src/test/ui/consts/const-eval/const_fn_ptr_fail.rs

// run-pass
// compile-flags: -Zunleash-the-miri-inside-of-you
#![feature(const_fn)]
#![allow(unused)]

fn double(x: usize) -> usize { x * 2 }
const X: fn(usize) -> usize = double;

const fn bar(x: usize) -> usize {
    X(x) // FIXME: this should error someday
    //~^ WARN: skipping const checks
}

fn main() {}