Remove unused import

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

diff --git a/compiler/types/FunDeps.lhs b/compiler/types/FunDeps.lhs
index 0d7eb24..06248b7 100644 (file)
--- a/compiler/types/FunDeps.lhs
+++ b/compiler/types/FunDeps.lhs
@@ -1,7 +1,9 @@
-
+%
+% (c) The University of Glasgow 2006
 % (c) The GRASP/AQUA Project, Glasgow University, 2000
 %
-\section[FunDeps]{FunDeps - functional dependencies}
+
+FunDeps - functional dependencies
 
 It's better to read it as: "if we know these, then we're going to know these"
 
@@ -15,23 +17,22 @@ module FunDeps (
 
 #include "HsVersions.h"
 
-import Name            ( Name, getSrcLoc )
-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,
-                         instanceCantMatch, roughMatchTcs )
+import Name
+import Var
+import Class
+import TcGadt
+import Type
+import Coercion
+import TcType
+import InstEnv
 import VarSet
 import VarEnv
 import Outputable
-import Util             ( notNull )
-import List            ( tails )
-import Maybe           ( isJust )
-import ListSetOps      ( equivClassesByUniq )
+import Util
+import ListSetOps
+
+import Data.List       ( tails )
+import Data.Maybe      ( isJust )
 \end{code}
 
 
@@ -222,7 +223,11 @@ NOTA BENE:
 improve inst_env preds
   = [ eqn | group <- equivClassesByUniq (predTyUnique . fst) (filterEqPreds preds),
            eqn   <- checkGroup inst_env group ]
-  where filterEqPreds = filter (not . isEqPred . fst)
+  where 
+    filterEqPreds = filter (not . isEqPred . fst)
+       -- Equality predicates don't have uniques
+       -- In any case, improvement *generates*, rather than
+       -- *consumes*, equality constraints
 
 ----------
 checkGroup :: (Class -> [Instance])