diff options
Diffstat (limited to 'compiler/rustc_borrowck/src/region_infer/mod.rs')
| -rw-r--r-- | compiler/rustc_borrowck/src/region_infer/mod.rs | 90 |
1 files changed, 54 insertions, 36 deletions
diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs index cfad071460b..dcb09d5be14 100644 --- a/compiler/rustc_borrowck/src/region_infer/mod.rs +++ b/compiler/rustc_borrowck/src/region_infer/mod.rs @@ -4,15 +4,13 @@ use std::rc::Rc; use rustc_data_structures::binary_search_util; use rustc_data_structures::frozen::Frozen; use rustc_data_structures::fx::{FxIndexMap, FxIndexSet}; -use rustc_data_structures::graph::scc::Sccs; +use rustc_data_structures::graph::scc::{self, Sccs}; use rustc_errors::Diag; use rustc_hir::def_id::CRATE_DEF_ID; use rustc_index::IndexVec; use rustc_infer::infer::outlives::test_type_match; -use rustc_infer::infer::region_constraints::{ - GenericKind, RegionVariableInfo, VerifyBound, VerifyIfEq, -}; -use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin, RegionVariableOrigin}; +use rustc_infer::infer::region_constraints::{GenericKind, VerifyBound, VerifyIfEq}; +use rustc_infer::infer::{InferCtxt, NllRegionVariableOrigin}; use rustc_middle::bug; use rustc_middle::mir::{ AnnotationSource, BasicBlock, Body, ConstraintCategory, Local, Location, ReturnConstraint, @@ -29,7 +27,7 @@ use crate::constraints::graph::{self, NormalConstraintGraph, RegionGraph}; use crate::constraints::{ConstraintSccIndex, OutlivesConstraint, OutlivesConstraintSet}; use crate::dataflow::BorrowIndex; use crate::diagnostics::{RegionErrorKind, RegionErrors, UniverseInfo}; -use crate::eliminate_placeholders::{LoweredConstraints, RegionTracker}; +use crate::handle_placeholders::{LoweredConstraints, RegionTracker}; use crate::member_constraints::{MemberConstraintSet, NllMemberConstraintIndex}; use crate::polonius::LiveLoans; use crate::polonius::legacy::PoloniusOutput; @@ -50,6 +48,47 @@ mod reverse_sccs; pub(crate) mod values; +/// The representative region variable for an SCC, tagged by its origin. +/// We prefer placeholders over existentially quantified variables, otherwise +/// it's the one with the smallest Region Variable ID. In other words, +/// the order of this enumeration really matters! +#[derive(Copy, Debug, Clone, PartialEq, PartialOrd, Eq, Ord)] +pub(crate) enum Representative { + FreeRegion(RegionVid), + Placeholder(RegionVid), + Existential(RegionVid), +} + +impl Representative { + pub(crate) fn rvid(self) -> RegionVid { + match self { + Representative::FreeRegion(region_vid) + | Representative::Placeholder(region_vid) + | Representative::Existential(region_vid) => region_vid, + } + } + + pub(crate) fn new(r: RegionVid, definition: &RegionDefinition<'_>) -> Self { + match definition.origin { + NllRegionVariableOrigin::FreeRegion => Representative::FreeRegion(r), + NllRegionVariableOrigin::Placeholder(_) => Representative::Placeholder(r), + NllRegionVariableOrigin::Existential { .. } => Representative::Existential(r), + } + } +} + +impl scc::Annotation for Representative { + fn merge_scc(self, other: Self) -> Self { + // Just pick the smallest one. Note that we order by tag first! + std::cmp::min(self, other) + } + + // For reachability, we do nothing since the representative doesn't change. + fn merge_reached(self, _other: Self) -> Self { + self + } +} + pub(crate) type ConstraintSccs = Sccs<RegionVid, ConstraintSccIndex>; pub struct RegionInferenceContext<'tcx> { @@ -351,7 +390,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { let mut result = Self { definitions, liveness_constraints, - constraints: Frozen::freeze(outlives_constraints), + constraints: outlives_constraints, constraint_graph, constraint_sccs, scc_annotations, @@ -510,11 +549,6 @@ impl<'tcx> RegionInferenceContext<'tcx> { self.scc_values.placeholders_contained_in(scc) } - /// Returns access to the value of `r` for debugging purposes. - pub(crate) fn region_universe(&self, r: RegionVid) -> ty::UniverseIndex { - self.scc_universe(self.constraint_sccs.scc(r)) - } - /// Once region solving has completed, this function will return the member constraints that /// were applied to the value of a given SCC `scc`. See `AppliedMemberConstraint`. pub(crate) fn applied_member_constraints( @@ -681,7 +715,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { // If the member region lives in a higher universe, we currently choose // the most conservative option by leaving it unchanged. - if !self.scc_universe(scc).is_root() { + if !self.max_nameable_universe(scc).is_root() { return; } @@ -861,7 +895,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { "lower_bound = {:?} r_scc={:?} universe={:?}", lower_bound, r_scc, - self.scc_universe(r_scc) + self.max_nameable_universe(r_scc) ); // If the type test requires that `T: 'a` where `'a` is a // placeholder from another universe, that effectively requires @@ -1339,10 +1373,9 @@ impl<'tcx> RegionInferenceContext<'tcx> { } } - /// The minimum universe of any variable reachable from this - /// SCC, inside or outside of it. - fn scc_universe(&self, scc: ConstraintSccIndex) -> UniverseIndex { - self.scc_annotations[scc].min_universe() + /// The largest universe of any region nameable from this SCC. + fn max_nameable_universe(&self, scc: ConstraintSccIndex) -> UniverseIndex { + self.scc_annotations[scc].max_nameable_universe() } /// Checks the final value for the free region `fr` to see if it @@ -1364,7 +1397,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { // Because this free region must be in the ROOT universe, we // know it cannot contain any bound universes. - assert!(self.scc_universe(longer_fr_scc).is_root()); + assert!(self.max_nameable_universe(longer_fr_scc).is_root()); // Only check all of the relations for the main representative of each // SCC, otherwise just check that we outlive said representative. This @@ -1755,7 +1788,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { #[instrument(skip(self), level = "trace", ret)] pub(crate) fn find_sub_region_live_at(&self, fr1: RegionVid, location: Location) -> RegionVid { trace!(scc = ?self.constraint_sccs.scc(fr1)); - trace!(universe = ?self.region_universe(fr1)); + trace!(universe = ?self.max_nameable_universe(self.constraint_sccs.scc(fr1))); self.find_constraint_paths_between_regions(fr1, |r| { // First look for some `r` such that `fr1: r` and `r` is live at `location` trace!(?r, liveness_constraints=?self.liveness_constraints.pretty_print_live_points(r)); @@ -2086,7 +2119,7 @@ impl<'tcx> RegionInferenceContext<'tcx> { /// they *must* be equal (though not having the same repr does not /// mean they are unequal). fn scc_representative(&self, scc: ConstraintSccIndex) -> RegionVid { - self.scc_annotations[scc].representative + self.scc_annotations[scc].representative.rvid() } pub(crate) fn liveness_constraints(&self) -> &LivenessValues { @@ -2108,21 +2141,6 @@ impl<'tcx> RegionInferenceContext<'tcx> { } } -impl<'tcx> RegionDefinition<'tcx> { - pub(crate) fn new(rv_info: &RegionVariableInfo) -> Self { - // Create a new region definition. Note that, for free - // regions, the `external_name` field gets updated later in - // [[crate::eliminate_placeholders]]. - - let origin = match rv_info.origin { - RegionVariableOrigin::Nll(origin) => origin, - _ => NllRegionVariableOrigin::Existential { from_forall: false }, - }; - - Self { origin, universe: rv_info.universe, external_name: None } - } -} - #[derive(Clone, Debug)] pub(crate) struct BlameConstraint<'tcx> { pub category: ConstraintCategory<'tcx>, |