RnBinds.lhs 31.8 KB
Newer Older
1
2
3
4
5
6
7
8
9
10
11
%
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
\section[RnBinds]{Renaming and dependency analysis of bindings}

This module does renaming and dependency analysis on value bindings in
the abstract syntax.  It does {\em not} do cycle-checks on class or
type-synonym declarations; those cannot be done at this stage because
they may be affected by renaming (which isn't fully worked out yet).

\begin{code}
Ian Lynagh's avatar
Ian Lynagh committed
12
13
14
15
16
17
18
{-# 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://hackage.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
-- for details

19
20
module RnBinds (
   -- Renaming top-level bindings
21
   rnTopBindsLHS, rnTopBindsRHS, rnValBindsRHS,
22
23
24
25
26
27
28
29

   -- Renaming local bindings
   rnLocalBindsAndThen, rnLocalValBindsLHS, rnLocalValBindsRHS,

   -- Other bindings
   rnMethodBinds, renameSigs, mkSigTvFn,
   rnMatchGroup, rnGRHSs,
   makeMiniFixityEnv, MiniFixityEnv,
30
   HsSigCtxt(..)
31
32
   ) where

33
import {-# SOURCE #-} RnExpr( rnLExpr, rnStmts )
34
35
36

import HsSyn
import RnHsSyn
37
import TcRnMonad
38
import TcEvidence     ( emptyTcEvBinds )
batterseapower's avatar
batterseapower committed
39
import RnTypes        ( rnIPName, rnHsSigType, rnLHsType, checkPrecMatch )
40
import RnPat
41
import RnEnv
42
import DynFlags
43
import Name
44
import NameEnv
45
import NameSet
46
import RdrName          ( RdrName, rdrNameOcc )
Ian Lynagh's avatar
Ian Lynagh committed
47
import SrcLoc
48
import ListSetOps	( findDupsEq )
49
import BasicTypes	( RecFlag(..) )
50
import Digraph		( SCC(..), stronglyConnCompFromEdgedVertices )
51
import Bag
52
import Outputable
53
import FastString
54
import Data.List	( partition )
simonpj@microsoft.com's avatar
simonpj@microsoft.com committed
55
import Maybes		( orElse )
Ian Lynagh's avatar
Ian Lynagh committed
56
import Control.Monad
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
\end{code}

-- ToDo: Put the annotations into the monad, so that they arrive in the proper
-- place and can be used when complaining.

The code tree received by the function @rnBinds@ contains definitions
in where-clauses which are all apparently mutually recursive, but which may
not really depend upon each other. For example, in the top level program
\begin{verbatim}
f x = y where a = x
	      y = x
\end{verbatim}
the definitions of @a@ and @y@ do not depend on each other at all.
Unfortunately, the typechecker cannot always check such definitions.
\footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
definitions. In Proceedings of the International Symposium on Programming,
Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
However, the typechecker usually can check definitions in which only the
strongly connected components have been collected into recursive bindings.
This is precisely what the function @rnBinds@ does.

ToDo: deal with case where a single monobinds binds the same variable
twice.

The vertag tag is a unique @Int@; the tags only need to be unique
within one @MonoBinds@, so that unique-Int plumbing is done explicitly
(heavy monad machinery not needed).


%************************************************************************
%*									*
%* naming conventions							*
%*									*
%************************************************************************

\subsection[name-conventions]{Name conventions}

The basic algorithm involves walking over the tree and returning a tuple
containing the new tree plus its free variables. Some functions, such
as those walking polymorphic bindings (HsBinds) and qualifier lists in
list comprehensions (@Quals@), return the variables bound in local
environments. These are then used to calculate the free variables of the
expression evaluated in these environments.

Conventions for variable names are as follows:
\begin{itemize}
\item
new code is given a prime to distinguish it from the old.

\item
a set of variables defined in @Exp@ is written @dvExp@

\item
a set of variables free in @Exp@ is written @fvExp@
\end{itemize}

%************************************************************************
%*									*
115
%* analysing polymorphic bindings (HsBindGroup, HsBind)
116
117
118
119
120
121
122
123
124
125
126
%*									*
%************************************************************************

\subsubsection[dep-HsBinds]{Polymorphic bindings}

Non-recursive expressions are reconstructed without any changes at top
level, although their component expressions may have to be altered.
However, non-recursive expressions are currently not expected as
\Haskell{} programs, and this code should not be executed.

Monomorphic bindings contain information that is returned in a tuple
127
(a @FlatMonoBinds@) containing:
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

\begin{enumerate}
\item
a unique @Int@ that serves as the ``vertex tag'' for this binding.

\item
the name of a function or the names in a pattern. These are a set
referred to as @dvLhs@, the defined variables of the left hand side.

\item
the free variables of the body. These are referred to as @fvBody@.

