Add code fix for CS8600, CS8610, CS8765, CS8767

ChangeLog.md

@@ -12,6 +12,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add analyzer "Add/remove blank line between switch sections" ([RCS0061](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS0061)) ([PR](https://github.com/dotnet/roslynator/pull/1302))
   - Option (required): `roslynator_blank_line_between_switch_sections = include|omit|omit_after_block` 
   - Make analyzer [RCS0014](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS0014) obsolete
+- Add code fix "Declare as nullable" ([PR](https://github.com/dotnet/roslynator/pull/1333))
+  - Applicable to: `CS8600`, `CS8610`, `CS8765` and `CS8767`
 
 ### Changed
 

src/CSharp/CSharp/CompilerDiagnosticIdentifiers.Generated.cs

@@ -175,10 +175,14 @@ internal static class CompilerDiagnosticIdentifiers
         public const string CS8139_CannotChangeTupleElementNameWhenOverridingInheritedMember = "CS8139";
         public const string CS8340_InstanceFieldsOfReadOnlyStructsMustBeReadOnly = "CS8340";
         public const string CS8403_MethodWithIteratorBlockMustBeAsyncToReturnIAsyncEnumerableOfT = "CS8403";
+        public const string CS8600_ConvertingNullLiteralOrPossibleNullValueToNonNullableType = "CS8600";
         public const string CS8602_DereferenceOfPossiblyNullReference = "CS8602";
         public const string CS8604_PossibleNullReferenceArgumentForParameter = "CS8604";
+        public const string CS8610_NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember = "CS8610";
         public const string CS8618_NonNullableMemberIsUninitialized = "CS8618";
         public const string CS8625_CannotConvertNullLiteralToNonNullableReferenceType = "CS8625";
         public const string CS8632_AnnotationForNullableReferenceTypesShouldOnlyBeUsedWithinNullableAnnotationsContext = "CS8632";
+        public const string CS8765_NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember = "CS8765";
+        public const string CS8767_NullabilityDoesNotMatchImplementedMember = "CS8767";
     }
 }

src/CodeFixes.xml

@@ -691,4 +691,12 @@
       <Id>CS8602</Id>
     </FixableDiagnosticIds>
   </CodeFix>
+  <CodeFix Id="RCF0122" Identifier="AddNullableAnnotation" Title="Add nullable annotation">
+    <FixableDiagnosticIds>
+      <Id>CS8600</Id>
+      <Id>CS8610</Id>
+      <Id>CS8765</Id>
+      <Id>CS8767</Id>
+    </FixableDiagnosticIds>
+  </CodeFix>
 </CodeFixes>

src/CodeFixes/CSharp/CodeFixDescriptors.Generated.cs

@@ -913,5 +913,15 @@ public static partial class CodeFixDescriptors
             isEnabledByDefault: true, 
             "CS8602");
 
+        /// <summary>RCF0122 (fixes CS8600, CS8610, CS8765, CS8767)</summary>
+        public static readonly CodeFixDescriptor AddNullableAnnotation = new CodeFixDescriptor(
+            id:                 CodeFixIdentifiers.AddNullableAnnotation, 
+            title:              "Add nullable annotation", 
+            isEnabledByDefault: true, 
+            "CS8600", 
+            "CS8610", 
+            "CS8765", 
+            "CS8767");
+
     }
 }

src/CodeFixes/CSharp/CodeFixIdentifiers.Generated.cs

@@ -124,5 +124,6 @@ public static partial class CodeFixIdentifiers
         public const string UseNullForgivingOperator = CodeFixIdentifier.CodeFixIdPrefix + "0119";
         public const string AddAsyncModifier = CodeFixIdentifier.CodeFixIdPrefix + "0120";
         public const string UseNullPropagationOperator = CodeFixIdentifier.CodeFixIdPrefix + "0121";
+        public const string AddNullableAnnotation = CodeFixIdentifier.CodeFixIdPrefix + "0122";
     }
 }

