RnBinds.lhs 31.7 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
batterseapower's avatar
batterseapower committed
38
import RnTypes        ( rnIPName, rnHsSigType, rnLHsType, checkPrecMatch )
39
import RnPat
40
import RnEnv
41
import DynFlags
42
import Name
43
import NameEnv
44
import NameSet
45
import RdrName          ( RdrName, rdrNameOcc )
Ian Lynagh's avatar
Ian Lynagh committed
46
import SrcLoc
47
import ListSetOps	( findDupsEq )
48
import BasicTypes	( RecFlag(..) )
49
import Digraph		( SCC(..), stronglyConnCompFromEdgedVertices )
50
import Bag
51
import Outputable
52
import FastString
53
import Data.List	( partition )
simonpj@microsoft.com's avatar
simonpj@microsoft.com committed
54
import Maybes		( orElse )
Ian Lynagh's avatar
Ian Lynagh committed
55
import Control.Monad
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
\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}

%************************************************************************
%*									*
114
%* analysing polymorphic bindings (HsBindGroup, HsBind)
115 116 117 118 119 120 121 122 123 124 125
%*									*
%************************************************************************

\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
126
(a @FlatMonoBinds@) containing:
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

\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}
165 166
-- for top-level bindings, we need to make top-level names,
-- so we have a different entry point than for local bindings
167
rnTopBindsLHS :: MiniFixityEnv
168 169
              -> HsValBinds RdrName 
              -> RnM (HsValBindsLR Name RdrName)
170
rnTopBindsLHS fix_env binds
171
  = rnValBindsLHS (topRecNameMaker fix_env) binds
172

173
rnTopBindsRHS :: HsValBindsLR Name RdrName 
174
              -> RnM (HsValBinds Name, DefUses)
175 176
rnTopBindsRHS binds
  = do { is_boot <- tcIsHsBoot
177 178
       ; if is_boot 
         then rnTopBindsBoot binds
179
         else rnValBindsRHS TopSigCtxt binds }
180 181

rnTopBindsBoot :: HsValBindsLR Name RdrName -> RnM (HsValBinds Name, DefUses)
182 183
-- A hs-boot file has no bindings. 
-- Return a single HsBindGroup with empty binds and renamed signatures
184
rnTopBindsBoot (ValBindsIn mbinds sigs)
185
  = do	{ checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
186
	; sigs' <- renameSigs HsBootCtxt sigs
187
	; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
Ian Lynagh's avatar
Ian Lynagh committed
188
rnTopBindsBoot b = pprPanic "rnTopBindsBoot" (ppr b)
189 190 191 192 193 194 195 196 197 198
\end{code}


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

\begin{code}
199 200 201 202 203
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
204 205 206 207 208
-- The parser doesn't produce ThenBinds
rnLocalBindsAndThen EmptyLocalBinds thing_inside
  = thing_inside EmptyLocalBinds

rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
209
  = rnLocalValBindsAndThen val_binds $ \ val_binds' -> 
210
      thing_inside (HsValBinds val_binds')
211

212 213 214 215
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)
216

Ian Lynagh's avatar
Ian Lynagh committed
217
rnIPBinds :: HsIPBinds RdrName -> RnM (HsIPBinds Name, FreeVars)
218 219
rnIPBinds (IPBinds ip_binds _no_dict_binds) = do
    (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
220
    return (IPBinds ip_binds' emptyTcEvBinds, plusFVs fvs_s)
221

Ian Lynagh's avatar
Ian Lynagh committed
222
rnIPBind :: IPBind RdrName -> RnM (IPBind Name, FreeVars)
223
rnIPBind (IPBind n expr) = do
batterseapower's avatar
batterseapower committed
224
    n' <- rnIPName n
225
    (expr',fvExpr) <- rnLExpr expr
batterseapower's avatar
batterseapower committed
226
    return (IPBind n' expr', fvExpr)
227 228
\end{code}