\item
the definition's actual code. This is referred to as just @code@.
\end{enumerate}

The function @nonRecDvFv@ returns two sets of variables. The first is
the set of variables defined in the set of monomorphic bindings, while the
second is the set of free variables in those bindings.

The set of variables defined in a non-recursive binding is just the
union of all of them, as @union@ removes duplicates. However, the
free variables in each successive set of cumulative bindings is the
union of those in the previous set plus those of the newest binding after
the defined variables of the previous set have been removed.

@rnMethodBinds@ deals only with the declarations in class and
instance declarations.	It expects only to see @FunMonoBind@s, and
it expects the global environment to contain bindings for the binders
(which are all class operations).

%************************************************************************
%*									*
\subsubsection{ Top-level bindings}
%*									*
%************************************************************************

\begin{code}
166
167
-- for top-level bindings, we need to make top-level names,
-- so we have a different entry point than for local bindings
168
rnTopBindsLHS :: MiniFixityEnv
169
170
              -> HsValBinds RdrName 
              -> RnM (HsValBindsLR Name RdrName)
171
rnTopBindsLHS fix_env binds
172
  = rnValBindsLHS (topRecNameMaker fix_env) binds
173

174
rnTopBindsRHS :: HsValBindsLR Name RdrName 
175
              -> RnM (HsValBinds Name, DefUses)
176
177
rnTopBindsRHS binds
  = do { is_boot <- tcIsHsBoot
178
179
       ; if is_boot 
         then rnTopBindsBoot binds
180
         else rnValBindsRHS TopSigCtxt binds }
181
182

rnTopBindsBoot :: HsValBindsLR Name RdrName -> RnM (HsValBinds Name, DefUses)
183
184
-- A hs-boot file has no bindings. 
-- Return a single HsBindGroup with empty binds and renamed signatures
185
rnTopBindsBoot (ValBindsIn mbinds sigs)
186
  = do	{ checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
187
	; sigs' <- renameSigs HsBootCtxt sigs
188
	; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
Ian Lynagh's avatar
Ian Lynagh committed
189
rnTopBindsBoot b = pprPanic "rnTopBindsBoot" (ppr b)
190
191
192
193
194
195
196
197
198
199
\end{code}


%*********************************************************
%*							*
		HsLocalBinds
%*							*
%*********************************************************

\begin{code}
200
201
202
203
204
rnLocalBindsAndThen :: HsLocalBinds RdrName
                    -> (HsLocalBinds Name -> RnM (result, FreeVars))
                    -> RnM (result, FreeVars)
-- This version (a) assumes that the binding vars are *not* already in scope
--		 (b) removes the binders from the free vars of the thing inside
205
206
207
208
209
-- The parser doesn't produce ThenBinds
rnLocalBindsAndThen EmptyLocalBinds thing_inside
  = thing_inside EmptyLocalBinds

rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
210
  = rnLocalValBindsAndThen val_binds $ \ val_binds' -> 
211
      thing_inside (HsValBinds val_binds')
212

213
214
215
216
rnLocalBindsAndThen (HsIPBinds binds) thing_inside = do
    (binds',fv_binds) <- rnIPBinds binds
    (thing, fvs_thing) <- thing_inside (HsIPBinds binds')
    return (thing, fvs_thing `plusFV` fv_binds)
217

Ian Lynagh's avatar
Ian Lynagh committed
218
rnIPBinds :: HsIPBinds RdrName -> RnM (HsIPBinds Name, FreeVars)
219
220
rnIPBinds (IPBinds ip_binds _no_dict_binds) = do
    (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
221
    return (IPBinds ip_binds' emptyTcEvBinds, plusFVs fvs_s)
222

Ian Lynagh's avatar
Ian Lynagh committed
223
rnIPBind :: IPBind RdrName -> RnM (IPBind Name, FreeVars)
224
rnIPBind (IPBind n expr) = do
batterseapower's avatar
batterseapower committed
225
    n' <- rnIPName n
226
    (expr',fvExpr) <- rnLExpr expr
batterseapower's avatar
batterseapower committed
227
    return (IPBind n' expr', fvExpr)
228
229
\end{code}

230

231
232
%************************************************************************
%*									*
233
		ValBinds
234
235
236
237
%*									*
%************************************************************************

\begin{code}
238
239
-- Renaming local binding gropus 
-- Does duplicate/shadow check
240
241
242
243
rnLocalValBindsLHS :: MiniFixityEnv
                   -> HsValBinds RdrName
                   -> RnM ([Name], HsValBindsLR Name RdrName)
rnLocalValBindsLHS fix_env binds 
244
245
246
247
248
249
250
  = do { binds' <- rnValBindsLHS (localRecNameMaker fix_env) binds 

         -- Check for duplicates and shadowing
	 -- Must do this *after* renaming the patterns
	 -- See Note [Collect binders only after renaming] in HsUtils

