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 2f31fc65..d1fe77e8 100644
8--- b/src/lib.rs
9+++ a/src/lib.rs
10@@ -3,6 +3,7 @@
11 #![crate_type = "proc-macro"]
12 #![forbid(unsafe_code)]
13 #![warn(rust_2018_idioms, trivial_casts, unused_qualifications)]
14+extern crate proc_macro;
15
16 use proc_macro2::{Ident, TokenStream};
17 use quote::{format_ident, quote};
18