--- /dev/null
+#![allow(dead_code)] // TODO
+
+use crate::rustc::ty::{self, Ty};
+use rustc::hir::def_id::DefId;
+use rustc::infer::region_constraints::PickConstraint;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_data_structures::indexed_vec::{Idx, IndexVec};
+use std::hash::Hash;
+use std::ops::Index;
+
+/// Compactly stores a set of `pick R0 in [R1...Rn]` constraints,
+/// indexed by the region R0.
+crate struct PickConstraintSet<'tcx, R>
+where
+ R: Copy + Hash + Eq,
+{
+ /// Stores the first "pick" constraint for a given R0. This is an
+ /// index into the `constraints` vector below.
+ first_constraints: FxHashMap<R, NllPickConstraintIndex>,
+
+ /// Stores the data about each `pick R0 from [R1..Rn]` constraint.
+ /// These are organized into a linked list, so each constraint
+ /// contains the index of the next constraint with the same R0.
+ constraints: IndexVec<NllPickConstraintIndex, NllPickConstraint<'tcx>>,
+
+ /// Stores the `R1..Rn` regions for *all* sets. For any given
+ /// constraint, we keep two indices so that we can pull out a
+ /// slice.
+ option_regions: Vec<ty::RegionVid>,
+}
+
+/// Represents a `pick R0 in [R1..Rn]` constraint
+crate struct NllPickConstraint<'tcx> {
+ next_constraint: Option<NllPickConstraintIndex>,
+
+ /// The opaque type whose hidden type is being inferred. (Used in error reporting.)
+ crate opaque_type_def_id: DefId,
+
+ /// The hidden type in which R0 appears. (Used in error reporting.)
+ crate hidden_ty: Ty<'tcx>,
+
+ /// The region R0.
+ crate pick_region_vid: ty::RegionVid,
+
+ /// Index of `R1` in `option_regions` vector from `PickConstraintSet`.
+ start_index: usize,
+
+ /// Index of `Rn` in `option_regions` vector from `PickConstraintSet`.
+ end_index: usize,
+}
+
+newtype_index! {
+ crate struct NllPickConstraintIndex {
+ DEBUG_FORMAT = "PickConstraintIndex({})"
+ }
+}
+
+impl<'tcx> PickConstraintSet<'tcx, ty::RegionVid> {
+ crate fn new() -> Self {
+ Self {
+ first_constraints: Default::default(),
+ constraints: Default::default(),
+ option_regions: Default::default(),
+ }
+ }
+
+ crate fn push_constraint(
+ &mut self,
+ p_c: PickConstraint<'tcx>,
+ mut to_region_vid: impl FnMut(ty::Region<'tcx>) -> ty::RegionVid,
+ ) {
+ let pick_region_vid: ty::RegionVid = to_region_vid(p_c.pick_region);
+ let next_constraint = self.first_constraints.get(&pick_region_vid).cloned();
+ let start_index = self.option_regions.len();
+ let end_index = start_index + p_c.option_regions.len();
+ let constraint_index = self.constraints.push(NllPickConstraint {
+ next_constraint,
+ pick_region_vid,
+ opaque_type_def_id: p_c.opaque_type_def_id,
+ hidden_ty: p_c.hidden_ty,
+ start_index,
+ end_index,
+ });
+ self.first_constraints.insert(pick_region_vid, constraint_index);
+ self.option_regions.extend(p_c.option_regions.iter().map(|&r| to_region_vid(r)));
+ }
+}
+
+impl<'tcx, R1> PickConstraintSet<'tcx, R1>
+where
+ R1: Copy + Hash + Eq,
+{
+ /// Remap the "pick region" key using `map_fn`, producing a new
+ /// pick-constraint set. This is used in the NLL code to map from
+ /// the original `RegionVid` to an scc index. In some cases, we
+ /// may have multiple R1 values mapping to the same R2 key -- that
+ /// is ok, the two sets will be merged.