         -- We need to check for dups here because we
251
252
253
254
255
256
257
258
259
260
261
262
263
     	 -- don't don't bind all of the variables from the ValBinds at once
     	 -- with bindLocatedLocals any more.
         -- 
     	 -- Note that we don't want to do this at the top level, since
     	 -- sorting out duplicates and shadowing there happens elsewhere.
     	 -- The behavior is even different. For example,
     	 --   import A(f)
     	 --   f = ...
     	 -- should not produce a shadowing warning (but it will produce
     	 -- an ambiguity warning if you use f), but
     	 --   import A(f)
     	 --   g = let f = ... in f
     	 -- should.
264
       ; let bound_names = collectHsValBinders binds'
265
266
       ; envs <- getRdrEnvs
       ; checkDupAndShadowedNames envs bound_names
267

268
       ; return (bound_names, binds') }
269
270
271
272

-- renames the left-hand sides
-- generic version used both at the top level and for local binds
-- does some error checking, but not what gets done elsewhere at the top level
273
274
275
276
rnValBindsLHS :: NameMaker 
              -> HsValBinds RdrName
              -> RnM (HsValBindsLR Name RdrName)
rnValBindsLHS topP (ValBindsIn mbinds sigs)
277
278
279
  = do { mbinds' <- mapBagM (rnBindLHS topP doc) mbinds
       ; return $ ValBindsIn mbinds' sigs }
  where
280
    bndrs = collectHsBindsBinders mbinds
281
282
    doc   = text "In the binding group for:" <+> pprWithCommas ppr bndrs

283
rnValBindsLHS _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
284

285
286
-- General version used both from the top-level and for local things
-- Assumes the LHS vars are in scope
287
--
288
-- Does not bind the local fixity declarations
289
290
291
rnValBindsRHS :: HsSigCtxt 
              -> HsValBindsLR Name RdrName
              -> RnM (HsValBinds Name, DefUses)
292

293
294
rnValBindsRHS ctxt (ValBindsIn mbinds sigs)
  = do { sigs' <- renameSigs ctxt sigs
295
       ; binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs')) mbinds
296
       ; case depAnalBinds binds_w_dus of
297
298
299
           (anal_binds, anal_dus) -> return (valbind', valbind'_dus)
              where
                valbind' = ValBindsOut anal_binds sigs'
300
301
302
303
                valbind'_dus = anal_dus `plusDU` usesOnly (hsSigsFVs sigs')
			       -- Put the sig uses *after* the bindings
			       -- so that the binders are removed from 
			       -- the uses in the sigs
304
305
       }

306
rnValBindsRHS _ b = pprPanic "rnValBindsRHS" (ppr b)
Ian Lynagh's avatar
Ian Lynagh committed
307

308
-- Wrapper for local binds
309
--
310
-- The *client* of this function is responsible for checking for unused binders;
311
312
-- it doesn't (and can't: we don't have the thing inside the binds) happen here
--
313
-- The client is also responsible for bringing the fixities into scope
314
315
316
317
rnLocalValBindsRHS :: NameSet  -- names bound by the LHSes
                   -> HsValBindsLR Name RdrName
                   -> RnM (HsValBinds Name, DefUses)
rnLocalValBindsRHS bound_names binds
318
  = rnValBindsRHS (LocalBindCtxt bound_names) binds
319
320
321
322
323
324

-- for local binds
-- wrapper that does both the left- and right-hand sides 
--
-- here there are no local fixity decls passed in;
-- the local fixity decls come from the ValBinds sigs
325
326
327
328
rnLocalValBindsAndThen :: HsValBinds RdrName
                       -> (HsValBinds Name -> RnM (result, FreeVars))
                       -> RnM (result, FreeVars)
rnLocalValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
329
330
 = do	{     -- (A) Create the local fixity environment 
	  new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
331

332
	      -- (B) Rename the LHSes 
333
	; (bound_names, new_lhs) <- rnLocalValBindsLHS new_fixities binds
334

335
	      --     ...and bring them (and their fixities) into scope
336
337
	; bindLocalNamesFV bound_names              $
          addLocalFixities new_fixities bound_names $ do
338

339
	{      -- (C) Do the RHS and thing inside
340
	  (binds', dus) <- rnLocalValBindsRHS (mkNameSet bound_names) new_lhs 
341
        ; (result, result_fvs) <- thing_inside binds'
342

343
344
345
346
347
		-- Report unused bindings based on the (accurate) 
		-- findUses.  E.g.
		-- 	let x = x in 3
		-- should report 'x' unused
	; let real_uses = findUses dus result_fvs
348
349
350
	      -- Insert fake uses for variables introduced implicitly by wildcards (#4404)
	      implicit_uses = hsValBindsImplicits binds'
	; warnUnusedLocalBinds bound_names (real_uses `unionNameSets` implicit_uses)
351

