Add more cases for recursive call analyzer (#297)

* Add more cases for recursive call analyzer

* Add the case with named parameters

* Add comments to RecursiveCallAnalyzer

Author: SergeyTeplyakov

src/ErrorProne.NET.CoreAnalyzers.Tests/RecursiveCallAnalyzerTests.cs

@@ -1,6 +1,5 @@
 using NUnit.Framework;
 using System.Threading.Tasks;
-using ErrorProne.NET.CoreAnalyzers;
 using Verify = ErrorProne.NET.TestHelpers.CSharpCodeFixVerifier<
     ErrorProne.NET.CoreAnalyzers.RecursiveCallAnalyzer,
     Microsoft.CodeAnalysis.Testing.EmptyCodeFixProvider>;
@@ -32,6 +31,48 @@ void Foo(bool b) {
         if (b) [|Foo(b)|];
     }
 }
+";
+            await Verify.VerifyAsync(test);
+        }
+        
+        [Test]
+        public async Task WarnsOnConditionalRecursiveCall_With_Named_Parameters()
+        {
+            var test = @"
+class C {
+    void Foo(bool b) {
+        if (b) [|Foo(b: b)|];
+    }
+}
+";
+            await Verify.VerifyAsync(test);
+        }
+
+        [Test]
+        public async Task NoWarn_When_Different_Argument_Is_Passed()
+        {
+            var test = @"
+class C {
+    void Foo(bool b) {
+        if (b) Foo(false);
+    }
+}
+";
+            await Verify.VerifyAsync(test);
+        }
+        
+        [Test]
+        public async Task NoWarn_For_Factorial()
+        {
+            var test = @"
+class C {
+    int Factorial(int n)
+    {
+        if (n <= 1)
+            return 1; // Base case
+        return n * Factorial(n - 1); // Recursive call with changing argument
+    }
+}
 ";
             await Verify.VerifyAsync(test);
         }

src/ErrorProne.NET.CoreAnalyzers/RecursiveCallAnalyzer.cs

@@ -26,7 +26,19 @@ private static void AnalyzeMethodBody(OperationAnalysisContext context)
             var methodBody = (IMethodBodyOperation)context.Operation;
             foreach (var invocation in methodBody.Descendants().OfType<IInvocationOperation>())
             {
-                if (SymbolEqualityComparer.Default.Equals(invocation.TargetMethod.OriginalDefinition, method.OriginalDefinition))
+                // Check if all parameters are passed as-is
+                // So Factorial(n - 1) should be totally fine!
+                if (invocation.Arguments.Length == method.Parameters.Length &&
+                    // Checking that the method is the same.
+                    SymbolEqualityComparer.Default.Equals(invocation.TargetMethod.OriginalDefinition, method.OriginalDefinition) &&
+
+                    // Checking if the parameters are passed as is.
+                    // It is possible to have a false positive here if the parameters are mutable.
+                    // But it is a very rare case, so we will ignore it for now.
+                    invocation.Arguments.Zip(method.Parameters, (arg, param) =>
+                        arg.Value is IParameterReferenceOperation paramRef &&
+                        SymbolEqualityComparer.Default.Equals(paramRef.Parameter, param)
+                    ).All(b => b))
                 {
                     context.ReportDiagnostic(Diagnostic.Create(
                         DiagnosticDescriptors.EPC30,