Add #nullable

src/Features/Core/Portable/UseSystemHashCode/Analyzer.OperationDeconstructor.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+#nullable enable
+
 using System;
 using System.Collections.Immutable;
+using System.Diagnostics.CodeAnalysis;
 using Microsoft.CodeAnalysis.Operations;
 using Microsoft.CodeAnalysis.PooledObjects;
 using Microsoft.CodeAnalysis.Shared.Extensions;
@@ -19,17 +22,17 @@ private struct OperationDeconstructor : IDisposable
         {
             private readonly Analyzer _analyzer;
             private readonly IMethodSymbol _method;
-            private readonly ILocalSymbol _hashCodeVariableOpt;
+            private readonly ILocalSymbol? _hashCodeVariable;
 
             private readonly ArrayBuilder<ISymbol> _hashedSymbols;
             private bool _accessesBase;
 
             public OperationDeconstructor(
-                Analyzer analyzer, IMethodSymbol method, ILocalSymbol hashCodeVariableOpt)
+                Analyzer analyzer, IMethodSymbol method, ILocalSymbol? hashCodeVariable)
             {
                 _analyzer = analyzer;
                 _method = method;
-                _hashCodeVariableOpt = hashCodeVariableOpt;
+                _hashCodeVariable = hashCodeVariable;
                 _hashedSymbols = ArrayBuilder<ISymbol>.GetInstance();
                 _accessesBase = false;
             }
@@ -63,7 +66,7 @@ public bool TryAddHashedSymbol(IOperation value, bool seenHash)
                     }
 
                     if (targetMethod.Name == nameof(GetHashCode) &&
-                        Equals(_analyzer._equalityComparerTypeOpt, targetMethod.ContainingType.OriginalDefinition) &&
+                        Equals(_analyzer._equalityComparerType, targetMethod.ContainingType.OriginalDefinition) &&
                         invocation.Arguments.Length == 1)
                     {
                         // EqualityComparer<T>.Default.GetHashCode(i)
@@ -77,10 +80,10 @@ public bool TryAddHashedSymbol(IOperation value, bool seenHash)
                 //
                 // This is generated by both VS and ReSharper.  Though each use different mathematical
                 // ops to combine the values.
-                if (_hashCodeVariableOpt != null && value is IBinaryOperation topBinary)
+                if (_hashCodeVariable != null && value is IBinaryOperation topBinary)
                 {
                     return topBinary.LeftOperand is IBinaryOperation leftBinary &&
-                           IsLocalReference(leftBinary.LeftOperand, _hashCodeVariableOpt) &&
+                           IsLocalReference(leftBinary.LeftOperand, _hashCodeVariable) &&
                            IsLiteralNumber(leftBinary.RightOperand) &&
                            TryAddHashedSymbol(topBinary.RightOperand, seenHash: true);
                 }
@@ -159,7 +162,7 @@ public bool TryAddHashedSymbol(IOperation value, bool seenHash)
                 return false;
             }
 
-            private static bool TryGetFieldOrProperty(IOperation operation, out ISymbol symbol)
+            private static bool TryGetFieldOrProperty(IOperation operation, [NotNullWhen(true)]out ISymbol? symbol)
             {
                 operation = Unwrap(operation);
 

src/Features/Core/Portable/UseSystemHashCode/Analyzer.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+#nullable enable
+
 using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Diagnostics;
@@ -17,7 +19,7 @@ internal partial struct Analyzer
     {
         private readonly Compilation _compilation;
         private readonly IMethodSymbol _objectGetHashCodeMethod;
-        private readonly INamedTypeSymbol _equalityComparerTypeOpt;
+        private readonly INamedTypeSymbol? _equalityComparerType;
 
         public readonly INamedTypeSymbol SystemHashCodeType;
 
@@ -26,8 +28,10 @@ public Analyzer(Compilation compilation)
             _compilation = compilation;
 
             var objectType = compilation.GetSpecialType(SpecialType.System_Object);
-            _objectGetHashCodeMethod = objectType?.GetMembers(nameof(GetHashCode)).FirstOrDefault() as IMethodSymbol;
-            _equalityComparerTypeOpt = compilation.GetTypeByMetadataName(typeof(EqualityComparer<>).FullName);
+            // This may not find anything.  However, CanAnalyze checks for this. So
+            // we represent the value as non-nullable for all future code.
+            _objectGetHashCodeMethod = (objectType?.GetMembers(nameof(GetHashCode)).FirstOrDefault() as IMethodSymbol)!;
+            _equalityComparerType = compilation.GetTypeByMetadataName(typeof(EqualityComparer<>).FullName);
             SystemHashCodeType = compilation.GetTypeByMetadataName("System.HashCode");
         }
 
@@ -96,7 +100,7 @@ public bool CanAnalyze()
                 return default;
             }
 
-            using var analyzer = new OperationDeconstructor(this, method, hashCodeVariableOpt: null);
+            using var analyzer = new OperationDeconstructor(this, method, hashCodeVariable: null);
             if (!analyzer.TryAddHashedSymbol(returnOperation.ReturnedValue, seenHash: false))
             {
                 return default;
@@ -204,7 +208,7 @@ public bool CanAnalyze()
             return valueAnalyzer.GetResult();
         }
 
-        private bool OverridesSystemObject(IMethodSymbol method)
+        private bool OverridesSystemObject(IMethodSymbol? method)
         {
             for (var current = method; current != null; current = current.OverriddenMethod)
             {

src/Features/Core/Portable/UseSystemHashCode/UseSystemHashCodeCodeFixProvider.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+#nullable enable
+
 using System;
 using System.Collections.Immutable;
 using System.Composition;
@@ -43,7 +45,7 @@ public override Task RegisterCodeFixesAsync(CodeFixContext context)
             var generator = SyntaxGenerator.GetGenerator(document);
             var declarationService = document.GetLanguageService<ISymbolDeclarationService>();
 
-            var semanticModel = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+            var semanticModel = await document.RequireSemanticModelAsync(cancellationToken).ConfigureAwait(false);
             var analyzer = new Analyzer(semanticModel.Compilation);
             Debug.Assert(analyzer.CanAnalyze());
 

src/Features/Core/Portable/UseSystemHashCode/UseSystemHashCodeDiagnosticAnalyzer.cs

 // Copyright (c) Microsoft.  All Rights Reserved.  Licensed under the Apache License, Version 2.0.  See License.txt in the project root for license information.
 
+#nullable enable
+
 using System.Collections.Immutable;
 using Microsoft.CodeAnalysis.CodeStyle;
 using Microsoft.CodeAnalysis.Diagnostics;

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

@@ -203,5 +203,11 @@ public static bool IsGeneratedCode(this Document document, CancellationToken can
             var generatedCodeRecognitionService = document.GetLanguageService<IGeneratedCodeRecognitionService>();
             return generatedCodeRecognitionService?.IsGeneratedCode(document, cancellationToken) == true;
         }
+
+        public static async Task<SemanticModel> RequireSemanticModelAsync(this Document document, CancellationToken cancellationToken)
+        {
+            var model = await document.GetSemanticModelAsync(cancellationToken).ConfigureAwait(false);
+            return model ?? throw new InvalidOperationException();
+        }
     }
 }