From c5b3cb5522a47d9d8766d04cdbf2c6b625b5dbe3 Mon Sep 17 00:00:00 2001
From: Thalia Archibald <thalia@archibald.dev>
Date: Fri, 7 Feb 2025 11:54:02 -0800
Subject: [PATCH] Skip scanning for surrogates when not known valid

---
 library/std/src/sys_common/wtf8.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs
index 21151aad9dc7a..fb16c90350b30 100644
--- a/library/std/src/sys_common/wtf8.rs
+++ b/library/std/src/sys_common/wtf8.rs
@@ -383,7 +383,7 @@ impl Wtf8Buf {
             _ => {
                 // If we'll be pushing a string containing a surrogate, we may
                 // no longer have UTF-8.
-                if other.next_surrogate(0).is_some() {
+                if self.is_known_utf8 && other.next_surrogate(0).is_some() {
                     self.is_known_utf8 = false;
                 }