mkDefaultMethodId dm_name ty = mkVanillaGlobal dm_name ty noCafIdInfo
mkDictFunId :: Name -- Name to use for the dict fun;
- -> Class
-> [TyVar]
- -> [Type]
-> ThetaType
+ -> Class
+ -> [Type]
-> Id
-mkDictFunId dfun_name clas inst_tyvars inst_tys dfun_theta
+mkDictFunId dfun_name inst_tyvars dfun_theta clas inst_tys
= mkVanillaGlobal dfun_name dfun_ty noCafIdInfo
where
dfun_ty = mkSigmaTy inst_tyvars dfun_theta (mkDictTy clas inst_tys)
-- always a class op, but with -fno-implicit-prelude GHC is
-- meant to find whatever thing is in scope, and that may
-- be an ordinary function.
- newMethod origin id [ty] `thenM` \ inst ->
- returnM (instToId inst)
+ newMethod origin id [ty]
newMethod :: InstOrigin
-> TcId
-> [TcType]
- -> TcM Inst
+ -> TcM Id
newMethod orig id tys
= -- Get the Id type and instantiate it at the specified types
let
= getInstLoc orig `thenM` \ loc ->
newMethodWith loc id tys theta tau `thenM` \ inst ->
extendLIE inst `thenM_`
- returnM inst
+ returnM (instToId inst)
--------------------------------------------
-- newMethodWith and newMethodAtLoc do *not* drop the
\begin{code}
module TcClassDcl ( tcClassDecl1, tcClassDecls2,
- tcMethodBind, mkMethodBind, badMethodErr
+ MethodSpec, tcMethodBind, mkMethodBind, badMethodErr
) where
#include "HsVersions.h"
tyvar sets.
\begin{code}
+type MethodSpec = (Id, -- Global selector Id
+ TcSigInfo, -- Signature
+ RenamedMonoBinds) -- Binding for the method
+
tcMethodBind
:: [(TyVar,TcTyVar)] -- Bindings for type environment
-> [TcTyVar] -- Instantiated type variables for the
-> [Inst] -- Available from context, used to simplify constraints
-- from the method body
-> [RenamedSig] -- Pragmas (e.g. inline pragmas)
- -> (Id, TcSigInfo, RenamedMonoBinds) -- Details of this method
+ -> MethodSpec -- Details of this method
-> TcM TcMonoBinds
tcMethodBind xtve inst_tyvars inst_theta avail_insts prags
-> RenamedMonoBinds -- Method binding (pick the right one from in here)
-> ClassOpItem
-> TcM (Inst, -- Method inst
- (Id, -- Global selector Id
- TcSigInfo, -- Signature
- RenamedMonoBinds)) -- Binding for the method
+ MethodSpec)
+-- Find the binding for the specified method, or make
+-- up a suitable default method if it isn't there
mkMethodBind origin clas inst_tys meth_binds (sel_id, dm_info)
= getInstLoc origin `thenM` \ inst_loc ->
import CmdLineOpts ( DynFlag(..) )
import TcRnMonad
-import TcEnv ( tcGetInstEnv, tcSetInstEnv, newDFunName, InstInfo(..), pprInstInfo,
+import TcEnv ( tcGetInstEnv, tcSetInstEnv, newDFunName,
+ InstInfo(..), pprInstInfo, InstBindings(..),
pprInstInfoDetails, tcLookupTyCon, tcExtendTyVarEnv
)
import TcGenDeriv -- Deriv stuff
import HscTypes ( DFunId )
import BasicTypes ( NewOrData(..) )
-import Class ( className, classKey, classTyVars, Class )
+import Class ( className, classKey, classTyVars, classSCTheta, Class )
+import Subst ( mkTyVarSubst, substTheta )
import ErrUtils ( dumpIfSet_dyn )
import MkId ( mkDictFunId )
import DataCon ( dataConRepArgTys, isNullaryDataCon, isExistentialDataCon )
)
import TcType ( TcType, ThetaType, mkTyVarTys, mkTyConApp, getClassPredTys_maybe,
isUnLiftedType, mkClassPred, tyVarsOfTypes, tcSplitFunTys,
- tcSplitTyConApp_maybe, tcEqTypes )
+ tcSplitTyConApp_maybe, tcEqTypes, mkAppTys )
+import Type ( splitAppTys )
import Var ( TyVar, tyVarKind )
import VarSet ( mkVarSet, subVarSet )
import PrelNames
\end{code}
-A note about contexts on data decls
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+[Data decl contexts] A note about contexts on data decls
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
data (RealFloat a) => Complex a = !a :+ !a deriving( Read )
-- Make a Real dfun instead of the dummy one we have so far
gen_inst_info :: DFunId -> RenamedMonoBinds -> InstInfo
gen_inst_info dfun binds
- = InstInfo { iDFunId = dfun, iBinds = binds, iPrags = [] }
+ = InstInfo { iDFunId = dfun, iBinds = VanillaInst binds [] }
rn_meths (cls, meths) = rnMethodBinds cls [] meths
\end{code}
not (isUnLiftedType arg_ty) -- No constraints for unlifted types?
]
- -- "extra_constraints": see notes above about contexts on data decls
+ -- "extra_constraints": see note [Data decl contexts] above
extra_constraints = tyConTheta tycon
- -- | offensive_class = tyConTheta tycon
- -- | otherwise = []
- -- offensive_class = classKey clas `elem` PrelInfo.needsDataDeclCtxtClassKeys
-
-
mk_eqn_help NewType tycon clas tys
= doptM Opt_GlasgowExts `thenM` \ gla_exts ->
if can_derive_via_isomorphism && (gla_exts || standard_instance) then
-- Go ahead and use the isomorphism
new_dfun_name clas tycon `thenM` \ dfun_name ->
- returnM (Nothing, Just (NewTypeDerived (mk_dfun dfun_name)))
+ returnM (Nothing, Just (InstInfo { iDFunId = mk_dfun dfun_name,
+ iBinds = NewTypeDerived rep_tys }))
else
if standard_instance then
mk_eqn_help DataType tycon clas [] -- Go via bale-out route
bale_out cant_derive_err
where
-- Here is the plan for newtype derivings. We see
- -- newtype T a1...an = T (t ak...an) deriving (C1...Cm)
- -- where aj...an do not occur free in t, and the Ci are *partial applications* of
- -- classes with the last parameter missing
+ -- newtype T a1...an = T (t ak...an) deriving (.., C s1 .. sm, ...)
+ -- where aj...an do not occur free in t, and the (C s1 ... sm) is a
+ -- *partial applications* of class C with the last parameter missing
--
-- We generate the instances
- -- instance Ci (t ak...aj) => Ci (T a1...aj)
+ -- instance C s1 .. sm (t ak...aj) => C s1 .. sm (T a1...aj)
-- where T a1...aj is the partial application of the LHS of the correct kind
--
-- Running example: newtype T s a = MkT (ST s a) deriving( Monad )
+ -- instance Monad (ST s) => Monad (T s) where
+ -- fail = coerce ... (fail @ ST s)
- kind = tyVarKind (last (classTyVars clas))
+ clas_tyvars = classTyVars clas
+ kind = tyVarKind (last clas_tyvars)
-- Kind of the thing we want to instance
-- e.g. argument kind of Monad, *->*
-- to get instance Monad (ST s) => Monad (T s)
(tyvars, rep_ty) = newTyConRep tycon
- maybe_rep_app = tcSplitTyConApp_maybe rep_ty
- Just (rep_tc, rep_ty_args) = maybe_rep_app
+ (rep_fn, rep_ty_args) = splitAppTys rep_ty
n_tyvars_to_keep = tyConArity tycon - n_args_to_drop
tyvars_to_drop = drop n_tyvars_to_keep tyvars
tyvars_to_keep = take n_tyvars_to_keep tyvars
- n_args_to_keep = tyConArity rep_tc - n_args_to_drop
+ n_args_to_keep = length rep_ty_args - n_args_to_drop
args_to_drop = drop n_args_to_keep rep_ty_args
args_to_keep = take n_args_to_keep rep_ty_args
- ctxt_pred = mkClassPred clas (tys ++ [mkTyConApp rep_tc args_to_keep])
-
- mk_dfun dfun_name = mkDictFunId dfun_name clas tyvars
- (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)] )
- [ctxt_pred]
+ rep_tys = tys ++ [mkAppTys rep_fn args_to_keep]
+ rep_pred = mkClassPred clas rep_tys
+ -- rep_pred is the representation dictionary, from where
+ -- we are gong to get all the methods for the newtype dictionary
+
+ inst_tys = (tys ++ [mkTyConApp tycon (mkTyVarTys tyvars_to_keep)])
+ -- The 'tys' here come from the partial application
+ -- in the deriving clause. The last arg is the new
+ -- instance type.
