2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1998
4 \section[StgLint]{A ``lint'' pass to check for Stg correctness}
7 module StgLint ( lintStgBindings ) where
9 #include "HsVersions.h"
13 import Bag ( Bag, emptyBag, isEmptyBag, snocBag, bagToList )
14 import Id ( Id, idType, isLocalId )
16 import DataCon ( DataCon, dataConArgTys, dataConRepType )
17 import PrimOp ( primOpType )
18 import Literal ( literalType, Literal )
19 import Maybes ( catMaybes )
20 import Name ( getSrcLoc )
21 import ErrUtils ( Message, addErrLocHdrLine )
22 import Type ( mkFunTys, splitFunTys, splitTyConApp_maybe,
23 isUnLiftedType, isTyVarTy, dropForAlls, Type
25 import TyCon ( TyCon, isAlgTyCon, isNewTyCon, tyConDataCons )
26 import Util ( zipEqual, equalLength )
29 infixr 9 `thenL`, `thenL_`, `thenMaybeL`, `thenMaybeL_`
33 (a) *some* type errors
34 (b) locally-defined variables used but not defined
37 Note: unless -dverbose-stg is on, display of lint errors will result
38 in "panic: bOGUS_LVs".
43 This module has suffered bit-rot; it is likely to yield lint errors
44 for Stg code that is currently perfectly acceptable for code
45 generation. Solution: don't use it! (KSW 2000-05).
48 %************************************************************************
50 \subsection{``lint'' for various constructs}
52 %************************************************************************
54 @lintStgBindings@ is the top-level interface function.
57 lintStgBindings :: String -> [StgBinding] -> [StgBinding]
59 lintStgBindings whodunnit binds
61 case (initL (lint_binds binds)) of
63 Just msg -> pprPanic "" (vcat [
64 ptext SLIT("*** Stg Lint ErrMsgs: in") <+> text whodunnit <+> ptext SLIT("***"),
66 ptext SLIT("*** Offending Program ***"),
68 ptext SLIT("*** End of Offense ***")])
70 lint_binds :: [StgBinding] -> LintM ()
72 lint_binds [] = returnL ()
73 lint_binds (bind:binds)
74 = lintStgBinds bind `thenL` \ binders ->
75 addInScopeVars binders (
82 lintStgArg :: StgArg -> LintM (Maybe Type)
83 lintStgArg (StgLitArg lit) = returnL (Just (literalType lit))
84 lintStgArg (StgVarArg v) = lintStgVar v
86 lintStgVar v = checkInScope v `thenL_`
87 returnL (Just (idType v))
91 lintStgBinds :: StgBinding -> LintM [Id] -- Returns the binders
92 lintStgBinds (StgNonRec _srt binder rhs)
93 = lint_binds_help (binder,rhs) `thenL_`
96 lintStgBinds (StgRec _srt pairs)
97 = addInScopeVars binders (
98 mapL lint_binds_help pairs `thenL_`
102 binders = [b | (b,_) <- pairs]
104 lint_binds_help (binder, rhs)
105 = addLoc (RhsOf binder) (
107 lintStgRhs rhs `thenL` \ maybe_rhs_ty ->
109 -- Check binder doesn't have unlifted type
110 checkL (not (isUnLiftedType binder_ty))
111 (mkUnLiftedTyMsg binder rhs) `thenL_`
113 -- Check match to RHS type
114 (case maybe_rhs_ty of
115 Nothing -> returnL ()
116 Just rhs_ty -> checkTys binder_ty
118 (mkRhsMsg binder rhs_ty)
124 binder_ty = idType binder
128 lintStgRhs :: StgRhs -> LintM (Maybe Type)
130 lintStgRhs (StgRhsClosure _ _ _ _ [] expr)
133 lintStgRhs (StgRhsClosure _ _ _ _ binders expr)
134 = addLoc (LambdaBodyOf binders) (
135 addInScopeVars binders (
136 lintStgExpr expr `thenMaybeL` \ body_ty ->
137 returnL (Just (mkFunTys (map idType binders) body_ty))
140 lintStgRhs (StgRhsCon _ con args)
141 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
142 case maybe_arg_tys of
143 Nothing -> returnL Nothing
144 Just arg_tys -> checkFunApp con_ty arg_tys (mkRhsConMsg con_ty arg_tys)
146 con_ty = dataConRepType con
150 lintStgExpr :: StgExpr -> LintM (Maybe Type) -- Nothing if error found
152 lintStgExpr (StgLit l) = returnL (Just (literalType l))
154 lintStgExpr e@(StgApp fun args)
155 = lintStgVar fun `thenMaybeL` \ fun_ty ->
