#![feature(raw, const_transmute)]
#![deny(bare_trait_objects)]

use ::std::*;

pub
trait Trait {
    fn method_1 (&'_ self);
    fn method_2 (&'_ self, _: i32) -> i32;
}

struct Double;
impl Trait for Double {
    fn method_1 (self: &'_ Self)
    {
        eprintln!("Double");
    }
    fn method_2 (self: &'_ Self, x: i32) -> i32 { 2 * x }
}

struct Triple;
impl Trait for Triple {
    fn method_1 (self: &'_ Self)
    {
        eprintln!("Triple");
    }
    fn method_2 (self: &'_ Self, x: i32) -> i32 { 3 * x }
}

const DOUBLE_AS_DYN_TRAIT_VTABLE: *mut () = unsafe {
    mem::transmute::<*const dyn Trait, raw::TraitObject>(
        ptr::null::<Double>()
    ).vtable
};

fn foo (object: &'_ dyn Trait)
{
    object.method_1();
    let _ = object.method_2(42);
}

fn main ()
{
    dbg!(DOUBLE_AS_DYN_TRAIT_VTABLE);
    foo(&Double);
    eprintln!("vtable: {:p}",
        unsafe { mem::transmute::<&dyn Trait, raw::TraitObject>(&Double) }.vtable,
        // unsafe { **(mem::transmute::<&dyn Trait, raw::TraitObject>(&Double).vtable as *mut *mut usize) },
    );
    foo(&Triple);
    eprintln!("vtable: {:p}",
        unsafe { mem::transmute::<&dyn Trait, raw::TraitObject>(&Triple) }.vtable,
    );
}