+
+ -- We must pass the superclasses; the newtype might be an instance
+ -- of them in a different way than the representation type
+ -- E.g. newtype Foo a = Foo a deriving( Show, Num, Eq )
+ -- Then the Show instance is not done via isomprphism; it shows
+ -- Foo 3 as "Foo 3"
+ -- The Num instance is derived via isomorphism, but the Show superclass
+ -- dictionary must the Show instance for Foo, *not* the Show dictionary
+ -- gotten from the Num dictionary. So we must build a whole new dictionary
+ -- not just use the Num one. The instance we want is something like:
+ -- instance (Num a, Show (Foo a), Eq (Foo a)) => Num (Foo a) where
+ -- (+) = ((+)@a)
+ -- ...etc...
+ -- There's no 'corece' needed because after the type checker newtypes
+ -- are transparent.
+
+ sc_theta = substTheta (mkTyVarSubst clas_tyvars inst_tys)
+ (classSCTheta clas)
+
+ -- If there are no tyvars, there's no need
+ -- to abstract over the dictionaries we need
+ dict_args | null tyvars = []
+ | otherwise = rep_pred : sc_theta
+
+ -- Finally! Here's where we build the dictionary Id
+ mk_dfun dfun_name = mkDictFunId dfun_name tyvars dict_args clas inst_tys
+
+ -------------------------------------------------------------------
+ -- Figuring out whether we can only do this newtype-deriving thing
- -- We can only do this newtype deriving thing if:
standard_instance = null tys && classKey clas `elem` derivableClassKeys
can_derive_via_isomorphism
&& not (clas `hasKey` showClassKey)
&& n_tyvars_to_keep >= 0 -- Well kinded;
-- eg not: newtype T = T Int deriving( Monad )
- && isJust maybe_rep_app -- The rep type is a type constructor app
&& n_args_to_keep >= 0 -- Well kinded:
-- eg not: newtype T a = T Int deriving( Monad )
&& eta_ok -- Eta reduction works
&& (tyVarsOfTypes args_to_keep `subVarSet` mkVarSet tyvars_to_keep)
cant_derive_err = derivingThingErr clas tys tycon tyvars_to_keep
- (ptext SLIT("too hard for cunning newtype deriving"))
+ (vcat [ptext SLIT("too hard for cunning newtype deriving"),
+ ppr n_tyvars_to_keep,
+ ppr n_args_to_keep,
+ ppr eta_ok,
+ ppr (isRecursiveTyCon tycon)
+ ])
bale_out err = addErrTc err `thenM_` returnM (Nothing, Nothing)
-- They'll appear later, when we do the top-level extendInstEnvs
mk_deriv_dfun (dfun_name, clas, tycon, tyvars, _) theta
- = mkDictFunId dfun_name clas tyvars
- [mkTyConApp tycon (mkTyVarTys tyvars)]
- theta
+ = mkDictFunId dfun_name tyvars theta
+ clas [mkTyConApp tycon (mkTyVarTys tyvars)]
\end{code}
%************************************************************************
tcGetInstEnv, tcSetInstEnv,
InstInfo(..), pprInstInfo, pprInstInfoDetails,
simpleInstInfoTy, simpleInstInfoTyCon,
+ InstBindings(..),
-- Global environment
tcExtendGlobalEnv,
data InstInfo
= InstInfo {
iDFunId :: DFunId, -- The dfun id
- iBinds :: RenamedMonoBinds, -- Bindings, b
- iPrags :: [RenamedSig] -- User pragmas recorded for generating specialised instances
+ iBinds :: InstBindings
}
- | NewTypeDerived { -- Used for deriving instances of newtypes, where the
- -- witness dictionary is identical to the argument dictionary
- -- Hence no bindings.
