Rust: 不能在没有中间 let 绑定的情况下解构盒装结构

此代码无法编译：

struct Foo;

struct Bar {
    a: Foo,
    b: Foo,
}

fn main() {
    let bar = Box::new(Bar { a: Foo, b: Foo });

    let Bar { a, b } = *bar;
}

error[E0382]: use of moved value: `bar`
  --> x.rs:11:18
   |
11 |     let Bar { a, b } = *bar;
   |               -  ^ value used here after move
   |               |
   |               value moved here
   |
   = note: move occurs because `bar.a` has type `Foo`, which does not implement the `Copy` trait

然而，在盒子 deref 和解构之间插入一个中间 let 绑定可以修复它：

fn main() {
    let bar = Box::new(Bar { a: Foo, b: Foo });

    let Bar { a, b } = { let intermediate = *bar; intermediate };
}

这感觉像一个错误。

受影响的版本：

• rustc 1.23.0 (766bd11c8 2018-01-01)

• rustc 1.25.0-nightly (73ac5d6a8 2018-01-11)