Fold base.git into ghc.git (re #8545)
[ghc.git] / compiler / ghci / RtClosureInspect.hs
1 -----------------------------------------------------------------------------
2 --
3 -- GHC Interactive support for inspecting arbitrary closures at runtime
4 --
5 -- Pepe Iborra (supported by Google SoC) 2006
6 --
7 -----------------------------------------------------------------------------
8
9 {-# OPTIONS -fno-warn-tabs #-}
10 -- The above warning supression flag is a temporary kludge.
11 -- While working on this module you are encouraged to remove it and
12 -- detab the module (please do the detabbing in a separate patch). See
13 -- http://ghc.haskell.org/trac/ghc/wiki/Commentary/CodingStyle#TabsvsSpaces
14 -- for details
15
16 module RtClosureInspect(
17 cvObtainTerm, -- :: HscEnv -> Int -> Bool -> Maybe Type -> HValue -> IO Term
18 cvReconstructType,
19 improveRTTIType,
20
21 Term(..),
22 isTerm, isSuspension, isPrim, isFun, isFunLike, isNewtypeWrap,
23 isFullyEvaluated, isFullyEvaluatedTerm,
24 termType, mapTermType, termTyVars,
25 foldTerm, TermFold(..), foldTermM, TermFoldM(..), idTermFold,
26 pprTerm, cPprTerm, cPprTermBase, CustomTermPrinter,
27
28 -- unsafeDeepSeq,
29
30 Closure(..), getClosureData, ClosureType(..), isConstr, isIndirection
31 ) where
32
33 #include "HsVersions.h"
34
35 import DebuggerUtils
36 import ByteCodeItbls ( StgInfoTable, peekItbl )
37 import qualified ByteCodeItbls as BCI( StgInfoTable(..) )
38 import BasicTypes ( HValue )
39 import HscTypes
40
41 import DataCon
42 import Type
43 import qualified Unify as U
44 import Var
45 import TcRnMonad
46 import TcType
47 import TcMType
48 import TcHsSyn ( zonkTcTypeToType, mkEmptyZonkEnv )
49 import TcUnify
50 import TcEnv
51
52 import TyCon
53 import Name
54 import VarEnv
55 import Util
56 import VarSet
57 import BasicTypes ( TupleSort(UnboxedTuple) )
58 import TysPrim
59 import PrelNames
60 import TysWiredIn
61 import DynFlags
62 import Outputable as Ppr
63 import GHC.Arr ( Array(..) )
64 import GHC.Exts
65 import GHC.IO ( IO(..) )
66
67 import StaticFlags( opt_PprStyle_Debug )
68 import Control.Monad
69 import Data.Maybe
70 import Data.Array.Base
71 import Data.Ix
72 import Data.List
73 import qualified Data.Sequence as Seq
74 import Data.Monoid (mappend)
75 import Data.Sequence (viewl, ViewL(..))
76 import Foreign.Safe
77 import System.IO.Unsafe
78
79 ---------------------------------------------
80 -- * A representation of semi evaluated Terms
81 ---------------------------------------------
82
83 data Term = Term { ty :: RttiType
84 , dc :: Either String DataCon
85 -- Carries a text representation if the datacon is
86 -- not exported by the .hi file, which is the case
87 -- for private constructors in -O0 compiled libraries
88 , val :: HValue
89 , subTerms :: [Term] }
90
91 | Prim { ty :: RttiType
92 , value :: [Word] }
93
94 | Suspension { ctype :: ClosureType
95 , ty :: RttiType
96 , val :: HValue
97 , bound_to :: Maybe Name -- Useful for printing
98 }
99 | NewtypeWrap{ -- At runtime there are no newtypes, and hence no
100 -- newtype constructors. A NewtypeWrap is just a
101 -- made-up tag saying "heads up, there used to be
102 -- a newtype constructor here".
103 ty :: RttiType
104 , dc :: Either String DataCon
105 , wrapped_term :: Term }
106 | RefWrap { -- The contents of a reference
107 ty :: RttiType
108 , wrapped_term :: Term }
109
110 isTerm, isSuspension, isPrim, isFun, isFunLike, isNewtypeWrap :: Term -> Bool
111 isTerm Term{} = True
112 isTerm _ = False
113 isSuspension Suspension{} = True
114 isSuspension _ = False
115 isPrim Prim{} = True
116 isPrim _ = False
117 isNewtypeWrap NewtypeWrap{} = True
118 isNewtypeWrap _ = False
119
120 isFun Suspension{ctype=Fun} = True
121 isFun _ = False
122
123 isFunLike s@Suspension{ty=ty} = isFun s || isFunTy ty
124 isFunLike _ = False
125
126 termType :: Term -> RttiType
127 termType t = ty t
128
129 isFullyEvaluatedTerm :: Term -> Bool
130 isFullyEvaluatedTerm Term {subTerms=tt} = all isFullyEvaluatedTerm tt
131 isFullyEvaluatedTerm Prim {} = True
132 isFullyEvaluatedTerm NewtypeWrap{wrapped_term=t} = isFullyEvaluatedTerm t
133 isFullyEvaluatedTerm RefWrap{wrapped_term=t} = isFullyEvaluatedTerm t
134 isFullyEvaluatedTerm _ = False
135
136 instance Outputable (Term) where
137 ppr t | Just doc <- cPprTerm cPprTermBase t = doc
138 | otherwise = panic "Outputable Term instance"
139
140 -------------------------------------------------------------------------
141 -- Runtime Closure Datatype and functions for retrieving closure related stuff
142 -------------------------------------------------------------------------
143 data ClosureType = Constr
144 | Fun
145 | Thunk Int
146 | ThunkSelector
147 | Blackhole
148 | AP
149 | PAP
150 | Indirection Int
151 | MutVar Int
152 | MVar Int
153 | Other Int
154 deriving (Show, Eq)
155
156 data Closure = Closure { tipe :: ClosureType
157 , infoPtr :: Ptr ()
158 , infoTable :: StgInfoTable
159 , ptrs :: Array Int HValue
160 , nonPtrs :: [Word]
161 }
162
163 instance Outputable ClosureType where
164 ppr = text . show
165
166 #include "../includes/rts/storage/ClosureTypes.h"
167
168 aP_CODE, pAP_CODE :: Int
169 aP_CODE = AP
170 pAP_CODE = PAP
171 #undef AP
172 #undef PAP
173
174 getClosureData :: DynFlags -> a -> IO Closure
175 getClosureData dflags a =
176 case unpackClosure# a of
177 (# iptr, ptrs, nptrs #) -> do
178 let iptr'
179 | ghciTablesNextToCode =
180 Ptr iptr
181 | otherwise =
182 -- the info pointer we get back from unpackClosure#
183 -- is to the beginning of the standard info table,
184 -- but the Storable instance for info tables takes
185 -- into account the extra entry pointer when
186 -- !ghciTablesNextToCode, so we must adjust here:
187 Ptr iptr `plusPtr` negate (wORD_SIZE dflags)
188 itbl <- peekItbl dflags iptr'
189 let tipe = readCType (BCI.tipe itbl)
190 elems = fromIntegral (BCI.ptrs itbl)
191 ptrsList = Array 0 (elems - 1) elems ptrs
192 nptrs_data = [W# (indexWordArray# nptrs i)
193 | I# i <- [0.. fromIntegral (BCI.nptrs itbl)-1] ]
194 ASSERT(elems >= 0) return ()
195 ptrsList `seq`
196 return (Closure tipe (Ptr iptr) itbl ptrsList nptrs_data)
197
198 readCType :: Integral a => a -> ClosureType
199 readCType i
200 | i >= CONSTR && i <= CONSTR_NOCAF_STATIC = Constr
201 | i >= FUN && i <= FUN_STATIC = Fun
202 | i >= THUNK && i < THUNK_SELECTOR = Thunk i'
203 | i == THUNK_SELECTOR = ThunkSelector
