{-# LANGUAGE CPP, DeriveDataTypeable, DeriveGeneric, FlexibleInstances, DefaultSignatures, RankNTypes, RoleAnnotations, ScopedTypeVariables, Trustworthy #-} {-# OPTIONS_GHC -fno-warn-inline-rule-shadowing #-} #if MIN_VERSION_base(4,9,0) # define HAS_MONADFAIL 1 #endif ----------------------------------------------------------------------------- -- | -- Module : Language.Haskell.Syntax -- Copyright : (c) The University of Glasgow 2003 -- License : BSD-style (see the file libraries/base/LICENSE) -- -- Maintainer : [email protected] -- Stability : experimental -- Portability : portable -- -- Abstract syntax definitions for Template Haskell. -- ----------------------------------------------------------------------------- module Language.Haskell.TH.Syntax ( module Language.Haskell.TH.Syntax -- * Language extensions , module Language.Haskell.TH.LanguageExtensions , ForeignSrcLang(..) ) where import Data.Data hiding (Fixity(..)) import Data.IORef import System.IO.Unsafe ( unsafePerformIO ) import Control.Monad (liftM) import System.IO ( hPutStrLn, stderr ) import Data.Char ( isAlpha, isAlphaNum, isUpper ) import Data.Int import Data.Word import Data.Ratio import GHC.Generics ( Generic ) import GHC.Lexeme ( startsVarSym, startsVarId ) import GHC.ForeignSrcLang.Type import Language.Haskell.TH.LanguageExtensions import Numeric.Natural #if HAS_MONADFAIL import qualified Control.Monad.Fail as Fail #endif ----------------------------------------------------- -- -- The Quasi class -- ----------------------------------------------------- #if HAS_MONADFAIL class Fail.MonadFail m => Quasi m where #else class Monad m => Quasi m where #endif qNewName :: String -> m Name -- ^ Fresh names -- Error reporting and recovery qReport :: Bool -> String -> m () -- ^ Report an error (True) or warning (False) -- ...but carry on; use 'fail' to stop qRecover :: m a -- ^ the error handler -> m a -- ^ action which may fail -> m a -- ^ Recover from the monadic 'fail' -- Inspect the type-checker's environment qLookupName :: Bool -> String -> m (Maybe Name) -- True <=> type namespace, False <=> value namespace qReify :: Name -> m Info qReifyFixity :: Name -> m (Maybe Fixity) qReifyInstances :: Name -> [Type] -> m [Dec] -- Is (n tys) an instance? -- Returns list of matching instance Decs -- (with empty sub-Decs) -- Works for classes and type functions qReifyRoles :: Name -> m [Role] qReifyAnnotations :: Data a => AnnLookup -> m [a] qReifyModule :: Module -> m ModuleInfo qReifyConStrictness :: Name -> m [DecidedStrictness] qLocation :: m Loc qRunIO :: IO a -> m a -- ^ Input/output (dangerous) qAddDependentFile :: FilePath -> m () qAddTopDecls :: [Dec] -> m () qAddForeignFile :: ForeignSrcLang -> String -> m () qAddModFinalizer :: Q () -> m () qGetQ :: Typeable a => m (Maybe a) qPutQ :: Typeable a => a -> m () qIsExtEnabled :: Extension -> m Bool qExtsEnabled :: m [Extension] ----------------------------------------------------- -- The IO instance of Quasi -- -- This instance is used only when running a Q -- computation in the IO monad, usually just to -- print the result. There is no interesting -- type environment, so reification isn't going to -- work. -- ----------------------------------------------------- instance Quasi IO where qNewName s = do { n <- atomicModifyIORef' counter (\x -> (x + 1, x)) ; pure (mkNameU s n) } qReport True msg = hPutStrLn stderr ("Template Haskell error: " ++ msg) qReport False msg = hPutStrLn stderr ("Template Haskell error: " ++ msg) qLookupName _ _ = badIO "lookupName" qReify _ = badIO "reify" qReifyFixity _ = badIO "reifyFixity" qReifyInstances _ _ = badIO "reifyInstances" qReifyRoles _ = badIO "reifyRoles" qReifyAnnotations _ = badIO "reifyAnnotations" qReifyModule _ = badIO "reifyModule" qReifyConStrictness _ = badIO "reifyConStrictness" qLocation = badIO "currentLocation" qRecover _ _ = badIO "recover" -- Maybe we could fix this? qAddDependentFile _ = badIO "addDependentFile" qAddTopDecls _ = badIO "addTopDecls" qAddForeignFile _ _ = badIO "addForeignFile" qAddModFinalizer _ = badIO "addModFinalizer" qGetQ = badIO "getQ" qPutQ _ = badIO "putQ" qIsExtEnabled _ = badIO "isExtEnabled" qExtsEnabled = badIO "extsEnabled" qRunIO m = m badIO :: String -> IO a badIO op = do { qReport True ("Can't do `" ++ op ++ "' in the IO monad") ; fail "Template Haskell failure" } -- Global variable to generate unique symbols counter :: IORef Int {-# NOINLINE counter #-} counter = unsafePerformIO (newIORef 0) ----------------------------------------------------- -- -- The Q monad -- ----------------------------------------------------- newtype Q a = Q { unQ :: forall m. Quasi m => m a } -- \"Runs\" the 'Q' monad. Normal users of Template Haskell -- should not need this function, as the splice brackets @$( ... )@ -- are the usual way of running a 'Q' computation. -- -- This function is primarily used in GHC internals, and for debugging -- splices by running them in 'IO'. -- -- Note that many functions in 'Q', such as 'reify' and other compiler -- queries, are not supported when running 'Q' in 'IO'; these operations -- simply fail at runtime. Indeed, the only operations guaranteed to succeed -- are 'newName', 'runIO', 'reportError' and 'reportWarning'. runQ :: Quasi m => Q a -> m a runQ (Q m) = m instance Monad Q where Q m >>= k = Q (m >>= \x -> unQ (k x)) (>>) = (*>) #if !HAS_MONADFAIL fail s = report True s >> Q (fail "Q monad failure") #else fail = Fail.fail instance Fail.MonadFail Q where fail s = report True s >> Q (Fail.fail "Q monad failure") #endif instance Functor Q where fmap f (Q x) = Q (fmap f x) instance Applicative Q where pure x = Q (pure x) Q f <*> Q x = Q (f <*> x) Q m *> Q n = Q (m *> n) ----------------------------------------------------- -- -- The TExp type -- ----------------------------------------------------- type role TExp nominal -- See Note [Role of TExp] newtype TExp a = TExp { unType :: Exp } unTypeQ :: Q (TExp a) -> Q Exp unTypeQ m = do { TExp e <- m ; return e } unsafeTExpCoerce :: Q Exp -> Q (TExp a) unsafeTExpCoerce m = do { e <- m ; return (TExp e) } {- Note [Role of TExp] ~~~~~~~~~~~~~~~~~~~~~~ TExp's argument must have a nominal role, not phantom as would be inferred (Trac #8459). Consider e :: TExp Age e = MkAge 3 foo = $(coerce e) + 4::Int The splice will evaluate to (MkAge 3) and you can't add that to 4::Int. So you can't coerce a (TExp Age) to a (TExp Int). -} ---------------------------------------------------- -- Packaged versions for the programmer, hiding the Quasi-ness {- | Generate a fresh name, which cannot be captured. For example, this: @f = $(do nm1 <- newName \"x\" let nm2 = 'mkName' \"x\" return ('LamE' ['VarP' nm1] (LamE [VarP nm2] ('VarE' nm1))) )@ will produce the splice >f = \x0 -> \x -> x0 In particular, the occurrence @VarE nm1@ refers to the binding @VarP nm1@, and is not captured by the binding @VarP nm2@. Although names generated by @newName@ cannot /be captured/, they can /capture/ other names. For example, this: >g = $(do > nm1 <- newName "x" > let nm2 = mkName "x" > return (LamE [VarP nm2] (LamE [VarP nm1] (VarE nm2))) > ) will produce the splice >g = \x -> \x0 -> x0 since the occurrence @VarE nm2@ is captured by the innermost binding of @x@, namely @VarP nm1@. -} newName :: String -> Q Name newName s = Q (qNewName s) -- | Report an error (True) or warning (False), -- but carry on; use 'fail' to stop. report :: Bool -> String -> Q () report b s = Q (qReport b s) {-# DEPRECATED report "Use reportError or reportWarning instead" #-} -- deprecated in 7.6 -- | Report an error to the user, but allow the current splice's computation to carry on. To abort the computation, use 'fail'. reportError :: String -> Q () reportError = report True -- | Report a warning to the user, and