Deny rust_2018_idioms and unused_qualifications in crate roots

[MarijnS95]

Suggestion

When using a local path reference to the windows-rs crate, from a project that denies a bunch of lints globally (via rustflags in .cargo/config.toml until workspace lints get implicit/forced inheritance), there are quite a few warnings from the windows crate which would be trivial and neat to resolve.

Most/all originate from the rust_2018_idioms lint (and a few more like unused_qualifications, I think https://github.com/ash-rs/ash/blob/e6d80badc389d94e2a747f442e5ed4189b66d7d3/ash/src/lib.rs#L1-L8 might be a good starting point). This lint isn't enabled by default despite windows already setting edition = "2021", and certain things like extern crate might be nice to clear out.

Some samples:

warning: unused extern crate
  --> windows-rs\crates\libs\windows\src\lib.rs:11:1
   |
11 | extern crate self as windows;
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: remove it
   |
   = note: `-W unused-extern-crates` implied by `-W rust-2018-idioms`
   = help: to override `-W rust-2018-idioms` add `#[allow(unused_extern_crates)]`

warning: unnecessary qualification
  --> windows-rs\crates\libs\core\src\strings\bstr.rs:87:21
   |
87 |     fn from(value: &std::string::String) -> Self {
   |                     ^^^^^^^^^^^^^^^^^^^
   |
help: remove the unnecessary path segments
   |
87 -     fn from(value: &std::string::String) -> Self {
87 +     fn from(value: &String) -> Self {
   |

warning: hidden lifetime parameters in types are deprecated
   --> windows-rs\crates\libs\implement\src\lib.rs:241:34
    |
241 |     fn parse(cursor: syn::parse::ParseStream) -> syn::parse::Result<Self> {
    |                      ------------^^^^^^^^^^^
    |                      |
    |                      expected lifetime parameter
    |
    = note: `-W elided-lifetimes-in-paths` implied by `-W rust-2018-idioms`
    = help: to override `-W rust-2018-idioms` add `#[allow(elided_lifetimes_in_paths)]`
help: indicate the anonymous lifetime
    |
241 |     fn parse(cursor: syn::parse::ParseStream<'_>) -> syn::parse::Result<Self> {
    |                                             ++++

[kennykerr]

Happy to tighten this up if there's a way to do so without adding more attributes to the various crates. Perhaps with a clippy config file, like rustfmt.toml, or through the yml workflows.

Note that the warning about the "unused extern crate" is a false positive and it is in fact needed.

[MarijnS95]

Note that the warning about the "unused extern crate" is a false positive and it is in fact needed.

Most are valid, especially in the custom .rs files for strings (self::convert::From, self::string::String etc), they're all part of the prelude and not shadowed.

[MarijnS95]

Happy to tighten this up if there's a way to do so without adding more attributes to the various crates. Perhaps with a clippy config file, like rustfmt.toml, or through the yml workflows.

Exactly that exists in the latest 1.74 Rust release: https://blog.rust-lang.org/2023/11/16/Rust-1.74.0.html#lint-configuration-through-cargo

It has one fatal flaw, which is having to opt-in every crate manually. That might work for windows-rs as there are not many crates and it's relatively easy to audit (and you probably don't care about having strict linting on most crates, like tools and tests. EDIT: On the other hand it improves readability, especially when tests are taken as examples).

[ChrisDenton]

Lints set in a workspace will be inherited by every crate.

[MarijnS95]

@ChrisDenton:

rust-lang/cargo#12208
rust-lang/cargo#12984

[ChrisDenton]

Right you need to add workspace = true to the crate's lints table but that's more annoying than a "fatal flaw", imho.

[MarijnS95]

For a workspace split across over 200 crates, with new ones being added on a weekly basis?

[ChrisDenton]

Tbh, in that case I'd be minded to automate it. There's probably a bunch of boiler plate stuff you need in any case.

But I admit I find that to be an unusual workflow, unless you're doing some kind of monorepo-like thing.

[kennykerr]

Thanks, workspace lints works nicely - I'll roll that into #2740.

[kennykerr]

Both rust_2018_idioms and unused_qualifications are now enforced as of #2741 and #2743.