\begin{code}
module TcClassDcl ( tcClassSigs, tcClassDecl2,
- findMethodBind, tcMethodBind,
- mkGenericDefMethBind, getGenericInstances, mkDefMethRdrName,
+ findMethodBind, instantiateMethod, tcInstanceMethodBody,
+ mkGenericDefMethBind, getGenericInstances,
tcAddDeclCtxt, badMethodErr, badATErr, omittedATWarn
) where
import HsSyn
import RnHsSyn
import RnExpr
-import RnEnv
import Inst
import InstEnv
import TcEnv
import TcBinds
+import TcSimplify
import TcHsType
import TcMType
import TcType
import TcRnMonad
+import BuildTyCl( TcMethInfo )
import Generics
import Class
import TyCon
-import Type
import MkId
import Id
import Name
import Var
import NameEnv
import NameSet
-import OccName
-import RdrName
import Outputable
import PrelNames
import DynFlags
import ErrUtils
import Util
-import Unique
import ListSetOps
import SrcLoc
import Maybes
-import List
import BasicTypes
import Bag
import FastString
import Control.Monad
+import Data.List
\end{code}
-> LHsBinds Name
-> TcM [TcMethInfo]
-type TcMethInfo = (Name, DefMeth, Type) -- A temporary intermediate, to communicate
- -- between tcClassSigs and buildClass
tcClassSigs clas sigs def_methods
- = do { dm_env <- checkDefaultBinds clas op_names def_methods
- ; mapM (tcClassSig dm_env) op_sigs }
+ = do { dm_env <- mapM (addLocM (checkDefaultBind clas op_names))
+ (bagToList def_methods)
+ ; mapM (tcClassSig (mkNameEnv dm_env)) op_sigs }
where
op_sigs = [sig | sig@(L _ (TypeSig _ _)) <- sigs]
op_names = [n | (L _ (TypeSig (L _ n) _)) <- op_sigs]
-
-checkDefaultBinds :: Name -> [Name] -> LHsBinds Name -> TcM (NameEnv Bool)
+checkDefaultBind :: Name -> [Name] -> HsBindLR Name Name -> TcM (Name, DefMethSpec)
-- Check default bindings
-- a) must be for a class op for this class
-- b) must be all generic or all non-generic
- -- and return a mapping from class-op to Bool
- -- where True <=> it's a generic default method
-checkDefaultBinds clas ops binds
- = do dm_infos <- mapM (addLocM (checkDefaultBind clas ops)) (bagToList binds)
- return (mkNameEnv dm_infos)
-
-checkDefaultBind :: Name -> [Name] -> HsBindLR Name Name -> TcM (Name, Bool)
checkDefaultBind clas ops (FunBind {fun_id = L _ op, fun_matches = MatchGroup matches _ })
= do { -- Check that the op is from this class
- checkTc (op `elem` ops) (badMethodErr clas op)
+ checkTc (op `elem` ops) (badMethodErr clas op)
-- Check that all the defns ar generic, or none are
- ; checkTc (all_generic || none_generic) (mixedGenericErr op)
-
- ; return (op, all_generic)
+ ; case (none_generic, all_generic) of
+ (True, _) -> return (op, VanillaDM)
+ (_, True) -> return (op, GenericDM)
+ _ -> failWith (mixedGenericErr op)
}
where
n_generic = count (isJust . maybeGenericMatch) matches
none_generic = n_generic == 0
all_generic = matches `lengthIs` n_generic
+
checkDefaultBind _ _ b = pprPanic "checkDefaultBind" (ppr b)
-tcClassSig :: NameEnv Bool -- Info about default methods;
+tcClassSig :: NameEnv DefMethSpec -- Info about default methods;
-> LSig Name
-> TcM TcMethInfo
tcClassSig dm_env (L loc (TypeSig (L _ op_name) op_hs_ty))
= setSrcSpan loc $ do
{ op_ty <- tcHsKindedType op_hs_ty -- Class tyvars already in scope
- ; let dm = case lookupNameEnv dm_env op_name of
- Nothing -> NoDefMeth
- Just False -> DefMeth
- Just True -> GenDefMeth
+ ; let dm = lookupNameEnv dm_env op_name `orElse` NoDM
; return (op_name, dm, op_ty) }
tcClassSig _ s = pprPanic "tcClassSig" (ppr s)
\end{code}
\begin{code}
tcClassDecl2 :: LTyClDecl Name -- The class declaration
- -> TcM (LHsBinds Id, [Id])
+ -> TcM (LHsBinds Id)
tcClassDecl2 (L loc (ClassDecl {tcdLName = class_name, tcdSigs = sigs,
tcdMeths = default_binds}))
- = recoverM (return (emptyLHsBinds, [])) $
- setSrcSpan loc $ do
- clas <- tcLookupLocatedClass class_name
+ = recoverM (return emptyLHsBinds) $
+ setSrcSpan loc $
+ do { clas <- tcLookupLocatedClass class_name
-- We make a separate binding for each default method.
