1 files changed, 63 insertions, 0 deletions
diff --git a/syn/build.rs b/syn/build.rs
new file mode 100644
index 0000000..c6040c1
--- /dev/null
+++ b/syn/build.rs
@@ -0,0 +1,63 @@
+use std::env;
+use std::process::Command;
+use std::str::{self, FromStr};
+
+// The rustc-cfg strings below are *not* public API. Please let us know by
+// opening a GitHub issue if your build environment requires some way to enable
+// these cfgs other than by executing our build script.
+fn main() {
+    let compiler = match rustc_version() {
+        Some(compiler) => compiler,
+        None => return,
+    };
+
+    if compiler.minor < 36 {
+        println!("cargo:rustc-cfg=syn_omit_await_from_token_macro");
+    }
+
+    if !compiler.nightly {
+        println!("cargo:rustc-cfg=syn_disable_nightly_tests");
+    }
+}
+
+struct Compiler {
+    minor: u32,
+    nightly: bool,
+}
+
+fn rustc_version() -> Option<Compiler> {
+    let rustc = match env::var_os("RUSTC") {
+        Some(rustc) => rustc,
+        None => return None,
+    };
+
+    let output = match Command::new(rustc).arg("--version").output() {
+        Ok(output) => output,
+        Err(_) => return None,
+    };
+
+    let version = match str::from_utf8(&output.stdout) {
+        Ok(version) => version,
+        Err(_) => return None,
+    };
+
+    let mut pieces = version.split('.');
+    if pieces.next() != Some("rustc 1") {
+        return None;
+    }
+
+    let next = match pieces.next() {
+        Some(next) => next,
+        None => return None,
+    };
+
+    let minor = match u32::from_str(next) {
+        Ok(minor) => minor,
+        Err(_) => return None,
+    };
+
+    Some(Compiler {
+        minor,
+        nightly: version.contains("nightly"),
+    })
+}