carry on. reportWarning :: String -> Q () reportWarning = report False -- | Recover from errors raised by 'reportError' or 'fail'. recover :: Q a -- ^ handler to invoke on failure -> Q a -- ^ computation to run -> Q a recover (Q r) (Q m) = Q (qRecover r m) -- We don't export lookupName; the Bool isn't a great API -- Instead we export lookupTypeName, lookupValueName lookupName :: Bool -> String -> Q (Maybe Name) lookupName ns s = Q (qLookupName ns s) -- | Look up the given name in the (type namespace of the) current splice's scope. See "Language.Haskell.TH.Syntax#namelookup" for more details. lookupTypeName :: String -> Q (Maybe Name) lookupTypeName s = Q (qLookupName True s) -- | Look up the given name in the (value namespace of the) current splice's scope. See "Language.Haskell.TH.Syntax#namelookup" for more details. lookupValueName :: String -> Q (Maybe Name) lookupValueName s = Q (qLookupName False s) {- Note [Name lookup] ~~~~~~~~~~~~~~~~~~ -} {- $namelookup #namelookup# The functions 'lookupTypeName' and 'lookupValueName' provide a way to query the current splice's context for what names are in scope. The function 'lookupTypeName' queries the type namespace, whereas 'lookupValueName' queries the value namespace, but the functions are otherwise identical. A call @lookupValueName s@ will check if there is a value with name @s@ in scope at the current splice's location. If there is, the @Name@ of this value is returned; if not, then @Nothing@ is returned. The returned name cannot be \"captured\". For example: > f = "global" > g = $( do > Just nm <- lookupValueName "f" > [| let f = "local" in $( varE nm ) |] In this case, @g = \"global\"@; the call to @lookupValueName@ returned the global @f@, and this name was /not/ captured by the local definition of @f@. The lookup is performed in the context of the /top-level/ splice being run. For example: > f = "global" > g = $( [| let f = "local" in > $(do > Just nm <- lookupValueName "f" > varE nm > ) |] ) Again in this example, @g = \"global\"@, because the call to @lookupValueName@ queries the context of the outer-most @$(...)@. Operators should be queried without any surrounding parentheses, like so: > lookupValueName "+" Qualified names are also supported, like so: > lookupValueName "Prelude.+" > lookupValueName "Prelude.map" -} {- | 'reify' looks up information about the 'Name'. It is sometimes useful to construct the argument name using 'lookupTypeName' or 'lookupValueName' to ensure that we are reifying from the right namespace. For instance, in this context: > data D = D which @D@ does @reify (mkName \"D\")@ return information about? (Answer: @D@-the-type, but don't rely on it.) To ensure we get information about @D@-the-value, use 'lookupValueName': > do > Just nm <- lookupValueName "D" > reify nm and to get information about @D@-the-type, use 'lookupTypeName'. -} reify :: Name -> Q Info reify v = Q (qReify v) {- | @reifyFixity nm@ attempts to find a fixity declaration for @nm@. For example, if the function @foo@ has the fixity declaration @infixr 7 foo@, then @reifyFixity 'foo@ would return @'Just' ('Fixity' 7 'InfixR')@. If the function @bar@ does not have a fixity declaration, then @reifyFixity 'bar@ returns 'Nothing', so you may assume @bar@ has 'defaultFixity'. -} reifyFixity :: Name -> Q (Maybe Fixity) reifyFixity nm = Q (qReifyFixity nm) {- | @reifyInstances nm tys@ returns a list of visible instances of @nm tys@. That is, if @nm@ is the name of a type class, then all instances of this class at the types @tys@ are returned. Alternatively, if @nm@ is the name of a data family or type family, all instances of this family at the types @tys@ are returned. -} reifyInstances :: Name -> [Type] -> Q [InstanceDec] reifyInstances cls tys = Q (qReifyInstances cls tys) {- | @reifyRoles nm@ returns the list of roles associated with the parameters of the tycon @nm@. Fails if @nm@ cannot be found or is not a tycon. The returned list should never contain 'InferR'. -} reifyRoles :: Name -> Q [Role] reifyRoles nm = Q (qReifyRoles nm) -- | @reifyAnnotations target@ returns the list of annotations -- associated with @target@. Only the annotations that are -- appropriately typed is returned. So if you have @Int@ and @String@ -- annotations for the same target, you have to call this function twice. reifyAnnotations :: Data a => AnnLookup -> Q [a] reifyAnnotations an = Q (qReifyAnnotations an) -- | @reifyModule mod@ looks up information about module @mod@. To -- look up the current module, call this function with the return -- value of @thisModule@. reifyModule :: Module -> Q ModuleInfo reifyModule m = Q (qReifyModule m) -- | @reifyConStrictness nm@ looks up the strictness information for the fields -- of the constructor with the name @nm@. Note that the strictness information -- that 'reifyConStrictness' returns may not correspond to what is written in -- the source code. For example, in the following data declaration: -- -- @ -- data Pair a = Pair a a -- @ -- -- 'reifyConStrictness' would return @['DecidedLazy', DecidedLazy]@ under most -- circumstances, but it would return @['DecidedStrict', DecidedStrict]@ if the -- @-XStrictData@ language extension was enabled. reifyConStrictness :: Name -> Q [DecidedStrictness] reifyConStrictness n = Q (qReifyConStrictness n) -- | Is the list of instances returned by 'reifyInstances' nonempty? isInstance :: Name -> [Type] -> Q Bool isInstance nm tys = do { decs <- reifyInstances nm tys ; return (not (null decs)) } -- | The location at which this computation is spliced. location :: Q Loc location = Q qLocation -- |The 'runIO' function lets you run an I\/O computation in the 'Q' monad. -- Take care: you are guaranteed the ordering of calls to 'runIO' within -- a single 'Q' computation, but not about the order in which splices are run. -- -- Note: for various murky reasons, stdout and stderr handles are not -- necessarily flushed when the compiler finishes running, so you should -- flush them yourself. runIO :: IO a -> Q a runIO m = Q (qRunIO m) -- | Record external files that runIO is using (dependent upon). -- The compiler can then recognize that it should re-compile the Haskell file -- when an external file changes. -- -- Expects an absolute file path. -- -- Notes: -- -- * ghc -M does not know about these dependencies - it does not execute TH. -- -- * The dependency is based on file content, not a modification time addDependentFile :: FilePath -> Q () addDependentFile fp = Q (qAddDependentFile fp) -- | Add additional top-level declarations. The added declarations will be type -- checked along with the current declaration group. addTopDecls :: [Dec] -> Q () addTopDecls ds = Q (qAddTopDecls ds) -- | Emit a foreign file which will be compiled and linked to the object for -- the current module. Currently only languages that can be compiled with -- the C compiler are supported, and the flags passed as part of -optc will -- be also applied to the C compiler invocation that will compile them. -- -- Note that for non-C languages (for example C++) @extern "C"@ directives -- must be used to get symbols that we can access from Haskell. -- -- To get better errors, it is reccomended to use #line pragmas when -- emitting C files, e.g. -- -- > {-# LANGUAGE CPP #-} -- > ... -- > addForeignFile LangC $ unlines -- > [ "#line " ++ show (__LINE__ + 1) ++ " " ++ show __FILE__ -- > , ... -- > ] addForeignFile :: ForeignSrcLang -> String -> Q () addForeignFile lang str = Q (qAddForeignFile lang str) -- | Add a finalizer that will run in the Q monad after the current module has -- been type checked. This only makes sense when run within a top-level splice. -- -- The finalizer is given the local type environment at the splice point. Thus -- 'reify' is able