summaryrefslogtreecommitdiff
path: root/compiler/hsSyn/HsUtils.lhs
blob: eff67df3cfbe4bc61cef0f585957363e44912af9 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
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
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
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
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
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
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
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
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
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
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
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
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
%
% (c) The University of Glasgow, 1992-2006
%

Here we collect a variety of helper functions that construct or
analyse HsSyn.  All these functions deal with generic HsSyn; functions
which deal with the intantiated versions are located elsewhere:

   Parameterised by	Module
   ----------------     -------------
   RdrName		parser/RdrHsSyn
   Name			rename/RnHsSyn
   Id			typecheck/TcHsSyn	

\begin{code}
{-# OPTIONS -fno-warn-tabs #-}
-- The above warning supression flag is a temporary kludge.
-- While working on this module you are encouraged to remove it and
-- detab the module (please do the detabbing in a separate patch). See
--     http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
-- for details

module HsUtils(
  -- Terms
  mkHsPar, mkHsApp, mkHsConApp, mkSimpleHsAlt,
  mkSimpleMatch, unguardedGRHSs, unguardedRHS, 
  mkMatchGroup, mkMatch, mkHsLam, mkHsIf,
  mkHsWrap, mkLHsWrap, mkHsWrapCo, mkLHsWrapCo,
  coToHsWrapper, mkHsDictLet, mkHsLams,
  mkHsOpApp, mkHsDo, mkHsComp, mkHsWrapPat, mkHsWrapPatCo,
  mkLHsPar, mkHsCmdCast,

  nlHsTyApp, nlHsVar, nlHsLit, nlHsApp, nlHsApps, nlHsIntLit, nlHsVarApps, 
  nlHsDo, nlHsOpApp, nlHsLam, nlHsPar, nlHsIf, nlHsCase, nlList,
  mkLHsTupleExpr, mkLHsVarTuple, missingTupArg,
  toHsType, toHsKind,

  -- Bindings
  mkFunBind, mkVarBind, mkHsVarBind, mk_easy_FunBind, mkTopFunBind, mkPatSynBind,

  -- Literals
  mkHsIntegral, mkHsFractional, mkHsIsString, mkHsString, 

  -- Patterns
  mkNPat, mkNPlusKPat, nlVarPat, nlLitPat, nlConVarPat, nlConPat, nlInfixConPat,
  nlNullaryConPat, nlWildConPat, nlWildPat, nlTuplePat, mkParPat,

  -- Types
  mkHsAppTy, userHsTyVarBndrs,
  nlHsAppTy, nlHsTyVar, nlHsFunTy, nlHsTyConApp, 

  -- Stmts
  mkTransformStmt, mkTransformByStmt, mkBodyStmt, mkBindStmt, mkLastStmt,
  emptyTransStmt, mkGroupUsingStmt, mkGroupByUsingStmt, 
  emptyRecStmt, mkRecStmt, 

  -- Template Haskell
  mkHsSpliceTy, mkHsSpliceE, mkHsSpliceTE, mkHsSplice,
  mkHsQuasiQuote, unqualQuasiQuote,

  -- Flags
  noRebindableInfo, 

  -- Collecting binders
  collectLocalBinders, collectHsValBinders, collectHsBindListBinders,
  collectHsBindsBinders, collectHsBindBinders, collectMethodBinders,
  collectPatBinders, collectPatsBinders,
  collectLStmtsBinders, collectStmtsBinders,
  collectLStmtBinders, collectStmtBinders,

  hsLTyClDeclBinders, hsTyClDeclsBinders, 
  hsForeignDeclsBinders, hsGroupBinders, hsDataFamInstBinders,
  
  -- Collecting implicit binders
  lStmtsImplicits, hsValBindsImplicits, lPatImplicits
  ) where

#include "HsVersions.h"

import HsDecls
import HsBinds
import HsExpr
import HsPat
import HsTypes	
import HsLit

import TcEvidence
import RdrName
import Var
import TypeRep
import TcType
import Kind
import DataCon
import Name
import NameSet
import BasicTypes
import SrcLoc
import FastString
import Util
import Bag
import Outputable
import Data.Either
\end{code}


%************************************************************************
%*									*
	Some useful helpers for constructing syntax
%*									*
%************************************************************************

These functions attempt to construct a not-completely-useless SrcSpan
from their components, compared with the nl* functions below which
just attach noSrcSpan to everything.

\begin{code}
mkHsPar :: LHsExpr id -> LHsExpr id
mkHsPar e = L (getLoc e) (HsPar e)

mkSimpleMatch :: [LPat id] -> Located (body id) -> LMatch id (Located (body id))
mkSimpleMatch pats rhs 
  = L loc $
    Match pats Nothing (unguardedGRHSs rhs)
  where
    loc = case pats of
		[]      -> getLoc rhs
		(pat:_) -> combineSrcSpans (getLoc pat) (getLoc rhs)

unguardedGRHSs :: Located (body id) -> GRHSs id (Located (body id))
unguardedGRHSs rhs = GRHSs (unguardedRHS rhs) emptyLocalBinds

