UI::queue_main and UI::on_should_quit are unsound

[jonas-schievink]

This program prints garbage to the console on my system:

    let ev = iui::UI::init().unwrap();

    {
        let v = vec![1, 2, 3, 4];
        ev.queue_main(|| {
            for i in &v {
                println!("{}", i);
            }
        });
    }

    ev.main();

This is a use-after-free on the vector v and should not compile. Both UI::queue_main and UI::on_should_quit must require the callback to be 'static.

This is probably the case for all functions that take a callback, not just those 2, but I just started using iui, so I don't which (if any) other functions are affected.

You can test that this code example doesn't compile using compiletest-rs.

[jonas-schievink]

Also affected:

• Window::on_closing
• Button::on_clicked
• Checkbox::on_toggled
• Combobox::on_selected
• ...probably most controls are affected

[NoraCodes]

You're absolutely right, thank you! They do need a 'static bound.

[jonas-schievink]

Err, this still seems to compile as of 2e3343b

[NoraCodes]

D'oh. I didn't push the second commit.
Let's add some shouldn't-compile tests...

[NoraCodes]

I can't seem to actually make them sound without adding a 'static bound, which is annoying but is also the way that gtk-rs does it and is probably the way to go :(