Syntax.hs 48.3 KB
Newer Older
1
{-# LANGUAGE DeriveDataTypeable, MagicHash, PolymorphicComponents, RoleAnnotations, UnboxedTuples #-}
2

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

17
module Language.Haskell.TH.Syntax where
18

19
import GHC.Exts
20
import Data.Data (Data(..), Typeable, mkConstr, mkDataType, constrIndex)
Ross Paterson's avatar
Ross Paterson committed
21
import qualified Data.Data as Data
22
import Control.Applicative( Applicative(..) )
23
import Data.IORef
24
import System.IO.Unsafe	( unsafePerformIO )
25
import Control.Monad (liftM)
26
import System.IO	( hPutStrLn, stderr )
27
import Data.Char        ( isAlpha, isAlphaNum, isUpper )
reinerp's avatar
reinerp committed
28
import Data.Word        ( Word8 )
29 30 31 32 33 34 35

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

36
class (Monad m, Applicative m) => Quasi m where
37
  qNewName :: String -> m Name
aavogt's avatar
aavogt committed
38
	-- ^ Fresh names
39 40

	-- Error reporting and recovery
aavogt's avatar
aavogt committed
41
  qReport  :: Bool -> String -> m ()	-- ^ Report an error (True) or warning (False)
42
					-- ...but carry on; use 'fail' to stop
aavogt's avatar
aavogt committed
43 44 45
  qRecover :: m a -- ^ the error handler
           -> m a -- ^ action which may fail
           -> m a		-- ^ Recover from the monadic 'fail'
Jan Stolarek's avatar
Jan Stolarek committed
46

47
	-- Inspect the type-checker's environment
48 49 50 51 52
  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?
Jan Stolarek's avatar
Jan Stolarek committed
53
       -- Returns list of matching instance Decs
54 55
       --    (with empty sub-Decs)
       -- Works for classes and type functions
Austin Seipp's avatar
Austin Seipp committed
56 57
  qReifyRoles       :: Name -> m [Role]
  qReifyAnnotations :: Data a => AnnLookup -> m [a]
58
  qReifyModule      :: Module -> m ModuleInfo
59

60
  qLocation :: m Loc
61 62

  qRunIO :: IO a -> m a
aavogt's avatar
aavogt committed
63
  -- ^ Input/output (dangerous)
64

GregWeber's avatar
GregWeber committed
65
  qAddDependentFile :: FilePath -> m ()
66

67 68
  qAddTopDecls :: [Dec] -> m ()

69 70
  qAddModFinalizer :: Q () -> m ()

gmainland's avatar
gmainland committed
71 72 73 74
  qGetQ :: Typeable a => m (Maybe a)

  qPutQ :: Typeable a => a -> m ()

75 76
-----------------------------------------------------
--	The IO instance of Quasi
Jan Stolarek's avatar
Jan Stolarek committed
77
--
78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93
--  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)

94
  qLookupName _ _     = badIO "lookupName"
95
  qReify _            = badIO "reify"
96
  qReifyInstances _ _ = badIO "reifyInstances"
97
  qReifyRoles _       = badIO "reifyRoles"
Austin Seipp's avatar
Austin Seipp committed
98
  qReifyAnnotations _ = badIO "reifyAnnotations"
99
  qReifyModule _      = badIO "reifyModule"
100 101
  qLocation    	      = badIO "currentLocation"
  qRecover _ _ 	      = badIO "recover" -- Maybe we could fix this?
GregWeber's avatar
GregWeber committed
102
  qAddDependentFile _ = badIO "addDependentFile"
103
  qAddTopDecls _      = badIO "addTopDecls"
104
  qAddModFinalizer _  = badIO "addModFinalizer"
gmainland's avatar
gmainland committed
105 106
  qGetQ               = badIO "getQ"
  qPutQ _             = badIO "putQ"
107 108

  qRunIO m = m
Jan Stolarek's avatar
Jan Stolarek committed
109

110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127
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 }

128 129 130 131 132
-- \"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
Jan Stolarek's avatar
Jan Stolarek committed
133
-- splices by running them in 'IO'.
134 135 136 137 138
--
-- 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'.
139 140 141 142 143 144 145
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)
146
  fail s     = report True s >> Q (fail "Q monad failure")
147

148 149 150
instance Functor Q where
  fmap f (Q x) = Q (fmap f x)

