Use compound assignment

src/Compilers/Core/Portable/Collections/OrderPreservingMultiDictionary.cs

@@ -79,7 +79,7 @@ public OrderPreservingMultiDictionary()
 
         private void EnsureDictionary()
         {
-            _dictionary = _dictionary ?? PooledDictionary<K, ValueSet>.GetInstance();
+            _dictionary ??= PooledDictionary<K, ValueSet>.GetInstance();
         }
 
         public bool IsEmpty => _dictionary == null;

src/Compilers/Core/Portable/DiagnosticAnalyzer/AnalyzerAssemblyLoader.cs

@@ -69,7 +69,7 @@ private Assembly LoadFromPathUncheckedCore(string fullPath, AssemblyIdentity ide
                 }
                 else
                 {
-                    identity = identity ?? GetOrAddAssemblyIdentity(fullPath);
+                    identity ??= GetOrAddAssemblyIdentity(fullPath);
                     if (identity != null && _loadedAssembliesByIdentity.TryGetValue(identity, out existingAssembly))
                     {
                         loadedAssembly = existingAssembly;

src/Compilers/Core/Portable/FileSystem/PathUtilities.cs

@@ -46,7 +46,7 @@ public static string TrimTrailingSeparators(string s)
             int lastSeparator = s.Length;
             while (lastSeparator > 0 && IsDirectorySeparator(s[lastSeparator - 1]))
             {
-                lastSeparator = lastSeparator - 1;
+                lastSeparator -= 1;
             }
 
             if (lastSeparator != s.Length)

src/Compilers/Core/Portable/InternalUtilities/BitArithmeticUtilities.cs

@@ -15,7 +15,7 @@ public static int CountBits(uint v)
         {
             unchecked
             {
-                v = v - ((v >> 1) & 0x55555555u);
+                v -= ((v >> 1) & 0x55555555u);
                 v = (v & 0x33333333u) + ((v >> 2) & 0x33333333u);
                 return (int)((v + (v >> 4) & 0xF0F0F0Fu) * 0x1010101u) >> 24;
             }

src/Workspaces/Core/Portable/AddImports/AbstractAddImportsService.cs

@@ -44,7 +44,7 @@ protected AbstractAddImportsService()
 
         private static ImmutableArray<SyntaxNode> GetAllContainers(SyntaxNode root, SyntaxNode contextLocation)
         {
-            contextLocation = contextLocation ?? root;
+            contextLocation ??= root;
 
             var applicableContainer = GetFirstApplicableContainer(contextLocation);
             return applicableContainer.GetAncestorsOrThis<SyntaxNode>().ToImmutableArray();
@@ -79,7 +79,7 @@ private static ImmutableArray<SyntaxNode> GetAllContainers(SyntaxNode root, Synt
 
         public SyntaxNode GetImportContainer(SyntaxNode root, SyntaxNode contextLocation, SyntaxNode import)
         {
-            contextLocation = contextLocation ?? root;
+            contextLocation ??= root;
             GetContainers(root, contextLocation,
                 out var externContainer, out var usingContainer, out var staticUsingContainer, out var aliasContainer);
 
@@ -110,7 +110,7 @@ public SyntaxNode GetImportContainer(SyntaxNode root, SyntaxNode contextLocation
             IEnumerable<SyntaxNode> newImports,
             bool placeSystemNamespaceFirst)
         {
-            contextLocation = contextLocation ?? root;
+            contextLocation ??= root;
 
             var globalImports = GetGlobalImports(compilation);
             var containers = GetAllContainers(root, contextLocation);

src/Workspaces/Core/Portable/CodeGeneration/AbstractCodeGenerationService.cs

@@ -176,7 +176,7 @@ protected static T Cast<T>(object value)
             IEnumerable<ISymbol> members,
             CancellationToken cancellationToken)
         {
-            options = options ?? CodeGenerationOptions.Default;
+            options ??= CodeGenerationOptions.Default;
 
             var (destinationDeclaration, availableIndices) =
                 await this.FindMostRelevantDeclarationAsync(solution, destination, options, cancellationToken).ConfigureAwait(false);
@@ -207,7 +207,7 @@ protected static T Cast<T>(object value)
 
         public async Task<Document> AddImportsAsync(Document document, CodeGenerationOptions options, CancellationToken cancellationToken)
         {
-            options = options ?? CodeGenerationOptions.Default;
+            options ??= CodeGenerationOptions.Default;
             var adder = this.CreateImportsAdder(document);
             var newDocument = await adder.AddAsync(options.PlaceSystemNamespaceFirst, options, cancellationToken).ConfigureAwait(false);
             return newDocument;

src/Workspaces/Core/Portable/CodeGeneration/AbstractCodeGenerationService_FindDeclaration.cs

