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: parser.rs
    path of file: ./repos/artichoke/artichoke-backend/src/state
    
    the code of the file until where you have to start completion: use std::borrow::Cow;
use std::ffi::{CStr, CString};
use std::ptr::NonNull;

use crate::core::IncrementLinenoError;
use crate::sys;

/// Filename of the top eval context.
pub const TOP_FILENAME: &[u8] = b"(eval)";

#[derive(Debug)]
pub struct State {
    context: NonNull<sys::mrbc_context>,
    stack: Vec<Context>,
}

impl State {
    pub fn new(mrb: &mut sys::mrb_state) -> Option<Self> {
  
    
    pub fn pop_context(&mut self, mrb: &mut sys::mrb_state) -> Option<Context> {
        let context = self.stack.pop();
        if let Some(current) = self.stack.last() {
            let filename = current.filename_as_c_str();
            unsafe {
                let ctx = self.context.as_mut();
                sys::mrbc_filename(mrb, ctx, filename.as_ptr());
            }
        } else {
            unsafe {
                let ctx = self.context.as_mut();
                reset_context_filename(mrb, ctx);
            }
        }
        context
    }