RnBinds.lhs 30.6 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}
12 13 14 15 16 17 18 19 20 21 22 23
module RnBinds (
   -- Renaming top-level bindings
   rnTopBinds, rnTopBindsLHS, rnTopBindsRHS, 

   -- Renaming local bindings
   rnLocalBindsAndThen, rnLocalValBindsLHS, rnLocalValBindsRHS,

   -- Other bindings
   rnMethodBinds, renameSigs, mkSigTvFn,
   rnMatchGroup, rnGRHSs,
   makeMiniFixityEnv, MiniFixityEnv,
   misplacedSigErr
24 25
   ) where

26
import {-# SOURCE #-} RnExpr( rnLExpr, rnStmts )
27 28 29 30

import HsSyn
import RdrHsSyn
import RnHsSyn
31
import TcRnMonad
32
import RnTypes        ( rnHsSigType, rnLHsType, checkPrecMatch)
33
import RnPat          (rnPats, rnBindPat,
34 35
                       NameMaker, localRecNameMaker, topRecNameMaker, applyNameMaker
                      )
36
                      
37
import RnEnv
38
import DynFlags
39
import Name
40
import NameEnv
41
import NameSet
42
import RdrName		( RdrName, rdrNameOcc )
Ian Lynagh's avatar
Ian Lynagh committed
43
import SrcLoc
44
import ListSetOps	( findDupsEq )
45
import BasicTypes	( RecFlag(..) )
46
import Digraph		( SCC(..), stronglyConnCompFromEdgedVertices )
47
import Bag
48
import Outputable
49
import FastString
50
import Data.List	( partition )
simonpj@microsoft.com's avatar
simonpj@microsoft.com committed
51
import Maybes		( orElse )
Ian Lynagh's avatar
Ian Lynagh committed
52
import Control.Monad
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
\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}

%************************************************************************
%*									*
111
%* analysing polymorphic bindings (HsBindGroup, HsBind)
112 113 114 115 116 117 118 119 120 121 122
%*									*
%************************************************************************

\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
123
(a @FlatMonoBinds@) containing:
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

\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}
162 163
-- for top-level bindings, we need to make top-level names,
-- so we have a different entry point than for local bindings
164
rnTopBindsLHS :: MiniFixityEnv
165 166
              -> HsValBinds RdrName 
              -> RnM (HsValBindsLR Name RdrName)
167
rnTopBindsLHS fix_env binds
168
  = rnValBindsLHS (topRecNameMaker fix_env) binds
169

170
rnTopBindsRHS :: HsValBindsLR Name RdrName 
171
              -> RnM (HsValBinds Name, DefUses)
172 173
rnTopBindsRHS binds
  = do { is_boot <- tcIsHsBoot
174 175
       ; if is_boot 
         then rnTopBindsBoot binds
176 177 178
         else rnValBindsRHS noTrimFVs -- don't trim free vars
                            Nothing   -- Allow SPEC prags for imports
                            binds }
179

180
-- Wrapper if we don't need to do anything in between the left and right,
181 182
-- or anything else in the scope of the left
--
183
-- Never used when there are fixity declarations
184 185
rnTopBinds :: HsValBinds RdrName 
           -> RnM (HsValBinds Name, DefUses)
186 187 188 189 190
rnTopBinds b
  = do { nl <- rnTopBindsLHS emptyFsEnv b
       ; let bound_names = collectHsValBinders nl
       ; bindLocalNames bound_names $ 
         rnValBindsRHS noTrimFVs (Just (mkNameSet bound_names)) nl }
191 192 193
       

rnTopBindsBoot :: HsValBindsLR Name RdrName -> RnM (HsValBinds Name, DefUses)
194 195
-- A hs-boot file has no bindings. 
-- Return a single HsBindGroup with empty binds and renamed signatures
196
rnTopBindsBoot (ValBindsIn mbinds sigs)
197
  = do	{ checkErr (isEmptyLHsBinds mbinds) (bindsInHsBootFile mbinds)
198
	; sigs' <- renameSigs Nothing okHsBootSig sigs
199
	; return (ValBindsOut [] sigs', usesOnly (hsSigsFVs sigs')) }
Ian Lynagh's avatar
Ian Lynagh committed
200
rnTopBindsBoot b = pprPanic "rnTopBindsBoot" (ppr b)
201 202 203 204 205 206 207 208 209 210
\end{code}


