Replaced two uses of head b explicit pattern matching

[ghc-hetmet.git] / compiler / ghci / RtClosureInspect.hs

diff --git a/compiler/ghci/RtClosureInspect.hs b/compiler/ghci/RtClosureInspect.hs
index 4025aa2..b9fd192 100644 (file)
--- a/compiler/ghci/RtClosureInspect.hs
+++ b/compiler/ghci/RtClosureInspect.hs
@@ -17,6 +17,7 @@ module RtClosureInspect(
      pprTerm, 
      cPprTerm, 
      cPprTermBase,
      pprTerm, 
      cPprTerm, 
      cPprTermBase,

+     CustomTermPrinter,

      termType,
      foldTerm, 
      TermFold(..), 
      termType,
      foldTerm, 
      TermFold(..), 

@@ -45,23 +46,24 @@ import qualified ByteCodeItbls as BCI( StgInfoTable(..) )
 import HscTypes         ( HscEnv )
 import Linker
 
 import HscTypes         ( HscEnv )
 import Linker
 

-import DataCon          
-import Type             
-import TcRnMonad        ( TcM, initTc, ioToTcRn, 
-                          tryTcErrs)
+import DataCon
+import Type
+import Var
+import TcRnMonad        ( TcM, initTc, ioToTcRn,
+                          tryTcErrs, traceTc)

 import TcType
 import TcMType
 import TcUnify
 import TcGadt
 import TcEnv
 import DriverPhases
 import TcType
 import TcMType
 import TcUnify
 import TcGadt
 import TcEnv
 import DriverPhases

-import TyCon           
-import Name 
+import TyCon
+import Name

 import VarEnv
 import Util
 import VarSet
 
 import VarEnv
 import Util
 import VarSet
 

-import TysPrim         
+import TysPrim

 import PrelNames
 import TysWiredIn
 
 import PrelNames
 import TysWiredIn
 

@@ -101,8 +103,6 @@ import System.IO.Unsafe
 
 data Term = Term { ty        :: Type 
                  , dc        :: Either String DataCon
 
 data Term = Term { ty        :: Type 
                  , dc        :: Either String DataCon

-                               -- The heap datacon. If ty is a newtype,
-                               -- this is NOT the newtype datacon.

                                -- Empty if the datacon aint exported by the .hi
                                -- (private constructors in -O0 libraries)
                  , val       :: HValue 
                                -- Empty if the datacon aint exported by the .hi
                                -- (private constructors in -O0 libraries)
                  , val       :: HValue 

@@ -116,14 +116,19 @@ data Term = Term { ty        :: Type
                        , val      :: HValue
                        , bound_to :: Maybe Name   -- Useful for printing
                        }
                        , val      :: HValue
                        , bound_to :: Maybe Name   -- Useful for printing
                        }

+          | NewtypeWrap{ ty           :: Type
+                       , dc           :: Either String DataCon
+                       , wrapped_term :: Term }

 
 

-isTerm, isSuspension, isPrim :: Term -> Bool
+isTerm, isSuspension, isPrim, isNewtypeWrap :: Term -> Bool

 isTerm Term{} = True
 isTerm   _    = False
 isSuspension Suspension{} = True
 isSuspension      _       = False
 isPrim Prim{} = True
 isPrim   _    = False
 isTerm Term{} = True
 isTerm   _    = False
 isSuspension Suspension{} = True
 isSuspension      _       = False
 isPrim Prim{} = True
 isPrim   _    = False

+isNewtypeWrap NewtypeWrap{} = True
+isNewtypeWrap _             = False

 
 termType :: Term -> Maybe Type
 termType t@(Suspension {}) = mb_ty t
 
 termType :: Term -> Maybe Type
 termType t@(Suspension {}) = mb_ty t

@@ -131,8 +136,9 @@ termType t = Just$ ty t
 
 isFullyEvaluatedTerm :: Term -> Bool
 isFullyEvaluatedTerm Term {subTerms=tt} = all isFullyEvaluatedTerm tt
 
 isFullyEvaluatedTerm :: Term -> Bool
 isFullyEvaluatedTerm Term {subTerms=tt} = all isFullyEvaluatedTerm tt