229

230 231
%************************************************************************
%*									*
232
		ValBinds
233 234 235 236
%*									*
%************************************************************************

\begin{code}
237 238
-- Renaming local binding gropus 
-- Does duplicate/shadow check
239 240 241 242
rnLocalValBindsLHS :: MiniFixityEnv
                   -> HsValBinds RdrName
                   -> RnM ([Name], HsValBindsLR Name RdrName)
rnLocalValBindsLHS fix_env binds 
243 244 245 246 247 248 249
  = 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
250 251 252 253 254 255 256 257 258 259 260 261 262
     	 -- 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.
263
       ; let bound_names = collectHsValBinders binds'
264 265
       ; envs <- getRdrEnvs
       ; checkDupAndShadowedNames envs bound_names
266

267
       ; return (bound_names, binds') }
268 269 270 271

-- 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
272 273 274 275
rnValBindsLHS :: NameMaker 
              -> HsValBinds RdrName
              -> RnM (HsValBindsLR Name RdrName)
rnValBindsLHS topP (ValBindsIn mbinds sigs)
276 277 278
  = do { mbinds' <- mapBagM (rnBindLHS topP doc) mbinds
       ; return $ ValBindsIn mbinds' sigs }
  where
279
    bndrs = collectHsBindsBinders mbinds
280 281
    doc   = text "In the binding group for:" <+> pprWithCommas ppr bndrs

282
rnValBindsLHS _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
283

284 285
-- General version used both from the top-level and for local things
-- Assumes the LHS vars are in scope
286
--
287
-- Does not bind the local fixity declarations
288 289 290
rnValBindsRHS :: HsSigCtxt 
              -> HsValBindsLR Name RdrName
              -> RnM (HsValBinds Name, DefUses)
291

292 293
rnValBindsRHS ctxt (ValBindsIn mbinds sigs)
  = do { sigs' <- renameSigs ctxt sigs
294
       ; binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs')) mbinds
295
       ; case depAnalBinds binds_w_dus of
296 297 298
           (anal_binds, anal_dus) -> return (valbind', valbind'_dus)
              where
                valbind' = ValBindsOut anal_binds sigs'
299 300 301 302
                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
303 304
       }

305
rnValBindsRHS _ b = pprPanic "rnValBindsRHS" (ppr b)
Ian Lynagh's avatar
Ian Lynagh committed
306

307
-- Wrapper for local binds
308
--
309
-- The *client* of this function is responsible for checking for unused binders;
310 311
-- it doesn't (and can't: we don't have the thing inside the binds) happen here
--
312
-- The client is also responsible for bringing the fixities into scope
313 314 315 316
rnLocalValBindsRHS :: NameSet  -- names bound by the LHSes
                   -> HsValBindsLR Name RdrName
                   -> RnM (HsValBinds Name, DefUses)
rnLocalValBindsRHS bound_names binds
317
  = rnValBindsRHS (LocalBindCtxt bound_names) binds
318 319 320 321 322 323

-- 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
324 325 326 327
rnLocalValBindsAndThen :: HsValBinds RdrName
                       -> (HsValBinds Name -> RnM (result, FreeVars))
                       -> RnM (result, FreeVars)
rnLocalValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
328 329
 = do	{     -- (A) Create the local fixity environment 
	  new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
330

331
	      -- (B) Rename the LHSes 
332
	; (bound_names, new_lhs) <- rnLocalValBindsLHS new_fixities binds
333

334
	      --     ...and bring them (and their fixities) into scope
335 336
	; bindLocalNamesFV bound_names              $
          addLocalFixities new_fixities bound_names $ do
337

338
	{      -- (C) Do the RHS and thing inside
339
	  (binds', dus) <- rnLocalValBindsRHS (mkNameSet bound_names) new_lhs 
340
        ; (result, result_fvs) <- thing_inside binds'
341

342 343 344 345 346
		-- 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
347 348 349
	      -- Insert fake uses for variables introduced implicitly by wildcards (#4404)
	      implicit_uses = hsValBindsImplicits binds'
	; warnUnusedLocalBinds bound_names (real_uses `unionNameSets` implicit_uses)
350

