Fix wrong ElementAt diagnostic (#49)

Author: cbersch

src/AwesomeAssertions.Analyzers.Tests/Tips/CollectionTests.cs

@@ -844,6 +844,28 @@ public void CollectionShouldContainSingle_TestAnalyzer_GenericIEnumerableShouldR
         public void CollectionShouldHaveElementAt_AccessPropertyOfIndexedValue_TestNoAnalyzer(string assertion) =>
             DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(GenerateCode.GenericIListCodeBlockAssertion(assertion));
 
+        [TestMethod]
+        public void CollectionShouldHaveElementAt_AccessObjectPropertyOfIndexedValue_TestNoAnalyzer()
+        {
+            // I cannot see the relevant difference to CollectionShouldHaveElementAt_AccessPropertyOfIndexedValue_TestNoAnalyzer,
+            // but it makes a difference.
+            string source = """
+                using System.Collections.Generic;
+                using AwesomeAssertions;
+
+                public record Value(object InstanceValue);
+
+                public sealed class TestClass
+                {
+                    public void TestMethod(List<Value> list)
+                    {
+                        list[0].InstanceValue.Should().Be(1);
+                    }
+                }
+                """;
+            DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(source);
+        }
+
         [TestMethod]
         [AssertionDiagnostic("var first = actual[0]; first[6].Should().Be(expectedItem{0});")]
         [Implemented]

src/AwesomeAssertions.Analyzers/Tips/AwesomeAssertionsAnalyzer.cs

@@ -388,8 +388,12 @@ private static void AnalyzeInvocation(OperationAnalysisContext context, AwesomeA
                                 return;
                         }
                     }
-                    
-                    if (subject.TryGetSingleChild<IPropertyReferenceOperation>(out var previousPropertyReference) && !previousPropertyReference.Property.IsIndexer)
+
+                    if (subject is IPropertyReferenceOperation propertyReferenceOperation)
+                    {
+                        return;
+                    }
+                    else if (subject.TryGetSingleChild<IPropertyReferenceOperation>(out var previousPropertyReference) && !previousPropertyReference.Property.IsIndexer)
                     {
                         return;
                     }