Use simpler null checks

src/Compilers/CSharp/Portable/Binder/Binder.ValueChecks.cs

@@ -3072,7 +3072,7 @@ internal enum AddressKind
             bool peVerifyCompatEnabled,
             HashSet<LocalSymbol> stackLocalsOpt)
         {
-            Debug.Assert(!(method is null));
+            Debug.Assert(method is object);
 
             switch (expression.Kind)
             {
@@ -3199,7 +3199,7 @@ internal enum AddressKind
             bool peVerifyCompatEnabled,
             HashSet<LocalSymbol> stackLocalsOpt)
         {
-            Debug.Assert(!(method is null));
+            Debug.Assert(method is object);
 
             FieldSymbol field = fieldAccess.FieldSymbol;
 

src/Compilers/CSharp/Portable/Binder/Binder_Attributes.cs

@@ -166,7 +166,7 @@ private BoundAttribute BindAttributeCore(AttributeSyntax node, NamedTypeSymbol a
             }
             diagnostics.Add(node, useSiteDiagnostics);
 
-            if (!(attributeConstructor is null))
+            if (attributeConstructor is object)
             {
                 ReportDiagnosticsIfObsolete(diagnostics, attributeConstructor, node, hasBaseReceiver: false);
 

src/Compilers/CSharp/Portable/Binder/Binder_Expressions.cs

@@ -2052,7 +2052,7 @@ private BoundExpression BindRangeExpression(RangeExpressionSyntax node, Diagnost
                     memberOpt = WellKnownMember.System_Range__StartAt;
                 }
 
-                if (!(memberOpt is null))
+                if (memberOpt is object)
                 {
                     symbolOpt = (MethodSymbol)GetWellKnownTypeMember(
                         Compilation,
@@ -7048,7 +7048,7 @@ private BoundExpression ConvertToArrayIndex(BoundExpression index, SyntaxNode no
                 if (result is null)
                 {
                     result = TryImplicitConversionToArrayIndex(index, WellKnownType.System_Range, node, diagnostics);
-                    if (!(result is null))
+                    if (result is object)
                     {
                         // This member is needed for lowering and should produce an error if not present
                         _ = GetWellKnownTypeMember(
@@ -7097,7 +7097,7 @@ private BoundExpression TryImplicitConversionToArrayIndex(BoundExpression expr,
 
             var attemptDiagnostics = DiagnosticBag.GetInstance();
             var result = TryImplicitConversionToArrayIndex(expr, type, node, attemptDiagnostics);
-            if (!(result is null))
+            if (result is object)
             {
                 diagnostics.AddRange(attemptDiagnostics);
             }
@@ -7113,7 +7113,7 @@ private BoundExpression TryImplicitConversionToArrayIndex(BoundExpression expr,
 
             var result = TryImplicitConversionToArrayIndex(expr, type, node, attemptDiagnostics);
 
-            if (!(result is null))
+            if (result is object)
             {
                 diagnostics.AddRange(attemptDiagnostics);
             }

src/Compilers/CSharp/Portable/Binder/Binder_Statements.cs

@@ -689,7 +689,7 @@ private BoundStatement BindDeclarationStatementParts(LocalDeclarationStatementSy
         /// <returns>The <see cref="MethodSymbol"/> of the Dispose method if one is found, otherwise null.</returns>
         internal MethodSymbol TryFindDisposePatternMethod(BoundExpression expr, SyntaxNode syntaxNode, bool hasAwait, DiagnosticBag diagnostics)
         {
-            Debug.Assert(!(expr is null));
+            Debug.Assert(expr is object);
             Debug.Assert(!(expr.Type is null));
             Debug.Assert(expr.Type.IsRefLikeType || hasAwait); // pattern dispose lookup is only valid on ref structs or asynchronous usings
 

