Fix the instantiation of data constructors in the GHCi debugger
[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://hackage.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 )
37 import qualified ByteCodeItbls as BCI( StgInfoTable(..) )
38 import HscTypes
39 import Linker
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 <- peek 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 succesful 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 == realWorldTyCon = text "<realworld>"
512 | t == threadIdPrimTyCon = text "<ThreadId>"
513 | t == weakPrimTyCon = text "<Weak>"
514 | t == arrayPrimTyCon = text "<array>"
515 | t == byteArrayPrimTyCon = text "<bytearray>"
516 | t == mutableArrayPrimTyCon = text "<mutableArray>"
517 | t == mutableByteArrayPrimTyCon = text "<mutableByteArray>"
518 | t == mutVarPrimTyCon = text "<mutVar>"
519 | t == mVarPrimTyCon = text "<mVar>"
520 | t == tVarPrimTyCon = text "<tVar>"
521 | otherwise = char '<' <> ppr t <> char '>'
522 where build ww = unsafePerformIO $ withArray ww (peek . castPtr)
523 -- This ^^^ relies on the representation of Haskell heap values being
524 -- the same as in a C array.
525
526 -----------------------------------
527 -- Type Reconstruction
528 -----------------------------------
529 {-
530 Type Reconstruction is type inference done on heap closures.
531 The algorithm walks the heap generating a set of equations, which
532 are solved with syntactic unification.
533 A type reconstruction equation looks like:
534
535 <datacon reptype> = <actual heap contents>
536
537 The full equation set is generated by traversing all the subterms, starting
538 from a given term.
539
540 The only difficult part is that newtypes are only found in the lhs of equations.
541 Right hand sides are missing them. We can either (a) drop them from the lhs, or
542 (b) reconstruct them in the rhs when possible.
543
544 The function congruenceNewtypes takes a shot at (b)
545 -}
546
547
548 -- A (non-mutable) tau type containing
549 -- existentially quantified tyvars.
550 -- (since GHC type language currently does not support
551 -- existentials, we leave these variables unquantified)
552 type RttiType = Type
553
554 -- An incomplete type as stored in GHCi:
555 -- no polymorphism: no quantifiers & all tyvars are skolem.
556 type GhciType = Type
557
558
559 -- The Type Reconstruction monad
560 --------------------------------
561 type TR a = TcM a
562
563 runTR :: HscEnv -> TR a -> IO a
564 runTR hsc_env thing = do
565 mb_val <- runTR_maybe hsc_env thing
566 case mb_val of
567 Nothing -> error "unable to :print the term"
568 Just x -> return x
569
570 runTR_maybe :: HscEnv -> TR a -> IO (Maybe a)
571 runTR_maybe hsc_env = fmap snd . initTc hsc_env HsSrcFile False iNTERACTIVE
572
573 traceTR :: SDoc -> TR ()
574 traceTR = liftTcM . traceOptTcRn Opt_D_dump_rtti
575
576
577 -- Semantically different to recoverM in TcRnMonad
578 -- recoverM retains the errors in the first action,
579 -- whereas recoverTc here does not
580 recoverTR :: TR a -> TR a -> TR a
581 recoverTR recover thing = do
582 (_,mb_res) <- tryTcErrs thing
583 case mb_res of
584 Nothing -> recover
585 Just res -> return res
586
587 trIO :: IO a -> TR a
588 trIO = liftTcM . liftIO
589
590 liftTcM :: TcM a -> TR a
591 liftTcM = id
592
593 newVar :: Kind -> TR TcType
594 newVar = liftTcM . newFlexiTyVarTy
595
596 instTyVars :: [TyVar] -> TR ([TcTyVar], [TcType], TvSubst)
597 -- Instantiate fresh mutable type variables from some TyVars
598 -- This function preserves the print-name, which helps error messages
599 instTyVars = liftTcM . tcInstTyVars
600
601 type RttiInstantiation = [(TcTyVar, TyVar)]
602 -- Associates the typechecker-world meta type variables
603 -- (which are mutable and may be refined), to their
604 -- debugger-world RuntimeUnk counterparts.
