imp_conv_disj is now declared as a "code unfold" lemma to avoid that
conclusion is evaluated eagerly.
--- a/src/HOL/Code_Setup.thy Mon Jan 07 11:40:20 2008 +0100
+++ b/src/HOL/Code_Setup.thy Tue Jan 08 10:24:34 2008 +0100
@@ -84,7 +84,7 @@
text {* type bool *}
-lemmas [code] = imp_conv_disj
+lemmas [code unfold] = imp_conv_disj
code_type bool
(SML "bool")