In what situations might `panic!` be considered idiomatic in Rust, even though `Result` is generally preferred for recoverable errors?

`panic!` can be considered idiomatic in a few specific situations: 1. **Development and Testing:** `assert!`, `debug_assert!`, `unreachable!`, and the use of `unwrap()`/`expect()` are common during development to quickly catch logical errors. 2. **Command-Line Tools/Prototypes:** For simple scripts or examples where a fatal error means the tool cannot proceed and should simply exit. 3. **Guaranteed Invariants:** If a piece of code relies on an invariant that you *know* should always hold true, and its violation indicates a fundamental bug in your code, `panic!` can be used to signal this bug rather than trying to recover from an impossible state. 4. **Unreachable Code Branches:** The `unreachable!` macro is used to indicate code that should never be reached, panicking if it is.