elastio/bon

Leverages the typestate pattern to enforce compile-time correctness—required parameters must be set before calling `build()` or `call()`, and duplicate setter calls are prevented entirely. Supports both structs via `#[derive(Builder)]` and functions/methods via `#[builder]` attributes, with full compatibility for `async`, generic, and fallible signatures. Works in `no_std` environments and requires only Rust 1.59.0+.

1,991 stars and 4,155,393 monthly downloads. Actively maintained with 4 commits in the last 30 days.