From 83d63c089db3ee84a340cd16a007817be63e22a3 Mon Sep 17 00:00:00 2001
From: khyperia <953151+khyperia@users.noreply.github.com>
Date: Wed, 9 Sep 2026 14:36:38 +0200
Subject: [PATCH 1/2] fix perf regression from abby canonical form

---
 compiler/rustc_type_ir/src/region_constraint.rs | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/compiler/rustc_type_ir/src/region_constraint.rs b/compiler/rustc_type_ir/src/region_constraint.rs
index 815acb11b9955..38477cb56e927 100644
--- a/compiler/rustc_type_ir/src/region_constraint.rs
+++ b/compiler/rustc_type_ir/src/region_constraint.rs
@@ -240,7 +240,7 @@ impl<I: Interner> Or<I> {
 }
 impl<I: Interner, S: Clone + std::hash::Hash + std::fmt::Debug + Eq> Or<I, S> {
     pub fn new_true() -> Self {
-        Self(Box::new([And::new([])]))
+        Self(Box::new([And::new_true()]))
     }
 
     pub fn is_true(&self) -> bool {
@@ -323,6 +323,10 @@ impl<I: Interner> And<I> {
     }
 }
 impl<I: Interner, S: Clone + std::hash::Hash + std::fmt::Debug + Eq> And<I, S> {
+    pub fn new_true() -> Self {
+        Self(Box::new([]))
+    }
+
     pub fn new(i: impl IntoIterator<Item = LeafRegionConstraint<I, S>>) -> Self {
         let mut seen = IndexSet::new();
         And(i
@@ -406,7 +410,7 @@ impl<I: Interner, S: Clone + std::fmt::Debug + Eq + std::hash::Hash> RegionConst
         }));
 
         Self {
-            and_constraint: if or_constraint.is_false() { And::new([]) } else { and_constraint },
+            and_constraint: if or_constraint.is_false() { And::new_true() } else { and_constraint },
             or_constraint,
         }
     }
@@ -422,7 +426,7 @@ impl<I: Interner, S: Clone + std::fmt::Debug + Eq + std::hash::Hash> RegionConst
         let or_constraint = Or::build_and(a.or_constraint, b.or_constraint);
 
         Self {
-            and_constraint: if or_constraint.is_false() { And::new([]) } else { and_constraint },
+            and_constraint: if or_constraint.is_false() { And::new_true() } else { and_constraint },
             or_constraint,
         }
     }
@@ -432,7 +436,7 @@ impl<I: Interner, S: Clone + std::fmt::Debug + Eq + std::hash::Hash> RegionConst
     }
 
     pub fn new_true() -> Self {
-        Self { and_constraint: And::new([]), or_constraint: Or::new_true() }
+        Self { and_constraint: And::new_true(), or_constraint: Or::new_true() }
     }
 
     pub fn is_true(&self) -> bool {
@@ -440,7 +444,7 @@ impl<I: Interner, S: Clone + std::fmt::Debug + Eq + std::hash::Hash> RegionConst
     }
 
     pub fn new_false() -> Self {
-        Self { and_constraint: And::new([]), or_constraint: Or::new_false() }
+        Self { and_constraint: And::new_true(), or_constraint: Or::new_false() }
     }
 
     pub fn is_false(&self) -> bool {

From a8f5602587693ee0bef99da56950f31131f8fd6a Mon Sep 17 00:00:00 2001
From: khyperia <953151+khyperia@users.noreply.github.com>
Date: Thu, 10 Sep 2026 10:55:03 +0200
Subject: [PATCH 2/2] lazily init SolverRegionConstraintStorage on access

---
 .../src/infer/solver_region_constraints.rs            | 11 +++++++----
 compiler/rustc_type_ir/src/region_constraint.rs       |  6 ------
 2 files changed, 7 insertions(+), 10 deletions(-)

diff --git a/compiler/rustc_infer/src/infer/solver_region_constraints.rs b/compiler/rustc_infer/src/infer/solver_region_constraints.rs
index 09baae2ca8a42..03363c9f57a94 100644
--- a/compiler/rustc_infer/src/infer/solver_region_constraints.rs
+++ b/compiler/rustc_infer/src/infer/solver_region_constraints.rs
@@ -6,20 +6,23 @@ pub type SolverRegionConstraint<'tcx> =
     rustc_type_ir::region_constraint::RegionConstraint<TyCtxt<'tcx>, Span>;
 
 #[derive(Clone, Debug)]
-pub(crate) struct SolverRegionConstraintStorage<'tcx>(SolverRegionConstraint<'tcx>);
+pub(crate) struct SolverRegionConstraintStorage<'tcx>(Option<SolverRegionConstraint<'tcx>>);
 
 impl<'tcx> SolverRegionConstraintStorage<'tcx> {
     pub(crate) fn new() -> Self {
-        Self(SolverRegionConstraint::new_true())
+        Self(None)
     }
 
     pub(crate) fn get_constraint(&self) -> SolverRegionConstraint<'tcx> {
-        self.0.clone()
+        match &self.0 {
+            Some(v) => v.clone(),
+            None => SolverRegionConstraint::new_true(),
+        }
     }
 
     #[instrument(level = "debug", skip(self))]
     pub(crate) fn overwrite(&mut self, constraint: SolverRegionConstraint<'tcx>) {
-        self.0 = constraint;
+        self.0 = Some(constraint);
     }
 }
 
diff --git a/compiler/rustc_type_ir/src/region_constraint.rs b/compiler/rustc_type_ir/src/region_constraint.rs
index 38477cb56e927..0dd79d8d0449e 100644
--- a/compiler/rustc_type_ir/src/region_constraint.rs
+++ b/compiler/rustc_type_ir/src/region_constraint.rs
@@ -481,12 +481,6 @@ impl<I: Interner, S: Clone + std::fmt::Debug + Eq + std::hash::Hash> RegionConst
     }
 }
 
-impl<I: Interner> Default for RegionConstraint<I> {
-    fn default() -> Self {
-        Self::new_true()
-    }
-}
-
 impl<I: Interner, S: Clone + std::fmt::Debug> LeafRegionConstraint<I, S> {
     pub fn is_ambig(&self) -> bool {
         matches!(self, Self::Ambiguity(_))