- iDFunId :: DFunId -- The dfun id
- }
+data InstBindings
+ = VanillaInst -- The normal case
+ RenamedMonoBinds -- Bindings
+ [RenamedSig] -- User pragmas recorded for generating
+ -- specialised instances
+
+ | NewTypeDerived -- Used for deriving instances of newtypes, where the
+ [Type] -- witness dictionary is identical to the argument
+ -- dictionary. Hence no bindings, no pragmas
+ -- The [Type] are the representation types
+ -- See notes in TcDeriv
pprInstInfo info = vcat [ptext SLIT("InstInfo:") <+> ppr (idType (iDFunId info))]
-pprInstInfoDetails (InstInfo { iBinds = b }) = ppr b
-pprInstInfoDetails (NewTypeDerived _) = text "Derived from the represenation type"
+
+pprInstInfoDetails (InstInfo { iBinds = VanillaInst b _ }) = ppr b
+pprInstInfoDetails (InstInfo { iBinds = NewTypeDerived _}) = text "Derived from the represenation type"
simpleInstInfoTy :: InstInfo -> Type
simpleInstInfoTy info = case tcSplitDFunTy (idType (iDFunId info)) of
newTyVarTy, newTyVarTys, zonkTcType, readHoleResult )
import TcType ( TcType, TcSigmaType, TcRhoType, TyVarDetails(VanillaTv),
tcSplitFunTys, tcSplitTyConApp, mkTyVarTys,
- isSigmaTy, isTauTy, mkFunTy, mkFunTys,
+ isSigmaTy, mkFunTy, mkFunTys,
mkTyConApp, mkClassPred, tcFunArgTy,
tyVarsOfTypes, isLinearPred,
liftedTypeKind, openTypeKind,
import FieldLabel ( FieldLabel, fieldLabelName, fieldLabelType, fieldLabelTyCon )
import Id ( Id, idType, recordSelectorFieldLabel, isRecordSelector, isDataConWrapId_maybe )
import DataCon ( DataCon, dataConFieldLabels, dataConSig, dataConStrictMarks )
-import Name ( Name, isExternalName )
+import Name ( Name )
import TyCon ( TyCon, tyConTyVars, tyConTheta, isAlgTyCon, tyConDataCons )
import Subst ( mkTopTyVarSubst, substTheta, substTy )
import VarSet ( emptyVarSet, elemVarSet )
| want_method_inst fun_ty
= tcInstType VanillaTv fun_ty `thenM` \ (tyvars, theta, tau) ->
newMethodWithGivenTy orig fun_id
- (mkTyVarTys tyvars) theta tau `thenM` \ meth ->
- loop (HsVar (instToId meth)) tau
+ (mkTyVarTys tyvars) theta tau `thenM` \ meth_id ->
+ loop (HsVar meth_id) tau
loop fun fun_ty
| isSigmaTy fun_ty
import TcMType ( tcInstType, checkValidTheta, checkValidInstHead, instTypeErr,
checkAmbiguity, UserTypeCtxt(..), SourceTyCtxt(..) )
import TcType ( mkClassPred, mkTyVarTy, tcSplitForAllTys, tyVarsOfType,
- tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe,
+ tcSplitSigmaTy, getClassPredTys, tcSplitPredTy_maybe, mkTyVarTys,
TyVarDetails(..)