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

\begin{code}
211 212 213 214 215
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
216 217 218 219 220
-- The parser doesn't produce ThenBinds
rnLocalBindsAndThen EmptyLocalBinds thing_inside
  = thing_inside EmptyLocalBinds

rnLocalBindsAndThen (HsValBinds val_binds) thing_inside
221
  = rnLocalValBindsAndThen val_binds $ \ val_binds' -> 
222
      thing_inside (HsValBinds val_binds')
223

224 225 226 227
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)
228

Ian Lynagh's avatar
Ian Lynagh committed
229
rnIPBinds :: HsIPBinds RdrName -> RnM (HsIPBinds Name, FreeVars)
230 231
rnIPBinds (IPBinds ip_binds _no_dict_binds) = do
    (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstM rnIPBind) ip_binds
232
    return (IPBinds ip_binds' emptyTcEvBinds, plusFVs fvs_s)
233

Ian Lynagh's avatar
Ian Lynagh committed
234
rnIPBind :: IPBind RdrName -> RnM (IPBind Name, FreeVars)
235 236 237
rnIPBind (IPBind n expr) = do
    name <- newIPNameRn  n
    (expr',fvExpr) <- rnLExpr expr
238
    return (IPBind name expr', fvExpr)
239 240
\end{code}

241

242 243
%************************************************************************
%*									*
244
		ValBinds
245 246 247 248
%*									*
%************************************************************************

\begin{code}
249 250
-- Renaming local binding gropus 
-- Does duplicate/shadow check
251 252 253 254
rnLocalValBindsLHS :: MiniFixityEnv
                   -> HsValBinds RdrName
                   -> RnM ([Name], HsValBindsLR Name RdrName)
rnLocalValBindsLHS fix_env binds 
255 256 257 258 259 260 261 262 263 264 265 266 267 268
  = do { -- Do error checking: we need to check for dups here because we
     	 -- 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.
269
       ; binds' <- rnValBindsLHS (localRecNameMaker fix_env) binds 
270
       ; let bound_names = collectHsValBinders binds'
271 272 273
       ; envs <- getRdrEnvs
       ; checkDupAndShadowedNames envs bound_names
       ; return (bound_names, binds') }
274 275 276 277

-- 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
278 279 280 281
rnValBindsLHS :: NameMaker 
              -> HsValBinds RdrName
              -> RnM (HsValBindsLR Name RdrName)
rnValBindsLHS topP (ValBindsIn mbinds sigs)
282 283 284
  = do { mbinds' <- mapBagM (rnBindLHS topP doc) mbinds
       ; return $ ValBindsIn mbinds' sigs }
  where
285
    bndrs = collectHsBindsBinders mbinds
286 287
    doc   = text "In the binding group for:" <+> pprWithCommas ppr bndrs

288
rnValBindsLHS _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
289

290 291
-- General version used both from the top-level and for local things
-- Assumes the LHS vars are in scope
292
--
293
-- Does not bind the local fixity declarations
294
rnValBindsRHS :: (FreeVars -> FreeVars)  -- for trimming free var sets
295 296
                     -- The trimming function trims the free vars we attach to a
                     -- binding so that it stays reasonably small
297 298 299 300 301 302 303
               -> Maybe NameSet	-- Names bound by the LHSes
	       	  		-- Nothing if expect sigs for imports
               -> HsValBindsLR Name RdrName
               -> RnM (HsValBinds Name, DefUses)

rnValBindsRHS trim mb_bound_names (ValBindsIn mbinds sigs)
  = do { sigs' <- renameSigs mb_bound_names okBindSig sigs
304 305
       ; binds_w_dus <- mapBagM (rnBind (mkSigTvFn sigs') trim) mbinds
       ; case depAnalBinds binds_w_dus of
306 307 308 309 310 311 312
           (anal_binds, anal_dus) -> return (valbind', valbind'_dus)
              where
                valbind' = ValBindsOut anal_binds sigs'
                valbind'_dus = usesOnly (hsSigsFVs sigs') `plusDU` anal_dus
       }

rnValBindsRHS _ _ b = pprPanic "rnValBindsRHS" (ppr b)
313

314 315
noTrimFVs :: FreeVars -> FreeVars
noTrimFVs fvs = fvs
Ian Lynagh's avatar
Ian Lynagh committed
316

