLIT("Fundeps in class") <+> quotes (ppr cls),
+ parens (ptext SLIT("Use -XFunctionalDependencies to allow fundeps"))]
noClassTyVarErr clas op
= sep [ptext SLIT("The class method") <+> quotes (ppr op),
badGadtDecl tc_name
= vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+> quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow GADTs")) ]
+ , nest 2 (parens $ ptext SLIT("Use -XGADTs to allow GADTs")) ]
badStupidTheta tc_name
= ptext SLIT("A data type declared in GADT style cannot have a context:") <+> quotes (ppr tc_name)
= sep [ptext SLIT("A newtype constructor cannot have an existential context,"),
nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does")]
+newtypeStrictError con
+ = sep [ptext SLIT("A newtype constructor cannot have a strictness annotation,"),
+ 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 a1 ... an"),
nest 2 $ ptext SLIT("but") <+> quotes (ppr con) <+> ptext SLIT("does not")]
badSigTyDecl tc_name
= vcat [ ptext SLIT("Illegal kind signature") <+>
quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -fglasgow-exts to allow kind signatures")) ]
+ , nest 2 (parens $ ptext SLIT("Use -XKindSignatures to allow kind signatures")) ]
badFamInstDecl tc_name
= vcat [ ptext SLIT("Illegal family instance for") <+>
quotes (ppr tc_name)
- , nest 2 (parens $ ptext SLIT("Use -findexed-types to allow indexed type families")) ]
+ , nest 2 (parens $ ptext SLIT("Use -XTypeFamilies to allow indexed type families")) ]
badGadtIdxTyDecl tc_name
= vcat [ ptext SLIT("Illegal generalised algebraic data declaration for") <+>
= ptext SLIT("Family instance has too many parameters:") <+>
quotes (ppr tc_name)
-tooFewParmsErr tc_name
- = ptext SLIT("Family instance has too few parameters:") <+>
- quotes (ppr tc_name)
+tooFewParmsErr arity
+ = ptext SLIT("Family instance has too few parameters; expected") <+>
+ ppr arity
+
+wrongNumberOfParmsErr exp_arity
+ = ptext SLIT("Number of parameters must match family declaration; expected")
+ <+> ppr exp_arity
badBootFamInstDeclErr =
ptext SLIT("Illegal family instance in hs-boot file")
ptext SLIT("Wrong category of family instance; declaration was for a") <+>
kindOfFamily
where
- kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
- | isDataTyCon family = ptext SLIT("data type")
- | isNewTyCon family = ptext SLIT("newtype")
+ kindOfFamily | isSynTyCon family = ptext SLIT("type synonym")
+ | isAlgTyCon family = ptext SLIT("data type")
+ | otherwise = pprPanic "wrongKindOfFamily" (ppr family)
emptyConDeclsErr tycon
= sep [quotes (ppr tycon) <+> ptext SLIT("has no constructors"),
- nest 2 $ ptext SLIT("(-fglasgow-exts permits this)")]
+ nest 2 $ ptext SLIT("(-XEmptyDataDecls permits this)")]
\end{code}
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