src/CodeFixes/CSharp/CodeFixes/DeclareAsNullableCodeFixProvider.cs

@@ -0,0 +1,88 @@
+// Copyright (c) .NET Foundation and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Composition;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.CodeActions;
+using Microsoft.CodeAnalysis.CodeFixes;
+using Microsoft.CodeAnalysis.CSharp;
+using Microsoft.CodeAnalysis.CSharp.Syntax;
+using Roslynator.CodeFixes;
+
+namespace Roslynator.CSharp.CodeFixes;
+
+[ExportCodeFixProvider(LanguageNames.CSharp, Name = nameof(DeclareAsNullableCodeFixProvider))]
+[Shared]
+public sealed class DeclareAsNullableCodeFixProvider : CompilerDiagnosticCodeFixProvider
+{
+    public override ImmutableArray<string> FixableDiagnosticIds
+    {
+        get { return ImmutableArray.Create(CompilerDiagnosticIdentifiers.CS8600_ConvertingNullLiteralOrPossibleNullValueToNonNullableType); }
+    }
+
+    public override async Task RegisterCodeFixesAsync(CodeFixContext context)
+    {
+        Diagnostic diagnostic = context.Diagnostics[0];
+
+        SyntaxNode root = await context.GetSyntaxRootAsync().ConfigureAwait(false);
+
+        if (!IsEnabled(diagnostic.Id, CodeFixIdentifiers.AddNullableAnnotation, context.Document, root.SyntaxTree))
+            return;
+
+        if (!TryFindFirstAncestorOrSelf(root, context.Span, out SyntaxNode node, predicate: f => f.IsKind(SyntaxKind.EqualsValueClause, SyntaxKind.DeclarationExpression, SyntaxKind.SimpleAssignmentExpression)))
+            return;
+
+        if (node is EqualsValueClauseSyntax equalsValueClause)
+        {
+            ExpressionSyntax expression = equalsValueClause.Value;
+
+            if (expression.Span == context.Span
+                && equalsValueClause.IsParentKind(SyntaxKind.VariableDeclarator)
+                && equalsValueClause.Parent.Parent is VariableDeclarationSyntax variableDeclaration
+                && variableDeclaration.Variables.Count == 1)
+            {
+                TryRegisterCodeFix(context, diagnostic, variableDeclaration.Type);
+            }
+        }
+        else if (node is DeclarationExpressionSyntax declarationExpression)
+        {
+            TryRegisterCodeFix(context, diagnostic, declarationExpression.Type);
+        }
+        else if (node is AssignmentExpressionSyntax assignmentExpression)
+        {
+            SemanticModel semanticModel = await context.GetSemanticModelAsync().ConfigureAwait(false);
+
+            var localSymbol = semanticModel.GetSymbol(assignmentExpression.Left, context.CancellationToken) as ILocalSymbol;
+
+            if (localSymbol is not null)
+            {
+                SyntaxNode declarator = await localSymbol.GetSyntaxAsync(context.CancellationToken).ConfigureAwait(false);
+
+                if (declarator.IsKind(SyntaxKind.VariableDeclarator)
+                    && declarator.Parent is VariableDeclarationSyntax variableDeclaration
+                    && variableDeclaration.Variables.Count == 1)
+                {
+                    TryRegisterCodeFix(context, diagnostic, variableDeclaration.Type);
+                }
+            }
+        }
+    }
+
+    private static void TryRegisterCodeFix(CodeFixContext context, Diagnostic diagnostic, TypeSyntax type)
+    {
+        if (type.IsKind(SyntaxKind.NullableType))
+            return;
+
+        CodeAction codeAction = CodeAction.Create(
+            "Declare as nullable",
+            ct =>
+            {
+                NullableTypeSyntax newType = SyntaxFactory.NullableType(type.WithoutTrivia()).WithTriviaFrom(type);
+                return context.Document.ReplaceNodeAsync(type, newType, ct);
+            },
+            GetEquivalenceKey(diagnostic));
+
+        context.RegisterCodeFix(codeAction, diagnostic);
+    }
+}