351 352
	; let
            -- The variables "used" in the val binds are: 
353
            --   (1) the uses of the binds (allUses)
354
            --   (2) the FVs of the thing-inside
355
            all_uses = allUses dus `plusFV` result_fvs
356 357 358 359 360
		-- 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:
361 362 363 364 365
                --	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
366 367 368 369 370 371 372
		--
		-- 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
373

374
rnLocalValBindsAndThen bs _ = pprPanic "rnLocalValBindsAndThen" (ppr bs)
375 376 377 378 379 380 381 382


-- 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.
383 384 385

makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv

386
makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
387 388 389 390 391 392
 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)
393 394
       let { fs = occNameFS (rdrNameOcc name)
           ; fix_item = L loc fixity };
395

396 397
       case lookupFsEnv env fs of
         Nothing -> return $ extendFsEnv env fs fix_item
398 399
         Just (L loc' _) -> do
           { setSrcSpan loc $ 
400
             addErrAt name_loc (dupFixityDecl loc' name)
401 402 403
           ; return env}
     }

Ian Lynagh's avatar
Ian Lynagh committed
404
dupFixityDecl :: SrcSpan -> RdrName -> SDoc
405
dupFixityDecl loc rdr_name
Ian Lynagh's avatar
Ian Lynagh committed
406 407
  = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
	  ptext (sLit "also at ") <+> ppr loc]
408

409
---------------------
410

411 412
-- renaming a single bind

413
rnBindLHS :: NameMaker
414 415 416 417 418 419 420
          -> 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)

421
rnBindLHS name_maker _ (L loc bind@(PatBind { pat_lhs = pat }))
422 423
  = setSrcSpan loc $ do
      -- we don't actually use the FV processing of rnPatsAndThen here
424
      (pat',pat'_fvs) <- rnBindPat name_maker pat
425 426 427 428 429 430
      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 _) }))
431
  = setSrcSpan loc $ 
432
    do { newname <- applyNameMaker name_maker name
433
       ; return (L loc (bind { fun_id = L nameLoc newname })) } 
434

Ian Lynagh's avatar
Ian Lynagh committed
435 436
rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)

437 438 439 440
-- assumes the left-hands-side vars are in scope
rnBind :: (Name -> [Name])		-- Signature tyvar function
       -> LHsBindLR Name RdrName
       -> RnM (LHsBind Name, [Name], Uses)
441 442
rnBind _ (L loc bind@(PatBind { pat_lhs = pat
                              , pat_rhs = grhss 
443
                                      -- pat fvs were stored in bind_fvs
444
                                      -- after processing the LHS
445
                              , bind_fvs = pat_fvs }))
446
  = setSrcSpan loc $ 
447 448
    do	{ mod <- getModule
        ; (grhss', rhs_fvs) <- rnGRHSs PatBindRhs grhss
449

450
		-- No scoped type variables for pattern bindings
451 452 453 454 455
	; 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
456

457
	; fvs' `seq` -- See Note [Free-variable space leak]
458 459
          return (L loc (bind { pat_rhs  = grhss' 
			      , bind_fvs = fvs' }),
460
		  collectPatBinders pat, all_fvs) }
461

462 463 464
rnBind sig_fn (L loc bind@(FunBind { fun_id = name 
                            	   , fun_infix = is_infix 
                            	   , fun_matches = matches })) 
465
       -- invariant: no free vars here when it's a FunBind
466
  = setSrcSpan loc $
467
    do	{ let plain_name = unLoc name
468

469
	; (matches', rhs_fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
470
				-- bindSigTyVars tests for Opt_ScopedTyVars
471
			         rnMatchGroup (FunRhs plain_name is_infix) matches
472
	; when is_infix $ checkPrecMatch plain_name matches'
473

474 475 476 477 478
        ; 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
479

480
	; fvs' `seq` -- See Note [Free-variable space leak]
481 482
          return (L loc (bind { fun_matches = matches'
			      , bind_fvs   = fvs' }), 
483
		  [plain_name], rhs_fvs)
484
      }
Ian Lynagh's avatar
Ian Lynagh committed
485

