DsMeta.hs 65.7 KB
Newer Older
1
-----------------------------------------------------------------------------
Simon Marlow's avatar
Simon Marlow committed
2 3 4
--
-- (c) The University of Glasgow 2006
--
5 6 7 8
-- The purpose of this module is to transform an HsExpr into a CoreExpr which
-- when evaluated, returns a (Meta.Q Meta.Exp) computation analogous to the
-- input HsExpr. We do this in the DsM monad, which supplies access to
-- CoreExpr's of the "smart constructors" of the Meta.Exp datatype.
9 10 11 12 13
--
-- It also defines a bunch of knownKeyNames, in the same way as is done
-- in prelude/PrelNames.  It's much more convenient to do it here, becuase
-- otherwise we have to recompile PrelNames whenever we add a Name, which is
-- a Royal Pain (triggers other recompilation).
14 15
-----------------------------------------------------------------------------

16
{-# OPTIONS -w #-}
17 18 19
-- The above warning supression flag is a temporary kludge.
-- While working on this module you are encouraged to remove it and fix
-- any warnings in the module. See
Ian Lynagh's avatar
Ian Lynagh committed
20
--     http://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#Warnings
21
-- for details
22

23 24
module DsMeta( dsBracket, 
	       templateHaskellNames, qTyConName, nameTyConName,
25 26 27
	       liftName, expQTyConName, patQTyConName, decQTyConName, typeQTyConName,
	       decTyConName, typeTyConName, mkNameG_dName, mkNameG_vName, mkNameG_tcName,
	       quoteExpName, quotePatName
28
	        ) where
29 30 31

import {-# SOURCE #-}	DsExpr ( dsExpr )

Simon Marlow's avatar
Simon Marlow committed
32 33
import MatchLit
import DsUtils
34 35
import DsMonad

36
import qualified Language.Haskell.TH as TH
37

38
import HsSyn
Simon Marlow's avatar
Simon Marlow committed
39 40 41 42 43 44
import Class
import PrelNames
-- To avoid clashes with DsMeta.varName we must make a local alias for
-- OccName.varName we do this by removing varName from the import of
-- OccName above, making a qualified instance of OccName and using
-- OccNameAlias.varName where varName ws previously used in this file.
45
import qualified OccName
46

Simon Marlow's avatar
Simon Marlow committed
47 48 49
import Module
import Id
import Name
50
import NameEnv
Simon Marlow's avatar
Simon Marlow committed
51 52 53
import TcType
import TyCon
import TysWiredIn
54
import CoreSyn
Simon Marlow's avatar
Simon Marlow committed
55 56 57 58 59
import CoreUtils
import SrcLoc
import PackageConfig
import Unique
import BasicTypes
60
import Outputable
Simon Marlow's avatar
Simon Marlow committed
61 62 63
import Bag
import FastString
import ForeignCall
64

Simon Marlow's avatar
Simon Marlow committed
65 66 67
import Data.Maybe
import Control.Monad
import Data.List
68 69 70
 
-----------------------------------------------------------------------------
dsBracket :: HsBracket Name -> [PendingSplice] -> DsM CoreExpr
71
-- Returns a CoreExpr of type TH.ExpQ
72 73 74
-- The quoted thing is parameterised over Name, even though it has
-- been type checked.  We don't want all those type decorations!

75 76
dsBracket brack splices
  = dsExtendMetaEnv new_bit (do_brack brack)
77
  where
78
    new_bit = mkNameEnv [(n, Splice (unLoc e)) | (n,e) <- splices]
79

80
    do_brack (VarBr n)  = do { MkC e1  <- lookupOcc n ; return e1 }
81 82
    do_brack (ExpBr e)  = do { MkC e1  <- repLE e     ; return e1 }
    do_brack (PatBr p)  = do { MkC p1  <- repLP p     ; return p1 }
83
    do_brack (TypBr t)  = do { MkC t1  <- repLTy t    ; return t1 }
84
    do_brack (DecBr ds) = do { MkC ds1 <- repTopDs ds ; return ds1 }
85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100

{- -------------- Examples --------------------

  [| \x -> x |]
====>
  gensym (unpackString "x"#) `bindQ` \ x1::String ->
  lam (pvar x1) (var x1)


  [| \x -> $(f [| x |]) |]
====>
  gensym (unpackString "x"#) `bindQ` \ x1::String ->
  lam (pvar x1) (f (var x1))
-}


101 102 103 104
-------------------------------------------------------
-- 			Declarations
-------------------------------------------------------

105
repTopDs :: HsGroup Name -> DsM (Core (TH.Q [TH.Dec]))
106
repTopDs group
107
 = do { let { bndrs = map unLoc (groupBinders group) } ;
108
	ss <- mkGenSyms bndrs ;
109

110 111 112 113 114
	-- Bind all the names mainly to avoid repeated use of explicit strings.
	-- Thus	we get
	--	do { t :: String <- genSym "T" ;
	--	     return (Data t [] ...more t's... }
	-- The other important reason is that the output must mention
115
	-- only "T", not "Foo:T" where Foo is the current module
116 117

	
118
	decls <- addBinds ss (do {
119
			val_ds  <- rep_val_binds (hs_valds group) ;
120
			tycl_ds <- mapM repTyClD (hs_tyclds group) ;
121
			inst_ds <- mapM repInstD' (hs_instds group) ;
122
			for_ds <- mapM repForD (hs_fords group) ;
123
			-- more needed
124
			return (de_loc $ sort_by_loc $ val_ds ++ catMaybes tycl_ds ++ inst_ds ++ for_ds) }) ;
125

126
	decl_ty <- lookupType decQTyConName ;
127
	let { core_list = coreList' decl_ty decls } ;
128 129 130

	dec_ty <- lookupType decTyConName ;
	q_decs  <- repSequenceQ dec_ty core_list ;
131 132

	wrapNongenSyms ss q_decs
133 134 135 136 137
	-- Do *not* gensym top-level binders
      }

groupBinders (HsGroup { hs_valds = val_decls, hs_tyclds = tycl_decls,
			hs_fords = foreign_decls })
138
-- Collect the binders of a Group
139
  = collectHsValBinders val_decls ++
140
    [n | d <- tycl_decls, n <- tyClDeclNames (unLoc d)] ++
141
    [n | L _ (ForeignImport n _ _) <- foreign_decls]
142 143


144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161
{- 	Note [Binders and occurrences]
	~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we desugar [d| data T = MkT |]
we want to get
	Data "T" [] [Con "MkT" []] []
and *not*
	Data "Foo:T" [] [Con "Foo:MkT" []] []
That is, the new data decl should fit into whatever new module it is
asked to fit in.   We do *not* clone, though; no need for this:
	Data "T79" ....

