Syntax.hs 44.4 KB
Newer Older
1
{-# LANGUAGE UnboxedTuples #-}
2

3 4 5 6 7 8 9 10 11 12 13 14 15 16
-----------------------------------------------------------------------------
-- |
-- Module      :  Language.Haskell.Syntax
-- Copyright   :  (c) The University of Glasgow 2003
-- License     :  BSD-style (see the file libraries/base/LICENSE)
-- 
-- Maintainer  :  libraries@haskell.org
-- Stability   :  experimental
-- Portability :  portable
--
-- Abstract syntax definitions for Template Haskell.
--
-----------------------------------------------------------------------------

17
module Language.Haskell.TH.Syntax where
18 19 20

import GHC.Base		( Int(..), Int#, (<#), (==#) )

21
import Data.Data (Data(..), Typeable, mkConstr, mkDataType, constrIndex)
Ross Paterson's avatar
Ross Paterson committed
22
import qualified Data.Data as Data
23
import Control.Applicative( Applicative(..) )
24
import Data.IORef
25
import System.IO.Unsafe	( unsafePerformIO )
26
import Control.Monad (liftM)
27
import System.IO	( hPutStrLn, stderr )
28
import Data.Char        ( isAlpha )
reinerp's avatar
reinerp committed
29
import Data.Word        ( Word8 )
30 31 32 33 34 35 36

-----------------------------------------------------
--
--		The Quasi class
--
-----------------------------------------------------

37
class (Monad m, Applicative m) => Quasi m where
38
  qNewName :: String -> m Name
aavogt's avatar
aavogt committed
39
	-- ^ Fresh names
40 41

	-- Error reporting and recovery
aavogt's avatar
aavogt committed
42
  qReport  :: Bool -> String -> m ()	-- ^ Report an error (True) or warning (False)
43
					-- ...but carry on; use 'fail' to stop
aavogt's avatar
aavogt committed
44 45 46
  qRecover :: m a -- ^ the error handler
           -> m a -- ^ action which may fail
           -> m a		-- ^ Recover from the monadic 'fail'
47 48
 
	-- Inspect the type-checker's environment
49 50 51 52 53 54 55 56
  qLookupName :: Bool -> String -> m (Maybe Name)
       -- True <=> type namespace, False <=> value namespace
  qReify          :: Name -> m Info
  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
57
  qReifyRoles     :: Name -> m [Role]
58

59
  qLocation :: m Loc
60 61

  qRunIO :: IO a -> m a
aavogt's avatar
aavogt committed
62
  -- ^ Input/output (dangerous)
63

GregWeber's avatar
GregWeber committed
64
  qAddDependentFile :: FilePath -> m ()
65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84

-----------------------------------------------------
--	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 <- readIORef counter
                 ; writeIORef counter (n+1)
                 ; return (mkNameU s n) }

  qReport True  msg = hPutStrLn stderr ("Template Haskell error: " ++ msg)
  qReport False msg = hPutStrLn stderr ("Template Haskell error: " ++ msg)

85
  qLookupName _ _     = badIO "lookupName"
86
  qReify _            = badIO "reify"
87
  qReifyInstances _ _ = badIO "classInstances"
88
  qReifyRoles _       = badIO "reifyRoles"
89 90
  qLocation    	      = badIO "currentLocation"
  qRecover _ _ 	      = badIO "recover" -- Maybe we could fix this?
GregWeber's avatar
GregWeber committed
91
  qAddDependentFile _ = badIO "addDependentFile"
92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112

  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 }

113 114 115 116 117 118 119 120 121 122 123
-- \"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'.
124 125 126 127 128 129 130
runQ :: Quasi m => Q a -> m a
runQ (Q m) = m

instance Monad Q where
  return x   = Q (return x)
  Q m >>= k  = Q (m >>= \x -> unQ (k x))
  Q m >> Q n = Q (m >> n)
131
  fail s     = report True s >> Q (fail "Q monad failure")
132

133 134 135
instance Functor Q where
  fmap f (Q x) = Q (fmap f x)

136 137 138 139
instance Applicative Q where 
  pure x = Q (pure x) 
  Q f <*> Q x = Q (f <*> x) 

