X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInstDcls.lhs;h=e7c472b4751cbf3d863b209687da1596e0256eea;hp=193736dd8e47567440e43cf1e49fa551f5d54cc3;hb=e79c9ce01d0ce4412bd4bcd99c8c728a6a2ec569;hpb=4f597914955e1eeb08243f8b0743387703fc62b6 diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs index 193736d..e7c472b 100644 --- a/compiler/typecheck/TcInstDcls.lhs +++ b/compiler/typecheck/TcInstDcls.lhs @@ -40,7 +40,6 @@ import DynFlags import SrcLoc import Util import Outputable -import Maybes import Bag import BasicTypes import HscTypes @@ -95,15 +94,17 @@ Running example: {-# INLINE [2] op1_i #-} -- From the instance decl bindings op1_i, op2_i :: forall a. C a => forall b. Ix b => [a] -> b -> b op1_i = /\a. \(d:C a). - let local_op1 :: forall a. (C a, C [a]) - => forall b. Ix b => [a] -> b -> b + let this :: C [a] + this = df_i a d -- Note [Subtle interaction of recursion and overlap] + + local_op1 :: forall b. Ix b => [a] -> b -> b local_op1 = -- Source code; run the type checker on this -- NB: Type variable 'a' (but not 'b') is in scope in -- Note [Tricky type variable scoping] - in local_op1 a d (df_i a d) + in local_op1 a d op2_i = /\a \d:C a. $dmop2 [a] (df_i a d) @@ -175,10 +176,12 @@ call 'nullFail' just like the example above. The DoCon package also does the same thing; it shows up in module Fraction.hs Conclusion: when typechecking the methods in a C [a] instance, we want -to have C [a] available. That is why we have the strange local let in -the definition of op1_i in the example above. We can typecheck the -defintion of local_op1, and then supply the "this" argument via an -explicit call to the dfun (which in turn will be inlined). +to have C [a] available. That is why we have the strange local +definition for 'this' in the definition of op1_i in the example above. +We can typecheck the defintion of local_op1, and when doing tcSimplifyCheck +we supply 'this' as a given dictionary. Only needed, though, if there +are some type variales involved; otherwise there can be no overlap and +none of this arises. Note [Tricky type variable scoping] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ @@ -568,7 +571,7 @@ tcInstDecl2 :: InstInfo Name -> TcM (LHsBinds Id) -- newtype N a = MkN (Tree [a]) deriving( Foo Int ) -- -- The newtype gives an FC axiom looking like --- axiom CoN a :: N a :=: Tree [a] +-- axiom CoN a :: N 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: @@ -585,7 +588,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived }) rigid_info = InstSkol origin = SigOrigin rigid_info inst_ty = idType dfun_id - ; (tvs, theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty + ; (inst_tvs', theta, inst_head_ty) <- tcSkolSigType rigid_info inst_ty -- inst_head_ty is a PredType ; let (cls, cls_inst_tys) = tcSplitDFunHead inst_head_ty @@ -602,18 +605,23 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived }) the_coercion = make_coercion cls_tycon initial_cls_inst_tys nt_tycon tc_args -- Coercion of kind (Foo Int (Tree [a]) ~ Foo Int (N a) - ; inst_loc <- getInstLoc origin ; sc_loc <- getInstLoc InstScOrigin - ; dfun_dicts <- newDictBndrs inst_loc theta ; sc_dicts <- newDictBndrs sc_loc sc_theta' + ; inst_loc <- getInstLoc origin + ; dfun_dicts <- newDictBndrs inst_loc theta ; this_dict <- newDictBndr inst_loc (mkClassPred cls cls_inst_tys) ; rep_dict <- newDictBndr inst_loc rep_pred -- Figure out bindings for the superclass context from dfun_dicts -- Don't include this_dict in the 'givens', else - -- wanted_sc_insts get bound by just selecting from this_dict!! + -- sc_dicts get bound by just selecting from this_dict!! ; sc_binds <- addErrCtxt superClassCtxt $ - tcSimplifySuperClasses inst_loc dfun_dicts (rep_dict:sc_dicts) + tcSimplifySuperClasses inst_loc this_dict dfun_dicts + (rep_dict:sc_dicts) + + -- It's possible that the superclass stuff might unified something + -- in the envt with one of the clas_tyvars + ; checkSigTyVars inst_tvs' ; let coerced_rep_dict = wrapId the_coercion (instToId rep_dict) @@ -621,15 +629,15 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = NewTypeDerived }) ; let dict_bind = noLoc $ VarBind (instToId this_dict) (noLoc body) ; return (unitBag $ noLoc $ - AbsBinds tvs (map instToVar dfun_dicts) - [(tvs, dfun_id, instToId this_dict, [])] + AbsBinds inst_tvs' (map instToVar dfun_dicts) + [(inst_tvs', dfun_id, instToId this_dict, [])] (dict_bind `consBag` sc_binds)) } where ----------------------- -- 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 ) + -- with kind (C s1 .. sm (T a1 .. ak) ~ C s1 .. sm ) -- 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 @@ -701,48 +709,38 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- Instantiate the super-class context with inst_tys sc_theta' = substTheta (zipOpenTvSubst class_tyvars inst_tys') sc_theta - (eq_sc_theta',dict_sc_theta') = partition isEqPred sc_theta' origin = SigOrigin rigid_info - (eq_dfun_theta',dict_dfun_theta') = partition isEqPred dfun_theta' -- Create dictionary Ids from the specified instance contexts. - sc_loc <- getInstLoc InstScOrigin - sc_dicts <- newDictBndrs sc_loc dict_sc_theta' - inst_loc <- getInstLoc origin - sc_covars <- mkMetaCoVars eq_sc_theta' - wanted_sc_eqs <- mkEqInsts eq_sc_theta' (map mkWantedCo sc_covars) - dfun_covars <- mkCoVars eq_dfun_theta' - dfun_eqs <- mkEqInsts eq_dfun_theta' (map mkGivenCo $ mkTyVarTys dfun_covars) - dfun_dicts <- newDictBndrs inst_loc dict_dfun_theta' - this_dict <- newDictBndr inst_loc (mkClassPred clas inst_tys') + sc_loc <- getInstLoc InstScOrigin + sc_dicts <- newDictOccs sc_loc sc_theta' -- These are wanted + inst_loc <- getInstLoc origin + dfun_dicts <- newDictBndrs inst_loc dfun_theta' -- Includes equalities + this_dict <- newDictBndr inst_loc (mkClassPred clas inst_tys') -- Default-method Ids may be mentioned in synthesised RHSs, -- but they'll already be in the environment. -- Typecheck the methods - let -- These insts are in scope; quite a few, eh? - dfun_insts = dfun_eqs ++ dfun_dicts - wanted_sc_insts = wanted_sc_eqs ++ sc_dicts - this_dict_id = instToId this_dict - sc_dict_ids = map instToId sc_dicts - dfun_dict_ids = map instToId dfun_dicts - prag_fn = mkPragFun uprags - tc_meth = tcInstanceMethod loc clas inst_tyvars' - (dfun_covars ++ dfun_dict_ids) - dfun_theta' inst_tys' - this_dict_id dfun_id - prag_fn monobinds - (meth_exprs, meth_binds) <- mapAndUnzipM tc_meth op_items + let this_dict_id = instToId this_dict + dfun_lam_vars = map instToVar dfun_dicts -- Includes equalities + prag_fn = mkPragFun uprags + tc_meth = tcInstanceMethod loc clas inst_tyvars' + dfun_dicts + dfun_theta' inst_tys' + this_dict dfun_id + prag_fn monobinds + (meth_exprs, meth_binds) <- tcExtendTyVarEnv inst_tyvars' $ + mapAndUnzipM tc_meth op_items -- Figure out bindings for the superclass context -- Don't include this_dict in the 'givens', else - -- wanted_sc_insts get bound by just selecting from this_dict!! + -- sc_dicts get bound by just selecting from this_dict!! sc_binds <- addErrCtxt superClassCtxt $ - tcSimplifySuperClasses inst_loc dfun_insts - wanted_sc_insts + tcSimplifySuperClasses inst_loc this_dict dfun_dicts sc_dicts -- Note [Recursive superclasses] - -- It's possible that the superclass stuff might unified one - -- of the inst_tyavars' with something in the envt + -- It's possible that the superclass stuff might unified something + -- in the envt with one of the inst_tyvars' checkSigTyVars inst_tyvars' -- Deal with 'SPECIALISE instance' pragmas @@ -751,7 +749,7 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- Create the result bindings let dict_constr = classDataCon clas - inline_prag | null dfun_insts = [] + inline_prag | null dfun_dicts = [] | otherwise = [L loc (InlinePrag (Inline AlwaysActive True))] -- Always inline the dfun; this is an experimental decision -- because it makes a big performance difference sometimes. @@ -764,8 +762,11 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- -- See Note [Inline dfuns] below - dict_rhs = mkHsConApp dict_constr (inst_tys' ++ mkTyVarTys sc_covars) - (map HsVar sc_dict_ids ++ meth_exprs) + sc_dict_vars = map instToVar sc_dicts + dict_bind = L loc (VarBind this_dict_id dict_rhs) + dict_rhs = foldl (\ f a -> L loc (HsApp f (L loc a))) inst_constr meth_exprs + inst_constr = L loc $ wrapId (mkWpApps sc_dict_vars <.> mkWpTyApps inst_tys') + (dataConWrapId dict_constr) -- We don't produce a binding for the dict_constr; instead we -- rely on the simplifier to unfold this saturated application -- We do this rather than generate an HsCon directly, because @@ -773,28 +774,15 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = VanillaInst monobinds uprags }) -- member) are dealt with by the common MkId.mkDataConWrapId code rather -- than needing to be repeated here. - dict_bind = noLoc (VarBind this_dict_id dict_rhs) main_bind = noLoc $ AbsBinds - (inst_tyvars' ++ dfun_covars) - dfun_dict_ids - [(inst_tyvars' ++ dfun_covars, dfun_id, this_dict_id, inline_prag ++ prags)] + inst_tyvars' + dfun_lam_vars + [(inst_tyvars', dfun_id, this_dict_id, inline_prag ++ prags)] (dict_bind `consBag` sc_binds) showLIE (text "instance") return (main_bind `consBag` unionManyBags meth_binds) - -mkCoVars :: [PredType] -> TcM [TyVar] -mkCoVars = newCoVars . map unEqPred - where - unEqPred (EqPred ty1 ty2) = (ty1, ty2) - unEqPred _ = panic "TcInstDcls.mkCoVars" - -mkMetaCoVars :: [PredType] -> TcM [TyVar] -mkMetaCoVars = mapM eqPredToCoVar - where - eqPredToCoVar (EqPred ty1 ty2) = newMetaCoVar ty1 ty2 - eqPredToCoVar _ = panic "TcInstDcls.mkMetaCoVars" \end{code} Note [Recursive superclasses] @@ -821,23 +809,36 @@ tcInstanceMethod - Use tcValBinds to do the checking \begin{code} -tcInstanceMethod :: SrcSpan -> Class -> [TcTyVar] -> [Var] +tcInstanceMethod :: SrcSpan -> Class -> [TcTyVar] -> [Inst] -> TcThetaType -> [TcType] - -> Id -> Id + -> Inst -> Id -> TcPragFun -> LHsBinds Name -> (Id, DefMeth) -> TcM (HsExpr Id, LHsBinds Id) -- The returned inst_meth_ids all have types starting -- forall tvs. theta => ... -tcInstanceMethod loc clas tyvars dfun_lam_vars theta inst_tys - this_dict_id dfun_id - prag_fn binds_in (sel_id, dm_info) - = do { uniq <- newUnique - ; let local_meth_name = mkInternalName uniq sel_occ loc -- Same OccName - tc_body = tcInstanceMethodBody clas tyvars dfun_lam_vars theta inst_tys - this_dict_id dfun_id sel_id - prags local_meth_name +tcInstanceMethod loc clas tyvars dfun_dicts theta inst_tys + this_dict dfun_id prag_fn binds_in (sel_id, dm_info) + = do { cloned_this <- cloneDict this_dict + -- Need to clone the dict in case it is floated out, and + -- then clashes with its friends + ; uniq1 <- newUnique + ; let local_meth_name = mkInternalName uniq1 sel_occ loc -- Same OccName + this_dict_bind = L loc $ VarBind (instToId cloned_this) $ + L loc $ wrapId meth_wrapper dfun_id + mb_this_bind | null tyvars = Nothing + | otherwise = Just (cloned_this, this_dict_bind) + -- 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] + + tc_body rn_bind = do { (meth_id, tc_binds) <- tcInstanceMethodBody + InstSkol clas tyvars dfun_dicts theta inst_tys + mb_this_bind sel_id + local_meth_name + meth_sig_fn meth_prag_fn rn_bind + ; return (wrapId meth_wrapper meth_id, tc_binds) } ; case (findMethodBind sel_name local_meth_name binds_in, dm_info) of -- There is a user-supplied method binding, so use it @@ -869,12 +870,21 @@ tcInstanceMethod loc clas tyvars dfun_lam_vars theta inst_tys where sel_name = idName sel_id sel_occ = nameOccName sel_name - prags = prag_fn sel_name - - error_rhs = HsApp (mkLHsWrap (WpTyApp meth_tau) error_id) error_msg - meth_tau = funResultTy (applyTys (idType sel_id) inst_tys) - error_id = L loc (HsVar nO_METHOD_BINDING_ERROR_ID) + this_dict_id = instToId this_dict + + meth_prag_fn _ = prag_fn sel_name + meth_sig_fn _ = Just [] -- The 'Just' says "yes, there's a type sig" + -- But there are no scoped type variables from local_method_id + -- Only the ones from the instance decl itself, which are already + -- in scope. Example: + -- class C a where { op :: forall b. Eq b => ... } + -- instance C [c] where { op = } + -- In , 'c' is scope but 'b' is not! + + error_rhs = HsApp error_fun error_msg + error_fun = L loc $ wrapId (WpTyApp meth_tau) nO_METHOD_BINDING_ERROR_ID error_msg = L loc (HsLit (HsStringPrim (mkFastString error_string))) + meth_tau = funResultTy (applyTys (idType sel_id) inst_tys) error_string = showSDoc (hcat [ppr loc, text "|", ppr sel_id ]) dm_wrapper = WpApp this_dict_id <.> mkWpTyApps inst_tys @@ -883,53 +893,10 @@ tcInstanceMethod loc clas tyvars dfun_lam_vars theta inst_tys omitted_meth_warn = ptext (sLit "No explicit method nor default method for") <+> quotes (ppr sel_id) ---------------- -tcInstanceMethodBody :: Class -> [TcTyVar] -> [Var] - -> TcThetaType -> [TcType] - -> Id -> Id -> Id - -> [LSig Name] -> Name -> LHsBind Name - -> TcM (HsExpr Id, LHsBinds Id) -tcInstanceMethodBody clas tyvars dfun_lam_vars theta inst_tys - this_dict_id dfun_id sel_id - prags local_meth_name bind@(L loc _) - = do { uniq <- newUnique - ; let (sel_tyvars,sel_rho) = tcSplitForAllTys (idType sel_id) - rho_ty = ASSERT( length sel_tyvars == length inst_tys ) - substTyWith sel_tyvars inst_tys sel_rho - - (first_pred, meth_tau) = tcSplitPredFunTy_maybe rho_ty - `orElse` pprPanic "tcInstanceMethod" (ppr sel_id) - - meth_name = mkInternalName uniq (getOccName local_meth_name) loc - meth_ty = mkSigmaTy tyvars theta meth_tau - meth_id = mkLocalId meth_name meth_ty - - local_meth_ty = mkSigmaTy tyvars (theta ++ [first_pred]) meth_tau - local_meth_id = mkLocalId local_meth_name local_meth_ty - - tv_names = map tyVarName tyvars - - -- The first predicate should be of form (C a b) - -- where C is the class in question - ; MASSERT( case getClassPredTys_maybe first_pred of - { Just (clas1, _tys) -> clas == clas1 ; Nothing -> False } ) - - ; local_meth_bind <- tcMethodBind tv_names prags local_meth_id bind - - ; let full_bind = unitBag $ L loc $ - VarBind meth_id $ L loc $ - mkHsWrap (mkWpTyLams tyvars <.> mkWpLams dfun_lam_vars) $ - HsLet (HsValBinds (ValBindsOut [(NonRecursive, local_meth_bind)] [])) $ L loc $ - mkHsWrap (WpLet this_dict_bind <.> WpApp this_dict_id) $ - wrapId meth_wrapper local_meth_id - this_dict_bind = unitBag $ L loc $ - VarBind this_dict_id $ L loc $ - wrapId meth_wrapper dfun_id - - ; return (wrapId meth_wrapper meth_id, full_bind) } - where + dfun_lam_vars = map instToVar dfun_dicts meth_wrapper = mkWpApps dfun_lam_vars <.> mkWpTyApps (mkTyVarTys tyvars) + wrapId :: HsWrapper -> id -> HsExpr id wrapId wrapper id = mkHsWrap wrapper (HsVar id) \end{code}