Update SA1113 for static anonymous functions

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp9/ReadabilityRules/SA1113CSharp9UnitTests.cs

@@ -3,9 +3,47 @@
 
 namespace StyleCop.Analyzers.Test.CSharp9.ReadabilityRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
+    using Microsoft.CodeAnalysis.Testing;
     using StyleCop.Analyzers.Test.CSharp8.ReadabilityRules;
+    using Xunit;
+    using static StyleCop.Analyzers.Test.Verifiers.StyleCopCodeFixVerifier<
+        StyleCop.Analyzers.ReadabilityRules.SA1113CommaMustBeOnSameLineAsPreviousParameter,
+        StyleCop.Analyzers.SpacingRules.TokenSpacingCodeFixProvider>;
 
     public partial class SA1113CSharp9UnitTests : SA1113CSharp8UnitTests
     {
+        [Fact]
+        [WorkItem(3973, "https://github.com/DotNetAnalyzers/StyleCopAnalyzers/issues/3973")]
+        public async Task TestStaticAnonymousFunctionCommaOnNextLineAsync()
+        {
+            var testCode = @"using System;
+
+public class TestClass
+{
+    public void TestMethod()
+    {
+        Func<int, int, int> func = static (int first
+            {|#0:,|} int second) => first + second;
+    }
+}
+";
+
+            var fixedCode = @"using System;
+
+public class TestClass
+{
+    public void TestMethod()
+    {
+        Func<int, int, int> func = static (int first,
+            int second) => first + second;
+    }
+}
+";
+
+            DiagnosticResult expected = Diagnostic().WithLocation(0);
+            await VerifyCSharpFixAsync(testCode, expected, fixedCode, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }