Title: Fix nullable reference type build errors

FolderDiffIL4DotNet.Benchmarks/FolderDiffBenchmarks.cs

@@ -58,8 +58,7 @@
         {
             var files = Directory.GetFiles(_smallDirPath).Take(2).ToArray();
             if (files.Length < 2) return false;
-            var comparer = new FileComparer();
-            return comparer.ComputeMd5Hash(files[0]) == comparer.ComputeMd5Hash(files[1]);
+            return FileComparer.ComputeFileMd5Hex(files[0]) == FileComparer.ComputeFileMd5Hex(files[1]);
         }
 
         private static string CreateTempFolderWithFiles(string prefix, int fileCount, int fileSizeBytes)
@@ -81,7 +80,7 @@
 
         private static void TryDeleteDir(string path)
         {
             try { if (Directory.Exists(path)) Directory.Delete(path, true); } catch { }
         }
     }
 }

FolderDiffIL4DotNet.Core/IO/FileSystemUtility.cs

@@ -284,7 +284,7 @@ private static bool IsLikelyWindowsNetworkPath(string absolutePath)
                 return true;
             }
 
-            string root = TryGetPathRoot(absolutePath);
+            string? root = TryGetPathRoot(absolutePath);
             return !string.IsNullOrEmpty(root) && IsNetworkDrive(root);
         }
 
@@ -325,13 +325,13 @@ private static bool IsLikelyMacNetworkPath(string absolutePath)
 
         private static bool IsLikelyUnixNetworkPath(string absolutePath)
         {
-            string mountsFile = GetUnixMountsFilePath();
+            string? mountsFile = GetUnixMountsFilePath();
             if (mountsFile == null)
             {
                 return false;
             }
 
-            string fullPath = TryGetFullPath(absolutePath);
+            string? fullPath = TryGetFullPath(absolutePath);
             if (fullPath == null)
             {
                 return false;
@@ -343,7 +343,7 @@ private static bool IsLikelyUnixNetworkPath(string absolutePath)
                 return false;
             }
 
-            string bestFsType = GetBestMatchingMountFileSystemType(fullPath, mountLines);
+            string? bestFsType = GetBestMatchingMountFileSystemType(fullPath, mountLines);
             return !string.IsNullOrEmpty(bestFsType) && s_unixNetworkFsTypes.Contains(bestFsType);
         }
 

FolderDiffIL4DotNet.Tests/Services/FileDiffServiceUnitTests.cs

@@ -468,7 +468,7 @@
 
         private sealed class FakeILOutputService : IILOutputService
         {
-            public (bool AreEqual, string DisassemblerLabel) DiffResult { get; set; }
+            public (bool AreEqual, string? DisassemblerLabel) DiffResult { get; set; }
 
             public Exception DiffException { get; set; }
 
@@ -482,7 +482,7 @@
                 return Task.CompletedTask;
             }
 
-            public Task<(bool AreEqual, string DisassemblerLabel)> DiffDotNetAssembliesAsync(string fileRelativePath, string oldFolderAbsolutePath, string newFolderAbsolutePath, bool shouldOutputIlText)
+            public Task<(bool AreEqual, string? DisassemblerLabel)> DiffDotNetAssembliesAsync(string fileRelativePath, string oldFolderAbsolutePath, string newFolderAbsolutePath, bool shouldOutputIlText)
             {
                 DiffCalls.Add(new DiffCall(fileRelativePath, oldFolderAbsolutePath, newFolderAbsolutePath, shouldOutputIlText));
                 if (DiffException != null)

FolderDiffIL4DotNet.csproj

@@ -3,7 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
-    <DefaultItemExcludes>$(DefaultItemExcludes);FolderDiffIL4DotNet.Tests/**;FolderDiffIL4DotNet.Core/**</DefaultItemExcludes>
+    <DefaultItemExcludes>$(DefaultItemExcludes);FolderDiffIL4DotNet.Tests/**;FolderDiffIL4DotNet.Core/**;FolderDiffIL4DotNet.Benchmarks/**</DefaultItemExcludes>
     <GenerateDocumentationFile>true</GenerateDocumentationFile>
     <EnableNETAnalyzers>true</EnableNETAnalyzers>
     <Nullable>enable</Nullable>

