ghc-8.2.1: stgSyn/StgLint.hs
{-
(c) The GRASP/AQUA Project, Glasgow University, 1993-1998
\section[StgLint]{A ``lint'' pass to check for Stg correctness}
-}
{-# LANGUAGE CPP #-}
module StgLint ( lintStgTopBindings ) where
import StgSyn
import Bag ( Bag, emptyBag, isEmptyBag, snocBag, bagToList )
import Id ( Id, idType, isLocalId )
import VarSet
import DataCon
import CoreSyn ( AltCon(..) )
import PrimOp ( primOpType )
import Literal ( literalType )
import Maybes
import Name ( getSrcLoc )
import ErrUtils ( MsgDoc, Severity(..), mkLocMessage )
import Type
import RepType
import TyCon
import Util
import SrcLoc
import Outputable
import Control.Monad
#include "HsVersions.h"
{-
Checks for
(a) *some* type errors
(b) locally-defined variables used but not defined
Note: unless -dverbose-stg is on, display of lint errors will result
in "panic: bOGUS_LVs".
WARNING:
~~~~~~~~
This module has suffered bit-rot; it is likely to yield lint errors
for Stg code that is currently perfectly acceptable for code
generation. Solution: don't use it! (KSW 2000-05).
************************************************************************
* *
\subsection{``lint'' for various constructs}
* *
************************************************************************
@lintStgTopBindings@ is the top-level interface function.
-}
lintStgTopBindings :: String -> [StgTopBinding] -> [StgTopBinding]
lintStgTopBindings whodunnit binds
= {-# SCC "StgLint" #-}
case (initL (lint_binds binds)) of
Nothing -> binds
Just msg -> pprPanic "" (vcat [
text "*** Stg Lint ErrMsgs: in" <+>
text whodunnit <+> text "***",
msg,
text "*** Offending Program ***",
pprStgTopBindings binds,
text "*** End of Offense ***"])
where
lint_binds :: [StgTopBinding] -> LintM ()
lint_binds [] = return ()
lint_binds (bind:binds) = do
binders <- lint_bind bind
addInScopeVars binders $
lint_binds binds
lint_bind (StgTopLifted bind) = lintStgBinds bind
lint_bind (StgTopStringLit v _) = return [v]
lintStgArg :: StgArg -> LintM (Maybe Type)
lintStgArg (StgLitArg lit) = return (Just (literalType lit))
lintStgArg (StgVarArg v) = lintStgVar v
lintStgVar :: Id -> LintM (Maybe Kind)
lintStgVar v = do checkInScope v
return (Just (idType v))
lintStgBinds :: StgBinding -> LintM [Id] -- Returns the binders
lintStgBinds (StgNonRec binder rhs) = do
lint_binds_help (binder,rhs)
return [binder]
lintStgBinds (StgRec pairs)
= addInScopeVars binders $ do
mapM_ lint_binds_help pairs
return binders
where
binders = [b | (b,_) <- pairs]
lint_binds_help :: (Id, StgRhs) -> LintM ()
lint_binds_help (binder, rhs)
= addLoc (RhsOf binder) $ do
-- Check the rhs
_maybe_rhs_ty <- lintStgRhs rhs
-- Check binder doesn't have unlifted type
checkL (not (isUnliftedType binder_ty))
(mkUnliftedTyMsg binder rhs)
-- Check match to RHS type
-- Actually we *can't* check the RHS type, because
-- unsafeCoerce means it really might not match at all
-- notably; eg x::Int = (error @Bool "urk") |> unsafeCoerce...