@@ -179,7 +179,7 @@ class NestedType
 
                 // Then, prefer a declaration from the same file.
                 declaration = await SelectFirstOrDefaultAsync(declarations.Where(r => r.SyntaxTree == locationOpt.SourceTree), node => true, cancellationToken).ConfigureAwait(false);
-                fallbackDeclaration = fallbackDeclaration ?? declaration;
+                fallbackDeclaration ??= declaration;
                 if (CanAddTo(declaration, solution, cancellationToken, out availableIndices))
                 {
                     return (declaration, availableIndices);

src/Workspaces/Core/Portable/CodeGeneration/AbstractImportsAdder.cs

@@ -57,7 +57,7 @@ protected AbstractImportsAdder(Document document)
                         cancellationToken.ThrowIfCancellationRequested();
                         if (!IsBuiltIn(namedType))
                         {
-                            namespaceScope = namespaceScope ?? this.GetInnermostNamespaceScope(annotatedNode);
+                            namespaceScope ??= this.GetInnermostNamespaceScope(annotatedNode);
                             var referencedDefinitions = namespaceScopeToReferencedDefinitions.GetOrAdd(
                                 namespaceScope, createSet);
                             referencedDefinitions.Add(namedType);

src/Workspaces/Core/Portable/CodeStyle/CodeStyleHelpers.cs

@@ -34,7 +34,7 @@ public static bool TryParseBoolEditorConfigCodeStyleOption(string arg, out CodeS
                     // 'true' must always be provided with a notification option.
                     if (isEnabled == false)
                     {
-                        notificationOpt = notificationOpt ?? NotificationOption.Silent;
+                        notificationOpt ??= NotificationOption.Silent;
                         option = new CodeStyleOption<bool>(false, notificationOpt);
                         return true;
                     }

src/Workspaces/Core/Portable/CodeStyle/CodeStyleOptions.cs

@@ -274,7 +274,7 @@ private static CodeStyleOption<AccessibilityModifiersRequired> ParseAccessibilit
                 if (value == "never")
                 {
                     // If they provide 'never', they don't need a notification level.
-                    notificationOpt = notificationOpt ?? NotificationOption.Silent;
+                    notificationOpt ??= NotificationOption.Silent;
                 }
 
                 if (notificationOpt != null)

src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResult.cs

@@ -69,7 +69,7 @@ internal struct DiagnosticAnalysisResult
             IsEmpty = false;
 
             // do after all fields are assigned.
-            DocumentIds = DocumentIds ?? CreateDocumentIds();
+            DocumentIds ??= CreateDocumentIds();
             IsEmpty = DocumentIds.IsEmpty && _others.IsEmpty;
         }
 

src/Workspaces/Core/Portable/Diagnostics/DiagnosticAnalysisResultBuilder.cs

@@ -83,7 +83,7 @@ public void AddExternalSemanticDiagnostics(DocumentId documentId, IEnumerable<Di
                             else
                             {
                                 // non local diagnostics without location
-                                _lazyOthers = _lazyOthers ?? new List<DiagnosticData>();
+                                _lazyOthers ??= new List<DiagnosticData>();
                                 _lazyOthers.Add(DiagnosticData.Create(Project, diagnostic));
                             }
 
@@ -91,7 +91,7 @@ public void AddExternalSemanticDiagnostics(DocumentId documentId, IEnumerable<Di
                         }
                     case LocationKind.None:
                         {
-                            _lazyOthers = _lazyOthers ?? new List<DiagnosticData>();
+                            _lazyOthers ??= new List<DiagnosticData>();
                             _lazyOthers.Add(DiagnosticData.Create(Project, diagnostic));
                             break;
                         }
@@ -123,7 +123,7 @@ private void AppendDiagnostics(ref Dictionary<DocumentId, List<DiagnosticData>>
                 return;
             }
 