src/Compilers/CSharp/Portable/Binder/ForEachLoopBinder.cs

@@ -868,7 +868,7 @@ private void GetDisposalInfoForEnumerator(ref ForEachEnumeratorInfo.Builder buil
                 var patternDisposeDiags = new DiagnosticBag();
                 var receiver = new BoundDisposableValuePlaceholder(_syntax, enumeratorType);
                 MethodSymbol disposeMethod = TryFindDisposePatternMethod(receiver, _syntax, isAsync, patternDisposeDiags);
-                if (!(disposeMethod is null))
+                if (disposeMethod is object)
                 {
                     builder.NeedsDisposal = true;
                     builder.DisposeMethod = disposeMethod;

src/Compilers/CSharp/Portable/Binder/Semantics/AccessCheck.cs

@@ -62,7 +62,7 @@ internal static class AccessCheck
         /// </summary>
         internal static bool IsEffectivelyPublicOrInternal(Symbol symbol, out bool isInternal)
         {
-            Debug.Assert(!(symbol is null));
+            Debug.Assert(symbol is object);
 
             switch (symbol.Kind)
             {
@@ -101,7 +101,7 @@ internal static bool IsEffectivelyPublicOrInternal(Symbol symbol, out bool isInt
 
                 symbol = symbol.ContainingType;
             }
-            while (!(symbol is null));
+            while (symbol is object);
 
             return true;
         }

src/Compilers/CSharp/Portable/Binder/SwitchExpressionBinder.cs

@@ -125,7 +125,7 @@ private TypeSymbol InferResultType(ImmutableArray<BoundSwitchExpressionArm> swit
             foreach (var @case in switchCases)
             {
                 var type = @case.Value.Type;
-                if (!(type is null) && seenTypes.Add(type))
+                if (type is object && seenTypes.Add(type))
                 {
                     typesInOrder.Add(type);
                 }

src/Compilers/CSharp/Portable/Binder/UsingStatementBinder.cs

@@ -189,14 +189,14 @@ bool populateDisposableConversionOrDisposeMethod(bool fromExpression)
 
                 // If this is a ref struct, or we're in a valid asynchronous using, try binding via pattern.
                 // We won't need to try and bind a second time if it fails, as async dispose can't be pattern based (ref structs are not allowed in async methods)
-                if (!(type is null) && (type.IsRefLikeType || hasAwait))
+                if (type is object && (type.IsRefLikeType || hasAwait))
                 {
                     BoundExpression receiver = fromExpression
                                                ? expressionOpt
                                                : new BoundLocal(syntax, declarationsOpt[0].LocalSymbol, null, type) { WasCompilerGenerated = true };
 
                     disposeMethodOpt = originalBinder.TryFindDisposePatternMethod(receiver, syntax, hasAwait, diagnostics);
-                    if (!(disposeMethodOpt is null))
+                    if (disposeMethodOpt is object)
                     {
                         if (hasAwait)
                         {

src/Compilers/CSharp/Portable/Compilation/CSharpCompilation.cs

@@ -3326,7 +3326,7 @@ internal bool EmitNullablePublicOnly
 
         internal bool ShouldEmitNullableAttributes(Symbol symbol)
         {
-            Debug.Assert(!(symbol is null));
+            Debug.Assert(symbol is object);
             Debug.Assert(symbol.IsDefinition);
 
             if (symbol.ContainingModule != SourceModule)

src/Compilers/CSharp/Portable/Errors/LazyMissingNonNullTypesContextDiagnosticInfo.cs

@@ -36,7 +36,7 @@ private static void GetRawDiagnosticInfos(bool isNullableEnabled, CSharpParseOpt
         {
             const MessageID featureId = MessageID.IDS_FeatureNullableReferenceTypes;
             var info = featureId.GetFeatureAvailabilityDiagnosticInfoOpt(options);
-            if (!(info is null))
+            if (info is object)
             {
                 infos.Add(info);
             }

