len_without_is_empty triggers for async len methods, but does not accept async is_empty methods

[zesterer]

The following will trigger the len_without_is_empty error:

impl Foo {
    pub async fn len(&self) -> usize { ... }
    pub async fn is_empty(&self) -> bool { ... }
}

It probably shouldn't expect the exact signature fn(&self) -> bool.

[0xPoe]

https://play.rust-lang.org/?version=stable&mode=debug&edition=2018&gist=79bfeb9fffa256435a1e315490842554

I can't reproduce the issue on rust playground. Could you provide some steps to reproduce it?

[zesterer]

Comment out is_empty. I see no warning. That implies to me that clippy isn't running on the snippet properly.

Actually, this is strange. It doesn't seem to produce this warning at all for async functions, and yet it did when I tested it earlier locally. Has this already been 'fixed'?

[giraffate]

It seems to be fixed by #6980.

[Jarcho]

That change basically whitelisted the allowed types for len to an integral type, Option, or Result. Since async functions return impl Future<Output=T> they'll be skipped over. It's a thing I considered adding, just haven't had the time.