eagerly initialize definitions in sub-fn

Author: lcnr

Diff for: compiler/rustc_borrowck/src/nll.rs

@@ -117,11 +117,6 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         Rc::clone(&location_map),
     );
 
-    // Create the region inference context, taking ownership of the
-    // region inference data that was contained in `infcx`, and the
-    // base constraints generated by the type-check.
-    let var_infos = infcx.get_region_var_infos();
-
     // If requested, emit legacy polonius facts.
     polonius::legacy::emit_facts(
         &mut polonius_facts,
@@ -134,13 +129,8 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         &constraints,
     );
 
-    let mut regioncx = RegionInferenceContext::new(
-        infcx,
-        var_infos,
-        constraints,
-        universal_region_relations,
-        location_map,
-    );
+    let mut regioncx =
+        RegionInferenceContext::new(infcx, constraints, universal_region_relations, location_map);
 
     // If requested for `-Zpolonius=next`, convert NLL constraints to localized outlives constraints
     // and use them to compute loan liveness.

Diff for: compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -145,7 +145,7 @@ pub struct RegionInferenceContext<'tcx> {
     /// variables are identified by their index (`RegionVid`). The
     /// definition contains information about where the region came
     /// from as well as its final inferred value.
-    pub(crate) definitions: IndexVec<RegionVid, RegionDefinition<'tcx>>,
+    pub(crate) definitions: Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>>,
 
     /// The liveness constraints added to each region. For most
     /// regions, these start out empty and steadily grow, though for
@@ -385,6 +385,26 @@ fn sccs_info<'tcx>(infcx: &BorrowckInferCtxt<'tcx>, sccs: &ConstraintSccs) {
     debug!("SCC edges {:#?}", scc_node_to_edges);
 }
 
+fn create_definitions<'tcx>(
+    infcx: &BorrowckInferCtxt<'tcx>,
+    universal_regions: &UniversalRegions<'tcx>,
+) -> Frozen<IndexVec<RegionVid, RegionDefinition<'tcx>>> {
+    // Create a RegionDefinition for each inference variable.
+    let mut definitions: IndexVec<_, _> = infcx
+        .get_region_var_infos()
+        .iter()
+        .map(|info| RegionDefinition::new(info.universe, info.origin))
+        .collect();
+
+    // Add the external name for all universal regions.
+    for (external_name, variable) in universal_regions.named_universal_regions_iter() {
+        debug!("region {variable:?} has external name {external_name:?}");
+        definitions[variable].external_name = Some(external_name);
+    }
+
+    Frozen::freeze(definitions)
+}
+
 impl<'tcx> RegionInferenceContext<'tcx> {
     /// Creates a new region inference context with a total of
     /// `num_region_variables` valid inference variables; the first N
@@ -395,7 +415,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// of constraints produced by the MIR type check.
     pub(crate) fn new(
         infcx: &BorrowckInferCtxt<'tcx>,
-        var_infos: VarInfos,
         constraints: MirTypeckRegionConstraints<'tcx>,
         universal_region_relations: Frozen<UniversalRegionRelations<'tcx>>,
         location_map: Rc<DenseLocationMap>,
@@ -426,11 +445,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             infcx.set_tainted_by_errors(guar);
         }
 
-        // Create a RegionDefinition for each inference variable.
-        let definitions: IndexVec<_, _> = var_infos
-            .iter()
-            .map(|info| RegionDefinition::new(info.universe, info.origin))
-            .collect();
+        let definitions = create_definitions(infcx, &universal_regions);
 
         let constraint_sccs =
             outlives_constraints.add_outlives_static(&universal_regions, &definitions);
@@ -526,18 +541,6 @@ impl<'tcx> RegionInferenceContext<'tcx> {
     /// means that the `R1: !1` constraint here will cause
     /// `R1` to become `'static`.
     fn init_free_and_bound_regions(&mut self) {
-        // Update the names (if any)
-        // This iterator has unstable order but we collect it all into an IndexVec
-        for (external_name, variable) in
-            self.universal_region_relations.universal_regions.named_universal_regions_iter()
-        {
-            debug!(
-                "init_free_and_bound_regions: region {:?} has external name {:?}",
-                variable, external_name
-            );
-            self.definitions[variable].external_name = Some(external_name);
-        }
-
         for variable in self.definitions.indices() {
             let scc = self.constraint_sccs.scc(variable);