140 141
----------------------------------------------------
-- Packaged versions for the programmer, hiding the Quasi-ness
142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176

{- | 
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@.
-}
177 178 179
newName :: String -> Q Name
newName s = Q (qNewName s)

180 181
-- | Report an error (True) or warning (False), 
-- but carry on; use 'fail' to stop.
182 183
report  :: Bool -> String -> Q ()
report b s = Q (qReport b s)
184
{-# DEPRECATED report "Use reportError or reportWarning instead" #-} -- deprecated in 7.6
185 186 187 188 189 190 191 192

-- | 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
193

194 195 196
-- | Recover from errors raised by 'reportError' or 'fail'.
recover :: Q a -- ^ handler to invoke on failure
        -> Q a -- ^ computation to run
aavogt's avatar
aavogt committed
197
        -> Q a
198 199
recover (Q r) (Q m) = Q (qRecover r m)

200 201 202 203 204
-- 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)

205 206
-- | 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)
207
lookupTypeName  s = Q (qLookupName True s)
208 209 210

-- | 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)
211 212
lookupValueName s = Q (qLookupName False s)

213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281
{-
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'.
-}
282 283 284
reify :: Name -> Q Info
reify v = Q (qReify v)

285 286 287 288 289 290
{- | @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]
291
reifyInstances cls tys = Q (qReifyInstances cls tys)
292

293 294 295 296 297 298 299
{- | @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)

300
-- | Is the list of instances returned by 'reifyInstances' nonempty?
301 302 303
isInstance :: Name -> [Type] -> Q Bool
isInstance nm tys = do { decs <- reifyInstances nm tys
                       ; return (not (null decs)) }
304

305
-- | The location at which this computation is spliced.
306 307
location :: Q Loc
location = Q qLocation
308

dons's avatar
dons committed
309
-- |The 'runIO' function lets you run an I\/O computation in the 'Q' monad.
310 311 312 313 314 315
-- 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 
-- necesarily flushed when the  compiler finishes running, so you should
-- flush them yourself.
316 317 318
runIO :: IO a -> Q a
runIO m = Q (qRunIO m)

GregWeber's avatar
GregWeber committed
319 320 321 322 323 324 325
-- | Record external files that runIO is using (dependent upon).
-- The compiler can then recognize that it should re-compile the file using this TH when the external file changes.
-- Note that ghc -M will still not know about these dependencies - it does not execute TH.
-- Expects an absolute file path.
addDependentFile :: FilePath -> Q ()
addDependentFile fp = Q (qAddDependentFile fp)

326
instance Quasi Q where
GregWeber's avatar
GregWeber committed
327 328 329 330 331
  qNewName  	    = newName
  qReport   	    = report
  qRecover  	    = recover 
  qReify    	    = reify
  qReifyInstances   = reifyInstances
332
  qReifyRoles       = reifyRoles
GregWeber's avatar
GregWeber committed
333 334 335 336
  qLookupName       = lookupName
  qLocation 	    = location
  qRunIO    	    = runIO
  qAddDependentFile = addDependentFile
337 338 339 340


----------------------------------------------------
-- The following operations are used solely in DsMeta when desugaring brackets
341
-- They are not necessary for the user, who can use ordinary return and (>>=) etc
342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374

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
--
-----------------------------------------------------

class Lift t where
  lift :: t -> Q Exp
  
instance Lift Integer where
  lift x = return (LitE (IntegerL x))

instance Lift Int where
  lift x= return (LitE (IntegerL (fromIntegral 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)

375 376 377 378 379 380 381 382
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)

383 384 385
instance Lift a => Lift [a] where
  lift xs = do { xs' <- mapM lift xs; return (ListE xs') }

386 387 388 389
liftString :: String -> Q Exp
-- Used in TcExpr to short-circuit the lifting for strings
liftString s = return (LitE (StringL s))

390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416
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]

417 418 419 420 421 422 423 424 425 426
-- 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
Ian Lynagh's avatar
Ian Lynagh committed
427 428
trueName  = mkNameG DataName "ghc-prim" "GHC.Types" "True"
falseName = mkNameG DataName "ghc-prim" "GHC.Types" "False"
429

