## MACRO_USE_EXTERN_CRATE

# Static MACRO_USE_EXTERN_CRATE

Source

    pub static MACRO_USE_EXTERN_CRATE: &'static 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.