{- Data/Singletons/Promote.hs (c) Richard Eisenberg 2013 rae@cs.brynmawr.edu This file contains functions to promote term-level constructs to the type level. It is an internal module to the singletons package. -} {-# LANGUAGE TemplateHaskell, MultiWayIf, LambdaCase, TupleSections #-} module Data.Singletons.Promote where import Language.Haskell.TH hiding ( Q, cxt ) import Language.Haskell.TH.Syntax ( Quasi(..) ) import Language.Haskell.TH.Desugar import Data.Singletons.Names import Data.Singletons.Promote.Monad import Data.Singletons.Promote.Eq import Data.Singletons.Promote.Defun import Data.Singletons.Promote.Type import Data.Singletons.Deriving.Ord import Data.Singletons.Deriving.Bounded import Data.Singletons.Deriving.Enum import Data.Singletons.Deriving.Show import Data.Singletons.Deriving.Util import Data.Singletons.Partition import Data.Singletons.Util import Data.Singletons.Syntax import Prelude hiding (exp) import Control.Applicative (Alternative(..)) import Control.Arrow (second) import Control.Monad import Control.Monad.Trans.Class (MonadTrans(..)) import Control.Monad.Trans.Maybe import Control.Monad.Writer import qualified Data.Map.Strict as Map import Data.Map.Strict ( Map ) import qualified Data.Set as Set import Data.Set ( Set ) import Data.Maybe import qualified GHC.LanguageExtensions.Type as LangExt -- | Generate promoted definitions from a type that is already defined. -- This is generally only useful with classes. genPromotions :: DsMonad q => [Name] -> q [Dec] genPromotions names = do checkForRep names infos <- mapM reifyWithLocals names dinfos <- mapM dsInfo infos ddecs <- promoteM_ [] $ mapM_ promoteInfo dinfos return $ decsToTH ddecs -- | Promote every declaration given to the type level, retaining the originals. promote :: DsMonad q => q [Dec] -> q [Dec] promote qdec = do decls <- qdec ddecls <- withLocalDeclarations decls $ dsDecs decls promDecls <- promoteM_ decls $ promoteDecs ddecls return $ decls ++ decsToTH promDecls -- | Promote each declaration, discarding the originals. Note that a promoted -- datatype uses the same definition as an original datatype, so this will -- not work with datatypes. Classes, instances, and functions are all fine. promoteOnly :: DsMonad q => q [Dec] -> q [Dec] promoteOnly qdec = do decls <- qdec ddecls <- dsDecs decls promDecls <- promoteM_ decls $ promoteDecs ddecls return $ decsToTH promDecls -- | Generate defunctionalization symbols for existing type families. -- -- 'genDefunSymbols' has reasonable support for type families that use -- dependent quantification. For instance, this: -- -- @ -- type family MyProxy k (a :: k) :: Type where -- MyProxy k (a :: k) = Proxy a -- -- $('genDefunSymbols' [''MyProxy]) -- @ -- -- Will generate the following defunctionalization symbols: -- -- @ -- data MyProxySym0 :: Type ~> k ~> Type -- data MyProxySym1 (k :: Type) :: k ~> Type -- @ -- -- Note that @MyProxySym0@ is a bit more general than it ought to be, since -- there is no dependency between the first kind (@Type@) and the second kind -- (@k@). But this would require the ability to write something like: -- -- @ -- data MyProxySym0 :: forall (k :: Type) ~> k ~> Type -- @ -- -- Which currently isn't possible. So for the time being, the kind of -- @MyProxySym0@ will be slightly more general, which means that under rare -- circumstances, you may have to provide extra type signatures if you write -- code which exploits the dependency in @MyProxy@'s kind. genDefunSymbols :: DsMonad q => [Name] -> q [Dec] genDefunSymbols names = do checkForRep names infos <- mapM (dsInfo <=< reifyWithLocals) names decs <- promoteMDecs [] $ concatMapM defunInfo infos return $ decsToTH decs -- | Produce instances for @(==)@ (type-level equality) from the given types promoteEqInstances :: DsMonad q => [Name] -> q [Dec] promoteEqInstances = concatMapM promoteEqInstance -- | Produce instances for 'POrd' from the given types promoteOrdInstances :: DsMonad q => [Name] -> q [Dec] promoteOrdInstances = concatMapM promoteOrdInstance -- | Produce an instance