2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
8 buildSynTyCon, buildAlgTyCon, buildDataCon,
10 mkAbstractTyConRhs, mkOpenDataTyConRhs,
11 mkNewTyConRhs, mkDataTyConRhs
14 #include "HsVersions.h"
39 ------------------------------------------------------
40 buildSynTyCon :: Name -> [TyVar]
42 -> Maybe (TyCon, [Type]) -- family instance if applicable
45 buildSynTyCon tc_name tvs rhs@(OpenSynTyCon rhs_ki _) _
47 kind = mkArrowKinds (map tyVarKind tvs) rhs_ki
49 return $ mkSynTyCon tc_name kind tvs rhs NoParentTyCon
51 buildSynTyCon tc_name tvs rhs@(SynonymTyCon rhs_ty) mb_family
52 = do { -- We need to tie a knot as the coercion of a data instance depends
53 -- on the instance representation tycon and vice versa.
54 ; tycon <- fixM (\ tycon_rec -> do
55 { parent <- mkParentInfo mb_family tc_name tvs tycon_rec
56 ; let { tycon = mkSynTyCon tc_name kind tvs rhs parent
57 ; kind = mkArrowKinds (map tyVarKind tvs) (typeKind rhs_ty)
64 ------------------------------------------------------
65 buildAlgTyCon :: Name -> [TyVar]
66 -> ThetaType -- Stupid theta
69 -> Bool -- True <=> want generics functions
70 -> Bool -- True <=> was declared in GADT syntax
71 -> Maybe (TyCon, [Type]) -- family instance if applicable
74 buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn
76 = do { -- We need to tie a knot as the coercion of a data instance depends
77 -- on the instance representation tycon and vice versa.
78 ; tycon <- fixM (\ tycon_rec -> do
79 { parent <- mkParentInfo mb_family tc_name tvs tycon_rec
80 ; let { tycon = mkAlgTyCon tc_name kind tvs stupid_theta rhs
81 fields parent is_rec want_generics gadt_syn
82 ; kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
83 ; fields = mkTyConSelIds tycon rhs
90 -- If a family tycon with instance types is given, the current tycon is an
91 -- instance of that family and we need to
93 -- (1) create a coercion that identifies the family instance type and the
94 -- representation type from Step (1); ie, it is of the form
95 -- `Co tvs :: F ts :=: R tvs', where `Co' is the name of the coercion,
96 -- `F' the family tycon and `R' the (derived) representation tycon,
98 -- (2) produce a `TyConParent' value containing the parent and coercion
101 mkParentInfo :: Maybe (TyCon, [Type])
104 -> TcRnIf m n TyConParent
105 mkParentInfo Nothing _ _ _ =
107 mkParentInfo (Just (family, instTys)) tc_name tvs rep_tycon =
108 do { -- Create the coercion
109 ; co_tycon_name <- newImplicitBinder tc_name mkInstTyCoOcc
110 ; let co_tycon = mkFamInstCoercion co_tycon_name tvs
111 family instTys rep_tycon
112 ; return $ FamilyTyCon family instTys co_tycon
115 ------------------------------------------------------
116 mkAbstractTyConRhs :: AlgTyConRhs
117 mkAbstractTyConRhs = AbstractTyCon
119 mkOpenDataTyConRhs :: AlgTyConRhs
120 mkOpenDataTyConRhs = OpenTyCon Nothing
122 mkDataTyConRhs :: [DataCon] -> AlgTyConRhs
124 = DataTyCon { data_cons = cons, is_enum = all isNullarySrcDataCon cons }
126 mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
127 -- Monadic because it makes a Name for the coercion TyCon
128 -- We pass the Name of the parent TyCon, as well as the TyCon itself,
129 -- because the latter is part of a knot, whereas the former is not.
