1 2--- 3 src/lib.rs | 1 + 4 1 file changed, 1 insertion(+) 5 6diff --git b/src/lib.rs a/src/lib.rs 7index d3eab1a0..8a9561ba 100644 8--- b/src/lib.rs 9+++ a/src/lib.rs 10@@ -1,3 +1,4 @@ 11+extern crate proc_macro; 12 use proc_macro::TokenStream; 13 use proc_macro2::{Group, TokenStream as TokenStream2, TokenTree}; 14 use quote::quote; 15