But if we see this:
	data T = MkT 
	foo = reifyDecl T

then we must desugar to
	foo = Data "Foo:T" [] [Con "Foo:MkT" []] []

162 163
So in repTopDs we bring the binders into scope with mkGenSyms and addBinds.
And we use lookupOcc, rather than lookupBinder
164 165 166 167
in repTyClD and repC.

-}

168
repTyClD :: LTyClDecl Name -> DsM (Maybe (SrcSpan, Core TH.DecQ))
169

170 171 172 173
repTyClD (L loc (TyData { tcdND = DataType, tcdCtxt = cxt, 
		    tcdLName = tc, tcdTyVars = tvs, 
		    tcdCons = cons, tcdDerivs = mb_derivs }))
 = do { tc1 <- lookupLOcc tc ;		-- See note [Binders and occurrences] 
174
        dec <- addTyVarBinds tvs $ \bndrs -> do {
175
      	       cxt1    <- repLContext cxt ;
176
               cons1   <- mapM repC cons ;
177
      	       cons2   <- coreList conQTyConName cons1 ;
178
      	       derivs1 <- repDerivs mb_derivs ;
179 180
	       bndrs1  <- coreList nameTyConName bndrs ;
      	       repData cxt1 tc1 bndrs1 cons2 derivs1 } ;
181
        return $ Just (loc, dec) }
182

183 184 185 186
repTyClD (L loc (TyData { tcdND = NewType, tcdCtxt = cxt, 
		    tcdLName = tc, tcdTyVars = tvs, 
		    tcdCons = [con], tcdDerivs = mb_derivs }))
 = do { tc1 <- lookupLOcc tc ;		-- See note [Binders and occurrences] 
187
        dec <- addTyVarBinds tvs $ \bndrs -> do {
188
      	       cxt1   <- repLContext cxt ;
189 190
               con1   <- repC con ;
      	       derivs1 <- repDerivs mb_derivs ;
191 192
	       bndrs1  <- coreList nameTyConName bndrs ;
      	       repNewtype cxt1 tc1 bndrs1 con1 derivs1 } ;
193 194
        return $ Just (loc, dec) }

195 196
repTyClD (L loc (TySynonym { tcdLName = tc, tcdTyVars = tvs, tcdSynRhs = ty }))
 = do { tc1 <- lookupLOcc tc ;		-- See note [Binders and occurrences] 
197
        dec <- addTyVarBinds tvs $ \bndrs -> do {
198
	       ty1     <- repLTy ty ;
199 200
	       bndrs1  <- coreList nameTyConName bndrs ;
	       repTySyn tc1 bndrs1 ty1 } ;
201
 	return (Just (loc, dec)) }
202

203
repTyClD (L loc (ClassDecl { tcdCtxt = cxt, tcdLName = cls, 
204
		      tcdTyVars = tvs, 
205
		      tcdFDs = fds,
206 207
		      tcdSigs = sigs, tcdMeths = meth_binds }))
 = do { cls1 <- lookupLOcc cls ;		-- See note [Binders and occurrences] 
208
    	dec  <- addTyVarBinds tvs $ \bndrs -> do {
209
 		  cxt1   <- repLContext cxt ;
210
 		  sigs1  <- rep_sigs sigs ;
211
 		  binds1 <- rep_binds meth_binds ;
212
	          fds1 <- repLFunDeps fds;
213
 		  decls1 <- coreList decQTyConName (sigs1 ++ binds1) ;
214
	          bndrs1 <- coreList nameTyConName bndrs ;
215
 		  repClass cxt1 cls1 bndrs1 fds1 decls1 } ;
216
    	return $ Just (loc, dec) }
217 218

-- Un-handled cases
219
repTyClD (L loc d) = putSrcSpanDs loc $
220
		     do { warnDs (hang ds_msg 4 (ppr d))
221
			; return Nothing }
222

223 224 225 226 227 228 229 230 231 232 233 234 235
-- represent fundeps
--
repLFunDeps :: [Located (FunDep Name)] -> DsM (Core [TH.FunDep])
repLFunDeps fds = do fds' <- mapM repLFunDep fds
                     fdList <- coreList funDepTyConName fds'
                     return fdList

repLFunDep :: Located (FunDep Name) -> DsM (Core TH.FunDep)
repLFunDep (L _ (xs, ys)) = do xs' <- mapM lookupBinder xs
                               ys' <- mapM lookupBinder ys
                               xs_list <- coreList nameTyConName xs'
                               ys_list <- coreList nameTyConName ys'
                               repFunDep xs_list ys_list
236

237
repInstD' (L loc (InstDecl ty binds _ _))		-- Ignore user pragmas for now
238 239 240 241 242 243 244 245 246 247 248 249 250 251
 = do	{ i <- addTyVarBinds tvs $ \tv_bndrs ->
		-- We must bring the type variables into scope, so their occurrences
		-- don't fail,  even though the binders don't appear in the resulting 
		-- data structure
		do {  cxt1 <- repContext cxt
		   ; inst_ty1 <- repPred (HsClassP cls tys)
		   ; ss <- mkGenSyms (collectHsBindBinders binds)
		   ; binds1 <- addBinds ss (rep_binds binds)
		   ; decls1 <- coreList decQTyConName binds1
		   ; decls2 <- wrapNongenSyms ss decls1
		   -- wrapNonGenSyms: do not clone the class op names!
		   -- They must be called 'op' etc, not 'op34'
		   ; repInst cxt1 inst_ty1 decls2 }