+ crate fn into_mapped<R2>(self, mut map_fn: impl FnMut(R1) -> R2) -> PickConstraintSet<'tcx, R2>
+ where
+ R2: Copy + Hash + Eq,
+ {
+ // We can re-use most of the original data, just tweaking the
+ // linked list links a bit.
+ //
+ // For example if we had two keys Ra and Rb that both now wind
+ // up mapped to the same key S, we would append the linked
+ // list for Ra onto the end of the linked list for Rb (or vice
+ // versa) -- this basically just requires rewriting the final
+ // link from one list to point at the othe other (see
+ // `append_list`).
+
+ let PickConstraintSet { first_constraints, mut constraints, option_regions } = self;
+
+ let mut first_constraints2 = FxHashMap::default();
+ first_constraints2.reserve(first_constraints.len());
+
+ for (r1, start1) in first_constraints {
+ let r2 = map_fn(r1);
+ if let Some(&start2) = first_constraints2.get(&r2) {
+ append_list(&mut constraints, start1, start2);
+ }
+ first_constraints2.insert(r2, start1);
+ }
+
+ PickConstraintSet {
+ first_constraints: first_constraints2,
+ constraints,
+ option_regions,
+ }
+ }
+}
+
+impl<'tcx, R> PickConstraintSet<'tcx, R>
+where
+ R: Copy + Hash + Eq,
+{
+ /// Iterate down the constraint indices associated with a given
+ /// peek-region. You can then use `option_regions` and other
+ /// methods to access data.
+ crate fn indices(
+ &self,
+ pick_region_vid: R,
+ ) -> impl Iterator<Item = NllPickConstraintIndex> + '_ {
+ let mut next = self.first_constraints.get(&pick_region_vid).cloned();
+ std::iter::from_fn(move || -> Option<NllPickConstraintIndex> {
+ if let Some(current) = next {
+ next = self.constraints[current].next_constraint;
+ Some(current)
+ } else {
+ None
+ }
+ })
+ }
+
+ /// Returns the "option regions" for a given pick constraint. This is the R1..Rn from
+ /// a constraint like:
+ ///
+ /// ```
+ /// pick R0 in [R1..Rn]
+ /// ```
+ crate fn option_regions(&self, pci: NllPickConstraintIndex) -> &[ty::RegionVid] {
+ let NllPickConstraint { start_index, end_index, .. } = &self.constraints[pci];
+ &self.option_regions[*start_index..*end_index]
+ }
+}
+
+impl<'tcx, R> Index<NllPickConstraintIndex> for PickConstraintSet<'tcx, R>
+where
+ R: Copy + Hash + Eq,
+{
+ type Output = NllPickConstraint<'tcx>;
+
+ fn index(&self, i: NllPickConstraintIndex) -> &NllPickConstraint<'tcx> {
+ &self.constraints[i]
+ }
+}
+
+/// Given a linked list starting at `source_list` and another linked
+/// list starting at `target_list`, modify `target_list` so that it is
+/// followed by `source_list`.
+///
+/// Before:
+///
+/// ```
+/// target_list: A -> B -> C -> (None)
+/// source_list: D -> E -> F -> (None)
+/// ```
+///
+/// After:
+///
+/// ```
+/// target_list: A -> B -> C -> D -> E -> F -> (None)
+/// ```
+fn append_list(
+ constraints: &mut IndexVec<NllPickConstraintIndex, NllPickConstraint<'_>>,
+ target_list: NllPickConstraintIndex,
+ source_list: NllPickConstraintIndex,
+) {
+ let mut p = target_list;
+ loop {
+ let mut r = &mut constraints[p];
+ match r.next_constraint {
+ Some(q) => p = q,
+ None => {
+ r.next_constraint = Some(source_list);
+ return;
+ }
+ }
+ }
+}
projects / rust.git / commitdiff