From 2ed53732932716647b72f5f3e32a06da8634d6e2 Mon Sep 17 00:00:00 2001 From: Amanda Stjerna Date: Thu, 18 Sep 2025 13:11:37 +0200 Subject: Clean up universe evaluation during type test evaluation The logic was, as the removed comments suggest, hackish and meant to implement previous logic that was factored out. The new logic does exactly what the comments say, and is much less surprising. --- compiler/rustc_borrowck/src/handle_placeholders.rs | 10 +++------- compiler/rustc_borrowck/src/region_infer/mod.rs | 20 +++++++++++++++----- 2 files changed, 18 insertions(+), 12 deletions(-) (limited to 'compiler') diff --git a/compiler/rustc_borrowck/src/handle_placeholders.rs b/compiler/rustc_borrowck/src/handle_placeholders.rs index 94379cdebf7..6be90994015 100644 --- a/compiler/rustc_borrowck/src/handle_placeholders.rs +++ b/compiler/rustc_borrowck/src/handle_placeholders.rs @@ -166,13 +166,9 @@ impl RegionTracker { } } - /// Determine if the tracked universes of the two SCCs are compatible. - pub(crate) fn universe_compatible_with(&self, other: Self) -> bool { - // HACK: We first check whether we can name the highest existential universe - // of `other`. This only exists to avoid errors in case that scc already - // depends on a placeholder it cannot name itself. - self.max_nameable_universe().can_name(other.max_nameable_universe()) - || other.reachable_placeholders.can_be_named_by(self.max_nameable_universe()) + /// Determine if we can name all the placeholders in `other`. + pub(crate) fn can_name_all_placeholders(&self, other: Self) -> bool { + other.reachable_placeholders.can_be_named_by(self.max_nameable_universe.0) } /// If this SCC reaches a placeholder it can't name, return it. diff --git a/compiler/rustc_borrowck/src/region_infer/mod.rs b/compiler/rustc_borrowck/src/region_infer/mod.rs index f57456949bb..5f4bfd9df48 100644 --- a/compiler/rustc_borrowck/src/region_infer/mod.rs +++ b/compiler/rustc_borrowck/src/region_infer/mod.rs @@ -571,11 +571,15 @@ impl<'tcx> RegionInferenceContext<'tcx> { } } - /// Returns `true` if all the elements in the value of `scc_b` are nameable + /// Returns `true` if all the placeholders in the value of `scc_b` are nameable /// in `scc_a`. Used during constraint propagation, and only once /// the value of `scc_b` has been computed. - fn universe_compatible(&self, scc_b: ConstraintSccIndex, scc_a: ConstraintSccIndex) -> bool { - self.scc_annotations[scc_a].universe_compatible_with(self.scc_annotations[scc_b]) + fn can_name_all_placeholders( + &self, + scc_a: ConstraintSccIndex, + scc_b: ConstraintSccIndex, + ) -> bool { + self.scc_annotations[scc_a].can_name_all_placeholders(self.scc_annotations[scc_b]) } /// Once regions have been propagated, this method is used to see @@ -964,16 +968,22 @@ impl<'tcx> RegionInferenceContext<'tcx> { return true; } + let fr_static = self.universal_regions().fr_static; + // If we are checking that `'sup: 'sub`, and `'sub` contains // some placeholder that `'sup` cannot name, then this is only // true if `'sup` outlives static. - if !self.universe_compatible(sub_region_scc, sup_region_scc) { + // + // Avoid infinite recursion if `sub_region` is already `'static` + if sub_region != fr_static + && !self.can_name_all_placeholders(sup_region_scc, sub_region_scc) + { debug!( "sub universe `{sub_region_scc:?}` is not nameable \ by super `{sup_region_scc:?}`, promoting to static", ); - return self.eval_outlives(sup_region, self.universal_regions().fr_static); + return self.eval_outlives(sup_region, fr_static); } // Both the `sub_region` and `sup_region` consist of the union -- cgit 1.4.1-3-g733a5