Merge pull request #47895 from CyrusNajmabadi/nrtFAR

Add NRT annotations to FAR engine

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -22,7 +24,7 @@ namespace Microsoft.CodeAnalysis.FindSymbols
     internal partial class FindReferencesSearchEngine
     {
         private readonly Solution _solution;
-        private readonly IImmutableSet<Document> _documents;
+        private readonly IImmutableSet<Document>? _documents;
         private readonly ImmutableArray<IReferenceFinder> _finders;
         private readonly IStreamingProgressTracker _progressTracker;
         private readonly IStreamingFindReferencesProgress _progress;
@@ -31,7 +33,7 @@ internal partial class FindReferencesSearchEngine
 
         public FindReferencesSearchEngine(
             Solution solution,
-            IImmutableSet<Document> documents,
+            IImmutableSet<Document>? documents,
             ImmutableArray<IReferenceFinder> finders,
             IStreamingFindReferencesProgress progress,
             FindReferencesSearchOptions options,

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

@@ -126,7 +126,8 @@ private async Task<ProjectMap> CreateProjectMapAsync(ConcurrentSet<ISymbol> symb
                 searchSymbol = sourceSymbol;
             }
 
-            if (searchSymbol != null && result.Add(searchSymbol))
+            Contract.ThrowIfNull(searchSymbol);
+            if (result.Add(searchSymbol))
             {
                 await _progress.OnDefinitionFoundAsync(searchSymbol).ConfigureAwait(false);
 
@@ -135,12 +136,12 @@ private async Task<ProjectMap> CreateProjectMapAsync(ConcurrentSet<ISymbol> symb
 
                 _cancellationToken.ThrowIfCancellationRequested();
 
-                var finderTasks = new List<Task>();
+                using var _ = ArrayBuilder<Task>.GetInstance(out var finderTasks);
                 foreach (var f in _finders)
                 {
                     finderTasks.Add(Task.Run(async () =>
                     {
-                        var symbolTasks = new List<Task>();
+                        using var _ = ArrayBuilder<Task>.GetInstance(out var symbolTasks);
 
                         var symbols = await f.DetermineCascadedSymbolsAsync(
                             searchSymbol, _solution, projects, _options, _cancellationToken).ConfigureAwait(false);
@@ -169,12 +170,13 @@ private async Task<ProjectMap> CreateProjectMapAsync(ConcurrentSet<ISymbol> symb
         private void AddSymbolTasks(
             ConcurrentSet<ISymbol> result,
             ImmutableArray<ISymbol> symbols,
-            List<Task> symbolTasks)
+            ArrayBuilder<Task> symbolTasks)
         {
             if (!symbols.IsDefault)
             {
                 foreach (var child in symbols)
                 {
+                    Contract.ThrowIfNull(child);
                     _cancellationToken.ThrowIfCancellationRequested();
                     symbolTasks.Add(Task.Run(() => DetermineAllSymbolsCoreAsync(child, result), _cancellationToken));
                 }
@@ -227,6 +229,7 @@ private static ISymbol MapToAppropriateSymbol(ISymbol symbol)
                 searchSymbol = symbol.ContainingType;
             }
 
+            Contract.ThrowIfNull(searchSymbol);
             return searchSymbol;
         }
     }

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
 using System.Collections.Immutable;
@@ -62,7 +64,7 @@ protected sealed override bool CanFind(TSymbol symbol)
 
             if (symbol.ContainingType != null && symbol.ContainingType.IsScriptClass)
             {
-                var syntaxTree = await document.GetSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
+                var syntaxTree = await document.GetRequiredSyntaxTreeAsync(cancellationToken).ConfigureAwait(false);
                 var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
                 var root = await syntaxTree.GetRootAsync(cancellationToken).ConfigureAwait(false);
                 var tokens = root.DescendantTokens();
@@ -74,7 +76,7 @@ protected sealed override bool CanFind(TSymbol symbol)
             return ImmutableArray<FinderLocation>.Empty;
         }
 
