| // check-pass |
| // revisions: e2018 e2021 |
| //[e2018] edition:2018 |
| //[e2021] edition:2021 |
| #![feature(never_patterns)] |
| #![allow(incomplete_features)] |
| |
| #[derive(Debug, PartialEq, Eq)] |
| struct Pattern; |
| #[derive(Debug, PartialEq, Eq)] |
| struct Never; |
| #[derive(Debug, PartialEq, Eq)] |
| struct Other; |
| |
| macro_rules! detect_pat { |
| ($p:pat) => { |
| Pattern |
| }; |
| (!) => { |
| Never |
| }; |
| ($($x:tt)*) => { |
| Other |
| }; |
| } |
| |
| // For backwards-compatibility, all the cases that parse as `Pattern` under the feature gate must |
| // have been parse errors before. |
| fn main() { |
| // For backwards compatibility this does not match `$p:pat`. |
| assert_eq!(detect_pat!(!), Never); |
| |
| // Edition 2018 parses both of these cases as `Other`. Both editions have been parsing the |
| // first case as `Other` before, so we mustn't change that. |
| assert_eq!(detect_pat!(! | true), Other); |
| #[cfg(e2018)] |
| assert_eq!(detect_pat!(true | !), Other); |
| #[cfg(e2021)] |
| assert_eq!(detect_pat!(true | !), Pattern); |
| |
| // These are never patterns; they take no body when they're in a match arm. |
| assert_eq!(detect_pat!((!)), Pattern); |
| assert_eq!(detect_pat!((true, !)), Pattern); |
| assert_eq!(detect_pat!(Some(!)), Pattern); |
| |
| // These count as normal patterns. |
| assert_eq!(detect_pat!((! | true)), Pattern); |
| assert_eq!(detect_pat!((Ok(x) | Err(&!))), Pattern); |
| } |