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