%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section[TcInstDecls]{Typechecking instance declarations}
+
+TcInstDecls: Typechecking instance declarations
\begin{code}
module TcInstDcls ( tcInstDecls1, tcInstDecls2 ) where
#include "HsVersions.h"
import HsSyn
-import TcBinds ( mkPragFun, tcPrags, badBootDeclErr )
-import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr,
- tcClassDecl2, getGenericInstances )
+import TcBinds
+import TcTyClsDecls
+import TcClassDcl
import TcRnMonad
-import TcMType ( tcSkolSigType, checkValidInstance, checkValidInstHead )
-import TcType ( mkClassPred, tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys,
- SkolemInfo(InstSkol), tcSplitDFunTy )
-import Inst ( tcInstClassOp, newDicts, instToId, showLIE,
- getOverlapFlag, tcExtendLocalInstEnv )
-import InstEnv ( mkLocalInstance, instanceDFunId )
-import TcDeriv ( tcDeriving )
-import TcEnv ( InstInfo(..), InstBindings(..),
- newDFunName, tcExtendIdEnv
- )
-import TcHsType ( kcHsSigType, tcHsKindedType )
-import TcUnify ( checkSigTyVars )
-import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses )
-import Type ( zipOpenTvSubst, substTheta, substTys )
-import DataCon ( classDataCon )
-import Class ( classBigSig )
-import Var ( Id, idName, idType )
-import MkId ( mkDictFunId )
-import Name ( Name, getSrcLoc )
-import Maybe ( catMaybes )
-import SrcLoc ( srcLocSpan, unLoc, noLoc, Located(..), srcSpanStart )
-import ListSetOps ( minusList )
+import TcMType
+import TcType
+import Inst
+import InstEnv
+import FamInst
+import FamInstEnv
+import TcDeriv
+import TcEnv
+import TcHsType
+import TcUnify
+import TcSimplify
+import Type
+import Coercion
+import TyCon
+import DataCon
+import Class
+import Var
+import MkId
+import Name
+import NameSet
+import DynFlags
+import SrcLoc
+import ListSetOps
+import Util
import Outputable
import Bag
-import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) )
+import BasicTypes
+import HscTypes
import FastString
+
+import Data.Maybe
+import Control.Monad hiding (zipWithM_, mapAndUnzipM)
+import Data.List
\end{code}
Typechecking instance declarations is done in two passes. The first
tcInstDecls1 -- Deal with both source-code and imported instance decls
:: [LTyClDecl Name] -- For deriving stuff
-> [LInstDecl Name] -- Source code instance decls
+ -> [LDerivDecl Name] -- Source code stand-alone deriving decls
-> TcM (TcGblEnv, -- The full inst env
[InstInfo], -- Source-code instance decls to process;
-- contains all dfuns for this module
HsValBinds Name) -- Supporting bindings for derived instances
-tcInstDecls1 tycl_decls inst_decls
+tcInstDecls1 tycl_decls inst_decls deriv_decls
= checkNoErrs $
- -- Stop if addInstInfos etc discovers any errors
- -- (they recover, so that we get more than one error each round)
-
- -- (1) Do the ordinary instance declarations
- mappM tcLocalInstDecl1 inst_decls `thenM` \ local_inst_infos ->
-
- let
- local_inst_info = catMaybes local_inst_infos
- clas_decls = filter (isClassDecl.unLoc) tycl_decls
- in
- -- (2) Instances from generic class declarations
- getGenericInstances clas_decls `thenM` \ generic_inst_info ->
-
- -- Next, construct the instance environment so far, consisting of
- -- a) local instance decls
- -- b) generic instances
- addInsts local_inst_info $
- addInsts generic_inst_info $
-
- -- (3) Compute instances from "deriving" clauses;
- -- This stuff computes a context for the derived instance decl, so it
- -- needs to know about all the instances possible; hence inst_env4
- tcDeriving tycl_decls `thenM` \ (deriv_inst_info, deriv_binds) ->
- addInsts deriv_inst_info $
-
- getGblEnv `thenM` \ gbl_env ->
- returnM (gbl_env,