-isFullyEvaluatedTerm Suspension {}      = False

 isFullyEvaluatedTerm Prim {}            = True
 isFullyEvaluatedTerm Prim {}            = True

+isFullyEvaluatedTerm NewtypeWrap{wrapped_term=t} = isFullyEvaluatedTerm t
+isFullyEvaluatedTerm _                  = False

 
 instance Outputable (Term) where
  ppr = head . cPprTerm cPprTermBase
 
 instance Outputable (Term) where
  ppr = head . cPprTerm cPprTermBase

@@ -173,13 +179,21 @@ getClosureData :: a -> IO Closure
 getClosureData a =
    case unpackClosure# a of 
      (# iptr, ptrs, nptrs #) -> do
 getClosureData a =
    case unpackClosure# a of 
      (# iptr, ptrs, nptrs #) -> do

+#ifndef GHCI_TABLES_NEXT_TO_CODE
+           -- the info pointer we get back from unpackClosure# is to the
+           -- beginning of the standard info table, but the Storable instance
+           -- for info tables takes into account the extra entry pointer
+           -- when !tablesNextToCode, so we must adjust here:
+           itbl <- peek (Ptr iptr `plusPtr` negate wORD_SIZE)
+#else

            itbl <- peek (Ptr iptr)
            itbl <- peek (Ptr iptr)

+#endif

            let tipe = readCType (BCI.tipe itbl)
                elems = fromIntegral (BCI.ptrs itbl)
                ptrsList = Array 0 (elems - 1) elems ptrs
                nptrs_data = [W# (indexWordArray# nptrs i)
                               | I# i <- [0.. fromIntegral (BCI.nptrs itbl)] ]
            let tipe = readCType (BCI.tipe itbl)
                elems = fromIntegral (BCI.ptrs itbl)
                ptrsList = Array 0 (elems - 1) elems ptrs
                nptrs_data = [W# (indexWordArray# nptrs i)
                               | I# i <- [0.. fromIntegral (BCI.nptrs itbl)] ]

-           ASSERT(fromIntegral elems >= 0) return ()
+           ASSERT(elems >= 0) return ()

            ptrsList `seq` 
             return (Closure tipe (Ptr iptr) itbl ptrsList nptrs_data)
 
            ptrsList `seq` 
             return (Closure tipe (Ptr iptr) itbl ptrsList nptrs_data)
 

@@ -263,31 +277,37 @@ data TermFold a = TermFold { fTerm :: TermProcessor a a
                            , fPrim :: Type -> [Word] -> a
                            , fSuspension :: ClosureType -> Maybe Type -> HValue
                                            -> Maybe Name -> a
                            , fPrim :: Type -> [Word] -> a
                            , fSuspension :: ClosureType -> Maybe Type -> HValue
                                            -> Maybe Name -> a

+                           , fNewtypeWrap :: Type -> Either String DataCon
+                                            -> a -> a

                            }
 
 foldTerm :: TermFold a -> Term -> a
 foldTerm tf (Term ty dc v tt) = fTerm tf ty dc v (map (foldTerm tf) tt)
 foldTerm tf (Prim ty    v   ) = fPrim tf ty v
 foldTerm tf (Suspension ct ty v b) = fSuspension tf ct ty v b
                            }
 
 foldTerm :: TermFold a -> Term -> a
 foldTerm tf (Term ty dc v tt) = fTerm tf ty dc v (map (foldTerm tf) tt)
 foldTerm tf (Prim ty    v   ) = fPrim tf ty v
 foldTerm tf (Suspension ct ty v b) = fSuspension tf ct ty v b

+foldTerm tf (NewtypeWrap ty dc t)  = fNewtypeWrap tf ty dc (foldTerm tf t)

 
 idTermFold :: TermFold Term
 idTermFold = TermFold {
               fTerm = Term,
               fPrim = Prim,
 
 idTermFold :: TermFold Term
 idTermFold = TermFold {
               fTerm = Term,
               fPrim = Prim,

