False positive for FakeItEasy0003 when using argument constraint in CallToSet with indexer property

[zivarah]

Version: FakeItEasy.Analyzer.CSharp 6.1.0

Consider this simple class:

using System.Collections.Generic;

namespace FakeItEasyAnalyzerReproduction
{
	public class MyClass
	{
		private readonly Dictionary<string, int> _dict = new();
		public virtual int this[string key]
		{
			get => _dict.TryGetValue(key, out int value) ? value : default;
			set => _dict[key] = value;
		}
	}
}

And this simple test:

using FakeItEasy;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace FakeItEasyAnalyzerReproduction.Test
{
	[TestClass]
	public class MyClassTests
	{
		[TestMethod]
		public void TestMethod1()
		{
			MyClass instance = A.Fake<MyClass>();
			A.CallTo(() => instance[A<string>._]).CallsBaseMethod();

			// This line throws FakeItEasy0003 warning, but this call configuration works as intended
			// and the tests won't pass without it
			A.CallToSet(() => instance[A<string>._]).CallsBaseMethod();

			// Also works, and does not throw any warnings
			A.CallToSet(() => instance["key3"]).Throws(() => new Exception());

			instance["key1"] = 1;
			instance["key2"] = 2;
			Assert.AreEqual(1, instance["key1"]);
			Assert.AreEqual(2, instance["key2"]);
			Assert.ThrowsException<Exception>(() => instance["key3"] = 3);
		}
		}
	}
}

Expected behavior: No warning for this code
Actual behavior: FakeItEasy0003 warning for A.CallToSet(() => instance[A<string>._]).CallsBaseMethod();

[zivarah]

FYI that I plan to tackle this myself, hopefully in the next day or two.

[thomaslevesque]

Hi @zivarah,
Nice catch! Thanks for giving it a shot. Let us know if you need any help!

[github-actions]

This change has been released as part of FakeItEasy.Analyzers 6.1.1.

[blairconrad]

Thanks again, @zivarah. You should be able to upgrade to 6.1.1 now and reap your own benefits.

🥇