)
-import Inst ( InstOrigin(..), newDicts, instToId, showLIE )
+import Inst ( InstOrigin(..), newMethod, newMethodAtLoc,
+ newDicts, instToId, showLIE )
import TcDeriv ( tcDeriving )
-import TcEnv ( tcExtendGlobalValEnv, tcExtendLocalValEnv2,
+import TcEnv ( tcExtendGlobalValEnv,
tcLookupClass, tcExtendTyVarEnv2,
tcExtendInstEnv, tcExtendLocalInstEnv, tcLookupGlobalId,
- InstInfo(..), pprInstInfo, simpleInstInfoTyCon,
+ InstInfo(..), InstBindings(..), pprInstInfo, simpleInstInfoTyCon,
simpleInstInfoTy, newDFunName
)
import PprType ( pprClassPred )
-import TcMonoType ( tcSigPolyId, tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
+import TcMonoType ( tcHsTyVars, kcHsSigType, tcHsType, tcHsSigType )
import TcUnify ( checkSigTyVars )
import TcSimplify ( tcSimplifyCheck, tcSimplifyTop )
import HscTypes ( DFunId )
-import Subst ( mkTyVarSubst, substTheta )
+import Subst ( mkTyVarSubst, substTheta, substTy )
import DataCon ( classDataCon )
import Class ( Class, classBigSig )
import Var ( idName, idType )
import NameSet
import Id ( setIdLocalExported )
-import MkId ( mkDictFunId, unsafeCoerceId, rUNTIME_ERROR_ID )
+import MkId ( mkDictFunId, rUNTIME_ERROR_ID )
import FunDeps ( checkInstFDs )
import Generics ( validGenericInstanceType )
import Name ( getSrcLoc )
import TysWiredIn ( genericTyCons )
import SrcLoc ( SrcLoc )
import Unique ( Uniquable(..) )
-import Util ( lengthExceeds, isSingleton )
+import Util ( lengthExceeds )
import BasicTypes ( NewOrData(..) )
import UnicodeUtil ( stringToUtf8 )
import ErrUtils ( dumpIfSet_dyn )
checkTc (checkInstFDs theta clas inst_tys)
(instTypeErr (pprClassPred clas inst_tys) msg) `thenM_`
newDFunName clas inst_tys src_loc `thenM` \ dfun_name ->
- returnM (Just (InstInfo { iDFunId = mkDictFunId dfun_name clas tyvars inst_tys theta,
- iBinds = binds, iPrags = uprags }))
+ returnM (Just (InstInfo { iDFunId = mkDictFunId dfun_name tyvars theta clas inst_tys,
+ iBinds = VanillaInst binds uprags }))
where
msg = parens (ptext SLIT("the instance types do not agree with the functional dependencies of the class"))
\end{code}
newDFunName clas [inst_ty] loc `thenM` \ dfun_name ->
let
inst_theta = [mkClassPred clas [mkTyVarTy tv] | tv <- tyvars]
- dfun_id = mkDictFunId dfun_name clas tyvars [inst_ty] inst_theta
+ dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
in
- returnM (InstInfo { iDFunId = dfun_id, iBinds = binds, iPrags = [] })
+ returnM (InstInfo { iDFunId = dfun_id, iBinds = VanillaInst binds [] })
\end{code}
\begin{code}
tcInstDecl2 :: InstInfo -> TcM TcMonoBinds
-tcInstDecl2 (NewTypeDerived { iDFunId = dfun_id })
- = tcInstType InstTv (idType dfun_id) `thenM` \ (inst_tyvars', dfun_theta', inst_head') ->
- newDicts InstanceDeclOrigin dfun_theta' `thenM` \ rep_dicts ->
- let
- rep_dict_id = ASSERT( isSingleton rep_dicts )
- instToId (head rep_dicts) -- Derived newtypes have just one dict arg
-
- body = TyLam inst_tyvars' $
- DictLam [rep_dict_id] $
- (HsVar unsafeCoerceId `TyApp` [idType rep_dict_id, inst_head'])
- `HsApp`
- (HsVar rep_dict_id)
- -- You might wonder why we have the 'coerce'. It's because the
- -- type equality mechanism isn't clever enough; see comments with Type.eqType.
