Convert '== null' and '!= null'

src/xunit.analyzers.fixes/X2000/AssertSingleShouldBeUsedForSingleParameterFixer.cs

@@ -44,7 +44,7 @@ static IEnumerable<SyntaxNode> GetLambdaStatements(SimpleLambdaExpressionSyntax
 	{
 		if (lambdaExpression.ExpressionBody is InvocationExpressionSyntax lambdaBody)
 			yield return ExpressionStatement(lambdaBody).WithAdditionalAnnotations(Formatter.Annotation, Simplifier.Annotation);
-		else if (lambdaExpression.Block != null && lambdaExpression.Block.Statements.Count != 0)
+		else if (lambdaExpression.Block is not null && lambdaExpression.Block.Statements.Count != 0)
 			foreach (var statement in lambdaExpression.Block.Statements)
 				yield return statement.WithAdditionalAnnotations(Formatter.Annotation, Simplifier.Annotation);
 	}
@@ -116,7 +116,7 @@ static async Task<Document> UseSingleMethod(
 			invocation.ArgumentList.Arguments[0].Expression is IdentifierNameSyntax collectionVariable)
 		{
 			var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
-			if (semanticModel != null && invocation.Parent != null)
+			if (semanticModel is not null && invocation.Parent is not null)
 			{
 				var statements = new List<SyntaxNode>();
 				var startLocation = invocation.GetLocation().SourceSpan.Start;

src/xunit.analyzers/Utility/CodeAnalysisExtensions.cs

@@ -35,7 +35,7 @@ public static bool IsInTestMethod(
 		if (semanticModel is null)
 			return false;
 
-		for (var parent = operation.Parent; parent != null; parent = parent.Parent)
+		for (var parent = operation.Parent; parent is not null; parent = parent.Parent)
 		{
 			if (parent is not IMethodBodyOperation methodBodyOperation)
 				continue;

src/xunit.analyzers/X1000/DoNotUseBlockingTaskOperations.cs

@@ -302,7 +302,7 @@ static bool WrappedInContinueWith(
 		INamedTypeSymbol taskType,
 		XunitContext xunitContext)
 	{
-		for (; operation != null; operation = operation.Parent)
+		for (; operation is not null; operation = operation.Parent)
 		{
 			if (operation is not IInvocationOperation invocation)
 				continue;

src/xunit.analyzers/X1000/EnsureFixturesHaveASource.cs

@@ -68,7 +68,7 @@ public override void AnalyzeCompilation(
 
 			// Add types from IClassFixture<> and ICollectionFixture<> on the collection definition
 			var collectionFixtureTypes = ImmutableHashSet<INamedTypeSymbol>.Empty;
-			if (collectionDefinitionName != null)
+			if (collectionDefinitionName is not null)
 			{
 				var collectionDefinitionAttributeType = xunitContext.Core.CollectionDefinitionAttributeType;
 

src/xunit.analyzers/X1000/InlineDataMustMatchTheoryParameters.cs

@@ -113,7 +113,7 @@ public override void AnalyzeCompilation(
 							: null;
 
 					// For params array of object, just consume everything that's left
-					if (paramsElementType != null
+					if (paramsElementType is not null
 						&& SymbolEqualityComparer.Default.Equals(paramsElementType, compilation.ObjectType)
 						&& paramsElementType.NullableAnnotation != NullableAnnotation.NotAnnotated)
 					{
@@ -124,12 +124,12 @@ public override void AnalyzeCompilation(
 					if (value.IsNull)
 					{
 						var isValueTypeParam =
-							paramsElementType != null
+							paramsElementType is not null
 								? paramsElementType.IsValueType && paramsElementType.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T
 								: parameter.Type.IsValueType && parameter.Type.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T;
 
 						var isNonNullableReferenceTypeParam =
-							paramsElementType != null
+							paramsElementType is not null
 								? paramsElementType.IsReferenceType && paramsElementType.NullableAnnotation == NullableAnnotation.NotAnnotated
 								: parameter.Type.IsReferenceType && parameter.Type.NullableAnnotation == NullableAnnotation.NotAnnotated;
 
