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//@ run-pass
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#![allow(non_camel_case_types)]
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trait double {
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fn double(self: Box<Self>) -> usize;
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}
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impl double for usize {
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fn double(self: Box<usize>) -> usize { *self * 2 }
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}
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pub fn main() {
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let x: Box<Box<_>> = Box::new(Box::new(3));
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assert_eq!(x.double(), 6);
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}
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