import HsSyn
import TcBinds ( mkPragFun, tcPrags, badBootDeclErr )
+import TcTyClsDecls ( tcIdxTyInstDecl )
import TcClassDcl ( tcMethodBind, mkMethodBind, badMethodErr,
tcClassDecl2, getGenericInstances )
import TcRnMonad
import TcMType ( tcSkolSigType, checkValidInstance, checkValidInstHead )
-import TcType ( mkClassPred, tcSplitSigmaTy, tcSplitDFunHead, mkTyVarTys,
- SkolemInfo(InstSkol), tcSplitDFunTy )
-import Inst ( tcInstClassOp, newDicts, instToId, showLIE,
+import TcType ( mkClassPred, tcSplitSigmaTy, tcSplitDFunHead,
+ SkolemInfo(InstSkol), tcSplitDFunTy, mkFunTy )
+import Inst ( newDictBndr, newDictBndrs, instToId, showLIE,
getOverlapFlag, tcExtendLocalInstEnv )
import InstEnv ( mkLocalInstance, instanceDFunId )
import TcDeriv ( tcDeriving )
import TcEnv ( InstInfo(..), InstBindings(..),
- newDFunName, tcExtendIdEnv
+ newDFunName, tcExtendIdEnv, tcExtendGlobalEnv
)
import TcHsType ( kcHsSigType, tcHsKindedType )
import TcUnify ( checkSigTyVars )
-import TcSimplify ( tcSimplifyCheck, tcSimplifySuperClasses )
-import Type ( zipOpenTvSubst, substTheta, substTys )
-import DataCon ( classDataCon )
+import TcSimplify ( tcSimplifySuperClasses )
+import Type ( zipOpenTvSubst, substTheta, mkTyConApp, mkTyVarTy,
+ splitFunTys, TyThing )
+import Coercion ( mkSymCoercion )
+import TyCon ( TyCon, newTyConCo, tyConTyVars )
+import DataCon ( classDataCon, dataConTyCon, dataConInstArgTys )
import Class ( classBigSig )
-import Var ( Id, idName, idType )
+import Var ( TyVar, Id, idName, idType, tyVarKind )
+import Id ( mkSysLocal )
+import UniqSupply ( uniqsFromSupply, splitUniqSupply )
import MkId ( mkDictFunId )
import Name ( Name, getSrcLoc )
import Maybe ( catMaybes )
import Outputable
import Bag
import BasicTypes ( Activation( AlwaysActive ), InlineSpec(..) )
+import HscTypes ( implicitTyThings )
import FastString
\end{code}
all the instance and value decls. Indeed that's the reason we need
two passes over the instance decls.
-
Here is the overall algorithm.
Assume that we have an instance declaration
tcInstDecls1 tycl_decls inst_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 the ordinary instance declarations and instances of
+ -- indexed types
+ ; let { idxty_decls = filter (isIdxTyDecl . unLoc) tycl_decls }
+ ; local_info_tycons <- mappM tcLocalInstDecl1 inst_decls
+ ; idxty_info_tycons <- mappM tcIdxTyInstDecl idxty_decls
+
+ ; let { (local_infos,
+ local_tycons) = unzip local_info_tycons
+ ; (idxty_infos,
+ idxty_tycons) = unzip idxty_info_tycons
+ ; local_idxty_info = concat local_infos ++ catMaybes idxty_infos
+ ; local_idxty_tycon = concat local_tycons ++
+ catMaybes idxty_tycons
+ ; clas_decls = filter (isClassDecl.unLoc) tycl_decls
+ ; implicit_things = concatMap implicitTyThings local_idxty_tycon
+ }
+
+ -- (2) Add the tycons of associated types and their implicit
+ -- tythings to the global environment
+ ; tcExtendGlobalEnv (local_idxty_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
+ ; addInsts local_idxty_info $ do {
+ ; addInsts generic_inst_info $ 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
+ ; addInsts deriv_inst_info $ do {
+
+ ; gbl_env <- getGblEnv
+ ; returnM (gbl_env,
+ generic_inst_info ++ deriv_inst_info ++ local_idxty_info,
+ deriv_binds)
+ }}}}}
addInsts :: [InstInfo] -> TcM a -> TcM a
addInsts infos thing_inside
\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))
+tcLocalInstDecl1 decl@(L loc (InstDecl poly_ty binds uprags ats))
= -- Prime error recovery, set source location
- recoverM (returnM Nothing) $
+ recoverM (returnM ([], [])) $
setSrcSpan loc $
addErrCtxt (instDeclCtxt1 poly_ty) $
; poly_ty' <- tcHsKindedType kinded_ty
; let (tyvars, theta, tau) = tcSplitSigmaTy poly_ty'
+ -- Now, check the validity of the instance.
; (clas, inst_tys) <- checkValidInstHead tau
; checkValidInstance tyvars theta clas inst_tys
+ -- Next, process any associated types.