for 'POrd' from the given type promoteOrdInstance :: DsMonad q => Name -> q [Dec] promoteOrdInstance = promoteInstance mkOrdInstance "Ord" -- | Produce instances for 'PBounded' from the given types promoteBoundedInstances :: DsMonad q => [Name] -> q [Dec] promoteBoundedInstances = concatMapM promoteBoundedInstance -- | Produce an instance for 'PBounded' from the given type promoteBoundedInstance :: DsMonad q => Name -> q [Dec] promoteBoundedInstance = promoteInstance mkBoundedInstance "Bounded" -- | Produce instances for 'PEnum' from the given types promoteEnumInstances :: DsMonad q => [Name] -> q [Dec] promoteEnumInstances = concatMapM promoteEnumInstance -- | Produce an instance for 'PEnum' from the given type promoteEnumInstance :: DsMonad q => Name -> q [Dec] promoteEnumInstance = promoteInstance mkEnumInstance "Enum" -- | Produce instances for 'PShow' from the given types promoteShowInstances :: DsMonad q => [Name] -> q [Dec] promoteShowInstances = concatMapM promoteShowInstance -- | Produce an instance for 'PShow' from the given type promoteShowInstance :: DsMonad q => Name -> q [Dec] promoteShowInstance = promoteInstance mkShowInstance "Show" -- | Produce an instance for @(==)@ (type-level equality) from the given type promoteEqInstance :: DsMonad q => Name -> q [Dec] promoteEqInstance name = do (tvbs, cons) <- getDataD "I cannot make an instance of (==) for it." name tvbs' <- mapM dsTvb tvbs let data_ty = foldTypeTvbs (DConT name) tvbs' cons' <- concatMapM (dsCon tvbs' data_ty) cons kind <- promoteType (foldTypeTvbs (DConT name) tvbs') inst_decs <- mkEqTypeInstance kind cons' return $ decsToTH inst_decs promoteInstance :: DsMonad q => DerivDesc q -> String -> Name -> q [Dec] promoteInstance mk_inst class_name name = do (tvbs, cons) <- getDataD ("I cannot make an instance of " ++ class_name ++ " for it.") name tvbs' <- mapM dsTvb tvbs let data_ty = foldTypeTvbs (DConT name) tvbs' cons' <- concatMapM (dsCon tvbs' data_ty) cons let data_decl = DataDecl name tvbs' cons' raw_inst <- mk_inst Nothing data_ty data_decl decs <- promoteM_ [] $ void $ promoteInstanceDec Map.empty raw_inst return $ decsToTH decs promoteInfo :: DInfo -> PrM () promoteInfo (DTyConI dec _instances) = promoteDecs [dec] promoteInfo (DPrimTyConI _name _numArgs _unlifted) = fail "Promotion of primitive type constructors not supported" promoteInfo (DVarI _name _ty _mdec) = fail "Promotion of individual values not supported" promoteInfo (DTyVarI _name _ty) = fail "Promotion of individual type variables not supported" promoteInfo (DPatSynI {}) = fail "Promotion of pattern synonyms not supported" -- Note [Promoting declarations in two stages] -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ -- -- It is necessary to know the types of things when promoting. So, -- we promote in two stages: first, we build a LetDecEnv, which allows -- for easy lookup. Then, we go through the actual elements of the LetDecEnv, -- performing the promotion. -- -- Why do we need the types? For kind annotations on the type family. We also -- need to have both the types and the actual function definition at the same -- time, because the function definition tells us how many patterns are -- matched. Note that an eta-contracted function needs to return a TyFun, -- not a proper type-level function. -- -- Consider this example: -- -- foo :: Nat -> Bool -> Bool -- foo Zero = id -- foo _ = not -- -- Here the first parameter to foo is non-uniform, because it is -- inspected in a pattern and can be different in each defining -- equation of foo. The second parameter to foo, specified in the type -- signature as Bool, is a uniform parameter - it is not inspected and -- each defining equation of foo uses it the same way. The foo -- function will be promoted to a type familty Foo like this: -- -- type family Foo (n :: Nat) :: Bool ~> Bool where -- Foo Zero = Id -- Foo a = Not -- -- To generate type signature for Foo type family we must first learn -- what is the actual number of patterns used in defining cequations -- of foo. In this