Better detect equivalence in our strong name provider

src/Compilers/CSharp/Test/Emit/Emit/DesktopStrongNameProviderTests.cs

@@ -31,6 +31,56 @@ public void RespectNullTempPath()
             Assert.Null(provider.FileSystem.GetSigningTempPath());
         }
 
+        [Fact]
+        public void EqualityUsingPath()
+        {
+            var tempDir = Temp.CreateDirectory();
+            var provider1 = new DesktopStrongNameProvider(tempPath: tempDir.Path);
+            var provider2 = new DesktopStrongNameProvider(tempPath: tempDir.Path);
+
+            Assert.Equal(provider1, provider2);
+        }
+
+        [Fact]
+        public void EqualityUsingKeyFileSearchPaths()
+        {
+            var tempDir = Temp.CreateDirectory();
+            var provider1 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path]);
+            var provider2 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path]);
+
+            Assert.Equal(provider1, provider2);
+        }
+
+        [Fact]
+        public void InequalityUsingPath()
+        {
+            var tempDir = Temp.CreateDirectory();
+            var provider1 = new DesktopStrongNameProvider(tempPath: tempDir.Path);
+            var provider2 = new DesktopStrongNameProvider(tempPath: tempDir.Path + "2");
+
+            Assert.NotEqual(provider1, provider2);
+        }
+
+        [Fact]
+        public void InequalityUsingKeyFileSearchPaths()
+        {
+            var tempDir = Temp.CreateDirectory();
+            var provider1 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path]);
+            var provider2 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path + "2"]);
+
+            Assert.NotEqual(provider1, provider2);
+        }
+
+        [Fact]
+        public void InequalityUsingKeyFileSearchPathsDueToCaseSensitivity()
+        {
+            var tempDir = Temp.CreateDirectory();
+            var provider1 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path]);
+            var provider2 = new DesktopStrongNameProvider(keyFileSearchPaths: [tempDir.Path.ToUpper()]);
+
+            Assert.NotEqual(provider1, provider2);
+        }
+
         [Fact]
         public void EmitWithCustomTempPath()
         {

src/Compilers/Core/Portable/StrongName/DesktopStrongNameProvider.cs

@@ -275,7 +275,7 @@ public override bool Equals(object? obj)
             }
 
             var other = (DesktopStrongNameProvider)obj;
-            if (FileSystem != other.FileSystem)
+            if (!FileSystem.Equals(other.FileSystem))
             {
                 return false;
             }

src/Compilers/Core/Portable/StrongName/StrongNameFileSystem.cs

@@ -41,5 +41,19 @@ internal virtual bool FileExists(string? fullPath)
         }
 
         internal string? GetSigningTempPath() => _signingTempPath;
+
+        public override int GetHashCode()
+            => _signingTempPath != null ? StringComparer.Ordinal.GetHashCode(_signingTempPath) : 0;
+
+        public override bool Equals(object? obj)
+            => Equals(obj as StrongNameFileSystem);
+
+        private bool Equals(StrongNameFileSystem? other)
+        {
+            if (this == other)
+                return true;
+
+            return this.GetType() == other?.GetType() && StringComparer.Ordinal.Equals(_signingTempPath, other?._signingTempPath);
+        }
     }
 }