Merge pull request #75352 from CyrusNajmabadi/makeSealed2

Make the types in CSharp Features sealed

src/Analyzers/CSharp/Analyzers/RemoveUnnecessaryNullableDirective/CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer.cs

@@ -257,7 +257,7 @@ internal void MarkComplete()
         }
     }
 
-    private class AnalyzerImpl(CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer analyzer)
+    private sealed class AnalyzerImpl(CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer analyzer)
     {
         private readonly CSharpRemoveUnnecessaryNullableDirectiveDiagnosticAnalyzer _analyzer = analyzer;
 

src/Analyzers/CSharp/Analyzers/UseIndexOrRangeOperator/CSharpUseIndexOperatorDiagnosticAnalyzer.InfoCache.cs

@@ -12,12 +12,12 @@ namespace Microsoft.CodeAnalysis.CSharp.UseIndexOrRangeOperator;
 
 using static Helpers;
 
-internal partial class CSharpUseIndexOperatorDiagnosticAnalyzer
+internal sealed partial class CSharpUseIndexOperatorDiagnosticAnalyzer
 {
     /// <summary>
     /// Helper type to cache information about types while analyzing the compilation.
     /// </summary>
-    private class InfoCache
+    private sealed class InfoCache
     {
         /// <summary>
         /// The <see cref="T:System.Index"/> type.  Needed so that we only fixup code if we see the type

src/Analyzers/CSharp/Analyzers/UseIndexOrRangeOperator/CSharpUseRangeOperatorDiagnosticAnalyzer.InfoCache.cs

@@ -13,7 +13,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseIndexOrRangeOperator;
 
 using static Helpers;
 
-internal partial class CSharpUseRangeOperatorDiagnosticAnalyzer
+internal sealed partial class CSharpUseRangeOperatorDiagnosticAnalyzer
 {
     /// <summary>
     /// Helper type to cache information about types while analyzing the compilation.

src/Analyzers/CSharp/Analyzers/UseIndexOrRangeOperator/CSharpUseRangeOperatorDiagnosticAnalyzer.Result.cs

@@ -8,7 +8,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.UseIndexOrRangeOperator;
 
-internal partial class CSharpUseRangeOperatorDiagnosticAnalyzer
+internal sealed partial class CSharpUseRangeOperatorDiagnosticAnalyzer
 {
     public enum ResultKind
     {

src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndMemberAccessDiagnosticAnalyzer.cs

@@ -23,7 +23,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UsePatternMatching;
 /// </code>
 /// </summary>
 [DiagnosticAnalyzer(LanguageNames.CSharp)]
-internal partial class CSharpAsAndMemberAccessDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
+internal sealed partial class CSharpAsAndMemberAccessDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
 {
     public CSharpAsAndMemberAccessDiagnosticAnalyzer()
         : base(IDEDiagnosticIds.UsePatternMatchingAsAndMemberAccessDiagnosticId,

src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.Analyzer.cs

@@ -11,7 +11,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.UsePatternMatching;
 
-internal partial class CSharpAsAndNullCheckDiagnosticAnalyzer
+internal sealed partial class CSharpAsAndNullCheckDiagnosticAnalyzer
 {
     private readonly struct Analyzer
     {

src/Analyzers/CSharp/Analyzers/UsePatternMatching/CSharpAsAndNullCheckDiagnosticAnalyzer.cs

