Do not offer 'use auto prop' with ref-fields (#76638)

Author: CyrusNajmabadi

src/Analyzers/CSharp/Analyzers/UseAutoProperty/CSharpUseAutoPropertyAnalyzer.cs

@@ -10,22 +10,21 @@
 using Microsoft.CodeAnalysis.CSharp.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Syntax;
 using Microsoft.CodeAnalysis.Diagnostics;
-using Microsoft.CodeAnalysis.LanguageService;
 using Microsoft.CodeAnalysis.Shared.Extensions;
 using Microsoft.CodeAnalysis.UseAutoProperty;
 using Roslyn.Utilities;
 
 namespace Microsoft.CodeAnalysis.CSharp.UseAutoProperty;
 
 [DiagnosticAnalyzer(LanguageNames.CSharp)]
-internal sealed class CSharpUseAutoPropertyAnalyzer : AbstractUseAutoPropertyAnalyzer<
+internal sealed class CSharpUseAutoPropertyAnalyzer() : AbstractUseAutoPropertyAnalyzer<
     SyntaxKind,
     PropertyDeclarationSyntax,
     ConstructorDeclarationSyntax,
     FieldDeclarationSyntax,
     VariableDeclaratorSyntax,
     ExpressionSyntax,
-    IdentifierNameSyntax>
+    IdentifierNameSyntax>(CSharpSemanticFacts.Instance)
 {
     protected override SyntaxKind PropertyDeclarationKind
         => SyntaxKind.PropertyDeclaration;
@@ -36,9 +35,6 @@ protected override bool CanExplicitInterfaceImplementationsBeFixed
     protected override bool SupportsFieldAttributesOnProperties
         => true;
 
-    protected override ISemanticFacts SemanticFacts
-        => CSharpSemanticFacts.Instance;
-
     protected override bool SupportsReadOnlyProperties(Compilation compilation)
         => compilation.LanguageVersion() >= LanguageVersion.CSharp6;
 

src/Analyzers/CSharp/Tests/UseAutoProperty/UseAutoPropertyTests.cs

@@ -5,7 +5,6 @@
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis.CodeFixes;
 using Microsoft.CodeAnalysis.CSharp;
-using Microsoft.CodeAnalysis.CSharp.Shared.Extensions;
 using Microsoft.CodeAnalysis.CSharp.Test.Utilities;
 using Microsoft.CodeAnalysis.CSharp.UseAutoProperty;
 using Microsoft.CodeAnalysis.Diagnostics;
@@ -3115,4 +3114,24 @@ public required string Action
             }
             """);
     }
+
+    [Fact, WorkItem("https://github.com/dotnet/roslyn/issues/76634")]
+    public async Task TestRefField()
+    {
+        await TestMissingInRegularAndScriptAsync(
+            """
+            class Class
+            {
+                [|ref int i|];
+
+                int P
+                {
+                    get
+                    {
+                        return i;
+                    }
+                }
+            }
+            """);
+    }
 }

src/Analyzers/Core/Analyzers/UseAutoProperty/AbstractUseAutoPropertyAnalyzer.cs

@@ -28,7 +28,12 @@ internal abstract partial class AbstractUseAutoPropertyAnalyzer<
     TFieldDeclaration,
     TVariableDeclarator,
     TExpression,
-    TIdentifierName> : AbstractBuiltInCodeStyleDiagnosticAnalyzer
+    TIdentifierName>(ISemanticFacts semanticFacts)
+    : AbstractBuiltInCodeStyleDiagnosticAnalyzer(IDEDiagnosticIds.UseAutoPropertyDiagnosticId,
+           EnforceOnBuildValues.UseAutoProperty,
+           CodeStyleOptions2.PreferAutoProperties,
+           new LocalizableResourceString(nameof(AnalyzersResources.Use_auto_property), AnalyzersResources.ResourceManager, typeof(AnalyzersResources)),
+           new LocalizableResourceString(nameof(AnalyzersResources.Use_auto_property), AnalyzersResources.ResourceManager, typeof(AnalyzersResources)))
     where TSyntaxKind : struct, Enum
     where TPropertyDeclaration : SyntaxNode
     where TConstructorDeclaration : SyntaxNode
@@ -48,17 +53,7 @@ internal abstract partial class AbstractUseAutoPropertyAnalyzer<
     /// <summary>
     /// Not static as this has different semantics around case sensitivity for C# and VB.
     /// </summary>
-    private readonly ObjectPool<HashSet<string>> _fieldNamesPool;
-
-    protected AbstractUseAutoPropertyAnalyzer()
-        : base(IDEDiagnosticIds.UseAutoPropertyDiagnosticId,
-               EnforceOnBuildValues.UseAutoProperty,
-               CodeStyleOptions2.PreferAutoProperties,
-               new LocalizableResourceString(nameof(AnalyzersResources.Use_auto_property), AnalyzersResources.ResourceManager, typeof(AnalyzersResources)),
-               new LocalizableResourceString(nameof(AnalyzersResources.Use_auto_property), AnalyzersResources.ResourceManager, typeof(AnalyzersResources)))
-    {
-        _fieldNamesPool = new(() => new(this.SyntaxFacts.StringComparer));
-    }
+    private readonly ObjectPool<HashSet<string>> _fieldNamesPool = new(() => new(semanticFacts.SyntaxFacts.StringComparer));
 
