2 % (c) The GRASP/AQUA Project, Glasgow University, 1993-1996
4 \section[StgLint]{A ``lint'' pass to check for Stg correctness}
7 #include "HsVersions.h"
9 module StgLint ( lintStgBindings ) where
15 import Bag ( emptyBag, isEmptyBag, snocBag, foldBag )
16 import Id ( idType, isDataCon, dataConArgTys,
17 emptyIdSet, isEmptyIdSet, elementOfIdSet,
18 mkIdSet, intersectIdSets,
19 unionIdSets, idSetToList, SYN_IE(IdSet),
20 GenId{-instanced NamedThing-}
22 import Literal ( literalType, Literal{-instance Outputable-} )
23 import Maybes ( catMaybes )
24 import Name ( isLocallyDefined, getSrcLoc )
25 import Outputable ( Outputable(..){-instance * []-} )
26 import PprType ( GenType{-instance Outputable-}, TyCon )
27 import Pretty -- quite a bit of it
28 import PrimOp ( primOpType )
29 import SrcLoc ( SrcLoc{-instance Outputable-} )
30 import Type ( mkFunTys, splitFunTy, maybeAppDataTyConExpandingDicts,
31 isTyVarTy, eqTy, splitFunTyExpandingDicts
33 import Util ( zipEqual, pprPanic, panic, panic# )
35 infixr 9 `thenL`, `thenL_`, `thenMaybeL`, `thenMaybeL_`
37 unDictifyTy = panic "StgLint.unDictifyTy (ToDo)"
41 (a) *some* type errors
42 (b) locally-defined variables used but not defined
44 %************************************************************************
46 \subsection{``lint'' for various constructs}
48 %************************************************************************
50 @lintStgBindings@ is the top-level interface function.
53 lintStgBindings :: PprStyle -> String -> [StgBinding] -> [StgBinding]
55 lintStgBindings sty whodunnit binds
57 case (initL (lint_binds binds)) of
59 Just msg -> pprPanic "" (ppAboves [
60 ppStr ("*** Stg Lint Errors: in "++whodunnit++" ***"),
62 ppStr "*** Offending Program ***",
63 ppAboves (map (pprPlainStgBinding sty) binds),
64 ppStr "*** End of Offense ***"])
66 lint_binds :: [StgBinding] -> LintM ()
68 lint_binds [] = returnL ()
69 lint_binds (bind:binds)
70 = lintStgBinds bind `thenL` \ binders ->
71 addInScopeVars binders (
78 lintStgArg :: StgArg -> LintM (Maybe Type)
80 lintStgArg (StgLitArg lit) = returnL (Just (literalType lit))
81 lintStgArg a@(StgVarArg v)
82 = checkInScope v `thenL_`
83 returnL (Just (idType v))
87 lintStgBinds :: StgBinding -> LintM [Id] -- Returns the binders
88 lintStgBinds (StgNonRec binder rhs)
89 = lint_binds_help (binder,rhs) `thenL_`
92 lintStgBinds (StgRec pairs)
93 = addInScopeVars binders (
94 mapL lint_binds_help pairs `thenL_`
98 binders = [b | (b,_) <- pairs]
100 lint_binds_help (binder, rhs)
101 = addLoc (RhsOf binder) (
103 lintStgRhs rhs `thenL` \ maybe_rhs_ty ->
105 -- Check match to RHS type
106 (case maybe_rhs_ty of
107 Nothing -> returnL ()
108 Just rhs_ty -> checkTys (idType binder)
110 (mkRhsMsg binder rhs_ty)
118 lintStgRhs :: StgRhs -> LintM (Maybe Type)
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)
137 lintStgExpr :: StgExpr -> LintM (Maybe Type) -- Nothing if error found
139 lintStgExpr e@(StgApp fun args _)
140 = lintStgArg 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 e@(StgPrim op args _)
155 = mapMaybeL lintStgArg args `thenL` \ maybe_arg_tys ->
