GADT fixes

[ghc-hetmet.git] / compiler / types / FunDeps.lhs

diff --git a/compiler/types/FunDeps.lhs b/compiler/types/FunDeps.lhs
index 1534dc6..0d7eb24 100644 (file)
--- a/compiler/types/FunDeps.lhs
+++ b/compiler/types/FunDeps.lhs
@@ -1,4 +1,4 @@
-%
+
 % (c) The GRASP/AQUA Project, Glasgow University, 2000
 %
 \section[FunDeps]{FunDeps - functional dependencies}
@@ -20,6 +20,7 @@ import Var            ( TyVar )
 import Class           ( Class, FunDep, pprFundeps, classTvsFds )
 import TcGadt          ( tcUnifyTys, BindFlag(..) )
 import Type            ( substTys, notElemTvSubst )
+import Coercion         ( isEqPred )
 import TcType          ( Type, PredType(..), tcEqType, 
                          predTyUnique, mkClassPred, tyVarsOfTypes, tyVarsOfPred )
 import InstEnv         ( Instance(..), InstEnv, instanceHead, classInstances,
@@ -219,8 +220,9 @@ NOTA BENE:
 
 \begin{code}
 improve inst_env preds
-  = [ eqn | group <- equivClassesByUniq (predTyUnique . fst) preds,
+  = [ eqn | group <- equivClassesByUniq (predTyUnique . fst) (filterEqPreds preds),
            eqn   <- checkGroup inst_env group ]
+  where filterEqPreds = filter (not . isEqPred . fst)
 
 ----------
 checkGroup :: (Class -> [Instance])