Fix analyzer RCS1043 (#1684)

Author: josefpihrt

ChangeLog.md

@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix analyzer [RCS1246](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1246) ([PR](https://github.com/dotnet/roslynator/pull/1676))
 - Fix analyzer [RCS1248](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1248) ([PR](https://github.com/dotnet/roslynator/pull/1677))
 - Fix analyzer [RCS1203](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1203) ([PR](https://github.com/dotnet/roslynator/pull/1683))
+- Fix analyzer [RCS1043](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1043) ([PR](https://github.com/dotnet/roslynator/pull/1684))
 - Fix refactoring [Check expression for null](https://josefpihrt.github.io/docs/roslynator/refactorings/RR0024) ([PR](https://github.com/dotnet/roslynator/pull/1682))
 
 ## [4.14.0] - 2025-07-26

src/Analyzers/CSharp/Analysis/RemovePartialModifierFromTypeWithSinglePartAnalyzer.cs

@@ -59,6 +59,12 @@ private static void AnalyzeTypeDeclaration(SyntaxNodeAnalysisContext context)
         if (_metadataNames.Any(c => symbol.InheritsFrom(c)))
             return;
 
+        foreach (ISymbol member in symbol.GetMembers())
+        {
+            if (member.HasAttribute(MetadataNames.System_Text_RegularExpressions_GeneratedRegexAttribute))
+                return;
+        }
+
         foreach (MemberDeclarationSyntax member in typeDeclaration.Members)
         {
             if (member is MethodDeclarationSyntax methodDeclaration

src/Core/MetadataNames.cs

@@ -63,6 +63,7 @@ internal static class MetadataNames
     public static readonly MetadataName System_Runtime_Serialization_StreamingContext = MetadataName.Parse("System.Runtime.Serialization.StreamingContext");
     public static readonly MetadataName System_Span_T = MetadataName.Parse("System.Span`1");
     public static readonly MetadataName System_StringComparison = MetadataName.Parse("System.StringComparison");
+    public static readonly MetadataName System_Text_RegularExpressions_GeneratedRegexAttribute = MetadataName.Parse("System.Text.RegularExpressions.GeneratedRegexAttribute");
     public static readonly MetadataName System_Text_RegularExpressions_Regex = MetadataName.Parse("System.Text.RegularExpressions.Regex");
     public static readonly MetadataName System_Text_RegularExpressions_RegexOptions = MetadataName.Parse("System.Text.RegularExpressions.RegexOptions");
     public static readonly MetadataName System_Text_StringBuilder = MetadataName.Parse("System.Text.StringBuilder");

src/Tests/Analyzers.Tests/RCS1043RemovePartialModifierFromTypeWithSinglePartTests.cs

@@ -245,4 +245,18 @@ class FrameworkElement
 }
 ");
     }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.RemovePartialModifierFromTypeWithSinglePart)]
+    public async Task TestNoDiagnostic_GeneratedRegexAttribute()
+    {
+        await VerifyNoDiagnosticAsync("""
+using System.Text.RegularExpressions;
+
+partial class C
+{
+    [GeneratedRegex("^[a-z]{2}$", RegexOptions.IgnoreCase | RegexOptions.CultureInvariant)]
+    private static partial Regex Pattern();
+}
+""", options: Options.AddAllowedCompilerDiagnosticId("CS8795"));
+    }
 }