Fix MA0202 false positive for comment-only branches

docs/Rules/MA0202.md

@@ -7,7 +7,9 @@ This rule reports duplicate code in a single `#if` / `#elif` / `#else` block.
 
 If a branch has the same code as any previous branch in the same conditional compilation block, the directive is redundant and should be simplified.
 
-The comparison ignores trivia (such as comments and whitespace), so only the actual code structure is considered.
+The comparison ignores trivia (such as comments and whitespace) when branches contain code, so only the actual code structure is considered.
+
+For comment-only branches, comments are compared textually to avoid false positives when comment content differs.
 
 ## Non-compliant code
 

src/Meziantou.Analyzer/Rules/ConditionalCompilationBranchesAreIdenticalCommon.cs

@@ -89,6 +89,9 @@ private static string ComputeBranchSignature(SourceText sourceText, TextSpan spa
             builder.Append(';');
         }
 
+        if (builder.Length == 0)
+            return text.Trim();
+
         return builder.ToString();
     }
 

tests/Meziantou.Analyzer.Test/Rules/ConditionalCompilationBranchesAreIdenticalAnalyzerTests.cs

@@ -62,6 +62,40 @@ public Task SameCodeWithDifferentComments() => CreateProjectBuilder()
             """)
         .ValidateAsync();
 
+    [Fact]
+    public Task DifferentXmlCommentsOnly() => CreateProjectBuilder()
+        .WithSourceCode("""
+            class C
+            {
+            #if A
+                /// <summary>net8</summary>
+            #else
+                /// <summary>net9</summary>
+            #endif
+                void M() { }
+            }
+
+            static class Program { static void Main() { } }
+            """)
+        .ValidateAsync();
+
+    [Fact]
+    public Task SameXmlCommentsOnly() => CreateProjectBuilder()
+        .WithSourceCode("""
+            class C
+            {
+            #if A
+                /// <summary>text</summary>
+            {|MA0202:#else|}
+                /// <summary>text</summary>
+            #endif
+                void M() { }
+            }
+
+            static class Program { static void Main() { } }
+            """)
+        .ValidateAsync();
+
     [Fact]
     public Task DifferentBranches() => CreateProjectBuilder()
         .WithSourceCode("""

tests/Meziantou.Analyzer.Test/Rules/UseStringComparerAnalyzerTests.cs

@@ -534,7 +534,7 @@ public void Test()
     }
 
     [Fact]
-    public async Task Dictionary_String_CollectionExpression_WithElements_ShouldReportDiagnostic()
+    public async Task HashSet_String_CollectionExpression_WithElements_Spread_ShouldReportDiagnostic()
     {
         await CreatePreviewProjectBuilder()
               .WithSourceCode("""