486
rnBind _ b = pprPanic "rnBind" (ppr b)
487 488 489 490 491 492 493 494 495 496 497 498 499 500

{-
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.
-}

501 502 503
---------------------
depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
	     -> ([(RecFlag, LHsBinds Name)], DefUses)
504 505
-- Dependency analysis; this is important so that 
-- unused-binding reporting is accurate
506 507 508
depAnalBinds binds_w_dus
  = (map get_binds sccs, map get_du sccs)
  where
509
    sccs = stronglyConnCompFromEdgedVertices edges
510 511 512

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

513 514
    edges = [ (node, key, [key | n <- nameSetToList uses,
			         Just key <- [lookupNameEnv key_map n] ])
515
	    | (node@(_,_,uses), key) <- keyd_nodes ]
516

517 518 519
    key_map :: NameEnv Int	-- Which binding it comes from
    key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
				     , bndr <- bndrs ]
520

521
    get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
Ian Lynagh's avatar
Ian Lynagh committed
522
    get_binds (CyclicSCC  binds_w_dus)  = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
523

524 525 526 527 528
    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]
529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548


---------------------
-- 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` []
549
  where
550 551
    env :: NameEnv [Name]
    env = mkNameEnv [ (name, map hsLTyVarName ltvs)
552 553 554
		    | L _ (TypeSig names
			           (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs
                    , (L _ name) <- names]
555 556
	-- Note the pattern-match on "Explicit"; we only bind
	-- type variables from signatures with an explicit top-level for-all
557 558 559 560
\end{code}


@rnMethodBinds@ is used for the method bindings of a class and an instance
561
declaration.   Like @rnBinds@ but without dependency analysis.
562 563 564 565 566 567 568 569 570 571 572 573 574 575

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}
576
rnMethodBinds :: Name			-- Class name
577
	      -> (Name -> [Name])	-- Signature tyvar function
578
	      -> LHsBinds RdrName
579
	      -> RnM (LHsBinds Name, FreeVars)
580

dreixel's avatar
dreixel committed
581
rnMethodBinds cls sig_fn binds
582 583 584 585 586 587 588 589 590 591 592 593
  = 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) }
594
  where 
595
    meth_names  = collectMethodBinders binds
596
    do_one (binds,fvs) bind 
dreixel's avatar
dreixel committed
597
       = do { (bind', fvs_bind) <- rnMethodBind cls sig_fn bind
598
	    ; return (binds `unionBags` bind', fvs_bind `plusFV` fvs) }
599

Ian Lynagh's avatar
Ian Lynagh committed
600 601 602 603
rnMethodBind :: Name
	      -> (Name -> [Name])
	      -> LHsBindLR RdrName RdrName
	      -> RnM (Bag (LHsBindLR Name Name), FreeVars)
dreixel's avatar
dreixel committed
604
rnMethodBind cls sig_fn 
605 606
             (L loc bind@(FunBind { fun_id = name, fun_infix = is_infix 
				  , fun_matches = MatchGroup matches _ }))
607
  = setSrcSpan loc $ do
608
    sel_name <- wrapLocM (lookupInstDeclBndr cls (ptext (sLit "method"))) name
609 610 611
    let plain_name = unLoc sel_name
        -- We use the selector name as the binder

612
    (new_matches, fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
dreixel's avatar
dreixel committed
613
                          mapFvRn (rnMatch (FunRhs plain_name is_infix)) matches
614
    let new_group = MatchGroup new_matches placeHolderType
615

616
    when is_infix $ checkPrecMatch plain_name new_group
617 618 619
    return (unitBag (L loc (bind { fun_id      = sel_name 
                                 , fun_matches = new_group
                                 , bind_fvs    = fvs })),
620 621
             fvs `addOneFV` plain_name)
        -- The 'fvs' field isn't used for method binds
622 623

