小编gav*_*rie的帖子

以下代码 ( playground ) 无法编译：

async fn wrapper<F, Fut>(func: F)
where
    F: FnOnce(&i32) -> Fut,
    Fut: Future<Output = ()>,
{
    let i = 5;
    func(&i).await;
}

async fn myfunc(_: &i32) {}

fn main() {
    wrapper(myfunc);
}

错误信息是：

error: implementation of `std::ops::FnOnce` is not general enough
   --> src/main.rs:15:5
    |
15  |       wrapper(myfunc);
    |       ^^^^^^^ implementation of `std::ops::FnOnce` is not general enough
    |
    = note: `std::ops::FnOnce<(&'0 i32,)>` would have to be implemented for the type `for<'_> fn(&i32) -> impl std::future::Future {myfunc}`, for …