Preserve original tokens of Signature
diff --git a/syntax/impls.rs b/syntax/impls.rs
index 57b42d1..27aa43a 100644
--- a/syntax/impls.rs
+++ b/syntax/impls.rs
@@ -116,6 +116,7 @@
             args,
             ret,
             throws,
+            tokens: _,
         } = self;
         let Signature {
             fn_token: _,
@@ -123,6 +124,7 @@
             args: args2,
             ret: ret2,
             throws: throws2,
+            tokens: _,
         } = other;
         receiver == receiver2 && args == args2 && ret == ret2 && throws == throws2
     }
@@ -136,6 +138,7 @@
             args,
             ret,
             throws,
+            tokens: _,
         } = self;
         receiver.hash(state);
         args.hash(state);