-        private static ISymbol GetContainer(ISymbol symbol)
+        private static ISymbol? GetContainer(ISymbol symbol)
         {
             for (var current = symbol; current != null; current = current.ContainingSymbol)
             {
@@ -126,11 +128,11 @@ private static ISymbol GetContainer(ISymbol symbol)
             Document document,
             SemanticModel semanticModel,
             IEnumerable<SyntaxToken> tokens,
-            Func<SyntaxToken, SyntaxNode> findParentNode,
+            Func<SyntaxToken, SyntaxNode>? findParentNode,
             CancellationToken cancellationToken)
         {
             var name = symbol.Name;
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             var symbolsMatch = GetStandardSymbolsMatchFunction(symbol, findParentNode, document.Project.Solution, cancellationToken);
 
             return FindReferencesInTokensAsync(
@@ -159,15 +161,15 @@ private static ISymbol GetContainer(ISymbol symbol)
             ISymbol container,
             Document document,
             SemanticModel semanticModel,
-            Func<SyntaxToken, SyntaxNode> findParentNode,
+            Func<SyntaxToken, SyntaxNode>? findParentNode,
             CancellationToken cancellationToken)
         {
-            var service = document.GetLanguageService<ISymbolDeclarationService>();
+            var service = document.GetRequiredLanguageService<ISymbolDeclarationService>();
             var declarations = service.GetDeclarations(container);
             var tokens = declarations.SelectMany(r => r.GetSyntax(cancellationToken).DescendantTokens());
 
             var name = symbol.Name;
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             var symbolsMatch = GetStandardSymbolsMatchFunction(symbol, findParentNode, document.Project.Solution, cancellationToken);
             var tokensMatch = GetTokensMatchFunction(syntaxFacts, name);
 

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

@@ -2,10 +2,13 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.LanguageServices;
+using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders
@@ -69,16 +72,22 @@ protected AbstractMethodOrPropertyOrEventSymbolReferenceFinder()
 
                 // the only accessor method referenced in a foreach-statement is the .Current's
                 // get-accessor
-                return ImmutableArray.Create(symbols.CurrentProperty.GetMethod);
+                return symbols.CurrentProperty.GetMethod == null
+                    ? ImmutableArray<IMethodSymbol>.Empty
+                    : ImmutableArray.Create(symbols.CurrentProperty.GetMethod);
             }
 
             if (semanticFacts.IsWrittenTo(model, node, cancellationToken))
             {
                 // if it was only written to, then only the setter was referenced.
                 // if it was written *and* read, then both accessors were referenced.
-                return semanticFacts.IsOnlyWrittenTo(model, node, cancellationToken)
-                    ? ImmutableArray.Create(property.SetMethod)
-                    : ImmutableArray.Create(property.GetMethod, property.SetMethod);
+                using var _ = ArrayBuilder<IMethodSymbol>.GetInstance(out var result);
+                result.AddIfNotNull(property.SetMethod);
+
+                if (!semanticFacts.IsOnlyWrittenTo(model, node, cancellationToken))
+                    result.AddIfNotNull(property.GetMethod);
+
+                return result.ToImmutable();
             }
             else
             {
@@ -93,7 +102,7 @@ protected AbstractMethodOrPropertyOrEventSymbolReferenceFinder()
                 var inNameOf = semanticFacts.IsInsideNameOfExpression(model, node, cancellationToken);
                 var inStructuredTrivia = node.IsPartOfStructuredTrivia();
 
-                return inNameOf || inStructuredTrivia
+                return inNameOf || inStructuredTrivia || property.GetMethod == null
                     ? ImmutableArray<IMethodSymbol>.Empty
                     : ImmutableArray.Create(property.GetMethod);
             }

