class Base
{
    public virtual void Foo(int x){}
}

class Derived : Base
{
    public override void Foo(int x)
    {
    }

    public void Foo(double x){}

    static void Main()
    {
        new Derived().Foo(|);
    }
}

Symbol | is the caret position. Signature (int x) should be grayed out, because it is inapplicable regardless of provided arguments.