--- a/src/HOL/Rings.thy Mon Aug 22 21:37:06 2022 +0200
+++ b/src/HOL/Rings.thy Wed Aug 24 06:21:06 2022 +0000
@@ -382,7 +382,7 @@
subclass semiring_1_cancel ..
-lemma of_bool_not_iff [simp]:
+lemma of_bool_not_iff:
\<open>of_bool (\<not> P) = 1 - of_bool P\<close>
by simp