352
353
	; let
            -- The variables "used" in the val binds are: 
354
            --   (1) the uses of the binds (allUses)
355
            --   (2) the FVs of the thing-inside
356
            all_uses = allUses dus `plusFV` result_fvs
357
358
359
360
361
		-- Note [Unused binding hack]
		-- ~~~~~~~~~~~~~~~~~~~~~~~~~~
		-- Note that *in contrast* to the above reporting of
		-- unused bindings, (1) above uses duUses to return *all* 
		-- the uses, even if the binding is unused.  Otherwise consider:
362
363
364
365
366
                --	x = 3
                --	y = let p = x in 'x'	-- NB: p not used
                -- If we don't "see" the dependency of 'y' on 'x', we may put the
                -- bindings in the wrong order, and the type checker will complain
                -- that x isn't in scope
367
368
369
370
371
372
373
		--
		-- But note that this means we won't report 'x' as unused, 
		-- whereas we would if we had { x = 3; p = x; y = 'x' }

	; return (result, all_uses) }}
         	-- The bound names are pruned out of all_uses
	        -- by the bindLocalNamesFV call above
Ian Lynagh's avatar
Ian Lynagh committed
374

375
rnLocalValBindsAndThen bs _ = pprPanic "rnLocalValBindsAndThen" (ppr bs)
376
377
378
379
380
381
382
383


-- Process the fixity declarations, making a FastString -> (Located Fixity) map
-- (We keep the location around for reporting duplicate fixity declarations.)
-- 
-- Checks for duplicates, but not that only locally defined things are fixed.
-- Note: for local fixity declarations, duplicates would also be checked in
--       check_sigs below.  But we also use this function at the top level.
384
385
386

makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv

387
makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
388
389
390
391
392
393
 where
   add_one env (L loc (FixitySig (L name_loc name) fixity)) = do
     { -- this fixity decl is a duplicate iff
       -- the ReaderName's OccName's FastString is already in the env
       -- (we only need to check the local fix_env because
       --  definitions of non-local will be caught elsewhere)
394
395
       let { fs = occNameFS (rdrNameOcc name)
           ; fix_item = L loc fixity };
396

397
398
       case lookupFsEnv env fs of
         Nothing -> return $ extendFsEnv env fs fix_item
399
400
         Just (L loc' _) -> do
           { setSrcSpan loc $ 
401
             addErrAt name_loc (dupFixityDecl loc' name)
402
403
404
           ; return env}
     }

Ian Lynagh's avatar
Ian Lynagh committed
405
dupFixityDecl :: SrcSpan -> RdrName -> SDoc
406
dupFixityDecl loc rdr_name
Ian Lynagh's avatar
Ian Lynagh committed
407
408
  = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
	  ptext (sLit "also at ") <+> ppr loc]
409

410
---------------------
411

412
413
-- renaming a single bind

414
rnBindLHS :: NameMaker
415
416
417
418
419
420
421
          -> SDoc 
          -> LHsBind RdrName
          -- returns the renamed left-hand side,
          -- and the FreeVars *of the LHS*
          -- (i.e., any free variables of the pattern)
          -> RnM (LHsBindLR Name RdrName)

422
rnBindLHS name_maker _ (L loc bind@(PatBind { pat_lhs = pat }))
423
424
  = setSrcSpan loc $ do
      -- we don't actually use the FV processing of rnPatsAndThen here
425
      (pat',pat'_fvs) <- rnBindPat name_maker pat
426
427
428
429
430
431
      return (L loc (bind { pat_lhs = pat', bind_fvs = pat'_fvs }))
                -- We temporarily store the pat's FVs in bind_fvs;
                -- gets updated to the FVs of the whole bind
                -- when doing the RHS below
                            
rnBindLHS name_maker _ (L loc bind@(FunBind { fun_id = name@(L nameLoc _) }))
432
  = setSrcSpan loc $ 
433
    do { newname <- applyNameMaker name_maker name
434
       ; return (L loc (bind { fun_id = L nameLoc newname })) } 
435

Ian Lynagh's avatar
Ian Lynagh committed
436
437
rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)

438
439
440
441
-- assumes the left-hands-side vars are in scope
rnBind :: (Name -> [Name])		-- Signature tyvar function
       -> LHsBindLR Name RdrName
       -> RnM (LHsBind Name, [Name], Uses)
442
443
rnBind _ (L loc bind@(PatBind { pat_lhs = pat
                              , pat_rhs = grhss 
444
                                      -- pat fvs were stored in bind_fvs
445
                                      -- after processing the LHS
446
                              , bind_fvs = pat_fvs }))
447
  = setSrcSpan loc $ 
448
449
    do	{ mod <- getModule
        ; (grhss', rhs_fvs) <- rnGRHSs PatBindRhs grhss
450

