As Rust approaches its 10th anniversary, "there is an important piece of documentation missing that many other languages provide," notes the Rust Foundation.
While there's documentation and tutorials — there's no official language specification:
In December 2022, an RFC was submitted to encourage the Rust Project to begin working on a specification. After much discussion, the RFC was approved in July 2023, and work began.
Initially, the Rust Project specification team (t-spec) were interested in creating the document from scratch using the Rust Reference as a guiding marker. However, the team knew there was already an external Rust specification that was being used successfully for compiler qualification purposes — the FLS.
Thank Berlin-based Ferrous Systems, a Rust-based consultancy who assembled that description "some years ago," according to a post on the Rust blog:
They've since been faithfully maintaining and updating this document for new versions of Rust, and they've successfully used it to qualify toolchains based on Rust for use in safety-critical industries. [The Rust Foundation notes it part of the consultancy's "Ferrocene" Rust compiler/toolchain.] Seeing this success, others have also begun to rely on the FLS for their own qualification efforts when building with Rust.
The Rust Foundation explains:
The FLS provides a structured and detailed reference for Rust's syntax, semantics, and behavior, serving as a foundation for verification, compliance, and standardization efforts. Since Rust did not have an official language specification back then, nor a plan to write one, the FLS represented a major step toward describing Rust in a way that aligns with industry requirements, particularly in high-assurance domains.
And the Rust Project is "passionate about shipping high quality tools that enable people to build reliable software at scale," adds the Rust blog. So...
It's in that light that we're pleased to announce that we'll be adopting the FLS into the Rust Project as part of our ongoing specification efforts. This adoption is being made possible by the gracious donation of the FLS by Ferrous Systems. We're grateful to them for the work they've done in assembling the FLS, in making it fit for qualification purposes, in promoting its use and the use of Rust generally in safety-critical industries, and now, for working with us to take the next step and to bring the FLS into the Project. ...
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