create context for errors and diagnostics for last borrowck phase

compiler/rustc_borrowck/src/lib.rs

@@ -198,7 +198,7 @@ fn do_mir_borrowck<'tcx>(
         polonius_output,
         opt_closure_req,
         nll_errors,
-        localized_outlives_constraints,
+        polonius_diagnostics,
     } = nll::compute_regions(
         &infcx,
         free_regions,
@@ -329,7 +329,7 @@ fn do_mir_borrowck<'tcx>(
         body,
         &regioncx,
         &borrow_set,
-        localized_outlives_constraints,
+        polonius_diagnostics,
         &opt_closure_req,
     );
 

compiler/rustc_borrowck/src/nll.rs

@@ -27,7 +27,7 @@ use tracing::{debug, instrument};
 use crate::borrow_set::BorrowSet;
 use crate::consumers::ConsumerOptions;
 use crate::diagnostics::{BorrowckDiagnosticsBuffer, RegionErrors};
-use crate::polonius::LocalizedOutlivesConstraintSet;
+use crate::polonius::PoloniusDiagnosticsContext;
 use crate::polonius::legacy::{
     PoloniusFacts, PoloniusFactsExt, PoloniusLocationTable, PoloniusOutput,
 };
@@ -46,8 +46,9 @@ pub(crate) struct NllOutput<'tcx> {
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
     pub nll_errors: RegionErrors<'tcx>,
 
-    /// When using `-Zpolonius=next`: the localized typeck and liveness constraints.
-    pub localized_outlives_constraints: Option<LocalizedOutlivesConstraintSet>,
+    /// When using `-Zpolonius=next`: the data used to compute errors and diagnostics, e.g.
+    /// localized typeck and liveness constraints.
+    pub polonius_diagnostics: Option<PoloniusDiagnosticsContext>,
 }
 
 /// Rewrites the regions in the MIR to use NLL variables, also scraping out the set of universal
@@ -144,7 +145,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
 
     // If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives constraints
     // and use them to compute loan liveness.
-    let localized_outlives_constraints = polonius_context.as_ref().map(|polonius_context| {
+    let polonius_diagnostics = polonius_context.as_ref().map(|polonius_context| {
         polonius_context.compute_loan_liveness(infcx.tcx, &mut regioncx, body, borrow_set)
     });
 
@@ -188,7 +189,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         polonius_output,
         opt_closure_req: closure_region_requirements,
         nll_errors,
-        localized_outlives_constraints,
+        polonius_diagnostics,
     }
 }
 

compiler/rustc_borrowck/src/polonius/dump.rs

@@ -12,7 +12,9 @@ use rustc_session::config::MirIncludeSpans;
 
 use crate::borrow_set::BorrowSet;
 use crate::constraints::OutlivesConstraint;
-use crate::polonius::{LocalizedOutlivesConstraint, LocalizedOutlivesConstraintSet};
+use crate::polonius::{
+    LocalizedOutlivesConstraint, LocalizedOutlivesConstraintSet, PoloniusDiagnosticsContext,
+};
 use crate::region_infer::values::LivenessValues;
 use crate::type_check::Locations;
 use crate::{BorrowckInferCtxt, RegionInferenceContext};
@@ -23,7 +25,7 @@ pub(crate) fn dump_polonius_mir<'tcx>(
     body: &Body<'tcx>,
     regioncx: &RegionInferenceContext<'tcx>,
     borrow_set: &BorrowSet<'tcx>,
-    localized_outlives_constraints: Option<LocalizedOutlivesConstraintSet>,
+    polonius_diagnostics: Option<PoloniusDiagnosticsContext>,
     closure_region_requirements: &Option<ClosureRegionRequirements<'tcx>>,
 ) {
     let tcx = infcx.tcx;
@@ -35,8 +37,8 @@ pub(crate) fn dump_polonius_mir<'tcx>(
         return;
     }
 
-    let localized_outlives_constraints = localized_outlives_constraints
-        .expect("missing localized constraints with `-Zpolonius=next`");
+    let polonius_diagnostics_context =
+        polonius_diagnostics.expect("missing diagnostics context with `-Zpolonius=next`");
 
     let _: io::Result<()> = try {
         let mut file = create_dump_file(tcx, "html", false, "polonius", &0, body)?;
@@ -45,7 +47,7 @@ pub(crate) fn dump_polonius_mir<'tcx>(
             body,
             regioncx,
             borrow_set,
-            localized_outlives_constraints,
+            polonius_diagnostics_context.localized_outlives_constraints,
             closure_region_requirements,
             &mut file,
         )?;

compiler/rustc_borrowck/src/polonius/mod.rs

@@ -39,9 +39,9 @@
 //! 2) once that is done, variance data is transferred, and the NLL region liveness is converted to
 //!    the polonius shape. That's the main [PoloniusContext].
 //! 3) during region inference, that data and the NLL outlives constraints are used to create the
-//!    localized outlives constraints, as described above.
-//! 4) transfer these constraints back to the main borrowck procedure: it handles computing errors
-//!    and diagnostics, debugging and MIR dumping concerns.
+//!    localized outlives constraints, as described above. That's the [PoloniusDiagnosticsContext].
+//! 4) transfer this back to the main borrowck procedure: it handles computing errors and
+//!    diagnostics, debugging and MIR dumping concerns.
 
 mod constraints;
 mod dump;
@@ -89,6 +89,12 @@ pub(crate) struct PoloniusContext {
     live_region_variances: BTreeMap<RegionVid, ConstraintDirection>,
 }
 
+/// This struct holds the data needed by the borrowck error computation and diagnostics. Its data is
+/// computed from the [PoloniusContext] when computing NLL regions.
+pub(crate) struct PoloniusDiagnosticsContext {
+    localized_outlives_constraints: LocalizedOutlivesConstraintSet,
+}
+
 /// The direction a constraint can flow into. Used to create liveness constraints according to
 /// variance.
 #[derive(Copy, Clone, PartialEq, Eq, Debug)]
@@ -135,13 +141,15 @@ impl PoloniusContext {
     ///
     /// Then, this graph is traversed, and combined with kills, reachability is recorded as loan
     /// liveness, to be used by the loan scope and active loans computations.
+    ///
+    /// The constraint data will be used to compute errors and diagnostics.
     pub(crate) fn compute_loan_liveness<'tcx>(
         &self,
         tcx: TyCtxt<'tcx>,
         regioncx: &mut RegionInferenceContext<'tcx>,
         body: &Body<'tcx>,
         borrow_set: &BorrowSet<'tcx>,
-    ) -> LocalizedOutlivesConstraintSet {
+    ) -> PoloniusDiagnosticsContext {
         let mut localized_outlives_constraints = LocalizedOutlivesConstraintSet::default();
         convert_typeck_constraints(
             tcx,
@@ -173,6 +181,6 @@ impl PoloniusContext {
         );
         regioncx.record_live_loans(live_loans);
 
-        localized_outlives_constraints
+        PoloniusDiagnosticsContext { localized_outlives_constraints }
     }
 }