diff --git a/src/librustc/hir/mod.rs b/src/librustc/hir/mod.rs
index caae79961a6d1..2b0e17bfb5cdc 100644
--- a/src/librustc/hir/mod.rs
+++ b/src/librustc/hir/mod.rs
@@ -930,7 +930,7 @@ pub enum PatKind {
     Slice(HirVec<P<Pat>>, Option<P<Pat>>, HirVec<P<Pat>>),
 }
 
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum Mutability {
     MutMutable,
     MutImmutable,
@@ -1523,7 +1523,7 @@ pub struct Destination {
     pub target_id: Result<NodeId, LoopIdError>,
 }
 
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum GeneratorMovability {
     Static,
     Movable,
@@ -1775,7 +1775,7 @@ pub enum IsAuto {
     No
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug)]
+#[derive(Copy, Clone, PartialEq, Eq,PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash, Debug)]
 pub enum Unsafety {
     Unsafe,
     Normal,
diff --git a/src/librustc/middle/const_val.rs b/src/librustc/middle/const_val.rs
index 3a76f75d01833..d7f116705113e 100644
--- a/src/librustc/middle/const_val.rs
+++ b/src/librustc/middle/const_val.rs
@@ -22,7 +22,7 @@ use rustc_data_structures::sync::Lrc;
 
 pub type EvalResult<'tcx> = Result<&'tcx ty::Const<'tcx>, ConstEvalErr<'tcx>>;
 
-#[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq)]
+#[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
 pub enum ConstVal<'tcx> {
     Unevaluated(DefId, &'tcx Substs<'tcx>),
     Value(ConstValue<'tcx>),
diff --git a/src/librustc/mir/interpret/mod.rs b/src/librustc/mir/interpret/mod.rs
index 9827ee51ba29d..48954b1f0aa7e 100644
--- a/src/librustc/mir/interpret/mod.rs
+++ b/src/librustc/mir/interpret/mod.rs
@@ -109,7 +109,7 @@ pub trait PointerArithmetic: layout::HasDataLayout {
 impl<T: layout::HasDataLayout> PointerArithmetic for T {}
 
 
-#[derive(Copy, Clone, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Hash)]
+#[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
 pub struct MemoryPointer {
     pub alloc_id: AllocId,
     pub offset: Size,
@@ -335,7 +335,7 @@ impl<'tcx, M: fmt::Debug + Eq + Hash + Clone> AllocMap<'tcx, M> {
     }
 }
 
-#[derive(Clone, Debug, Eq, PartialEq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct Allocation {
     /// The actual bytes of the allocation.
     /// Note that the bytes of a pointer represent the offset of the pointer
@@ -384,7 +384,7 @@ impl Allocation {
 
 impl<'tcx> ::serialize::UseSpecializedDecodable for &'tcx Allocation {}
 
-#[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct Relocations(SortedMap<Size, AllocId>);
 
 impl Relocations {
@@ -455,7 +455,7 @@ pub fn read_target_uint(endianness: layout::Endian, mut source: &[u8]) -> Result
 type Block = u64;
 const BLOCK_SIZE: u64 = 64;
 
-#[derive(Clone, Debug, Eq, PartialEq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct UndefMask {
     blocks: Vec<Block>,
     len: Size,
diff --git a/src/librustc/mir/interpret/value.rs b/src/librustc/mir/interpret/value.rs
index 5ac2f7f356ead..7ad6826b2f678 100644
--- a/src/librustc/mir/interpret/value.rs
+++ b/src/librustc/mir/interpret/value.rs
@@ -7,7 +7,7 @@ use super::{EvalResult, MemoryPointer, PointerArithmetic, Allocation};
 