156 case maybe_arg_tys of
157 Nothing -> returnL Nothing
158 Just arg_tys -> checkFunApp op_ty arg_tys (mkFunAppMsg op_ty arg_tys e)
160 op_ty = primOpType op
162 lintStgExpr (StgLet binds body)
163 = lintStgBinds binds `thenL` \ binders ->
164 addLoc (BodyOfLetRec binders) (
165 addInScopeVars binders (
169 lintStgExpr (StgLetNoEscape _ _ binds body)
170 = lintStgBinds binds `thenL` \ binders ->
171 addLoc (BodyOfLetRec binders) (
172 addInScopeVars binders (
176 lintStgExpr (StgSCC _ _ expr) = lintStgExpr expr
178 lintStgExpr e@(StgCase scrut _ _ _ alts)
179 = lintStgExpr scrut `thenMaybeL` \ _ ->
181 -- Check that it is a data type
182 case (maybeAppDataTyConExpandingDicts scrut_ty) of
183 Nothing -> addErrL (mkCaseDataConMsg e) `thenL_`
186 -> lintStgAlts alts scrut_ty tycon
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 -> TyCon -- TyCon pinned on the case
198 -> LintM (Maybe Type) -- Type of alternatives
200 lintStgAlts alts scrut_ty case_tycon
202 StgAlgAlts _ alg_alts deflt ->
203 mapL (lintAlgAlt scrut_ty) alg_alts `thenL` \ maybe_alt_tys ->
204 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
205 returnL (maybe_deflt_ty : maybe_alt_tys)
207 StgPrimAlts _ prim_alts deflt ->
208 mapL (lintPrimAlt scrut_ty) prim_alts `thenL` \ maybe_alt_tys ->
209 lintDeflt deflt scrut_ty `thenL` \ maybe_deflt_ty ->
210 returnL (maybe_deflt_ty : maybe_alt_tys)
211 ) `thenL` \ maybe_result_tys ->
212 -- Check the result types
213 case catMaybes (maybe_result_tys) of
214 [] -> returnL Nothing
216 (first_ty:tys) -> mapL check tys `thenL_`
217 returnL (Just first_ty)
219 check ty = checkTys first_ty ty (mkCaseAltMsg alts)
221 lintAlgAlt scrut_ty (con, args, _, rhs)
222 = (case maybeAppDataTyConExpandingDicts scrut_ty of
224 addErrL (mkAlgAltMsg1 scrut_ty)
225 Just (tycon, tys_applied, cons) ->
227 arg_tys = dataConArgTys con tys_applied
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 binder _ rhs) scrut_ty
253 = checkTys (idType binder) scrut_ty (mkDefltMsg deflt) `thenL_`
254 addInScopeVars [binder] (
260 %************************************************************************
262 \subsection[lint-monad]{The Lint monad}
264 %************************************************************************
267 type LintM a = [LintLocInfo] -- Locations
268 -> IdSet -- Local vars in scope
269 -> Bag ErrMsg -- Error messages so far
270 -> (a, Bag ErrMsg) -- Result and error messages (if any)
272 type ErrMsg = PprStyle -> Pretty
275 = RhsOf Id -- The variable bound
276 | LambdaBodyOf [Id] -- The lambda-binder
277 | BodyOfLetRec [Id] -- One of the binders
279 instance Outputable LintLocInfo where
281 = ppBesides [ppr sty (getSrcLoc v), ppStr ": [RHS of ", pp_binders sty [v], ppStr "]"]
283 ppr sty (LambdaBodyOf bs)
284 = ppBesides [ppr sty (getSrcLoc (head bs)),
285 ppStr ": [in body of lambda with binders ", pp_binders sty bs, ppStr "]"]
287 ppr sty (BodyOfLetRec bs)
288 = ppBesides [ppr sty (getSrcLoc (head bs)),
289 ppStr ": [in body of letrec with binders ", pp_binders sty bs, ppStr "]"]
291 pp_binders :: PprStyle -> [Id] -> Pretty
293 = ppInterleave ppComma (map pp_binder bs)
