X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=blobdiff_plain;f=compiler%2Ftypecheck%2FTcTyClsDecls.lhs;h=a433d697b9d8d5667899e15968f32ae517134833;hp=1658e0bee65e9d11704200bd4d191fa5643da0b5;hb=6ea06bbf08517d9805feb82df65cc56ecbaf23a4;hpb=338cac018258e0c5540e18e0efe7dc84dfce8c86 diff --git a/compiler/typecheck/TcTyClsDecls.lhs b/compiler/typecheck/TcTyClsDecls.lhs index 1658e0b..a433d69 100644 --- a/compiler/typecheck/TcTyClsDecls.lhs +++ b/compiler/typecheck/TcTyClsDecls.lhs @@ -60,180 +60,78 @@ import Data.List %* * %************************************************************************ -Dealing with a group -~~~~~~~~~~~~~~~~~~~~ -Consider a mutually-recursive group, binding -a type constructor T and a class C. - -Step 1: getInitialKind - Construct a KindEnv by binding T and C to a kind variable - -Step 2: kcTyClDecl - In that environment, do a kind check - -Step 3: Zonk the kinds - -Step 4: buildTyConOrClass - Construct an environment binding T to a TyCon and C to a Class. - a) Their kinds comes from zonking the relevant kind variable - b) Their arity (for synonyms) comes direct from the decl - c) The funcional dependencies come from the decl - d) The rest comes a knot-tied binding of T and C, returned from Step 4 - e) The variances of the tycons in the group is calculated from - the knot-tied stuff - -Step 5: tcTyClDecl1 - In this environment, walk over the decls, constructing the TyCons and Classes. - This uses in a strict way items (a)-(c) above, which is why they must - be constructed in Step 4. Feed the results back to Step 4. - For this step, pass the is-recursive flag as the wimp-out flag - to tcTyClDecl1. - - -Step 6: Extend environment - We extend the type environment with bindings not only for the TyCons and Classes, - but also for their "implicit Ids" like data constructors and class selectors - -Step 7: checkValidTyCl - For a recursive group only, check all the decls again, just - to check all the side conditions on validity. We could not - do this before because we were in a mutually recursive knot. - -Identification of recursive TyCons -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -The knot-tying parameters: @rec_details_list@ is an alist mapping @Name@s to -@TyThing@s. - -Identifying a TyCon as recursive serves two purposes - -1. Avoid infinite types. Non-recursive newtypes are treated as -"transparent", like type synonyms, after the type checker. If we did -this for all newtypes, we'd get infinite types. So we figure out for -each newtype whether it is "recursive", and add a coercion if so. In -effect, we are trying to "cut the loops" by identifying a loop-breaker. - -2. Avoid infinite unboxing. This is nothing to do with newtypes. -Suppose we have - data T = MkT Int T - f (MkT x t) = f t -Well, this function diverges, but we don't want the strictness analyser -to diverge. But the strictness analyser will diverge because it looks -deeper and deeper into the structure of T. (I believe there are -examples where the function does something sane, and the strictness -analyser still diverges, but I can't see one now.) - -Now, concerning (1), the FC2 branch currently adds a coercion for ALL -newtypes. I did this as an experiment, to try to expose cases in which -the coercions got in the way of optimisations. If it turns out that we -can indeed always use a coercion, then we don't risk recursive types, -and don't need to figure out what the loop breakers are. - -For newtype *families* though, we will always have a coercion, so they -are always loop breakers! So you can easily adjust the current -algorithm by simply treating all newtype families as loop breakers (and -indeed type families). I think. - \begin{code} -tcTyAndClassDecls :: ModDetails -> [LTyClDecl