use pattern matching

src/Compilers/CSharp/CSharpAnalyzerDriver/CSharpDeclarationComputer.cs

@@ -155,8 +155,7 @@ private static bool InvalidLevel(int? level)
                 case SyntaxKind.ArrowExpressionClause:
                     {
                         // Arrow expression clause declares getter symbol for properties and indexers.
-                        var parentProperty = node.Parent as BasePropertyDeclarationSyntax;
-                        if (parentProperty != null)
+                        if (node.Parent is BasePropertyDeclarationSyntax parentProperty)
                         {
                             builder.Add(GetExpressionBodyDeclarationInfo(parentProperty, (ArrowExpressionClauseSyntax)node, model, getSymbol, cancellationToken));
                         }
@@ -233,8 +232,7 @@ private static bool InvalidLevel(int? level)
                         var codeBlocks = GetParameterListInitializersAndAttributes(t.ParameterList);
                         codeBlocks = codeBlocks.Concat(t.Body);
 
-                        var ctorDecl = t as ConstructorDeclarationSyntax;
-                        if (ctorDecl != null && ctorDecl.Initializer != null)
+                        if (t is ConstructorDeclarationSyntax ctorDecl && ctorDecl.Initializer != null)
                         {
                             codeBlocks = codeBlocks.Concat(ctorDecl.Initializer);
                         }

src/Features/CSharp/Portable/ChangeSignature/CSharpChangeSignatureService.cs

@@ -349,10 +349,9 @@ private SyntaxNode GetNodeContainingTargetNode(SyntaxNode matchingNode)
                 var semanticModel = document.GetSemanticModelAsync(cancellationToken).WaitAndGetResult(cancellationToken);
 
                 var symbolInfo = semanticModel.GetSymbolInfo((InvocationExpressionSyntax)originalNode, cancellationToken);
-                var methodSymbol = symbolInfo.Symbol as IMethodSymbol;
                 var isReducedExtensionMethod = false;
 
-                if (methodSymbol != null && methodSymbol.MethodKind == MethodKind.ReducedExtension)
+                if (symbolInfo.Symbol is IMethodSymbol methodSymbol && methodSymbol.MethodKind == MethodKind.ReducedExtension)
                 {
                     isReducedExtensionMethod = true;
                 }
@@ -576,8 +575,7 @@ private List<SyntaxTrivia> GetPermutedTrivia(CSharpSyntaxNode node, List<XmlElem
                     continue;
                 }
 
-                var structuredTrivia = trivia.GetStructure() as DocumentationCommentTriviaSyntax;
-                if (structuredTrivia == null)
+                if (!(trivia.GetStructure() is DocumentationCommentTriviaSyntax structuredTrivia))
                 {
                     updatedLeadingTrivia.Add(trivia);
                     continue;

src/Features/CSharp/Portable/CodeFixes/Async/CSharpAddAwaitCodeFixProvider.cs

@@ -63,8 +63,7 @@ public CSharpAddAwaitCodeFixProvider()
             Document document,
             CancellationToken cancellationToken)
         {
-            var expression = oldNode as ExpressionSyntax;
-            if (expression == null)
+            if (!(oldNode is ExpressionSyntax expression))
             {
                 return SpecializedTasks.Default<SyntaxNode>();
             }

src/Features/CSharp/Portable/CodeFixes/Async/CSharpConvertToAsyncMethodCodeFixProvider.cs

@@ -68,8 +68,7 @@ public override ImmutableArray<string> FixableDiagnosticIds
                 return null;
             }
 
-            var methodSymbol = semanticModel.GetSymbolInfo(invocationExpression, cancellationToken).Symbol as IMethodSymbol;
-            if (methodSymbol == null)
+            if (!(semanticModel.GetSymbolInfo(invocationExpression, cancellationToken).Symbol is IMethodSymbol methodSymbol))
             {
                 return null;
             }
@@ -80,8 +79,7 @@ public override ImmutableArray<string> FixableDiagnosticIds
                 return null;
             }
 
-            var methodDeclaration = (await methodReference.GetSyntaxAsync(cancellationToken).ConfigureAwait(false)) as MethodDeclarationSyntax;
-            if (methodDeclaration == null)
+            if (!((await methodReference.GetSyntaxAsync(cancellationToken).ConfigureAwait(false)) is MethodDeclarationSyntax methodDeclaration))
             {
                 return null;
             }

src/Features/CSharp/Portable/CodeRefactorings/LambdaSimplifier/LambdaSimplifierCodeRefactoringProvider.cs

@@ -150,10 +150,7 @@ public override async Task ComputeRefactoringsAsync(CodeRefactoringContext conte
                 // Don't offer this if there are any errors or ambiguities.
                 return false;
             }
-
-            var lambdaMethod = lambdaSemanticInfo.Symbol as IMethodSymbol;
-            var invocationMethod = invocationSemanticInfo.Symbol as IMethodSymbol;
-            if (lambdaMethod == null || invocationMethod == null)
+            if (!(lambdaSemanticInfo.Symbol is IMethodSymbol lambdaMethod) || !(invocationSemanticInfo.Symbol is IMethodSymbol invocationMethod))
             {
                 return false;
             }

