diff --git a/src/librustc_mir/borrow_check/nll/constraint_generation.rs b/src/librustc_mir/borrow_check/nll/constraint_generation.rs index 25d0eaafc00..95c3299693b 100644 --- a/src/librustc_mir/borrow_check/nll/constraint_generation.rs +++ b/src/librustc_mir/borrow_check/nll/constraint_generation.rs @@ -3,12 +3,15 @@ use crate::borrow_check::location::LocationTable; use crate::borrow_check::nll::ToRegionVid; use crate::borrow_check::nll::facts::AllFacts; use crate::borrow_check::nll::region_infer::values::LivenessValues; +use crate::borrow_check::places_conflict; use rustc::infer::InferCtxt; use rustc::mir::visit::TyContext; use rustc::mir::visit::Visitor; -use rustc::mir::{BasicBlock, BasicBlockData, Location, Body, Place, PlaceBase, Rvalue, TerminatorKind}; -use rustc::mir::{Local, SourceInfo, Statement, StatementKind, Terminator}; -use rustc::mir::UserTypeProjection; +use rustc::mir::{ + BasicBlock, BasicBlockData, Body, Local, Location, Place, PlaceBase, Projection, + ProjectionElem, Rvalue, SourceInfo, Statement, StatementKind, Terminator, TerminatorKind, + UserTypeProjection, +}; use rustc::ty::fold::TypeFoldable; use rustc::ty::{self, ClosureSubsts, GeneratorSubsts, RegionVid, Ty}; use rustc::ty::subst::SubstsRef; @@ -27,6 +30,7 @@ pub(super) fn generate_constraints<'cx, 'tcx>( liveness_constraints, location_table, all_facts, + body, }; for (bb, data) in body.basic_blocks().iter_enumerated() { @@ -41,6 +45,7 @@ struct ConstraintGeneration<'cg, 'cx, 'tcx> { location_table: &'cg LocationTable, liveness_constraints: &'cg mut LivenessValues, borrow_set: &'cg BorrowSet<'tcx>, + body: &'cg Body<'tcx>, } impl<'cg, 'cx, 'tcx> Visitor<'tcx> for ConstraintGeneration<'cg, 'cx, 'tcx> { @@ -212,17 +217,73 @@ impl<'cx, 'cg, 'tcx> ConstraintGeneration<'cx, 'cg, 'tcx> { /// as `killed`. For example, when assigning to a local, or on a call's return destination. fn record_killed_borrows_for_place(&mut self, place: &Place<'tcx>, location: Location) { if let Some(all_facts) = self.all_facts { - if let Place { - base: PlaceBase::Local(local), - projection: None, - } = place { - record_killed_borrows_for_local( - all_facts, - self.borrow_set, - self.location_table, - local, - location, - ); + // Depending on the `Place` we're killing: + // - if it's a local, or a single deref of a local, + // we kill all the borrows on the local. + // - if it's a deeper projection, we have to filter which + // of the borrows are killed: the ones whose `borrowed_place` + // conflicts with the `place`. + match place { + Place { + base: PlaceBase::Local(local), + projection: None, + } | + Place { + base: PlaceBase::Local(local), + projection: Some(box Projection { + base: None, + elem: ProjectionElem::Deref, + }), + } => { + debug!( + "Recording `killed` facts for borrows of local={:?} at location={:?}", + local, location + ); + + record_killed_borrows_for_local( + all_facts, + self.borrow_set, + self.location_table, + local, + location, + ); + } + + Place { + base: PlaceBase::Static(_), + .. + } => { + // Ignore kills of static or static mut variables. + } + + Place { + base: PlaceBase::Local(local), + projection: Some(_), + } => { + // Kill conflicting borrows of the innermost local. + debug!( + "Recording `killed` facts for borrows of \ + innermost projected local={:?} at location={:?}", + local, location + ); + + if let Some(borrow_indices) = self.borrow_set.local_map.get(local) { + for &borrow_index in borrow_indices { + let places_conflict = places_conflict::places_conflict( + self.infcx.tcx, + self.body, + &self.borrow_set.borrows[borrow_index].borrowed_place, + place, + places_conflict::PlaceConflictBias::NoOverlap, + ); + + if places_conflict { + let location_index = self.location_table.mid_index(location); + all_facts.killed.push((borrow_index, location_index)); + } + } + } + } } } }