Syntax.hs 21 KB
Newer Older
1
{-# OPTIONS_GHC -fglasgow-exts #-}
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
	-- Need GlaExts for the nested forall in defn of Q
-----------------------------------------------------------------------------
-- |
-- 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.
--
-----------------------------------------------------------------------------

module Language.Haskell.TH.Syntax(
	Quasi(..), Lift(..), 

	Q, runQ, 
	report,	recover, reify,
	currentModule, runIO,

	-- Names
25
	Name(..), mkName, newName, nameBase, nameModule,
26 27 28

	-- The algebraic data types
	Dec(..), Exp(..), Con(..), Type(..), Cxt, Match(..), 
29
	Clause(..), Body(..), Guard(..), Stmt(..), Range(..),
30 31
	Lit(..), Pat(..), FieldExp, FieldPat, 
	Strict(..), Foreign(..), Callconv(..), Safety(..),
32
	StrictType, VarStrictType, FunDep(..),
33 34 35 36 37 38
	Info(..), 
	Fixity(..), FixityDirection(..), defaultFixity, maxPrecedence,

	-- Internal functions
	returnQ, bindQ, sequenceQ,
	NameFlavour(..), NameSpace (..), 
39
	mkNameG_v, mkNameG_d, mkNameG_tc, Uniq, mkNameL, mkNameU,
40
 	tupleTypeName, tupleDataName,
41
	OccName, mkOccName, occString,
42 43
	ModName, mkModName, modString,
	PkgName, mkPkgName, pkgString
44 45 46 47 48 49 50
    ) where

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

import Data.IORef
import GHC.IOBase	( unsafePerformIO )
51
import Control.Monad (liftM)
52
import System.IO	( hPutStrLn, stderr )
53 54 55 56 57 58 59

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

60
class (Monad m, Functor m) => Quasi m where
61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129
	-- Fresh names
  qNewName :: String -> m Name

	-- 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 -> m a -> m a		-- Recover from the monadic 'fail'
					-- The first arg is the error handler
 
	-- Inspect the type-checker's environment
  qReify :: Name -> m Info
  qCurrentModule :: m String

	-- Input/output (dangerous)
  qRunIO :: IO a -> m a


-----------------------------------------------------
--	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)

  qReify v       = badIO "reify"
  qCurrentModule = badIO "currentModule"
  qRecover a b   = badIO "recover"	-- Maybe we could fix this?

  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 }

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)
  fail s     = Q (fail s)

130 131 132
instance Functor Q where
  fmap f (Q x) = Q (fmap f x)

133 134 135 136 137 138 139 140 141 142 143
----------------------------------------------------
-- Packaged versions for the programmer, hiding the Quasi-ness
newName :: String -> Q Name
newName s = Q (qNewName s)

report  :: Bool -> String -> Q ()
report b s = Q (qReport b s)

recover :: Q a -> Q a -> Q a
recover (Q r) (Q m) = Q (qRecover r m)

144
-- | 'reify' looks up information about the 'Name'
145 146 147
reify :: Name -> Q Info
reify v = Q (qReify v)

148 149
-- | 'currentModule' gives you the name of the module in which this 
-- computation is spliced.
150 151 152
currentModule :: Q String
currentModule = Q qCurrentModule

dons's avatar
dons committed
153
-- |The 'runIO' function lets you run an I\/O computation in the 'Q' monad.
154 155 156 157 158 159
-- 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.
160 161 162 163 164 165 166 167 168 169 170 171 172 173
runIO :: IO a -> Q a
runIO m = Q (qRunIO m)

instance Quasi Q where
  qNewName        = newName
  qReport 	 = report
  qRecover  	 = recover 
  qReify    	 = reify
  qCurrentModule = currentModule
  qRunIO         = runIO


----------------------------------------------------
-- The following operations are used solely in DsMeta when desugaring brackets
174
-- They are not necessary for the user, who can use ordinary return and (>>=) etc
175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207

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)

208 209 210 211 212 213 214 215
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)

