X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcInstDcls.lhs;h=d7aafc1f11736bbebd7ba500aedcd84538254277;hb=1a9245caefb80a3c4c5965aaacdf9a607e792e1c;hp=1af025e355bd643e9b819973f7e0c755e1b5f04d;hpb=9a4c93a59e008ddc376fde5f9eb468b762f0d0a7;p=ghc-hetmet.git diff --git a/compiler/typecheck/TcInstDcls.lhs b/compiler/typecheck/TcInstDcls.lhs index 1af025e..d7aafc1 100644 --- a/compiler/typecheck/TcInstDcls.lhs +++ b/compiler/typecheck/TcInstDcls.lhs @@ -21,7 +21,6 @@ import FamInst import FamInstEnv import TcDeriv import TcEnv -import RnEnv ( lookupGlobalOccRn ) import RnSource ( addTcgDUs ) import TcHsType import TcUnify @@ -33,8 +32,7 @@ import DataCon import Class import Var import CoreUnfold ( mkDFunUnfolding ) --- import CoreUtils ( mkPiTypes ) -import PrelNames ( inlineIdName ) +import CoreSyn ( Expr(Var) ) import Id import MkId import Name @@ -199,14 +197,15 @@ a top-level axiom: df :: forall a. C a => C [a] {-# NOINLINE df DFun[ $cop_list ] #-} - df = /\a. \d. MkD ($cop_list a d) + df = /\a. \d. MkC ($cop_list a d) - $cop_list :: forall a. C a => a -> a + $cop_list :: forall a. C a => [a] -> [a] $cop_list = -The "constructor" MkD expands to a cast, as does the class-op selector. +The "constructor" MkC expands to a cast, as does the class-op selector. The RULE works just like for multi-field dictionaries: - * (df a d) returns (Just (MkD,..,[$cop_list a d])) + + * (df a d) returns (Just (MkC,..,[$cop_list a d])) to exprIsConApp_Maybe * The RULE for op picks the right result @@ -216,18 +215,25 @@ application. But it works just fine in this case, exprIsConApp_maybe is otherwise used only when we hit a case expression which will have a real data constructor in it. -The biggest reason for doing it this way, apart form uniformity, is +The biggest reason for doing it this way, apart from uniformity, is that we want to be very careful when we have instance C a => C [a] where {-# INLINE op #-} op = ... -then we'll get an INLINE pragma on $cop_list. The danger is that -we'll get something like - foo = /\a.\d. $cop_list a d +then we'll get an INLINE pragma on $cop_list but it's important that +$cop_list only inlines when it's applied to *two* arguments (the +dictionary and the list argument + +The danger is that we'll get something like + op_list :: C a => [a] -> [a] + op_list = /\a.\d. $cop_list a d and then we'll eta expand, and then we'll inline TOO EARLY. This happened in -Trac #3772 and I spent far too long fiddling arond trying to fix it. +Trac #3772 and I spent far too long fiddling around trying to fix it. Look at the test for Trac #3772. + (Note: re-reading the above, I can't see how using the + uniform story solves the problem.) + Note [Subtle interaction of recursion and overlap] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this @@ -316,16 +322,16 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls -- round) -- (1) Do class and family instance declarations - ; let { idxty_decls = filter (isFamInstDecl . unLoc) tycl_decls } + ; idx_tycons <- mapAndRecoverM (tcFamInstDecl TopLevel) $ + filter (isFamInstDecl . unLoc) tycl_decls ; local_info_tycons <- mapAndRecoverM tcLocalInstDecl1 inst_decls - ; idx_tycons <- mapAndRecoverM tcIdxTyInstDeclTL idxty_decls ; let { (local_info, at_tycons_s) = unzip local_info_tycons ; at_idx_tycons = concat at_tycons_s ++ idx_tycons ; clas_decls = filter (isClassDecl.unLoc) tycl_decls ; implicit_things = concatMap implicitTyThings at_idx_tycons - ; aux_binds = mkAuxBinds at_idx_tycons + ; aux_binds = mkRecSelBinds at_idx_tycons } -- (2) Add the tycons of indexed types and their implicit @@ -337,9 +343,9 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls -- Next, construct the instance environment so far, consisting -- of - -- a) local instance decls - -- b) generic instances - -- c) local family instance decls + -- (a) local instance decls + -- (b) generic instances + -- (c) local family instance decls ; addInsts local_info $ addInsts generic_inst_info $ addFamInsts at_idx_tycons $ do { @@ -359,27 +365,6 @@ tcInstDecls1 tycl_decls inst_decls deriv_decls generic_inst_info ++ deriv_inst_info ++ local_info, aux_binds `plusHsValBinds` 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 <- tcFamInstDecl ldecl - ; setSrcSpan loc $ - when (isAssocFamily tything) $ - addErr $ assocInClassErr (tcdName decl) - ; return tything - } - isAssocFamily (ATyCon tycon) = - case tyConFamInst_maybe tycon of - Nothing -> panic "isAssocFamily: no family?!?" - Just (fam, _) -> isTyConAssoc fam - isAssocFamily _ = panic "isAssocFamily: no tycon?!?" - -assocInClassErr :: Name -> SDoc -assocInClassErr name = - ptext (sLit "Associated type") <+> quotes (ppr name) <+> - ptext (sLit "must be inside a class instance") addInsts :: [InstInfo Name] -> TcM a -> TcM a addInsts infos thing_inside @@ -412,12 +397,12 @@ tcLocalInstDecl1 (L loc (InstDecl poly_ty binds uprags ats)) ; (tyvars, theta, tau) <- tcHsInstHead poly_ty -- Now, check the validity of the instance. - ; (clas, inst_tys) <- checkValidInstHead tau - ; checkValidInstance tyvars theta clas inst_tys + ; (clas, inst_tys) <- checkValidInstance poly_ty tyvars theta tau -- Next, process any associated types. ; idx_tycons <- recoverM (return []) $ - do { idx_tycons <- checkNoErrs $ mapAndRecoverM tcFamInstDecl ats + do { idx_tycons <- checkNoErrs $ + mapAndRecoverM (tcFamInstDecl NotTopLevel) ats ; checkValidAndMissingATs clas (tyvars, inst_tys) (zip ats idx_tycons) ; return idx_tycons } @@ -544,7 +529,7 @@ tcLocalInstDecl1 (L loc (InstDecl poly_ty binds uprags ats)) \begin{code} tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo Name] - -> TcM (LHsBinds Id, TcLclEnv) + -> TcM (LHsBinds Id) -- (a) From each class declaration, -- generate any default-method bindings -- (b) From each instance decl @@ -553,18 +538,18 @@ tcInstDecls2 :: [LTyClDecl Name] -> [InstInfo Name] tcInstDecls2 tycl_decls inst_decls = do { -- (a) Default methods from class decls let class_decls = filter (isClassDecl . unLoc) tycl_decls - ; (dm_ids_s, dm_binds_s) <- mapAndUnzipM tcClassDecl2 class_decls + ; dm_binds_s <- mapM tcClassDecl2 class_decls + ; let dm_binds = unionManyBags dm_binds_s - ; tcExtendIdEnv (concat dm_ids_s) $ do - -- (b) instance declarations - { inst_binds_s <- mapM tcInstDecl2 inst_decls + ; let dm_ids = collectHsBindsBinders dm_binds + -- Add the default method Ids (again) + -- See Note [Default methods and instances] + ; inst_binds_s <- tcExtendIdEnv dm_ids $ + mapM tcInstDecl2 inst_decls -- Done - ; let binds = unionManyBags dm_binds_s `unionBags` - unionManyBags inst_binds_s - ; tcl_env <- getLclEnv -- Default method Ids in here - ; return (binds, tcl_env) } } + ; return (dm_binds `unionBags` unionManyBags inst_binds_s) } tcInstDecl2 :: InstInfo Name -> TcM (LHsBinds Id) tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds }) @@ -577,6 +562,18 @@ tcInstDecl2 (InstInfo { iSpec = ispec, iBinds = ibinds }) loc = getSrcSpan dfun_id \end{code} +See Note [Default methods and instances] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The default method Ids are already in the type environment (see Note +[Default method Ids and Template Haskell] in TcTyClsDcls), BUT they +don't have their InlinePragmas yet. Usually that would not matter, +because the simplifier propagates information from binding site to +use. But, unusually, when compiling instance decls we *copy* the +INLINE pragma from the default method to the method for that +particular operation (see Note [INLINE and default methods] below). + +So right here in tcInstDecl2 we must re-extend the type envt with +the default method Ids replete with their INLINE pragmas. Urk. \begin{code} tc_inst_decl2 :: Id -> InstBindings Name -> TcM (LHsBinds Id) @@ -601,7 +598,7 @@ tc_inst_decl2 :: Id -> InstBindings Name -> TcM (LHsBinds Id) -- If there are no superclasses, matters are simpler, because we don't need the case -- see Note [Newtype deriving superclasses] in TcDeriv.lhs -tc_inst_decl2 dfun_id (NewTypeDerived coi) +tc_inst_decl2 dfun_id (NewTypeDerived coi _) = do { let rigid_info = InstSkol origin = SigOrigin rigid_info inst_ty = idType dfun_id @@ -667,7 +664,7 @@ tc_inst_decl2 dfun_id (NewTypeDerived coi) ; return (unitBag $ noLoc $ AbsBinds inst_tvs' (map instToVar dfun_dicts) - [(inst_tvs', dfun_id, instToId this_dict, [])] + [(inst_tvs', dfun_id, instToId this_dict, noSpecPrags)] (dict_bind `consBag` sc_binds)) } where ----------------------- @@ -708,9 +705,9 @@ tc_inst_decl2 dfun_id (NewTypeDerived coi) -- Ordinary instances tc_inst_decl2 dfun_id (VanillaInst monobinds uprags standalone_deriv) - = do { let rigid_info = InstSkol - inst_ty = idType dfun_id - loc = getSrcSpan dfun_id + = do { let rigid_info = InstSkol + inst_ty = idType dfun_id + loc = getSrcSpan dfun_id -- Instantiate the instance decl with skolem constants ; (inst_tyvars', dfun_theta', inst_head') <- tcSkolSigType rigid_info inst_ty @@ -753,7 +750,7 @@ tc_inst_decl2 dfun_id (VanillaInst monobinds uprags standalone_deriv) ; spec_inst_prags <- mapM (wrapLocM (tcSpecInst dfun_id)) spec_inst_sigs -- Typecheck the methods - ; let prag_fn = mkPragFun uprags + ; let prag_fn = mkPragFun uprags monobinds tc_meth = tcInstanceMethod loc standalone_deriv clas inst_tyvars' dfun_dicts inst_tys' @@ -777,7 +774,8 @@ tc_inst_decl2 dfun_id (VanillaInst monobinds uprags standalone_deriv) ; let dict_constr = classDataCon clas this_dict_id = instToId this_dict dict_bind = mkVarBind this_dict_id dict_rhs - dict_rhs = foldl mk_app inst_constr (sc_ids ++ meth_ids) + dict_rhs = foldl mk_app inst_constr sc_meth_ids + sc_meth_ids = sc_ids ++ meth_ids inst_constr = L loc $ wrapId (mkWpTyApps inst_tys') (dataConWrapId dict_constr) -- We don't produce a binding for the dict_constr; instead we @@ -795,13 +793,13 @@ tc_inst_decl2 dfun_id (VanillaInst monobinds uprags standalone_deriv) -- See Note [ClassOp/DFun selection] -- See also note [Single-method classes] dfun_id_w_fun = dfun_id - `setIdUnfolding` mkDFunUnfolding