Wrong compiler suggestion for no_mangle statics inside private module

[phil-opp]

Defining a pub static inside a private module like this

mod test {
    #[no_mangle]
    pub static FOO: usize = 1;
}

yields the following warning:

warning: static is marked #[no_mangle], but not exported
 --> src/main.rs:7:5
  |
7 |     pub static FOO: usize = 1;
  |     -^^^^^^^^^^^^^^^^^^^^^^^^^
  |     |
  |     help: try making it public: `pub`
  |
  = note: #[warn(private_no_mangle_statics)] on by default

The suggestion wrongly tells us to add a pub to the already public FOO.

(playpen)