1 files changed, 75 insertions, 0 deletions
diff --git a/third_party/rust/rustversion/build/build.rs b/third_party/rust/rustversion/build/build.rs
new file mode 100644
index 0000000000..0a45f4c2d2
--- /dev/null
+++ b/third_party/rust/rustversion/build/build.rs
@@ -0,0 +1,75 @@
+#![allow(
+    clippy::enum_glob_use,
+    clippy::must_use_candidate,
+    clippy::single_match_else
+)]
+
+mod rustc;
+
+use std::env;
+use std::ffi::OsString;
+use std::fs;
+use std::path::Path;
+use std::process::{self, Command};
+
+fn main() {
+    println!("cargo:rerun-if-changed=build/build.rs");
+
+    let rustc = env::var_os("RUSTC").unwrap_or_else(|| OsString::from("rustc"));
+
+    let mut is_clippy_driver = false;
+    let version = loop {
+        let mut command = Command::new(&rustc);
+        if is_clippy_driver {
+            command.arg("--rustc");
+        }
+        command.arg("--version");
+
+        let output = match command.output() {
+            Ok(output) => output,
+            Err(e) => {
+                let rustc = rustc.to_string_lossy();
+                eprintln!("Error: failed to run `{} --version`: {}", rustc, e);
+                process::exit(1);
+            }
+        };
+
+        let string = match String::from_utf8(output.stdout) {
+            Ok(string) => string,
+            Err(e) => {
+                let rustc = rustc.to_string_lossy();
+                eprintln!(
+                    "Error: failed to parse output of `{} --version`: {}",
+                    rustc, e,
+                );
+                process::exit(1);
+            }
+        };
+
+        break match rustc::parse(&string) {
+            rustc::ParseResult::Success(version) => version,
+            rustc::ParseResult::OopsClippy if !is_clippy_driver => {
+                is_clippy_driver = true;
+                continue;
+            }
+            rustc::ParseResult::Unrecognized | rustc::ParseResult::OopsClippy => {
+                eprintln!(
+                    "Error: unexpected output from `rustc --version`: {:?}\n\n\
+                    Please file an issue in https://github.com/dtolnay/rustversion",
+                    string
+                );
+                process::exit(1);
+            }
+        };
+    };
+
+    if version.minor < 38 {
+        // Prior to 1.38, a #[proc_macro] is not allowed to be named `cfg`.
+        println!("cargo:rustc-cfg=cfg_macro_not_allowed");
+    }
+
+    let version = format!("{:#?}\n", version);
+    let out_dir = env::var_os("OUT_DIR").expect("OUT_DIR not set");
+    let out_file = Path::new(&out_dir).join("version.expr");
+    fs::write(out_file, version).expect("failed to write version.expr");
+}