130 mkNewTyConRhs tycon_name tycon con
131 = do { co_tycon_name <- newImplicitBinder tycon_name mkNewTyCoOcc
132 ; let co_tycon = mkNewTypeCoercion co_tycon_name tycon etad_tvs etad_rhs
133 cocon_maybe | all_coercions || isRecursiveTyCon tycon
137 ; traceIf (text "mkNewTyConRhs" <+> ppr cocon_maybe)
138 ; return (NewTyCon { data_con = con,
140 nt_etad_rhs = (etad_tvs, etad_rhs),
141 nt_co = cocon_maybe } ) }
142 -- Coreview looks through newtypes with a Nothing
143 -- for nt_co, or uses explicit coercions otherwise
145 -- If all_coercions is True then we use coercions for all newtypes
146 -- otherwise we use coercions for recursive newtypes and look through
147 -- non-recursive newtypes
149 tvs = tyConTyVars tycon
150 rhs_ty = ASSERT(not (null (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs))))
151 -- head (dataConInstOrigArgTys con (mkTyVarTys tvs))
152 head (dataConInstOrigDictsAndArgTys con (mkTyVarTys tvs))
153 -- Instantiate the data con with the
154 -- type variables from the tycon
155 -- NB: a newtype DataCon has no existentials; hence the
156 -- call to dataConInstOrigArgTys has the right type args
158 etad_tvs :: [TyVar] -- Matched lazily, so that mkNewTypeCoercion can
159 etad_rhs :: Type -- return a TyCon without pulling on rhs_ty
160 -- See Note [Tricky iface loop] in LoadIface
161 (etad_tvs, etad_rhs) = eta_reduce (reverse tvs) rhs_ty
163 eta_reduce :: [TyVar] -- Reversed
165 -> ([TyVar], Type) -- Eta-reduced version (tyvars in normal order)
166 eta_reduce (a:as) ty | Just (fun, arg) <- splitAppTy_maybe ty,
167 Just tv <- getTyVar_maybe arg,
169 not (a `elemVarSet` tyVarsOfType fun)
171 eta_reduce tvs ty = (reverse tvs, ty)
174 ------------------------------------------------------
175 buildDataCon :: Name -> Bool
177 -> [Name] -- Field labels
178 -> [TyVar] -> [TyVar] -- Univ and ext
179 -> [(TyVar,Type)] -- Equality spec
180 -> ThetaType -- Does not include the "stupid theta"
181 -- or the GADT equalities
183 -> TcRnIf m n DataCon
184 -- A wrapper for DataCon.mkDataCon that
185 -- a) makes the worker Id
186 -- b) makes the wrapper Id if necessary, including
187 -- allocating its unique (hence monadic)
188 buildDataCon src_name declared_infix arg_stricts field_lbls
189 univ_tvs ex_tvs eq_spec ctxt arg_tys tycon
190 = do { wrap_name <- newImplicitBinder src_name mkDataConWrapperOcc
191 ; work_name <- newImplicitBinder src_name mkDataConWorkerOcc
192 -- This last one takes the name of the data constructor in the source
193 -- code, which (for Haskell source anyway) will be in the DataName name
194 -- space, and puts it into the VarName name space
197 stupid_ctxt = mkDataConStupidTheta tycon arg_tys univ_tvs
198 data_con = mkDataCon src_name declared_infix
199 arg_stricts field_lbls
200 univ_tvs ex_tvs eq_spec ctxt
203 dc_ids = mkDataConIds wrap_name work_name data_con
208 -- The stupid context for a data constructor should be limited to
209 -- the type variables mentioned in the arg_tys
210 -- ToDo: Or functionally dependent on?
211 -- This whole stupid theta thing is, well, stupid.
212 mkDataConStupidTheta :: TyCon -> [Type] -> [TyVar] -> [PredType]
213 mkDataConStupidTheta tycon arg_tys univ_tvs
214 | null stupid_theta = [] -- The common case
215 | otherwise = filter in_arg_tys stupid_theta
217 tc_subst = zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs)
218 stupid_theta = substTheta tc_subst (tyConStupidTheta tycon)
219 -- Start by instantiating the master copy of the
220 -- stupid theta, taken from the TyCon
222 arg_tyvars = tyVarsOfTypes arg_tys
223 in_arg_tys pred = not $ isEmptyVarSet $
224 tyVarsOfPred pred `intersectVarSet` arg_tyvars
226 ------------------------------------------------------
227 mkTyConSelIds :: TyCon -> AlgTyConRhs -> [Id]
228 mkTyConSelIds tycon rhs
229 = [ mkRecordSelId tycon fld
230 | fld <- nub (concatMap dataConFieldLabels (visibleDataCons rhs)) ]
231 -- We'll check later that fields with the same name
232 -- from different constructors have the same type.