252
	; return (loc, i)}
253
 where
254
   (tvs, cxt, cls, tys) = splitHsInstDeclTy (unLoc ty)
255

256
repForD :: Located (ForeignDecl Name) -> DsM (SrcSpan, Core TH.DecQ)
257
repForD (L loc (ForeignImport name typ (CImport cc s ch cn cis)))
258 259 260 261
 = do MkC name' <- lookupLOcc name
      MkC typ' <- repLTy typ
      MkC cc' <- repCCallConv cc
      MkC s' <- repSafety s
262
      cis' <- conv_cimportspec cis
263 264 265
      MkC str <- coreStringLit $ static
                              ++ unpackFS ch ++ " "
                              ++ unpackFS cn ++ " "
266
                              ++ cis'
267 268 269
      dec <- rep2 forImpDName [cc', s', str, name', typ']
      return (loc, dec)
 where
270 271 272 273
    conv_cimportspec (CLabel cls) = notHandled "Foreign label" (doubleQuotes (ppr cls))
    conv_cimportspec (CFunction DynamicTarget) = return "dynamic"
    conv_cimportspec (CFunction (StaticTarget fs)) = return (unpackFS fs)
    conv_cimportspec CWrapper = return "wrapper"
274 275 276
    static = case cis of
                 CFunction (StaticTarget _) -> "static "
                 _ -> ""
277
repForD decl = notHandled "Foreign declaration" (ppr decl)
278 279 280 281 282 283 284 285 286 287

repCCallConv :: CCallConv -> DsM (Core TH.Callconv)
repCCallConv CCallConv = rep2 cCallName []
repCCallConv StdCallConv = rep2 stdCallName []

repSafety :: Safety -> DsM (Core TH.Safety)
repSafety PlayRisky = rep2 unsafeName []
repSafety (PlaySafe False) = rep2 safeName []
repSafety (PlaySafe True) = rep2 threadsafeName []

Ian Lynagh's avatar
Ian Lynagh committed
288
ds_msg = ptext (sLit "Cannot desugar this Template Haskell declaration:")
289

290 291 292 293
-------------------------------------------------------
-- 			Constructors
-------------------------------------------------------

294
repC :: LConDecl Name -> DsM (Core TH.ConQ)
295
repC (L loc (ConDecl con expl [] (L _ []) details ResTyH98 _))
296
  = do { con1 <- lookupLOcc con ;		-- See note [Binders and occurrences] 
297
	 repConstr con1 details }
298
repC (L loc (ConDecl con expl tvs (L cloc ctxt) details ResTyH98 doc))
299
  = do { addTyVarBinds tvs $ \bndrs -> do {
300
             c' <- repC (L loc (ConDecl con expl [] (L cloc []) details ResTyH98 doc));
301 302 303 304 305
             ctxt' <- repContext ctxt;
             bndrs' <- coreList nameTyConName bndrs;
             rep2 forallCName [unC bndrs', unC ctxt', unC c']
         }
       }
306
repC (L loc con_decl)		-- GADTs
307 308
  = putSrcSpanDs loc $
    notHandled "GADT declaration" (ppr con_decl) 
309

310
repBangTy :: LBangType Name -> DsM (Core (TH.StrictTypeQ))
311 312 313
repBangTy ty= do 
  MkC s <- rep2 str []
  MkC t <- repLTy ty'
314
  rep2 strictTypeName [s, t]
315 316 317 318
  where 
    (str, ty') = case ty of
		   L _ (HsBangTy _ ty) -> (isStrictName,  ty)
		   other	       -> (notStrictName, ty)
319 320 321 322 323

-------------------------------------------------------
-- 			Deriving clause
-------------------------------------------------------

324
repDerivs :: Maybe [LHsType Name] -> DsM (Core [TH.Name])
325
repDerivs Nothing = coreList nameTyConName []
326
repDerivs (Just ctxt)
327
  = do { strs <- mapM rep_deriv ctxt ; 
328
	 coreList nameTyConName strs }
329
  where
330
    rep_deriv :: LHsType Name -> DsM (Core TH.Name)
331
	-- Deriving clauses must have the simple H98 form
332
    rep_deriv (L _ (HsPredTy (HsClassP cls []))) = lookupOcc cls
333
    rep_deriv other = notHandled "Non-H98 deriving clause" (ppr other)
334 335 336 337 338 339


-------------------------------------------------------
--   Signatures in a class decl, or a group of bindings
-------------------------------------------------------

340
rep_sigs :: [LSig Name] -> DsM [Core TH.DecQ]
341 342 343
rep_sigs sigs = do locs_cores <- rep_sigs' sigs
                   return $ de_loc $ sort_by_loc locs_cores

344
rep_sigs' :: [LSig Name] -> DsM [(SrcSpan, Core TH.DecQ)]
345
	-- We silently ignore ones we don't recognise
346
rep_sigs' sigs = do { sigs1 <- mapM rep_sig sigs ;
347 348
		     return (concat sigs1) }

349
rep_sig :: LSig Name -> DsM [(SrcSpan, Core TH.DecQ)]
350 351
	-- Singleton => Ok
	-- Empty     => Too hard, signature ignored
352 353
rep_sig (L loc (TypeSig nm ty)) = rep_proto nm ty loc
rep_sig other		        = return []
354

355 356 357
rep_proto :: Located Name -> LHsType Name -> SrcSpan -> DsM [(SrcSpan, Core TH.DecQ)]
rep_proto nm ty loc = do { nm1 <- lookupLOcc nm ; 
		       ty1 <- repLTy ty ; 
358
		       sig <- repProto nm1 ty1 ;
359
		       return [(loc, sig)] }
360 361 362 363 364


