MSRV Update Notice

This release raises the minimum supported Rust version from 1.59.0 to 1.88.0. If you are on an older compiler, stay on bon@3.9.

The new MSRV also comes with the deprecation of the implied-bounds cargo feature. Implied bounds are now added by default without any feature gate, so be sure to remove that feature from your Cargo.toml if you have it enabled. It's currently a no-op, and it won't be removed until a major release, for which there are no plans yet.

The MSRV bump comes from the darling@0.24 update, which is the first version that uses syn@3.0.

Added

• Support the default switch in the on(...) clause (#398). Thanks @ChrisJr404 for the contribution!

Changed

• Bump MSRV to 1.88.0, move to the 2024 edition, update to syn@3.0 and darling@0.24 (#399)
• Deprecate the implied-bounds cargo feature. Implied bounds are now generated by default (#399)

Internal

• Regular maintenance (#392)

Fixed

• Fix clippy::missing_docs_in_private_items triggering for start_fn members (#389)

Fixed

• Fix rust-analyzer "Go to Definition" inside #[builder] functions (#385)

Internal

• Regular maintenance (#379, #381, #386)

This is purely a minutiae update with zero changes to the Rust API. Enjoy the stability 🍸.

Fixed

• Redistribute license files with the crates sources (#376)

Internal

• Regular maintenance (#377)

Added

• Introduce a new experimental attribute builder(generics(setters)) for overwriting generic types on the builder. (#364, #368, #370). Thanks @dflemstr for the contribution!
• Support builder(overwritable) with builder(getter) (#369)

Internal

• Regular maintenance (#365)

Fixed

• Don't attempt to compile big default value showcases as ignored rust doctests (#360)

Internal

• Regular maintenance (#361, #354, #363)

Fixed

• Fix clippy::wrong_self_convention warning for fields with is_ prefix etc. (#349). Thanks @nicmue for the contribution!

Internal

• Add a regression test for clippy::wrong_self_convention (#350)

Lint Update Notice

This release brings some rustdoc improvements and no other visible API changes except that rustc and clippy will start reporting some more true-positive lints. For example builder methods defined via an impl block annotated with #[bon] will now be correctly reported as unused if they are not used. Also, using a private type in a public builder method will trigger a private_interfaces lint now.

This is all thanks to the updated span handling design researched and implemented by @Eisverygoodletter. It's not clear what other new lints the new span handling may trigger in other realworld codebases. If you see a lint from the code generated by bon that you think shouldn't be there, please, open an issue, and it'll be fixed as soon as possible!

Changed

• Make rustdoc source links for the starting function reference original function (#341). Thanks @Eisverygoodletter for the contribution!
• Make rustdoc source links for setters/getters reference original member (#345)

Internal

• Regular maintenance (#342, #343, #347)

Fixed

• Add missing lifetime replacement for generic param declarations on derive(IntoFuture) impl block (#337)
• Set the lower bound requirement of rustversion to v1.0.19 (#336). Thanks @Fokko for the contribution!

This is a small patch release to make bon easier to package for Debian.

Other

• Add Copyright header to the MIT License (#331)

Internal

• Fix MSRV tests and lints from nightly 13-08-2025 (#329)
• Revert refactoring PR 320 to make code compatible with darling 0.20 (#332)