hint::select_unpredictable forgets to drop one argument if dropping another panics. #145148
Description
I tried this code:
struct Thing { label: &'static str, panic_on_drop: bool, } impl Drop for Thing { fn drop(&mut self) { println!("Dropping: {}", self.label); if self.panic_on_drop { println!("Panicking..."); panic!("Drop panicked"); } else { println!("Not panicking.") } } } fn main() { let a = Thing { label: "a", panic_on_drop: false, }; let b = Thing { label: "b", panic_on_drop: true, }; let _ = std::hint::select_unpredictable(true, a, b); }I expected b to be dropped, at which point a panic occurs, then a is dropped. Instead, a is not dropped at all.
Dropping: b Panicking... thread 'main' (133912) panicked at src/main.rs:11:13: Drop panicked note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace Meta
rustc --version --verbose:
rustc 1.91.0-nightly (de3efa79f 2025-08-08) binary: rustc commit-hash: de3efa79f95852c7427587f1d535bfea7c0d6779 commit-date: 2025-08-08 host: aarch64-apple-darwin release: 1.91.0-nightly LLVM version: 21.1.0