Clippy lint · Suspicious · checked with Clippy 0.1.99

clippy::crate_in_macro_def: `crate` references the macro call's crate

What it meansChecks for usage of crate as opposed to $crate in a macro definition. It is in the suspicious group and warns by default.

What you see

warning: `crate` references the macro call's crate
 --> main.rs:6:24
  |
6 |         println!("{}", crate::MESSAGE);
  |                        ^^^^^ help: to reference the macro definition's crate, use: `$crate`
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#crate_in_macro_def
  = note: `#[warn(clippy::crate_in_macro_def)]` on by default

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

crate refers to the macro call’s crate, whereas $crate refers to the macro definition’s crate. Rarely is the former intended. See: https://doc.rust-lang.org/reference/macros-by-example.html#hygiene

Code that is most likely wrong or useless. Warns by default.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

#[macro_export]
macro_rules! print_message {
    () => {
        println!("{}", crate::MESSAGE);
    };
}
pub const MESSAGE: &str = "Hello!";

Write this instead

#[macro_export]
macro_rules! print_message {
    () => {
        println!("{}", $crate::MESSAGE);
    };
}
pub const MESSAGE: &str = "Hello!";

Turn it off, or on

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

On one item

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

Whole crate (Cargo.toml)

[lints.clippy]
crate_in_macro_def = "allow"

One run

cargo clippy -- -A clippy::crate-in-macro-def

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.

Suspiciousgroup

warndefault level

yesfixed by cargo clippy --fix

1.62.0added in Rust

Clippy's own documentation

What it does

Checks for usage of crate as opposed to $crate in a macro definition.

Why is this bad?

crate refers to the macro call’s crate, whereas $crate refers to the macro definition’s crate. Rarely is the former intended. See: https://doc.rust-lang.org/reference/macros-by-example.html#hygiene

Example

#[macro_export]
macro_rules! print_message {
    () => {
        println!("{}", crate::MESSAGE);
    };
}
pub const MESSAGE: &str = "Hello!";

Use instead:

#[macro_export]
macro_rules! print_message {
    () => {
        println!("{}", $crate::MESSAGE);
    };
}
pub const MESSAGE: &str = "Hello!";

Note that if the use of crate is intentional, an allow attribute can be applied to the macro definition, e.g.:

#[allow(clippy::crate_in_macro_def)]
macro_rules! ok { ... crate::foo ... }

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

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