src/test/ui/cast-rfc0401-vtable-kinds.rs

   1 // run-pass
   2 // Check that you can cast between different pointers to trait objects
   3 // whose vtable have the same kind (both lengths, or both trait pointers).
   4
   5 #![feature(unsized_tuple_coercion)]
   6
   7 trait Foo<T> {
   8     fn foo(&self, _: T) -> u32 { 42 }
   9 }
  10
  11 trait Bar {
  12     fn bar(&self) { println!("Bar!"); }
  13 }
  14
  15 impl<T> Foo<T> for () {}
  16 impl Foo<u32> for u32 { fn foo(&self, _: u32) -> u32 { self+43 } }
  17 impl Bar for () {}
  18
  19 unsafe fn round_trip_and_call<'a>(t: *const (dyn Foo<u32>+'a)) -> u32 {
  20     let foo_e : *const dyn Foo<u16> = t as *const _;
  21     let r_1 = foo_e as *mut dyn Foo<u32>;
  22
  23     (&*r_1).foo(0)
  24 }
  25
  26 #[repr(C)]
  27 struct FooS<T:?Sized>(T);
  28 #[repr(C)]
  29 struct BarS<T:?Sized>(T);
  30
  31 fn foo_to_bar<T:?Sized>(u: *const FooS<T>) -> *const BarS<T> {
  32     u as *const BarS<T>
  33 }
  34
  35 fn tuple_i32_to_u32<T:?Sized>(u: *const (i32, T)) -> *const (u32, T) {
  36     u as *const (u32, T)
  37 }
  38
  39
  40 fn main() {
  41     let x = 4u32;
  42     let y : &dyn Foo<u32> = &x;
  43     let fl = unsafe { round_trip_and_call(y as *const dyn Foo<u32>) };
  44     assert_eq!(fl, (43+4));
  45
  46     let s = FooS([0,1,2]);
  47     let u: &FooS<[u32]> = &s;
  48     let u: *const FooS<[u32]> = u;
  49     let bar_ref : *const BarS<[u32]> = foo_to_bar(u);
  50     let z : &BarS<[u32]> = unsafe{&*bar_ref};
  51     assert_eq!(&z.0, &[0,1,2]);
  52
  53     // this assumes that tuple reprs for (i32, _) and (u32, _) are
  54     // the same.
  55     let s = (0i32, [0, 1, 2]);
  56     let u: &(i32, [u8]) = &s;
  57     let u: *const (i32, [u8]) = u;
  58     let u_u32 : *const (u32, [u8]) = tuple_i32_to_u32(u);
  59     unsafe {
  60         assert_eq!(&(*u_u32).1, &[0, 1, 2]);
  61     }
  62 }