605 -- If the TcTyVar has not been refined by the runtime type
606 -- elaboration, then we want to turn it back into the
607 -- original RuntimeUnk
608
609 -- | Returns the instantiated type scheme ty', and the
610 -- mapping from new (instantiated) -to- old (skolem) type variables
611 instScheme :: QuantifiedType -> TR (TcType, RttiInstantiation)
612 instScheme (tvs, ty)
613 = liftTcM $ do { (tvs', _, subst) <- tcInstTyVars tvs
614 ; let rtti_inst = [(tv',tv) | (tv',tv) <- tvs' `zip` tvs]
615 ; return (substTy subst ty, rtti_inst) }
616
617 applyRevSubst :: RttiInstantiation -> TR ()
618 -- Apply the *reverse* substitution in-place to any un-filled-in
619 -- meta tyvars. This recovers the original debugger-world variable
620 -- unless it has been refined by new information from the heap
621 applyRevSubst pairs = liftTcM (mapM_ do_pair pairs)
622 where
623 do_pair (tc_tv, rtti_tv)
624 = do { tc_ty <- zonkTcTyVar tc_tv
625 ; case tcGetTyVar_maybe tc_ty of
626 Just tv | isMetaTyVar tv -> writeMetaTyVar tv (mkTyVarTy rtti_tv)
627 _ -> return () }
628
629 -- Adds a constraint of the form t1 == t2
630 -- t1 is expected to come from walking the heap
631 -- t2 is expected to come from a datacon signature
632 -- Before unification, congruenceNewtypes needs to
633 -- do its magic.
634 addConstraint :: TcType -> TcType -> TR ()
635 addConstraint actual expected = do
636 traceTR (text "add constraint:" <+> fsep [ppr actual, equals, ppr expected])
637 recoverTR (traceTR $ fsep [text "Failed to unify", ppr actual,
638 text "with", ppr expected]) $
639 do { (ty1, ty2) <- congruenceNewtypes actual expected
640 ; _ <- captureConstraints $ unifyType ty1 ty2
641 ; return () }
642 -- TOMDO: what about the coercion?
643 -- we should consider family instances
644
645
646 -- Type & Term reconstruction
647 ------------------------------
648 cvObtainTerm :: HscEnv -> Int -> Bool -> RttiType -> HValue -> IO Term
649 cvObtainTerm hsc_env max_depth force old_ty hval = runTR hsc_env $ do
650 -- we quantify existential tyvars as universal,
651 -- as this is needed to be able to manipulate
652 -- them properly
653 let quant_old_ty@(old_tvs, old_tau) = quantifyType old_ty
654 sigma_old_ty = mkForAllTys old_tvs old_tau
655 traceTR (text "Term reconstruction started with initial type " <> ppr old_ty)
656 term <-
657 if null old_tvs
658 then do
659 term <- go max_depth sigma_old_ty sigma_old_ty hval
660 term' <- zonkTerm term
661 return $ fixFunDictionaries $ expandNewtypes term'
662 else do
663 (old_ty', rev_subst) <- instScheme quant_old_ty
664 my_ty <- newVar openTypeKind
665 when (check1 quant_old_ty) (traceTR (text "check1 passed") >>
666 addConstraint my_ty old_ty')
667 term <- go max_depth my_ty sigma_old_ty hval
668 new_ty <- zonkTcType (termType term)
669 if isMonomorphic new_ty || check2 (quantifyType new_ty) quant_old_ty
670 then do
671 traceTR (text "check2 passed")
672 addConstraint new_ty old_ty'
673 applyRevSubst rev_subst
674 zterm' <- zonkTerm term
675 return ((fixFunDictionaries . expandNewtypes) zterm')
676 else do
677 traceTR (text "check2 failed" <+> parens
678 (ppr term <+> text "::" <+> ppr new_ty))
679 -- we have unsound types. Replace constructor types in
680 -- subterms with tyvars
681 zterm' <- mapTermTypeM
682 (\ty -> case tcSplitTyConApp_maybe ty of
683 Just (tc, _:_) | tc /= funTyCon
684 -> newVar openTypeKind
685 _ -> return ty)
686 term
687 zonkTerm zterm'
688 traceTR (text "Term reconstruction completed." $$
689 text "Term obtained: " <> ppr term $$
690 text "Type obtained: " <> ppr (termType term))
691 return term
692 where
693 dflags = hsc_dflags hsc_env
694
695 go :: Int -> Type -> Type -> HValue -> TcM Term
696 -- [SPJ May 11] I don't understand the difference between my_ty and old_ty
697
698 go max_depth _ _ _ | seq max_depth False = undefined
699 go 0 my_ty _old_ty a = do
700 traceTR (text "Gave up reconstructing a term after" <>
701 int max_depth <> text " steps")
702 clos <- trIO $ getClosureData dflags a
703 return (Suspension (tipe clos) my_ty a Nothing)
704 go max_depth my_ty old_ty a = do
705 let monomorphic = not(isTyVarTy my_ty)
706 -- This ^^^ is a convention. The ancestor tests for
707 -- monomorphism and passes a type instead of a tv
708 clos <- trIO $ getClosureData dflags a
709 case tipe clos of
710 -- Thunks we may want to force
711 t | isThunk t && force -> traceTR (text "Forcing a " <> text (show t)) >>
712 seq a (go (pred max_depth) my_ty old_ty a)
713 -- Blackholes are indirections iff the payload is not TSO or BLOCKING_QUEUE. So we
714 -- treat them like indirections; if the payload is TSO or BLOCKING_QUEUE, we'll end up
715 -- showing '_' which is what we want.