-- Can't handle method pattern-bindings which bind multiple methods.
dreixel's avatar
dreixel committed
624
rnMethodBind _ _ (L loc bind@(PatBind {})) = do
625
    addErrAt loc (methodBindErr bind)
626
    return (emptyBag, emptyFVs)
Ian Lynagh's avatar
Ian Lynagh committed
627

dreixel's avatar
dreixel committed
628
rnMethodBind _ _ b = pprPanic "rnMethodBind" (ppr b)
629 630 631
\end{code}


632

633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648
%************************************************************************
%*									*
\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}
649
renameSigs :: HsSigCtxt 
650 651
	   -> [LSig RdrName]
	   -> RnM [LSig Name]
652
-- Renames the signatures and performs error checks
653
renameSigs ctxt sigs 
654
  = do	{ mapM_ dupSigDeclErr (findDupsEq overlapHsSig sigs)  -- Duplicate
655 656 657
	  	-- Check for duplicates on RdrName version, 
		-- because renamed version has unboundName for
		-- not-in-scope binders, which gives bogus dup-sig errors
658 659 660 661
		-- 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
662
 		--             default op :: Eq a => a -> a
663
		
664
	; sigs' <- mapM (wrapLocM (renameSig ctxt)) sigs
665

666
	; let (good_sigs, bad_sigs) = partition (okHsSig ctxt) sigs'
667 668 669
	; mapM_ misplacedSigErr bad_sigs		 -- Misplaced

	; return good_sigs } 
670 671

----------------------
672
-- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
673 674 675 676 677 678 679 680
-- 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.

681
renameSig :: HsSigCtxt -> Sig RdrName -> RnM (Sig Name)
682
-- FixitySig is renamed elsewhere.
683 684
renameSig _ (IdSig x)
  = return (IdSig x)	  -- Actually this never occurs
685 686 687

renameSig ctxt sig@(TypeSig vs ty)
  = do	{ new_vs <- mapM (lookupSigOccRn ctxt sig) vs
688
	; new_ty <- rnHsSigType (ppr_sig_bndrs vs) ty
689
	; return (TypeSig new_vs new_ty) }
690

691
renameSig ctxt sig@(GenericSig vs ty)
692 693
  = do	{ defaultSigs_on <- xoptM Opt_DefaultSignatures
        ; unless defaultSigs_on (addErr (defaultSigErr sig))
694
        ; new_v <- mapM (lookupSigOccRn ctxt sig) vs
695
	; new_ty <- rnHsSigType (ppr_sig_bndrs vs) ty
dreixel's avatar
dreixel committed
696
	; return (GenericSig new_v new_ty) }
697

698
renameSig _ (SpecInstSig ty)
dreixel's avatar
dreixel committed
699
  = do	{ new_ty <- rnLHsType SpecInstSigCtx ty
700 701
	; return (SpecInstSig new_ty) }

702 703 704
-- {-# 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
705
-- then the SPECIALISE pragma is ambiguous, unlike all other signatures
706 707 708 709
renameSig ctxt sig@(SpecSig v ty inl)
  = do	{ new_v <- case ctxt of 
                     TopSigCtxt -> lookupLocatedOccRn v
                     _          -> lookupSigOccRn ctxt sig v
710 711 712
	; new_ty <- rnHsSigType (quotes (ppr v)) ty
	; return (SpecSig new_v new_ty inl) }

713 714
renameSig ctxt sig@(InlineSig v s)
  = do	{ new_v <- lookupSigOccRn ctxt sig v
715 716
	; return (InlineSig new_v s) }

717 718
renameSig ctxt sig@(FixSig (FixitySig v f))
  = do	{ new_v <- lookupSigOccRn ctxt sig v
719
	; return (FixSig (FixitySig new_v f)) }
720 721 722

ppr_sig_bndrs :: [Located RdrName] -> SDoc
ppr_sig_bndrs bs = quotes (pprWithCommas ppr bs)
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

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

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

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

     (IdSig {}, TopSigCtxt) -> True
     (IdSig {}, _)          -> False

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

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

     (SpecInstSig {}, InstDeclCtxt {}) -> True
     (SpecInstSig {}, _)               -> False
749 750 751
\end{code}