Models/FileDiffResultLists.cs

@@ -212,7 +212,7 @@ public void RecordIgnoredFile(string fileRelativePath, IgnoredFileLocation locat
         /// Records the disassembler tool name and version used.
         /// 使用した逆アセンブラ名とバージョンを記録します。
         /// </summary>
-        public void RecordDisassemblerToolVersion(string toolName, string version, bool fromCache = false)
+        public void RecordDisassemblerToolVersion(string toolName, string? version, bool fromCache = false)
         {
             if (string.IsNullOrWhiteSpace(toolName))
             {

ProgramRunner.cs

@@ -123,33 +123,33 @@ private async Task<ProgramRunResult> RunWithResultAsync(string[] args, CliOption
                 var runArgumentsResult = TryValidateAndBuildRunArguments(args, opts);
                 if (!runArgumentsResult.IsSuccess)
                 {
-                    return runArgumentsResult.Failure;
+                    return runArgumentsResult.Failure!;
                 }
 
-                var runArguments = runArgumentsResult.Value;
+                var runArguments = runArgumentsResult.Value!;
                 var prepareReportsDirectoryResult = TryPrepareReportsDirectory(runArguments.ReportsFolderAbsolutePath);
                 if (!prepareReportsDirectoryResult.IsSuccess)
                 {
-                    return prepareReportsDirectoryResult.Failure;
+                    return prepareReportsDirectoryResult.Failure!;
                 }
 
                 var configResult = await TryLoadConfigurationAsync(opts.ConfigPath);
                 if (!configResult.IsSuccess)
                 {
-                    return configResult.Failure;
+                    return configResult.Failure!;
                 }
 
-                var config = configResult.Value;
+                var config = configResult.Value!;
                 ApplyCliOverrides(config, opts);
 
                 var completionStateResult = await TryExecuteRunAsync(runArguments, config, appVersion, computerName);
                 if (!completionStateResult.IsSuccess)
                 {
-                    return completionStateResult.Failure;
+                    return completionStateResult.Failure!;
                 }
 
                 _logger.LogMessage(AppLogLevel.Info, LOG_APP_FINISHED, shouldOutputMessageToConsole: true, ConsoleColor.Green);
-                return ProgramRunResult.Success(completionStateResult.Value);
+                return ProgramRunResult.Success(completionStateResult.Value!);
             }
             catch (Exception ex)
             {
@@ -274,7 +274,7 @@ private StepResult<bool> TryPrepareReportsDirectory(string reportsFolderAbsolute
         /// Returns the configuration loading phase as a typed result.
         /// 設定読込フェーズを型付き結果として返します。
         /// </summary>
-        private async Task<StepResult<ConfigSettings>> TryLoadConfigurationAsync(string configPath)
+        private async Task<StepResult<ConfigSettings>> TryLoadConfigurationAsync(string? configPath)
         {
             try
             {
@@ -373,7 +373,7 @@ private static void PrepareReportsDirectory(string reportsFolderAbsolutePath)
             Directory.CreateDirectory(reportsFolderAbsolutePath);
         }
 
-        private async Task<ConfigSettings> LoadConfigurationAsync(string configPath)
+        private async Task<ConfigSettings> LoadConfigurationAsync(string? configPath)
         {
             _logger.LogMessage(AppLogLevel.Info, LOG_LOADING_CONFIGURATION, shouldOutputMessageToConsole: true);
             var config = await _configService.LoadConfigAsync(configPath);
@@ -472,7 +472,7 @@ private static bool ShouldSkipExitPrompt(CliOptions opts)
                 || Console.IsOutputRedirected
                 || Console.IsErrorRedirected;
 
