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// run-pass
// compile-flags:-Zmir-opt-level=3
use std::mem::MaybeUninit;
const N: usize = 2;
trait CollectArray<A>: Iterator<Item = A> {
fn inner_array(&mut self) -> [A; N];
fn collect_array(&mut self) -> [A; N] {
let result = self.inner_array();
assert!(self.next().is_none());
result
}
}
impl<A, I: ?Sized> CollectArray<A> for I
where
I: Iterator<Item = A>,
{
fn inner_array(&mut self) -> [A; N] {
let mut result: [MaybeUninit<A>; N] = unsafe { MaybeUninit::uninit().assume_init() };
for (dest, item) in result.iter_mut().zip(self) {
*dest = MaybeUninit::new(item);
}
let temp_ptr: *const [MaybeUninit<A>; N] = &result;
unsafe { std::ptr::read(temp_ptr as *const [A; N]) }
}
}
fn main() {
assert_eq!(
[[1, 2], [3, 4]]
.iter()
.map(|row| row.iter().collect_array())
.collect_array(),
[[&1, &2], [&3, &4]]
);
}
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