-              fSuspension = Suspension
+              fSuspension  = Suspension,
+              fNewtypeWrap = NewtypeWrap

                       }
 idTermFoldM :: Monad m => TermFold (m Term)
 idTermFoldM = TermFold {
               fTerm       = \ty dc v tt -> sequence tt >>= return . Term ty dc v,
               fPrim       = (return.). Prim,
                       }
 idTermFoldM :: Monad m => TermFold (m Term)
 idTermFoldM = TermFold {
               fTerm       = \ty dc v tt -> sequence tt >>= return . Term ty dc v,
               fPrim       = (return.). Prim,

-              fSuspension = (((return.).).). Suspension
+              fSuspension = (((return.).).). Suspension,
+              fNewtypeWrap= \ty dc t -> NewtypeWrap ty dc `liftM` t

                        }
 
 mapTermType :: (Type -> Type) -> Term -> Term
 mapTermType f = foldTerm idTermFold {
           fTerm       = \ty dc hval tt -> Term (f ty) dc hval tt,
           fSuspension = \ct mb_ty hval n ->
                        }
 
 mapTermType :: (Type -> Type) -> Term -> Term
 mapTermType f = foldTerm idTermFold {
           fTerm       = \ty dc hval tt -> Term (f ty) dc hval tt,
           fSuspension = \ct mb_ty hval n ->

-                          Suspension ct (fmap f mb_ty) hval n }
+                          Suspension ct (fmap f mb_ty) hval n,
+          fNewtypeWrap= \ty dc t -> NewtypeWrap (f ty) dc t}

 
 termTyVars :: Term -> TyVarSet
 termTyVars = foldTerm TermFold {
 
 termTyVars :: Term -> TyVarSet
 termTyVars = foldTerm TermFold {

@@ -295,8 +315,10 @@ termTyVars = foldTerm TermFold {
                           tyVarsOfType ty `plusVarEnv` concatVarEnv tt,
             fSuspension = \_ mb_ty _ _ -> 
                           maybe emptyVarEnv tyVarsOfType mb_ty,
                           tyVarsOfType ty `plusVarEnv` concatVarEnv tt,
             fSuspension = \_ mb_ty _ _ -> 
                           maybe emptyVarEnv tyVarsOfType mb_ty,

-            fPrim       = \ _ _ -> emptyVarEnv }
+            fPrim       = \ _ _ -> emptyVarEnv,
+            fNewtypeWrap= \ty _ t -> tyVarsOfType ty `plusVarEnv` t}

     where concatVarEnv = foldr plusVarEnv emptyVarEnv
     where concatVarEnv = foldr plusVarEnv emptyVarEnv

+

 ----------------------------------
 -- Pretty printing of terms
 ----------------------------------
 ----------------------------------
 -- Pretty printing of terms
 ----------------------------------

@@ -309,26 +331,24 @@ pprTerm :: (Int -> Term -> Maybe SDoc) -> Int -> Term -> SDoc
 pprTerm y p t | Just doc <- pprTermM y p t = doc
 pprTerm _ _ _ = panic "pprTerm"
 
 pprTerm y p t | Just doc <- pprTermM y p t = doc
 pprTerm _ _ _ = panic "pprTerm"
 

-pprTermM :: Monad m => (Int -> Term -> m SDoc) -> Int -> Term -> m SDoc
+pprTermM, pprNewtypeWrap :: Monad m => 
+                           (Int -> Term -> m SDoc) -> Int -> Term -> m SDoc

 pprTermM y p Term{dc=Left dc_tag, subTerms=tt} = do
   tt_docs <- mapM (y app_prec) tt
   return$ cparen (not(null tt) && p >= app_prec) (text dc_tag <+> sep tt_docs)
   
 pprTermM y p Term{dc=Left dc_tag, subTerms=tt} = do
   tt_docs <- mapM (y app_prec) tt
   return$ cparen (not(null tt) && p >= app_prec) (text dc_tag <+> sep tt_docs)
   

-pprTermM y p t@Term{dc=Right dc, subTerms=tt, ty=ty} 
+pprTermM y p Term{dc=Right dc, subTerms=tt} 