716 Blackhole -> do traceTR (text "Following a BLACKHOLE")
717 appArr (go max_depth my_ty old_ty) (ptrs clos) 0
718 -- We always follow indirections
719 Indirection i -> do traceTR (text "Following an indirection" <> parens (int i) )
720 go max_depth my_ty old_ty $! (ptrs clos ! 0)
721 -- We also follow references
722 MutVar _ | Just (tycon,[world,contents_ty]) <- tcSplitTyConApp_maybe old_ty
723 -> do
724 -- Deal with the MutVar# primitive
725 -- It does not have a constructor at all,
726 -- so we simulate the following one
727 -- MutVar# :: contents_ty -> MutVar# s contents_ty
728 traceTR (text "Following a MutVar")
729 contents_tv <- newVar liftedTypeKind
730 contents <- trIO$ IO$ \w -> readMutVar# (unsafeCoerce# a) w
731 ASSERT(isUnliftedTypeKind $ typeKind my_ty) return ()
732 (mutvar_ty,_) <- instScheme $ quantifyType $ mkFunTy
733 contents_ty (mkTyConApp tycon [world,contents_ty])
734 addConstraint (mkFunTy contents_tv my_ty) mutvar_ty
735 x <- go (pred max_depth) contents_tv contents_ty contents
736 return (RefWrap my_ty x)
737
738 -- The interesting case
739 Constr -> do
740 traceTR (text "entering a constructor " <>
741 if monomorphic
742 then parens (text "already monomorphic: " <> ppr my_ty)
743 else Ppr.empty)
744 Right dcname <- dataConInfoPtrToName (infoPtr clos)
745 (_,mb_dc) <- tryTcErrs (tcLookupDataCon dcname)
746 case mb_dc of
747 Nothing -> do -- This can happen for private constructors compiled -O0
748 -- where the .hi descriptor does not export them
749 -- In such case, we return a best approximation:
750 -- ignore the unpointed args, and recover the pointeds
751 -- This preserves laziness, and should be safe.
752 traceTR (text "Not constructor" <+> ppr dcname)
753 let dflags = hsc_dflags hsc_env
754 tag = showPpr dflags dcname
755 vars <- replicateM (length$ elems$ ptrs clos)
756 (newVar liftedTypeKind)
757 subTerms <- sequence [appArr (go (pred max_depth) tv tv) (ptrs clos) i
758 | (i, tv) <- zip [0..] vars]
759 return (Term my_ty (Left ('<' : tag ++ ">")) a subTerms)
760 Just dc -> do
761 traceTR (text "Is constructor" <+> (ppr dc $$ ppr my_ty))
762 subTtypes <- getDataConArgTys dc my_ty
763 subTerms <- extractSubTerms (\ty -> go (pred max_depth) ty ty) clos subTtypes
764 return (Term my_ty (Right dc) a subTerms)
765
766 -- The otherwise case: can be a Thunk,AP,PAP,etc.
767 tipe_clos ->
768 return (Suspension tipe_clos my_ty a Nothing)
769
770 -- insert NewtypeWraps around newtypes
771 expandNewtypes = foldTerm idTermFold { fTerm = worker } where
772 worker ty dc hval tt
773 | Just (tc, args) <- tcSplitTyConApp_maybe ty
774 , isNewTyCon tc
775 , wrapped_type <- newTyConInstRhs tc args
776 , Just dc' <- tyConSingleDataCon_maybe tc
777 , t' <- worker wrapped_type dc hval tt
778 = NewtypeWrap ty (Right dc') t'
779 | otherwise = Term ty dc hval tt
780
781
782 -- Avoid returning types where predicates have been expanded to dictionaries.
