|
| 1 | +use super::*; |
| 2 | +use crate::infer::{CombinedSnapshot, PlaceholderMap}; |
| 3 | +use crate::ty::error::TypeError; |
| 4 | +use crate::ty::relate::RelateResult; |
| 5 | + |
| 6 | +impl<'tcx> RegionConstraintCollector<'tcx> { |
| 7 | + /// Searches region constraints created since `snapshot` that |
| 8 | + /// affect one of the placeholders in `placeholder_map`, returning |
| 9 | + /// an error if any of the placeholders are related to another |
| 10 | + /// placeholder or would have to escape into some parent universe |
| 11 | + /// that cannot name them. |
| 12 | + /// |
| 13 | + /// This is a temporary backwards compatibility measure to try and |
| 14 | + /// retain the older (arguably incorrect) behavior of the |
| 15 | + /// compiler. |
| 16 | + /// |
| 17 | + /// NB. The use of snapshot here is mostly an efficiency thing -- |
| 18 | + /// we could search *all* region constraints, but that'd be a |
| 19 | + /// bigger set and the data structures are not setup for that. If |
| 20 | + /// we wind up keeping some form of this check long term, it would |
| 21 | + /// probably be better to remove the snapshot parameter and to |
| 22 | + /// refactor the constraint set. |
| 23 | + pub fn leak_check( |
| 24 | + &mut self, |
| 25 | + tcx: TyCtxt<'_, '_, 'tcx>, |
| 26 | + overly_polymorphic: bool, |
| 27 | + placeholder_map: &PlaceholderMap<'tcx>, |
| 28 | + _snapshot: &CombinedSnapshot<'_, 'tcx>, |
| 29 | + ) -> RelateResult<'tcx, ()> { |
| 30 | + debug!("leak_check(placeholders={:?})", placeholder_map); |
| 31 | + |
| 32 | + assert!(self.in_snapshot()); |
| 33 | + |
| 34 | + // Go through each placeholder that we created. |
| 35 | + for (_, &placeholder_region) in placeholder_map { |
| 36 | + // Find the universe this placeholder inhabits. |
| 37 | + let placeholder = match placeholder_region { |
| 38 | + ty::RePlaceholder(p) => p, |
| 39 | + _ => bug!( |
| 40 | + "leak_check: expected placeholder found {:?}", |
| 41 | + placeholder_region, |
| 42 | + ), |
| 43 | + }; |
| 44 | + |
| 45 | + // Find all regions that are related to this placeholder |
| 46 | + // in some way. This means any region that either outlives |
| 47 | + // or is outlived by a placeholder. |
| 48 | + let mut taint_set = TaintSet::new( |
| 49 | + TaintDirections::both(), |
| 50 | + placeholder_region, |
| 51 | + ); |
| 52 | + taint_set.fixed_point(tcx, &self.undo_log, &self.data.verifys); |
| 53 | + let tainted_regions = taint_set.into_set(); |
| 54 | + |
| 55 | + // Report an error if two placeholders in the same universe |
| 56 | + // are related to one another, or if a placeholder is related |
| 57 | + // to something from a parent universe. |
| 58 | + for &tainted_region in &tainted_regions { |
| 59 | + if let ty::RePlaceholder(_) = tainted_region { |
| 60 | + // Two placeholders cannot be related: |
| 61 | + if tainted_region == placeholder_region { |
| 62 | + continue; |
| 63 | + } |
| 64 | + } else if self.universe(tainted_region).can_name(placeholder.universe) { |
| 65 | + continue; |
| 66 | + } |
| 67 | + |
