Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

3 files changed, 1343 insertions, 0 deletions

diff --git a/vendor/ena/src/unify/backing_vec.rs b/vendor/ena/src/unify/backing_vec.rs
new file mode 100644
index 000000000..7c1eb2ced
--- /dev/null
+++ b/vendor/ena/src/unify/backing_vec.rs
@@ -0,0 +1,263 @@
+#[cfg(feature = "persistent")]
+use dogged::DVec;
+use snapshot_vec as sv;
+use std::marker::PhantomData;
+use std::ops::{self, Range};
+
+use undo_log::{Rollback, Snapshots, UndoLogs, VecLog};
+
+use super::{UnifyKey, UnifyValue, VarValue};
+
+#[allow(dead_code)] // rustc BUG
+#[allow(type_alias_bounds)]
+type Key<S: UnificationStoreBase> = <S as UnificationStoreBase>::Key;
+
+/// Largely internal trait implemented by the unification table
+/// backing store types. The most common such type is `InPlace`,
+/// which indicates a standard, mutable unification table.
+pub trait UnificationStoreBase: ops::Index<usize, Output = VarValue<Key<Self>>> {
+    type Key: UnifyKey<Value = Self::Value>;
+    type Value: UnifyValue;
+
+    fn len(&self) -> usize;
+
+    fn tag() -> &'static str {
+        Self::Key::tag()
+    }
+}
+
+pub trait UnificationStoreMut: UnificationStoreBase {
+    fn reset_unifications(&mut self, value: impl FnMut(u32) -> VarValue<Self::Key>);
+
+    fn push(&mut self, value: VarValue<Self::Key>);
+
+    fn reserve(&mut self, num_new_values: usize);
+
+    fn update<F>(&mut self, index: usize, op: F)
+    where
+        F: FnOnce(&mut VarValue<Self::Key>);
+}
+
+pub trait UnificationStore: UnificationStoreMut {
+    type Snapshot;
+
+    fn start_snapshot(&mut self) -> Self::Snapshot;
+
+    fn rollback_to(&mut self, snapshot: Self::Snapshot);
+
+    fn commit(&mut self, snapshot: Self::Snapshot);
+
+    fn values_since_snapshot(&self, snapshot: &Self::Snapshot) -> Range<usize>;
+}
+
+/// Backing store for an in-place unification table.
+/// Not typically used directly.
+#[derive(Clone, Debug)]
+pub struct InPlace<
+    K: UnifyKey,
+    V: sv::VecLike<Delegate<K>> = Vec<VarValue<K>>,
+    L = VecLog<sv::UndoLog<Delegate<K>>>,
+> {
+    pub(crate) values: sv::SnapshotVec<Delegate<K>, V, L>,
+}
+
+// HACK(eddyb) manual impl avoids `Default` bound on `K`.
+impl<K: UnifyKey, V: sv::VecLike<Delegate<K>> + Default, L: Default> Default for InPlace<K, V, L> {
+    fn default() -> Self {
+        InPlace {
+            values: sv::SnapshotVec::new(),
+        }
+    }
+}
+
+impl<K, V, L> UnificationStoreBase for InPlace<K, V, L>
+where
+    K: UnifyKey,
+    V: sv::VecLike<Delegate<K>>,
+{
+    type Key = K;
+    type Value = K::Value;
+
+    fn len(&self) -> usize {
+        self.values.len()
+    }
+}
+
+impl<K, V, L> UnificationStoreMut for InPlace<K, V, L>
+where
+    K: UnifyKey,
+    V: sv::VecLike<Delegate<K>>,
+    L: UndoLogs<sv::UndoLog<Delegate<K>>>,
+{
+    #[inline]
+    fn reset_unifications(&mut self, mut value: impl FnMut(u32) -> VarValue<Self::Key>) {
+        self.values.set_all(|i| value(i as u32));
+    }
+
+    #[inline]
+    fn push(&mut self, value: VarValue<Self::Key>) {
+        self.values.push(value);
+    }
+
+    #[inline]
+    fn reserve(&mut self, num_new_values: usize) {
+        self.values.reserve(num_new_values);
+    }
+
+    #[inline]
+    fn update<F>(&mut self, index: usize, op: F)
+    where
+        F: FnOnce(&mut VarValue<Self::Key>),
+    {
+        self.values.update(index, op)
+    }
+}
+
+impl<K, V, L> UnificationStore for InPlace<K, V, L>
+where
+    K: UnifyKey,
+    V: sv::VecLike<Delegate<K>>,
+    L: Snapshots<sv::UndoLog<Delegate<K>>>,
+{
+    type Snapshot = sv::Snapshot<L::Snapshot>;
+
+    #[inline]
+    fn start_snapshot(&mut self) -> Self::Snapshot {
+        self.values.start_snapshot()
+    }
+
+    #[inline]
+    fn rollback_to(&mut self, snapshot: Self::Snapshot) {
+        self.values.rollback_to(snapshot);
+    }
+
+    #[inline]
+    fn commit(&mut self, snapshot: Self::Snapshot) {
+        self.values.commit(snapshot);
+    }
+
+    #[inline]
+    fn values_since_snapshot(&self, snapshot: &Self::Snapshot) -> Range<usize> {
+        snapshot.value_count..self.len()
+    }
+}
+
+impl<K, V, L> ops::Index<usize> for InPlace<K, V, L>
+where
+    V: sv::VecLike<Delegate<K>>,
+    K: UnifyKey,
+{
+    type Output = VarValue<K>;
+    fn index(&self, index: usize) -> &VarValue<K> {
+        &self.values[index]
+    }
+}
+
+#[doc(hidden)]
+#[derive(Copy, Clone, Debug)]
+pub struct Delegate<K>(PhantomData<K>);
+
+impl<K: UnifyKey> sv::SnapshotVecDelegate for Delegate<K> {
+    type Value = VarValue<K>;
+    type Undo = ();
+
+    fn reverse(_: &mut Vec<VarValue<K>>, _: ()) {}
+}
+
+impl<K: UnifyKey> Rollback<sv::UndoLog<Delegate<K>>> for super::UnificationTableStorage<K> {
+    fn reverse(&mut self, undo: sv::UndoLog<Delegate<K>>) {
+        self.values.values.reverse(undo);
+    }
+}
+
+#[cfg(feature = "persistent")]
+#[derive(Clone, Debug)]
+pub struct Persistent<K: UnifyKey> {
+    values: DVec<VarValue<K>>,
+}
+
+// HACK(eddyb) manual impl avoids `Default` bound on `K`.
