Attribute Macro segment 

#[segment]

Writes type Installs = (); and the install that goes with it, for a page or layout that installs nothing.

Only that. Declaring what a segment installs is what makes the declaration an obligation of the body; declaring that it installs nothing is ceremony, and stable Rust has no conditional default body to remove it.

#[segment]
impl Page for Splash {
    type Params = ();
    fn view(cx: &mut PageCx<'_>) { .. }
}