From 5aa65217fa928a42d56e2802e5364edf58696545 Mon Sep 17 00:00:00 2001
From: Josef Pihrt <josef@pihrt.net>
Date: Wed, 8 May 2024 22:23:51 +0200
Subject: [PATCH] Fix analyzer RCS1077 (#1463)

---
 ChangeLog.md                                  |  1 +
 .../OptimizeLinqMethodCallAnalysis.cs         |  3 ++-
 .../RCS1077OptimizeLinqMethodCallTests.cs     | 22 +++++++++++++++++++
 3 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/ChangeLog.md b/ChangeLog.md
index 1b9117d4ab..72761bcad1 100644
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Fix analyzer [RCS1246](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1246) ([PR](https://github.com/dotnet/roslynator/pull/1460))
 - Fix analyzer [RCS1085](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1085) ([PR](https://github.com/dotnet/roslynator/pull/1461))
+- Fix analyzer [RCS1077](https://josefpihrt.github.io/docs/roslynator/analyzers/RCS1077) ([PR](https://github.com/dotnet/roslynator/pull/1463))
 
 ## [4.12.2] - 2024-04-23
 
diff --git a/src/Analyzers/CSharp/Analysis/OptimizeLinqMethodCallAnalysis.cs b/src/Analyzers/CSharp/Analysis/OptimizeLinqMethodCallAnalysis.cs
index 5a2ca58ee9..9718196baa 100644
--- a/src/Analyzers/CSharp/Analysis/OptimizeLinqMethodCallAnalysis.cs
+++ b/src/Analyzers/CSharp/Analysis/OptimizeLinqMethodCallAnalysis.cs
@@ -232,7 +232,8 @@ public static void AnalyzeFirstOrDefault(SyntaxNodeAnalysisContext context, in S
             if (parameterCount == 2)
             {
                 if (parameters[0].Type.OriginalDefinition.IsIEnumerableOfT()
-                    && SymbolUtility.IsPredicateFunc(parameters[1].Type, methodSymbol.TypeArguments[0]))
+                    && SymbolUtility.IsPredicateFunc(parameters[1].Type, methodSymbol.TypeArguments[0])
+                    && invocationInfo.Arguments[0].Expression is LambdaExpressionSyntax)
                 {
                     ITypeSymbol typeSymbol = context.SemanticModel.GetTypeSymbol(invocationInfo.Expression, context.CancellationToken);
 
diff --git a/src/Tests/Analyzers.Tests/RCS1077OptimizeLinqMethodCallTests.cs b/src/Tests/Analyzers.Tests/RCS1077OptimizeLinqMethodCallTests.cs
index 398148e264..fb5f6719ba 100644
--- a/src/Tests/Analyzers.Tests/RCS1077OptimizeLinqMethodCallTests.cs
+++ b/src/Tests/Analyzers.Tests/RCS1077OptimizeLinqMethodCallTests.cs
@@ -1503,6 +1503,28 @@ void M()
 
     Func<string, IEnumerable<string>> M2() => null;
 }
+");
+    }
+
+    [Fact, Trait(Traits.Analyzer, DiagnosticIdentifiers.OptimizeLinqMethodCall)]
+    public async Task TestNoDiagnostic_CannotConvertFuncToPredicate()
+    {
+        await VerifyNoDiagnosticAsync(@"
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+class C
+{
+    void M()
+    {
+        var list = new List<string>();
+
+        Func<string, bool> predicate = null;
+
+        list.FirstOrDefault(predicate);
+    }
+}
 ");
     }
 }