Name] +tcTyAndClassDecls :: ModDetails + -> [[LTyClDecl Name]] -- Mutually-recursive groups in dependency order -> TcM (TcGblEnv, -- Input env extended by types and classes -- and their implicit Ids,DataCons HsValBinds Name, -- Renamed bindings for record selectors [Id]) -- Default method ids - -- Fails if there are any errors -tcTyAndClassDecls boot_details allDecls +tcTyAndClassDecls boot_details decls_s = checkNoErrs $ -- The code recovers internally, but if anything gave rise to -- an error we'd better stop now, to avoid a cascade - do { -- Omit instances of type families; they are handled together - -- with the *heads* of class instances - ; let decls = filter (not . isFamInstDecl . unLoc) allDecls - - -- First check for cyclic type synonysm or classes - -- See notes with checkCycleErrs - ; checkCycleErrs decls - ; mod <- getModule - ; traceTc "tcTyAndCl" (ppr mod) - ; (syn_tycons, alg_tyclss) <- fixM (\ ~(_rec_syn_tycons, rec_alg_tyclss) -> - do { let { -- Seperate ordinary synonyms from all other type and - -- class declarations and add all associated type - -- declarations from type classes. The latter is - -- required so that the temporary environment for the - -- knot includes all associated family declarations. - ; (syn_decls, alg_decls) = partition (isSynDecl . unLoc) - decls - ; alg_at_decls = concatMap addATs alg_decls - } - -- Extend the global env with the knot-tied results - -- for data types and classes - -- - -- We must populate the environment with the loop-tied - -- T's right away, because the kind checker may "fault - -- in" some type constructors that recursively - -- mention T - ; let gbl_things = mkGlobalThings alg_at_decls rec_alg_tyclss - ; tcExtendRecEnv gbl_things $ do - - -- Kind-check the declarations - { (kc_syn_decls, kc_alg_decls) <- kcTyClDecls syn_decls alg_decls - - ; let { -- Calculate rec-flag - ; calc_rec = calcRecFlags boot_details rec_alg_tyclss - ; tc_decl = addLocM (tcTyClDecl calc_rec) } - - -- Type-check the type synonyms, and extend the envt - ; syn_tycons <- tcSynDecls kc_syn_decls - ; tcExtendGlobalEnv syn_tycons $ do - - -- Type-check the data types and classes - { alg_tyclss <- mapM tc_decl kc_alg_decls - ; return (syn_tycons, concat alg_tyclss) - }}}) - -- Finished with knot-tying now - -- Extend the environment with the finished things - ; tcExtendGlobalEnv (syn_tycons ++ alg_tyclss) $ do - - -- Perform the validity check - { traceTc "ready for validity check" empty - ; mapM_ (addLocM checkValidTyCl) decls + do { let tyclds_s = map (filterOut (isFamInstDecl . unLoc)) decls_s + -- Remove family instance decls altogether + -- They are dealt with by TcInstDcls + + ; tyclss <- fixM $ \ rec_tyclss -> + tcExtendRecEnv (zipRecTyClss tyclds_s rec_tyclss) $ + -- We must populate the environment with the loop-tied + -- T's right away (even before kind checking), because + -- the kind checker may "fault in" some type constructors + -- that recursively mention T + + do { -- Kind-check in dependency order + -- See Note [Kind checking for type and class decls] + kc_decls <- kcTyClDecls tyclds_s + + -- And now build the TyCons/Classes + ; let rec_flags = calcRecFlags boot_details rec_tyclss + ; concatMapM (tcTyClDecl rec_flags) kc_decls } + + ; tcExtendGlobalEnv tyclss $ do + { -- Perform the validity check + -- We can do this now because we are done with the recursive knot + traceTc "ready for validity check" empty + ; mapM_ (addLocM checkValidTyCl) (concat tyclds_s) ; traceTc "done" empty - + -- Add the implicit things; - -- we want them in the environment because + -- we want them in the environment because -- they may be mentioned in interface files -- NB: All associated types and their implicit things will be added a -- second time here. This