Function parse_big_integer

crates/codegen/src/compile.rs:10520–10547

Converts a `ruff` ast integer into a `BigInt`. Unlike small integers, big integers may be stored in one of four possible radix representations.

(int: &ast::Int)

/// Converts a `ruff` ast integer into a `BigInt`.
/// Unlike small integers, big integers may be stored in one of four possible radix representations.
fn parse_big_integer(int: &ast::Int) -> Result<BigInt, CodegenErrorType> {
    // TODO: Improve ruff API
    // Can we avoid this copy?
    let s = format!("{int}");
    let mut s = s.as_str();
    // See: https://peps.python.org/pep-0515/#literal-grammar
    let radix = match s.get(0..2) {
        Some("0b" | "0B") => {
            s = s.get(2..).unwrap_or(s);
            2
        }
        Some("0o" | "0O") => {
            s = s.get(2..).unwrap_or(s);
            8
        }
        Some("0x" | "0X") => {
            s = s.get(2..).unwrap_or(s);
            16
        }
        _ => 10,
    };

    BigInt::from_str_radix(s, radix).map_err(|e| {
        CodegenErrorType::SyntaxError(format!(
            "unparsed integer literal (radix {radix}): {s} ({e})"
        ))
    })
}

// Note: Not a good practice in general. Keep this trait private only for compiler
trait ToU32 {