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