| #![feature(type_alias_impl_trait)] |
| |
| //@ build-pass |
| |
| trait Bar { |
| fn bar(&self); |
| } |
| |
| type FooFn<B> = impl FnOnce(B); |
| |
| #[define_opaque(FooFn)] |
| fn foo<B: Bar>() -> FooFn<B> { |
| fn mop<B: Bar>(bar: B) { |
| bar.bar() |
| } |
| mop as fn(B) |
| // function pointers don't have any obligations on them, |
| // thus the above compiles. It's obviously unsound to just |
| // procure a `FooFn` from the ether without making sure that |
| // the pointer is actually legal for all `B` |
| } |
| |
| fn main() { |
| let boom: FooFn<u32> = unsafe { core::mem::zeroed() }; |
| boom(42); |
| } |