- generic_inst_info ++ deriv_inst_info ++ local_inst_info,
- deriv_binds)
+ do { -- Stop if addInstInfos etc discovers any errors
+ -- (they recover, so that we get more than one error each
+ -- round)
+
+ -- (1) Do class instance declarations and instances of indexed
+ -- types
+ ; let { idxty_decls = filter (isIdxTyDecl . unLoc) tycl_decls }
+ ; local_info_tycons <- mappM tcLocalInstDecl1 inst_decls
+ ; idx_tycons <- mappM tcIdxTyInstDeclTL idxty_decls
+
+ ; let { (local_infos,
+ at_tycons) = unzip local_info_tycons
+ ; local_info = concat local_infos
+ ; at_idx_tycon = concat at_tycons ++ catMaybes idx_tycons
+ ; clas_decls = filter (isClassDecl.unLoc) tycl_decls
+ ; implicit_things = concatMap implicitTyThings at_idx_tycon
+ }
+
+ -- (2) Add the tycons of indexed types and their implicit
+ -- tythings to the global environment
+ ; tcExtendGlobalEnv (at_idx_tycon ++ implicit_things) $ do {
+
+ -- (3) Instances from generic class declarations
+ ; generic_inst_info <- getGenericInstances clas_decls
+
+ -- Next, construct the instance environment so far, consisting
+ -- of
+ -- a) local instance decls
+ -- b) generic instances
+ -- c) local family instance decls
+ ; addInsts local_info $ do {
+ ; addInsts generic_inst_info $ do {
+ ; addFamInsts at_idx_tycon $ do {
+
+ -- (4) Compute instances from "deriving" clauses;
+ -- This stuff computes a context for the derived instance
+ -- decl, so it needs to know about all the instances possible
+ ; (deriv_inst_info, deriv_binds) <- tcDeriving tycl_decls deriv_decls
+ ; addInsts deriv_inst_info $ do {
+
+ ; gbl_env <- getGblEnv
+ ; returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_info,
+ deriv_binds)
+ }}}}}}
+ where
+ -- Make sure that toplevel type instance are not for associated types.
+ -- !!!TODO: Need to perform this check for the TyThing of type functions,
+ -- too.
+ tcIdxTyInstDeclTL ldecl@(L loc decl) =
+ do { tything <- tcIdxTyInstDecl ldecl
+ ; setSrcSpan loc $
+ when (isAssocFamily tything) $
+ addErr $ assocInClassErr (tcdName decl)
+ ; return tything
+ }
+ isAssocFamily (Just (ATyCon tycon)) =
+ case tyConFamInst_maybe tycon of
+ Nothing -> panic "isAssocFamily: no family?!?"
+ Just (fam, _) -> isTyConAssoc fam
+ isAssocFamily (Just _ ) = panic "isAssocFamily: no tycon?!?"
+ isAssocFamily Nothing = False
+
+assocInClassErr name =
+ ptext SLIT("Associated type") <+> quotes (ppr name) <+>
+ ptext SLIT("must be inside a class instance")
addInsts :: [InstInfo] -> TcM a -> TcM a
addInsts infos thing_inside
= tcExtendLocalInstEnv (map iSpec infos) thing_inside
-\end{code}
+
+addFamInsts :: [TyThing] -> TcM a -> TcM a
+addFamInsts tycons thing_inside
+ = tcExtendLocalFamInstEnv (map mkLocalFamInstTyThing tycons) thing_inside
+ where
+ mkLocalFamInstTyThing (ATyCon tycon) = mkLocalFamInst tycon
+ mkLocalFamInstTyThing tything = pprPanic "TcInstDcls.addFamInsts"
+ (ppr tything)
+\end{code}
\begin{code}
tcLocalInstDecl1 :: LInstDecl Name
- -> TcM (Maybe InstInfo) -- Nothing if there was an error
+ -> TcM ([InstInfo], [TyThing]) -- [] if there was an error
-- A source-file instance declaration
-- Type-check all the stuff before the "where"
--
-- We check for respectable instance type, and context
tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags ats))
- -- !!!TODO: Handle the `ats' parameter!!! -=chak
= -- Prime error recovery, set source location
- recoverM (returnM Nothing) $
+ recoverM (returnM ([], [])) $
setSrcSpan loc $
addErrCtxt (instDeclCtxt1 poly_ty) $
; checkTc (not is_boot || (isEmptyLHsBinds binds && null uprags))
badBootDeclErr
- -- Typecheck the instance type itself. We can't use
- -- tcHsSigType, because it's not a valid user type.
