rust-play

fn main() {
    Box::new("qwe".into()) as Box<std::error::Error>;
}

rust-play

fn main() {
    let _ = Box::<std::error::Error>::from("oh no");
}

rust-play

fn foo() -> Box<std::error::Error> {
    "oh no".into()
}

fn main() {
    let _ = foo();
}

rust-play

#![feature(ptr_internals)]
use std::ptr::Unique;

fn main() {
    let mut arr = [1u8, 2, 3];
    let slice = &mut arr[..];
    let unique : Unique<[u8]> = Unique::new(slice as *mut [u8]).unwrap();
    // Cast unique to an usize
    let ptr = unsafe { (&(*unique.as_ptr())[0] as *const u8 as usize) };
    println!("{:?} {:x}", unique, ptr);

rust-play

extern crate futures;
extern crate tokio_core;

use futures::executor::spawn;
use futures::future::{FutureResult, ok, Future};
use tokio_core::reactor::Core;
use std::fmt::Error;

fn main() {
    let s = ok::<String, Error>(String::new())

rust-play

use std::collections::HashMap;
use std::cell::RefCell;

fn main() {
    let mut cache = HashMap::new();
    cache.insert(0, 0);
    let cache = RefCell::new(cache);
    let x = if let Some(cached) = cache.borrow().get(&0).cloned() {
        cached
    } else {

rust-play

#[feature(nll)]

use std::collections::HashMap;
use std::cell::RefCell;

fn main() {
    let mut cache = HashMap::new();
    cache.insert(0, 0);
    let cache = RefCell::new(cache);
    let x = if let Some(cached) = cache.borrow().get(&1).cloned() {

rust-play

use std::collections::HashMap;
use std::cell::RefCell;

fn main() {
    let mut cache = HashMap::new();
    cache.insert(0, 0);
    let cache = RefCell::new(cache);
    let x = if let Some(cached) = {cache.borrow().get(&1).cloned()} {
        cached
    } else {

rust-play

use std::collections::HashMap;
use std::cell::RefCell;

fn main() {
    let mut cache = HashMap::new();
    cache.insert(0, 0);
    let cache = RefCell::new(cache);
    let x = if let Some(cached) = {let x = cache.borrow().get(&1).cloned(); x} {
        cached
    } else {

rust-play

fn main() {
    let a = (1, 2, 3);
    
    let mut b = 0;
    println!("b: {} {:p}", b, &b);
    
    let (x, b, y) = a;
    println!("b: {} {:p}", b, &b);
}