783 fixFunDictionaries = foldTerm idTermFold {fSuspension = worker} where
784 worker ct ty hval n | isFunTy ty = Suspension ct (dictsView ty) hval n
785 | otherwise = Suspension ct ty hval n
786
787 extractSubTerms :: (Type -> HValue -> TcM Term)
788 -> Closure -> [Type] -> TcM [Term]
789 extractSubTerms recurse clos = liftM thirdOf3 . go 0 (nonPtrs clos)
790 where
791 go ptr_i ws [] = return (ptr_i, ws, [])
792 go ptr_i ws (ty:tys)
793 | Just (tc, elem_tys) <- tcSplitTyConApp_maybe ty
794 , isUnboxedTupleTyCon tc
795 = do (ptr_i, ws, terms0) <- go ptr_i ws elem_tys
796 (ptr_i, ws, terms1) <- go ptr_i ws tys
797 return (ptr_i, ws, unboxedTupleTerm ty terms0 : terms1)
798 | otherwise
799 = case repType ty of
800 UnaryRep rep_ty -> do
801 (ptr_i, ws, term0) <- go_rep ptr_i ws ty (typePrimRep rep_ty)
802 (ptr_i, ws, terms1) <- go ptr_i ws tys
803 return (ptr_i, ws, term0 : terms1)
804 UbxTupleRep rep_tys -> do
805 (ptr_i, ws, terms0) <- go_unary_types ptr_i ws rep_tys
806 (ptr_i, ws, terms1) <- go ptr_i ws tys
807 return (ptr_i, ws, unboxedTupleTerm ty terms0 : terms1)
808
809 go_unary_types ptr_i ws [] = return (ptr_i, ws, [])
810 go_unary_types ptr_i ws (rep_ty:rep_tys) = do
811 tv <- newVar liftedTypeKind
812 (ptr_i, ws, term0) <- go_rep ptr_i ws tv (typePrimRep rep_ty)
813 (ptr_i, ws, terms1) <- go_unary_types ptr_i ws rep_tys
814 return (ptr_i, ws, term0 : terms1)
815
816 go_rep ptr_i ws ty rep = case rep of
817 PtrRep -> do
818 t <- appArr (recurse ty) (ptrs clos) ptr_i
819 return (ptr_i + 1, ws, t)
820 _ -> do
821 dflags <- getDynFlags
822 let (ws0, ws1) = splitAt (primRepSizeW dflags rep) ws
823 return (ptr_i, ws1, Prim ty ws0)
824
825 unboxedTupleTerm ty terms = Term ty (Right (tupleCon UnboxedTuple (length terms)))
826 (error "unboxedTupleTerm: no HValue for unboxed tuple") terms
827
828
829 -- Fast, breadth-first Type reconstruction
830 ------------------------------------------
831 cvReconstructType :: HscEnv -> Int -> GhciType -> HValue -> IO (Maybe Type)
832 cvReconstructType hsc_env max_depth old_ty hval = runTR_maybe hsc_env $ do
833 traceTR (text "RTTI started with initial type " <> ppr old_ty)
834 let sigma_old_ty@(old_tvs, _) = quantifyType old_ty
835 new_ty <-
836 if null old_tvs
837 then return old_ty
838 else do
839 (old_ty', rev_subst) <- instScheme sigma_old_ty
840 my_ty <- newVar openTypeKind
841 when (check1 sigma_old_ty) (traceTR (text "check1 passed") >>
842 addConstraint my_ty old_ty')
843 search (isMonomorphic `fmap` zonkTcType my_ty)
844 (\(ty,a) -> go ty a)
845 (Seq.singleton (my_ty, hval))
846 max_depth
847 new_ty <- zonkTcType my_ty
848 if isMonomorphic new_ty || check2 (quantifyType new_ty) sigma_old_ty
849 then do
850 traceTR (text "check2 passed" <+> ppr old_ty $$ ppr new_ty)
851 addConstraint my_ty old_ty'
852 applyRevSubst rev_subst
853 zonkRttiType new_ty
854 else traceTR (text "check2 failed" <+> parens (ppr new_ty)) >>
855 return old_ty
856 traceTR (text "RTTI completed. Type obtained:" <+> ppr new_ty)
857 return new_ty
858 where
859 dflags = hsc_dflags hsc_env
860
861 -- search :: m Bool -> ([a] -> [a] -> [a]) -> [a] -> m ()
862 search _ _ _ 0 = traceTR (text "Failed to reconstruct a type after " <>
863 int max_depth <> text " steps")
864 search stop expand l d =
865 case viewl l of
866 EmptyL -> return ()
867 x :< xx -> unlessM stop $ do
868 new <- expand x
869 search stop expand (xx `mappend` Seq.fromList new) $! (pred d)
870
871 -- returns unification tasks,since we are going to want a breadth-first search
872 go :: Type -> HValue -> TR [(Type, HValue)]
873 go my_ty a = do
874 traceTR (text "go" <+> ppr my_ty)
875 clos <- trIO $ getClosureData dflags a
876 case tipe clos of
877 Blackhole -> appArr (go my_ty) (ptrs clos) 0 -- carefully, don't eval the TSO
878 Indirection _ -> go my_ty $! (ptrs clos ! 0)
879 MutVar _ -> do
880 contents <- trIO$ IO$ \w -> readMutVar# (unsafeCoerce# a) w
881 tv' <- newVar liftedTypeKind
882 world <- newVar liftedTypeKind
883 addConstraint my_ty (mkTyConApp mutVarPrimTyCon [world,tv'])
884 return [(tv', contents)]
885 Constr -> do
