diff --git a/parser/src/subclass_attrs.rs b/parser/src/subclass_attrs.rs
new file mode 100644
index 0000000..9174bec
--- /dev/null
+++ b/parser/src/subclass_attrs.rs
@@ -0,0 +1,58 @@
+// Copyright 2021 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// https://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use proc_macro2::Ident;
+use quote::ToTokens;
+use syn::Result as ParseResult;
+use syn::{
+    parse::{Parse, ParseStream},
+    token::Comma,
+};
+
+#[derive(Default)]
+pub struct SubclassAttrs {
+    pub self_owned: bool,
+    pub superclass: Option<String>,
+}
+
+impl Parse for SubclassAttrs {
+    fn parse(input: ParseStream) -> ParseResult<Self> {
+        let mut me = Self::default();
+        let mut id = input.parse::<Option<Ident>>()?;
+        while id.is_some() {
+            match id {
+                Some(id) if id == "self_owned" => me.self_owned = true,
+                Some(id) if id == "superclass" => {
+                    let args;
+                    syn::parenthesized!(args in input);
+                    let superclass: syn::LitStr = args.parse()?;
+                    if me.superclass.is_some() {
+                        return Err(syn::Error::new_spanned(
+                            id.into_token_stream(),
+                            "Expected single superclass specification",
+                        ));
+                    }
+                    me.superclass = Some(superclass.value());
+                }
+                Some(id) => {
+                    return Err(syn::Error::new_spanned(
+                        id.into_token_stream(),
+                        "Expected self_owned or superclass",
+                    ))
+                }
+                None => {}
+            };
+            let comma = input.parse::<Option<Comma>>()?;
+            if comma.is_none() {
+                break;
+            }
+            id = input.parse::<Option<Ident>>()?;
+        }
+        Ok(me)
+    }
+}