let_unit_value should be allowed in macros

[durka]

I have the following macro:

#[macro_export]
macro_rules! prof {
    ($b:expr) => { prof!(stringify!($b), $b) };
    //($n:expr, $b:expr) => ($b)
    ($n:expr, $b:expr) => {{
        $crate::PROF.with(|wrapped_prof| {
            let appease_borrowck = wrapped_prof.borrow();
            let g = match *appease_borrowck {
                Some(ref prof) => prof.enter($n),
                None => $crate::hprof::enter($n)
            };
            let ret = { $b }; //~ WARN let_unit_value
            drop(g);
            ret
        })
    }}
}

clippy warns let_unit_value on the commented line when the macro is invoked with a $b which returns ().

[llogiq]

The in_macro-check seems to fail here. I'm investigating.

[llogiq]

Strangely, we need both the check of decl.span and local.pat.span. I'll push a PR shortly.

[durka]

Yep, the warning is gone!

[llogiq]

Thanks for the heads-up!

The PR included a test case, so we can be sure it stays that way 😄