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: build.rs
    path of file: ./repos/ezno/checker/specification
    
    the code of the file until where you have to start completion: use std::error::Error;
use std::fs::{read_to_string, File};
use std::io::Write;
use std::mem;
us
    
fn main() -> Result<(), Box<dyn Error>> {
	println!("cargo:rerun-if-changed=specification.md");
	println!("cargo:rerun-if-changed=staging.md");
	println!("cargo:rerun-if-changed=to_implement.md");

	let out_path = Path::new(&std::env::var("OUT_DIR")?).join("specification.rs");
	let mut out = File::create(out_path)?;

	if cfg!(not(feature = "just-staging")) {
		let specification = read_to_string("./specification.md")?;
		markdown_lines_append_test_to_rust(specification.lines().enumerate(), &mut out)?;
	}

	if cfg!(feature = "staging") {
		let staging = read_to_string("./staging.md")?;
		writeln!(&mut out, "mod staging {{ use super::check_errors; ").unwrap();
		markdown_lines_append_test_to_rust(staging.lines().enumerate(), &mut out)?;
		writeln!(&mut out, "}}").unwrap();
	}

	if cfg!(feature = "all") {
		let to_implement = read_to_string("./to_implement.md")?;
		writeln!(&mut out, "mod to_implement {{ use super::check_errors; ").unwrap();
		markdown_lines_append_test_to_rust(to_implement.lines().enumerate(), &mut out)?;
		writeln!(&mut out, "}}").unwrap();
	}

	Ok(())
}