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 )
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 ( ErrMsg, Message, addErrLocHdrLine, pprBagOfErrors, dontAddErrLoc )
22 import Type ( mkFunTys, splitFunTys, splitAlgTyConApp_maybe, splitTyConApp_maybe,
23 isUnLiftedType, isTyVarTy, splitForAllTys, Type
25 import TyCon ( TyCon )
26 import Util ( zipEqual )
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 binder rhs)
93 = lint_binds_help (binder,rhs) `thenL_`
96 lintStgBinds (StgRec 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@(StgPrimApp op args _)
170 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
171 case maybe_arg_tys of
172 Nothing -> returnL Nothing
173 Just arg_tys -> checkFunApp op_ty arg_tys (mkFunAppMsg op_ty arg_tys e)
175 op_ty = primOpType op
177 lintStgExpr (StgLam _ bndrs _)
178 = addErrL (ptext SLIT("Unexpected StgLam") <+> ppr bndrs) `thenL_`
181 lintStgExpr (StgLet binds body)
182 = lintStgBinds binds `thenL` \ binders ->
183 addLoc (BodyOfLetRec binders) (
184 addInScopeVars binders (
188 lintStgExpr (StgLetNoEscape _ _ binds body)
189 = lintStgBinds binds `thenL` \ binders ->
190 addLoc (BodyOfLetRec binders) (
191 addInScopeVars binders (
195 lintStgExpr (StgSCC _ expr) = lintStgExpr expr
197 lintStgExpr e@(StgCase scrut _ _ bndr _ alts)
198 = lintStgExpr scrut `thenMaybeL` \ _ ->
201 StgPrimAlts tc _ _ -> check_bndr tc
202 StgAlgAlts (Just tc) _ _ -> check_bndr tc
203 StgAlgAlts Nothing _ _ -> returnL ()
206 (trace (showSDoc (ppr e)) $
207 -- we only allow case of tail-call or primop.
209 StgApp _ _ -> returnL ()
210 StgConApp _ _ -> returnL ()
211 other -> addErrL (mkCaseOfCaseMsg e)) `thenL_`
213 addInScopeVars [bndr] (lintStgAlts alts scrut_ty)
216 scrut_ty = idType bndr
217 bad_bndr = mkDefltMsg bndr
218 check_bndr tc = case splitTyConApp_maybe scrut_ty of
219 Just (bndr_tc, _) -> checkL (tc == bndr_tc) bad_bndr
220 Nothing -> addErrL bad_bndr
224 lintStgAlts :: StgCaseAlts
225 -> Type -- Type of scrutinee
226 -> LintM (Maybe Type) -- Type of alternatives
228 lintStgAlts alts scrut_ty
230 StgAlgAlts _ alg_alts deflt ->
231 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
232 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
233 returnL (maybe_deflt_ty : maybe_alt_tys)
235 StgPrimAlts _ prim_alts deflt ->
236 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
237 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
238 returnL (maybe_deflt_ty : maybe_alt_tys)
239 ) `thenL` \ maybe_result_tys ->
240 -- Check the result types
241 case catMaybes (maybe_result_tys) of
242 [] -> returnL Nothing
244 (first_ty:tys) -> mapL check tys `thenL_`
245 returnL (Just first_ty)
247 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
249 lintAlgAlt scrut_ty (con, args, _, rhs)
250 = (case splitAlgTyConApp_maybe scrut_ty of
252 addErrL (mkAlgAltMsg1 scrut_ty)
253 Just (tycon, tys_applied, cons) ->
255 arg_tys = dataConArgTys con tys_applied
256 -- This almost certainly does not work for existential constructors
258 checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con) `thenL_`
259 checkL (length arg_tys == length args) (mkAlgAltMsg3 con args)
261 mapL check (zipEqual "lintAlgAlt:stg" arg_tys args) `thenL_`
264 addInScopeVars args (
268 check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
270 -- elem: yes, the elem-list here can sometimes be long-ish,
271 -- but as it's use-once, probably not worth doing anything different
272 -- We give it its own copy, so it isn't overloaded.