886 Right dcname <- dataConInfoPtrToName (infoPtr clos)
887 traceTR (text "Constr1" <+> ppr dcname)
888 (_,mb_dc) <- tryTcErrs (tcLookupDataCon dcname)
889 case mb_dc of
890 Nothing-> do
891 -- TODO: Check this case
892 forM [0..length (elems $ ptrs clos)] $ \i -> do
893 tv <- newVar liftedTypeKind
894 return$ appArr (\e->(tv,e)) (ptrs clos) i
895
896 Just dc -> do
897 arg_tys <- getDataConArgTys dc my_ty
898 (_, itys) <- findPtrTyss 0 arg_tys
899 traceTR (text "Constr2" <+> ppr dcname <+> ppr arg_tys)
900 return $ [ appArr (\e-> (ty,e)) (ptrs clos) i
901 | (i,ty) <- itys]
902 _ -> return []
903
904 findPtrTys :: Int -- Current pointer index
905 -> Type -- Type
906 -> TR (Int, [(Int, Type)])
907 findPtrTys i ty
908 | Just (tc, elem_tys) <- tcSplitTyConApp_maybe ty
909 , isUnboxedTupleTyCon tc
910 = findPtrTyss i elem_tys
911
912 | otherwise
913 = case repType ty of
914 UnaryRep rep_ty | typePrimRep rep_ty == PtrRep -> return (i + 1, [(i, ty)])
915 | otherwise -> return (i, [])
916 UbxTupleRep rep_tys -> foldM (\(i, extras) rep_ty -> if typePrimRep rep_ty == PtrRep
917 then newVar liftedTypeKind >>= \tv -> return (i + 1, extras ++ [(i, tv)])
918 else return (i, extras))
919 (i, []) rep_tys
920
921 findPtrTyss :: Int
922 -> [Type]
923 -> TR (Int, [(Int, Type)])
924 findPtrTyss i tys = foldM step (i, []) tys
925 where step (i, discovered) elem_ty = findPtrTys i elem_ty >>= \(i, extras) -> return (i, discovered ++ extras)
926
927
928 -- Compute the difference between a base type and the type found by RTTI
929 -- improveType <base_type> <rtti_type>
930 -- The types can contain skolem type variables, which need to be treated as normal vars.
931 -- In particular, we want them to unify with things.
932 improveRTTIType :: HscEnv -> RttiType -> RttiType -> Maybe TvSubst
933 improveRTTIType _ base_ty new_ty
934 = U.tcUnifyTys (const U.BindMe) [base_ty] [new_ty]
935
936 getDataConArgTys :: DataCon -> Type -> TR [Type]
937 -- Given the result type ty of a constructor application (D a b c :: ty)
938 -- return the types of the arguments. This is RTTI-land, so 'ty' might
939 -- not be fully known. Moreover, the arg types might involve existentials;
940 -- if so, make up fresh RTTI type variables for them
941 getDataConArgTys dc con_app_ty
942 = do { (_, ex_tys, ex_subst) <- instTyVars ex_tvs
943 ; let UnaryRep rep_con_app_ty = repType con_app_ty
944 ; traceTR (text "getDataConArgTys 1" <+> (ppr con_app_ty $$ ppr rep_con_app_ty))
945 ; ty_args <- case tcSplitTyConApp_maybe rep_con_app_ty of
946 Just (tc, ty_args) | dataConTyCon dc == tc
947 -> ASSERT( univ_tvs `equalLength` ty_args)
948 return ty_args
949 _ -> do { (_, ty_args, univ_subst) <- instTyVars univ_tvs
950 ; let res_ty = substTy ex_subst (substTy univ_subst (dataConOrigResTy dc))
951 -- See Note [Constructor arg types]
952 ; addConstraint rep_con_app_ty res_ty
953 ; return ty_args }
954 -- It is necessary to check dataConTyCon dc == tc
955 -- because it may be the case that tc is a recursive
956 -- newtype and tcSplitTyConApp has not removed it. In
957 -- that case, we happily give up and don't match
958 ; let subst = zipTopTvSubst (univ_tvs ++ ex_tvs) (ty_args ++ ex_tys)
959 ; traceTR (text "getDataConArgTys 2" <+> (ppr rep_con_app_ty $$ ppr ty_args $$ ppr subst))
960 ; return (substTys subst (dataConRepArgTys dc)) }
961 where
962 univ_tvs = dataConUnivTyVars dc
963 ex_tvs = dataConExTyVars dc
964
965 {- Note [Constructor arg types]
966 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
967 Consider a GADT (cf Trac #7386)
968 data family D a b
969 data instance D [a] b where
970 MkT :: b -> D [a] (Maybe b)
971
972 In getDataConArgTys
973 * con_app_ty is the known type (from outside) of the constructor application,
974 say D [Int] Bool
975
976 * The data constructor MkT has a (representation) dataConTyCon = DList,
977 say where
978 data DList a b where
979 MkT :: b -> DList a (Maybe b)
980
981 So the dataConTyCon of the data constructor, DList, differs from
982 the "outside" type, D. So we can't straightforwardly decompose the
983 "outside" type, and we end up in the "_" branch of the case.