- ; kinded_ty <- kcHsSigType poly_ty
- ; poly_ty' <- tcHsKindedType kinded_ty
- ; let (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
+ ; (tyvars, theta, tau) <- tcHsInstHead poly_ty
+ -- Next, process any associated types.
+ ; idx_tycons <- mappM tcIdxTyInstDecl ats
+
+ -- Now, check the validity of the instance.
; (clas, inst_tys) <- checkValidInstHead tau
; checkValidInstance tyvars theta clas inst_tys
+ ; checkValidAndMissingATs clas (tyvars, inst_tys)
+ (zip ats idx_tycons)
+ -- Finally, construct the Core representation of the instance.
+ -- (This no longer includes the associated types.)
; dfun_name <- newDFunName clas inst_tys (srcSpanStart loc)
; overlap_flag <- getOverlapFlag
- ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys
- ispec = mkLocalInstance dfun overlap_flag
+ ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys
+ ispec = mkLocalInstance dfun overlap_flag
- ; return (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) }
+ ; return ([InstInfo { iSpec = ispec,
+ iBinds = VanillaInst binds uprags }],
+ catMaybes idx_tycons)
+ }
+ where
+ -- We pass in the source form and the type checked form of the ATs. We
+ -- really need the source form only to be able to produce more informative
+ -- error messages.
+ checkValidAndMissingATs :: Class
+ -> ([TyVar], [TcType]) -- instance types
+ -> [(LTyClDecl Name, -- source form of AT
+ Maybe TyThing)] -- Core form of AT
+ -> TcM ()
+ checkValidAndMissingATs clas inst_tys ats
+ = do { -- Issue a warning for each class AT that is not defined in this
+ -- instance.
+ ; let classDefATs = listToNameSet . map tyConName . classATs $ clas
+ definedATs = listToNameSet . map (tcdName.unLoc.fst) $ ats
+ omitted = classDefATs `minusNameSet` definedATs
+ ; warn <- doptM Opt_WarnMissingMethods
+ ; mapM_ (warnTc warn . omittedATWarn) (nameSetToList omitted)
+
+ -- Ensure that all AT indexes that correspond to class parameters
+ -- coincide with the types in the instance head. All remaining
+ -- AT arguments must be variables. Also raise an error for any
+ -- type instances that are not associated with this class.
+ ; mapM_ (checkIndexes clas inst_tys) ats
+ }
+
+ checkIndexes _ _ (hsAT, Nothing) =
+ return () -- skip, we already had an error here
+ checkIndexes clas inst_tys (hsAT, Just (ATyCon tycon)) =
+-- !!!TODO: check that this does the Right Thing for indexed synonyms, too!
+ checkIndexes' clas inst_tys hsAT
+ (tyConTyVars tycon,
+ snd . fromJust . tyConFamInst_maybe $ tycon)
+ checkIndexes _ _ _ = panic "checkIndexes"
+
+ checkIndexes' clas (instTvs, instTys) hsAT (atTvs, atTys)
+ = let atName = tcdName . unLoc $ hsAT
+ in
+ setSrcSpan (getLoc hsAT) $
+ addErrCtxt (atInstCtxt atName) $
+ case find ((atName ==) . tyConName) (classATs clas) of
+ Nothing -> addErrTc $ badATErr clas atName -- not in this class
+ Just atDecl ->
+ case assocTyConArgPoss_maybe atDecl of
+ Nothing -> panic "checkIndexes': AT has no args poss?!?"
+ Just poss ->
+
+ -- The following is tricky! We need to deal with three
+ -- complications: (1) The AT possibly only uses a subset of
+ -- the class parameters as indexes and those it uses may be in
+ -- a different order; (2) the AT may have extra arguments,
+ -- which must be type variables; and (3) variables in AT and
+ -- instance head will be different `Name's even if their
+ -- source lexemes are identical.
+ --
+ -- Re (1), `poss' contains a permutation vector to extract the
+ -- class parameters in the right order.
+ --
+ -- Re (2), we wrap the (permuted) class parameters in a Maybe
+ -- type and use Nothing for any extra AT arguments. (First
+ -- equation of `checkIndex' below.)
+ --
+ -- Re (3), we replace any type variable in the AT parameters
+ -- that has the same source lexeme as some variable in the
+ -- instance types with the instance type variable sharing its
+ -- source lexeme.