@@ -27,7 +27,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UsePatternMatching;
 /// </code>
 /// </summary>
 [DiagnosticAnalyzer(LanguageNames.CSharp)]
-internal partial class CSharpAsAndNullCheckDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
+internal sealed partial class CSharpAsAndNullCheckDiagnosticAnalyzer : AbstractBuiltInCodeStyleDiagnosticAnalyzer
 {
     public CSharpAsAndNullCheckDiagnosticAnalyzer()
         : base(IDEDiagnosticIds.InlineAsTypeCheckId,

src/Analyzers/CSharp/CodeFixes/AddExplicitCast/ArgumentFixer.cs

@@ -12,7 +12,7 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeFixes.AddExplicitCast;
 
 internal sealed partial class CSharpAddExplicitCastCodeFixProvider
 {
-    private class ArgumentFixer : Fixer<ArgumentSyntax, ArgumentListSyntax, SyntaxNode>
+    private sealed class ArgumentFixer : Fixer<ArgumentSyntax, ArgumentListSyntax, SyntaxNode>
     {
         protected override ExpressionSyntax GetExpressionOfArgument(ArgumentSyntax argument)
             => argument.Expression;

src/Analyzers/CSharp/CodeFixes/AddExplicitCast/AttributeArgumentFixer.cs

@@ -12,7 +12,7 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeFixes.AddExplicitCast;
 
 internal sealed partial class CSharpAddExplicitCastCodeFixProvider
 {
-    private class AttributeArgumentFixer : Fixer<AttributeArgumentSyntax, AttributeArgumentListSyntax, AttributeSyntax>
+    private sealed class AttributeArgumentFixer : Fixer<AttributeArgumentSyntax, AttributeArgumentListSyntax, AttributeSyntax>
     {
         protected override ExpressionSyntax GetExpressionOfArgument(AttributeArgumentSyntax argument)
             => argument.Expression;

src/Analyzers/CSharp/CodeFixes/HideBase/HideBaseCodeFixProvider.AddNewKeywordAction.cs

@@ -18,9 +18,9 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeFixes.HideBase;
 
 using static CSharpSyntaxTokens;
 
-internal partial class HideBaseCodeFixProvider
+internal sealed partial class HideBaseCodeFixProvider
 {
-    private class AddNewKeywordAction(Document document, SyntaxNode node) : CodeAction
+    private sealed class AddNewKeywordAction(Document document, SyntaxNode node) : CodeAction
     {
         private readonly Document _document = document;
         private readonly SyntaxNode _node = node;

src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForArrayCodeFixProvider.cs

@@ -25,7 +25,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionExpression;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionExpressionForArray), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUseCollectionExpressionForArrayCodeFixProvider()
+internal sealed partial class CSharpUseCollectionExpressionForArrayCodeFixProvider()
     : AbstractUseCollectionExpressionCodeFixProvider<ExpressionSyntax>(
         CSharpCodeFixesResources.Use_collection_expression,
         IDEDiagnosticIds.UseCollectionExpressionForArrayDiagnosticId)

src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForBuilderCodeFixProvider.cs

@@ -27,7 +27,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionExpression;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionExpressionForBuilder), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUseCollectionExpressionForBuilderCodeFixProvider()
+internal sealed partial class CSharpUseCollectionExpressionForBuilderCodeFixProvider()
     : AbstractUseCollectionExpressionCodeFixProvider<InvocationExpressionSyntax>(
         CSharpCodeFixesResources.Use_collection_expression,
         IDEDiagnosticIds.UseCollectionExpressionForBuilderDiagnosticId)

src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForCreateCodeFixProvider.cs

@@ -25,7 +25,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionExpression;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionExpressionForCreate), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUseCollectionExpressionForCreateCodeFixProvider()
+internal sealed partial class CSharpUseCollectionExpressionForCreateCodeFixProvider()
     : AbstractUseCollectionExpressionCodeFixProvider<InvocationExpressionSyntax>(
         CSharpCodeFixesResources.Use_collection_expression,
         IDEDiagnosticIds.UseCollectionExpressionForCreateDiagnosticId)

src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForFluentCodeFixProvider.cs

@@ -34,7 +34,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionExpression;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionExpressionForFluent), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUseCollectionExpressionForFluentCodeFixProvider()
+internal sealed partial class CSharpUseCollectionExpressionForFluentCodeFixProvider()
     : AbstractUseCollectionExpressionCodeFixProvider<InvocationExpressionSyntax>(
         CSharpCodeFixesResources.Use_collection_expression,
         IDEDiagnosticIds.UseCollectionExpressionForFluentDiagnosticId)

src/Analyzers/CSharp/CodeFixes/UseCollectionExpression/CSharpUseCollectionExpressionForStackAllocCodeFixProvider.cs