-------------------------------------------------------
-- 			Types
-------------------------------------------------------
365

366 367
-- gensym a list of type variables and enter them into the meta environment;
-- the computations passed as the second argument is executed in that extended
368
-- meta environment and gets the *new* names on Core-level as an argument
369
--
370
addTyVarBinds :: [LHsTyVarBndr Name]	         -- the binders to be added
371 372
	      -> ([Core TH.Name] -> DsM (Core (TH.Q a))) -- action in the ext env
	      -> DsM (Core (TH.Q a))
373
addTyVarBinds tvs m =
374
  do
375
    let names = map (hsTyVarName.unLoc) tvs
376
    freshNames <- mkGenSyms names
377 378 379
    term       <- addBinds freshNames $ do
		    bndrs <- mapM lookupBinder names 
		    m bndrs
380
    wrapGenSyns freshNames term
381

382 383
-- represent a type context
--
384 385 386
repLContext :: LHsContext Name -> DsM (Core TH.CxtQ)
repLContext (L _ ctxt) = repContext ctxt

387
repContext :: HsContext Name -> DsM (Core TH.CxtQ)
388
repContext ctxt = do 
389
	            preds    <- mapM repLPred ctxt
390
		    predList <- coreList typeQTyConName preds
391
		    repCtxt predList
392

393 394
-- represent a type predicate
--
395 396 397
repLPred :: LHsPred Name -> DsM (Core TH.TypeQ)
repLPred (L _ p) = repPred p

398
repPred :: HsPred Name -> DsM (Core TH.TypeQ)
399 400
repPred (HsClassP cls tys) = do
			       tcon <- repTy (HsTyVar cls)
401
			       tys1 <- repLTys tys
402
			       repTapps tcon tys1
403
repPred p@(HsEqualP _ _) = notHandled "Equational constraint" (ppr p)
404
repPred p@(HsIParam _ _) = notHandled "Implicit parameter constraint" (ppr p)
405 406 407

-- yield the representation of a list of types
--
408 409
repLTys :: [LHsType Name] -> DsM [Core TH.TypeQ]
repLTys tys = mapM repLTy tys
410

411 412
-- represent a type
--
413 414 415
repLTy :: LHsType Name -> DsM (Core TH.TypeQ)
repLTy (L _ ty) = repTy ty

416 417 418
repTy :: HsType Name -> DsM (Core TH.TypeQ)
repTy (HsForAllTy _ tvs ctxt ty)  = 
  addTyVarBinds tvs $ \bndrs -> do
419 420
    ctxt1  <- repLContext ctxt
    ty1    <- repLTy ty
421 422
    bndrs1 <- coreList nameTyConName bndrs
    repTForall bndrs1 ctxt1 ty1
423

424
repTy (HsTyVar n)
425
  | isTvOcc (nameOccName n)       = do 
426
				      tv1 <- lookupTvOcc n
427 428 429 430 431
				      repTvar tv1
  | otherwise		          = do 
				      tc1 <- lookupOcc n
				      repNamedTyCon tc1
repTy (HsAppTy f a)               = do 
432 433
				      f1 <- repLTy f
				      a1 <- repLTy a
434 435
				      repTapp f1 a1
repTy (HsFunTy f a)               = do 
436 437
				      f1   <- repLTy f
				      a1   <- repLTy a
438 439 440
				      tcon <- repArrowTyCon
				      repTapps tcon [f1, a1]
repTy (HsListTy t)		  = do
441
				      t1   <- repLTy t
442 443 444
				      tcon <- repListTyCon
				      repTapp tcon t1
repTy (HsPArrTy t)                = do
445
				      t1   <- repLTy t
446
				      tcon <- repTy (HsTyVar (tyConName parrTyCon))
447 448
				      repTapp tcon t1
repTy (HsTupleTy tc tys)	  = do
449
				      tys1 <- repLTys tys 
450 451
				      tcon <- repTupleTyCon (length tys)
				      repTapps tcon tys1
452 453 454
repTy (HsOpTy ty1 n ty2) 	  = repLTy ((nlHsTyVar (unLoc n) `nlHsAppTy` ty1) 
					   `nlHsAppTy` ty2)
repTy (HsParTy t)  	       	  = repLTy t
455
repTy (HsPredTy pred)             = repPred pred
456 457
repTy ty@(HsNumTy _)              = notHandled "Number types (for generics)" (ppr ty)
repTy ty			  = notHandled "Exotic form of type" (ppr ty)
458 459


460
-----------------------------------------------------------------------------
461
-- 		Expressions
462
-----------------------------------------------------------------------------
463

464 465 466
repLEs :: [LHsExpr Name] -> DsM (Core [TH.ExpQ])
repLEs es = do { es'  <- mapM repLE es ;
		 coreList expQTyConName es' }
467

468 469 470
-- FIXME: some of these panics should be converted into proper error messages
--	  unless we can make sure that constructs, which are plainly not
--	  supported in TH already lead to error messages at an earlier stage
471
repLE :: LHsExpr Name -> DsM (Core TH.ExpQ)
472
repLE (L loc e) = putSrcSpanDs loc (repE e)
473

474
repE :: HsExpr Name -> DsM (Core TH.ExpQ)
475 476 477
repE (HsVar x)            =
  do { mb_val <- dsLookupMetaEnv x 
     ; case mb_val of
478
	Nothing	         -> do { str <- globalVar x
479 480 481 482
			       ; repVarOrCon x str }
	Just (Bound y)   -> repVarOrCon x (coreVar y)
	Just (Splice e)  -> do { e' <- dsExpr e
			       ; return (MkC e') } }
483
repE e@(HsIPVar x) = notHandled "Implicit parameters" (ppr e)
484 485 486 487 488

