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: mod.rs
    path of file: ./repos/prusti-dev/vir-gen/src/parser
    
    the code of the file until where you have to start completion: use std::{fs::File, io::Read, mem, path::PathBuf};
use syn::{fold::Fold, spanned::Spanned};

mod ast;

/// Expand the ast by reading in all modules.
pub(crate) fn expand(item: syn::ItemMod, path: PathBuf) -> (syn::ItemMod, Vec<sy
    
fn load_file(mut current_path: PathBuf, ident: &syn::Ident) -> syn::Result<(PathBuf, syn::File)> {
    current_path.pop();
    current_path.push(format!("{ident}.rs"));
    if !current_path.exists() {
        current_path.pop();
        current_path.push(format!("{ident}/mod.rs"));
    }
    let mut file = File::open(&current_path).map_err(|err| {
        syn::Error::new(
            ident.span(),
            format!("could not open {current_path:?}: {err}"),
        )
    })?;
    let mut content = String::new();
    file.read_to_string(&mut content).map_err(|err| {
        syn::Error::new(
            ident.span(),
            format!("could not read {current_path:?}: {err}"),
        )
    })?;

    let file = syn::parse_file(&content)?;
    Ok((current_path, file))
}