case there is only one so we declare Foo to take -- one argument and have return type of Bool -> Bool. -- Promote a list of top-level declarations. promoteDecs :: [DDec] -> PrM () promoteDecs raw_decls = do decls <- expand raw_decls -- expand type synonyms checkForRepInDecls decls PDecs { pd_let_decs = let_decs , pd_class_decs = classes , pd_instance_decs = insts , pd_data_decs = datas , pd_ty_syn_decs = ty_syns , pd_open_type_family_decs = o_tyfams , pd_closed_type_family_decs = c_tyfams , pd_derived_eq_decs = derived_eq_decs } <- partitionDecs decls defunTypeDecls ty_syns c_tyfams o_tyfams -- promoteLetDecs returns LetBinds, which we don't need at top level _ <- promoteLetDecs noPrefix let_decs mapM_ promoteClassDec classes let orig_meth_sigs = foldMap (lde_types . cd_lde) classes mapM_ (promoteInstanceDec orig_meth_sigs) insts mapM_ promoteDerivedEqDec derived_eq_decs promoteDataDecs datas promoteDataDecs :: [DataDecl] -> PrM () promoteDataDecs data_decs = do rec_selectors <- concatMapM extract_rec_selectors data_decs _ <- promoteLetDecs noPrefix rec_selectors mapM_ promoteDataDec data_decs where extract_rec_selectors :: DataDecl -> PrM [DLetDec] extract_rec_selectors (DataDecl data_name tvbs cons) = let arg_ty = foldTypeTvbs (DConT data_name) tvbs in getRecordSelectors arg_ty cons -- curious about ALetDecEnv? See the LetDecEnv module for an explanation. promoteLetDecs :: (String, String) -- (alpha, symb) prefixes to use -> [DLetDec] -> PrM ([LetBind], ALetDecEnv) -- See Note [Promoting declarations in two stages] promoteLetDecs prefixes decls = do let_dec_env <- buildLetDecEnv decls all_locals <- allLocals let binds = [ (name, foldType (DConT sym) (map DVarT all_locals)) | name <- Map.keys $ lde_defns let_dec_env , let proName = promoteValNameLhsPrefix prefixes name sym = promoteTySym proName (length all_locals) ] (decs, let_dec_env') <- letBind binds $ promoteLetDecEnv prefixes let_dec_env emitDecs decs return (binds, let_dec_env' { lde_proms = Map.fromList binds }) -- Promotion of data types to kinds is automatic (see "Giving Haskell a -- Promotion" paper for more details). Here we "plug into" the promotion -- mechanism to add some extra stuff to the promotion: -- -- * if data type derives Eq we generate a type family that implements the -- equality test for the data type. -- -- * for each data constructor with arity greater than 0 we generate type level -- symbols for use with Apply type family. In this way promoted data -- constructors and promoted functions can be used in a uniform way at the -- type level in the same way they can be used uniformly at the type level. -- -- * for each nullary data constructor we generate a type synonym promoteDataDec :: DataDecl -> PrM () promoteDataDec (DataDecl _name _tvbs ctors) = do ctorSyms <- buildDefunSymsDataD ctors emitDecs ctorSyms -- Note [CUSKification] -- ~~~~~~~~~~~~~~~~~~~~ -- GHC #12928 means that sometimes, this TH code will produce a declaration -- that has a kind signature even when we want kind inference to work. There -- seems to be no way to avoid this, so we embrace it: -- -- * If a class type variable has no explicit kind, we make no effort to -- guess it and default to *. This is OK because before GHC 8.0, we were -- limited by KProxy anyway. -- -- * If a class type variable has an explicit kind, it is preserved. -- -- This way, we always get proper CUSKs where we need them. promoteClassDec :: UClassDecl -> PrM AClassDecl promoteClassDec decl@(ClassDecl { cd_cxt = cxt , cd_name = cls_name , cd_tvbs = tvbs' , cd_fds = fundeps , cd_lde = lde@LetDecEnv { lde_defns = defaults , lde_types = meth_sigs , lde_infix = infix_decls } }) = do let -- a workaround for GHC Trac #12928; see Note [CUSKification] tvbs = map cuskify tvbs' let pClsName = promoteClassName cls_name pCxt <- mapM promote_superclass_pred cxt forallBind cls_kvs_to_bind $ do sig_decs <- mapM (uncurry promote_sig) (Map.toList meth_sigs) let defaults_list = Map.toList defaults defaults_names = map fst defaults_list (default_decs, ann_rhss, prom_rhss) <- mapAndUnzip3M (promoteMethod Map.empty Nothing meth_sigs) defaults_list let infix_decls' = catMaybes $ map (uncurry promoteInfixDecl) $ Map.toList infix_decls -- no need to do anything to the fundeps. They work as is! emitDecs [DClassD pCxt pClsName tvbs fundeps (sig_decs ++ default_decs ++ infix_decls')] let defaults_list' = zip defaults_names ann_rhss proms = zip defaults_names prom_rhss cls_kvs_to_bind' = cls_kvs_to_bind <$ meth_sigs return (decl { cd_lde = lde { lde_defns = Map.fromList defaults_list' , lde_proms = Map.fromList proms , lde_bound_kvs = cls_kvs_to_bind' } }) where cls_kvb_names, cls_tvb_names, cls_kvs_to_bind :: Set Name cls_kvb_names = foldMap (foldMap fvDType . extractTvbKind) tvbs' cls_tvb_names = Set.fromList $ map extractTvbName tvbs' cls_kvs_to_bind = cls_kvb_names `Set.union` cls_tvb_names promote_sig :: Name -> DType -> PrM DDec promote_sig name ty = do let proName = promoteValNameLhs name (argKs, resK) <- promoteUnraveled ty args <- mapM (const $ qNewName "arg") argKs let tvbs = zipWith DKindedTV args argKs emitDecsM $ defunReifyFixity proName tvbs (Just resK) return $ DOpenTypeFamilyD (DTypeFamilyHead proName tvbs (DKindSig resK) Nothing) promote_superclass_pred :: DPred -> PrM DPred promote_superclass_pred = go where go (DForallPr {}) = fail "Cannot promote quantified constraints" go (DAppPr pr ty) = DAppPr <$> go pr <*> promoteType ty go (DSigPr pr _k) = go pr -- just ignore the kind; it can't matter go (DVarPr name) = fail $ "Cannot promote ConstraintKinds variables like " ++ show name go (DConPr name) = return $ DConPr (promoteClassName name) go DWildCardPr = return DWildCardPr -- returns (unpromoted method name, ALetDecRHS) pairs promoteInstanceDec :: Map Name DType -> UInstDecl -> PrM AInstDecl promoteInstanceDec orig_meth_sigs decl@(InstDecl { id_name = cls_name , id_arg_tys = inst_tys , id_sigs = inst_sigs , id_meths = meths }) = do cls_tvb_names <- lookup_cls_tvb_names inst_kis <- mapM promoteType inst_tys let kvs_to_bind = foldMap fvDType inst_kis forallBind kvs_to_bind $ do let subst = Map.fromList $ zip cls_tvb_names inst_kis (meths', ann_rhss, _) <- mapAndUnzip3M (promoteMethod inst_sigs (Just subst) orig_meth_sigs) meths emitDecs [DInstanceD Nothing [] (foldType (DConT pClsName) inst_kis) meths'] return (decl { id_meths = zip (map fst meths) ann_rhss }) where pClsName = promoteClassName cls_name lookup_cls_tvb_names :: PrM [Name] lookup_cls_tvb_names = do let mk_tvb_names = extract_tvb_names (dsReifyTypeNameInfo pClsName) <|> extract_tvb_names (dsReifyTypeNameInfo cls_name) -- See Note [Using dsReifyTypeNameInfo when promoting instances] mb_tvb_names <- runMaybeT mk_tvb_names case mb_tvb_names of Just tvb_names -> pure tvb_names Nothing -> fail $ "Cannot find class declaration annotation for " ++ show cls_name extract_tvb_names :: PrM (Maybe DInfo) -> MaybeT PrM [Name] extract_tvb_names reify_info = do mb_info <- lift reify_info case mb_info of Just (DTyConI (DClassD _ _ tvbs _ _) _) -> pure $ map extractTvbName tvbs _ -> empty {- Note [Using dsReifyTypeNameInfo when promoting instances] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ During the promotion of a class instance, it becomes necessary to reify the original promoted class's info to learn various things. It's tempting to think that just calling dsReify on the class name will be sufficient, but it's not. Consider this class and its promotion: class Eq a where (==) :: a -> a -> Bool class PEq a where type (==) (x :: a) (y :: a) :: Bool Notice how both of these classes have an identifier named (==), one at the value level, and one at the type level. Now imagine what happens when you attempt to promote this Template Haskell declaration: [d| f :: Bool f = () == () |] When promoting ==, singletons will come up with its promoted equivalent (which also happens to be ==). However, this promoted name is a raw Name, since it is created with mkName. This becomes an issue when we call dsReify the raw "==" Name, as Template Haskell has to arbitrarily choose between reifying