letr

The lazy way out.

```rust fn simple() { enum Items { RevItem(Option), ForItem(u32), }

fn foo(x: Items) -> i32 {
    letr! {
        Items::RevItem(ret) = x, else -1;
        Some(ret) = ret, else -1;
    };
    ret
}
assert_eq!(foo(Items::RevItem(Some(0))), 0);
assert_eq!(foo(Items::ForItem(0)), -1);

} ```