-- case maybe_rhs_ty of
-- Nothing -> return ()
-- Just rhs_ty -> checkTys binder_ty
-- rhs_ty
--- (mkRhsMsg binder rhs_ty)
return ()
where
binder_ty = idType binder
lintStgRhs :: StgRhs -> LintM (Maybe Type) -- Just ty => type is exact
lintStgRhs (StgRhsClosure _ _ _ _ [] expr)
= lintStgExpr expr
lintStgRhs (StgRhsClosure _ _ _ _ binders expr)
= addLoc (LambdaBodyOf binders) $
addInScopeVars binders $ runMaybeT $ do
body_ty <- MaybeT $ lintStgExpr expr
return (mkFunTys (map idType binders) body_ty)
lintStgRhs rhs@(StgRhsCon _ con args) = do
-- TODO: Check arg_tys
when (isUnboxedTupleCon con || isUnboxedSumCon con) $
addErrL (text "StgRhsCon is an unboxed tuple or sum application" $$
ppr rhs)
runMaybeT $ do
arg_tys <- mapM (MaybeT . lintStgArg) args
MaybeT $ checkFunApp con_ty arg_tys (mkRhsConMsg con_ty arg_tys)
where
con_ty = dataConRepType con
lintStgExpr :: StgExpr -> LintM (Maybe Type) -- Just ty => type is exact
lintStgExpr (StgLit l) = return (Just (literalType l))
lintStgExpr e@(StgApp fun args) = runMaybeT $ do
fun_ty <- MaybeT $ lintStgVar fun
arg_tys <- mapM (MaybeT . lintStgArg) args
MaybeT $ checkFunApp fun_ty arg_tys (mkFunAppMsg fun_ty arg_tys e)
lintStgExpr e@(StgConApp con args _arg_tys) = runMaybeT $ do
-- TODO: Check arg_tys
arg_tys <- mapM (MaybeT . lintStgArg) args
MaybeT $ checkFunApp con_ty arg_tys (mkFunAppMsg con_ty arg_tys e)
where
con_ty = dataConRepType con
lintStgExpr e@(StgOpApp (StgPrimOp op) args _) = runMaybeT $ do
arg_tys <- mapM (MaybeT . lintStgArg) args
MaybeT $ checkFunApp op_ty arg_tys (mkFunAppMsg op_ty arg_tys e)
where
op_ty = primOpType op
lintStgExpr (StgOpApp _ args res_ty) = runMaybeT $ do
-- We don't have enough type information to check
-- the application for StgFCallOp and StgPrimCallOp; ToDo
_maybe_arg_tys <- mapM (MaybeT . lintStgArg) args
return res_ty
lintStgExpr (StgLam bndrs _) = do
addErrL (text "Unexpected StgLam" <+> ppr bndrs)
return Nothing
lintStgExpr (StgLet binds body) = do
binders <- lintStgBinds binds
addLoc (BodyOfLetRec binders) $
addInScopeVars binders $
lintStgExpr body
lintStgExpr (StgLetNoEscape binds body) = do
binders <- lintStgBinds binds
addLoc (BodyOfLetRec binders) $
addInScopeVars binders $
lintStgExpr body
lintStgExpr (StgTick _ expr) = lintStgExpr expr
lintStgExpr (StgCase scrut bndr alts_type alts) = runMaybeT $ do
_ <- MaybeT $ lintStgExpr scrut
in_scope <- MaybeT $ liftM Just $
case alts_type of
AlgAlt tc -> check_bndr (tyConPrimRep tc) >> return True
PrimAlt rep -> check_bndr [rep] >> return True
MultiValAlt _ -> return False -- Binder is always dead in this case
PolyAlt -> return True
MaybeT $ addInScopeVars [bndr | in_scope] $
lintStgAlts alts scrut_ty
where
scrut_ty = idType bndr
scrut_reps = typePrimRep scrut_ty
check_bndr reps = checkL (scrut_reps == reps) bad_bndr
where
bad_bndr = mkDefltMsg bndr reps
lintStgAlts :: [StgAlt]
-> Type -- Type of scrutinee
-> LintM (Maybe Type) -- Just ty => type is accurage
lintStgAlts alts scrut_ty = do
maybe_result_tys <- mapM (lintAlt scrut_ty) alts
-- Check the result types
case catMaybes (maybe_result_tys) of
[] -> return Nothing
(first_ty:_tys) -> do -- mapM_ check tys
return (Just first_ty)
where
-- check ty = checkTys first_ty ty (mkCaseAltMsg alts)
-- We can't check that the alternatives have the
