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, 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 _ _ _ _ _ binders expr)
118 = addLoc (LambdaBodyOf binders) (
119 addInScopeVars binders (
120 lintStgExpr expr `thenMaybeL` \ body_ty ->
121 returnL (Just (mkFunTys (map idType binders) body_ty))
124 lintStgRhs (StgRhsCon _ con args)
125 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
126 case maybe_arg_tys of
127 Nothing -> returnL Nothing
128 Just arg_tys -> checkFunApp con_ty arg_tys (mkRhsConMsg con_ty arg_tys)
130 con_ty = dataConType con
134 lintStgExpr :: StgExpr -> LintM (Maybe Type) -- Nothing if error found
136 lintStgExpr e@(StgApp fun args)
137 = lintStgVar fun `thenMaybeL` \ fun_ty ->
138 mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
139 case maybe_arg_tys of
140 Nothing -> returnL Nothing
141 Just arg_tys -> checkFunApp fun_ty arg_tys (mkFunAppMsg fun_ty arg_tys e)
143 lintStgExpr e@(StgCon con args _)
144 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
145 case maybe_arg_tys of
146 Nothing -> returnL Nothing
147 Just arg_tys -> checkFunApp con_ty arg_tys (mkFunAppMsg con_ty arg_tys e)
151 lintStgExpr (StgLet binds body)
152 = lintStgBinds binds `thenL` \ binders ->
153 addLoc (BodyOfLetRec binders) (
154 addInScopeVars binders (
158 lintStgExpr (StgLetNoEscape _ _ binds body)
159 = lintStgBinds binds `thenL` \ binders ->
160 addLoc (BodyOfLetRec binders) (
161 addInScopeVars binders (
165 lintStgExpr (StgSCC _ expr) = lintStgExpr expr
167 lintStgExpr e@(StgCase scrut _ _ bndr _ alts)
168 = lintStgExpr scrut `thenMaybeL` \ _ ->
169 checkTys (idType bndr) scrut_ty (mkDefltMsg bndr) `thenL_`
171 -- Check that it is a data type
172 case (splitAlgTyConApp_maybe scrut_ty) of
173 Just (tycon, _, _) | isDataTyCon tycon
174 -> addInScopeVars [bndr] (lintStgAlts alts scrut_ty tycon)
175 other -> addErrL (mkCaseDataConMsg e) `thenL_`
178 scrut_ty = get_ty alts
180 get_ty (StgAlgAlts ty _ _) = ty
181 get_ty (StgPrimAlts ty _ _) = ty
185 lintStgAlts :: StgCaseAlts
186 -> Type -- Type of scrutinee
187 -> TyCon -- TyCon pinned on the case
188 -> LintM (Maybe Type) -- Type of alternatives
190 lintStgAlts alts scrut_ty case_tycon
192 StgAlgAlts _ alg_alts deflt ->
193 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
194 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
195 returnL (maybe_deflt_ty : maybe_alt_tys)
197 StgPrimAlts _ prim_alts deflt ->
198 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
199 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
200 returnL (maybe_deflt_ty : maybe_alt_tys)
201 ) `thenL` \ maybe_result_tys ->
202 -- Check the result types
203 case catMaybes (maybe_result_tys) of
204 [] -> returnL Nothing
206 (first_ty:tys) -> mapL check tys `thenL_`
207 returnL (Just first_ty)
209 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
211 lintAlgAlt scrut_ty (con, args, _, rhs)
212 = (case splitAlgTyConApp_maybe scrut_ty of
214 addErrL (mkAlgAltMsg1 scrut_ty)
215 Just (tycon, tys_applied, cons) ->
217 arg_tys = dataConArgTys con tys_applied
219 checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con) `thenL_`
220 checkL (length arg_tys == length args) (mkAlgAltMsg3 con args)
222 mapL check (zipEqual "lintAlgAlt:stg" arg_tys args) `thenL_`
225 addInScopeVars args (
229 check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
231 -- elem: yes, the elem-list here can sometimes be long-ish,
232 -- but as it's use-once, probably not worth doing anything different
233 -- We give it its own copy, so it isn't overloaded.
