Function understand_lifetime_for_closure

pub fn understand_lifetime_for_closure()

闭包 与 高阶生命周期

fn main() {
    let f = |x: &i32| x; // error
    // 假如支持下面的语法就方便多了，目前还未支持
    // let f: for<'a> Fn(&'a i32) -> &'a i32 = |x| x;
    let i = &3;
    let j = f(i);
}

修正：

相关：Explicit lifetime bounds RFC 0192

// fn annotate<'a, T: 'a ,F>(f: F) -> F where F: Fn(&'a T) -> &'a T { f }

fn annotate<T,F>(f: F) -> F where for<'a> F: Fn(&'a T) -> &'a T { f }

fn main() {
    let f = annotate(|x| x);
    let i = &3;
    let j = f(i);
    assert_eq!(*j, 3);
}