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 (StgLam _ bndrs _)
152 = addErrL (ptext SLIT("Unexpected StgLam") <+> ppr bndrs) `thenL_`
155 lintStgExpr (StgLet binds body)
156 = lintStgBinds binds `thenL` \ binders ->
157 addLoc (BodyOfLetRec binders) (
158 addInScopeVars binders (
162 lintStgExpr (StgLetNoEscape _ _ binds body)
163 = lintStgBinds binds `thenL` \ binders ->
164 addLoc (BodyOfLetRec binders) (
165 addInScopeVars binders (
169 lintStgExpr (StgSCC _ expr) = lintStgExpr expr
171 lintStgExpr e@(StgCase scrut _ _ bndr _ alts)
172 = lintStgExpr scrut `thenMaybeL` \ _ ->
173 checkTys (idType bndr) scrut_ty (mkDefltMsg bndr) `thenL_`
175 -- Check that it is a data type
176 case (splitAlgTyConApp_maybe scrut_ty) of
177 Just (tycon, _, _) | isDataTyCon tycon
178 -> addInScopeVars [bndr] (lintStgAlts alts scrut_ty tycon)
179 other -> addErrL (mkCaseDataConMsg e) `thenL_`
182 scrut_ty = get_ty alts
184 get_ty (StgAlgAlts ty _ _) = ty
185 get_ty (StgPrimAlts ty _ _) = ty
189 lintStgAlts :: StgCaseAlts
190 -> Type -- Type of scrutinee
191 -> TyCon -- TyCon pinned on the case
192 -> LintM (Maybe Type) -- Type of alternatives
194 lintStgAlts alts scrut_ty case_tycon
196 StgAlgAlts _ alg_alts deflt ->
197 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
198 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
199 returnL (maybe_deflt_ty : maybe_alt_tys)
201 StgPrimAlts _ prim_alts deflt ->
202 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
203 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
204 returnL (maybe_deflt_ty : maybe_alt_tys)
205 ) `thenL` \ maybe_result_tys ->
206 -- Check the result types
207 case catMaybes (maybe_result_tys) of
208 [] -> returnL Nothing
210 (first_ty:tys) -> mapL check tys `thenL_`
211 returnL (Just first_ty)
213 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
215 lintAlgAlt scrut_ty (con, args, _, rhs)
216 = (case splitAlgTyConApp_maybe scrut_ty of
218 addErrL (mkAlgAltMsg1 scrut_ty)
219 Just (tycon, tys_applied, cons) ->
221 arg_tys = dataConArgTys con tys_applied
223 checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con) `thenL_`
224 checkL (length arg_tys == length args) (mkAlgAltMsg3 con args)
226 mapL check (zipEqual "lintAlgAlt:stg" arg_tys args) `thenL_`
229 addInScopeVars args (
233 check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
235 -- elem: yes, the elem-list here can sometimes be long-ish,
236 -- but as it's use-once, probably not worth doing anything different
237 -- We give it its own copy, so it isn't overloaded.
239 elem x (y:ys) = x==y || elem x ys
241 lintPrimAlt scrut_ty alt@(lit,rhs)
242 = checkTys (literalType lit) scrut_ty (mkPrimAltMsg alt) `thenL_`
245 lintDeflt StgNoDefault scrut_ty = returnL Nothing
246 lintDeflt deflt@(StgBindDefault rhs) scrut_ty = lintStgExpr rhs
250 %************************************************************************
252 \subsection[lint-monad]{The Lint monad}
254 %************************************************************************
257 type LintM a = [LintLocInfo] -- Locations
258 -> IdSet -- Local vars in scope
259 -> Bag ErrMsg -- Error messages so far
260 -> (a, Bag ErrMsg) -- Result and error messages (if any)
263 = RhsOf Id -- The variable bound
264 | LambdaBodyOf [Id] -- The lambda-binder
265 | BodyOfLetRec [Id] -- One of the binders
268 (getSrcLoc v, ptext SLIT(" [RHS of ") <> pp_binders [v] <> char ']' )
269 dumpLoc (LambdaBodyOf bs) =
270 (getSrcLoc (head bs), ptext SLIT(" [in body of lambda with binders ") <> pp_binders bs <> char ']' )
272 dumpLoc (BodyOfLetRec bs) =
273 (getSrcLoc (head bs), ptext SLIT(" [in body of letrec with binders ") <> pp_binders bs <> char ']' )
276 pp_binders :: [Id] -> SDoc
278 = sep (punctuate comma (map pp_binder bs))
281 = hsep [ppr b, dcolon, ppr (idType b)]
285 initL :: LintM a -> Maybe Message
287 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
288 if isEmptyBag errs then
291 Just (pprBagOfErrors errs)
294 returnL :: a -> LintM a
295 returnL r loc scope errs = (r, errs)
297 thenL :: LintM a -> (a -> LintM b) -> LintM b
298 thenL m k loc scope errs
299 = case m loc scope errs of
300 (r, errs') -> k r loc scope errs'
302 thenL_ :: LintM a -> LintM b -> LintM b
303 thenL_ m k loc scope errs
304 = case m loc scope errs of
305 (_, errs') -> k loc scope errs'
307 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
308 thenMaybeL m k loc scope errs
309 = case m loc scope errs of
310 (Nothing, errs2) -> (Nothing, errs2)
311 (Just r, errs2) -> k r loc scope errs2
313 thenMaybeL_ :: LintM (Maybe 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 _, errs2) -> k loc scope errs2
319 mapL :: (a -> LintM b) -> [a] -> LintM [b]
320 mapL f [] = returnL []
323 mapL f xs `thenL` \ rs ->
326 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
327 -- Returns Nothing if anything fails