235 elem x (y:ys) = x==y || elem x ys
237 lintPrimAlt scrut_ty alt@(lit,rhs)
238 = checkTys (literalType lit) scrut_ty (mkPrimAltMsg alt) `thenL_`
241 lintDeflt StgNoDefault scrut_ty = returnL Nothing
242 lintDeflt deflt@(StgBindDefault rhs) scrut_ty = lintStgExpr rhs
246 %************************************************************************
248 \subsection[lint-monad]{The Lint monad}
250 %************************************************************************
253 type LintM a = [LintLocInfo] -- Locations
254 -> IdSet -- Local vars in scope
255 -> Bag ErrMsg -- Error messages so far
256 -> (a, Bag ErrMsg) -- Result and error messages (if any)
259 = RhsOf Id -- The variable bound
260 | LambdaBodyOf [Id] -- The lambda-binder
261 | BodyOfLetRec [Id] -- One of the binders
264 (getSrcLoc v, ptext SLIT(" [RHS of ") <> pp_binders [v] <> char ']' )
265 dumpLoc (LambdaBodyOf bs) =
266 (getSrcLoc (head bs), ptext SLIT(" [in body of lambda with binders ") <> pp_binders bs <> char ']' )
268 dumpLoc (BodyOfLetRec bs) =
269 (getSrcLoc (head bs), ptext SLIT(" [in body of letrec with binders ") <> pp_binders bs <> char ']' )
272 pp_binders :: [Id] -> SDoc
274 = sep (punctuate comma (map pp_binder bs))
277 = hsep [ppr b, dcolon, ppr (idType b)]
281 initL :: LintM a -> Maybe Message
283 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
284 if isEmptyBag errs then
287 Just (pprBagOfErrors errs)
290 returnL :: a -> LintM a
291 returnL r loc scope errs = (r, errs)
293 thenL :: LintM a -> (a -> LintM b) -> LintM b
294 thenL m k loc scope errs
295 = case m loc scope errs of
296 (r, errs') -> k r loc scope errs'
298 thenL_ :: LintM a -> LintM b -> LintM b
299 thenL_ m k loc scope errs
300 = case m loc scope errs of
301 (_, errs') -> k loc scope errs'
303 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
304 thenMaybeL m k loc scope errs
305 = case m loc scope errs of
306 (Nothing, errs2) -> (Nothing, errs2)
307 (Just r, errs2) -> k r loc scope errs2
309 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
310 thenMaybeL_ m k loc scope errs
311 = case m loc scope errs of
312 (Nothing, errs2) -> (Nothing, errs2)
313 (Just _, errs2) -> k loc scope errs2
315 mapL :: (a -> LintM b) -> [a] -> LintM [b]
316 mapL f [] = returnL []
319 mapL f xs `thenL` \ rs ->
322 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
323 -- Returns Nothing if anything fails
324 mapMaybeL f [] = returnL (Just [])
326 = f x `thenMaybeL` \ r ->
327 mapMaybeL f xs `thenMaybeL` \ rs ->
328 returnL (Just (r:rs))
332 checkL :: Bool -> Message -> LintM ()
333 checkL True msg loc scope errs = ((), errs)
334 checkL False msg loc scope errs = ((), addErr errs msg loc)
336 addErrL :: Message -> LintM ()
337 addErrL msg loc scope errs = ((), addErr errs msg loc)
339 addErr :: Bag ErrMsg -> Message -> [LintLocInfo] -> Bag ErrMsg
341 addErr errs_so_far msg locs
342 = errs_so_far `snocBag` mk_msg locs
344 mk_msg (loc:_) = let (l,hdr) = dumpLoc loc in addErrLocHdrLine l hdr msg
345 mk_msg [] = dontAddErrLoc "" msg
347 addLoc :: LintLocInfo -> LintM a -> LintM a
348 addLoc extra_loc m loc scope errs
349 = m (extra_loc:loc) scope errs
351 addInScopeVars :: [Id] -> LintM a -> LintM a
352 addInScopeVars ids m loc scope errs
353 = -- We check if these "new" ids are already
354 -- in scope, i.e., we have *shadowing* going on.