- -- So Lint complains if we don't have this.
- in
- returnM (VarMonoBind dfun_id body)
-
-tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = monobinds, iPrags = uprags })
+tcInstDecl2 (InstInfo { iDFunId = dfun_id, iBinds = binds })
= -- Prime error recovery
recoverM (returnM EmptyMonoBinds) $
addSrcLoc (getSrcLoc dfun_id) $
-- Default-method Ids may be mentioned in synthesised RHSs,
-- but they'll already be in the environment.
- -- Check that all the method bindings come from this class
- mkMethodBinds clas inst_tys' op_items monobinds `thenM` \ (meth_insts, meth_infos) ->
-
- let -- These insts are in scope; quite a few, eh?
- avail_insts = [this_dict] ++ dfun_arg_dicts ++
- sc_dicts ++ meth_insts
-
- xtve = inst_tyvars `zip` inst_tyvars'
- tc_meth = tcMethodBind xtve inst_tyvars' dfun_theta' avail_insts uprags
+ ------------------
+ -- Typecheck the methods
+ let -- These insts are in scope; quite a few, eh?
+ avail_insts = [this_dict] ++ dfun_arg_dicts ++ sc_dicts
in
- mappM tc_meth meth_infos `thenM` \ meth_binds_s ->
+ tcMethods clas inst_tyvars inst_tyvars'
+ dfun_theta' inst_tys' avail_insts
+ op_items binds `thenM` \ (meth_ids, meth_binds) ->
-- Figure out bindings for the superclass context
tcSuperClasses inst_tyvars' dfun_arg_dicts sc_dicts
`thenM` \ (zonked_inst_tyvars, sc_binds_inner, sc_binds_outer) ->
- -- Deal with SPECIALISE instance pragmas by making them
+ -- Deal with 'SPECIALISE instance' pragmas by making them
-- look like SPECIALISE pragmas for the dfun
let
+ uprags = case binds of
+ VanillaInst _ uprags -> uprags
+ other -> []
spec_prags = [ SpecSig (idName dfun_id) ty loc
- | SpecInstSig ty loc <- uprags]
+ | SpecInstSig ty loc <- uprags ]
+ xtve = inst_tyvars `zip` inst_tyvars'
in
-
tcExtendGlobalValEnv [dfun_id] (
- tcExtendTyVarEnv2 xtve $
- tcExtendLocalValEnv2 [(idName sel_id, tcSigPolyId sig)
- | (sel_id, sig, _) <- meth_infos] $
- -- Map sel_id to the local method name we are using
+ tcExtendTyVarEnv2 xtve $
tcSpecSigs spec_prags
) `thenM` \ prag_binds ->
-- Reason for setIdLocalExported: see notes with MkId.mkDictFunId
dict_constr = classDataCon clas
- scs_and_meths = map instToId (sc_dicts ++ meth_insts)
+ scs_and_meths = map instToId sc_dicts ++ meth_ids
this_dict_id = instToId this_dict
inlines | null dfun_arg_dicts = emptyNameSet
| otherwise = unitNameSet (idName dfun_id)
-- BUT: don't inline it if it's a constant dictionary;
-- we'll get all the benefit without inlining, and we get
-- a **lot** of code duplication if we inline it
+ --
+ -- See Note [Inline dfuns] below
dict_rhs
| null scs_and_meths
msg = "Compiler error: bad dictionary " ++ showSDoc (ppr clas)
dict_bind = VarMonoBind this_dict_id dict_rhs
- meth_binds = andMonoBindList meth_binds_s
all_binds = sc_binds_inner `AndMonoBinds` meth_binds `AndMonoBinds` dict_bind
main_bind = AbsBinds
in
showLIE "instance" `thenM_`
returnM (main_bind `AndMonoBinds` prag_binds `AndMonoBinds` sc_binds_outer)
+
+
+tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (VanillaInst monobinds uprags)
+ = -- Check that all the method bindings come from this class
+ let