Jan Stolarek's avatar
Jan Stolarek committed
151 152 153
instance Applicative Q where
  pure x = Q (pure x)
  Q f <*> Q x = Q (f <*> x)
154

gmainland's avatar
gmainland committed
155 156 157 158 159 160
-----------------------------------------------------
--
--		The TExp type
--
-----------------------------------------------------

161
type role TExp nominal   -- See Note [Role of TExp]
162 163 164 165 166 167 168 169 170
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) }
gmainland's avatar
gmainland committed
171

172 173 174 175 176 177 178 179 180 181 182 183 184
{- 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). -}

185 186
----------------------------------------------------
-- Packaged versions for the programmer, hiding the Quasi-ness
187

Jan Stolarek's avatar
Jan Stolarek committed
188 189
{- |
Generate a fresh name, which cannot be captured.
190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221

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@.
-}
222 223 224
newName :: String -> Q Name
newName s = Q (qNewName s)

Jan Stolarek's avatar
Jan Stolarek committed
225
-- | Report an error (True) or warning (False),
226
-- but carry on; use 'fail' to stop.
227 228
report  :: Bool -> String -> Q ()
report b s = Q (qReport b s)
229
{-# DEPRECATED report "Use reportError or reportWarning instead" #-} -- deprecated in 7.6
230 231 232 233 234 235 236 237

-- | 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
238

239 240 241
-- | 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
242
        -> Q a
243 244
recover (Q r) (Q m) = Q (qRecover r m)

245 246 247 248 249
-- 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)

250 251
-- | 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)
252
lookupTypeName  s = Q (qLookupName True s)
253 254 255

-- | 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)
256 257
lookupValueName s = Q (qLookupName False s)

258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273
{-
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.

Jan Stolarek's avatar
Jan Stolarek committed
274
The returned name cannot be \"captured\".
275 276 277 278 279 280 281 282 283 284 285 286 287 288 289
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"
Jan Stolarek's avatar
Jan Stolarek committed
290
> g = $( [| let f = "local" in
291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326
>            $(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'.
-}
327 328 329
reify :: Name -> Q Info
reify v = Q (qReify v)

Jan Stolarek's avatar
Jan Stolarek committed
330
{- | @reifyInstances nm tys@ returns a list of visible instances of @nm tys@. That is,
331 332 333 334 335
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]
336
reifyInstances cls tys = Q (qReifyInstances cls tys)
337

338 339 340 341 342 343 344
{- | @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)

Austin Seipp's avatar
Austin Seipp committed
345 346 347 348 349 350 351
-- | @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)

352 353 354 355 356 357
-- | @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)

358
-- | Is the list of instances returned by 'reifyInstances' nonempty?
359 360 361
isInstance :: Name -> [Type] -> Q Bool
isInstance nm tys = do { decs <- reifyInstances nm tys
                       ; return (not (null decs)) }
362

363
-- | The location at which this computation is spliced.
364 365
location :: Q Loc
location = Q qLocation
366

dons's avatar
dons committed
367
-- |The 'runIO' function lets you run an I\/O computation in the 'Q' monad.
Jan Stolarek's avatar
Jan Stolarek committed
368 369
-- 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.
370
--
Jan Stolarek's avatar
Jan Stolarek committed
371
-- Note: for various murky reasons, stdout and stderr handles are not
372 373
-- necesarily flushed when the  compiler finishes running, so you should
-- flush them yourself.
374 375 376
runIO :: IO a -> Q a
runIO m = Q (qRunIO m)

GregWeber's avatar
GregWeber committed
377 378 379 380 381 382 383
-- | 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)

384 385 386 387 388
-- | 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)

389 390 391 392 393
-- | 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.
addModFinalizer :: Q () -> Q ()
addModFinalizer act = Q (qAddModFinalizer (unQ act))

gmainland's avatar
gmainland committed
394 395 396 397 398 399 400 401
-- | Get state from the Q monad.
getQ :: Typeable a => Q (Maybe a)
getQ = Q qGetQ

-- | Replace the state in the Q monad.
putQ :: Typeable a => a -> Q ()
putQ x = Q (qPutQ x)