src/CodeFixes/CSharp/CodeFixes/TokenCodeFixProvider.cs

@@ -1,5 +1,6 @@
 // Copyright (c) .NET Foundation and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
+using System.Collections.Generic;
 using System.Collections.Immutable;
 using System.Composition;
 using System.Diagnostics;
@@ -38,7 +39,10 @@ public override ImmutableArray<string> FixableDiagnosticIds
                 CompilerDiagnosticIdentifiers.CS8618_NonNullableMemberIsUninitialized,
                 CompilerDiagnosticIdentifiers.CS8403_MethodWithIteratorBlockMustBeAsyncToReturnIAsyncEnumerableOfT,
                 CompilerDiagnosticIdentifiers.CS8602_DereferenceOfPossiblyNullReference,
-                CompilerDiagnosticIdentifiers.CS8604_PossibleNullReferenceArgumentForParameter
+                CompilerDiagnosticIdentifiers.CS8604_PossibleNullReferenceArgumentForParameter,
+                CompilerDiagnosticIdentifiers.CS8610_NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember,
+                CompilerDiagnosticIdentifiers.CS8765_NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember,
+                CompilerDiagnosticIdentifiers.CS8767_NullabilityDoesNotMatchImplementedMember
                 );
         }
     }
@@ -607,6 +611,85 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
                             additionalKey: CodeFixIdentifiers.AddAsyncModifier);
                     }
 
+                    break;
+                }
+            case CompilerDiagnosticIdentifiers.CS8610_NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember:
+            case CompilerDiagnosticIdentifiers.CS8765_NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember:
+            case CompilerDiagnosticIdentifiers.CS8767_NullabilityDoesNotMatchImplementedMember:
+                {
+                    if (!IsEnabled(diagnostic.Id, CodeFixIdentifiers.AddNullableAnnotation, document, root.SyntaxTree))
+                        break;
+
+                    if (token.Parent is not MemberDeclarationSyntax memberDeclaration)
+                        return;
+
+                    SemanticModel semanticModel = await context.GetSemanticModelAsync().ConfigureAwait(false);
+
+                    ISymbol symbol = semanticModel.GetDeclaredSymbol(memberDeclaration, context.CancellationToken);
+
+                    if (symbol is null)
+                        return;
+
+                    ISymbol baseSymbol = null;
+                    if (diagnostic.Id == CompilerDiagnosticIdentifiers.CS8767_NullabilityDoesNotMatchImplementedMember)
+                    {
+                        using IEnumerator<ISymbol> en = symbol.FindImplementedInterfaceMembers().GetEnumerator();
+
+                        if (en.MoveNext())
+                        {
+                            baseSymbol = en.Current;
+
+                            if (en.MoveNext())
+                                return;
+                        }
+                    }
+                    else
+                    {
+                        baseSymbol = symbol.OverriddenSymbol();
+
+                        if (baseSymbol is null)
+                            return;
+                    }
+
+                    SeparatedSyntaxList<ParameterSyntax> parameters = CSharpUtility.GetParameters(memberDeclaration);
+
+                    ImmutableArray<IParameterSymbol> parameterSymbols = symbol.GetParameters();
+
+                    if (parameters.Count != parameterSymbols.Length)
+                        return;
+
+                    ImmutableArray<IParameterSymbol> parametersSymbols2 = baseSymbol.GetParameters();
+
+                    if (parameters.Count != parametersSymbols2.Length)
+                        return;
+
+                    MemberDeclarationSyntax newNode = memberDeclaration;
+                    int offset = 0;
+
+                    for (int i = parameters.Count - 1; i >= 0; i--)
+                    {
+                        if (!SymbolEqualityComparer.IncludeNullability.Equals(parameterSymbols[i].Type, parametersSymbols2[i].Type))
+                        {
+                            var parameter = (BaseParameterSyntax)newNode.FindNode(parameters[i].Span.Offset(-offset));
+
+                            TypeSyntax newType = parametersSymbols2[i].Type.ToTypeSyntax()
+                                .WithTriviaFrom(parameter.Type)
+                                .WithSimplifierAnnotation();
+
+                            if (newNode == memberDeclaration)
+                                offset = newNode.FullSpan.Start;
+
+                            newNode = newNode.ReplaceNode(parameter, parameter.WithType(newType));
+                        }
+                    }
+
+                    context.RegisterCodeFix(
+                        CodeAction.Create(
+                            "Declare as nullable",
+                            ct => document.ReplaceNodeAsync(memberDeclaration, newNode, ct),
+                            GetEquivalenceKey(diagnostic)),
+                        diagnostic);
+
                     break;
                 }
         }

