Unusual Panic Location for Dividing by a Reference to Zero

[tim-burget]

I tried this code:

#[allow(unconditional_panic, unused)] // for minimal test case; doesn't cause problem
fn main() {
    1 / &0;
}

I expected to see this happen: program panics with main.rs or the actual location on disk of the standard library source code file that caused the panic given as the location

Instead, this happened: program gives /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library/core/src/ops/arith.rs:484:1 (internal compiler location?) as the panic location

Meta

rustc --version --verbose:

rustc 1.71.1 (eb26296b5 2023-08-03)
binary: rustc
commit-hash: eb26296b556cef10fb713a38f3d16b9886080f26
commit-date: 2023-08-03
host: x86_64-pc-windows-msvc
release: 1.71.1
LLVM version: 16.0.5

I also checked that it happened in WSL:
rustc --version --verbose:

rustc 1.71.1 (eb26296b5 2023-08-03)
binary: rustc
commit-hash: eb26296b556cef10fb713a38f3d16b9886080f26
commit-date: 2023-08-03
host: x86_64-unknown-linux-gnu
release: 1.71.1
LLVM version: 16.0.5

Backtrace

No build errors, but the backtrace for the program also contains references to internal compiler locations that I would expect to point to the actual locations of standard library source files on disk, as well.

   0: std::panicking::begin_panic_handler
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library\std\src\panicking.rs:593
   1: core::panicking::panic_fmt
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library\core\src\panicking.rs:67
   2: core::panicking::panic
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26/library\core\src\panicking.rs:117
   3: core::ops::arith::impl$177::div
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26\library\core\src\ops\arith.rs:484
   4: core::ops::arith::impl$208::div
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26\library\core\src\internal_macros.rs:45
   5: bug::main
             at .\src\main.rs:3
   6: core::ops::function::FnOnce::call_once<void (*)(),tuple$<> >
             at /rustc/eb26296b556cef10fb713a38f3d16b9886080f26\library\core\src\ops\function.rs:250

[tim-burget]

Full output of cargo run (without RUST_BACKTRACE set):

    Finished dev [unoptimized + debuginfo] target(s) in 0.04s
     Running `target\debug\bug.exe`
thread 'main' panicked at 'attempt to divide by zero', /rustc/eb26296b556cef10fb713a38f3d16b9886080f26\library\core\src\ops\arith.rs:484:1
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
error: process didn't exit successfully: `target\debug\bug.exe` (exit code: 101)

[scottmcm]

That goes through this trait implementation: https://doc.rust-lang.org/std/primitive.i32.html#impl-Div%3C%26i32%3E-for-i32

So technically it's happening there, but I agree that's not helpful.

Want to try making a PR to add #[track_caller] to those division and remainder implementations and see if it improves the location?