+ ; idxty_info_tycons <- mappM tcIdxTyInstDecl ats
+
+ -- 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
-
- ; return (Just (InstInfo { iSpec = ispec, iBinds = VanillaInst binds uprags })) }
+ ; let dfun = mkDictFunId dfun_name tyvars theta clas inst_tys
+ ispec = mkLocalInstance dfun overlap_flag
+ (idxty_infos,
+ idxty_tycons) = unzip idxty_info_tycons
+
+ ; return ([InstInfo { iSpec = ispec,
+ iBinds = VanillaInst binds uprags }] ++
+ catMaybes idxty_infos,
+ catMaybes idxty_tycons)
+ }
\end{code}
\begin{code}
tcInstDecl2 :: InstInfo -> TcM (LHsBinds Id)
+-- Returns a binding for the dfun
-tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = binds })
+------------------------
+-- Derived newtype instances
+--
+-- We need to make a copy of the dictionary we are deriving from
+-- because we may need to change some of the superclass dictionaries
+-- see Note [Newtype deriving superclasses] in TcDeriv.lhs
+--
+-- 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]
+--
+-- 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
+
+tcInstDecl2 (InstInfo { iSpec = ispec,
+ iBinds = NewTypeDerived tycon rep_tys })
+ = do { let dfun_id = instanceDFunId ispec
+ rigid_info = InstSkol dfun_id
+ origin = SigOrigin rigid_info
+ inst_ty = idType dfun_id
+ ; inst_loc <- getInstLoc origin
+ ; (tvs, theta, inst_head) <- tcSkolSigType rigid_info inst_ty
+ ; dicts <- newDictBndrs inst_loc theta
+ ; uniqs <- newUniqueSupply
+ ; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head
+ ; this_dict <- newDictBndr inst_loc (mkClassPred cls rep_tys)
+ ; let (rep_dict_id:sc_dict_ids)
+ | null dicts = [instToId this_dict]
+ | otherwise = map instToId dicts
+
+ -- (Here, we are relying on the order of dictionary
+ -- arguments built by NewTypeDerived in TcDeriv.)
+
+ wrap_fn = mkCoTyLams tvs <.> mkCoLams (rep_dict_id:sc_dict_ids)
+
+ -- we need to find the kind that this class applies to
+ -- and drop trailing tvs appropriately
+ cls_kind = tyVarKind (head (reverse (tyConTyVars cls_tycon)))
+ the_tvs = drop_tail (length (fst (splitFunTys cls_kind))) tvs
+
+ coerced_rep_dict = mkHsCoerce (co_fn the_tvs cls_tycon cls_inst_tys) (HsVar rep_dict_id)
+
+ body | null sc_dict_ids = coerced_rep_dict
+ | otherwise = HsCase (noLoc coerced_rep_dict) $
+ MatchGroup [the_match] (mkFunTy in_dict_ty inst_head)
+ in_dict_ty = mkTyConApp cls_tycon cls_inst_tys
+
+ the_match = mkSimpleMatch [noLoc the_pat] the_rhs
+ the_rhs = mkHsConApp cls_data_con cls_inst_tys (map HsVar (sc_dict_ids ++ op_ids))
+
+ (uniqs1, uniqs2) = splitUniqSupply uniqs
+
+ op_ids = zipWith (mkSysLocal FSLIT("op"))
+ (uniqsFromSupply uniqs1) op_tys
+
+ dict_ids = zipWith (mkSysLocal FSLIT("dict"))
+ (uniqsFromSupply uniqs2) (map idType sc_dict_ids)
+
+ the_pat = ConPatOut { pat_con = noLoc cls_data_con, pat_tvs = [],
+ pat_dicts = dict_ids,
+ pat_binds = emptyLHsBinds,
+ pat_args = PrefixCon (map nlVarPat op_ids),
+ pat_ty = in_dict_ty}
+
+ cls_data_con = classDataCon cls
+ cls_tycon = dataConTyCon cls_data_con
+ cls_arg_tys = dataConInstArgTys cls_data_con cls_inst_tys
+
+ n_dict_args = if length dicts == 0 then 0 else length dicts - 1
+ op_tys = drop n_dict_args cls_arg_tys
+
+ dict = mkHsCoerce wrap_fn body
+ ; return (unitBag (noLoc $ VarBind dfun_id (noLoc dict))) }
+ where
+ -- For newtype T a = MkT <ty>
+ -- The returned coercion has kind :: C (T a):=:C <ty>
+ co_fn tvs cls_tycon cls_inst_tys | Just co_con <- newTyConCo tycon
+ = ExprCoFn (mkTyConApp cls_tycon (drop_tail 1 cls_inst_tys ++
+ [mkSymCoercion (mkTyConApp co_con (map mkTyVarTy tvs))]))
+ | otherwise
+ = idCoercion
+ drop_tail n l = take (length l - n) l
+
+------------------------
+-- Ordinary instances
+
+tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags })
= let
dfun_id = instanceDFunId ispec
rigid_info = InstSkol dfun_id
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
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]
let
prag_fn = mkPragFun uprags
all_insts = avail_insts ++ catMaybes meth_insts
- tc_method_bind = tcMethodBind inst_tyvars' dfun_theta' all_insts prag_fn
+ sig_fn n = Just [] -- No scoped type variables, but every method has
+ -- a type signature, in effect, so that we check
+ -- the method has the right type
+ tc_method_bind = tcMethodBind inst_tyvars' dfun_theta' all_insts sig_fn prag_fn
meth_ids = [meth_id | (_,meth_id,_) <- meth_infos]
in
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}
projects / ghc-hetmet.git / blobdiff