204 | i == BLACKHOLE = Blackhole
205 | i >= IND && i <= IND_STATIC = Indirection i'
206 | i' == aP_CODE = AP
207 | i == AP_STACK = AP
208 | i' == pAP_CODE = PAP
209 | i == MUT_VAR_CLEAN || i == MUT_VAR_DIRTY= MutVar i'
210 | i == MVAR_CLEAN || i == MVAR_DIRTY = MVar i'
211 | otherwise = Other i'
212 where i' = fromIntegral i
213
214 isConstr, isIndirection, isThunk :: ClosureType -> Bool
215 isConstr Constr = True
216 isConstr _ = False
217
218 isIndirection (Indirection _) = True
219 isIndirection _ = False
220
221 isThunk (Thunk _) = True
222 isThunk ThunkSelector = True
223 isThunk AP = True
224 isThunk _ = False
225
226 isFullyEvaluated :: DynFlags -> a -> IO Bool
227 isFullyEvaluated dflags a = do
228 closure <- getClosureData dflags a
229 case tipe closure of
230 Constr -> do are_subs_evaluated <- amapM (isFullyEvaluated dflags) (ptrs closure)
231 return$ and are_subs_evaluated
232 _ -> return False
233 where amapM f = sequence . amap' f
234
235 -- TODO: Fix it. Probably the otherwise case is failing, trace/debug it
236 {-
237 unsafeDeepSeq :: a -> b -> b
238 unsafeDeepSeq = unsafeDeepSeq1 2
239 where unsafeDeepSeq1 0 a b = seq a $! b
240 unsafeDeepSeq1 i a b -- 1st case avoids infinite loops for non reducible thunks
241 | not (isConstr tipe) = seq a $! unsafeDeepSeq1 (i-1) a b
242 -- | unsafePerformIO (isFullyEvaluated a) = b
243 | otherwise = case unsafePerformIO (getClosureData a) of
244 closure -> foldl' (flip unsafeDeepSeq) b (ptrs closure)
245 where tipe = unsafePerformIO (getClosureType a)
246 -}
247
248 -----------------------------------
249 -- * Traversals for Terms
250 -----------------------------------
251 type TermProcessor a b = RttiType -> Either String DataCon -> HValue -> [a] -> b
252
253 data TermFold a = TermFold { fTerm :: TermProcessor a a
254 , fPrim :: RttiType -> [Word] -> a
255 , fSuspension :: ClosureType -> RttiType -> HValue
256 -> Maybe Name -> a
257 , fNewtypeWrap :: RttiType -> Either String DataCon
258 -> a -> a
259 , fRefWrap :: RttiType -> a -> a
260 }
261
262
263 data TermFoldM m a =
264 TermFoldM {fTermM :: TermProcessor a (m a)
265 , fPrimM :: RttiType -> [Word] -> m a
266 , fSuspensionM :: ClosureType -> RttiType -> HValue
267 -> Maybe Name -> m a
268 , fNewtypeWrapM :: RttiType -> Either String DataCon
269 -> a -> m a
270 , fRefWrapM :: RttiType -> a -> m a
271 }
272
273 foldTerm :: TermFold a -> Term -> a
274 foldTerm tf (Term ty dc v tt) = fTerm tf ty dc v (map (foldTerm tf) tt)
275 foldTerm tf (Prim ty v ) = fPrim tf ty v
276 foldTerm tf (Suspension ct ty v b) = fSuspension tf ct ty v b
277 foldTerm tf (NewtypeWrap ty dc t) = fNewtypeWrap tf ty dc (foldTerm tf t)
278 foldTerm tf (RefWrap ty t) = fRefWrap tf ty (foldTerm tf t)
279
280
281 foldTermM :: Monad m => TermFoldM m a -> Term -> m a
282 foldTermM tf (Term ty dc v tt) = mapM (foldTermM tf) tt >>= fTermM tf ty dc v
283 foldTermM tf (Prim ty v ) = fPrimM tf ty v
284 foldTermM tf (Suspension ct ty v b) = fSuspensionM tf ct ty v b
285 foldTermM tf (NewtypeWrap ty dc t) = foldTermM tf t >>= fNewtypeWrapM tf ty dc
286 foldTermM tf (RefWrap ty t) = foldTermM tf t >>= fRefWrapM tf ty
287
288 idTermFold :: TermFold Term
289 idTermFold = TermFold {
290 fTerm = Term,
291 fPrim = Prim,
292 fSuspension = Suspension,
293 fNewtypeWrap = NewtypeWrap,
294 fRefWrap = RefWrap
295 }
296
297 mapTermType :: (RttiType -> Type) -> Term -> Term
298 mapTermType f = foldTerm idTermFold {
299 fTerm = \ty dc hval tt -> Term (f ty) dc hval tt,
300 fSuspension = \ct ty hval n ->
301 Suspension ct (f ty) hval n,
302 fNewtypeWrap= \ty dc t -> NewtypeWrap (f ty) dc t,
303 fRefWrap = \ty t -> RefWrap (f ty) t}
304
305 mapTermTypeM :: Monad m => (RttiType -> m Type) -> Term -> m Term
306 mapTermTypeM f = foldTermM TermFoldM {
307 fTermM = \ty dc hval tt -> f ty >>= \ty' -> return $ Term ty' dc hval tt,
308 fPrimM = (return.) . Prim,
309 fSuspensionM = \ct ty hval n ->
310 f ty >>= \ty' -> return $ Suspension ct ty' hval n,
311 fNewtypeWrapM= \ty dc t -> f ty >>= \ty' -> return $ NewtypeWrap ty' dc t,
312 fRefWrapM = \ty t -> f ty >>= \ty' -> return $ RefWrap ty' t}
313
314 termTyVars :: Term -> TyVarSet
315 termTyVars = foldTerm TermFold {
316 fTerm = \ty _ _ tt ->
317 tyVarsOfType ty `plusVarEnv` concatVarEnv tt,
318 fSuspension = \_ ty _ _ -> tyVarsOfType ty,
319 fPrim = \ _ _ -> emptyVarEnv,
320 fNewtypeWrap= \ty _ t -> tyVarsOfType ty `plusVarEnv` t,
321 fRefWrap = \ty t -> tyVarsOfType ty `plusVarEnv` t}
322 where concatVarEnv = foldr plusVarEnv emptyVarEnv
323
324 ----------------------------------
325 -- Pretty printing of terms
326 ----------------------------------
327
328 type Precedence = Int
329 type TermPrinter = Precedence -> Term -> SDoc
330 type TermPrinterM m = Precedence -> Term -> m SDoc
331
332 app_prec,cons_prec, max_prec ::Int
333 max_prec = 10
334 app_prec = max_prec
335 cons_prec = 5 -- TODO Extract this info from GHC itself
336
337 pprTerm :: TermPrinter -> TermPrinter
338 pprTerm y p t | Just doc <- pprTermM (\p -> Just . y p) p t = doc
339 pprTerm _ _ _ = panic "pprTerm"
340
341 pprTermM, ppr_termM, pprNewtypeWrap :: Monad m => TermPrinterM m -> TermPrinterM m
342 pprTermM y p t = pprDeeper `liftM` ppr_termM y p t
343
344 ppr_termM y p Term{dc=Left dc_tag, subTerms=tt} = do
345 tt_docs <- mapM (y app_prec) tt
346 return $ cparen (not (null tt) && p >= app_prec)
347 (text dc_tag <+> pprDeeperList fsep tt_docs)
348
349 ppr_termM y p Term{dc=Right dc, subTerms=tt}
350 {- | dataConIsInfix dc, (t1:t2:tt') <- tt --TODO fixity
351 = parens (ppr_term1 True t1 <+> ppr dc <+> ppr_term1 True ppr t2)
352 <+> hsep (map (ppr_term1 True) tt)
353 -} -- TODO Printing infix constructors properly
354 | null sub_terms_to_show
355 = return (ppr dc)
356 | otherwise
357 = do { tt_docs <- mapM (y app_prec) sub_terms_to_show
358 ; return $ cparen (p >= app_prec) $
359 sep [ppr dc, nest 2 (pprDeeperList fsep tt_docs)] }
360 where
361 sub_terms_to_show -- Don't show the dictionary arguments to
362 -- constructors unless -dppr-debug is on
363 | opt_PprStyle_Debug = tt
364 | otherwise = dropList (dataConTheta dc) tt
365
366 ppr_termM y p t@NewtypeWrap{} = pprNewtypeWrap y p t
367 ppr_termM y p RefWrap{wrapped_term=t} = do
368 contents <- y app_prec t
369 return$ cparen (p >= app_prec) (text "GHC.Prim.MutVar#" <+> contents)
370 -- The constructor name is wired in here ^^^ for the sake of simplicity.
