[swift-users] Exclamation mark's in swift parameter listings?

[Ethin Probst]

Hello all,
I was wondering what an exclamation mark in a swift parameter listing
means. For instance, I used Elements Oxidizer Live to translate some
C# code into Swift. Reviewing it, I found the following (among
others):
@DllImport("ScriptHookV.dll")
private static __extern func scriptRegister(_ module: System.IntPtr!,
_ LP_SCRIPT_MAIN: LP_SCRIPT_MAINDelegate!)
What I'm wondering is what does the '!' in that list of parameters
mean? I also saw it when writing another program:
    func MainForm_Load(_ sender: System.Object!, _ e: System.EventArgs!) {
// ...
}
I don't recall the swift book teaching you what that means, so could
someone tell me what those mean?
-- 
Signed,
Ethin D. Probst