From ccac989ddab7aa0827c16f355c3cf305aa65fa8a Mon Sep 17 00:00:00 2001
From: Patrick Massot <patrickmassot@free.fr>
Date: Thu, 7 Mar 2024 15:02:23 -0500
Subject: [PATCH] doc: expand an error message about compacting closures
 (#3627)

Provide a hint of where the error message may come from.
---
 src/runtime/compact.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/runtime/compact.cpp b/src/runtime/compact.cpp
index b2269a4cd6..2dcd60d1e3 100644
--- a/src/runtime/compact.cpp
+++ b/src/runtime/compact.cpp
@@ -342,7 +342,7 @@ void object_compactor::operator()(object * o) {
             g_tag_counters[lean_ptr_tag(curr)]++;
 #endif
             switch (lean_ptr_tag(curr)) {
-            case LeanClosure:         lean_internal_panic("closures cannot be compacted");
+            case LeanClosure:         lean_internal_panic("closures cannot be compacted. One possible cause of this error is trying to store a function in a persistent environment extension.");
             case LeanArray:           r = insert_array(curr); break;
             case LeanScalarArray:     insert_sarray(curr); break;
             case LeanString:          insert_string(curr); break;