diff -r 295e1c9d2994 -r 91c16c5ad3e9 src/HOL/Library/Poly_Mapping.thy
--- a/src/HOL/Library/Poly_Mapping.thy	Wed May 11 10:42:24 2022 +0200
+++ b/src/HOL/Library/Poly_Mapping.thy	Tue May 17 14:10:14 2022 +0100
@@ -1688,7 +1688,7 @@
   
 
 lemma keys_cmul_iff [iff]: "i \<in> Poly_Mapping.keys (frag_cmul c x) \<longleftrightarrow> i \<in> Poly_Mapping.keys x \<and> c \<noteq> 0"
-  apply (auto simp: )
+  apply auto
   apply (meson subsetD keys_cmul)
   by (metis in_keys_iff lookup_frag_cmul mult_eq_0_iff)