+#[cfg(feature = "persistent")]
+impl<K: UnifyKey> Default for Persistent<K> {
+    fn default() -> Self {
+        Persistent {
+            values: DVec::new(),
+        }
+    }
+}
+
+#[cfg(feature = "persistent")]
+impl<K: UnifyKey> UnificationStoreBase for Persistent<K> {
+    type Key = K;
+    type Value = K::Value;
+
+    fn len(&self) -> usize {
+        self.values.len()
+    }
+}
+
+#[cfg(feature = "persistent")]
+impl<K: UnifyKey> UnificationStoreMut for Persistent<K> {
+    #[inline]
+    fn reset_unifications(&mut self, mut value: impl FnMut(u32) -> VarValue<Self::Key>) {
+        // Without extending dogged, there isn't obviously a more
+        // efficient way to do this. But it's pretty dumb. Maybe
+        // dogged needs a `map`.
+        for i in 0..self.values.len() {
+            self.values[i] = value(i as u32);
+        }
+    }
+
+    #[inline]
+    fn push(&mut self, value: VarValue<Self::Key>) {
+        self.values.push(value);
+    }
+
+    #[inline]
+    fn reserve(&mut self, _num_new_values: usize) {
+        // not obviously relevant to DVec.
+    }
+
+    #[inline]
+    fn update<F>(&mut self, index: usize, op: F)
+    where
+        F: FnOnce(&mut VarValue<Self::Key>),
+    {
+        let p = &mut self.values[index];
+        op(p);
+    }
+}
+
+#[cfg(feature = "persistent")]
+impl<K: UnifyKey> UnificationStore for Persistent<K> {
+    type Snapshot = Self;
+
+    #[inline]
+    fn start_snapshot(&mut self) -> Self::Snapshot {
+        self.clone()
+    }
+
+    #[inline]
+    fn rollback_to(&mut self, snapshot: Self::Snapshot) {
+        *self = snapshot;
+    }
+
+    #[inline]
+    fn commit(&mut self, _snapshot: Self::Snapshot) {}
+
+    #[inline]
+    fn values_since_snapshot(&self, snapshot: &Self::Snapshot) -> Range<usize> {
+        snapshot.len()..self.len()
+    }
+}
+
+#[cfg(feature = "persistent")]
+impl<K> ops::Index<usize> for Persistent<K>
+where
+    K: UnifyKey,
+{
+    type Output = VarValue<K>;
+    fn index(&self, index: usize) -> &VarValue<K> {
+        &self.values[index]
+    }
+}
diff --git a/vendor/ena/src/unify/mod.rs b/vendor/ena/src/unify/mod.rs
new file mode 100644
index 000000000..a26d699d8
--- /dev/null
+++ b/vendor/ena/src/unify/mod.rs
@@ -0,0 +1,594 @@
+// Copyright 2012-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Union-find implementation. The main type is `UnificationTable`.
+//!
+//! You can define your own type for the *keys* in the table, but you
+//! must implement `UnifyKey` for that type. The assumption is that
+//! keys will be newtyped integers, hence we require that they
+//! implement `Copy`.
+//!
+//! Keys can have values associated with them. The assumption is that
+//! these values are cheaply cloneable (ideally, `Copy`), and some of
+//! the interfaces are oriented around that assumption. If you just
+//! want the classical "union-find" algorithm where you group things
+//! into sets, use the `Value` type of `()`.
+//!
+//! When you have keys with non-trivial values, you must also define
+//! how those values can be merged. As part of doing this, you can
+//! define the "error" type to return on error; if errors are not
+//! possible, use `NoError` (an uninstantiable struct). Using this
+//! type also unlocks various more ergonomic methods (e.g., `union()`
+//! in place of `unify_var_var()`).
+//!
+//! The best way to see how it is used is to read the `tests.rs` file;
+//! search for e.g. `UnitKey`.
+
+use std::fmt::Debug;
+use std::marker;
+use std::ops::Range;
+
+use snapshot_vec::{self as sv, UndoLog};
+use undo_log::{UndoLogs, VecLog};
+
+mod backing_vec;
+pub use self::backing_vec::{
+    Delegate, InPlace, UnificationStore, UnificationStoreBase, UnificationStoreMut,
+};
+
+#[cfg(feature = "persistent")]
+pub use self::backing_vec::Persistent;
+
+#[cfg(test)]
+mod tests;
+
+/// This trait is implemented by any type that can serve as a type
+/// variable. We call such variables *unification keys*. For example,
+/// this trait is implemented by `IntVid`, which represents integral
+/// variables.
