我正在尝试创建一个过程宏（CountOf），它统计集合中特定枚举变体的发生率，在本例中是向量。
这个src/macros.rs就是我用来测试宏的

#[derive(count_of::CountOf, Clone)]
pub enum SomeEnum {
    Variant1,
    Variant2,
    Variant3,
}

#[cfg(test)]
mod tests {
    use super::*;
#[test]
    fn count_of_works() {
        use SomeEnum::*;
        let enums = vec![
            Variant1,
            Variant1,
            Variant2,
            Variant3,
            Variant2,
            Variant2,
        ];

        assert_eq!(enums.variant1_count(), 2);
        assert_eq!(enums.variant2_count(), 3);
        assert_eq!(enums.variant3_count(), 1);
    }
}

这是我在count_of板条箱中的lib.rs：

use inflector::Inflector;
use quote::quote;

#[proc_macro_derive(CountOf)]
pub fn count_of(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
    let input = syn::parse_macro_input!(input as syn::ItemEnum);
    let name = input.ident;

    let variants = input.variants.iter().map(|variant| {
        let variant_name = &variant.ident;
        let variant_count = variant_name.to_string().to_lowercase();

        quote! {
            pub fn #variant_count(&self) -> usize {
                self.iter().filter(|&&x| x == &#name::#variant_name).count()
            }
        }
    });

    let output = quote! {
        impl #name {
            #(#variants)*
        }
    };

    proc_macro::TokenStream::from(output)
}

这是我在Cargo.toml中的依赖项：

[dependencies]
count-of           = { path = "./count-of" }

这是：

[package]
name    = "count-of"
version = "0.1.0"

[lib]
proc-macro = true

[dependencies]
syn         = { version = "2.0.15", features = ["full"] }
quote       = "1.0.26"
Inflector   = "0.11.4"
proc-macro2 = "1.0.56"

获取此错误：

error: expected identifier, found `"Variant1"`
  --> src/macros.rs:92:10
   |
92 | #[derive(count_of::CountOf, Clone)]
   |          ^^^^^^^^^^^^^^^^^
   |          |
   |          expected identifier
   |          while parsing this item list starting here
   |          the item list ends here
   |
   = note: this error originates in the derive macro `count_of::CountOf` (in Nightly builds, run with -Z macro-backtrace for more info)

error: proc-macro derive produced unparseable tokens
  --> src/macros.rs:92:10
   |
92 | #[derive(count_of::CountOf, Clone)]
   |          ^^^^^^^^^^^^^^^^^
error[E0599]: no method named `variant1_count` found for struct `Vec<SomeEnum>` in the current scope
   --> src/macros.rs:135:23
    |
135 |         assert_eq!(enums.variant1_count(), 2);
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^ method not found in `Vec<SomeEnum>`

error[E0599]: no method named `variant2_count` found for struct `Vec<SomeEnum>` in the current scope
   --> src/macros.rs:136:23
    |
136 |         assert_eq!(enums.variant2_count(), 3);
    |                             ^^^^^^^^^^^^^^^^^ method not found in `Vec<SomeEnum>`

error[E0599]: no method named `variant3_count` found for struct `Vec<SomeEnum>` in the current scope
   --> src/macros.rs:137:23
    |
137 |         assert_eq!(enums.variant3_count(), 1);
    |                             ^^^^^^^^ method not found in `Vec<SomeEnum>`

我认为我的程序宏是问题，但找不到解决方法。如果有人有一个解决方案，会非常感激。