Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 1 | use std::env; |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 2 | use std::fs; |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 3 | use std::iter; |
| 4 | use std::path::Path; |
| 5 | |
| 6 | /* |
| 7 | #[doc(hidden)] |
| 8 | #[macro_export] |
| 9 | macro_rules! count { |
| 10 | () => { proc_macro_call_0!() }; |
| 11 | (!) => { proc_macro_call_1!() }; |
| 12 | (!!) => { proc_macro_call_2!() }; |
| 13 | ... |
| 14 | } |
| 15 | */ |
| 16 | |
| 17 | fn main() { |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 18 | // Tell Cargo not to rerun on src/lib.rs changes. |
| 19 | println!("cargo:rerun-if-changed=build.rs"); |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 20 | |
| 21 | let mut content = String::new(); |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 22 | content += "#[doc(hidden)]\n"; |
| 23 | content += "#[macro_export]\n"; |
| 24 | content += "macro_rules! count {\n"; |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 25 | for i in 0..=64 { |
| 26 | let bangs = iter::repeat("!").take(i).collect::<String>(); |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 27 | content += &format!(" ({}) => {{ proc_macro_call_{}!() }};\n", bangs, i); |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 28 | } |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 29 | content += " ($(!)+) => {\n"; |
| 30 | content += " compile_error! { \"this macro does not support >64 nested macro invocations\" }\n"; |
| 31 | content += " };\n"; |
| 32 | content += "}\n"; |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 33 | |
Haibo Huang | 58095de | 2020-07-10 20:23:47 -0700 | [diff] [blame] | 34 | let content = content.as_bytes(); |
| 35 | let out_dir = env::var("OUT_DIR").unwrap(); |
| 36 | let ref dest_path = Path::new(&out_dir).join("count.rs"); |
| 37 | |
| 38 | // Avoid bumping filetime if content is up to date. Possibly related to |
| 39 | // https://github.com/dtolnay/proc-macro-hack/issues/56 ...? |
| 40 | if fs::read(dest_path) |
| 41 | .map(|existing| existing != content) |
| 42 | .unwrap_or(true) |
| 43 | { |
| 44 | fs::write(dest_path, content).unwrap(); |
| 45 | } |
Jason Macnak | bbac34b | 2020-03-25 01:28:44 +0000 | [diff] [blame] | 46 | } |