Add code fix for CS0037 (#929)

Author: josefpihrt

ChangeLog.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Added
 
 - Convert more syntax to implicit object creation (RCS1250) ([#910](https://github.com/josefpihrt/roslynator/pull/910)).
+- Add code fix for CS0037 ([#929](https://github.com/josefpihrt/roslynator/pull/929)).
 
 ### Changed
 

docs/cs/CS0037.md

@@ -9,6 +9,8 @@
 
 ## Code Fixes
 
+* Remove property or field initializer
 * Replace 'null' with default value
 
+
 *\(Generated with [DotMarkdown](http://github.com/JosefPihrt/DotMarkdown)\)*

src/CodeFixes/CSharp/CodeFixes/RemovePropertyOrFieldInitializerCodeFixProvider.cs

@@ -2,7 +2,6 @@
 
 using System.Collections.Immutable;
 using System.Composition;
-using System.Diagnostics;
 using System.Threading.Tasks;
 using Microsoft.CodeAnalysis;
 using Microsoft.CodeAnalysis.CodeActions;
@@ -24,6 +23,7 @@ public override ImmutableArray<string> FixableDiagnosticIds
             get
             {
                 return ImmutableArray.Create(
+                    CompilerDiagnosticIdentifiers.CS0037_CannotConvertNullToTypeBecauseItIsNonNullableValueType,
                     CompilerDiagnosticIdentifiers.CS0573_CannotHaveInstancePropertyOrFieldInitializersInStruct,
                     CompilerDiagnosticIdentifiers.CS8050_OnlyAutoImplementedPropertiesCanHaveInitializers);
             }
@@ -41,12 +41,9 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
             if (!TryFindToken(root, context.Span.Start, out SyntaxToken token))
                 return;
 
-            SyntaxDebug.Assert(token.IsKind(SyntaxKind.IdentifierToken), token);
+            SyntaxDebug.Assert(token.IsKind(SyntaxKind.IdentifierToken, SyntaxKind.NullKeyword), token);
 
-            if (!token.IsKind(SyntaxKind.IdentifierToken))
-                return;
-
-            switch (token.Parent)
+            switch (GetNode(token))
             {
                 case PropertyDeclarationSyntax propertyDeclaration:
                     {
@@ -83,12 +80,36 @@ public override async Task RegisterCodeFixesAsync(CodeFixContext context)
 
                                 return context.Document.ReplaceNodeAsync(variableDeclarator, newNode, ct);
                             },
-                            GetEquivalenceKey(CompilerDiagnosticIdentifiers.CS0573_CannotHaveInstancePropertyOrFieldInitializersInStruct, CodeFixIdentifiers.RemovePropertyOrFieldInitializer));
+                            GetEquivalenceKey(diagnostic, CodeFixIdentifiers.RemovePropertyOrFieldInitializer));
 
                         context.RegisterCodeFix(codeAction, diagnostic);
                         break;
                     }
             }
+
+            static SyntaxNode GetNode(SyntaxToken token)
+            {
+                if (token.IsKind(SyntaxKind.IdentifierToken))
+                    return token.Parent;
+
+                if (token.IsKind(SyntaxKind.NullKeyword))
+                {
+                    SyntaxNode node = token.Parent;
+
+                    if (node.IsKind(SyntaxKind.NullLiteralExpression))
+                    {
+                        node = node.Parent;
+
+                        if (node.IsKind(SyntaxKind.SuppressNullableWarningExpression))
+                            node = node.Parent;
+
+                        if (node.IsKind(SyntaxKind.EqualsValueClause))
+                            return node.Parent;
+                    }
+                }
+
+                return null;
+            }
         }
     }
 }

src/CodeFixes/CodeFixes.xml

@@ -120,6 +120,7 @@
   </CodeFix>
   <CodeFix Id="RCF0024" Identifier="RemovePropertyOrFieldInitializer" Title="Remove property or field initializer">
     <FixableDiagnosticIds>
+      <Id>CS0037</Id>
       <Id>CS0573</Id>
       <Id>CS8050</Id>
     </FixableDiagnosticIds>

src/Tests/CodeFixes.Tests/CS0037CannotConvertNullToTypeBecauseItIsNonNullableValueTypeTests.cs

@@ -0,0 +1,73 @@
+// Copyright (c) Josef Pihrt and Contributors. Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Threading.Tasks;
+using Roslynator.Testing.CSharp;
+using Xunit;
+
+namespace Roslynator.CSharp.CodeFixes.Tests
+{
+    public class CS0037CannotConvertNullToTypeBecauseItIsNonNullableValueTypeTests : AbstractCSharpCompilerDiagnosticFixVerifier<RemovePropertyOrFieldInitializerCodeFixProvider>
+    {
+        public override string DiagnosticId { get; } = CompilerDiagnosticIdentifiers.CS0037_CannotConvertNullToTypeBecauseItIsNonNullableValueType;
+
+        [Fact, Trait(Traits.CodeFix, CompilerDiagnosticIdentifiers.CS0037_CannotConvertNullToTypeBecauseItIsNonNullableValueType)]
+        public async Task Test_RemovePropertyInitializer()
+        {
+            await VerifyFixAsync(@"
+using System;
+
+class C
+{
+    public StringSplitOptions Options { get; set } = null;
+}
+", @"
+using System;
+
+class C
+{
+    public StringSplitOptions Options { get; set }
+}
+", equivalenceKey: EquivalenceKey.Create(DiagnosticId, CodeFixIdentifiers.RemovePropertyOrFieldInitializer));
+        }
+
+        [Fact, Trait(Traits.CodeFix, CompilerDiagnosticIdentifiers.CS0037_CannotConvertNullToTypeBecauseItIsNonNullableValueType)]
+        public async Task Test_RemovePropertyInitializer_NullForgivingOperator()
+        {
+            await VerifyFixAsync(@"
+using System;
+
+class C
+{
+    public StringSplitOptions Options { get; set } = null!;
+}
+", @"
+using System;
+
+class C
+{
+    public StringSplitOptions Options { get; set }
+}
+", equivalenceKey: EquivalenceKey.Create(DiagnosticId, CodeFixIdentifiers.RemovePropertyOrFieldInitializer));
+        }
+
+        [Fact, Trait(Traits.CodeFix, CompilerDiagnosticIdentifiers.CS0037_CannotConvertNullToTypeBecauseItIsNonNullableValueType)]
+        public async Task Test_RemoveFieldInitializer()
+        {
+            await VerifyFixAsync(@"
+using System;
+
+class C
+{
+    public StringSplitOptions Options = null!;
+}
+", @"
+using System;
+
+class C
+{
+    public StringSplitOptions Options;
+}
+", equivalenceKey: EquivalenceKey.Create(DiagnosticId, CodeFixIdentifiers.RemovePropertyOrFieldInitializer));
+        }
+    }
+}