dict_constr (sc_ids ++ meth_ids) + `setIdUnfolding` mkDFunUnfolding inst_ty (map Var sc_meth_ids) `setInlinePragma` dfunInlinePragma main_bind = AbsBinds inst_tyvars' dfun_lam_vars - [(inst_tyvars', dfun_id_w_fun, this_dict_id, spec_inst_prags)] + [(inst_tyvars', dfun_id_w_fun, this_dict_id, SpecPrags spec_inst_prags)] (unitBag dict_bind) ; showLIE (text "instance") @@ -891,7 +889,7 @@ tcSuperClass inst_loc tyvars dicts (this_dict, this_bind) sc_id = instToVar sc_dict sc_op_bind = AbsBinds tyvars (map instToVar dicts) - [(tyvars, sc_op_id, sc_id, [])] + [(tyvars, sc_op_id, sc_id, noSpecPrags)] (this_bind `unionBags` sc_binds) ; return (sc_op_id, noLoc sc_op_bind) } @@ -948,7 +946,7 @@ SpecPrag which, as it turns out, can be used unchanged for each method. The "it turns out" bit is delicate, but it works fine! \begin{code} -tcSpecInst :: Id -> Sig Name -> TcM SpecPrag +tcSpecInst :: Id -> Sig Name -> TcM TcSpecPrag tcSpecInst dfun_id prag@(SpecInstSig hs_ty) = addErrCtxt (spec_ctxt prag) $ do { let name = idName dfun_id @@ -981,7 +979,7 @@ tcInstanceMethod :: SrcSpan -> Bool -> Class -> [TcTyVar] -> [Inst] -> [TcType] -> (Inst, LHsBinds Id) -- "This" and its binding -> TcPragFun -- Local prags - -> [LSpecPrag] -- Arising from 'SPECLALISE instance' + -> [Located TcSpecPrag] -- Arising from 'SPECLALISE instance' -> LHsBinds Name -> (Id, DefMeth) -> TcM (Id, LHsBind Id) @@ -1006,14 +1004,15 @@ tcInstanceMethod loc standalone_deriv clas tyvars dfun_dicts inst_tys tc_body rn_bind = add_meth_ctxt rn_bind $ do { (meth_id1, spec_prags) <- tcPrags NonRecursive False True - meth_id (prag_fn sel_name) - ; tcInstanceMethodBody (instLoc this_dict) + meth_id (prag_fn sel_name) + ; bind <- tcInstanceMethodBody (instLoc this_dict) tyvars dfun_dicts ([this_dict], this_dict_bind) meth_id1 local_meth_id meth_sig_fn - (spec_inst_prags ++ spec_prags) - rn_bind } + (SpecPrags (spec_inst_prags ++ spec_prags)) + rn_bind + ; return (meth_id1, bind) } -------------- tc_default :: DefMeth -> TcM (Id, LHsBind Id) @@ -1029,7 +1028,7 @@ tcInstanceMethod loc standalone_deriv clas tyvars dfun_dicts inst_tys = do { meth_bind <- mkGenericDefMethBind clas inst_tys sel_id local_meth_name ; tc_body meth_bind } - tc_default DefMeth -- An polymorphic default method + tc_default (DefMeth dm_name) -- An polymorphic default method = do { -- Build the typechecked version directly, -- without calling typecheck_method; -- see Note [Default methods in instances] @@ -1037,17 +1036,11 @@ tcInstanceMethod loc standalone_deriv clas tyvars dfun_dicts inst_tys -- in $dm inst_tys this -- The 'let' is necessary only because HsSyn doesn't allow -- you to apply a function to a dictionary *expression*. - dm_name <- lookupGlobalOccRn (mkDefMethRdrName sel_name) - -- Might not be imported, but will be an OrigName + ; dm_id <- tcLookupId dm_name - ; inline_id <- tcLookupId inlineIdName ; let dm_inline_prag = idInlinePragma dm_id - dm_app = HsWrap (WpApp (instToId this_dict) <.> mkWpTyApps inst_tys) $ - HsVar dm_id - rhs | isInlinePragma dm_inline_prag -- See Note [INLINE and default methods] - = HsApp (L loc (HsWrap (WpTyApp local_meth_ty) (HsVar inline_id))) - (L loc dm_app) - | otherwise = dm_app + rhs = HsWrap (WpApp (instToId this_dict) <.