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, foldBag )
14 import Id ( Id, idType )
16 import DataCon ( DataCon, dataConArgTys, dataConType )
17 import Const ( literalType, conType, Literal )
18 import Maybes ( catMaybes )
19 import Name ( isLocallyDefined, getSrcLoc )
20 import ErrUtils ( ErrMsg, Message, addErrLocHdrLine, pprBagOfErrors, dontAddErrLoc )
21 import Type ( mkFunTys, splitFunTys, splitAlgTyConApp_maybe,
22 isUnLiftedType, isTyVarTy, splitForAllTys, Type
24 import TyCon ( TyCon, isDataTyCon )
25 import Util ( zipEqual )
28 infixr 9 `thenL`, `thenL_`, `thenMaybeL`, `thenMaybeL_`
32 (a) *some* type errors
33 (b) locally-defined variables used but not defined
35 %************************************************************************
37 \subsection{``lint'' for various constructs}
39 %************************************************************************
41 @lintStgBindings@ is the top-level interface function.
44 lintStgBindings :: String -> [StgBinding] -> [StgBinding]
46 lintStgBindings whodunnit binds
48 case (initL (lint_binds binds)) of
50 Just msg -> pprPanic "" (vcat [
51 ptext SLIT("*** Stg Lint ErrMsgs: in") <+> text whodunnit <+> ptext SLIT("***"),
53 ptext SLIT("*** Offending Program ***"),
55 ptext SLIT("*** End of Offense ***")])
57 lint_binds :: [StgBinding] -> LintM ()
59 lint_binds [] = returnL ()
60 lint_binds (bind:binds)
61 = lintStgBinds bind `thenL` \ binders ->
62 addInScopeVars binders (
69 lintStgArg :: StgArg -> LintM (Maybe Type)
70 lintStgArg (StgConArg con) = returnL (Just (conType con))
71 lintStgArg (StgVarArg v) = lintStgVar v
73 lintStgVar v = checkInScope v `thenL_`
74 returnL (Just (idType v))
78 lintStgBinds :: StgBinding -> LintM [Id] -- Returns the binders
79 lintStgBinds (StgNonRec binder rhs)
80 = lint_binds_help (binder,rhs) `thenL_`
83 lintStgBinds (StgRec pairs)
84 = addInScopeVars binders (
85 mapL lint_binds_help pairs `thenL_`
89 binders = [b | (b,_) <- pairs]
91 lint_binds_help (binder, rhs)
92 = addLoc (RhsOf binder) (
94 lintStgRhs rhs `thenL` \ maybe_rhs_ty ->
96 -- Check binder doesn't have unlifted type
97 checkL (not (isUnLiftedType binder_ty))
98 (mkUnLiftedTyMsg binder rhs) `thenL_`
100 -- Check match to RHS type
101 (case maybe_rhs_ty of
102 Nothing -> returnL ()
103 Just rhs_ty -> checkTys binder_ty
105 (mkRhsMsg binder rhs_ty)
111 binder_ty = idType binder
115 lintStgRhs :: StgRhs -> LintM (Maybe Type)
117 lintStgRhs (StgRhsClosure _ _ _ _ _ [] expr)
120 lintStgRhs (StgRhsClosure _ _ _ _ _ binders expr)
121 = addLoc (LambdaBodyOf binders) (
122 addInScopeVars binders (
123 lintStgExpr expr `thenMaybeL` \ body_ty ->
124 returnL (Just (mkFunTys (map idType binders) body_ty))
127 lintStgRhs (StgRhsCon _ con args)
128 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
129 case maybe_arg_tys of
130 Nothing -> returnL Nothing
131 Just arg_tys -> checkFunApp con_ty arg_tys (mkRhsConMsg con_ty arg_tys)
133 con_ty = dataConType con
137 lintStgExpr :: StgExpr -> LintM (Maybe Type) -- Nothing if error found
139 lintStgExpr e@(StgApp fun args)
140 = lintStgVar fun `thenMaybeL` \ fun_ty ->
141 mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
142 case maybe_arg_tys of
143 Nothing -> returnL Nothing
144 Just arg_tys -> checkFunApp fun_ty arg_tys (mkFunAppMsg fun_ty arg_tys e)
146 lintStgExpr e@(StgCon con args _)
147 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
148 case maybe_arg_tys of
149 Nothing -> returnL Nothing
150 Just arg_tys -> checkFunApp con_ty arg_tys (mkFunAppMsg con_ty arg_tys e)
154 lintStgExpr (StgLam _ bndrs _)
155 = addErrL (ptext SLIT("Unexpected StgLam") <+> ppr bndrs) `thenL_`
158 lintStgExpr (StgLet binds body)
159 = lintStgBinds binds `thenL` \ binders ->
160 addLoc (BodyOfLetRec binders) (
161 addInScopeVars binders (
165 lintStgExpr (StgLetNoEscape _ _ binds body)
166 = lintStgBinds binds `thenL` \ binders ->
167 addLoc (BodyOfLetRec binders) (
168 addInScopeVars binders (
172 lintStgExpr (StgSCC _ expr) = lintStgExpr expr
174 lintStgExpr e@(StgCase scrut _ _ bndr _ alts)
175 = lintStgExpr scrut `thenMaybeL` \ _ ->
176 checkTys (idType bndr) scrut_ty (mkDefltMsg bndr) `thenL_`
178 (trace (showSDoc (ppr e)) $
179 -- we only allow case of tail-call or primop.
