From 19f04a7d6878fc4c258ba3d4374e81c8bbeca2e0 Mon Sep 17 00:00:00 2001
From: Chris Denton <chris@chrisdenton.dev>
Date: Mon, 8 Apr 2024 11:42:16 +0000
Subject: [PATCH] Add comment on UTF-16 surrogates

---
 library/std/src/sys/pal/windows/api.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/library/std/src/sys/pal/windows/api.rs b/library/std/src/sys/pal/windows/api.rs
index 8613dba42d2dc..555ad581b8568 100644
--- a/library/std/src/sys/pal/windows/api.rs
+++ b/library/std/src/sys/pal/windows/api.rs
@@ -68,6 +68,8 @@ pub const fn utf16_len(s: &str) -> usize {
             n => n as usize,
         };
         i += utf8_len;
+        // Note that UTF-16 surrogates (U+D800 to U+DFFF) are not encodable as UTF-8,
+        // so (unlike with WTF-8) we don't have to worry about how they'll get re-encoded.
         len += if utf8_len < 4 { 1 } else { 2 };
     }
     len