-- At one time I used a single AbsBinds for all of them, thus
-- dm1 = \d -> case ds d of (a,b,c) -> a
-- And since ds is big, it doesn't get inlined, so we don't get good
-- default methods. Better to make separate AbsBinds for each
- let
- (tyvars, _, _, op_items) = classBigSig clas
- rigid_info = ClsSkol clas
- prag_fn = mkPragFun sigs
- sig_fn = mkTcSigFun sigs
- clas_tyvars = tcSkolSigTyVars rigid_info tyvars
- tc_dm = tcDefMeth clas_tyvars default_binds
- sig_fn prag_fn
- -- tc_dm is called only for a sel_id
- -- that has a binding in default_binds
-
- dm_sel_ids = [sel_id | (sel_id, DefMeth) <- op_items]
- -- Generate code for polymorphic default methods only
- -- (Generic default methods have turned into instance decls by now.)
- -- This is incompatible with Hugs, which expects a polymorphic
- -- default method for every class op, regardless of whether or not
- -- the programmer supplied an explicit default decl for the class.
- -- (If necessary we can fix that, but we don't have a convenient Id to hand.)
-
- (defm_binds, dm_ids) <- mapAndUnzipM tc_dm dm_sel_ids
- return (unionManyBags defm_binds, dm_ids)
+ ; let
+ (tyvars, _, _, op_items) = classBigSig clas
+ rigid_info = ClsSkol clas
+ prag_fn = mkPragFun sigs default_binds
+ sig_fn = mkTcSigFun sigs
+ clas_tyvars = tcSkolSigTyVars rigid_info tyvars
+ pred = mkClassPred clas (mkTyVarTys clas_tyvars)
+ ; inst_loc <- getInstLoc (SigOrigin rigid_info)
+ ; this_dict <- newDictBndr inst_loc pred
+
+ ; let tc_dm = tcDefMeth clas clas_tyvars
+ this_dict default_binds
+ sig_fn prag_fn
+
+ ; dm_binds <- tcExtendTyVarEnv clas_tyvars $
+ mapM tc_dm op_items
+
+ ; return (listToBag (catMaybes dm_binds)) }
+
tcClassDecl2 d = pprPanic "tcClassDecl2" (ppr d)
-tcDefMeth :: [TyVar] -> LHsBinds Name
- -> TcSigFun -> TcPragFun -> Id
- -> TcM (LHsBinds Id, Id)
-tcDefMeth tyvars binds_in sig_fn prag_fn sel_id
- = do { let sel_name = idName sel_id
- ; dm_name <- lookupTopBndrRn (mkDefMethRdrName sel_name)
- ; uniq <- newUnique
- ; let dm_ty = idType sel_id -- Same as dict selector!
- local_dm_name = setNameUnique sel_name uniq
- local_dm_id = mkLocalId local_dm_name dm_ty
- top_dm_id = mkDefaultMethodId dm_name dm_ty
- all_tvs = map tyVarName tyvars ++ (sig_fn sel_name `orElse` [])
- -- Tyvars in scope are *both* the ones from the
- -- class decl *and* ones from the method sig
+tcDefMeth :: Class -> [TyVar] -> Inst -> LHsBinds Name
+ -> TcSigFun -> TcPragFun -> ClassOpItem
+ -> TcM (Maybe (LHsBind Id))
+-- Generate code for polymorphic default methods only (hence DefMeth)
+-- (Generic default methods have turned into instance decls by now.)
