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: select.rs
    path of file: ./repos/phaser/phaser/vendor/tokio-macros/src
    
    the code of the file until where you have to start completion: use proc_macro::{TokenStream, TokenTree};
use proc_macro2::Span;
use quote::quote;
use syn::Ident;

pub(crate) fn declare_output_enum(input: TokenStream) -> TokenStream {
    // passed in is: `(_ _ _)` with one `_` per branch
    let branches = match input.into_iter().next() {
        Some(TokenTree::Group(group)) => group.stream().into_iter().count(),
        _ => panic!("unexpected macro input"),
    };

    let variants = (0..branches)
        .map(|num| Ident::new(&format!("_{}", num), Span::call_site()))
        .collect::<Vec<_>>();

    // Use a bitfield to track which futures completed
    let mask = Ident::new(
        if branches <= 8 {
            "u8"
      
    
pub(crate) fn declare_output_enum(input: TokenStream) -> TokenStream {
    // passed in is: `(_ _ _)` with one `_` per branch
    let branches = match input.into_iter().next() {
        Some(TokenTree::Group(group)) => group.stream().into_iter().count(),
        _ => panic!("unexpected macro input"),
    };

    let variants = (0..branches)
        .map(|num| Ident::new(&format!("_{}", num), Span::call_site()))
        .collect::<Vec<_>>();

    // Use a bitfield to track which futures completed
    let mask = Ident::new(
        if branches <= 8 {
            "u8"
        } else if branches <= 16 {
            "u16"
        } else if branches <= 32 {
            "u32"
        } else if branches <= 64 {
            "u64"
        } else {
            panic!("up to 64 branches supported");
        },
        Span::call_site(),
    );

    TokenStream::from(quote! {
        pub(super) enum Out<#( #variants ),*> {
            #( #variants(#variants), )*
            // Include a `Disabled` variant signifying that all select branches
            // failed to resolve.
            Disabled,
        }

        pub(super) type Mask = #mask;
    })
}