Fix incomplete ICH implementation for ty::subst::UnpackedKind.

Author: michaelwoerister

src/librustc/ich/impls_ty.rs

@@ -67,6 +67,7 @@ for ty::subst::UnpackedKind<'gcx> {
     fn hash_stable<W: StableHasherResult>(&self,
                                           hcx: &mut StableHashingContext<'a>,
                                           hasher: &mut StableHasher<W>) {
+        mem::discriminant(self).hash_stable(hcx, hasher);
         match self {
             ty::subst::UnpackedKind::Lifetime(lt) => lt.hash_stable(hcx, hasher),
             ty::subst::UnpackedKind::Type(ty) => ty.hash_stable(hcx, hasher),