This crate exposes the Rustdoc JSON API as a set of types with serde implementations. These types are part of the public interface of the rustdoc JSON output, and making them their own crate allows them to be versioned and distributed without having to depend on any rustc/rustdoc internals. This way, consumers can rely on this crate for both documentation of the output, and as a way to read the output easily, and its versioning is intended to follow semver guarantees about the version of the format. JSON format X will always be compatible with rustdoc-json-types version N.
Currently, this crate is only used by rustdoc itself. Upon the stabilization of rustdoc-json, it may be distributed separately for consumers of the API.