doesn't matter as the definitions are -- the same. - ; let { implicit_things = concatMap implicitTyThings alg_tyclss - ; rec_sel_binds = mkRecSelBinds alg_tyclss - ; dm_ids = mkDefaultMethodIds alg_tyclss } - ; traceTc "Adding types and classes" $ vcat - [ ppr alg_tyclss - , text "and" <+> ppr implicit_things ] + ; let { implicit_things = concatMap implicitTyThings tyclss + ; rec_sel_binds = mkRecSelBinds tyclss + ; dm_ids = mkDefaultMethodIds tyclss } + ; env <- tcExtendGlobalEnv implicit_things getGblEnv - ; return (env, rec_sel_binds, dm_ids) } - } - where - -- Pull associated types out of class declarations, to tie them into the - -- knot above. - -- NB: We put them in the same place in the list as `tcTyClDecl' will - -- eventually put the matching `TyThing's. That's crucial; otherwise, - -- the two argument lists of `mkGlobalThings' don't match up. - addATs decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats - addATs decl = [decl] - -mkGlobalThings :: [LTyClDecl Name] -- The decls - -> [TyThing] -- Knot-tied, in 1-1 correspondence with the decls - -> [(Name,TyThing)] --- Driven by the Decls, and treating the TyThings lazily --- make a TypeEnv for the new things -mkGlobalThings decls things - = map mk_thing (decls `zipLazy` things) + ; return (env, rec_sel_binds, dm_ids) } } + +zipRecTyClss :: [[LTyClDecl Name]] + -> [TyThing] -- Knot-tied + -> [(Name,TyThing)] +-- Build a name-TyThing mapping for the things bound by decls +-- being careful not to look at the [TyThing] +-- The TyThings in the result list must have a visible ATyCon/AClass, +-- because typechecking types (in, say, tcTyClDecl) looks at this outer constructor +zipRecTyClss decls_s rec_things + = [ get decl | decls <- decls_s, L _ decl <- flattenATs decls ] where - mk_thing (L _ (ClassDecl {tcdLName = L _ name}), ~(AClass cl)) - = (name, AClass cl) - mk_thing (L _ decl, ~(ATyCon tc)) - = (tcdName decl, ATyCon tc) + rec_type_env :: TypeEnv + rec_type_env = mkTypeEnv rec_things + + get :: TyClDecl Name -> (Name, TyThing) + get (ClassDecl {tcdLName = L _ name}) = (name, AClass cl) + where + Just (AClass cl) = lookupTypeEnv rec_type_env name + get decl = (name, ATyCon tc) + where + name = tcdName decl + Just (ATyCon tc) = lookupTypeEnv rec_type_env name \end{code} @@ -425,6 +323,25 @@ kcIdxTyPats decl thing_inside %* * %************************************************************************ +Note [Kind checking for type and class decls] +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Kind checking is done thus: + + 1. Make up a kind variable for each parameter of the *data* type, + and class, decls, and extend the kind environment (which is in + the TcLclEnv) + + 2. Dependency-analyse the type *synonyms* (which must be non-recursive), + and kind-check them in dependency order. Extend the kind envt. + + 3. Kind check the data type and class decls + +Synonyms are treated differently to data type and classes, +because a type synonym can be an unboxed type + type Foo = Int# +and a kind variable can't unify with UnboxedTypeKind +So we infer their kinds in dependency order + We need to kind check all types in the mutually recursive group before we know the kind of the type variables. For example: @@ -459,48 +376,52 @@ instances of families altogether in the following. However, we need to include the kinds of associated families into the construction of the initial kind environment. (This is handled by `allDecls'). + \begin{code} -kcTyClDecls :: [LTyClDecl Name] -> [Located (TyClDecl Name)] - -> TcM ([LTyClDecl Name], [Located (TyClDecl Name)]) -kcTyClDecls syn_decls alg_decls - = do { -- First extend the kind env with each data type, class, and - -- indexed type, mapping them to a type variable - let initialKindDecls = concat [allDecls decl | L _ decl <- alg_decls] - ; alg_kinds <- mapM getInitialKind initialKindDecls - ; tcExtendKindEnv alg_kinds $ do - - -- Now kind-check the type synonyms, in dependency order - -- We do these differently to data type and classes, - -- because a type synonym can be an unboxed type - -- type Foo = Int# - -- and a kind variable can't unify with UnboxedTypeKind - -- So we infer their kinds in dependency order - { (kc_syn_decls, syn_kinds) <- kcSynDecls (calcSynCycles syn_decls) - ; tcExtendKindEnv syn_kinds $ do - - -- Now kind-check the data type, class, and kind signatures, - -- returning kind-annotated decls; we don't kind-check - -- instances of indexed types yet, but leave this to - -- `tcInstDecls1' - { kc_alg_decls <- mapM (wrapLocM kcTyClDecl) - (filter (not . isFamInstDecl . unLoc) alg_decls) - - ; return (kc_syn_decls, kc_alg_decls) }}} +kcTyClDecls :: [[LTyClDecl Name]] -> TcM [LTyClDecl Name] +kcTyClDecls [] = return [] +kcTyClDecls (decls : decls_s) = do { (tcl_env, kc_decls1) <- kcTyClDecls1 decls + ; kc_decls2 <- setLclEnv tcl_env (kcTyClDecls decls_s) + ; return (kc_decls1 ++ kc_decls2) } + +kcTyClDecls1 :: [LTyClDecl Name] -> TcM (TcLclEnv, [LTyClDecl Name]) +kcTyClDecls1 decls + = do { -- Omit instances of type families; they are handled together + -- with the *heads* of class instances + ; let (syn_decls, alg_decls) = partition (isSynDecl . unLoc) decls + alg_at_decls = flattenATs alg_decls + + ; mod <- getModule + ; traceTc "tcTyAndCl" (ptext (sLit "module") <+> ppr mod $$ vcat (map ppr decls)) + + -- First check for cyclic classes + ; checkClassCycleErrs alg_decls + + -- Kind checking; see Note [Kind checking for type and class decls] + ; alg_kinds <- mapM getInitialKind alg_at_decls + ; tcExtendKindEnv alg_kinds $ do + + { (kc_syn_decls, tcl_env) <- kcSynDecls (calcSynCycles syn_decls) + ; setLclEnv tcl_env $ do + { kc_alg_decls <- mapM (wrapLocM kcTyClDecl) alg_decls + + -- Kind checking done for this group, so zonk the kind variables + -- See Note [Kind checking for type and class decls] + ; mapM_ (zonkTcKindToKind . snd) alg_kinds + + ; return (tcl_env, kc_syn_decls ++ kc_alg_decls) } } } + +flattenATs :: [LTyClDecl Name] -> [LTyClDecl Name] +flattenATs decls = concatMap flatten decls where - -- get all declarations relevant for determining the initial kind - -- environment - allDecls (decl@ClassDecl {tcdATs = ats}) = decl : [ at - | L _ at <- ats - , isFamilyDecl at] - allDecls decl | isFamInstDecl decl = [] - | otherwise = [decl] + flatten decl@(L _ (ClassDecl {tcdATs = ats})) = decl : ats + flatten decl = [decl] ------------------------------------------------------------------------- -getInitialKind :: TyClDecl Name -> TcM (Name, TcKind) +getInitialKind :: LTyClDecl Name -> TcM (Name, TcKind) -- Only for data type, class, and indexed type declarations -- Get as much info as possible from the data, class, or indexed type decl, -- so as to maximise usefulness of error messages -getInitialKind decl +getInitialKind (L _ decl) = do { arg_kinds <- mapM (mk_arg_kind . unLoc) (tyClDeclTyVars decl) ; res_kind <- mk_res_kind decl ; return (tcdName decl, mkArrowKinds arg_kinds res_kind) } @@ -518,13 +439,13 @@ getInitialKind decl ---------------- kcSynDecls :: [SCC (LTyClDecl Name)] -> TcM ([LTyClDecl Name], -- Kind-annotated decls - [(Name,TcKind)]) -- Kind bindings + TcLclEnv) -- Kind bindings kcSynDecls [] - = return ([], []) + = do { tcl_env <- getLclEnv; return ([], tcl_env) } kcSynDecls (group : groups) - = do { (decl, nk) <- kcSynDecl group - ; (decls, nks) <- tcExtendKindEnv [nk] (kcSynDecls groups) - ; return (decl:decls, nk:nks) } + = do { (decl, nk) <- kcSynDecl group + ; (decls, tcl_env) <- tcExtendKindEnv [nk] (kcSynDecls