Clippy lint · Correctness · checked with Clippy 0.1.99

clippy::useless_attribute: Checks for extern crate and use items annotated with lint attributes. This lint permits lint attributes for lints emitted on the items themself. For use items these lints are: ambiguous_glob_reexports dead_code deprecated hidden_glob_reexports unreachable_pub unused unused_braces unused_import_braces clippy::disallowed_types clippy::enum_glob_use clippy::macro_use_imports clippy::module_name_repetitions clippy::redundant_pub_crate clippy::single_component_path_imports clippy::unsafe_removed_from_name clippy::wildcard_imports For extern crate items these lints are: unused_imports on items with #[macro_use]

What it meansChecks for extern crate and use items annotated with lint attributes. This lint permits lint attributes for lints emitted on the items themself. For use items these lints are: ambiguous_glob_reexports dead_code deprecated hidden_glob_reexports unreachable_pub unused unused_braces unused_import_braces clippy::disallowed_types clippy::enum_glob_use clippy::macro_use_imports clippy::module_name_repetitions clippy::redundant_pub_crate clippy::single_component_path_imports clippy::unsafe_removed_from_name clippy::wildcard_imports For extern crate items these lints are: unused_imports on items with #[macro_use] It is in the correctness group and denied by default (the build fails).

Does it matter?

Lint attributes have no effect on crate imports. Most likely a ! was forgotten.

Code that is almost certainly wrong. Denied by default: the build fails until you fix it or allow it.

How to fix it

Clippy does not fix this one automatically (its suggestion may change behaviour, so it only shows it). Change the code by hand:

Flagged

#[deny(dead_code)]
extern crate foo;
#[forbid(dead_code)]
use foo::bar;

Write this instead

#[allow(unused_imports)]
use foo::baz;
#[allow(unused_imports)]
#[macro_use]
extern crate baz;

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

On one item

#[allow(clippy::useless_attribute)]
fn my_function() { /* ... */ }

Whole crate (Cargo.toml)

[lints.clippy]
useless_attribute = "allow"

One run

cargo clippy -- -A clippy::useless-attribute

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.

Correctnessgroup

denydefault level

nofixed by cargo clippy --fix

pre 1.29.0added in Rust

Clippy's own documentation

What it does

Checks for extern crate and use items annotated with lint attributes.

This lint permits lint attributes for lints emitted on the items themself. For use items these lints are:

ambiguous_glob_reexports
dead_code
deprecated
hidden_glob_reexports
unreachable_pub
unused
unused_braces
unused_import_braces
clippy::disallowed_types
clippy::enum_glob_use
clippy::macro_use_imports
clippy::module_name_repetitions
clippy::redundant_pub_crate
clippy::single_component_path_imports
clippy::unsafe_removed_from_name
clippy::wildcard_imports

For extern crate items these lints are:

unused_imports on items with #[macro_use]

Why is this bad?

Lint attributes have no effect on crate imports. Most likely a ! was forgotten.

Example

#[deny(dead_code)]
extern crate foo;
#[forbid(dead_code)]
use foo::bar;

Use instead:

#[allow(unused_imports)]
use foo::baz;
#[allow(unused_imports)]
#[macro_use]
extern crate baz;

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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