Can ItemImpl::parse not consume attrs in syn::parse::ParseStream of a free-standing function?

[CNCSMonster]

code example

write below to src/main.rs

use quote::quote;
use syn::{ItemFn, ItemImpl};

pub enum ItemImplOrFn {
    Fn(ItemFn),
    Impl(ItemImpl),
}

impl syn::parse::Parse for ItemImplOrFn {
    fn parse(input: syn::parse::ParseStream) -> syn::Result<Self> {
        println!("parse {}", input);
        ItemImpl::parse(input).map(Self::Impl).or_else(|_| {
            println!("or parse {}", input);
            ItemFn::parse(input).map(Self::Fn)
        })
    }
}

fn main() {
    let code = quote! {
        /// Hello
        fn hello(){}
    };
    let func: ItemFn = syn::parse2(code.clone()).unwrap();
    assert!(!func.attrs.is_empty());

    let ItemImplOrFn::Fn(func) = syn::parse2(code).unwrap() else {
        unreachable!()
    };
    assert!(func.attrs.is_empty());
}

the Cargo.toml dependencies for this code:

[dependencies]
quote = "1.0.38"
syn = { version = "2.0.96", features = ["full"] }

cargo run , then you will see:

parse # [doc = r" Hello"] fn hello () { }
or parse fn hello () { }

which means the parse of the ItemImpl will consume the attrs in its input ParseStream.
which cause if i want to use parse_macro_input! to get my own ItemImplOrFn, i will loss func attrs.
which also not match below declaration in official docs:

Expected: Stop Consuming attrsr

ItemImpl::parse not consume attrs ,then below can be pass

    let code = quote! {
        /// Hello
        fn hello(){}
    };
    let ItemImplOrFn::Fn(func) = syn::parse2(code).unwrap() else {
        unreachable!()
    };
    assert!(!func.attrs.is_empty());