You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: prompt.rs
    path of file: ./repos/nix-init/src
    
    the code of the file until where you have to start completion: use std::{fmt::Display, path::Path};

use owo_colors::{OwoColorize, Style};
use rustyline::{
    completion::{Completer, FilenameCompleter, Pair},
    hint::{Hint, Hinter},
    history::History,
    validate::{ValidationContext, ValidationResult, Validator},
    Context, Editor, Helper, Highlighter,
};

use crate::{
    build::BuildType,
    fetcher::{Revisions, Version},
};

#[derive(Helper, Highlighter)]
pub enum Prompter {
    Path(FilenameCompleter),
    Revision(Revisions),
    NonEmpty,
    YesNo,
    Build(Vec<BuildType>),
}

impl Completer for Prompter {
    type Candidate = Pair;

    fn complete(
        &self,
        line: &str,
        pos: usize,
        _: &Context<'_>,
    ) -> rustyline::Result<(usize, Vec<Self::Candidate>)> {
        match self {
            Prompter::Path(completer) => {
                let mut compl
    
    fn validate(&self, ctx: &mut ValidationContext) -> rustyline::Result<ValidationResult> {
        Ok(match self {
            Prompter::Path(_) => {
                ValidationResult::Valid(ctx.input().is_empty().then(|| ".".into()))
            }

            Prompter::Revision(revisions) => {
                if ctx.input().is_empty() {
                    if revisions.latest.is_empty() {
                        ValidationResult::Invalid(None)
                    } else {
                        ValidationResult::Valid(Some(revisions.latest.clone()))
                    }
                } else {
                    ValidationResult::Valid(None)
                }
            }

            Prompter::NonEmpty => {
                if ctx.input().is_empty() {
                    ValidationResult::Invalid(None)
                } else {
                    ValidationResult::Valid(None)
                }
            }

            Prompter::YesNo => ValidationResult::Valid(None),

            Prompter::Build(choices) => {
                let input = ctx.input();
                if input.is_empty() {
                    ValidationResult::Valid(Some(choices[0].to_string()))
                } else if let Some(choice) = input
                    .parse::<usize>()
                    .ok()
                    .and_then(|choice| choices.get(choice))
                {
                    ValidationResult::Valid(Some(format!(" - {choice}")))
                } else {
                    ValidationResult::Invalid(None)
                }
            }
        })
    }