feat: improve TryGetFirstDescendent logic

Author: Meir017

src/FluentAssertions.Analyzers/Tips/FluentAssertionsAnalyzer.cs

@@ -312,7 +312,7 @@ private static void AnalyzeInvocation(OperationAnalysisContext context, FluentAs
                 return;
             case "Be" when assertion.IsContainedInType(metadata.NumericAssertionsOfT2):
                 {
-                    if (invocation.TryGetFirstDescendent<IInvocationOperation>(out var invocationBeforeShould))
+                    if (invocation.TryGetSingleArgumentAs<IInvocationOperation>(out var invocationBeforeShould))
                     {
                         switch (invocationBeforeShould.TargetMethod.Name)
                         {
@@ -334,8 +334,8 @@ private static void AnalyzeInvocation(OperationAnalysisContext context, FluentAs
 
                         }
                     }
-                    var argument = invocation.Arguments[0].Value.UnwrapConversion();
-                    if (argument is IPropertyReferenceOperation propertyBeforeShould)
+
+                    if (invocation.TryGetSingleArgumentAs<IPropertyReferenceOperation>(out var propertyBeforeShould))
                     {
                         switch (propertyBeforeShould.Property.Name)
                         {

src/FluentAssertions.Analyzers/Utilities/OperartionExtensions.cs

@@ -192,6 +192,18 @@ public static bool TryGetChainedInvocationAfterAndConstraint(this IInvocationOpe
         return false;
     }
 
+    public static bool TryGetSingleArgumentAs<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