From 35e78b5cddc04c6bd13da2a1290d27cfb8ae8db8 Mon Sep 17 00:00:00 2001
From: Niko Matsakis <niko@alum.mit.edu>
Date: Mon, 31 Jul 2017 07:40:24 +0300
Subject: [PATCH] change skolemizations to use universe index

---
 src/librustc/ty/mod.rs     | 18 +++++++++++++++---
 src/librustc/ty/sty.rs     |  7 +------
 src/librustc/util/ppaux.rs |  2 +-
 3 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 4315d1f2c8ca3..88422a3ef8235 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -69,7 +69,7 @@ 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::*;
@@ -1345,7 +1345,7 @@ 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 {
@@ -1365,7 +1365,19 @@ 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
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index a18e8f578364d..7bcc816b5f03d 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -1028,7 +1028,7 @@ 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
@@ -1079,11 +1079,6 @@ newtype_index!(RegionVid
         DEBUG_FORMAT = custom,
     });
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, PartialOrd, Ord)]
-pub struct SkolemizedRegionVid {
-    pub index: u32,
-}
-
 #[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum InferTy {
     TyVar(TyVid),
diff --git a/src/librustc/util/ppaux.rs b/src/librustc/util/ppaux.rs
index d390d1c15e2aa..40c8e8aa4a29a 100644
--- a/src/librustc/util/ppaux.rs
+++ b/src/librustc/util/ppaux.rs
@@ -786,7 +786,7 @@ 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"),