From 4c523f861b66cf038025cd7a7a2de7a164a92c6f Mon Sep 17 00:00:00 2001
From: Eric Arndt <erarndt@microsoft.com>
Date: Tue, 23 Sep 2025 16:45:48 -0700
Subject: [PATCH] Check for ICollection<T>in GetEnumerator()

---
 src/Build/Collections/CopyOnReadEnumerable.cs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Build/Collections/CopyOnReadEnumerable.cs b/src/Build/Collections/CopyOnReadEnumerable.cs
index 72da4089325..ed425af9171 100644
--- a/src/Build/Collections/CopyOnReadEnumerable.cs
+++ b/src/Build/Collections/CopyOnReadEnumerable.cs
@@ -72,6 +72,10 @@ public IEnumerator<TResult> GetEnumerator()
 #endif
                 list = new List<TResult>(count);
             }
+            else if (_backingEnumerable is ICollection<TSource> collection)
+            {
+                list = new List<TResult>(collection.Count);
+            }
             else if (_backingEnumerable is IReadOnlyCollection<TSource> readOnlyCollection)
             {
                 list = new List<TResult>(readOnlyCollection.Count);