Add required lifetime parameter to BitDenotation.

This avoids all sorts of confusing issues with using both `dest_place`
and `self` in the `propagate_call_return` function in the
`BitDenotation` implementation for `Borrows`.

Author: davidtwco

src/librustc_mir/borrow_check/flows.rs

@@ -33,19 +33,19 @@ use std::rc::Rc;
 
 // (forced to be `pub` due to its use as an associated type below.)
 crate struct Flows<'b, 'gcx: 'tcx, 'tcx: 'b> {
-    borrows: FlowAtLocation<Borrows<'b, 'gcx, 'tcx>>,
-    pub uninits: FlowAtLocation<MaybeUninitializedPlaces<'b, 'gcx, 'tcx>>,
-    pub ever_inits: FlowAtLocation<EverInitializedPlaces<'b, 'gcx, 'tcx>>,
+    borrows: FlowAtLocation<'tcx, Borrows<'b, 'gcx, 'tcx>>,
+    pub uninits: FlowAtLocation<'tcx, MaybeUninitializedPlaces<'b, 'gcx, 'tcx>>,
+    pub ever_inits: FlowAtLocation<'tcx, EverInitializedPlaces<'b, 'gcx, 'tcx>>,
 
     /// Polonius Output
     pub polonius_output: Option<Rc<Output<RegionVid, BorrowIndex, LocationIndex>>>,
 }
 
 impl<'b, 'gcx, 'tcx> Flows<'b, 'gcx, 'tcx> {
     crate fn new(
-        borrows: FlowAtLocation<Borrows<'b, 'gcx, 'tcx>>,
-        uninits: FlowAtLocation<MaybeUninitializedPlaces<'b, 'gcx, 'tcx>>,
-        ever_inits: FlowAtLocation<EverInitializedPlaces<'b, 'gcx, 'tcx>>,
+        borrows: FlowAtLocation<'tcx, Borrows<'b, 'gcx, 'tcx>>,
+        uninits: FlowAtLocation<'tcx, MaybeUninitializedPlaces<'b, 'gcx, 'tcx>>,
+        ever_inits: FlowAtLocation<'tcx, EverInitializedPlaces<'b, 'gcx, 'tcx>>,
         polonius_output: Option<Rc<Output<RegionVid, BorrowIndex, LocationIndex>>>,
     ) -> Self {
         Flows {

src/librustc_mir/borrow_check/nll/mod.rs

@@ -85,7 +85,7 @@ pub(in borrow_check) fn compute_regions<'cx, 'gcx, 'tcx>(
     mir: &Mir<'tcx>,
     location_table: &LocationTable,
     param_env: ty::ParamEnv<'gcx>,
-    flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'cx, 'gcx, 'tcx>>,
+    flow_inits: &mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'cx, 'gcx, 'tcx>>,
     move_data: &MoveData<'tcx>,
     borrow_set: &BorrowSet<'tcx>,
     errors_buffer: &mut Vec<Diagnostic>,

src/librustc_mir/borrow_check/nll/type_check/liveness/mod.rs

@@ -39,7 +39,7 @@ pub(super) fn generate<'gcx, 'tcx>(
     typeck: &mut TypeChecker<'_, 'gcx, 'tcx>,
     mir: &Mir<'tcx>,
     elements: &Rc<RegionValueElements>,
-    flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
+    flow_inits: &mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
     move_data: &MoveData<'tcx>,
     location_table: &LocationTable,
 ) {

src/librustc_mir/borrow_check/nll/type_check/liveness/trace.rs

@@ -46,7 +46,7 @@ pub(super) fn trace(
     typeck: &mut TypeChecker<'_, 'gcx, 'tcx>,
     mir: &Mir<'tcx>,
     elements: &Rc<RegionValueElements>,
-    flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
+    flow_inits: &mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
     move_data: &MoveData<'tcx>,
     liveness_map: &NllLivenessMap,
     location_table: &LocationTable,
@@ -99,7 +99,7 @@ where
 
