MBE template parsing fails with ///

[lnicola]

macro_rules! features {
        {
            $(
                $name:ident {
                    ///
                }
            ),+
            ,
        } => {};
        {} => {}
}

features! {
    NEON { },
}

fn main() {}

Adapted from ring.

[edwin0cheng]

This part in rustc is quite ambitious :

This one works:

macro_rules! m{
    {{
       #[doc=r"abcde"]
    }
    } => { }
}
m!({/**abcde*/});
fn main() {}

This one doesn't works:

macro_rules! m{
    {{
       /**abcde*/
    }
    } => { }
}

m!({/**abcde*/});
fn main() {}

This one works:

macro_rules! m{
    {{
       /***/
    }
    } => { }
}

m!({/***/});
fn main() {}

This one doesn't work:

macro_rules! m{
    {{
       ///
    }
    } => { }
}

m!({
    ///
});

fn main() {}

(ノಠ益ಠ)ノ彡┻━┻

[lnicola]

Might be worth asking in #t-compiler.

[lnicola]

I didn't realize that features! {} actually works with my updated example.

And we also seem to expose the #[doc] desugaring:

[edwin0cheng]

I didn't realize that features! {} actually works with my updated example.

The second branch couldn't be matched because of the "NEON" and the comma.

And we also seem to expose the #[doc] desugaring:

Yes, we desugar all doc comment in mbe included empty one, and that's why we failed because we expect a doc comment in macro invocation.

[bjorn3]

This one doesn't work:

macro_rules! m{
    {{
       ///
    }
    } => { }
}

m!({
    ///
});

fn main() {}

I did guess that rustc doesn't desugar /// into #[doc = "..."] inside the macro rules matcher.