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21 lines
399 B
Rust
21 lines
399 B
Rust
// build-pass
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#![feature(trait_upcasting)]
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pub trait A {}
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pub trait B {}
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pub trait C: A + B {}
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impl<X: A + B> C for X {}
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pub fn test<'a, T>(view: T) -> Option<&'a mut dyn B>
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where
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T: IntoIterator<Item = &'a mut dyn B>,
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{
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return Some(view.into_iter().next().unwrap());
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}
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fn main() {
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let mut a: Vec<Box<dyn C>> = Vec::new();
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test(a.iter_mut().map(|c| c.as_mut() as &mut dyn B));
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}
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