984
985 Then we match the dataConOrigResTy of the data constructor against the
986 outside type, hoping to get a substituion that tells how to instantiate
987 the *representation* type constructor. This looks a bit delicate to
988 me, but it seems to work.
989 -}
990
991 -- Soundness checks
992 --------------------
993 {-
994 This is not formalized anywhere, so hold to your seats!
995 RTTI in the presence of newtypes can be a tricky and unsound business.
996
997 Example:
998 ~~~~~~~~~
999 Suppose we are doing RTTI for a partially evaluated
1000 closure t, the real type of which is t :: MkT Int, for
1001
1002 newtype MkT a = MkT [Maybe a]
1003
1004 The table below shows the results of RTTI and the improvement
1005 calculated for different combinations of evaluatedness and :type t.
1006 Regard the two first columns as input and the next two as output.
1007
1008 # | t | :type t | rtti(t) | improv. | result
1009 ------------------------------------------------------------
1010 1 | _ | t b | a | none | OK
1011 2 | _ | MkT b | a | none | OK
1012 3 | _ | t Int | a | none | OK
1013
1014 If t is not evaluated at *all*, we are safe.
1015
1016 4 | (_ : _) | t b | [a] | t = [] | UNSOUND
1017 5 | (_ : _) | MkT b | MkT a | none | OK (compensating for the missing newtype)
1018 6 | (_ : _) | t Int | [Int] | t = [] | UNSOUND
1019
1020 If a is a minimal whnf, we run into trouble. Note that
1021 row 5 above does newtype enrichment on the ty_rtty parameter.
1022
1023 7 | (Just _:_)| t b |[Maybe a] | t = [], | UNSOUND
1024 | | | b = Maybe a|
1025
1026 8 | (Just _:_)| MkT b | MkT a | none | OK
1027 9 | (Just _:_)| t Int | FAIL | none | OK
1028
1029 And if t is any more evaluated than whnf, we are still in trouble.
1030 Because constraints are solved in top-down order, when we reach the
1031 Maybe subterm what we got is already unsound. This explains why the
1032 row 9 fails to complete.
1033
1034 10 | (Just _:_)| t Int | [Maybe a] | FAIL | OK
1035 11 | (Just 1:_)| t Int | [Maybe Int] | FAIL | OK
1036
1037 We can undo the failure in row 9 by leaving out the constraint
1038 coming from the type signature of t (i.e., the 2nd column).
1039 Note that this type information is still used
1040 to calculate the improvement. But we fail
1041 when trying to calculate the improvement, as there is no unifier for
1042 t Int = [Maybe a] or t Int = [Maybe Int].
1043
1044
1045 Another set of examples with t :: [MkT (Maybe Int)] \equiv [[Maybe (Maybe Int)]]
1046
1047 # | t | :type t | rtti(t) | improvement | result
1048 ---------------------------------------------------------------------
1049 1 |(Just _:_) | [t (Maybe a)] | [[Maybe b]] | t = [] |
1050 | | | | b = Maybe a |
1051
1052 The checks:
1053 ~~~~~~~~~~~
1054 Consider a function obtainType that takes a value and a type and produces
1055 the Term representation and a substitution (the improvement).
1056 Assume an auxiliar rtti' function which does the actual job if recovering
1057 the type, but which may produce a false type.
1058
1059 In pseudocode:
1060
1061 rtti' :: a -> IO Type -- Does not use the static type information
1062
1063 obtainType :: a -> Type -> IO (Maybe (Term, Improvement))
1064 obtainType v old_ty = do
1065 rtti_ty <- rtti' v
1066 if monomorphic rtti_ty || (check rtti_ty old_ty)
1067 then ...
1068 else return Nothing
1069 where check rtti_ty old_ty = check1 rtti_ty &&
1070 check2 rtti_ty old_ty
1071
1072 check1 :: Type -> Bool
1073 check2 :: Type -> Type -> Bool
1074
1075 Now, if rtti' returns a monomorphic type, we are safe.
1076 If that is not the case, then we consider two conditions.
1077
1078
1079 1. To prevent the class of unsoundness displayed by
1080 rows 4 and 7 in the example: no higher kind tyvars
1081 accepted.
1082
1083 check1 (t a) = NO
1084 check1 (t Int) = NO
1085 check1 ([] a) = YES
1086
1087 2. To prevent the class of unsoundness shown by row 6,
1088 the rtti type should be structurally more
1089 defined than the old type we are comparing it to.
