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: lib.rs
    path of file: ./repos/ZLUDA/optix_base/src
    
    the code of the file until where you have to start completion: extern crate proc_macro;

use proc_macro::TokenStream;
use proc_macro2::TokenStream as TokenStream2;
use proc_macro2::{Ident, Span};
use quote::{format_ident, quote, ToTokens};
use rustc_hash::{FxHashMap, FxHashSet};
use syn::spanned::Spanned;
use syn::Fields;
use syn::{
    bracketed,
    parse::{Parse, ParseStream},
    parse_macro_input,
    punctuated::Punctuated,
    visit::Visit,
    File, ImplItem, Item, Path, Token, Type, TypePath,
};

const OPTIX_RS: &'static str = include_str! {"optix.rs"};
const OPTIX6_RS: &'static str = include_str! {"optix6.rs"};

// This macro copies optix.rs as-is with some changes:
// * All function declarations are filtered out
// * All CUDA types are skipped
#[proc_macro]
pub fn optix_type_declarations(_: TokenStream) -> TokenStream {
    let mut optix_module = syn::parse_str::<File>(OPTIX_RS).unwrap();
    optix_module.items = optix_module
        .items
        .into_iter()
        .filter_map(|item| match item {
            Item::ForeignMod(_) => None,
            Item::Type(type_) => {
                if type_.ident.to_string().starts_with("CU") {
                    None
                } else {
                    Some(Item::Type(type_))
                }
            }
            Item::Struct(struct_) => {
                if stru
    
    fn generate(self) -> TokenStream2 {
        let mut token_stream = TokenStream2::new();
        for (enum_, (underlying_type, items)) in self.enums {
            let safe_enum = format_ident!("{}Safe", enum_);
            let underlying_type = Self::to_ident(underlying_type.unwrap());
            token_stream.extend(quote! {
                #[repr(#underlying_type)]
                #[derive(Copy, Clone, PartialEq, Eq)]
                pub enum #safe_enum {
                    #(
                        #items = #enum_ :: #items .0,
                    )*
                }

                impl #safe_enum {
                    pub fn new(e: #enum_) -> Option<Self> {
                        match e {
                            #(
                                #enum_ :: #items => Some(#safe_enum :: #items),
                            )*
                            _ => None
                        }
                    }
                }

                impl From<#safe_enum> for #enum_ {
                    fn from(value: #safe_enum) -> #enum_ {
                        match value {
                            #(
                                #safe_enum :: #items => #enum_ :: #items,
                            )*
                        }
                    }
                }
            });
        }
        token_stream
    }