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

@@ -54,10 +54,7 @@ public override async Task ProvideCompletionsAsync(CompletionContext context)
                 {
                     return;
                 }
-
-                var attributeArgumentList = token.Parent as AttributeArgumentListSyntax;
-                var attributeSyntax = token.Parent.Parent as AttributeSyntax;
-                if (attributeSyntax == null || attributeArgumentList == null)
+                if (!(token.Parent.Parent is AttributeSyntax attributeSyntax) || !(token.Parent is AttributeArgumentListSyntax attributeArgumentList))
                 {
                     return;
                 }
@@ -96,8 +93,7 @@ public override async Task ProvideCompletionsAsync(CompletionContext context)
 
         private bool IsAfterNameColonArgument(SyntaxToken token)
         {
-            var argumentList = token.Parent as AttributeArgumentListSyntax;
-            if (token.Kind() == SyntaxKind.CommaToken && argumentList != null)
+            if (token.Kind() == SyntaxKind.CommaToken && token.Parent is AttributeArgumentListSyntax argumentList)
             {
                 foreach (var item in argumentList.Arguments.GetWithSeparators())
                 {
@@ -122,8 +118,7 @@ private bool IsAfterNameColonArgument(SyntaxToken token)
 
         private bool IsAfterNameEqualsArgument(SyntaxToken token)
         {
-            var argumentList = token.Parent as AttributeArgumentListSyntax;
-            if (token.Kind() == SyntaxKind.CommaToken && argumentList != null)
+            if (token.Kind() == SyntaxKind.CommaToken && token.Parent is AttributeArgumentListSyntax argumentList)
             {
                 foreach (var item in argumentList.Arguments.GetWithSeparators())
                 {
@@ -216,8 +211,7 @@ private ISet<string> GetExistingNamedParameters(AttributeArgumentListSyntax argu
             CancellationToken cancellationToken)
         {
             var within = semanticModel.GetEnclosingNamedTypeOrAssembly(position, cancellationToken);
-            var attributeType = semanticModel.GetTypeInfo(attribute, cancellationToken).Type as INamedTypeSymbol;
-            if (within != null && attributeType != null)
+            if (within != null && semanticModel.GetTypeInfo(attribute, cancellationToken).Type is INamedTypeSymbol attributeType)
             {
                 return attributeType.InstanceConstructors.Where(c => c.IsAccessibleWithin(within))
                                                          .Select(c => c.Parameters);

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

@@ -58,8 +58,7 @@ public override async Task ProvideCompletionsAsync(CompletionContext context)
                     return;
                 }
 
-                var argumentList = token.Parent as BaseArgumentListSyntax;
-                if (argumentList == null)
+                if (!(token.Parent is BaseArgumentListSyntax argumentList))
                 {
                     return;
                 }
@@ -157,9 +156,8 @@ private ISet<string> GetExistingNamedParameters(BaseArgumentListSyntax argumentL
             ObjectCreationExpressionSyntax objectCreationExpression,
             CancellationToken cancellationToken)
         {
-            var type = semanticModel.GetTypeInfo(objectCreationExpression, cancellationToken).Type as INamedTypeSymbol;
             var within = semanticModel.GetEnclosingNamedType(position, cancellationToken);
-            if (type != null && within != null && type.TypeKind != TypeKind.Delegate)
+            if (semanticModel.GetTypeInfo(objectCreationExpression, cancellationToken).Type is INamedTypeSymbol type && within != null && type.TypeKind != TypeKind.Delegate)
             {
                 return type.InstanceConstructors.Where(c => c.IsAccessibleWithin(within))
                                                 .Select(c => c.Parameters);

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

@@ -70,8 +70,7 @@ protected override IEnumerable<INamedTypeSymbol> LookupCandidateSymbols(SyntaxCo
 
         private static bool IsPartialTypeDeclaration(SyntaxNode syntax)
         {
-            var declarationSyntax = syntax as BaseTypeDeclarationSyntax;
-            return declarationSyntax != null && declarationSyntax.Modifiers.Any(modifier => modifier.IsKind(SyntaxKind.PartialKeyword));
+            return syntax is BaseTypeDeclarationSyntax declarationSyntax && declarationSyntax.Modifiers.Any(modifier => modifier.IsKind(SyntaxKind.PartialKeyword));
         }
 
         protected override ImmutableDictionary<string, string> GetProperties(

src/Features/CSharp/Portable/DesignerAttributes/CSharpDesignerAttributeService.cs

@@ -31,8 +31,7 @@ public CSharpDesignerAttributeService(Workspace workspace) : base(workspace)
 
         protected override IEnumerable<SyntaxNode> GetAllTopLevelTypeDefined(SyntaxNode node)
         {
-            var compilationUnit = node as CompilationUnitSyntax;
-            if (compilationUnit == null)
+            if (!(node is CompilationUnitSyntax compilationUnit))
             {
                 return SpecializedCollections.EmptyEnumerable<SyntaxNode>();
             }

src/Features/CSharp/Portable/Diagnostics/Analyzers/CSharpSimplifyTypeNamesDiagnosticAnalyzer.cs