451
		-- No scoped type variables for pattern bindings
452
453
454
455
456
	; let all_fvs = pat_fvs `plusFV` rhs_fvs
              fvs'    = filterNameSet (nameIsLocalOrFrom mod) all_fvs
	        -- Keep locally-defined Names
		-- As well as dependency analysis, we need these for the
		-- MonoLocalBinds test in TcBinds.decideGeneralisationPlan
457

458
	; fvs' `seq` -- See Note [Free-variable space leak]
459
460
          return (L loc (bind { pat_rhs  = grhss' 
			      , bind_fvs = fvs' }),
461
		  collectPatBinders pat, all_fvs) }
462

463
464
465
rnBind sig_fn (L loc bind@(FunBind { fun_id = name 
                            	   , fun_infix = is_infix 
                            	   , fun_matches = matches })) 
466
       -- invariant: no free vars here when it's a FunBind
467
  = setSrcSpan loc $
468
    do	{ let plain_name = unLoc name
469

470
	; (matches', rhs_fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
471
				-- bindSigTyVars tests for Opt_ScopedTyVars
472
			         rnMatchGroup (FunRhs plain_name is_infix) matches
473
	; when is_infix $ checkPrecMatch plain_name matches'
474

475
476
477
478
479
        ; mod <- getModule
        ; let fvs' = filterNameSet (nameIsLocalOrFrom mod) rhs_fvs
	        -- Keep locally-defined Names
		-- As well as dependency analysis, we need these for the
		-- MonoLocalBinds test in TcBinds.decideGeneralisationPlan
480

481
	; fvs' `seq` -- See Note [Free-variable space leak]
482
483
          return (L loc (bind { fun_matches = matches'
			      , bind_fvs   = fvs' }), 
484
		  [plain_name], rhs_fvs)
485
      }
Ian Lynagh's avatar
Ian Lynagh committed
486

487
rnBind _ b = pprPanic "rnBind" (ppr b)
488
489
490
491
492
493
494
495
496
497
498
499
500
501

{-
Note [Free-variable space leak]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We have
    fvs' = trim fvs
and we seq fvs' before turning it as part of a record.

The reason is that trim is sometimes something like
    \xs -> intersectNameSet (mkNameSet bound_names) xs
and we don't want to retain the list bound_names. This showed up in
trac ticket #1136.
-}

502
503
504
---------------------
depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
	     -> ([(RecFlag, LHsBinds Name)], DefUses)
505
506
-- Dependency analysis; this is important so that 
-- unused-binding reporting is accurate
507
508
509
depAnalBinds binds_w_dus
  = (map get_binds sccs, map get_du sccs)
  where
510
    sccs = stronglyConnCompFromEdgedVertices edges
511
512
513

    keyd_nodes = bagToList binds_w_dus `zip` [0::Int ..]

514
515
    edges = [ (node, key, [key | n <- nameSetToList uses,
			         Just key <- [lookupNameEnv key_map n] ])
516
	    | (node@(_,_,uses), key) <- keyd_nodes ]
517

518
519
520
    key_map :: NameEnv Int	-- Which binding it comes from
    key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
				     , bndr <- bndrs ]
521

522
    get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
Ian Lynagh's avatar
Ian Lynagh committed
523
    get_binds (CyclicSCC  binds_w_dus)  = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
524

525
526
527
528
529
    get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
    get_du (CyclicSCC  binds_w_dus)      = (Just defs, uses)
	where
	  defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
	  uses = unionManyNameSets [u | (_,_,u) <- binds_w_dus]
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549


---------------------
-- Bind the top-level forall'd type variables in the sigs.
-- E.g 	f :: a -> a
--	f = rhs
--	The 'a' scopes over the rhs
--
-- NB: there'll usually be just one (for a function binding)
--     but if there are many, one may shadow the rest; too bad!
--	e.g  x :: [a] -> [a]
--	     y :: [(a,a)] -> a
--	     (x,y) = e
--      In e, 'a' will be in scope, and it'll be the one from 'y'!

mkSigTvFn :: [LSig Name] -> (Name -> [Name])
-- Return a lookup function that maps an Id Name to the names
-- of the type variables that should scope over its body..
mkSigTvFn sigs
  = \n -> lookupNameEnv env n `orElse` []
550
  where
551
552
    env :: NameEnv [Name]
    env = mkNameEnv [ (name, map hsLTyVarName ltvs)
553
554
555
		    | L _ (TypeSig names
			           (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs
                    , (L _ name) <- names]
556
557
	-- Note the pattern-match on "Explicit"; we only bind
	-- type variables from signatures with an explicit top-level for-all
558
559
560
561
\end{code}


