Failure: Unexpected ShallowInitBox

[R1kM]

Charon commit e0b2b31 aborts on the following code with error message Compilation failed: error: Unexpected ShallowInitBox``

use std::vec;

pub struct Error {
    messages: Vec<u8>,
}

pub struct IntoIter {
  messages: vec::IntoIter<u8>
}

impl Iterator for IntoIter {
    type Item = Error;

    fn next(&mut self) -> Option<Self::Item> {
        Some(Error {
            messages: vec![self.messages.next()?],
        })
    }
}