// revisions: full min #![cfg_attr(full, feature(adt_const_params))] #![cfg_attr(full, allow(incomplete_features))] use std::ffi::{CStr, CString}; unsafe fn unsafely_do_the_thing<const F: fn(&CStr) -> usize>(ptr: *const i8) -> usize { //~^ ERROR: using function pointers as const generic parameters is forbidden F(CStr::from_ptr(ptr)) } fn safely_do_the_thing(s: &CStr) -> usize { s.to_bytes().len() } fn main() { let baguette = CString::new("baguette").unwrap(); let ptr = baguette.as_ptr(); println!("{}", unsafe { unsafely_do_the_thing::<safely_do_the_thing>(ptr) }); }