tuned;

--- a/src/Provers/classical.ML	Sun Jul 13 17:29:48 2025 +0100
+++ b/src/Provers/classical.ML	Mon Jul 14 10:57:46 2025 +0200
@@ -287,6 +287,9 @@
 
 fun err_thm ctxt msg th = error (msg ^ "\n" ^ Thm.string_of_thm ctxt th);
 
+fun err_thm_illformed ctxt kind th =
+  err_thm ctxt ("Ill-formed " ^ Bires.kind_name kind) th;
+
 fun make_elim ctxt th =
   if Thm.no_prems th then err_thm ctxt "Ill-formed destruction rule" th
   else Tactic.make_elim th;
@@ -405,27 +408,30 @@
     (th, make_info1 (maybe_swapped_rl (flat_rule ctxt th)) th) cs;
 
 fun addSE w ctxt th cs =
-  if Thm.no_prems th then err_thm ctxt "Ill-formed elimination rule" th
-  else
-    let val info = make_info1 (no_swapped_rl (classical_rule ctxt (flat_rule ctxt th))) th
-    in extend_rules ctxt Bires.elim_bang_kind w (th, info) cs end;
+  let
+    val kind = Bires.elim_bang_kind;
+    val _ = Thm.no_prems th andalso err_thm_illformed ctxt kind th;
+    val info = make_info1 (no_swapped_rl (classical_rule ctxt (flat_rule ctxt th))) th;
+  in extend_rules ctxt kind w (th, info) cs end;
 
 fun addSD w ctxt th = addSE w ctxt (make_elim ctxt th);
 
 fun addI w ctxt th cs =
   let
+    val kind = Bires.intro_kind;
     val th' = flat_rule ctxt th;
-    val dup_th' = dup_intr th' handle THM _ => err_thm ctxt "Ill-formed introduction rule" th;
+    val dup_th' = dup_intr th' handle THM _ => err_thm_illformed ctxt kind th;
     val info = make_info (maybe_swapped_rl th') (maybe_swapped_rl dup_th') th;
-  in extend_rules ctxt Bires.intro_kind w (th, info) cs end;
+  in extend_rules ctxt kind w (th, info) cs end;
 
 fun addE w ctxt th cs =
   let
-    val _ = Thm.no_prems th andalso err_thm ctxt "Ill-formed elimination rule" th;
+    val kind = Bires.elim_kind;
+    val _ = Thm.no_prems th andalso err_thm_illformed ctxt kind th;
     val th' = classical_rule ctxt (flat_rule ctxt th);
-    val dup_th' = dup_elim ctxt th' handle THM _ => err_thm ctxt "Ill-formed elimination rule" th;
+    val dup_th' = dup_elim ctxt th' handle THM _ => err_thm_illformed ctxt kind th th;
     val info = make_info (no_swapped_rl th') (no_swapped_rl dup_th') th;
-  in extend_rules ctxt Bires.elim_kind w (th, info) cs end;
+  in extend_rules ctxt kind w (th, info) cs end;
 
 fun addD w ctxt th = addE w ctxt (make_elim ctxt th);
 

--- a/src/Pure/bires.ML	Sun Jul 13 17:29:48 2025 +0100
+++ b/src/Pure/bires.ML	Mon Jul 14 10:57:46 2025 +0200
@@ -32,6 +32,7 @@
   val kind_extra: kind -> bool
   val kind_index: kind -> int
   val kind_elim: kind -> bool
+  val kind_name: kind -> string
   val kind_domain: kind list
   val kind_values: 'a -> 'a list
   val kind_map: kind -> ('a -> 'a) -> 'a list -> 'a list
@@ -130,6 +131,9 @@
 fun kind_index (Kind (i, _)) = i;
 fun kind_elim (Kind (_, b)) = b;
 
+fun kind_name kind =
+  if kind_elim kind then "elimination rule" else "introduction rule";
+
 val kind_domain = map #1 kind_infos;
 
 fun kind_values x =