use std::{ffi::OsStr, path::Path, ptr};

/// Until [`Box::map()`] is stable, there's no way to do this that is safe, stable, and
/// allocationless.
pub trait BoxedPathExt {
    fn into_boxed_os_str(self) -> Box<OsStr>;
}

impl BoxedPathExt for Box<Path> {
    fn into_boxed_os_str(self) -> Box<OsStr> {
        let path_mut_ptr: *mut Path = Box::into_raw(self);

        // SAFETY: we just got `path_mut_ptr` from a valid Box.
        let os_str_mut_ptr: *mut OsStr = unsafe {
            let os_str_mut_ref = path_mut_ptr
                .as_mut()
                .expect("avoided undefined behavior")
                .as_mut_os_str();

            ptr::from_mut(os_str_mut_ref)
        };

        // SAFETY: allocation came from `Box::into_raw()`, and we are not extending
        // its lifetime. There are also no shared or exclusive references.
        unsafe { Box::<OsStr>::from_raw(os_str_mut_ptr) }
    }
}