@rnMethodBinds@ is used for the method bindings of a class and an instance
562
declaration.   Like @rnBinds@ but without dependency analysis.
563
564
565
566
567
568
569
570
571
572
573
574
575
576

NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
That's crucial when dealing with an instance decl:
\begin{verbatim}
	instance Foo (T a) where
	   op x = ...
\end{verbatim}
This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
and unless @op@ occurs we won't treat the type signature of @op@ in the class
decl for @Foo@ as a source of instance-decl gates.  But we should!  Indeed,
in many ways the @op@ in an instance decl is just like an occurrence, not
a binder.

\begin{code}
577
rnMethodBinds :: Name			-- Class name
578
	      -> (Name -> [Name])	-- Signature tyvar function
579
	      -> LHsBinds RdrName
580
	      -> RnM (LHsBinds Name, FreeVars)
581

dreixel's avatar
dreixel committed
582
rnMethodBinds cls sig_fn binds
583
584
585
586
587
588
589
590
591
592
593
594
  = do { checkDupRdrNames meth_names
	     -- Check that the same method is not given twice in the
	     -- same instance decl	instance C T where
	     --			      f x = ...
	     --			      g y = ...
	     --			      f x = ...
	     -- We must use checkDupRdrNames because the Name of the
	     -- method is the Name of the class selector, whose SrcSpan
	     -- points to the class declaration; and we use rnMethodBinds
	     -- for instance decls too

       ; foldlM do_one (emptyBag, emptyFVs) (bagToList binds) }
595
  where 
596
    meth_names  = collectMethodBinders binds
597
    do_one (binds,fvs) bind 
dreixel's avatar
dreixel committed
598
       = do { (bind', fvs_bind) <- rnMethodBind cls sig_fn bind
599
	    ; return (binds `unionBags` bind', fvs_bind `plusFV` fvs) }
600

Ian Lynagh's avatar
Ian Lynagh committed
601
602
603
604
rnMethodBind :: Name
	      -> (Name -> [Name])
	      -> LHsBindLR RdrName RdrName
	      -> RnM (Bag (LHsBindLR Name Name), FreeVars)
dreixel's avatar
dreixel committed
605
rnMethodBind cls sig_fn 
606
607
             (L loc bind@(FunBind { fun_id = name, fun_infix = is_infix 
				  , fun_matches = MatchGroup matches _ }))
608
  = setSrcSpan loc $ do
609
    sel_name <- wrapLocM (lookupInstDeclBndr cls (ptext (sLit "method"))) name
610
611
612
    let plain_name = unLoc sel_name
        -- We use the selector name as the binder

613
    (new_matches, fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
dreixel's avatar
dreixel committed
614
                          mapFvRn (rnMatch (FunRhs plain_name is_infix)) matches
615
    let new_group = MatchGroup new_matches placeHolderType
616

617
    when is_infix $ checkPrecMatch plain_name new_group
618
619
620
    return (unitBag (L loc (bind { fun_id      = sel_name 
                                 , fun_matches = new_group
                                 , bind_fvs    = fvs })),
621
622
             fvs `addOneFV` plain_name)
        -- The 'fvs' field isn't used for method binds
623
624

-- Can't handle method pattern-bindings which bind multiple methods.
dreixel's avatar
dreixel committed
625
rnMethodBind _ _ (L loc bind@(PatBind {})) = do
626
    addErrAt loc (methodBindErr bind)
627
    return (emptyBag, emptyFVs)
Ian Lynagh's avatar
Ian Lynagh committed
628

dreixel's avatar
dreixel committed
629
rnMethodBind _ _ b = pprPanic "rnMethodBind" (ppr b)
630
631
632
\end{code}


633

634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
%************************************************************************
%*									*
\subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
%*									*
%************************************************************************

@renameSigs@ checks for:
\begin{enumerate}
\item more than one sig for one thing;
\item signatures given for things not bound here;
\end{enumerate}
%
At the moment we don't gather free-var info from the types in
signatures.  We'd only need this if we wanted to report unused tyvars.

\begin{code}
650
renameSigs :: HsSigCtxt 
651
652
	   -> [LSig RdrName]
	   -> RnM [LSig Name]
653
-- Renames the signatures and performs error checks
654
renameSigs ctxt sigs 
655
  = do	{ mapM_ dupSigDeclErr (findDupsEq overlapHsSig sigs)  -- Duplicate
656
657
658
	  	-- Check for duplicates on RdrName version, 
		-- because renamed version has unboundName for
		-- not-in-scope binders, which gives bogus dup-sig errors
659
660
661
662
		-- NB: in a class decl, a 'generic' sig is not considered 
		--     equal to an ordinary sig, so we allow, say
		--     	     class C a where
		--	       op :: a -> a
dreixel's avatar
dreixel committed
663
 		--             default op :: Eq a => a -> a
664
		
665
	; sigs' <- mapM (wrapLocM (renameSig ctxt)) sigs
666

667
	; let (good_sigs, bad_sigs) = partition (okHsSig ctxt) sigs'
668
669
670
	; mapM_ misplacedSigErr bad_sigs		 -- Misplaced

	; return good_sigs } 
671
672

----------------------
673
-- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
674
675
676
677
678
679
680
681
-- because this won't work for:
--	instance Foo T where
--	  {-# INLINE op #-}
--	  Baz.op = ...
-- We'll just rename the INLINE prag to refer to whatever other 'op'
-- is in scope.  (I'm assuming that Baz.op isn't in scope unqualified.)
-- Doesn't seem worth much trouble to sort this.