-            map = map ?? new Dictionary<DocumentId, List<DiagnosticData>>();
+            map ??= new Dictionary<DocumentId, List<DiagnosticData>>();
             map.GetOrAdd(documentOpt.Id, _ => new List<DiagnosticData>()).Add(DiagnosticData.Create(documentOpt, diagnostic));
 
             AddDocumentToSet(documentOpt);
@@ -163,7 +163,7 @@ public void AddCompilationDiagnostics(IEnumerable<Diagnostic> diagnostics)
                         }
                     case LocationKind.None:
                         {
-                            _lazyOthers = _lazyOthers ?? new List<DiagnosticData>();
+                            _lazyOthers ??= new List<DiagnosticData>();
                             _lazyOthers.Add(DiagnosticData.Create(Project, diagnostic));
                             break;
                         }
@@ -182,7 +182,7 @@ public void AddCompilationDiagnostics(IEnumerable<Diagnostic> diagnostics)
                             else
                             {
                                 // non local diagnostics without location
-                                _lazyOthers = _lazyOthers ?? new List<DiagnosticData>();
+                                _lazyOthers ??= new List<DiagnosticData>();
                                 _lazyOthers.Add(DiagnosticData.Create(Project, diagnostic));
                             }
 
@@ -205,7 +205,7 @@ public void AddCompilationDiagnostics(IEnumerable<Diagnostic> diagnostics)
 
         private void AddDocumentToSet(Document document)
         {
-            _lazySet = _lazySet ?? new HashSet<DocumentId>();
+            _lazySet ??= new HashSet<DocumentId>();
             _lazySet.Add(document.Id);
         }
 

src/Workspaces/Core/Portable/Editing/ImportAdderService.cs

@@ -22,7 +22,7 @@ internal abstract class ImportAdderService : ILanguageService
             Document document, IEnumerable<TextSpan> spans,
             OptionSet options, CancellationToken cancellationToken)
         {
-            options = options ?? await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
+            options ??= await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
 
             var model = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
             var root = await model.SyntaxTree.GetRootAsync(cancellationToken).ConfigureAwait(false);

src/Workspaces/Core/Portable/Editing/SyntaxEditor.cs

@@ -45,7 +45,7 @@ private SyntaxNode ApplyTrackingToNewNode(SyntaxNode node)
                 return null;
             }
 
-            _lazyTrackedNewNodesOpt = _lazyTrackedNewNodesOpt ?? new HashSet<SyntaxNode>();
+            _lazyTrackedNewNodesOpt ??= new HashSet<SyntaxNode>();
             foreach (var descendant in node.DescendantNodesAndSelf())
             {
                 _lazyTrackedNewNodesOpt.Add(descendant);

src/Workspaces/Core/Portable/FindSymbols/FindReferences/DependentTypeFinder.cs

@@ -282,7 +282,7 @@ bool metadataTypeMatches(SymbolAndProjectIdSet s, INamedTypeSymbol t)
             CancellationToken cancellationToken)
         {
             type = type.WithSymbol(type.Symbol.OriginalDefinition);
-            projects = projects ?? ImmutableHashSet.Create(solution.Projects.ToArray());
+            projects ??= ImmutableHashSet.Create(solution.Projects.ToArray());
             var searchInMetadata = type.Symbol.Locations.Any(s_isInMetadata);
 
             // Note: it is not sufficient to just walk the list of projects passed in,

src/Workspaces/Core/Portable/FindSymbols/FindReferences/Finders/AbstractReferenceFinder.cs

@@ -182,7 +182,7 @@ protected static bool IdentifiersMatch(ISyntaxFactsService syntaxFacts, string n
             ISymbol symbol, Func<SyntaxToken, SyntaxNode> findParentNode, Solution solution, CancellationToken cancellationToken)
         {
             var nodeMatch = GetStandardSymbolsNodeMatchFunction(symbol, solution, cancellationToken);
-            findParentNode = findParentNode ?? (t => t.Parent);
+            findParentNode ??= (t => t.Parent);
             (bool matched, CandidateReason reason) symbolsMatch(SyntaxToken token, SemanticModel model)
                 => nodeMatch(findParentNode(token), model);
 

