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use std::env;
use std::fs;
use std::iter;
use std::path::{self, Path};
/*
#[doc(hidden)]
#[macro_export]
macro_rules! count {
() => { proc_macro_call_0!() };
(!) => { proc_macro_call_1!() };
(!!) => { proc_macro_call_2!() };
...
}
*/
fn main() {
// Tell Cargo not to rerun on src/lib.rs changes.
println!("cargo:rerun-if-changed=build.rs");
let mut content = String::new();
content += "#[doc(hidden)]\n";
content += "#[macro_export]\n";
content += "macro_rules! count {\n";
for i in 0..=64 {
let bangs = iter::repeat("!").take(i).collect::<String>();
content += &format!(" ({}) => {{ proc_macro_call_{}!() }};\n", bangs, i);
}
content += " ($(!)+) => {\n";
content += " compile_error! {\n";
content += " \"this macro does not support >64 nested macro invocations\"\n";
content += " }\n";
content += " };\n";
content += "}\n";
let content = content.as_bytes();
let out_dir = env::var("OUT_DIR").unwrap();
let ref dest_path = Path::new(&out_dir).join("count.rs");
// Avoid bumping filetime if content is up to date. Possibly related to
// https://github.com/dtolnay/proc-macro-hack/issues/56 ...?
if fs::read(dest_path)
.map(|existing| existing != content)
.unwrap_or(true)
{
fs::write(dest_path, content).unwrap();
}
println!("cargo:rustc-env=PATH_SEPARATOR={}", path::MAIN_SEPARATOR);
}
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