Signature help not offered in positional pattern.

[CyrusNajmabadi]

public class Point
{
    public int X;
    public int Y;
    public void Deconstruct(out int XX, out int YY) => throw null;
    void M()
    {
        object o = null;
        if (o is Point($)) // <-- i should get sighelp here to make it clear what is being matched
        {

        }
    }
}

[gafter]

There is no positional pattern support at the moment. It is out of scope for the current punch-through.

[gafter]

Updated issue to reflect current status of language.