mööööp

Author: lcnr

compiler/rustc_borrowck/src/region_infer/opaque_types.rs

@@ -83,6 +83,15 @@ pub(crate) fn handle_opaque_type_uses<'tcx>(
     let placeholder_indices = Default::default();
     let mut scc_values =
         RegionValues::new(location_map, universal_regions.len(), placeholder_indices);
+    for variable in definitions.indices() {
+        let scc = constraint_sccs.scc(variable);
+        match definitions[variable].origin {
+            NllRegionVariableOrigin::FreeRegion => {
+                scc_values.add_element(scc, variable);
+            }
+            _ => {}
+        }
+    }
     scc_values.propagate_constraints(&constraint_sccs);
     for entry in &mut opaque_types {
         // Map all opaque types to their SCC representatives.
@@ -274,7 +283,8 @@ impl<'tcx> OpaqueHiddenTypeFolder<'_, 'tcx> {
     #[instrument(level = "debug", skip(self))]
     fn apply_member_constraint(&mut self, member_vid: RegionVid) -> Option<Region<'tcx>> {
         let member = self.constraint_sccs.scc(member_vid);
-        if let Some((_, reg)) = self.arg_regions.iter().copied().find(|&(vid, _)| vid == member_vid) {
+        if let Some((_, reg)) = self.arg_regions.iter().copied().find(|&(vid, _)| vid == member_vid)
+        {
             debug!("member equal to arg");
             return Some(reg);
         }
@@ -305,8 +315,14 @@ impl<'tcx> OpaqueHiddenTypeFolder<'_, 'tcx> {
         // free region that must outlive the member region `R0` (`UB:
         // R0`). Therefore, we need only keep an option `O` if `UB: O`
         // for all UB.
+        //
+        // If we have a requirement `'upper_bound: 'member`, equating `'member`
+        // with some region `'choice` means we now also require `'upper_bound: 'choice`.
+        // Avoid choice regions for which this does not hold.
         for ub in self.rev_scc_graph.upper_bounds(member) {
-            choice_regions.retain(|&(o_r, _)| self.universal_region_relations.outlives(ub, o_r));
+            choice_regions.retain(|&(choice_region, _)| {
+                self.universal_region_relations.outlives(ub, choice_region)
+            });
         }
 
         debug!(?choice_regions, "after enforcing upper-bound");