216 217 218
instance Lift a => Lift [a] where
  lift xs = do { xs' <- mapM lift xs; return (ListE xs') }

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
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]

246 247 248 249 250 251 252 253 254 255
-- 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
256 257
trueName  = mkNameG DataName "base" "GHC.Base" "True"
falseName = mkNameG DataName "base" "GHC.Base" "False"
258

259 260 261 262 263 264 265 266
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"

267 268 269 270 271 272

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

type ModName = PackedString	-- Module name
273

274 275 276 277 278 279
mkModName :: String -> ModName
mkModName s = packString s

modString :: ModName -> String
modString m = unpackPS m

280

281 282 283 284 285 286 287 288 289
type PkgName = PackedString	-- package name

mkPkgName :: String -> PkgName
mkPkgName s = packString s

pkgString :: PkgName -> String
pkgString m = unpackPS m


290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321
-----------------------------------------------------
--		OccName
-----------------------------------------------------

type OccName = PackedString

mkOccName :: String -> OccName
mkOccName s = packString s

occString :: OccName -> String
occString occ = unpackPS 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

data Name = Name OccName NameFlavour

data NameFlavour
322 323
  = NameS 			-- An unqualified name; dynamically bound
  | NameQ ModName		-- A qualified name; dynamically bound
324

325
  | NameU Int#			-- A unique local name
326

327 328 329 330 331 332 333 334
	-- The next two are for lexically-scoped names that
	-- are bound *outside* the TH syntax tree, 
	-- either globally (NameG) or locally (NameL)
	-- e.g. 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

  | NameL Int#			-- 
335
  | NameG NameSpace PkgName ModName	-- An original name (occurrences only, not binders)
336 337 338 339 340 341 342 343 344 345 346 347 348 349
				-- Need the namespace too to be sure which 
				-- thing we are naming

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 )

type Uniq = Int

nameBase :: Name -> String
nameBase (Name occ _) = occString occ

350
nameModule :: Name -> Maybe String
351
nameModule (Name _ (NameQ m))   = Just (modString m)
352
nameModule (Name _ (NameG _ _ m)) = Just (modString m)
353 354
nameModule other_name		= Nothing

355
mkName :: String -> Name
356 357 358 359 360 361 362 363 364 365 366 367 368
-- 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
369 370 371 372 373 374 375 376 377
    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
378
    split occ (c:rev)   = split (c:occ) rev
379 380 381 382

mkNameU :: String -> Uniq -> Name	-- Only used internally
mkNameU s (I# u) = Name (mkOccName s) (NameU u)

383 384 385
mkNameL :: String -> Uniq -> Name	-- Only used internally
mkNameL s (I# u) = Name (mkOccName s) (NameL u)

386 387 388
mkNameG :: NameSpace -> String -> String -> String -> Name	-- Used for 'x etc, but not available
mkNameG ns pkg mod occ 					-- to the programmer
  = Name (mkOccName occ) (NameG ns (mkPkgName pkg) (mkModName mod))
389

390
mkNameG_v, mkNameG_tc, mkNameG_d :: String -> String -> String -> Name
391 392 393 394 395 396 397 398 399 400 401 402 403 404 405
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
406
	-- NameS < NameQ < NameU < NameL < NameG
407 408 409
  NameS `compare` NameS = EQ
  NameS `compare` other = LT

410 411 412 413 414 415
  (NameQ _)  `compare` NameS      = GT
  (NameQ m1) `compare` (NameQ m2) = m1 `compare` m2
  (NameQ _)  `compare` other      = LT

  (NameU _)  `compare` NameS      = GT
  (NameU _)  `compare` (NameQ _)  = GT
416 417 418 419 420
  (NameU u1) `compare` (NameU u2) | u1  <# u2 = LT
				  | u1 ==# u2 = EQ
				  | otherwise = GT
  (NameU _)  `compare` other = LT

421 422 423 424 425 426 427 428
  (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
  (NameL _)  `compare` other      = LT