+ --
+ let relevantInstTys = map (instTys !!) poss
+ instArgs = map Just relevantInstTys ++
+ repeat Nothing -- extra arguments
+ renaming = substSameTyVar atTvs instTvs
+ in
+ zipWithM_ checkIndex (substTys renaming atTys) instArgs
+
+ checkIndex ty Nothing
+ | isTyVarTy ty = return ()
+ | otherwise = addErrTc $ mustBeVarArgErr ty
+ checkIndex ty (Just instTy)
+ | ty `tcEqType` instTy = return ()
+ | otherwise = addErrTc $ wrongATArgErr ty instTy
+
+ listToNameSet = addListToNameSet emptyNameSet
+
+ substSameTyVar [] _ = emptyTvSubst
+ substSameTyVar (tv:tvs) replacingTvs =
+ let replacement = case find (tv `sameLexeme`) replacingTvs of
+ Nothing -> mkTyVarTy tv
+ Just rtv -> mkTyVarTy rtv
+ --
+ tv1 `sameLexeme` tv2 =
+ nameOccName (tyVarName tv1) == nameOccName (tyVarName tv2)
+ in
+ extendTvSubst (substSameTyVar tvs replacingTvs) tv replacement
\end{code}
\begin{code}
tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
+-- Returns a binding for the dfun
+
+------------------------
+-- Derived newtype instances; surprisingly tricky!
+--
+-- In the case of a newtype, things are rather easy
+-- class Show a => Foo a b where ...
+-- newtype T a = MkT (Tree [a]) deriving( Foo Int )
+-- The newtype gives an FC axiom looking like
+-- axiom CoT a :: T a :=: Tree [a]
+-- (see Note [Newtype coercions] in TyCon for this unusual form of axiom)
+--
+-- So all need is to generate a binding looking like:
+-- dfunFooT :: forall a. (Foo Int (Tree [a], Show (T a)) => Foo Int (T a)
+-- dfunFooT = /\a. \(ds:Show (T a)) (df:Foo (Tree [a])).
+-- case df `cast` (Foo Int (sym (CoT a))) of
+-- Foo _ op1 .. opn -> Foo ds op1 .. opn
+--
+-- If there are no superclasses, matters are simpler, because we don't need the case
+-- see Note [Newtype deriving superclasses] in TcDeriv.lhs
+
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived mb_preds })
+ = do { let dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol
+ origin = SigOrigin rigid_info
+ inst_ty = idType dfun_id
+ ; (tvs, theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty
+ -- inst_head_ty is a PredType
+
+ ; inst_loc <- getInstLoc origin
+ ; (rep_dict_id : sc_dict_ids, wrap_fn, sc_binds)
+ <- make_wrapper inst_loc tvs theta mb_preds
+ -- Here, we are relying on the order of dictionary
+ -- arguments built by NewTypeDerived in TcDeriv;
+ -- namely, that the rep_dict_id comes first
+
+ ; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head_ty
+ cls_tycon = classTyCon cls
+ the_coercion = make_coercion cls_tycon cls_inst_tys
+ coerced_rep_dict = mkHsWrap the_coercion (HsVar rep_dict_id)
+
+ ; body <- make_body cls_tycon cls_inst_tys sc_dict_ids coerced_rep_dict
+
+ ; return (sc_binds `snocBag` (noLoc $ VarBind dfun_id $ noLoc $ mkHsWrap wrap_fn body)) }
+ where
-tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+ -----------------------
+ -- make_wrapper
+ -- We distinguish two cases:
+ -- (a) there is no tyvar abstraction in the dfun, so all dicts are constant,
+ -- and the new dict can just be a constant
+ -- (mb_preds = Just preds)
+ -- (b) there are tyvars, so we must make a dict *fun*
+ -- (mb_preds = Nothing)
+ -- See the defn of NewTypeDerived for the meaning of mb_preds
+ make_wrapper inst_loc tvs theta (Just preds) -- Case (a)
+ = ASSERT( null tvs && null theta )
+ do { dicts <- newDictBndrs inst_loc preds
+ ; sc_binds <- addErrCtxt superClassCtxt $
+ tcSimplifySuperClasses inst_loc [] dicts
+ -- Use tcSimplifySuperClasses to avoid creating loops, for the
