No equivalent of into_boxed_str for CString/CStr

[jonhoo]

I'm working on implementing serde::Deserialize for CStr (in serde-rs/serde#801), and am running into the need for an equivalent of String::into_boxed_str for CString/CStr. With the current internals for CStr, I believe the implementation could be very similar; namely:

pub fn into_boxed_cstr(self) -> Box<CStr> {
    unsafe { mem::transmute::<Box<[u8]>, Box<CStr>>(self.inner) }
}

Is this something that could be added in line with #18283 ?

[alexcrichton]

I think this was added in #39594, but can you confirm that the one you're looking for was there?

[jonhoo]

Ah, yes, that looks perfect! Thanks.