2 % (c) The AQUA Project, Glasgow University, 1996-1998
4 \section[TcTyDecls]{Typecheck type declarations}
7 module TcTyDecls ( tcTyDecl, checkValidTyCon, kcConDetails ) where
9 #include "HsVersions.h"
11 import HsSyn ( TyClDecl(..), ConDecl(..), ConDetails(..),
12 getBangType, getBangStrictness, conDetailsTys
14 import RnHsSyn ( RenamedTyClDecl, RenamedConDecl, RenamedContext )
15 import BasicTypes ( NewOrData(..) )
17 import TcMonoType ( tcHsTyVars, tcHsTheta, tcHsType,
18 kcHsContext, kcHsSigType, kcHsLiftedSigType
20 import TcEnv ( tcExtendTyVarEnv,
21 tcLookupTyCon, tcLookupRecId,
22 TyThingDetails(..), RecTcEnv
24 import TcType ( tcEqType, tyVarsOfTypes, tyVarsOfPred, ThetaType )
25 import TcMType ( checkValidType, UserTypeCtxt(..), checkValidTheta, SourceTyCtxt(..) )
28 import DataCon ( DataCon, mkDataCon, dataConFieldLabels, dataConWrapId, dataConName )
29 import MkId ( mkDataConId, mkDataConWrapId, mkRecordSelId )
31 import Var ( TyVar, idType )
32 import Name ( Name, NamedThing(..) )
34 import TyCon ( TyCon, DataConDetails(..), visibleDataCons,
35 tyConName, tyConTheta, getSynTyConDefn,
36 tyConTyVars, tyConDataCons, isSynTyCon )
37 import VarSet ( intersectVarSet, isEmptyVarSet )
38 import PrelNames ( unpackCStringName, unpackCStringUtf8Name )
39 import ListSetOps ( equivClasses )
43 %************************************************************************
45 \subsection{Type checking}
47 %************************************************************************
50 tcTyDecl :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
51 tcTyDecl unf_env (TySynonym {tcdName = tycon_name, tcdSynRhs = rhs})
52 = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
53 tcExtendTyVarEnv (tyConTyVars tycon) $
54 tcHsType rhs `thenTc` \ rhs_ty ->
55 returnTc (tycon_name, SynTyDetails rhs_ty)
57 tcTyDecl unf_env (TyData {tcdND = new_or_data, tcdCtxt = context,
58 tcdName = tycon_name, tcdCons = con_decls})
59 = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
61 tyvars = tyConTyVars tycon
63 tcExtendTyVarEnv tyvars $
64 tcHsTheta context `thenTc` \ ctxt ->
65 tcConDecls new_or_data tycon tyvars ctxt con_decls `thenTc` \ data_cons ->
67 sel_ids = mkRecordSelectors unf_env tycon data_cons
69 returnTc (tycon_name, DataTyDetails ctxt data_cons sel_ids)
71 tcTyDecl unf_env (ForeignType {tcdName = tycon_name})
72 = returnTc (tycon_name, ForeignTyDetails)
75 mkRecordSelectors unf_env tycon data_cons
76 = -- We'll check later that fields with the same name
77 -- from different constructors have the same type.
78 [ mkRecordSelId tycon field unpack_id unpackUtf8_id
79 | field <- nubBy eq_name fields ]
81 fields = [ field | con <- visibleDataCons data_cons,
82 field <- dataConFieldLabels con ]
83 eq_name field1 field2 = fieldLabelName field1 == fieldLabelName field2
85 unpack_id = tcLookupRecId unf_env unpackCStringName
86 unpackUtf8_id = tcLookupRecId unf_env unpackCStringUtf8Name
90 %************************************************************************
92 \subsection{Validity check}
94 %************************************************************************
96 checkValidTyCon is called once the mutually-recursive knot has been
97 tied, so we can look at things freely.