-- same type, because they don't, with unsafeCoerce#
lintAlt :: Type -> (AltCon, [Id], StgExpr) -> LintM (Maybe Type)
lintAlt _ (DEFAULT, _, rhs)
= lintStgExpr rhs
lintAlt scrut_ty (LitAlt lit, _, rhs) = do
checkTys (literalType lit) scrut_ty (mkAltMsg1 scrut_ty)
lintStgExpr rhs
lintAlt scrut_ty (DataAlt con, args, rhs) = do
case splitTyConApp_maybe scrut_ty of
Just (tycon, tys_applied) | isAlgTyCon tycon &&
not (isNewTyCon tycon) -> do
let
cons = tyConDataCons tycon
arg_tys = dataConInstArgTys con tys_applied
-- This does not work for existential constructors
checkL (con `elem` cons) (mkAlgAltMsg2 scrut_ty con)
checkL (length args == dataConRepArity con) (mkAlgAltMsg3 con args)
when (isVanillaDataCon con) $
mapM_ check (zipEqual "lintAlgAlt:stg" arg_tys args)
return ()
_ ->
addErrL (mkAltMsg1 scrut_ty)
addInScopeVars args $
lintStgExpr rhs
where
check (ty, arg) = checkTys ty (idType arg) (mkAlgAltMsg4 ty arg)
-- elem: yes, the elem-list here can sometimes be long-ish,
-- but as it's use-once, probably not worth doing anything different
-- We give it its own copy, so it isn't overloaded.
elem _ [] = False
elem x (y:ys) = x==y || elem x ys
{-
************************************************************************
* *
\subsection[lint-monad]{The Lint monad}
* *
************************************************************************
-}
newtype LintM a = LintM
{ unLintM :: [LintLocInfo] -- Locations
-> IdSet -- Local vars in scope
-> Bag MsgDoc -- Error messages so far
-> (a, Bag MsgDoc) -- Result and error messages (if any)
}
data LintLocInfo
= RhsOf Id -- The variable bound
| LambdaBodyOf [Id] -- The lambda-binder
| BodyOfLetRec [Id] -- One of the binders
dumpLoc :: LintLocInfo -> (SrcSpan, SDoc)
dumpLoc (RhsOf v) =
(srcLocSpan (getSrcLoc v), text " [RHS of " <> pp_binders [v] <> char ']' )
dumpLoc (LambdaBodyOf bs) =
(srcLocSpan (getSrcLoc (head bs)), text " [in body of lambda with binders " <> pp_binders bs <> char ']' )
dumpLoc (BodyOfLetRec bs) =
(srcLocSpan (getSrcLoc (head bs)), text " [in body of letrec with binders " <> pp_binders bs <> char ']' )
pp_binders :: [Id] -> SDoc
pp_binders bs
= sep (punctuate comma (map pp_binder bs))
where
pp_binder b
= hsep [ppr b, dcolon, ppr (idType b)]
initL :: LintM a -> Maybe MsgDoc
initL (LintM m)
= case (m [] emptyVarSet emptyBag) of { (_, errs) ->
if isEmptyBag errs then
Nothing
else
Just (vcat (punctuate blankLine (bagToList errs)))
}
instance Functor LintM where
fmap = liftM
instance Applicative LintM where
pure a = LintM $ \_loc _scope errs -> (a, errs)
(<*>) = ap
(*>) = thenL_
instance Monad LintM where
(>>=) = thenL
(>>) = (*>)
thenL :: LintM a -> (a -> LintM b) -> LintM b
thenL m k = LintM $ \loc scope errs
-> case unLintM m loc scope errs of
(r, errs') -> unLintM (k r) loc scope errs'
thenL_ :: LintM a -> LintM b -> LintM b
thenL_ m k = LintM $ \loc scope errs
-> case unLintM m loc scope errs of
(_, errs') -> unLintM k loc scope errs'
checkL :: Bool -> MsgDoc -> LintM ()
checkL True _ = return ()
checkL False msg = addErrL msg
addErrL :: MsgDoc -> LintM ()
addErrL msg = LintM $ \loc _scope errs -> ((), addErr errs msg loc)
addErr :: Bag MsgDoc -> MsgDoc -> [LintLocInfo] -> Bag MsgDoc
addErr errs_so_far msg locs
= errs_so_far `snocBag` mk_msg locs