unguardedRHS :: Located (body id) -> [LGRHS id (Located (body id))]
unguardedRHS rhs@(L loc _) = [L loc (GRHS [] rhs)]

mkMatchGroup :: Origin -> [LMatch id (Located (body id))] -> MatchGroup id (Located (body id))
mkMatchGroup origin matches = MG { mg_alts = matches, mg_arg_tys = [], mg_res_ty = placeHolderType, mg_origin = origin }

mkHsAppTy :: LHsType name -> LHsType name -> LHsType name
mkHsAppTy t1 t2 = addCLoc t1 t2 (HsAppTy t1 t2)

mkHsApp :: LHsExpr name -> LHsExpr name -> LHsExpr name
mkHsApp e1 e2 = addCLoc e1 e2 (HsApp e1 e2)

mkHsLam :: [LPat id] -> LHsExpr id -> LHsExpr id
mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam matches))
	where
          matches = mkMatchGroup Generated [mkSimpleMatch pats body]

mkHsLams :: [TyVar] -> [EvVar] -> LHsExpr Id -> LHsExpr Id
mkHsLams tyvars dicts expr = mkLHsWrap (mkWpTyLams tyvars <.> mkWpLams dicts) expr

mkHsConApp :: DataCon -> [Type] -> [HsExpr Id] -> LHsExpr Id
-- Used for constructing dictionary terms etc, so no locations 
mkHsConApp data_con tys args 
  = foldl mk_app (nlHsTyApp (dataConWrapId data_con) tys) args
  where
    mk_app f a = noLoc (HsApp f (noLoc a))

mkSimpleHsAlt :: LPat id -> (Located (body id)) -> LMatch id (Located (body id))
-- A simple lambda with a single pattern, no binds, no guards; pre-typechecking
mkSimpleHsAlt pat expr 
  = mkSimpleMatch [pat] expr

nlHsTyApp :: name -> [Type] -> LHsExpr name
nlHsTyApp fun_id tys = noLoc (HsWrap (mkWpTyApps tys) (HsVar fun_id))

--------- Adding parens ---------
mkLHsPar :: LHsExpr name -> LHsExpr name
-- Wrap in parens if hsExprNeedsParens says it needs them
-- So   'f x'  becomes '(f x)', but '3' stays as '3'
mkLHsPar le@(L loc e) | hsExprNeedsParens e = L loc (HsPar le)
                      | otherwise           = le

mkParPat :: LPat name -> LPat name
mkParPat lp@(L loc p) | hsPatNeedsParens p = L loc (ParPat lp)
                      | otherwise          = lp


-------------------------------
-- These are the bits of syntax that contain rebindable names
-- See RnEnv.lookupSyntaxName

mkHsIntegral   :: Integer -> PostTcType -> HsOverLit id
mkHsFractional :: FractionalLit -> PostTcType -> HsOverLit id
mkHsIsString   :: FastString -> PostTcType -> HsOverLit id
mkHsDo         :: HsStmtContext Name -> [ExprLStmt id] -> HsExpr id
mkHsComp       :: HsStmtContext Name -> [ExprLStmt id] -> LHsExpr id -> HsExpr id

mkNPat      :: HsOverLit id -> Maybe (SyntaxExpr id) -> Pat id
mkNPlusKPat :: Located id -> HsOverLit id -> Pat id

mkLastStmt :: Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR))
mkBodyStmt :: Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR))
mkBindStmt :: LPat idL -> Located (bodyR idR) -> StmtLR idL idR (Located (bodyR idR))

emptyRecStmt :: StmtLR idL idR bodyR
mkRecStmt    :: [LStmtLR idL idR bodyR] -> StmtLR idL idR bodyR


mkHsIntegral   i       = OverLit (HsIntegral   i)  noRebindableInfo noSyntaxExpr
mkHsFractional f       = OverLit (HsFractional f)  noRebindableInfo noSyntaxExpr
mkHsIsString   s       = OverLit (HsIsString   s)  noRebindableInfo noSyntaxExpr

noRebindableInfo :: Bool
noRebindableInfo = error "noRebindableInfo" 	-- Just another placeholder; 

mkHsDo ctxt stmts = HsDo ctxt stmts placeHolderType
mkHsComp ctxt stmts expr = mkHsDo ctxt (stmts ++ [last_stmt])
  where
    last_stmt = L (getLoc expr) $ mkLastStmt expr

mkHsIf :: LHsExpr id -> LHsExpr id -> LHsExpr id -> HsExpr id
mkHsIf c a b = HsIf (Just noSyntaxExpr) c a b

mkNPat lit neg     = NPat lit neg noSyntaxExpr
mkNPlusKPat id lit = NPlusKPat id lit noSyntaxExpr noSyntaxExpr

mkTransformStmt    :: [ExprLStmt idL] -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkTransformByStmt  :: [ExprLStmt idL] -> LHsExpr idR -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkGroupUsingStmt   :: [ExprLStmt idL]                -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)
mkGroupByUsingStmt :: [ExprLStmt idL] -> LHsExpr idR -> LHsExpr idR
                   -> StmtLR idL idR (LHsExpr idL)