-        private static ILCache CreateIlCache(ConfigSettings config, ILoggerService logger)
+        private static ILCache? CreateIlCache(ConfigSettings config, ILoggerService logger)
         {
             return RunScopeBuilder.CreateIlCache(config, logger);
         }
@@ -496,7 +496,7 @@ internal static string FormatElapsedTime(TimeSpan elapsed)
         /// Prints the effective configuration (after JSON load + environment variable overrides) to stdout as JSON.
         /// 有効な設定（JSON 読込 + 環境変数オーバーライド適用後）を JSON として標準出力に書き出します。
         /// </summary>
-        private async Task<int> PrintConfigAsync(string configPath)
+        private async Task<int> PrintConfigAsync(string? configPath)
         {
             try
             {

Runner/RunScopeBuilder.cs

@@ -51,7 +51,7 @@ internal static ServiceProvider Build(ConfigSettings config, DiffExecutionContex
             services.AddSingleton(executionContext);
             services.AddScoped<FileDiffResultLists>();
             services.AddScoped<DotNetDisassemblerCache>();
-            services.AddScoped<ILCache>(sp => CreateIlCache(config, sp.GetRequiredService<ILoggerService>()));
+            services.AddScoped<ILCache>(sp => CreateIlCache(config, sp.GetRequiredService<ILoggerService>())!);
             services.AddScoped<ProgressReportService>();
             services.AddScoped<ReportGenerateService>();
             services.AddScoped<HtmlReportGenerateService>();

Services/Caching/DotNetDisassemblerCache.cs

@@ -54,9 +54,9 @@ public async Task<string> GetDisassemblerVersionAsync(string disassembleCommandW
             var (disassemblerKind, disassemblerVersionCacheKey, disassemblerExe) = GetDisassemblerInfo(disassembleCommandWithArguments);
             return disassemblerKind switch
             {
-                DisassemblerKind.DotnetIldasm => await GetVersionForDotnetIldasmAsync(disassemblerVersionCacheKey, disassemblerExe),
-                DisassemblerKind.Ildasm => await GetVersionForIldasmAsync(disassemblerVersionCacheKey, disassemblerExe),
-                DisassemblerKind.Ilspy => await GetVersionForIlspyAsync(disassemblerVersionCacheKey, disassemblerExe),
+                DisassemblerKind.DotnetIldasm => await GetVersionForDotnetIldasmAsync(disassemblerVersionCacheKey!, disassemblerExe!),
+                DisassemblerKind.Ildasm => await GetVersionForIldasmAsync(disassemblerVersionCacheKey!, disassemblerExe!),
+                DisassemblerKind.Ilspy => await GetVersionForIlspyAsync(disassemblerVersionCacheKey!, disassemblerExe!),
                 _ => throw new InvalidOperationException($"Failed to determine disassembler version for label: '{disassembleCommandWithArguments}'.")
             };
         }
@@ -65,7 +65,7 @@ public async Task<string> GetDisassemblerVersionAsync(string disassembleCommandW
         /// Extracts the disassembler kind, cache key, and executable from a command label.
         /// コマンドラベルから逆アセンブラ種別・キャッシュキー・実行ファイル名を抽出します。
         /// </summary>
-        private static (DisassemblerKind disassemblerKind, string disassemblerVersionCacheKey, string disassemblerExe) GetDisassemblerInfo(string disassembleCommandWithArguments)
+        private static (DisassemblerKind disassemblerKind, string? disassemblerVersionCacheKey, string? disassemblerExe) GetDisassemblerInfo(string disassembleCommandWithArguments)
         {
             var tokens = ProcessHelper.TokenizeCommand(disassembleCommandWithArguments);
             if (tokens.Count == 0)

Services/ConfigService.cs

@@ -26,7 +26,7 @@ public sealed class ConfigService
         /// config.json を指定パス（または既定のアプリケーションベースディレクトリ）から非同期で読み込み、
         /// <see cref="ConfigSettings"/> にデシリアライズした後、設定値の整合性を検証します。
         /// </summary>
-        public async Task<ConfigSettings> LoadConfigAsync(string configFilePath = null)
+        public async Task<ConfigSettings> LoadConfigAsync(string? configFilePath = null)
         {
             try
             {