+///
+/// Each key type has an associated value type `V`. For example, for
+/// `IntVid`, this is `Option<IntVarValue>`, representing some
+/// (possibly not yet known) sort of integer.
+///
+/// Clients are expected to provide implementations of this trait; you
+/// can see some examples in the `test` module.
+pub trait UnifyKey: Copy + Clone + Debug + PartialEq {
+    type Value: UnifyValue;
+
+    fn index(&self) -> u32;
+
+    fn from_index(u: u32) -> Self;
+
+    fn tag() -> &'static str;
+
+    /// If true, then `self` should be preferred as root to `other`.
+    /// Note that we assume a consistent partial ordering, so
+    /// returning true implies that `other.prefer_as_root_to(self)`
+    /// would return false.  If there is no ordering between two keys
+    /// (i.e., `a.prefer_as_root_to(b)` and `b.prefer_as_root_to(a)`
+    /// both return false) then the rank will be used to determine the
+    /// root in an optimal way.
+    ///
+    /// NB. The only reason to implement this method is if you want to
+    /// control what value is returned from `find()`. In general, it
+    /// is better to let the unification table determine the root,
+    /// since overriding the rank can cause execution time to increase
+    /// dramatically.
+    #[allow(unused_variables)]
+    fn order_roots(
+        a: Self,
+        a_value: &Self::Value,
+        b: Self,
+        b_value: &Self::Value,
+    ) -> Option<(Self, Self)> {
+        None
+    }
+}
+
+/// Trait implemented for **values** associated with a unification
+/// key. This trait defines how to merge the values from two keys that
+/// are unioned together. This merging can be fallible. If you attempt
+/// to union two keys whose values cannot be merged, then the error is
+/// propagated up and the two keys are not unioned.
+///
+/// This crate provides implementations of `UnifyValue` for `()`
+/// (which is infallible) and `Option<T>` (where `T: UnifyValue`). The
+/// option implementation merges two sum-values using the `UnifyValue`
+/// implementation of `T`.
+///
+/// See also `EqUnifyValue`, which is a convenience trait for cases
+/// where the "merge" operation succeeds only if the two values are
+/// equal.
+pub trait UnifyValue: Clone + Debug {
+    /// Defines the type to return when merging of two values fails.
+    /// If merging is infallible, use the special struct `NoError`
+    /// found in this crate, which unlocks various more convenient
+    /// methods on the unification table.
+    type Error;
+
+    /// Given two values, produce a new value that combines them.
+    /// If that is not possible, produce an error.
+    fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error>;
+}
+
+/// A convenient helper for unification values which must be equal or
+/// else an error occurs. For example, if you are unifying types in a
+/// simple functional language, this may be appropriate, since (e.g.)
+/// you can't unify a type variable bound to `int` with one bound to
+/// `float` (but you can unify two type variables both bound to
+/// `int`).
+///
+/// Any type which implements `EqUnifyValue` automatially implements
+/// `UnifyValue`; if the two values are equal, merging is permitted.
+/// Otherwise, the error `(v1, v2)` is returned, where `v1` and `v2`
+/// are the two unequal values.
+pub trait EqUnifyValue: Eq + Clone + Debug {}
+
+impl<T: EqUnifyValue> UnifyValue for T {
+    type Error = (T, T);
+
+    fn unify_values(value1: &Self, value2: &Self) -> Result<Self, Self::Error> {
+        if value1 == value2 {
+            Ok(value1.clone())
+        } else {
+            Err((value1.clone(), value2.clone()))
+        }
+    }
+}
+
+/// A struct which can never be instantiated. Used
+/// for the error type for infallible cases.
+#[derive(Debug)]
+pub struct NoError {
+    _dummy: (),
+}
+
+/// Value of a unification key. We implement Tarjan's union-find
+/// algorithm: when two keys are unified, one of them is converted
+/// into a "redirect" pointing at the other. These redirects form a
+/// DAG: the roots of the DAG (nodes that are not redirected) are each
+/// associated with a value of type `V` and a rank. The rank is used
+/// to keep the DAG relatively balanced, which helps keep the running
+/// time of the algorithm under control. For more information, see
+/// <http://en.wikipedia.org/wiki/Disjoint-set_data_structure>.
+#[derive(PartialEq, Clone, Debug)]
+pub struct VarValue<K: UnifyKey> {
+    parent: K,       // if equal to self, this is a root
+    value: K::Value, // value assigned (only relevant to root)
+    rank: u32,       // max depth (only relevant to root)
+}
+
+/// Table of unification keys and their values. You must define a key type K
+/// that implements the `UnifyKey` trait. Unification tables can be used in two-modes:
+///
+/// - in-place (`UnificationTable<InPlace<K>>` or `InPlaceUnificationTable<K>`):
+///   - This is the standard mutable mode, where the array is modified
+///     in place.
+///   - To do backtracking, you can employ the `snapshot` and `rollback_to`
+///     methods.
+/// - persistent (`UnificationTable<Persistent<K>>` or `PersistentUnificationTable<K>`):
+///   - In this mode, we use a persistent vector to store the data, so that
+///     cloning the table is an O(1) operation.
+///   - This implies that ordinary operations are quite a bit slower though.
+///   - Requires the `persistent` feature be selected in your Cargo.toml file.
+#[derive(Clone, Debug, Default)]
+pub struct UnificationTable<S: UnificationStoreBase> {
+    /// Indicates the current value of each key.
+    values: S,
+}
+
+pub type UnificationStorage<K> = Vec<VarValue<K>>;
+pub type UnificationTableStorage<K> = UnificationTable<InPlace<K, UnificationStorage<K>, ()>>;
+
+/// A unification table that uses an "in-place" vector.
