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#![allow(bare_trait_objects)]
// check-pass
pub struct FormatWith<'a, I, F> {
sep: &'a str,
/// FormatWith uses interior mutability because Display::fmt takes &self.
inner: RefCell<Option<(I, F)>>,
}
use std::cell::RefCell;
use std::fmt;
struct Layout;
pub fn new_format<'a, I, F>(iter: I, separator: &'a str, f: F) -> FormatWith<'a, I, F>
where
I: Iterator,
F: FnMut(I::Item, &mut FnMut(&fmt::Display) -> fmt::Result) -> fmt::Result,
{
FormatWith { sep: separator, inner: RefCell::new(Some((iter, f))) }
}
fn main() {
let _ = new_format(0..32, " | ", |i, f| f(&format_args!("0x{:x}", i)));
}
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