+-- This is incompatible with Hugs, which expects a polymorphic
+-- default method for every class op, regardless of whether or not
+-- the programmer supplied an explicit default decl for the class.
+-- (If necessary we can fix that, but we don't have a convenient Id to hand.)
+tcDefMeth clas tyvars this_dict binds_in sig_fn prag_fn (sel_id, dm_info)
+ = case dm_info of
+ NoDefMeth -> return Nothing
+ GenDefMeth -> return Nothing
+ DefMeth dm_name -> do
+ { let sel_name = idName sel_id
+ ; local_dm_name <- newLocalName sel_name
+ -- Base the local_dm_name on the selector name, because
+ -- type errors from tcInstanceMethodBody come from here
+
+ -- See Note [Silly default-method bind]
+ -- (possibly out of date)
; let meth_bind = findMethodBind sel_name local_dm_name binds_in
`orElse` pprPanic "tcDefMeth" (ppr sel_id)
- -- We only call tcDefMeth on selectors for which
- -- there is a binding in binds_in
+ -- dm_info = DefMeth dm_name only if there is a binding in binds_in
+
+ dm_sig_fn _ = sig_fn sel_name
+ dm_id = mkDefaultMethodId sel_id dm_name
+ local_dm_type = instantiateMethod clas sel_id (mkTyVarTys tyvars)
+ local_dm_id = mkLocalId local_dm_name local_dm_type
+
+ ; (dm_id_w_inline, spec_prags)
+ <- tcPrags NonRecursive False True dm_id (prag_fn sel_name)
+
+ ; warnTc (not (null spec_prags))
+ (ptext (sLit "Ignoring SPECIALISE pragmas on default method")
+ <+> quotes (ppr sel_name))
+
+ ; liftM Just $
+ tcInstanceMethodBody (instLoc this_dict)
+ tyvars [this_dict]
+ ([], emptyBag)
+ dm_id_w_inline local_dm_id
+ dm_sig_fn IsDefaultMethod meth_bind }
+
+---------------
+tcInstanceMethodBody :: InstLoc -> [TcTyVar] -> [Inst]
+ -> ([Inst], LHsBinds Id) -> Id -> Id
+ -> TcSigFun -> TcSpecPrags -> LHsBind Name
+ -> TcM (LHsBind Id)
+tcInstanceMethodBody inst_loc tyvars dfun_dicts
+ (this_dict, this_bind) meth_id local_meth_id
+ meth_sig_fn spec_prags bind@(L loc _)
+ = do { -- Typecheck the binding, first extending the envt
+ -- so that when tcInstSig looks up the local_meth_id to find
+ -- its signature, we'll find it in the environment
+ ; ((tc_bind, _), lie) <- getLIE $
+ tcExtendIdEnv [local_meth_id] $
+ tcPolyBinds TopLevel meth_sig_fn no_prag_fn
+ NonRecursive NonRecursive
+ (unitBag bind)
+
+ ; let avails = this_dict ++ dfun_dicts
+ -- Only need the this_dict stuff if there are type
+ -- variables involved; otherwise overlap is not possible
+ -- See Note [Subtle interaction of recursion and overlap]
+ -- in TcInstDcls
+ ; lie_binds <- tcSimplifyCheck inst_loc tyvars avails lie
+
+ ; let full_bind = AbsBinds tyvars dfun_lam_vars
+ [(tyvars, meth_id, local_meth_id, spec_prags)]
+ (this_bind `unionBags` lie_binds
+ `unionBags` tc_bind)
+
+ dfun_lam_vars = map instToVar dfun_dicts -- Includes equalities
+
+ ; return (L loc full_bind) }
+ where
+ no_prag_fn _ = [] -- No pragmas for local_meth_id;
+ -- they are all for meth_id
+\end{code}
- ; tc_meth_bind <- tcMethodBind all_tvs (prag_fn sel_name)
- local_dm_id meth_bind
+\begin{code}
+instantiateMethod :: Class -> Id -> [TcType] -> TcType
+-- Take a class operation, say
+-- op :: forall ab. C a => forall c. Ix c => (b,c) -> a
+-- Instantiate it at [ty1,ty2]
+-- Return the "local method type":
+-- forall c. Ix x => (ty2,c) -> ty1
+instantiateMethod clas sel_id inst_tys
+ = ASSERT( ok_first_pred ) local_meth_ty
+ where