430 431 432 433 434 435 436 437
nothingName, justName :: Name
nothingName = mkNameG DataName "base" "Data.Maybe" "Nothing"
justName    = mkNameG DataName "base" "Data.Maybe" "Just"

leftName, rightName :: Name
leftName  = mkNameG DataName "base" "Data.Either" "Left"
rightName = mkNameG DataName "base" "Data.Either" "Right"

438 439 440 441 442

-----------------------------------------------------
--		Names and uniques 
-----------------------------------------------------

443 444 445 446 447 448 449 450 451
newtype ModName = ModName String	-- Module name
 deriving (Eq,Ord,Typeable,Data)

newtype PkgName = PkgName String	-- package name
 deriving (Eq,Ord,Typeable,Data)

newtype OccName = OccName String
 deriving (Eq,Ord,Typeable,Data)

452
mkModName :: String -> ModName
453
mkModName s = ModName s
454 455

modString :: ModName -> String
456
modString (ModName m) = m
457

458 459

mkPkgName :: String -> PkgName
460
mkPkgName s = PkgName s
461 462

pkgString :: PkgName -> String
463
pkgString (PkgName m) = m
464 465


466 467 468 469 470
-----------------------------------------------------
--		OccName
-----------------------------------------------------

mkOccName :: String -> OccName
471
mkOccName s = OccName s
472 473

occString :: OccName -> String
474
occString (OccName occ) = occ
475 476 477 478 479


-----------------------------------------------------
--		 Names
-----------------------------------------------------
480
-- 
aavogt's avatar
aavogt committed
481
-- For "global" names ('NameG') we need a totally unique name,
482 483
-- so we must include the name-space of the thing
--
aavogt's avatar
aavogt committed
484
-- For unique-numbered things ('NameU'), we've got a unique reference
485 486
-- anyway, so no need for name space
--
aavogt's avatar
aavogt committed
487
-- For dynamically bound thing ('NameS') we probably want them to
488 489
-- in a context-dependent way, so again we don't want the name
-- space.  For example:
aavogt's avatar
aavogt committed
490 491 492
--
-- > let v = mkName "T" in [| data $v = $v |]
--
493
-- Here we use the same Name for both type constructor and data constructor
aavogt's avatar
aavogt committed
494 495 496 497 498 499 500 501 502 503
--
--
-- 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
504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560

{- $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.
-}
561
data Name = Name OccName NameFlavour deriving (Typeable, Data)
562 563

data NameFlavour
aavogt's avatar
aavogt committed
564 565 566 567 568 569
  = 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)
570 571
		-- Need the namespace too to be sure which 
		-- thing we are naming
572 573
  deriving ( Typeable )

aavogt's avatar
aavogt committed
574
-- |
575 576 577 578 579 580 581
-- Although the NameFlavour type is abstract, the Data instance is not. The reason for this
-- is that currently we use Data to serialize values in annotations, and in order for that to
-- work for Template Haskell names introduced via the 'x syntax we need gunfold on NameFlavour
-- to work. Bleh!
--
-- The long term solution to this is to use the binary package for annotation serialization and
-- then remove this instance. However, to do _that_ we need to wait on binary to become stable, since
Gabor Greif's avatar
Gabor Greif committed
582
-- boot libraries cannot be upgraded separately from GHC itself.
583 584
--
-- This instance cannot be derived automatically due to bug #2701
585
instance Data NameFlavour where
586 587 588 589 590 591 592 593 594 595 596 597
     gfoldl _ z NameS          = z NameS
     gfoldl k z (NameQ mn)     = z NameQ `k` mn
     gfoldl k z (NameU i)      = z (\(I# i') -> NameU i') `k` (I# i)
     gfoldl k z (NameL i)      = z (\(I# i') -> NameL i') `k` (I# i)
     gfoldl k z (NameG ns p m) = z NameG `k` ns `k` p `k` m
     gunfold k z c = case constrIndex c of
         1 -> z NameS
         2 -> k $ z NameQ
         3 -> k $ z (\(I# i) -> NameU i)
         4 -> k $ z (\(I# i) -> NameL i)
         5 -> k $ k $ k $ z NameG
         _ -> error "gunfold: NameFlavour"
598 599 600 601 602 603 604
     toConstr NameS = con_NameS
     toConstr (NameQ _) = con_NameQ
     toConstr (NameU _) = con_NameU
     toConstr (NameL _) = con_NameL
     toConstr (NameG _ _ _) = con_NameG
     dataTypeOf _ = ty_NameFlavour

