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