156 mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
157 case maybe_arg_tys of
158 Nothing -> returnL Nothing
159 Just arg_tys -> checkFunApp fun_ty arg_tys (mkFunAppMsg fun_ty arg_tys e)
161 lintStgExpr e@(StgConApp con args)
162 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
163 case maybe_arg_tys of
164 Nothing -> returnL Nothing
165 Just arg_tys -> checkFunApp con_ty arg_tys (mkFunAppMsg con_ty arg_tys e)
167 con_ty = dataConRepType con
169 lintStgExpr e@(StgOpApp (StgFCallOp _ _) args res_ty)
170 = -- We don't have enough type information to check
171 -- the application; ToDo
172 mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
173 returnL (Just res_ty)
175 lintStgExpr e@(StgOpApp (StgPrimOp op) args _)
176 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
177 case maybe_arg_tys of
178 Nothing -> returnL Nothing
179 Just arg_tys -> checkFunApp op_ty arg_tys (mkFunAppMsg op_ty arg_tys e)
181 op_ty = primOpType op
183 lintStgExpr (StgLam _ bndrs _)
184 = addErrL (ptext SLIT("Unexpected StgLam") <+> ppr bndrs) `thenL_`
187 lintStgExpr (StgLet binds body)
188 = lintStgBinds binds `thenL` \ binders ->
189 addLoc (BodyOfLetRec binders) (
190 addInScopeVars binders (
194 lintStgExpr (StgLetNoEscape _ _ binds body)
195 = lintStgBinds binds `thenL` \ binders ->
196 addLoc (BodyOfLetRec binders) (
197 addInScopeVars binders (
201 lintStgExpr (StgSCC _ expr) = lintStgExpr expr
203 lintStgExpr e@(StgCase scrut _ _ bndr _ alts)
204 = lintStgExpr scrut `thenMaybeL` \ _ ->
207 StgPrimAlts tc _ _ -> check_bndr tc
208 StgAlgAlts (Just tc) _ _ -> check_bndr tc
209 StgAlgAlts Nothing _ _ -> returnL ()
212 (trace (showSDoc (ppr e)) $
213 -- we only allow case of tail-call or primop.
215 StgApp _ _ -> returnL ()
216 StgConApp _ _ -> returnL ()
217 other -> addErrL (mkCaseOfCaseMsg e)) `thenL_`
219 addInScopeVars [bndr] (lintStgAlts alts scrut_ty)
222 scrut_ty = idType bndr
223 bad_bndr = mkDefltMsg bndr
224 check_bndr tc = case splitTyConApp_maybe scrut_ty of
225 Just (bndr_tc, _) -> checkL (tc == bndr_tc) bad_bndr
226 Nothing -> addErrL bad_bndr
230 lintStgAlts :: StgCaseAlts
231 -> Type -- Type of scrutinee
232 -> LintM (Maybe Type) -- Type of alternatives
234 lintStgAlts alts scrut_ty
236 StgAlgAlts _ alg_alts deflt ->
237 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
238 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
239 returnL (maybe_deflt_ty : maybe_alt_tys)
241 StgPrimAlts _ prim_alts deflt ->
242 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
243 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
244 returnL (maybe_deflt_ty : maybe_alt_tys)
245 ) `thenL` \ maybe_result_tys ->
246 -- Check the result types
247 case catMaybes (maybe_result_tys) of
248 [] -> returnL Nothing
250 (first_ty:tys) -> mapL check tys `thenL_`
251 returnL (Just first_ty)
253 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
255 lintAlgAlt scrut_ty (con, args, _, rhs)
256 = (case splitTyConApp_maybe scrut_ty of
257 Just (tycon, tys_applied) | isAlgTyCon tycon &&
258 not (isNewTyCon tycon) ->
260 cons = tyConDataCons tycon
261 arg_tys = dataConArgTys con tys_applied
262 -- This almost certainly does not work for existential constructors
264 checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con) `thenL_`
265 checkL (equalLength arg_tys args) (mkAlgAltMsg3 con args)
267 mapL check (zipEqual "lintAlgAlt:stg" arg_tys args) `thenL_`
270 addErrL (mkAlgAltMsg1 scrut_ty)
272 addInScopeVars args (
276 check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
278 -- elem: yes, the elem-list here can sometimes be long-ish,
279 -- but as it's use-once, probably not worth doing anything different
280 -- We give it its own copy, so it isn't overloaded.