 {-  | dataConIsInfix dc, (t1:t2:tt') <- tt  --TODO fixity
   = parens (pprTerm1 True t1 <+> ppr dc <+> pprTerm1 True ppr t2) 
     <+> hsep (map (pprTerm1 True) tt) 
 -} -- TODO Printing infix constructors properly
   | null tt   = return$ ppr dc
 {-  | dataConIsInfix dc, (t1:t2:tt') <- tt  --TODO fixity
   = parens (pprTerm1 True t1 <+> ppr dc <+> pprTerm1 True ppr t2) 
     <+> hsep (map (pprTerm1 True) tt) 
 -} -- TODO Printing infix constructors properly
   | null tt   = return$ ppr dc

-  | Just (tc,_) <- splitNewTyConApp_maybe ty
-  , isNewTyCon tc
-  , Just new_dc <- maybeTyConSingleCon tc = do 
-         real_value <- y 10 t{ty=repType ty}
-         return$ cparen (p >= app_prec) (ppr new_dc <+> real_value)

   | otherwise = do
          tt_docs <- mapM (y app_prec) tt
          return$ cparen (p >= app_prec) (ppr dc <+> sep tt_docs)
 
   | otherwise = do
          tt_docs <- mapM (y app_prec) tt
          return$ cparen (p >= app_prec) (ppr dc <+> sep tt_docs)
 

+pprTermM y p t@NewtypeWrap{} = pprNewtypeWrap y p t
+

 pprTermM _ _ t = pprTermM1 t
 
 pprTermM1 :: Monad m => Term -> m SDoc
 pprTermM _ _ t = pprTermM1 t
 
 pprTermM1 :: Monad m => Term -> m SDoc

@@ -341,56 +361,87 @@ pprTermM1 Suspension{mb_ty=Just ty, bound_to=Just n}
   | otherwise = return$ parens$ ppr n <> text "::" <> ppr ty 
 pprTermM1 _ = panic "pprTermM1"
 
   | otherwise = return$ parens$ ppr n <> text "::" <> ppr ty 
 pprTermM1 _ = panic "pprTermM1"
 

-type CustomTermPrinter m = Int -> TermProcessor Term (m (Maybe SDoc))
+pprNewtypeWrap y p NewtypeWrap{ty=ty, wrapped_term=t} 
+  | Just (tc,_) <- splitNewTyConApp_maybe ty
+  , ASSERT(isNewTyCon tc) True
+  , Just new_dc <- maybeTyConSingleCon tc = do 
+         real_term <- y 10 t
+         return$ cparen (p >= app_prec) (ppr new_dc <+> real_term)
+pprNewtypeWrap _ _ _ = panic "pprNewtypeWrap"
+
+-------------------------------------------------------
+-- Custom Term Pretty Printers
+-------------------------------------------------------
+
+-- We can want to customize the representation of a 
+--  term depending on its type. 
+-- However, note that custom printers have to work with
+--  type representations, instead of directly with types.
+-- We cannot use type classes here, unless we employ some 
+--  typerep trickery (e.g. Weirich's RepLib tricks),
+--  which I didn't. Therefore, this code replicates a lot
+--  of what type classes provide for free.
+
+-- Concretely a custom term printer takes an explicit
+--  recursion knot, and produces a list of Term Processors,
+--  which additionally need a precedence value to
+--  either produce a SDoc or fail (and they do this in some monad m).
+
+type Precedence          = Int
+type RecursionKnot m     = Precedence -> Term -> m SDoc
+type CustomTermPrinter m = RecursionKnot m
+                         -> [Precedence -> Term -> (m (Maybe SDoc))]

 
 -- Takes a list of custom printers with a explicit recursion knot and a term, 
 -- and returns the output of the first succesful printer, or the default printer
 
 -- Takes a list of custom printers with a explicit recursion knot and a term, 
 -- and returns the output of the first succesful printer, or the default printer

-cPprTerm :: Monad m => 
-           ((Int->Term->m SDoc)->[CustomTermPrinter m]) -> Term -> m SDoc
+cPprTerm :: Monad m => CustomTermPrinter m -> Term -> m SDoc

 cPprTerm printers_ = go 0 where
   printers = printers_ go
 cPprTerm printers_ = go 0 where
   printers = printers_ go

