doc does not correctly display macro match arms if they are created inside of a proc macro

[lcnr]

When creating a macro tagged with #[macro_export] inside of a proc_macro_derive the documentation incorrectly displays the name of the derive instead of the match pattern.

I tried this code: (everything is the same as here except for "main.rs" and "impl_hello_world()").

main.rs:

#[macro_use]
extern crate hello_world_derive;

#[derive(HelloWorld)]
struct Foo {
}

fn main() {
    Foo!("Hi");
}

hello-world-derive/src/lib.rs:

/* ... */

fn impl_hello_world(ast: &syn::DeriveInput) -> quote::Tokens {
    let name = &ast.ident;
    quote! {
        #[macro_export]
        macro_rules! #name {
            ($expr:expr) => {
                println!("expr: {}", $expr);
            }
        }
    }
}

When opening the automatic documentation(cargo doc --open) I expected Foo! to look like this:

macro_rules! Foo {
    ($expr:expr) => { ... };
}

Instead, Foo looked like this: ( the name of the derive instead of the actual match pattern.)

macro_rules! Foo {
    HelloWorld => { ... };
}

In case the created macro has more than 1 match arm it looks like this:

macro_rules! Foo {
    HelloWorld => { ... };
    HelloWorld => { ... };
}

Meta

rustc --version --verbose:

rustc 1.19.0 (0ade339 2017-07-17)
binary: rustc
commit-hash: 0ade339
commit-date: 2017-07-17
host: x86_64-pc-windows-msvc
release: 1.19.0
LLVM version: 4.0

[camelid]

I tested this, and it is fixed now. I believe it was fixed in #86282.

Updated proc-macro code based on modern Rust:

use proc_macro::TokenStream;
use quote::quote;

#[proc_macro_derive(HelloWorld)]
pub fn impl_hello_world(input: TokenStream) -> TokenStream {
    let ast: syn::DeriveInput = syn::parse(input).unwrap();
    let name = &ast.ident;
    quote! {
        #[macro_export]
        macro_rules! #name {
            ($expr:expr) => {
                println!("expr: {}", $expr);
            }
        }
    }.into()
}