consider a type state builder

[cgwalters]

derive-builder requires unwrap() and does runtime checks. There's a few popular crates that use type state, e.g.:

• https://lib.rs/crates/typed-builder
• https://lib.rs/crates/bon

I don't have experience with either, but I definitely don't like the pervasive requirement for unwrap() we have here.

[ariel-miculas]

I wonder if we can have multiple builders so we don't introduce a breaking change.