macro_rules blocks shouldn't allow fragment specifiers

[sugar700]

I often make this mistake, and it's tricky to debug while being VERY unlikely to be what is wanted.

macro_rules! x { ($a:expr) => {$a:expr} }

This should be:

macro_rules! x { ($a:expr) => {$a} }

[oli-obk]

I don't think we can be of any help here, since by the time clippy acts, we don't see any macros anymore. We can try though