Use version_check crate

Cargo.toml

@@ -23,6 +23,9 @@ members = ["test_suite"]
 [lib]
 proc-macro = true
 
+[build-dependencies]
+version_check = "0.9.2"
+
 [dependencies]
 proc-macro2 = "1.0"
 quote = "1.0"

build.rs

@@ -1,17 +1,9 @@
-use std::{env, fs, path::PathBuf, process::Command, str};
+use std::{env, fs, path::PathBuf};
 
 fn main() {
-    let rustc = env::var_os("RUSTC").map_or_else(|| "rustc".into(), PathBuf::from);
-    let output = Command::new(&rustc)
-        .arg("--version")
-        .output()
-        .unwrap_or_else(|e| panic!("failed to run `{} --version`: {}", rustc.display(), e));
-    let version = str::from_utf8(&output.stdout).unwrap_or_else(|e| {
-        panic!("failed to parse output of `{} --version`: {}", rustc.display(), e)
-    });
-    let version = match parse(&version) {
+    let version = match Version::new() {
         Some(version) => format!("{:#?}\n", version),
-        None => panic!("unexpected output from `rustc --version`: {}", version),
+        None => panic!("unexpected output from `rustc --version`"),
     };
 
     let out_dir = env::var_os("OUT_DIR").map(PathBuf::from).expect("OUT_DIR not set");
@@ -21,50 +13,16 @@ fn main() {
 
 #[derive(Debug)]
 struct Version {
-    minor: usize,
-    patch: usize,
+    minor: u16,
+    patch: u16,
     nightly: bool,
 }
 
-fn parse(string: &str) -> Option<Version> {
-    let last_line = string.lines().last().unwrap_or(&string);
-    let mut words = last_line.trim().split(' ');
-
-    if words.next()? != "rustc" {
-        return None;
-    }
-
-    let mut version_channel = words.next()?.split('-');
-    let version = version_channel.next()?;
-    let channel = version_channel.next();
-
-    let mut digits = version.split('.');
-    let major = digits.next()?;
-    if major != "1" {
-        return None;
+impl Version {
+    fn new() -> Option<Self> {
+        let (version, channel, _date) = version_check::triple()?;
+        let (_major, minor, patch) = version.to_mmp();
+        let nightly = channel.is_nightly() || channel.is_dev();
+        Some(Version { minor, patch, nightly })
     }
-    let minor = digits.next()?.parse().ok()?;
-    let patch = digits.next().unwrap_or("0").parse().ok()?;
-
-    let nightly = match channel {
-        None => false,
-        Some(channel) if channel.starts_with("beta") => false,
-        Some(channel) if channel == "dev" => true,
-        Some(channel) if channel == "nightly" => match words.next() {
-            Some(hash) => {
-                if !hash.starts_with('(') {
-                    return None;
-                }
-                let date = words.next()?;
-                if !date.ends_with(')') {
-                    return None;
-                }
-                true
-            }
-            None => true,
-        },
-        Some(_) => return None,
-    };
-
-    Some(Version { minor, patch, nightly })
 }