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

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

diff --git a/compiler/typecheck/TcDeriv.lhs b/compiler/typecheck/TcDeriv.lhs
index 30e57ff..4d1d448 100644 (file)
--- a/compiler/typecheck/TcDeriv.lhs
+++ b/compiler/typecheck/TcDeriv.lhs
@@ -373,14 +373,14 @@ renameDeriv is_boot gen_binds insts
                  , mkFVs (map dataConName (tyConDataCons tc)))
          -- See Note [Newtype deriving and unused constructors]
 
-    rn_inst_info (InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs standalone_deriv })
+    rn_inst_info inst_info@(InstInfo { iSpec = inst, iBinds = VanillaInst binds sigs standalone_deriv })
        =       -- Bring the right type variables into 
                -- scope (yuk), and rename the method binds
           ASSERT( null sigs )
           bindLocalNames (map Var.varName tyvars) $
           do { (rn_binds, fvs) <- rnMethodBinds clas_nm (\_ -> []) [] binds
              ; let binds' = VanillaInst rn_binds [] standalone_deriv
-             ; return (InstInfo { iSpec = inst, iBinds = binds' }, fvs) }
+              ; return (inst_info { iBinds = binds' }, fvs) }
        where
          (tyvars,_, clas,_) = instanceHead inst
          clas_nm            = className clas
@@ -467,12 +467,13 @@ deriveStandalone (L loc (DerivDecl deriv_ty))
   = setSrcSpan loc                   $
     addErrCtxt (standaloneCtxt deriv_ty)  $
     do { traceTc "Standalone deriving decl for" (ppr deriv_ty)
-       ; (tvs, theta, tau) <- tcHsInstHead deriv_ty
+       ; (tvs, theta, cls, inst_tys) <- tcHsInstHead deriv_ty
        ; traceTc "Standalone deriving;" $ vcat
               [ text "tvs:" <+> ppr tvs
               , text "theta:" <+> ppr theta
-              , text "tau:" <+> ppr tau ]
-       ; (cls, inst_tys) <- checkValidInstance deriv_ty tvs theta tau
+              , text "cls:" <+> ppr cls
+              , text "tys:" <+> ppr inst_tys ]
+       ; checkValidInstance deriv_ty tvs theta cls inst_tys
                -- C.f. TcInstDcls.tcLocalInstDecl1
 
        ; let cls_tys = take (length inst_tys - 1) inst_tys
@@ -1400,26 +1401,26 @@ the renamer.  What a great hack!
 genInst :: Bool        -- True <=> standalone deriving
        -> OverlapFlag
         -> DerivSpec -> TcM (InstInfo RdrName, DerivAuxBinds)
-genInst standalone_deriv oflag spec
-  | ds_newtype spec
-  = return (InstInfo { iSpec  = mkInstance oflag (ds_theta spec) spec
-                    , iBinds = NewTypeDerived co rep_tycon }, [])
+genInst standalone_deriv oflag
+        spec@(DS { ds_tc = rep_tycon, ds_tc_args = rep_tc_args
+                 , ds_theta = theta, ds_newtype = is_newtype
+                 , ds_name = name, ds_cls = clas })
+  | is_newtype
+  = return (InstInfo { iSpec   = inst_spec
+                     , iBinds  = NewTypeDerived co rep_tycon }, [])
 
   | otherwise
-  = do { let loc  = getSrcSpan (ds_name spec)
-             inst = mkInstance oflag (ds_theta spec) spec
-             clas = ds_cls spec
-
-          -- In case of a family instance, we need to use the representation
-          -- tycon (after all, it has the data constructors)
-       ; fix_env <- getFixityEnv
-       ; let (meth_binds, aux_binds) = genDerivBinds loc fix_env clas rep_tycon
-             binds = VanillaInst meth_binds [] standalone_deriv
-       ; return (InstInfo { iSpec = inst, iBinds = binds }, aux_binds)
-        }
+  = do  { fix_env <- getFixityEnv
+        ; let loc   = getSrcSpan name
+              (meth_binds, aux_binds) = genDerivBinds loc fix_env clas rep_tycon
+                   -- In case of a family instance, we need to use the representation
+                   -- tycon (after all, it has the data constructors)
+
+        ; return (InstInfo { iSpec   = inst_spec
+                           , iBinds  = VanillaInst meth_binds [] standalone_deriv }
+                 , aux_binds) }
   where
-    rep_tycon   = ds_tc spec
-    rep_tc_args = ds_tc_args spec
+    inst_spec = mkInstance oflag theta spec
     co1 = case tyConFamilyCoercion_maybe rep_tycon of
              Just co_con -> ACo (mkTyConApp co_con rep_tc_args)
              Nothing     -> id_co