| 68 | + return Err(if overly_polymorphic { |
| 69 | + debug!("Overly polymorphic!"); |
| 70 | + TypeError::RegionsOverlyPolymorphic(placeholder.name, tainted_region) |
| 71 | + } else { |
| 72 | + debug!("Not as polymorphic!"); |
| 73 | + TypeError::RegionsInsufficientlyPolymorphic(placeholder.name, tainted_region) |
| 74 | + }); |
| 75 | + } |
| 76 | + } |
| 77 | + |
| 78 | + Ok(()) |
| 79 | + } |
| 80 | +} |
| 81 | + |
| 82 | +#[derive(Debug)] |
| 83 | +struct TaintSet<'tcx> { |
| 84 | + directions: TaintDirections, |
| 85 | + regions: FxHashSet<ty::Region<'tcx>>, |
| 86 | +} |
| 87 | + |
| 88 | +impl<'tcx> TaintSet<'tcx> { |
| 89 | + fn new(directions: TaintDirections, initial_region: ty::Region<'tcx>) -> Self { |
| 90 | + let mut regions = FxHashSet::default(); |
| 91 | + regions.insert(initial_region); |
| 92 | + TaintSet { |
| 93 | + directions: directions, |
| 94 | + regions: regions, |
| 95 | + } |
| 96 | + } |
| 97 | + |
| 98 | + fn fixed_point( |
| 99 | + &mut self, |
| 100 | + tcx: TyCtxt<'_, '_, 'tcx>, |
| 101 | + undo_log: &[UndoLog<'tcx>], |
| 102 | + verifys: &[Verify<'tcx>], |
| 103 | + ) { |
| 104 | + let mut prev_len = 0; |
| 105 | + while prev_len < self.len() { |
| 106 | + debug!( |
| 107 | + "tainted: prev_len = {:?} new_len = {:?}", |
| 108 | + prev_len, |
| 109 | + self.len() |
| 110 | + ); |
| 111 | + |
| 112 | + prev_len = self.len(); |
| 113 | + |
| 114 | + for undo_entry in undo_log { |
| 115 | + match undo_entry { |
| 116 | + &AddConstraint(Constraint::VarSubVar(a, b)) => { |
| 117 | + self.add_edge(tcx.mk_region(ReVar(a)), tcx.mk_region(ReVar(b))); |
| 118 | + } |
| 119 | + &AddConstraint(Constraint::RegSubVar(a, b)) => { |
| 120 | + self.add_edge(a, tcx.mk_region(ReVar(b))); |
| 121 | + } |
| 122 | + &AddConstraint(Constraint::VarSubReg(a, b)) => { |
| 123 | + self.add_edge(tcx.mk_region(ReVar(a)), b); |
| 124 | + } |
| 125 | + &AddConstraint(Constraint::RegSubReg(a, b)) => { |
| 126 | + self.add_edge(a, b); |
| 127 | + } |
| 128 | + &AddGiven(a, b) => { |
| 129 | + self.add_edge(a, tcx.mk_region(ReVar(b))); |
| 130 | + } |
| 131 | + &AddVerify(i) => span_bug!( |
| 132 | + verifys[i].origin.span(), |
| 133 | + "we never add verifications while doing higher-ranked things", |
| 134 | + ), |
| 135 | + &Purged | &AddCombination(..) | &AddVar(..) => {} |
| 136 | + } |
| 137 | + } |
| 138 | + } |
| 139 | + } |
| 140 | + |
| 141 | + fn into_set(self) -> FxHashSet<ty::Region<'tcx>> { |
| 142 | + self.regions |
| 143 | + } |
| 144 | + |
| 145 | + fn len(&self) -> usize { |
| 146 | + self.regions.len() |
| 147 | + } |
| 148 | + |
| 149 | + fn add_edge(&mut self, source: ty::Region<'tcx>, target: ty::Region<'tcx>) { |
| 150 | + if self.directions.incoming { |
| 151 | + if self.regions.contains(&target) { |
| 152 | + self.regions.insert(source); |
| 153 | + } |
| 154 | + } |
| 155 | + |
| 156 | + if self.directions.outgoing { |
| 157 | + if self.regions.contains(&source) { |
| 158 | + self.regions.insert(target); |
| 159 | + } |
| 160 | + } |
| 161 | + } |
| 162 | +} |
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