296 = ppCat [ppr sty b, ppStr "::", ppr sty (idType b)]
300 initL :: LintM a -> Maybe ErrMsg
302 = case (m [] emptyIdSet emptyBag) of { (_, errs) ->
303 if isEmptyBag errs then
307 foldBag ppAbove ( \ msg -> msg sty ) ppNil errs
311 returnL :: a -> LintM a
312 returnL r loc scope errs = (r, errs)
314 thenL :: LintM a -> (a -> LintM b) -> LintM b
315 thenL m k loc scope errs
316 = case m loc scope errs of
317 (r, errs') -> k r loc scope errs'
319 thenL_ :: LintM a -> LintM b -> LintM b
320 thenL_ m k loc scope errs
321 = case m loc scope errs of
322 (_, errs') -> k loc scope errs'
324 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
325 thenMaybeL m k loc scope errs
326 = case m loc scope errs of
327 (Nothing, errs2) -> (Nothing, errs2)
328 (Just r, errs2) -> k r loc scope errs2
330 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
331 thenMaybeL_ m k loc scope errs
332 = case m loc scope errs of
333 (Nothing, errs2) -> (Nothing, errs2)
334 (Just _, errs2) -> k loc scope errs2
336 mapL :: (a -> LintM b) -> [a] -> LintM [b]
337 mapL f [] = returnL []
340 mapL f xs `thenL` \ rs ->
343 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
344 -- Returns Nothing if anything fails
345 mapMaybeL f [] = returnL (Just [])
347 = f x `thenMaybeL` \ r ->
348 mapMaybeL f xs `thenMaybeL` \ rs ->
349 returnL (Just (r:rs))
353 checkL :: Bool -> ErrMsg -> LintM ()
354 checkL True msg loc scope errs = ((), errs)
355 checkL False msg loc scope errs = ((), addErr errs msg loc)
357 addErrL :: ErrMsg -> LintM ()
358 addErrL msg loc scope errs = ((), addErr errs msg loc)
360 addErr :: Bag ErrMsg -> ErrMsg -> [LintLocInfo] -> Bag ErrMsg
362 addErr errs_so_far msg locs
363 = errs_so_far `snocBag` ( \ sty ->
364 ppHang (ppr sty (head locs)) 4 (msg sty)
367 addLoc :: LintLocInfo -> LintM a -> LintM a
368 addLoc extra_loc m loc scope errs
369 = m (extra_loc:loc) scope errs
371 addInScopeVars :: [Id] -> LintM a -> LintM a
372 addInScopeVars ids m loc scope errs
373 = -- We check if these "new" ids are already
374 -- in scope, i.e., we have *shadowing* going on.
375 -- For now, it's just a "trace"; we may make
376 -- a real error out of it...
378 new_set = mkIdSet ids
380 shadowed = scope `intersectIdSets` new_set
382 -- After adding -fliberate-case, Simon decided he likes shadowed
383 -- names after all. WDP 94/07
384 -- (if isEmptyIdSet shadowed
386 -- else pprTrace "Shadowed vars:" (ppr PprDebug (idSetToList shadowed))) $
387 m loc (scope `unionIdSets` new_set) errs
391 checkFunApp :: Type -- The function type
392 -> [Type] -- The arg type(s)
393 -> ErrMsg -- Error messgae
394 -> LintM (Maybe Type) -- The result type
396 checkFunApp fun_ty arg_tys msg loc scope errs
397 = cfa res_ty expected_arg_tys arg_tys
399 (expected_arg_tys, res_ty) = splitFunTyExpandingDicts fun_ty
401 cfa res_ty expected [] -- Args have run out; that's fine
402 = (Just (mkFunTys expected res_ty), errs)
404 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
405 -- first see if res_ty is a tyvar template;
406 -- otherwise, maybe res_ty is a
407 -- dictionary type which is actually a function?
