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35 lines
1.2 KiB
Rust
35 lines
1.2 KiB
Rust
// run-pass
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use std::mem;
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pub fn main() {
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// By Ref Capture
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let a = 10i32;
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let b = Some(|| println!("{}", a));
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// When we capture by reference we can use any of the
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// captures as the discriminant since they're all
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// behind a pointer.
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assert_eq!(mem::size_of_val(&b), mem::size_of::<usize>());
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// By Value Capture
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let a = Box::new(12i32);
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let b = Some(move || println!("{}", a));
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// We captured `a` by value and since it's a `Box` we can use it
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// as the discriminant.
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assert_eq!(mem::size_of_val(&b), mem::size_of::<Box<i32>>());
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// By Value Capture - Transitive case
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let a = "Hello".to_string(); // String -> Vec -> Unique -> NonZero
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let b = Some(move || println!("{}", a));
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// We captured `a` by value and since down the chain it contains
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// a `NonZero` field, we can use it as the discriminant.
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assert_eq!(mem::size_of_val(&b), mem::size_of::<String>());
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// By Value - No Optimization
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let a = 14i32;
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let b = Some(move || println!("{}", a));
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// We captured `a` by value but we can't use it as the discriminant
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// thus we end up with an extra field for the discriminant
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assert_eq!(mem::size_of_val(&b), mem::size_of::<(i32, i32)>());
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}
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