@@ -111,8 +111,7 @@ private static bool IsCrefCandidate(SyntaxNode node)
             issueSpan = default;
             diagnosticId = IDEDiagnosticIds.SimplifyNamesDiagnosticId;
 
-            var memberAccess = node as MemberAccessExpressionSyntax;
-            if (memberAccess != null && memberAccess.Expression.IsKind(SyntaxKind.ThisExpression))
+            if (node is MemberAccessExpressionSyntax memberAccess && memberAccess.Expression.IsKind(SyntaxKind.ThisExpression))
             {
                 // don't bother analyzing "this.Goo" expressions.  They will be analyzed by
                 // the CSharpSimplifyThisOrMeDiagnosticAnalyzer.

src/Features/CSharp/Portable/EditAndContinue/BreakpointSpans.cs

@@ -293,14 +293,12 @@ private static int GetEndPosition(SyntaxNodeOrToken nodeOrToken)
                         TryCreateSpanForNode(localFunction.ExpressionBody.Expression, position);
 
                 default:
-                    var expression = node as ExpressionSyntax;
-                    if (expression != null)
+                    if (node is ExpressionSyntax expression)
                     {
                         return IsBreakableExpression(expression) ? CreateSpan(expression) : default(TextSpan?);
                     }
 
-                    var statement = node as StatementSyntax;
-                    if (statement != null)
+                    if (node is StatementSyntax statement)
                     {
                         return TryCreateSpanForStatement(statement, position);
                     }
@@ -343,8 +341,7 @@ private static TextSpan CreateSpanForConstructorInitializer(ConstructorInitializ
 
         private static TextSpan? TryCreateSpanForSwitchLabel(SwitchLabelSyntax switchLabel, int position)
         {
-            var switchSection = switchLabel.Parent as SwitchSectionSyntax;
-            if (switchSection == null || switchSection.Statements.Count == 0)
+            if (!(switchLabel.Parent is SwitchSectionSyntax switchSection) || switchSection.Statements.Count == 0)
             {
                 return null;
             }
@@ -666,14 +663,12 @@ private static int GetItemIndexByPosition<TNode>(SeparatedSyntaxList<TNode> list
 
         private static SyntaxTokenList GetModifiers(VariableDeclarationSyntax declaration)
         {
-            BaseFieldDeclarationSyntax fieldDeclaration;
-            LocalDeclarationStatementSyntax localDeclaration;
-            if ((fieldDeclaration = declaration.Parent as BaseFieldDeclarationSyntax) != null)
+            if (declaration.Parent is BaseFieldDeclarationSyntax fieldDeclaration)
             {
                 return fieldDeclaration.Modifiers;
             }
 
-            if ((localDeclaration = declaration.Parent as LocalDeclarationStatementSyntax) != null)
+            if (declaration.Parent is LocalDeclarationStatementSyntax localDeclaration)
             {
                 return localDeclaration.Modifiers;
             }

src/Features/CSharp/Portable/EditAndContinue/CSharpEditAndContinueAnalyzer.cs

@@ -907,8 +907,7 @@ internal override bool IsDeclarationWithInitializer(SyntaxNode declaration)
 
         internal override bool IsConstructorWithMemberInitializers(SyntaxNode constructorDeclaration)
         {
-            var ctor = constructorDeclaration as ConstructorDeclarationSyntax;
-            return ctor != null && (ctor.Initializer == null || ctor.Initializer.IsKind(SyntaxKind.BaseConstructorInitializer));
+            return constructorDeclaration is ConstructorDeclarationSyntax ctor && (ctor.Initializer == null || ctor.Initializer.IsKind(SyntaxKind.BaseConstructorInitializer));
         }
 
         internal override bool IsPartial(INamedTypeSymbol type)

src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.CSharpCodeGenerator.cs

@@ -283,8 +283,7 @@ private OperationStatus CheckActiveStatements(IEnumerable<StatementSyntax> state
 
                 foreach (var statement in statements)
                 {
-                    var declStatement = statement as LocalDeclarationStatementSyntax;
-                    if (declStatement == null)
+                    if (!(statement is LocalDeclarationStatementSyntax declStatement))
                     {
                         // found one
                         return OperationStatus.Succeeded;
@@ -452,8 +451,7 @@ private OperationStatus CheckActiveStatements(IEnumerable<StatementSyntax> state
                                 // We don't have a good refactoring for this, so we just annotate the conflict
                                 // For instance, when a local declared by a pattern declaration (`3 is int i`) is
                                 // used outside the block we're trying to extract.
-                                var designation = pattern.Designation as SingleVariableDesignationSyntax;
-                                if (designation == null)
+                                if (!(pattern.Designation is SingleVariableDesignationSyntax designation))
                                 {
                                     break;
                                 }

src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.PostProcessor.cs

@@ -32,8 +32,7 @@ public IEnumerable<StatementSyntax> RemoveRedundantBlock(IEnumerable<StatementSy
                 }
 