 /// Represents a constant value in Rust. ByVal and ByValPair are optimizations which
 /// matches Value's optimizations for easy conversions between these two types
-#[derive(Clone, Copy, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Hash)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash)]
 pub enum ConstValue<'tcx> {
     /// Used only for types with layout::abi::Scalar ABI and ZSTs which use PrimVal::Undef
     ByVal(PrimVal),
@@ -76,7 +76,7 @@ impl<'tcx> ConstValue<'tcx> {
 /// For optimization of a few very common cases, there is also a representation for a pair of
 /// primitive values (`ByValPair`). It allows Miri to avoid making allocations for checked binary
 /// operations and fat pointers. This idea was taken from rustc's codegen.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Hash)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
 pub enum Value {
     ByRef(Pointer, Align),
     ByVal(PrimVal),
@@ -99,7 +99,7 @@ impl<'tcx> ty::TypeFoldable<'tcx> for Value {
 /// I (@oli-obk) believe it is less easy to mix up generic primvals and primvals that are just
 /// the representation of pointers. Also all the sites that convert between primvals and pointers
 /// are explicit now (and rare!)
-#[derive(Clone, Copy, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Hash)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
 pub struct Pointer {
     pub primval: PrimVal,
 }
@@ -194,7 +194,7 @@ impl ::std::convert::From<MemoryPointer> for Pointer {
 /// `memory::Allocation`. It is in many ways like a small chunk of a `Allocation`, up to 8 bytes in
 /// size. Like a range of bytes in an `Allocation`, a `PrimVal` can either represent the raw bytes
 /// of a simple value, a pointer into another `Allocation`, or be undefined.
-#[derive(Clone, Copy, Debug, Eq, PartialEq, RustcEncodable, RustcDecodable, Hash)]
+#[derive(Clone, Copy, Debug, Eq, PartialEq, Ord, PartialOrd, RustcEncodable, RustcDecodable, Hash)]
 pub enum PrimVal {
     /// The raw bytes of a simple value.
     Bytes(u128),
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index b975f9e519586..4507da1c698e9 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -39,7 +39,7 @@ use util::nodemap::{NodeSet, DefIdMap, FxHashMap};
 
 use serialize::{self, Encodable, Encoder};
 use std::cell::RefCell;
-use std::cmp;
+use std::cmp::{self, Ordering};
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::ops::Deref;
@@ -491,6 +491,18 @@ pub struct TyS<'tcx> {
     region_depth: u32,
 }
 
+impl<'tcx> Ord for TyS<'tcx> {
+    fn cmp(&self, other: &TyS<'tcx>) -> Ordering {
+        self.sty.cmp(&other.sty)
+    }
+}
+
+impl<'tcx> PartialOrd for TyS<'tcx> {
+    fn partial_cmp(&self, other: &TyS<'tcx>) -> Option<Ordering> {
+        Some(self.sty.cmp(&other.sty))
+    }
+}
+
 impl<'tcx> PartialEq for TyS<'tcx> {
     #[inline]
     fn eq(&self, other: &TyS<'tcx>) -> bool {
@@ -578,6 +590,22 @@ impl <'gcx: 'tcx, 'tcx> Canonicalize<'gcx, 'tcx> for Ty<'tcx> {
 #[derive(Debug, RustcEncodable)]
 pub struct Slice<T>([T]);
 
+impl<T> Ord for Slice<T> where T: Ord {
+    fn cmp(&self, other: &Slice<T>) -> Ordering {
+        if self == other { Ordering::Equal } else {
+            <[T] as Ord>::cmp(&self.0, &other.0)
+        }
+    }
+}
+
+impl<T> PartialOrd for Slice<T> where T: PartialOrd {
+    fn partial_cmp(&self, other: &Slice<T>) -> Option<Ordering> {
+        if self == other { Some(Ordering::Equal) } else {
+            <[T] as PartialOrd>::partial_cmp(&self.0, &other.0)
+        }
+    }
+}
+
 impl<T> PartialEq for Slice<T> {
     #[inline]
     fn eq(&self, other: &Slice<T>) -> bool {
@@ -1104,7 +1132,7 @@ impl<'tcx> PolyTraitPredicate<'tcx> {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct OutlivesPredicate<A,B>(pub A, pub B); // `A : B`
 pub type PolyOutlivesPredicate<A,B> = ty::Binder<OutlivesPredicate<A,B>>;
 pub type RegionOutlivesPredicate<'tcx> = OutlivesPredicate<ty::Region<'tcx>,
@@ -1606,6 +1634,20 @@ pub struct AdtDef {
     pub repr: ReprOptions,
 }
 
+impl PartialOrd for AdtDef {
+    fn partial_cmp(&self, other: &AdtDef) -> Option<Ordering> {
+        Some(self.cmp(&other))
+    }
+}
+
+/// There should be only one AdtDef for each `did`, therefore
+/// it is fine to implement `Ord` only based on `did`.
+impl Ord for AdtDef {
+    fn cmp(&self, other: &AdtDef) -> Ordering {
+        self.did.cmp(&other.did)
+    }
+}
+
 impl PartialEq for AdtDef {
     // AdtDef are always interned and this is part of TyS equality
     #[inline]
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index d9797bf4985b4..faf93ab30b70a 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -34,7 +34,7 @@ use hir;
 use self::InferTy::*;
 use self::TypeVariants::*;
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct TypeAndMut<'tcx> {
     pub ty: Ty<'tcx>,
     pub mutbl: hir::Mutability,
@@ -80,7 +80,7 @@ impl BoundRegion {
 