371 -- I don't think mutvars are going to change in a near future.
372 -- In any case this is solely a presentation matter: MutVar# is
373 -- a datatype with no constructors, implemented by the RTS
374 -- (hence there is no way to obtain a datacon and print it).
375 ppr_termM _ _ t = ppr_termM1 t
376
377
378 ppr_termM1 :: Monad m => Term -> m SDoc
379 ppr_termM1 Prim{value=words, ty=ty} =
380 return $ repPrim (tyConAppTyCon ty) words
381 ppr_termM1 Suspension{ty=ty, bound_to=Nothing} =
382 return (char '_' <+> ifPprDebug (text "::" <> ppr ty))
383 ppr_termM1 Suspension{ty=ty, bound_to=Just n}
384 -- | Just _ <- splitFunTy_maybe ty = return$ ptext (sLit("<function>")
385 | otherwise = return$ parens$ ppr n <> text "::" <> ppr ty
386 ppr_termM1 Term{} = panic "ppr_termM1 - Term"
387 ppr_termM1 RefWrap{} = panic "ppr_termM1 - RefWrap"
388 ppr_termM1 NewtypeWrap{} = panic "ppr_termM1 - NewtypeWrap"
389
390 pprNewtypeWrap y p NewtypeWrap{ty=ty, wrapped_term=t}
391 | Just (tc,_) <- tcSplitTyConApp_maybe ty
392 , ASSERT(isNewTyCon tc) True
393 , Just new_dc <- tyConSingleDataCon_maybe tc = do
394 real_term <- y max_prec t
395 return $ cparen (p >= app_prec) (ppr new_dc <+> real_term)
396 pprNewtypeWrap _ _ _ = panic "pprNewtypeWrap"
397
398 -------------------------------------------------------
399 -- Custom Term Pretty Printers
400 -------------------------------------------------------
401
402 -- We can want to customize the representation of a
403 -- term depending on its type.
404 -- However, note that custom printers have to work with
405 -- type representations, instead of directly with types.
406 -- We cannot use type classes here, unless we employ some
407 -- typerep trickery (e.g. Weirich's RepLib tricks),
408 -- which I didn't. Therefore, this code replicates a lot
409 -- of what type classes provide for free.
410
411 type CustomTermPrinter m = TermPrinterM m
412 -> [Precedence -> Term -> (m (Maybe SDoc))]
413
414 -- | Takes a list of custom printers with a explicit recursion knot and a term,
415 -- and returns the output of the first successful printer, or the default printer
416 cPprTerm :: Monad m => CustomTermPrinter m -> Term -> m SDoc
417 cPprTerm printers_ = go 0 where
418 printers = printers_ go
419 go prec t = do
420 let default_ = Just `liftM` pprTermM go prec t
421 mb_customDocs = [pp prec t | pp <- printers] ++ [default_]
422 Just doc <- firstJustM mb_customDocs
423 return$ cparen (prec>app_prec+1) doc
424
425 firstJustM (mb:mbs) = mb >>= maybe (firstJustM mbs) (return . Just)
426 firstJustM [] = return Nothing
427
428 -- Default set of custom printers. Note that the recursion knot is explicit
429 cPprTermBase :: forall m. Monad m => CustomTermPrinter m
430 cPprTermBase y =
431 [ ifTerm (isTupleTy.ty) (\_p -> liftM (parens . hcat . punctuate comma)
432 . mapM (y (-1))
433 . subTerms)
434 , ifTerm (\t -> isTyCon listTyCon (ty t) && subTerms t `lengthIs` 2)
435 ppr_list
436 , ifTerm (isTyCon intTyCon . ty) ppr_int
437 , ifTerm (isTyCon charTyCon . ty) ppr_char
438 , ifTerm (isTyCon floatTyCon . ty) ppr_float
439 , ifTerm (isTyCon doubleTyCon . ty) ppr_double
440 , ifTerm (isIntegerTy . ty) ppr_integer
441 ]
442 where
443 ifTerm :: (Term -> Bool)
444 -> (Precedence -> Term -> m SDoc)
445 -> Precedence -> Term -> m (Maybe SDoc)
446 ifTerm pred f prec t@Term{}
447 | pred t = Just `liftM` f prec t
448 ifTerm _ _ _ _ = return Nothing
449
450 isTupleTy ty = fromMaybe False $ do
451 (tc,_) <- tcSplitTyConApp_maybe ty
452 return (isBoxedTupleTyCon tc)
453
454 isTyCon a_tc ty = fromMaybe False $ do
455 (tc,_) <- tcSplitTyConApp_maybe ty
456 return (a_tc == tc)
457
458 isIntegerTy ty = fromMaybe False $ do
459 (tc,_) <- tcSplitTyConApp_maybe ty
460 return (tyConName tc == integerTyConName)
461
462 ppr_int, ppr_char, ppr_float, ppr_double, ppr_integer
463 :: Precedence -> Term -> m SDoc
464 ppr_int _ v = return (Ppr.int (unsafeCoerce# (val v)))
465 ppr_char _ v = return (Ppr.char '\'' <> Ppr.char (unsafeCoerce# (val v)) <> Ppr.char '\'')
466 ppr_float _ v = return (Ppr.float (unsafeCoerce# (val v)))
467 ppr_double _ v = return (Ppr.double (unsafeCoerce# (val v)))
468 ppr_integer _ v = return (Ppr.integer (unsafeCoerce# (val v)))
469
470 --Note pprinting of list terms is not lazy
471 ppr_list :: Precedence -> Term -> m SDoc
472 ppr_list p (Term{subTerms=[h,t]}) = do
473 let elems = h : getListTerms t
474 isConsLast = not(termType(last elems) `eqType` termType h)
475 is_string = all (isCharTy . ty) elems
476
477 print_elems <- mapM (y cons_prec) elems
478 if is_string
479 then return (Ppr.doubleQuotes (Ppr.text (unsafeCoerce# (map val elems))))
480 else if isConsLast
481 then return $ cparen (p >= cons_prec)
482 $ pprDeeperList fsep
483 $ punctuate (space<>colon) print_elems
484 else return $ brackets
485 $ pprDeeperList fcat
486 $ punctuate comma print_elems
487
488 where getListTerms Term{subTerms=[h,t]} = h : getListTerms t
489 getListTerms Term{subTerms=[]} = []
490 getListTerms t@Suspension{} = [t]
491 getListTerms t = pprPanic "getListTerms" (ppr t)
492 ppr_list _ _ = panic "doList"
493
494
495 repPrim :: TyCon -> [Word] -> SDoc
496 repPrim t = rep where
497 rep x
498 | t == charPrimTyCon = text $ show (build x :: Char)
499 | t == intPrimTyCon = text $ show (build x :: Int)
500 | t == wordPrimTyCon = text $ show (build x :: Word)
501 | t == floatPrimTyCon = text $ show (build x :: Float)
502 | t == doublePrimTyCon = text $ show (build x :: Double)
503 | t == int32PrimTyCon = text $ show (build x :: Int32)
504 | t == word32PrimTyCon = text $ show (build x :: Word32)
505 | t == int64PrimTyCon = text $ show (build x :: Int64)
506 | t == word64PrimTyCon = text $ show (build x :: Word64)
507 | t == addrPrimTyCon = text $ show (nullPtr `plusPtr` build x)
508 | t == stablePtrPrimTyCon = text "<stablePtr>"
509 | t == stableNamePrimTyCon = text "<stableName>"
510 | t == statePrimTyCon = text "<statethread>"
511 | t == proxyPrimTyCon = text "<proxy>"
512 | t == realWorldTyCon = text "<realworld>"
513 | t == threadIdPrimTyCon = text "<ThreadId>"
514 | t == weakPrimTyCon = text "<Weak>"
515 | t == arrayPrimTyCon = text "<array>"
516 | t == smallArrayPrimTyCon = text "<smallArray>"
517 | t == byteArrayPrimTyCon = text "<bytearray>"
518 | t == mutableArrayPrimTyCon = text "<mutableArray>"
519 | t == smallMutableArrayPrimTyCon = text "<smallMutableArray>"
520 | t == mutableByteArrayPrimTyCon = text "<mutableByteArray>"
521 | t == mutVarPrimTyCon = text "<mutVar>"
522 | t == mVarPrimTyCon = text "<mVar>"
523 | t == tVarPrimTyCon = text "<tVar>"
524 | otherwise = char '<' <> ppr t <> char '>'
525 where build ww = unsafePerformIO $ withArray ww (peek . castPtr)
526 -- This ^^^ relies on the representation of Haskell heap values being
527 -- the same as in a C array.
