Fix S8969 FP: assignment from nullable out parameter

[akurone]

Description

hi,
S8969 reports false positive when value comes from a nullable out parameter. (VS 2026 18.8.1, .net SDK 10.0.302)

Reproducer

//think of something like try get from a dictionary
static bool SomeMtd([NotNullWhen(true)] out object? x)
{
  x = new();
 return true;
}
//...
object x = null!;
if(!SomeMtd(out x!))
return;
//...

omitting the ! in out parameter triggers CS8601:

//...
if(!SomeMtd(out x)) //CS8601
//...

not %100 sure but CS8601 seems right to be conservative here: non-nullable x might come back as null from that method.

Product and Version

10.30.0.144632

[bdovaz]

Similar:

if (httpContext.Request.Headers.TryGetValue(ForwardedHeadersDefaults.XForwardedPrefixHeaderName, out StringValues prefix))
{
    // Sonar suggests removing the “!” from the "prefix" variable usage here, but if I don't use it as "prefix!", it reports a CS8604 error.
}