pub static MACRO_USE_EXTERN_CRATE: &Lint
Expand description
The macro_use_extern_crate
lint detects the use of the macro_use
attribute.
§Example
ⓘ
#![deny(macro_use_extern_crate)]
#[macro_use]
extern crate serde_json;
fn main() {
let _ = json!{{}};
}
This will produce:
error: applying the `#[macro_use]` attribute to an `extern crate` item is deprecated
--> src/main.rs:3:1
|
3 | #[macro_use]
| ^^^^^^^^^^^^
|
= help: remove it and import macros at use sites with a `use` item instead
note: the lint level is defined here
--> src/main.rs:1:9
|
1 | #![deny(macro_use_extern_crate)]
| ^^^^^^^^^^^^^^^^^^^^^^
§Explanation
The macro_use
attribute on an [extern crate
] item causes
macros in that external crate to be brought into the prelude of the
crate, making the macros in scope everywhere. As part of the efforts
to simplify handling of dependencies in the [2018 edition], the use of
extern crate
is being phased out. To bring macros from extern crates
into scope, it is recommended to use a use
import.
This lint is “allow” by default because this is a stylistic choice that has not been settled, see issue #52043 for more information.