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 )
21 import Type ( mkFunTys, splitFunTys, splitAlgTyConApp_maybe,
22 isUnLiftedType, isTyVarTy, Type
24 import TyCon ( TyCon, isDataTyCon )
25 import Util ( zipEqual, trace )
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
263 instance Outputable LintLocInfo where
265 = hcat [ppr (getSrcLoc v), ptext SLIT(": [RHS of "), pp_binders [v], char ']']
267 ppr (LambdaBodyOf bs)
268 = hcat [ptext SLIT(": [in body of lambda with binders "), pp_binders bs, char ']']
270 ppr (BodyOfLetRec bs)
271 = hcat [ppr (getSrcLoc (head bs)),
272 ptext SLIT(": [in body of letrec with binders "), pp_binders bs, char ']']
274 pp_binders :: [Id] -> SDoc
276 = sep (punctuate comma (map pp_binder bs))
279 = hsep [ppr b, ptext SLIT("::"), ppr (idType b)]
283 initL :: LintM a -> Maybe ErrMsg
285 = case (m [] emptyVarSet emptyBag) of { (_, errs) ->
286 if isEmptyBag errs then
289 Just (foldBag ($$) (\ msg -> msg) empty errs)
292 returnL :: a -> LintM a
293 returnL r loc scope errs = (r, errs)
295 thenL :: LintM a -> (a -> LintM b) -> LintM b
296 thenL m k loc scope errs
297 = case m loc scope errs of
298 (r, errs') -> k r loc scope errs'
300 thenL_ :: LintM a -> LintM b -> LintM b
301 thenL_ m k loc scope errs
302 = case m loc scope errs of
303 (_, errs') -> k loc scope errs'
305 thenMaybeL :: LintM (Maybe a) -> (a -> LintM (Maybe b)) -> LintM (Maybe b)
306 thenMaybeL m k loc scope errs
307 = case m loc scope errs of
308 (Nothing, errs2) -> (Nothing, errs2)
309 (Just r, errs2) -> k r loc scope errs2
311 thenMaybeL_ :: LintM (Maybe a) -> LintM (Maybe b) -> LintM (Maybe b)
312 thenMaybeL_ m k loc scope errs
313 = case m loc scope errs of
314 (Nothing, errs2) -> (Nothing, errs2)
315 (Just _, errs2) -> k loc scope errs2
317 mapL :: (a -> LintM b) -> [a] -> LintM [b]
318 mapL f [] = returnL []
321 mapL f xs `thenL` \ rs ->
324 mapMaybeL :: (a -> LintM (Maybe b)) -> [a] -> LintM (Maybe [b])
325 -- Returns Nothing if anything fails
326 mapMaybeL f [] = returnL (Just [])
328 = f x `thenMaybeL` \ r ->
329 mapMaybeL f xs `thenMaybeL` \ rs ->
330 returnL (Just (r:rs))
334 checkL :: Bool -> ErrMsg -> LintM ()
335 checkL True msg loc scope errs = ((), errs)
336 checkL False msg loc scope errs = ((), addErr errs msg loc)
338 addErrL :: ErrMsg -> LintM ()
339 addErrL msg loc scope errs = ((), addErr errs msg loc)
341 addErr :: Bag ErrMsg -> ErrMsg -> [LintLocInfo] -> Bag ErrMsg
343 addErr errs_so_far msg locs
344 = errs_so_far `snocBag` mk_msg locs
346 mk_msg (loc:_) = hang (ppr loc) 4 msg
349 addLoc :: LintLocInfo -> LintM a -> LintM a
350 addLoc extra_loc m loc scope errs
351 = m (extra_loc:loc) scope errs
353 addInScopeVars :: [Id] -> LintM a -> LintM a
354 addInScopeVars ids m loc scope errs
355 = -- We check if these "new" ids are already
356 -- in scope, i.e., we have *shadowing* going on.
357 -- For now, it's just a "trace"; we may make
358 -- a real error out of it...
360 new_set = mkVarSet ids
362 shadowed = scope `intersectVarSet` new_set
364 -- After adding -fliberate-case, Simon decided he likes shadowed
365 -- names after all. WDP 94/07
366 -- (if isEmptyVarSet shadowed
368 -- else pprTrace "Shadowed vars:" (ppr (varSetElems shadowed))) $
369 m loc (scope `unionVarSet` new_set) errs
373 checkFunApp :: Type -- The function type
374 -> [Type] -- The arg type(s)
375 -> ErrMsg -- Error messgae
376 -> LintM (Maybe Type) -- The result type
378 checkFunApp fun_ty arg_tys msg loc scope errs
379 = cfa res_ty expected_arg_tys arg_tys
381 (expected_arg_tys, res_ty) = splitFunTys fun_ty
383 cfa res_ty expected [] -- Args have run out; that's fine
384 = (Just (mkFunTys expected res_ty), errs)
386 cfa res_ty [] arg_tys -- Expected arg tys ran out first;
387 -- first see if res_ty is a tyvar template;
388 -- otherwise, maybe res_ty is a
389 -- dictionary type which is actually a function?