528
529 -----------------------------------
530 -- Type Reconstruction
531 -----------------------------------
532 {-
533 Type Reconstruction is type inference done on heap closures.
534 The algorithm walks the heap generating a set of equations, which
535 are solved with syntactic unification.
536 A type reconstruction equation looks like:
537
538 <datacon reptype> = <actual heap contents>
539
540 The full equation set is generated by traversing all the subterms, starting
541 from a given term.
542
543 The only difficult part is that newtypes are only found in the lhs of equations.
544 Right hand sides are missing them. We can either (a) drop them from the lhs, or
545 (b) reconstruct them in the rhs when possible.
546
547 The function congruenceNewtypes takes a shot at (b)
548 -}
549
550
551 -- A (non-mutable) tau type containing
552 -- existentially quantified tyvars.
553 -- (since GHC type language currently does not support
554 -- existentials, we leave these variables unquantified)
555 type RttiType = Type
556
557 -- An incomplete type as stored in GHCi:
558 -- no polymorphism: no quantifiers & all tyvars are skolem.
559 type GhciType = Type
560
561
562 -- The Type Reconstruction monad
563 --------------------------------
564 type TR a = TcM a
565
566 runTR :: HscEnv -> TR a -> IO a
567 runTR hsc_env thing = do
568 mb_val <- runTR_maybe hsc_env thing
569 case mb_val of
570 Nothing -> error "unable to :print the term"
571 Just x -> return x
572
573 runTR_maybe :: HscEnv -> TR a -> IO (Maybe a)
574 runTR_maybe hsc_env thing_inside
575 = do { (_errs, res) <- initTc hsc_env HsSrcFile False
576 (icInteractiveModule (hsc_IC hsc_env))
577 thing_inside
578 ; return res }
579
580 traceTR :: SDoc -> TR ()
581 traceTR = liftTcM . traceOptTcRn Opt_D_dump_rtti
582
583
584 -- Semantically different to recoverM in TcRnMonad
585 -- recoverM retains the errors in the first action,
586 -- whereas recoverTc here does not
587 recoverTR :: TR a -> TR a -> TR a
588 recoverTR recover thing = do
589 (_,mb_res) <- tryTcErrs thing
590 case mb_res of
591 Nothing -> recover
592 Just res -> return res
593
594 trIO :: IO a -> TR a
595 trIO = liftTcM . liftIO
596
597 liftTcM :: TcM a -> TR a
598 liftTcM = id
599
600 newVar :: Kind -> TR TcType
601 newVar = liftTcM . newFlexiTyVarTy
602
603 instTyVars :: [TyVar] -> TR ([TcTyVar], [TcType], TvSubst)
604 -- Instantiate fresh mutable type variables from some TyVars
605 -- This function preserves the print-name, which helps error messages
606 instTyVars = liftTcM . tcInstTyVars
607
608 type RttiInstantiation = [(TcTyVar, TyVar)]
609 -- Associates the typechecker-world meta type variables
610 -- (which are mutable and may be refined), to their
611 -- debugger-world RuntimeUnk counterparts.
612 -- If the TcTyVar has not been refined by the runtime type
613 -- elaboration, then we want to turn it back into the
614 -- original RuntimeUnk
615
616 -- | Returns the instantiated type scheme ty', and the
617 -- mapping from new (instantiated) -to- old (skolem) type variables
618 instScheme :: QuantifiedType -> TR (TcType, RttiInstantiation)
619 instScheme (tvs, ty)
620 = liftTcM $ do { (tvs', _, subst) <- tcInstTyVars tvs
621 ; let rtti_inst = [(tv',tv) | (tv',tv) <- tvs' `zip` tvs]
622 ; return (substTy subst ty, rtti_inst) }
623
624 applyRevSubst :: RttiInstantiation -> TR ()
625 -- Apply the *reverse* substitution in-place to any un-filled-in
626 -- meta tyvars. This recovers the original debugger-world variable
627 -- unless it has been refined by new information from the heap
628 applyRevSubst pairs = liftTcM (mapM_ do_pair pairs)
629 where
630 do_pair (tc_tv, rtti_tv)
631 = do { tc_ty <- zonkTcTyVar tc_tv
632 ; case tcGetTyVar_maybe tc_ty of
633 Just tv | isMetaTyVar tv -> writeMetaTyVar tv (mkTyVarTy rtti_tv)
634 _ -> return () }
635
636 -- Adds a constraint of the form t1 == t2
637 -- t1 is expected to come from walking the heap
638 -- t2 is expected to come from a datacon signature
639 -- Before unification, congruenceNewtypes needs to
640 -- do its magic.
641 addConstraint :: TcType -> TcType -> TR ()
642 addConstraint actual expected = do
643 traceTR (text "add constraint:" <+> fsep [ppr actual, equals, ppr expected])
644 recoverTR (traceTR $ fsep [text "Failed to unify", ppr actual,
645 text "with", ppr expected]) $
646 do { (ty1, ty2) <- congruenceNewtypes actual expected
647 ; _ <- captureConstraints $ unifyType ty1 ty2
648 ; return () }
649 -- TOMDO: what about the coercion?
