syn 2.0.117

Parser for Rust source code
Documentation 
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#![allow(
    clippy::elidable_lifetime_names,
    clippy::needless_lifetimes,
    clippy::uninlined_format_args
)]

use syn::punctuated::{Pair, Punctuated};
use syn::Token;

macro_rules! punctuated {
    ($($e:expr,)+) => {{
        let mut seq = ::syn::punctuated::Punctuated::new();
        $(
            seq.push($e);
        )+
        seq
    }};

    ($($e:expr),+) => {
        punctuated!($($e,)+)
    };
}

macro_rules! check_exact_size_iterator {
    ($iter:expr) => {{
        let iter = $iter;
        let size_hint = iter.size_hint();
        let len = iter.len();
        let count = iter.count();
        assert_eq!(len, count);
        assert_eq!(size_hint, (count, Some(count)));
    }};
}

#[test]
fn pairs() {
    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);

    check_exact_size_iterator!(p.pairs());
    check_exact_size_iterator!(p.pairs_mut());
    check_exact_size_iterator!(p.into_pairs());

    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);

    assert_eq!(p.pairs().next_back().map(Pair::into_value), Some(&4));
    assert_eq!(
        p.pairs_mut().next_back().map(Pair::into_value),
        Some(&mut 4)
    );
    assert_eq!(p.into_pairs().next_back().map(Pair::into_value), Some(4));
}

#[test]
fn iter() {
    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);

    check_exact_size_iterator!(p.iter());
    check_exact_size_iterator!(p.iter_mut());
    check_exact_size_iterator!(p.into_iter());

    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);

    assert_eq!(p.iter().next_back(), Some(&4));
    assert_eq!(p.iter_mut().next_back(), Some(&mut 4));
    assert_eq!(p.into_iter().next_back(), Some(4));
}

#[test]
fn may_dangle() {
    let p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
    for element in &p {
        if *element == 2 {
            drop(p);
            break;
        }
    }

    let mut p: Punctuated<_, Token![,]> = punctuated!(2, 3, 4);
    for element in &mut p {
        if *element == 2 {
            drop(p);
            break;
        }
    }
}

#[test]
#[should_panic = "index out of bounds: the len is 0 but the index is 0"]
fn index_out_of_bounds() {
    let p = Punctuated::<syn::Ident, Token![,]>::new();
    let _ = p[0].clone();
}