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: length.rs
    path of file: ./repos/ferrocarril/mruby/src/extn/core/matchdata
    
    the code of the file until where you have to start completion: //! [`MatchData#length`](https://ruby-doc.org/core-2.6.3/MatchData.html#method-i-length)

use std::convert::TryFrom;

use crate::convert::{FromMrb, RustBackedValue};
use crate::extn::core::matchdata::MatchData;
use crate::value::Value;
use crate::Mrb;

#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq)]
pub enum Error {
    Fatal,
}

pub fn method(interp: &Mrb, value: &Value) -> Result<Value, Error> {
    let data = unsafe { MatchD
    
pub fn method(interp: &Mrb, value: &Value) -> Result<Value, Error> {
    let data = unsafe { MatchData::try_from_ruby(interp, value) }.map_err(|_| Error::Fatal)?;
    let borrow = data.borrow();
    let regex = (*borrow.regexp.regex).as_ref().ok_or(Error::Fatal)?;
    let match_against = &borrow.string[borrow.region.start..borrow.region.end];
    let captures = regex.captures(match_against);
    if let Some(captures) = captures {
        let len = i64::try_from(captures.len()).map_err(|_| Error::Fatal)?;
        Ok(Value::from_mrb(interp, len))
    } else {
        Ok(Value::from_mrb(interp, 0))
    }
}