650 -- we should consider family instances
651
652
653 -- Type & Term reconstruction
654 ------------------------------
655 cvObtainTerm :: HscEnv -> Int -> Bool -> RttiType -> HValue -> IO Term
656 cvObtainTerm hsc_env max_depth force old_ty hval = runTR hsc_env $ do
657 -- we quantify existential tyvars as universal,
658 -- as this is needed to be able to manipulate
659 -- them properly
660 let quant_old_ty@(old_tvs, old_tau) = quantifyType old_ty
661 sigma_old_ty = mkForAllTys old_tvs old_tau
662 traceTR (text "Term reconstruction started with initial type " <> ppr old_ty)
663 term <-
664 if null old_tvs
665 then do
666 term <- go max_depth sigma_old_ty sigma_old_ty hval
667 term' <- zonkTerm term
668 return $ fixFunDictionaries $ expandNewtypes term'
669 else do
670 (old_ty', rev_subst) <- instScheme quant_old_ty
671 my_ty <- newVar openTypeKind
672 when (check1 quant_old_ty) (traceTR (text "check1 passed") >>
673 addConstraint my_ty old_ty')
674 term <- go max_depth my_ty sigma_old_ty hval
675 new_ty <- zonkTcType (termType term)
676 if isMonomorphic new_ty || check2 (quantifyType new_ty) quant_old_ty
677 then do
678 traceTR (text "check2 passed")
679 addConstraint new_ty old_ty'
680 applyRevSubst rev_subst
681 zterm' <- zonkTerm term
682 return ((fixFunDictionaries . expandNewtypes) zterm')
683 else do
684 traceTR (text "check2 failed" <+> parens
685 (ppr term <+> text "::" <+> ppr new_ty))
686 -- we have unsound types. Replace constructor types in
687 -- subterms with tyvars
688 zterm' <- mapTermTypeM
689 (\ty -> case tcSplitTyConApp_maybe ty of
690 Just (tc, _:_) | tc /= funTyCon
691 -> newVar openTypeKind
692 _ -> return ty)
693 term
694 zonkTerm zterm'
695 traceTR (text "Term reconstruction completed." $$
696 text "Term obtained: " <> ppr term $$
697 text "Type obtained: " <> ppr (termType term))
698 return term
699 where
700 dflags = hsc_dflags hsc_env
701
702 go :: Int -> Type -> Type -> HValue -> TcM Term
703 -- I believe that my_ty should not have any enclosing
704 -- foralls, nor any free RuntimeUnk skolems;
705 -- that is partly what the quantifyType stuff achieved
706 --
707 -- [SPJ May 11] I don't understand the difference between my_ty and old_ty
708
709 go max_depth _ _ _ | seq max_depth False = undefined
710 go 0 my_ty _old_ty a = do
711 traceTR (text "Gave up reconstructing a term after" <>
712 int max_depth <> text " steps")
713 clos <- trIO $ getClosureData dflags a
714 return (Suspension (tipe clos) my_ty a Nothing)
715 go max_depth my_ty old_ty a = do
716 let monomorphic = not(isTyVarTy my_ty)
717 -- This ^^^ is a convention. The ancestor tests for
718 -- monomorphism and passes a type instead of a tv
719 clos <- trIO $ getClosureData dflags a
720 case tipe clos of
721 -- Thunks we may want to force
722 t | isThunk t && force -> traceTR (text "Forcing a " <> text (show t)) >>
723 seq a (go (pred max_depth) my_ty old_ty a)
724 -- Blackholes are indirections iff the payload is not TSO or BLOCKING_QUEUE. So we
725 -- treat them like indirections; if the payload is TSO or BLOCKING_QUEUE, we'll end up
726 -- showing '_' which is what we want.
727 Blackhole -> do traceTR (text "Following a BLACKHOLE")
728 appArr (go max_depth my_ty old_ty) (ptrs clos) 0
729 -- We always follow indirections
730 Indirection i -> do traceTR (text "Following an indirection" <> parens (int i) )
731 go max_depth my_ty old_ty $! (ptrs clos ! 0)
732 -- We also follow references
733 MutVar _ | Just (tycon,[world,contents_ty]) <- tcSplitTyConApp_maybe old_ty
734 -> do
735 -- Deal with the MutVar# primitive
736 -- It does not have a constructor at all,
737 -- so we simulate the following one
738 -- MutVar# :: contents_ty -> MutVar# s contents_ty
739 traceTR (text "Following a MutVar")
740 contents_tv <- newVar liftedTypeKind
741 contents <- trIO$ IO$ \w -> readMutVar# (unsafeCoerce# a) w
742 ASSERT(isUnliftedTypeKind $ typeKind my_ty) return ()
743 (mutvar_ty,_) <- instScheme $ quantifyType $ mkFunTy
744 contents_ty (mkTyConApp tycon [world,contents_ty])
745 addConstraint (mkFunTy contents_tv my_ty) mutvar_ty
746 x <- go (pred max_depth) contents_tv contents_ty contents
747 return (RefWrap my_ty x)
748
749 -- The interesting case
750 Constr -> do
751 traceTR (text "entering a constructor " <>
752 if monomorphic
753 then parens (text "already monomorphic: " <> ppr my_ty)
754 else Ppr.empty)
755 Right dcname <- dataConInfoPtrToName (infoPtr clos)
756 (_,mb_dc) <- tryTcErrs (tcLookupDataCon dcname)
757 case mb_dc of
758 Nothing -> do -- This can happen for private constructors compiled -O0
759 -- where the .hi descriptor does not export them
760 -- In such case, we return a best approximation:
761 -- ignore the unpointed args, and recover the pointeds
762 -- This preserves laziness, and should be safe.
763 traceTR (text "Not constructor" <+> ppr dcname)
764 let dflags = hsc_dflags hsc_env
765 tag = showPpr dflags dcname
766 vars <- replicateM (length$ elems$ ptrs clos)
767 (newVar liftedTypeKind)
768 subTerms <- sequence [appArr (go (pred max_depth) tv tv) (ptrs clos) i
769 | (i, tv) <- zip [0..] vars]
770 return (Term my_ty (Left ('<' : tag ++ ">")) a subTerms)
771 Just dc -> do
772 traceTR (text "Is constructor" <+> (ppr dc $$ ppr my_ty))
773 subTtypes <- getDataConArgTys dc my_ty
774 subTerms <- extractSubTerms (\ty -> go (pred max_depth) ty ty) clos subTtypes
775 return (Term my_ty (Right dc) a subTerms)
776
777 -- The otherwise case: can be a Thunk,AP,PAP,etc.
778 tipe_clos ->
779 return (Suspension tipe_clos my_ty a Nothing)
780
781 -- insert NewtypeWraps around newtypes
782 expandNewtypes = foldTerm idTermFold { fTerm = worker } where
783 worker ty dc hval tt
784 | Just (tc, args) <- tcSplitTyConApp_maybe ty
785 , isNewTyCon tc
786 , wrapped_type <- newTyConInstRhs tc args
787 , Just dc' <- tyConSingleDataCon_maybe tc
788 , t' <- worker wrapped_type dc hval tt
789 = NewtypeWrap ty (Right dc') t'
790 | otherwise = Term ty dc hval tt
791
792
793 -- Avoid returning types where predicates have been expanded to dictionaries.