282 elem x (y:ys) = x==y || elem x ys
284 lintPrimAlt scrut_ty alt@(lit,rhs)
285 = checkTys (literalType lit) scrut_ty (mkPrimAltMsg alt) `thenL_`
288 lintDeflt StgNoDefault scrut_ty = returnL Nothing
289 lintDeflt deflt@(StgBindDefault rhs) scrut_ty = lintStgExpr rhs
293 %************************************************************************
295 \subsection[lint-monad]{The Lint monad}
297 %************************************************************************
300 type LintM a = [LintLocInfo] -- Locations
301 -> IdSet -- Local vars in scope
302 -> Bag Message -- Error messages so far
303 -> (a, Bag Message) -- Result and error messages (if any)
306 = RhsOf Id -- The variable bound
307 | LambdaBodyOf [Id] -- The lambda-binder
308 | BodyOfLetRec [Id] -- One of the binders
311 (getSrcLoc v, ptext SLIT(" [RHS of ") <> pp_binders [v] <> char ']' )
312 dumpLoc (LambdaBodyOf bs) =
313 (getSrcLoc (head bs), ptext SLIT(" [in body of lambda with binders ") <> pp_binders bs <> char ']' )
315 dumpLoc (BodyOfLetRec bs) =
316 (getSrcLoc (head bs), ptext SLIT(" [in body of letrec with binders ") <> pp_binders bs <> char ']' )
319 pp_binders :: [Id] -> SDoc
321 = sep (punctuate comma (map pp_binder bs))
324 = hsep [ppr b, dcolon, ppr (idType b)]
328 initL :: LintM a -> Maybe Message
330 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
331 if isEmptyBag errs then
334 Just (vcat (punctuate (text "") (bagToList errs)))
337 returnL :: a -> LintM a
338 returnL r loc scope errs = (r, errs)
340 thenL :: LintM a -> (a -> LintM b) -> LintM b
341 thenL m k loc scope errs
342 = case m loc scope errs of
343 (r, errs') -> k r loc scope errs'
345 thenL_ :: LintM a -> LintM b -> LintM b
346 thenL_ m k loc scope errs
347 = case m loc scope errs of
348 (_, errs') -> k loc scope errs'
350 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
351 thenMaybeL m k loc scope errs
352 = case m loc scope errs of
353 (Nothing, errs2) -> (Nothing, errs2)
354 (Just r, errs2) -> k r loc scope errs2
356 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
357 thenMaybeL_ m k loc scope errs
358 = case m loc scope errs of
359 (Nothing, errs2) -> (Nothing, errs2)
360 (Just _, errs2) -> k loc scope errs2
362 mapL :: (a -> LintM b) -> [a] -> LintM [b]
363 mapL f [] = returnL []
366 mapL f xs `thenL` \ rs ->
369 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
370 -- Returns Nothing if anything fails
371 mapMaybeL f [] = returnL (Just [])
373 = f x `thenMaybeL` \ r ->
374 mapMaybeL f xs `thenMaybeL` \ rs ->
375 returnL (Just (r:rs))
379 checkL :: Bool -> Message -> LintM ()
380 checkL True msg loc scope errs = ((), errs)
381 checkL False msg loc scope errs = ((), addErr errs msg loc)
383 addErrL :: Message -> LintM ()
384 addErrL msg loc scope errs = ((), addErr errs msg loc)
386 addErr :: Bag Message -> Message -> [LintLocInfo] -> Bag Message
388 addErr errs_so_far msg locs
389 = errs_so_far `snocBag` mk_msg locs
391 mk_msg (loc:_) = let (l,hdr) = dumpLoc loc
392 in addErrLocHdrLine l hdr msg
395 addLoc :: LintLocInfo -> LintM a -> LintM a
396 addLoc extra_loc m loc scope errs
397 = m (extra_loc:loc) scope errs
399 addInScopeVars :: [Id] -> LintM a -> LintM a
400 addInScopeVars ids m loc scope errs
401 = -- We check if these "new" ids are already
402 -- in scope, i.e., we have *shadowing* going on.
