1 files changed, 1 insertions, 3 deletions
diff --git a/compiler/rustc_builtin_macros/src/format.rs b/compiler/rustc_builtin_macros/src/format.rs
index 6dbd8a7ac01..12654001a1e 100644
--- a/compiler/rustc_builtin_macros/src/format.rs
+++ b/compiler/rustc_builtin_macros/src/format.rs
@@ -711,11 +711,9 @@ fn report_missing_placeholders(
                     };
 
                     let pos = sub.position();
-                    let sub = String::from(sub.as_str());
-                    if explained.contains(&sub) {
+                    if !explained.insert(sub.to_string()) {
                         continue;
                     }
-                    explained.insert(sub);
 
                     if !found_foreign {
                         found_foreign = true;