`1 == 1` produces no warning while `1 is 1` produces CS8520

[rampaa]

Version Used:
Visual Studio 2026 v18.4.1
.NET 9

Steps to Reproduce:

1. See the following minimal code sample:

    public static void Test()
    {
        if (1 == 1) // Does not produce a warning like CS8520
        {
            Console.WriteLine("Test 1");
        }

        if (1 is 1) // CS8520
        {
            Console.WriteLine("Test 1");
        }
    }

Expected Behavior:
1 == 1 should raise a warning like how 1 is 1 raises CS8520

Actual Behavior:
No warning is raised for 1 == 1

[jjonescz]

That warning is a feature of patterns (which are in use with is but not with ==), so that's likely expected. We could implement a subset of such warnings that would apply to == I guess (it would probably need a language design proposal in https://github.com/dotnet/csharplang), although that could be also just a CA analyzer in https://github.com/dotnet/sdk.