 /// NB: If you change this, you'll probably want to change the corresponding
 /// AST structure in libsyntax/ast.rs as well.
-#[derive(Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub enum TypeVariants<'tcx> {
     /// The primitive boolean type. Written as `bool`.
     TyBool,
@@ -268,7 +268,7 @@ pub enum TypeVariants<'tcx> {
 ///
 /// It'd be nice to split this struct into ClosureSubsts and
 /// GeneratorSubsts, I believe. -nmatsakis
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct ClosureSubsts<'tcx> {
     /// Lifetime and type parameters from the enclosing function,
     /// concatenated with the types of the upvars.
@@ -351,7 +351,7 @@ impl<'tcx> ClosureSubsts<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct GeneratorSubsts<'tcx> {
     pub substs: &'tcx Substs<'tcx>,
 }
@@ -484,7 +484,7 @@ impl<'tcx> UpvarSubsts<'tcx> {
     }
 }
 
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Debug, Copy, Clone, PartialEq, PartialOrd, Ord, Eq, Hash, RustcEncodable, RustcDecodable)]
 pub enum ExistentialPredicate<'tcx> {
     /// e.g. Iterator
     Trait(ExistentialTraitRef<'tcx>),
@@ -660,7 +660,7 @@ impl<'tcx> PolyTraitRef<'tcx> {
 ///
 /// The substitutions don't include the erased `Self`, only trait
 /// type and lifetime parameters (`[X, Y]` and `['a, 'b]` above).
-#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct ExistentialTraitRef<'tcx> {
     pub def_id: DefId,
     pub substs: &'tcx Substs<'tcx>,
@@ -728,7 +728,7 @@ impl<'tcx> PolyExistentialTraitRef<'tcx> {
 /// erase, or otherwise "discharge" these bound regions, we change the
 /// type from `Binder<T>` to just `T` (see
 /// e.g. `liberate_late_bound_regions`).
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct Binder<T>(T);
 
 impl<T> Binder<T> {
@@ -834,7 +834,7 @@ impl<T> Binder<T> {
 
 /// Represents the projection of an associated type. In explicit UFCS
 /// form this would be written `<T as Trait<..>>::N`.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct ProjectionTy<'tcx> {
     /// The parameters of the associated item.
     pub substs: &'tcx Substs<'tcx>,
@@ -902,7 +902,7 @@ impl<'tcx> PolyGenSig<'tcx> {
 /// - `inputs` is the list of arguments and their modes.
 /// - `output` is the return type.
 /// - `variadic` indicates whether this is a variadic function. (only true for foreign fns)
-#[derive(Copy, Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct FnSig<'tcx> {
     pub inputs_and_output: &'tcx Slice<Ty<'tcx>>,
     pub variadic: bool,
@@ -946,7 +946,7 @@ impl<'tcx> PolyFnSig<'tcx> {
     }
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct ParamTy {
     pub idx: u32,
     pub name: InternedString,
@@ -1148,17 +1148,17 @@ pub struct EarlyBoundRegion {
     pub name: InternedString,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct TyVid {
     pub index: u32,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct IntVid {
     pub index: u32,
 }
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub struct FloatVid {
     pub index: u32,
 }
@@ -1169,7 +1169,7 @@ newtype_index!(RegionVid
         DEBUG_FORMAT = custom,
     });
 
-#[derive(Clone, Copy, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable)]
 pub enum InferTy {
     TyVar(TyVid),
     IntVar(IntVid),
@@ -1189,7 +1189,7 @@ pub enum InferTy {
 newtype_index!(CanonicalVar);
 
 /// A `ProjectionPredicate` for an `ExistentialTraitRef`.
-#[derive(Clone, Copy, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct ExistentialProjection<'tcx> {
     pub item_def_id: DefId,
     pub substs: &'tcx Substs<'tcx>,
@@ -1758,7 +1758,7 @@ impl<'a, 'gcx, 'tcx> TyS<'tcx> {
 }
 
 /// Typed constant value.
-#[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq)]
+#[derive(Copy, Clone, Debug, Hash, RustcEncodable, RustcDecodable, Eq, PartialEq, Ord, PartialOrd)]
 pub struct Const<'tcx> {
     pub ty: Ty<'tcx>,
 
diff --git a/src/librustc/ty/subst.rs b/src/librustc/ty/subst.rs
index f44e1533f520a..2e3c6df9754df 100644
--- a/src/librustc/ty/subst.rs
+++ b/src/librustc/ty/subst.rs
@@ -20,6 +20,7 @@ use rustc_data_structures::accumulate_vec::AccumulateVec;
 use rustc_data_structures::array_vec::ArrayVec;
 
 use core::intrinsics;
+use std::cmp::Ordering;
 use std::fmt;
 use std::marker::PhantomData;
 use std::mem;
@@ -70,6 +71,28 @@ impl<'tcx> UnpackedKind<'tcx> {
     }
 }
 