+#[allow(type_alias_bounds)]
+pub type InPlaceUnificationTable<
+    K: UnifyKey,
+    V: sv::VecLike<Delegate<K>> = Vec<VarValue<K>>,
+    L = VecLog<UndoLog<Delegate<K>>>,
+> = UnificationTable<InPlace<K, V, L>>;
+
+/// A unification table that uses a "persistent" vector.
+#[cfg(feature = "persistent")]
+#[allow(type_alias_bounds)]
+pub type PersistentUnificationTable<K: UnifyKey> = UnificationTable<Persistent<K>>;
+
+/// At any time, users may snapshot a unification table.  The changes
+/// made during the snapshot may either be *committed* or *rolled back*.
+pub struct Snapshot<S: UnificationStore> {
+    // Link snapshot to the unification store `S` of the table.
+    marker: marker::PhantomData<S>,
+    snapshot: S::Snapshot,
+}
+
+impl<K: UnifyKey> VarValue<K> {
+    fn new_var(key: K, value: K::Value) -> VarValue<K> {
+        VarValue::new(key, value, 0)
+    }
+
+    fn new(parent: K, value: K::Value, rank: u32) -> VarValue<K> {
+        VarValue {
+            parent: parent, // this is a root
+            value: value,
+            rank: rank,
+        }
+    }
+
+    fn redirect(&mut self, to: K) {
+        self.parent = to;
+    }
+
+    fn root(&mut self, rank: u32, value: K::Value) {
+        self.rank = rank;
+        self.value = value;
+    }
+
+    fn parent(&self, self_key: K) -> Option<K> {
+        self.if_not_self(self.parent, self_key)
+    }
+
+    fn if_not_self(&self, key: K, self_key: K) -> Option<K> {
+        if key == self_key {
+            None
+        } else {
+            Some(key)
+        }
+    }
+}
+impl<K> UnificationTableStorage<K>
+where
+    K: UnifyKey,
+{
+    /// Creates a `UnificationTable` using an external `undo_log`, allowing mutating methods to be
+    /// called if `L` does not implement `UndoLogs`
+    pub fn with_log<'a, L>(
+        &'a mut self,
+        undo_log: L,
+    ) -> UnificationTable<InPlace<K, &'a mut UnificationStorage<K>, L>>
+    where
+        L: UndoLogs<sv::UndoLog<Delegate<K>>>,
+    {
+        UnificationTable {
+            values: InPlace {
+                values: self.values.values.with_log(undo_log),
+            },
+        }
+    }
+}
+
+// We can't use V:LatticeValue, much as I would like to,
+// because frequently the pattern is that V=Option<U> for some
+// other type parameter U, and we have no way to say
+// Option<U>:LatticeValue.
+
+impl<S: UnificationStoreBase + Default> UnificationTable<S> {
+    pub fn new() -> Self {
+        Self::default()
+    }
+}
+
+impl<S: UnificationStore> UnificationTable<S> {
+    /// Starts a new snapshot. Each snapshot must be either
+    /// rolled back or committed in a "LIFO" (stack) order.
+    pub fn snapshot(&mut self) -> Snapshot<S> {
+        Snapshot {
+            marker: marker::PhantomData::<S>,
+            snapshot: self.values.start_snapshot(),
+        }
+    }
+
+    /// Reverses all changes since the last snapshot. Also
+    /// removes any keys that have been created since then.
+    pub fn rollback_to(&mut self, snapshot: Snapshot<S>) {
+        debug!("{}: rollback_to()", S::tag());
+        self.values.rollback_to(snapshot.snapshot);
+    }
+
+    /// Commits all changes since the last snapshot. Of course, they
+    /// can still be undone if there is a snapshot further out.
+    pub fn commit(&mut self, snapshot: Snapshot<S>) {
+        debug!("{}: commit()", S::tag());
+        self.values.commit(snapshot.snapshot);
+    }
+
+    /// Returns the keys of all variables created since the `snapshot`.
+    pub fn vars_since_snapshot(&self, snapshot: &Snapshot<S>) -> Range<S::Key> {
+        let range = self.values.values_since_snapshot(&snapshot.snapshot);
+        S::Key::from_index(range.start as u32)..S::Key::from_index(range.end as u32)
+    }
+}
+
+impl<S: UnificationStoreBase> UnificationTable<S> {
+    /// Returns the number of keys created so far.
+    pub fn len(&self) -> usize {
+        self.values.len()
+    }
+}
+
+impl<S: UnificationStoreMut> UnificationTable<S> {
+    /// Starts a new snapshot. Each snapshot must be either
+    /// Creates a fresh key with the given value.
+    pub fn new_key(&mut self, value: S::Value) -> S::Key {
+        let len = self.values.len();
+        let key: S::Key = UnifyKey::from_index(len as u32);
+        self.values.push(VarValue::new_var(key, value));
+        debug!("{}: created new key: {:?}", S::tag(), key);
+        key
+    }
+
+    /// Reserve memory for `num_new_keys` to be created. Does not
+    /// actually create the new keys; you must then invoke `new_key`.
+    pub fn reserve(&mut self, num_new_keys: usize) {
+        self.values.reserve(num_new_keys);
+    }
+
+    /// Clears all unifications that have been performed, resetting to
+    /// the initial state. The values of each variable are given by
+    /// the closure.
+    pub fn reset_unifications(&mut self, mut value: impl FnMut(S::Key) -> S::Value) {
+        self.values.reset_unifications(|i| {
+            let key = UnifyKey::from_index(i as u32);
+            let value = value(key);
+            VarValue::new_var(key, value)
+        });
+    }
+
+    /// Obtains the current value for a particular key.
