mirror of https://github.com/rust-lang/rust
39 lines
1.0 KiB
Rust
39 lines
1.0 KiB
Rust
//@ 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>();
|
|
}
|