Thomas Schilling's avatar
Thomas Schilling committed
752 753
%************************************************************************
%*									*
754
\subsection{Match}
Thomas Schilling's avatar
Thomas Schilling committed
755 756
%*									*
%************************************************************************
757 758 759

\begin{code}
rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
760 761 762
rnMatchGroup ctxt (MatchGroup ms _) 
  = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
       ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
763 764 765 766

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

Ian Lynagh's avatar
Ian Lynagh committed
767
rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
768 769 770 771
rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
  = do 	{ 	-- Result type signatures are no longer supported
	  case maybe_rhs_sig of	
	        Nothing -> return ()
772
	        Just (L loc ty) -> addErrAt loc (resSigErr ctxt match ty)
773 774 775

	       -- Now the main event
	       -- note that there are no local ficity decls for matches
776
	; rnPats ctxt pats	$ \ pats' -> do
777 778 779
	{ (grhss', grhss_fvs) <- rnGRHSs ctxt grhss

	; return (Match pats' Nothing grhss', grhss_fvs) }}
780
	-- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
781 782 783 784 785 786

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 ]
787 788 789 790 791 792 793 794 795 796 797 798 799
\end{code}


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

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

rnGRHSs ctxt (GRHSs grhss binds)
800 801 802
  = rnLocalBindsAndThen binds	$ \ binds' -> do
    (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
    return (GRHSs grhss' binds', fvGRHSs)
803 804 805 806

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

Ian Lynagh's avatar
Ian Lynagh committed
807
rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
808
rnGRHS' ctxt (GRHS guards rhs)
809
  = do	{ pattern_guards_allowed <- xoptM Opt_PatternGuards
810
        ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $ \ _ ->
811
				    rnLExpr rhs
812

813
	; unless (pattern_guards_allowed || is_standard_guard guards')
814 815
	  	 (addWarn (nonStdGuardErr guards'))

816 817 818 819 820
	; 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
821 822 823
    is_standard_guard []                       = True
    is_standard_guard [L _ (ExprStmt _ _ _ _)] = True
    is_standard_guard _                        = False
824 825
\end{code}

826 827 828 829 830 831 832
%************************************************************************
%*									*
\subsection{Error messages}
%*									*
%************************************************************************

\begin{code}
833
dupSigDeclErr :: [LSig RdrName] -> RnM ()
834
dupSigDeclErr sigs@(L loc sig : _)
835
  = addErrAt loc $
Ian Lynagh's avatar
Ian Lynagh committed
836
	vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
837
	      nest 2 (vcat (map ppr_sig sigs))]
838
  where
839 840
    what_it_is = hsSigDoc sig
    ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
Ian Lynagh's avatar
Ian Lynagh committed
841
dupSigDeclErr [] = panic "dupSigDeclErr"
842

843 844
misplacedSigErr :: LSig Name -> RnM ()
misplacedSigErr (L loc sig)
845 846
  = addErrAt loc $
    sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
847

848 849
defaultSigErr :: Sig RdrName -> SDoc
defaultSigErr sig = vcat [ hang (ptext (sLit "Unexpected default signature:"))
850
                              2 (ppr sig)
851
                         , ptext (sLit "Use -XDefaultSignatures to enable default signatures") ] 
852

Ian Lynagh's avatar
Ian Lynagh committed
853
methodBindErr :: HsBindLR RdrName RdrName -> SDoc
854
methodBindErr mbind
Ian Lynagh's avatar
Ian Lynagh committed
855
 =  hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
856 857
       2 (ppr mbind)

Ian Lynagh's avatar
Ian Lynagh committed
858
bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
859
bindsInHsBootFile mbinds
Ian Lynagh's avatar
Ian Lynagh committed
860
  = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
861
       2 (ppr mbinds)
862

Ian Lynagh's avatar
Ian Lynagh committed
863
nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
864
nonStdGuardErr guards
Ian Lynagh's avatar
Ian Lynagh committed
865
  = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
866
       4 (interpp'SP guards)
867

868
\end{code}