-  go prec t@(Term ty dc val tt) = do
+  go prec t | isTerm t || isNewtypeWrap t = do

     let default_ = Just `liftM` pprTermM go prec t
     let default_ = Just `liftM` pprTermM go prec t

-        mb_customDocs = [pp prec ty dc val tt | pp <- printers] ++ [default_]
+        mb_customDocs = [pp prec t | pp <- printers] ++ [default_]

     Just doc <- firstJustM mb_customDocs
     return$ cparen (prec>app_prec+1) doc
   go _ t = pprTermM1 t
     Just doc <- firstJustM mb_customDocs
     return$ cparen (prec>app_prec+1) doc
   go _ t = pprTermM1 t

+

   firstJustM (mb:mbs) = mb >>= maybe (firstJustM mbs) (return . Just)
   firstJustM [] = return Nothing
 
 -- Default set of custom printers. Note that the recursion knot is explicit
   firstJustM (mb:mbs) = mb >>= maybe (firstJustM mbs) (return . Just)
   firstJustM [] = return Nothing
 
 -- Default set of custom printers. Note that the recursion knot is explicit

-cPprTermBase :: Monad m => (Int->Term-> m SDoc)->[CustomTermPrinter m]
+cPprTermBase :: Monad m => CustomTermPrinter m

 cPprTermBase y =
 cPprTermBase y =

-  [ 
-    ifTerm isTupleTy             (\ _ _ tt -> 
-                                      liftM (parens . hcat . punctuate comma) 
-                                    . mapM (y (-1))
-                                    $ tt)
-  , ifTerm (\ty tt -> isTyCon listTyCon ty tt && tt `lengthIs` 2)
-                                 (\ p _ [h,t] -> doList p h t)
-  , ifTerm (isTyCon intTyCon)    (coerceShow$ \(a::Int)->a)
-  , ifTerm (isTyCon charTyCon)   (coerceShow$ \(a::Char)->a)
---  , ifTerm (isTyCon wordTyCon) (coerceShow$ \(a::Word)->a)
-  , ifTerm (isTyCon floatTyCon)  (coerceShow$ \(a::Float)->a)
-  , ifTerm (isTyCon doubleTyCon) (coerceShow$ \(a::Double)->a)
-  , ifTerm isIntegerTy           (coerceShow$ \(a::Integer)->a)
+  [ ifTerm (isTupleTy.ty) (\_p -> liftM (parens . hcat . punctuate comma) 
+                                      . mapM (y (-1))
+                                      . subTerms)
+  , ifTerm (\t -> isTyCon listTyCon (ty t) && subTerms t `lengthIs` 2)
+           (\ p Term{subTerms=[h,t]} -> doList p h t)
+  , ifTerm (isTyCon intTyCon    . ty) (coerceShow$ \(a::Int)->a)
+  , ifTerm (isTyCon charTyCon   . ty) (coerceShow$ \(a::Char)->a)
+  , ifTerm (isTyCon floatTyCon  . ty) (coerceShow$ \(a::Float)->a)
+  , ifTerm (isTyCon doubleTyCon . ty) (coerceShow$ \(a::Double)->a)
+  , ifTerm (isIntegerTy         . ty) (coerceShow$ \(a::Integer)->a)

   ]
   ]

-     where ifTerm pred f prec ty _ val tt 
-               | pred ty tt = liftM Just (f prec val tt)
-               | otherwise     = return Nothing
-           isIntegerTy ty _ = fromMaybe False $ do
+     where ifTerm pred f prec t@Term{}
+               | pred t    = Just `liftM` f prec t
+           ifTerm _ _ _ _  = return Nothing
+
+           isIntegerTy ty  = fromMaybe False $ do

              (tc,_) <- splitTyConApp_maybe ty 
              return (tyConName tc == integerTyConName)
              (tc,_) <- splitTyConApp_maybe ty 
              return (tyConName tc == integerTyConName)

