4 #![crate_type = "proc-macro"]
6 extern crate proc_macro;
8 use proc_macro::TokenStream;
10 #[proc_macro_derive(AToB)]
11 pub fn derive(input: TokenStream) -> TokenStream {
12 let input = input.to_string();
13 assert_eq!(input, "struct A ;");
14 "struct B;".parse().unwrap()