+    /// Not for end-users; they can use `probe_value`.
+    fn value(&self, key: S::Key) -> &VarValue<S::Key> {
+        &self.values[key.index() as usize]
+    }
+
+    /// Find the root node for `vid`. This uses the standard
+    /// union-find algorithm with path compression:
+    /// <http://en.wikipedia.org/wiki/Disjoint-set_data_structure>.
+    ///
+    /// NB. This is a building-block operation and you would probably
+    /// prefer to call `probe` below.
+    ///
+    /// This is an always-inlined version of this function for the hot
+    /// callsites. `uninlined_get_root_key` is the never-inlined version.
+    #[inline(always)]
+    fn inlined_get_root_key(&mut self, vid: S::Key) -> S::Key {
+        let redirect = {
+            match self.value(vid).parent(vid) {
+                None => return vid,
+                Some(redirect) => redirect,
+            }
+        };
+
+        let root_key: S::Key = self.uninlined_get_root_key(redirect);
+        if root_key != redirect {
+            // Path compression
+            self.update_value(vid, |value| value.parent = root_key);
+        }
+
+        root_key
+    }
+
+    // This is a never-inlined version of this function for cold callsites.
+    // 'inlined_get_root_key` is the always-inlined version.
+    #[inline(never)]
+    fn uninlined_get_root_key(&mut self, vid: S::Key) -> S::Key {
+        self.inlined_get_root_key(vid)
+    }
+
+    fn update_value<OP>(&mut self, key: S::Key, op: OP)
+    where
+        OP: FnOnce(&mut VarValue<S::Key>),
+    {
+        self.values.update(key.index() as usize, op);
+        debug!("Updated variable {:?} to {:?}", key, self.value(key));
+    }
+
+    /// Either redirects `node_a` to `node_b` or vice versa, depending
+    /// on the relative rank. The value associated with the new root
+    /// will be `new_value`.
+    ///
+    /// NB: This is the "union" operation of "union-find". It is
+    /// really more of a building block. If the values associated with
+    /// your key are non-trivial, you would probably prefer to call
+    /// `unify_var_var` below.
+    fn unify_roots(&mut self, key_a: S::Key, key_b: S::Key, new_value: S::Value) {
+        debug!("unify(key_a={:?}, key_b={:?})", key_a, key_b);
+
+        let rank_a = self.value(key_a).rank;
+        let rank_b = self.value(key_b).rank;
+        if let Some((new_root, redirected)) = S::Key::order_roots(
+            key_a,
+            &self.value(key_a).value,
+            key_b,
+            &self.value(key_b).value,
+        ) {
+            // compute the new rank for the new root that they chose;
+            // this may not be the optimal choice.
+            let new_rank = if new_root == key_a {
+                debug_assert!(redirected == key_b);
+                if rank_a > rank_b {
+                    rank_a
+                } else {
+                    rank_b + 1
+                }
+            } else {
+                debug_assert!(new_root == key_b);
+                debug_assert!(redirected == key_a);
+                if rank_b > rank_a {
+                    rank_b
+                } else {
+                    rank_a + 1
+                }
+            };
+            self.redirect_root(new_rank, redirected, new_root, new_value);
+        } else if rank_a > rank_b {
+            // a has greater rank, so a should become b's parent,
+            // i.e., b should redirect to a.
+            self.redirect_root(rank_a, key_b, key_a, new_value);
+        } else if rank_a < rank_b {
+            // b has greater rank, so a should redirect to b.
+            self.redirect_root(rank_b, key_a, key_b, new_value);
+        } else {
+            // If equal, redirect one to the other and increment the
+            // other's rank.
+            self.redirect_root(rank_a + 1, key_a, key_b, new_value);
+        }
+    }
+
+    /// Internal method to redirect `old_root_key` (which is currently
+    /// a root) to a child of `new_root_key` (which will remain a
+    /// root). The rank and value of `new_root_key` will be updated to
+    /// `new_rank` and `new_value` respectively.
+    fn redirect_root(
+        &mut self,
+        new_rank: u32,
+        old_root_key: S::Key,
+        new_root_key: S::Key,
+        new_value: S::Value,
+    ) {
+        self.update_value(old_root_key, |old_root_value| {
+            old_root_value.redirect(new_root_key);
+        });
+        self.update_value(new_root_key, |new_root_value| {
+            new_root_value.root(new_rank, new_value);
+        });
+    }
+}
+
+/// ////////////////////////////////////////////////////////////////////////
+/// Public API
+
+impl<S, K, V> UnificationTable<S>
+where
+    S: UnificationStoreMut<Key = K, Value = V>,
+    K: UnifyKey<Value = V>,
+    V: UnifyValue,
+{
+    /// Unions two keys without the possibility of failure; only
+    /// applicable when unify values use `NoError` as their error
+    /// type.
+    pub fn union<K1, K2>(&mut self, a_id: K1, b_id: K2)
+    where
+        K1: Into<K>,
+        K2: Into<K>,
+        V: UnifyValue<Error = NoError>,
+    {
+        self.unify_var_var(a_id, b_id).unwrap();
+    }
+
+    /// Unions a key and a value without the possibility of failure;
+    /// only applicable when unify values use `NoError` as their error
+    /// type.
+    pub fn union_value<K1>(&mut self, id: K1, value: V)
+    where
+        K1: Into<K>,
+        V: UnifyValue<Error = NoError>,
+    {
+        self.unify_var_value(id, value).unwrap();
+    }
+
+    /// Given two keys, indicates whether they have been unioned together.
