"A nullable type parameter must be known to be a value type or non-nullable reference type" on type parameter with `notnull` constraint

[Ramobo]

Version Used: C# 9 preview as of Visual Studio 2019 Preview 16.7 preview 4.0.

Steps to Reproduce: Here's an example instead.

public bool TryGetComponent<T>([NotNullWhen(true)] out T? component) where T : notnull // [at `T?`] CS8627: A nullable type parameter must be known to be a value type or non-nullable reference type. Consider adding a 'class', 'struct', or type constraint.
{
    if (TryGetComponent(component => component is T, out object? foundComponent))
    {
        component = (T)foundComponent;

        return true;
    }
    else
    {
        component = null; // CS0403: Cannot convert null to type parameter 'T' because it could be a non-nullable value type. Consider using 'default(T)' instead.

        return false;
    }
}

Expected Behavior: The compiler detects that T has the notnull constraint and doesn't emit the errors:

• CS8627 on the component parameter — from my understanding, the class/struct knowledge must exist purely because of nullability, but that's already defined as "not allowed" by the notnull constraint.
• CS0403 on component = null — the variable in question is of a nullable type. It could be that this error is due to the previous one.

Actual Behavior:

• The compiler emits errors for both of the scenarios above.

I know of two solutions, but neither are suitable for me:

• The [MaybeNull] attribute — other nullable warnings will be emitted at call sites if the type itself is not nullable, for reasons irrelevant to this issue.
• Adding the class or struct constraint — I need both to be usable with a single method.

[peter-perot]

Does this bug still exist in VS 2022? I don't get the [at 'T?'] CS8627: A nullable type parameter must be known to be a value type or non-nullable reference type. Consider adding a 'class', 'struct', or type constraint. error anymore.