328 mapMaybeL f [] = returnL (Just [])
330 = f x `thenMaybeL` \ r ->
331 mapMaybeL f xs `thenMaybeL` \ rs ->
332 returnL (Just (r:rs))
336 checkL :: Bool -> Message -> LintM ()
337 checkL True msg loc scope errs = ((), errs)
338 checkL False msg loc scope errs = ((), addErr errs msg loc)
340 addErrL :: Message -> LintM ()
341 addErrL msg loc scope errs = ((), addErr errs msg loc)
343 addErr :: Bag ErrMsg -> Message -> [LintLocInfo] -> Bag ErrMsg
345 addErr errs_so_far msg locs
346 = errs_so_far `snocBag` mk_msg locs
348 mk_msg (loc:_) = let (l,hdr) = dumpLoc loc in addErrLocHdrLine l hdr msg
349 mk_msg [] = dontAddErrLoc "" msg
351 addLoc :: LintLocInfo -> LintM a -> LintM a
352 addLoc extra_loc m loc scope errs
353 = m (extra_loc:loc) scope errs
355 addInScopeVars :: [Id] -> LintM a -> LintM a
356 addInScopeVars ids m loc scope errs
357 = -- We check if these "new" ids are already
358 -- in scope, i.e., we have *shadowing* going on.
359 -- For now, it's just a "trace"; we may make
360 -- a real error out of it...
362 new_set = mkVarSet ids
364 shadowed = scope `intersectVarSet` new_set
366 -- After adding -fliberate-case, Simon decided he likes shadowed
367 -- names after all. WDP 94/07
368 -- (if isEmptyVarSet shadowed
370 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
371 m loc (scope `unionVarSet` new_set) errs
375 checkFunApp :: Type -- The function type
376 -> [Type] -- The arg type(s)
377 -> Message -- Error messgae
378 -> LintM (Maybe Type) -- The result type
380 checkFunApp fun_ty arg_tys msg loc scope errs
381 = cfa res_ty expected_arg_tys arg_tys
383 (expected_arg_tys, res_ty) = splitFunTys fun_ty
385 cfa res_ty expected [] -- Args have run out; that's fine
386 = (Just (mkFunTys expected res_ty), errs)
388 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
389 -- first see if res_ty is a tyvar template;
390 -- otherwise, maybe res_ty is a
391 -- dictionary type which is actually a function?
393 = (Just res_ty, errs)
395 = case splitFunTys res_ty of
396 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
397 (new_expected, new_res) -> cfa new_res new_expected arg_tys
399 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
400 = if (expected_arg_ty == arg_ty)
401 then cfa res_ty expected_arg_tys arg_tys
402 else (Nothing, addErr errs msg loc) -- Arg mis-match
406 checkInScope :: Id -> LintM ()
407 checkInScope id loc scope errs
408 = if isLocallyDefined id && not (id `elemVarSet` scope) then
409 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
413 checkTys :: Type -> Type -> Message -> LintM ()
414 checkTys ty1 ty2 msg loc scope errs
417 else ((), addErr errs msg loc)
421 mkCaseAltMsg :: StgCaseAlts -> Message
423 = ($$) (text "In some case alternatives, type of alternatives not all same:")
425 (panic "mkCaseAltMsg")
427 mkCaseDataConMsg :: StgExpr -> Message
428 mkCaseDataConMsg expr
429 = ($$) (ptext SLIT("A case scrutinee not a type-constructor type:"))
432 mkCaseAbstractMsg :: TyCon -> Message
433 mkCaseAbstractMsg tycon
434 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
437 mkDefltMsg :: Id -> Message
439 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
442 mkFunAppMsg :: Type -> [Type] -> StgExpr -> Message
443 mkFunAppMsg fun_ty arg_tys expr
444 = vcat [text "In a function application, function type doesn't match arg types:",
445 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
446 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
447 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
449 mkRhsConMsg :: Type -> [Type] -> Message
450 mkRhsConMsg fun_ty arg_tys
451 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
452 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
453 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
455 mkUnappTyMsg :: Id -> Type -> Message
457 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
458 (<>) (ptext SLIT("Var: ")) (ppr var),
459 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
461 mkAlgAltMsg1 :: Type -> Message
463 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
466 mkAlgAltMsg2 :: Type -> DataCon -> Message
469 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
474 mkAlgAltMsg3 :: DataCon -> [Id] -> Message
475 mkAlgAltMsg3 con alts
477 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
482 mkAlgAltMsg4 :: Type -> Id -> Message
485 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
490 mkPrimAltMsg :: (Literal, StgExpr) -> Message
492 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
495 mkRhsMsg :: Id -> Type -> Message
497 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
499 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
500 hsep [ptext SLIT("Rhs type:"), ppr ty]
503 mkUnLiftedTyMsg binder rhs
504 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
505 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
507 (ptext SLIT("RHS:") <+> ppr rhs)