402
instance Quasi Q where
GregWeber's avatar
GregWeber committed
403 404
  qNewName  	    = newName
  qReport   	    = report
Jan Stolarek's avatar
Jan Stolarek committed
405
  qRecover  	    = recover
GregWeber's avatar
GregWeber committed
406 407
  qReify    	    = reify
  qReifyInstances   = reifyInstances
408
  qReifyRoles       = reifyRoles
Austin Seipp's avatar
Austin Seipp committed
409
  qReifyAnnotations = reifyAnnotations
410
  qReifyModule      = reifyModule
GregWeber's avatar
GregWeber committed
411 412 413 414
  qLookupName       = lookupName
  qLocation 	    = location
  qRunIO    	    = runIO
  qAddDependentFile = addDependentFile
415
  qAddTopDecls      = addTopDecls
416
  qAddModFinalizer  = addModFinalizer
gmainland's avatar
gmainland committed
417 418
  qGetQ             = getQ
  qPutQ             = putQ
419 420 421 422


----------------------------------------------------
-- The following operations are used solely in DsMeta when desugaring brackets
423
-- They are not necessary for the user, who can use ordinary return and (>>=) etc
424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442

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
Jan Stolarek's avatar
Jan Stolarek committed
443

444 445 446 447 448 449 450 451 452 453 454 455 456
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)

457 458 459 460 461 462 463 464
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)

465 466 467
instance Lift a => Lift [a] where
  lift xs = do { xs' <- mapM lift xs; return (ListE xs') }

468 469 470 471
liftString :: String -> Q Exp
-- Used in TcExpr to short-circuit the lifting for strings
liftString s = return (LitE (StringL s))

472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498
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]

499 500 501 502
-- 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
Jan Stolarek's avatar
Jan Stolarek committed
503
--     which happens to be the way the type checker
504 505 506 507 508
--     creates it.
{-# RULES "TH:liftString" lift = \s -> return (LitE (StringL s)) #-}


trueName, falseName :: Name
Ian Lynagh's avatar
Ian Lynagh committed
509 510
trueName  = mkNameG DataName "ghc-prim" "GHC.Types" "True"
falseName = mkNameG DataName "ghc-prim" "GHC.Types" "False"
511

512 513 514 515 516 517 518 519
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"

520 521

-----------------------------------------------------
Jan Stolarek's avatar
Jan Stolarek committed
522
--		Names and uniques
523 524
-----------------------------------------------------

525
newtype ModName = ModName String	-- Module name
Austin Seipp's avatar
Austin Seipp committed
526
 deriving (Show,Eq,Ord,Typeable,Data)
527 528

newtype PkgName = PkgName String	-- package name
Austin Seipp's avatar
Austin Seipp committed
529
 deriving (Show,Eq,Ord,Typeable,Data)
530

531 532 533 534
-- | Obtained from 'reifyModule' and 'thisModule'.
data Module = Module PkgName ModName -- package qualified module name
 deriving (Show,Eq,Ord,Typeable,Data)

535
newtype OccName = OccName String
536
 deriving (Show,Eq,Ord,Typeable,Data)
537

538
mkModName :: String -> ModName
539
mkModName s = ModName s
540 541

modString :: ModName -> String
542
modString (ModName m) = m
543

544 545

mkPkgName :: String -> PkgName
546
mkPkgName s = PkgName s
547 548

pkgString :: PkgName -> String
549
pkgString (PkgName m) = m
550 551


552 553 554 555 556
-----------------------------------------------------
--		OccName
-----------------------------------------------------

mkOccName :: String -> OccName
557
mkOccName s = OccName s
558 559

occString :: OccName -> String
560
occString (OccName occ) = occ
561 562 563 564 565


-----------------------------------------------------
--		 Names
-----------------------------------------------------
Jan Stolarek's avatar
Jan Stolarek committed
566
--
aavogt's avatar
aavogt committed
567
-- For "global" names ('NameG') we need a totally unique name,
568 569
-- so we must include the name-space of the thing
--
aavogt's avatar
aavogt committed
570
-- For unique-numbered things ('NameU'), we've got a unique reference
571 572
-- anyway, so no need for name space
--
aavogt's avatar
aavogt committed
573
-- For dynamically bound thing ('NameS') we probably want them to
574 575
-- in a context-dependent way, so again we don't want the name
-- space.  For example:
aavogt's avatar
aavogt committed
576 577 578
--
-- > let v = mkName "T" in [| data $v = $v |]
--
579
-- Here we use the same Name for both type constructor and data constructor
aavogt's avatar
aavogt committed
580 581 582 583 584 585 586 587 588 589
--
--
-- 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
590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614