403 -- For now, it's just a "trace"; we may make
404 -- a real error out of it...
406 new_set = mkVarSet ids
408 -- After adding -fliberate-case, Simon decided he likes shadowed
409 -- names after all. WDP 94/07
410 -- (if isEmptyVarSet shadowed
412 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
413 m loc (scope `unionVarSet` new_set) errs
416 Checking function applications: we only check that the type has the
417 right *number* of arrows, we don't actually compare the types. This
418 is because we can't expect the types to be equal - the type
419 applications and type lambdas that we use to calculate accurate types
420 have long since disappeared.
423 checkFunApp :: Type -- The function type
424 -> [Type] -- The arg type(s)
425 -> Message -- Error messgae
426 -> LintM (Maybe Type) -- The result type
428 checkFunApp fun_ty arg_tys msg loc scope errs
429 = cfa res_ty expected_arg_tys arg_tys
431 (expected_arg_tys, res_ty) = splitFunTys (dropForAlls fun_ty)
433 cfa res_ty expected [] -- Args have run out; that's fine
434 = (Just (mkFunTys expected res_ty), errs)
436 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
437 -- first see if res_ty is a tyvar template;
438 -- otherwise, maybe res_ty is a
439 -- dictionary type which is actually a function?
441 = (Just res_ty, errs)
443 = case splitFunTys res_ty of
444 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
445 (new_expected, new_res) -> cfa new_res new_expected arg_tys
447 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
448 = cfa res_ty expected_arg_tys arg_tys
452 checkInScope :: Id -> LintM ()
453 checkInScope id loc scope errs
454 = if isLocalId id && not (id `elemVarSet` scope) then
455 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
459 checkTys :: Type -> Type -> Message -> LintM ()
460 checkTys ty1 ty2 msg loc scope errs
461 = -- if (ty1 == ty2) then
463 -- else ((), addErr errs msg loc)
467 mkCaseAltMsg :: StgCaseAlts -> Message
469 = ($$) (text "In some case alternatives, type of alternatives not all same:")
470 (empty) -- LATER: ppr alts
472 mkCaseAbstractMsg :: TyCon -> Message
473 mkCaseAbstractMsg tycon
474 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
477 mkDefltMsg :: Id -> Message
479 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
482 mkFunAppMsg :: Type -> [Type] -> StgExpr -> Message
483 mkFunAppMsg fun_ty arg_tys expr
484 = vcat [text "In a function application, function type doesn't match arg types:",
485 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
486 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
487 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
489 mkRhsConMsg :: Type -> [Type] -> Message
490 mkRhsConMsg fun_ty arg_tys
491 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
492 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
493 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
495 mkUnappTyMsg :: Id -> Type -> Message
497 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
498 (<>) (ptext SLIT("Var: ")) (ppr var),
499 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
501 mkAlgAltMsg1 :: Type -> Message
503 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
506 mkAlgAltMsg2 :: Type -> DataCon -> Message
509 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
514 mkAlgAltMsg3 :: DataCon -> [Id] -> Message
515 mkAlgAltMsg3 con alts
517 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
522 mkAlgAltMsg4 :: Type -> Id -> Message
525 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
530 mkPrimAltMsg :: (Literal, StgExpr) -> Message
532 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
535 mkCaseOfCaseMsg :: StgExpr -> Message
537 = text "Case of non-tail-call:" $$ ppr e
539 mkRhsMsg :: Id -> Type -> Message
541 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
543 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
544 hsep [ptext SLIT("Rhs type:"), ppr ty]
547 mkUnLiftedTyMsg binder rhs
548 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
549 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
551 (ptext SLIT("RHS:") <+> ppr rhs)