+impl<'tcx> Ord for Kind<'tcx> {
+    fn cmp(&self, other: &Kind) -> Ordering {
+        match (self.unpack(), other.unpack()) {
+            (UnpackedKind::Type(_), UnpackedKind::Lifetime(_)) => Ordering::Greater,
+
+            (UnpackedKind::Type(ty1), UnpackedKind::Type(ty2)) => {
+                ty1.sty.cmp(&ty2.sty)
+            }
+
+            (UnpackedKind::Lifetime(reg1), UnpackedKind::Lifetime(reg2)) => reg1.cmp(reg2),
+
+            (UnpackedKind::Lifetime(_), UnpackedKind::Type(_))  => Ordering::Less,
+        }
+    }
+}
+
+impl<'tcx> PartialOrd for Kind<'tcx> {
+    fn partial_cmp(&self, other: &Kind) -> Option<Ordering> {
+        Some(self.cmp(&other))
+    }
+}
+
 impl<'tcx> From<ty::Region<'tcx>> for Kind<'tcx> {
     fn from(r: ty::Region<'tcx>) -> Kind<'tcx> {
         UnpackedKind::Lifetime(r).pack()
diff --git a/src/librustc_data_structures/sorted_map.rs b/src/librustc_data_structures/sorted_map.rs
index e14bd33c82c1a..9f1a795b35004 100644
--- a/src/librustc_data_structures/sorted_map.rs
+++ b/src/librustc_data_structures/sorted_map.rs
@@ -22,7 +22,8 @@ use std::ops::{RangeBounds, Bound, Index, IndexMut};
 /// stores data in a more compact way. It also supports accessing contiguous
 /// ranges of elements as a slice, and slices of already sorted elements can be
 /// inserted efficiently.
-#[derive(Clone, PartialEq, Eq, Hash, Default, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, Hash, Default, Debug, RustcEncodable,
+         RustcDecodable)]
 pub struct SortedMap<K: Ord, V> {
     data: Vec<(K,V)>
 }
diff --git a/src/librustc_target/abi/mod.rs b/src/librustc_target/abi/mod.rs
index 7f593aff21d2b..4b11de097738e 100644
--- a/src/librustc_target/abi/mod.rs
+++ b/src/librustc_target/abi/mod.rs
@@ -332,7 +332,7 @@ impl AddAssign for Size {
 /// Each field is a power of two, giving the alignment a maximum value
 /// of 2<sup>(2<sup>8</sup> - 1)</sup>, which is limited by LLVM to a
 /// maximum capacity of 2<sup>29</sup> or 536870912.
-#[derive(Copy, Clone, PartialEq, Eq, Hash, Debug, RustcEncodable, RustcDecodable)]
+#[derive(Copy, Clone, PartialEq, Eq, Ord, PartialOrd, Hash, Debug, RustcEncodable, RustcDecodable)]
 pub struct Align {
     abi_pow2: u8,
     pref_pow2: u8,
diff --git a/src/librustc_target/spec/abi.rs b/src/librustc_target/spec/abi.rs
index ed2eb20990695..927d224389ffc 100644
--- a/src/librustc_target/spec/abi.rs
+++ b/src/librustc_target/spec/abi.rs
@@ -10,7 +10,7 @@
 
 use std::fmt;
 
-#[derive(PartialEq, Eq, Hash, RustcEncodable, RustcDecodable, Clone, Copy, Debug)]
+#[derive(PartialEq, Eq, PartialOrd, Ord, Hash, RustcEncodable, RustcDecodable, Clone, Copy, Debug)]
 pub enum Abi {
     // NB: This ordering MUST match the AbiDatas array below.
     // (This is ensured by the test indices_are_correct().)
diff --git a/src/libsyntax/ast.rs b/src/libsyntax/ast.rs
index 72d5323a8722a..e1e220f49c97c 100644
--- a/src/libsyntax/ast.rs
+++ b/src/libsyntax/ast.rs
@@ -667,7 +667,7 @@ pub enum PatKind {
     Mac(Mac),
 }
 
-#[derive(Clone, PartialEq, Eq, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
+#[derive(Clone, PartialEq, Eq, PartialOrd, Ord, RustcEncodable, RustcDecodable, Hash, Debug, Copy)]
 pub enum Mutability {
     Mutable,
     Immutable,