
diff -r 8fb767245822 -r d3cc5398bad5 src/HOL/Statespace/DistinctTreeProver.thy
--- a/src/HOL/Statespace/DistinctTreeProver.thy	Thu Jan 01 14:23:39 2009 +0100
+++ b/src/HOL/Statespace/DistinctTreeProver.thy	Thu Jan 01 17:47:12 2009 +0100
@@ -452,7 +452,7 @@
   case Tip thus ?case by simp
 next
   case (Node l x d r)
-  have sub: "subtract (Node l x d r) t\<^isub>2 = Some t".
+  have sub: "subtract (Node l x d r) t\<^isub>2 = Some t" by fact
   show ?case
   proof (cases "delete x t\<^isub>2")
     case (Some t\<^isub>2')




