Fix SA1515 handling of comment after pattern-matching case label

Author: sharwell

StyleCop.Analyzers/StyleCop.Analyzers.Test.CSharp7/LayoutRules/SA1515CSharp7UnitTests.cs

@@ -3,9 +3,32 @@
 
 namespace StyleCop.Analyzers.Test.CSharp7.LayoutRules
 {
+    using System.Threading;
+    using System.Threading.Tasks;
     using StyleCop.Analyzers.Test.LayoutRules;
+    using Xunit;
 
     public class SA1515CSharp7UnitTests : SA1515UnitTests
     {
+        [Fact]
+        public async Task TestCommentAfterCasePatternSwitchLabelAsync()
+        {
+            var testCode = @"
+public class ClassName
+{
+    public void Method()
+    {
+        switch (new object())
+        {
+            case int x:
+                // Single line comment after pattern-matching case statement is valid
+                break;
+        }
+    }
+}
+";
+
+            await this.VerifyCSharpDiagnosticAsync(testCode, EmptyDiagnosticResults, CancellationToken.None).ConfigureAwait(false);
+        }
     }
 }

StyleCop.Analyzers/StyleCop.Analyzers/LayoutRules/SA1515SingleLineCommentMustBePrecededByBlankLine.cs

@@ -12,6 +12,7 @@ namespace StyleCop.Analyzers.LayoutRules
     using Microsoft.CodeAnalysis.Diagnostics;
     using Microsoft.CodeAnalysis.Text;
     using StyleCop.Analyzers.Helpers;
+    using StyleCop.Analyzers.Lightup;
 
     /// <summary>
     /// A single-line comment within C# code is not preceded by a blank line.
@@ -259,6 +260,7 @@ private static bool IsAtStartOfScope(SyntaxTrivia trivia)
             var prevToken = token.GetPreviousToken();
             return prevToken.IsKind(SyntaxKind.OpenBraceToken)
                    || prevToken.Parent.IsKind(SyntaxKind.CaseSwitchLabel)
+                   || prevToken.Parent.IsKind(SyntaxKindEx.CasePatternSwitchLabel)
                    || prevToken.Parent.IsKind(SyntaxKind.DefaultSwitchLabel);
         }