groups) + ; return (decl:decls, tcl_env) } ---------------- kcSynDecl :: SCC (LTyClDecl Name) @@ -675,31 +596,11 @@ kcFamilyDecl _ d = pprPanic "kcFamilyDecl" (ppr d) %************************************************************************ \begin{code} -tcSynDecls :: [LTyClDecl Name] -> TcM [TyThing] -tcSynDecls [] = return [] -tcSynDecls (decl : decls) - = do { syn_tc <- addLocM tcSynDecl decl - ; syn_tcs <- tcExtendGlobalEnv [syn_tc] (tcSynDecls decls) - ; return (syn_tc : syn_tcs) } +tcTyClDecl :: (Name -> RecFlag) -> LTyClDecl Name -> TcM [TyThing] - -- "type" -tcSynDecl :: TyClDecl Name -> TcM TyThing -tcSynDecl - (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty}) - = tcTyVarBndrs tvs $ \ tvs' -> do - { traceTc "tcd1" (ppr tc_name) - ; rhs_ty' <- tcHsKindedType rhs_ty - ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') - (typeKind rhs_ty') NoParentTyCon Nothing - ; return (ATyCon tycon) - } -tcSynDecl d = pprPanic "tcSynDecl" (ppr d) - --------------------- -tcTyClDecl :: (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing] - -tcTyClDecl calc_isrec decl - = tcAddDeclCtxt decl (tcTyClDecl1 NoParentTyCon calc_isrec decl) +tcTyClDecl calc_isrec (L loc decl) + = setSrcSpan loc $ tcAddDeclCtxt decl $ + tcTyClDecl1 NoParentTyCon calc_isrec decl -- "type family" declarations tcTyClDecl1 :: TyConParent -> (Name -> RecFlag) -> TyClDecl Name -> TcM [TyThing] @@ -738,12 +639,24 @@ tcTyClDecl1 parent _calc_isrec ; return [ATyCon tycon] } + -- "type" +tcTyClDecl1 _parent _calc_isrec + (TySynonym {tcdLName = L _ tc_name, tcdTyVars = tvs, tcdSynRhs = rhs_ty}) + = ASSERT( isNoParent _parent ) + tcTyVarBndrs tvs $ \ tvs' -> do + { traceTc "tcd1" (ppr tc_name) + ; rhs_ty' <- tcHsKindedType rhs_ty + ; tycon <- buildSynTyCon tc_name tvs' (SynonymTyCon rhs_ty') + (typeKind rhs_ty') NoParentTyCon Nothing + ; return [ATyCon tycon] } + -- "newtype" and "data" -- NB: not used for newtype/data instances (whether associated or not) -tcTyClDecl1 parent calc_isrec +tcTyClDecl1 _parent calc_isrec (TyData {tcdND = new_or_data, tcdCtxt = ctxt, tcdTyVars = tvs, tcdLName = L _ tc_name, tcdKindSig = mb_ksig, tcdCons = cons}) - = tcTyVarBndrs tvs $ \ tvs' -> do + = ASSERT( isNoParent _parent ) + tcTyVarBndrs tvs $ \ tvs' -> do { extra_tvs <- tcDataKindSig mb_ksig ; let final_tvs = tvs' ++ extra_tvs ; stupid_theta <- tcHsKindedContext ctxt @@ -790,7 +703,7 @@ tcTyClDecl1 parent calc_isrec mkNewTyConRhs tc_name tycon (head data_cons) ; buildAlgTyCon tc_name final_tvs stupid_theta tc_rhs is_rec (want_generic && canDoGenerics data_cons) (not h98_syntax) - parent Nothing + NoParentTyCon Nothing }) ; return [ATyCon tycon] } @@ -802,7 +715,8 @@ tcTyClDecl1 _parent calc_isrec (ClassDecl {tcdLName = L _ class_name, tcdTyVars = tvs, tcdCtxt = ctxt, tcdMeths = meths, tcdFDs = fundeps, tcdSigs = sigs, tcdATs = ats} ) - = tcTyVarBndrs tvs $ \ tvs' -> do + = ASSERT( isNoParent _parent ) + tcTyVarBndrs tvs $ \ tvs' -> do { ctxt' <- tcHsKindedContext ctxt ; fds' <- mapM (addLocM tc_fundep) fundeps ; sig_stuff <- tcClassSigs class_name sigs meths @@ -1038,8 +952,8 @@ Validity checking is done once the mutually-recursive knot has been tied, so we can look at things freely. \begin{code} -checkCycleErrs :: [LTyClDecl Name] -> TcM () -checkCycleErrs tyclss +checkClassCycleErrs :: [LTyClDecl Name] -> TcM () +checkClassCycleErrs tyclss | null cls_cycles = return () | otherwise @@ -1058,8 +972,9 @@ checkValidTyCl decl ; traceTc "Validity of" (ppr thing) ; case thing of ATyCon tc -> checkValidTyCon tc - AClass cl -> checkValidClass cl - _ -> panic "checkValidTyCl" + AClass cl -> do { checkValidClass cl + ; mapM_ (addLocM checkValidTyCl) (tcdATs decl) } + _ -> panic "checkValidTyCl" ; traceTc "Done validity of" (ppr thing) }