Ross Paterson's avatar
Ross Paterson committed
605 606 607 608 609 610
con_NameS, con_NameQ, con_NameU, con_NameL, con_NameG :: Data.Constr
con_NameS = mkConstr ty_NameFlavour "NameS" [] Data.Prefix
con_NameQ = mkConstr ty_NameFlavour "NameQ" [] Data.Prefix
con_NameU = mkConstr ty_NameFlavour "NameU" [] Data.Prefix
con_NameL = mkConstr ty_NameFlavour "NameL" [] Data.Prefix
con_NameG = mkConstr ty_NameFlavour "NameG" [] Data.Prefix
Ian Lynagh's avatar
Ian Lynagh committed
611

Ross Paterson's avatar
Ross Paterson committed
612
ty_NameFlavour :: Data.DataType
613 614 615
ty_NameFlavour = mkDataType "Language.Haskell.TH.Syntax.NameFlavour"
                            [con_NameS, con_NameQ, con_NameU,
                             con_NameL, con_NameG]
616

aavogt's avatar
aavogt committed
617 618 619
data NameSpace = VarName	-- ^ Variables
	       | DataName	-- ^ Data constructors 
	       | TcClsName	-- ^ Type constructors and classes; Haskell has them
620
				-- in the same name space for now.
621
	       deriving( Eq, Ord, Data, Typeable )
622 623 624

type Uniq = Int

625
-- | The name without its module prefix
626 627 628
nameBase :: Name -> String
nameBase (Name occ _) = occString occ

629
-- | Module prefix of a name, if it exists
630
nameModule :: Name -> Maybe String
Ian Lynagh's avatar
Ian Lynagh committed
631
nameModule (Name _ (NameQ m))     = Just (modString m)
632
nameModule (Name _ (NameG _ _ m)) = Just (modString m)
Ian Lynagh's avatar
Ian Lynagh committed
633
nameModule _                      = Nothing
634

635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658
{- | 
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") |]
-}
659
mkName :: String -> Name
660
-- The string can have a '.', thus "Foo.baz",
661 662 663 664 665 666
-- 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 
aavogt's avatar
aavogt committed
667 668 669
--
-- > Foo.Baz.x   as    Qual Foo.Baz x
--
670 671 672 673 674
-- So we parse it from back to front
mkName str
  = split [] (reverse str)
  where
    split occ []        = Name (mkOccName occ) NameS
675 676 677 678 679 680 681 682 683
    split occ ('.':rev)	| not (null occ), 
			  not (null rev), head rev /= '.'
			= Name (mkOccName occ) (NameQ (mkModName (reverse rev)))
	-- The 'not (null occ)' guard ensures that
	-- 	mkName "&." = Name "&." NameS
	-- The 'rev' guards ensure that
	--	mkName ".&" = Name ".&" NameS
	--	mkName "Data.Bits..&" = Name ".&" (NameQ "Data.Bits")
	-- This rather bizarre case actually happened; (.&.) is in Data.Bits
684
    split occ (c:rev)   = split (c:occ) rev
685

aavogt's avatar
aavogt committed
686 687
-- | Only used internally
mkNameU :: String -> Uniq -> Name
688 689
mkNameU s (I# u) = Name (mkOccName s) (NameU u)

aavogt's avatar
aavogt committed
690 691
-- | Only used internally
mkNameL :: String -> Uniq -> Name
692 693
mkNameL s (I# u) = Name (mkOccName s) (NameL u)

aavogt's avatar
aavogt committed
694 695 696
-- | Used for 'x etc, but not available to the programmer
mkNameG :: NameSpace -> String -> String -> String -> Name
mkNameG ns pkg modu occ
Ian Lynagh's avatar
Ian Lynagh committed
697
  = Name (mkOccName occ) (NameG ns (mkPkgName pkg) (mkModName modu))
698