429 430 431 432
  (NameG ns1 p1 m1) `compare` (NameG ns2 p2 m2) = (ns1 `compare` ns2) `thenCmp`
                                            (p1 `compare` p2) `thenCmp`
					    (m1 `compare` m2) 
  (NameG _ _ _)    `compare` other	  = GT
433 434

instance Show Name where
435 436 437 438 439 440 441
  show (Name occ NameS) = occString occ

	-- 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.
442
  show (Name occ (NameQ m))      = modString m ++ "." ++ occString occ
443
  show (Name occ (NameG ns p m)) = modString m ++ "." ++ occString occ
444

445 446 447 448
	-- Ditto NameU and NameL  
  show (Name occ (NameU u)) = occString occ ++ "_" ++ show (I# u)
  show (Name occ (NameL u)) = occString occ ++ "_" ++ show (I# u)

449

450 451 452 453 454 455 456 457 458 459 460 461 462
-- 	Tuple data and type constructors
tupleDataName  :: Int -> Name	-- Data constructor
tupleTypeName :: Int -> Name 	-- Type constructor

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 n_commas space
463
  = Name occ (NameG space (mkPkgName "base") tup_mod)
464 465
  where
    occ = mkOccName ('(' : replicate n_commas ',' ++ ")")
466
    tup_mod = mkModName "Data.Tuple"
467 468


469 470


471 472 473 474 475 476 477 478 479 480 481 482 483 484 485
-----------------------------------------------------
--
--	The Info returned by reification
--
-----------------------------------------------------

data Info 
  = ClassI Dec
  | ClassOpI
	Name	-- The class op itself
	Type 	-- Type of the class-op (fully polymoprhic)
	Name 	-- Name of the parent class
	Fixity

  | TyConI Dec
486 487 488 489 490 491 492

  | PrimTyConI 	-- Ones that can't be expressed with a data type 
		-- decl, such as (->), Int#
	Name 
	Int	-- Arity
	Bool	-- False => lifted type; True => unlifted

493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509
  | DataConI 
	Name	-- The data con itself
	Type 	-- Type of the constructor (fully polymorphic)
	Name 	-- Name of the parent TyCon
	Fixity

  | VarI 
	Name	-- The variable itself
	Type 
	(Maybe Dec)	-- Nothing for lambda-bound variables, and 
			-- for anything else TH can't figure out
			-- E.g. [| let x = 1 in $(do { d <- reify 'x; .. }) |]
	Fixity

  | TyVarI 	-- Scoped type variable
	Name
	Type	-- What it is bound to
simonpj@microsoft.com's avatar
simonpj@microsoft.com committed
510
  deriving( Show )
511

simonpj@microsoft.com's avatar
simonpj@microsoft.com committed
512 513
data Fixity 	     = Fixity Int FixityDirection deriving( Eq, Show )
data FixityDirection = InfixL | InfixR | InfixN   deriving( Eq, Show )
514

515
maxPrecedence :: Int
516
maxPrecedence = (9::Int)
517 518

defaultFixity :: Fixity
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
defaultFixity = Fixity maxPrecedence InfixL


-----------------------------------------------------
--
--	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
         | FloatPrimL Rational
         | DoublePrimL Rational
    deriving( Show, Eq )

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

data Pat 
  = LitP Lit                      -- { 5 or 'c' }
  | VarP Name                   -- { x }
  | TupP [Pat]                    -- { (p1,p2) }
  | ConP Name [Pat]             -- data T1 = C1 t1 t2; {C1 p1 p1} = e 
549
  | InfixP Pat Name Pat           -- foo ({x :+ y}) = e 
550 551 552 553 554
  | TildeP Pat                    -- { ~p }
  | AsP Name Pat                -- { x @ p }
  | WildP                         -- { _ }
  | RecP Name [FieldPat]        -- f (Pt { pointx = x }) = g x
  | ListP [ Pat ]                 -- { [1,2,3] }
555
  | SigP Pat Type                 -- p :: t
556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598
  deriving( Show, Eq )

type FieldPat = (Name,Pat)

data Match = Match Pat Body [Dec]
                                    -- case e of { pat -> body where decs } 
    deriving( Show, Eq )
data Clause = Clause [Pat] Body [Dec]
                                    -- f { p1 p2 = body where decs }
    deriving( Show, Eq )
 