	-- Remember, we're desugaring renamer output here, so
	-- HsOverlit can definitely occur
repE (HsOverLit l) = do { a <- repOverloadedLiteral l; repLit a }
repE (HsLit l)     = do { a <- repLiteral l;           repLit a }
489
repE (HsLam (MatchGroup [m] _)) = repLambda m
490
repE (HsApp x y)   = do {a <- repLE x; b <- repLE y; repApp a b}
491

492
repE (OpApp e1 op fix e2) =
493 494 495
  do { arg1 <- repLE e1; 
       arg2 <- repLE e2; 
       the_op <- repLE op ;
496
       repInfixApp arg1 the_op arg2 } 
497
repE (NegApp x nm)        = do
498
			      a         <- repLE x
499 500
			      negateVar <- lookupOcc negateName >>= repVar
			      negateVar `repApp` a
501 502 503
repE (HsPar x)            = repLE x
repE (SectionL x y)       = do { a <- repLE x; b <- repLE y; repSectionL a b } 
repE (SectionR x y)       = do { a <- repLE x; b <- repLE y; repSectionR a b } 
504 505 506
repE (HsCase e (MatchGroup ms _)) = do { arg <- repLE e
				       ; ms2 <- mapM repMatchTup ms
				       ; repCaseE arg (nonEmptyCoreList ms2) }
507 508 509 510
repE (HsIf x y z)         = do
			      a <- repLE x
			      b <- repLE y
			      c <- repLE z
511 512
			      repCond a b c
repE (HsLet bs e)         = do { (ss,ds) <- repBinds bs
513
			       ; e2 <- addBinds ss (repLE e)
514
			       ; z <- repLetE ds e2
515
			       ; wrapGenSyns ss z }
516
-- FIXME: I haven't got the types here right yet
517
repE (HsDo DoExpr sts body ty) 
518
 = do { (ss,zs) <- repLSts sts; 
519
	body'	<- addBinds ss $ repLE body;
520 521
	ret	<- repNoBindSt body';	
        e       <- repDoE (nonEmptyCoreList (zs ++ [ret]));
522
        wrapGenSyns ss e }
523
repE (HsDo ListComp sts body ty) 
524
 = do { (ss,zs) <- repLSts sts; 
525
	body'	<- addBinds ss $ repLE body;
526 527
	ret	<- repNoBindSt body';	
        e       <- repComp (nonEmptyCoreList (zs ++ [ret]));
528
        wrapGenSyns ss e }
529
repE e@(HsDo _ _ _ _) = notHandled "mdo and [: :]" (ppr e)
530
repE (ExplicitList ty es) = do { xs <- repLEs es; repListExp xs } 
531 532
repE e@(ExplicitPArr ty es) = notHandled "Parallel arrays" (ppr e)
repE e@(ExplicitTuple es boxed) 
533
  | isBoxed boxed         = do { xs <- repLEs es; repTup xs }
534
  | otherwise		  = notHandled "Unboxed tuples" (ppr e)
535
repE (RecordCon c _ flds)
536
 = do { x <- lookupLOcc c;
537 538
        fs <- repFields flds;
        repRecCon x fs }
539
repE (RecordUpd e flds _ _ _)
540
 = do { x <- repLE e;
541 542
        fs <- repFields flds;
        repRecUpd x fs }
543

544
repE (ExprWithTySig e ty) = do { e1 <- repLE e; t1 <- repLTy ty; repSigExp e1 t1 }
545
repE (ArithSeq _ aseq) =
546
  case aseq of
547
    From e              -> do { ds1 <- repLE e; repFrom ds1 }
548
    FromThen e1 e2      -> do 
549 550
		             ds1 <- repLE e1
			     ds2 <- repLE e2
551 552
			     repFromThen ds1 ds2
    FromTo   e1 e2      -> do 
553 554
			     ds1 <- repLE e1
			     ds2 <- repLE e2
555 556
			     repFromTo ds1 ds2
    FromThenTo e1 e2 e3 -> do 
557 558 559
			     ds1 <- repLE e1
			     ds2 <- repLE e2
			     ds3 <- repLE e3
560
			     repFromThenTo ds1 ds2 ds3
561 562 563 564 565
repE (HsSpliceE (HsSplice n _)) 
  = do { mb_val <- dsLookupMetaEnv n
       ; case mb_val of
		 Just (Splice e) -> do { e' <- dsExpr e
				       ; return (MkC e') }
566 567
		 other -> pprPanic "HsSplice" (ppr n) }
			-- Should not happen; statically checked
568

569 570 571
repE e@(PArrSeq {})      = notHandled "Parallel arrays" (ppr e)
repE e@(HsCoreAnn {})    = notHandled "Core annotations" (ppr e)
repE e@(HsSCC {})        = notHandled "Cost centres" (ppr e)
andy@galois.com's avatar
andy@galois.com committed
572
repE e@(HsTickPragma {}) = notHandled "Tick Pragma" (ppr e)
573 574
repE e@(HsBracketOut {}) = notHandled "TH brackets" (ppr e)
repE e 			 = notHandled "Expression form" (ppr e)
575 576 577 578

-----------------------------------------------------------------------------
-- Building representations of auxillary structures like Match, Clause, Stmt, 

579
repMatchTup ::  LMatch Name -> DsM (Core TH.MatchQ) 
580
repMatchTup (L _ (Match [p] ty (GRHSs guards wheres))) =
581
  do { ss1 <- mkGenSyms (collectPatBinders p) 
582
     ; addBinds ss1 $ do {
583
     ; p1 <- repLP p
584
     ; (ss2,ds) <- repBinds wheres
585 586 587
     ; addBinds ss2 $ do {
     ; gs    <- repGuards guards
     ; match <- repMatch p1 gs ds
588
     ; wrapGenSyns (ss1++ss2) match }}}
589
repMatchTup other = panic "repMatchTup: case alt with more than one arg"
590