409 = (Just res_ty, errs)
411 = case splitFunTy (unDictifyTy res_ty) of
412 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
413 (new_expected, new_res) -> cfa new_res new_expected arg_tys
415 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
416 = if (sleazy_eq_ty expected_arg_ty arg_ty)
417 then cfa res_ty expected_arg_tys arg_tys
418 else (Nothing, addErr errs msg loc) -- Arg mis-match
422 checkInScope :: Id -> LintM ()
423 checkInScope id loc scope errs
424 = if isLocallyDefined id && not (isDataCon id) && not (id `elementOfIdSet` scope) then
425 ((), addErr errs (\ sty -> ppCat [ppr sty id, ppStr "is out of scope"]) loc)
429 checkTys :: Type -> Type -> ErrMsg -> LintM ()
430 checkTys ty1 ty2 msg loc scope errs
431 = if (sleazy_eq_ty ty1 ty2)
433 else ((), addErr errs msg loc)
437 mkCaseAltMsg :: StgCaseAlts -> ErrMsg
438 mkCaseAltMsg alts sty
439 = ppAbove (ppStr "In some case alternatives, type of alternatives not all same:")
440 -- LATER: (ppr sty alts)
441 (panic "mkCaseAltMsg")
443 mkCaseDataConMsg :: StgExpr -> ErrMsg
444 mkCaseDataConMsg expr sty
445 = ppAbove (ppStr "A case scrutinee not a type-constructor type:")
448 mkCaseAbstractMsg :: TyCon -> ErrMsg
449 mkCaseAbstractMsg tycon sty
450 = ppAbove (ppStr "An algebraic case on an abstract type:")
453 mkDefltMsg :: StgCaseDefault -> ErrMsg
455 = ppAbove (ppStr "Binder in default case of a case expression doesn't match type of scrutinee:")
456 --LATER: (ppr sty deflt)
459 mkFunAppMsg :: Type -> [Type] -> StgExpr -> ErrMsg
460 mkFunAppMsg fun_ty arg_tys expr sty
461 = ppAboves [ppStr "In a function application, function type doesn't match arg types:",
462 ppHang (ppStr "Function type:") 4 (ppr sty fun_ty),
463 ppHang (ppStr "Arg types:") 4 (ppAboves (map (ppr sty) arg_tys)),
464 ppHang (ppStr "Expression:") 4 (pp_expr sty expr)]
466 mkRhsConMsg :: Type -> [Type] -> ErrMsg
467 mkRhsConMsg fun_ty arg_tys sty
468 = ppAboves [ppStr "In a RHS constructor application, con type doesn't match arg types:",
469 ppHang (ppStr "Constructor type:") 4 (ppr sty fun_ty),
470 ppHang (ppStr "Arg types:") 4 (ppAboves (map (ppr sty) arg_tys))]
472 mkUnappTyMsg :: Id -> Type -> ErrMsg
473 mkUnappTyMsg var ty sty
474 = ppAboves [ppStr "Variable has a for-all type, but isn't applied to any types.",
475 ppBeside (ppStr "Var: ") (ppr sty var),
476 ppBeside (ppStr "Its type: ") (ppr sty ty)]
478 mkAlgAltMsg1 :: Type -> ErrMsg
480 = ppAbove (ppStr "In some case statement, type of scrutinee is not a data type:")
483 mkAlgAltMsg2 :: Type -> Id -> ErrMsg
484 mkAlgAltMsg2 ty con sty
486 ppStr "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
491 mkAlgAltMsg3 :: Id -> [Id] -> ErrMsg
492 mkAlgAltMsg3 con alts sty
494 ppStr "In some algebraic case alternative, number of arguments doesn't match constructor:",
499 mkAlgAltMsg4 :: Type -> Id -> ErrMsg
500 mkAlgAltMsg4 ty arg sty
502 ppStr "In some algebraic case alternative, type of argument doesn't match data constructor:",
507 mkPrimAltMsg :: (Literal, StgExpr) -> ErrMsg
509 = ppAbove (ppStr "In a primitive case alternative, type of literal doesn't match type of scrutinee:")
512 mkRhsMsg :: Id -> Type -> ErrMsg
513 mkRhsMsg binder ty sty
514 = ppAboves [ppCat [ppStr "The type of this binder doesn't match the type of its RHS:",
516 ppCat [ppStr "Binder's type:", ppr sty (idType binder)],
517 ppCat [ppStr "Rhs type:", ppr sty ty]
520 pp_expr :: PprStyle -> StgExpr -> Pretty
521 pp_expr sty expr = ppr sty expr
524 -- NB: probably severe overkill (WDP 95/04)
525 = trace "StgLint.sleazy_eq_ty:use eqSimplTy?" $
526 case (splitFunTyExpandingDicts ty1) of { (tyargs1,tyres1) ->
527 case (splitFunTyExpandingDicts ty2) of { (tyargs2,tyres2) ->
529 ty11 = mkFunTys tyargs1 tyres1
530 ty22 = mkFunTys tyargs2 tyres2