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_FindReferences_Current.cs

@@ -48,7 +48,7 @@ public static partial class SymbolFinder
             FindReferencesSearchOptions options, CancellationToken cancellationToken)
         {
             var finders = ReferenceFinders.DefaultReferenceFinders;
-            progress = progress ?? StreamingFindReferencesProgress.Instance;
+            progress ??= StreamingFindReferencesProgress.Instance;
             var engine = new FindReferencesSearchEngine(
                 solution, documents, finders, progress, options, cancellationToken);
             return engine.FindReferencesAsync(symbolAndProjectId);

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_FindReferences_Legacy.cs

@@ -79,7 +79,7 @@ public static partial class SymbolFinder
             FindReferencesSearchOptions options,
             CancellationToken cancellationToken)
         {
-            progress = progress ?? FindReferencesProgress.Instance;
+            progress ??= FindReferencesProgress.Instance;
             var streamingProgress = new StreamingProgressCollector(
                 new StreamingFindReferencesProgressAdapter(progress));
             await FindReferencesAsync(

src/Workspaces/Core/Portable/FindSymbols/SymbolFinder_Hierarchy.cs

@@ -256,7 +256,7 @@ public static partial class SymbolFinder
                         var bestDef = sourceDef.Symbol != null ? sourceDef : implementation;
                         if (IsAccessible(bestDef))
                         {
-                            results = results ?? ImmutableArray.CreateBuilder<SymbolAndProjectId>();
+                            results ??= ImmutableArray.CreateBuilder<SymbolAndProjectId>();
                             results.Add(bestDef.WithSymbol(bestDef.Symbol.OriginalDefinition));
                         }
                     }
@@ -317,7 +317,7 @@ public static async Task<IEnumerable<SymbolCallerInfo>> FindCallersAsync(ISymbol
             {
                 foreach (var kvp in await directReferences.Locations.FindReferencingSymbolsAsync(cancellationToken).ConfigureAwait(false))
                 {
-                    results = results ?? new List<SymbolCallerInfo>();
+                    results ??= new List<SymbolCallerInfo>();
                     results.Add(new SymbolCallerInfo(kvp.Key, symbol, kvp.Value, isDirect: true));
                 }
             }
@@ -326,7 +326,7 @@ public static async Task<IEnumerable<SymbolCallerInfo>> FindCallersAsync(ISymbol
                 var indirectLocations = indirectReferences.SelectMany(r => r.Locations);
                 foreach (var kvp in await indirectLocations.FindReferencingSymbolsAsync(cancellationToken).ConfigureAwait(false))
                 {
-                    results = results ?? new List<SymbolCallerInfo>();
+                    results ??= new List<SymbolCallerInfo>();
                     results.Add(new SymbolCallerInfo(kvp.Key, symbol, kvp.Value, isDirect: false));
                 }
             }

src/Workspaces/Core/Portable/FindSymbols/SymbolTree/SymbolTreeInfo.cs

@@ -211,7 +211,7 @@ public SymbolTreeInfo WithChecksum(Checksum checksum)
             foreach (var node in FindNodeIndices(name, comparer))
             {
                 cancellationToken.ThrowIfCancellationRequested();
-                assemblySymbol = assemblySymbol ?? await lazyAssembly.GetValueAsync(cancellationToken).ConfigureAwait(false);
+                assemblySymbol ??= await lazyAssembly.GetValueAsync(cancellationToken).ConfigureAwait(false);
 
                 Bind(node, assemblySymbol.GlobalNamespace, results, cancellationToken);
             }

src/Workspaces/Core/Portable/FlowAnalysis/LValueFlowCaptureProvider.cs

@@ -50,7 +50,7 @@ internal static class LValueFlowCapturesProvider
                         assignment.Target == flowCaptureReference ||
                         flowCaptureReference.IsInLeftOfDeconstructionAssignment(out _))
                     {
-                        lvalueFlowCaptureIdBuilder = lvalueFlowCaptureIdBuilder ?? ImmutableDictionary.CreateBuilder<CaptureId, FlowCaptureKind>();
+                        lvalueFlowCaptureIdBuilder ??= ImmutableDictionary.CreateBuilder<CaptureId, FlowCaptureKind>();
                         var captureKind = flowCaptureReference.Parent.IsAnyCompoundAssignment() || rvalueFlowCaptureIds.Contains(flowCaptureReference.Id)
                             ? FlowCaptureKind.LValueAndRValueCapture
                             : FlowCaptureKind.LValueCapture;

src/Workspaces/Core/Portable/Formatting/AbstractSyntaxFormattingService.cs

@@ -76,7 +76,7 @@ public IFormattingResult Format(SyntaxNode node, IEnumerable<TextSpan> spans, Op
                     continue;
                 }
 