                 // that statement must be a block
-                var block = statements.Single() as BlockSyntax;
-                if (block == null)
+                if (!(statements.Single() is BlockSyntax block))
                 {
                     return statements;
                 }
@@ -159,8 +158,7 @@ private bool IsDeclarationMergable(StatementSyntax statement)
                 // 3. no trivia except whitespace
                 // 4. type must be known
 
-                var declarationStatement = statement as LocalDeclarationStatementSyntax;
-                if (declarationStatement == null)
+                if (!(statement is LocalDeclarationStatementSyntax declarationStatement))
                 {
                     return false;
                 }
@@ -231,10 +229,7 @@ public IEnumerable<StatementSyntax> RemoveInitializedDeclarationAndReturnPattern
                 {
                     return statements;
                 }
-
-                var declaration = statements.ElementAtOrDefault(0) as LocalDeclarationStatementSyntax;
-                var returnStatement = statements.ElementAtOrDefault(1) as ReturnStatementSyntax;
-                if (declaration == null || returnStatement == null)
+                if (!(statements.ElementAtOrDefault(0) is LocalDeclarationStatementSyntax declaration) || !(statements.ElementAtOrDefault(1) is ReturnStatementSyntax returnStatement))
                 {
                     return statements;
                 }
@@ -266,11 +261,7 @@ public IEnumerable<StatementSyntax> RemoveInitializedDeclarationAndReturnPattern
 
             public IEnumerable<StatementSyntax> RemoveDeclarationAssignmentPattern(IEnumerable<StatementSyntax> statements)
             {
-                // if we have inline temp variable as service, we could just use that service here.
-                // since it is not a service right now, do very simple clean up
-                var declaration = statements.ElementAtOrDefault(0) as LocalDeclarationStatementSyntax;
-                var assignment = statements.ElementAtOrDefault(1) as ExpressionStatementSyntax;
-                if (declaration == null || assignment == null)
+                if (!(statements.ElementAtOrDefault(0) is LocalDeclarationStatementSyntax declaration) || !(statements.ElementAtOrDefault(1) is ExpressionStatementSyntax assignment))
                 {
                     return statements;
                 }

src/Features/CSharp/Portable/ExtractMethod/CSharpMethodExtractor.TriviaResult.cs

@@ -32,8 +32,7 @@ private CSharpTriviaResult(SemanticDocument document, ITriviaSavedResult result)
 
             protected override AnnotationResolver GetAnnotationResolver(SyntaxNode callsite, SyntaxNode method)
             {
-                var methodDefinition = method as MethodDeclarationSyntax;
-                if (callsite == null || methodDefinition == null)
+                if (callsite == null || !(method is MethodDeclarationSyntax methodDefinition))
                 {
                     return null;
                 }

src/Features/CSharp/Portable/ExtractMethod/Extensions.cs

@@ -18,8 +18,7 @@ internal static class Extensions
     {
         public static ExpressionSyntax GetUnparenthesizedExpression(this SyntaxNode node)
         {
-            var parenthesizedExpression = node as ParenthesizedExpressionSyntax;
-            if (parenthesizedExpression == null)
+            if (!(node is ParenthesizedExpressionSyntax parenthesizedExpression))
             {
                 return node as ExpressionSyntax;
             }
@@ -146,8 +145,7 @@ public static bool ContainArgumentlessThrowWithoutEnclosingCatch(this IEnumerabl
                     continue;
                 }
 
-                var throwStatement = token.Parent as ThrowStatementSyntax;
-                if (throwStatement == null || throwStatement.Expression != null)
+                if (!(token.Parent is ThrowStatementSyntax throwStatement) || throwStatement.Expression != null)
                 {
                     continue;
                 }

src/Features/CSharp/Portable/FullyQualify/CSharpFullyQualifyCodeFixProvider.cs

@@ -56,8 +56,7 @@ public override ImmutableArray<string> FixableDiagnosticIds
 
         protected override bool CanFullyQualify(Diagnostic diagnostic, ref SyntaxNode node)
         {
-            var simpleName = node as SimpleNameSyntax;
-            if (simpleName == null)
+            if (!(node is SimpleNameSyntax simpleName))
             {
                 return false;
             }

src/Features/CSharp/Portable/GenerateConstructor/CSharpGenerateConstructorService.cs

@@ -230,8 +230,7 @@ protected override bool IsConversionImplicit(Compilation compilation, ITypeSymbo
                 {
                     while (true)
                     {
-                        var parentType = typeNameToReplace.Parent as TypeSyntax;
-                        if (parentType == null)
+                        if (!(typeNameToReplace.Parent is TypeSyntax parentType))
                         {
                             break;
                         }

src/Features/CSharp/Portable/GenerateMember/GenerateEnumMember/CSharpGenerateEnumMemberService.cs

