::cfg_eval

#[cfg_eval] 在稳定版Rust。

示例

use ::macro_rules_attribute::apply;

#[macro_use]
extern crate cfg_eval;

fn main()
{
    let output_without_cfg_eval = {
        #[apply(stringify!)]
        enum Foo {
            Bar,

            #[cfg(FALSE)]
            NonExisting,
        }
    };
    // This is usually not great.
    assert!(output_without_cfg_eval.contains("NonExisting"));

    let output_with_cfg_eval = {
        #[cfg_eval]
        #[apply(stringify!)]
        enum Foo {
            Bar,

            #[cfg(FALSE)]
            NonExisting,
        }
    };
    assert_eq!(output_with_cfg_eval, stringify! {
        enum Foo {
            Bar,
        }
    });
}