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An assortment of polonius tweaks #162922

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cba3954
fix and clean up variance recording in liveness
lqd Sep 17, 2026
8a699c7
simplify `make_all_regions_live`
lqd Sep 17, 2026
942dcc9
add quick links
lqd Sep 17, 2026
ada6d89
more visual improvements
lqd Sep 17, 2026
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2 changes: 2 additions & 0 deletions compiler/rustc_borrowck/src/polonius/dump.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -543,13 +543,15 @@ fn emit_loan_reachability(
// It's useful to know whether the region we're reaching is live at this point.
let node_liveness =
if liveness.is_live_at(node.region, location) { "live" } else { "not live" };
writeln!(out, "<span class='trace-suffix'>")?;
writeln!(
out,
"/ at <code>{:?}</code>: <code>'{}</code> is {}",
location,
node.region.index(),
node_liveness,
)?;
writeln!(out, "</span>")?;
writeln!(out, "</li>")?;
}
writeln!(out, "</ul>")?;
Expand Down
41 changes: 31 additions & 10 deletions compiler/rustc_borrowck/src/polonius/dump/polonius-mir-dump.template.html
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,9 @@
<head>
<title>Polonius MIR dump</title>
<style>
.hidden {
display: none;
pre {
margin-top: 0;
white-space: pre-wrap;
}

.section + .section {
Expand All @@ -13,8 +14,8 @@
padding-top: 10px;
}

.traces .section-header {
margin-bottom: 10px;
.section-header {
margin-bottom: 6px;
}

.trace + .trace {
Expand All @@ -25,43 +26,63 @@
margin: 5px 0px;
padding-left: 15px;
}

.trace-suffix {
opacity: 0.8;
margin-left: 10px;
}

.hidden {
display: none;
}
</style>
</head>

<body>

<!-- The NLL + Polonius MIR -->
<!-- Links to the other sections -->
<div class="section">
<div class="section-header">Quick links</div>
<a href="#mir">Polonius MIR</a>
<a href="#polonius-region-graph">Polonius constraint graph</a>
<a href="#loan-traces">Loan traces</a>
<a href="#cfg-graph">Control-flow graph</a>
<a href="#nll-region-graph">NLL region graph</a>
<a href="#nll-scc-graph">NLL SCC graph</a>
</div>

<!-- The NLL + Polonius MIR -->
<div class="section" id="mir">
<div class="section-header">Raw MIR dump</div>
<pre><code>$SECTION_MIR</code></pre>
</div>

<!-- Mermaid visualization of the polonius constraint graph -->
<div class="section">
<div class="section" id="polonius-region-graph">
<div class="section-header">Polonius constraint graph</div>
<pre class='mermaid'>$SECTION_POLONIUS_CONSTRAINTS</pre>
</div>

<!-- The reachability of loans while traversing the polonius constraint graph -->
<div class="section traces">
<div class="section traces" id="loan-traces">
<div class="section-header">Loan Traces</div>
$SECTION_POLONIUS_REACHABILITY
</div>

<!-- Mermaid visualization of the CFG -->
<div class="section">
<div class="section" id="cfg-graph">
<div class="section-header">Control-flow graph</div>
<pre class='mermaid'>$SECTION_CFG</pre>
</div>

<!-- Mermaid visualization of the NLL region graph -->
<div class="section">
<div class="section" id="nll-region-graph">
<div class="section-header">NLL regions</div>
<pre class='mermaid'>$SECTION_NLL_CONSTRAINTS</pre>
</div>

<!-- Mermaid visualization of the NLL SCC graph -->
<div class="section">
<div class="section" id="nll-scc-graph">
<div class="section-header">NLL SCCs</div>
<pre class='mermaid'>$SECTION_NLL_SCCS</pre>
</div>
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38 changes: 20 additions & 18 deletions compiler/rustc_borrowck/src/type_check/liveness/trace.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -6,7 +6,7 @@ use rustc_infer::infer::canonical::QueryRegionConstraints;
use rustc_infer::traits::TraitErrors;
use rustc_middle::mir::{BasicBlock, Body, ConstraintCategory, Local, Location};
use rustc_middle::traits::query::DropckOutlivesResult;
use rustc_middle::ty::{GenericArg, Ty, TypeVisitable, TypeVisitableExt};
use rustc_middle::ty::{Ty, TyCtxt, TypeVisitable, TypeVisitableExt};
use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
use rustc_mir_dataflow::move_paths::{HasMoveData, MoveData, MovePathIndex};
use rustc_mir_dataflow::points::{DenseLocationMap, PointIndex};
Expand Down Expand Up @@ -553,8 +553,17 @@ impl<'tcx> LivenessContext<'_, '_, 'tcx> {
/// points `live_at`.
fn add_use_live_facts_for(&mut self, value: Ty<'tcx>, live_at: &IntervalSet<PointIndex>) {
debug!("add_use_live_facts_for(value={:?})", value);
Self::record_region_variance(self.typeck, value.into());
Self::make_all_regions_live(self.location_map, self.typeck, value.into(), live_at);
Self::make_all_regions_live(self.location_map, self.typeck, value, live_at);

// When using `-Zpolonius=next`, we also record the variance of regions in this live type.
if let Some(polonius_context) = self.typeck.polonius_context.as_mut() {
record_live_region_variance(
self.typeck.infcx.tcx,
&mut polonius_context.live_region_variances,
self.typeck.universal_regions,
value,
);
}
}

/// Some variable with type `live_ty` is "drop live" at `location`
Expand Down Expand Up @@ -595,9 +604,6 @@ impl<'tcx> LivenessContext<'_, '_, 'tcx> {
}
}

// Since the entire dropped local is live, record the variance of its regions.
Self::record_region_variance(self.typeck, dropped_ty.into());

// All things in the `outlives` array may be touched by
// the destructor and must be live at this point.
for &kind in &drop_data.dropck_result.kinds {
Expand All @@ -610,27 +616,24 @@ impl<'tcx> LivenessContext<'_, '_, 'tcx> {
self.typeck.polonius_facts,
);
}
}

/// `live_kind` is the type of a (use- or drop-) live local.
/// Record the variance of any region(s) appearing in it for Polonius. Does
/// nothing if Polonius is not active.
fn record_region_variance(typeck: &mut TypeChecker<'_, 'tcx>, live_kind: GenericArg<'tcx>) {
// When using `-Zpolonius=next`, we record the variance of each live region.
if let Some(polonius_context) = typeck.polonius_context.as_mut() {
// For polonius: since the local is drop live, record the variance of the regions in its
// type, not the ones in the type's live components seen in the dropck results above. See
// issue #160670.
if let Some(polonius_context) = self.typeck.polonius_context.as_mut() {
record_live_region_variance(
typeck.infcx.tcx,
self.typeck.infcx.tcx,
&mut polonius_context.live_region_variances,
typeck.universal_regions,
live_kind,
self.typeck.universal_regions,
dropped_ty,
);
}
}

fn make_all_regions_live(
location_map: &DenseLocationMap,
typeck: &mut TypeChecker<'_, 'tcx>,
value: GenericArg<'tcx>,
value: impl TypeVisitable<TyCtxt<'tcx>>,
live_at: &IntervalSet<PointIndex>,
) {
debug!("make_all_regions_live(value={:?})", value);
Expand All @@ -647,7 +650,6 @@ impl<'tcx> LivenessContext<'_, '_, 'tcx> {
typeck.constraints.liveness_constraints.add_points(live_region_vid, live_at);
},
});
Self::record_region_variance(typeck, value);
}
}

Expand Down
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