Fix analyzer RCS1231 (#1769)

ChangeLog.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+- Fix analyzer [RCS1231](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1231) ([PR](https://github.com/dotnet/roslynator/pull/1744) by @cbersch)
 - Fix enum contained flags check for partial matches in [RCS1258](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1258) ([PR](https://github.com/dotnet/roslynator/pull/1740) by @ovska)
 - Fix analyzer [RCS1146](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1146) ([PR](https://github.com/dotnet/roslynator/pull/1747))
 - Fix analyzer [RCS1194](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1194) ([PR](https://github.com/dotnet/roslynator/pull/1733))

src/Analyzers/CSharp/Analysis/RefReadOnlyParameterAnalyzer.cs

@@ -145,6 +145,9 @@ private static void Analyze(
             if (parameter.RefKind != RefKind.None)
                 continue;
 
+            if (parameter.IsParams)
+                continue;
+
             if (walker is null)
             {
                 if (methodSymbol.ImplementsInterfaceMember(allInterfaces: true))

src/Tests/Analyzers.Tests/RCS1231MakeParameterRefReadOnlyTests.cs

@@ -122,6 +122,36 @@ void M(C c, C c)
 ", options: Options.AddAllowedCompilerDiagnosticId("CS0100"));
     }
 
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MakeParameterRefReadOnly)]
+    public async Task TestNoDiagnostic_ParamsArray()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+
+readonly struct C
+{
+    void M(params C[] c)
+    {
+    }
+}
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MakeParameterRefReadOnly)]
+    public async Task TestNoDiagnostic_ParamsCollection()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+
+readonly struct C
+{
+    void M(params ReadOnlySpan<C> c)
+    {
+    }
+}
+");
+    }
+
     [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.MakeParameterRefReadOnly)]
     public async Task TestNoDiagnostic_MethodReferencedAsMethodGroup()
     {