1 files changed, 44 insertions, 0 deletions
diff --git a/third_party/rust/syn/src/reserved.rs b/third_party/rust/syn/src/reserved.rs
new file mode 100644
index 0000000000..abfdf43a91
--- /dev/null
+++ b/third_party/rust/syn/src/reserved.rs
@@ -0,0 +1,44 @@
+// Type for a syntax tree node that is reserved for future use.
+//
+// For example ExprReference contains a field `raw` of type Reserved. If `&raw
+// place` syntax becomes a thing as per https://github.com/rust-lang/rfcs/pull/2582,
+// we can backward compatibly change `raw`'s type to Option<Token![raw]> without
+// the possibility of breaking any code.
+
+use proc_macro2::Span;
+use std::marker::PhantomData;
+
+#[cfg(feature = "extra-traits")]
+use std::fmt::{self, Debug};
+
+ast_struct! {
+    pub struct Reserved {
+        _private: PhantomData<Span>,
+    }
+}
+
+impl Default for Reserved {
+    fn default() -> Self {
+        Reserved {
+            _private: PhantomData,
+        }
+    }
+}
+
+#[cfg(feature = "clone-impls")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "clone-impls")))]
+impl Clone for Reserved {
+    fn clone(&self) -> Self {
+        Reserved {
+            _private: self._private,
+        }
+    }
+}
+
+#[cfg(feature = "extra-traits")]
+#[cfg_attr(doc_cfg, doc(cfg(feature = "extra-traits")))]
+impl Debug for Reserved {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        formatter.debug_struct("Reserved").finish()
+    }
+}