the info for the value-level (==) and the type-level (==), and in this case, it happens to pick the value-level (==) info. We want the type-level (==) info, however, because we care about the promoted version of (==). Fortunately, there's a serviceable workaround. Instead of dsReify, we can use dsReifyTypeNameInfo, which first calls lookupTypeName (to ensure we can find a Name that's in the type namespace) and _then_ reifies it. -} promoteMethod :: Map Name DType -- InstanceSigs for methods -> Maybe (Map Name DKind) -- ^ instantiations for class tyvars (Nothing for default decls) -- See Note [Promoted class method kinds] -> Map Name DType -- method types -> (Name, ULetDecRHS) -> PrM (DDec, ALetDecRHS, DType) -- returns (type instance, ALetDecRHS, promoted RHS) promoteMethod inst_sigs_map m_subst orig_sigs_map (meth_name, meth_rhs) = do (meth_arg_kis, meth_res_ki) <- lookup_meth_ty ((_, _, _, eqns), _defuns, ann_rhs) <- promoteLetDecRHS (Just (meth_arg_kis, meth_res_ki)) Map.empty Map.empty noPrefix meth_name meth_rhs meth_arg_tvs <- mapM (const $ qNewName "a") meth_arg_kis let helperNameBase = case nameBase proName of first:_ | not (isHsLetter first) -> "TFHelper" alpha -> alpha -- family_args are the type variables in a promoted class's -- associated type family instance (or default implementation), e.g., -- -- class C k where -- type T (a :: k) (b :: Bool) -- type T a b = THelper1 a b -- family_args = [a, b] -- -- instance C Bool where -- type T a b = THelper2 a b -- family_args = [a, b] -- -- We could annotate these variables with explicit kinds, but it's not -- strictly necessary, as kind inference can figure them out just as well. family_args = map DVarT meth_arg_tvs helperName <- newUniqueName helperNameBase let tvbs = zipWith DKindedTV meth_arg_tvs meth_arg_kis emitDecs [DClosedTypeFamilyD (DTypeFamilyHead helperName tvbs (DKindSig meth_res_ki) Nothing) eqns] emitDecsM (defunctionalize helperName Nothing tvbs (Just meth_res_ki)) return ( DTySynInstD proName (DTySynEqn family_args (foldApply (promoteValRhs helperName) (map DVarT meth_arg_tvs))) , ann_rhs , DConT (promoteTySym helperName 0) ) where proName = promoteValNameLhs meth_name lookup_meth_ty :: PrM ([DKind], DKind) lookup_meth_ty = case Map.lookup meth_name inst_sigs_map of Just ty -> -- We have an InstanceSig. These are easy: no substitution for clas -- variables is required at all! promoteUnraveled ty Nothing -> do -- We don't have an InstanceSig, so we must compute the kind to use -- ourselves (possibly substituting for class variables below). (arg_kis, res_ki) <- case Map.lookup meth_name orig_sigs_map of Nothing -> do mb_info <- dsReifyTypeNameInfo proName -- See Note [Using dsReifyTypeNameInfo when promoting instances] case mb_info of Just (DTyConI (DOpenTypeFamilyD (DTypeFamilyHead _ tvbs mb_res_ki _)) _) -> let arg_kis = map (default_to_star . extractTvbKind) tvbs res_ki = default_to_star (resultSigToMaybeKind mb_res_ki) in return (arg_kis, res_ki) _ -> fail $ "Cannot find type annotation for " ++ show proName Just ty -> promoteUnraveled ty let -- If we're dealing with an associated type family instance, substitute -- in the kind of the instance for better kind information in the RHS -- helper function. If we're dealing with a default family implementation -- (m_subst = Nothing), there's no need for a substitution. -- See Note [Promoted class method kinds] do_subst = maybe id substKind m_subst meth_arg_kis' = map do_subst arg_kis meth_res_ki' = do_subst res_ki pure (meth_arg_kis', meth_res_ki') default_to_star Nothing = DConT typeKindName default_to_star (Just k) = k {- Note [Promoted class method kinds] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Consider this example of a type class (and instance): class C a where m :: a -> Bool -> Bool m _ x = x instance C [a] where m l _ = null l The promoted version of these declarations would be: class PC a where type M (x :: a) (y :: Bool) (z :: Bool) type M x y z = MHelper1 x y z instance PC [a] where type M x y z = MHelper2 x y z type family MHelper1 (x :: a) (y :: Bool) (z :: Bool) where ... type family MHelper2 (x :: [a]) (y :: Bool) (z :: Bool) where ... Getting the kind signature for MHelper1 (the promoted default implementation of M) is quite simple, as it corresponds exactly to the kind of M. We might even choose to make that the kind of MHelper2, but then it would be overly general (and more difficult to find in -ddump-splices output). For this reason, we substitute in the kinds of the instance itself to determine the kinds of promoted method implementations like MHelper2. -} promoteLetDecEnv :: (String, String) -> ULetDecEnv -> PrM ([DDec], ALetDecEnv) promoteLetDecEnv prefixes (LetDecEnv { lde_defns = value_env , lde_types = type_env , lde_infix = fix_env }) = do let infix_decls = catMaybes $ map (uncurry promoteInfixDecl) $ Map.toList fix_env -- promote all the declarations, producing annotated declarations let (names, rhss) = unzip $ Map.toList value_env (payloads, defun_decss, ann_rhss) <- fmap unzip3 $ zipWithM (promoteLetDecRHS Nothing type_env fix_env prefixes) names rhss emitDecs $ concat defun_decss bound_kvs <- allBoundKindVars let decs = map payload_to_dec payloads ++ infix_decls -- build the ALetDecEnv let let_dec_env' = LetDecEnv { lde_defns = Map.fromList $ zip names ann_rhss , lde_types = type_env , lde_infix = fix_env , lde_proms = Map.empty -- filled in promoteLetDecs , lde_bound_kvs = Map.fromList $ map (, bound_kvs) names } return (decs, let_dec_env') where payload_to_dec (name, tvbs, m_ki, eqns) = DClosedTypeFamilyD (DTypeFamilyHead name tvbs sig Nothing) eqns where sig = maybe DNoSig DKindSig m_ki promoteInfixDecl :: Name -> Fixity -> Maybe DDec promoteInfixDecl name fixity | nameBase name == nameBase promoted_name -- If a name and its promoted counterpart are the same (modulo module -- prefixes), then there's no need to promote a fixity declaration for -- that name, since the existing fixity declaration will cover both -- the term- and type-level versions of that name, -- -- Names that fall into this category include data constructor names -- and infix names, with the exceptions of (.) and (!). -- See Note [Special cases for (.) and (!)] in Data.Singletons.Names. = Nothing | otherwise = Just $ DLetDec $ DInfixD fixity promoted_name where promoted_name = promoteValNameLhs name -- This function is used both to promote class method defaults and normal -- let bindings. Thus, it can't quite do all the work locally and returns -- an intermediate structure. Perhaps a better design is available. promoteLetDecRHS :: Maybe ([DKind], DKind) -- the promoted type of the RHS (if known) -- needed to fix #136 -> Map Name DType -- local type env't -> Map Name Fixity -- local fixity env't -> (String, String) -- let-binding prefixes -> Name -- name of the thing being promoted -> ULetDecRHS -- body of the thing -> PrM ( (Name, [DTyVarBndr], Maybe DKind, [DTySynEqn]) -- "type family" , [DDec] -- defunctionalization , ALetDecRHS ) -- annotated RHS promoteLetDecRHS m_rhs_ki type_env fix_env prefixes name (UValue exp) = do (res_kind, num_arrows) <- case m_rhs_ki of Just (arg_kis, res_ki) -> return ( Just (ravelTyFun (arg_kis ++ [res_ki])) , length arg_kis ) _ | Just ty <- Map.lookup name type_env -> do ki <- promoteType ty return (Just ki, countArgs ty) | otherwise -> return (Nothing, 0) case num_arrows of 0 -> do all_locals <- allLocals let lde_kvs_to_bind = foldMap fvDType res_kind (exp', ann_exp) <- forallBind lde_kvs_to_bind $ promoteExp exp let proName = promoteValNameLhsPrefix prefixes name m_fixity = Map.lookup name fix_env tvbs = map DPlainTV all_locals defuns <- defunctionalize proName m_fixity tvbs res_kind return ( ( proName, tvbs, res_kind , [DTySynEqn (map DVarT all_locals) exp'] ) , defuns , AValue (foldType (DConT proName) (map DVarT all_locals)) num_arrows ann_exp ) _ -> do names <- replicateM num_arrows (newUniqueName "a") let pats = map DVarPa names newArgs = map DVarE names promoteLetDecRHS m_rhs_ki type_env fix_env prefixes name (UFunction [DClause pats (foldExp exp newArgs)]) promoteLetDecRHS