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//@ run-pass
use std::mem::MaybeUninit;
trait CollectSlice<'a>: Iterator {
fn inner_array<const N: usize>(&mut self) -> [Self::Item; N];
fn collect_array<const N: usize>(&mut self) -> [Self::Item; N] {
let result = self.inner_array();
assert!(self.next().is_none());
result
}
}
impl<'a, I: ?Sized> CollectSlice<'a> for I
where
I: Iterator,
{
fn inner_array<const N: usize>(&mut self) -> [Self::Item; N] {
let mut result: [MaybeUninit<Self::Item>; N] =
unsafe { MaybeUninit::uninit().assume_init() };
let mut count = 0;
for (dest, item) in result.iter_mut().zip(self) {
*dest = MaybeUninit::new(item);
count += 1;
}
assert_eq!(N, count);
let temp_ptr: *const [MaybeUninit<Self::Item>; N] = &result;
unsafe { std::ptr::read(temp_ptr as *const [Self::Item; N]) }
}
}
fn main() {
let mut foos = [0u64; 9].iter().cloned();
let _bar: [u64; 9] = foos.collect_array::<9_usize>();
}
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