317
-- Wrapper for local binds
318
--
319
-- The *client* of this function is responsible for checking for unused binders;
320 321
-- it doesn't (and can't: we don't have the thing inside the binds) happen here
--
322
-- The client is also responsible for bringing the fixities into scope
323 324 325 326 327
rnLocalValBindsRHS :: NameSet  -- names bound by the LHSes
                   -> HsValBindsLR Name RdrName
                   -> RnM (HsValBinds Name, DefUses)
rnLocalValBindsRHS bound_names binds
  = rnValBindsRHS trim (Just bound_names) binds
328 329 330
  where
    trim fvs = intersectNameSet bound_names fvs 
	-- Only keep the names the names from this group
331 332 333 334 335 336

-- 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
337 338 339 340
rnLocalValBindsAndThen :: HsValBinds RdrName
                       -> (HsValBinds Name -> RnM (result, FreeVars))
                       -> RnM (result, FreeVars)
rnLocalValBindsAndThen binds@(ValBindsIn _ sigs) thing_inside
341 342
 = do	{     -- (A) Create the local fixity environment 
	  new_fixities <- makeMiniFixityEnv [L loc sig | L loc (FixSig sig) <- sigs]
343

344
	      -- (B) Rename the LHSes 
345
	; (bound_names, new_lhs) <- rnLocalValBindsLHS new_fixities binds
346

347
	      --     ...and bring them (and their fixities) into scope
348 349
	; bindLocalNamesFV bound_names              $
          addLocalFixities new_fixities bound_names $ do
350

351
	{      -- (C) Do the RHS and thing inside
352
	  (binds', dus) <- rnLocalValBindsRHS (mkNameSet bound_names) new_lhs 
353
        ; (result, result_fvs) <- thing_inside binds'
354

355 356 357 358 359
		-- 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
360 361 362
	      -- Insert fake uses for variables introduced implicitly by wildcards (#4404)
	      implicit_uses = hsValBindsImplicits binds'
	; warnUnusedLocalBinds bound_names (real_uses `unionNameSets` implicit_uses)
363

364 365
	; let
            -- The variables "used" in the val binds are: 
366
            --   (1) the uses of the binds (allUses)
367
            --   (2) the FVs of the thing-inside
368
            all_uses = allUses dus `plusFV` result_fvs
369 370 371 372 373
		-- 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:
374 375 376 377 378
                --	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
379 380 381 382 383 384 385
		--
		-- 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
386

387
rnLocalValBindsAndThen bs _ = pprPanic "rnLocalValBindsAndThen" (ppr bs)
388 389 390 391 392 393 394 395


-- 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.
396 397 398

makeMiniFixityEnv :: [LFixitySig RdrName] -> RnM MiniFixityEnv

399
makeMiniFixityEnv decls = foldlM add_one emptyFsEnv decls
400 401 402 403 404 405
 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)
406 407
       let { fs = occNameFS (rdrNameOcc name)
           ; fix_item = L loc fixity };
408

409 410
       case lookupFsEnv env fs of
         Nothing -> return $ extendFsEnv env fs fix_item
411 412
         Just (L loc' _) -> do
           { setSrcSpan loc $ 
413
             addErrAt name_loc (dupFixityDecl loc' name)
414 415 416
           ; return env}
     }

Ian Lynagh's avatar
Ian Lynagh committed
417
dupFixityDecl :: SrcSpan -> RdrName -> SDoc
418
dupFixityDecl loc rdr_name
Ian Lynagh's avatar
Ian Lynagh committed
419 420
  = vcat [ptext (sLit "Multiple fixity declarations for") <+> quotes (ppr rdr_name),
	  ptext (sLit "also at ") <+> ppr loc]
421

