Warn about C-style octal literals by GrigorenkoPV · Pull Request #131309 · rust-lang/rust (original) (raw)
Uplifts clippy::zero_prefixed_literal as leading_zeros_in_decimal_literals, warn-by-default.
The leading_zeros_in_decimal_literals lint detects decimal integral literals with leading zeros.
Example
fn is_executable(unix_mode: u32) -> bool { unix_mode & 0111 != 0
Explanation
In some languages (including the infamous C language and most of its family), a leading zero marks an octal constant. In Rust however, a 0o prefix is used instead.
Thus, a leading zero can be confusing for both the writer and a reader.
In Rust:
fn main() { let a = 0123; println!("{}", a); }
prints 123, while in C:
#include <stdio.h>
int main() { int a = 0123; printf("%d\n", a); }
prints 83 (as 83 == 0o123 while 123 == 0o173).
Notes
Compared to the Clippy lint, this will not warn if the literal is unambiguous, i.e. it has 8's or 9's in it (clearly not octal) or it is <10 (in this case the value does not depend on the base).