1 #![deny(rustc::untranslatable_diagnostic)]
2 #![deny(rustc::diagnostic_outside_of_impl)]
3 use rustc_data_structures::captures::Captures;
4 use rustc_data_structures::fx::FxHashMap;
5 use rustc_index::vec::IndexVec;
6 use rustc_middle::infer::MemberConstraint;
7 use rustc_middle::ty::{self, Ty};
12 /// Compactly stores a set of `R0 member of [R1...Rn]` constraints,
13 /// indexed by the region `R0`.
15 pub(crate) struct MemberConstraintSet<'tcx, R>
19 /// Stores the first "member" constraint for a given `R0`. This is an
20 /// index into the `constraints` vector below.
21 first_constraints: FxHashMap<R, NllMemberConstraintIndex>,
23 /// Stores the data about each `R0 member of [R1..Rn]` constraint.
24 /// These are organized into a linked list, so each constraint
25 /// contains the index of the next constraint with the same `R0`.
26 constraints: IndexVec<NllMemberConstraintIndex, NllMemberConstraint<'tcx>>,
28 /// Stores the `R1..Rn` regions for *all* sets. For any given
29 /// constraint, we keep two indices so that we can pull out a
31 choice_regions: Vec<ty::RegionVid>,
34 /// Represents a `R0 member of [R1..Rn]` constraint
36 pub(crate) struct NllMemberConstraint<'tcx> {
37 next_constraint: Option<NllMemberConstraintIndex>,
39 /// The span where the hidden type was instantiated.
40 pub(crate) definition_span: Span,
42 /// The hidden type in which `R0` appears. (Used in error reporting.)
43 pub(crate) hidden_ty: Ty<'tcx>,
45 pub(crate) key: ty::OpaqueTypeKey<'tcx>,
48 pub(crate) member_region_vid: ty::RegionVid,
50 /// Index of `R1` in `choice_regions` vector from `MemberConstraintSet`.
53 /// Index of `Rn` in `choice_regions` vector from `MemberConstraintSet`.
57 rustc_index::newtype_index! {
58 pub(crate) struct NllMemberConstraintIndex {
59 DEBUG_FORMAT = "MemberConstraintIndex({})"
63 impl Default for MemberConstraintSet<'_, ty::RegionVid> {
64 fn default() -> Self {
66 first_constraints: Default::default(),
67 constraints: Default::default(),
68 choice_regions: Default::default(),
73 impl<'tcx> MemberConstraintSet<'tcx, ty::RegionVid> {
74 /// Pushes a member constraint into the set.
76 /// The input member constraint `m_c` is in the form produced by
77 /// the `rustc_middle::infer` code.
79 /// The `to_region_vid` callback fn is used to convert the regions
80 /// within into `RegionVid` format -- it typically consults the
81 /// `UniversalRegions` data structure that is known to the caller
82 /// (but which this code is unaware of).
83 pub(crate) fn push_constraint(
85 m_c: &MemberConstraint<'tcx>,
86 mut to_region_vid: impl FnMut(ty::Region<'tcx>) -> ty::RegionVid,
88 debug!("push_constraint(m_c={:?})", m_c);
89 let member_region_vid: ty::RegionVid = to_region_vid(m_c.member_region);
90 let next_constraint = self.first_constraints.get(&member_region_vid).cloned();
91 let start_index = self.choice_regions.len();
92 let end_index = start_index + m_c.choice_regions.len();
93 debug!("push_constraint: member_region_vid={:?}", member_region_vid);
94 let constraint_index = self.constraints.push(NllMemberConstraint {
97 definition_span: m_c.definition_span,
98 hidden_ty: m_c.hidden_ty,
103 self.first_constraints.insert(member_region_vid, constraint_index);
104 self.choice_regions.extend(m_c.choice_regions.iter().map(|&r| to_region_vid(r)));
108 impl<'tcx, R1> MemberConstraintSet<'tcx, R1>
110 R1: Copy + Hash + Eq,
112 /// Remap the "member region" key using `map_fn`, producing a new
113 /// member constraint set. This is used in the NLL code to map from
114 /// the original `RegionVid` to an scc index. In some cases, we
115 /// may have multiple `R1` values mapping to the same `R2` key -- that
116 /// is ok, the two sets will be merged.
117 pub(crate) fn into_mapped<R2>(
119 mut map_fn: impl FnMut(R1) -> R2,
120 ) -> MemberConstraintSet<'tcx, R2>
122 R2: Copy + Hash + Eq,
124 // We can re-use most of the original data, just tweaking the
125 // linked list links a bit.
127 // For example if we had two keys `Ra` and `Rb` that both now
128 // wind up mapped to the same key `S`, we would append the
129 // linked list for `Ra` onto the end of the linked list for
130 // `Rb` (or vice versa) -- this basically just requires
131 // rewriting the final link from one list to point at the other
132 // other (see `append_list`).
134 let MemberConstraintSet { first_constraints, mut constraints, choice_regions } = self;
136 let mut first_constraints2 = FxHashMap::default();
137 first_constraints2.reserve(first_constraints.len());
139 for (r1, start1) in first_constraints {
141 if let Some(&start2) = first_constraints2.get(&r2) {
142 append_list(&mut constraints, start1, start2);
144 first_constraints2.insert(r2, start1);
147 MemberConstraintSet { first_constraints: first_constraints2, constraints, choice_regions }
151 impl<'tcx, R> MemberConstraintSet<'tcx, R>
155 pub(crate) fn all_indices(
157 ) -> impl Iterator<Item = NllMemberConstraintIndex> + Captures<'tcx> + '_ {
158 self.constraints.indices()
161 /// Iterate down the constraint indices associated with a given
162 /// peek-region. You can then use `choice_regions` and other
163 /// methods to access data.
164 pub(crate) fn indices(
166 member_region_vid: R,
167 ) -> impl Iterator<Item = NllMemberConstraintIndex> + Captures<'tcx> + '_ {
168 let mut next = self.first_constraints.get(&member_region_vid).cloned();
169 std::iter::from_fn(move || -> Option<NllMemberConstraintIndex> {
170 if let Some(current) = next {
171 next = self.constraints[current].next_constraint;
179 /// Returns the "choice regions" for a given member
180 /// constraint. This is the `R1..Rn` from a constraint like:
183 /// R0 member of [R1..Rn]
185 pub(crate) fn choice_regions(&self, pci: NllMemberConstraintIndex) -> &[ty::RegionVid] {
186 let NllMemberConstraint { start_index, end_index, .. } = &self.constraints[pci];
187 &self.choice_regions[*start_index..*end_index]
191 impl<'tcx, R> Index<NllMemberConstraintIndex> for MemberConstraintSet<'tcx, R>
195 type Output = NllMemberConstraint<'tcx>;
197 fn index(&self, i: NllMemberConstraintIndex) -> &NllMemberConstraint<'tcx> {
202 /// Given a linked list starting at `source_list` and another linked
203 /// list starting at `target_list`, modify `target_list` so that it is
204 /// followed by `source_list`.
209 /// target_list: A -> B -> C -> (None)
210 /// source_list: D -> E -> F -> (None)
216 /// target_list: A -> B -> C -> D -> E -> F -> (None)
219 constraints: &mut IndexVec<NllMemberConstraintIndex, NllMemberConstraint<'_>>,
220 target_list: NllMemberConstraintIndex,
221 source_list: NllMemberConstraintIndex,
223 let mut p = target_list;
225 let mut r = &mut constraints[p];
226 match r.next_constraint {
229 r.next_constraint = Some(source_list);