699
mkNameG_v, mkNameG_tc, mkNameG_d :: String -> String -> String -> Name
700 701 702 703 704 705 706 707 708 709 710 711 712 713 714
mkNameG_v  = mkNameG VarName
mkNameG_tc = mkNameG TcClsName
mkNameG_d  = mkNameG DataName

instance Eq Name where
  v1 == v2 = cmpEq (v1 `compare` v2)

instance Ord Name where
  (Name o1 f1) `compare` (Name o2 f2) = (f1 `compare` f2)   `thenCmp`
				        (o1 `compare` o2)

instance Eq NameFlavour where
  f1 == f2 = cmpEq (f1 `compare` f2)

instance Ord NameFlavour where
715
	-- NameS < NameQ < NameU < NameL < NameG
716
  NameS `compare` NameS = EQ
Ian Lynagh's avatar
Ian Lynagh committed
717
  NameS `compare` _     = LT
718

719 720
  (NameQ _)  `compare` NameS      = GT
  (NameQ m1) `compare` (NameQ m2) = m1 `compare` m2
Ian Lynagh's avatar
Ian Lynagh committed
721
  (NameQ _)  `compare` _          = LT
722 723 724

  (NameU _)  `compare` NameS      = GT
  (NameU _)  `compare` (NameQ _)  = GT
725 726 727
  (NameU u1) `compare` (NameU u2) | u1  <# u2 = LT
				  | u1 ==# u2 = EQ
				  | otherwise = GT
Ian Lynagh's avatar
Ian Lynagh committed
728
  (NameU _)  `compare` _     = LT
729

730 731 732 733 734 735
  (NameL _)  `compare` NameS      = GT
  (NameL _)  `compare` (NameQ _)  = GT
  (NameL _)  `compare` (NameU _)  = GT
  (NameL u1) `compare` (NameL u2) | u1  <# u2 = LT
				  | u1 ==# u2 = EQ
				  | otherwise = GT
Ian Lynagh's avatar
Ian Lynagh committed
736
  (NameL _)  `compare` _          = LT
737

738 739 740
  (NameG ns1 p1 m1) `compare` (NameG ns2 p2 m2) = (ns1 `compare` ns2) `thenCmp`
                                            (p1 `compare` p2) `thenCmp`
					    (m1 `compare` m2) 
Ian Lynagh's avatar
Ian Lynagh committed
741
  (NameG _ _ _)    `compare` _ = GT
742

Ian Lynagh's avatar
Ian Lynagh committed
743 744 745 746 747 748 749 750 751 752 753 754 755 756 757
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
758
    where
759 760 761 762 763
	-- 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.
764 765
	-- Ditto NameU and NameL
        nms = case nm of
Ian Lynagh's avatar
Ian Lynagh committed
766 767 768 769 770
                    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 (I# u)
                    Name occ (NameL u)     -> occString occ ++ "_" ++ show (I# u)
771 772 773

        pnam = classify nms

Ian Lynagh's avatar
Ian Lynagh committed
774 775
        -- True if we are function style, e.g. f, [], (,)
        -- False if we are operator style, e.g. +, :+
776
        classify "" = False -- shouldn't happen; . operator is handled below
Ian Lynagh's avatar
Ian Lynagh committed
777
        classify (x:xs) | isAlpha x || (x `elem` "_[]()") =
778 779 780 781
                            case dropWhile (/='.') xs of
                                  (_:xs') -> classify xs'
                                  []      -> True
                        | otherwise = False
782

783
instance Show Name where
Ian Lynagh's avatar
Ian Lynagh committed
784
  show = showName
785

786
-- Tuple data and type constructors
787 788 789 790
-- | Tuple data constructor
tupleDataName :: Int -> Name
-- | Tuple type constructor
tupleTypeName :: Int -> Name
791

792
tupleDataName 0 = mk_tup_name 0 DataName
793
tupleDataName 1 = error "tupleDataName 1"
794
tupleDataName n = mk_tup_name (n-1) DataName
795

796
tupleTypeName 0 = mk_tup_name 0 TcClsName
797
tupleTypeName 1 = error "tupleTypeName 1"
798
tupleTypeName n = mk_tup_name (n-1) TcClsName
799

