63 lines
1.6 KiB
Rust
63 lines
1.6 KiB
Rust
//@ run-pass
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// Check that you can cast between different pointers to trait objects
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// whose vtable have the same kind (both lengths, or both trait pointers).
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#![feature(unsized_tuple_coercion)]
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trait Foo<T> {
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fn foo(&self, _: T) -> u32 { 42 }
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}
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trait Bar { //~ WARN trait `Bar` is never used
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fn bar(&self) { println!("Bar!"); }
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}
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impl<T> Foo<T> for () {}
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impl Foo<u32> for u32 { fn foo(&self, _: u32) -> u32 { self+43 } }
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impl Bar for () {}
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unsafe fn round_trip_and_call<'a>(t: *const (dyn Foo<u32>+'a)) -> u32 {
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let foo_e : *const dyn Foo<u32> = t as *const _;
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let r_1 = foo_e as *mut dyn Foo<u32>;
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(&*r_1).foo(0)
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}
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#[repr(C)]
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struct FooS<T:?Sized>(T);
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#[repr(C)]
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struct BarS<T:?Sized>(T);
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fn foo_to_bar<T:?Sized>(u: *const FooS<T>) -> *const BarS<T> {
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u as *const BarS<T>
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}
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fn tuple_i32_to_u32<T:?Sized>(u: *const (i32, T)) -> *const (u32, T) {
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u as *const (u32, T)
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}
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fn main() {
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let x = 4u32;
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let y : &dyn Foo<u32> = &x;
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let fl = unsafe { round_trip_and_call(y as *const dyn Foo<u32>) };
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assert_eq!(fl, (43+4));
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let s = FooS([0,1,2]);
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let u: &FooS<[u32]> = &s;
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let u: *const FooS<[u32]> = u;
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let bar_ref : *const BarS<[u32]> = foo_to_bar(u);
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let z : &BarS<[u32]> = unsafe{&*bar_ref};
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assert_eq!(&z.0, &[0,1,2]);
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// this assumes that tuple reprs for (i32, _) and (u32, _) are
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// the same.
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let s = (0i32, [0, 1, 2]);
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let u: &(i32, [u8]) = &s;
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let u: *const (i32, [u8]) = u;
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let u_u32 : *const (u32, [u8]) = tuple_i32_to_u32(u);
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unsafe {
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assert_eq!(&(*u_u32).1, &[0, 1, 2]);
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}
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}
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