emptyTransStmt :: StmtLR idL idR (LHsExpr idR)
emptyTransStmt = TransStmt { trS_form = panic "emptyTransStmt: form"
                           , trS_stmts = [], trS_bndrs = [] 
                           , trS_by = Nothing, trS_using = noLoc noSyntaxExpr
                           , trS_ret = noSyntaxExpr, trS_bind = noSyntaxExpr
                           , trS_fmap = noSyntaxExpr }
mkTransformStmt    ss u   = emptyTransStmt { trS_form = ThenForm,  trS_stmts = ss, trS_using = u }
mkTransformByStmt  ss u b = emptyTransStmt { trS_form = ThenForm,  trS_stmts = ss, trS_using = u, trS_by = Just b }
mkGroupUsingStmt   ss u   = emptyTransStmt { trS_form = GroupForm, trS_stmts = ss, trS_using = u }
mkGroupByUsingStmt ss b u = emptyTransStmt { trS_form = GroupForm, trS_stmts = ss, trS_using = u, trS_by = Just b }

mkLastStmt body     = LastStmt body noSyntaxExpr
mkBodyStmt body     = BodyStmt body noSyntaxExpr noSyntaxExpr placeHolderType
mkBindStmt pat body = BindStmt pat body noSyntaxExpr noSyntaxExpr

emptyRecStmt = RecStmt { recS_stmts = [], recS_later_ids = [], recS_rec_ids = []
                       , recS_ret_fn = noSyntaxExpr, recS_mfix_fn = noSyntaxExpr
                       , recS_bind_fn = noSyntaxExpr, recS_later_rets = []
                       , recS_rec_rets = [], recS_ret_ty = placeHolderType }

mkRecStmt stmts = emptyRecStmt { recS_stmts = stmts }

-------------------------------
--- A useful function for building @OpApps@.  The operator is always a
-- variable, and we don't know the fixity yet.
mkHsOpApp :: LHsExpr id -> id -> LHsExpr id -> HsExpr id
mkHsOpApp e1 op e2 = OpApp e1 (noLoc (HsVar op)) (error "mkOpApp:fixity") e2

mkHsSplice :: LHsExpr RdrName -> HsSplice RdrName
mkHsSplice e = HsSplice unqualSplice e

mkHsSpliceE :: LHsExpr RdrName -> HsExpr RdrName
mkHsSpliceE e = HsSpliceE False (mkHsSplice e)

mkHsSpliceTE :: LHsExpr RdrName -> HsExpr RdrName
mkHsSpliceTE e = HsSpliceE True (mkHsSplice e)

mkHsSpliceTy :: LHsExpr RdrName -> HsType RdrName
mkHsSpliceTy e = HsSpliceTy (mkHsSplice e) placeHolderKind

unqualSplice :: RdrName
unqualSplice = mkRdrUnqual (mkVarOccFS (fsLit "splice"))
		-- A name (uniquified later) to
		-- identify the splice

mkHsQuasiQuote :: RdrName -> SrcSpan -> FastString -> HsQuasiQuote RdrName
mkHsQuasiQuote quoter span quote = HsQuasiQuote quoter span quote

unqualQuasiQuote :: RdrName
unqualQuasiQuote = mkRdrUnqual (mkVarOccFS (fsLit "quasiquote"))
		-- A name (uniquified later) to
		-- identify the quasi-quote

mkHsString :: String -> HsLit
mkHsString s = HsString (mkFastString s)

-------------
userHsTyVarBndrs :: SrcSpan -> [name] -> [Located (HsTyVarBndr name)]
-- Caller sets location
userHsTyVarBndrs loc bndrs = [ L loc (UserTyVar v) | v <- bndrs ]
\end{code}


%************************************************************************
%*									*
	Constructing syntax with no location info
%*									*
%************************************************************************

\begin{code}
nlHsVar :: id -> LHsExpr id
nlHsVar n = noLoc (HsVar n)

nlHsLit :: HsLit -> LHsExpr id
nlHsLit n = noLoc (HsLit n)

nlVarPat :: id -> LPat id
nlVarPat n = noLoc (VarPat n)

nlLitPat :: HsLit -> LPat id
nlLitPat l = noLoc (LitPat l)

nlHsApp :: LHsExpr id -> LHsExpr id -> LHsExpr id
nlHsApp f x = noLoc (HsApp f x)

nlHsIntLit :: Integer -> LHsExpr id
nlHsIntLit n = noLoc (HsLit (HsInt n))

nlHsApps :: id -> [LHsExpr id] -> LHsExpr id
nlHsApps f xs = foldl nlHsApp (nlHsVar f) xs
	     
nlHsVarApps :: id -> [id] -> LHsExpr id
nlHsVarApps f xs = noLoc (foldl mk (HsVar f) (map HsVar xs))
		 where
		   mk f a = HsApp (noLoc f) (noLoc a)

nlConVarPat :: id -> [id] -> LPat id
nlConVarPat con vars = nlConPat con (map nlVarPat vars)

nlInfixConPat :: id -> LPat id -> LPat id -> LPat id
nlInfixConPat con l r = noLoc (ConPatIn (noLoc con) (InfixCon l r))

nlConPat :: id -> [LPat id] -> LPat id
nlConPat con pats = noLoc (ConPatIn (noLoc con) (PrefixCon pats))

