[BUGFIX: equal vars were added to substitution during unification
martin.hofmann@uni-bamberg.de**20091008142332] hunk ./src/Syntax/Expressions.hs 246
-    match s@(TVarE i1 _) t@(TVarE i2 _)     = do
-        checkMatch s t >> matchVar s t
-       -- if  i1 == i2 then return () else matchVar s t
+    match s@(TVarE i1 _) t@(TVarE i2 _)     = 
+        checkMatch s t >> if  i1 == i2 then return () else matchVar s t