2 % (c) The University of Glasgow 2011
7 module Generics ( canDoGenerics,
8 mkBindsRep, tc_mkRepTyCon, mkBindsMetaD,
9 MetaTyCons(..), metaTyCons2TyCons
19 import Name hiding (varName)
20 import Module (moduleName, moduleNameString)
25 -- For generation of representation types
26 import TcEnv (tcLookupTyCon)
27 import TcRnMonad (TcM, newUnique)
35 #include "HsVersions.h"
38 %************************************************************************
40 \subsection{Generating representation types}
42 %************************************************************************
45 canDoGenerics :: TyCon -> Maybe SDoc
46 -- Called on source-code data types, to see if we should generate
47 -- generic functions for them.
49 -- Just s == no, because of `s`
53 -- We do not support datatypes with context
54 (if (not (null (tyConStupidTheta tycon)))
55 then (Just (ppr tycon <+> text "has a datatype context"))
57 -- We don't like type families
58 : (if (isFamilyTyCon tycon)
59 then (Just (ppr tycon <+> text "is a family instance"))
62 : (map bad_con (tyConDataCons tycon)))
64 -- If any of the constructor has an unboxed type as argument,
65 -- then we can't build the embedding-projection pair, because
66 -- it relies on instantiating *polymorphic* sum and product types
67 -- at the argument types of the constructors
68 bad_con dc = if (any bad_arg_type (dataConOrigArgTys dc))
69 then (Just (ppr dc <+> text "has unlifted or polymorphic arguments"))
70 else (if (not (isVanillaDataCon dc))
71 then (Just (ppr dc <+> text "is not a vanilla data constructor"))
75 -- Nor can we do the job if it's an existential data constructor,
77 -- Nor if the args are polymorphic types (I don't think)
78 bad_arg_type ty = isUnLiftedType ty || not (isTauTy ty)
80 mergeErrors :: [Maybe SDoc] -> Maybe SDoc
81 mergeErrors [] = Nothing
82 mergeErrors ((Just s):t) = case mergeErrors t of
84 Just s' -> Just (s $$ s')
85 mergeErrors (Nothing :t) = mergeErrors t
88 %************************************************************************
90 \subsection{Generating the RHS of a generic default method}
92 %************************************************************************
95 type US = Int -- Local unique supply, just a plain Int
96 type Alt = (LPat RdrName, LHsExpr RdrName)
98 -- Bindings for the Generic instance
99 mkBindsRep :: TyCon -> LHsBinds RdrName
101 unitBag (L loc (mkFunBind (L loc from_RDR) from_matches))
103 unitBag (L loc (mkFunBind (L loc to_RDR) to_matches))
105 from_matches = [mkSimpleHsAlt pat rhs | (pat,rhs) <- from_alts]
106 to_matches = [mkSimpleHsAlt pat rhs | (pat,rhs) <- to_alts ]
107 loc = srcLocSpan (getSrcLoc tycon)
108 datacons = tyConDataCons tycon
110 -- Recurse over the sum first
111 from_alts, to_alts :: [Alt]
112 (from_alts, to_alts) = mkSum (1 :: US) tycon datacons
114 --------------------------------------------------------------------------------
115 -- Type representation
116 --------------------------------------------------------------------------------
118 tc_mkRepTy :: -- The type to generate representation for
120 -- Metadata datatypes to refer to
122 -- Generated representation0 type
124 tc_mkRepTy tycon metaDts =
126 d1 <- tcLookupTyCon d1TyConName
127 c1 <- tcLookupTyCon c1TyConName
128 s1 <- tcLookupTyCon s1TyConName
129 nS1 <- tcLookupTyCon noSelTyConName
130 rec0 <- tcLookupTyCon rec0TyConName
131 par0 <- tcLookupTyCon par0TyConName
132 u1 <- tcLookupTyCon u1TyConName
133 v1 <- tcLookupTyCon v1TyConName
134 plus <- tcLookupTyCon sumTyConName
135 times <- tcLookupTyCon prodTyConName
137 let mkSum' a b = mkTyConApp plus [a,b]
138 mkProd a b = mkTyConApp times [a,b]
139 mkRec0 a = mkTyConApp rec0 [a]
140 mkPar0 a = mkTyConApp par0 [a]
141 mkD a = mkTyConApp d1 [metaDTyCon, sumP (tyConDataCons a)]
142 mkC i d a = mkTyConApp c1 [d, prod i (dataConOrigArgTys a)
143 (null (dataConFieldLabels a))]
144 -- This field has no label
145 mkS True _ a = mkTyConApp s1 [mkTyConTy nS1, a]
146 -- This field has a label
147 mkS False d a = mkTyConApp s1 [d, a]
149 sumP [] = mkTyConTy v1
150 sumP l = ASSERT (length metaCTyCons == length l)
151 foldBal mkSum' [ mkC i d a
152 | (d,(a,i)) <- zip metaCTyCons (zip l [0..])]
