Fail better on some old compilers
This message will appear on 1.22 through 1.26. Before 1.22, the build.rs
does not compile. On 1.27 through 1.30 it never runs because editions
are detected as unstable.
diff --git a/build.rs b/build.rs
index 5ff440e..c9c3c73 100644
--- a/build.rs
+++ b/build.rs
@@ -31,19 +31,22 @@
// location inside spans is a performance hit.
use std::env;
-use std::process::Command;
+use std::process::{self, Command};
use std::str;
fn main() {
println!("cargo:rerun-if-changed=build.rs");
- let target = env::var("TARGET").unwrap();
-
let version = match rustc_version() {
Some(version) => version,
None => return,
};
+ if version.minor < 31 {
+ eprintln!("Minimum supported rustc version is 1.31");
+ process::exit(1);
+ }
+
let semver_exempt = cfg!(procmacro2_semver_exempt);
if semver_exempt {
// https://github.com/alexcrichton/proc-macro2/issues/147
@@ -54,6 +57,7 @@
println!("cargo:rustc-cfg=span_locations");
}
+ let target = env::var("TARGET").unwrap();
if !enable_use_proc_macro(&target) {
return;
}
@@ -84,6 +88,7 @@
}
struct RustcVersion {
+ minor: u32,
nightly: bool,
}
@@ -92,7 +97,12 @@
let output = Command::new(rustc).arg("--version").output().ok()?;
let version = str::from_utf8(&output.stdout).ok()?;
let nightly = version.contains("nightly");
- Some(RustcVersion { nightly })
+ let mut pieces = version.split('.');
+ if pieces.next() != Some("rustc 1") {
+ return None;
+ }
+ let minor = pieces.next()?.parse().ok()?;
+ Some(RustcVersion { minor, nightly })
}
fn feature_allowed(feature: &str) -> bool {