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# `box_patterns`
The tracking issue for this feature is: [#29641]
[#29641]: https://github.com/rust-lang/rust/issues/29641
------------------------
Box patterns let you match on `Box<T>`s:
```rust
#![feature(box_patterns)]
fn main() {
let b = Some(Box::new(5));
match b {
Some(box n) if n < 0 => {
println!("Box contains negative number {n}");
},
Some(box n) if n >= 0 => {
println!("Box contains non-negative number {n}");
},
None => {
println!("No box");
},
_ => unreachable!()
}
}
```
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