@@ -31,8 +31,7 @@ protected override bool IsIdentifierNameGeneration(SyntaxNode node)
             if (identifierToken.ValueText != string.Empty &&
                 !identifierName.IsVar)
             {
-                var memberAccess = identifierName.Parent as MemberAccessExpressionSyntax;
-                simpleNameOrMemberAccessExpression = memberAccess != null && memberAccess.Name == identifierName
+                simpleNameOrMemberAccessExpression = identifierName.Parent is MemberAccessExpressionSyntax memberAccess && memberAccess.Name == identifierName
                     ? (ExpressionSyntax)memberAccess
                     : identifierName;
 

src/Features/CSharp/Portable/GenerateMember/GenerateParameterizedMember/CSharpGenerateConversionService.cs

@@ -148,8 +148,7 @@ protected override bool IsValidSymbol(ISymbol symbol, SemanticModel semanticMode
         {
             methodSymbol = null;
             typeToGenerateIn = document.SemanticModel.GetTypeInfo(castExpression.Type, cancellationToken).Type as INamedTypeSymbol;
-            var parameterSymbol = document.SemanticModel.GetTypeInfo(castExpression.Expression, cancellationToken).Type as INamedTypeSymbol;
-            if (typeToGenerateIn == null || parameterSymbol == null || typeToGenerateIn.IsErrorType() || parameterSymbol.IsErrorType())
+            if (typeToGenerateIn == null || !(document.SemanticModel.GetTypeInfo(castExpression.Expression, cancellationToken).Type is INamedTypeSymbol parameterSymbol) || typeToGenerateIn.IsErrorType() || parameterSymbol.IsErrorType())
             {
                 return false;
             }
@@ -179,8 +178,7 @@ protected override bool IsValidSymbol(ISymbol symbol, SemanticModel semanticMode
         {
             methodSymbol = null;
             typeToGenerateIn = document.SemanticModel.GetTypeInfo(expression, cancellationToken).ConvertedType as INamedTypeSymbol;
-            var parameterSymbol = document.SemanticModel.GetTypeInfo(expression, cancellationToken).Type as INamedTypeSymbol;
-            if (typeToGenerateIn == null || parameterSymbol == null || typeToGenerateIn.IsErrorType() || parameterSymbol.IsErrorType())
+            if (typeToGenerateIn == null || !(document.SemanticModel.GetTypeInfo(expression, cancellationToken).Type is INamedTypeSymbol parameterSymbol) || typeToGenerateIn.IsErrorType() || parameterSymbol.IsErrorType())
             {
                 return false;
             }

src/Features/CSharp/Portable/GenerateType/CSharpGenerateTypeService.cs

@@ -414,14 +414,12 @@ protected override bool TryGetNameParts(ExpressionSyntax expression, out IList<s
                 {
                     foreach (var expression in objectCreationExpressionOpt.Initializer.Expressions)
                     {
-                        var simpleAssignmentExpression = expression as AssignmentExpressionSyntax;
-                        if (simpleAssignmentExpression == null)
+                        if (!(expression is AssignmentExpressionSyntax simpleAssignmentExpression))
                         {
                             continue;
                         }
 
-                        var name = simpleAssignmentExpression.Left as SimpleNameSyntax;
-                        if (name == null)
+                        if (!(simpleAssignmentExpression.Left is SimpleNameSyntax name))
                         {
                             continue;
                         }
@@ -648,8 +646,7 @@ private NamespaceDeclarationSyntax GetDeclaringNamespace(List<string> containers
 
         private NamespaceDeclarationSyntax GetDeclaringNamespace(List<string> containers, int indexDone, SyntaxNode localRoot)
         {
-            var namespaceDecl = localRoot as NamespaceDeclarationSyntax;
-            if (namespaceDecl == null || namespaceDecl.Name is AliasQualifiedNameSyntax)
+            if (!(localRoot is NamespaceDeclarationSyntax namespaceDecl) || namespaceDecl.Name is AliasQualifiedNameSyntax)
             {
                 return null;
             }
@@ -824,8 +821,7 @@ internal override bool IsGenericName(SimpleNameSyntax simpleName)
                 return false;
             }
 
-            var genericName = simpleName as GenericNameSyntax;
-            return genericName != null;
+            return simpleName is GenericNameSyntax genericName;
         }
 
         internal override bool IsSimpleName(ExpressionSyntax expression)

src/Features/CSharp/Portable/ImplementInterface/CSharpImplementInterfaceService.cs

@@ -40,10 +40,9 @@ public CSharpImplementInterfaceService()
                         var interfaceSymbolInfo = model.GetSymbolInfo(interfaceNode, cancellationToken);
                         if (interfaceSymbolInfo.CandidateReason != CandidateReason.WrongArity)
                         {
-                            var interfaceType = interfaceSymbolInfo.GetAnySymbol() as INamedTypeSymbol;
                             cancellationToken.ThrowIfCancellationRequested();
 
