import TcMonoType ( tcHsType )
import TcSimplify ( tcSimplifyAndCheck )
import TcType ( TcType, TcTyVar, TcTyVarSet,
- zonkSigTyVar, tcInstSigTyVars, tcInstType, tcInstTheta
+ zonkSigTyVar, tcInstSigType, tcInstTheta
)
import Bag ( emptyBag, unitBag, unionBags, unionManyBags,
)
import CmdLineOpts ( opt_GlasgowExts )
import Class ( classBigSig, Class )
-import Id ( isNullaryDataCon, dataConArgTys, replaceIdInfo, idName, Id )
-import Maybes ( maybeToBool, seqMaybe, catMaybes )
+import Id ( isNullaryDataCon, dataConArgTys, replaceIdInfo, idName, idType, Id )
+import Maybes ( maybeToBool, seqMaybe, catMaybes, expectJust )
import Name ( nameOccName, mkLocalName,
isLocallyDefined, Module,
NamedThing(..)
splitSigmaTy, isTyVarTy, mkSigmaTy,
splitTyConApp_maybe, splitDictTy_maybe,
splitAlgTyConApp_maybe, splitRhoTy,
- tyVarsOfTypes
+ tyVarsOfTypes, mkTyVarTys,
)
import TyVar ( zipTyVarEnv, mkTyVarSet, tyVarSetToList, TyVar )
import TysPrim ( byteArrayPrimTyCon, mutableByteArrayPrimTyCon )
Just pair -> pair
in
- -- Check for respectable instance type
- scrutiniseInstanceType clas inst_tys `thenTc_`
+ -- Check for respectable instance type, and context
+ scrutiniseInstanceHead clas inst_tys `thenNF_Tc_`
+ mapNF_Tc scrutiniseInstanceConstraint theta `thenNF_Tc_`
-- Make the dfun id and constant-method ids
let
recoverNF_Tc (returnNF_Tc (emptyLIE, EmptyMonoBinds)) $
tcAddSrcLoc locn $
- -- Get the class signature
- let
- origin = InstanceDeclOrigin
+ -- Instantiate the instance decl with tc-style type variables
+ tcInstSigType (idType dfun_id) `thenNF_Tc` \ dfun_ty' ->
+ let
+ (inst_tyvars',
+ dfun_theta', dict_ty') = splitSigmaTy dfun_ty'
+
+ (clas, inst_tys') = expectJust "tcInstDecl2" (splitDictTy_maybe dict_ty')
+
(class_tyvars,
sc_theta, sc_sel_ids,
- op_sel_ids, defm_ids) = classBigSig clas
+ op_sel_ids, defm_ids) = classBigSig clas
+
+ origin = InstanceDeclOrigin
in
-
- -- Instantiate the instance decl with tc-style type variables
- tcInstSigTyVars inst_tyvars `thenNF_Tc` \ (inst_tyvars', _, tenv) ->
- mapNF_Tc (tcInstType tenv) inst_tys `thenNF_Tc` \ inst_tys' ->
- tcInstTheta tenv dfun_theta `thenNF_Tc` \ dfun_theta' ->
- tcInstTheta tenv inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
+ -- Instantiate the theta found in the original instance decl
+ tcInstTheta (zipTyVarEnv inst_tyvars (mkTyVarTys inst_tyvars'))
+ inst_decl_theta `thenNF_Tc` \ inst_decl_theta' ->
- -- Instantiate the super-class context with inst_tys
- tcInstTheta (zipTyVarEnv class_tyvars inst_tys') sc_theta `thenNF_Tc` \ sc_theta' ->
+ -- Instantiate the super-class context with the instance types
+ tcInstTheta (zipTyVarEnv class_tyvars inst_tys') sc_theta `thenNF_Tc` \ sc_theta' ->
-- Create dictionary Ids from the specified instance contexts.
newDicts origin sc_theta' `thenNF_Tc` \ (sc_dicts, sc_dict_ids) ->
%* *
%************************************************************************
-@scrutiniseInstanceType@ checks the type {\em and} its syntactic constraints:
+@scrutiniseInstanceHead@ checks the type {\em and} its syntactic constraints:
it must normally look like: @instance Foo (Tycon a b c ...) ...@
The exceptions to this syntactic checking: (1)~if the @GlasgowExts@
We can also have instances for functions: @instance Foo (a -> b) ...@.
\begin{code}
-scrutiniseInstanceType clas inst_taus
+scrutiniseInstanceConstraint (clas, tys)
+ | all isTyVarTy tys = returnNF_Tc ()
+ | otherwise = addErrTc (instConstraintErr clas tys)
+
+scrutiniseInstanceHead clas inst_taus
| -- CCALL CHECK (a).... urgh!
-- To verify that a user declaration of a CCallable/CReturnable
-- instance is OK, we must be able to see the constructor(s)
--
(uniqueOf clas == cCallableClassKey || uniqueOf clas == cReturnableClassKey)
&& is_alg_tycon_app && not constructors_visible
- = failWithTc (invisibleDataConPrimCCallErr clas first_inst_tau)
+ = addErrTc (invisibleDataConPrimCCallErr clas first_inst_tau)
| -- CCALL CHECK (b)
-- A user declaration of a CCallable/CReturnable instance
-- must be for a "boxed primitive" type.
(uniqueOf clas == cCallableClassKey && not (ccallable_type first_inst_tau)) ||
(uniqueOf clas == cReturnableClassKey && not (creturnable_type first_inst_tau))
- = failWithTc (nonBoxedPrimCCallErr clas first_inst_tau)
+ = addErrTc (nonBoxedPrimCCallErr clas first_inst_tau)
-- DERIVING CHECK
-- It is obviously illegal to have an explicit instance
-- for something that we are also planning to `derive'
| maybeToBool alg_tycon_app_maybe && clas `elem` (tyConDerivings alg_tycon)
- = failWithTc (derivingWhenInstanceExistsErr clas first_inst_tau)
+ = addErrTc (derivingWhenInstanceExistsErr clas first_inst_tau)
-- Kind check will have ensured inst_taus is of length 1
-- WITH HASKELL 1.4, MUST HAVE C (T a b c)
length (tyVarSetToList (tyVarsOfTypes arg_tys)) == length arg_tys
-- This last condition checks that all the type variables are distinct
)
- = failWithTc (instTypeErr clas inst_taus
+ = addErrTc (instTypeErr clas inst_taus
(text "the instance type must be of form (T a b c)" $$
text "where T is not a synonym, and a,b,c are distinct type variables")
)
| otherwise
- = returnTc ()
+ = returnNF_Tc ()
where
(first_inst_tau : _) = inst_taus
\end{code}
\begin{code}
-
+instConstraintErr clas tys
+ = hang (ptext SLIT("Illegal constaint") <+>
+ quotes (pprConstraint clas tys) <+>
+ ptext SLIT("in instance context"))
+ 4 (ptext SLIT("(Instance contexts must constrain only type variables)"))
+
instTypeErr clas tys msg
= sep [ptext SLIT("Illegal instance declaration for") <+> quotes (pprConstraint clas tys),
nest 4 (parens msg)
projects / ghc-hetmet.git / blobdiff