+    pub fn unioned<K1, K2>(&mut self, a_id: K1, b_id: K2) -> bool
+    where
+        K1: Into<K>,
+        K2: Into<K>,
+    {
+        self.find(a_id) == self.find(b_id)
+    }
+
+    /// Given a key, returns the (current) root key.
+    pub fn find<K1>(&mut self, id: K1) -> K
+    where
+        K1: Into<K>,
+    {
+        let id = id.into();
+        self.uninlined_get_root_key(id)
+    }
+
+    /// Unions together two variables, merging their values. If
+    /// merging the values fails, the error is propagated and this
+    /// method has no effect.
+    pub fn unify_var_var<K1, K2>(&mut self, a_id: K1, b_id: K2) -> Result<(), V::Error>
+    where
+        K1: Into<K>,
+        K2: Into<K>,
+    {
+        let a_id = a_id.into();
+        let b_id = b_id.into();
+
+        let root_a = self.uninlined_get_root_key(a_id);
+        let root_b = self.uninlined_get_root_key(b_id);
+
+        if root_a == root_b {
+            return Ok(());
+        }
+
+        let combined = V::unify_values(&self.value(root_a).value, &self.value(root_b).value)?;
+
+        Ok(self.unify_roots(root_a, root_b, combined))
+    }
+
+    /// Sets the value of the key `a_id` to `b`, attempting to merge
+    /// with the previous value.
+    pub fn unify_var_value<K1>(&mut self, a_id: K1, b: V) -> Result<(), V::Error>
+    where
+        K1: Into<K>,
+    {
+        let a_id = a_id.into();
+        let root_a = self.uninlined_get_root_key(a_id);
+        let value = V::unify_values(&self.value(root_a).value, &b)?;
+        self.update_value(root_a, |node| node.value = value);
+        Ok(())
+    }
+
+    /// Returns the current value for the given key. If the key has
+    /// been union'd, this will give the value from the current root.
+    pub fn probe_value<K1>(&mut self, id: K1) -> V
+    where
+        K1: Into<K>,
+    {
+        self.inlined_probe_value(id)
+    }
+
+    // An always-inlined version of `probe_value`, for hot callsites.
+    #[inline(always)]
+    pub fn inlined_probe_value<K1>(&mut self, id: K1) -> V
+    where
+        K1: Into<K>,
+    {
+        let id = id.into();
+        let id = self.inlined_get_root_key(id);
+        self.value(id).value.clone()
+    }
+}
+
+///////////////////////////////////////////////////////////////////////////
+
+impl UnifyValue for () {
+    type Error = NoError;
+
+    fn unify_values(_: &(), _: &()) -> Result<(), NoError> {
+        Ok(())
+    }
+}
+
+impl<V: UnifyValue> UnifyValue for Option<V> {
+    type Error = V::Error;
+
+    fn unify_values(a: &Option<V>, b: &Option<V>) -> Result<Self, V::Error> {
+        match (a, b) {
+            (&None, &None) => Ok(None),
+            (&Some(ref v), &None) | (&None, &Some(ref v)) => Ok(Some(v.clone())),
+            (&Some(ref a), &Some(ref b)) => match V::unify_values(a, b) {
+                Ok(v) => Ok(Some(v)),
+                Err(err) => Err(err),
+            },
+        }
+    }
+}
diff --git a/vendor/ena/src/unify/tests.rs b/vendor/ena/src/unify/tests.rs
new file mode 100644
index 000000000..5665aba0c
--- /dev/null
+++ b/vendor/ena/src/unify/tests.rs
@@ -0,0 +1,486 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// Naming the benchmarks using uppercase letters helps them sort
+// better.
+#![allow(non_snake_case)]
+
+#[cfg(feature = "bench")]
+extern crate test;
+#[cfg(feature = "bench")]
+use self::test::Bencher;
+use std::cmp;
+#[cfg(feature = "persistent")]
+use unify::Persistent;
+use unify::{EqUnifyValue, InPlace, InPlaceUnificationTable, NoError, UnifyKey, UnifyValue};
+use unify::{UnificationStore, UnificationTable};
+
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+struct UnitKey(u32);
+
+impl UnifyKey for UnitKey {
+    type Value = ();
+    fn index(&self) -> u32 {
+        self.0
+    }
+    fn from_index(u: u32) -> UnitKey {
+        UnitKey(u)
+    }
+    fn tag() -> &'static str {
+        "UnitKey"
+    }
+}
+
+macro_rules! all_modes {
+    ($name:ident for $t:ty => $body:tt) => {
+        fn test_body<
+            $name: Clone + Default + UnificationStore<Key = $t, Value = <$t as UnifyKey>::Value>,
+        >() {
+            $body
+        }
+
+        test_body::<InPlace<$t>>();
+
+        #[cfg(feature = "persistent")]
+        test_body::<Persistent<$t>>();
+    };
+}
+
+#[test]
+fn basic() {
+    all_modes! {
+        S for UnitKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(());
+            let k2 = ut.new_key(());
+            assert_eq!(ut.unioned(k1, k2), false);
+            ut.union(k1, k2);
+            assert_eq!(ut.unioned(k1, k2), true);
+        }
+    }
+}
+
+#[test]
+fn big_array() {
+    all_modes! {
+        S for UnitKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let mut keys = Vec::new();
+            const MAX: usize = 1 << 15;
+
+            for _ in 0..MAX {
+                keys.push(ut.new_key(()));
+            }
+
+            for i in 1..MAX {
+                let l = keys[i - 1];
+                let r = keys[i];
