26 lines
657 B
Rust
26 lines
657 B
Rust
//@ run-pass
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// Elaborated version of the opening example from RFC 738. This failed
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// to compile before variance because invariance of `Option` prevented
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// us from approximating the lifetimes of `field1` and `field2` to a
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// common intersection.
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#![allow(dead_code)]
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struct List<'l> {
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field1: &'l i32,
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field2: Option<&'l i32>,
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}
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fn foo(field1: &i32, field2: Option<&i32>) -> i32 {
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let list = List { field1: field1, field2: field2 };
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*list.field1 + list.field2.cloned().unwrap_or(0)
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}
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fn main() {
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let x = 22;
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let y = Some(3);
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let z = None;
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assert_eq!(foo(&x, y.as_ref()), 25);
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assert_eq!(foo(&x, z.as_ref()), 22);
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}
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