[patrick-immometrica]

With the no-panic feature enabled, formatting a value that isn't a compile-time constant fails to link for u32, u64, u128, i32, i128 and usize:

// Cargo.toml: itoa = { version = "1", features = ["no-panic"] }
fn main() {
    let n: u64 = std::env::args().count() as u64;
    println!("{}", itoa::Buffer::new().format(n));
}

ERROR[no-panic]: detected panic in function `fmt`

It's the bounds checks on buf[offset] in the digit loops. LLVM can't prove offset stays in range, so panic_bounds_check stays in the binary. u8/u16/i8/i16/i64/isize happen to link fine.

CI didn't catch this because the tests only format literals, so in the release build every call folds away and there's nothing left to check. The test macro now passes the value through black_box. Without the fix, cargo build --tests --features no-panic --release fails; with it, it passes.

The fix uses get_unchecked_mut for those writes, as the table lookups next to them already do. I checked a downstream crate on aarch64 and x86_64 macOS: all 12 types link with no-panic now. There's no measurable difference in speed.