153 -- The Bool is True if this constructor has labelled fields
154 prod :: Int -> [Type] -> Bool -> Type
155 prod i [] _ = ASSERT (length metaSTyCons > i)
156 ASSERT (length (metaSTyCons !! i) == 0)
158 prod i l b = ASSERT (length metaSTyCons > i)
159 ASSERT (length l == length (metaSTyCons !! i))
160 foldBal mkProd [ arg d t b
161 | (d,t) <- zip (metaSTyCons !! i) l ]
163 arg :: Type -> Type -> Bool -> Type
164 arg d t b = mkS b d (recOrPar t (getTyVar_maybe t))
165 -- Argument is not a type variable, use Rec0
166 recOrPar t Nothing = mkRec0 t
167 -- Argument is a type variable, use Par0
168 recOrPar t (Just _) = mkPar0 t
170 metaDTyCon = mkTyConTy (metaD metaDts)
171 metaCTyCons = map mkTyConTy (metaC metaDts)
172 metaSTyCons = map (map mkTyConTy) (metaS metaDts)
176 tc_mkRepTyCon :: TyCon -- The type to generate representation for
177 -> MetaTyCons -- Metadata datatypes to refer to
178 -> TcM TyCon -- Generated representation0 type
179 tc_mkRepTyCon tycon metaDts =
180 -- Consider the example input tycon `D`, where data D a b = D_ a
184 -- `rep0Ty` = D1 ... (C1 ... (S1 ... (Rec0 a))) :: * -> *
185 rep0Ty <- tc_mkRepTy tycon metaDts
186 -- `rep0` = GHC.Generics.Rep (type family)
187 rep0 <- tcLookupTyCon repTyConName
189 let modl = nameModule (tyConName tycon)
190 loc = nameSrcSpan (tyConName tycon)
191 -- `repName` is a name we generate for the synonym
192 repName = mkExternalName uniq1 modl (mkGenR0 (nameOccName (tyConName tycon))) loc
193 -- `coName` is a name for the coercion
194 coName = mkExternalName uniq2 modl (mkGenR0 (nameOccName (tyConName tycon))) loc
196 tyvars = tyConTyVars tycon
198 appT = [mkTyConApp tycon (mkTyVarTys tyvars)]
200 res = mkSynTyCon repName
201 -- rep0Ty has kind `kind of D` -> *
202 (tyConKind tycon `mkArrowKind` liftedTypeKind)
203 tyvars (SynonymTyCon rep0Ty)
204 (FamInstTyCon rep0 appT
205 (mkCoercionTyCon coName (tyConArity tycon)
206 -- co : forall a b. Rep (D a b) ~ `rep0Ty` a b
207 (CoAxiom tyvars (mkTyConApp rep0 appT) rep0Ty)))
211 --------------------------------------------------------------------------------
213 --------------------------------------------------------------------------------
215 data MetaTyCons = MetaTyCons { -- One meta datatype per dataype
217 -- One meta datatype per constructor
219 -- One meta datatype per selector per constructor
220 , metaS :: [[TyCon]] }
222 instance Outputable MetaTyCons where
223 ppr (MetaTyCons d c s) = ppr d <+> ppr c <+> ppr s
225 metaTyCons2TyCons :: MetaTyCons -> [TyCon]
226 metaTyCons2TyCons (MetaTyCons d c s) = d : c ++ concat s
229 -- Bindings for Datatype, Constructor, and Selector instances
230 mkBindsMetaD :: FixityEnv -> TyCon
231 -> ( LHsBinds RdrName -- Datatype instance
232 , [LHsBinds RdrName] -- Constructor instances
233 , [[LHsBinds RdrName]]) -- Selector instances
234 mkBindsMetaD fix_env tycon = (dtBinds, allConBinds, allSelBinds)
236 mkBag l = foldr1 unionBags
237 [ unitBag (L loc (mkFunBind (L loc name) matches))
