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: spanned.rs
    path of file: ./repos/clap/clap_derive/src/utils
    
    the code of the file until where you have to start completion: use proc_macro2::{Ident, Span, TokenStream};
use quote::ToTokens;
use syn::LitStr;

use std::ops::{Deref, DerefMut};

/// An entity with a span attached.
#[derive(Debug, Copy, Clo
    
    fn to_tokens(&self, stream: &mut TokenStream) {
        // this is the simplest way out of correct ones to change span on
        // arbitrary token tree I could come up with
        let tt = self.val.to_token_stream().into_iter().map(|mut tt| {
            tt.set_span(self.span);
            tt
        });

        stream.extend(tt);
    }