-                            if (interfaceType != null && interfaceType.TypeKind == TypeKind.Interface)
+                            if (interfaceSymbolInfo.GetAnySymbol() is INamedTypeSymbol interfaceType && interfaceType.TypeKind == TypeKind.Interface)
                             {
                                 classOrStructDecl = interfaceNode.Parent.Parent.Parent as TypeDeclarationSyntax;
                                 classOrStructType = model.GetDeclaredSymbol(classOrStructDecl, cancellationToken) as INamedTypeSymbol;

src/Features/CSharp/Portable/InlineDeclaration/CSharpInlineDeclarationDiagnosticAnalyzer.cs

@@ -92,8 +92,7 @@ private void AnalyzeSyntaxNode(SyntaxNodeAnalysisContext context, INamedTypeSymb
                 return;
             }
 
-            var argumentList = argumentNode.Parent as ArgumentListSyntax;
-            if (argumentList == null)
+            if (!(argumentNode.Parent is ArgumentListSyntax argumentList))
             {
                 return;
             }
@@ -125,8 +124,7 @@ private void AnalyzeSyntaxNode(SyntaxNodeAnalysisContext context, INamedTypeSymb
             }
 
             var semanticModel = context.SemanticModel;
-            var outLocalSymbol = semanticModel.GetSymbolInfo(argumentExpression, cancellationToken).Symbol as ILocalSymbol;
-            if (outLocalSymbol == null)
+            if (!(semanticModel.GetSymbolInfo(argumentExpression, cancellationToken).Symbol is ILocalSymbol outLocalSymbol))
             {
                 // The out-argument wasn't referencing a local.  So we don't have an local
                 // declaration that we can attempt to inline here.
@@ -138,15 +136,13 @@ private void AnalyzeSyntaxNode(SyntaxNodeAnalysisContext context, INamedTypeSymb
             // esoteric and would make us have to write a lot more complex code to support
             // that scenario.
             var localReference = outLocalSymbol.DeclaringSyntaxReferences.FirstOrDefault();
-            var localDeclarator = localReference?.GetSyntax(cancellationToken) as VariableDeclaratorSyntax;
-            if (localDeclarator == null)
+            if (!(localReference?.GetSyntax(cancellationToken) is VariableDeclaratorSyntax localDeclarator))
             {
                 return;
             }
 
             var localDeclaration = localDeclarator.Parent as VariableDeclarationSyntax;
-            var localStatement = localDeclaration?.Parent as LocalDeclarationStatementSyntax;
-            if (localStatement == null)
+            if (!(localDeclaration?.Parent is LocalDeclarationStatementSyntax localStatement))
             {
                 return;
             }
@@ -175,8 +171,7 @@ private void AnalyzeSyntaxNode(SyntaxNodeAnalysisContext context, INamedTypeSymb
             // for references to the local to make sure that no reads/writes happen before
             // the out-argument.  If there are any reads/writes we can't inline as those
             // accesses will become invalid.
-            var enclosingBlockOfLocalStatement = localStatement.Parent as BlockSyntax;
-            if (enclosingBlockOfLocalStatement == null)
+            if (!(localStatement.Parent is BlockSyntax enclosingBlockOfLocalStatement))
             {
                 return;
             }

src/Features/CSharp/Portable/IntroduceVariable/CSharpIntroduceVariableService_IntroduceField.cs

@@ -152,8 +152,7 @@ internal partial class CSharpIntroduceVariableService
 
         private static bool IsConstantField(MemberDeclarationSyntax member)
         {
-            var field = member as FieldDeclarationSyntax;
-            return field != null && field.Modifiers.Any(SyntaxKind.ConstKeyword);
+            return member is FieldDeclarationSyntax field && field.Modifiers.Any(SyntaxKind.ConstKeyword);
         }
 
         protected static int DetermineFirstChange(SyntaxList<MemberDeclarationSyntax> oldMembers, SyntaxList<MemberDeclarationSyntax> newMembers)

src/Features/CSharp/Portable/IntroduceVariable/CSharpIntroduceVariableService_IntroduceLocal.cs

@@ -87,9 +87,8 @@ internal partial class CSharpIntroduceVariableService
             var rewrittenBody = Rewrite(
                 document, expression, newLocalName, document, oldBody, allOccurrences, cancellationToken);
 
-            var delegateType = document.SemanticModel.GetTypeInfo(oldLambda, cancellationToken).ConvertedType as INamedTypeSymbol;
 
-            var newBody = delegateType != null && delegateType.DelegateInvokeMethod != null && delegateType.DelegateInvokeMethod.ReturnsVoid
+            var newBody = document.SemanticModel.GetTypeInfo(oldLambda, cancellationToken).ConvertedType is INamedTypeSymbol delegateType && delegateType.DelegateInvokeMethod != null && delegateType.DelegateInvokeMethod.ReturnsVoid
                 ? SyntaxFactory.Block(declarationStatement)
                 : SyntaxFactory.Block(declarationStatement, SyntaxFactory.ReturnStatement(rewrittenBody));
 

src/Features/CSharp/Portable/InvokeDelegateWithConditionalAccess/InvokeDelegateWithConditionalAccessAnalyzer.cs

