bugfix: improve CollectionShouldNotHaveSameCount_CountShouldNotBeOtherCollectionCount detection (#393)

* bugfix: improve CollectionShouldNotHaveSameCount_CountShouldNotBeOtherCollectionCount detection

Author: Meir017

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

@@ -659,6 +659,7 @@ public void CollectionShouldHaveCount_LengthShouldBe_TestNoAnalyzer(string asser
 
         [DataTestMethod]
         [AssertionDiagnostic("(actual.Count() + 1).Should().NotBe(unexpected.Count(){0});")]
+        [AssertionDiagnostic("actual.Count().Should().NotBe((unexpected.Count() + 1){0});")]
         [AssertionDiagnostic("actual.Count().ToString().Length.Should().NotBe(unexpected.Count(){0});")]
         [Implemented]
         public void CollectionShouldNotHaveSameCount_TestNotAnalyzer(string assertion) => DiagnosticVerifier.VerifyCSharpDiagnosticUsingAllAnalyzers(GenerateCode.GenericIListCodeBlockAssertion(assertion));

src/FluentAssertions.Analyzers/Tips/FluentAssertionsAnalyzer.cs

@@ -408,7 +408,7 @@ private static void AnalyzeInvocation(OperationAnalysisContext context, FluentAs
                         {
                             // TODO: add support for Enumerable.LongCount
                             case nameof(Enumerable.Count) when IsEnumerableMethodWithoutArguments(invocationBeforeShould, metadata):
-                                if (assertion.Arguments[0].HasFirstDescendentInvocation(nameof(Enumerable.Count)))
+                                if (assertion.TryGetFirstArgumentAs<IInvocationOperation>(out var assertionInvocation) && IsEnumerableMethodWithoutArguments(assertionInvocation, metadata))
                                 {
                                     context.ReportDiagnostic(CreateDiagnostic(assertion, DiagnosticMetadata.CollectionShouldNotHaveSameCount_CountShouldNotBeOtherCollectionCount));
                                 }

src/FluentAssertions.Analyzers/Utilities/OperartionExtensions.cs

@@ -60,11 +60,6 @@ public static TOperation GetFirstAncestor<TOperation>(this IOperation parent) wh
         return default;
     }
 
-    public static bool HasFirstDescendentInvocation(this IOperation parent, string invocationMethod)
-    {
-        return parent.TryGetFirstDescendent<IInvocationOperation>(out var invocation) && invocation.TargetMethod.Name == invocationMethod;
-    }
-
     public static bool IsContainedInType(this IPropertyReferenceOperation property, SpecialType type)
         => property.Property.ContainingType.ConstructedFromType(type);
     public static bool IsContainedInType(this IPropertyReferenceOperation property, INamedTypeSymbol type)
@@ -204,6 +199,18 @@ public static bool TryGetSingleArgumentAs<TOperation>(this IInvocationOperation
         return false;
     }
 
+    public static bool TryGetFirstArgumentAs<TOperation>(this IInvocationOperation invocation, out TOperation operation)
+    {
+        if (invocation.Arguments.Length is >= 1 && invocation.Arguments[0].Value.UnwrapConversion() is TOperation op)
+        {
+            operation = op;
+            return true;
+        }
+
+        operation = default;
+        return false;
+    }
+
     public static IOperation UnwrapConversion(this IOperation operation)
     {
         return operation switch