-           isTupleTy ty _  = fromMaybe False $ do 
+
+           isTupleTy ty    = fromMaybe False $ do 

              (tc,_) <- splitTyConApp_maybe ty 
              return (tc `elem` (fst.unzip.elems) boxedTupleArr)
              (tc,_) <- splitTyConApp_maybe ty 
              return (tc `elem` (fst.unzip.elems) boxedTupleArr)

-           isTyCon a_tc ty _ = fromMaybe False $ do 
+
+           isTyCon a_tc ty = fromMaybe False $ do 

              (tc,_) <- splitTyConApp_maybe ty
              return (a_tc == tc)
              (tc,_) <- splitTyConApp_maybe ty
              return (a_tc == tc)

-           coerceShow f _ val _ = (return . text . show . f . unsafeCoerce#) val
+
+           coerceShow f _p = return . text . show . f . unsafeCoerce# . val
+

            --TODO pprinting of list terms is not lazy
            doList p h t = do
            --TODO pprinting of list terms is not lazy
            doList p h t = do

-               let elems = h : getListTerms t
+               let elems      = h : getListTerms t

                    isConsLast = termType(last elems) /= termType h
                print_elems <- mapM (y cons_prec) elems
                return$ if isConsLast
                    isConsLast = termType(last elems) /= termType h
                print_elems <- mapM (y cons_prec) elems
                return$ if isConsLast

@@ -473,6 +524,9 @@ runTR hsc_env c = do
 runTR_maybe :: HscEnv -> TR a -> IO (Maybe a)
 runTR_maybe hsc_env = fmap snd . initTc hsc_env HsSrcFile False iNTERACTIVE
 
 runTR_maybe :: HscEnv -> TR a -> IO (Maybe a)
 runTR_maybe hsc_env = fmap snd . initTc hsc_env HsSrcFile False iNTERACTIVE
 

+traceTR :: SDoc -> TR ()
+traceTR = liftTcM . traceTc
+

 trIO :: IO a -> TR a 
 trIO = liftTcM . ioToTcRn
 
 trIO :: IO a -> TR a 
 trIO = liftTcM . ioToTcRn
 

@@ -504,14 +558,18 @@ cvObtainTerm :: HscEnv -> Int -> Bool -> Maybe Type -> HValue -> IO Term
 cvObtainTerm hsc_env bound force mb_ty hval = runTR hsc_env $ do
    tv <- newVar argTypeKind
    case mb_ty of
 cvObtainTerm hsc_env bound force mb_ty hval = runTR hsc_env $ do
    tv <- newVar argTypeKind
    case mb_ty of

-     Nothing -> go bound tv tv hval >>= zonkTerm
-     Just ty | isMonomorphic ty -> go bound ty ty hval >>= zonkTerm
+     Nothing ->      go bound tv tv hval 
+                >>= zonkTerm 
+                >>= return . expandNewtypes
+     Just ty | isMonomorphic ty ->     go bound ty ty hval 
+                                   >>= zonkTerm
+                                   >>= return . expandNewtypes

      Just ty -> do 
               (ty',rev_subst) <- instScheme (sigmaType ty)
               addConstraint tv ty'
               term <- go bound tv tv hval >>= zonkTerm
               --restore original Tyvars
      Just ty -> do 
               (ty',rev_subst) <- instScheme (sigmaType ty)
               addConstraint tv ty'
               term <- go bound tv tv hval >>= zonkTerm
               --restore original Tyvars

-              return$ mapTermType (substTy rev_subst) term
+              return$ expandNewtypes $ mapTermType (substTy rev_subst) term

     where 
   go bound _ _ _ | seq bound False = undefined
   go 0 tv _ty a = do
     where 
   go bound _ _ _ | seq bound False = undefined
   go 0 tv _ty a = do

@@ -529,7 +587,7 @@ cvObtainTerm hsc_env bound force mb_ty hval = runTR hsc_env $ do
 -- and showing the '_' is more useful.
       t | isThunk t && force -> seq a $ go (pred bound) tv ty a
 -- We always follow indirections 
 -- and showing the '_' is more useful.
       t | isThunk t && force -> seq a $ go (pred bound) tv ty a
 -- We always follow indirections 

