rewrite region constraints to smaller universes

Author: BoxyUwU

compiler/rustc_middle/src/ty/list.rs

@@ -153,6 +153,17 @@ impl<'a, H, T: Copy> rustc_type_ir::inherent::SliceLike for &'a RawList<H, T> {
     }
 }
 
+impl<'tcx> rustc_type_ir::inherent::BoundVarKinds<TyCtxt<'tcx>>
+    for &'tcx RawList<(), crate::ty::BoundVariableKind<'tcx>>
+{
+    fn from_vars(
+        tcx: TyCtxt<'tcx>,
+        iter: impl IntoIterator<Item = crate::ty::BoundVariableKind<'tcx>>,
+    ) -> Self {
+        tcx.mk_bound_variable_kinds_from_iter(iter.into_iter())
+    }
+}
+
 macro_rules! impl_list_empty {
     ($header_ty:ty, $header_init:expr) => {
         impl<T> RawList<$header_ty, T> {

compiler/rustc_next_trait_solver/src/solve/eval_ctxt/mod.rs

@@ -1863,12 +1863,11 @@ where
             .map(|u| UniverseIndex::from_usize(u))
             .rev()
             .fold(constraint, |constraint, u| {
-                // rustc_type_ir::region_constraint::eagerly_handle_placeholders_in_universe(
-                //     &**self.delegate,
-                //     constraint,
-                //     u,
-                // )
-                todo!() as RegionConstraint::<I>
+                rustc_type_ir::region_constraint::eagerly_handle_placeholders_in_universe(
+                    &**self.delegate,
+                    constraint,
+                    u,
+                )
             });
 
         if constraint.is_false() {

compiler/rustc_type_ir/src/inherent.rs

@@ -702,6 +702,12 @@ pub trait OpaqueTypeStorageEntries: Debug + Copy + Default {
     fn needs_reevaluation(self, canonicalized: usize) -> bool;
 }
 
+pub trait BoundVarKinds<I: Interner>:
+    Copy + Debug + Hash + Eq + SliceLike<Item = ty::BoundVariableKind<I>> + Default
+{
+    fn from_vars(cx: I, iter: impl IntoIterator<Item = ty::BoundVariableKind<I>>) -> Self;
+}
+
 pub trait SliceLike: Sized + Copy {
     type Item: Copy;
     type IntoIter: Iterator<Item = Self::Item> + DoubleEndedIterator;

compiler/rustc_type_ir/src/interner.rs

@@ -96,12 +96,7 @@ pub trait Interner:
     type GenericArg: GenericArg<Self>;
     type Term: Term<Self>;
 
-    type BoundVarKinds: Copy
-        + Debug
-        + Hash
-        + Eq
-        + SliceLike<Item = ty::BoundVariableKind<Self>>
-        + Default;
+    type BoundVarKinds: BoundVarKinds<Self>;
 
     type PredefinedOpaques: Copy
         + Debug