diff -r c0587d661ea8 -r 267db8c321c4 src/HOL/Library/DAList.thy
--- a/src/HOL/Library/DAList.thy	Fri May 02 16:25:38 2025 +0100
+++ b/src/HOL/Library/DAList.thy	Fri May 02 17:24:43 2025 +0200
@@ -37,6 +37,10 @@
 lemma impl_of_distinct [simp, intro]: "distinct (map fst (impl_of xs))"
   using impl_of[of xs] by simp
 
+lemma impl_of_Alist:
+  \<open>impl_of (Alist xs) = xs\<close> if \<open>distinct (map fst xs)\<close>
+  using Alist_inverse [of xs] that by simp
+
 lemma Alist_impl_of [code abstype]: "Alist (impl_of xs) = xs"
   by (rule impl_of_inverse)