607[`ParseResult`]: https://doc.rust-lang.org/nightly/nightly-rustc/rustc_expand/mbe/macro_parser/enum.ParseResult.html
608
609▶<!-- TODO(rylev): more here. [#1160](https://github.com/rust-lang/rustc-dev-guide/issues/1160) -->
610
611### Custom Derive
· · ·
620additional syntactic sugar and are allowed to be in namespaces.
621
622▶<!-- TODO(rylev): more? [#1160](https://github.com/rust-lang/rustc-dev-guide/issues/1160) -->
623