isPointed,
isFullyEvaluatedTerm,
mapTermType,
- termTyVars
+ termTyVars,
-- unsafeDeepSeq,
+ cvReconstructType
) where
#include "HsVersions.h"
| t == tVarPrimTyCon = "<tVar>"
| otherwise = showSDoc (char '<' <> ppr t <> char '>')
where build ww = unsafePerformIO $ withArray ww (peek . castPtr)
+
-----------------------------------
-- Type Reconstruction
-----------------------------------
+{-
+Type Reconstruction is type inference done on heap closures.
+The algorithm walks the heap generating a set of equations, which
+are solved with syntactic unification.
+A type reconstruction equation looks like:
+
+ <datacon reptype> = <actual heap contents>
+
+The full equation set is generated by traversing all the subterms, starting
+from a given term.
+
+The only difficult part is that newtypes are only found in the lhs of equations.
+Right hand sides are missing them. We can either (a) drop them from the lhs, or
+(b) reconstruct them in the rhs when possible.
+
+The function congruenceNewtypes takes a shot at (b)
+-}
-- The Type Reconstruction monad
type TR a = TcM a
-runTR :: HscEnv -> TR Term -> IO Term
+runTR :: HscEnv -> TR a -> IO a
runTR hsc_env c = do
mb_term <- initTcPrintErrors hsc_env iNTERACTIVE c
case mb_term of
Nothing -> panic "Can't unify"
- Just term -> return term
+ Just x -> return x
trIO :: IO a -> TR a
trIO = liftTcM . ioToTcRn
-addConstraint :: TcType -> TcType -> TR ()
-addConstraint t1 t2 = congruenceNewtypes t1 t2 >>= uncurry unifyType
-
-{-
- A parallel fold over two Type values,
- compensating for missing newtypes on both sides.
- This is necessary because newtypes are not present
- in runtime, but since sometimes there is evidence
- available we do our best to reconstruct them.
- Evidence can come from DataCon signatures or
- from compile-time type inference.
- I am using the words congruence and rewriting
- because what we are doing here is an approximation
- of unification modulo a set of equations, which would
- come from newtype definitions. These should be the
- equality coercions seen in System Fc. Rewriting
- is performed, taking those equations as rules,
- before launching unification.
-
- It doesn't make sense to rewrite everywhere,
- or we would end up with all newtypes. So we rewrite
- only in presence of evidence.
- The lhs comes from the heap structure of ptrs,nptrs.
- The rhs comes from a DataCon type signature.
- Rewriting in the rhs is restricted to the result type.
-
- Note that it is very tricky to make this 'rewriting'
- work with the unification implemented by TcM, where
- substitutions are 'inlined'. The order in which
- constraints are unified is vital for this (or I am
- using TcM wrongly).
--}
-congruenceNewtypes :: TcType -> TcType -> TcM (TcType,TcType)
-congruenceNewtypes = go True
- where
- go rewriteRHS lhs rhs
- -- TyVar lhs inductive case
- | Just tv <- getTyVar_maybe lhs
- = recoverM (return (lhs,rhs)) $ do
- Indirect ty_v <- readMetaTyVar tv
- (lhs', rhs') <- go rewriteRHS ty_v rhs
- writeMutVar (metaTvRef tv) (Indirect lhs')
- return (lhs, rhs')
- -- TyVar rhs inductive case
- | Just tv <- getTyVar_maybe rhs
- = recoverM (return (lhs,rhs)) $ do
- Indirect ty_v <- readMetaTyVar tv
- (lhs', rhs') <- go rewriteRHS lhs ty_v
- writeMutVar (metaTvRef tv) (Indirect rhs')
- return (lhs', rhs)
--- FunTy inductive case
- | Just (l1,l2) <- splitFunTy_maybe lhs
- , Just (r1,r2) <- splitFunTy_maybe rhs
- = do (l2',r2') <- go True l2 r2
- (l1',r1') <- go False l1 r1
- return (mkFunTy l1' l2', mkFunTy r1' r2')
--- TyconApp Inductive case; this is the interesting bit.
