You can encode not-a-bool, not-a-(utf-8)-string and not-an-enum using one of the invalid bit patterns – that's exactly what the Rust compiler can do with its "n

You can encode not-a-bool, not-a-(utf-8)-string and not-an-enum using one of the invalid bit patterns – that's exactly what the Rust compiler can do with its "niche optimization": https://www.0xatticus.com/posts/understanding_rust_niche/ https://www.0xatticus.com/posts/understanding_rust_niche/