tokio-macros 1.8.1 regression

[taiki-e]

NOTE(taiki-e): I yanked 1.8.1 for now.

---

I have a suspicion that this cause an interesting regression, but I'm not certain.

In our codebase, we have something along the lines of

macro_rules! custom_test {
    (async fn $name:ident() $b:block) => {
        #[::tokio::test]
        async fn $name() {
            dbg!("foo");
            $b
        }
    };
}

// usage normally with macro_rules_attribute, but for demonstration
custom_test!(
    async fn foo() {
        dbg!("bar");
    }
);

This compiles with tokio-macros 1.8.0 but does not with 1.8.1

error[E0425]: cannot find value `body` in this scope
  --> tests/main.rs:74:20
   |
74 |       async fn foo() {
   |  ____________________^
75 | |         dbg!("bar");
76 | |     }
   | |_____^ not found in this scope

Originally posted by @conradludgate in #5092 (comment)

[taiki-e]

This issue reminds me of dtolnay/async-trait#104...

[taiki-e]

Filed #5244 to fix this.