to find the local definitions when executed inside the -- finalizer. addModFinalizer :: Q () -> Q () addModFinalizer act = Q (qAddModFinalizer (unQ act)) -- | Get state from the 'Q' monad. Note that the state is local to the -- Haskell module in which the Template Haskell expression is executed. getQ :: Typeable a => Q (Maybe a) getQ = Q qGetQ -- | Replace the state in the 'Q' monad. Note that the state is local to the -- Haskell module in which the Template Haskell expression is executed. putQ :: Typeable a => a -> Q () putQ x = Q (qPutQ x) -- | Determine whether the given language extension is enabled in the 'Q' monad. isExtEnabled :: Extension -> Q Bool isExtEnabled ext = Q (qIsExtEnabled ext) -- | List all enabled language extensions. extsEnabled :: Q [Extension] extsEnabled = Q qExtsEnabled instance Quasi Q where qNewName = newName qReport = report qRecover = recover qReify = reify qReifyFixity = reifyFixity qReifyInstances = reifyInstances qReifyRoles = reifyRoles qReifyAnnotations = reifyAnnotations qReifyModule = reifyModule qReifyConStrictness = reifyConStrictness qLookupName = lookupName qLocation = location qRunIO = runIO qAddDependentFile = addDependentFile qAddTopDecls = addTopDecls qAddForeignFile = addForeignFile qAddModFinalizer = addModFinalizer qGetQ = getQ qPutQ = putQ qIsExtEnabled = isExtEnabled qExtsEnabled = extsEnabled ---------------------------------------------------- -- The following operations are used solely in DsMeta when desugaring brackets -- They are not necessary for the user, who can use ordinary return and (>>=) etc returnQ :: a -> Q a returnQ = return bindQ :: Q a -> (a -> Q b) -> Q b bindQ = (>>=) sequenceQ :: [Q a] -> Q [a] sequenceQ = sequence ----------------------------------------------------- -- -- The Lift class -- ----------------------------------------------------- -- | A 'Lift' instance can have any of its values turned into a Template -- Haskell expression. This is needed when a value used within a Template -- Haskell quotation is bound outside the Oxford brackets (@[| ... |]@) but not -- at the top level. As an example: -- -- > add1 :: Int -> Q Exp -- > add1 x = [| x + 1 |] -- -- Template Haskell has no way of knowing what value @x@ will take on at -- splice-time, so it requires the type of @x@ to be an instance of 'Lift'. -- -- 'Lift' instances can be derived automatically by use of the @-XDeriveLift@ -- GHC language extension: -- -- > {-# LANGUAGE DeriveLift #-} -- > module Foo where -- > -- > import Language.Haskell.TH.Syntax -- > -- > data Bar a = Bar1 a (Bar a) | Bar2 String -- > deriving Lift class Lift t where -- | Turn a value into a Template Haskell expression, suitable for use in -- a splice. lift :: t -> Q Exp default lift :: Data t => t -> Q Exp lift = liftData -- If you add any instances here, consider updating test th/TH_Lift instance Lift Integer where lift x = return (LitE (IntegerL x)) instance Lift Int where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Int8 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Int16 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Int32 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Int64 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Word where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Word8 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Word16 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Word32 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Word64 where lift x = return (LitE (IntegerL (fromIntegral x))) instance Lift Natural where lift x = return (LitE (IntegerL (fromIntegral x))) instance Integral a => Lift (Ratio a) where lift x = return (LitE (RationalL (toRational x))) instance Lift Float where lift x = return (LitE (RationalL (toRational x))) instance Lift Double where lift x = return (LitE (RationalL (toRational x))) instance Lift Char where lift x = return (LitE (CharL x)) instance Lift Bool where lift True = return (ConE trueName) lift False = return (ConE falseName) instance Lift a => Lift (Maybe a) where lift Nothing = return (ConE nothingName) lift (Just x) = liftM (ConE justName `AppE`) (lift x) instance (Lift a, Lift b) => Lift (Either a b) where lift (Left x) = liftM (ConE leftName `AppE`) (lift x) lift (Right y) = liftM (ConE rightName `AppE`) (lift y) instance Lift a => Lift [a] where lift xs = do { xs' <- mapM lift xs; return (ListE xs') } liftString :: String -> Q Exp -- Used in TcExpr to short-circuit the lifting for strings liftString s = return (LitE (StringL s)) instance Lift () where lift () = return (ConE (tupleDataName 0)) instance (Lift a, Lift b) => Lift (a, b) where lift (a, b) = liftM TupE $ sequence [lift a, lift b] instance (Lift a, Lift b, Lift c) => Lift (a, b, c) where lift (a, b, c) = liftM TupE $ sequence [lift a, lift b, lift c] instance (Lift a, Lift b, Lift c, Lift d) => Lift (a, b, c, d) where lift (a, b, c, d) = liftM TupE $ sequence [lift a, lift b, lift c, lift d] instance (Lift a, Lift b, Lift c, Lift d, Lift e) => Lift (a, b, c, d, e) where lift (a, b, c, d, e) = liftM TupE $ sequence [lift a, lift b, lift c, lift d, lift e] instance (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f) => Lift (a, b, c, d, e, f) where lift (a, b, c, d, e, f) = liftM TupE $ sequence [lift a, lift b, lift c, lift d, lift e, lift f] instance (Lift a, Lift b, Lift c, Lift d, Lift e, Lift f, Lift g) => Lift (a, b, c, d, e, f, g) where lift (a, b, c, d, e, f, g) = liftM TupE $ sequence [lift a, lift b, lift c, lift d, lift e, lift f, lift g] -- TH has a special form for literal strings, -- which we should take advantage of. -- NB: the lhs of the rule has no args, so that -- the rule will apply to a 'lift' all on its own -- which happens to be the way the type checker -- creates it. {-# RULES "TH:liftString" lift = \s -> return (LitE (StringL s)) #-} trueName, falseName :: Name trueName = mkNameG DataName "ghc-prim" "GHC.Types" "True" falseName = mkNameG DataName "ghc-prim" "GHC.Types" "False" nothingName, justName :: Name nothingName = mkNameG DataName "base" "GHC.Base" "Nothing" justName = mkNameG DataName "base" "GHC.Base" "Just" leftName, rightName :: Name leftName = mkNameG DataName "base" "Data.Either" "Left" rightName = mkNameG DataName "base" "Data.Either" "Right" ----------------------------------------------------- -- -- Generic Lift implementations -- ----------------------------------------------------- -- | 'dataToQa' is an internal utility function for constructing generic -- conversion functions from types with 'Data' instances to various -- quasi-quoting representations. See the source of 'dataToExpQ' and -- 'dataToPatQ' for two example usages: @mkCon@, @mkLit@ -- and @appQ@ are overloadable to account for different syntax for -- expressions and patterns; @antiQ@ allows you to override type-specific -- cases, a common usage is just @const Nothing@, which results in -- no overloading. dataToQa :: forall a k q. Data a => (Name -> k) -> (Lit -> Q q) -> (k -> [Q q] -> Q q) -> (forall b . Data b => b -> Maybe (Q q)) -> a -> Q q dataToQa mkCon mkLit appCon antiQ t = case antiQ t of Nothing -> case constrRep constr of AlgConstr _ -> appCon (mkCon funOrConName) conArgs where funOrConName :: Name funOrConName = case showConstr constr of "(:)" -> Name (mkOccName ":") (NameG DataName (mkPkgName "ghc-prim") (mkModName "GHC.Types")) con@"[]" -> Name (mkOccName con) (NameG DataName (mkPkgName "ghc-prim") (mkModName "GHC.Types")) con@('(':_) -> Name (mkOccName con) (NameG DataName (mkPkgName "ghc-prim") (mkModName "GHC.Tuple")) -- Tricky case: see Note [Data for non-algebraic types] fun@(x:_) | startsVarSym x || startsVarId x -> mkNameG_v tyconPkg tyconMod fun con -> mkNameG_d tyconPkg tyconMod con where tycon :: TyCon tycon = (typeRepTyCon . typeOf) t tyconPkg, tyconMod :: String tyconPkg = tyConPackage tycon tyconMod = tyConModule tycon conArgs :: [Q q] conArgs = gmapQ (dataToQa mkCon mkLit appCon antiQ) t IntConstr n -> mkLit $ IntegerL n FloatConstr n -> mkLit $ RationalL n CharConstr c -> mkLit $ CharL c where constr :: Constr constr = toConstr t Just y -> y {- Note [Data for non-algebraic types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Class Data was originally intended for algebraic data types. But it is possible to use it for abstract types too. For example, in package `text` we find instance Data Text where ... toConstr _ = packConstr packConstr :: Constr packConstr = mkConstr textDataType "pack" [] Prefix Here `packConstr` isn't a real data constructor, it's an ordinary function. Two complications * In such a case, we must take care to build the Name using mkNameG_v (for values), not mkNameG_d (for data constructors). See Trac #10796. * The pseudo-constructor is named only by its string, here "pack". But 'dataToQa' needs the TyCon of its defining module, and has to assume it's defined in the same module as the TyCon itself. But nothing enforces that; Trac #12596 shows what goes wrong if "pack" is defined in a different module than the data type "Text". -} -- | 'dataToExpQ' converts a value to a 'Q Exp' representation of the -- same value, in the SYB style. It is generalized to take a function -- override type-specific cases; see 'liftData' for a more commonly -- used variant. dataToExpQ :: Data a => (forall b . Data b => b -> Maybe (Q Exp)) -> a -> Q Exp dataToExpQ = dataToQa varOrConE litE (foldl appE) where -- Make sure that VarE is used if the Constr value relies on a -- function underneath the surface (instead of a constructor). -- See Trac #10796. varOrConE s = case nameSpace s of Just VarName -> return (VarE s) Just DataName -> return (ConE s) _ -> fail $ "Can't construct an expression from name " ++ showName s appE x y = do { a <- x; b <- y; return (AppE a b)} litE c = return (LitE c) -- | 'liftData' is a variant of 'lift' in the 'Lift' type class which -- works for any type with a 'Data' instance. liftData :: Data a => a -> Q Exp liftData = dataToExpQ (const Nothing) -- | 'dataToPatQ' converts a value to a 'Q Pat' representation of the same -- value, in the SYB style. It takes a function to handle type-specific cases, -- alternatively, pass @const Nothing@ to get default behavior. dataToPatQ :: Data a => (forall b . Data b => b -> Maybe (Q Pat)) -> a -> Q Pat dataToPatQ = dataToQa id litP conP where litP l = return (LitP l) conP n ps = case nameSpace n of Just DataName -> do ps' <- sequence ps return (ConP n ps') _ -> fail $ "Can't construct a pattern from name " ++ showName n ----------------------------------------------------- -- Names and uniques ----------------------------------------------------- newtype ModName = ModName String -- Module name deriving (Show,Eq,Ord,Data,Generic) newtype PkgName = PkgName String -- package name deriving (Show,Eq,Ord,Data,Generic) -- | Obtained from 'reifyModule' and 'thisModule'. data Module = Module PkgName ModName -- package qualified module name deriving (Show,Eq,Ord,Data,Generic) newtype OccName = OccName String deriving (Show,Eq,Ord,Data,Generic) mkModName :: String -> ModName mkModName s = ModName s modString :: ModName -> String modString (ModName m) = m mkPkgName :: String -> PkgName mkPkgName s = PkgName s pkgString :: PkgName -> String pkgString (PkgName m) = m ----------------------------------------------------- -- OccName ----------------------------------------------------- mkOccName :: String -> OccName mkOccName s = OccName s occString :: OccName -> String occString (OccName occ) = occ ----------------------------------------------------- -- Names ----------------------------------------------------- -- -- For "global" names ('NameG') we need a totally unique name, -- so we must include the name-space of the thing -- -- For unique-numbered things ('NameU'), we've got a unique reference -- anyway, so no need for name space -- -- For dynamically bound thing ('NameS') we probably want them to -- in a context-dependent way, so again we don't want the name -- space. For example: -- -- > let v = mkName "T" in [| data $v = $v |] -- -- Here we use the same Name for both type constructor and data constructor -- -- -- NameL and NameG are bound *outside* the TH syntax tree -- either globally (NameG) or locally (NameL). Ex: -- -- > f x = $(h [| (map, x) |]) -- -- The 'map' will be a NameG, and 'x' wil be a NameL -- -- These Names should never appear in a binding position in a TH syntax tree {- $namecapture #namecapture# Much of 'Name' API is concerned with the problem of /name capture/, which can be seen in the following example. > f expr = [| let x = 0 in $expr |] > ... > g x = $( f [| x |] ) > h y = $( f [| y |] ) A naive desugaring of this would yield: > g x = let x = 0 in x > h y = let x = 0 in y All of a sudden, @g@ and @h@ have different meanings! In this case, we say that the @x@ in the RHS of @g@ has been /captured/ by the binding of @x@ in @f@. What we actually want is for the @x@ in @f@ to be distinct from the @x@ in @g@, so we get the following desugaring: > g x = let x' = 0 in x > h y = let x' = 0 in y which avoids name capture as desired. In the general case, we say that a @Name@ can be captured if the thing it refers to can be changed by adding new declarations. -} {- | An abstract type representing names in the syntax tree. 'Name's can be constructed in several ways, which come with different name-capture guarantees (see "Language.Haskell.TH.Syntax#namecapture" for an explanation of name capture): * the built-in syntax @'f@ and @''T@ can be used to construct names, The expression @'f@ gives a @Name@ which refers to the value @f@ currently in scope, and @''T@ gives a @Name@ which refers to the type @T@ currently in scope. These names can never be captured. * 'lookupValueName' and 'lookupTypeName' are similar to @'f@ and @''T@ respectively, but the @Name@s are looked up at the point where the current splice is being run. These names can never be captured. * 'newName' monadically generates a new name, which can never be captured. * 'mkName' generates a capturable name. Names constructed using @newName@ and @mkName@ may be used in bindings (such as @let x = ...@ or @\x -> ...@), but names constructed using @lookupValueName@, @lookupTypeName@, @'f@, @''T@ may not. -} data Name = Name OccName NameFlavour deriving (Data, Eq, Generic) instance Ord Name where -- check if unique is different before looking at strings (Name o1 f1) `compare` (Name o2 f2) = (f1 `compare` f2) `thenCmp` (o1 `compare` o2) data NameFlavour = NameS -- ^ An unqualified name; dynamically bound | NameQ ModName -- ^ A qualified name; dynamically bound | NameU !Int -- ^ A unique local name | NameL !Int -- ^ Local name bound outside of the TH AST | NameG NameSpace PkgName ModName -- ^ Global name bound outside of the TH AST: -- An original name (occurrences only, not binders) -- Need the namespace too to be sure which -- thing we are naming deriving ( Data, Eq, Ord, Show, Generic ) data NameSpace = VarName -- ^ Variables | DataName -- ^ Data constructors | TcClsName -- ^ Type constructors and classes; Haskell has them -- in the same name space for now. deriving( Eq, Ord, Show, Data, Generic ) type Uniq = Int -- | The name without its module prefix. -- -- ==== __Examples__ -- -- >>> nameBase ''Data.Either.Either -- "Either" -- >>> nameBase (mkName "foo") -- "foo" -- >>> nameBase (mkName "Module.foo") -- "foo" nameBase :: Name -> String nameBase (Name occ _) = occString occ -- | Module prefix of a name, if it exists. -- -- ==== __Examples__ -- -- >>> nameModule ''Data.Either.Either -- Just "Data.Either" -- >>> nameModule (mkName "foo") -- Nothing -- >>> nameModule (mkName "Module.foo") -- Just "Module" nameModule :: Name -> Maybe String nameModule (Name _ (NameQ m)) = Just (modString m) nameModule (Name _ (NameG _ _ m)) = Just (modString m) nameModule _ = Nothing -- | A name's package, if it exists. -- -- ==== __Examples__ -- -- >>> namePackage ''Data.Either.Either -- Just "base" -- >>> namePackage (mkName "foo") -- Nothing -- >>> namePackage (mkName "Module.foo") -- Nothing namePackage :: Name -> Maybe String namePackage (Name _ (NameG _ p _)) = Just (pkgString p) namePackage _ = Nothing -- | Returns whether a name represents an occurrence of a top-level variable -- ('VarName'), data constructor ('DataName'), type constructor, or type class -- ('TcClsName'). If we can't be sure, it returns 'Nothing'. -- -- ==== __Examples__ -- -- >>> nameSpace 'Prelude.id -- Just VarName -- >>> nameSpace (mkName "id") -- Nothing -- only works for top-level variable names -- >>> nameSpace 'Data.Maybe.Just -- Just DataName -- >>> nameSpace ''Data.Maybe.Maybe -- Just TcClsName -- >>> nameSpace ''Data.Ord.Ord -- Just TcClsName nameSpace :: Name -> Maybe NameSpace nameSpace (Name _ (NameG ns _ _)) = Just ns nameSpace _ = Nothing {- | Generate a capturable name. Occurrences of such names will be resolved according to the Haskell scoping rules at the occurrence site. For example: > f = [| pi + $(varE (mkName "pi")) |] > ... > g = let pi = 3 in $f In this case, @g@ is desugared to > g = Prelude.pi + 3 Note that @mkName@ may be used with qualified names: > mkName "Prelude.pi" See also 'Language.Haskell.TH.Lib.dyn' for a useful combinator. The above example could be rewritten using 'dyn' as > f = [| pi + $(dyn "pi") |] -} mkName :: String -> Name -- The string can have a '.', thus "Foo.baz", -- giving a dynamically-bound qualified name, -- in which case we want to generate a NameQ -- -- Parse the string to see if it has a "." in it -- so we know whether to generate a qualified or unqualified name -- It's a bit tricky because we need to parse -- -- > Foo.Baz.x as Qual Foo.Baz x -- -- So we parse it from back to front mkName str = split [] (reverse str) where split occ [] = Name (mkOccName occ) NameS split occ ('.':rev) | not (null occ) , is_rev_mod_name rev = Name (mkOccName occ) (NameQ (mkModName (reverse rev))) -- The 'not (null occ)' guard ensures that -- mkName "&." = Name "&." NameS -- The 'is_rev_mod' guards ensure that -- mkName ".&" = Name ".&" NameS -- mkName "^.." = Name "^.." NameS -- Trac #8633 -- mkName "Data.Bits..&" = Name ".&" (NameQ "Data.Bits") -- This rather bizarre case actually happened; (.&.) is in Data.Bits split occ (c:rev) = split (c:occ) rev -- Recognises a reversed module name xA.yB.C, -- with at least one component, -- and each component looks like a module name -- (i.e. non-empty, starts with capital, all alpha) is_rev_mod_name rev_mod_str | (compt, rest) <- break (== '.') rev_mod_str , not (null compt), isUpper (last compt), all is_mod_char compt = case rest of [] -> True (_dot : rest') -> is_rev_mod_name rest' | otherwise = False is_mod_char c = isAlphaNum c || c == '_' || c == '\'' -- | Only used internally mkNameU :: String -> Uniq -> Name mkNameU s u = Name (mkOccName s) (NameU u) -- | Only used internally mkNameL :: String -> Uniq -> Name mkNameL s u = Name (mkOccName s) (NameL u) -- | Used for 'x etc, but not available to the programmer mkNameG :: NameSpace -> String -> String -> String -> Name mkNameG ns pkg modu occ = Name (mkOccName occ) (NameG ns (mkPkgName pkg) (mkModName modu)) mkNameS :: String -> Name mkNameS n = Name (mkOccName n) NameS mkNameG_v, mkNameG_tc, mkNameG_d :: String -> String -> String -> Name mkNameG_v = mkNameG VarName mkNameG_tc = mkNameG TcClsName mkNameG_d = mkNameG DataName data NameIs = Alone | Applied | Infix showName :: Name -> String showName = showName' Alone showName' :: NameIs -> Name -> String showName' ni nm = case ni of Alone -> nms Applied | pnam -> nms | otherwise -> "(" ++ nms ++ ")" Infix | pnam -> "`" ++ nms ++ "`" | otherwise -> nms where -- For now, we make the NameQ and NameG print the same, even though -- NameQ is a qualified name (so what it means depends on what the -- current scope is), and NameG is an original name (so its meaning -- should be independent of what's in scope. -- We may well want to distinguish them in the end. -- Ditto NameU and NameL nms = case nm of Name occ NameS -> occString occ Name occ (NameQ m) -> modString m ++ "." ++ occString occ Name occ (NameG _ _ m) -> modString m ++ "." ++ occString occ Name occ (NameU u) -> occString occ ++ "_" ++ show u Name occ (NameL u) -> occString occ ++ "_" ++ show u pnam = classify nms -- True if we are function style, e.g. f, [], (,) -- False if we are operator style, e.g. +, :+ classify "" = False -- shouldn't happen; . operator is handled below classify (x:xs) | isAlpha x || (x `elem` "_[]()") = case dropWhile (/='.') xs of (_:xs') -> classify xs' [] -> True | otherwise = False instance Show Name where show = showName -- Tuple data and type constructors -- | Tuple data constructor tupleDataName :: Int -> Name -- | Tuple type constructor tupleTypeName :: Int -> Name tupleDataName 0 = mk_tup_name 0 DataName tupleDataName 1 = error "tupleDataName 1" tupleDataName n = mk_tup_name (n-1) DataName tupleTypeName 0 = mk_tup_name 0 TcClsName tupleTypeName 1 = error "tupleTypeName 1" tupleTypeName n = mk_tup_name (n-1) TcClsName mk_tup_name :: Int -> NameSpace -> Name mk_tup_name n_commas space = Name occ (NameG space (mkPkgName "ghc-prim") tup_mod) where occ = mkOccName ('(' : replicate n_commas ',' ++ ")") tup_mod = mkModName "GHC.Tuple" -- Unboxed tuple data and type constructors -- | Unboxed tuple data constructor unboxedTupleDataName :: Int -> Name -- | Unboxed tuple type constructor unboxedTupleTypeName :: Int -> Name unboxedTupleDataName n = mk_unboxed_tup_name n DataName unboxedTupleTypeName n = mk_unboxed_tup_name n TcClsName mk_unboxed_tup_name :: Int -> NameSpace -> Name mk_unboxed_tup_name n space = Name (mkOccName tup_occ) (NameG space (mkPkgName "ghc-prim") tup_mod) where tup_occ | n == 1 = "Unit#" -- See Note [One-tuples] in TysWiredIn | otherwise = "(#" ++ replicate n_commas ',' ++ "#)" n_commas = n - 1 tup_mod = mkModName "GHC.Tuple" -- Unboxed sum data and type constructors -- | Unboxed sum data constructor unboxedSumDataName :: SumAlt -> SumArity -> Name -- | Unboxed sum type constructor unboxedSumTypeName :: SumArity -> Name unboxedSumDataName alt arity | alt > arity = error $ prefix ++ "Index out of bounds." ++ debug_info | alt <= 0 = error $ prefix ++ "Alt must be > 0." ++ debug_info | arity < 2 = error $ prefix ++ "Arity must be >= 2." ++ debug_info | otherwise = Name (mkOccName sum_occ) (NameG DataName (mkPkgName "ghc-prim") (mkModName "GHC.Prim")) where prefix = "unboxedSumDataName: " debug_info = " (alt: " ++ show alt ++ ", arity: " ++ show arity ++ ")" -- Synced with the definition of mkSumDataConOcc in TysWiredIn sum_occ = '(' : '#' : bars nbars_before ++ '_' : bars nbars_after ++ "#)" bars i = replicate i '|' nbars_before = alt - 1 nbars_after = arity - alt unboxedSumTypeName arity | arity < 2 = error $ "unboxedSumTypeName: Arity must be >= 2." ++ " (arity: " ++ show arity ++ ")" | otherwise = Name (mkOccName sum_occ) (NameG TcClsName (mkPkgName "ghc-prim") (mkModName "GHC.Prim")) where -- Synced with the definition of mkSumTyConOcc in TysWiredIn sum_occ = '(' : '#' : replicate (arity - 1) '|' ++ "#)" ----------------------------------------------------- -- Locations ----------------------------------------------------- data Loc = Loc { loc_filename :: String , loc_package :: String , loc_module :: String , loc_start :: CharPos , loc_end :: CharPos } deriving( Show, Eq, Ord, Data, Generic ) type CharPos = (Int, Int) -- ^ Line and character position ----------------------------------------------------- -- -- The Info returned by reification -- ----------------------------------------------------- -- | Obtained from 'reify' in the 'Q' Monad. data Info = -- | A class, with a list of its visible instances ClassI Dec [InstanceDec] -- | A class method | ClassOpI Name Type ParentName -- | A \"plain\" type constructor. \"Fancier\" type constructors are returned using 'PrimTyConI' or 'FamilyI' as appropriate | TyConI Dec -- | A type or data family, with a list of its visible instances. A closed -- type family is returned with 0 instances. | FamilyI Dec [InstanceDec] -- | A \"primitive\" type constructor, which can't be expressed with a 'Dec'. Examples: @(->)@, @Int#@. | PrimTyConI Name Arity Unlifted -- | A data constructor | DataConI Name Type ParentName -- | A pattern synonym. | PatSynI Name PatSynType {- | A \"value\" variable (as opposed to a type variable, see 'TyVarI'). The @Maybe Dec@ field contains @Just@ the declaration which defined the variable -- including the RHS of the declaration -- or else @Nothing@, in the case where the RHS is unavailable to the compiler. At present, this value is _always_ @Nothing@: returning the RHS has not yet been implemented because of lack of interest. -} | VarI Name Type (Maybe Dec) {- | A type variable. The @Type@ field contains the type which underlies the variable. At present, this is always @'VarT' theName@, but future changes may permit refinement of this. -} | TyVarI -- Scoped type variable Name Type -- What it is bound to deriving( Show, Eq, Ord, Data, Generic ) -- | Obtained from 'reifyModule' in the 'Q' Monad. data ModuleInfo = -- | Contains the import list of the module. ModuleInfo [Module] deriving( Show, Eq, Ord, Data, Generic ) {- | In 'ClassOpI' and 'DataConI', name of the parent class or type -} type ParentName = Name -- | In 'UnboxedSumE' and 'UnboxedSumP', the number associated with a -- particular data constructor. 'SumAlt's are one-indexed and should never -- exceed the value of its corresponding 'SumArity'. For example: -- -- * @(\#_|\#)@ has 'SumAlt' 1 (out of a total 'SumArity' of 2) -- -- * @(\#|_\#)@ has 'SumAlt' 2 (out of a total 'SumArity' of 2) type SumAlt = Int -- | In 'UnboxedSumE', 'UnboxedSumT', and 'UnboxedSumP', the total number of -- 'SumAlt's. For example, @(\#|\#)@ has a 'SumArity' of 2. type SumArity = Int -- | In 'PrimTyConI', arity of the type constructor type Arity = Int -- | In 'PrimTyConI', is the type constructor unlifted? type Unlifted = Bool -- | 'InstanceDec' desribes a single instance of a class or type function. -- It is just a 'Dec', but guaranteed to be one of the following: -- -- * 'InstanceD' (with empty @['Dec']@) -- -- * 'DataInstD' or 'NewtypeInstD' (with empty derived @['Name']@) -- -- * 'TySynInstD' type InstanceDec = Dec data Fixity = Fixity Int FixityDirection deriving( Eq, Ord, Show, Data, Generic ) data FixityDirection = InfixL | InfixR | InfixN deriving( Eq, Ord, Show, Data, Generic ) -- | Highest allowed operator precedence for 'Fixity' constructor (answer: 9) maxPrecedence :: Int maxPrecedence = (9::Int) -- | Default fixity: @infixl 9@ defaultFixity :: Fixity defaultFixity = Fixity maxPrecedence InfixL {- Note [Unresolved infix] ~~~~~~~~~~~~~~~~~~~~~~~ -} {- $infix #infix# When implementing antiquotation for quasiquoters, one often wants to parse strings into expressions: > parse :: String -> Maybe Exp But how should we parse @a + b * c@? If we don't know the fixities of @+@ and @*@, we don't know whether to parse it as @a + (b * c)@ or @(a + b) * c@. In cases like this, use 'UInfixE', 'UInfixP', or 'UInfixT', which stand for \"unresolved infix expression/pattern/type\", respectively. When the compiler is given a splice containing a tree of @UInfixE@ applications such as > UInfixE > (UInfixE e1 op1 e2) > op2 > (UInfixE e3 op3 e4) it will look up and the fixities of the relevant operators and reassociate the tree as necessary. * trees will not be reassociated across 'ParensE', 'ParensP', or 'ParensT', which are of use for parsing expressions like > (a + b * c) + d * e * 'InfixE', 'InfixP', and 'InfixT' expressions are never reassociated. * The 'UInfixE' constructor doesn't support sections. Sections such as @(a *)@ have no ambiguity, so 'InfixE' suffices. For longer sections such as @(a + b * c -)@, use an 'InfixE' constructor for the outer-most section, and use 'UInfixE' constructors for all other operators: > InfixE > Just (UInfixE ...a + b * c...) > op > Nothing Sections such as @(a + b +)@ and @((a + b) +)@ should be rendered into 'Exp's differently: > (+ a + b) ---> InfixE Nothing + (Just $ UInfixE a + b) > -- will result in a fixity error if (+) is left-infix > (+ (a + b)) ---> InfixE Nothing + (Just $ ParensE $ UInfixE a + b) > -- no fixity errors * Quoted expressions such as > [| a * b + c |] :: Q Exp > [p| a : b : c |] :: Q Pat > [t| T + T |] :: Q Type will never contain 'UInfixE', 'UInfixP', 'UInfixT', 'InfixT', 'ParensE', 'ParensP', or 'ParensT' constructors. -} ----------------------------------------------------- -- -- The main syntax data types -- ----------------------------------------------------- data Lit = CharL Char | StringL String | IntegerL Integer -- ^ Used for overloaded and non-overloaded -- literals. We don't have a good way to -- represent non-overloaded literals at -- the moment. Maybe that doesn't matter? | RationalL Rational -- Ditto | IntPrimL Integer | WordPrimL Integer | FloatPrimL Rational | DoublePrimL Rational | StringPrimL [Word8] -- ^ A primitive C-style string, type Addr# | CharPrimL Char deriving( Show, Eq, Ord, Data, Generic ) -- We could add Int, Float, Double etc, as we do in HsLit, -- but that could complicate the -- supposedly-simple TH.Syntax literal type -- | Pattern in Haskell given in @{}@ data Pat = LitP Lit -- ^ @{ 5 or \'c\' }@ | VarP Name -- ^ @{ x }@ | TupP [Pat] -- ^ @{ (p1,p2) }@ | UnboxedTupP [Pat] -- ^ @{ (\# p1,p2 \#) }@ | UnboxedSumP Pat SumAlt SumArity -- ^ @{ (\#|p|\#) }@ | ConP Name [Pat] -- ^ @data T1 = C1 t1 t2; {C1 p1 p1} = e@ | InfixP Pat Name Pat -- ^ @foo ({x :+ y}) = e@ | UInfixP Pat Name Pat -- ^ @foo ({x :+ y}) = e@ -- -- See "Language.Haskell.TH.Syntax#infix" | ParensP Pat -- ^ @{(p)}@ -- -- See "Language.Haskell.TH.Syntax#infix" | TildeP Pat -- ^ @{ ~p }@ | BangP Pat -- ^ @{ !p }@ | AsP Name Pat -- ^ @{ x \@ p }@ | WildP -- ^ @{ _ }@ | RecP Name [FieldPat] -- ^ @f (Pt { pointx = x }) = g x@ | ListP [ Pat ] -- ^ @{ [1,2,3] }@ | SigP Pat Type -- ^ @{ p :: t }@ | ViewP Exp Pat -- ^ @{ e -> p }@ deriving( Show, Eq, Ord, Data, Generic ) type FieldPat = (Name,Pat) data Match = Match Pat Body [Dec] -- ^ @case e of { pat -> body where decs }@ deriving( Show, Eq, Ord, Data, Generic ) data Clause = Clause [Pat] Body [Dec] -- ^ @f { p1 p2 = body where decs }@ deriving( Show, Eq, Ord, Data, Generic ) data Exp = VarE Name -- ^ @{ x }@ | ConE Name -- ^ @data T1 = C1 t1 t2; p = {C1} e1 e2 @ | LitE Lit -- ^ @{ 5 or \'c\'}@ | AppE Exp Exp -- ^ @{ f x }@ | AppTypeE Exp Type -- ^ @{ f \@Int } | InfixE (Maybe Exp) Exp (Maybe Exp) -- ^ @{x + y} or {(x+)} or {(+ x)} or {(+)}@ -- It's a bit gruesome to use an Exp as the -- operator, but how else can we distinguish -- constructors from non-constructors? -- Maybe there should be a var-or-con type? -- Or maybe we should leave it to the String itself? | UInfixE Exp Exp Exp -- ^ @{x + y}@ -- -- See "Language.Haskell.TH.Syntax#infix" | ParensE Exp -- ^ @{ (e) }@ -- -- See "Language.Haskell.TH.Syntax#infix" | LamE [Pat] Exp -- ^ @{ \\ p1 p2 -> e }@ | LamCaseE [Match] -- ^ @{ \\case m1; m2 }@ | TupE [Exp] -- ^ @{ (e1,e2) } @ | UnboxedTupE [Exp] -- ^ @{ (\# e1,e2 \#) } @ | UnboxedSumE Exp SumAlt SumArity -- ^ @{ (\#|e|\#) }@ | CondE Exp Exp Exp -- ^ @{ if e1 then e2 else e3 }@ | MultiIfE [(Guard, Exp)] -- ^ @{ if | g1 -> e1 | g2 -> e2 }@ | LetE [Dec] Exp -- ^ @{ let x=e1; y=e2 in e3 }@ | CaseE Exp [Match] -- ^ @{ case e of m1; m2 }@ | DoE [Stmt] -- ^ @{ do { p <- e1; e2 } }@ | CompE [Stmt] -- ^ @{ [ (x,y) | x <- xs, y <- ys ] }@ -- -- The result expression of the comprehension is -- the /last/ of the @'Stmt'@s, and should be a 'NoBindS'. -- -- E.g. translation: -- -- > [ f x | x <- xs ] -- -- > CompE [BindS (VarP x) (VarE xs), NoBindS (AppE (VarE f) (VarE x))] | ArithSeqE Range -- ^ @{ [ 1 ,2 .. 