-- "newtype instance" and "data instance"
tcFamInstDecl1 (decl@TyData {tcdND = new_or_data, tcdLName = L loc tc_name,
tcdCons = cons})
- = kcIdxTyPats decl $ \k_tvs k_typats resKind family ->
+ = kcIdxTyPats decl $ \k_tvs k_typats resKind fam_tycon ->
do { -- check that the family declaration is for the right kind
- unless (isAlgTyCon family) $
- addErr (wrongKindOfFamily family)
+ unless (isAlgTyCon fam_tycon) $
+ addErr (wrongKindOfFamily fam_tycon)
; -- (1) kind check the data declaration as usual
; k_decl <- kcDataDecl decl k_tvs
k_cons = tcdCons k_decl
-- result kind must be '*' (otherwise, we have too few patterns)
- ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity family)
+ ; checkTc (isLiftedTypeKind resKind) $ tooFewParmsErr (tyConArity fam_tycon)
-- (2) type check indexed data type declaration
; tcTyVarBndrs k_tvs $ \t_tvs -> do { -- turn kinded into proper tyvars
; 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)
+ -- (a) left-hand side contains no type family applications
+ -- (vanilla synonyms are fine, though, and we checked for
+ -- foralls earlier)
; mapM_ checkTyFamFreeness t_typats
- -- - we don't use GADT syntax for indexed types
- ; checkTc h98_syntax (badGadtIdxTyDecl tc_name)
-
- -- - a newtype has exactly one constructor
+ -- (b) a newtype has exactly one constructor
; checkTc (new_or_data == DataType || isSingleton k_cons) $
- newtypeConError tc_name (length k_cons)
+ newtypeConError tc_name (length k_cons)
-- (4) construct representation tycon
; rep_tc_name <- newFamInstTyConName tc_name loc
; let ex_ok = True -- Existentials ok for type families!
- ; fixM (\ tycon -> do
- { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon t_tvs))
- k_cons
+ ; fixM (\ rep_tycon -> do
+ { let orig_res_ty = mkTyConApp fam_tycon t_typats
+ ; data_cons <- tcConDecls unbox_strict ex_ok rep_tycon
+ (t_tvs, orig_res_ty) k_cons
; tc_rhs <-
case new_or_data of
DataType -> return (mkDataTyConRhs data_cons)
NewType -> ASSERT( not (null data_cons) )
- mkNewTyConRhs rep_tc_name tycon (head data_cons)
+ mkNewTyConRhs rep_tc_name rep_tycon (head data_cons)
; buildAlgTyCon rep_tc_name t_tvs stupid_theta tc_rhs Recursive
- False h98_syntax (Just (family, t_typats))
+ False h98_syntax (Just (fam_tycon, t_typats))
-- We always assume that indexed types are recursive. Why?
-- (1) Due to their open nature, we can never be sure that a
-- further instance might not introduce a new recursive
-> TcM a
kcIdxTyPats decl thing_inside
= kcHsTyVars (tcdTyVars decl) $ \tvs ->
- do { family <- tcLookupLocatedTyCon (tcdLName decl)
- ; let { (kinds, resKind) = splitKindFunTys (tyConKind family)
+ do { fam_tycon <- tcLookupLocatedTyCon (tcdLName decl)
+ ; let { (kinds, resKind) = splitKindFunTys (tyConKind fam_tycon)
; hs_typats = fromJust $ tcdTyPats decl }
-- we may not have more parameters than the kind indicates
-- type functions can have a higher-kinded result
; let resultKind = mkArrowKinds (drop (length hs_typats) kinds) resKind
; typats <- zipWithM kcCheckHsType hs_typats kinds
- ; thing_inside tvs typats resultKind family
+ ; thing_inside tvs typats resultKind fam_tycon
}
where
\end{code}
(emptyConDeclsErr tc_name)
; tycon <- fixM (\ tycon -> do
- { data_cons <- mapM (addLocM (tcConDecl unbox_strict ex_ok tycon final_tvs))
- cons
+ { let res_ty = mkTyConApp tycon (mkTyVarTys final_tvs)
+ ; data_cons <- tcConDecls unbox_strict ex_ok
+ tycon (final_tvs, res_ty) cons
; tc_rhs <-
if null cons && is_boot -- In a hs-boot file, empty cons means
then return AbstractTyCon -- "don't know"; hence Abstract
else case new_or_data of
DataType -> return (mkDataTyConRhs data_cons)
- NewType ->
- ASSERT( not (null data_cons) )
- mkNewTyConRhs tc_name tycon (head data_cons)
+ NewType -> 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
})
tcTyClDecl1 _ d = pprPanic "tcTyClDecl1" (ppr d)
-----------------------------------