391 = (Just res_ty, errs)
393 = case splitFunTys res_ty of
394 ([], _) -> (Nothing, addErr errs msg loc) -- Too many args
395 (new_expected, new_res) -> cfa new_res new_expected arg_tys
397 cfa res_ty (expected_arg_ty:expected_arg_tys) (arg_ty:arg_tys)
398 = if (expected_arg_ty == arg_ty)
399 then cfa res_ty expected_arg_tys arg_tys
400 else (Nothing, addErr errs msg loc) -- Arg mis-match
404 checkInScope :: Id -> LintM ()
405 checkInScope id loc scope errs
406 = if isLocallyDefined id && not (id `elemVarSet` scope) then
407 ((), addErr errs (hsep [ppr id, ptext SLIT("is out of scope")]) loc)
411 checkTys :: Type -> Type -> ErrMsg -> LintM ()
412 checkTys ty1 ty2 msg loc scope errs
415 else ((), addErr errs msg loc)
419 mkCaseAltMsg :: StgCaseAlts -> ErrMsg
421 = ($$) (text "In some case alternatives, type of alternatives not all same:")
423 (panic "mkCaseAltMsg")
425 mkCaseDataConMsg :: StgExpr -> ErrMsg
426 mkCaseDataConMsg expr
427 = ($$) (ptext SLIT("A case scrutinee not a type-constructor type:"))
430 mkCaseAbstractMsg :: TyCon -> ErrMsg
431 mkCaseAbstractMsg tycon
432 = ($$) (ptext SLIT("An algebraic case on an abstract type:"))
435 mkDefltMsg :: Id -> ErrMsg
437 = ($$) (ptext SLIT("Binder of a case expression doesn't match type of scrutinee:"))
440 mkFunAppMsg :: Type -> [Type] -> StgExpr -> ErrMsg
441 mkFunAppMsg fun_ty arg_tys expr
442 = vcat [text "In a function application, function type doesn't match arg types:",
443 hang (ptext SLIT("Function type:")) 4 (ppr fun_ty),
444 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys)),
445 hang (ptext SLIT("Expression:")) 4 (ppr expr)]
447 mkRhsConMsg :: Type -> [Type] -> ErrMsg
448 mkRhsConMsg fun_ty arg_tys
449 = vcat [text "In a RHS constructor application, con type doesn't match arg types:",
450 hang (ptext SLIT("Constructor type:")) 4 (ppr fun_ty),
451 hang (ptext SLIT("Arg types:")) 4 (vcat (map (ppr) arg_tys))]
453 mkUnappTyMsg :: Id -> Type -> ErrMsg
455 = vcat [text "Variable has a for-all type, but isn't applied to any types.",
456 (<>) (ptext SLIT("Var: ")) (ppr var),
457 (<>) (ptext SLIT("Its type: ")) (ppr ty)]
459 mkAlgAltMsg1 :: Type -> ErrMsg
461 = ($$) (text "In some case statement, type of scrutinee is not a data type:")
464 mkAlgAltMsg2 :: Type -> DataCon -> ErrMsg
467 text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
472 mkAlgAltMsg3 :: DataCon -> [Id] -> ErrMsg
473 mkAlgAltMsg3 con alts
475 text "In some algebraic case alternative, number of arguments doesn't match constructor:",
480 mkAlgAltMsg4 :: Type -> Id -> ErrMsg
483 text "In some algebraic case alternative, type of argument doesn't match data constructor:",
488 mkPrimAltMsg :: (Literal, StgExpr) -> ErrMsg
490 = text "In a primitive case alternative, type of literal doesn't match type of scrutinee:"
493 mkRhsMsg :: Id -> Type -> ErrMsg
495 = vcat [hsep [ptext SLIT("The type of this binder doesn't match the type of its RHS:"),
497 hsep [ptext SLIT("Binder's type:"), ppr (idType binder)],
498 hsep [ptext SLIT("Rhs type:"), ppr ty]
501 mkUnLiftedTyMsg binder rhs
502 = (ptext SLIT("Let(rec) binder") <+> quotes (ppr binder) <+>
503 ptext SLIT("has unlifted type") <+> quotes (ppr (idType binder)))
505 (ptext SLIT("RHS:") <+> ppr rhs)