Automatically use rich API on 1.30.0+
This commit detects the rustc version in the build script of proc-macro2
to determine whether the compiler supports the necessary backend APIs.
This should hopefully allow the crate to compile on stable by default
but have a better implementation on 1.30.0+ compilers.
diff --git a/build.rs b/build.rs
index aaa92b6..cd91b4b 100644
--- a/build.rs
+++ b/build.rs
@@ -1,21 +1,53 @@
use std::env;
+use std::process::Command;
+use std::str;
fn main() {
println!("cargo:rerun-if-changed=build.rs");
let target = env::var("TARGET").unwrap();
- maybe_enable_use_proc_macro(&target);
+ if !enable_use_proc_macro(&target) {
+ return
+ }
+ println!("cargo:rustc-cfg=use_proc_macro");
+
+ let minor = match rustc_minor_version() {
+ Some(n) => n,
+ None => return,
+ };
+
+ // Rust 1.30 stabilized the necessary APIs in the `proc_macro` crate
+ if minor >= 30 || cfg!(feature = "nightly") {
+ println!("cargo:rustc-cfg=wrap_proc_macro");
+
+ if cfg!(procmacro2_semver_exempt) {
+ println!("cargo:rustc-cfg=super_unstable");
+ }
+ } else {
+ }
}
-fn maybe_enable_use_proc_macro(target: &str) {
+fn enable_use_proc_macro(target: &str) -> bool {
// wasm targets don't have the `proc_macro` crate, disable this feature.
if target.contains("wasm32") {
- return;
+ return false;
}
// Otherwise, only enable it if our feature is actually enabled.
- if cfg!(feature = "proc-macro") {
- println!("cargo:rustc-cfg=use_proc_macro");
+ cfg!(feature = "proc-macro")
+}
+
+fn rustc_minor_version() -> Option<u32> {
+ macro_rules! otry {
+ ($e:expr) => (match $e { Some(e) => e, None => return None })
}
+ let rustc = otry!(env::var_os("RUSTC"));
+ let output = otry!(Command::new(rustc).arg("--version").output().ok());
+ let version = otry!(str::from_utf8(&output.stdout).ok());
+ let mut pieces = version.split('.');
+ if pieces.next() != Some("rustc 1") {
+ return None;
+ }
+ otry!(pieces.next()).parse().ok()
}