Allow putting Ident and Lifetime in a btree set
diff --git a/src/generics.rs b/src/generics.rs
index 276a7b0..0aeb29a 100644
--- a/src/generics.rs
+++ b/src/generics.rs
@@ -58,7 +58,7 @@
     }
 }
 
-#[derive(Debug, Clone, Eq, PartialEq, Hash)]
+#[derive(Debug, Clone, Eq, PartialEq, Hash, Ord, PartialOrd)]
 pub struct Lifetime {
     pub ident: Ident,
 }
diff --git a/src/ident.rs b/src/ident.rs
index 5989aae..8f698be 100644
--- a/src/ident.rs
+++ b/src/ident.rs
@@ -1,7 +1,7 @@
 use std::borrow::Cow;
 use std::fmt::{self, Display};
 
-#[derive(Debug, Clone, Eq, Hash)]
+#[derive(Debug, Clone, Eq, Hash, Ord, PartialOrd)]
 pub struct Ident(String);
 
 impl Ident {