diff options
Diffstat (limited to 'compiler/rustc_infer/src/infer/region_constraints/leak_check.rs')
| -rw-r--r-- | compiler/rustc_infer/src/infer/region_constraints/leak_check.rs | 144 |
1 files changed, 71 insertions, 73 deletions
diff --git a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs index 89cfc9ea3..dd65f66cc 100644 --- a/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs +++ b/compiler/rustc_infer/src/infer/region_constraints/leak_check.rs @@ -3,7 +3,6 @@ use crate::infer::CombinedSnapshot; use rustc_data_structures::{ fx::FxIndexMap, graph::{scc::Sccs, vec_graph::VecGraph}, - undo_log::UndoLogs, }; use rustc_index::Idx; use rustc_middle::ty::error::TypeError; @@ -13,7 +12,9 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> { /// Searches new universes created during `snapshot`, looking for /// placeholders that may "leak" out from the universes they are contained /// in. If any leaking placeholders are found, then an `Err` is returned - /// (typically leading to the snapshot being reversed). + /// (typically leading to the snapshot being reversed). This algorithm + /// only looks at placeholders which cannot be named by `outer_universe`, + /// as this is the universe we're currently checking for a leak. /// /// The leak check *used* to be the only way we had to handle higher-ranked /// obligations. Now that we have integrated universes into the region @@ -55,6 +56,12 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> { /// * if they must also be equal to a placeholder P, and U cannot name P, report an error, as that /// indicates `P: R` and `R` is in an incompatible universe /// + /// To improve performance and for the old trait solver caching to be sound, this takes + /// an optional snapshot in which case we only look at region constraints added in that + /// snapshot. If we were to not do that the `leak_check` during evaluation can rely on + /// region constraints added outside of that evaluation. As that is not reflected in the + /// cache key this would be unsound. + /// /// # Historical note /// /// Older variants of the leak check used to report errors for these @@ -62,36 +69,21 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> { /// /// * R: P1, even if R cannot name P1, because R = 'static is a valid sol'n /// * R: P1, R: P2, as above + #[instrument(level = "debug", skip(self, tcx, only_consider_snapshot), ret)] pub fn leak_check( &mut self, tcx: TyCtxt<'tcx>, - overly_polymorphic: bool, + outer_universe: ty::UniverseIndex, max_universe: ty::UniverseIndex, - snapshot: &CombinedSnapshot<'tcx>, + only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>, ) -> RelateResult<'tcx, ()> { - debug!( - "leak_check(max_universe={:?}, snapshot.universe={:?}, overly_polymorphic={:?})", - max_universe, snapshot.universe, overly_polymorphic - ); - - assert!(UndoLogs::<super::UndoLog<'_>>::in_snapshot(&self.undo_log)); - - let universe_at_start_of_snapshot = snapshot.universe; - if universe_at_start_of_snapshot == max_universe { + if outer_universe == max_universe { return Ok(()); } - let mini_graph = - &MiniGraph::new(tcx, self.undo_log.region_constraints(), &self.storage.data.verifys); + let mini_graph = &MiniGraph::new(tcx, &self, only_consider_snapshot); - let mut leak_check = LeakCheck::new( - tcx, - universe_at_start_of_snapshot, - max_universe, - overly_polymorphic, - mini_graph, - self, - ); + let mut leak_check = LeakCheck::new(tcx, outer_universe, max_universe, mini_graph, self); leak_check.assign_placeholder_values()?; leak_check.propagate_scc_value()?; Ok(()) @@ -100,9 +92,7 @@ impl<'tcx> RegionConstraintCollector<'_, 'tcx> { struct LeakCheck<'me, 'tcx> { tcx: TyCtxt<'tcx>, - universe_at_start_of_snapshot: ty::UniverseIndex, - /// Only used when reporting region errors. - overly_polymorphic: bool, + outer_universe: ty::UniverseIndex, mini_graph: &'me MiniGraph<'tcx>, rcc: &'me RegionConstraintCollector<'me, 'tcx>, @@ -130,17 +120,15 @@ struct LeakCheck<'me, 'tcx> { impl<'me, 'tcx> LeakCheck<'me, 'tcx> { fn new( tcx: TyCtxt<'tcx>, - universe_at_start_of_snapshot: ty::UniverseIndex, + outer_universe: ty::UniverseIndex, max_universe: ty::UniverseIndex, - overly_polymorphic: bool, mini_graph: &'me MiniGraph<'tcx>, rcc: &'me RegionConstraintCollector<'me, 'tcx>, ) -> Self { let dummy_scc_universe = SccUniverse { universe: max_universe, region: None }; Self { tcx, - universe_at_start_of_snapshot, - overly_polymorphic, + outer_universe, mini_graph, rcc, scc_placeholders: IndexVec::from_elem_n(None, mini_graph.sccs.num_sccs()), @@ -165,7 +153,7 @@ impl<'me, 'tcx> LeakCheck<'me, 'tcx> { // Detect those SCCs that directly contain a placeholder if let ty::RePlaceholder(placeholder) = **region { - if self.universe_at_start_of_snapshot.cannot_name(placeholder.universe) { + if self.outer_universe.cannot_name(placeholder.universe) { self.assign_scc_value(scc, placeholder)?; } } @@ -280,7 +268,7 @@ impl<'me, 'tcx> LeakCheck<'me, 'tcx> { placeholder1: ty::PlaceholderRegion, placeholder2: ty::PlaceholderRegion, ) -> TypeError<'tcx> { - self.error(placeholder1, self.tcx.mk_re_placeholder(placeholder2)) + self.error(placeholder1, ty::Region::new_placeholder(self.tcx, placeholder2)) } fn error( @@ -289,11 +277,7 @@ impl<'me, 'tcx> LeakCheck<'me, 'tcx> { other_region: ty::Region<'tcx>, ) -> TypeError<'tcx> { debug!("error: placeholder={:?}, other_region={:?}", placeholder, other_region); - if self.overly_polymorphic { - TypeError::RegionsOverlyPolymorphic(placeholder.bound.kind, other_region) - } else { - TypeError::RegionsInsufficientlyPolymorphic(placeholder.bound.kind, other_region) - } + TypeError::RegionsInsufficientlyPolymorphic(placeholder.bound.kind, other_region) } } @@ -379,56 +363,70 @@ struct MiniGraph<'tcx> { } impl<'tcx> MiniGraph<'tcx> { - fn new<'a>( + fn new( tcx: TyCtxt<'tcx>, - undo_log: impl Iterator<Item = &'a UndoLog<'tcx>>, - verifys: &[Verify<'tcx>], - ) -> Self - where - 'tcx: 'a, - { + region_constraints: &RegionConstraintCollector<'_, 'tcx>, + only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>, + ) -> Self { let mut nodes = FxIndexMap::default(); let mut edges = Vec::new(); // Note that if `R2: R1`, we get a callback `r1, r2`, so `target` is first parameter. - Self::iterate_undo_log(tcx, undo_log, verifys, |target, source| { - let source_node = Self::add_node(&mut nodes, source); - let target_node = Self::add_node(&mut nodes, target); - edges.push((source_node, target_node)); - }); + Self::iterate_region_constraints( + tcx, + region_constraints, + only_consider_snapshot, + |target, source| { + let source_node = Self::add_node(&mut nodes, source); + let target_node = Self::add_node(&mut nodes, target); + edges.push((source_node, target_node)); + }, + ); let graph = VecGraph::new(nodes.len(), edges); let sccs = Sccs::new(&graph); Self { nodes, sccs } } /// Invokes `each_edge(R1, R2)` for each edge where `R2: R1` - fn iterate_undo_log<'a>( + fn iterate_region_constraints( tcx: TyCtxt<'tcx>, - undo_log: impl Iterator<Item = &'a UndoLog<'tcx>>, - verifys: &[Verify<'tcx>], + region_constraints: &RegionConstraintCollector<'_, 'tcx>, + only_consider_snapshot: Option<&CombinedSnapshot<'tcx>>, mut each_edge: impl FnMut(ty::Region<'tcx>, ty::Region<'tcx>), - ) where - 'tcx: 'a, - { - for undo_entry in undo_log { - match undo_entry { - &AddConstraint(Constraint::VarSubVar(a, b)) => { - each_edge(tcx.mk_re_var(a), tcx.mk_re_var(b)); - } - &AddConstraint(Constraint::RegSubVar(a, b)) => { - each_edge(a, tcx.mk_re_var(b)); - } - &AddConstraint(Constraint::VarSubReg(a, b)) => { - each_edge(tcx.mk_re_var(a), b); - } - &AddConstraint(Constraint::RegSubReg(a, b)) => { - each_edge(a, b); + ) { + let mut each_constraint = |constraint| match constraint { + &Constraint::VarSubVar(a, b) => { + each_edge(ty::Region::new_var(tcx, a), ty::Region::new_var(tcx, b)); + } + &Constraint::RegSubVar(a, b) => { + each_edge(a, ty::Region::new_var(tcx, b)); + } + &Constraint::VarSubReg(a, b) => { + each_edge(ty::Region::new_var(tcx, a), b); + } + &Constraint::RegSubReg(a, b) => { + each_edge(a, b); + } + }; + + if let Some(snapshot) = only_consider_snapshot { + for undo_entry in + region_constraints.undo_log.region_constraints_in_snapshot(&snapshot.undo_snapshot) + { + match undo_entry { + AddConstraint(constraint) => { + each_constraint(constraint); + } + &AddVerify(i) => span_bug!( + region_constraints.data().verifys[i].origin.span(), + "we never add verifications while doing higher-ranked things", + ), + &AddCombination(..) | &AddVar(..) => {} } - &AddVerify(i) => span_bug!( - verifys[i].origin.span(), - "we never add verifications while doing higher-ranked things", - ), - &AddCombination(..) | &AddVar(..) => {} + } + } else { + for (constraint, _origin) in ®ion_constraints.data().constraints { + each_constraint(constraint) } } } |