1090 check2 :: NewType -> OldType -> Bool
1091 check2 a _ = True
1092 check2 [a] a = True
1093 check2 [a] (t Int) = False
1094 check2 [a] (t a) = False -- By check1 we never reach this equation
1095 check2 [Int] a = True
1096 check2 [Int] (t Int) = True
1097 check2 [Maybe a] (t Int) = False
1098 check2 [Maybe Int] (t Int) = True
1099 check2 (Maybe [a]) (m [Int]) = False
1100 check2 (Maybe [Int]) (m [Int]) = True
1101
1102 -}
1103
1104 check1 :: QuantifiedType -> Bool
1105 check1 (tvs, _) = not $ any isHigherKind (map tyVarKind tvs)
1106 where
1107 isHigherKind = not . null . fst . splitKindFunTys
1108
1109 check2 :: QuantifiedType -> QuantifiedType -> Bool
1110 check2 (_, rtti_ty) (_, old_ty)
1111 | Just (_, rttis) <- tcSplitTyConApp_maybe rtti_ty
1112 = case () of
1113 _ | Just (_,olds) <- tcSplitTyConApp_maybe old_ty
1114 -> and$ zipWith check2 (map quantifyType rttis) (map quantifyType olds)
1115 _ | Just _ <- splitAppTy_maybe old_ty
1116 -> isMonomorphicOnNonPhantomArgs rtti_ty
1117 _ -> True
1118 | otherwise = True
1119
1120 -- Dealing with newtypes
1121 --------------------------
1122 {-
1123 congruenceNewtypes does a parallel fold over two Type values,
1124 compensating for missing newtypes on both sides.
1125 This is necessary because newtypes are not present
1126 in runtime, but sometimes there is evidence available.
1127 Evidence can come from DataCon signatures or
1128 from compile-time type inference.
1129 What we are doing here is an approximation
1130 of unification modulo a set of equations derived
1131 from newtype definitions. These equations should be the
1132 same as the equality coercions generated for newtypes
1133 in System Fc. The idea is to perform a sort of rewriting,
1134 taking those equations as rules, before launching unification.
1135
1136 The caller must ensure the following.
1137 The 1st type (lhs) comes from the heap structure of ptrs,nptrs.
1138 The 2nd type (rhs) comes from a DataCon type signature.
1139 Rewriting (i.e. adding/removing a newtype wrapper) can happen
1140 in both types, but in the rhs it is restricted to the result type.
1141
1142 Note that it is very tricky to make this 'rewriting'
1143 work with the unification implemented by TcM, where
1144 substitutions are operationally inlined. The order in which
1145 constraints are unified is vital as we cannot modify
1146 anything that has been touched by a previous unification step.
1147 Therefore, congruenceNewtypes is sound only if the types
1148 recovered by the RTTI mechanism are unified Top-Down.
1149 -}
1150 congruenceNewtypes :: TcType -> TcType -> TR (TcType,TcType)
1151 congruenceNewtypes lhs rhs = go lhs rhs >>= \rhs' -> return (lhs,rhs')
1152 where
1153 go l r
1154 -- TyVar lhs inductive case
1155 | Just tv <- getTyVar_maybe l
1156 , isTcTyVar tv
1157 , isMetaTyVar tv
1158 = recoverTR (return r) $ do
1159 Indirect ty_v <- readMetaTyVar tv
1160 traceTR $ fsep [text "(congruence) Following indirect tyvar:",
1161 ppr tv, equals, ppr ty_v]
1162 go ty_v r
1163 -- FunTy inductive case
1164 | Just (l1,l2) <- splitFunTy_maybe l
1165 , Just (r1,r2) <- splitFunTy_maybe r
1166 = do r2' <- go l2 r2
1167 r1' <- go l1 r1
1168 return (mkFunTy r1' r2')
1169 -- TyconApp Inductive case; this is the interesting bit.