+ -- same reason as Note [SUPERCLASS-LOOP 1] in TcSimplify
+ ; return (map instToId dicts, idHsWrapper, sc_binds) }
+
+ make_wrapper inst_loc tvs theta Nothing -- Case (b)
+ = do { dicts <- newDictBndrs inst_loc theta
+ ; let dict_ids = map instToId dicts
+ ; return (dict_ids, mkWpTyLams tvs <.> mkWpLams dict_ids, emptyBag) }
+
+ -----------------------
+ -- make_coercion
+ -- The inst_head looks like (C s1 .. sm (T a1 .. ak))
+ -- But we want the coercion (C s1 .. sm (sym (CoT a1 .. ak)))
+ -- with kind (C s1 .. sm (T a1 .. ak) :=: C s1 .. sm <rep_ty>)
+ -- where rep_ty is the (eta-reduced) type rep of T
+ -- So we just replace T with CoT, and insert a 'sym'
+ -- NB: we know that k will be >= arity of CoT, because the latter fully eta-reduced
+
+ make_coercion cls_tycon cls_inst_tys
+ | Just (all_tys_but_last, last_ty) <- snocView cls_inst_tys
+ , (tycon, tc_args) <- tcSplitTyConApp last_ty -- Should not fail
+ , Just co_con <- newTyConCo_maybe tycon
+ , let co = mkSymCoercion (mkTyConApp co_con tc_args)
+ = WpCo (mkTyConApp cls_tycon (all_tys_but_last ++ [co]))
+ | otherwise -- The newtype is transparent; no need for a cast
+ = idHsWrapper
+
+ -----------------------
+ -- make_body
+ -- Two cases; see Note [Newtype deriving superclasses] in TcDeriv.lhs
+ -- (a) no superclasses; then we can just use the coerced dict
+ -- (b) one or more superclasses; then new need to do the unpack/repack
+
+ make_body cls_tycon cls_inst_tys sc_dict_ids coerced_rep_dict
+ | null sc_dict_ids -- Case (a)
+ = return coerced_rep_dict
+ | otherwise -- Case (b)
+ = do { op_ids <- newSysLocalIds FSLIT("op") op_tys
+ ; dummy_sc_dict_ids <- newSysLocalIds FSLIT("sc") (map idType sc_dict_ids)
+ ; let the_pat = ConPatOut { pat_con = noLoc cls_data_con, pat_tvs = [],
+ pat_dicts = dummy_sc_dict_ids,
+ pat_binds = emptyLHsBinds,
+ pat_args = PrefixCon (map nlVarPat op_ids),
+ pat_ty = pat_ty}
+ the_match = mkSimpleMatch [noLoc the_pat] the_rhs
+ the_rhs = mkHsConApp cls_data_con cls_inst_tys $
+ map HsVar (sc_dict_ids ++ op_ids)
+
+ -- Warning: this HsCase scrutinises a value with a PredTy, which is
+ -- never otherwise seen in Haskell source code. It'd be
+ -- nicer to generate Core directly!
+ ; return (HsCase (noLoc coerced_rep_dict) $
+ MatchGroup [the_match] (mkFunTy pat_ty pat_ty)) }
+ where
+ pat_ty = mkTyConApp cls_tycon cls_inst_tys
+ cls_data_con = head (tyConDataCons cls_tycon)
+ cls_arg_tys = dataConInstArgTys cls_data_con cls_inst_tys
+ op_tys = dropList sc_dict_ids cls_arg_tys
+
+------------------------
+-- Ordinary instances
+
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags })
= let
dfun_id = instanceDFunId ispec
- rigid_info = InstSkol dfun_id
+ rigid_info = InstSkol
inst_ty = idType dfun_id
in
-- Prime error recovery
origin = SigOrigin rigid_info
in
-- Create dictionary Ids from the specified instance contexts.
- newDicts InstScOrigin sc_theta' `thenM` \ sc_dicts ->
- newDicts origin dfun_theta' `thenM` \ dfun_arg_dicts ->
- newDicts origin [mkClassPred clas inst_tys'] `thenM` \ [this_dict] ->
+ getInstLoc InstScOrigin `thenM` \ sc_loc ->
+ newDictBndrs sc_loc sc_theta' `thenM` \ sc_dicts ->
+ getInstLoc origin `thenM` \ inst_loc ->
+ newDictBndrs inst_loc dfun_theta' `thenM` \ dfun_arg_dicts ->
+ newDictBndr inst_loc (mkClassPred clas inst_tys') `thenM` \ this_dict ->
-- Default-method Ids may be mentioned in synthesised RHSs,
-- but they'll already be in the environment.