-                results = results ?? new List<AbstractFormattingResult>();
+                results ??= new List<AbstractFormattingResult>();
                 results.Add(Format(node, options, rules, pair.Item1, pair.Item2, cancellationToken));
             }
 

src/Workspaces/Core/Portable/Formatting/Formatter.cs

@@ -243,9 +243,9 @@ internal static IFormattingResult GetFormattingResult(SyntaxNode node, IEnumerab
                 return null;
             }
 
-            options = options ?? workspace.Options;
-            rules = rules ?? GetDefaultFormattingRules(workspace, node.Language);
-            spans = spans ?? SpecializedCollections.SingletonEnumerable(node.FullSpan);
+            options ??= workspace.Options;
+            rules ??= GetDefaultFormattingRules(workspace, node.Language);
+            spans ??= SpecializedCollections.SingletonEnumerable(node.FullSpan);
             return languageFormatter.Format(node, spans, options, rules, cancellationToken);
         }
 

src/Workspaces/Core/Portable/LinkedFileDiffMerging/LinkedFileDiffMergingSession.cs

@@ -112,7 +112,7 @@ internal async Task<LinkedFileMergeSessionResult> MergeDiffsAsync(IMergeConflict
 
             if (unmergedChanges.Any())
             {
-                mergeConflictHandler = mergeConflictHandler ?? _oldSolution.GetDocument(linkedDocumentGroup.First()).GetLanguageService<ILinkedFileMergeConflictCommentAdditionService>();
+                mergeConflictHandler ??= _oldSolution.GetDocument(linkedDocumentGroup.First()).GetLanguageService<ILinkedFileMergeConflictCommentAdditionService>();
                 var mergeConflictTextEdits = mergeConflictHandler.CreateEdits(originalSourceText, unmergedChanges);
 
                 allChanges = MergeChangesWithMergeFailComments(appliedChanges, mergeConflictTextEdits, mergeConflictResolutionSpan, groupSessionInfo);

src/Workspaces/Core/Portable/PatternMatching/PatternMatcher.cs

@@ -48,7 +48,7 @@ internal abstract partial class PatternMatcher : IDisposable
             CultureInfo culture,
             bool allowFuzzyMatching = false)
         {
-            culture = culture ?? CultureInfo.CurrentCulture;
+            culture ??= CultureInfo.CurrentCulture;
 
             _compareInfo = culture.CompareInfo;
             _textInfo = culture.TextInfo;
@@ -534,12 +534,12 @@ private bool PartStartsWith(string candidate, TextSpan candidatePart, string pat
                     matchSpans.Add(new TextSpan(candidateHump.Start, patternChunkCharacterSpan.Length));
                     gotOneMatchThisCandidate = true;
 
-                    firstMatch = firstMatch ?? currentCandidateHump;
+                    firstMatch ??= currentCandidateHump;
 
                     // If we were contiguous, then keep that value.  If we weren't, then keep that
                     // value.  If we don't know, then set the value to 'true' as an initial match is
                     // obviously contiguous.
-                    contiguous = contiguous ?? true;
+                    contiguous ??= true;
 
                     candidateHump = new TextSpan(candidateHump.Start + patternChunkCharacterSpan.Length, candidateHump.Length - patternChunkCharacterSpan.Length);
                 }

src/Workspaces/Core/Portable/Recommendations/Recommender.cs

@@ -44,7 +44,7 @@ public static class Recommender
             OptionSet options = null,
             CancellationToken cancellationToken = default)
         {
-            options = options ?? workspace.Options;
+            options ??= workspace.Options;
             var languageRecommender = workspace.Services.GetLanguageServices(semanticModel.Language).GetService<IRecommendationService>();
 
             return await languageRecommender.GetRecommendedSymbolsAtPositionAsync(

src/Workspaces/Core/Portable/Rename/ConflictEngine/ConflictResolver.Session.cs

@@ -345,7 +345,7 @@ private async Task DebugVerifyNoErrorsAsync(ConflictResolution conflictResolutio
                             var hasConflict = _renameAnnotations.HasAnnotation(tokenOrNode, RenameInvalidIdentifierAnnotation.Instance);
                             if (!hasConflict)
                             {
-                                newDocumentSemanticModel = newDocumentSemanticModel ?? await newDocument.GetSemanticModelAsync(_cancellationToken).ConfigureAwait(false);
+                                newDocumentSemanticModel ??= await newDocument.GetSemanticModelAsync(_cancellationToken).ConfigureAwait(false);
                                 newReferencedSymbols = GetSymbolsInNewSolution(newDocument, newDocumentSemanticModel, conflictAnnotation, tokenOrNode);
 