274 elem x (y:ys) = x==y || elem x ys
276 lintPrimAlt scrut_ty alt@(lit,rhs)
277 = checkTys (literalType lit) scrut_ty (mkPrimAltMsg alt) `thenL_`
280 lintDeflt StgNoDefault scrut_ty = returnL Nothing
281 lintDeflt deflt@(StgBindDefault rhs) scrut_ty = lintStgExpr rhs
285 %************************************************************************
287 \subsection[lint-monad]{The Lint monad}
289 %************************************************************************
292 type LintM a = [LintLocInfo] -- Locations
293 -> IdSet -- Local vars in scope
294 -> Bag ErrMsg -- Error messages so far
295 -> (a, Bag ErrMsg) -- Result and error messages (if any)
298 = RhsOf Id -- The variable bound
299 | LambdaBodyOf [Id] -- The lambda-binder
300 | BodyOfLetRec [Id] -- One of the binders
303 (getSrcLoc v, ptext SLIT(" [RHS of ") <> pp_binders [v] <> char ']' )
304 dumpLoc (LambdaBodyOf bs) =
305 (getSrcLoc (head bs), ptext SLIT(" [in body of lambda with binders ") <> pp_binders bs <> char ']' )
307 dumpLoc (BodyOfLetRec bs) =
308 (getSrcLoc (head bs), ptext SLIT(" [in body of letrec with binders ") <> pp_binders bs <> char ']' )
311 pp_binders :: [Id] -> SDoc
313 = sep (punctuate comma (map pp_binder bs))
316 = hsep [ppr b, dcolon, ppr (idType b)]
320 initL :: LintM a -> Maybe Message
322 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
323 if isEmptyBag errs then
326 Just (pprBagOfErrors errs)
329 returnL :: a -> LintM a
330 returnL r loc scope errs = (r, errs)
332 thenL :: LintM a -> (a -> LintM b) -> LintM b
333 thenL m k loc scope errs
334 = case m loc scope errs of
335 (r, errs') -> k r loc scope errs'
337 thenL_ :: LintM a -> LintM b -> LintM b
338 thenL_ m k loc scope errs
339 = case m loc scope errs of
340 (_, errs') -> k loc scope errs'
342 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
343 thenMaybeL m k loc scope errs
344 = case m loc scope errs of
345 (Nothing, errs2) -> (Nothing, errs2)
346 (Just r, errs2) -> k r loc scope errs2
348 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
349 thenMaybeL_ m k loc scope errs
350 = case m loc scope errs of
351 (Nothing, errs2) -> (Nothing, errs2)
352 (Just _, errs2) -> k loc scope errs2
354 mapL :: (a -> LintM b) -> [a] -> LintM [b]
355 mapL f [] = returnL []
358 mapL f xs `thenL` \ rs ->
361 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
362 -- Returns Nothing if anything fails
363 mapMaybeL f [] = returnL (Just [])
365 = f x `thenMaybeL` \ r ->
366 mapMaybeL f xs `thenMaybeL` \ rs ->
367 returnL (Just (r:rs))
371 checkL :: Bool -> Message -> LintM ()
372 checkL True msg loc scope errs = ((), errs)
373 checkL False msg loc scope errs = ((), addErr errs msg loc)
375 addErrL :: Message -> LintM ()
376 addErrL msg loc scope errs = ((), addErr errs msg loc)
378 addErr :: Bag ErrMsg -> Message -> [LintLocInfo] -> Bag ErrMsg
380 addErr errs_so_far msg locs
381 = errs_so_far `snocBag` mk_msg locs
383 mk_msg (loc:_) = let (l,hdr) = dumpLoc loc in addErrLocHdrLine l hdr msg
384 mk_msg [] = dontAddErrLoc msg
386 addLoc :: LintLocInfo -> LintM a -> LintM a
387 addLoc extra_loc m loc scope errs
388 = m (extra_loc:loc) scope errs
390 addInScopeVars :: [Id] -> LintM a -> LintM a
391 addInScopeVars ids m loc scope errs
392 = -- We check if these "new" ids are already
393 -- in scope, i.e., we have *shadowing* going on.
