Rust-clippy: allow many_single_char_names is broken

[gnzlbg]

Playground:

#[cfg_attr(
    feature = "cargo-clippy",
    allow(clippy::many_single_char_names)
)]
pub fn append_to() {
    let (a, b, c, d, e) = (0, 0, 0, 0, 0);
}

produces

warning: 5th binding whose name is just one char
 --> src/main.rs:7:22
  |
7 |     let (a, b, c, d, e) = (0, 0, 0, 0, 0);
  |                      ^
  |
  = note: #[warn(clippy::many_single_char_names)] on by default
  = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#many_single_char_names

That lint should not trigger, since it is allowed for the function.

[flip1995]

Applying the allow to a function does not change the behavior of the lint inside the function. This is weird, since the lint is produced through EarlyLintPass::check_[impl_]item() and a function is an item.

It works if you turn the cfg_attr into an inner attribute. Probably something you don't want to do.

Removing the clippy:: and checking this with cargo +stable clippy doesn't produce a warning. I'm afraid that this could have something to do with tool_lints...

[gnzlbg]

I'm hitting this issue with other lints like shadow_unrelated as well. Moving the cfg_attr into an inner attribute does not work around this form me, can you show on the play ground how you are doing that ? This still produces the warning for me:

pub fn append_to() {
    #![cfg_attr(
        feature = "cargo-clippy",
        allow(clippy::many_single_char_names)
    )]
    let (a, b, c, d, e) = (0, 0, 0, 0, 0);
}

[flip1995]

Sure: Playground

#![feature(tool_lints)]

#![cfg_attr(
    feature = "cargo-clippy",
    allow(clippy::many_single_char_names)
)]

#[allow(unused_variables)] 
pub fn main() {
    let (a, b, c, d, e) = (0, 0, 0, 0, 0);
}

[flip1995]

Hm maybe something changed how lint attributes are processed... Since when do you have these issues?

[gnzlbg]

Ah, you meant making it an inner attribute of the scope where the function is, yeah I'd prefer not to do that. I've just disabled the lint globally as a workaround for now.

Since when do you have these issues?

I just started updating criterion to the latest clippy, and the last Rust nightly version criterion used was from june... so... I'd guess between june and today, which isn't probably very helpful.

[flip1995]

I'm looking into that!

[flip1995]

This error started with nightly-2018-08-24. The previous nightly-2018-08-19 does not produce a warning for your example. (That means, it is not connected to the tool_lints :tada:)

Repo: https://github.com/flip1995/test_allow_on_fn
Travis: https://travis-ci.org/flip1995/test_allow_on_fn/builds/430632901

[flip1995]

One of these commits are at fault here:

https://github.com/rust-lang/rust/commit/758239c9c9e00b7c0daba6496ef246a85e7b5ce5
https://github.com/rust-lang/rust/commit/d2048b6db375299b681d4f4728b8e7cad9f74d5f
https://github.com/rust-lang/rust/commit/6bf6d50a6ff7685b4aa09172d9d09f03f250da9d

Travis: https://travis-ci.org/flip1995/test_allow_on_fn

[flip1995]

This is no longer an issue: Playground

[gnzlbg]

Is there a test that prevents this from breaking again?

[flip1995]

Oh good point!