682
renameSig :: HsSigCtxt -> Sig RdrName -> RnM (Sig Name)
683
-- FixitySig is renamed elsewhere.
684
685
renameSig _ (IdSig x)
  = return (IdSig x)	  -- Actually this never occurs
686
687
688

renameSig ctxt sig@(TypeSig vs ty)
  = do	{ new_vs <- mapM (lookupSigOccRn ctxt sig) vs
689
	; new_ty <- rnHsSigType (ppr_sig_bndrs vs) ty
690
	; return (TypeSig new_vs new_ty) }
691

692
renameSig ctxt sig@(GenericSig vs ty)
693
694
  = do	{ defaultSigs_on <- xoptM Opt_DefaultSignatures
        ; unless defaultSigs_on (addErr (defaultSigErr sig))
695
        ; new_v <- mapM (lookupSigOccRn ctxt sig) vs
696
	; new_ty <- rnHsSigType (ppr_sig_bndrs vs) ty
dreixel's avatar
dreixel committed
697
	; return (GenericSig new_v new_ty) }
698

699
renameSig _ (SpecInstSig ty)
dreixel's avatar
dreixel committed
700
  = do	{ new_ty <- rnLHsType SpecInstSigCtx ty
701
702
	; return (SpecInstSig new_ty) }

703
704
705
-- {-# SPECIALISE #-} pragmas can refer to imported Ids
-- so, in the top-level case (when mb_names is Nothing)
-- we use lookupOccRn.  If there's both an imported and a local 'f'
simonpj's avatar
simonpj committed
706
-- then the SPECIALISE pragma is ambiguous, unlike all other signatures
707
708
709
710
renameSig ctxt sig@(SpecSig v ty inl)
  = do	{ new_v <- case ctxt of 
                     TopSigCtxt -> lookupLocatedOccRn v
                     _          -> lookupSigOccRn ctxt sig v
711
712
713
	; new_ty <- rnHsSigType (quotes (ppr v)) ty
	; return (SpecSig new_v new_ty inl) }

714
715
renameSig ctxt sig@(InlineSig v s)
  = do	{ new_v <- lookupSigOccRn ctxt sig v
716
717
	; return (InlineSig new_v s) }

718
719
renameSig ctxt sig@(FixSig (FixitySig v f))
  = do	{ new_v <- lookupSigOccRn ctxt sig v
720
	; return (FixSig (FixitySig new_v f)) }
721
722
723

ppr_sig_bndrs :: [Located RdrName] -> SDoc
ppr_sig_bndrs bs = quotes (pprWithCommas ppr bs)
724
725
726
727
728
729
730

okHsSig :: HsSigCtxt -> LSig a -> Bool
okHsSig ctxt (L _ sig) 
  = case (sig, ctxt) of
     (GenericSig {}, ClsDeclCtxt {}) -> True
     (GenericSig {}, _)              -> False

731
     (TypeSig {}, _)              -> True
732
733
734
735

     (FixSig {}, InstDeclCtxt {}) -> False
     (FixSig {}, _)               -> True

736
737
738
     (IdSig {}, TopSigCtxt)      -> True
     (IdSig {}, InstDeclCtxt {}) -> True
     (IdSig {}, _)               -> False
739
740
741
742
743
744
745
746
747
748
749

     (InlineSig {}, HsBootCtxt) -> False
     (InlineSig {}, _)          -> True

     (SpecSig {}, TopSigCtxt)       -> True
     (SpecSig {}, LocalBindCtxt {}) -> True
     (SpecSig {}, InstDeclCtxt {})  -> True
     (SpecSig {}, _)                -> False

     (SpecInstSig {}, InstDeclCtxt {}) -> True
     (SpecInstSig {}, _)               -> False
750
751
752
\end{code}


Thomas Schilling's avatar
Thomas Schilling committed
753
754
%************************************************************************
%*									*
755
\subsection{Match}
Thomas Schilling's avatar
Thomas Schilling committed
756
757
%*									*
%************************************************************************
758
759
760

\begin{code}
rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
761
762
763
rnMatchGroup ctxt (MatchGroup ms _) 
  = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
       ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
764
765
766
767

rnMatch :: HsMatchContext Name -> LMatch RdrName -> RnM (LMatch Name, FreeVars)
rnMatch ctxt  = wrapLocFstM (rnMatch' ctxt)