{- $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

Jan Stolarek's avatar
Jan Stolarek committed
615
which avoids name capture as desired.
616 617 618 619 620 621 622 623 624 625 626 627

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):

Jan Stolarek's avatar
Jan Stolarek committed
628 629
  * 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@
630 631
    currently in scope, and @''T@ gives a @Name@ which refers to the
    type @T@ currently in scope. These names can never be captured.
Jan Stolarek's avatar
Jan Stolarek committed
632 633

  * 'lookupValueName' and 'lookupTypeName' are similar to @'f@ and
634 635 636 637 638 639
     @''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.
Jan Stolarek's avatar
Jan Stolarek committed
640

641 642 643 644 645 646
  * '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.
-}
647
data Name = Name OccName NameFlavour deriving (Typeable, Data)
648 649

data NameFlavour
aavogt's avatar
aavogt committed
650 651 652 653 654 655
  = 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)
Jan Stolarek's avatar
Jan Stolarek committed
656
		-- Need the namespace too to be sure which
657
		-- thing we are naming
658 659
  deriving ( Typeable )

aavogt's avatar
aavogt committed
660
-- |
661 662 663 664 665 666 667
-- 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
668
-- boot libraries cannot be upgraded separately from GHC itself.
669 670
--
-- This instance cannot be derived automatically due to bug #2701
671
instance Data NameFlavour where
672 673 674 675 676 677 678 679 680 681 682 683
     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"
684 685 686 687 688 689 690
     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
691 692 693 694 695 696
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
697

Ross Paterson's avatar
Ross Paterson committed
698
ty_NameFlavour :: Data.DataType
699 700 701
ty_NameFlavour = mkDataType "Language.Haskell.TH.Syntax.NameFlavour"
                            [con_NameS, con_NameQ, con_NameU,
                             con_NameL, con_NameG]
702

aavogt's avatar
aavogt committed
703
data NameSpace = VarName	-- ^ Variables
Jan Stolarek's avatar
Jan Stolarek committed
704
	       | DataName	-- ^ Data constructors
aavogt's avatar
aavogt committed
705
	       | TcClsName	-- ^ Type constructors and classes; Haskell has them
706
				-- in the same name space for now.
707
	       deriving( Eq, Ord, Data, Typeable )
708 709 710

type Uniq = Int

711
-- | The name without its module prefix
712 713 714
nameBase :: Name -> String
nameBase (Name occ _) = occString occ

715
-- | Module prefix of a name, if it exists
716
nameModule :: Name -> Maybe String
Ian Lynagh's avatar
Ian Lynagh committed
717
nameModule (Name _ (NameQ m))     = Just (modString m)
718
nameModule (Name _ (NameG _ _ m)) = Just (modString m)
Ian Lynagh's avatar
Ian Lynagh committed
719
nameModule _                      = Nothing
720

Jan Stolarek's avatar
Jan Stolarek committed
721
{- |
722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744
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") |]
-}
745
mkName :: String -> Name
746
-- The string can have a '.', thus "Foo.baz",
747 748 749 750 751
-- 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
Jan Stolarek's avatar
Jan Stolarek committed
752
-- It's a bit tricky because we need to parse
aavogt's avatar
aavogt committed
753 754 755
--
-- > Foo.Baz.x   as    Qual Foo.Baz x
--
756 757 758 759 760
-- So we parse it from back to front
mkName str
  = split [] (reverse str)
  where
    split occ []        = Name (mkOccName occ) NameS
761 762
    split occ ('.':rev)	| not (null occ)
			, is_rev_mod_name rev
763 764 765
			= Name (mkOccName occ) (NameQ (mkModName (reverse rev)))
	-- The 'not (null occ)' guard ensures that
	-- 	mkName "&." = Name "&." NameS
766
	-- The 'is_rev_mod' guards ensure that
767
	--	mkName ".&" = Name ".&" NameS
768
	--	mkName "^.." = Name "^.." NameS      -- Trac #8633
769 770
	--	mkName "Data.Bits..&" = Name ".&" (NameQ "Data.Bits")
	-- This rather bizarre case actually happened; (.&.) is in Data.Bits
771
    split occ (c:rev)   = split (c:occ) rev
772

