From: Pepe Iborra Date: Wed, 7 Feb 2007 20:59:47 +0000 (+0000) Subject: Type reconstruction/RTTI: improve handling of newtypes X-Git-Url: http://git.megacz.com/?p=ghc-hetmet.git;a=commitdiff_plain;h=eeaa039982364fb658d4e6824e078c553ba8c748 Type reconstruction/RTTI: improve handling of newtypes Newtypes have always been a problem because they are not there at runtime, but we need to take them into account. Tests ghci.debugger/print011 and ghci.debugger/print012 cover this --- diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs index efeb976..f653de6 100644 --- a/compiler/ghci/RtClosureInspect.hs +++ b/compiler/ghci/RtClosureInspect.hs @@ -403,47 +403,81 @@ trIO :: IO a -> TR a trIO = liftTcM . ioToTcRn addConstraint :: TcType -> TcType -> TR () -addConstraint t1 t2 = congruenceNewtypes t1 t2 >> unifyType t1 t2 - --- A parallel fold over a Type value, replacing --- in the right side reptypes for newtypes as found in the lhs --- Sadly it doesn't cover all the possibilities. It does not always manage --- to recover the highest level type. See test print016 for an example --- This is used for approximating a unification over types modulo newtypes that recovers --- the most concrete, with-newtypes type -congruenceNewtypes :: TcType -> TcType -> TcM TcType -congruenceNewtypes lhs rhs --- | pprTrace "Congruence" (ppr lhs $$ ppr rhs) False = undefined - -- We have a tctyvar at the other side +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 --- , trace "congruence, entering tyvar" True - = recoverM (return rhs) $ do + = recoverM (return (lhs,rhs)) $ do Indirect ty_v <- readMetaTyVar tv - newtyped_tytv <- congruenceNewtypes lhs ty_v - writeMutVar (metaTvRef tv) (Indirect newtyped_tytv) - return newtyped_tytv --- We have a function type: go on inductively - | Just (r1,r2) <- splitFunTy_maybe rhs - , Just (l1,l2) <- splitFunTy_maybe lhs - = liftM2 mkFunTy ( congruenceNewtypes l1 r1) - (congruenceNewtypes l2 r2) --- There is a newtype at the top level tycon and we can manage it - | Just (tycon, args) <- splitNewTyConApp_maybe lhs - , isNewTyCon tycon - , (tvs, realtipe) <- newTyConRep tycon - = case tcUnifyTys (const BindMe) [realtipe] [rhs] of - Just subst -> - let tvs' = substTys subst (map mkTyVarTy tvs) in - liftM (mkTyConApp tycon) (zipWithM congruenceNewtypes args tvs') - otherwise -> panic "congruenceNewtypes: Can't unify a newtype" - --- We have a TyconApp: go on inductively - | Just (tycon, args) <- splitNewTyConApp_maybe lhs - , Just (tycon_v, args_v) <- splitNewTyConApp_maybe rhs - = liftM (mkTyConApp tycon_v) (zipWithM congruenceNewtypes args args_v) - - | otherwise = return rhs - + (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" newVar :: Kind -> TR TcTyVar newVar = liftTcM . newFlexiTyVar @@ -473,27 +507,21 @@ cvObtainTerm hsc_env force mb_ty a = where vars = varSetElems$ tyVarsOfType ty cvObtainTerm1 :: HscEnv -> Bool -> Maybe Type -> HValue -> IO Term -cvObtainTerm1 hsc_env force mb_ty hval - | Nothing <- mb_ty = runTR hsc_env . go argTypeKind $ hval - | Just ty <- mb_ty = runTR hsc_env $ do - term <- go argTypeKind hval - ty' <- instScheme (sigmaType ty) - addConstraint ty' (fromMaybe (error "by definition") - (termType term)) - return term +cvObtainTerm1 hsc_env force mb_ty hval = runTR hsc_env $ do + tv <- liftM mkTyVarTy (newVar argTypeKind) + when (isJust mb_ty) $ + instScheme (sigmaType$ fromJust mb_ty) >>= addConstraint tv + go tv hval where - go k a = do + go tv a = do ctype <- trIO$ getClosureType a case ctype of -- Thunks we may want to force - Thunk _ | force -> seq a $ go k a + Thunk _ | force -> seq a $ go tv a -- We always follow indirections - _ | isIndirection ctype - -> do + _ | isIndirection ctype -> do clos <- trIO$ getClosureData a --- dflags <- getSessionDynFlags session --- debugTraceMsg dflags 2 (text "Following an indirection") - go k $! (ptrs clos ! 0) + (go tv $! (ptrs clos ! 0)) -- The interesting case Constr -> do m_dc <- trIO$ tcRnRecoverDataCon hsc_env a @@ -504,30 +532,27 @@ cvObtainTerm1 hsc_env force mb_ty hval let extra_args = length(dataConRepArgTys dc) - length(dataConOrigArgTys dc) subTtypes = drop extra_args (dataConRepArgTys dc) (subTtypesP, subTtypesNP) = partition isPointed subTtypes - - subTermsP <- mapM (\i->extractSubterm i (ptrs clos) - (subTtypesP!!(i-extra_args))) - [extra_args..extra_args + length subTtypesP - 1] + n_subtermsP= length subTtypesP + subTermTvs <- mapM (liftM mkTyVarTy . newVar ) (map typeKind subTtypesP) + baseType <- instScheme (dataConRepType dc) + let myType = mkFunTys (reOrderTerms subTermTvs subTtypesNP subTtypes) tv + addConstraint myType baseType + subTermsP <- sequence [ extractSubterm i tv (ptrs clos) + | (i,tv) <- zip [extra_args..extra_args + n_subtermsP - 1] + subTermTvs ] let unboxeds = extractUnboxed subTtypesNP (nonPtrs clos) subTermsNP = map (uncurry Prim) (zip subTtypesNP unboxeds) subTerms = reOrderTerms subTermsP subTermsNP subTtypes - resType <- liftM mkTyVarTy (newVar k) - baseType <- instScheme (dataConRepType dc) - let myType = mkFunTys (map (fromMaybe (error "cvObtainTerm1") . termType) - subTerms) - resType - addConstraint baseType myType - return (Term resType dc a subTerms) + return (Term tv dc a subTerms) -- The otherwise case: can be a Thunk,AP,PAP,etc. otherwise -> do - x <- liftM mkTyVarTy (newVar k) - return (Suspension ctype (Just x) a Nothing) + return (Suspension ctype (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 - extractSubterm (I# i#) ptrs ty = case ptrs of + extractSubterm (I# i#) tv ptrs = case ptrs of (Array _ _ ptrs#) -> case indexArray# ptrs# i# of - (# e #) -> go (typeKind ty) e + (# e #) -> go tv e -- This is used to put together pointed and nonpointed subterms in the -- correct order.