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use crate::table::AnswerIndex;
use crate::{ExClause, TableIndex, TimeStamp};
use std::fmt::Debug;
use chalk_derive::HasInterner;
use chalk_ir::fold::{Fold, Folder};
use chalk_ir::interner::Interner;
use chalk_ir::{Canonical, DebruijnIndex, UniverseMap};
#[derive(Clone, Debug, HasInterner)]
pub(crate) struct Strand<I: Interner> {
pub(super) ex_clause: ExClause<I>,
/// Index into `ex_clause.subgoals`.
pub(crate) selected_subgoal: Option<SelectedSubgoal>,
pub(crate) last_pursued_time: TimeStamp,
}
pub(crate) type CanonicalStrand<I> = Canonical<Strand<I>>;
#[derive(Clone, Debug)]
pub(crate) struct SelectedSubgoal {
/// The index of the subgoal in `ex_clause.subgoals`
pub(crate) subgoal_index: usize,
/// The index of the table that we created or found for this subgoal
pub(super) subgoal_table: TableIndex,
/// Index of the answer we should request next from the table
pub(crate) answer_index: AnswerIndex,
/// Maps the universes of the subgoal to the canonical universes
/// used in the table
pub(crate) universe_map: UniverseMap,
}
impl<I: Interner> Fold<I> for Strand<I> {
type Result = Strand<I>;
fn fold_with<E>(
self,
folder: &mut dyn Folder<I, Error = E>,
outer_binder: DebruijnIndex,
) -> Result<Self::Result, E> {
Ok(Strand {
ex_clause: self.ex_clause.fold_with(folder, outer_binder)?,
last_pursued_time: self.last_pursued_time,
selected_subgoal: self.selected_subgoal,
})
}
}
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