#![feature(type_ascription)]
#![allow(dead_code)]

// SUMMARY OF BEHAVIOR
//
// EDITION        WILD      VAR       EXPR      ARG
// -----------    ------    ------    ------    ------
// 2015/AST       accept    accept    reject    accept
// 2018/AST       accept    accept    reject    accept
// #55748 hack    reject    accept    reject    accept

#[derive(Copy, Clone)]
struct Covariant<'a> {
    f: extern "Rust" fn(&'a isize)
}

fn co_arg(_co_s: Covariant<'static>) { }

#[cfg(not_now)]
fn ascribe_wild<'a>(co: Covariant<'a>) {
    let _: Covariant<'static> = co;     // (ascribe on) WILD(card)
}

#[cfg(not_now)]
fn ascribe_var<'a>(co: Covariant<'a>) {
    let _c: Covariant<'static> = co; // (ascribe on) VAR
}

#[cfg(not_now)]
fn ascribe_expr<'a>(co: Covariant<'a>) {
    let _ = co: Covariant<'static>;  // (ascribe on) EXPR
}

// #[cfg(not_now)]
fn pass_actual_arg<'a>(co: Covariant<'a>) {
    co_arg(co);                      // (actual )ARG(ument)
}

pub fn main() {}