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#![feature(no_core)] #![feature(lang_items)] #![no_core] #[lang = "sized"] trait Sized {} trait A<T: ?Sized> {} struct Cell<X> { // { dg-warning "struct is never constructed" "" { target *-*-* } .-1 } x: X, } impl<T, U> A<Cell<U>> for Cell<T> where T: A<U> {}