-      Indirection _ -> go (pred bound) tv ty $! (ptrs clos ! 0)
+      Indirection _ -> go bound tv ty $! (ptrs clos ! 0)

  -- The interesting case
       Constr -> do
         Right dcname <- dataConInfoPtrToName (infoPtr clos)
  -- The interesting case
       Constr -> do
         Right dcname <- dataConInfoPtrToName (infoPtr clos)

@@ -577,7 +635,6 @@ cvObtainTerm hsc_env bound force mb_ty hval = runTR hsc_env $ do
       tipe_clos -> 
          return (Suspension tipe_clos (Just tv) a Nothing)
 
       tipe_clos -> 
          return (Suspension tipe_clos (Just tv) a Nothing)
 

---  matchSubTypes dc ty | pprTrace "matchSubtypes" (ppr dc <+> ppr ty) False = undefined

   matchSubTypes dc ty
     | Just (_,ty_args) <- splitTyConApp_maybe (repType ty) 
 --     assumption:             ^^^ looks through newtypes 
   matchSubTypes dc ty
     | Just (_,ty_args) <- splitTyConApp_maybe (repType ty) 
 --     assumption:             ^^^ looks through newtypes 

@@ -592,12 +649,24 @@ cvObtainTerm hsc_env bound force mb_ty hval = runTR hsc_env $ do
    | isPointed ty = ASSERT2(not(null pointed)
                             , ptext SLIT("reOrderTerms") $$ 
                                         (ppr pointed $$ ppr unpointed))
    | isPointed ty = ASSERT2(not(null pointed)
                             , ptext SLIT("reOrderTerms") $$ 
                                         (ppr pointed $$ ppr unpointed))

-                    head pointed : reOrderTerms (tail pointed) unpointed tys
+                    let (t:tt) = pointed in t : reOrderTerms tt unpointed tys

    | otherwise    = ASSERT2(not(null unpointed)
                            , ptext SLIT("reOrderTerms") $$ 
                                        (ppr pointed $$ ppr unpointed))
    | otherwise    = ASSERT2(not(null unpointed)
                            , ptext SLIT("reOrderTerms") $$ 
                                        (ppr pointed $$ ppr unpointed))

-                    head unpointed : reOrderTerms pointed (tail unpointed) tys
+                    let (t:tt) = unpointed in t : reOrderTerms pointed tt tys
+  
+  expandNewtypes t@Term{ ty=ty, subTerms=tt }
+   | Just (tc, args) <- splitNewTyConApp_maybe ty
+   , isNewTyCon tc
+   , wrapped_type    <- newTyConInstRhs tc args
+   , Just dc         <- maybeTyConSingleCon tc
+   , t'              <- expandNewtypes t{ ty = wrapped_type
+                                        , subTerms = map expandNewtypes tt }
+   = NewtypeWrap ty (Right dc) t'
+
+   | otherwise = t{ subTerms = map expandNewtypes tt }

 
 

+  expandNewtypes t = t

 
 
 -- Fast, breadth-first Type reconstruction
 
 
 -- Fast, breadth-first Type reconstruction

@@ -621,8 +690,8 @@ cvReconstructType hsc_env max_depth mb_ty hval = runTR_maybe hsc_env $ do
               substTy rev_subst `fmap` zonkTcType tv
     where 
 --  search :: m Bool -> ([a] -> [a] -> [a]) -> [a] -> m ()
               substTy rev_subst `fmap` zonkTcType tv
     where 
 --  search :: m Bool -> ([a] -> [a] -> [a]) -> [a] -> m ()

-  search _ _ _ 0 = fail$ "Failed to reconstruct a type after " ++
-                                show max_depth ++ " steps"
+  search _ _ _ 0 = traceTR (text "Failed to reconstruct a type after " <>
+                                int max_depth <> text " steps")

   search stop expand l d =
     case viewl l of 
       EmptyL  -> return ()
   search stop expand l d =
     case viewl l of 
       EmptyL  -> return ()

@@ -705,10 +774,12 @@ computeRTTIsubst ty rtti_ty =
    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 
    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).
+ constraints are unified is vital for this.
+   This is a simple form of residuation, the technique of 
+ delaying unification steps until enough information
+ is available.

