Spurious CA2012 on lhs of pattern match

[poizan42]

Analyzer

Diagnostic ID: CA2012: Use ValueTasks correctly

Analyzer source

SDK: Built-in CA analyzers in .NET 5 SDK or later

Version: SDK 8.0.101

Describe the bug

The following generates CA2012

if (x?.SomeActionReturningValueTaskAsync()) is ValueTask vt)
    await vt;

Steps To Reproduce

Put the following code in any .cs file in Visual Studio

public class Foo
{
    public ValueTask FrobAsync() => default;
    public static async ValueTask FrobFooAsync(Foo? foo)
    {
        if (foo?.FrobAsync() is ValueTask vt)
            await vt;
    }
}

Expected behavior

CA2012 should not be emitted as long as the ValueTask is only consumed once and not otherwise escapes.

Actual behavior

CA2012 is emitted at the "." of foo?.FrobAsync()

[Cyberboss]

I suspect this is similar to this notice that plagues my codebase wherever I use my custom WhenAll for ValueTasks. (It accepts a params ValueTask[])

public ValueTask DisposeAsync()
    => ValueTaskExtensions.WhenAll(
        RestClient.DisposeAsync(),
        GraphQLClient.DisposeAsync());