tait-hidden-erased-unsoundness-2.rs

// This test should never pass!

#![feature(type_alias_impl_trait)]

pub trait Captures<'a> {}
impl<T> Captures<'_> for T {}

pub struct MyTy<'a, 'b>(Option<*mut &'a &'b ()>);
unsafe impl Send for MyTy<'_, 'static> {}

pub mod step1 {
    use super::*;
    pub type Step1<'a, 'b: 'a> = impl Sized + Captures<'b> + 'a;
    pub fn step1<'a, 'b: 'a>() -> Step1<'a, 'b> {
        MyTy::<'a, 'b>(None)
    }
}

pub mod step2 {
    pub type Step2<'a> = impl Send + 'a;

    // Although `Step2` is WF at the definition site, it's not WF in its
    // declaration site (above). We check this in `check_opaque_meets_bounds`,
    // which must remain sound.
    pub fn step2<'a, 'b: 'a>() -> Step2<'a>
        where crate::step1::Step1<'a, 'b>: Send
    {
        crate::step1::step1::<'a, 'b>()
        //~^ ERROR hidden type for `Step2<'a>` captures lifetime that does not appear in bounds
    }
}

fn step3<'a, 'b>() {
    fn is_send<T: Send>() {}
    is_send::<crate::step2::Step2::<'a>>();
}

fn main() {}