next.rs

let (next, _) = linearization.get_items_adjacent(parent.id);
let next = next.and_then(|item| match item.kind {
    TermKind::RecordField {
        ident,
        record,
        value: ValueState::Known(value),
        ..
    } if value == parent.id => Some((ident, record)),
    _ => None,
});

// Oops.. leaking internals
// let next =
//     linearization
//         .id_to_index
//         .get(&parent.id)
//         .copied()
//         .and_then(|index| {
//             linearization.linearization.get(index - 1).and_then(|item| {
//                 match item.kind {
//                     TermKind::RecordField {
//                         ident,
//                         record,
//                         value: ValueState::Known(value),
//                         ..
//                     } if value == parent.id => Some((ident, record)),
//                     _ => None,
//                 }
//             })
//         });

// let next =
//     // Oops.. linear search
//     // we can do better!
//     // a record field comes before it's value for sure
//     // 1. we can split the linearization and search the left.
//     // 2. we can use the position and our knowledge from the linearization
//     //    algorithm to calculate the exact position.
//     linearization
//         .linearization
//         .iter()
//         .find_map(|item| match item.kind {
//             TermKind::RecordField {
//                 ident,
//                 record,
//                 value: ValueState::Known(value),
//                 ..
//             } if value == parent.id => Some((ident, record)),
//             _ => None,
//         });