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use std::env;
use std::process::Command;
use std::str;
// The rustc-cfg strings below are *not* public API. Please let us know by
// opening a GitHub issue if your build environment requires some way to enable
// these cfgs other than by executing our build script.
fn main() {
let minor = match rustc_minor_version() {
Some(minor) => minor,
None => return,
};
// Function-like procedural macros in expressions, patterns, and statements
// stabilized in Rust 1.45:
// https://blog.rust-lang.org/2020/07/16/Rust-1.45.0.html#stabilizing-function-like-procedural-macros-in-expressions-patterns-and-statements
if minor < 45 {
println!("cargo:rustc-cfg=need_proc_macro_hack");
}
}
fn rustc_minor_version() -> Option<u32> {
let rustc = env::var_os("RUSTC")?;
let output = Command::new(rustc).arg("--version").output().ok()?;
let version = str::from_utf8(&output.stdout).ok()?;
let mut pieces = version.split('.');
if pieces.next() != Some("rustc 1") {
return None;
}
pieces.next()?.parse().ok()
}
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