591
repClauseTup ::  LMatch Name -> DsM (Core TH.ClauseQ)
592
repClauseTup (L _ (Match ps ty (GRHSs guards wheres))) =
593
  do { ss1 <- mkGenSyms (collectPatsBinders ps) 
594
     ; addBinds ss1 $ do {
595
       ps1 <- repLPs ps
596
     ; (ss2,ds) <- repBinds wheres
597 598 599
     ; addBinds ss2 $ do {
       gs <- repGuards guards
     ; clause <- repClause ps1 gs ds
600
     ; wrapGenSyns (ss1++ss2) clause }}}
601

602
repGuards ::  [LGRHS Name] ->  DsM (Core TH.BodyQ)
603
repGuards [L _ (GRHS [] e)]
604
  = do {a <- repLE e; repNormal a }
605
repGuards other 
606 607 608 609
  = do { zs <- mapM process other;
     let {(xs, ys) = unzip zs};
	 gd <- repGuarded (nonEmptyCoreList ys);
     wrapGenSyns (concat xs) gd }
610
  where 
611
    process :: LGRHS Name -> DsM ([GenSymBind], (Core (TH.Q (TH.Guard, TH.Exp))))
612
    process (L _ (GRHS [L _ (ExprStmt e1 _ _)] e2))
613 614
           = do { x <- repLNormalGE e1 e2;
                  return ([], x) }
615
    process (L _ (GRHS ss rhs))
616
           = do (gs, ss') <- repLSts ss
617
		rhs' <- addBinds gs $ repLE rhs
618
                g <- repPatGE (nonEmptyCoreList ss') rhs'
619
                return (gs, g)
620

621 622
repFields :: HsRecordBinds Name -> DsM (Core [TH.Q TH.FieldExp])
repFields (HsRecFields { rec_flds = flds })
623 624 625 626
  = do	{ fnames <- mapM lookupLOcc (map hsRecFieldId flds)
	; es <- mapM repLE (map hsRecFieldArg flds)
	; fs <- zipWithM repFieldExp fnames es
	; coreList fieldExpQTyConName fs }
627

628 629 630

-----------------------------------------------------------------------------
-- Representing Stmt's is tricky, especially if bound variables
631
-- shadow each other. Consider:  [| do { x <- f 1; x <- f x; g x } |]
632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653
-- First gensym new names for every variable in any of the patterns.
-- both static (x'1 and x'2), and dynamic ((gensym "x") and (gensym "y"))
-- if variables didn't shaddow, the static gensym wouldn't be necessary
-- and we could reuse the original names (x and x).
--
-- do { x'1 <- gensym "x"
--    ; x'2 <- gensym "x"   
--    ; doE [ BindSt (pvar x'1) [| f 1 |]
--          , BindSt (pvar x'2) [| f x |] 
--          , NoBindSt [| g x |] 
--          ]
--    }

-- The strategy is to translate a whole list of do-bindings by building a
-- bigger environment, and a bigger set of meta bindings 
-- (like:  x'1 <- gensym "x" ) and then combining these with the translations
-- of the expressions within the Do
      
-----------------------------------------------------------------------------
-- The helper function repSts computes the translation of each sub expression
-- and a bunch of prefix bindings denoting the dynamic renaming.

654 655 656
repLSts :: [LStmt Name] -> DsM ([GenSymBind], [Core TH.StmtQ])
repLSts stmts = repSts (map unLoc stmts)

657
repSts :: [Stmt Name] -> DsM ([GenSymBind], [Core TH.StmtQ])
658
repSts (BindStmt p e _ _ : ss) =
659
   do { e2 <- repLE e 
660
      ; ss1 <- mkGenSyms (collectPatBinders p) 
661
      ; addBinds ss1 $ do {
662
      ; p1 <- repLP p; 
663 664 665 666
      ; (ss2,zs) <- repSts ss
      ; z <- repBindSt p1 e2
      ; return (ss1++ss2, z : zs) }}
repSts (LetStmt bs : ss) =
667
   do { (ss1,ds) <- repBinds bs
668 669 670
      ; z <- repLetSt ds
      ; (ss2,zs) <- addBinds ss1 (repSts ss)
      ; return (ss1++ss2, z : zs) } 
671
repSts (ExprStmt e _ _ : ss) =       
672
   do { e2 <- repLE e
673 674 675
      ; z <- repNoBindSt e2 
      ; (ss2,zs) <- repSts ss
      ; return (ss2, z : zs) }
676 677
repSts []    = return ([],[])
repSts other = notHandled "Exotic statement" (ppr other)
678 679


680 681 682
-----------------------------------------------------------
--			Bindings
-----------------------------------------------------------
683

684 685 686 687 688
repBinds :: HsLocalBinds Name -> DsM ([GenSymBind], Core [TH.DecQ]) 
repBinds EmptyLocalBinds
  = do	{ core_list <- coreList decQTyConName []
	; return ([], core_list) }

689
repBinds b@(HsIPBinds _) = notHandled "Implicit parameters" (ppr b)
690 691 692

repBinds (HsValBinds decs)
 = do	{ let { bndrs = map unLoc (collectHsValBinders decs) }
693 694 695 696
		-- No need to worrry about detailed scopes within
		-- the binding group, because we are talking Names
		-- here, so we can safely treat it as a mutually 
		-- recursive group
697
	; ss        <- mkGenSyms bndrs
698 699 700
	; prs       <- addBinds ss (rep_val_binds decs)
	; core_list <- coreList decQTyConName 
				(de_loc (sort_by_loc prs))
701
	; return (ss, core_list) }
702

703
rep_val_binds :: HsValBinds Name -> DsM [(SrcSpan, Core TH.DecQ)]
704
-- Assumes: all the binders of the binding are alrady in the meta-env
705 706
rep_val_binds (ValBindsOut binds sigs)
 = do { core1 <- rep_binds' (unionManyBags (map snd binds))
707
      ;	core2 <- rep_sigs' sigs
708
      ;	return (core1 ++ core2) }
709 710
rep_val_binds (ValBindsIn binds sigs)
 = panic "rep_val_binds: ValBindsIn"
711