     protected static void AddFieldUsage(ConcurrentDictionary<IFieldSymbol, ConcurrentSet<SyntaxNode>> fieldWrites, IFieldSymbol field, SyntaxNode location)
         => fieldWrites.GetOrAdd(field, static _ => s_nodeSetPool.Allocate()).Add(location);
@@ -78,8 +73,8 @@ private static void ClearAndFree(ConcurrentDictionary<IFieldSymbol, ConcurrentSe
     public override DiagnosticAnalyzerCategory GetAnalyzerCategory()
         => DiagnosticAnalyzerCategory.SemanticDocumentAnalysis;
 
-    protected abstract ISemanticFacts SemanticFacts { get; }
-    protected ISyntaxFacts SyntaxFacts => this.SemanticFacts.SyntaxFacts;
+    private ISemanticFacts SemanticFacts { get; } = semanticFacts;
+    private ISyntaxFacts SyntaxFacts => SemanticFacts.SyntaxFacts;
 
     protected abstract TSyntaxKind PropertyDeclarationKind { get; }
 
@@ -139,6 +134,8 @@ protected sealed override void InitializeWorker(AnalysisContext context)
                         IsConst: false,
                         // Can't preserve volatile semantics on a property.
                         IsVolatile: false,
+                        // Can't have an autoprop that returns by-ref. 
+                        RefKind: RefKind.None,
                         // To make processing later on easier, limit to well-behaved fields (versus having multiple
                         // fields merged together in error recoery scenarios).
                         DeclaringSyntaxReferences.Length: 1,

src/Analyzers/VisualBasic/Analyzers/UseAutoProperty/VisualBasicUseAutoPropertyAnalyzer.vb

@@ -3,16 +3,14 @@
 ' See the LICENSE file in the project root for more information.
 
 Imports System.Collections.Concurrent
-Imports System.Collections.Immutable
 Imports System.Threading
 Imports Microsoft.CodeAnalysis.Diagnostics
-Imports Microsoft.CodeAnalysis.LanguageService
 Imports Microsoft.CodeAnalysis.UseAutoProperty
 Imports Microsoft.CodeAnalysis.VisualBasic.Syntax
 
 Namespace Microsoft.CodeAnalysis.VisualBasic.UseAutoProperty
     <DiagnosticAnalyzer(LanguageNames.VisualBasic)>
-    Friend Class VisualBasicUseAutoPropertyAnalyzer
+    Friend NotInheritable Class VisualBasicUseAutoPropertyAnalyzer
         Inherits AbstractUseAutoPropertyAnalyzer(Of
             SyntaxKind,
             PropertyBlockSyntax,
@@ -22,9 +20,11 @@ Namespace Microsoft.CodeAnalysis.VisualBasic.UseAutoProperty
             ExpressionSyntax,
             IdentifierNameSyntax)
 
-        Protected Overrides ReadOnly Property PropertyDeclarationKind As SyntaxKind = SyntaxKind.PropertyBlock
+        Public Sub New()
+            MyBase.New(VisualBasicSemanticFacts.Instance)
+        End Sub
 
-        Protected Overrides ReadOnly Property SemanticFacts As ISemanticFacts = VisualBasicSemanticFacts.Instance
+        Protected Overrides ReadOnly Property PropertyDeclarationKind As SyntaxKind = SyntaxKind.PropertyBlock
 
         Protected Overrides Function SupportsReadOnlyProperties(compilation As Compilation) As Boolean
             Return DirectCast(compilation, VisualBasicCompilation).LanguageVersion >= LanguageVersion.VisualBasic14