422
---------------------
423

424 425
-- renaming a single bind

426
rnBindLHS :: NameMaker
427 428 429 430 431 432 433
          -> 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)

434
rnBindLHS name_maker _ (L loc bind@(PatBind { pat_lhs = pat }))
435 436
  = setSrcSpan loc $ do
      -- we don't actually use the FV processing of rnPatsAndThen here
437
      (pat',pat'_fvs) <- rnBindPat name_maker pat
438 439 440 441 442 443
      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 _) }))
444
  = setSrcSpan loc $ 
445
    do { newname <- applyNameMaker name_maker name
446
       ; return (L loc (bind { fun_id = L nameLoc newname })) } 
447

Ian Lynagh's avatar
Ian Lynagh committed
448 449
rnBindLHS _ _ b = pprPanic "rnBindLHS" (ppr b)

450 451 452 453 454
-- assumes the left-hands-side vars are in scope
rnBind :: (Name -> [Name])		-- Signature tyvar function
       -> (FreeVars -> FreeVars)	-- Trimming function for rhs free vars
       -> LHsBindLR Name RdrName
       -> RnM (LHsBind Name, [Name], Uses)
455 456 457 458 459
rnBind _ trim (L loc bind@(PatBind { pat_lhs = pat
                                   , pat_rhs = grhss 
                                      -- pat fvs were stored in bind_fvs
                                      -- after processing the LHS          
                                   , bind_fvs = pat_fvs }))
460
  = setSrcSpan loc $ 
461
    do	{ let bndrs = collectPatBinders pat
462

463 464
	; (grhss', fvs) <- rnGRHSs PatBindRhs grhss
		-- No scoped type variables for pattern bindings
465 466
	; let all_fvs = pat_fvs `plusFV` fvs
              fvs'    = trim all_fvs
467

468
	; fvs' `seq` -- See Note [Free-variable space leak]
469 470
          return (L loc (bind { pat_rhs  = grhss' 
			      , bind_fvs = fvs' }),
471
		  bndrs, all_fvs) }
472

473 474 475 476
rnBind sig_fn trim 
       (L loc bind@(FunBind { fun_id = name 
                            , fun_infix = is_infix 
                            , fun_matches = matches })) 
477 478 479
       -- invariant: no free vars here when it's a FunBind
  = setSrcSpan loc $ 
    do	{ let plain_name = unLoc name
480

481 482
	; (matches', fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
				-- bindSigTyVars tests for Opt_ScopedTyVars
483
			     rnMatchGroup (FunRhs plain_name is_infix) matches
Ian Lynagh's avatar
Ian Lynagh committed
484
	; let fvs' = trim fvs
485

486
	; when is_infix $ checkPrecMatch plain_name matches'
487

488
	; fvs' `seq` -- See Note [Free-variable space leak]
489

490 491
          return (L loc (bind { fun_matches = matches'
			      , bind_fvs   = fvs' }), 
492 493
		  [plain_name], fvs)
      }
Ian Lynagh's avatar
Ian Lynagh committed
494 495

rnBind _ _ b = pprPanic "rnBind" (ppr b)
496 497 498 499 500 501 502 503 504 505 506 507 508 509

{-
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.
-}

510 511 512
---------------------
depAnalBinds :: Bag (LHsBind Name, [Name], Uses)
	     -> ([(RecFlag, LHsBinds Name)], DefUses)
513 514
-- Dependency analysis; this is important so that 
-- unused-binding reporting is accurate
515 516 517
depAnalBinds binds_w_dus
  = (map get_binds sccs, map get_du sccs)
  where
518
    sccs = stronglyConnCompFromEdgedVertices edges
519 520 521

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

522 523
    edges = [ (node, key, [key | n <- nameSetToList uses,
			         Just key <- [lookupNameEnv key_map n] ])
524
	    | (node@(_,_,uses), key) <- keyd_nodes ]
525