100 checkValidTyCon :: TyCon -> TcM ()
102 | isSynTyCon tc = checkValidType (TySynCtxt name) syn_rhs
104 = -- Check the context on the data decl
105 checkValidTheta (DataTyCtxt name) (tyConTheta tc) `thenTc_`
107 -- Check arg types of data constructors
108 mapTc_ check_data_con data_cons `thenTc_`
110 -- Check that fields with the same name share a type
111 mapTc_ check_fields groups
115 (_, syn_rhs) = getSynTyConDefn tc
116 data_cons = tyConDataCons tc
118 fields = [field | con <- data_cons, field <- dataConFieldLabels con]
119 groups = equivClasses cmp_name fields
120 cmp_name field1 field2 = fieldLabelName field1 `compare` fieldLabelName field2
122 check_data_con con = checkValidType (ConArgCtxt (dataConName con))
123 (idType (dataConWrapId con))
124 -- This checks the argument types and
125 -- the existential context (if any)
127 check_fields fields@(first_field_label : other_fields)
128 -- These fields all have the same name, but are from
129 -- different constructors in the data type
130 = -- Check that all the fields in the group have the same type
131 -- NB: this check assumes that all the constructors of a given
132 -- data type use the same type variables
133 checkTc (all (tcEqType field_ty) other_tys) (fieldTypeMisMatch field_name)
135 field_ty = fieldLabelType first_field_label
136 field_name = fieldLabelName first_field_label
137 other_tys = map fieldLabelType other_fields
142 %************************************************************************
144 \subsection{Kind and type check constructors}
146 %************************************************************************
149 kcConDetails :: NewOrData -> RenamedContext -> ConDetails Name -> TcM ()
150 kcConDetails new_or_data ex_ctxt details
151 = kcHsContext ex_ctxt `thenTc_`
152 mapTc_ kc_sig_type (conDetailsTys details)
154 kc_sig_type = case new_or_data of
155 DataType -> kcHsSigType
156 NewType -> kcHsLiftedSigType
157 -- Can't allow an unlifted type here, because we're effectively
158 -- going to remove the constructor while coercing it to a lifted type.
161 tcConDecls :: NewOrData -> TyCon -> [TyVar] -> ThetaType
162 -> DataConDetails RenamedConDecl -> TcM (DataConDetails DataCon)
164 tcConDecls new_or_data tycon tyvars ctxt con_decls
166 Unknown -> returnTc Unknown
167 HasCons n -> returnTc (HasCons n)
168 DataCons cs -> mapTc tc_con_decl cs `thenTc` \ data_cons ->
169 returnTc (DataCons data_cons)
171 tc_con_decl (ConDecl name wkr_name ex_tvs ex_ctxt details src_loc)
172 = tcAddSrcLoc src_loc $
173 tcHsTyVars ex_tvs (kcConDetails new_or_data ex_ctxt details) $ \ ex_tyvars ->
174 tcHsTheta ex_ctxt `thenTc` \ ex_theta ->
176 VanillaCon btys -> tc_datacon ex_tyvars ex_theta btys
177 InfixCon bty1 bty2 -> tc_datacon ex_tyvars ex_theta [bty1,bty2]
178 RecCon fields -> tc_rec_con ex_tyvars ex_theta fields
181 tc_datacon ex_tyvars ex_theta btys
182 = mapTc tcHsType (map getBangType btys) `thenTc` \ arg_tys ->
183 mk_data_con ex_tyvars ex_theta (map getBangStrictness btys) arg_tys []
185 tc_rec_con ex_tyvars ex_theta fields
186 = checkTc (null ex_tyvars) (exRecConErr name) `thenTc_`
187 mapTc tc_field (fields `zip` allFieldLabelTags) `thenTc` \ field_labels_s ->
189 field_labels = concat field_labels_s
190 arg_stricts = [str | (ns, bty) <- fields,
191 let str = getBangStrictness bty,
192 n <- ns -- One for each. E.g x,y,z :: !Int
195 mk_data_con ex_tyvars ex_theta arg_stricts
196 (map fieldLabelType field_labels) field_labels
198 tc_field ((field_label_names, bty), tag)
199 = tcHsType (getBangType bty) `thenTc` \ field_ty ->
200 returnTc [mkFieldLabel (getName name) tycon field_ty tag | name <- field_label_names]
202 mk_data_con ex_tyvars ex_theta arg_stricts arg_tys fields
204 data_con = mkDataCon name arg_stricts fields
205 tyvars (thinContext arg_tys ctxt)
208 tycon data_con_id data_con_wrap_id
210 data_con_id = mkDataConId wkr_name data_con
211 data_con_wrap_id = mkDataConWrapId data_con
215 -- The context for a data constructor should be limited to
216 -- the type variables mentioned in the arg_tys
217 thinContext arg_tys ctxt
218 = filter in_arg_tys ctxt
220 arg_tyvars = tyVarsOfTypes arg_tys
221 in_arg_tys pred = not $ isEmptyVarSet $
222 tyVarsOfPred pred `intersectVarSet` arg_tyvars
226 %************************************************************************
228 \subsection{Errors and contexts}
230 %************************************************************************
234 fieldTypeMisMatch field_name
235 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
238 = ptext SLIT("Can't combine named fields with locally-quantified type variables")
240 (ptext SLIT("In the declaration of data constructor") <+> ppr name)