 -}
 -}

-congruenceNewtypes ::  TcType -> TcType -> TcM (TcType,TcType)
+congruenceNewtypes ::  TcType -> TcType -> TR (TcType,TcType)

 congruenceNewtypes lhs rhs 
  -- TyVar lhs inductive case
     | Just tv <- getTyVar_maybe lhs 
 congruenceNewtypes lhs rhs 
  -- TyVar lhs inductive case
     | Just tv <- getTyVar_maybe lhs 

@@ -726,18 +797,20 @@ congruenceNewtypes lhs rhs
     | Just (tycon_l, _) <- splitNewTyConApp_maybe lhs
     , Just (tycon_r, _) <- splitNewTyConApp_maybe rhs 
     , tycon_l /= tycon_r 
     | Just (tycon_l, _) <- splitNewTyConApp_maybe lhs
     , Just (tycon_r, _) <- splitNewTyConApp_maybe rhs 
     , tycon_l /= tycon_r 

-    = return (lhs, upgrade tycon_l rhs)
+    = do rhs' <- upgrade tycon_l rhs
+         return (lhs, rhs')

 
     | otherwise = return (lhs,rhs)
 
 
     | otherwise = return (lhs,rhs)
 

-    where upgrade :: TyCon -> Type -> Type
+    where upgrade :: TyCon -> Type -> TR Type

           upgrade new_tycon ty
           upgrade new_tycon ty

-            | not (isNewTyCon new_tycon) = ty 
-            | ty' <- mkTyConApp new_tycon (map mkTyVarTy $ tyConTyVars new_tycon)
-            , Just subst <- tcUnifyTys (const BindMe) [ty] [repType ty']
-            = substTy subst ty'
-          upgrade _ _ = panic "congruenceNewtypes.upgrade"
-        -- assumes that reptype doesn't touch tyconApp args ^^^
+            | not (isNewTyCon new_tycon) = return ty 
+            | otherwise = do 
+               vars <- mapM (newVar . tyVarKind) (tyConTyVars new_tycon)
+               let ty' = mkTyConApp new_tycon vars
+               liftTcM (unifyType ty (repType ty'))
+        -- assumes that reptype doesn't ^^^^ touch tyconApp args 
+               return ty'

 
 
 --------------------------------------------------------------------------------
 
 
 --------------------------------------------------------------------------------

@@ -766,7 +839,7 @@ unlessM condM acc = condM >>= \c -> unless c acc
 
 -- Strict application of f at index i
 appArr :: Ix i => (e -> a) -> Array i e -> Int -> a
 
 -- Strict application of f at index i
 appArr :: Ix i => (e -> a) -> Array i e -> Int -> a

-appArr f (Array _ _ _ ptrs#) (I# i#)
+appArr f a@(Array _ _ _ ptrs#) i@(I# i#)

  = ASSERT (i < length(elems a))
    case indexArray# ptrs# i# of
        (# e #) -> f e
  = ASSERT (i < length(elems a))
    case indexArray# ptrs# i# of
        (# e #) -> f e

@@ -777,7 +850,9 @@ zonkTerm = foldTerm idTermFoldM {
                                      zonkTcType ty    >>= \ty' ->
                                      return (Term ty' dc v tt)
              ,fSuspension = \ct ty v b -> fmapMMaybe zonkTcType ty >>= \ty ->
                                      zonkTcType ty    >>= \ty' ->
                                      return (Term ty' dc v tt)
              ,fSuspension = \ct ty v b -> fmapMMaybe zonkTcType ty >>= \ty ->

-                                          return (Suspension ct ty v b)}  
+                                          return (Suspension ct ty v b)
+             ,fNewtypeWrap= \ty dc t -> 
+                   return NewtypeWrap `ap` zonkTcType ty `ap` return dc `ap` t}

 
 
 -- Is this defined elsewhere?
 
 
 -- Is this defined elsewhere?