794 fixFunDictionaries = foldTerm idTermFold {fSuspension = worker} where
795 worker ct ty hval n | isFunTy ty = Suspension ct (dictsView ty) hval n
796 | otherwise = Suspension ct ty hval n
797
798 extractSubTerms :: (Type -> HValue -> TcM Term)
799 -> Closure -> [Type] -> TcM [Term]
800 extractSubTerms recurse clos = liftM thirdOf3 . go 0 (nonPtrs clos)
801 where
802 go ptr_i ws [] = return (ptr_i, ws, [])
803 go ptr_i ws (ty:tys)
804 | Just (tc, elem_tys) <- tcSplitTyConApp_maybe ty
805 , isUnboxedTupleTyCon tc
806 = do (ptr_i, ws, terms0) <- go ptr_i ws elem_tys
807 (ptr_i, ws, terms1) <- go ptr_i ws tys
808 return (ptr_i, ws, unboxedTupleTerm ty terms0 : terms1)
809 | otherwise
810 = case repType ty of
811 UnaryRep rep_ty -> do
812 (ptr_i, ws, term0) <- go_rep ptr_i ws ty (typePrimRep rep_ty)
813 (ptr_i, ws, terms1) <- go ptr_i ws tys
814 return (ptr_i, ws, term0 : terms1)
815 UbxTupleRep rep_tys -> do
816 (ptr_i, ws, terms0) <- go_unary_types ptr_i ws rep_tys
817 (ptr_i, ws, terms1) <- go ptr_i ws tys
818 return (ptr_i, ws, unboxedTupleTerm ty terms0 : terms1)
819
820 go_unary_types ptr_i ws [] = return (ptr_i, ws, [])
821 go_unary_types ptr_i ws (rep_ty:rep_tys) = do
822 tv <- newVar liftedTypeKind
823 (ptr_i, ws, term0) <- go_rep ptr_i ws tv (typePrimRep rep_ty)
824 (ptr_i, ws, terms1) <- go_unary_types ptr_i ws rep_tys
825 return (ptr_i, ws, term0 : terms1)
826
827 go_rep ptr_i ws ty rep = case rep of
828 PtrRep -> do
829 t <- appArr (recurse ty) (ptrs clos) ptr_i
830 return (ptr_i + 1, ws, t)
831 _ -> do
832 dflags <- getDynFlags
833 let (ws0, ws1) = splitAt (primRepSizeW dflags rep) ws
834 return (ptr_i, ws1, Prim ty ws0)
835
836 unboxedTupleTerm ty terms = Term ty (Right (tupleCon UnboxedTuple (length terms)))
837 (error "unboxedTupleTerm: no HValue for unboxed tuple") terms
838
839
840 -- Fast, breadth-first Type reconstruction
841 ------------------------------------------
842 cvReconstructType :: HscEnv -> Int -> GhciType -> HValue -> IO (Maybe Type)
843 cvReconstructType hsc_env max_depth old_ty hval = runTR_maybe hsc_env $ do
844 traceTR (text "RTTI started with initial type " <> ppr old_ty)
845 let sigma_old_ty@(old_tvs, _) = quantifyType old_ty
846 new_ty <-
847 if null old_tvs
848 then return old_ty
849 else do
850 (old_ty', rev_subst) <- instScheme sigma_old_ty
851 my_ty <- newVar openTypeKind
852 when (check1 sigma_old_ty) (traceTR (text "check1 passed") >>
853 addConstraint my_ty old_ty')
854 search (isMonomorphic `fmap` zonkTcType my_ty)
855 (\(ty,a) -> go ty a)
856 (Seq.singleton (my_ty, hval))
857 max_depth
858 new_ty <- zonkTcType my_ty
859 if isMonomorphic new_ty || check2 (quantifyType new_ty) sigma_old_ty
860 then do
861 traceTR (text "check2 passed" <+> ppr old_ty $$ ppr new_ty)
862 addConstraint my_ty old_ty'
863 applyRevSubst rev_subst
864 zonkRttiType new_ty
865 else traceTR (text "check2 failed" <+> parens (ppr new_ty)) >>
866 return old_ty
867 traceTR (text "RTTI completed. Type obtained:" <+> ppr new_ty)
868 return new_ty
869 where
870 dflags = hsc_dflags hsc_env
871
872 -- search :: m Bool -> ([a] -> [a] -> [a]) -> [a] -> m ()
873 search _ _ _ 0 = traceTR (text "Failed to reconstruct a type after " <>
874 int max_depth <> text " steps")
875 search stop expand l d =
876 case viewl l of
877 EmptyL -> return ()
878 x :< xx -> unlessM stop $ do
879 new <- expand x
880 search stop expand (xx `mappend` Seq.fromList new) $! (pred d)
881
882 -- returns unification tasks,since we are going to want a breadth-first search
883 go :: Type -> HValue -> TR [(Type, HValue)]
884 go my_ty a = do
885 traceTR (text "go" <+> ppr my_ty)
886 clos <- trIO $ getClosureData dflags a
887 case tipe clos of
888 Blackhole -> appArr (go my_ty) (ptrs clos) 0 -- carefully, don't eval the TSO
889 Indirection _ -> go my_ty $! (ptrs clos ! 0)
890 MutVar _ -> do
891 contents <- trIO$ IO$ \w -> readMutVar# (unsafeCoerce# a) w
892 tv' <- newVar liftedTypeKind
893 world <- newVar liftedTypeKind
894 addConstraint my_ty (mkTyConApp mutVarPrimTyCon [world,tv'])
895 return [(tv', contents)]
896 Constr -> do
897 Right dcname <- dataConInfoPtrToName (infoPtr clos)
898 traceTR (text "Constr1" <+> ppr dcname)
899 (_,mb_dc) <- tryTcErrs (tcLookupDataCon dcname)
900 case mb_dc of
901 Nothing-> do
902 -- TODO: Check this case
903 forM [0..length (elems $ ptrs clos)] $ \i -> do
904 tv <- newVar liftedTypeKind
905 return$ appArr (\e->(tv,e)) (ptrs clos) i
906
907 Just dc -> do
908 arg_tys <- getDataConArgTys dc my_ty
909 (_, itys) <- findPtrTyss 0 arg_tys
910 traceTR (text "Constr2" <+> ppr dcname <+> ppr arg_tys)
911 return $ [ appArr (\e-> (ty,e)) (ptrs clos) i
912 | (i,ty) <- itys]
913 _ -> return []
914
915 findPtrTys :: Int -- Current pointer index
916 -> Type -- Type
917 -> TR (Int, [(Int, Type)])
918 findPtrTys i ty
919 | Just (tc, elem_tys) <- tcSplitTyConApp_maybe ty
920 , isUnboxedTupleTyCon tc
921 = findPtrTyss i elem_tys
922
923 | otherwise
924 = case repType ty of
925 UnaryRep rep_ty | typePrimRep rep_ty == PtrRep -> return (i + 1, [(i, ty)])
926 | otherwise -> return (i, [])
927 UbxTupleRep rep_tys -> foldM (\(i, extras) rep_ty -> if typePrimRep rep_ty == PtrRep
928 then newVar liftedTypeKind >>= \tv -> return (i + 1, extras ++ [(i, tv)])
929 else return (i, extras))
930 (i, []) rep_tys
931
932 findPtrTyss :: Int
933 -> [Type]
934 -> TR (Int, [(Int, Type)])
935 findPtrTyss i tys = foldM step (i, []) tys
936 where step (i, discovered) elem_ty = findPtrTys i elem_ty >>= \(i, extras) -> return (i, discovered ++ extras)
937
938
939 -- Compute the difference between a base type and the type found by RTTI
940 -- improveType <base_type> <rtti_type>
941 -- The types can contain skolem type variables, which need to be treated as normal vars.
942 -- In particular, we want them to unify with things.