@@ -156,7 +156,7 @@ public override void AnalyzeCompilation(
 							continue;
 
 						var isCompatible = ConversionChecker.IsConvertible(compilation, value.Type, parameter.Type, xunitContext);
-						if (!isCompatible && paramsElementType != null)
+						if (!isCompatible && paramsElementType is not null)
 							isCompatible = ConversionChecker.IsConvertible(compilation, value.Type, paramsElementType, xunitContext);
 
 						if (!isCompatible)

src/xunit.analyzers/X1000/MemberDataShouldReferenceValidMember.cs

@@ -580,7 +580,7 @@ static void VerifyDataMethodParameterUsage(
 					: null;
 
 			// For params array of object, just consume everything that's left
-			if (paramsElementType != null
+			if (paramsElementType is not null
 				&& SymbolEqualityComparer.Default.Equals(paramsElementType, compilation.ObjectType)
 				&& paramsElementType.NullableAnnotation != NullableAnnotation.NotAnnotated)
 			{
@@ -591,12 +591,12 @@ static void VerifyDataMethodParameterUsage(
 			if (!value.HasValue || value.Value is null)
 			{
 				var isValueTypeParam =
-					paramsElementType != null
+					paramsElementType is not null
 						? paramsElementType.IsValueType && paramsElementType.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T
 						: parameter.Type.IsValueType && parameter.Type.OriginalDefinition.SpecialType != SpecialType.System_Nullable_T;
 
 				var isNonNullableReferenceTypeParam =
-					paramsElementType != null
+					paramsElementType is not null
 						? paramsElementType.IsReferenceType && paramsElementType.NullableAnnotation == NullableAnnotation.NotAnnotated
 						: parameter.Type.IsReferenceType && parameter.Type.NullableAnnotation == NullableAnnotation.NotAnnotated;
 
@@ -617,7 +617,7 @@ static void VerifyDataMethodParameterUsage(
 					continue;
 
 				var isCompatible = ConversionChecker.IsConvertible(compilation, valueType, parameter.Type, xunitContext);
-				if (!isCompatible && paramsElementType != null)
+				if (!isCompatible && paramsElementType is not null)
 					isCompatible = ConversionChecker.IsConvertible(compilation, valueType, paramsElementType, xunitContext);
 
 				if (!isCompatible)

src/xunit.analyzers/X1000/TestMethodMustNotHaveMultipleFactAttributes.cs

@@ -34,7 +34,7 @@ public override void AnalyzeCompilation(
 			foreach (var attribute in symbol.GetAttributes())
 			{
 				var attributeType = attribute.AttributeClass;
-				if (attributeType != null && xunitContext.Core.FactAttributeType.IsAssignableFrom(attributeType))
+				if (attributeType is not null && xunitContext.Core.FactAttributeType.IsAssignableFrom(attributeType))
 				{
 					attributeTypes.Add(attributeType);
 					count++;

src/xunit.analyzers/X1000/TheoryMethodShouldUseAllParameters.cs

@@ -34,7 +34,7 @@ public override void AnalyzeCompilation(
 				return;
 
 			var methodSymbol = context.SemanticModel.GetDeclaredSymbol(methodSyntax);
-			if (methodSymbol == null)
+			if (methodSymbol is null)
 				return;
 
 			var attributes = methodSymbol.GetAttributes();

src/xunit.analyzers/X2000/AssertEqualShouldNotBeUsedForCollectionSizeCheck.cs

@@ -139,13 +139,13 @@ static bool IsCountPropertyOf(
 		INamedTypeSymbol? collectionType,
 		ISymbol symbol)
 	{
-		if (collectionType == null)
+		if (collectionType is null)
 			return false;
 
 		var memberSymbol = symbol;
 		var containingType = memberSymbol.ContainingType;
 		var countSymbol = collectionType.GetMember(nameof(ICollection.Count));
-		if (countSymbol == null)
+		if (countSymbol is null)
 			return false;
 
 		if (SymbolEqualityComparer.Default.Equals(countSymbol, symbol))

src/xunit.analyzers/X2000/AssertIsTypeShouldUseGenericOverloadType.cs

@@ -46,7 +46,7 @@ protected override void AnalyzeInvocation(
 		if (type.TypeKind == TypeKind.Interface)
 		{
 			var allInterfaces = (type as INamedTypeSymbol)?.AllInterfaces;
-			if (allInterfaces != null)
+			if (allInterfaces is not null)
 			{
 				var allMembers =
 					allInterfaces