                                 // The semantic correctness, after rename, for each token of interest in the

src/Workspaces/Core/Portable/Rename/Renamer.cs

@@ -44,7 +44,7 @@ public static class Renamer
 
             cancellationToken.ThrowIfCancellationRequested();
 
-            options = options ?? solution.Options;
+            options ??= solution.Options;
             return RenameLocations.FindAsync(
                 symbolAndProjectId, solution, options, cancellationToken);
         }
@@ -100,7 +100,7 @@ public static class Renamer
 
             cancellationToken.ThrowIfCancellationRequested();
 
-            options = options ?? solution.Workspace.Options;
+            options ??= solution.Workspace.Options;
             var renameLocations = await GetRenameLocationsAsync(solution, symbolAndProjectId, options, cancellationToken).ConfigureAwait(false);
             return await RenameAsync(renameLocations, newName, filter, hasConflict, cancellationToken).ConfigureAwait(false);
         }

src/Workspaces/Core/Portable/Shared/Extensions/DocumentExtensions.cs

@@ -122,7 +122,7 @@ public static async Task<ImmutableArray<Diagnostic>> GetErrorsAsync(this Documen
                 return ImmutableArray<Diagnostic>.Empty;
             }
 
-            ignoreErrorCode = ignoreErrorCode ?? SpecializedCollections.EmptyList<string>();
+            ignoreErrorCode ??= SpecializedCollections.EmptyList<string>();
             var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
             return semanticModel.GetDiagnostics(cancellationToken: cancellationToken).WhereAsArray(
                 diag => diag.Severity == DiagnosticSeverity.Error && !ignoreErrorCode.Contains(diag.Id));

src/Workspaces/Core/Portable/Shared/Extensions/ISymbolExtensions.cs

@@ -711,7 +711,7 @@ public static bool IsInaccessibleLocal(this ISymbol symbol, int position)
             }
 
             attributes = attributes.IsDefault ? symbol.GetAttributes() : attributes;
-            hideModuleNameAttribute = hideModuleNameAttribute ?? compilation.HideModuleNameAttribute();
+            hideModuleNameAttribute ??= compilation.HideModuleNameAttribute();
             foreach (var attribute in attributes)
             {
                 if (Equals(attribute.AttributeClass, hideModuleNameAttribute))
@@ -726,7 +726,7 @@ public static bool IsInaccessibleLocal(this ISymbol symbol, int position)
         private static bool IsBrowsingProhibitedByEditorBrowsableAttribute(
             ISymbol symbol, ImmutableArray<AttributeData> attributes, bool hideAdvancedMembers, Compilation compilation, IMethodSymbol constructor)
         {
-            constructor = constructor ?? EditorBrowsableHelpers.GetSpecialEditorBrowsableAttributeConstructor(compilation);
+            constructor ??= EditorBrowsableHelpers.GetSpecialEditorBrowsableAttributeConstructor(compilation);
             if (constructor == null)
             {
                 return false;

src/Workspaces/Core/Portable/Shared/Extensions/ITypeSymbolExtensions.cs

@@ -217,7 +217,7 @@ public static ITypeSymbol RemoveNullableIfPresent(this ITypeSymbol symbol)
             this ITypeSymbol type,
             HashSet<INamedTypeSymbol> symbols = null)
         {
-            symbols = symbols ?? new HashSet<INamedTypeSymbol>(SymbolEquivalenceComparer.Instance);
+            symbols ??= new HashSet<INamedTypeSymbol>(SymbolEquivalenceComparer.Instance);
 
