core: no #![warn(missing_docs)], zero compiling doc examples, and clippy flags 16 undocumented error conditions

[MaximeGaudin]

Summary

The crate has no #![warn(missing_docs)] (or deny), so cargo doc reports zero warnings despite many public items lacking documentation, and cargo test --doc runs 0 doc tests, so no example in the public API has ever been verified to compile.

Scope

• Severity (reporter's assessment): medium
• Area: api
• Code: packages/core/src/lib.rs:1-26, packages/core/Cargo.toml
• Reproduced empirically: yes

Minimal reproduction

1. grep -rn missing_docs packages/core/src/lib.rs packages/core/Cargo.toml -> no matches. 2. cargo doc --no-deps --package slint -> 'Finished ... target(s)' with no warnings at all (because the lint that would catch missing docs is off). 3. cargo test --doc -p slint -> 'running 0 tests ... test result: ok. 0 passed'. 4. cargo clippy --workspace --all-targets -- -W clippy::pedantic reports 16 occurrences of 'docs for function returning Result missing # Errors section' (e.g. packages/core/src/config.rs:79).

Actual

cargo doc: 'Documenting slint v0.2.0 ... Finished `dev` profile ... Generated /Users/.../target/doc/slint/index.html' with no missing-docs warnings printed; cargo test --doc: 'running 0 tests'.

Expected

For a library meant for external consumption, #![warn(missing_docs)] (ideally deny in CI) should be set so undocumented public items are caught automatically, and at least the primary entry point (engine::run) should carry a doctest that compiles and runs under cargo test --doc.

Sources

• https://doc.rust-lang.org/rustdoc/how-to-write-documentation.html#documentation-tests — doctests are the mechanism rustdoc provides for verifying examples compile
• https://rust-lang.github.io/api-guidelines/documentation.html#c-crate-doc — crate-level docs and examples are part of the Rust API guidelines

Notes

The crate-level //! doc comment in lib.rs is well written prose; the gap is enforcement and worked examples, not intent.

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Filed as part of a systematic pre-release audit. Triage and de-duplication pending.