526 527 528
    key_map :: NameEnv Int	-- Which binding it comes from
    key_map = mkNameEnv [(bndr, key) | ((_, bndrs, _), key) <- keyd_nodes
				     , bndr <- bndrs ]
529

530
    get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, unitBag bind)
Ian Lynagh's avatar
Ian Lynagh committed
531
    get_binds (CyclicSCC  binds_w_dus)  = (Recursive, listToBag [b | (b,_,_) <- binds_w_dus])
532

533 534 535 536 537
    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]
538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557


---------------------
-- 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` []
558
  where
559 560
    env :: NameEnv [Name]
    env = mkNameEnv [ (name, map hsLTyVarName ltvs)
561 562
		    | L _ (TypeSig (L _ name) 
			           (L _ (HsForAllTy Explicit ltvs _ _))) <- sigs]
563 564
	-- Note the pattern-match on "Explicit"; we only bind
	-- type variables from signatures with an explicit top-level for-all
565 566 567 568
\end{code}


@rnMethodBinds@ is used for the method bindings of a class and an instance
569
declaration.   Like @rnBinds@ but without dependency analysis.
570 571 572 573 574 575 576 577 578 579 580 581 582 583

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}
584
rnMethodBinds :: Name			-- Class name
585
	      -> (Name -> [Name])	-- Signature tyvar function
586
	      -> [Name]			-- Names for generic type variables
587
	      -> LHsBinds RdrName
588
	      -> RnM (LHsBinds Name, FreeVars)
589

590
rnMethodBinds cls sig_fn gen_tyvars binds
591 592 593 594 595
  = foldlM do_one (emptyBag,emptyFVs) (bagToList binds)
  where 
    do_one (binds,fvs) bind 
       = do { (bind', fvs_bind) <- rnMethodBind cls sig_fn gen_tyvars bind
	    ; return (binds `unionBags` bind', fvs_bind `plusFV` fvs) }
596

Ian Lynagh's avatar
Ian Lynagh committed
597 598 599 600 601
rnMethodBind :: Name
	      -> (Name -> [Name])
	      -> [Name]
	      -> LHsBindLR RdrName RdrName
	      -> RnM (Bag (LHsBindLR Name Name), FreeVars)
602 603 604
rnMethodBind cls sig_fn gen_tyvars 
             (L loc bind@(FunBind { fun_id = name, fun_infix = is_infix 
				  , fun_matches = MatchGroup matches _ }))
605
  = setSrcSpan loc $ do
606
    sel_name <- wrapLocM (lookupInstDeclBndr cls) name
607 608 609
    let plain_name = unLoc sel_name
        -- We use the selector name as the binder

610 611 612
    (new_matches, fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
                          mapFvRn (rn_match (FunRhs plain_name is_infix)) matches
    let new_group = MatchGroup new_matches placeHolderType
613

614
    when is_infix $ checkPrecMatch plain_name new_group
615 616 617
    return (unitBag (L loc (bind { fun_id      = sel_name 
                                 , fun_matches = new_group
                                 , bind_fvs    = fvs })),
618 619
             fvs `addOneFV` plain_name)
        -- The 'fvs' field isn't used for method binds
620
  where
621 622
	-- Truly gruesome; bring into scope the correct members of the generic 
	-- type variables.  See comments in RnSource.rnSourceDecl(ClassDecl)
623
    rn_match info match@(L _ (Match (L _ (TypePat ty) : _) _ _))
624
	= extendTyVarEnvFVRn gen_tvs 	$
625
	  rnMatch info match
626
	where
627
	  tvs     = map (rdrNameOcc.unLoc) (extractHsTyRdrTyVars ty)
628 629
	  gen_tvs = [tv | tv <- gen_tyvars, nameOccName tv `elem` tvs] 