nlNullaryConPat :: id -> LPat id
nlNullaryConPat con = noLoc (ConPatIn (noLoc con) (PrefixCon []))

nlWildConPat :: DataCon -> LPat RdrName
nlWildConPat con = noLoc (ConPatIn (noLoc (getRdrName con))
				   (PrefixCon (nOfThem (dataConSourceArity con) nlWildPat)))

nlWildPat :: LPat id
nlWildPat  = noLoc (WildPat placeHolderType)	-- Pre-typechecking

nlHsDo :: HsStmtContext Name -> [LStmt id (LHsExpr id)] -> LHsExpr id
nlHsDo ctxt stmts = noLoc (mkHsDo ctxt stmts)

nlHsOpApp :: LHsExpr id -> id -> LHsExpr id -> LHsExpr id
nlHsOpApp e1 op e2 = noLoc (mkHsOpApp e1 op e2)

nlHsLam  :: LMatch id (LHsExpr id) -> LHsExpr id
nlHsPar  :: LHsExpr id -> LHsExpr id
nlHsIf   :: LHsExpr id -> LHsExpr id -> LHsExpr id -> LHsExpr id
nlHsCase :: LHsExpr id -> [LMatch id (LHsExpr id)] -> LHsExpr id
nlList   :: [LHsExpr id] -> LHsExpr id

nlHsLam	match          = noLoc (HsLam (mkMatchGroup Generated [match]))
nlHsPar e              = noLoc (HsPar e)
nlHsIf cond true false = noLoc (mkHsIf cond true false)
nlHsCase expr matches  = noLoc (HsCase expr (mkMatchGroup Generated matches))
nlList exprs           = noLoc (ExplicitList placeHolderType Nothing exprs)

nlHsAppTy :: LHsType name -> LHsType name -> LHsType name
nlHsTyVar :: name                         -> LHsType name
nlHsFunTy :: LHsType name -> LHsType name -> LHsType name

nlHsAppTy f t		= noLoc (HsAppTy f t)
nlHsTyVar x		= noLoc (HsTyVar x)
nlHsFunTy a b		= noLoc (HsFunTy a b)

nlHsTyConApp :: name -> [LHsType name] -> LHsType name
nlHsTyConApp tycon tys  = foldl nlHsAppTy (nlHsTyVar tycon) tys
\end{code}

Tuples.  All these functions are *pre-typechecker* because they lack
types on the tuple.

\begin{code}
mkLHsTupleExpr :: [LHsExpr a] -> LHsExpr a
-- Makes a pre-typechecker boxed tuple, deals with 1 case
mkLHsTupleExpr [e] = e
mkLHsTupleExpr es  = noLoc $ ExplicitTuple (map Present es) Boxed

mkLHsVarTuple :: [a] -> LHsExpr a
mkLHsVarTuple ids  = mkLHsTupleExpr (map nlHsVar ids)

nlTuplePat :: [LPat id] -> Boxity -> LPat id
nlTuplePat pats box = noLoc (TuplePat pats box placeHolderType)

missingTupArg :: HsTupArg a
missingTupArg = Missing placeHolderType
\end{code}


%************************************************************************
%*									*
        Converting a Type to an HsType RdrName
%*									*
%************************************************************************

This is needed to implement GeneralizedNewtypeDeriving.

\begin{code}
toHsType :: Type -> LHsType RdrName
toHsType ty
  | [] <- tvs_only
  , [] <- theta
  = to_hs_type tau
  | otherwise
  = noLoc $
    mkExplicitHsForAllTy (map mk_hs_tvb tvs_only)
                         (noLoc $ map toHsType theta)
                         (to_hs_type tau)

  where
    (tvs, theta, tau) = tcSplitSigmaTy ty
    tvs_only = filter isTypeVar tvs

    to_hs_type (TyVarTy tv) = nlHsTyVar (getRdrName tv)
    to_hs_type (AppTy t1 t2) = nlHsAppTy (toHsType t1) (toHsType t2)
    to_hs_type (TyConApp tc args) = nlHsTyConApp (getRdrName tc) (map toHsType args')
       where 
         args' = filterOut isKind args
         -- Source-language types have _implicit_ kind arguments,
         -- so we must remove them here (Trac #8563)
    to_hs_type (FunTy arg res) = ASSERT( not (isConstraintKind (typeKind arg)) )
                                 nlHsFunTy (toHsType arg) (toHsType res)
    to_hs_type t@(ForAllTy {}) = pprPanic "toHsType" (ppr t)
    to_hs_type (LitTy (NumTyLit n)) = noLoc $ HsTyLit (HsNumTy n)
    to_hs_type (LitTy (StrTyLit s)) = noLoc $ HsTyLit (HsStrTy s)

    mk_hs_tvb tv = noLoc $ KindedTyVar (getRdrName tv) (toHsKind (tyVarKind tv))

toHsKind :: Kind -> LHsKind RdrName
toHsKind = toHsType

\end{code}

\begin{code}
--------- HsWrappers: type args, dict args, casts ---------
mkLHsWrap :: HsWrapper -> LHsExpr id -> LHsExpr id
mkLHsWrap co_fn (L loc e) = L loc (mkHsWrap co_fn e)

