Optimizations on System.Linq.Enumerable.ToArray

src/libraries/Common/src/System/Collections/Generic/EnumerableHelpers.Linq.SizeOpt.cs

@@ -0,0 +1,40 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Linq;
+
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Internal helper functions for working with enumerables.
+    /// </summary>
+    internal static partial class EnumerableHelpers
+    {
+        /// <summary>Converts an enumerable to an array.</summary>
+        /// <param name="source">The enumerable to convert.</param>
+        /// <returns>The resulting array.</returns>
+        internal static T[] ToArray<T>(IEnumerable<T> source)
+        {
+            Debug.Assert(source != null);
+
+            if (source is ICollection<T> collection)
+            {
+                int count = collection.Count;
+                if (count == 0)
+                {
+                    return Array.Empty<T>();
+                }
+
+                var result = new T[count];
+                collection.CopyTo(result, arrayIndex: 0);
+                return result;
+            }
+
+            var builder = new LargeArrayBuilder<T>(initialize: true);
+            builder.AddRange(source);
+            return builder.ToArray();
+        }
+    }
+}

src/libraries/Common/src/System/Collections/Generic/EnumerableHelpers.Linq.SpeedOpt.cs

@@ -0,0 +1,20 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Diagnostics;
+using System.Linq;
+
+namespace System.Collections.Generic
+{
+    /// <summary>
+    /// Internal helper functions for working with enumerables.
+    /// </summary>
+    internal static partial class EnumerableHelpers
+    {
+        /// <summary>Converts an enumerable to an array.</summary>
+        /// <param name="source">The enumerable to convert.</param>
+        /// <returns>The resulting array.</returns>
+        internal static T[] ToArray<T>(IEnumerable<T> source) => ToArrayEnumerable<T>.Instance.ToArray(source);
+    }
+}

src/libraries/Common/src/System/Collections/Generic/EnumerableHelpers.Linq.cs

@@ -86,30 +86,5 @@ internal static void IterativeCopy<T>(IEnumerable<T> source, T[] array, int arra
 
             Debug.Assert(arrayIndex == endIndex);
         }
-
-        /// <summary>Converts an enumerable to an array.</summary>
-        /// <param name="source">The enumerable to convert.</param>
-        /// <returns>The resulting array.</returns>
-        internal static T[] ToArray<T>(IEnumerable<T> source)
-        {
-            Debug.Assert(source != null);
-
-            if (source is ICollection<T> collection)
-            {
-                int count = collection.Count;
-                if (count == 0)
-                {
-                    return Array.Empty<T>();
-                }
-
-                var result = new T[count];
-                collection.CopyTo(result, arrayIndex: 0);
-                return result;
-            }
-
-            var builder = new LargeArrayBuilder<T>(initialize: true);
-            builder.AddRange(source);
-            return builder.ToArray();
-        }
     }
 }