@@ -92,8 +92,7 @@ private void SyntaxNodeAction(SyntaxNodeAnalysisContext syntaxContext)
             var expressionStatement = (ExpressionStatementSyntax)innerStatement;
 
             // Check that it's of the form: "if (a != null) { a(); }
-            var invocationExpression = ((ExpressionStatementSyntax)innerStatement).Expression as InvocationExpressionSyntax;
-            if (invocationExpression == null)
+            if (!(((ExpressionStatementSyntax)innerStatement).Expression is InvocationExpressionSyntax invocationExpression))
             {
                 return;
             }

src/Features/CSharp/Portable/RemoveUnreachableCode/CSharpRemoveUnreachableCodeDiagnosticAnalyzer.cs

@@ -36,8 +36,7 @@ protected override void InitializeWorker(AnalysisContext context)
 
         private void AnalyzeSemanticModel(SemanticModelAnalysisContext context)
         {
-            var options = context.Options as WorkspaceAnalyzerOptions;
-            if (options == null)
+            if (!(context.Options is WorkspaceAnalyzerOptions options))
             {
                 return;
             }

src/Features/CSharp/Portable/ReplaceMethodWithProperty/CSharpReplaceMethodWithPropertyService.cs

@@ -36,8 +36,7 @@ public void RemoveSetMethod(SyntaxEditor editor, SyntaxNode setMethodDeclaration
             GetAndSetMethods getAndSetMethods,
             string propertyName, bool nameChanged)
         {
-            var getMethodDeclaration = getAndSetMethods.GetMethodDeclaration as MethodDeclarationSyntax;
-            if (getMethodDeclaration == null)
+            if (!(getAndSetMethods.GetMethodDeclaration is MethodDeclarationSyntax getMethodDeclaration))
             {
                 return;
             }
@@ -226,9 +225,8 @@ private static AccessorDeclarationSyntax CreateGetAccessorWorker(GetAndSetMethod
         private static AccessorDeclarationSyntax CreateSetAccessorWorker(
             SemanticModel semanticModel, SyntaxGenerator generator, GetAndSetMethods getAndSetMethods)
         {
-            var setMethodDeclaration = getAndSetMethods.SetMethodDeclaration as MethodDeclarationSyntax;
             var setMethod = getAndSetMethods.SetMethod;
-            if (setMethodDeclaration == null || setMethod?.Parameters.Length != 1)
+            if (!(getAndSetMethods.SetMethodDeclaration is MethodDeclarationSyntax setMethodDeclaration) || setMethod?.Parameters.Length != 1)
             {
                 return null;
             }
@@ -352,8 +350,7 @@ public void ReplaceSetReference(SyntaxEditor editor, SyntaxToken nameToken, stri
                 return;
             }
 
-            var nameNode = nameToken.Parent as IdentifierNameSyntax;
-            if (nameNode == null)
+            if (!(nameToken.Parent is IdentifierNameSyntax nameNode))
             {
                 return;
             }

src/Features/CSharp/Portable/ReplacePropertyWithMethods/CSharpReplacePropertyWithMethodsService.cs

@@ -36,8 +36,7 @@ public CSharpReplacePropertyWithMethodsService()
             string desiredSetMethodName,
             CancellationToken cancellationToken)
         {
-            var propertyDeclaration = propertyDeclarationNode as PropertyDeclarationSyntax;
-            if (propertyDeclaration == null)
+            if (!(propertyDeclarationNode is PropertyDeclarationSyntax propertyDeclaration))
             {
                 return SpecializedCollections.EmptyList<SyntaxNode>();
             }

src/Features/CSharp/Portable/SignatureHelp/AttributeSignatureHelpProvider.cs

@@ -71,8 +71,7 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
             }
 
             var semanticModel = await document.GetSemanticModelForNodeAsync(attribute, cancellationToken).ConfigureAwait(false);
-            var attributeType = semanticModel.GetTypeInfo(attribute, cancellationToken).Type as INamedTypeSymbol;
-            if (attributeType == null)
+            if (!(semanticModel.GetTypeInfo(attribute, cancellationToken).Type is INamedTypeSymbol attributeType))
             {
                 return null;
             }

src/Features/CSharp/Portable/SignatureHelp/GenericNameSignatureHelpProvider.cs

@@ -80,8 +80,7 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
                 return null;
             }
 
-            var simpleName = genericIdentifier.Parent as SimpleNameSyntax;
-            if (simpleName == null)
+            if (!(genericIdentifier.Parent is SimpleNameSyntax simpleName))
             {
                 return null;
             }

src/Features/CSharp/Portable/SignatureHelp/InvocationExpressionSignatureHelpProvider.cs

@@ -90,7 +90,6 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
             methodGroup = methodGroup.Sort(
                 symbolDisplayService, semanticModel, invocationExpression.SpanStart);
 