712
rep_binds :: LHsBinds Name -> DsM [Core TH.DecQ]
713 714 715 716 717
rep_binds binds = do { binds_w_locs <- rep_binds' binds
		     ; return (de_loc (sort_by_loc binds_w_locs)) }

rep_binds' :: LHsBinds Name -> DsM [(SrcSpan, Core TH.DecQ)]
rep_binds' binds = mapM rep_bind (bagToList binds)
718

719
rep_bind :: LHsBind Name -> DsM (SrcSpan, Core TH.DecQ)
720
-- Assumes: all the binders of the binding are alrady in the meta-env
721 722 723 724

-- Note GHC treats declarations of a variable (not a pattern) 
-- e.g.  x = g 5 as a Fun MonoBinds. This is indicated by a single match 
-- with an empty list of patterns
725 726
rep_bind (L loc (FunBind { fun_id = fn, 
			   fun_matches = MatchGroup [L _ (Match [] ty (GRHSs guards wheres))] _ }))
727
 = do { (ss,wherecore) <- repBinds wheres
728
	; guardcore <- addBinds ss (repGuards guards)
729 730 731 732 733
	; fn'  <- lookupLBinder fn
	; p    <- repPvar fn'
	; ans  <- repVal p guardcore wherecore
	; ans' <- wrapGenSyns ss ans
	; return (loc, ans') }
734

735
rep_bind (L loc (FunBind { fun_id = fn, fun_matches = MatchGroup ms _ }))
736
 =   do { ms1 <- mapM repClauseTup ms
737
	; fn' <- lookupLBinder fn
738
        ; ans <- repFun fn' (nonEmptyCoreList ms1)
739
        ; return (loc, ans) }
740

741
rep_bind (L loc (PatBind { pat_lhs = pat, pat_rhs = GRHSs guards wheres }))
742
 =   do { patcore <- repLP pat 
743
        ; (ss,wherecore) <- repBinds wheres
744
	; guardcore <- addBinds ss (repGuards guards)
745 746 747
        ; ans  <- repVal patcore guardcore wherecore
	; ans' <- wrapGenSyns ss ans
        ; return (loc, ans') }
748

749
rep_bind (L loc (VarBind { var_id = v, var_rhs = e}))
750
 =   do { v' <- lookupBinder v 
751
	; e2 <- repLE e
752 753
        ; x <- repNormal e2
        ; patcore <- repPvar v'
754
	; empty_decls <- coreList decQTyConName [] 
755
        ; ans <- repVal patcore x empty_decls
756
        ; return (srcLocSpan (getSrcLoc v), ans) }
757

758 759
rep_bind other = panic "rep_bind: AbsBinds"

760
-----------------------------------------------------------------------------
761
-- Since everything in a Bind is mutually recursive we need rename all
762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777
-- all the variables simultaneously. For example: 
-- [| AndMonoBinds (f x = x + g 2) (g x = f 1 + 2) |] would translate to
-- do { f'1 <- gensym "f"
--    ; g'2 <- gensym "g"
--    ; [ do { x'3 <- gensym "x"; fun f'1 [pvar x'3] [| x + g2 |]},
--        do { x'4 <- gensym "x"; fun g'2 [pvar x'4] [| f 1 + 2 |]}
--      ]}
-- This requires collecting the bindings (f'1 <- gensym "f"), and the 
-- environment ( f |-> f'1 ) from each binding, and then unioning them 
-- together. As we do this we collect GenSymBinds's which represent the renamed 
-- variables bound by the Bindings. In order not to lose track of these 
-- representations we build a shadow datatype MB with the same structure as 
-- MonoBinds, but which has slots for the representations


-----------------------------------------------------------------------------
778
-- GHC allows a more general form of lambda abstraction than specified
779 780 781 782 783
-- by Haskell 98. In particular it allows guarded lambda's like : 
-- (\  x | even x -> 0 | odd x -> 1) at the moment we can't represent this in
-- Haskell Template's Meta.Exp type so we punt if it isn't a simple thing like
-- (\ p1 .. pn -> exp) by causing an error.  

784
repLambda :: LMatch Name -> DsM (Core TH.ExpQ)
785
repLambda (L _ (Match ps _ (GRHSs [L _ (GRHS [] e)] EmptyLocalBinds)))
786
 = do { let bndrs = collectPatsBinders ps ;
787
      ; ss  <- mkGenSyms bndrs
788
      ; lam <- addBinds ss (
789
		do { xs <- repLPs ps; body <- repLE e; repLam xs body })
790
      ; wrapGenSyns ss lam }
791

792
repLambda (L _ m) = notHandled "Guarded labmdas" (pprMatch (LambdaExpr :: HsMatchContext Name) m)
793 794 795

  
-----------------------------------------------------------------------------
796
--			Patterns
797 798 799 800 801 802
-- repP deals with patterns.  It assumes that we have already
-- walked over the pattern(s) once to collect the binders, and 
-- have extended the environment.  So every pattern-bound 
-- variable should already appear in the environment.