- | Just (tycon_l, args_l) <- splitNewTyConApp_maybe lhs
- , Just (tycon_r, args_r) <- splitNewTyConApp_maybe rhs = do
-
- let (tycon_l',args_l') = if isNewTyCon tycon_r && not(isNewTyCon tycon_l)
- then (tycon_r, rewrite tycon_r lhs)
- else (tycon_l, args_l)
- (tycon_r',args_r') = if rewriteRHS && isNewTyCon tycon_l && not(isNewTyCon tycon_r)
- then (tycon_l, rewrite tycon_l rhs)
- else (tycon_r, args_r)
- (args_l'', args_r'') <- unzip `liftM` zipWithM (go rewriteRHS) args_l' args_r'
- return (mkTyConApp tycon_l' args_l'', mkTyConApp tycon_r' args_r'')
-
- | otherwise = return (lhs,rhs)
-
- where rewrite newtyped_tc lame_tipe
- | (tvs, tipe) <- newTyConRep newtyped_tc
- = case tcUnifyTys (const BindMe) [tipe] [lame_tipe] of
- Just subst -> substTys subst (map mkTyVarTy tvs)
- otherwise -> panic "congruenceNewtypes: Can't unify a newtype"
+liftTcM = id
newVar :: Kind -> TR TcTyVar
newVar = liftTcM . newFlexiTyVar
-liftTcM = id
-
-- | Returns the instantiated type scheme ty', and the substitution sigma
-- such that sigma(ty') = ty
instScheme :: Type -> TR (TcType, TvSubst)
(tvs',theta,ty') <- tcInstType (mapM tcInstTyVar) ty
return (ty', zipTopTvSubst tvs' (mkTyVarTys tvs))
+addConstraint :: TcType -> TcType -> TR ()
+addConstraint t1 t2 = congruenceNewtypes t1 t2 >>= uncurry unifyType
+
+
+
+-- Type & Term reconstruction
cvObtainTerm :: HscEnv -> Bool -> Maybe Type -> HValue -> IO Term
cvObtainTerm hsc_env force mb_ty hval = runTR hsc_env $ do
tv <- liftM mkTyVarTy (newVar argTypeKind)
otherwise ->
return (Suspension (tipe clos) (Just tv) a Nothing)
--- Access the array of pointers and recurse down. Needs to be done with
--- care of no introducing a thunk! or go will fail to do its job
- appArr f arr (I# i#) = case arr of
- (Array _ _ ptrs#) -> case indexArray# ptrs# i# of
- (# e #) -> f e
-
matchSubTypes dc ty
| Just (_,ty_args) <- splitTyConApp_maybe (repType ty)
, null (dataConExTyVars dc) --TODO Handle the case of extra existential tyvars
, ptext SLIT("reOrderTerms") $$ (ppr pointed $$ ppr unpointed))
head unpointed : reOrderTerms pointed (tail unpointed) tys
-isMonomorphic ty | isForAllTy ty = False
-isMonomorphic ty = (isEmptyVarSet . tyVarsOfType) ty
-
-zonkTerm :: Term -> TcM Term
-zonkTerm = foldTerm idTermFoldM {
- fTerm = \ty dc v tt -> sequence tt >>= \tt ->
- zonkTcType ty >>= \ty' ->
- return (Term ty' dc v tt)
- ,fSuspension = \ct ty v b -> fmapMMaybe zonkTcType ty >>= \ty ->
- return (Suspension ct ty v b)}
-
--- Is this defined elsewhere?
--- Generalize the type: find all free tyvars and wrap in the appropiate ForAll.
-sigmaType ty = mkForAllTys (varSetElems$ tyVarsOfType (dropForAlls ty)) ty
-{-
-Example of Type Reconstruction
---------------------------------
-Suppose we have an existential type such as
+-- Fast, breadth-first version of obtainTerm that deals only with type reconstruction
-data Opaque = forall a. Opaque a
-
-And we have a term built as:
-
-t = Opaque (map Just [[1,1],[2,2]])
+cvReconstructType :: HscEnv -> Bool -> Maybe Type -> HValue -> IO Type
+cvReconstructType hsc_env force mb_ty hval = runTR hsc_env $ do
+ tv <- liftM mkTyVarTy (newVar argTypeKind)
+ case mb_ty of
+ Nothing -> search (isMonomorphic `fmap` zonkTcType tv) (++) [(tv, hval)] >>
+ zonkTcType tv -- TODO untested!