@@ -21,7 +21,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionExpression;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionExpressionForStackAlloc), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUseCollectionExpressionForStackAllocCodeFixProvider()
+internal sealed partial class CSharpUseCollectionExpressionForStackAllocCodeFixProvider()
     : AbstractUseCollectionExpressionCodeFixProvider<ExpressionSyntax>(
         CSharpCodeFixesResources.Use_collection_expression,
         IDEDiagnosticIds.UseCollectionExpressionForStackAllocDiagnosticId)

src/Analyzers/CSharp/CodeFixes/UseCollectionInitializer/CSharpUseCollectionInitializerCodeFixProvider.cs

@@ -17,7 +17,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionInitializer;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseCollectionInitializer), Shared]
 [method: ImportingConstructor]
 [method: SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]
-internal partial class CSharpUseCollectionInitializerCodeFixProvider() :
+internal sealed partial class CSharpUseCollectionInitializerCodeFixProvider() :
     AbstractUseCollectionInitializerCodeFixProvider<
         SyntaxKind,
         ExpressionSyntax,

src/Analyzers/CSharp/CodeFixes/UseCollectionInitializer/CSharpUseCollectionInitializerCodeFixProvider_CollectionExpression.cs

@@ -12,7 +12,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.UseCollectionInitializer;
 
-internal partial class CSharpUseCollectionInitializerCodeFixProvider
+internal sealed partial class CSharpUseCollectionInitializerCodeFixProvider
 {
     /// <summary>
     /// Creates the final collection-expression <c>[...]</c> that will replace the given <paramref

src/Analyzers/CSharp/CodeFixes/UseCollectionInitializer/CSharpUseCollectionInitializerCodeFixProvider_CollectionInitializer.cs

@@ -20,7 +20,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UseCollectionInitializer;
 using static CSharpSyntaxTokens;
 using static SyntaxFactory;
 
-internal partial class CSharpUseCollectionInitializerCodeFixProvider
+internal sealed partial class CSharpUseCollectionInitializerCodeFixProvider
 {
     private static BaseObjectCreationExpressionSyntax CreateObjectInitializerExpression(
         BaseObjectCreationExpressionSyntax objectCreation,

src/Analyzers/CSharp/CodeFixes/UseExpressionBody/UseExpressionBodyCodeFixProvider.cs

@@ -21,7 +21,7 @@
 namespace Microsoft.CodeAnalysis.CSharp.UseExpressionBody;
 
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UseExpressionBody), Shared]
-internal partial class UseExpressionBodyCodeFixProvider : SyntaxEditorBasedCodeFixProvider
+internal sealed partial class UseExpressionBodyCodeFixProvider : SyntaxEditorBasedCodeFixProvider
 {
     public sealed override ImmutableArray<string> FixableDiagnosticIds { get; }
 

src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider.cs

@@ -34,7 +34,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UsePrimaryConstructor;
 [ExportCodeFixProvider(LanguageNames.CSharp, Name = PredefinedCodeFixProviderNames.UsePrimaryConstructor), Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class CSharpUsePrimaryConstructorCodeFixProvider() : CodeFixProvider
+internal sealed partial class CSharpUsePrimaryConstructorCodeFixProvider() : CodeFixProvider
 {
     public override ImmutableArray<string> FixableDiagnosticIds
         => [IDEDiagnosticIds.UsePrimaryConstructorDiagnosticId];

src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorCodeFixProvider_DocComments.cs

@@ -23,7 +23,7 @@ namespace Microsoft.CodeAnalysis.CSharp.UsePrimaryConstructor;
 
 using static SyntaxFactory;
 
