Remove Common Extensions HashCodeCombiner

src/libraries/Microsoft.Extensions.FileSystemGlobbing/src/FilePatternMatch.cs

@@ -2,7 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
-using Microsoft.Extensions.Internal;
+using System.Numerics.Hashing;
 
 namespace Microsoft.Extensions.FileSystemGlobbing
 {
@@ -66,13 +66,10 @@ public override bool Equals(object obj)
         /// Gets a hash for the file pattern match.
         /// </summary>
         /// <returns>Some number</returns>
-        public override int GetHashCode()
-        {
-            var hashCodeCombiner = HashCodeCombiner.Start();
-            hashCodeCombiner.Add(Path, StringComparer.OrdinalIgnoreCase);
-            hashCodeCombiner.Add(Stem, StringComparer.OrdinalIgnoreCase);
+        public override int GetHashCode() =>
+            HashHelpers.Combine(GetHashCode(Path), GetHashCode(Stem));
 
-            return hashCodeCombiner;
-        }
+        private static int GetHashCode(string value) =>
+            value != null ? StringComparer.OrdinalIgnoreCase.GetHashCode(value) : 0;
     }
 }

src/libraries/Microsoft.Extensions.FileSystemGlobbing/src/Microsoft.Extensions.FileSystemGlobbing.csproj

@@ -6,8 +6,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="$(CommonPath)Extensions\HashCodeCombiner\HashCodeCombiner.cs"
-             Link="Common\src\Extensions\HashCodeCombiner\HashCodeCombiner.cs" />
+    <Compile Include="$(CoreLibSharedDir)\System\Numerics\Hashing\HashHelpers.cs"
+             Link="System\Numerics\Hashing\HashHelpers.cs" />
   </ItemGroup>
 
 </Project>

src/libraries/Microsoft.Extensions.FileSystemGlobbing/tests/FilePatternMatchTests.cs

@@ -0,0 +1,41 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Xunit;
+
+namespace Microsoft.Extensions.FileSystemGlobbing.Tests
+{
+    public class FilePatternMatchTests
+    {
+        [Fact]
+        public void TestGetHashCode()
+        {
+            FilePatternMatch match1 = new FilePatternMatch("sub/sub2/bar/baz/three.txt", "sub2/bar/baz/three.txt");
+            FilePatternMatch match2 = new FilePatternMatch("sub/sub2/bar/baz/three.txt", "sub2/bar/baz/three.txt");
+            FilePatternMatch match3 = new FilePatternMatch("sub/sub2/bar/baz/one.txt", "sub2/bar/baz/three.txt");
+            FilePatternMatch match4 = new FilePatternMatch("sub/sub2/bar/baz/three.txt", "sub2/bar/baz/one.txt");
+
+            Assert.Equal(match1.GetHashCode(), match2.GetHashCode());
+            Assert.NotEqual(match1.GetHashCode(), match3.GetHashCode());
+            Assert.NotEqual(match1.GetHashCode(), match4.GetHashCode());
+
+            // FilePatternMatch is case insensitive
+            FilePatternMatch matchCase1 = new FilePatternMatch("Sub/Sub2/bar/baz/three.txt", "sub2/bar/baz/three.txt");
+            FilePatternMatch matchCase2 = new FilePatternMatch("sub/sub2/bar/baz/three.txt", "Sub2/bar/baz/thrEE.txt");
+            Assert.Equal(matchCase1.GetHashCode(), matchCase2.GetHashCode());
+        }
+
+        [Fact]
+        public void TestGetHashCodeWithNull()
+        {
+            FilePatternMatch match = new FilePatternMatch(null, null);
+            Assert.Equal(0, match.GetHashCode());
+
+            int hash1 = new FilePatternMatch("non null", null).GetHashCode();
+            int hash2 = new FilePatternMatch(null, "non null").GetHashCode();
+            Assert.NotEqual(0, hash1);
+            Assert.NotEqual(0, hash2);
+            Assert.NotEqual(hash1, hash2);
+        }
+    }
+}

src/libraries/Microsoft.Extensions.Primitives/src/Microsoft.Extensions.Primitives.csproj

@@ -9,8 +9,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <Compile Include="$(CommonPath)Extensions\HashCodeCombiner\HashCodeCombiner.cs"
-             Link="Common\src\Extensions\HashCodeCombiner\HashCodeCombiner.cs" />
+    <Compile Include="$(CoreLibSharedDir)\System\Numerics\Hashing\HashHelpers.cs"
+             Link="System\Numerics\Hashing\HashHelpers.cs" />
     <Compile Condition="'$(TargetFramework)' == 'netstandard2.0' or
                         $(TargetFramework.StartsWith('net4'))"
              Include="$(CommonPath)System\Text\ValueStringBuilder.cs"

src/libraries/Microsoft.Extensions.Primitives/src/StringValues.cs

@@ -5,9 +5,9 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Numerics.Hashing;
 using System.Runtime.CompilerServices;
 using System.Text;
-using Microsoft.Extensions.Internal;
 
 namespace Microsoft.Extensions.Primitives
 {
@@ -740,12 +740,12 @@ public override int GetHashCode()
                 {
                     return Unsafe.As<string>(this[0])?.GetHashCode() ?? Count.GetHashCode();
                 }
-                var hcc = default(HashCodeCombiner);
+                int hashCode = 0;
                 for (int i = 0; i < values.Length; i++)
                 {
-                    hcc.Add(values[i]);
+                    hashCode = HashHelpers.Combine(hashCode, values[i]?.GetHashCode() ?? 0);
                 }
-                return hcc.CombinedHash;
+                return hashCode;
             }
             else
             {