in
tcMethods origin clas inst_tyvars'
dfun_theta' inst_tys' avail_insts
- op_items binds `thenM` \ (meth_ids, meth_binds) ->
+ op_items monobinds uprags `thenM` \ (meth_ids, meth_binds) ->
-- Figure out bindings for the superclass context
-- Don't include this_dict in the 'givens', else
-- sc_dicts get bound by just selecting from this_dict!!
addErrCtxt superClassCtxt
- (tcSimplifySuperClasses inst_tyvars'
- dfun_arg_dicts
- sc_dicts) `thenM` \ sc_binds ->
+ (tcSimplifySuperClasses inst_loc
+ dfun_arg_dicts sc_dicts) `thenM` \ sc_binds ->
-- It's possible that the superclass stuff might unified one
-- of the inst_tyavars' with something in the envt
checkSigTyVars inst_tyvars' `thenM_`
-- Deal with 'SPECIALISE instance' pragmas
- let
- specs = case binds of
- VanillaInst _ prags -> filter isSpecInstLSig prags
- other -> []
- in
- tcPrags dfun_id specs `thenM` \ prags ->
+ tcPrags dfun_id (filter isSpecInstLSig uprags) `thenM` \ prags ->
-- Create the result bindings
let
tcMethods origin clas inst_tyvars' dfun_theta' inst_tys'
- avail_insts op_items (VanillaInst monobinds uprags)
+ avail_insts op_items monobinds uprags
= -- Check that all the method bindings come from this class
let
sel_names = [idName sel_id | (sel_id, _) <- op_items]
mapM tc_method_bind meth_infos `thenM` \ meth_binds_s ->
returnM (meth_ids, unionManyBags meth_binds_s)
-
-
--- Derived newtype instances
-tcMethods origin clas inst_tyvars' dfun_theta' inst_tys'
- avail_insts op_items (NewTypeDerived rep_tys)
- = getInstLoc origin `thenM` \ inst_loc ->
- mapAndUnzip3M (do_one inst_loc) op_items `thenM` \ (meth_ids, meth_binds, rhs_insts) ->
-
- tcSimplifyCheck
- (ptext SLIT("newtype derived instance"))
- inst_tyvars' avail_insts rhs_insts `thenM` \ lie_binds ->
-
- -- I don't think we have to do the checkSigTyVars thing
-
- returnM (meth_ids, lie_binds `unionBags` listToBag meth_binds)
-
- where
- do_one inst_loc (sel_id, _)
- = -- The binding is like "op @ NewTy = op @ RepTy"
- -- Make the *binder*, like in mkMethodBind
- tcInstClassOp inst_loc sel_id inst_tys' `thenM` \ meth_inst ->
-
- -- Make the *occurrence on the rhs*
- tcInstClassOp inst_loc sel_id rep_tys' `thenM` \ rhs_inst ->
- let
- meth_id = instToId meth_inst
- in
- return (meth_id, noLoc (VarBind meth_id (nlHsVar (instToId rhs_inst))), rhs_inst)
-
- -- Instantiate rep_tys with the relevant type variables
- -- This looks a bit odd, because inst_tyvars' are the skolemised version
- -- of the type variables in the instance declaration; but rep_tys doesn't
- -- have the skolemised version, so we substitute them in here
- rep_tys' = substTys subst rep_tys
- subst = zipOpenTvSubst inst_tyvars' (mkTyVarTys inst_tyvars')
\end{code}
inst_decl_ctxt doc = ptext SLIT("In the instance declaration for") <+> quotes doc
superClassCtxt = ptext SLIT("When checking the super-classes of an instance declaration")
+
+atInstCtxt name = ptext SLIT("In the associated type instance for") <+>
+ quotes (ppr name)
+
+mustBeVarArgErr ty =
+ sep [ ptext SLIT("Arguments that do not correspond to a class parameter") <+>
+ ptext SLIT("must be variables")
+ , ptext SLIT("Instead of a variable, found") <+> ppr ty
+ ]
+
+wrongATArgErr ty instTy =
+ sep [ ptext SLIT("Type indexes must match class instance head")
+ , ptext SLIT("Found") <+> ppr ty <+> ptext SLIT("but expected") <+>
+ ppr instTy
+ ]
\end{code}
projects / ghc-hetmet.git / blobdiff