+                ut.union(l, r);
+            }
+
+            for i in 0..MAX {
+                assert!(ut.unioned(keys[0], keys[i]));
+            }
+        }
+    }
+}
+
+#[cfg(feature = "bench")]
+fn big_array_bench_generic<S: Default + UnificationStore<Key = UnitKey, Value = ()>>(
+    b: &mut Bencher,
+) {
+    let mut ut: UnificationTable<S> = UnificationTable::new();
+    let mut keys = Vec::new();
+    const MAX: usize = 1 << 15;
+
+    for _ in 0..MAX {
+        keys.push(ut.new_key(()));
+    }
+
+    b.iter(|| {
+        for i in 1..MAX {
+            let l = keys[i - 1];
+            let r = keys[i];
+            ut.union(l, r);
+        }
+
+        for i in 0..MAX {
+            assert!(ut.unioned(keys[0], keys[i]));
+        }
+    })
+}
+
+#[cfg(feature = "bench")]
+#[bench]
+fn big_array_bench_InPlace(b: &mut Bencher) {
+    big_array_bench_generic::<InPlace<UnitKey>>(b);
+}
+
+#[cfg(all(feature = "bench", feature = "persistent"))]
+#[bench]
+fn big_array_bench_Persistent(b: &mut Bencher) {
+    big_array_bench_generic::<Persistent<UnitKey>>(b);
+}
+
+#[cfg(feature = "bench")]
+fn big_array_bench_in_snapshot_generic<S: Default + UnificationStore<Key = UnitKey, Value = ()>>(
+    b: &mut Bencher,
+) {
+    let mut ut: UnificationTable<S> = UnificationTable::new();
+    let mut keys = Vec::new();
+    const MAX: usize = 1 << 15;
+
+    for _ in 0..MAX {
+        keys.push(ut.new_key(()));
+    }
+
+    b.iter(|| {
+        let snapshot = ut.snapshot();
+
+        for i in 1..MAX {
+            let l = keys[i - 1];
+            let r = keys[i];
+            ut.union(l, r);
+        }
+
+        for i in 0..MAX {
+            assert!(ut.unioned(keys[0], keys[i]));
+        }
+
+        ut.rollback_to(snapshot);
+    })
+}
+
+#[cfg(feature = "bench")]
+#[bench]
+fn big_array_bench_in_snapshot_InPlace(b: &mut Bencher) {
+    big_array_bench_in_snapshot_generic::<InPlace<UnitKey>>(b);
+}
+
+#[cfg(all(feature = "bench", feature = "persistent"))]
+#[bench]
+fn big_array_bench_in_snapshot_Persistent(b: &mut Bencher) {
+    big_array_bench_in_snapshot_generic::<Persistent<UnitKey>>(b);
+}
+
+#[cfg(feature = "bench")]
+fn big_array_bench_clone_generic<
+    S: Default + Clone + UnificationStore<Key = UnitKey, Value = ()>,
+>(
+    b: &mut Bencher,
+) {
+    let mut ut: UnificationTable<S> = UnificationTable::new();
+    let mut keys = Vec::new();
+    const MAX: usize = 1 << 15;
+
+    for _ in 0..MAX {
+        keys.push(ut.new_key(()));
+    }
+
+    b.iter(|| {
+        let saved_table = ut.clone();
+
+        for i in 1..MAX {
+            let l = keys[i - 1];
+            let r = keys[i];
+            ut.union(l, r);
+        }
+
+        for i in 0..MAX {
+            assert!(ut.unioned(keys[0], keys[i]));
+        }
+
+        ut = saved_table;
+    })
+}
+
+#[cfg(feature = "bench")]
+#[bench]
+fn big_array_bench_clone_InPlace(b: &mut Bencher) {
+    big_array_bench_clone_generic::<InPlace<UnitKey>>(b);
+}
+
+#[cfg(all(feature = "bench", feature = "persistent"))]
+#[bench]
+fn big_array_bench_clone_Persistent(b: &mut Bencher) {
+    big_array_bench_clone_generic::<Persistent<UnitKey>>(b);
+}
+
+#[test]
+fn even_odd() {
+    all_modes! {
+        S for UnitKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let mut keys = Vec::new();
+            const MAX: usize = 1 << 10;
+
+            for i in 0..MAX {
+                let key = ut.new_key(());
+                keys.push(key);
+
+                if i >= 2 {
+                    ut.union(key, keys[i - 2]);
+                }
+            }
+
+            for i in 1..MAX {
+                assert!(!ut.unioned(keys[i - 1], keys[i]));
+            }
+
+            for i in 2..MAX {
+                assert!(ut.unioned(keys[i - 2], keys[i]));
+            }
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+struct IntKey(u32);
+
+impl UnifyKey for IntKey {
+    type Value = Option<i32>;
+    fn index(&self) -> u32 {
+        self.0
+    }
+    fn from_index(u: u32) -> IntKey {
+        IntKey(u)
+    }
+    fn tag() -> &'static str {
+        "IntKey"
+    }
+}
+
+impl EqUnifyValue for i32 {}
+
+#[test]
+fn unify_same_int_twice() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_value(k2, Some(22)).is_ok());
+            assert!(ut.unify_var_var(k1, k2).is_ok());
+            assert_eq!(ut.probe_value(k1), Some(22));
+        }
+    }
+}
+
+#[test]
+fn unify_vars_then_int_indirect() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            assert!(ut.unify_var_var(k1, k2).is_ok());
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert_eq!(ut.probe_value(k2), Some(22));
+        }
+    }
+}
+
+#[test]
+fn unify_vars_different_ints_1() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            assert!(ut.unify_var_var(k1, k2).is_ok());
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_value(k2, Some(23)).is_err());
+        }
+    }
+}
+
+#[test]