10 ] }@ | ListE [ Exp ] -- ^ @{ [1,2,3] }@ | SigE Exp Type -- ^ @{ e :: t }@ | RecConE Name [FieldExp] -- ^ @{ T { x = y, z = w } }@ | RecUpdE Exp [FieldExp] -- ^ @{ (f x) { z = w } }@ | StaticE Exp -- ^ @{ static e }@ | UnboundVarE Name -- ^ @{ _x }@ (hole) deriving( Show, Eq, Ord, Data, Generic ) type FieldExp = (Name,Exp) -- Omitted: implicit parameters data Body = GuardedB [(Guard,Exp)] -- ^ @f p { | e1 = e2 -- | e3 = e4 } -- where ds@ | NormalB Exp -- ^ @f p { = e } where ds@ deriving( Show, Eq, Ord, Data, Generic ) data Guard = NormalG Exp -- ^ @f x { | odd x } = x@ | PatG [Stmt] -- ^ @f x { | Just y <- x, Just z <- y } = z@ deriving( Show, Eq, Ord, Data, Generic ) data Stmt = BindS Pat Exp | LetS [ Dec ] | NoBindS Exp | ParS [[Stmt]] deriving( Show, Eq, Ord, Data, Generic ) data Range = FromR Exp | FromThenR Exp Exp | FromToR Exp Exp | FromThenToR Exp Exp Exp deriving( Show, Eq, Ord, Data, Generic ) data Dec = FunD Name [Clause] -- ^ @{ f p1 p2 = b where decs }@ | ValD Pat Body [Dec] -- ^ @{ p = b where decs }@ | DataD Cxt Name [TyVarBndr] (Maybe Kind) -- Kind signature (allowed only for GADTs) [Con] [DerivClause] -- ^ @{ data Cxt x => T x = A x | B (T x) -- deriving (Z,W) -- deriving stock Eq }@ | NewtypeD Cxt Name [TyVarBndr] (Maybe Kind) -- Kind signature Con [DerivClause] -- ^ @{ newtype Cxt x => T x = A (B x) -- deriving (Z,W Q) -- deriving stock Eq }@ | TySynD Name [TyVarBndr] Type -- ^ @{ type T x = (x,x) }@ | ClassD Cxt Name [TyVarBndr] [FunDep] [Dec] -- ^ @{ class Eq a => Ord a where ds }@ | InstanceD (Maybe Overlap) Cxt Type [Dec] -- ^ @{ instance {\-\# OVERLAPS \#-\} -- Show w => Show [w] where ds }@ | SigD Name Type -- ^ @{ length :: [a] -> Int }@ | ForeignD Foreign -- ^ @{ foreign import ... } --{ foreign export ... }@ | InfixD Fixity Name -- ^ @{ infix 3 foo }@ -- | pragmas | PragmaD Pragma -- ^ @{ {\-\# INLINE [1] foo \#-\} }@ -- | data families (may also appear in [Dec] of 'ClassD' and 'InstanceD') | DataFamilyD Name [TyVarBndr] (Maybe Kind) -- ^ @{ data family T a b c :: * }@ | DataInstD Cxt Name [Type] (Maybe Kind) -- Kind signature [Con] [DerivClause] -- ^ @{ data instance Cxt x => T [x] -- = A x | B (T x) -- deriving (Z,W) -- deriving stock Eq }@ | NewtypeInstD Cxt Name [Type] (Maybe Kind) -- Kind signature Con [DerivClause] -- ^ @{ newtype instance Cxt x => T [x] -- = A (B x) -- deriving (Z,W) -- deriving stock Eq }@ | TySynInstD Name TySynEqn -- ^ @{ type instance ... }@ -- | open type families (may also appear in [Dec] of 'ClassD' and 'InstanceD') | OpenTypeFamilyD TypeFamilyHead -- ^ @{ type family T a b c = (r :: *) | r -> a b }@ | ClosedTypeFamilyD TypeFamilyHead [TySynEqn] -- ^ @{ type family F a b = (r :: *) | r -> a where ... }@ | RoleAnnotD Name [Role] -- ^ @{ type role T nominal representational }@ | StandaloneDerivD (Maybe DerivStrategy) Cxt Type -- ^ @{ deriving stock instance Ord a => Ord (Foo a) }@ | DefaultSigD Name Type -- ^ @{ default size :: Data a => a -> Int }@ -- | Pattern Synonyms | PatSynD Name PatSynArgs PatSynDir Pat -- ^ @{ pattern P v1 v2 .. vn <- p }@ unidirectional or -- @{ pattern P v1 v2 .. vn = p }@ implicit bidirectional or -- @{ pattern P v1 v2 .. vn <- p -- where P v1 v2 .. vn = e }@ explicit bidirectional -- -- also, besides prefix pattern synonyms, both infix and record -- pattern synonyms are supported. See 'PatSynArgs' for details | PatSynSigD Name PatSynType -- ^ A pattern synonym's type signature. deriving( Show, Eq, Ord, Data, Generic ) -- | Varieties of allowed instance overlap. data Overlap = Overlappable -- ^ May be overlapped by more specific instances | Overlapping -- ^ May overlap a more general instance | Overlaps -- ^ Both 'Overlapping' and 'Overlappable' | Incoherent -- ^ Both 'Overlappable' and 'Overlappable', and -- pick an arbitrary one if multiple choices are -- available. deriving( Show, Eq, Ord, Data, Generic ) -- | A single @deriving@ clause at the end of a datatype. data DerivClause = DerivClause (Maybe DerivStrategy) Cxt -- ^ @{ deriving stock (Eq, Ord) }@ deriving( Show, Eq, Ord, Data, Generic ) -- | What the user explicitly requests when deriving an instance. data DerivStrategy = StockStrategy -- ^ A \"standard\" derived instance | AnyclassStrategy -- ^ @-XDeriveAnyClass@ | NewtypeStrategy -- ^ @-XGeneralizedNewtypeDeriving@ deriving( Show, Eq, Ord, Data, Generic ) -- | A Pattern synonym's type. Note that a pattern synonym's *fully* -- specified type has a peculiar shape coming with two forall -- quantifiers and two constraint contexts. For example, consider the -- pattern synonym -- -- pattern P x1 x2 ... xn = <some-pattern> -- -- P's complete type is of the following form -- -- forall universals. required constraints -- => forall existentials. provided constraints -- => t1 -> t2 -> ... -> tn -> t -- -- consisting of four parts: -- -- 1) the (possibly empty lists of) universally quantified type -- variables and required constraints on them. -- 2) the (possibly empty lists of) existentially quantified -- type variables and the provided constraints on them. -- 3) the types t1, t2, .., tn of x1, x2, .., xn, respectively -- 4) the type t of <some-pattern>, mentioning only universals. -- -- Pattern synonym types interact with TH when (a) reifying a pattern -- synonym, (b) pretty printing, or (c) specifying a pattern synonym's -- type signature explicitly: -- -- (a) Reification always returns a pattern synonym's *fully* specified -- type in abstract syntax. -- -- (b) Pretty printing via 'pprPatSynType' abbreviates a pattern -- synonym's type unambiguously in concrete syntax: The rule of -- thumb is to print initial empty universals and the required -- context as `() =>`, if existentials and a provided context -- follow. If only universals and their required context, but no -- existentials are specified, only the universals and their -- required context are printed. If both or none are specified, so -- both (or none) are printed. -- -- (c) When specifying a pattern synonym's type explicitly with -- 'PatSynSigD' either one of the universals, the existentials, or -- their contexts may be left empty. -- -- See the GHC user's guide for more information on pattern synonyms -- and their types: https://downloads.haskell.org/~ghc/latest/docs/html/ -- users_guide/syntax-extns.html#pattern-synonyms. type PatSynType = Type -- | Common elements of 'OpenTypeFamilyD' and 'ClosedTypeFamilyD'. By -- analogy with "head" for type classes and type class instances as -- defined in /Type classes: an exploration of the design space/, the -- @TypeFamilyHead@ is defined to be the elements of the declaration -- between @type family@ and @where@. data TypeFamilyHead = TypeFamilyHead Name [TyVarBndr] FamilyResultSig (Maybe InjectivityAnn) deriving( Show, Eq, Ord, Data, Generic ) -- | One equation of a type family instance or closed type family. The -- arguments are the left-hand-side type patterns and the right-hand-side -- result. data TySynEqn = TySynEqn [Type] Type deriving( Show, Eq, Ord, Data, Generic ) data FunDep = FunDep [Name] [Name] deriving( Show, Eq, Ord, Data, Generic ) data FamFlavour = TypeFam | DataFam