From 511280aa2ea37844e8ea6f9cfd9b192e0feae6f1 Mon Sep 17 00:00:00 2001
From: Josh Stone <cuviper@gmail.com>
Date: Thu, 19 May 2022 15:38:42 -0700
Subject: [PATCH] Add an MSRV note for retain_mut

(cherry picked from commit 6b425e4e216634a0475ada0e17a56fa7c050d63f)
---
 src/map/core.rs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/map/core.rs b/src/map/core.rs
index 0bc54621..b74e6f35 100644
--- a/src/map/core.rs
+++ b/src/map/core.rs
@@ -399,6 +399,7 @@ impl<K, V> IndexMapCore<K, V> {
     where
         F: FnMut(&mut K, &mut V) -> bool,
     {
+        // FIXME: This could use Vec::retain_mut with MSRV 1.61.
         // Like Vec::retain in self.entries, but with mutable K and V.
         // We swap-shift all the items we want to keep, truncate the rest,
         // then rebuild the raw hash table with the new indexes.