| use std::env; |
| use std::fs::File; |
| use std::io::Write; |
| use std::iter; |
| use std::path::Path; |
| |
| /* |
| #[doc(hidden)] |
| #[macro_export] |
| macro_rules! count { |
| () => { proc_macro_call_0!() }; |
| (!) => { proc_macro_call_1!() }; |
| (!!) => { proc_macro_call_2!() }; |
| ... |
| } |
| */ |
| |
| fn main() { |
| let out_dir = env::var("OUT_DIR").unwrap(); |
| let dest_path = Path::new(&out_dir).join("count.rs"); |
| let mut f = File::create(&dest_path).unwrap(); |
| |
| let mut content = String::new(); |
| content += " |
| #[doc(hidden)] |
| #[macro_export] |
| macro_rules! count { |
| "; |
| for i in 0..=64 { |
| let bangs = iter::repeat("!").take(i).collect::<String>(); |
| content += &format!("({}) => {{ proc_macro_call_{}!() }};", bangs, i); |
| } |
| content += " |
| ($(!)+) => { |
| compile_error!(\"this macro does not support >64 nested macro invocations\") |
| }; |
| } |
| "; |
| |
| f.write_all(content.as_bytes()).unwrap(); |
| } |