From ac5c16ba916763673da2ccd81404f5266fb99979 Mon Sep 17 00:00:00 2001
From: Josef Pihrt <josef.pihrt@outlook.com>
Date: Fri, 11 Nov 2022 19:35:45 +0100
Subject: [PATCH] Fix RCS1080 (#986)

---
 ChangeLog.md                                  |  4 ++
 src/Core/SymbolUtility.cs                     | 25 ++++++++---
 ...OrLengthPropertyInsteadOfAnyMethodTests.cs | 44 +++++++++++++++++++
 3 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 7d8ce00d7a..7e7ec8cb8d 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -11,6 +11,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Disable [RCS1080](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1080.md) by default ([#980](https://github.com/josefpihrt/roslynator/pull/980).
 
+### Fixed
+
+- Fix ([RCS1080](https://github.com/JosefPihrt/Roslynator/blob/main/docs/analyzers/RCS1080.md)) when collection is derived from `List<T>` ([#986](https://github.com/josefpihrt/roslynator/pull/986).
+
 ## [4.1.2] - 2022-10-31
 
 ### Added
diff --git a/src/Core/SymbolUtility.cs b/src/Core/SymbolUtility.cs
index cde1727d63..50c5e7e84f 100644
--- a/src/Core/SymbolUtility.cs
+++ b/src/Core/SymbolUtility.cs
@@ -191,15 +191,30 @@ public static bool IsEventHandlerMethod(IMethodSymbol methodSymbol)
                 if (originalDefinition.TypeKind == TypeKind.Interface)
                     return "Count";
 
-                foreach (ISymbol symbol in typeSymbol.GetMembers())
+                while (typeSymbol is not null
+                    && typeSymbol.SpecialType != SpecialType.System_Object)
                 {
-                    if (symbol.Kind == SymbolKind.Property
-                        && StringUtility.Equals(symbol.Name, "Count", "Length")
-                        && semanticModel.IsAccessible(position, symbol))
+                    foreach (ISymbol symbol in typeSymbol.GetMembers("Count"))
                     {
-                        return symbol.Name;
+                        if (symbol.Kind == SymbolKind.Property
+                            && semanticModel.IsAccessible(position, symbol))
+                        {
+                            return symbol.Name;
+                        }
                     }
+
+                    foreach (ISymbol symbol in typeSymbol.GetMembers("Length"))
+                    {
+                        if (symbol.Kind == SymbolKind.Property
+                            && semanticModel.IsAccessible(position, symbol))
+                        {
+                            return symbol.Name;
+                        }
+                    }
+
+                    typeSymbol = typeSymbol.BaseType;
                 }
+
             }
 
             return null;
diff --git a/src/Tests/Analyzers.Tests/RCS1080UseCountOrLengthPropertyInsteadOfAnyMethodTests.cs b/src/Tests/Analyzers.Tests/RCS1080UseCountOrLengthPropertyInsteadOfAnyMethodTests.cs
index 593c6617c3..1cf187c36a 100644
--- a/src/Tests/Analyzers.Tests/RCS1080UseCountOrLengthPropertyInsteadOfAnyMethodTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1080UseCountOrLengthPropertyInsteadOfAnyMethodTests.cs
@@ -548,6 +548,50 @@ void M()
 ");
         }
 
+        [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseCountOrLengthPropertyInsteadOfAnyMethod)]
+        public async Task Test_DerivedFromListOfT()
+        {
+            await VerifyDiagnosticAndFixAsync(@"
+using System.Collections.Generic;
+using System.Linq;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        List2 items = new List2();
+
+        if (items.[|Any()|])
+        {
+        }
+    }
+}
+
+public class List2 : List<string>
+{
+}
+", @"
+using System.Collections.Generic;
+using System.Linq;
+
+class Program
+{
+    static void Main(string[] args)
+    {
+        List2 items = new List2();
+
+        if (items.Count > 0)
+        {
+        }
+    }
+}
+
+public class List2 : List<string>
+{
+}
+");
+        }
+
         [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.UseCountOrLengthPropertyInsteadOfAnyMethod)]
         public async Task TestNoDiagnostic_ImmutableArray()
         {