From 2c8d5973f39c64a08b81483992928933a4f8fa02 Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Wed, 2 Jun 2021 15:08:29 -0700
Subject: [PATCH] Add a hand-written error message for the `seek_internal`
 precondition

---
 zed/src/sum_tree/cursor.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/zed/src/sum_tree/cursor.rs b/zed/src/sum_tree/cursor.rs
index 5e1624aa87..649b3ad28a 100644
--- a/zed/src/sum_tree/cursor.rs
+++ b/zed/src/sum_tree/cursor.rs
@@ -413,7 +413,12 @@ where
         D: Dimension<'a, T::Summary>,
     {
         if let Some(target) = target {
-            debug_assert!(target.cmp(&self.seek_dimension, cx) >= Ordering::Equal);
+            debug_assert!(
+                target.cmp(&self.seek_dimension, cx) >= Ordering::Equal,
+                "cannot seek backward from {:?} to {:?}",
+                self.seek_dimension,
+                target
+            );
         }
 
         if !self.did_seek {