rust/tests/ui/traits/pointee-tail-is-generic.rs

//@ check-pass
//@ edition:2018

#![feature(ptr_metadata)]
#![feature(type_alias_impl_trait)]

mod opaque {
    pub type Opaque = impl std::future::Future;

    fn opaque() -> Opaque {
        async {}
    }
}

fn a<T>() {
    // type parameter T is known to be sized
    is_thin::<T>();
    // tail of ADT (which is a type param) is known to be sized
    is_thin::<std::cell::Cell<T>>();
    // opaque type is known to be sized
    is_thin::<opaque::Opaque>();
}

fn a2<T: Iterator>() {
    // associated type is known to be sized
    is_thin::<T::Item>();
}

fn is_thin<T: std::ptr::Pointee<Metadata = ()>>() {}

fn main() {}