773 774 775 776 777 778 779 780 781 782 783 784 785 786 787
    -- 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 == '\''

aavogt's avatar
aavogt committed
788 789
-- | Only used internally
mkNameU :: String -> Uniq -> Name
790 791
mkNameU s (I# u) = Name (mkOccName s) (NameU u)

aavogt's avatar
aavogt committed
792 793
-- | Only used internally
mkNameL :: String -> Uniq -> Name
794 795
mkNameL s (I# u) = Name (mkOccName s) (NameL u)

aavogt's avatar
aavogt committed
796 797 798
-- | 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
799
  = Name (mkOccName occ) (NameG ns (mkPkgName pkg) (mkModName modu))
800

801
mkNameG_v, mkNameG_tc, mkNameG_d :: String -> String -> String -> Name
802 803 804 805 806 807 808 809 810 811 812 813 814 815 816
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
817
	-- NameS < NameQ < NameU < NameL < NameG
818
  NameS `compare` NameS = EQ
Ian Lynagh's avatar
Ian Lynagh committed
819
  NameS `compare` _     = LT
820

821 822
  (NameQ _)  `compare` NameS      = GT
  (NameQ m1) `compare` (NameQ m2) = m1 `compare` m2
Ian Lynagh's avatar
Ian Lynagh committed
823
  (NameQ _)  `compare` _          = LT
824 825 826

  (NameU _)  `compare` NameS      = GT
  (NameU _)  `compare` (NameQ _)  = GT
827 828 829
  (NameU u1) `compare` (NameU u2) | isTrue# (u1  <# u2) = LT
				  | isTrue# (u1 ==# u2) = EQ
				  | otherwise           = GT
Ian Lynagh's avatar
Ian Lynagh committed
830
  (NameU _)  `compare` _     = LT
831

832 833 834
  (NameL _)  `compare` NameS      = GT
  (NameL _)  `compare` (NameQ _)  = GT
  (NameL _)  `compare` (NameU _)  = GT
835 836 837
  (NameL u1) `compare` (NameL u2) | isTrue# (u1  <# u2) = LT
				  | isTrue# (u1 ==# u2) = EQ
				  | otherwise           = GT
Ian Lynagh's avatar
Ian Lynagh committed
838
  (NameL _)  `compare` _          = LT
839

840 841
  (NameG ns1 p1 m1) `compare` (NameG ns2 p2 m2) = (ns1 `compare` ns2) `thenCmp`
                                            (p1 `compare` p2) `thenCmp`
842
					    (m1 `compare` m2)
Ian Lynagh's avatar
Ian Lynagh committed
843
  (NameG _ _ _)    `compare` _ = GT
844

Ian Lynagh's avatar
Ian Lynagh committed
845 846 847 848 849 850 851 852 853 854 855 856 857 858 859
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
860
    where
861 862 863 864 865
	-- 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.
866 867
	-- Ditto NameU and NameL
        nms = case nm of
Ian Lynagh's avatar
Ian Lynagh committed
868 869 870 871 872
                    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)
873 874 875

        pnam = classify nms

Ian Lynagh's avatar
Ian Lynagh committed
876 877
        -- True if we are function style, e.g. f, [], (,)
        -- False if we are operator style, e.g. +, :+
878
        classify "" = False -- shouldn't happen; . operator is handled below
Ian Lynagh's avatar
Ian Lynagh committed
879
        classify (x:xs) | isAlpha x || (x `elem` "_[]()") =
880 881 882 883
                            case dropWhile (/='.') xs of
                                  (_:xs') -> classify xs'
                                  []      -> True
                        | otherwise = False
884

885
instance Show Name where
Ian Lynagh's avatar
Ian Lynagh committed
886
  show = showName
887

888
-- Tuple data and type constructors
889 890 891 892
-- | Tuple data constructor
tupleDataName :: Int -> Name
-- | Tuple type constructor
tupleTypeName :: Int -> Name
893

894
tupleDataName 0 = mk_tup_name 0 DataName
895
tupleDataName 1 = error "tupleDataName 1"
896
tupleDataName n = mk_tup_name (n-1) DataName
897

898
tupleTypeName 0 = mk_tup_name 0 TcClsName
899
tupleTypeName 1 = error "tupleTypeName 1"
900
tupleTypeName n = mk_tup_name (n-1) TcClsName
901