+ sel_names = [idName sel_id | (sel_id, _) <- op_items]
+ bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
+ in
+ mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
+
+ -- Make the method bindings
+ mapAndUnzipM do_one op_items `thenM` \ (meth_ids, meth_binds_s) ->
+
+ returnM (meth_ids, andMonoBindList meth_binds_s)
+
+ where
+ xtve = inst_tyvars `zip` inst_tyvars'
+ do_one op_item
+ = mkMethodBind InstanceDeclOrigin clas
+ inst_tys' monobinds op_item `thenM` \ (meth_inst, meth_info) ->
+ tcMethodBind xtve inst_tyvars' dfun_theta'
+ avail_insts uprags meth_info `thenM` \ meth_bind ->
+ -- Could add meth_insts to avail_insts, but not worth the bother
+ returnM (instToId meth_inst, meth_bind)
+
+-- Derived newtype instances
+tcMethods clas inst_tyvars inst_tyvars' dfun_theta' inst_tys'
+ avail_insts op_items (NewTypeDerived rep_tys)
+ = getInstLoc InstanceDeclOrigin `thenM` \ inst_loc ->
+ getLIE (mapAndUnzipM (do_one inst_loc) op_items) `thenM` \ ((meth_ids, meth_binds), lie) ->
+
+ tcSimplifyCheck
+ (ptext SLIT("newtype derived instance"))
+ inst_tyvars' avail_insts lie `thenM` \ lie_binds ->
+
+ -- I don't think we have to do the checkSigTyVars thing
+
+ returnM (meth_ids, lie_binds `AndMonoBinds` andMonoBindList meth_binds)
+
+ where
+ do_one inst_loc (sel_id, _)
+ = newMethodAtLoc inst_loc sel_id inst_tys' `thenM` \ meth_inst ->
+ -- Like in mkMethodBind
+ newMethod InstanceDeclOrigin sel_id rep_tys' `thenM` \ rhs_id ->
+ -- The binding is like "op @ NewTy = op @ RepTy"
+ let
+ meth_id = instToId meth_inst
+ in
+ return (meth_id, VarMonoBind meth_id (HsVar rhs_id))
+
+ -- Instantiate rep_tys with the relevant type variables
+ rep_tys' = map (substTy subst) rep_tys
+ subst = mkTyVarSubst inst_tyvars (mkTyVarTys inst_tyvars')
\end{code}
-Superclass loops
-~~~~~~~~~~~~~~~~
+Note: [Superclass loops]
+~~~~~~~~~~~~~~~~~~~~~~~~~
We have to be very, very careful when generating superclasses, lest we
accidentally build a loop. Here's an example:
-- We must simplify this all the way down
-- lest we build superclass loops
- -- See notes about superclass loops above
+ -- See Note [Superclass loops] above
tcSimplifyTop sc_lie `thenM` \ sc_binds2 ->
returnM (zonked_inst_tyvars, sc_binds1, sc_binds2)
doc = ptext SLIT("instance declaration superclass context")
\end{code}
-\begin{code}
-mkMethodBinds clas inst_tys' op_items monobinds
- = -- Check that all the method bindings come from this class
- mappM (addErrTc . badMethodErr clas) bad_bndrs `thenM_`
-
- -- Make the method bindings
- mapAndUnzipM mk_method_bind op_items
-
- where
- mk_method_bind op_item = mkMethodBind InstanceDeclOrigin clas
- inst_tys' monobinds op_item
-
- -- Find any definitions in monobinds that aren't from the class
- sel_names = [idName sel_id | (sel_id, _) <- op_items]
- bad_bndrs = collectMonoBinders monobinds `minusList` sel_names
-\end{code}
-
------------------------------
- Inlining dfuns unconditionally
+ [Inline dfuns] Inlining dfuns unconditionally
------------------------------
The code above unconditionally inlines dict funs. Here's why.
projects / ghc-hetmet.git / commitdiff