630
    rn_match info match = rnMatch info match
631 632

-- Can't handle method pattern-bindings which bind multiple methods.
633 634
rnMethodBind _ _ _ (L loc bind@(PatBind {})) = do
    addErrAt loc (methodBindErr bind)
635
    return (emptyBag, emptyFVs)
Ian Lynagh's avatar
Ian Lynagh committed
636 637

rnMethodBind _ _ _ b = pprPanic "rnMethodBind" (ppr b)
638 639 640
\end{code}


641

642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657
%************************************************************************
%*									*
\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}
658
renameSigs :: Maybe NameSet		-- If (Just ns) complain if the sig isn't for one of ns
659
	   -> (Sig Name -> Bool) 	-- Complain about the wrong kind of signature if this is False
660 661
	   -> [LSig RdrName]
	   -> RnM [LSig Name]
662
-- Renames the signatures and performs error checks
663
renameSigs mb_names ok_sig sigs 
664 665 666 667 668 669 670 671 672 673 674
  = do	{ mapM_ dupSigDeclErr (findDupsEq eqHsSig sigs)  -- Duplicate
	  	-- Check for duplicates on RdrName version, 
		-- because renamed version has unboundName for
		-- not-in-scope binders, which gives bogus dup-sig errors

	; sigs' <- mapM (wrapLocM (renameSig mb_names)) sigs

	; let (good_sigs, bad_sigs) = partition (ok_sig . unLoc) sigs'
	; mapM_ misplacedSigErr bad_sigs		 -- Misplaced

	; return good_sigs } 
675 676

----------------------
677
-- We use lookupSigOccRn in the signatures, which is a little bit unsatisfactory
678 679 680 681 682 683 684 685
-- 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.

686 687
renameSig :: Maybe NameSet -> Sig RdrName -> RnM (Sig Name)
-- FixitySig is renamed elsewhere.
688 689
renameSig _ (IdSig x)
  = return (IdSig x)	  -- Actually this never occurs
690
renameSig mb_names sig@(TypeSig v ty)
691
  = do	{ new_v <- lookupSigOccRn mb_names sig v
692 693 694 695 696 697 698
	; new_ty <- rnHsSigType (quotes (ppr v)) ty
	; return (TypeSig new_v new_ty) }

renameSig _ (SpecInstSig ty)
  = do	{ new_ty <- rnLHsType (text "A SPECIALISE instance pragma") ty
	; return (SpecInstSig new_ty) }

699 700 701
-- {-# 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
702
-- then the SPECIALISE pragma is ambiguous, unlike all other signatures
703
renameSig mb_names sig@(SpecSig v ty inl)
704 705 706
  = do	{ new_v <- case mb_names of
                     Just {} -> lookupSigOccRn mb_names sig v
                     Nothing -> lookupLocatedOccRn v
707 708 709 710
	; new_ty <- rnHsSigType (quotes (ppr v)) ty
	; return (SpecSig new_v new_ty inl) }

renameSig mb_names sig@(InlineSig v s)
711
  = do	{ new_v <- lookupSigOccRn mb_names sig v
712 713 714
	; return (InlineSig new_v s) }

renameSig mb_names sig@(FixSig (FixitySig v f))
715
  = do	{ new_v <- lookupSigOccRn mb_names sig v
716
	; return (FixSig (FixitySig new_v f)) }
717 718 719
\end{code}


Thomas Schilling's avatar
Thomas Schilling committed
720 721
%************************************************************************
%*									*
722
\subsection{Match}
Thomas Schilling's avatar
Thomas Schilling committed
723 724
%*									*
%************************************************************************
725 726 727

\begin{code}
rnMatchGroup :: HsMatchContext Name -> MatchGroup RdrName -> RnM (MatchGroup Name, FreeVars)
728 729 730
rnMatchGroup ctxt (MatchGroup ms _) 
  = do { (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt) ms
       ; return (MatchGroup new_ms placeHolderType, ms_fvs) }
731 732 733 734

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

Ian Lynagh's avatar
Ian Lynagh committed
735
rnMatch' :: HsMatchContext Name -> Match RdrName -> RnM (Match Name, FreeVars)
736 737 738 739
rnMatch' ctxt match@(Match pats maybe_rhs_sig grhss)
  = do 	{ 	-- Result type signatures are no longer supported
	  case maybe_rhs_sig of	
	        Nothing -> return ()
740
	        Just (L loc ty) -> addErrAt loc (resSigErr ctxt match ty)
741 742 743