+ Just ty | isMonomorphic ty -> return ty
+ Just ty -> do
+ (ty',rev_subst) <- instScheme (sigmaType ty)
+ addConstraint tv ty'
+ search (isMonomorphic `fmap` zonkTcType tv) (++) [(tv, hval)]
+ substTy rev_subst `fmap` zonkTcType tv
+ where
+-- search :: m Bool -> ([a] -> [a] -> [a]) -> [a] -> m ()
+ search stop combine [] = return ()
+ search stop combine ((t,a):jj) = (jj `combine`) `fmap` go t a >>=
+ unlessM stop . search stop combine
+
+ -- returns unification tasks, since we are going to want a breadth-first search
+ go :: Type -> HValue -> TR [(Type, HValue)]
+ go tv a = do
+ clos <- trIO $ getClosureData a
+ case tipe clos of
+ Indirection _ -> go tv $! (ptrs clos ! 0)
+ Constr -> do
+ m_dc <- trIO$ tcRnRecoverDataCon hsc_env (infoPtr clos)
+ case m_dc of
+ Nothing -> panic "Can't find the DataCon for a term"
+ Just dc -> do
+ let extra_args = length(dataConRepArgTys dc) - length(dataConOrigArgTys dc)
+ subTtypes <- mapMif (not . isMonomorphic)
+ (\t -> mkTyVarTy `fmap` newVar (typeKind t))
+ (dataConRepArgTys dc)
+ -- It is vital for newtype reconstruction that the unification step is done
+ -- right here, _before_ the subterms are RTTI reconstructed.
+ let myType = mkFunTys subTtypes tv
+ fst `fmap` instScheme(dataConRepType dc) >>= addConstraint myType
+ return $map (\(I# i#,t) -> case ptrs clos of
+ (Array _ _ ptrs#) -> case indexArray# ptrs# i# of
+ (# e #) -> (t,e))
+ (drop extra_args $ zip [0..] subTtypes)
+ otherwise -> return []
-The type of t as far as the typechecker goes is t :: Opaque
-If we seq the head of t, we obtain:
-t - O (_1::a)
+-- Dealing with newtypes
+{-
+ A parallel fold over two Type values,
+ compensating for missing newtypes on both sides.
+ This is necessary because newtypes are not present
+ in runtime, but since sometimes there is evidence
+ available we do our best to reconstruct them.
+ Evidence can come from DataCon signatures or
+ from compile-time type inference.
+ I am using the words congruence and rewriting
+ because what we are doing here is an approximation
+ of unification modulo a set of equations, which would
+ come from newtype definitions. These should be the
+ equality coercions seen in System Fc. Rewriting
+ is performed, taking those equations as rules,
+ before launching unification.
-seq _1 ()
+ It doesn't make sense to rewrite everywhere,
+ or we would end up with all newtypes. So we rewrite
+ only in presence of evidence.
+ The lhs comes from the heap structure of ptrs,nptrs.
+ The rhs comes from a DataCon type signature.
+ Rewriting in the rhs is restricted to the result type.
-t - O ( (_3::b) : (_4::[b]) )
+ Note that it is very tricky to make this 'rewriting'
+ work with the unification implemented by TcM, where
+ substitutions are 'inlined'. The order in which
+ constraints are unified is vital for this (or I am
+ using TcM wrongly).
+-}
+congruenceNewtypes :: TcType -> TcType -> TcM (TcType,TcType)
+congruenceNewtypes = go True
+ where
+ go rewriteRHS lhs rhs
+ -- TyVar lhs inductive case
+ | Just tv <- getTyVar_maybe lhs
+ = recoverM (return (lhs,rhs)) $ do
+ Indirect ty_v <- readMetaTyVar tv
+ (lhs', rhs') <- go rewriteRHS ty_v rhs
+ writeMutVar (metaTvRef tv) (Indirect lhs')
+ return (lhs, rhs')
+ -- TyVar rhs inductive case
+ | Just tv <- getTyVar_maybe rhs
+ = recoverM (return (lhs,rhs)) $ do
+ Indirect ty_v <- readMetaTyVar tv
+ (lhs', rhs') <- go rewriteRHS lhs ty_v
+ writeMutVar (metaTvRef tv) (Indirect rhs')
+ return (lhs', rhs)
+-- FunTy inductive case
+ | Just (l1,l2) <- splitFunTy_maybe lhs
+ , Just (r1,r2) <- splitFunTy_maybe rhs
+ = do (l2',r2') <- go True l2 r2
+ (l1',r1') <- go False l1 r1
+ return (mkFunTy l1' l2', mkFunTy r1' r2')
+-- TyconApp Inductive case; this is the interesting bit.