Ian Lynagh's avatar
Ian Lynagh committed
800
mk_tup_name :: Int -> NameSpace -> Name
801
mk_tup_name n_commas space
Ian Lynagh's avatar
Ian Lynagh committed
802
  = Name occ (NameG space (mkPkgName "ghc-prim") tup_mod)
803 804
  where
    occ = mkOccName ('(' : replicate n_commas ',' ++ ")")
Ian Lynagh's avatar
Ian Lynagh committed
805
    tup_mod = mkModName "GHC.Tuple"
806

807
-- Unboxed tuple data and type constructors
808 809 810 811
-- | Unboxed tuple data constructor
unboxedTupleDataName :: Int -> Name
-- | Unboxed tuple type constructor
unboxedTupleTypeName :: Int -> Name
812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827

unboxedTupleDataName 0 = error "unboxedTupleDataName 0"
unboxedTupleDataName 1 = error "unboxedTupleDataName 1"
unboxedTupleDataName n = mk_unboxed_tup_name (n-1) DataName

unboxedTupleTypeName 0 = error "unboxedTupleTypeName 0"
unboxedTupleTypeName 1 = error "unboxedTupleTypeName 1"
unboxedTupleTypeName n = mk_unboxed_tup_name (n-1) TcClsName

mk_unboxed_tup_name :: Int -> NameSpace -> Name
mk_unboxed_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"

828

829

830 831 832 833 834 835 836 837 838 839 840
-----------------------------------------------------
--		Locations
-----------------------------------------------------

data Loc
  = Loc { loc_filename :: String
	, loc_package  :: String
	, loc_module   :: String
	, loc_start    :: CharPos
	, loc_end      :: CharPos }

841
type CharPos = (Int, Int)	-- ^ Line and character position
842

843

844 845 846 847 848 849
-----------------------------------------------------
--
--	The Info returned by reification
--
-----------------------------------------------------

aavogt's avatar
aavogt committed
850 851
-- | Obtained from 'reify' in the 'Q' Monad.
data Info
852 853 854 855 856 857 858
  = 
  -- | A class, with a list of its visible instances
  ClassI 
      Dec
      [InstanceDec]
  
  -- | A class method
859
  | ClassOpI
860 861 862 863 864 865
       Name
       Type
       ParentName
       Fixity
  
  -- | A \"plain\" type constructor. \"Fancier\" type constructors are returned using 'PrimTyConI' or 'FamilyI' as appropriate
866 867 868
  | TyConI 
        Dec

869 870
  -- | A type or data family, with a list of its visible instances. A closed
  -- type family is returned with 0 instances.
871
  | FamilyI 
872 873
        Dec
        [InstanceDec]
874 875 876 877 878 879 880 881
  
  -- | A \"primitive\" type constructor, which can't be expressed with a 'Dec'. Examples: @(->)@, @Int#@.
  | PrimTyConI 
       Name
       Arity
       Unlifted
  
  -- | A data constructor
882
  | DataConI 
883 884 885 886
       Name
       Type
       ParentName
       Fixity
887

888 889 890 891 892 893 894 895 896 897
  {- | 
  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.
  -}
898
  | VarI 
899 900 901 902
       Name
       Type
       (Maybe Dec)
       Fixity
903

904 905 906 907 908 909 910
  {- | 
  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.
  -}
911 912 913
  | TyVarI 	-- Scoped type variable
	Name
	Type	-- What it is bound to
914
  deriving( Show, Data, Typeable )
915

916 917 918 919 920 921 922 923 924 925 926 927
{- | 
In 'ClassOpI' and 'DataConI', name of the parent class or type
-}
type ParentName = Name

-- | 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.
928
-- It is just a 'Dec', but guaranteed to be one of the following:
929 930 931 932 933 934
--
--   * 'InstanceD' (with empty @['Dec']@)
--
--   * 'DataInstD' or 'NewtypeInstD' (with empty derived @['Name']@)
--
--   * 'TySynInstD'
935
type InstanceDec = Dec
936

