tests/ui/cast/cast-rfc0401-vtable-kinds.rs

//@ run-pass
// Check that you can cast between different pointers to trait objects
// whose vtable have the same kind (both lengths, or both trait pointers).

#![feature(unsized_tuple_coercion)]

trait Bar { //~ WARN trait `Bar` is never used
    fn bar(&self) { println!("Bar!"); }
}

impl Bar for () {}

#[repr(C)]
struct FooS<T:?Sized>(T);
#[repr(C)]
struct BarS<T:?Sized>(T);

fn foo_to_bar<T:?Sized>(u: *const FooS<T>) -> *const BarS<T> {
    u as *const BarS<T>
}

fn tuple_i32_to_u32<T:?Sized>(u: *const (i32, T)) -> *const (u32, T) {
    u as *const (u32, T)
}


fn main() {
    let s = FooS([0,1,2]);
    let u: &FooS<[u32]> = &s;
    let u: *const FooS<[u32]> = u;
    let bar_ref : *const BarS<[u32]> = foo_to_bar(u);
    let z : &BarS<[u32]> = unsafe{&*bar_ref};
    assert_eq!(&z.0, &[0,1,2]);

    // this assumes that tuple reprs for (i32, _) and (u32, _) are
    // the same.
    let s = (0i32, [0, 1, 2]);
    let u: &(i32, [u8]) = &s;
    let u: *const (i32, [u8]) = u;
    let u_u32 : *const (u32, [u8]) = tuple_i32_to_u32(u);
    unsafe {
        assert_eq!(&(*u_u32).1, &[0, 1, 2]);
    }
}