src/test/run-pass/dst-coerce-custom.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 // Test a very simple custom DST coercion.
  12
  13 #![feature(unsize, coerce_unsized)]
  14
  15 use std::ops::CoerceUnsized;
  16 use std::marker::Unsize;
  17
  18 struct Bar<T: ?Sized> {
  19     x: *const T,
  20 }
  21
  22 impl<T: ?Sized+Unsize<U>, U: ?Sized> CoerceUnsized<Bar<U>> for Bar<T> {}
  23
  24 trait Baz {
  25     fn get(&self) -> i32;
  26 }
  27
  28 impl Baz for i32 {
  29     fn get(&self) -> i32 {
  30         *self
  31     }
  32 }
  33
  34 fn main() {
  35     // Arrays.
  36     let a: Bar<[i32; 3]> = Bar { x: &[1, 2, 3] };
  37     // This is the actual coercion.
  38     let b: Bar<[i32]> = a;
  39
  40     unsafe {
  41         assert_eq!((*b.x)[0], 1);
  42         assert_eq!((*b.x)[1], 2);
  43         assert_eq!((*b.x)[2], 3);
  44     }
  45
  46     // Trait objects.
  47     let a: Bar<i32> = Bar { x: &42 };
  48     let b: Bar<Baz> = a;
  49     unsafe {
  50         assert_eq!((*b.x).get(), 42);
  51     }
  52 }