181 StgApp _ _ -> returnL ()
182 StgCon _ _ _ -> returnL ()
183 other -> addErrL (mkCaseOfCaseMsg e)) `thenL_`
185 addInScopeVars [bndr] (lintStgAlts alts scrut_ty)
188 scrut_ty = get_ty alts
190 get_ty (StgAlgAlts ty _ _) = ty
191 get_ty (StgPrimAlts ty _ _) = ty
195 lintStgAlts :: StgCaseAlts
196 -> Type -- Type of scrutinee
197 -> LintM (Maybe Type) -- Type of alternatives
199 lintStgAlts alts scrut_ty
201 StgAlgAlts _ alg_alts deflt ->
202 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
203 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
204 returnL (maybe_deflt_ty : maybe_alt_tys)
206 StgPrimAlts _ prim_alts deflt ->
207 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
208 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
209 returnL (maybe_deflt_ty : maybe_alt_tys)
210 ) `thenL` \ maybe_result_tys ->
211 -- Check the result types
212 case catMaybes (maybe_result_tys) of
213 [] -> returnL Nothing
215 (first_ty:tys) -> mapL check tys `thenL_`
216 returnL (Just first_ty)
218 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
220 lintAlgAlt scrut_ty (con, args, _, rhs)
221 = (case splitAlgTyConApp_maybe scrut_ty of
223 addErrL (mkAlgAltMsg1 scrut_ty)
224 Just (tycon, tys_applied, cons) ->
226 arg_tys = dataConArgTys con tys_applied
227 -- This almost certainly does not work for existential constructors
229 checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con) `thenL_`
230 checkL (length arg_tys == length args) (mkAlgAltMsg3 con args)
232 mapL check (zipEqual "lintAlgAlt:stg" arg_tys args) `thenL_`
235 addInScopeVars args (
239 check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
241 -- elem: yes, the elem-list here can sometimes be long-ish,
242 -- but as it's use-once, probably not worth doing anything different
243 -- We give it its own copy, so it isn't overloaded.
245 elem x (y:ys) = x==y || elem x ys
247 lintPrimAlt scrut_ty alt@(lit,rhs)
248 = checkTys (literalType lit) scrut_ty (mkPrimAltMsg alt) `thenL_`
251 lintDeflt StgNoDefault scrut_ty = returnL Nothing
252 lintDeflt deflt@(StgBindDefault rhs) scrut_ty = lintStgExpr rhs
256 %************************************************************************
258 \subsection[lint-monad]{The Lint monad}
260 %************************************************************************
263 type LintM a = [LintLocInfo] -- Locations
264 -> IdSet -- Local vars in scope
265 -> Bag ErrMsg -- Error messages so far
266 -> (a, Bag ErrMsg) -- Result and error messages (if any)
269 = RhsOf Id -- The variable bound
270 | LambdaBodyOf [Id] -- The lambda-binder
271 | BodyOfLetRec [Id] -- One of the binders
274 (getSrcLoc v, ptext SLIT(" [RHS of ") <> pp_binders [v] <> char ']' )
275 dumpLoc (LambdaBodyOf bs) =
276 (getSrcLoc (head bs), ptext SLIT(" [in body of lambda with binders ") <> pp_binders bs <> char ']' )
278 dumpLoc (BodyOfLetRec bs) =
279 (getSrcLoc (head bs), ptext SLIT(" [in body of letrec with binders ") <> pp_binders bs <> char ']' )
282 pp_binders :: [Id] -> SDoc
284 = sep (punctuate comma (map pp_binder bs))
287 = hsep [ppr b, dcolon, ppr (idType b)]
291 initL :: LintM a -> Maybe Message
293 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
294 if isEmptyBag errs then
297 Just (pprBagOfErrors errs)
300 returnL :: a -> LintM a
301 returnL r loc scope errs = (r, errs)
303 thenL :: LintM a -> (a -> LintM b) -> LintM b
304 thenL m k loc scope errs
305 = case m loc scope errs of
306 (r, errs') -> k r loc scope errs'
308 thenL_ :: LintM a -> LintM b -> LintM b
309 thenL_ m k loc scope errs
310 = case m loc scope errs of
311 (_, errs') -> k loc scope errs'
313 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
314 thenMaybeL m k loc scope errs
315 = case m loc scope errs of
316 (Nothing, errs2) -> (Nothing, errs2)
317 (Just r, errs2) -> k r loc scope errs2
319 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
320 thenMaybeL_ m k loc scope errs
321 = case m loc scope errs of
322 (Nothing, errs2) -> (Nothing, errs2)
323 (Just _, errs2) -> k loc scope errs2
325 mapL :: (a -> LintM b) -> [a] -> LintM [b]
326 mapL f [] = returnL []
329 mapL f xs `thenL` \ rs ->
332 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
333 -- Returns Nothing if anything fails
334 mapMaybeL f [] = returnL (Just [])
336 = f x `thenMaybeL` \ r ->
337 mapMaybeL f xs `thenMaybeL` \ rs ->
338 returnL (Just (r:rs))
342 checkL :: Bool -> Message -> LintM ()
343 checkL True msg loc scope errs = ((), errs)
344 checkL False msg loc scope errs = ((), addErr errs msg loc)
346 addErrL :: Message -> LintM ()
347 addErrL msg loc scope errs = ((), addErr errs msg loc)
349 addErr :: Bag ErrMsg -> Message -> [LintLocInfo] -> Bag ErrMsg
351 addErr errs_so_far msg locs
352 = errs_so_far `snocBag` mk_msg locs
354 mk_msg (loc:_) = let (l,hdr) = dumpLoc loc in addErrLocHdrLine l hdr msg
355 mk_msg [] = dontAddErrLoc "" msg
357 addLoc :: LintLocInfo -> LintM a -> LintM a
358 addLoc extra_loc m loc scope errs
359 = m (extra_loc:loc) scope errs
361 addInScopeVars :: [Id] -> LintM a -> LintM a
362 addInScopeVars ids m loc scope errs
363 = -- We check if these "new" ids are already
364 -- in scope, i.e., we have *shadowing* going on.