mkHsWrap :: HsWrapper -> HsExpr id -> HsExpr id
mkHsWrap co_fn e | isIdHsWrapper co_fn = e
		 | otherwise	       = HsWrap co_fn e

mkHsWrapCo :: TcCoercion -> HsExpr id -> HsExpr id
mkHsWrapCo co e = mkHsWrap (coToHsWrapper co) e

mkLHsWrapCo :: TcCoercion -> LHsExpr id -> LHsExpr id
mkLHsWrapCo co (L loc e) = L loc (mkHsWrapCo co e)

mkHsCmdCast :: TcCoercion -> HsCmd id -> HsCmd id
mkHsCmdCast co cmd | isTcReflCo co = cmd
                   | otherwise     = HsCmdCast co cmd

coToHsWrapper :: TcCoercion -> HsWrapper
coToHsWrapper co | isTcReflCo co = idHsWrapper
                 | otherwise     = mkWpCast (mkTcSubCo co)

mkHsWrapPat :: HsWrapper -> Pat id -> Type -> Pat id
mkHsWrapPat co_fn p ty | isIdHsWrapper co_fn = p
		       | otherwise	     = CoPat co_fn p ty

mkHsWrapPatCo :: TcCoercion -> Pat id -> Type -> Pat id
mkHsWrapPatCo co pat ty | isTcReflCo co = pat
                        | otherwise     = CoPat (mkWpCast co) pat ty

mkHsDictLet :: TcEvBinds -> LHsExpr Id -> LHsExpr Id
mkHsDictLet ev_binds expr = mkLHsWrap (mkWpLet ev_binds) expr
\end{code}
l
%************************************************************************
%*									*
		Bindings; with a location at the top
%*									*
%************************************************************************

\begin{code}
mkFunBind :: Located RdrName -> [LMatch RdrName (LHsExpr RdrName)] -> HsBind RdrName
-- Not infix, with place holders for coercion and free vars
mkFunBind fn ms = FunBind { fun_id = fn, fun_infix = False
                          , fun_matches = mkMatchGroup Generated ms
                          , fun_co_fn = idHsWrapper
                          , bind_fvs = placeHolderNames
                          , fun_tick = Nothing }

mkTopFunBind :: Origin -> Located Name -> [LMatch Name (LHsExpr Name)] -> HsBind Name
-- In Name-land, with empty bind_fvs
mkTopFunBind origin fn ms = FunBind { fun_id = fn, fun_infix = False
                                    , fun_matches = mkMatchGroup origin ms
                                    , fun_co_fn = idHsWrapper
                                    , bind_fvs = emptyNameSet	-- NB: closed binding
                                    , fun_tick = Nothing }

mkHsVarBind :: SrcSpan -> RdrName -> LHsExpr RdrName -> LHsBind RdrName
mkHsVarBind loc var rhs = mk_easy_FunBind loc var [] rhs

mkVarBind :: id -> LHsExpr id -> LHsBind id
mkVarBind var rhs = L (getLoc rhs) $
		    VarBind { var_id = var, var_rhs = rhs, var_inline = False }

mkPatSynBind :: Located RdrName -> HsPatSynDetails (Located RdrName) -> LPat RdrName -> HsPatSynDir RdrName -> HsBind RdrName
mkPatSynBind name details lpat dir = PatSynBind{ patsyn_id = name
                                               , patsyn_args = details
                                               , patsyn_def = lpat
                                               , patsyn_dir = dir
                                               , bind_fvs = placeHolderNames }

------------
mk_easy_FunBind :: SrcSpan -> RdrName -> [LPat RdrName]
		-> LHsExpr RdrName -> LHsBind RdrName
mk_easy_FunBind loc fun pats expr
  = L loc $ mkFunBind (L loc fun) [mkMatch pats expr emptyLocalBinds]

------------
mkMatch :: [LPat id] -> LHsExpr id -> HsLocalBinds id -> LMatch id (LHsExpr id)
mkMatch pats expr binds
  = noLoc (Match (map paren pats) Nothing 
		 (GRHSs (unguardedRHS expr) binds))
  where
    paren lp@(L l p) | hsPatNeedsParens p = L l (ParPat lp) 
		     | otherwise          = lp
\end{code}


%************************************************************************
%*									*
	Collecting binders
%*									*
%************************************************************************

Get all the binders in some HsBindGroups, IN THE ORDER OF APPEARANCE. eg.

...
where
  (x, y) = ...
  f i j  = ...
  [a, b] = ...

it should return [x, y, f, a, b] (remember, order important).

