From 8d47d71144cf6803cde3e2a78c48b15d90490e64 Mon Sep 17 00:00:00 2001
From: Josef Pihrt <josef@pihrt.net>
Date: Sat, 23 Nov 2024 10:33:40 +0100
Subject: [PATCH] Fix Unity method detection (#1586)

---
 ChangeLog.md                                  |  4 ++++
 .../UnusedMember/UnusedMemberAnalyzer.cs      |  4 +++-
 ...S1213RemoveUnusedMemberDeclarationTests.cs | 24 +++++++++++++++++++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 969cbff900..bcf23fb26d 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Fixed
+
+- Fix analyzer [RCS1213](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1213) ([PR](https://github.com/dotnet/roslynator/pull/1586))
+
 ## [4.12.9] - 2024-10-25
 
 ### Fixed
diff --git a/src/Analyzers/CSharp/Analysis/UnusedMember/UnusedMemberAnalyzer.cs b/src/Analyzers/CSharp/Analysis/UnusedMember/UnusedMemberAnalyzer.cs
index f9f88ca165..6bdc0e5239 100644
--- a/src/Analyzers/CSharp/Analysis/UnusedMember/UnusedMemberAnalyzer.cs
+++ b/src/Analyzers/CSharp/Analysis/UnusedMember/UnusedMemberAnalyzer.cs
@@ -155,7 +155,9 @@ private static void AnalyzeTypeDeclaration(SyntaxNodeAnalysisContext context)
                         if (IsMainMethod(declaration, modifiers, methodName))
                             break;
 
-                        if (declaration.ReturnsVoid()
+                        if ((declaration.ReturnsVoid()
+                            || (methodName == "Start"
+                                && semanticModel.GetDeclaredSymbol(declaration, cancellationToken)?.ReturnType.SpecialType == SpecialType.System_Collections_IEnumerator))
                             && context.IsUnityCodeAnalysisEnabled() == true)
                         {
                             if (canContainUnityScriptMethods is null)
diff --git a/src/Tests/Analyzers.Tests/RCS1213RemoveUnusedMemberDeclarationTests.cs b/src/Tests/Analyzers.Tests/RCS1213RemoveUnusedMemberDeclarationTests.cs
index b2b05d2f65..e5d94a74a7 100644
--- a/src/Tests/Analyzers.Tests/RCS1213RemoveUnusedMemberDeclarationTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1213RemoveUnusedMemberDeclarationTests.cs
@@ -380,6 +380,30 @@ private void Awake()
     }
 }
 
+namespace UnityEngine
+{
+    class MonoBehaviour
+    {
+    }
+}
+", options: Options.AddConfigOption(ConfigOptionKeys.UnityCodeAnalysisEnabled, true));
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.RemoveUnusedMemberDeclaration)]
+    public async Task TestNoDiagnostic_UnityScriptMethods_Start()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System.Collections;
+using UnityEngine;
+
+class C : MonoBehaviour
+{
+    private IEnumerator Start()
+    {
+        yield break;
+    }
+}
+
 namespace UnityEngine
 {
     class MonoBehaviour