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playground.rs

#![feature(fnbox)]
use std::boxed::FnBox;

struct Foo;
impl Foo {
    pub fn new() -> Foo { 
        println!("foo: new");
        Foo
    }
    pub fn dowork(&self) {
        println!("foo: doing work");
    }
}

impl Drop for Foo {
    fn drop(&mut self) {
        println!("foo: drop");
    }
}

fn process(foo: Foo) -> Box<FnBox()> {
    Box::new(move || {
        foo.dowork();
        
        /* info: foo is never dropped 
         * at the end of this closure despite
         * being owned by the closure, this
         * requires the caller to explicitly
         * drop() captured members.
         */
        
        // uncomment
        // drop(foo); // explicit drop!!
    })
}

fn main() {
    let f = process(Foo::new());
    f();
    println!("main: exit");
}