365 -- For now, it's just a "trace"; we may make
366 -- a real error out of it...
368 new_set = mkVarSet ids
370 shadowed = scope `intersectVarSet` new_set
372 -- After adding -fliberate-case, Simon decided he likes shadowed
373 -- names after all. WDP 94/07
374 -- (if isEmptyVarSet shadowed
376 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
377 m loc (scope `unionVarSet` new_set) errs
380 Checking function applications: we only check that the type has the
381 right *number* of arrows, we don't actually compare the types. This
382 is because we can't expect the types to be equal - the type
383 applications and type lambdas that we use to calculate accurate types
384 have long since disappeared.
387 checkFunApp :: Type -- The function type
388 -> [Type] -- The arg type(s)
389 -> Message -- Error messgae
390 -> LintM (Maybe Type) -- The result type
392 checkFunApp fun_ty arg_tys msg loc scope errs
393 = cfa res_ty expected_arg_tys arg_tys
395 (_, de_forall_ty) = splitForAllTys fun_ty
396 (expected_arg_tys, res_ty) = splitFunTys de_forall_ty
398 cfa res_ty expected [] -- Args have run out; that's fine
399 = (Just (mkFunTys expected res_ty), errs)
401 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
402 -- first see if res_ty is a tyvar template;
403 -- otherwise, maybe res_ty is a
404 -- dictionary type which is actually a function?
406 = (Just res_ty, errs)
408 = case splitFunTys res_ty of
409 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
410 (new_expected, new_res) -> cfa new_res new_expected arg_tys
412 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
413 = cfa res_ty expected_arg_tys arg_tys
417 checkInScope :: Id -> LintM ()
418 checkInScope id loc scope errs
419 = if isLocallyDefined id && not (id `elemVarSet` scope) then
420 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
424 checkTys :: Type -> Type -> Message -> LintM ()
425 checkTys ty1 ty2 msg loc scope errs
426 = -- if (ty1 == ty2) then
428 -- else ((), addErr errs msg loc)
432 mkCaseAltMsg :: StgCaseAlts -> Message
434 = ($$) (text "In some case alternatives, type of alternatives not all same:")
435 (empty) -- LATER: ppr alts
437 mkCaseAbstractMsg :: TyCon -> Message
438 mkCaseAbstractMsg tycon
439 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
442 mkDefltMsg :: Id -> Message
444 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
447 mkFunAppMsg :: Type -> [Type] -> StgExpr -> Message
448 mkFunAppMsg fun_ty arg_tys expr
449 = vcat [text "In a function application, function type doesn't match arg types:",
450 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
451 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
452 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
454 mkRhsConMsg :: Type -> [Type] -> Message
455 mkRhsConMsg fun_ty arg_tys
456 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
457 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
458 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
460 mkUnappTyMsg :: Id -> Type -> Message
462 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
463 (<>) (ptext SLIT("Var: ")) (ppr var),
464 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
466 mkAlgAltMsg1 :: Type -> Message
468 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
471 mkAlgAltMsg2 :: Type -> DataCon -> Message
474 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
479 mkAlgAltMsg3 :: DataCon -> [Id] -> Message
480 mkAlgAltMsg3 con alts
482 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
487 mkAlgAltMsg4 :: Type -> Id -> Message
490 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
495 mkPrimAltMsg :: (Literal, StgExpr) -> Message
497 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
500 mkCaseOfCaseMsg :: StgExpr -> Message
502 = text "Case of non-tail-call:" $$ ppr e
504 mkRhsMsg :: Id -> Type -> Message
506 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
508 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
509 hsep [ptext SLIT("Rhs type:"), ppr ty]
512 mkUnLiftedTyMsg binder rhs
513 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
514 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
516 (ptext SLIT("RHS:") <+> ppr rhs)