     /// Results of dataflow tracking which variables (and paths) have been
     /// initialized.
-    flow_inits: &'me mut FlowAtLocation<MaybeInitializedPlaces<'flow, 'gcx, 'tcx>>,
+    flow_inits: &'me mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'flow, 'gcx, 'tcx>>,
 
     /// Index indicating where each variable is assigned, used, or
     /// dropped.

src/librustc_mir/borrow_check/nll/type_check/mod.rs

@@ -122,7 +122,7 @@ pub(crate) fn type_check<'gcx, 'tcx>(
     location_table: &LocationTable,
     borrow_set: &BorrowSet<'tcx>,
     all_facts: &mut Option<AllFacts>,
-    flow_inits: &mut FlowAtLocation<MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
+    flow_inits: &mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
     move_data: &MoveData<'tcx>,
     elements: &Rc<RegionValueElements>,
 ) -> MirTypeckResults<'tcx> {

src/librustc_mir/dataflow/at_location.rs

@@ -70,19 +70,19 @@ pub trait FlowsAtLocation {
 /// (e.g. via `reconstruct_statement_effect` and
 /// `reconstruct_terminator_effect`; don't forget to call
 /// `apply_local_effect`).
-pub struct FlowAtLocation<BD>
+pub struct FlowAtLocation<'tcx, BD>
 where
-    BD: BitDenotation,
+    BD: BitDenotation<'tcx>,
 {
-    base_results: DataflowResults<BD>,
+    base_results: DataflowResults<'tcx, BD>,
     curr_state: BitSet<BD::Idx>,
     stmt_gen: HybridBitSet<BD::Idx>,
     stmt_kill: HybridBitSet<BD::Idx>,
 }
 
-impl<BD> FlowAtLocation<BD>
+impl<'tcx, BD> FlowAtLocation<'tcx, BD>
 where
-    BD: BitDenotation,
+    BD: BitDenotation<'tcx>,
 {
     /// Iterate over each bit set in the current state.
     pub fn each_state_bit<F>(&self, f: F)
@@ -102,7 +102,7 @@ where
         self.stmt_gen.iter().for_each(f)
     }
 
-    pub fn new(results: DataflowResults<BD>) -> Self {
+    pub fn new(results: DataflowResults<'tcx, BD>) -> Self {
         let bits_per_block = results.sets().bits_per_block();
         let curr_state = BitSet::new_empty(bits_per_block);
         let stmt_gen = HybridBitSet::new_empty(bits_per_block);
@@ -143,8 +143,8 @@ where
     }
 }
 
-impl<BD> FlowsAtLocation for FlowAtLocation<BD>
-    where BD: BitDenotation
+impl<'tcx, BD> FlowsAtLocation for FlowAtLocation<'tcx, BD>
+    where BD: BitDenotation<'tcx>
 {
     fn reset_to_entry_of(&mut self, bb: BasicBlock) {
         self.curr_state.overwrite(self.base_results.sets().on_entry_set_for(bb.index()));
@@ -213,9 +213,9 @@ impl<BD> FlowsAtLocation for FlowAtLocation<BD>
 }
 
 
-impl<'tcx, T> FlowAtLocation<T>
+impl<'tcx, T> FlowAtLocation<'tcx, T>
 where
-    T: HasMoveData<'tcx> + BitDenotation<Idx = MovePathIndex>,
+    T: HasMoveData<'tcx> + BitDenotation<'tcx, Idx = MovePathIndex>,
 {
     pub fn has_any_child_of(&self, mpi: T::Idx) -> Option<T::Idx> {
         // We process `mpi` before the loop below, for two reasons:

src/librustc_mir/dataflow/graphviz.rs

@@ -25,19 +25,19 @@ use super::DataflowBuilder;
 use super::DebugFormatted;
 
 pub trait MirWithFlowState<'tcx> {
-    type BD: BitDenotation;
+    type BD: BitDenotation<'tcx>;
     fn node_id(&self) -> NodeId;
     fn mir(&self) -> &Mir<'tcx>;
-    fn flow_state(&self) -> &DataflowState<Self::BD>;
+    fn flow_state(&self) -> &DataflowState<'tcx, Self::BD>;
 }
 