+fn unify_vars_different_ints_2() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            assert!(ut.unify_var_var(k2, k1).is_ok());
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_value(k2, Some(23)).is_err());
+        }
+    }
+}
+
+#[test]
+fn unify_distinct_ints_then_vars() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_value(k2, Some(23)).is_ok());
+            assert!(ut.unify_var_var(k2, k1).is_err());
+        }
+    }
+}
+
+#[test]
+fn unify_root_value_1() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            let k3 = ut.new_key(None);
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_var(k1, k2).is_ok());
+            assert!(ut.unify_var_value(k3, Some(23)).is_ok());
+            assert!(ut.unify_var_var(k1, k3).is_err());
+        }
+    }
+}
+
+#[test]
+fn unify_root_value_2() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            let k3 = ut.new_key(None);
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_var(k2, k1).is_ok());
+            assert!(ut.unify_var_value(k3, Some(23)).is_ok());
+            assert!(ut.unify_var_var(k1, k3).is_err());
+        }
+    }
+}
+
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq)]
+struct OrderedKey(u32);
+
+#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, PartialOrd, Ord)]
+struct OrderedRank(u32);
+
+impl UnifyKey for OrderedKey {
+    type Value = OrderedRank;
+    fn index(&self) -> u32 {
+        self.0
+    }
+    fn from_index(u: u32) -> OrderedKey {
+        OrderedKey(u)
+    }
+    fn tag() -> &'static str {
+        "OrderedKey"
+    }
+    fn order_roots(
+        a: OrderedKey,
+        a_rank: &OrderedRank,
+        b: OrderedKey,
+        b_rank: &OrderedRank,
+    ) -> Option<(OrderedKey, OrderedKey)> {
+        println!("{:?} vs {:?}", a_rank, b_rank);
+        if a_rank > b_rank {
+            Some((a, b))
+        } else if b_rank > a_rank {
+            Some((b, a))
+        } else {
+            None
+        }
+    }
+}
+
+impl UnifyValue for OrderedRank {
+    type Error = NoError;
+
+    fn unify_values(value1: &Self, value2: &Self) -> Result<Self, NoError> {
+        Ok(OrderedRank(cmp::max(value1.0, value2.0)))
+    }
+}
+
+#[test]
+fn ordered_key() {
+    all_modes! {
+        S for OrderedKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+
+            let k0_1 = ut.new_key(OrderedRank(0));
+            let k0_2 = ut.new_key(OrderedRank(0));
+            let k0_3 = ut.new_key(OrderedRank(0));
+            let k0_4 = ut.new_key(OrderedRank(0));
+
+            ut.union(k0_1, k0_2); // rank of one of those will now be 1
+            ut.union(k0_3, k0_4); // rank of new root also 1
+            ut.union(k0_1, k0_3); // rank of new root now 2
+
+            let k0_5 = ut.new_key(OrderedRank(0));
+            let k0_6 = ut.new_key(OrderedRank(0));
+            ut.union(k0_5, k0_6); // rank of new root now 1
+
+            ut.union(k0_1, k0_5); // new root rank 2, should not be k0_5 or k0_6
+            assert!(vec![k0_1, k0_2, k0_3, k0_4].contains(&ut.find(k0_1)));
+        }
+    }
+}
+
+#[test]
+fn ordered_key_k1() {
+    all_modes! {
+        S for UnitKey => {
+            let mut ut: InPlaceUnificationTable<OrderedKey> = UnificationTable::new();
+
+            let k0_1 = ut.new_key(OrderedRank(0));
+            let k0_2 = ut.new_key(OrderedRank(0));
+            let k0_3 = ut.new_key(OrderedRank(0));
+            let k0_4 = ut.new_key(OrderedRank(0));
+
+            ut.union(k0_1, k0_2); // rank of one of those will now be 1
+            ut.union(k0_3, k0_4); // rank of new root also 1
+            ut.union(k0_1, k0_3); // rank of new root now 2
+
+            let k1_5 = ut.new_key(OrderedRank(1));
+            let k1_6 = ut.new_key(OrderedRank(1));
+            ut.union(k1_5, k1_6); // rank of new root now 1
+
+            ut.union(k0_1, k1_5); // even though k1 has lower rank, it wins
+            assert!(
+                vec![k1_5, k1_6].contains(&ut.find(k0_1)),
+                "unexpected choice for root: {:?}",
+                ut.find(k0_1)
+            );
+        }
+    }
+}
+
+/// Test that we *can* clone.
+#[test]
+fn clone_table() {
+    all_modes! {
+        S for IntKey => {
+            let mut ut: UnificationTable<S> = UnificationTable::new();
+            let k1 = ut.new_key(None);
+            let k2 = ut.new_key(None);
+            let k3 = ut.new_key(None);
+            assert!(ut.unify_var_value(k1, Some(22)).is_ok());
+            assert!(ut.unify_var_value(k2, Some(22)).is_ok());
+            assert!(ut.unify_var_var(k1, k2).is_ok());
+            assert_eq!(ut.probe_value(k3), None);
+
+            let mut ut1 = ut.clone();
+            assert_eq!(ut1.probe_value(k1), Some(22));
+            assert_eq!(ut1.probe_value(k3), None);
+
+            assert!(ut.unify_var_value(k3, Some(44)).is_ok());
+
+            assert_eq!(ut1.probe_value(k1), Some(22));
+            assert_eq!(ut1.probe_value(k3), None);
+            assert_eq!(ut.probe_value(k3), Some(44));
+        }
+    }
+}