#![allow(clippy::uninlined_format_args)]

use std::env;

use std::ffi::OsString;

use std::iter;

use std::process::{self, Command, Stdio};

fn main() {

println!("cargo:rerun-if-changed=build.rs");

// Note: add "/build.rs" to package.include in Cargo.toml if adding any

// conditional compilation within the library.

println!("cargo:rustc-cfg=check_cfg");

println!("cargo:rustc-check-cfg=cfg(check_cfg)");

println!("cargo:rustc-check-cfg=cfg(fuzzing)");

println!("cargo:rustc-check-cfg=cfg(syn_disable_nightly_tests)");

println!("cargo:rustc-check-cfg=cfg(syn_only)");

if !unstable() {

println!("cargo:rustc-cfg=syn_disable_nightly_tests");

}

}

fn unstable() -> bool {

let rustc = cargo_env_var("RUSTC");

let rustc_wrapper = env::var_os("RUSTC_WRAPPER").filter(|wrapper| !wrapper.is_empty());

let rustc_workspace_wrapper =

env::var_os("RUSTC_WORKSPACE_WRAPPER").filter(|wrapper| !wrapper.is_empty());

let mut rustc = rustc_wrapper

.into_iter()

.chain(rustc_workspace_wrapper)

.chain(iter::once(rustc));

let mut cmd = Command::new(rustc.next().unwrap());

cmd.args(rustc);

cmd.stdin(Stdio::null());

cmd.stdout(Stdio::null());

cmd.stderr(Stdio::null());

cmd.arg("-");

// Find out whether this is a nightly or dev build.

cmd.env_remove("RUSTC_BOOTSTRAP");

cmd.arg("-Zcrate-attr=feature(rustc_private)");

// Pass `-Zunpretty` to terminate earlier without writing out any "emit"

// files. Use `expanded` to proceed far enough to actually apply crate

// attrs. With `unpretty=normal` or `--print`, not enough compilation

// happens to recognize that the feature attribute is unstable.

cmd.arg("-Zunpretty=expanded");

// Set #![no_std] to bypass loading libstd.rlib. This is a 7.5% speedup.

cmd.arg("-Zcrate-attr=no_std");

cmd.arg("--crate-type=lib");

cmd.arg("--edition=2021");

if let Some(target) = env::var_os("TARGET") {

cmd.arg("--target").arg(target);

}

// If Cargo wants to set RUSTFLAGS, use that.

if let Ok(rustflags) = env::var("CARGO_ENCODED_RUSTFLAGS") {

if !rustflags.is_empty() {

for arg in rustflags.split('\x1f') {

cmd.arg(arg);

}

}

}

// This rustc invocation should take around 0.03 seconds.

match cmd.status() {

Ok(status) => status.success(),

Err(_) => false,

}

}

fn cargo_env_var(key: &str) -> OsString {

env::var_os(key).unwrap_or_else(|| {

eprintln!(

"Environment variable ${} is not set during execution of build script",

key,

);

process::exit(1);

})

}