943 improveRTTIType :: HscEnv -> RttiType -> RttiType -> Maybe TvSubst
944 improveRTTIType _ base_ty new_ty = U.tcUnifyTy base_ty new_ty
945
946 getDataConArgTys :: DataCon -> Type -> TR [Type]
947 -- Given the result type ty of a constructor application (D a b c :: ty)
948 -- return the types of the arguments. This is RTTI-land, so 'ty' might
949 -- not be fully known. Moreover, the arg types might involve existentials;
950 -- if so, make up fresh RTTI type variables for them
951 --
952 -- I believe that con_app_ty should not have any enclosing foralls
953 getDataConArgTys dc con_app_ty
954 = do { let UnaryRep rep_con_app_ty = repType con_app_ty
955 ; traceTR (text "getDataConArgTys 1" <+> (ppr con_app_ty $$ ppr rep_con_app_ty
956 $$ ppr (tcSplitTyConApp_maybe rep_con_app_ty)))
957 ; (_, _, subst) <- instTyVars (univ_tvs ++ ex_tvs)
958 ; addConstraint rep_con_app_ty (substTy subst (dataConOrigResTy dc))
959 -- See Note [Constructor arg types]
960 ; let con_arg_tys = substTys subst (dataConRepArgTys dc)
961 ; traceTR (text "getDataConArgTys 2" <+> (ppr rep_con_app_ty $$ ppr con_arg_tys $$ ppr subst))
962 ; return con_arg_tys }
963 where
964 univ_tvs = dataConUnivTyVars dc
965 ex_tvs = dataConExTyVars dc
966
967 {- Note [Constructor arg types]
968 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
969 Consider a GADT (cf Trac #7386)
970 data family D a b
971 data instance D [a] a where
972 MkT :: a -> D [a] (Maybe a)
973 ...
974
975 In getDataConArgTys
976 * con_app_ty is the known type (from outside) of the constructor application,
977 say D [Int] Int
978
979 * The data constructor MkT has a (representation) dataConTyCon = DList,
980 say where
981 data DList a where
982 MkT :: a -> DList a (Maybe a)
983 ...
984
985 So the dataConTyCon of the data constructor, DList, differs from
986 the "outside" type, D. So we can't straightforwardly decompose the
987 "outside" type, and we end up in the "_" branch of the case.
988
989 Then we match the dataConOrigResTy of the data constructor against the
990 outside type, hoping to get a substitution that tells how to instantiate
991 the *representation* type constructor. This looks a bit delicate to
992 me, but it seems to work.
993 -}
994
995 -- Soundness checks
996 --------------------
997 {-
998 This is not formalized anywhere, so hold to your seats!
999 RTTI in the presence of newtypes can be a tricky and unsound business.
1000
1001 Example:
1002 ~~~~~~~~~
1003 Suppose we are doing RTTI for a partially evaluated
1004 closure t, the real type of which is t :: MkT Int, for
1005
1006 newtype MkT a = MkT [Maybe a]
1007
1008 The table below shows the results of RTTI and the improvement
1009 calculated for different combinations of evaluatedness and :type t.
1010 Regard the two first columns as input and the next two as output.
1011
1012 # | t | :type t | rtti(t) | improv. | result
1013 ------------------------------------------------------------
1014 1 | _ | t b | a | none | OK
1015 2 | _ | MkT b | a | none | OK
1016 3 | _ | t Int | a | none | OK
1017
1018 If t is not evaluated at *all*, we are safe.
1019
1020 4 | (_ : _) | t b | [a] | t = [] | UNSOUND
1021 5 | (_ : _) | MkT b | MkT a | none | OK (compensating for the missing newtype)
1022 6 | (_ : _) | t Int | [Int] | t = [] | UNSOUND
1023
1024 If a is a minimal whnf, we run into trouble. Note that
1025 row 5 above does newtype enrichment on the ty_rtty parameter.
1026
1027 7 | (Just _:_)| t b |[Maybe a] | t = [], | UNSOUND
1028 | | | b = Maybe a|
1029
1030 8 | (Just _:_)| MkT b | MkT a | none | OK
1031 9 | (Just _:_)| t Int | FAIL | none | OK
1032
1033 And if t is any more evaluated than whnf, we are still in trouble.
1034 Because constraints are solved in top-down order, when we reach the
1035 Maybe subterm what we got is already unsound. This explains why the
1036 row 9 fails to complete.
1037
1038 10 | (Just _:_)| t Int | [Maybe a] | FAIL | OK
1039 11 | (Just 1:_)| t Int | [Maybe Int] | FAIL | OK
1040
1041 We can undo the failure in row 9 by leaving out the constraint
1042 coming from the type signature of t (i.e., the 2nd column).
1043 Note that this type information is still used
1044 to calculate the improvement. But we fail
1045 when trying to calculate the improvement, as there is no unifier for
1046 t Int = [Maybe a] or t Int = [Maybe Int].
1047
1048
1049 Another set of examples with t :: [MkT (Maybe Int)] \equiv [[Maybe (Maybe Int)]]
1050
1051 # | t | :type t | rtti(t) | improvement | result
1052 ---------------------------------------------------------------------
1053 1 |(Just _:_) | [t (Maybe a)] | [[Maybe b]] | t = [] |
1054 | | | | b = Maybe a |
1055
1056 The checks:
1057 ~~~~~~~~~~~
1058 Consider a function obtainType that takes a value and a type and produces
1059 the Term representation and a substitution (the improvement).
1060 Assume an auxiliar rtti' function which does the actual job if recovering
1061 the type, but which may produce a false type.
1062
1063 In pseudocode:
1064
1065 rtti' :: a -> IO Type -- Does not use the static type information
1066
1067 obtainType :: a -> Type -> IO (Maybe (Term, Improvement))
1068 obtainType v old_ty = do
1069 rtti_ty <- rtti' v
1070 if monomorphic rtti_ty || (check rtti_ty old_ty)
1071 then ...
1072 else return Nothing
1073 where check rtti_ty old_ty = check1 rtti_ty &&
1074 check2 rtti_ty old_ty
1075
1076 check1 :: Type -> Bool
1077 check2 :: Type -> Type -> Bool
1078
1079 Now, if rtti' returns a monomorphic type, we are safe.
1080 If that is not the case, then we consider two conditions.
1081
1082
1083 1. To prevent the class of unsoundness displayed by
1084 rows 4 and 7 in the example: no higher kind tyvars
1085 accepted.
1086
1087 check1 (t a) = NO
1088 check1 (t Int) = NO
1089 check1 ([] a) = YES
1090
1091 2. To prevent the class of unsoundness shown by row 6,
1092 the rtti type should be structurally more
1093 defined than the old type we are comparing it to.
1094 check2 :: NewType -> OldType -> Bool
1095 check2 a _ = True
1096 check2 [a] a = True
1097 check2 [a] (t Int) = False
1098 check2 [a] (t a) = False -- By check1 we never reach this equation
1099 check2 [Int] a = True
1100 check2 [Int] (t Int) = True
1101 check2 [Maybe a] (t Int) = False
1102 check2 [Maybe Int] (t Int) = True
1103 check2 (Maybe [a]) (m [Int]) = False
1104 check2 (Maybe [Int]) (m [Int]) = True
1105
1106 -}
1107
1108 check1 :: QuantifiedType -> Bool
1109 check1 (tvs, _) = not $ any isHigherKind (map tyVarKind tvs)
1110 where
1111 isHigherKind = not . null . fst . splitKindFunTys
1112
1113 check2 :: QuantifiedType -> QuantifiedType -> Bool
1114 check2 (_, rtti_ty) (_, old_ty)
1115 | Just (_, rttis) <- tcSplitTyConApp_maybe rtti_ty
1116 = case () of
1117 _ | Just (_,olds) <- tcSplitTyConApp_maybe old_ty
1118 -> and$ zipWith check2 (map quantifyType rttis) (map quantifyType olds)
1119 _ | Just _ <- splitAppTy_maybe old_ty
1120 -> isMonomorphicOnNonPhantomArgs rtti_ty
1121 _ -> True
1122 | otherwise = True
1123
1124 -- Dealing with newtypes
1125 --------------------------
1126 {-
1127 congruenceNewtypes does a parallel fold over two Type values,
1128 compensating for missing newtypes on both sides.
1129 This is necessary because newtypes are not present
1130 in runtime, but sometimes there is evidence available.
1131 Evidence can come from DataCon signatures or
1132 from compile-time type inference.