+ (sel_tyvars,sel_rho) = tcSplitForAllTys (idType sel_id)
+ rho_ty = ASSERT( length sel_tyvars == length inst_tys )
+ substTyWith sel_tyvars inst_tys sel_rho
- -- See Note [Silly default-method bind]
- ; let loc = getLoc meth_bind
- top_bind = L loc $ VarBind top_dm_id $
- L loc $ HsWrap (WpLet tc_meth_bind) $
- HsVar local_dm_id
+ (first_pred, local_meth_ty) = tcSplitPredFunTy_maybe rho_ty
+ `orElse` pprPanic "tcInstanceMethod" (ppr sel_id)
- ; return (unitBag top_bind, top_dm_id) }
+ ok_first_pred = case getClassPredTys_maybe first_pred of
+ Just (clas1, _tys) -> clas == clas1
+ Nothing -> False
+ -- The first predicate should be of form (C a b)
+ -- where C is the class in question
-mkDefMethRdrName :: Name -> RdrName
-mkDefMethRdrName sel_name = mkDerivedRdrName sel_name mkDefaultMethodOcc
---------------------------
-- The renamer just puts the selector ID as the binder in the method binding
| op_name == sel_name
= Just (L loc1 (bind { fun_id = L loc2 meth_name }))
f _other = Nothing
-
----------------------------
-tcMethodBind :: [Name] -> [LSig Name] -> Id
- -> LHsBind Name -> TcM (LHsBinds Id)
-tcMethodBind tyvars prags meth_id bind
- = do { let sig_fn _ = Just tyvars
- prag_fn _ = prags
-
- -- Typecheck the binding, first extending the envt
- -- so that when tcInstSig looks up the meth_id to find
- -- its signature, we'll find it in the environment
- --
- -- If scoped type variables is on, they are brought
- -- into scope by tcPolyBinds (via sig_fn)
- --
- -- See Note [Polymorphic methods]
- ; traceTc (text "tcMethodBind" <+> ppr meth_id <+> ppr tyvars)
- ; (tc_binds, ids) <- tcExtendIdEnv [meth_id] $
- tcPolyBinds TopLevel sig_fn prag_fn
- NonRecursive NonRecursive
- (unitBag bind)
-
- ; ASSERT( ids == [meth_id] ) -- Binding for ONE method
- return (unionManyBags tc_binds) }
\end{code}
Note [Polymorphic methods]
When we pass the default method binding to the type checker, it must
look like op2 = e
not $dmop2 = e
-otherwise the "$dm" stuff comes out in the interface file. So we
-typecheck the former, and wrap it in a let, thus
+otherwise the "$dm" stuff comes out error messages. But we want the
+"$dm" to come out in the interface file. So we typecheck the former,
+and wrap it in a let, thus
$dmop2 = let op2 = e in op2
This makes the error messages right.
instance C 1 where
op Unit = ...
-
\begin{code}
mkGenericDefMethBind :: Class -> [Type] -> Id -> Name -> TcM (LHsBind Name)
mkGenericDefMethBind clas inst_tys sel_id meth_name
group `lengthExceeds` 1]
get_uniq (tc,_) = getUnique tc
- mapM (addErrTc . dupGenericInsts) bad_groups
+ mapM_ (addErrTc . dupGenericInsts) bad_groups
-- Check that there is an InstInfo for each generic type constructor
let
-- and wrap them as forall'd tyvars, so that kind inference
-- works in the standard way
let
- sig_tvs = map (noLoc.UserTyVar) (nameSetToList (extractHsTyVars (noLoc hs_ty)))
+ sig_tvs = userHsTyVarBndrs $ map noLoc $ nameSetToList $
+ extractHsTyVars (noLoc hs_ty)
hs_forall_ty = noLoc $ mkExplicitHsForAllTy sig_tvs (noLoc []) (noLoc hs_ty)
-- Type-check the instance type, and check its form
dfun_id = mkDictFunId dfun_name tyvars inst_theta clas [inst_ty]
ispec = mkLocalInstance dfun_id overlap_flag
- return (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] })
+ return (InstInfo { iSpec = ispec, iBinds = VanillaInst binds [] False })
\end{code}