             foreach (var interfaceType in type.Interfaces)
             {
@@ -467,7 +467,7 @@ public static bool IsFormattableString(this ITypeSymbol symbol)
         public static IList<ITypeParameterSymbol> GetReferencedMethodTypeParameters(
             this ITypeSymbol type, IList<ITypeParameterSymbol> result = null)
         {
-            result = result ?? new List<ITypeParameterSymbol>();
+            result ??= new List<ITypeParameterSymbol>();
             type?.Accept(new CollectTypeParameterSymbolsVisitor(result, onlyMethodTypeParameters: true));
             return result;
         }
@@ -475,7 +475,7 @@ public static bool IsFormattableString(this ITypeSymbol symbol)
         public static IList<ITypeParameterSymbol> GetReferencedTypeParameters(
             this ITypeSymbol type, IList<ITypeParameterSymbol> result = null)
         {
-            result = result ?? new List<ITypeParameterSymbol>();
+            result ??= new List<ITypeParameterSymbol>();
             type?.Accept(new CollectTypeParameterSymbolsVisitor(result, onlyMethodTypeParameters: false));
             return result;
         }

src/Workspaces/Core/Portable/Shared/Utilities/BloomFilter.cs

@@ -324,7 +324,7 @@ public void Add(string value)
         private int GetBitArrayIndex(string value, int i)
         {
             var hash = ComputeHash(value, i);
-            hash = hash % _bitArray.Length;
+            hash %= _bitArray.Length;
             return Math.Abs(hash);
         }
 
@@ -339,7 +339,7 @@ public void Add(long value)
         private int GetBitArrayIndex(long value, int i)
         {
             var hash = ComputeHash(value, i);
-            hash = hash % _bitArray.Length;
+            hash %= _bitArray.Length;
             return Math.Abs(hash);
         }
 

src/Workspaces/Core/Portable/Shared/Utilities/NameGenerator.cs

@@ -61,7 +61,7 @@ internal static IList<string> EnsureUniqueness(IList<string> names, bool isCaseS
             Func<string, bool> canUse,
             bool isCaseSensitive = true)
         {
-            canUse = canUse ?? (s => true);
+            canUse ??= (s => true);
 
             // Don't enumerate as we will be modifying the collection in place.
             for (var i = 0; i < names.Count; i++)

src/Workspaces/Core/Portable/Simplification/AbstractSimplificationService.cs

@@ -59,7 +59,7 @@ protected virtual SyntaxNode TransformReducedNode(SyntaxNode reducedNode, Syntax
                     return document;
                 }
 
-                optionSet = optionSet ?? await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
+                optionSet ??= await document.GetOptionsAsync(cancellationToken).ConfigureAwait(false);
 
                 var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 

src/Workspaces/Core/Portable/Utilities/BKTree.cs

@@ -85,7 +85,7 @@ public IList<string> Find(string value, int? threshold = null)
                     lowerCaseCharacters[i] = CaseInsensitiveComparison.ToLower(value[i]);
                 }
 
-                threshold = threshold ?? WordSimilarityChecker.GetThreshold(value);
+                threshold ??= WordSimilarityChecker.GetThreshold(value);
                 var result = new List<string>();
                 Lookup(_nodes[0], lowerCaseCharacters, value.Length, threshold.Value, result, recursionCount: 0);
                 return result;

src/Workspaces/Core/Portable/Utilities/CompilerUtilities/ImmutableHashMap.cs

@@ -1003,7 +1003,7 @@ private static int CountBits(uint v)
             {
                 unchecked
                 {
-                    v = v - ((v >> 1) & 0x55555555u);
+                    v -= ((v >> 1) & 0x55555555u);
                     v = (v & 0x33333333u) + ((v >> 2) & 0x33333333u);
                     return (int)((v + (v >> 4) & 0xF0F0F0Fu) * 0x1010101u) >> 24;
                 }

src/Workspaces/Core/Portable/Utilities/Contract.cs

@@ -15,7 +15,7 @@ internal static class Contract
         {
             if (value == null)
             {
-                message = message ?? "Unexpected Null";
+                message ??= "Unexpected Null";
                 Fail(message);
             }
         }
@@ -28,7 +28,7 @@ public static void ThrowIfFalse(bool condition, string message = null)
         {
             if (!condition)
             {
-                message = message ?? "Unexpected false";
+                message ??= "Unexpected false";
                 Fail(message);
             }
         }
@@ -41,7 +41,7 @@ public static void ThrowIfTrue(bool condition, string message = null)
         {
             if (condition)
             {
-                message = message ?? "Unexpected true";
+                message ??= "Unexpected true";
                 Fail(message);
             }
         }