where
mk_msg (loc:_) = let (l,hdr) = dumpLoc loc
in mkLocMessage SevWarning l (hdr $$ msg)
mk_msg [] = msg
addLoc :: LintLocInfo -> LintM a -> LintM a
addLoc extra_loc m = LintM $ \loc scope errs
-> unLintM m (extra_loc:loc) scope errs
addInScopeVars :: [Id] -> LintM a -> LintM a
addInScopeVars ids m = LintM $ \loc scope errs
-> let
new_set = mkVarSet ids
in unLintM m loc (scope `unionVarSet` new_set) errs
{-
Checking function applications: we only check that the type has the
right *number* of arrows, we don't actually compare the types. This
is because we can't expect the types to be equal - the type
applications and type lambdas that we use to calculate accurate types
have long since disappeared.
-}
checkFunApp :: Type -- The function type
-> [Type] -- The arg type(s)
-> MsgDoc -- Error message
-> LintM (Maybe Type) -- Just ty => result type is accurate
checkFunApp fun_ty arg_tys msg
= do { case mb_msg of
Just msg -> addErrL msg
Nothing -> return ()
; return mb_ty }
where
(mb_ty, mb_msg) = cfa True fun_ty arg_tys
cfa :: Bool -> Type -> [Type] -> (Maybe Type -- Accurate result?
, Maybe MsgDoc) -- Errors?
cfa accurate fun_ty [] -- Args have run out; that's fine
= (if accurate then Just fun_ty else Nothing, Nothing)
cfa accurate fun_ty arg_tys@(arg_ty':arg_tys')
| Just (arg_ty, res_ty) <- splitFunTy_maybe fun_ty
= if accurate && not (arg_ty `stgEqType` arg_ty')
then (Nothing, Just msg) -- Arg type mismatch
else cfa accurate res_ty arg_tys'
| Just (_, fun_ty') <- splitForAllTy_maybe fun_ty
= cfa False fun_ty' arg_tys
| Just (tc,tc_args) <- splitTyConApp_maybe fun_ty
, isNewTyCon tc
= if length tc_args < tyConArity tc
then WARN( True, text "cfa: unsaturated newtype" <+> ppr fun_ty $$ msg )
(Nothing, Nothing) -- This is odd, but I've seen it
else cfa False (newTyConInstRhs tc tc_args) arg_tys
| Just tc <- tyConAppTyCon_maybe fun_ty
, not (isTypeFamilyTyCon tc) -- Definite error
= (Nothing, Just msg) -- Too many args
| otherwise
= (Nothing, Nothing)
stgEqType :: Type -> Type -> Bool
-- Compare types, but crudely because we have discarded
-- both casts and type applications, so types might look
-- different but be the same. So reply "True" if in doubt.
-- "False" means that the types are definitely different.
--
-- Fundamentally this is a losing battle because of unsafeCoerce
stgEqType orig_ty1 orig_ty2
= gos orig_ty1 orig_ty2
where
gos :: Type -> Type -> Bool
gos ty1 ty2
-- These have no prim rep
| isRuntimeRepKindedTy ty1 && isRuntimeRepKindedTy ty2
= True
-- We have a unary type
| [_] <- reps1, [_] <- reps2
= go ty1 ty2
-- In the case of a tuple just compare prim reps
| otherwise
= reps1 == reps2
where
reps1 = typePrimRep ty1
reps2 = typePrimRep ty2
go :: UnaryType -> UnaryType -> Bool
go ty1 ty2
| Just (tc1, tc_args1) <- splitTyConApp_maybe ty1
, Just (tc2, tc_args2) <- splitTyConApp_maybe ty2
, let res = if tc1 == tc2
then equalLength tc_args1 tc_args2
&& and (zipWith gos tc_args1 tc_args2)
else -- TyCons don't match; but don't bleat if either is a
-- family TyCon because a coercion might have made it
-- equal to something else
(isFamilyTyCon tc1 || isFamilyTyCon tc2)
= if res then True
else
pprTrace "stgEqType: unequal" (vcat [ppr ty1, ppr ty2])
False
| otherwise = True -- Conservatively say "fine".
