mut struct member var(ref) bind to new obj still hint: does not live long enough

#[derive(Debug)]
struct ImportantExcerpt<'a> {
    part: &'a str,
}

fn main() {
    let mut root = ImportantExcerpt {part: "abc"};
    {
        let novel = String::from("Call me Ishmael. Some years ago...");
        let first_sentence = novel.split('.').next().expect("Could not find a '.'");
        root = ImportantExcerpt {part: first_sentence};
        root.part = "1234";  // bind to new static str
    }
    println!("{:?}", root);  // error does not live long enough
}

Start by compiling the standalone Rust reproducer in the issue and inspect the lifetime diagnostic around the assignment to root.part. Compare the reported error with the intended lifetime behavior; done requires establishing whether this is a compiler bug and, if so, adding an appropriate regression test.