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 compiler = match rustc_version() { Some(compiler) => compiler, None => return, }; if compiler.minor < 36 { println!("cargo:rustc-cfg=syn_omit_await_from_token_macro"); } if !compiler.nightly { println!("cargo:rustc-cfg=syn_disable_nightly_tests"); } } struct Compiler { minor: u32, nightly: bool, } fn rustc_version() -> Option { 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; } let minor = pieces.next()?.parse().ok()?; let nightly = version.contains("nightly"); Some(Compiler { minor, nightly }) }