+ | Just (tycon_l, args_l) <- splitNewTyConApp_maybe lhs
+ , Just (tycon_r, args_r) <- splitNewTyConApp_maybe rhs = do
-seq _3 ()
+ let (tycon_l',args_l') = if isNewTyCon tycon_r && not(isNewTyCon tycon_l)
+ then (tycon_r, rewrite tycon_r lhs)
+ else (tycon_l, args_l)
+ (tycon_r',args_r') = if rewriteRHS && isNewTyCon tycon_l && not(isNewTyCon tycon_r)
+ then (tycon_l, rewrite tycon_l rhs)
+ else (tycon_r, args_r)
+ (args_l'', args_r'') <- unzip `liftM` zipWithM (go rewriteRHS) args_l' args_r'
+ return (mkTyConApp tycon_l' args_l'', mkTyConApp tycon_r' args_r'')
-t - O ( (Just (_5::c)) : (_4::[b]) )
+ | otherwise = return (lhs,rhs)
-At this point, we know that b = (Maybe c)
+ where rewrite newtyped_tc lame_tipe
+ | (tvs, tipe) <- newTyConRep newtyped_tc
+ = case tcUnifyTys (const BindMe) [tipe] [lame_tipe] of
+ Just subst -> substTys subst (map mkTyVarTy tvs)
+ otherwise -> panic "congruenceNewtypes: Can't unify a newtype"
-seq _5 ()
-t - O ( (Just ((_6::d) : (_7::[d]) )) : (_4::[b]) )
+------------------------------------------------------------------------------------
-At this point, we know that c = [d]
+isMonomorphic ty | (tvs, ty') <- splitForAllTys ty
+ = null tvs && (isEmptyVarSet . tyVarsOfType) ty'
-seq _6 ()
+mapMif :: Monad m => (a -> Bool) -> (a -> m a) -> [a] -> m [a]
+mapMif pred f xx = sequence $ mapMif_ pred f xx
+mapMif_ pred f [] = []
+mapMif_ pred f (x:xx) = (if pred x then f x else return x) : mapMif_ pred f xx
-t - O ( (Just (1 : (_7::[d]) )) : (_4::[b]) )
+unlessM condM acc = condM >>= \c -> unless c acc
-At this point, we know that d = Integer
+-- Strict application of f at index i
+appArr f (Array _ _ ptrs#) (I# i#) = case indexArray# ptrs# i# of
+ (# e #) -> f e
-The fully reconstructed expressions, with propagation, would be:
+zonkTerm :: Term -> TcM Term
+zonkTerm = foldTerm idTermFoldM {
+ fTerm = \ty dc v tt -> sequence tt >>= \tt ->
+ zonkTcType ty >>= \ty' ->
+ return (Term ty' dc v tt)
+ ,fSuspension = \ct ty v b -> fmapMMaybe zonkTcType ty >>= \ty ->
+ return (Suspension ct ty v b)}
-t - O ( (Just (_5::c)) : (_4::[Maybe c]) )
-t - O ( (Just ((_6::d) : (_7::[d]) )) : (_4::[Maybe [d]]) )
-t - O ( (Just (1 : (_7::[Integer]) )) : (_4::[Maybe [Integer]]) )
+-- Is this defined elsewhere?
+-- Generalize the type: find all free tyvars and wrap in the appropiate ForAll.
+sigmaType ty = mkForAllTys (varSetElems$ tyVarsOfType (dropForAlls ty)) ty
-For reference, the type of the thing inside the opaque is
-map Just [[1,1],[2,2]] :: [Maybe [Integer]]
-NOTE: (Num t) contexts have been manually replaced by Integer for clarity
--}