src/Workspaces/Core/Portable/Utilities/SerializableBytes.cs

@@ -49,7 +49,7 @@ internal async static Task<PooledStream> CreateReadableStreamAsync(Stream stream
                         var bytesRead = await stream.ReadAsync(chunk, chunkOffset, count, cancellationToken).ConfigureAwait(false);
                         if (bytesRead > 0)
                         {
-                            count = count - bytesRead;
+                            count -= bytesRead;
                             chunkOffset += bytesRead;
                         }
                         else

src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceTaskSchedulerFactory.WorkspaceTaskQueue.cs

@@ -22,7 +22,7 @@ public WorkspaceTaskQueue(WorkspaceTaskSchedulerFactory factory, TaskScheduler t
 
             private T3 ScheduleTask<T1, T2, T3>(Func<T1, T2, T3> taskScheduler, string taskName, T1 arg1, T2 arg2) where T3 : Task
             {
-                taskName = taskName ?? GetType().Name + ".Task";
+                taskName ??= GetType().Name + ".Task";
                 var asyncToken = _factory.BeginAsyncOperation(taskName);
 
                 var task = taskScheduler(arg1, arg2);

src/Workspaces/Core/Portable/Workspace/Host/TaskScheduler/WorkspaceTaskSchedulerFactory.WorkspaceTaskScheduler.cs

@@ -24,7 +24,7 @@ public WorkspaceTaskScheduler(WorkspaceTaskSchedulerFactory factory, TaskSchedul
                 string taskName, Func<TTask> taskCreator)
                 where TTask : Task
             {
-                taskName = taskName ?? GetType().Name + ".ScheduleTask";
+                taskName ??= GetType().Name + ".ScheduleTask";
                 var asyncToken = _factory.BeginAsyncOperation(taskName);
 
                 var task = taskCreator();

src/Workspaces/Core/Portable/Workspace/Solution/SolutionId.cs

@@ -42,7 +42,7 @@ public static SolutionId CreateFromSerialized(Guid id, string debugName = null)
                 throw new ArgumentException(nameof(id));
             }
 
-            debugName = debugName ?? "unsaved";
+            debugName ??= "unsaved";
 
             return new SolutionId(id, debugName);
         }

src/Workspaces/Core/Portable/Workspace/Solution/SolutionState.cs

@@ -185,13 +185,13 @@ private void CheckInvariants()
         {
             var branchId = GetBranchId();
 
-            solutionAttributes = solutionAttributes ?? _solutionAttributes;
-            projectIds = projectIds ?? _projectIds;
-            idToProjectStateMap = idToProjectStateMap ?? _projectIdToProjectStateMap;
-            projectIdToTrackerMap = projectIdToTrackerMap ?? _projectIdToTrackerMap;
-            filePathToDocumentIdsMap = filePathToDocumentIdsMap ?? _filePathToDocumentIdsMap;
-            dependencyGraph = dependencyGraph ?? _dependencyGraph;
-            lazyLatestProjectVersion = lazyLatestProjectVersion ?? _lazyLatestProjectVersion;
+            solutionAttributes ??= _solutionAttributes;
+            projectIds ??= _projectIds;
+            idToProjectStateMap ??= _projectIdToProjectStateMap;
+            projectIdToTrackerMap ??= _projectIdToTrackerMap;
+            filePathToDocumentIdsMap ??= _filePathToDocumentIdsMap;
+            dependencyGraph ??= _dependencyGraph;
+            lazyLatestProjectVersion ??= _lazyLatestProjectVersion;
 
             if (branchId == _branchId &&
                 solutionAttributes == _solutionAttributes &&
@@ -1670,7 +1670,7 @@ private SolutionState WithAnalyzerConfigDocumentState(AnalyzerConfigDocumentStat
             var projectId = newProjectState.Id;
 
             var newStateMap = _projectIdToProjectStateMap.SetItem(projectId, newProjectState);
-            newDependencyGraph = newDependencyGraph ?? _dependencyGraph;
+            newDependencyGraph ??= _dependencyGraph;
             var newTrackerMap = CreateCompilationTrackerMap(projectId, newDependencyGraph);
             // If we have a tracker for this project, then fork it as well (along with the
             // translation action and store it in the tracker map.