-internal partial class CSharpUsePrimaryConstructorCodeFixProvider : CodeFixProvider
+internal sealed partial class CSharpUsePrimaryConstructorCodeFixProvider : CodeFixProvider
 {
     private const string s_summaryTagName = "summary";
     private const string s_remarksTagName = "remarks";

src/Analyzers/CSharp/CodeFixes/UsePrimaryConstructor/CSharpUsePrimaryConstructorFixAllProvider.cs

@@ -17,7 +17,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.UsePrimaryConstructor;
 
-internal partial class CSharpUsePrimaryConstructorCodeFixProvider
+internal sealed partial class CSharpUsePrimaryConstructorCodeFixProvider
 {
 #if !CODE_STYLE // Currently depends on helpers only available in workspace layer.
 

src/Features/CSharp/Portable/CodeRefactorings/AddAwait/CSharpAddAwaitCodeRefactoringProvider.cs

@@ -16,7 +16,7 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.AddAwait;
 /// This refactoring complements the AddAwait fixer. It allows adding `await` and `await ... .ConfigureAwait(false)` even there is no compiler error to trigger the fixer.
 /// </summary>
 [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.AddAwait), Shared]
-internal partial class CSharpAddAwaitCodeRefactoringProvider : AbstractAddAwaitCodeRefactoringProvider<ExpressionSyntax>
+internal sealed partial class CSharpAddAwaitCodeRefactoringProvider : AbstractAddAwaitCodeRefactoringProvider<ExpressionSyntax>
 {
     [ImportingConstructor]
     [SuppressMessage("RoslynDiagnosticsReliability", "RS0033:Importing constructor should be [Obsolete]", Justification = "Used in test code: https://github.com/dotnet/roslyn/issues/42814")]

src/Features/CSharp/Portable/CodeRefactorings/EnableNullable/EnableNullableCodeRefactoringProvider.FixAllProvider.cs

@@ -15,7 +15,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.EnableNullable;
 
-internal partial class EnableNullableCodeRefactoringProvider : CodeRefactoringProvider
+internal sealed partial class EnableNullableCodeRefactoringProvider : CodeRefactoringProvider
 {
     internal sealed override CodeAnalysis.CodeRefactorings.FixAllProvider? GetFixAllProvider()
         => FixAllProvider.Instance;

src/Features/CSharp/Portable/CodeRefactorings/EnableNullable/EnableNullableCodeRefactoringProvider.cs

@@ -21,7 +21,7 @@ namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.EnableNullable;
 using static CSharpSyntaxTokens;
 
 [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.EnableNullable), Shared]
-internal partial class EnableNullableCodeRefactoringProvider : CodeRefactoringProvider
+internal sealed partial class EnableNullableCodeRefactoringProvider : CodeRefactoringProvider
 {
     private static readonly Func<DirectiveTriviaSyntax, bool> s_isNullableDirectiveTriviaPredicate =
         directive => directive.IsKind(SyntaxKind.NullableDirectiveTrivia);

src/Features/CSharp/Portable/CodeRefactorings/InlineTemporary/InlineTemporaryCodeRefactoringProvider.ReferenceRewriter.cs

@@ -10,9 +10,9 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.InlineTemporary;
 
-internal partial class CSharpInlineTemporaryCodeRefactoringProvider
+internal sealed partial class CSharpInlineTemporaryCodeRefactoringProvider
 {
-    private class ReferenceRewriter : CSharpSyntaxRewriter
+    private sealed class ReferenceRewriter : CSharpSyntaxRewriter
     {
         private readonly ISet<IdentifierNameSyntax> _conflictReferences;
         private readonly ISet<IdentifierNameSyntax> _nonConflictReferences;

src/Features/CSharp/Portable/CodeRefactorings/InlineTemporary/InlineTemporaryCodeRefactoringProvider.cs

@@ -25,7 +25,7 @@
 namespace Microsoft.CodeAnalysis.CSharp.CodeRefactorings.InlineTemporary;
 