Note [Collect binders only after renaming]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
These functions should only be used on HsSyn *after* the renamer,
to return a [Name] or [Id].  Before renaming the record punning
and wild-card mechanism makes it hard to know what is bound.
So these functions should not be applied to (HsSyn RdrName)

\begin{code}
----------------- Bindings --------------------------
collectLocalBinders :: HsLocalBindsLR idL idR -> [idL]
collectLocalBinders (HsValBinds val_binds) = collectHsValBinders val_binds
collectLocalBinders (HsIPBinds _)   = []
collectLocalBinders EmptyLocalBinds = []

collectHsValBinders :: HsValBindsLR idL idR -> [idL]
collectHsValBinders (ValBindsIn  binds _) = collectHsBindsBinders binds
collectHsValBinders (ValBindsOut binds _) = foldr collect_one [] binds
  where
   collect_one (_,binds) acc = collect_binds binds acc

collectHsBindBinders :: HsBindLR idL idR -> [idL]
collectHsBindBinders b = collect_bind b []

collect_bind :: HsBindLR idL idR -> [idL] -> [idL]
collect_bind (PatBind { pat_lhs = p })    acc = collect_lpat p acc
collect_bind (FunBind { fun_id = L _ f }) acc = f : acc
collect_bind (VarBind { var_id = f })     acc = f : acc
collect_bind (AbsBinds { abs_exports = dbinds, abs_binds = _binds }) acc
  = map abe_poly dbinds ++ acc 
	-- ++ foldr collect_bind acc binds
	-- I don't think we want the binders from the nested binds
	-- The only time we collect binders from a typechecked 
	-- binding (hence see AbsBinds) is in zonking in TcHsSyn
collect_bind (PatSynBind { patsyn_id = L _ ps }) acc = ps : acc

collectHsBindsBinders :: LHsBindsLR idL idR -> [idL]
collectHsBindsBinders binds = collect_binds binds []

collectHsBindListBinders :: [LHsBindLR idL idR] -> [idL]
collectHsBindListBinders = foldr (collect_bind . unLoc) []

collect_binds :: LHsBindsLR idL idR -> [idL] -> [idL]
collect_binds binds acc = foldrBag (collect_bind . unLoc) acc binds

collectMethodBinders :: LHsBindsLR RdrName idR -> [Located RdrName]
-- Used exclusively for the bindings of an instance decl which are all FunBinds
collectMethodBinders binds = foldrBag (get . unLoc) [] binds
  where
    get (FunBind { fun_id = f }) fs = f : fs
    get _                        fs = fs	
       -- Someone else complains about non-FunBinds

----------------- Statements --------------------------
collectLStmtsBinders :: [LStmtLR idL idR body] -> [idL]
collectLStmtsBinders = concatMap collectLStmtBinders

collectStmtsBinders :: [StmtLR idL idR body] -> [idL]
collectStmtsBinders = concatMap collectStmtBinders

collectLStmtBinders :: LStmtLR idL idR body -> [idL]
collectLStmtBinders = collectStmtBinders . unLoc

collectStmtBinders :: StmtLR idL idR body -> [idL]
  -- Id Binders for a Stmt... [but what about pattern-sig type vars]?
collectStmtBinders (BindStmt pat _ _ _) = collectPatBinders pat
collectStmtBinders (LetStmt binds)      = collectLocalBinders binds
collectStmtBinders (BodyStmt {})        = []
collectStmtBinders (LastStmt {})        = []
collectStmtBinders (ParStmt xs _ _)     = collectLStmtsBinders
                                        $ [s | ParStmtBlock ss _ _ <- xs, s <- ss]
collectStmtBinders (TransStmt { trS_stmts = stmts }) = collectLStmtsBinders stmts
collectStmtBinders (RecStmt { recS_stmts = ss })     = collectLStmtsBinders ss


----------------- Patterns --------------------------
collectPatBinders :: LPat a -> [a]
collectPatBinders pat = collect_lpat pat []

collectPatsBinders :: [LPat a] -> [a]
collectPatsBinders pats = foldr collect_lpat [] pats

-------------
collect_lpat :: LPat name -> [name] -> [name]
collect_lpat (L _ pat) bndrs
  = go pat
  where
    go (VarPat var) 	   	  = var : bndrs
    go (WildPat _)	      	  = bndrs
    go (LazyPat pat)     	  = collect_lpat pat bndrs
    go (BangPat pat)     	  = collect_lpat pat bndrs
    go (AsPat (L _ a) pat)     	  = a : collect_lpat pat bndrs
    go (ViewPat _ pat _)          = collect_lpat pat bndrs
    go (ParPat  pat)     	  = collect_lpat pat bndrs
				  
    go (ListPat pats _ _)         = foldr collect_lpat bndrs pats
    go (PArrPat pats _)    	  = foldr collect_lpat bndrs pats
    go (TuplePat pats _ _)  	  = foldr collect_lpat bndrs pats
				  
    go (ConPatIn _ ps)            = foldr collect_lpat bndrs (hsConPatArgs ps)
    go (ConPatOut {pat_args=ps})  = foldr collect_lpat bndrs (hsConPatArgs ps)
	-- See Note [Dictionary binders in ConPatOut]
    go (LitPat _)	      	  = bndrs
    go (NPat _ _ _)		  = bndrs
    go (NPlusKPat (L _ n) _ _ _)  = n : bndrs
 				  
    go (SigPatIn pat _)	 	  = collect_lpat pat bndrs
    go (SigPatOut pat _)	  = collect_lpat pat bndrs
    go (SplicePat _)              = bndrs
    go (QuasiQuotePat _)          = bndrs
    go (CoPat _ pat _)            = go pat
\end{code}

Note [Dictionary binders in ConPatOut] See also same Note in DsArrows
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Do *not* gather (a) dictionary and (b) dictionary bindings as binders
of a ConPatOut pattern.  For most calls it doesn't matter, because
it's pre-typechecker and there are no ConPatOuts.  But it does matter
more in the desugarer; for example, DsUtils.mkSelectorBinds uses
collectPatBinders.  In a lazy pattern, for example f ~(C x y) = ...,
we want to generate bindings for x,y but not for dictionaries bound by
C.  (The type checker ensures they would not be used.)