Ian Lynagh's avatar
Ian Lynagh committed
768
rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
769
770
771
772
rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
  = do 	{ 	-- Result type signatures are no longer supported
	  case maybe_rhs_sig of	
	        Nothing -> return ()
773
	        Just (L loc ty) -> addErrAt loc (resSigErr ctxt match ty)
774
775
776

	       -- Now the main event
	       -- note that there are no local ficity decls for matches
777
	; rnPats ctxt pats	$ \ pats' -> do
778
779
780
	{ (grhss', grhss_fvs) <- rnGRHSs ctxt grhss

	; return (Match pats' Nothing grhss', grhss_fvs) }}
781
	-- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
782
783
784
785
786
787

resSigErr :: HsMatchContext Name -> Match RdrName -> HsType RdrName -> SDoc 
resSigErr ctxt match ty
   = vcat [ ptext (sLit "Illegal result type signature") <+> quotes (ppr ty)
	  , nest 2 $ ptext (sLit "Result signatures are no longer supported in pattern matches")
 	  , pprMatchInCtxt ctxt match ]
788
789
790
791
792
793
794
795
796
797
798
799
800
\end{code}


%************************************************************************
%*									*
\subsubsection{Guarded right-hand sides (GRHSs)}
%*									*
%************************************************************************

\begin{code}
rnGRHSs :: HsMatchContext Name -> GRHSs RdrName -> RnM (GRHSs Name, FreeVars)

rnGRHSs ctxt (GRHSs grhss binds)
801
802
803
  = rnLocalBindsAndThen binds	$ \ binds' -> do
    (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
    return (GRHSs grhss' binds', fvGRHSs)
804
805
806
807

rnGRHS :: HsMatchContext Name -> LGRHS RdrName -> RnM (LGRHS Name, FreeVars)
rnGRHS ctxt = wrapLocFstM (rnGRHS' ctxt)

Ian Lynagh's avatar
Ian Lynagh committed
808
rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
809
rnGRHS' ctxt (GRHS guards rhs)
810
  = do	{ pattern_guards_allowed <- xoptM Opt_PatternGuards
811
        ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $ \ _ ->
812
				    rnLExpr rhs
813

814
	; unless (pattern_guards_allowed || is_standard_guard guards')
815
816
	  	 (addWarn (nonStdGuardErr guards'))

817
818
819
820
821
	; return (GRHS guards' rhs', fvs) }
  where
	-- Standard Haskell 1.4 guards are just a single boolean
	-- expression, rather than a list of qualifiers as in the
	-- Glasgow extension
822
823
824
    is_standard_guard []                       = True
    is_standard_guard [L _ (ExprStmt _ _ _ _)] = True
    is_standard_guard _                        = False
825
826
\end{code}

827
828
829
830
831
832
833
%************************************************************************
%*									*
\subsection{Error messages}
%*									*
%************************************************************************

\begin{code}
834
dupSigDeclErr :: [LSig RdrName] -> RnM ()
835
dupSigDeclErr sigs@(L loc sig : _)
836
  = addErrAt loc $
Ian Lynagh's avatar
Ian Lynagh committed
837
	vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
838
	      nest 2 (vcat (map ppr_sig sigs))]
839
  where
840
841
    what_it_is = hsSigDoc sig
    ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
Ian Lynagh's avatar
Ian Lynagh committed
842
dupSigDeclErr [] = panic "dupSigDeclErr"
843

844
845
misplacedSigErr :: LSig Name -> RnM ()
misplacedSigErr (L loc sig)
846
847
  = addErrAt loc $
    sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
848

849
850
defaultSigErr :: Sig RdrName -> SDoc
defaultSigErr sig = vcat [ hang (ptext (sLit "Unexpected default signature:"))
851
                              2 (ppr sig)
852
                         , ptext (sLit "Use -XDefaultSignatures to enable default signatures") ] 
853

Ian Lynagh's avatar
Ian Lynagh committed
854
methodBindErr :: HsBindLR RdrName RdrName -> SDoc
855
methodBindErr mbind
Ian Lynagh's avatar
Ian Lynagh committed
856
 =  hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
857
858
       2 (ppr mbind)

Ian Lynagh's avatar
Ian Lynagh committed
859
bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
860
bindsInHsBootFile mbinds
Ian Lynagh's avatar
Ian Lynagh committed
861
  = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
862
       2 (ppr mbinds)
863

Ian Lynagh's avatar
Ian Lynagh committed
864
nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
865
nonStdGuardErr guards
Ian Lynagh's avatar
Ian Lynagh committed
866
  = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
867
       4 (interpp'SP guards)
868

869
\end{code}