937 938 939 940
data Fixity          = Fixity Int FixityDirection
    deriving( Eq, Show, Data, Typeable )
data FixityDirection = InfixL | InfixR | InfixN
    deriving( Eq, Show, Data, Typeable )
941

942
-- | Highest allowed operator precedence for 'Fixity' constructor (answer: 9)
943
maxPrecedence :: Int
944
maxPrecedence = (9::Int)
945

946
-- | Default fixity: @infixl 9@
947
defaultFixity :: Fixity
948 949 950
defaultFixity = Fixity maxPrecedence InfixL


951
{-
952 953
Note [Unresolved infix]
~~~~~~~~~~~~~~~~~~~~~~~
954 955
-}
{- $infix #infix#
956 957 958
When implementing antiquotation for quasiquoters, one often wants
to parse strings into expressions:

959
> parse :: String -> Maybe Exp
960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013

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' or 'UInfixP', which stand for
\"unresolved infix expression\" and \"unresolved infix pattern\". 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' or 'ParensP',
    which are of use for parsing expressions like

    > (a + b * c) + d * e

  * 'InfixE' and 'InfixP' 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

    will never contain 'UInfixE', 'UInfixP', 'ParensE', or 'ParensP'
    constructors.

-}

1014 1015 1016 1017 1018 1019
-----------------------------------------------------
--
--	The main syntax data types
--
-----------------------------------------------------

1020 1021
data Lit = CharL Char 
         | StringL String 
aavogt's avatar
aavogt committed
1022
         | IntegerL Integer     -- ^ Used for overloaded and non-overloaded
1023 1024 1025 1026 1027
                                -- 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
1028
         | WordPrimL Integer
1029 1030
         | FloatPrimL Rational
         | DoublePrimL Rational
reinerp's avatar
reinerp committed
1031
         | StringPrimL [Word8]	-- ^ A primitive C-style string, type Addr#
1032
    deriving( Show, Eq, Data, Typeable )
1033 1034 1035 1036 1037

    -- We could add Int, Float, Double etc, as we do in HsLit, 
    -- but that could complicate the
    -- suppposedly-simple TH.Syntax literal type

aavogt's avatar
aavogt committed
1038
-- | Pattern in Haskell given in @{}@
1039
data Pat 
aavogt's avatar
aavogt committed
1040 1041 1042
  = LitP Lit                      -- ^ @{ 5 or 'c' }@
  | VarP Name                     -- ^ @{ x }@
  | TupP [Pat]                    -- ^ @{ (p1,p2) }@
1043
  | UnboxedTupP [Pat]             -- ^ @{ (# p1,p2 #) }@
aavogt's avatar
aavogt committed
1044 1045
  | ConP Name [Pat]               -- ^ @data T1 = C1 t1 t2; {C1 p1 p1} = e@
  | InfixP Pat Name Pat           -- ^ @foo ({x :+ y}) = e@
1046 1047
  | UInfixP Pat Name Pat          -- ^ @foo ({x :+ y}) = e@
                                  --
1048
                                  -- See "Language.Haskell.TH.Syntax#infix"
1049 1050
  | ParensP Pat                   -- ^ @{(p)}@
                                  --
1051
                                  -- See "Language.Haskell.TH.Syntax#infix"
aavogt's avatar
aavogt committed
1052 1053 1054 1055 1056 1057 1058
  | 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 }@
reinerp's avatar
reinerp committed
1059
  | ViewP Exp Pat                 -- ^ @{ e -> p }@
1060
  deriving( Show, Eq, Data, Typeable )
1061 1062 1063

type FieldPat = (Name,Pat)

aavogt's avatar
aavogt committed
1064
data Match = Match Pat Body [Dec] -- ^ @case e of { pat -> body where decs }@
1065
    deriving( Show, Eq, Data, Typeable )
1066
data Clause = Clause [Pat] Body [Dec]
aavogt's avatar
aavogt committed
1067
                                  -- ^ @f { p1 p2 = body where decs }@