Desugaring of arrow case expressions needs these bindings (see DsArrows
and arrowcase1), but SPJ (Jan 2007) says it's safer for it to use its
own pat-binder-collector:

Here's the problem.  Consider

data T a where
   C :: Num a => a -> Int -> T a

f ~(C (n+1) m) = (n,m)

Here, the pattern (C (n+1)) binds a hidden dictionary (d::Num a),
and *also* uses that dictionary to match the (n+1) pattern.  Yet, the
variables bound by the lazy pattern are n,m, *not* the dictionary d.
So in mkSelectorBinds in DsUtils, we want just m,n as the variables bound.

\begin{code}
hsGroupBinders :: HsGroup Name -> [Name]
hsGroupBinders (HsGroup { hs_valds = val_decls, hs_tyclds = tycl_decls,
                          hs_instds = inst_decls, hs_fords = foreign_decls })
-- Collect the binders of a Group
  =  collectHsValBinders val_decls
  ++ hsTyClDeclsBinders tycl_decls inst_decls
  ++ hsForeignDeclsBinders foreign_decls

hsForeignDeclsBinders :: [LForeignDecl Name] -> [Name]
hsForeignDeclsBinders foreign_decls
  = [n | L _ (ForeignImport (L _ n) _ _ _) <- foreign_decls]

hsTyClDeclsBinders :: [TyClGroup Name] -> [Located (InstDecl Name)] -> [Name]
-- We need to look at instance declarations too, 
-- because their associated types may bind data constructors
hsTyClDeclsBinders tycl_decls inst_decls
  = map unLoc (concatMap (concatMap hsLTyClDeclBinders . group_tyclds) tycl_decls ++
               concatMap (hsInstDeclBinders . unLoc) inst_decls)

-------------------
hsLTyClDeclBinders :: Eq name => Located (TyClDecl name) -> [Located name]
-- ^ Returns all the /binding/ names of the decl.
-- The first one is guaranteed to be the name of the decl. For record fields
-- mentioned in multiple constructors, the SrcLoc will be from the first
-- occurrence.  We use the equality to filter out duplicate field names.
--
-- Each returned (Located name) is wrapped in a @SrcSpan@ of the whole
-- /declaration/, not just the name itself (which is how it appears in
-- the syntax tree).  This SrcSpan (for the entire declaration) is used
-- as the SrcSpan for the Name that is finally produced, and hence for
-- error messages.  (See Trac #8607.)

hsLTyClDeclBinders (L loc (FamDecl { tcdFam = FamilyDecl { fdLName = L _ name } }))
  = [L loc name]
hsLTyClDeclBinders (L loc (ForeignType { tcdLName = L _ name })) = [L loc name]
hsLTyClDeclBinders (L loc (SynDecl     { tcdLName = L _ name })) = [L loc name]
hsLTyClDeclBinders (L loc (ClassDecl   { tcdLName = L _ cls_name
                                       , tcdSigs = sigs, tcdATs = ats }))
  = L loc cls_name :
    [ L fam_loc fam_name | L fam_loc (FamilyDecl { fdLName = L _ fam_name }) <- ats ] ++
    [ L mem_loc mem_name | L mem_loc (TypeSig ns _) <- sigs, L _ mem_name <- ns ]
hsLTyClDeclBinders (L loc (DataDecl    { tcdLName = L _ name, tcdDataDefn = defn }))
  = L loc name : hsDataDefnBinders defn

-------------------
hsInstDeclBinders :: Eq name => InstDecl name -> [Located name]
hsInstDeclBinders (ClsInstD { cid_inst = ClsInstDecl { cid_datafam_insts = dfis } })
  = concatMap (hsDataFamInstBinders . unLoc) dfis
hsInstDeclBinders (DataFamInstD { dfid_inst = fi }) = hsDataFamInstBinders fi
hsInstDeclBinders (TyFamInstD {}) = []

-------------------
-- the SrcLoc returned are for the whole declarations, not just the names
hsDataFamInstBinders :: Eq name => DataFamInstDecl name -> [Located name]
hsDataFamInstBinders (DataFamInstDecl { dfid_defn = defn })
  = hsDataDefnBinders defn
  -- There can't be repeated symbols because only data instances have binders

-------------------
-- the SrcLoc returned are for the whole declarations, not just the names
hsDataDefnBinders :: Eq name => HsDataDefn name -> [Located name]
hsDataDefnBinders (HsDataDefn { dd_cons = cons }) = hsConDeclsBinders cons
  -- See Note [Binders in family instances]

