From ebe7a7b21a9e46f4b5b10250598fd74a30fcdee9 Mon Sep 17 00:00:00 2001
From: Antonin Delpeuch <antonin@delpeuch.eu>
Date: Sat, 30 Aug 2025 23:21:47 +0200
Subject: [PATCH 1/2] =?UTF-8?q?fix:=C2=A0Panic=20in=20unicode=20boundary?=
 =?UTF-8?q?=20checking=20code?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Since the full length of the string is a valid unicode boundary,
the range of lengths to check needs to end with the "len + 1" excluded
upper bound.
---
 src/std_ext.rs | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/std_ext.rs b/src/std_ext.rs
index 24949c3..41a78c4 100644
--- a/src/std_ext.rs
+++ b/src/std_ext.rs
@@ -34,9 +34,25 @@ impl StrExt for &'_ str {
         if index > len {
             len
         } else {
-            (index..len)
+            (index..(len + 1))
                 .find(|&i| self.is_char_boundary(i))
                 .expect("`i = len` must be a char boundary") // otherwise `self` wouldn't have been a valid `&str` to begin with
         }
     }
 }
+
+#[cfg(test)]
+mod test {
+    use crate::StrExt;
+
+    #[allow(unstable_name_collisions)]
+    #[test]
+    fn char_boundary_at_end() {
+        let string = "❤️🧡💛";
+        assert_eq!(string.ceil_char_boundary(0), 0);
+        assert_eq!(string.ceil_char_boundary(1), 3);
+        assert_eq!(string.ceil_char_boundary(3), 3);
+        assert_eq!(string.ceil_char_boundary(4), 6);
+        assert_eq!(string.ceil_char_boundary(13), string.len());
+    }
+}
-- 
2.47.3


From dfb6c5a2d2e14e6ea1641143da8746a24b2c404f Mon Sep 17 00:00:00 2001
From: Antonin Delpeuch <antonin@delpeuch.eu>
Date: Sun, 31 Aug 2025 09:03:03 +0200
Subject: [PATCH 2/2] Integrate review feedback

---
 src/std_ext.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/std_ext.rs b/src/std_ext.rs
index 41a78c4..8b9c906 100644
--- a/src/std_ext.rs
+++ b/src/std_ext.rs
@@ -34,7 +34,7 @@ impl StrExt for &'_ str {
         if index > len {
             len
         } else {
-            (index..(len + 1))
+            (index..=len)
                 .find(|&i| self.is_char_boundary(i))
                 .expect("`i = len` must be a char boundary") // otherwise `self` wouldn't have been a valid `&str` to begin with
         }
@@ -43,7 +43,7 @@ impl StrExt for &'_ str {
 
 #[cfg(test)]
 mod test {
-    use crate::StrExt;
+    use super::*;
 
     #[allow(unstable_name_collisions)]
     #[test]
-- 
2.47.3