Arithmetic overflow is suppressed by taking a reference to a variable

This code does not throw arithmetic_overflow at compile time:

fn no_error() -> u8 {
    let a: u8 = 20;
    let b: u8 = 32;
    let _ = &a;
    a * b
}

But this code does:

fn errors() -> u8 {
    let a: u8 = 20;
    let b: u8 = 32;
    a * b
}

It seems that borrowing one of the operands suppresses arithmetic_overflow.

Perhaps related to this: https://github.com/rust-lang/rust/issues/104578

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rustc --version --verbose:

rustc 1.91.1 (ed61e7d7e 2025-11-07)
binary: rustc
commit-hash: ed61e7d7e242494fb7057f2657300d9e77bb4fcb
commit-date: 2025-11-07
host: aarch64-apple-darwin
release: 1.91.1
LLVM version: 21.1.2

Start by reproducing both Rust snippets with the reported rustc version and compare their compile-time diagnostics, then read the related issue #104578 for context on overflow analysis. No source file or test is named; done means identifying the borrow-sensitive behavior, correcting it, and adding a regression test that verifies the overflow is consistently reported.