Signed integer division can panic even when overflow checks are disabled

[syvb]

I tried this code with -C overflow-checks=off:

#[allow(arithmetic_overflow)]
fn main() {
    i32::MIN % -1;
    i32::MIN / -1;
}

I expected to see this happen: It does not panic since overflow checks are disabled, and per the reference this doesn't panic when overflow checks are disabled

Instead, this happened: It panics with attempt to calculate the remainder with overflow

Meta

rustc --version --verbose:

$ rustc +local --version --verbose
rustc 1.54.0-dev
binary: rustc
commit-hash: unknown
commit-date: unknown
host: x86_64-unknown-linux-gnu
release: 1.54.0-dev
LLVM version: 12.0.1

Backtrace

thread 'main' panicked at 'attempt to calculate the remainder with overflow', ov.rs:3:5
stack backtrace:
   0: rust_begin_unwind
             at /home/smit/rustc-dev/rust/library/std/src/panicking.rs:515:5
   1: core::panicking::panic_fmt
             at /home/smit/rustc-dev/rust/library/core/src/panicking.rs:92:14
   2: core::panicking::panic
             at /home/smit/rustc-dev/rust/library/core/src/panicking.rs:50:5
   3: ov::main
   4: core::ops::function::FnOnce::call_once
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

I'm not sure if the issue is with rustc or the reference here.

[luqmana]

RFC 560: Integer overflow says:

The operations /, % for the arguments INT_MIN and -1 will unconditionally panic. This is unconditional for legacy reasons.

Hence, it's by design at the moment. See rust-lang/rfcs#1276

[syvb]

See rust-lang/reference#1049 for the PR to the reference.