-- Type variables in particular
checkInScope :: Id -> LintM ()
checkInScope id = LintM $ \loc scope errs
-> if isLocalId id && not (id `elemVarSet` scope) then
((), addErr errs (hsep [ppr id, text "is out of scope"]) loc)
else
((), errs)
checkTys :: Type -> Type -> MsgDoc -> LintM ()
checkTys ty1 ty2 msg = LintM $ \loc _scope errs
-> if (ty1 `stgEqType` ty2)
then ((), errs)
else ((), addErr errs msg loc)
_mkCaseAltMsg :: [StgAlt] -> MsgDoc
_mkCaseAltMsg _alts
= ($$) (text "In some case alternatives, type of alternatives not all same:")
(Outputable.empty) -- LATER: ppr alts
mkDefltMsg :: Id -> [PrimRep] -> MsgDoc
mkDefltMsg bndr reps
= ($$) (text "Binder of a case expression doesn't match representation of scrutinee:")
(ppr bndr $$ ppr (idType bndr) $$ ppr reps)
mkFunAppMsg :: Type -> [Type] -> StgExpr -> MsgDoc
mkFunAppMsg fun_ty arg_tys expr
= vcat [text "In a function application, function type doesn't match arg types:",
hang (text "Function type:") 4 (ppr fun_ty),
hang (text "Arg types:") 4 (vcat (map (ppr) arg_tys)),
hang (text "Expression:") 4 (ppr expr)]
mkRhsConMsg :: Type -> [Type] -> MsgDoc
mkRhsConMsg fun_ty arg_tys
= vcat [text "In a RHS constructor application, con type doesn't match arg types:",
hang (text "Constructor type:") 4 (ppr fun_ty),
hang (text "Arg types:") 4 (vcat (map (ppr) arg_tys))]
mkAltMsg1 :: Type -> MsgDoc
mkAltMsg1 ty
= ($$) (text "In a case expression, type of scrutinee does not match patterns")
(ppr ty)
mkAlgAltMsg2 :: Type -> DataCon -> MsgDoc
mkAlgAltMsg2 ty con
= vcat [
text "In some algebraic case alternative, constructor is not a constructor of scrutinee type:",
ppr ty,
ppr con
]
mkAlgAltMsg3 :: DataCon -> [Id] -> MsgDoc
mkAlgAltMsg3 con alts
= vcat [
text "In some algebraic case alternative, number of arguments doesn't match constructor:",
ppr con,
ppr alts
]
mkAlgAltMsg4 :: Type -> Id -> MsgDoc
mkAlgAltMsg4 ty arg
= vcat [
text "In some algebraic case alternative, type of argument doesn't match data constructor:",
ppr ty,
ppr arg
]
_mkRhsMsg :: Id -> Type -> MsgDoc
_mkRhsMsg binder ty
= vcat [hsep [text "The type of this binder doesn't match the type of its RHS:",
ppr binder],
hsep [text "Binder's type:", ppr (idType binder)],
hsep [text "Rhs type:", ppr ty]
]
mkUnliftedTyMsg :: Id -> StgRhs -> SDoc
mkUnliftedTyMsg binder rhs
= (text "Let(rec) binder" <+> quotes (ppr binder) <+>
text "has unlifted type" <+> quotes (ppr (idType binder)))
$$
(text "RHS:" <+> ppr rhs)