change skolemizations to use universe index

These changes were meant to be in
2b18d8fe9dc05415a8e6b7cadf879c7f7ebe020a (rebased from
12a2305), but I messed up the rebase a
bit as the file had been moved.

src/librustc/infer/region_constraints/mod.rs

@@ -18,7 +18,7 @@ use super::unify_key;
 
 use rustc_data_structures::indexed_vec::{IndexVec, Idx};
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
-use rustc_data_structures::unify::{self, UnificationTable};
+use rustc_data_structures::unify as ut;
 use ty::{self, Ty, TyCtxt};
 use ty::{Region, RegionVid};
 use ty::ReStatic;
@@ -48,7 +48,7 @@ pub struct RegionConstraintCollector<'tcx> {
     glbs: CombineMap<'tcx>,
 
     /// Number of skolemized variables currently active.
-    skolemization_count: u32,
+    skolemization_count: ty::UniverseIndex,
 
     /// Global counter used during the GLB algorithm to create unique
     /// names for fresh bound regions
@@ -73,7 +73,7 @@ pub struct RegionConstraintCollector<'tcx> {
     /// is iterating to a fixed point, because otherwise we sometimes
     /// would wind up with a fresh stream of region variables that
     /// have been equated but appear distinct.
-    unification_table: UnificationTable<ty::RegionVid>,
+    unification_table: ut::UnificationTable<ut::InPlace<ty::RegionVid>>,
 }
 
 pub type VarOrigins = IndexVec<RegionVid, RegionVariableOrigin>;
@@ -232,8 +232,8 @@ type CombineMap<'tcx> = FxHashMap<TwoRegions<'tcx>, RegionVid>;
 
 pub struct RegionSnapshot {
     length: usize,
-    region_snapshot: unify::Snapshot<ty::RegionVid>,
-    skolemization_count: u32,
+    region_snapshot: ut::Snapshot<ut::InPlace<ty::RegionVid>>,
+    skolemization_count: ty::UniverseIndex,
 }
 
 /// When working with skolemized regions, we often wish to find all of
@@ -277,10 +277,10 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
             data: RegionConstraintData::default(),
             lubs: FxHashMap(),
             glbs: FxHashMap(),
-            skolemization_count: 0,
+            skolemization_count: ty::UniverseIndex::ROOT,
             bound_count: 0,
             undo_log: Vec::new(),
-            unification_table: UnificationTable::new(),
+            unification_table: ut::UnificationTable::new(),
         }
     }
 
@@ -329,7 +329,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
             unification_table,
         } = self;
 
-        assert_eq!(*skolemization_count, 0);
+        assert_eq!(skolemization_count.as_usize(), 0);
 
         // Clear the tables of (lubs, glbs), so that we will create
         // fresh regions if we do a LUB operation. As it happens,
@@ -342,7 +342,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         // un-unified" state. Note that when we unify `a` and `b`, we
         // also insert `a <= b` and a `b <= a` edges, so the
         // `RegionConstraintData` contains the relationship here.
-        *unification_table = UnificationTable::new();
+        *unification_table = ut::UnificationTable::new();
         for vid in var_origins.indices() {
             unification_table.new_key(unify_key::RegionVidKey { min_vid: vid });
         }
@@ -371,7 +371,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         assert!(self.undo_log[snapshot.length] == OpenSnapshot);
         assert!(
             self.skolemization_count == snapshot.skolemization_count,
-            "failed to pop skolemized regions: {} now vs {} at start",
+            "failed to pop skolemized regions: {:?} now vs {:?} at start",
             self.skolemization_count,
             snapshot.skolemization_count
         );
@@ -479,9 +479,9 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         assert!(self.in_snapshot());
         assert!(self.undo_log[snapshot.length] == OpenSnapshot);
 
-        let sc = self.skolemization_count;
-        self.skolemization_count = sc + 1;
-        tcx.mk_region(ReSkolemized(ty::SkolemizedRegionVid { index: sc }, br))
+        let universe = self.skolemization_count.subuniverse();
+        self.skolemization_count = universe;
+        tcx.mk_region(ReSkolemized(universe, br))
     }
 
     /// Removes all the edges to/from the skolemized regions that are
@@ -499,34 +499,34 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         assert!(self.in_snapshot());
         assert!(self.undo_log[snapshot.length] == OpenSnapshot);
         assert!(
-            self.skolemization_count as usize >= skols.len(),
+            self.skolemization_count.as_usize() >= skols.len(),
             "popping more skolemized variables than actually exist, \
              sc now = {}, skols.len = {}",
-            self.skolemization_count,
+            self.skolemization_count.as_usize(),
             skols.len()
         );
 
-        let last_to_pop = self.skolemization_count;
-        let first_to_pop = last_to_pop - (skols.len() as u32);
+        let last_to_pop = self.skolemization_count.subuniverse();
+        let first_to_pop = ty::UniverseIndex::from(last_to_pop.as_u32() - (skols.len() as u32));
 
         assert!(
             first_to_pop >= snapshot.skolemization_count,
             "popping more regions than snapshot contains, \
-             sc now = {}, sc then = {}, skols.len = {}",
+             sc now = {:?}, sc then = {:?}, skols.len = {}",
             self.skolemization_count,
             snapshot.skolemization_count,
             skols.len()
         );
         debug_assert! {
             skols.iter()
                  .all(|&k| match *k {
-                     ty::ReSkolemized(index, _) =>
-                         index.index >= first_to_pop &&
-                         index.index < last_to_pop,
+                     ty::ReSkolemized(universe, _) =>
+                         universe >= first_to_pop &&
+                         universe < last_to_pop,
                      _ =>
                          false
                  }),
-            "invalid skolemization keys or keys out of range ({}..{}): {:?}",
+            "invalid skolemization keys or keys out of range ({:?}..{:?}): {:?}",
             snapshot.skolemization_count,
             self.skolemization_count,
             skols
@@ -776,7 +776,7 @@ impl<'tcx> RegionConstraintCollector<'tcx> {
         tcx: TyCtxt<'_, '_, 'tcx>,
         rid: RegionVid,
     ) -> ty::Region<'tcx> {
-        let vid = self.unification_table.find_value(rid).min_vid;
+        let vid = self.unification_table.probe_value(rid).min_vid;
         tcx.mk_region(ty::ReVar(vid))
     }
 
@@ -861,7 +861,7 @@ impl fmt::Debug for RegionSnapshot {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         write!(
             f,
-            "RegionSnapshot(length={},skolemization={})",
+            "RegionSnapshot(length={},skolemization={:?})",
             self.length,
             self.skolemization_count
         )