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

@@ -105,7 +105,7 @@ static bool SupportsGlobalSuppression(ISymbol symbol)
                 if (IsCandidate(token, expectedDocCommentId, semanticModel, syntaxFacts, suppressMessageAttribute, cancellationToken, out var offsetOfReferenceInToken))
                 {
                     var referenceLocation = CreateReferenceLocation(offsetOfReferenceInToken, token, root, document, syntaxFacts);
-                    locations.Add(new FinderLocation(token.Parent, referenceLocation));
+                    locations.Add(new FinderLocation(token.GetRequiredParent(), referenceLocation));
                 }
             }
 

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
@@ -56,7 +58,7 @@ protected override bool CanFind(IMethodSymbol symbol)
             FindReferencesSearchOptions options,
             CancellationToken cancellationToken)
         {
-            var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFactsService = document.GetRequiredLanguageService<ISyntaxFactsService>();
             var typeName = methodSymbol.ContainingType.Name;
 
             var tokens = await document.GetConstructorInitializerTokensAsync(semanticModel, cancellationToken).ConfigureAwait(false);

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders
 {
     internal readonly struct FinderLocation

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using Microsoft.CodeAnalysis.LanguageServices;
 

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -25,7 +27,7 @@ internal class LinkedFileReferenceFinder : IReferenceFinder
             return SpecializedTasks.EmptyImmutableArray<Document>();
         }
 
-        public Task<ImmutableArray<Project>> DetermineProjectsToSearchAsync(ISymbol symbol, Solution solution, IImmutableSet<Project> projects = null, CancellationToken cancellationToken = default)
+        public Task<ImmutableArray<Project>> DetermineProjectsToSearchAsync(ISymbol symbol, Solution solution, IImmutableSet<Project>? projects = null, CancellationToken cancellationToken = default)
             => SpecializedTasks.EmptyImmutableArray<Project>();
 
         public Task<ImmutableArray<FinderLocation>> FindReferencesInDocumentAsync(

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using Microsoft.CodeAnalysis.LanguageServices;
 

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -59,6 +61,7 @@ protected override bool CanFind(ITypeParameterSymbol symbol)
             //
             // Also, we only look for files that have the name of the owning type.  This helps filter
             // down the set considerably.
+            Contract.ThrowIfNull(symbol.DeclaringMethod);
             return FindDocumentsAsync(project, documents, findInGlobalSuppressions: false, cancellationToken, symbol.Name,
                 GetMemberNameWithoutInterfaceName(symbol.DeclaringMethod.Name),
                 symbol.DeclaringMethod.ContainingType.Name);

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Linq;
 using System.Threading;
@@ -53,9 +55,11 @@ protected override bool CanFind(INamedTypeSymbol symbol)
             FindReferencesSearchOptions options,
             CancellationToken cancellationToken)
         {
+            var syntaxFacts = project.LanguageServices.GetRequiredService<ISyntaxFactsService>();
+
             var documentsWithName = await FindDocumentsAsync(project, documents, findInGlobalSuppressions: true, cancellationToken, symbol.Name).ConfigureAwait(false);
             var documentsWithType = await FindDocumentsAsync(project, documents, symbol.SpecialType.ToPredefinedType(), cancellationToken).ConfigureAwait(false);
-            var documentsWithAttribute = TryGetNameWithoutAttributeSuffix(symbol.Name, project.LanguageServices.GetService<ISyntaxFactsService>(), out var simpleName)
+            var documentsWithAttribute = TryGetNameWithoutAttributeSuffix(symbol.Name, syntaxFacts, out var simpleName)
                 ? await FindDocumentsAsync(project, documents, findInGlobalSuppressions: false, cancellationToken, simpleName).ConfigureAwait(false)
                 : ImmutableArray<Document>.Empty;
 
@@ -127,7 +131,7 @@ protected override bool CanFind(INamedTypeSymbol symbol)
                 return SpecializedTasks.EmptyImmutableArray<FinderLocation>();
             }
 