236 ------------------------------------------------------
238 buildClass :: Bool -- True <=> do not include unfoldings
240 -- Used when importing a class without -O
241 -> Name -> [TyVar] -> ThetaType
242 -> [FunDep TyVar] -- Functional dependencies
243 -> [TyThing] -- Associated types
244 -> [(Name, DefMeth, Type)] -- Method info
245 -> RecFlag -- Info for type constructor
248 buildClass no_unf class_name tvs sc_theta fds ats sig_stuff tc_isrec
249 = do { traceIf (text "buildClass")
250 ; tycon_name <- newImplicitBinder class_name mkClassTyConOcc
251 ; datacon_name <- newImplicitBinder class_name mkClassDataConOcc
252 -- The class name is the 'parent' for this datacon, not its tycon,
253 -- because one should import the class to get the binding for
256 ; fixM (\ rec_clas -> do { -- Only name generation inside loop
258 let { rec_tycon = classTyCon rec_clas
259 ; op_tys = [ty | (_,_,ty) <- sig_stuff]
260 ; op_items = [ (mkDictSelId no_unf op_name rec_clas, dm_info)
261 | (op_name, dm_info, _) <- sig_stuff ] }
262 -- Build the selector id and default method id
264 ; dict_con <- buildDataCon datacon_name
265 False -- Not declared infix
266 (map (const NotMarkedStrict) op_tys)
267 [{- No labelled fields -}]
268 tvs [{- no existentials -}]
269 [{- No GADT equalities -}] sc_theta
273 ; let n_value_preds = count (not . isEqPred) sc_theta
274 all_value_preds = n_value_preds == length sc_theta
275 -- We only make selectors for the *value* superclasses,
276 -- not equality predicates
278 ; sc_sel_names <- mapM (newImplicitBinder class_name . mkSuperDictSelOcc)
280 ; let sc_sel_ids = [mkDictSelId no_unf sc_name rec_clas | sc_name <- sc_sel_names]
281 -- We number off the Dict superclass selectors, 1, 2, 3 etc so that we
282 -- can construct names for the selectors. Thus
283 -- class (C a, C b) => D a b where ...
284 -- gives superclass selectors
286 -- (We used to call them D_C, but now we can have two different
287 -- superclasses both called C!)
290 ; let use_newtype = (n_value_preds + length sig_stuff == 1) && all_value_preds
291 -- Use a newtype if the data constructor has
292 -- (a) exactly one value field
293 -- (b) no existential or equality-predicate fields
294 -- i.e. exactly one operation or superclass taken together
295 -- See note [Class newtypes and equality predicates]
297 ; rhs <- if use_newtype
298 then mkNewTyConRhs tycon_name rec_tycon dict_con
299 else return (mkDataTyConRhs [dict_con])
301 ; let { clas_kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
303 ; tycon = mkClassTyCon tycon_name clas_kind tvs
304 rhs rec_clas tc_isrec
305 -- A class can be recursive, and in the case of newtypes
306 -- this matters. For example
307 -- class C a where { op :: C b => a -> b -> Int }
308 -- Because C has only one operation, it is represented by
309 -- a newtype, and it should be a *recursive* newtype.
310 -- [If we don't make it a recursive newtype, we'll expand the
311 -- newtype like a synonym, but that will lead to an infinite
313 ; atTyCons = [tycon | ATyCon tycon <- ats]
315 ; result = mkClass class_name tvs fds
316 sc_theta sc_sel_ids atTyCons
319 ; traceIf (text "buildClass" <+> ppr tycon)
324 Note [Class newtypes and equality predicates]
325 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
327 class (a ~ F b) => C a b where
330 We cannot represent this by a newtype, even though it's not
331 existential, and there's only one value field, because we do
332 capture an equality predicate:
335 MkC :: forall a b. (a ~ F b) => (a->b) -> C a b
337 We need to access this equality predicate when we get passes a C
338 dictionary. See Trac #2238