error[E0507]: cannot move out of borrowed content

main.rs

extern crate unidiff;

use unidiff::PatchSet; // http://messense.github.io/unidiff-rs/unidiff/struct.PatchSet.html

pub struct Printer {
    patch_set: PatchSet,
}

impl Printer {
    pub fn new(source: &str) -> Self {
        let mut patch_set = PatchSet::new();

        patch_set
            .parse(source)
            .ok()
            .expect("Error parsing source diff");

        Printer {
            patch_set,
        }
    }

    fn write_patches(&self, output: &mut dyn fmt::Write) {
        for patched_file in &self.patch_set {
//                          ^^^^^^^^^^^^^^ cannot move out of borrowed content
            // ...do something with `patched_file`
        }
    }
}