deriving( Show, Eq, Ord, Data, Generic ) data Foreign = ImportF Callconv Safety String Name Type | ExportF Callconv String Name Type deriving( Show, Eq, Ord, Data, Generic ) -- keep Callconv in sync with module ForeignCall in ghc/compiler/prelude/ForeignCall.hs data Callconv = CCall | StdCall | CApi | Prim | JavaScript deriving( Show, Eq, Ord, Data, Generic ) data Safety = Unsafe | Safe | Interruptible deriving( Show, Eq, Ord, Data, Generic ) data Pragma = InlineP Name Inline RuleMatch Phases | SpecialiseP Name Type (Maybe Inline) Phases | SpecialiseInstP Type | RuleP String [RuleBndr] Exp Exp Phases | AnnP AnnTarget Exp | LineP Int String | CompleteP [Name] (Maybe Name) -- ^ @{ {\-\# COMPLETE C_1, ..., C_i [ :: T ] \#-} }@ deriving( Show, Eq, Ord, Data, Generic ) data Inline = NoInline | Inline | Inlinable deriving (Show, Eq, Ord, Data, Generic) data RuleMatch = ConLike | FunLike deriving (Show, Eq, Ord, Data, Generic) data Phases = AllPhases | FromPhase Int | BeforePhase Int deriving (Show, Eq, Ord, Data, Generic) data RuleBndr = RuleVar Name | TypedRuleVar Name Type deriving (Show, Eq, Ord, Data, Generic) data AnnTarget = ModuleAnnotation | TypeAnnotation Name | ValueAnnotation Name deriving (Show, Eq, Ord, Data, Generic) type Cxt = [Pred] -- ^ @(Eq a, Ord b)@ -- | Since the advent of @ConstraintKinds@, constraints are really just types. -- Equality constraints use the 'EqualityT' constructor. Constraints may also -- be tuples of other constraints. type Pred = Type data SourceUnpackedness = NoSourceUnpackedness -- ^ @C a@ | SourceNoUnpack -- ^ @C { {\-\# NOUNPACK \#-\} } a@ | SourceUnpack -- ^ @C { {\-\# UNPACK \#-\} } a@ deriving (Show, Eq, Ord, Data, Generic) data SourceStrictness = NoSourceStrictness -- ^ @C a@ | SourceLazy -- ^ @C {~}a@ | SourceStrict -- ^ @C {!}a@ deriving (Show, Eq, Ord, Data, Generic) -- | Unlike 'SourceStrictness' and 'SourceUnpackedness', 'DecidedStrictness' -- refers to the strictness that the compiler chooses for a data constructor -- field, which may be different from what is written in source code. See -- 'reifyConStrictness' for more information. data DecidedStrictness = DecidedLazy | DecidedStrict | DecidedUnpack deriving (Show, Eq, Ord, Data, Generic) data Con = NormalC Name [BangType] -- ^ @C Int a@ | RecC Name [VarBangType] -- ^ @C { v :: Int, w :: a }@ | InfixC BangType Name BangType -- ^ @Int :+ a@ | ForallC [TyVarBndr] Cxt Con -- ^ @forall a. Eq a => C [a]@ | GadtC [Name] [BangType] Type -- See Note [GADT return type] -- ^ @C :: a -> b -> T b Int@ | RecGadtC [Name] [VarBangType] Type -- See Note [GADT return type] -- ^ @C :: { v :: Int } -> T b Int@ deriving (Show, Eq, Ord, Data, Generic) -- Note [GADT return type] -- ~~~~~~~~~~~~~~~~~~~~~~~ -- -- The return type of a GADT constructor does not necessarily match the name of -- the data type: -- -- type S = T -- -- data T a where -- MkT :: S Int -- -- -- type S a = T -- -- data T a where -- MkT :: S Char Int -- -- -- type Id a = a -- type S a = T -- -- data T a where -- MkT :: Id (S Char Int) -- -- -- That is why we allow the return type stored by a constructor to be an -- arbitrary type. See also #11341 data Bang = Bang SourceUnpackedness SourceStrictness -- ^ @C { {\-\# UNPACK \#-\} !}a@ deriving (Show, Eq, Ord, Data, Generic) type BangType = (Bang, Type) type VarBangType = (Name, Bang, Type) -- | As of @template-haskell-2.11.0.0@, 'Strict' has been replaced by 'Bang'. type Strict = Bang -- | As of @template-haskell-2.11.0.0@, 'StrictType' has been replaced by -- 'BangType'. type StrictType = BangType -- | As of @template-haskell-2.11.0.0@, 'VarStrictType' has been replaced by -- 'VarBangType'. type VarStrictType = VarBangType -- | A pattern synonym's directionality. data PatSynDir = Unidir -- ^ @pattern P x {<-} p@ | ImplBidir -- ^ @pattern P x {=} p@ | ExplBidir [Clause] -- ^ @pattern P x {<-} p where P x = e@ deriving( Show, Eq, Ord, Data, Generic ) -- | A pattern synonym's argument type. data PatSynArgs = PrefixPatSyn [Name] -- ^ @pattern P {x y z} = p@ | InfixPatSyn Name Name -- ^ @pattern {x P y} = p@ | RecordPatSyn [Name] -- ^ @pattern P { {x,y,z} } = p@ deriving( Show, Eq, Ord, Data, Generic ) data Type = ForallT [TyVarBndr] Cxt Type -- ^ @forall \<vars\>. \<ctxt\> -> \<type\>@ | AppT Type Type -- ^ @T a b@ | SigT Type Kind -- ^ @t :: k@ | VarT Name -- ^ @a@ | ConT Name -- ^ @T@ | PromotedT Name -- ^ @'T@ | InfixT Type Name Type -- ^ @T + T@ | UInfixT Type Name Type -- ^ @T + T@ -- -- See "Language.Haskell.TH.Syntax#infix" | ParensT Type -- ^ @(T)@ -- See Note [Representing concrete syntax in types] | TupleT Int -- ^ @(,), (,,), etc.@ | UnboxedTupleT Int -- ^ @(\#,\#), (\#,,\#), etc.@ | UnboxedSumT SumArity -- ^ @(\#|\#), (\#||\#), etc.@ | ArrowT -- ^ @->@ | EqualityT -- ^ @~@ | ListT -- ^ @[]@ | PromotedTupleT Int -- ^ @'(), '(,), '(,,), etc.@ | PromotedNilT -- ^ @'[]@ | PromotedConsT -- ^ @(':)@ | StarT -- ^ @*@ | ConstraintT -- ^ @Constraint@ | LitT TyLit -- ^ @0,1,2, etc.@ | WildCardT -- ^ @_, deriving( Show, Eq, Ord, Data, Generic ) data TyVarBndr = PlainTV Name -- ^ @a@ | KindedTV Name Kind -- ^ @(a :: k)@ deriving( Show, Eq, Ord, Data, Generic ) -- | Type family result signature data FamilyResultSig = NoSig -- ^ no signature | KindSig Kind -- ^ @k@ | TyVarSig TyVarBndr -- ^ @= r, = (r :: k)@ deriving( Show, Eq, Ord, Data, Generic ) -- | Injectivity annotation data InjectivityAnn = InjectivityAnn Name [Name] deriving ( Show, Eq, Ord, Data, Generic ) data TyLit = NumTyLit Integer -- ^ @2@ | StrTyLit String -- ^ @"Hello"@ deriving ( Show, Eq, Ord, Data, Generic ) -- | Role annotations data Role = NominalR -- ^ @nominal@ | RepresentationalR -- ^ @representational@ | PhantomR -- ^ @phantom@ | InferR -- ^ @_@ deriving( Show, Eq, Ord, Data, Generic ) -- | Annotation target for reifyAnnotations data AnnLookup = AnnLookupModule Module | AnnLookupName Name deriving( Show, Eq, Ord, Data, Generic ) -- | To avoid duplication between kinds and types, they -- are defined to be the same. Naturally, you would never -- have a type be 'StarT' and you would never have a kind -- be 'SigT', but many of the other constructors are shared. -- Note that the kind @Bool@ is denoted with 'ConT', not -- 'PromotedT'. Similarly, tuple kinds are made with 'TupleT', -- not 'PromotedTupleT'. type Kind = Type {- Note [Representing concrete syntax in types] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Haskell has a rich concrete syntax for types, including t1 -> t2, (t1,t2), [t], and so on In TH we represent all of this using AppT, with a distinguished type constructor at the head. So, Type TH representation ----------------------------------------------- t1 -> t2 ArrowT `AppT` t2 `AppT` t2 [t] ListT `AppT` t (t1,t2) TupleT 2 `AppT` t1 `AppT` t2 '(t1,t2) PromotedTupleT 2 `AppT` t1 `AppT` t2 But if the original HsSyn used prefix application, we won't use these special TH constructors. For example [] t ConT "[]" `AppT` t (->) t ConT "->" `AppT` t In this way we can faithfully represent in TH whether the original HsType used concrete syntax or not. The one case that doesn't fit this pattern is that of promoted lists '[ Maybe, IO ] PromotedListT 2 `AppT` t1 `AppT` t2 but it's very smelly because there really is no type constructor corresponding to PromotedListT. So we encode HsExplicitListTy with PromotedConsT and PromotedNilT (which *do* have underlying type constructors): '[ Maybe, IO ] PromotedConsT `AppT` Maybe `AppT` (PromotedConsT `AppT` IO `AppT` PromotedNilT) -} ----------------------------------------------------- -- Internal helper functions ----------------------------------------------------- cmpEq :: Ordering -> Bool cmpEq EQ = True cmpEq _ = False thenCmp :: Ordering -> Ordering -> Ordering thenCmp EQ o2 = o2 thenCmp o1 _ = o1