iife-thing.rs

use std::thread;

struct Bees;
impl Drop for Bees {
    fn drop(&mut self) { panic!("Not the bees!"); }
}

struct Msg(&'static str);
impl Drop for Msg {
    fn drop(&mut self) { println!("Destructor: {}", self.0); }
}

fn without_iife() {
    let _m0 = Msg("outside block");
    {
        let _m1 = Msg("before decl");
        let _b = Bees;
        let _m2 = Msg("after decl");
    }
}

fn with_iife() {
    let _m0 = Msg("outside block");
    (move || {
        let _m1 = Msg("before decl");
        let _b = Bees;
        let _m2 = Msg("after decl");
    })()
}

pub fn main() {
    println!("Without IIFE:");
    let _ = thread::spawn(move || without_iife()).join().unwrap_err();
    println!("");
    println!("With IIFE:");
    let _ = thread::spawn(move || with_iife()).join().unwrap_err();
}

// Without IIFE:
// Destructor: after decl
// thread '<unnamed>' panicked at 'Not the bees!', src/iife-thing.rs:5
// 
// With IIFE:
// Destructor: after decl
// thread '<unnamed>' panicked at 'Not the bees!', src/iife-thing.rs:5
// Destructor: outside block