Rust wants me to write `pub pub`

[jD91mZM2]

Hi! Another fun error message for you:

warning: function is marked #[no_mangle], but not exported
  --> src/c_api.rs:63:1
   |
63 |   pub extern fn rot26_decrypt_any(input: *const c_char, amount: u32) -> *const c_char {
   |   ^
   |   |
   |  _help: try making it public: `pub `
   | |
64 | |     let input = match unsafe { CStr::from_ptr(input).to_str() } {
65 | |         Ok(input) => input,
66 | |         Err(_) => return ptr::null()
...  |
75 | |     ptr
76 | | }
   | |_^

(The problem is actually that the module is hidden. So I should use pub mod.)

[kennytm]

Minimal reproduction:

#![crate_type="lib"]
mod private {
    #[no_mangle]
    pub fn public() {}
}

[petrochenkov]

Fixed in #47479