+tcConDecls :: Bool -> Bool -> TyCon -> ([TyVar], Type)
+ -> [LConDecl Name] -> TcM [DataCon]
+tcConDecls unbox ex_ok rep_tycon res_tmpl cons
+ = mapM (addLocM (tcConDecl unbox ex_ok rep_tycon res_tmpl)) cons
+
tcConDecl :: Bool -- True <=> -funbox-strict_fields
-> Bool -- True <=> -XExistentialQuantificaton or -XGADTs
- -> TyCon -> [TyVar]
+ -> TyCon -- Representation tycon
+ -> ([TyVar], Type) -- Return type template (with its template tyvars)
-> ConDecl Name
-> TcM DataCon
-tcConDecl unbox_strict existential_ok tycon tc_tvs -- Data types
+tcConDecl unbox_strict existential_ok rep_tycon res_tmpl -- Data types
(ConDecl name _ tvs ctxt details res_ty _)
= addErrCtxt (dataConCtxt name) $
tcTyVarBndrs tvs $ \ tvs' -> do
{ ctxt' <- tcHsKindedContext ctxt
; checkTc (existential_ok || (null tvs && null (unLoc ctxt)))
(badExistential name)
- ; (univ_tvs, ex_tvs, eq_preds, data_tc) <- tcResultType tycon tc_tvs tvs' res_ty
+ ; (univ_tvs, ex_tvs, eq_preds, res_ty') <- tcResultType res_tmpl 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 <- mapM tcHsBangType btys
+ = do { (arg_tys, stricts) <- mapAndUnzipM (tcConArg unbox_strict) btys
; buildDataCon (unLoc name) is_infix
- (argStrictness unbox_strict bangs arg_tys)
- (map unLoc field_lbls)
+ stricts field_lbls
univ_tvs ex_tvs eq_preds ctxt' arg_tys
- data_tc }
+ res_ty' rep_tycon }
-- NB: we put data_tc, the type constructor gotten from the
-- constructor type signature into the data constructor;
-- that way checkValidDataCon can complain if it's wrong.
InfixCon bty1 bty2 -> tc_datacon True [] [bty1,bty2]
RecCon fields -> tc_datacon False field_names btys
where
- field_names = map cd_fld_name fields
+ field_names = map (unLoc . cd_fld_name) fields
btys = map cd_fld_type fields
}
-tcResultType :: TyCon
- -> [TyVar] -- data T a b c = ...
+-- Example
+-- data instance T (b,c) where
+-- TI :: forall e. e -> T (e,e)
+--
+-- The representation tycon looks like this:
+-- data :R7T b c where
+-- TI :: forall b1 c1. (b1 ~ c1) => b1 -> :R7T b1 c1
+-- In this case orig_res_ty = T (e,e)
+
+tcResultType :: ([TyVar], Type) -- Template for result type; e.g.
+ -- data T a b c = ... gives ([a,b,c], T a b)
-> [TyVar] -- where MkT :: forall a b c. ...
-> ResType Name
-> TcM ([TyVar], -- Universal
[TyVar], -- Existential (distinct OccNames from univs)
[(TyVar,Type)], -- Equality predicates
- TyCon) -- TyCon given in the ResTy
+ Type) -- Typechecked return type
-- We don't check that the TyCon given in the ResTy is
-- the same as the parent tycon, becuase we are in the middle
-- of a recursive knot; so it's postponed until checkValidDataCon
-tcResultType decl_tycon tc_tvs dc_tvs ResTyH98
- = return (tc_tvs, dc_tvs, [], decl_tycon)
+tcResultType (tmpl_tvs, res_ty) dc_tvs ResTyH98
+ = return (tmpl_tvs, dc_tvs, [], res_ty)
-- In H98 syntax the dc_tvs are the existential ones
-- data T a b c = forall d e. MkT ...
-- The {a,b,c} are tc_tvs, and {d,e} are dc_tvs
-tcResultType _ tc_tvs dc_tvs (ResTyGADT res_ty)
- -- E.g. data T a b c where
- -- MkT :: forall x y z. T (x,y) z z
+tcResultType (tmpl_tvs, res_tmpl) dc_tvs (ResTyGADT res_ty)
+ -- E.g. data T [a] b c where
+ -- MkT :: forall x y z. T [(x,y)] z z
-- Then we generate
- -- ([a,z,c], [x,y], [a~(x,y), c~z], T)
-
- = do { (dc_tycon, res_tys) <- tcLHsConResTy res_ty
-
- ; let univ_tvs = choose_univs [] tidy_tc_tvs res_tys
- -- Each univ_tv is either a dc_tv or a tc_tv
+ -- Univ tyvars Eq-spec
+ -- a a~(x,y)
+ -- b b~z
+ -- z
+ -- Existentials are the leftover type vars: [x,y]
+ = do { res_ty' <- tcHsKindedType res_ty
+ ; let Just subst = tcMatchTy (mkVarSet tmpl_tvs) res_tmpl res_ty'
+
+ -- *Lazily* figure out the univ_tvs etc
+ -- Each univ_tv is either a dc_tv or a tmpl_tv
+ (univ_tvs, eq_spec) = foldr choose ([], []) tidy_tmpl_tvs
+ choose tmpl (univs, eqs)
+ | Just ty <- lookupTyVar subst tmpl
+ = case tcGetTyVar_maybe ty of
+ Just tv | not (tv `elem` univs)
