From 5c33c3e308a4fb6d93352115ec00e99d1920eff7 Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 21 Jun 2019 12:08:26 -0400
Subject: [PATCH] Stop calling format! to check feature gate

---
 src/tools/tidy/src/features.rs | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/tools/tidy/src/features.rs b/src/tools/tidy/src/features.rs
index ced30eb6d58a..da1387942976 100644
--- a/src/tools/tidy/src/features.rs
+++ b/src/tools/tidy/src/features.rs
@@ -186,9 +186,11 @@ fn test_find_attr_val() {
 }
 
 fn test_filen_gate(filen_underscore: &str, features: &mut Features) -> bool {
-    if filen_underscore.starts_with("feature_gate") {
+    let prefix = "feature_gate_";
+    if filen_underscore.starts_with(prefix) {
         for (n, f) in features.iter_mut() {
-            if filen_underscore == format!("feature_gate_{}", n) {
+            // Equivalent to filen_underscore == format!("feature_gate_{}", n)
+            if &filen_underscore[prefix.len()..] == n {
                 f.has_gate_test = true;
                 return true;
             }