src/CodeFixes/CSharp/CompilerDiagnosticRules.Generated.cs

@@ -2036,6 +2036,18 @@ public static partial class CompilerDiagnosticRules
             helpLinkUri:        "https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/cs8403", 
             customTags:         WellKnownDiagnosticTags.Compiler);
 
+        /// <summary>CS8600</summary>
+        public static readonly DiagnosticDescriptor ConvertingNullLiteralOrPossibleNullValueToNonNullableType = new DiagnosticDescriptor(
+            id:                 CompilerDiagnosticIdentifiers.CS8600_ConvertingNullLiteralOrPossibleNullValueToNonNullableType, 
+            title:              "Converting null literal or possible null value to non-nullable type.", 
+            messageFormat:      "Converting null literal or possible null value to non-nullable type", 
+            category:           "Compiler", 
+            defaultSeverity:    DiagnosticSeverity.Warning, 
+            isEnabledByDefault: true, 
+            description:        null, 
+            helpLinkUri:        "https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings", 
+            customTags:         WellKnownDiagnosticTags.Compiler);
+
         /// <summary>CS8602</summary>
         public static readonly DiagnosticDescriptor DereferenceOfPossiblyNullReference = new DiagnosticDescriptor(
             id:                 CompilerDiagnosticIdentifiers.CS8602_DereferenceOfPossiblyNullReference, 
@@ -2060,6 +2072,18 @@ public static partial class CompilerDiagnosticRules
             helpLinkUri:        "", 
             customTags:         WellKnownDiagnosticTags.Compiler);
 
+        /// <summary>CS8610</summary>
+        public static readonly DiagnosticDescriptor NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember = new DiagnosticDescriptor(
+            id:                 CompilerDiagnosticIdentifiers.CS8610_NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember, 
+            title:              "Nullability of reference types in type of parameter doesn't match overridden member.", 
+            messageFormat:      "Nullability of reference types in type of parameter '{0}' doesn't match overridden member.", 
+            category:           "Compiler", 
+            defaultSeverity:    DiagnosticSeverity.Warning, 
+            isEnabledByDefault: true, 
+            description:        null, 
+            helpLinkUri:        "https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings", 
+            customTags:         WellKnownDiagnosticTags.Compiler);
+
         /// <summary>CS8618</summary>
         public static readonly DiagnosticDescriptor NonNullableMemberIsUninitialized = new DiagnosticDescriptor(
             id:                 CompilerDiagnosticIdentifiers.CS8618_NonNullableMemberIsUninitialized, 
@@ -2096,5 +2120,29 @@ public static partial class CompilerDiagnosticRules
             helpLinkUri:        "", 
             customTags:         WellKnownDiagnosticTags.Compiler);
 