Ian Lynagh's avatar
Ian Lynagh committed
902
mk_tup_name :: Int -> NameSpace -> Name
903
mk_tup_name n_commas space
Ian Lynagh's avatar
Ian Lynagh committed
904
  = Name occ (NameG space (mkPkgName "ghc-prim") tup_mod)
905 906
  where
    occ = mkOccName ('(' : replicate n_commas ',' ++ ")")
Ian Lynagh's avatar
Ian Lynagh committed
907
    tup_mod = mkModName "GHC.Tuple"
908

909
-- Unboxed tuple data and type constructors
910 911 912 913
-- | Unboxed tuple data constructor
unboxedTupleDataName :: Int -> Name
-- | Unboxed tuple type constructor
unboxedTupleTypeName :: Int -> Name
914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929

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"

930

931

932 933 934 935 936 937 938 939 940 941 942
-----------------------------------------------------
--		Locations
-----------------------------------------------------

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

943
type CharPos = (Int, Int)	-- ^ Line and character position
944

945

946 947 948 949 950 951
-----------------------------------------------------
--
--	The Info returned by reification
--
-----------------------------------------------------

aavogt's avatar
aavogt committed
952 953
-- | Obtained from 'reify' in the 'Q' Monad.
data Info
Jan Stolarek's avatar
Jan Stolarek committed
954
  =
955
  -- | A class, with a list of its visible instances
Jan Stolarek's avatar
Jan Stolarek committed
956
  ClassI
957 958
      Dec
      [InstanceDec]
Jan Stolarek's avatar
Jan Stolarek committed
959

960
  -- | A class method
961
  | ClassOpI
962 963 964 965
       Name
       Type
       ParentName
       Fixity
Jan Stolarek's avatar
Jan Stolarek committed
966

967
  -- | A \"plain\" type constructor. \"Fancier\" type constructors are returned using 'PrimTyConI' or 'FamilyI' as appropriate
Jan Stolarek's avatar
Jan Stolarek committed
968
  | TyConI
969 970
        Dec

971 972
  -- | A type or data family, with a list of its visible instances. A closed
  -- type family is returned with 0 instances.
Jan Stolarek's avatar
Jan Stolarek committed
973
  | FamilyI
974 975
        Dec
        [InstanceDec]
Jan Stolarek's avatar
Jan Stolarek committed
976

977
  -- | A \"primitive\" type constructor, which can't be expressed with a 'Dec'. Examples: @(->)@, @Int#@.
Jan Stolarek's avatar
Jan Stolarek committed
978
  | PrimTyConI
979 980 981
       Name
       Arity
       Unlifted
Jan Stolarek's avatar
Jan Stolarek committed
982

983
  -- | A data constructor
Jan Stolarek's avatar
Jan Stolarek committed
984
  | DataConI
985 986 987 988
       Name
       Type
       ParentName
       Fixity
989

Jan Stolarek's avatar
Jan Stolarek committed
990
  {- |
991
  A \"value\" variable (as opposed to a type variable, see 'TyVarI').
Jan Stolarek's avatar
Jan Stolarek committed
992 993 994

  The @Maybe Dec@ field contains @Just@ the declaration which
  defined the variable -- including the RHS of the declaration --
995 996 997 998 999
  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.
  -}
Jan Stolarek's avatar
Jan Stolarek committed
1000
  | VarI
1001 1002 1003 1004
       Name
       Type
       (Maybe Dec)
       Fixity
1005

Jan Stolarek's avatar
Jan Stolarek committed
1006
  {- |
1007
  A type variable.
Jan Stolarek's avatar
Jan Stolarek committed
1008

1009 1010 1011 1012
  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.
  -}
1013 1014 1015
  | TyVarI 	-- Scoped type variable
	Name
	Type	-- What it is bound to
1016
  deriving( Show, Data, Typeable )
1017

1018 1019 1020 1021 1022 1023
-- | Obtained from 'reifyModule' in the 'Q' Monad.
data ModuleInfo =
  -- | Contains the import list of the module.
  ModuleInfo [Module]
  deriving( Show, Data, Typeable )

Jan Stolarek's avatar
Jan Stolarek committed
1024
{- |
1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035
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.
1036
-- It is just a 'Dec', but guaranteed to be one of the following:
1037 1038 1039 1040 1041 1042
--
--   * 'InstanceD' (with empty @['Dec']@)
--
--   * 'DataInstD' or 'NewtypeInstD' (with empty derived @['Name']@)
--
--   * 'TySynInstD'
1043
type InstanceDec = Dec
1044

1045