-            var expressionType = semanticModel.GetTypeInfo(invocationExpression.Expression, cancellationToken).Type as INamedTypeSymbol;
 
             var anonymousTypeDisplayService = document.GetLanguageService<IAnonymousTypeDisplayService>();
             var documentationCommentFormattingService = document.GetLanguageService<IDocumentationCommentFormattingService>();
@@ -109,7 +108,7 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
                     GetCurrentArgumentState(root, position, syntaxFacts, textSpan, cancellationToken),
                     selectedItem);
             }
-            else if (expressionType != null && expressionType.TypeKind == TypeKind.Delegate)
+            else if (semanticModel.GetTypeInfo(invocationExpression.Expression, cancellationToken).Type is INamedTypeSymbol expressionType && expressionType.TypeKind == TypeKind.Delegate)
             {
                 var items = GetDelegateInvokeItems(invocationExpression, semanticModel, symbolDisplayService, anonymousTypeDisplayService,
                     documentationCommentFormattingService, within, expressionType, out var selectedItem, cancellationToken);

src/Features/CSharp/Portable/SignatureHelp/ObjectCreationExpressionSignatureHelpProvider.cs

@@ -61,8 +61,7 @@ protected override async Task<SignatureHelpItems> GetItemsWorkerAsync(Document d
             }
 
             var semanticModel = await document.GetSemanticModelForNodeAsync(objectCreationExpression, cancellationToken).ConfigureAwait(false);
-            var type = semanticModel.GetTypeInfo(objectCreationExpression, cancellationToken).Type as INamedTypeSymbol;
-            if (type == null)
+            if (!(semanticModel.GetTypeInfo(objectCreationExpression, cancellationToken).Type is INamedTypeSymbol type))
             {
                 return null;
             }

src/Features/CSharp/Portable/Structure/Providers/ParenthesizedLambdaExpressionStructureProvider.cs

@@ -22,8 +22,7 @@ internal class ParenthesizedLambdaExpressionStructureProvider : AbstractSyntaxNo
                 return;
             }
 
-            var lambdaBlock = lambdaExpression.Body as BlockSyntax;
-            if (lambdaBlock == null ||
+            if (!(lambdaExpression.Body is BlockSyntax lambdaBlock) ||
                 lambdaBlock.OpenBraceToken.IsMissing ||
                 lambdaBlock.CloseBraceToken.IsMissing)
             {

src/Features/CSharp/Portable/Structure/Providers/SimpleLambdaExpressionStructureProvider.cs

@@ -22,8 +22,7 @@ internal class SimpleLambdaExpressionStructureProvider : AbstractSyntaxNodeStruc
                 return;
             }
 
-            var lambdaBlock = lambdaExpression.Body as BlockSyntax;
-            if (lambdaBlock == null ||
+            if (!(lambdaExpression.Body is BlockSyntax lambdaBlock) ||
                 lambdaBlock.OpenBraceToken.IsMissing ||
                 lambdaBlock.CloseBraceToken.IsMissing)
             {

src/Features/CSharp/Portable/UseExpressionBodyForLambda/UseExpressionBodyForLambdaHelpers.cs

@@ -94,8 +94,7 @@ public static ExpressionSyntax GetExpressionBody(LambdaExpressionSyntax declarat
             // able to create the right sort of block body (i.e. with a return-statement or
             // expr-statement).  So, if we can't figure out what lambda type this is, we should not
             // proceed.
-            var lambdaType = semanticModel.GetTypeInfo(declaration, cancellationToken).ConvertedType as INamedTypeSymbol;
-            if (lambdaType == null || lambdaType.DelegateInvokeMethod == null)
+            if (!(semanticModel.GetTypeInfo(declaration, cancellationToken).ConvertedType is INamedTypeSymbol lambdaType) || lambdaType.DelegateInvokeMethod == null)
             {
                 return (canOffer: false, fixesError: false);
             }

src/Features/CSharp/Portable/UseIndexOrRangeOperator/CSharpUseRangeOperatorDiagnosticAnalyzer.cs

@@ -83,8 +83,7 @@ protected override void InitializeWorker(AnalysisContext context)
         {
             // Validate we're on a piece of syntax we expect.  While not necessary for analysis, we
             // want to make sure we're on something the fixer will know how to actually fix.
-            var invocationSyntax = invocation.Syntax as InvocationExpressionSyntax;
-            if (invocationSyntax is null ||
+            if (!(invocation.Syntax is InvocationExpressionSyntax invocationSyntax) ||
                 invocationSyntax.ArgumentList is null)
             {
                 return default;

src/Features/CSharp/Portable/UseNullPropagation/CSharpUseNullPropagationDiagnosticAnalyzer.cs

@@ -44,14 +44,12 @@ protected override bool IsNotEquals(BinaryExpressionSyntax condition)
             conditionPartToCheck = null;
             isEquals = true;
 
-            var patternExpression = conditionNode as IsPatternExpressionSyntax;
-            if (patternExpression == null)
+            if (!(conditionNode is IsPatternExpressionSyntax patternExpression))
             {
                 return false;
             }
 
-            var constantPattern = patternExpression.Pattern as ConstantPatternSyntax;
-            if (constantPattern == null)
+            if (!(patternExpression.Pattern is ConstantPatternSyntax constantPattern))
             {
                 return false;
             }