	       -- Now the main event
	       -- note that there are no local ficity decls for matches
744
	; rnPats ctxt pats	$ \ pats' -> do
745 746 747
	{ (grhss', grhss_fvs) <- rnGRHSs ctxt grhss

	; return (Match pats' Nothing grhss', grhss_fvs) }}
748
	-- The bindPatSigTyVarsFV and rnPatsAndThen will remove the bound FVs
749 750 751 752 753 754

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 ]
755 756 757 758 759 760 761 762 763 764 765 766 767
\end{code}


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

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

rnGRHSs ctxt (GRHSs grhss binds)
768 769 770
  = rnLocalBindsAndThen binds	$ \ binds' -> do
    (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt) grhss
    return (GRHSs grhss' binds', fvGRHSs)
771 772 773 774

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

Ian Lynagh's avatar
Ian Lynagh committed
775
rnGRHS' :: HsMatchContext Name -> GRHS RdrName -> RnM (GRHS Name, FreeVars)
776
rnGRHS' ctxt (GRHS guards rhs)
777
  = do	{ pattern_guards_allowed <- xoptM Opt_PatternGuards
778
        ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) guards $ \ _ ->
779
				    rnLExpr rhs
780

781
	; unless (pattern_guards_allowed || is_standard_guard guards')
782 783
	  	 (addWarn (nonStdGuardErr guards'))

784 785 786 787 788 789 790
	; 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
    is_standard_guard []                     = True
    is_standard_guard [L _ (ExprStmt _ _ _)] = True
Ian Lynagh's avatar
Ian Lynagh committed
791
    is_standard_guard _                      = False
792 793
\end{code}

794 795 796 797 798 799 800
%************************************************************************
%*									*
\subsection{Error messages}
%*									*
%************************************************************************

\begin{code}
801
dupSigDeclErr :: [LSig RdrName] -> RnM ()
802
dupSigDeclErr sigs@(L loc sig : _)
803
  = addErrAt loc $
Ian Lynagh's avatar
Ian Lynagh committed
804
	vcat [ptext (sLit "Duplicate") <+> what_it_is <> colon,
805
	      nest 2 (vcat (map ppr_sig sigs))]
806
  where
807 808
    what_it_is = hsSigDoc sig
    ppr_sig (L loc sig) = ppr loc <> colon <+> ppr sig
Ian Lynagh's avatar
Ian Lynagh committed
809
dupSigDeclErr [] = panic "dupSigDeclErr"
810

811 812
misplacedSigErr :: LSig Name -> RnM ()
misplacedSigErr (L loc sig)
813 814
  = addErrAt loc $
    sep [ptext (sLit "Misplaced") <+> hsSigDoc sig <> colon, ppr sig]
815

Ian Lynagh's avatar
Ian Lynagh committed
816
methodBindErr :: HsBindLR RdrName RdrName -> SDoc
817
methodBindErr mbind
Ian Lynagh's avatar
Ian Lynagh committed
818
 =  hang (ptext (sLit "Pattern bindings (except simple variables) not allowed in instance declarations"))
819 820
       2 (ppr mbind)

Ian Lynagh's avatar
Ian Lynagh committed
821
bindsInHsBootFile :: LHsBindsLR Name RdrName -> SDoc
822
bindsInHsBootFile mbinds
Ian Lynagh's avatar
Ian Lynagh committed
823
  = hang (ptext (sLit "Bindings in hs-boot files are not allowed"))
824
       2 (ppr mbinds)
825

Ian Lynagh's avatar
Ian Lynagh committed
826
nonStdGuardErr :: [LStmtLR Name Name] -> SDoc
827
nonStdGuardErr guards
Ian Lynagh's avatar
Ian Lynagh committed
828
  = hang (ptext (sLit "accepting non-standard pattern guards (use -XPatternGuards to suppress this message)"))
829
       4 (interpp'SP guards)
830
\end{code}