 [ExportCodeRefactoringProvider(LanguageNames.CSharp, Name = PredefinedCodeRefactoringProviderNames.InlineTemporary), Shared]
-internal partial class CSharpInlineTemporaryCodeRefactoringProvider
+internal sealed partial class CSharpInlineTemporaryCodeRefactoringProvider
     : AbstractInlineTemporaryCodeRefactoringProvider<IdentifierNameSyntax, VariableDeclaratorSyntax>
 {
     private static readonly SyntaxAnnotation DefinitionAnnotation = new();

src/Features/CSharp/Portable/Completion/CompletionProviders/DeclarationName/DeclarationNameCompletionProvider.cs

@@ -26,7 +26,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [Shared]
 [method: ImportingConstructor]
 [method: Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
-internal partial class DeclarationNameCompletionProvider([ImportMany] IEnumerable<Lazy<IDeclarationNameRecommender, OrderableMetadata>> recommenders) : LSPCompletionProvider
+internal sealed partial class DeclarationNameCompletionProvider([ImportMany] IEnumerable<Lazy<IDeclarationNameRecommender, OrderableMetadata>> recommenders) : LSPCompletionProvider
 {
     private ImmutableArray<Lazy<IDeclarationNameRecommender, OrderableMetadata>> Recommenders { get; } = [.. ExtensionOrderer.Order(recommenders)];
 

src/Features/CSharp/Portable/Completion/CompletionProviders/DeclarationName/DeclarationNameRecommender.NameGenerator.cs

@@ -12,7 +12,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers.DeclarationName;
 
-internal partial class DeclarationNameRecommender
+internal sealed partial class DeclarationNameRecommender
 {
     internal class NameGenerator
     {

src/Features/CSharp/Portable/Completion/CompletionProviders/EnumAndCompletionListTagCompletionProvider.cs

@@ -26,7 +26,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [ExportCompletionProvider(nameof(EnumAndCompletionListTagCompletionProvider), LanguageNames.CSharp)]
 [ExtensionOrder(After = nameof(CSharpSuggestionModeCompletionProvider))]
 [Shared]
-internal partial class EnumAndCompletionListTagCompletionProvider : LSPCompletionProvider
+internal sealed partial class EnumAndCompletionListTagCompletionProvider : LSPCompletionProvider
 {
     private static readonly CompletionItemRules s_enumTypeRules =
         CompletionItemRules.Default.WithCommitCharacterRules([CharacterSetModificationRule.Create(CharacterSetModificationKind.Replace, '.')])

src/Features/CSharp/Portable/Completion/CompletionProviders/ExplicitInterfaceMemberCompletionProvider.CompletionSymbolDisplay.cs

@@ -10,7 +10,7 @@
 
 namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 
-internal partial class ExplicitInterfaceMemberCompletionProvider
+internal sealed partial class ExplicitInterfaceMemberCompletionProvider
 {
     private static class CompletionSymbolDisplay
     {

src/Features/CSharp/Portable/Completion/CompletionProviders/ExplicitInterfaceMemberCompletionProvider.cs

@@ -21,7 +21,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 
 [ExportCompletionProvider(nameof(ExplicitInterfaceMemberCompletionProvider), LanguageNames.CSharp), Shared]
 [ExtensionOrder(After = nameof(UnnamedSymbolCompletionProvider))]
-internal partial class ExplicitInterfaceMemberCompletionProvider : LSPCompletionProvider
+internal sealed partial class ExplicitInterfaceMemberCompletionProvider : LSPCompletionProvider
 {
     [ImportingConstructor]
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]

src/Features/CSharp/Portable/Completion/CompletionProviders/ExplicitInterfaceTypeCompletionProvider.cs