m_rhs_ki type_env fix_env prefixes name (UFunction clauses) = do numArgs <- count_args clauses (m_argKs, m_resK, ty_num_args) <- case m_rhs_ki of Just (arg_kis, res_ki) -> return (map Just arg_kis, Just res_ki, length arg_kis) _ | Just ty <- Map.lookup name type_env -> do -- promoteType turns arrows into TyFun. So, we unravel first to -- avoid this behavior. Note the use of ravelTyFun in resultK -- to make the return kind work out (argKs, resultK) <- promoteUnraveled ty -- invariant: countArgs ty == length argKs return (map Just argKs, Just resultK, length argKs) | otherwise -> return (replicate numArgs Nothing, Nothing, numArgs) let proName = promoteValNameLhsPrefix prefixes name m_fixity = Map.lookup name fix_env all_locals <- allLocals let local_tvbs = map DPlainTV all_locals tyvarNames <- mapM (const $ qNewName "a") m_argKs let args = zipWith inferMaybeKindTV tyvarNames m_argKs all_args = local_tvbs ++ args defun_decs <- defunctionalize proName m_fixity all_args m_resK expClauses <- mapM (etaContractOrExpand ty_num_args numArgs) clauses let lde_kvs_to_bind = foldMap (foldMap fvDType) m_argKs <> foldMap fvDType m_resK (eqns, ann_clauses) <- forallBind lde_kvs_to_bind $ mapAndUnzipM promoteClause expClauses prom_fun <- lookupVarE name return ( (proName, all_args, m_resK, eqns) , defun_decs , AFunction prom_fun ty_num_args ann_clauses ) where etaContractOrExpand :: Int -> Int -> DClause -> PrM DClause etaContractOrExpand ty_num_args clause_num_args (DClause pats exp) | n >= 0 = do -- Eta-expand names <- replicateM n (newUniqueName "a") let newPats = map DVarPa names newArgs = map DVarE names return $ DClause (pats ++ newPats) (foldExp exp newArgs) | otherwise = do -- Eta-contract let (clausePats, lamPats) = splitAt ty_num_args pats lamExp <- mkDLamEFromDPats lamPats exp return $ DClause clausePats lamExp where n = ty_num_args - clause_num_args count_args (DClause pats _ : _) = return $ length pats count_args _ = fail $ "Impossible! A function without clauses." promoteClause :: DClause -> PrM (DTySynEqn, ADClause) promoteClause (DClause pats exp) = do -- promoting the patterns creates variable bindings. These are passed -- to the function promoted the RHS ((types, pats'), prom_pat_infos) <- evalForPair $ mapAndUnzipM promotePat pats let PromDPatInfos { prom_dpat_vars = new_vars , prom_dpat_sig_kvs = sig_kvs } = prom_pat_infos (ty, ann_exp) <- forallBind sig_kvs $ lambdaBind new_vars $ promoteExp exp all_locals <- allLocals -- these are bound *outside* of this clause return ( DTySynEqn (map DVarT all_locals ++ types) ty , ADClause new_vars pats' ann_exp ) promoteMatch :: DMatch -> PrM (DTySynEqn, ADMatch) promoteMatch (DMatch pat exp) = do -- promoting the patterns creates variable bindings. These are passed -- to the function promoted the RHS ((ty, pat'), prom_pat_infos) <- evalForPair $ promotePat pat let PromDPatInfos { prom_dpat_vars = new_vars , prom_dpat_sig_kvs = sig_kvs } = prom_pat_infos (rhs, ann_exp) <- forallBind sig_kvs $ lambdaBind new_vars $ promoteExp exp all_locals <- allLocals return $ ( DTySynEqn (map DVarT all_locals ++ [ty]) rhs , ADMatch new_vars pat' ann_exp) -- promotes a term pattern into a type pattern, accumulating bound variable names promotePat :: DPat -> QWithAux PromDPatInfos PrM (DType, ADPat) promotePat (DLitPa lit) = (, ADLitPa lit) <$> promoteLitPat lit promotePat (DVarPa name) = do -- term vars can be symbols... type vars can't! tyName <- mkTyName name tell $ PromDPatInfos [(name, tyName)] Set.empty return (DVarT tyName, ADVarPa name) promotePat (DConPa name pats) = do (types, pats') <- mapAndUnzipM promotePat pats let name' = unboxed_tuple_to_tuple name return (foldType (DConT name') types, ADConPa name pats') where unboxed_tuple_to_tuple n | Just deg <- unboxedTupleNameDegree_maybe n = tupleDataName deg | otherwise = n promotePat (DTildePa pat) = do qReportWarning "Lazy pattern converted into regular pattern in promotion" second ADTildePa <$> promotePat pat promotePat (DBangPa pat) = do qReportWarning "Strict pattern converted into