53 lines
1.0 KiB
Rust
53 lines
1.0 KiB
Rust
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use std::marker::PhantomData;
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trait DistributedIterator {
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fn reduce(self)
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where
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Self: Sized,
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{
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unreachable!()
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}
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}
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trait DistributedIteratorMulti<Source> {
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type Item;
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}
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struct Connect<I>(PhantomData<fn(I)>);
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impl<I: for<'a> DistributedIteratorMulti<&'a ()>> DistributedIterator for Connect<I> where {}
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struct Cloned<Source>(PhantomData<fn(Source)>);
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impl<'a, Source> DistributedIteratorMulti<&'a Source> for Cloned<&'a Source> {
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type Item = ();
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}
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struct Map<I, F> {
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i: I,
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f: F,
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}
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impl<I: DistributedIteratorMulti<Source>, F, Source> DistributedIteratorMulti<Source> for Map<I, F>
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where
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F: A<<I as DistributedIteratorMulti<Source>>::Item>,
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{
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type Item = ();
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}
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trait A<B> {}
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struct X;
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impl A<()> for X {}
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fn multi<I>(_reducer: I)
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where
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I: for<'a> DistributedIteratorMulti<&'a ()>,
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{
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DistributedIterator::reduce(Connect::<I>(PhantomData))
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}
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fn main() {
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multi(Map { //~ ERROR implementation of `DistributedIteratorMulti` is not general enough
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i: Cloned(PhantomData),
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f: X,
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});
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}
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