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, tyConName, tyConTheta, getSynTyConDefn, tyConTyVars, tyConDataCons, isSynTyCon )
35 import VarSet ( intersectVarSet, isEmptyVarSet )
36 import PrelNames ( unpackCStringName, unpackCStringUtf8Name )
37 import ListSetOps ( equivClasses )
41 %************************************************************************
43 \subsection{Type checking}
45 %************************************************************************
48 tcTyDecl :: RecTcEnv -> RenamedTyClDecl -> TcM (Name, TyThingDetails)
49 tcTyDecl unf_env (TySynonym {tcdName = tycon_name, tcdSynRhs = rhs})
50 = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
51 tcExtendTyVarEnv (tyConTyVars tycon) $
52 tcHsType rhs `thenTc` \ rhs_ty ->
53 returnTc (tycon_name, SynTyDetails rhs_ty)
55 tcTyDecl unf_env (TyData {tcdND = new_or_data, tcdCtxt = context,
56 tcdName = tycon_name, tcdCons = con_decls})
57 = tcLookupTyCon tycon_name `thenNF_Tc` \ tycon ->
59 tyvars = tyConTyVars tycon
61 tcExtendTyVarEnv tyvars $
62 tcHsTheta context `thenTc` \ ctxt ->
63 mapTc (tcConDecl new_or_data tycon tyvars ctxt) con_decls `thenTc` \ data_cons ->
65 sel_ids = mkRecordSelectors unf_env tycon data_cons
67 returnTc (tycon_name, DataTyDetails ctxt data_cons sel_ids)
69 tcTyDecl unf_env (ForeignType {tcdName = tycon_name})
70 = returnTc (tycon_name, ForeignTyDetails)
73 mkRecordSelectors unf_env tycon data_cons
74 = -- We'll check later that fields with the same name
75 -- from different constructors have the same type.
76 [ mkRecordSelId tycon field unpack_id unpackUtf8_id
77 | field <- nubBy eq_name fields ]
79 fields = [ field | con <- data_cons, field <- dataConFieldLabels con ]
80 eq_name field1 field2 = fieldLabelName field1 == fieldLabelName field2
82 unpack_id = tcLookupRecId unf_env unpackCStringName
83 unpackUtf8_id = tcLookupRecId unf_env unpackCStringUtf8Name
87 %************************************************************************
89 \subsection{Validity check}
91 %************************************************************************
93 checkValidTyCon is called once the mutually-recursive knot has been
94 tied, so we can look at things freely.
97 checkValidTyCon :: TyCon -> TcM ()
99 | isSynTyCon tc = checkValidType (TySynCtxt name) syn_rhs
101 = -- Check the context on the data decl
102 checkValidTheta (DataTyCtxt name) (tyConTheta tc) `thenTc_`
104 -- Check arg types of data constructors
105 mapTc_ check_data_con data_cons `thenTc_`
107 -- Check that fields with the same name share a type
108 mapTc_ check_fields groups
112 (_, syn_rhs) = getSynTyConDefn tc
113 data_cons = tyConDataCons tc
115 fields = [field | con <- data_cons, field <- dataConFieldLabels con]
116 groups = equivClasses cmp_name fields
117 cmp_name field1 field2 = fieldLabelName field1 `compare` fieldLabelName field2
119 check_data_con con = checkValidType (ConArgCtxt (dataConName con))
120 (idType (dataConWrapId con))
121 -- This checks the argument types and
122 -- the existential context (if any)
124 check_fields fields@(first_field_label : other_fields)
125 -- These fields all have the same name, but are from
126 -- different constructors in the data type
127 = -- Check that all the fields in the group have the same type
128 -- NB: this check assumes that all the constructors of a given
129 -- data type use the same type variables
130 checkTc (all (tcEqType field_ty) other_tys) (fieldTypeMisMatch field_name)
132 field_ty = fieldLabelType first_field_label
133 field_name = fieldLabelName first_field_label
134 other_tys = map fieldLabelType other_fields
139 %************************************************************************
141 \subsection{Kind and type check constructors}
143 %************************************************************************
146 kcConDetails :: NewOrData -> RenamedContext -> ConDetails Name -> TcM ()
147 kcConDetails new_or_data ex_ctxt details
148 = kcHsContext ex_ctxt `thenTc_`
149 mapTc_ kc_sig_type (conDetailsTys details)
151 kc_sig_type = case new_or_data of
152 DataType -> kcHsSigType
153 NewType -> kcHsLiftedSigType
154 -- Can't allow an unlifted type here, because we're effectively
155 -- going to remove the constructor while coercing it to a lifted type.
158 tcConDecl :: NewOrData -> TyCon -> [TyVar] -> ThetaType -> RenamedConDecl -> TcM DataCon
159 tcConDecl new_or_data tycon tyvars ctxt (ConDecl name wkr_name ex_tvs ex_ctxt details src_loc)
160 = tcAddSrcLoc src_loc $
161 tcHsTyVars ex_tvs (kcConDetails new_or_data ex_ctxt details) $ \ ex_tyvars ->
162 tcHsTheta ex_ctxt `thenTc` \ ex_theta ->
164 VanillaCon btys -> tc_datacon ex_tyvars ex_theta btys
165 InfixCon bty1 bty2 -> tc_datacon ex_tyvars ex_theta [bty1,bty2]
166 RecCon fields -> tc_rec_con ex_tyvars ex_theta fields
168 tc_datacon ex_tyvars ex_theta btys
169 = mapTc tcHsType (map getBangType btys) `thenTc` \ arg_tys ->
170 mk_data_con ex_tyvars ex_theta (map getBangStrictness btys) arg_tys []
172 tc_rec_con ex_tyvars ex_theta fields
173 = checkTc (null ex_tyvars) (exRecConErr name) `thenTc_`
174 mapTc tc_field (fields `zip` allFieldLabelTags) `thenTc` \ field_labels_s ->
176 field_labels = concat field_labels_s
177 arg_stricts = [str | (ns, bty) <- fields,
178 let str = getBangStrictness bty,
179 n <- ns -- One for each. E.g x,y,z :: !Int
182 mk_data_con ex_tyvars ex_theta arg_stricts
183 (map fieldLabelType field_labels) field_labels
185 tc_field ((field_label_names, bty), tag)
186 = tcHsType (getBangType bty) `thenTc` \ field_ty ->
187 returnTc [mkFieldLabel (getName name) tycon field_ty tag | name <- field_label_names]
189 mk_data_con ex_tyvars ex_theta arg_stricts arg_tys fields
191 data_con = mkDataCon name arg_stricts fields
192 tyvars (thinContext arg_tys ctxt)
195 tycon data_con_id data_con_wrap_id
197 data_con_id = mkDataConId wkr_name data_con
198 data_con_wrap_id = mkDataConWrapId data_con
202 -- The context for a data constructor should be limited to
203 -- the type variables mentioned in the arg_tys
204 thinContext arg_tys ctxt
205 = filter in_arg_tys ctxt
207 arg_tyvars = tyVarsOfTypes arg_tys
208 in_arg_tys pred = not $ isEmptyVarSet $
209 tyVarsOfPred pred `intersectVarSet` arg_tyvars
213 %************************************************************************
215 \subsection{Errors and contexts}
217 %************************************************************************
221 fieldTypeMisMatch field_name
222 = sep [ptext SLIT("Different constructors give different types for field"), quotes (ppr field_name)]
225 = ptext SLIT("Can't combine named fields with locally-quantified type variables")
227 (ptext SLIT("In the declaration of data constructor") <+> ppr name)