src/Compilers/CSharp/Portable/Errors/MessageID.cs

@@ -233,7 +233,7 @@ internal static string RequiredFeature(this MessageID feature)
         internal static bool CheckFeatureAvailability(this MessageID feature, DiagnosticBag diagnostics, Location errorLocation)
         {
             var diag = GetFeatureAvailabilityDiagnosticInfoOpt(feature, (CSharpParseOptions)errorLocation.SourceTree.Options);
-            if (!(diag is null))
+            if (diag is object)
             {
                 diagnostics.Add(diag, errorLocation);
                 return false;

src/Compilers/CSharp/Portable/FlowAnalysis/NullableWalker.cs

@@ -412,7 +412,7 @@ protected override ImmutableArray<PendingBranch> Scan(ref bool badRegion)
             {
                 ParameterSymbol methodThisParameter = MethodThisParameter;
                 EnterParameters(); // assign parameters
-                if (!(methodThisParameter is null))
+                if (methodThisParameter is object)
                 {
                     EnterParameter(methodThisParameter, methodThisParameter.TypeWithAnnotations);
                 }
@@ -1869,7 +1869,7 @@ public override BoundNode VisitAnonymousObjectCreationExpression(BoundAnonymousO
                     TrackNullableStateForAssignment(argument, property.TypeWithAnnotations, GetOrCreateSlot(property, receiverSlot), argumentType, MakeSlot(argument));
 
                     var currentDeclaration = getDeclaration(node, property, ref currentDeclarationIndex);
-                    if (!(currentDeclaration is null))
+                    if (currentDeclaration is object)
                     {
                         TakeIncrementalSnapshot(currentDeclaration);
                         SetAnalyzedNullability(currentDeclaration, new VisitResult(argumentType, property.TypeWithAnnotations));
@@ -2509,7 +2509,7 @@ public override BoundNode VisitNullCoalescingOperator(BoundNullCoalescingOperato
 
             TypeSymbol getLeftResultType(TypeSymbol leftType, TypeSymbol rightType)
             {
-                Debug.Assert(!(rightType is null));
+                Debug.Assert(rightType is object);
                 // If there was an identity conversion between the two operands (in short, if there
                 // is no implicit conversion on the right operand), then check nullable conversions
                 // in both directions since it's possible the right operand is the better result type.

src/Compilers/CSharp/Portable/Lowering/LocalRewriter/LocalRewriter_UsingStatement.cs

@@ -424,7 +424,7 @@ private BoundExpression GenerateDisposeCall(SyntaxNode syntax, BoundExpression d
             {
                 disposeCall = MakeCallWithNoExplicitArgument(syntax, disposedExpression, methodOpt);
 
-                if (!(awaitOpt is null))
+                if (awaitOpt is object)
                 {
                     // await local.DisposeAsync()
                     _sawAwaitInExceptionHandler = true;

src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PEModuleSymbol.cs

@@ -711,7 +711,7 @@ internal IEnumerable<NamedTypeSymbol> GetForwardedTypes()
 
         internal bool ShouldDecodeNullableAttributes(Symbol symbol)
         {
-            Debug.Assert(!(symbol is null));
+            Debug.Assert(symbol is object);
             Debug.Assert(symbol.IsDefinition);
             Debug.Assert((object)symbol.ContainingModule == this);
 

src/Compilers/CSharp/Portable/Symbols/Metadata/PE/PENamedTypeSymbol.cs

@@ -434,7 +434,7 @@ private NamedTypeSymbol GetDeclaredBaseType(bool skipTransformsIfNecessary)
             if (ReferenceEquals(_lazyDeclaredBaseType, ErrorTypeSymbol.UnknownResultType))
             {
                 var baseType = MakeDeclaredBaseType();
-                if (!(baseType is null))
+                if (baseType is object)
                 {
                     if (skipTransformsIfNecessary)
                     {

src/Compilers/CSharp/Portable/Symbols/Source/LocalFunctionSymbol.cs

@@ -229,7 +229,7 @@ internal void ComputeReturnType()
 