+        /// <summary>CS8765</summary>
+        public static readonly DiagnosticDescriptor NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember = new DiagnosticDescriptor(
+            id:                 CompilerDiagnosticIdentifiers.CS8765_NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember, 
+            title:              "Nullability of type of parameter doesn't match overridden member.", 
+            messageFormat:      "Nullability of type of parameter 'arg0' doesn't match overridden member.", 
+            category:           "Compiler", 
+            defaultSeverity:    DiagnosticSeverity.Warning, 
+            isEnabledByDefault: true, 
+            description:        null, 
+            helpLinkUri:        "https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings", 
+            customTags:         WellKnownDiagnosticTags.Compiler);
+
+        /// <summary>CS8767</summary>
+        public static readonly DiagnosticDescriptor NullabilityDoesNotMatchImplementedMember = new DiagnosticDescriptor(
+            id:                 CompilerDiagnosticIdentifiers.CS8767_NullabilityDoesNotMatchImplementedMember, 
+            title:              "Nullability of reference types in type of parameter doesn't match implicitly implemented member.", 
+            messageFormat:      "Nullability of reference types in type of parameter '{0}' of '{1}' doesn't match implicitly implemented member '{2}'.", 
+            category:           "Compiler", 
+            defaultSeverity:    DiagnosticSeverity.Warning, 
+            isEnabledByDefault: true, 
+            description:        null, 
+            helpLinkUri:        "https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings", 
+            customTags:         WellKnownDiagnosticTags.Compiler);
+
     }
 }

src/Diagnostics.xml

@@ -1183,6 +1183,13 @@
     Title="Method with an iterator block must be 'async' to return 'IAsyncEnumerable<T<'."
     Message="Method '{0}' with an iterator block must be 'async' to return '{1}'"
     HelpUrl="https://docs.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/cs8403" />
+  <Diagnostic
+    Id="CS8600"
+    Identifier="ConvertingNullLiteralOrPossibleNullValueToNonNullableType"
+    Severity="Warning"
+    Title="Converting null literal or possible null value to non-nullable type."
+    Message="Converting null literal or possible null value to non-nullable type"
+    HelpUrl="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings" />
   <Diagnostic
     Id="CS8602"
     Identifier="DereferenceOfPossiblyNullReference"
@@ -1197,6 +1204,13 @@
     Title="Possible null reference argument for parameter."
     Message="Possible null reference argument for parameter '{0}' in '{1}'"
     HelpUrl="" />
+  <Diagnostic
+    Id="CS8610"
+    Identifier="NullabilityOfReferenceTypesInTypeOfParameterDoesNotMatchOverriddenMember"
+    Severity="Warning"
+    Title="Nullability of reference types in type of parameter doesn't match overridden member."
+    Message="Nullability of reference types in type of parameter '{0}' doesn't match overridden member."
+    HelpUrl="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings" />
   <Diagnostic
     Id="CS8618"
     Identifier="NonNullableMemberIsUninitialized"
@@ -1218,4 +1232,18 @@
     Title="The annotation for nullable reference types should only be used in code within a '#nullable' annotations context." 
     Message="The annotation for nullable reference types should only be used in code within a '#nullable' annotations context" 
     HelpUrl="" />
+  <Diagnostic
+    Id="CS8765"
+    Identifier="NullabilityOfTypeOfParameterDoesNotMatchOverriddenMember"
+    Severity="Warning"
+    Title="Nullability of type of parameter doesn't match overridden member."
+    Message="Nullability of type of parameter 'arg0' doesn't match overridden member."
+    HelpUrl="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings" />
+  <Diagnostic
+    Id="CS8767"
+    Identifier="NullabilityDoesNotMatchImplementedMember"
+    Severity="Warning"
+    Title="Nullability of reference types in type of parameter doesn't match implicitly implemented member."
+    Message="Nullability of reference types in type of parameter '{0}' of '{1}' doesn't match implicitly implemented member '{2}'."
+    HelpUrl="https://learn.microsoft.com/en-us/dotnet/csharp/language-reference/compiler-messages/nullable-warnings" />
 </Diagnostics>