238 | (name, matches) <- l ]
239 dtBinds = mkBag [ (datatypeName_RDR, dtName_matches)
240 , (moduleName_RDR, moduleName_matches)]
242 allConBinds = map conBinds datacons
243 conBinds c = mkBag ( [ (conName_RDR, conName_matches c)]
244 ++ ifElseEmpty (dataConIsInfix c)
245 [ (conFixity_RDR, conFixity_matches c) ]
246 ++ ifElseEmpty (length (dataConFieldLabels c) > 0)
247 [ (conIsRecord_RDR, conIsRecord_matches c) ]
250 ifElseEmpty p x = if p then x else []
251 fixity c = case lookupFixity fix_env (dataConName c) of
252 Fixity n InfixL -> buildFix n leftAssocDataCon_RDR
253 Fixity n InfixR -> buildFix n rightAssocDataCon_RDR
254 Fixity n InfixN -> buildFix n notAssocDataCon_RDR
255 buildFix n assoc = nlHsApps infixDataCon_RDR [nlHsVar assoc
256 , nlHsIntLit (toInteger n)]
258 allSelBinds = map (map selBinds) datasels
259 selBinds s = mkBag [(selName_RDR, selName_matches s)]
261 loc = srcLocSpan (getSrcLoc tycon)
262 mkStringLHS s = [mkSimpleHsAlt nlWildPat (nlHsLit (mkHsString s))]
263 datacons = tyConDataCons tycon
264 datasels = map dataConFieldLabels datacons
266 dtName_matches = mkStringLHS . showPpr . nameOccName . tyConName
268 moduleName_matches = mkStringLHS . moduleNameString . moduleName
269 . nameModule . tyConName $ tycon
271 conName_matches c = mkStringLHS . showPpr . nameOccName
273 conFixity_matches c = [mkSimpleHsAlt nlWildPat (fixity c)]
274 conIsRecord_matches _ = [mkSimpleHsAlt nlWildPat (nlHsVar true_RDR)]
276 selName_matches s = mkStringLHS (showPpr (nameOccName s))
279 --------------------------------------------------------------------------------
281 --------------------------------------------------------------------------------
283 mkSum :: US -- Base for generating unique names
284 -> TyCon -- The type constructor
285 -> [DataCon] -- The data constructors
286 -> ([Alt], -- Alternatives for the T->Trep "from" function
287 [Alt]) -- Alternatives for the Trep->T "to" function
289 -- Datatype without any constructors
290 mkSum _us tycon [] = ([from_alt], [to_alt])
292 from_alt = (nlWildPat, mkM1_E (makeError errMsgFrom))
293 to_alt = (mkM1_P nlWildPat, makeError errMsgTo)
294 -- These M1s are meta-information for the datatype
295 makeError s = nlHsApp (nlHsVar error_RDR) (nlHsLit (mkHsString s))
296 errMsgFrom = "No generic representation for empty datatype " ++ showPpr tycon
297 errMsgTo = "No values for empty datatype " ++ showPpr tycon
299 -- Datatype with at least one constructor
300 mkSum us _tycon datacons =
301 unzip [ mk1Sum us i (length datacons) d | (d,i) <- zip datacons [1..] ]
303 -- Build the sum for a particular constructor
304 mk1Sum :: US -- Base for generating unique names
305 -> Int -- The index of this constructor
306 -> Int -- Total number of constructors
307 -> DataCon -- The data constructor
308 -> (Alt, -- Alternative for the T->Trep "from" function
309 Alt) -- Alternative for the Trep->T "to" function
310 mk1Sum us i n datacon = (from_alt, to_alt)
