1 #![feature(coerce_unsized, unsize)]
3 use std::marker::Unsize;
4 use std::ops::CoerceUnsized;
6 fn identity_coercion(x: &(dyn Fn(u32) -> u32 + Send)) -> &dyn Fn(u32) -> u32 {
9 fn fn_coercions(f: &fn(u32) -> u32) -> (unsafe fn(u32) -> u32, &(dyn Fn(u32) -> u32 + Send)) {
13 fn simple_array_coercion(x: &[u8; 3]) -> &[u8] {
17 fn square(a: u32) -> u32 {
21 #[derive(PartialEq, Eq)]
22 struct PtrWrapper<'a, T: 'a + ?Sized>(u32, u32, (), &'a T);
23 impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<PtrWrapper<'a, U>> for PtrWrapper<'a, T> {}
25 struct TrivPtrWrapper<'a, T: 'a + ?Sized>(&'a T);
26 impl<'a, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<TrivPtrWrapper<'a, U>>
27 for TrivPtrWrapper<'a, T>
31 fn coerce_ptr_wrapper(p: PtrWrapper<[u8; 3]>) -> PtrWrapper<[u8]> {
35 fn coerce_triv_ptr_wrapper(p: TrivPtrWrapper<[u8; 3]>) -> TrivPtrWrapper<[u8]> {
39 fn coerce_fat_ptr_wrapper(
40 p: PtrWrapper<dyn Fn(u32) -> u32 + Send>,
41 ) -> PtrWrapper<dyn Fn(u32) -> u32> {
45 fn coerce_ptr_wrapper_poly<'a, T, Trait: ?Sized>(p: PtrWrapper<'a, T>) -> PtrWrapper<'a, Trait>
47 PtrWrapper<'a, T>: CoerceUnsized<PtrWrapper<'a, Trait>>,
54 let square_local: fn(u32) -> u32 = square;
55 let (f, g) = fn_coercions(&square_local);
56 // cannot use `square as *const ()` because we can't know whether the compiler duplicates
57 // functions, so two function pointers are only equal if they result from the same function
58 // to function pointer cast
59 assert_eq!(f as *const (), square_local as *const ());
61 assert_eq!(identity_coercion(g)(5), 25);
63 assert_eq!(simple_array_coercion(&a), &a);
64 let w = coerce_ptr_wrapper(PtrWrapper(2, 3, (), &a));
65 assert!(w == PtrWrapper(2, 3, (), &a) as PtrWrapper<[u8]>);
67 let w = coerce_triv_ptr_wrapper(TrivPtrWrapper(&a));
70 let z = coerce_fat_ptr_wrapper(PtrWrapper(2, 3, (), &square_local));
71 assert_eq!((z.3)(6), 36);
73 let z: PtrWrapper<dyn Fn(u32) -> u32> =
74 coerce_ptr_wrapper_poly(PtrWrapper(2, 3, (), &square_local));
75 assert_eq!((z.3)(6), 36);