Cannot resolve size of either Self or generic type in method signature

[npmccallum]

It seems like this should work:

trait IntoBytes: Sized + Copy {
    fn into_bytes(&self, bytes: &mut [u8; size_of::<Self>()]) {
        let src = self as *const Self as *const u8;
        let dst: *mut u8 = &mut bytes[0];

        unsafe { std::ptr::copy_nonoverlapping::<u8>(src, dst, bytes.len()); }
    }
}

impl IntoBytes for u64 {}
impl IntoBytes for i64 {}

Or at least this:

trait IntoBytes<T: Sized>: Sized + Copy {
    fn into_bytes(&self, bytes: &mut [u8; size_of::<T>()]) {
        let src = self as *const Self as *const u8;
        let dst: *mut u8 = &mut bytes[0];

        unsafe { std::ptr::copy_nonoverlapping::<u8>(src, dst, bytes.len()); }
    }
}

impl IntoBytes<u8> for u64 {}
impl IntoBytes<u8> for i64 {}

[npmccallum]

This seems to be related to #43408, but I also raise the possibility of Self.

[hanna-kruppe]

Self in traits is essentially a generic parameter so this is really the same issue.

[pietroalbini]

Closing as a duplicate.