312 n_args = dataConSourceArity datacon -- Existentials already excluded
314 datacon_vars = map mkGenericLocal [us .. us+n_args-1]
317 datacon_rdr = getRdrName datacon
318 app_exp = nlHsVarApps datacon_rdr datacon_vars
320 from_alt = (nlConVarPat datacon_rdr datacon_vars, from_alt_rhs)
321 from_alt_rhs = mkM1_E (genLR_E i n (mkProd_E us' datacon_vars))
323 to_alt = (mkM1_P (genLR_P i n (mkProd_P us' datacon_vars)), to_alt_rhs)
324 -- These M1s are meta-information for the datatype
327 -- Generates the L1/R1 sum pattern
328 genLR_P :: Int -> Int -> LPat RdrName -> LPat RdrName
330 | n == 0 = error "impossible"
332 | i <= div n 2 = nlConPat l1DataCon_RDR [genLR_P i (div n 2) p]
333 | otherwise = nlConPat r1DataCon_RDR [genLR_P (i-m) (n-m) p]
336 -- Generates the L1/R1 sum expression
337 genLR_E :: Int -> Int -> LHsExpr RdrName -> LHsExpr RdrName
339 | n == 0 = error "impossible"
341 | i <= div n 2 = nlHsVar l1DataCon_RDR `nlHsApp` genLR_E i (div n 2) e
342 | otherwise = nlHsVar r1DataCon_RDR `nlHsApp` genLR_E (i-m) (n-m) e
345 --------------------------------------------------------------------------------
346 -- Dealing with products
347 --------------------------------------------------------------------------------
349 -- Build a product expression
350 mkProd_E :: US -- Base for unique names
351 -> [RdrName] -- List of variables matched on the lhs
352 -> LHsExpr RdrName -- Resulting product expression
353 mkProd_E _ [] = mkM1_E (nlHsVar u1DataCon_RDR)
354 mkProd_E _ vars = mkM1_E (foldBal prod appVars)
355 -- These M1s are meta-information for the constructor
357 appVars = map wrapArg_E vars
358 prod a b = prodDataCon_RDR `nlHsApps` [a,b]
360 wrapArg_E :: RdrName -> LHsExpr RdrName
361 wrapArg_E v = mkM1_E (k1DataCon_RDR `nlHsVarApps` [v])
362 -- This M1 is meta-information for the selector
364 -- Build a product pattern
365 mkProd_P :: US -- Base for unique names
366 -> [RdrName] -- List of variables to match
367 -> LPat RdrName -- Resulting product pattern
368 mkProd_P _ [] = mkM1_P (nlNullaryConPat u1DataCon_RDR)
369 mkProd_P _ vars = mkM1_P (foldBal prod appVars)
370 -- These M1s are meta-information for the constructor
372 appVars = map wrapArg_P vars
373 prod a b = prodDataCon_RDR `nlConPat` [a,b]
375 wrapArg_P :: RdrName -> LPat RdrName
376 wrapArg_P v = mkM1_P (k1DataCon_RDR `nlConVarPat` [v])
377 -- This M1 is meta-information for the selector
379 mkGenericLocal :: US -> RdrName
380 mkGenericLocal u = mkVarUnqual (mkFastString ("g" ++ show u))
382 mkM1_E :: LHsExpr RdrName -> LHsExpr RdrName
383 mkM1_E e = nlHsVar m1DataCon_RDR `nlHsApp` e
385 mkM1_P :: LPat RdrName -> LPat RdrName
386 mkM1_P p = m1DataCon_RDR `nlConPat` [p]
388 -- | Variant of foldr1 for producing balanced lists
389 foldBal :: (a -> a -> a) -> [a] -> a
390 foldBal op = foldBal' op (error "foldBal: empty list")
392 foldBal' :: (a -> a -> a) -> a -> [a] -> a
395 foldBal' op x l = let (a,b) = splitAt (length l `div` 2) l
396 in foldBal' op x a `op` foldBal' op x b