CS8602 should fire within subsequent arguments of validating function

[AArnott]

Version Used: VS 16.5 Preview 1 (29502.12.master)

Steps to Reproduce:

1. Create a .NET Core 3.0 library or console app.
2. Install-Package Microsoft.VisualStudio.Validation -Version 15.5.31
3. Introduce a source file with this content:

using Microsoft;

#nullable enable

class Program
{
    static object? v;
    static void Main(string[] args)
    {
        Verify.Operation(v != null, v.ToString());
        v.ToString();
    }
}

Expected Behavior:

CS8602 identifies that v.ToString() is a dereference of a possibly null value.

Actual Behavior:

No warning is emitted of the null reference.
It seems that the Verify.Operation call, which is annotated to not return if the condition passed as the first argument is false is inappropriately applied as validated even for the subsequent arguments passed to that method.

[jcouv]

What is the signature of Verify.Operation? Does it have any attributes?
Even better would be to provide a standalone repro (sharplab link for instance). Thanks

[AArnott]

Sure: here is a sharplab link. that demonstrates the problem.

[jcouv]

Ah, thanks!
Relates to #29865 (order of effect of nullable attributes)