> mkWpTyApps inst_tys) $ + HsVar dm_id meth_bind = L loc $ VarBind { var_id = local_meth_id , var_rhs = L loc rhs @@ -1057,8 +1050,8 @@ tcInstanceMethod loc standalone_deriv clas tyvars dfun_dicts inst_tys -- method to this version. Note [INLINE and default methods] bind = AbsBinds { abs_tvs = tyvars, abs_dicts = dfun_lam_vars - , abs_exports = [( tyvars, meth_id1 - , local_meth_id, spec_inst_prags)] + , abs_exports = [( tyvars, meth_id1, local_meth_id + , SpecPrags spec_inst_prags)] , abs_binds = this_dict_bind `unionBags` unitBag meth_bind } -- Default methods in an instance declaration can't have their own -- INLINE or SPECIALISE pragmas. It'd be possible to allow them, but @@ -1143,7 +1136,8 @@ From the class decl we get $dmfoo :: forall v x. Baz v x => x -> x $dmfoo y = -Notice that the type is ambiguous. That's fine, though. The instance decl generates +Notice that the type is ambiguous. That's fine, though. The instance +decl generates $dBazIntInt = MkBaz fooIntInt fooIntInt = $dmfoo Int Int $dBazIntInt @@ -1155,8 +1149,9 @@ less work to generate the translated version! Note [INLINE and default methods] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -We *copy* any INLINE pragma from the default method to the instance. -Example: +Default methods need special case. They are supposed to behave rather like +macros. For exmample + class Foo a where op1, op2 :: Bool -> a -> a @@ -1164,31 +1159,57 @@ Example: op1 b x = op2 (not b) x instance Foo Int where + -- op1 via default method op2 b x = + +The instance declaration should behave + + just as if 'op1' had been defined with the + code, and INLINE pragma, from its original + definition. + +That is, just as if you'd written + + instance Foo Int where + op2 b x = + + {-# INLINE op1 #-} + op1 b x = op2 (not b) x + +So for the above example we generate: -Then we generate: {-# INLINE $dmop1 #-} + -- $dmop1 has an InlineCompulsory unfolding $dmop1 d b x = op2 d (not b) x $fFooInt = MkD $cop1 $cop2 {-# INLINE $cop1 #-} - $cop1 = inline $dmop1 $fFooInt + $cop1 = $dmop1 $fFooInt $cop2 = -Note carefully: - a) We copy $dmop1's inline pragma to $cop1. Otherwise - we'll just inline the former in the latter and stop, which - isn't what the user expected - - b) We use the magic 'inline' Id to ensure that $dmop1 really is - inlined in $cop1, even though - (i) the latter itself has an INLINE pragma - (ii) $dmop1 is not saturated - That is important to allow the mutual recursion between $fooInt and - $cop1 to be broken +Note carefullly: + +* We *copy* any INLINE pragma from the default method $dmop1 to the + instance $cop1. Otherwise we'll just inline the former in the + latter and stop, which isn't what the user expected + +* Regardless of its pragma, we give the default method an + unfolding with an InlineCompulsory source. That means + that it'll be inlined at every use site, notably in + each instance declaration, such as $cop1. This inlining + must happen even though + a) $dmop1 is not saturated in $cop1 + b) $cop1 itself has an INLINE pragma + + It's vital that $dmop1 *is* inlined in this way, to allow the mutual + recursion between $fooInt and $cop1 to be broken + +* To communicate the need for an InlineCompulsory to the desugarer + (which makes the Unfoldings), we use the IsDefaultMethod constructor + in TcSpecPrags. %************************************************************************