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: filter_map_bool_then.rs
    path of file: ./repos/rust-clippy/tests/ui
    
    the code of the file until where you have to start completion: //@aux-build:proc_macros.rs
#![allow(
    clippy::clone_on_copy,
    clippy::map_identity,
    clippy::unnecessary_lazy_evaluations,
    clippy::unnecessary_filter_map,
    unused
)]
#![warn(clippy::filter_map_bool_then)]

#[macro_use]
extern crate proc_macros;

#[derive(Clone, PartialEq)]
struct NonCopy;

fn main() {
    let v = vec![1, 2, 3, 4, 5, 6];
    v.clone().iter().filter_map(|i| (i % 2 == 0).then(|| i + 1));
    v.clone().into_iter().filter_map(|i| (i % 2 == 0).then(|| i + 1));
    v.clone()
        .into_iter()
        .filter_map(|i| -> Option<_> { (i % 2 == 0).then(|| i + 1) });
    v.clone()
        
    
fn issue11503() {
    let bools: &[bool] = &[true, false, false, true];
    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();

    // Need to insert multiple derefs if there is more than one layer of references
    let bools: &[&&bool] = &[&&true, &&false, &&false, &&true];
    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();

    // Should also suggest derefs when going through a mutable reference
    let bools: &[&mut bool] = &[&mut true];
    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();

    // Should also suggest derefs when going through a custom deref
    struct DerefToBool;
    impl std::ops::Deref for DerefToBool {
        type Target = bool;
        fn deref(&self) -> &Self::Target {
            &true
        }
    }
    let bools: &[&&DerefToBool] = &[&&DerefToBool];
    let _: Vec<usize> = bools.iter().enumerate().filter_map(|(i, b)| b.then(|| i)).collect();
}