From 04602a24a38033c6ef20fe0ecb53316b808542ce Mon Sep 17 00:00:00 2001
From: Arpad Borsos <arpad.borsos@sentry.io>
Date: Thu, 15 Feb 2024 17:36:21 +0100
Subject: [PATCH] Add a fast-path to `Debug` ASCII `&str`
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Instead of going through the `EscapeDebug` machinery, we can just skip over ASCII chars that don’t need any escaping.
---
 library/core/src/fmt/mod.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/library/core/src/fmt/mod.rs b/library/core/src/fmt/mod.rs
index e1b7b46a1ed2f..f625c9f565d7f 100644
--- a/library/core/src/fmt/mod.rs
+++ b/library/core/src/fmt/mod.rs
@@ -2340,6 +2340,11 @@ impl Debug for str {
         f.write_char('"')?;
         let mut from = 0;
         for (i, c) in self.char_indices() {
+            // a fast path for ASCII chars that do not need escapes:
+            if matches!(c, ' '..='~') && !matches!(c, '\\' | '\"') {
+                continue;
+            }
+
             let esc = c.escape_debug_ext(EscapeDebugExtArgs {
                 escape_grapheme_extended: true,
                 escape_single_quote: false,