X-Git-Url: http://git.megacz.com/?a=blobdiff_plain;f=compiler%2Ftypes%2FFunDeps.lhs;h=06248b7b3cd4a79ee1ee6f534fb050be078e2b89;hb=d29f86b1fe7daf919e9b47a9003daed74b812790;hp=9347f5f665d7c04d7b6387001bae2d0213b3f419;hpb=0065d5ab628975892cea1ec7303f968c3338cbe1;p=ghc-hetmet.git

diff --git a/compiler/types/FunDeps.lhs b/compiler/types/FunDeps.lhs
index 9347f5f..06248b7 100644
--- 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"
 
@@ -15,22 +17,22 @@ module FunDeps (
 
 #include "HsVersions.h"
 
-import Name		( Name, getSrcLoc )
-import Var		( TyVar )
-import Class		( Class, FunDep, classTvsFds )
-import Unify		( tcUnifyTys, BindFlag(..) )
-import Type		( substTys, notElemTvSubst )
-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}
 
 
@@ -125,6 +127,7 @@ oclose preds fixed_tvs
 
 \begin{code}
 grow :: [PredType] -> TyVarSet -> TyVarSet
+-- See Note [Ambiguity] in TcSimplify
 grow preds fixed_tvs 
   | null preds = fixed_tvs
   | otherwise  = loop fixed_tvs
@@ -218,8 +221,13 @@ 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)
+	-- Equality predicates don't have uniques
+	-- In any case, improvement *generates*, rather than
+	-- *consumes*, equality constraints
 
 ----------
 checkGroup :: (Class -> [Instance])
@@ -484,17 +492,4 @@ trimRoughMatchTcs clas_tvs (ltvs,_) mb_tcs
 \end{code}
 
 
-%************************************************************************
-%*									*
-\subsection{Miscellaneous}
-%*									*
-%************************************************************************
-
-\begin{code}
-pprFundeps :: Outputable a => [FunDep a] -> SDoc
-pprFundeps [] = empty
-pprFundeps fds = hsep (ptext SLIT("|") : punctuate comma (map ppr_fd fds))
-
-ppr_fd (us, vs) = hsep [interppSP us, ptext SLIT("->"), interppSP vs]
-\end{code}