1133 What we are doing here is an approximation
1134 of unification modulo a set of equations derived
1135 from newtype definitions. These equations should be the
1136 same as the equality coercions generated for newtypes
1137 in System Fc. The idea is to perform a sort of rewriting,
1138 taking those equations as rules, before launching unification.
1139
1140 The caller must ensure the following.
1141 The 1st type (lhs) comes from the heap structure of ptrs,nptrs.
1142 The 2nd type (rhs) comes from a DataCon type signature.
1143 Rewriting (i.e. adding/removing a newtype wrapper) can happen
1144 in both types, but in the rhs it is restricted to the result type.
1145
1146 Note that it is very tricky to make this 'rewriting'
1147 work with the unification implemented by TcM, where
1148 substitutions are operationally inlined. The order in which
1149 constraints are unified is vital as we cannot modify
1150 anything that has been touched by a previous unification step.
1151 Therefore, congruenceNewtypes is sound only if the types
1152 recovered by the RTTI mechanism are unified Top-Down.
1153 -}
1154 congruenceNewtypes :: TcType -> TcType -> TR (TcType,TcType)
1155 congruenceNewtypes lhs rhs = go lhs rhs >>= \rhs' -> return (lhs,rhs')
1156 where
1157 go l r
1158 -- TyVar lhs inductive case
1159 | Just tv <- getTyVar_maybe l
1160 , isTcTyVar tv
1161 , isMetaTyVar tv
1162 = recoverTR (return r) $ do
1163 Indirect ty_v <- readMetaTyVar tv
1164 traceTR $ fsep [text "(congruence) Following indirect tyvar:",
1165 ppr tv, equals, ppr ty_v]
1166 go ty_v r
1167 -- FunTy inductive case
1168 | Just (l1,l2) <- splitFunTy_maybe l
1169 , Just (r1,r2) <- splitFunTy_maybe r
1170 = do r2' <- go l2 r2
1171 r1' <- go l1 r1
1172 return (mkFunTy r1' r2')
1173 -- TyconApp Inductive case; this is the interesting bit.
1174 | Just (tycon_l, _) <- tcSplitTyConApp_maybe lhs
1175 , Just (tycon_r, _) <- tcSplitTyConApp_maybe rhs
1176 , tycon_l /= tycon_r
1177 = upgrade tycon_l r
1178
1179 | otherwise = return r
1180
1181 where upgrade :: TyCon -> Type -> TR Type
1182 upgrade new_tycon ty
1183 | not (isNewTyCon new_tycon) = do
1184 traceTR (text "(Upgrade) Not matching newtype evidence: " <>
1185 ppr new_tycon <> text " for " <> ppr ty)
1186 return ty
1187 | otherwise = do
1188 traceTR (text "(Upgrade) upgraded " <> ppr ty <>
1189 text " in presence of newtype evidence " <> ppr new_tycon)
1190 (_, vars, _) <- instTyVars (tyConTyVars new_tycon)
1191 let ty' = mkTyConApp new_tycon vars
1192 UnaryRep rep_ty = repType ty'
1193 _ <- liftTcM (unifyType ty rep_ty)
1194 -- assumes that reptype doesn't ^^^^ touch tyconApp args
1195 return ty'
1196
1197
1198 zonkTerm :: Term -> TcM Term
1199 zonkTerm = foldTermM (TermFoldM
1200 { fTermM = \ty dc v tt -> zonkRttiType ty >>= \ty' ->
1201 return (Term ty' dc v tt)
1202 , fSuspensionM = \ct ty v b -> zonkRttiType ty >>= \ty ->
1203 return (Suspension ct ty v b)
1204 , fNewtypeWrapM = \ty dc t -> zonkRttiType ty >>= \ty' ->
1205 return$ NewtypeWrap ty' dc t
1206 , fRefWrapM = \ty t -> return RefWrap `ap`
1207 zonkRttiType ty `ap` return t
1208 , fPrimM = (return.) . Prim })
1209
1210 zonkRttiType :: TcType -> TcM Type
1211 -- Zonk the type, replacing any unbound Meta tyvars
1212 -- by skolems, safely out of Meta-tyvar-land
1213 zonkRttiType = zonkTcTypeToType (mkEmptyZonkEnv zonk_unbound_meta)
1214 where
1215 zonk_unbound_meta tv
1216 = ASSERT( isTcTyVar tv )
1217 do { tv' <- skolemiseUnboundMetaTyVar tv RuntimeUnk
1218 -- This is where RuntimeUnks are born:
1219 -- otherwise-unconstrained unification variables are
1220 -- turned into RuntimeUnks as they leave the
1221 -- typechecker's monad
1222 ; return (mkTyVarTy tv') }
1223
1224 --------------------------------------------------------------------------------
1225 -- Restore Class predicates out of a representation type
1226 dictsView :: Type -> Type
1227 dictsView ty = ty
1228
1229
1230 -- Use only for RTTI types
1231 isMonomorphic :: RttiType -> Bool
1232 isMonomorphic ty = noExistentials && noUniversals
1233 where (tvs, _, ty') = tcSplitSigmaTy ty
1234 noExistentials = isEmptyVarSet (tyVarsOfType ty')
1235 noUniversals = null tvs
1236
1237 -- Use only for RTTI types
1238 isMonomorphicOnNonPhantomArgs :: RttiType -> Bool
1239 isMonomorphicOnNonPhantomArgs ty
1240 | UnaryRep rep_ty <- repType ty
1241 , Just (tc, all_args) <- tcSplitTyConApp_maybe rep_ty
1242 , phantom_vars <- tyConPhantomTyVars tc
1243 , concrete_args <- [ arg | (tyv,arg) <- tyConTyVars tc `zip` all_args
1244 , tyv `notElem` phantom_vars]
1245 = all isMonomorphicOnNonPhantomArgs concrete_args
1246 | Just (ty1, ty2) <- splitFunTy_maybe ty
1247 = all isMonomorphicOnNonPhantomArgs [ty1,ty2]
1248 | otherwise = isMonomorphic ty
1249
1250 tyConPhantomTyVars :: TyCon -> [TyVar]
1251 tyConPhantomTyVars tc
1252 | isAlgTyCon tc
1253 , Just dcs <- tyConDataCons_maybe tc
1254 , dc_vars <- concatMap dataConUnivTyVars dcs
1255 = tyConTyVars tc \\ dc_vars
1256 tyConPhantomTyVars _ = []
1257
1258 type QuantifiedType = ([TyVar], Type)
1259 -- Make the free type variables explicit
1260 -- The returned Type should have no top-level foralls (I believe)
1261
1262 quantifyType :: Type -> QuantifiedType
1263 -- Generalize the type: find all free and forall'd tyvars
1264 -- and return them, together with the type inside, which
1265 -- should not be a forall type.
1266 --
1267 -- Thus (quantifyType (forall a. a->[b]))
1268 -- returns ([a,b], a -> [b])
1269
1270 quantifyType ty = (varSetElems (tyVarsOfType rho), rho)
1271 where
1272 (_tvs, rho) = tcSplitForAllTys ty
1273
1274 unlessM :: Monad m => m Bool -> m () -> m ()
1275 unlessM condM acc = condM >>= \c -> unless c acc
1276
1277
1278 -- Strict application of f at index i
1279 appArr :: Ix i => (e -> a) -> Array i e -> Int -> a
1280 appArr f a@(Array _ _ _ ptrs#) i@(I# i#)
1281 = ASSERT2(i < length(elems a), ppr(length$ elems a, i))
1282 case indexArray# ptrs# i# of
1283 (# e #) -> f e
1284
1285 amap' :: (t -> b) -> Array Int t -> [b]
1286 amap' f (Array i0 i _ arr#) = map g [0 .. i - i0]
1287 where g (I# i#) = case indexArray# arr# i# of
1288 (# e #) -> f e