@@ -25,7 +25,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [ExportCompletionProvider(nameof(ExplicitInterfaceTypeCompletionProvider), LanguageNames.CSharp)]
 [ExtensionOrder(After = nameof(ExplicitInterfaceMemberCompletionProvider))]
 [Shared]
-internal partial class ExplicitInterfaceTypeCompletionProvider : AbstractSymbolCompletionProvider<CSharpSyntaxContext>
+internal sealed partial class ExplicitInterfaceTypeCompletionProvider : AbstractSymbolCompletionProvider<CSharpSyntaxContext>
 {
     [ImportingConstructor]
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]

src/Features/CSharp/Portable/Completion/CompletionProviders/FunctionPointerUnmanagedCallingConventionCompletionProvider.cs

@@ -23,7 +23,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [ExportCompletionProvider(nameof(FunctionPointerUnmanagedCallingConventionCompletionProvider), LanguageNames.CSharp)]
 [ExtensionOrder(After = nameof(AggregateEmbeddedLanguageCompletionProvider))]
 [Shared]
-internal partial class FunctionPointerUnmanagedCallingConventionCompletionProvider : LSPCompletionProvider
+internal sealed partial class FunctionPointerUnmanagedCallingConventionCompletionProvider : LSPCompletionProvider
 {
     [ImportingConstructor]
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]
@@ -122,7 +122,7 @@ private static void AddTypes(HashSet<CompletionItem> completionItems, int contex
     internal override Task<CompletionDescription> GetDescriptionWorkerAsync(Document document, CompletionItem item, CompletionOptions options, SymbolDescriptionOptions displayOptions, CancellationToken cancellationToken)
         => SymbolCompletionItem.GetDescriptionAsync(item, document, displayOptions, cancellationToken);
 
-    private class CompletionItemComparer : IEqualityComparer<CompletionItem>
+    private sealed class CompletionItemComparer : IEqualityComparer<CompletionItem>
     {
         public static readonly IEqualityComparer<CompletionItem> Instance = new CompletionItemComparer();
 

src/Features/CSharp/Portable/Completion/CompletionProviders/ImportCompletion/TypeImportCompletionServiceFactory.cs

@@ -22,7 +22,7 @@ public TypeImportCompletionServiceFactory()
     public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
         => new CSharpTypeImportCompletionService(languageServices.LanguageServices.SolutionServices);
 
-    private class CSharpTypeImportCompletionService(SolutionServices services) : AbstractTypeImportCompletionService(services)
+    private sealed class CSharpTypeImportCompletionService(SolutionServices services) : AbstractTypeImportCompletionService(services)
     {
         protected override string GenericTypeSuffix
             => "<>";

src/Features/CSharp/Portable/Completion/CompletionProviders/NamedParameterCompletionProvider.cs

@@ -28,7 +28,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [ExportCompletionProvider(nameof(NamedParameterCompletionProvider), LanguageNames.CSharp)]
 [ExtensionOrder(After = nameof(AttributeNamedParameterCompletionProvider))]
 [Shared]
-internal partial class NamedParameterCompletionProvider : LSPCompletionProvider, IEqualityComparer<IParameterSymbol>
+internal sealed partial class NamedParameterCompletionProvider : LSPCompletionProvider, IEqualityComparer<IParameterSymbol>
 {
     private const string ColonString = ":";
 

src/Features/CSharp/Portable/Completion/CompletionProviders/ObjectCreationCompletionProvider.cs

@@ -23,7 +23,7 @@ namespace Microsoft.CodeAnalysis.CSharp.Completion.Providers;
 [ExportCompletionProvider(nameof(ObjectCreationCompletionProvider), LanguageNames.CSharp)]
 [ExtensionOrder(After = nameof(ExplicitInterfaceTypeCompletionProvider))]
 [Shared]
-internal partial class ObjectCreationCompletionProvider : AbstractObjectCreationCompletionProvider<CSharpSyntaxContext>
+internal sealed partial class ObjectCreationCompletionProvider : AbstractObjectCreationCompletionProvider<CSharpSyntaxContext>
 {
     [ImportingConstructor]
     [Obsolete(MefConstruction.ImportingConstructorMessage, error: true)]