Fix recursive superclasses (again). Fixes Trac #4809.

[ghc-hetmet.git] / compiler / typecheck / TcSMonad.lhs

diff --git a/compiler/typecheck/TcSMonad.lhs b/compiler/typecheck/TcSMonad.lhs
index a45f9a5..1e99876 100644 (file)
--- a/compiler/typecheck/TcSMonad.lhs
+++ b/compiler/typecheck/TcSMonad.lhs
@@ -11,7 +11,7 @@ module TcSMonad (
     mkWantedConstraints, deCanonicaliseWanted, 
     makeGivens, makeSolvedByInst,
 
-    CtFlavor (..), isWanted, isGiven, isDerived, isDerivedSC, isDerivedByInst, 
+    CtFlavor (..), isWanted, isGiven, isDerived, 
     isGivenCt, isWantedCt, pprFlavorArising,
 
     isFlexiTcsTv,
@@ -87,14 +87,11 @@ import InstEnv
 import FamInst 
 import FamInstEnv
 
-import NameSet ( addOneToNameSet ) 
-
 import qualified TcRnMonad as TcM
 import qualified TcMType as TcM
 import qualified TcEnv as TcM 
        ( checkWellStaged, topIdLvl, tcLookupFamInst, tcGetDefaultTys )
 import TcType
-import Module 
 import DynFlags
 
 import Coercion
@@ -184,8 +181,9 @@ data CanonicalCt
 compatKind :: Kind -> Kind -> Bool 
 compatKind k1 k2 = k1 `isSubKind` k2 || k2 `isSubKind` k1 
 
-makeGivens :: CanonicalCts -> CanonicalCts
-makeGivens = mapBag (\ct -> ct { cc_flavor = mkGivenFlavor (cc_flavor ct) UnkSkol })
+makeGivens :: Bag WantedEvVar -> Bag (CtFlavor,EvVar) 
+makeGivens = mapBag (\(WantedEvVar ev wloc) -> (mkGivenFlavor (Wanted wloc) UnkSkol, ev))
+-- ct { cc_flavor = mkGivenFlavor (cc_flavor ct) UnkSkol })
           -- The UnkSkol doesn't matter because these givens are
           -- not contradictory (else we'd have rejected them already)
 
@@ -300,9 +298,10 @@ data CtFlavor
                       --   these wanteds 
   | Wanted WantedLoc  -- We have no evidence bindings for this constraint. 
 
-data DerivedOrig = DerSC | DerInst 
+data DerivedOrig = DerSC | DerInst | DerSelf
 -- Deriveds are either superclasses of other wanteds or deriveds, or partially 
--- solved wanteds from instances. 
+-- solved wanteds from instances, or 'self' dictionaries containing yet wanted
+-- superclasses. 
 
 instance Outputable CtFlavor where 
   ppr (Given _)    = ptext (sLit "[Given]")
@@ -321,14 +320,6 @@ isDerived :: CtFlavor -> Bool
 isDerived (Derived {}) = True
 isDerived _            = False
 
-isDerivedSC :: CtFlavor -> Bool 
-isDerivedSC (Derived _ DerSC) = True 
-isDerivedSC _                 = False 
-
-isDerivedByInst :: CtFlavor -> Bool 
-isDerivedByInst (Derived _ DerInst) = True 
-isDerivedByInst _                   = False 
-
 pprFlavorArising :: CtFlavor -> SDoc
 pprFlavorArising (Derived wl _) = pprArisingAt wl
 pprFlavorArising (Wanted  wl)   = pprArisingAt wl
@@ -469,6 +460,7 @@ data SimplContext
   | SimplRuleLhs       -- Inferring type of a RULE lhs
   | SimplInteractive   -- Inferring type at GHCi prompt
   | SimplCheck         -- Checking a type signature or RULE rhs
+  deriving Eq
 
 instance Outputable SimplContext where
   ppr SimplInfer       = ptext (sLit "SimplInfer")
@@ -909,9 +901,9 @@ isGoodRecEv ev_var wv
 
         chase_ev assocs trg curr_grav visited (EvCoercion co)
             = chase_co assocs trg curr_grav visited co
-        chase_ev assocs trg curr_grav visited (EvDFunApp _ _ ev_vars) 
-            = do { chase_results <- mapM (chase_ev_var assocs trg (curr_grav+1) visited) ev_vars
-                 ; return (comb_chase_res Nothing chase_results) } 
+        chase_ev assocs trg curr_grav visited (EvDFunApp _ _ ev_deps)
+            = do { chase_results <- mapM (chase_ev_var assocs trg (curr_grav+1) visited) ev_deps
+                 ; return (comb_chase_res Nothing chase_results) }
 
         chase_co assocs trg curr_grav visited co 
             = -- Look for all the coercion variables in the coercion 
@@ -943,7 +935,7 @@ matchClass :: Class -> [Type] -> TcS (MatchInstResult (DFunId, [Either TyVar TcT
 matchClass clas tys
   = do { let pred = mkClassPred clas tys 
         ; instEnvs <- getInstEnvs
-       ; case lookupInstEnv instEnvs clas tys of {
+        ; case lookupInstEnv instEnvs clas tys of {
             ([], unifs)               -- Nothing matches  
                 -> do { traceTcS "matchClass not matching"
                                  (vcat [ text "dict" <+> ppr pred, 
@@ -955,10 +947,9 @@ matchClass clas tys
                        ; traceTcS "matchClass success"
                                   (vcat [text "dict" <+> ppr pred, 
                                          text "witness" <+> ppr dfun_id
-                                          <+> ppr (idType dfun_id) ])
+                                           <+> ppr (idType dfun_id), ppr instEnvs ])
                                  -- Record that this dfun is needed
-                       ; record_dfun_usage dfun_id
-                       ; return $ MatchInstSingle (dfun_id, inst_tys) 
+                        ; return $ MatchInstSingle (dfun_id, inst_tys)
                         } ;
            (matches, unifs)          -- More than one matches 
                -> do   { traceTcS "matchClass multiple matches, deferring choice"
@@ -969,26 +960,8 @@ matchClass clas tys
                        }
        }
         }
-  where record_dfun_usage :: Id -> TcS () 
-        record_dfun_usage dfun_id 
-          = do { hsc_env <- getTopEnv 
-               ; let  dfun_name = idName dfun_id
-                     dfun_mod  = ASSERT( isExternalName dfun_name ) 
-                                 nameModule dfun_name
-               ; if isInternalName dfun_name ||    -- Internal name => defined in this module
-                   modulePackageId dfun_mod /= thisPackage (hsc_dflags hsc_env)
-                then return () -- internal, or in another package
-                else do updInstUses dfun_id 
-               }
-
-        updInstUses :: Id -> TcS () 
-        updInstUses dfun_id 
-            = do { tcg_env <- getGblEnv 
-                 ; wrapTcS $ TcM.updMutVar (tcg_inst_uses tcg_env) 
-                                            (`addOneToNameSet` idName dfun_id) 
-                 }
-
-matchFam :: TyCon 
+
+matchFam :: TyCon
          -> [Type] 
          -> TcS (MatchInstResult (TyCon, [Type]))
 matchFam tycon args