src/test/ui/rfc-2632-const-trait-impl/const-check-fns-in-const-impl.rs

#![allow(incomplete_features)]
#![feature(const_trait_impl)]

struct S;
trait T {
    fn foo();
}

fn non_const() {}

impl const T for S {
    fn foo() { non_const() }
    //~^ ERROR can only call other `const fn`
}

fn main() {}