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// Test a case where you have an impl of `Foo<X>` for all `X` that
// is being applied to `for<'a> Foo<&'a mut X>`. Issue #19730.
trait Foo<X> {
fn foo(&mut self, x: X) {}
}
trait Bar<X> {
fn bar(&mut self, x: X) {}
}
impl<'a, X, F> Foo<X> for &'a mut F where F: Foo<X> + Bar<X> {}
impl<'a, X, F> Bar<X> for &'a mut F where F: Bar<X> {}
fn no_hrtb<'b, T>(mut t: T) //~ WARN function cannot return
where
T: Bar<&'b isize>,
{
// OK -- `T : Bar<&'b isize>`, and thus the impl above ensures that
// `&mut T : Bar<&'b isize>`.
no_hrtb(&mut t);
}
fn bar_hrtb<T>(mut t: T) //~ WARN function cannot return
where
T: for<'b> Bar<&'b isize>,
{
// OK -- `T : for<'b> Bar<&'b isize>`, and thus the impl above
// ensures that `&mut T : for<'b> Bar<&'b isize>`. This is an
// example of a "perfect forwarding" impl.
bar_hrtb(&mut t);
}
fn foo_hrtb_bar_not<'b, T>(mut t: T) //~ WARN function cannot return
where
T: for<'a> Foo<&'a isize> + Bar<&'b isize>,
{
// Not OK -- The forwarding impl for `Foo` requires that `Bar` also
// be implemented. Thus to satisfy `&mut T : for<'a> Foo<&'a
// isize>`, we require `T : for<'a> Bar<&'a isize>`, but the where
// clause only specifies `T : Bar<&'b isize>`.
foo_hrtb_bar_not(&mut t);
//~^ ERROR implementation of `Bar` is not general enough
//~^^ ERROR lifetime may not live long enough
}
fn foo_hrtb_bar_hrtb<T>(mut t: T) //~ WARN function cannot return
where
T: for<'a> Foo<&'a isize> + for<'b> Bar<&'b isize>,
{
// OK -- now we have `T : for<'b> Bar<&'b isize>`.
foo_hrtb_bar_hrtb(&mut t);
}
fn main() {}
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