1170 | Just (tycon_l, _) <- tcSplitTyConApp_maybe lhs
1171 , Just (tycon_r, _) <- tcSplitTyConApp_maybe rhs
1172 , tycon_l /= tycon_r
1173 = upgrade tycon_l r
1174
1175 | otherwise = return r
1176
1177 where upgrade :: TyCon -> Type -> TR Type
1178 upgrade new_tycon ty
1179 | not (isNewTyCon new_tycon) = do
1180 traceTR (text "(Upgrade) Not matching newtype evidence: " <>
1181 ppr new_tycon <> text " for " <> ppr ty)
1182 return ty
1183 | otherwise = do
1184 traceTR (text "(Upgrade) upgraded " <> ppr ty <>
1185 text " in presence of newtype evidence " <> ppr new_tycon)
1186 (_, vars, _) <- instTyVars (tyConTyVars new_tycon)
1187 let ty' = mkTyConApp new_tycon vars
1188 UnaryRep rep_ty = repType ty'
1189 _ <- liftTcM (unifyType ty rep_ty)
1190 -- assumes that reptype doesn't ^^^^ touch tyconApp args
1191 return ty'
1192
1193
1194 zonkTerm :: Term -> TcM Term
1195 zonkTerm = foldTermM (TermFoldM
1196 { fTermM = \ty dc v tt -> zonkRttiType ty >>= \ty' ->
1197 return (Term ty' dc v tt)
1198 , fSuspensionM = \ct ty v b -> zonkRttiType ty >>= \ty ->
1199 return (Suspension ct ty v b)
1200 , fNewtypeWrapM = \ty dc t -> zonkRttiType ty >>= \ty' ->
1201 return$ NewtypeWrap ty' dc t
1202 , fRefWrapM = \ty t -> return RefWrap `ap`
1203 zonkRttiType ty `ap` return t
1204 , fPrimM = (return.) . Prim })
1205
1206 zonkRttiType :: TcType -> TcM Type
1207 -- Zonk the type, replacing any unbound Meta tyvars
1208 -- by skolems, safely out of Meta-tyvar-land
1209 zonkRttiType = zonkTcTypeToType (mkEmptyZonkEnv zonk_unbound_meta)
1210 where
1211 zonk_unbound_meta tv
1212 = ASSERT( isTcTyVar tv )
1213 do { tv' <- skolemiseUnboundMetaTyVar tv RuntimeUnk
1214 -- This is where RuntimeUnks are born:
1215 -- otherwise-unconstrained unification variables are
1216 -- turned into RuntimeUnks as they leave the
1217 -- typechecker's monad
1218 ; return (mkTyVarTy tv') }
1219
1220 --------------------------------------------------------------------------------
1221 -- Restore Class predicates out of a representation type
1222 dictsView :: Type -> Type
1223 dictsView ty = ty
1224
1225
1226 -- Use only for RTTI types
1227 isMonomorphic :: RttiType -> Bool
1228 isMonomorphic ty = noExistentials && noUniversals
1229 where (tvs, _, ty') = tcSplitSigmaTy ty
1230 noExistentials = isEmptyVarSet (tyVarsOfType ty')
1231 noUniversals = null tvs
1232
1233 -- Use only for RTTI types
1234 isMonomorphicOnNonPhantomArgs :: RttiType -> Bool
1235 isMonomorphicOnNonPhantomArgs ty
1236 | UnaryRep rep_ty <- repType ty
1237 , Just (tc, all_args) <- tcSplitTyConApp_maybe rep_ty
1238 , phantom_vars <- tyConPhantomTyVars tc
1239 , concrete_args <- [ arg | (tyv,arg) <- tyConTyVars tc `zip` all_args
1240 , tyv `notElem` phantom_vars]
1241 = all isMonomorphicOnNonPhantomArgs concrete_args
1242 | Just (ty1, ty2) <- splitFunTy_maybe ty
1243 = all isMonomorphicOnNonPhantomArgs [ty1,ty2]
1244 | otherwise = isMonomorphic ty
1245
1246 tyConPhantomTyVars :: TyCon -> [TyVar]
1247 tyConPhantomTyVars tc
1248 | isAlgTyCon tc
1249 , Just dcs <- tyConDataCons_maybe tc
1250 , dc_vars <- concatMap dataConUnivTyVars dcs
1251 = tyConTyVars tc \\ dc_vars
1252 tyConPhantomTyVars _ = []
1253
1254 type QuantifiedType = ([TyVar], Type) -- Make the free type variables explicit
1255
1256 quantifyType :: Type -> QuantifiedType
1257 -- Generalize the type: find all free tyvars and wrap in the appropiate ForAll.
1258 quantifyType ty = (varSetElems (tyVarsOfType ty), ty)
1259
1260 unlessM :: Monad m => m Bool -> m () -> m ()
1261 unlessM condM acc = condM >>= \c -> unless c acc
1262
1263
1264 -- Strict application of f at index i
1265 appArr :: Ix i => (e -> a) -> Array i e -> Int -> a
1266 appArr f a@(Array _ _ _ ptrs#) i@(I# i#)
1267 = ASSERT2 (i < length(elems a), ppr(length$ elems a, i))
1268 case indexArray# ptrs# i# of
1269 (# e #) -> f e
1270
1271 amap' :: (t -> b) -> Array Int t -> [b]
1272 amap' f (Array i0 i _ arr#) = map g [0 .. i - i0]
1273 where g (I# i#) = case indexArray# arr# i# of
1274 (# e #) -> f e