355 -- For now, it's just a "trace"; we may make
356 -- a real error out of it...
358 new_set = mkVarSet ids
360 shadowed = scope `intersectVarSet` new_set
362 -- After adding -fliberate-case, Simon decided he likes shadowed
363 -- names after all. WDP 94/07
364 -- (if isEmptyVarSet shadowed
366 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
367 m loc (scope `unionVarSet` new_set) errs
371 checkFunApp :: Type -- The function type
372 -> [Type] -- The arg type(s)
373 -> Message -- Error messgae
374 -> LintM (Maybe Type) -- The result type
376 checkFunApp fun_ty arg_tys msg loc scope errs
377 = cfa res_ty expected_arg_tys arg_tys
379 (expected_arg_tys, res_ty) = splitFunTys fun_ty
381 cfa res_ty expected [] -- Args have run out; that's fine
382 = (Just (mkFunTys expected res_ty), errs)
384 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
385 -- first see if res_ty is a tyvar template;
386 -- otherwise, maybe res_ty is a
387 -- dictionary type which is actually a function?
389 = (Just res_ty, errs)
391 = case splitFunTys res_ty of
392 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
393 (new_expected, new_res) -> cfa new_res new_expected arg_tys
395 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
396 = if (expected_arg_ty == arg_ty)
397 then cfa res_ty expected_arg_tys arg_tys
398 else (Nothing, addErr errs msg loc) -- Arg mis-match
402 checkInScope :: Id -> LintM ()
403 checkInScope id loc scope errs
404 = if isLocallyDefined id && not (id `elemVarSet` scope) then
405 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
409 checkTys :: Type -> Type -> Message -> LintM ()
410 checkTys ty1 ty2 msg loc scope errs
413 else ((), addErr errs msg loc)
417 mkCaseAltMsg :: StgCaseAlts -> Message
419 = ($$) (text "In some case alternatives, type of alternatives not all same:")
421 (panic "mkCaseAltMsg")
423 mkCaseDataConMsg :: StgExpr -> Message
424 mkCaseDataConMsg expr
425 = ($$) (ptext SLIT("A case scrutinee not a type-constructor type:"))
428 mkCaseAbstractMsg :: TyCon -> Message
429 mkCaseAbstractMsg tycon
430 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
433 mkDefltMsg :: Id -> Message
435 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
438 mkFunAppMsg :: Type -> [Type] -> StgExpr -> Message
439 mkFunAppMsg fun_ty arg_tys expr
440 = vcat [text "In a function application, function type doesn't match arg types:",
441 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
442 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
443 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
445 mkRhsConMsg :: Type -> [Type] -> Message
446 mkRhsConMsg fun_ty arg_tys
447 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
448 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
449 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
451 mkUnappTyMsg :: Id -> Type -> Message
453 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
454 (<>) (ptext SLIT("Var: ")) (ppr var),
455 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
457 mkAlgAltMsg1 :: Type -> Message
459 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
462 mkAlgAltMsg2 :: Type -> DataCon -> Message
465 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
470 mkAlgAltMsg3 :: DataCon -> [Id] -> Message
471 mkAlgAltMsg3 con alts
473 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
478 mkAlgAltMsg4 :: Type -> Id -> Message
481 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
486 mkPrimAltMsg :: (Literal, StgExpr) -> Message
488 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
491 mkRhsMsg :: Id -> Type -> Message
493 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
495 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
496 hsep [ptext SLIT("Rhs type:"), ppr ty]
499 mkUnLiftedTyMsg binder rhs
500 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
501 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
503 (ptext SLIT("RHS:") <+> ppr rhs)