 impl<'a, 'tcx, BD> MirWithFlowState<'tcx> for DataflowBuilder<'a, 'tcx, BD>
-    where BD: BitDenotation
+    where BD: BitDenotation<'tcx>
 {
     type BD = BD;
     fn node_id(&self) -> NodeId { self.node_id }
     fn mir(&self) -> &Mir<'tcx> { self.flow_state.mir() }
-    fn flow_state(&self) -> &DataflowState<Self::BD> { &self.flow_state.flow_state }
+    fn flow_state(&self) -> &DataflowState<'tcx, Self::BD> { &self.flow_state.flow_state }
 }
 
 struct Graph<'a, 'tcx, MWF:'a, P> where
@@ -53,8 +53,8 @@ pub(crate) fn print_borrowck_graph_to<'a, 'tcx, BD, P>(
     path: &Path,
     render_idx: P)
     -> io::Result<()>
-    where BD: BitDenotation,
-          P: Fn(&BD, BD::Idx) -> DebugFormatted
+    where BD: BitDenotation<'tcx>,
+          P: Fn(&BD, BD::Idx) -> DebugFormatted,
 {
     let g = Graph { mbcx, phantom: PhantomData, render_idx };
     let mut v = Vec::new();
@@ -76,7 +76,7 @@ fn outgoing(mir: &Mir, bb: BasicBlock) -> Vec<Edge> {
 
 impl<'a, 'tcx, MWF, P> dot::Labeller<'a> for Graph<'a, 'tcx, MWF, P>
     where MWF: MirWithFlowState<'tcx>,
-          P: Fn(&MWF::BD, <MWF::BD as BitDenotation>::Idx) -> DebugFormatted,
+          P: Fn(&MWF::BD, <MWF::BD as BitDenotation<'tcx>>::Idx) -> DebugFormatted,
 {
     type Node = Node;
     type Edge = Edge;
@@ -128,7 +128,7 @@ impl<'a, 'tcx, MWF, P> dot::Labeller<'a> for Graph<'a, 'tcx, MWF, P>
 
 impl<'a, 'tcx, MWF, P> Graph<'a, 'tcx, MWF, P>
 where MWF: MirWithFlowState<'tcx>,
-      P: Fn(&MWF::BD, <MWF::BD as BitDenotation>::Idx) -> DebugFormatted,
+      P: Fn(&MWF::BD, <MWF::BD as BitDenotation<'tcx>>::Idx) -> DebugFormatted,
 {
     /// Generate the node label
     fn node_label_internal<W: io::Write>(&self,

src/librustc_mir/dataflow/impls/borrowed_locals.rs

@@ -36,7 +36,7 @@ impl<'a, 'tcx: 'a> HaveBeenBorrowedLocals<'a, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> BitDenotation for HaveBeenBorrowedLocals<'a, 'tcx> {
+impl<'a, 'tcx> BitDenotation<'tcx> for HaveBeenBorrowedLocals<'a, 'tcx> {
     type Idx = Local;
     fn name() -> &'static str { "has_been_borrowed_locals" }
     fn bits_per_block(&self) -> usize {
@@ -71,11 +71,13 @@ impl<'a, 'tcx> BitDenotation for HaveBeenBorrowedLocals<'a, 'tcx> {
         }.visit_terminator(loc.block, self.mir[loc.block].terminator(), loc);
     }
 
