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use std::env;
use std::fs;
use std::path::Path;
use std::process::{Command, ExitStatus, Stdio};
use std::str;
// This code exercises the surface area that we expect of the Provider API. If
// the current toolchain is able to compile it, then thiserror is able to use
// providers for backtrace support.
const PROBE: &str = r#"
#![feature(provide_any)]
use std::any::{Demand, Provider};
fn _f<'a, P: Provider>(p: &'a P, demand: &mut Demand<'a>) {
p.provide(demand);
}
"#;
fn main() {
match compile_probe() {
Some(status) if status.success() => println!("cargo:rustc-cfg=provide_any"),
_ => {}
}
}
fn compile_probe() -> Option<ExitStatus> {
let rustc = env::var_os("RUSTC")?;
let out_dir = env::var_os("OUT_DIR")?;
let probefile = Path::new(&out_dir).join("probe.rs");
fs::write(&probefile, PROBE).ok()?;
// Make sure to pick up Cargo rustc configuration.
let mut cmd = if let Some(wrapper) = env::var_os("RUSTC_WRAPPER") {
let mut cmd = Command::new(wrapper);
// The wrapper's first argument is supposed to be the path to rustc.
cmd.arg(rustc);
cmd
} else {
Command::new(rustc)
};
cmd.stderr(Stdio::null())
.arg("--edition=2018")
.arg("--crate-name=thiserror_build")
.arg("--crate-type=lib")
.arg("--emit=metadata")
.arg("--out-dir")
.arg(out_dir)
.arg(probefile);
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);
}
}
}
cmd.status().ok()
}
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