change skolemizations to use universe index

Author: nikomatsakis

src/librustc/infer/region_inference/mod.rs

@@ -216,7 +216,7 @@ pub struct RegionVarBindings<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 
     lubs: RefCell<CombineMap<'tcx>>,
     glbs: RefCell<CombineMap<'tcx>>,
-    skolemization_count: Cell<u32>,
+    skolemization_count: Cell<ty::UniverseIndex>,
     bound_count: Cell<u32>,
 
     /// The undo log records actions that might later be undone.
@@ -240,7 +240,7 @@ pub struct RegionVarBindings<'a, 'gcx: 'a+'tcx, 'tcx: 'a> {
 pub struct RegionSnapshot {
     length: usize,
     region_snapshot: ut::Snapshot<ut::InPlace<ty::RegionVid>>,
-    skolemization_count: u32,
+    skolemization_count: ty::UniverseIndex,
 }
 
 /// When working with skolemized regions, we often wish to find all of
@@ -362,7 +362,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
             givens: RefCell::new(FxHashSet()),
             lubs: RefCell::new(FxHashMap()),
             glbs: RefCell::new(FxHashMap()),
-            skolemization_count: Cell::new(0),
+            skolemization_count: Cell::new(ty::UniverseIndex::ROOT),
             bound_count: Cell::new(0),
             undo_log: RefCell::new(Vec::new()),
             unification_table: RefCell::new(ut::UnificationTable::new()),
@@ -389,7 +389,7 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
         assert!(self.undo_log.borrow().len() > snapshot.length);
         assert!((*self.undo_log.borrow())[snapshot.length] == OpenSnapshot);
         assert!(self.skolemization_count.get() == snapshot.skolemization_count,
-                "failed to pop skolemized regions: {} now vs {} at start",
+                "failed to pop skolemized regions: {:?} now vs {:?} at start",
                 self.skolemization_count.get(),
                 snapshot.skolemization_count);
 
@@ -501,9 +501,9 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
         assert!(self.in_snapshot());
         assert!(self.undo_log.borrow()[snapshot.length] == OpenSnapshot);
 
-        let sc = self.skolemization_count.get();
-        self.skolemization_count.set(sc + 1);
-        self.tcx.mk_region(ReSkolemized(ty::SkolemizedRegionVid { index: sc }, br))
+        let universe = self.skolemization_count.get().subuniverse();
+        self.skolemization_count.set(universe);
+        self.tcx.mk_region(ReSkolemized(universe, br))
     }
 
     /// Removes all the edges to/from the skolemized regions that are
@@ -517,31 +517,31 @@ impl<'a, 'gcx, 'tcx> RegionVarBindings<'a, 'gcx, 'tcx> {
 
         assert!(self.in_snapshot());
         assert!(self.undo_log.borrow()[snapshot.length] == OpenSnapshot);
-        assert!(self.skolemization_count.get() as usize >= skols.len(),
+        assert!(self.skolemization_count.get().as_usize() >= skols.len(),
                 "popping more skolemized variables than actually exist, \
                  sc now = {}, skols.len = {}",
-                self.skolemization_count.get(),
+                self.skolemization_count.get().as_usize(),
                 skols.len());
 
-        let last_to_pop = self.skolemization_count.get();
-        let first_to_pop = last_to_pop - (skols.len() as u32);
+        let last_to_pop = self.skolemization_count.get().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.get(),
                 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.get(),
             skols
@@ -1523,7 +1523,7 @@ impl<'tcx> fmt::Debug for RegionAndOrigin<'tcx> {
 
 impl fmt::Debug for RegionSnapshot {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "RegionSnapshot(length={},skolemization={})",
+        write!(f, "RegionSnapshot(length={},skolemization={:?})",
                self.length, self.skolemization_count)
     }
 }

src/librustc/ty/mod.rs

@@ -68,7 +68,7 @@ pub use self::sty::{ExistentialTraitRef, PolyExistentialTraitRef};
 pub use self::sty::{ExistentialProjection, PolyExistentialProjection, Const};
 pub use self::sty::{BoundRegion, EarlyBoundRegion, FreeRegion, Region};
 pub use self::sty::RegionKind;
-pub use self::sty::{TyVid, IntVid, FloatVid, RegionVid, SkolemizedRegionVid};
+pub use self::sty::{TyVid, IntVid, FloatVid, RegionVid};
 pub use self::sty::BoundRegion::*;
 pub use self::sty::InferTy::*;
 pub use self::sty::RegionKind::*;
@@ -1275,7 +1275,7 @@ impl<'tcx> InstantiatedPredicates<'tcx> {
 /// type name in a non-zero universe is a skolemized type -- an
 /// idealized representative of "types in general" that we use for
 /// checking generic functions.
-#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash)]
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct UniverseIndex(u32);
 
 impl UniverseIndex {
@@ -1295,7 +1295,19 @@ impl UniverseIndex {
     /// region `'a`, but that region was not nameable from `U` because
     /// it was not in scope there.
     pub fn subuniverse(self) -> UniverseIndex {
-        UniverseIndex(self.0 + 1)
+        UniverseIndex(self.0.checked_add(1).unwrap())
+    }
+
+    pub fn from(v: u32) -> UniverseIndex {
+        UniverseIndex(v)
+    }
+
+    pub fn as_u32(&self) -> u32 {
+        self.0
+    }
+
+    pub fn as_usize(&self) -> usize {
+        self.0 as usize
     }
 
     /// Gets the "depth" of this universe in the universe tree. This

src/librustc/ty/sty.rs

@@ -854,7 +854,7 @@ pub enum RegionKind {
 
     /// A skolemized region - basically the higher-ranked version of ReFree.
     /// Should not exist after typeck.
-    ReSkolemized(SkolemizedRegionVid, BoundRegion),
+    ReSkolemized(ty::UniverseIndex, BoundRegion),
 
     /// Empty lifetime is for data that is never accessed.
     /// Bottom in the region lattice. We treat ReEmpty somewhat
@@ -898,11 +898,6 @@ pub struct RegionVid {
     pub index: u32,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
-pub struct SkolemizedRegionVid {
-    pub index: u32,
-}
-
 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum InferTy {
     TyVar(TyVid),

src/librustc/util/ppaux.rs

@@ -762,7 +762,7 @@ define_print! {
                 }
 
                 ty::ReSkolemized(id, ref bound_region) => {
-                    write!(f, "ReSkolemized({}, {:?})", id.index, bound_region)
+                    write!(f, "ReSkolemized({:?}, {:?})", id, bound_region)
                 }
 
                 ty::ReEmpty => write!(f, "ReEmpty"),