2 Warns if an integral constant literal starts with `0`.
5 In some languages (including the infamous C language
7 family), this marks an octal constant. In Rust however, this is a decimal
9 be confusing for both the writer and a reader of the constant.
21 prints `123`, while in C:
32 prints `83` (as `83 == 0o123` while `123 == 0o173`).