Preserve lifetimes on parsed references
diff --git a/syntax/mod.rs b/syntax/mod.rs
index 3a2bb93..cf811cf 100644
--- a/syntax/mod.rs
+++ b/syntax/mod.rs
@@ -19,7 +19,7 @@
 use proc_macro2::{Ident, Span};
 use syn::punctuated::Punctuated;
 use syn::token::{Brace, Bracket, Paren};
-use syn::{LitStr, Token};
+use syn::{Lifetime, LitStr, Token};
 
 pub use self::atom::Atom;
 pub use self::doc::Doc;
@@ -76,6 +76,7 @@
 
 pub struct Receiver {
     pub ampersand: Token![&],
+    pub lifetime: Option<Lifetime>,
     pub mutability: Option<Token![mut]>,
     pub var: Token![self],
     pub ty: Ident,
@@ -102,6 +103,7 @@
 
 pub struct Ref {
     pub ampersand: Token![&],
+    pub lifetime: Option<Lifetime>,
     pub mutability: Option<Token![mut]>,
     pub inner: Type,
 }