#[no_mangle] should not be applied to non-ASCII items

[tamaroning]

Items with an ASCII name and #[no_mangle] should not compile.

input:

#[no_mangle]
pub fn ぽ() {}

pub fn main() {}

output: compiled.

expected: rustc's output

error[[E0754]](https://doc.rust-lang.org/stable/error_codes/E0754.html): `#[no_mangle]` requires ASCII identifier
 --> src/main.rs:2:1
  |
2 | pub fn ぽ() {}
  | ^^^^^^^^^^^