1 files changed, 31 insertions, 0 deletions
diff --git a/third_party/rust/async-trait/build.rs b/third_party/rust/async-trait/build.rs
new file mode 100644
index 0000000000..d7f6b159c5
--- /dev/null
+++ b/third_party/rust/async-trait/build.rs
@@ -0,0 +1,31 @@
+use std::env;
+use std::process::Command;
+use std::str;
+
+fn main() {
+    println!("cargo:rerun-if-changed=build.rs");
+
+    let compiler = match rustc_minor_version() {
+        Some(compiler) => compiler,
+        None => return,
+    };
+
+    if compiler < 45 {
+        println!("cargo:rustc-cfg=no_span_mixed_site");
+    }
+
+    if compiler < 47 {
+        println!("cargo:rustc-cfg=self_span_hack");
+    }
+}
+
+fn rustc_minor_version() -> Option<u32> {
+    let rustc = env::var_os("RUSTC")?;
+    let output = Command::new(rustc).arg("--version").output().ok()?;
+    let version = str::from_utf8(&output.stdout).ok()?;
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+    pieces.next()?.parse().ok()
+}