regular pattern in promotion" second ADBangPa <$> promotePat pat promotePat (DSigPa pat ty) = do -- We must maintain the invariant that any promoted pattern signature must -- not have any wildcards in the underlying pattern. -- See Note [Singling pattern signatures]. wildless_pat <- removeWilds pat (promoted, pat') <- promotePat wildless_pat ki <- promoteType ty tell $ PromDPatInfos [] (fvDType ki) return (DSigT promoted ki, ADSigPa promoted pat' ki) promotePat DWildPa = return (DWildCardT, ADWildPa) promoteExp :: DExp -> PrM (DType, ADExp) promoteExp (DVarE name) = fmap (, ADVarE name) $ lookupVarE name promoteExp (DConE name) = return $ (promoteValRhs name, ADConE name) promoteExp (DLitE lit) = fmap (, ADLitE lit) $ promoteLitExp lit promoteExp (DAppE exp1 exp2) = do (exp1', ann_exp1) <- promoteExp exp1 (exp2', ann_exp2) <- promoteExp exp2 return (apply exp1' exp2', ADAppE ann_exp1 ann_exp2) -- Until we get visible kind applications, this is the best we can do. promoteExp (DAppTypeE exp _) = do qReportWarning "Visible type applications are ignored by `singletons`." promoteExp exp promoteExp (DLamE names exp) = do lambdaName <- newUniqueName "Lambda" tyNames <- mapM mkTyName names let var_proms = zip names tyNames (rhs, ann_exp) <- lambdaBind var_proms $ promoteExp exp tyFamLamTypes <- mapM (const $ qNewName "t") names all_locals <- allLocals let all_args = all_locals ++ tyFamLamTypes tvbs = map DPlainTV all_args emitDecs [DClosedTypeFamilyD (DTypeFamilyHead lambdaName tvbs DNoSig Nothing) [DTySynEqn (map DVarT (all_locals ++ tyNames)) rhs]] emitDecsM $ defunctionalize lambdaName Nothing tvbs Nothing let promLambda = foldl apply (DConT (promoteTySym lambdaName 0)) (map DVarT all_locals) return (promLambda, ADLamE tyNames promLambda names ann_exp) promoteExp (DCaseE exp matches) = do caseTFName <- newUniqueName "Case" all_locals <- allLocals let prom_case = foldType (DConT caseTFName) (map DVarT all_locals) (exp', ann_exp) <- promoteExp exp (eqns, ann_matches) <- mapAndUnzipM promoteMatch matches tyvarName <- qNewName "t" let all_args = all_locals ++ [tyvarName] tvbs = map DPlainTV all_args emitDecs [DClosedTypeFamilyD (DTypeFamilyHead caseTFName tvbs DNoSig Nothing) eqns] -- See Note [Annotate case return type] in Single let applied_case = prom_case `DAppT` exp' return ( applied_case , ADCaseE ann_exp ann_matches applied_case ) promoteExp (DLetE decs exp) = do unique <- qNewUnique let letPrefixes = uniquePrefixes "Let" "<<<" unique (binds, ann_env) <- promoteLetDecs letPrefixes decs (exp', ann_exp) <- letBind binds $ promoteExp exp return (exp', ADLetE ann_env ann_exp) promoteExp (DSigE exp ty) = do (exp', ann_exp) <- promoteExp exp ty' <- promoteType ty return (DSigT exp' ty', ADSigE exp' ann_exp ty) promoteExp e@(DStaticE _) = fail ("Static expressions cannot be promoted: " ++ show e) promoteLitExp :: Quasi q => Lit -> q DType promoteLitExp (IntegerL n) | n >= 0 = return $ (DConT tyFromIntegerName `DAppT` DLitT (NumTyLit n)) | otherwise = return $ (DConT tyNegateName `DAppT` (DConT tyFromIntegerName `DAppT` DLitT (NumTyLit (-n)))) promoteLitExp (StringL str) = do let prom_str_lit = DLitT (StrTyLit str) os_enabled <- qIsExtEnabled LangExt.OverloadedStrings pure $ if os_enabled then DConT tyFromStringName `DAppT` prom_str_lit else prom_str_lit promoteLitExp lit = fail ("Only string and natural number literals can be promoted: " ++ show lit) promoteLitPat :: Monad m => Lit -> m DType promoteLitPat (IntegerL n) | n >= 0 = return $ (DLitT (NumTyLit n)) | otherwise = fail $ "Negative literal patterns are not allowed,\n" ++ "because literal patterns are promoted to natural numbers." promoteLitPat (StringL str) = return $ DLitT (StrTyLit str) promoteLitPat lit = fail ("Only string and natural number literals can be promoted: " ++ show lit) -- See Note [DerivedDecl] promoteDerivedEqDec :: DerivedEqDecl -> PrM () promoteDerivedEqDec (DerivedDecl { ded_type = ty , ded_decl = DataDecl _ _ cons }) = do kind <- promoteType ty inst_decs <- mkEqTypeInstance kind cons emitDecs inst_decs