-    fn propagate_call_return(&self,
-                             _in_out: &mut BitSet<Local>,
-                             _call_bb: mir::BasicBlock,
-                             _dest_bb: mir::BasicBlock,
-                             _dest_place: &mir::Place) {
+    fn propagate_call_return(
+        &self,
+        _in_out: &mut BitSet<Local>,
+        _call_bb: mir::BasicBlock,
+        _dest_bb: mir::BasicBlock,
+        _dest_place: &mir::Place<'tcx>,
+    ) {
         // Nothing to do when a call returns successfully
     }
 }

src/librustc_mir/dataflow/impls/borrows.rs

@@ -195,18 +195,14 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
     fn kill_borrows_on_place(
         &self,
         sets: &mut BlockSets<BorrowIndex>,
-        location: Location,
         place: &Place<'tcx>
     ) {
-        debug!("kill_borrows_on_place: location={:?} place={:?}", location, place);
+        debug!("kill_borrows_on_place: place={:?}", place);
         // Handle the `Place::Local(..)` case first and exit early.
         if let Place::Local(local) = place {
-            if let Some(borrow_indexes) = self.borrow_set.local_map.get(&local) {
-                debug!(
-                    "kill_borrows_on_place: local={:?} borrow_indexes={:?}",
-                    local, borrow_indexes,
-                );
-                sets.kill_all(borrow_indexes);
+            if let Some(borrow_indices) = self.borrow_set.local_map.get(&local) {
+                debug!("kill_borrows_on_place: borrow_indices={:?}", borrow_indices);
+                sets.kill_all(borrow_indices);
                 return;
             }
         }
@@ -234,16 +230,16 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
                 places_conflict::PlaceConflictBias::NoOverlap,
             ) {
                 debug!(
-                    "kill_borrows_on_place: (kill) place={:?} borrow_index={:?} borrow_data={:?}",
-                    place, borrow_index, borrow_data,
+                    "kill_borrows_on_place: (kill) borrow_index={:?} borrow_data={:?}",
+                    borrow_index, borrow_data,
                 );
                 sets.kill(borrow_index);
             }
         }
     }
 }
 
-impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
+impl<'a, 'gcx, 'tcx> BitDenotation<'tcx> for Borrows<'a, 'gcx, 'tcx> {
     type Idx = BorrowIndex;
     fn name() -> &'static str { "borrows" }
     fn bits_per_block(&self) -> usize {
@@ -278,12 +274,8 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
             mir::StatementKind::Assign(ref lhs, ref rhs) => {
                 // Make sure there are no remaining borrows for variables
                 // that are assigned over.
-                self.kill_borrows_on_place(sets, location, lhs);
+                self.kill_borrows_on_place(sets, lhs);
 
-                // NOTE: if/when the Assign case is revised to inspect
-                // the assigned_place here, make sure to also
-                // re-consider the current implementations of the
-                // propagate_call_return method.
                 if let mir::Rvalue::Ref(_, _, ref place) = **rhs {
                     if place.ignore_borrow(
                         self.tcx,
@@ -317,13 +309,13 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
             mir::StatementKind::StorageDead(local) => {
                 // Make sure there are no remaining borrows for locals that
                 // are gone out of scope.
-                self.kill_borrows_on_place(sets, location, &Place::Local(local));
+                self.kill_borrows_on_place(sets, &Place::Local(local));
             }
 
             mir::StatementKind::InlineAsm { ref outputs, ref asm, .. } => {
                 for (output, kind) in outputs.iter().zip(&asm.outputs) {
                     if !kind.is_indirect && !kind.is_rw {
-                        self.kill_borrows_on_place(sets, location, output);
+                        self.kill_borrows_on_place(sets, output);
                     }
                 }
             }
@@ -348,16 +340,13 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
 
     fn terminator_effect(&self, _: &mut BlockSets<BorrowIndex>, _: Location) {}
 
-    fn propagate_call_return(&self,
-                             _in_out: &mut BitSet<BorrowIndex>,
-                             _call_bb: mir::BasicBlock,
-                             _dest_bb: mir::BasicBlock,
-                             _dest_place: &mir::Place) {
-        // there are no effects on borrows from method call return...
-        //
-        // ... but if overwriting a place can affect flow state, then
-        // latter is not true; see NOTE on Assign case in
-        // statement_effect_on_borrows.
+    fn propagate_call_return(
+        &self,
+        _in_out: &mut BitSet<BorrowIndex>,
+        _call_bb: mir::BasicBlock,
+        _dest_bb: mir::BasicBlock,
+        _dest_place: &mir::Place<'tcx>,
+    ) {
     }
 }