Function ghost 

pub fn ghost(
    text: &str,
    caret: usize,
    cand: Option<&Candidate>,
) -> Option<String>

The ghost text after the caret, which must end text. While completing (cand is the selected candidate for the word there) it is the rest of that name, and a function’s (params); else, inside a call, the parameters from the current argument on: after PMT(0.05, it is nper, pv, [fv], [type]), after PMT(0.05 it is , nper, …).