Given a program like:

pub type ReallyLongTypeNameLongLongLong = Option<unsafe extern "C" fn(a: *const u8, b: *const u8) -> *const u8>;

fn main() {
    println!("Hello, world!");
}

The type's summary in the grey box at the top of the page overflows:

Example at:

https://jacob.hoffman-andrews.com/rust/longname/longname/type.ReallyLongTypeNameLongLongLong.html

Note that this does not happen for structs. I haven't tested for other item kinds.