From 24efefafcbddfba5d26330d33f2516ae04aa454f Mon Sep 17 00:00:00 2001
From: Oli Scherer <github333195615777966@oli-obk.de>
Date: Wed, 9 Apr 2025 13:40:00 +0000
Subject: Avoid a reverse map that is only used in diagnostics paths

---
 compiler/rustc_data_structures/src/unord.rs | 10 ++++++++++
 1 file changed, 10 insertions(+)

(limited to 'compiler/rustc_data_structures')

diff --git a/compiler/rustc_data_structures/src/unord.rs b/compiler/rustc_data_structures/src/unord.rs
index baa66cd7c85..3d44fb1fd48 100644
--- a/compiler/rustc_data_structures/src/unord.rs
+++ b/compiler/rustc_data_structures/src/unord.rs
@@ -109,6 +109,16 @@ impl<T, I: Iterator<Item = T>> UnordItems<T, I> {
     pub fn collect<C: From<UnordItems<T, I>>>(self) -> C {
         self.into()
     }
+
+    /// If the iterator has only one element, returns it, otherwise returns `None`.
+    #[track_caller]
+    pub fn get_only(mut self) -> Option<T> {
+        let item = self.0.next();
+        if self.0.next().is_some() {
+            return None;
+        }
+        item
+    }
 }
 
 impl<T> UnordItems<T, std::iter::Empty<T>> {
-- 
cgit 1.4.1-3-g733a5