#![deny(deref_into_dyn_supertrait)] extern crate core; use core::ops::Deref; // issue 89190 trait A {} trait B: A {} impl<'a> Deref for dyn 'a + B { //~^ ERROR `(dyn B + 'a)` implements `Deref` with supertrait `A` as target //~| WARN this was previously accepted by the compiler but is being phased out; type Target = dyn A; fn deref(&self) -> &Self::Target { todo!() } } fn take_a(_: &dyn A) {} fn whoops(b: &dyn B) { take_a(b) } fn main() {}