             // Skip some diagnostics when the local function is not associated with a compilation
             // (specifically, local functions nested in expressions in the EE).
-            if (!(compilation is null))
+            if (compilation is object)
             {
                 if (this.IsAsync)
                 {

src/Compilers/CSharp/Portable/Symbols/Source/SourceMemberContainerSymbol.cs

@@ -3339,7 +3339,7 @@ private void AddAccessorIfAvailable(ArrayBuilder<Symbol> symbols, MethodSymbol a
 
             var builder = new MostCommonNullableValueBuilder();
             var baseType = BaseTypeNoUseSiteDiagnostics;
-            if (!(baseType is null))
+            if (baseType is object)
             {
                 builder.AddValue(TypeWithAnnotations.Create(baseType));
             }
@@ -3366,7 +3366,7 @@ internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, r
             var compilation = DeclaringCompilation;
             NamedTypeSymbol baseType = this.BaseTypeNoUseSiteDiagnostics;
 
-            if (!(baseType is null))
+            if (baseType is object)
             {
                 if (baseType.ContainsDynamic())
                 {
@@ -3386,7 +3386,7 @@ internal override void AddSynthesizedAttributes(PEModuleBuilder moduleBuilder, r
                     AddSynthesizedAttribute(ref attributes, moduleBuilder.SynthesizeNullableContextAttribute(this, nullableContextValue));
                 }
 
-                if (!(baseType is null))
+                if (baseType is object)
                 {
                     AddSynthesizedAttribute(ref attributes, moduleBuilder.SynthesizeNullableAttributeIfNecessary(this, nullableContextValue, TypeWithAnnotations.Create(baseType)));
                 }

src/Compilers/CSharp/Test/Emit/Attributes/AttributeTests_NullablePublicOnly.cs

@@ -593,7 +593,7 @@ private static void AssertNullablePublicOnlyAttribute(ModuleSymbol module, bool
                     type = attribute.AttributeClass;
                 }
             }
-            if (!(type is null))
+            if (type is object)
             {
                 Assert.Equal(publicDefinition ? Accessibility.Public : Accessibility.Internal, type.DeclaredAccessibility);
             }

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

@@ -37,7 +37,7 @@ private static void RunInThread(Action action)
             thread.Start();
             thread.Join();
 
-            if (!(exception is null))
+            if (exception is object)
             {
                 throw exception;
             }

src/Compilers/Core/Portable/Compilation/Compilation.cs

@@ -1261,7 +1261,7 @@ public bool HasImplicitConversion(ITypeSymbol fromType, ITypeSymbol toType)
 
             checkInCompilationReferences(symbol, nameof(symbol));
             checkInCompilationReferences(within, nameof(within));
-            if (!(throughType is null))
+            if (throughType is object)
             {
                 checkInCompilationReferences(throughType, nameof(throughType));
             }

src/Compilers/Core/Portable/Operations/Operation.cs

@@ -181,7 +181,7 @@ protected void SetParentOperation(IOperation parent)
         [Conditional("DEBUG")]
         internal static void VerifyParentOperation(IOperation parent, IOperation child)
         {
-            if (!(child is null))
+            if (child is object)
             {
                 Debug.Assert((object)child.Parent == parent);
             }

src/Workspaces/Core/Portable/Workspace/Host/SyntaxTreeFactory/AbstractSyntaxTreeFactoryService.AbstractRecoverableSyntaxRoot.cs

@@ -32,7 +32,7 @@ internal struct SyntaxTreeInfo
                 int length,
                 ImmutableDictionary<string, ReportDiagnostic> diagnosticOptions)
             {
-                Debug.Assert(!(diagnosticOptions is null));
+                Debug.Assert(diagnosticOptions is object);
 
                 FilePath = filePath ?? string.Empty;
                 Options = options;
@@ -86,7 +86,7 @@ internal SyntaxTreeInfo WithOptionsAndLength(ParseOptions options, int length)
 
             internal SyntaxTreeInfo WithDiagnosticOptions(ImmutableDictionary<string, ReportDiagnostic> options)
             {
-                Debug.Assert(!(options is null));
+                Debug.Assert(options is object);
                 return new SyntaxTreeInfo(
                     FilePath,
                     Options,