From 0947d2d523d18ad1a9e25b92f89452a1c9a70350 Mon Sep 17 00:00:00 2001
From: Simon Cruanes <simon.cruanes.2007@m4x.org>
Date: Tue, 9 Dec 2025 12:11:03 -0500
Subject: [PATCH] better error message

---
 src/ppx/ppx_trace.ml | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/ppx/ppx_trace.ml b/src/ppx/ppx_trace.ml
index 6b1b2cc..f6327da 100644
--- a/src/ppx/ppx_trace.ml
+++ b/src/ppx/ppx_trace.ml
@@ -73,7 +73,10 @@ let expand_top_let ~ctxt rec_flag (vbs : _ list) =
                 pstr_eval ~loc
                   (pexp_constant ~loc
                      (Pconst_string
-                        ("ppxtrace: cannot trace `function`", loc, None)))
+                        ( "ppxtrace: cannot trace `function`, please unsugar \
+                           to `fun`+`match`.",
+                          loc,
+                          None )))
                   [];
               ] )
       | _ ->