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: fuzz.rs
    path of file: ./repos/rust-analyzer/crates/syntax/src
    
    the code of the file until where you have to start completion: //! Some infrastructure for fuzzy testing.
//!
//! We don't normally run fuzzying, so this is hopelessly bitrotten :(

use std::str::{self, FromStr};

use text_edit::Indel;

use crate::{validation, AstNode, SourceFile, TextRange};

fn check_file_invariants(file: &SourceFile) {
    let root = file.syntax();
    validation::validate_block_structure(root);
}

pub fn check_parser(text: &str) {
    let file = SourceFile::parse(text);
    check_file_invariants(&file.tree());
}

#[derive(Debug, Clone)]
pub struct CheckReparse {
    text: String,
    edit: Indel,
    edited_text: String,
}

impl CheckReparse {
    pub fn from_data(data: &[u8]) -> Option<Self> {
        const PREFIX: &str = "fn main(){\n\t";
        const SUFFIX: &str = "\n}";

        let data = str::f
    
    pub fn from_data(data: &[u8]) -> Option<Self> {
        const PREFIX: &str = "fn main(){\n\t";
        const SUFFIX: &str = "\n}";

        let data = str::from_utf8(data).ok()?;
        let mut lines = data.lines();
        let delete_start = usize::from_str(lines.next()?).ok()? + PREFIX.len();
        let delete_len = usize::from_str(lines.next()?).ok()?;
        let insert = lines.next()?.to_owned();
        let text = lines.collect::<Vec<_>>().join("\n");
        let text = format!("{PREFIX}{text}{SUFFIX}");
        text.get(delete_start..delete_start.checked_add(delete_len)?)?; // make sure delete is a valid range
        let delete =
            TextRange::at(delete_start.try_into().unwrap(), delete_len.try_into().unwrap());
        let edited_text =
            format!("{}{}{}", &text[..delete_start], &insert, &text[delete_start + delete_len..]);
        let edit = Indel { insert, delete };
        Some(CheckReparse { text, edit, edited_text })
    }