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             return FindReferencesInDocumentAsync(document, semanticModel, t =>
                 IsPotentialReference(predefinedType, syntaxFacts, t),
                 (t, m) => new ValueTask<(bool matched, CandidateReason reason)>((matched: true, reason: CandidateReason.None)),
@@ -143,7 +147,7 @@ protected override bool CanFind(INamedTypeSymbol symbol)
             CancellationToken cancellationToken)
         {
             var symbolsMatch = GetStandardSymbolsMatchFunction(namedType, null, document.Project.Solution, cancellationToken);
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             return TryGetNameWithoutAttributeSuffix(namedType.Name, syntaxFacts, out var simpleName)
                 ? FindReferencesInDocumentUsingIdentifierAsync(simpleName, document, semanticModel,
                     symbolsMatch, docCommentId: null, findInGlobalSuppressions: false, cancellationToken)

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -42,7 +44,7 @@ private static string GetNamespaceIdentifierName(INamespaceSymbol symbol)
             CancellationToken cancellationToken)
         {
             var identifierName = GetNamespaceIdentifierName(symbol);
-            var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
 
             var tokens = await GetIdentifierOrGlobalNamespaceTokensWithTextAsync(
                 document, semanticModel, identifierName, cancellationToken).ConfigureAwait(false);
@@ -50,14 +52,14 @@ private static string GetNamespaceIdentifierName(INamespaceSymbol symbol)
                 document,
                 semanticModel,
                 tokens,
-                t => syntaxFactsService.TextMatch(t.ValueText, identifierName),
+                t => syntaxFacts.TextMatch(t.ValueText, identifierName),
                 cancellationToken).ConfigureAwait(false);
 
             var aliasReferences = await FindAliasReferencesAsync(nonAliasReferences, symbol, document, semanticModel, cancellationToken).ConfigureAwait(false);
 
             var suppressionReferences = ShouldFindReferencesInGlobalSuppressions(symbol, out var docCommentId)
                 ? await FindReferencesInDocumentInsideGlobalSuppressionsAsync(document, semanticModel,
-                    syntaxFactsService, docCommentId, cancellationToken).ConfigureAwait(false)
+                    syntaxFacts, docCommentId, cancellationToken).ConfigureAwait(false)
                 : ImmutableArray<FinderLocation>.Empty;
 
             return nonAliasReferences.Concat(aliasReferences).Concat(suppressionReferences);

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -33,7 +35,7 @@ protected override bool CanFind(IMethodSymbol symbol)
             FindReferencesSearchOptions options,
             CancellationToken cancellationToken)
         {
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             var op = symbol.GetPredefinedOperator();
 
             return FindReferencesInDocumentAsync(symbol, document, semanticModel, t =>

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using System.Collections.Immutable;
 using System.Linq;
@@ -131,18 +133,18 @@ protected override bool CanFind(IParameterSymbol symbol)
                     var document = solution.GetDocument(parameterNode.SyntaxTree);
                     if (document != null)
                     {
-                        var semanticFacts = document.GetLanguageService<ISemanticFactsService>();
+                        var semanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
                         if (semanticFacts.ExposesAnonymousFunctionParameterNames)
                         {
-                            var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+                            var semanticModel = await document.GetRequiredSemanticModelAsync(cancellationToken).ConfigureAwait(false);
 
                             var lambdaNode = parameter.ContainingSymbol.DeclaringSyntaxReferences.Select(r => r.GetSyntax(cancellationToken)).FirstOrDefault();
                             var convertedType = semanticModel.GetTypeInfo(lambdaNode, cancellationToken).ConvertedType;
 
                             if (convertedType != null)
                             {
-                                var syntaxFactsService = document.GetLanguageService<ISyntaxFactsService>();
-                                var container = GetContainer(semanticModel, parameterNode, syntaxFactsService);
+                                var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
+                                var container = GetContainer(semanticModel, parameterNode, syntaxFacts);
                                 if (container != null)
                                 {
                                     CascadeBetweenAnonymousFunctionParameters(
@@ -165,12 +167,12 @@ protected override bool CanFind(IParameterSymbol symbol)
             ArrayBuilder<ISymbol> results,
             CancellationToken cancellationToken)
         {
-            var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
+            var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
             foreach (var token in container.DescendantTokens())
             {
                 if (IdentifiersMatch(syntaxFacts, parameter.Name, token))
                 {
-                    var symbol = semanticModel.GetDeclaredSymbol(token.Parent, cancellationToken);
+                    var symbol = semanticModel.GetDeclaredSymbol(token.GetRequiredParent(), cancellationToken);
                     if (symbol is IParameterSymbol &&
                         symbol.ContainingSymbol.IsAnonymousFunction() &&
                         SignatureComparer.Instance.HaveSameSignatureAndConstraintsAndReturnTypeAndAccessors(parameter.ContainingSymbol, symbol.ContainingSymbol, syntaxFacts.IsCaseSensitive) &&

