让我们假设我有一个枚举，并且我想以某种方式注释或关联每个变体与`&str`。例如：
```rust
enum MyEnum {
    A, // "foo"
    B(String), // "bar"
    C(i32) // "baz"
}

const arr: [&'static str; 3] = ["foo", "bar", "baz"];

<details>
<summary>英文:</summary>
Let&#39;s say I have an enum, and I want to somehow annotate or associate each variant with a `&amp;str`. E.g.:

I would also like to collect these `&str`'s into an array like

Is there a nice way to do this automatically at compile time? Rather than having to write out the constant array separately? Perhaps with macros?
A `const fn` would answer the first part, but I believe it requires `#![feature(const_if_match)]`, and I would prefer using stable Rust if possible. I'm also not sure it answered the second part. I also considered attribute macros, but I don't know how (or whether) you can collect these attributes together at compile time.
</details>
# 答案1
**得分**: 0
您可以使用声明性宏来实现这一点：
```rust
macro_rules! str_variants {
    { enum $enum_name:ident {
        $(
        #[str = $variant_str:literal]
        $variant_name:ident $variant_fields:tt
        ),* $(,)*
    } } => {
        enum $enum_name {
            $(
                $variant_name $variant_fields,
            )*
        }
        impl $enum_name {
            const ARR: &[&'static str] = &[
                $(
                    $variant_str,
                )*
            ];
        }
    }
}
str_variants! { enum MyEnum {
    #[str = "foo"]
    A(),
    #[str = "bar"]
    B(String),
    #[str = "baz"]
    C(i32)
} }
fn main() {
    dbg!(MyEnum::ARR);
    // [src/main.rs:34] MyEnum::ARR = [
    //     "foo",
    //     "bar",
    //     "baz",
    // ]
}