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 }

  | 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?

  | LamE [Pat] Exp                     -- { \ p1 p2 -> e }
  | TupE [Exp]                         -- { (e1,e2) }  
  | CondE Exp Exp Exp                  -- { if e1 then e2 else e3 }
  | 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 ] }
  | 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 } }
  deriving( Show, Eq )

type FieldExp = (Name,Exp)

-- Omitted: implicit parameters

data Body
599
  = GuardedB [(Guard,Exp)]   -- f p { | e1 = e2 | e3 = e4 } where ds
600 601 602
  | NormalB Exp              -- f p { = e } where ds
  deriving( Show, Eq )

603 604 605 606 607
data Guard
  = NormalG Exp
  | PatG [Stmt]
  deriving( Show, Eq )

608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628
data Stmt
  = BindS Pat Exp
  | LetS [ Dec ]
  | NoBindS Exp
  | ParS [[Stmt]]
  deriving( Show, Eq )

data Range = FromR Exp | FromThenR Exp Exp
           | FromToR Exp Exp | FromThenToR Exp Exp Exp
          deriving( Show, Eq )
  
data Dec 
  = FunD Name [Clause]            -- { f p1 p2 = b where decs }
  | ValD Pat Body [Dec]           -- { p = b where decs }
  | DataD Cxt Name [Name] 
         [Con] [Name]             -- { data Cxt x => T x = A x | B (T x)
                                  --       deriving (Z,W)}
  | NewtypeD Cxt Name [Name] 
         Con [Name]               -- { newtype Cxt x => T x = A (B x)
                                  --       deriving (Z,W)}
  | TySynD Name [Name] Type       -- { type T x = (x,x) }
629 630
  | ClassD Cxt Name [Name] [FunDep] [Dec]
                                  -- { class Eq a => Ord a where ds }
631 632 633 634 635 636
  | InstanceD Cxt Type [Dec]      -- { instance Show w => Show [w]
                                  --       where ds }
  | SigD Name Type                -- { length :: [a] -> Int }
  | ForeignD Foreign
  deriving( Show, Eq )

637 638 639
data FunDep = FunDep [Name] [Name]
  deriving( Show, Eq )

640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657
data Foreign = ImportF Callconv Safety String Name Type
             | ExportF Callconv        String Name Type
         deriving( Show, Eq )

data Callconv = CCall | StdCall
          deriving( Show, Eq )

data Safety = Unsafe | Safe | Threadsafe
        deriving( Show, Eq )

type Cxt = [Type]    -- (Eq a, Ord b)

data Strict = IsStrict | NotStrict
         deriving( Show, Eq )

data Con = NormalC Name [StrictType]
         | RecC Name [VarStrictType]
         | InfixC StrictType Name StrictType
658
         | ForallC [Name] Cxt Con
659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686
         deriving( Show, Eq )

type StrictType = (Strict, Type)
type VarStrictType = (Name, Strict, Type)

-- FIXME: Why this special status for "List" (even tuples might be handled
--      differently)? -=chak
data Type = ForallT [Name] Cxt Type   -- forall <vars>. <ctxt> -> <type>
          | VarT Name                 -- a
          | ConT Name                 -- T
          | TupleT Int                -- (,), (,,), etc.
          | ArrowT                    -- ->
          | ListT                     -- []
          | AppT Type Type            -- T a b
      deriving( Show, Eq )

-----------------------------------------------------
--		Internal helper functions
-----------------------------------------------------

cmpEq :: Ordering -> Bool
cmpEq EQ = True
cmpEq _  = False

thenCmp :: Ordering -> Ordering -> Ordering
thenCmp EQ o2 = o2
thenCmp o1 o2 = o1