1068
    deriving( Show, Eq, Data, Typeable )
1069 1070
 
data Exp 
aavogt's avatar
aavogt committed
1071 1072 1073 1074
  = VarE Name                          -- ^ @{ x }@
  | ConE Name                          -- ^ @data T1 = C1 t1 t2; p = {C1} e1 e2  @
  | LitE Lit                           -- ^ @{ 5 or 'c'}@
  | AppE Exp Exp                       -- ^ @{ f x }@
1075

aavogt's avatar
aavogt committed
1076
  | InfixE (Maybe Exp) Exp (Maybe Exp) -- ^ @{x + y} or {(x+)} or {(+ x)} or {(+)}@
1077

1078 1079 1080 1081 1082 1083
    -- 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?

1084 1085
  | UInfixE Exp Exp Exp                -- ^ @{x + y}@
                                       --
1086
                                       -- See "Language.Haskell.TH.Syntax#infix"
1087 1088
  | ParensE Exp                        -- ^ @{ (e) }@
                                       --
1089
                                       -- See "Language.Haskell.TH.Syntax#infix"
aavogt's avatar
aavogt committed
1090
  | LamE [Pat] Exp                     -- ^ @{ \ p1 p2 -> e }@
1091
  | LamCaseE [Match]                   -- ^ @{ \case m1; m2 }@
aavogt's avatar
aavogt committed
1092
  | TupE [Exp]                         -- ^ @{ (e1,e2) }  @
1093
  | UnboxedTupE [Exp]                  -- ^ @{ (# e1,e2 #) }  @
aavogt's avatar
aavogt committed
1094
  | CondE Exp Exp Exp                  -- ^ @{ if e1 then e2 else e3 }@
1095
  | MultiIfE [(Guard, Exp)]            -- ^ @{ if | g1 -> e1 | g2 -> e2 }@
aavogt's avatar
aavogt committed
1096 1097 1098
  | LetE [Dec] Exp                     -- ^ @{ let x=e1;   y=e2 in e3 }@
  | CaseE Exp [Match]                  -- ^ @{ case e of m1; m2 }@
  | DoE [Stmt]                         -- ^ @{ do { p <- e1; e2 }  }@
1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109
  | 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))]

aavogt's avatar
aavogt committed
1110 1111 1112 1113 1114
  | 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 } }@
1115
  deriving( Show, Eq, Data, Typeable )
1116 1117 1118 1119 1120 1121

type FieldExp = (Name,Exp)

-- Omitted: implicit parameters

data Body
1122 1123 1124
  = GuardedB [(Guard,Exp)]   -- ^ @f p { | e1 = e2 
                                 --      | e3 = e4 } 
                                 -- where ds@
aavogt's avatar
aavogt committed
1125
  | NormalB Exp              -- ^ @f p { = e } where ds@
1126
  deriving( Show, Eq, Data, Typeable )
1127

1128
data Guard
1129 1130
  = NormalG Exp -- ^ @f x { | odd x } = x@
  | PatG [Stmt] -- ^ @f x { | Just y <- x, Just z <- y } = z@
1131
  deriving( Show, Eq, Data, Typeable )
1132

1133 1134 1135 1136 1137
data Stmt
  = BindS Pat Exp
  | LetS [ Dec ]
  | NoBindS Exp
  | ParS [[Stmt]]
1138
  deriving( Show, Eq, Data, Typeable )
1139 1140 1141

data Range = FromR Exp | FromThenR Exp Exp
           | FromToR Exp Exp | FromThenToR Exp Exp Exp
1142
          deriving( Show, Eq, Data, Typeable )
1143 1144
  
data Dec 
aavogt's avatar
aavogt committed
1145 1146
  = FunD Name [Clause]            -- ^ @{ f p1 p2 = b where decs }@
  | ValD Pat Body [Dec]           -- ^ @{ p = b where decs }@
1147
  | DataD Cxt Name [TyVarBndr] 
aavogt's avatar
aavogt committed
1148 1149
         [Con] [Name]             -- ^ @{ data Cxt x => T x = A x | B (T x)
                                  --       deriving (Z,W)}@
1150
  | NewtypeD Cxt Name [TyVarBndr] 
aavogt's avatar
aavogt committed
1151 1152 1153
         Con [Name]               -- ^ @{ newtype Cxt x => T x = A (B x)
                                  --       deriving (Z,W)}@
  | TySynD Name [TyVarBndr] Type  -- ^ @{ type T x = (x,x) }@</