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -80,8 +82,8 @@ protected override bool CanFind(IMethodSymbol symbol)
                     options.WithAssociatePropertyReferencesWithSpecificAccessor(false),
                     cancellationToken).ConfigureAwait(false);
 
-                var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
-                var semanticFacts = document.GetLanguageService<ISemanticFactsService>();
+                var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
+                var semanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
 
                 var accessorReferences = propertyReferences.WhereAsArray(
                     loc =>

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

@@ -95,8 +95,8 @@ private static bool IsForEachProperty(IPropertySymbol symbol)
                 // We want to associate property references to a specific accessor (if an accessor
                 // is being referenced).  Check if this reference would match an accessor. If so, do
                 // not add it.  It will be added by PropertyAccessorSymbolReferenceFinder.
-                var syntaxFacts = document.GetLanguageService<ISyntaxFactsService>();
-                var semanticFacts = document.GetLanguageService<ISemanticFactsService>();
+                var syntaxFacts = document.GetRequiredLanguageService<ISyntaxFactsService>();
+                var semanticFacts = document.GetRequiredLanguageService<ISemanticFactsService>();
 
                 nameReferences = nameReferences.WhereAsArray(loc =>
                 {

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System;
 using Microsoft.CodeAnalysis.LanguageServices;
 

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 
 namespace Microsoft.CodeAnalysis.FindSymbols.Finders

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;

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

@@ -58,7 +58,7 @@ public static partial class SymbolFinder
         }
 
         internal static Task FindReferencesInCurrentProcessAsync(
-            ISymbol symbolAndProjectId,
+            ISymbol symbol,
             Solution solution,
             IStreamingFindReferencesProgress progress,
             IImmutableSet<Document> documents,
@@ -69,7 +69,7 @@ public static partial class SymbolFinder
             progress ??= NoOpStreamingFindReferencesProgress.Instance;
             var engine = new FindReferencesSearchEngine(
                 solution, documents, finders, progress, options, cancellationToken);
-            return engine.FindReferencesAsync(symbolAndProjectId);
+            return engine.FindReferencesAsync(symbol);
         }
     }
 }

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

@@ -2,6 +2,8 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using System.Threading;
 using System.Threading.Tasks;
@@ -21,10 +23,9 @@ public static partial class SymbolFinder
             {
                 var streamingProgress = new StreamingProgressCollector();
 
-                IImmutableSet<Document> documents = null;
                 var engine = new FindReferencesSearchEngine(
                     solution,
-                    documents,
+                    documents: null,
                     ReferenceFinders.DefaultRenameReferenceFinders,
                     streamingProgress,
                     FindReferencesSearchOptions.Default,

src/Workspaces/SharedUtilitiesAndExtensions/Compiler/Core/Extensions/SyntaxTokenExtensions.cs

@@ -159,5 +159,8 @@ public static SyntaxToken With(this SyntaxToken token, SyntaxTriviaList leading,
 
         public static SyntaxTrivia[] GetTrivia(this IEnumerable<SyntaxToken> tokens)
             => tokens.SelectMany(token => SyntaxNodeOrTokenExtensions.GetTrivia(token)).ToArray();
+
+        public static SyntaxNode GetRequiredParent(this SyntaxToken token)
+            => token.Parent ?? throw new InvalidOperationException("Token's parent was null");
     }
 }