-------------------
hsConDeclsBinders :: (Eq name) => [LConDecl name] -> [Located name]
  -- See hsLTyClDeclBinders for what this does
  -- The function is boringly complicated because of the records
  -- And since we only have equality, we have to be a little careful
hsConDeclsBinders cons
  = snd (foldl do_one ([], []) cons)
  where
    do_one (flds_seen, acc) (L loc (ConDecl { con_name = L _ name
                                            , con_details = RecCon flds }))
	= (map unLoc new_flds ++ flds_seen, L loc name : new_flds ++ acc)
	where
          -- don't re-mangle the location of field names, because we don't
          -- have a record of the full location of the field declaration anyway
	  new_flds = filterOut (\f -> unLoc f `elem` flds_seen) 
			       (map cd_fld_name flds)

    do_one (flds_seen, acc) (L loc (ConDecl { con_name = L _ name }))
	= (flds_seen, L loc name : acc)
\end{code}

Note [Binders in family instances]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In a type or data family instance declaration, the type 
constructor is an *occurrence* not a binding site
    type instance T Int = Int -> Int   -- No binders
    data instance S Bool = S1 | S2     -- Binders are S1,S2


%************************************************************************
%*									*
	Collecting binders the user did not write
%*									*
%************************************************************************

The job of this family of functions is to run through binding sites and find the set of all Names
that were defined "implicitly", without being explicitly written by the user.

The main purpose is to find names introduced by record wildcards so that we can avoid
warning the user when they don't use those names (#4404)

\begin{code}
lStmtsImplicits :: [LStmtLR Name idR (Located (body idR))] -> NameSet
lStmtsImplicits = hs_lstmts
  where
    hs_lstmts :: [LStmtLR Name idR (Located (body idR))] -> NameSet
    hs_lstmts = foldr (\stmt rest -> unionNameSets (hs_stmt (unLoc stmt)) rest) emptyNameSet
    
    hs_stmt (BindStmt pat _ _ _) = lPatImplicits pat
    hs_stmt (LetStmt binds)      = hs_local_binds binds
    hs_stmt (BodyStmt {})        = emptyNameSet
    hs_stmt (LastStmt {})        = emptyNameSet
    hs_stmt (ParStmt xs _ _)     = hs_lstmts [s | ParStmtBlock ss _ _ <- xs, s <- ss]
    hs_stmt (TransStmt { trS_stmts = stmts }) = hs_lstmts stmts
    hs_stmt (RecStmt { recS_stmts = ss })     = hs_lstmts ss
    
    hs_local_binds (HsValBinds val_binds) = hsValBindsImplicits val_binds
    hs_local_binds (HsIPBinds _)         = emptyNameSet
    hs_local_binds EmptyLocalBinds       = emptyNameSet

hsValBindsImplicits :: HsValBindsLR Name idR -> NameSet
hsValBindsImplicits (ValBindsOut binds _)
  = foldr (unionNameSets . lhsBindsImplicits . snd) emptyNameSet binds
hsValBindsImplicits (ValBindsIn binds _) 
  = lhsBindsImplicits binds

lhsBindsImplicits :: LHsBindsLR Name idR -> NameSet
lhsBindsImplicits = foldBag unionNameSets (lhs_bind . unLoc) emptyNameSet
  where
    lhs_bind (PatBind { pat_lhs = lpat }) = lPatImplicits lpat
    lhs_bind _ = emptyNameSet

lPatImplicits :: LPat Name -> NameSet
lPatImplicits = hs_lpat
  where
    hs_lpat (L _ pat) = hs_pat pat
    
    hs_lpats = foldr (\pat rest -> hs_lpat pat `unionNameSets` rest) emptyNameSet
    
    hs_pat (LazyPat pat)       = hs_lpat pat
    hs_pat (BangPat pat)       = hs_lpat pat
    hs_pat (AsPat _ pat)       = hs_lpat pat
    hs_pat (ViewPat _ pat _)   = hs_lpat pat
    hs_pat (ParPat  pat)       = hs_lpat pat
    hs_pat (ListPat pats _ _)  = hs_lpats pats
    hs_pat (PArrPat pats _)    = hs_lpats pats
    hs_pat (TuplePat pats _ _) = hs_lpats pats

    hs_pat (SigPatIn pat _)  = hs_lpat pat
    hs_pat (SigPatOut pat _) = hs_lpat pat
    hs_pat (CoPat _ pat _)   = hs_pat pat
    
    hs_pat (ConPatIn _ ps)           = details ps
    hs_pat (ConPatOut {pat_args=ps}) = details ps
    
    hs_pat _ = emptyNameSet
    
    details (PrefixCon ps)   = hs_lpats ps
    details (RecCon fs)      = hs_lpats explicit `unionNameSets` mkNameSet (collectPatsBinders implicit)
      where (explicit, implicit) = partitionEithers [if pat_explicit then Left pat else Right pat
                                                    | (i, fld) <- [0..] `zip` rec_flds fs
                                                    , let pat = hsRecFieldArg fld
                                                          pat_explicit = maybe True (i<) (rec_dotdot fs)]
    details (InfixCon p1 p2) = hs_lpat p1 `unionNameSets` hs_lpat p2
\end{code}