-- Process a list of patterns
803
repLPs :: [LPat Name] -> DsM (Core [TH.PatQ])
804
repLPs ps = do { ps' <- mapM repLP ps ;
805
		 coreList patQTyConName ps' }
806

807
repLP :: LPat Name -> DsM (Core TH.PatQ)
808
repLP (L _ p) = repP p
809

810
repP :: Pat Name -> DsM (Core TH.PatQ)
811 812 813 814 815 816 817 818
repP (WildPat _)       = repPwild 
repP (LitPat l)        = do { l2 <- repLiteral l; repPlit l2 }
repP (VarPat x)        = do { x' <- lookupBinder x; repPvar x' }
repP (LazyPat p)       = do { p1 <- repLP p; repPtilde p1 }
repP (AsPat x p)       = do { x' <- lookupLBinder x; p1 <- repLP p; repPaspat x' p1 }
repP (ParPat p)        = repLP p 
repP (ListPat ps _)    = do { qs <- repLPs ps; repPlist qs }
repP (TuplePat ps _ _) = do { qs <- repLPs ps; repPtup qs }
819
repP (ConPatIn dc details)
820
 = do { con_str <- lookupLOcc dc
821
      ; case details of
822 823 824 825
         PrefixCon ps -> do { qs <- repLPs ps; repPcon con_str qs }
         RecCon rec   -> do { let flds = rec_flds rec
			    ; vs <- sequence $ map lookupLOcc (map hsRecFieldId flds)
                            ; ps <- sequence $ map repLP (map hsRecFieldArg flds)
826
                            ; fps <- zipWithM (\x y -> rep2 fieldPatName [unC x,unC y]) vs ps
827
                            ; fps' <- coreList fieldPatQTyConName fps
828
                            ; repPrec con_str fps' }
829 830 831
         InfixCon p1 p2 -> do { p1' <- repLP p1;
                                p2' <- repLP p2;
                                repPinfix p1' con_str p2' }
832
   }
833 834
repP (NPat l Nothing _)  = do { a <- repOverloadedLiteral l; repPlit a }
repP p@(NPat l (Just _) _) = notHandled "Negative overloaded patterns" (ppr p)
835 836 837 838 839 840 841 842 843
repP p@(SigPatIn {})  = notHandled "Type signatures in patterns" (ppr p)
	-- The problem is to do with scoped type variables.
	-- To implement them, we have to implement the scoping rules
	-- here in DsMeta, and I don't want to do that today!
	--	 do { p' <- repLP p; t' <- repLTy t; repPsig p' t' }
	--	repPsig :: Core TH.PatQ -> Core TH.TypeQ -> DsM (Core TH.PatQ)
	--	repPsig (MkC p) (MkC t) = rep2 sigPName [p, t]

repP other = notHandled "Exotic pattern" (ppr other)
844

845 846 847
----------------------------------------------------------
-- Declaration ordering helpers

848
sort_by_loc :: [(SrcSpan, a)] -> [(SrcSpan, a)]
849 850 851
sort_by_loc xs = sortBy comp xs
    where comp x y = compare (fst x) (fst y)

852
de_loc :: [(a, b)] -> [b]
853 854
de_loc = map snd

855 856 857
----------------------------------------------------------
--	The meta-environment

858
-- A name/identifier association for fresh names of locally bound entities
859 860 861 862
type GenSymBind = (Name, Id)	-- Gensym the string and bind it to the Id
				-- I.e.		(x, x_id) means
				--	let x_id = gensym "x" in ...

863
-- Generate a fresh name for a locally bound entity
864

865 866
mkGenSyms :: [Name] -> DsM [GenSymBind]
-- We can use the existing name.  For example:
867 868 869 870 871
--	[| \x_77 -> x_77 + x_77 |]
-- desugars to
--	do { x_77 <- genSym "x"; .... }
-- We use the same x_77 in the desugared program, but with the type Bndr
-- instead of Int
872
--
873 874 875 876 877 878
-- We do make it an Internal name, though (hence localiseName)
--
-- Nevertheless, it's monadic because we have to generate nameTy
mkGenSyms ns = do { var_ty <- lookupType nameTyConName
		  ; return [(nm, mkLocalId (localiseName nm) var_ty) | nm <- ns] }

879
	     
880
addBinds :: [GenSymBind] -> DsM a -> DsM a
881 882 883
-- Add a list of fresh names for locally bound entities to the 
-- meta environment (which is part of the state carried around 
-- by the desugarer monad) 
884 885 886 887
addBinds bs m = dsExtendMetaEnv (mkNameEnv [(n,Bound id) | (n,id) <- bs]) m

-- Look up a locally bound name
--
888 889 890
lookupLBinder :: Located Name -> DsM (Core TH.Name)
lookupLBinder (L _ n) = lookupBinder n

891
lookupBinder :: Name -> DsM (Core TH.Name)
892 893 894 895
lookupBinder n 
  = do { mb_val <- dsLookupMetaEnv n;
	 case mb_val of
	    Just (Bound x) -> return (coreVar x)
896 897
	    other	   -> failWithDs msg }
  where
Ian Lynagh's avatar
Ian Lynagh committed
898
    msg = ptext (sLit "DsMeta: failed binder lookup when desugaring a TH bracket:") <+> ppr n
899

900 901
-- Look up a name that is either locally bound or a global name
--
902
--  * If it is a global name, generate the "original name" representation (ie,
903 904
--   the <module>:<name> form) for the associated entity
--
905
lookupLOcc :: Located Name -> DsM (Core TH.Name)
906 907
-- Lookup an occurrence; it can't be a splice.
-- Use the in-scope bindings if they exist
908 909 910
lookupLOcc (L _ n) = lookupOcc n

lookupOcc :: Name -> DsM (Core TH.Name)
911 912 913 914 915 916 917 918
lookupOcc n
  = do {  mb_val <- dsLookupMetaEnv n ;
          case mb_val of
		Nothing         -> globalVar n
		Just (Bound x)  -> return (coreVar x)
		Just (Splice _) -> pprPanic "repE:lookupOcc" (ppr n) 
    }

919 920 921 922 923 924 925 926 927
lookupTvOcc :: Name -> DsM (Core TH.Name)
-- Type variables can't be staged and are not lexically scoped in TH
lookupTvOcc n	
  = do {  mb_val <- dsLookupMetaEnv n ;
          case mb_val of
		Just (Bound x)  -> return (coreVar x)
		other	        -> failWithDs msg
    }
  where
Ian Lynagh's avatar
Ian Lynagh committed
928 929
    msg = vcat  [ ptext (sLit "Illegal lexically-scoped type variable") <+> quotes (ppr n)
		, ptext (sLit "Lexically scoped type variables are not supported by Template Haskell") ]
<