394 -- For now, it's just a "trace"; we may make
395 -- a real error out of it...
397 new_set = mkVarSet ids
399 -- After adding -fliberate-case, Simon decided he likes shadowed
400 -- names after all. WDP 94/07
401 -- (if isEmptyVarSet shadowed
403 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
404 m loc (scope `unionVarSet` new_set) errs
407 Checking function applications: we only check that the type has the
408 right *number* of arrows, we don't actually compare the types. This
409 is because we can't expect the types to be equal - the type
410 applications and type lambdas that we use to calculate accurate types
411 have long since disappeared.
414 checkFunApp :: Type -- The function type
415 -> [Type] -- The arg type(s)
416 -> Message -- Error messgae
417 -> LintM (Maybe Type) -- The result type
419 checkFunApp fun_ty arg_tys msg loc scope errs
420 = cfa res_ty expected_arg_tys arg_tys
422 (_, de_forall_ty) = splitForAllTys fun_ty
423 (expected_arg_tys, res_ty) = splitFunTys de_forall_ty
425 cfa res_ty expected [] -- Args have run out; that's fine
426 = (Just (mkFunTys expected res_ty), errs)
428 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
429 -- first see if res_ty is a tyvar template;
430 -- otherwise, maybe res_ty is a
431 -- dictionary type which is actually a function?
433 = (Just res_ty, errs)
435 = case splitFunTys res_ty of
436 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
437 (new_expected, new_res) -> cfa new_res new_expected arg_tys
439 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
440 = cfa res_ty expected_arg_tys arg_tys
444 checkInScope :: Id -> LintM ()
445 checkInScope id loc scope errs
446 = if isLocalId id && not (id `elemVarSet` scope) then
447 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
451 checkTys :: Type -> Type -> Message -> LintM ()
452 checkTys ty1 ty2 msg loc scope errs
453 = -- if (ty1 == ty2) then
455 -- else ((), addErr errs msg loc)
459 mkCaseAltMsg :: StgCaseAlts -> Message
461 = ($$) (text "In some case alternatives, type of alternatives not all same:")
462 (empty) -- LATER: ppr alts
464 mkCaseAbstractMsg :: TyCon -> Message
465 mkCaseAbstractMsg tycon
466 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
469 mkDefltMsg :: Id -> Message
471 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
474 mkFunAppMsg :: Type -> [Type] -> StgExpr -> Message
475 mkFunAppMsg fun_ty arg_tys expr
476 = vcat [text "In a function application, function type doesn't match arg types:",
477 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
478 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
479 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
481 mkRhsConMsg :: Type -> [Type] -> Message
482 mkRhsConMsg fun_ty arg_tys
483 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
484 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
485 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
487 mkUnappTyMsg :: Id -> Type -> Message
489 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
490 (<>) (ptext SLIT("Var: ")) (ppr var),
491 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
493 mkAlgAltMsg1 :: Type -> Message
495 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
498 mkAlgAltMsg2 :: Type -> DataCon -> Message
501 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
506 mkAlgAltMsg3 :: DataCon -> [Id] -> Message
507 mkAlgAltMsg3 con alts
509 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
514 mkAlgAltMsg4 :: Type -> Id -> Message
517 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
522 mkPrimAltMsg :: (Literal, StgExpr) -> Message
524 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
527 mkCaseOfCaseMsg :: StgExpr -> Message
529 = text "Case of non-tail-call:" $$ ppr e
531 mkRhsMsg :: Id -> Type -> Message
533 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
535 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
536 hsep [ptext SLIT("Rhs type:"), ppr ty]
539 mkUnLiftedTyMsg binder rhs
540 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
541 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
543 (ptext SLIT("RHS:") <+> ppr rhs)