+ -> (tv:univs, eqs)
+ _other -> (tmpl:univs, (tmpl,ty):eqs)
+ | otherwise = pprPanic "tcResultType" (ppr res_ty)
ex_tvs = dc_tvs `minusList` univ_tvs
- eq_spec = [ (tv, ty) | (tv,ty) <- univ_tvs `zip` res_tys,
- tv `elem` tc_tvs]
- ; return (univ_tvs, ex_tvs, eq_spec, dc_tycon) }
+
+ ; return (univ_tvs, ex_tvs, eq_spec, res_ty') }
where
- -- choose_univs uses the res_ty itself if it's a type variable
- -- and hasn't already been used; otherwise it uses one of the tc_tvs
- choose_univs _ tc_tvs []
- = ASSERT( null tc_tvs ) []
- choose_univs used (tc_tv:tc_tvs) (res_ty:res_tys)
- | Just tv <- tcGetTyVar_maybe res_ty, not (tv `elem` used)
- = tv : choose_univs (tv:used) tc_tvs res_tys
- | otherwise
- = tc_tv : choose_univs used tc_tvs res_tys
-
- -- NB: tc_tvs and dc_tvs are distinct, but
+ -- NB: tmpl_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)
- choose_univs _ _ _ = panic "tcResultType/choose_univs"
- 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'))
+ (_, tidy_tmpl_tvs) = mapAccumL tidy_one init_occ_env tmpl_tvs
+ init_occ_env = initTidyOccEnv (map getOccName dc_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
- -> [HsBang]
- -> [TcType] -> [StrictnessMark]
-argStrictness unbox_strict bangs arg_tys
- = ASSERT( length bangs == length arg_tys )
- zipWith (chooseBoxingStrategy unbox_strict) arg_tys bangs
+-------------------
+tcConArg :: Bool -- True <=> -funbox-strict_fields
+ -> LHsType Name
+ -> TcM (TcType, StrictnessMark)
+tcConArg unbox_strict bty
+ = do { arg_ty <- tcHsBangType bty
+ ; let bang = getBangStrictness bty
+ ; return (arg_ty, chooseBoxingStrategy unbox_strict arg_ty bang) }
-- We attempt to unbox/unpack a strict field when either:
-- (i) The field is marked '!!', or
-- (b) has the same type for 'f'
-- module alpha conversion of the quantified type variables
-- of the constructor.
+--
+-- Note that we allow existentials to match becuase the
+-- fields can never meet. E.g
+-- data T where
+-- T1 { f1 :: b, f2 :: a, f3 ::Int } :: T
+-- T2 { f1 :: c, f2 :: c, f3 ::Int } :: T
+-- Here we do not complain about f1,f2 because they are existential
checkValidTyCon :: TyCon -> TcM ()
checkValidTyCon tc
checkValidDataCon tc con
= setSrcSpan (srcLocSpan (getSrcLoc con)) $
addErrCtxt (dataConCtxt con) $
- do { checkTc (dataConTyCon con == tc) (badDataConTyCon con)
+ do { let tc_tvs = tyConTyVars tc
+ res_ty_tmpl = mkFamilyTyConApp tc (mkTyVarTys tc_tvs)
+ actual_res_ty = dataConOrigResTy con
+ ; checkTc (isJust (tcMatchTy (mkVarSet tc_tvs)
+ res_ty_tmpl
+ actual_res_ty))
+ (badDataConTyCon con res_ty_tmpl actual_res_ty)
; checkValidMonoType (dataConOrigResTy con)
-- Disallow MkT :: T (forall a. a->a)
-- Reason: it's really the argument of an equality constraint
where
le (L l1 _) (L l2 _) = l1 <= l2
-badDataConTyCon :: DataCon -> SDoc
-badDataConTyCon data_con
+badDataConTyCon :: DataCon -> Type -> Type -> SDoc
+badDataConTyCon data_con res_ty_tmpl actual_res_ty
= hang (ptext (sLit "Data constructor") <+> quotes (ppr data_con) <+>
- ptext (sLit "returns type") <+> quotes (ppr (dataConTyCon data_con)))
- 2 (ptext (sLit "instead of its parent type"))
+ ptext (sLit "returns type") <+> quotes (ppr actual_res_ty))
+ 2 (ptext (sLit "instead of an instance of its parent type") <+> quotes (ppr res_ty_tmpl))
badGadtDecl :: Name -> SDoc
badGadtDecl tc_name
quotes (ppr tc_name)
, nest 2 (parens $ ptext (sLit "Use -XTypeFamilies to allow indexed type families")) ]
+{-
badGadtIdxTyDecl :: Name -> SDoc
badGadtIdxTyDecl tc_name
= vcat [ ptext (sLit "Illegal generalised algebraic data declaration for") <+>
quotes (ppr tc_name)
, nest 2 (parens $ ptext (sLit "Family instances can not yet use GADT declarations")) ]
-
+-}
tooManyParmsErr :: Located Name -> SDoc
tooManyParmsErr tc_name
= ptext (sLit "Family instance has too many parameters:") <+>
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