Problem

Can't invoke nested macro without increasing internal_macro_calls. In test example this value in join_all! macro attribute is 5 because in code

let results = join_all!(ready(join_all!(ready(7usize)).0), ready(join_all!(ready(8usize)).0), ready(join_all!(ready(join_all!(ready(9usize)).0)).0));

we have 5 calls of join_all! macro each of which inserts 1 nested join! macro. Of course this problem can be solved by setting internal_macro_calls to maximum value, but...

Unfortunately, in situation with join_all_x2! even value of 60 doesn't help.

Run tests:

cargo test

Expand macros:

cargo rustc --profile=check -- -Zunstable-options --pretty=expanded -Z external-macro-backtrace