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: syntax.rs
    path of file: ./repos/diem/language/move-lang/src/parser
    
    the code of the file until where you have to start completion: // Copyright (c) The Diem Core Contributors
// SPDX-License-Identifier: Apache-2.0

use move_ir_types::location::*;
use move_symbol_pool::Symbol;

use crate::{
    diag,
    diagnostics::{Diagnostic, Diagnostics},
    parser::{ast::*, lexer::*},
    shared::*,
    MatchedFileComm
    
fn parse_byte_string(tokens: &mut Lexer) -> Result<Value_, Diagnostic> {
    if tokens.peek() != Tok::ByteStringValue {
        return Err(unexpected_token_error(tokens, "a byte string value"));
    }
    let s = tokens.content();
    let text = Symbol::from(&s[2..s.len() - 1]);
    let value_ = if s.starts_with("x\"") {
        Value_::HexString(text)
    } else {
        assert!(s.starts_with("b\""));
        Value_::ByteString(text)
    };
    tokens.advance()?;
    Ok(value_)
}